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Potential Risks of Nanomaterials and How to Safely Handle Materials of Uncertain Toxicity

“It is a mistake for someone to say nanoparticles are safe, and it is a mistake to say nanoparticles are dangerous. They are probably going to be somewhere in the middle. And it will depend very much on the specifics.”

V. Colvin, Director of Center for Biological and Environmental Nanotechnolgy at Rice University, quoted in Technology Review
What are nanomaterials?
What are the toxic effects of nanomaterials tested to date?
Quantum Dots
Carbon nanotubes
How to work safely with nanomaterials
Nanomaterial Waste Management
Additional information sources
Web sites posting current information about nanotoxicity
Review articles or reports
Research articles

In the last year and a half, there have been a number of research articles on the toxicity of different types of nanomaterials. These studies have suggested effects at the cellular level and in short-term animal tests. The effects seen depend on the base material of the nanoparticle, its size and structure, and its substituents and coatings. Additional toxicology testing is being funded or planned by the National Science Foundation (NSF), the National Toxicology Program, and other research organizations in the US and in Europe. Nanomaterials of uncertain toxicity can be handled using the same precautions currently used at MIT to handle toxic materials: use of exhaust ventilation (such as fume hoods and vented enclosures) to prevent inhalation exposure during procedures that may release aerosols or fibers and use of gloves to prevent dermal exposure. The EHS Office will continue to review health and safety information about nanomaterials as it becomes available and distribute it to the MIT community.

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What are nanomaterials?

The ASTM Committee on Nanotechnology has defined a nanoparticle as a particle with lengths in 2 or 3 dimensions between 1 to 100 nm that may or may not have a size related intensive properties. Nanomaterials are generally in the 1-100 nm range and can be composed of many different base materials (carbon, silicon, and metals such as gold, cadmium, and selenium). Nanomaterials also have different shapes: referred to by terms such as nanotubes, nanowires, crystalline structures such as quantum dots, and fullerenes. Nanomaterials often exhibit very different properties from their respective bulk materials: greater strength, conductivity, and fluorescence, among other properties. For many types of nanoparticles, 50-100% of the atoms may be on the surface, resulting in greater reactivity than bulk materials.

Particles in the nanometer size range do occur both in nature and as an incidental byproduct of existing industrial processes. Nanosized particles are part of the range of atmospheric particles generated by natural events such as volcanic eruptions and forest fires. They also form part of the fumes generated during welding, metal smelting, automobile exhaust, and other industrial processes. One concern about small particles that are less than 10 um is that they are respirable and reach the alveolar spaces of the lungs

The current nanotechnology revolution differs from past industrial processes because nanomaterials are being engineered and fabricated from the “bottom up”, rather than occurring as a byproduct of other activities. The nanomaterials being engineered have different and unexpected properties compared to those of the parent compounds. Since their properties are different when they are small, it is expected that they will have different effects on the body and will need to be evaluated separately from the parent compounds for toxicity.
Currently nanomaterials have a limited commercial market. Some nanmoaterials are used as catalyst supports in catalytic converters; nanosized titanium dioxide particles are used as a component of sunscreens; carbon nanotubes have been used to strengthen tennis rackets; components in silicon chips are reaching the 45 to 65 nm range. Research and industrial labs are working at the intersection of engineering and biology to extend uses to medicine as well as all areas of engineering. The impact is expected to revolutionize these areas. Government agencies in the US and Europe are beginning to fund toxicology research to understand the hazards of these materials before they become widely available.
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What are the toxic effects of nanomaterials tested to date?

This article will give a overview of the testing done to date. A list of review articles and research citations are given at the end for further information.

Any toxic effects of nanomaterials will be very specific to the type of base material, size, ligands, and coatings. One of the earliest observations was that nanomaterials, also called ultrafine particles (<100 nm), showed greater toxicity than fine particulates (<2.5 um) of the same material on a mass basis. This has been observed with different types of nanomaterials, including titanium dioxide, aluminum trioxide, carbon black, cobalt, and nickel. For example, Oberdorster et al. (1994) found that 21 nm titanium dioxide particles produced 43 fold more inflammation (as measured by the influx of polymorphonuclear leucocytes, a type of white blood cell, into the lung) than 250 nm particles based on the same mass instilled into animal lungs. The increase in inflammation is believed to due to the much greater surface area of the small particles for the same mass of material. Though multiple studies have shown that nano-sized particles may be more toxic than micro-sized particles, this is not always the case. Intrinsic surface reactivity may also be as important as surface area. Warheit et al. (2007) found that the toxicity for cytotoxic crystalline quartz did not relate to particle size, but did relate to surface reactivity as measured by hemoglobin release from cells in vitro. Warheit et al. (2006) also found that other types of crystalline anatase titanium dioxide did not show size intensive toxicity for nano sized particles.
Nanoparticles (<0.1 um) are generally similar in size to proteins in the body. They are considerably smaller than many cells in the body. Human alveolar macrophages are 24 um in diameter and red blood cells are 7-8 um in diameter. Cells growing in tissue culture will pick up most nanoparticles.

The ability to be taken up by cells is being used to develop nanosized drug delivery systems and does not inherently indicate toxicity. One study by Goodman et al. (2004) found that cellular toxicity depended upon cationic charge of side chains substituted onto nanoparticles with a 2 nm gold core. Gold nanoparticles are being investigated as transfection agents, DNA-binding agents, protein inhibitors and other biomedical applications. Goldman et al. found that positively charged gold particles with quaternary ammonium substituted side chains were toxic to two types of mammalian cells (red blood cells and Cos-1 cells) and E coli. bacteria, causing 50% of the cell to die at 1-3 uM concentrations. Negatively charged cells with carboxylate substituted side chains did not show cellular toxicity even when tested at much higher concentrations. The researchers attributed the cell lysis to binding by cationic particles to negatively charged cell membranes and subsequent membrane leakage. They are currently designing nanoparticles with different properties to prevent this type of toxicity.

Once in the body, some types of nanoparticles may have the ability to translocate and be distributed to other organs, including the central nervous system. Silver, albumin, and carbon nanoparticles all showed systemic availability after inhalation exposure. Significant amounts of 13C labeled carbon particles (22-30 nm in diameter) were found in the livers of rats after 6 hours of inhalation exposure to 80 or 180 ug/m3 (Oberdorster et al. 2002). In contrast, only very small amounts of 192Ir particles (15 nm) were found systemically. Oberdorster et al. (2004) also found that inhaled 13 C labeled carbon particles reached the olfactory bulb and also the cerebrum and cerebellum, suggesting that translocation to the brain occurred through the nasal mucosa along the olfactory nerve to the brain. The ability of nanomaterials to move about the body may depend on their chemical reactivity, surface characteristics, and ability to bind to body proteins.

There is currently no consensus about the ability of nanoparticles to penetrate through the skin. Particles in the micrometer range are generally thought to be unable to penetrate through the skin. The outer skin consists of a 10 um thick, tough layer of dead keratinized cells (stratum corneum) that is difficult to pass for particles, ionic compounds, and water soluble compounds. Tinkle et al. (2003) found that 0.5 and 1 um dextran spheres penetrated “flexed” human skin in an in vitro experiment. Particles penetrated into the epidermis and a few entered the dermis only during flexing of the skin. Particles 2 and 4 um in diameter did not penetrate. Rymen-Rasmussen et al. (2006) also found that quantum dots penetrated through pig skin and into living dermis using an in vitro pig skin bioassay which is considered a good model for human skin.

Micronized titanium dioxide (40 nm) is currently being used in sunscreens and cosmetics as sun protection. The nm particles are transparent and do not give the cosmetics the white, chalky appearance that coarser preparations did. The nm particles have been found to penetrate into the stratum corneum and more deeply into hair follicles and sweat glands than um particles though they did not reach the epidermis layer and dermis layers (Laddeman et al., 1999). There is also a concern that nm titanium dioxide particles have higher photo-reactivity than coarser particles and may generate free radicals that can cause cell damage. Some manufacturers have addressed this issue by coating the particles to prevent free radical formation. The FDA has reviewed available information and determined that nm titanium dioxide particles are not a new ingredient but a specific grade of the original product (Luther, 2004).
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Quantum dots (QD) are nanocrystals containing 1000 to 100,000 atoms and exhibiting unusual “quantum effects” such as prolonged fluorescence. They are being investigated for use in immunostaining as alternatives to fluorescent dyes. The most commonly used material for the core crystal is cadmium-selenium, which exhibits bright fluorescence and high photostability. Both bulk cadmium and selenium are toxic to cells. One of the primary sites of cadmium toxicity in vivo is the liver.

Early studies found that Cd-Se quantum dots were not toxic to immortalized cell lines used for these studies. Recently Shiohara et al. (2004) found that three types mercapto-undecanoic acid (MUA) substituted Cd-Se quantum dots decrease viability in three types of cells in vitro (monkey kidney, HeLA cells, and human hepatocytes) and caused cell death after 4-6 hours of incubation. One type of MUA-QD was less toxic than the other two. Derfus et al. (2004) also found that Cd-Se QDs were toxic to liver hepatocytes if exposed to air or UV light, as a result of oxygen combining with Se and releasing free Cd+2 from the crystal lattice. They found that coating the Cd-Se QDs with ZnS, polyethylene glycol, or other coatings prevented toxicity during a two week incubation with hepatocytes. They concluded that Cd-Se QDs can be made nontoxic with appropriate surface coatings but future use in vivo must be carefully evaluated to rule out release of Cd+2 over time.
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Carbon nanotubes (CNT) can have either single or multiple layers of carbon atoms arranged in a cylinder. The dimensions of typical single wall carbon nanotubes (SWCNT) are about 1-2 nm in diameter by 0.1 um in length. Multiple wall carbon nanotubes (MWCNT) are 20 nm in diameter and 1 mm long. CNT may behave like fibers in the lung. They have properties very different from bulk carbon or graphite. They have great tensile strength and are potentially the strongest, smallest fibers known. CNT have been tested in short term animal tests of pulmonary toxicity and the results suggest the potential for lung toxicity though there are questions about the nature of the toxicity observed and the doses used.

Lam et al. (2004) instilled three types of SWCNT into rat lungs and found granulomas, a type of cellular accumulation in the lung in which clumps of fibers were surrounded by mononuclear macrophages. Quartz, a dust known to be very toxic to human lungs, also produced lung damagebut carbon black did not. Warheit et al. (2004), using a different type of SWCNT, also found granulomas but did not see increases in other markers of pulmonary inflammation whereas quartz produced both macrophage accumulation and increased pulmonary inflammation. Warheit et al. interpreted their SWCNT results as possibly of limited physiological relevance but requiring further inhalation studies.

Shvedova et al. (2005) using more physiologically relevant doses, found granulomas, fibrosis, and increased markers of inflammation from both SWCNT. SWCNT also affected lung function: breathing rate and the ability to clear bacteria were decreased. More extensive inhalation studies are currently underway in several research centers. One mitigating factor regarding lung toxicity is that CNTs have a tendency to clump together to form nanoropes, which are large, non-respirable clumps, and may prevent inhalation exposure in many instances (see discussion below Maynard et al. [2004] study).

The addition of functional groups such as phenyl-sulfite and phenyl-carboxylic acid onto CNTs can decrease toxicity, as demonstrated using in vitro tests by Sayes et al. (2006). Other in vitro tests have found inhibited cell growth and viability. Good recent reviews of CNT toxicity which cover pulmonary toxicity and also in vitro testing and environmental considerations are provided by Donaldson et al. (2006) and Helland et al. (2007). A recent report by Zheng Li et al. (2007) found that instillation of CNTs produced cardiovascular effects in transgenic artherogenesis prone mice; the mice developed accelerated plaque formation after four doses of CNTs over an 8 week period.
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Fullerenes are another category of carbon based nanoparticles. The most common type has a molecular structure of C60 which take the shape of a ball shaped cage of carbon particles arranged in pentagons and hexagons. Fullerenes have many potential medical applications as well as applications in industrial coatings and fuel cells, so a number of preliminary toxicology studies have been done with them. In cell culture, different types of fullerenes produced cell death at concentrations of 1 to 15 ppm in different mammalian cells when activated by light (as discussed in Colvin, 2003). Sayes et al. (2004) found that toxicity could be eliminated when carboxyl groups were substituted on the fullerene surface to increase water solubility. Cell death in this study appeared to be a function of damage to the cell membranes. In an in vivo study, Chen et al. (2004) found that water soluble polyalkylsulfonated C60 produced no deaths in rats when given orally but was moderately toxic when administered intraperitoneally (LD50=600 mg/kg). Doses of 100 to 600 mg/kg also produced an unusual form of kidney toxicity. Finally, in the first study investigating aquatic toxicology, Oberdorster (2004) found that 48 hours of exposure to 0.5 and 1.0 ppm of uncoated pure C60 produced cell membrane lipid peroxidation in the brains of fish (juvenile large mouth bass). The changes in the brain as a result of the short exposure did not appear to affect the behavior of the fish but were an indication of oxidative stress. An additional concern generated by this study is the effects of release of durable carbon nanomaterials into the environment.

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How to Work Safely with Nanomaterials

The preliminary conclusions to be drawn from the toxicology studies to date is that some types of nanomaterials can be toxic, if they are not bound up in a substrate and they are available to the body. Multiple government organizations are working to fund and assemble toxicology information on these materials. In the interim, MIT researchers must use procedures that prevent inhalation and dermal exposures because at this time nanotoxicology information is limited.

Based on particles physics and studies of fine atmospheric pollutants, nanoparticles are in the size range that remains suspended for days to weeks if released into air. Nanoparticles can be inhaled and will be collected in all regions of the respiratory tract; about 35% will deposit in the deep alveolar region of the lungs.

Because they are so small, nanoparticles follow airstreams more easily than larger particles, so they will be easily collected and retained in standard ventilated enclosures such as fume hoods. In addition, nanoparticles are readily collected by HEPA filters. Respirators with HEPA filters will be adequate protection for nanoparticles in case of spills of large amounts of material.

Working safely with nanomaterials involves following standard procedures that would be followed for any particulate material with known or uncertain toxicity: preventing inhalation, dermal, and ingestion exposure. Many nanomaterials are synthesized in enclosed reactors or glove boxes. The enclosures are under vacuum or exhaust ventilation, which prevent exposure during the actual synthesis. Inhalation exposure can occur during additional processing of materials removed from reactors, and this processing should be done in fume hoods. In addition, maintenance on reactor parts that may release residual particles in the air should be done in fume hoods. Another process, the synthesis of particles using sol-gel chemistry, should be carried out in ventilated fume hoods or glove boxes.

The type of surface coating on nanoparticles often causes them to clump together so that few particles are actually released when particles are removed from reactors. In one of the few workplace industrial hygiene studies of nanoparticles, Maynard et al. (2004) found almost no release of fibers when carbon nanotubes were removed from a reactor and transferred into a secondary container. The SWCNT clumped together into nanoropes and remained attached to the substrate as it was removed from the reactor. Maynard et al. (2004) also found that it took considerable energy to break up the nanoropes and release them into air: the highest settings on a fluidized bed vortex shaker were needed to produce aerosol release. The type of SWCNT investigated in this study were uncoated with about 30% Fe catalyst remaining as part of the nanoropes. Researchers are attempting to coat CNT and other nanoparticles with materials that make them less sticky and more easily dispersed; if successful, this would make them more easily aerosolized and require additional care when handling.

Concerning skin contact, Maynard et al. found clumps of nanoropes on the gloves of workers removing the synthesized materials from the reactors. Since the ability of nanoparticles to penetrate the skin is uncertain at this point, gloves should be worn when handling particulate and solutions containing particles. A glove having good chemical resistance to any solution the particles are suspended in should be used. If working with dry particulate, a sturdy glove with good integrity should be used. Disposable nitrile gloves commonly used in many labs would provide good protection from nanoparticles for most procedures that don’t involve extensive skin contact. Two pairs of gloves can be worn if extensive skin contact is anticipated, as well as gloves with gauntlets or extended sleeve nitrile gloves, to prevent contamination of lab coats or clothing.

One potential safety concern with nanoparticles is fires and explosions if large quantities of dust are generated during reactions or production. This is expected to become more of a concern when reactions are scaled up to pilot plant or production levels. Both carbonaceous and metal dusts can burn and explode if an oxidant such as air and an ignition source are present. Nanodusts can be anticipated to have a greater potential for explosivity than larger particles. Determination of lower flammability limits using standard test bomb protocols is being planned in Europe.
There are currently no government occupational exposure standards for nanomaterials. When they are eventually developed, different standards for different types of nanomaterials will be needed. One should also be aware that Material Safety Data Sheets (MSDS) may not have accurate information at this point in time. For example, the MSDSs that are accompanying some commercially available carbon nanotubes are referring to the graphite Permissible Exposure Limit as a relevant exposure standard. Both graphite and carbon nanotubes are composed of carbon arranged in a honeycomb pattern. However CNTs have very different tensile and conductive properties than graphite. Additionally CNTs are much more toxic in the short-term animal tests that have been performed to date. Consequently, the graphite PEL and toxicity information is not appropriate for MSDSs of CNTs. CNTs should be treated as potentially toxic fibers, if capable of being released into the air and not bound up in a substrate, and should be handled with appropriate controls as described previously.
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Nanomaterial Waste Management

As nanotechnology emerges and evolves, potential environmental applications and human health and environmental implications are under consideration by the EPA and local regulators.

EPA has a number of different offices coordinating their review of this rapidly evolving technology. The EPA is currently trying a voluntary approach to testing and developing a stewardship program. There are currently no guidelines from the EPA specifically addressing disposal of waste nanomaterials. It seems that regulation at some level is inevitable. Some political subdivisions, including the City of Cambridge, are already evaluating local regulation.

MIT is taking a cautious approach to nano waste management. It is our belief that regulation is inevitable. In order to better understand the potential volumes and characteristics of these waste streams we are advising that all waste materials potentially contaminated with nano materials be identified and evaluated or collected for special waste disposal. On the content section note that it contains nano sized particles and indicate what they are.

The following waste management guidance applies to nanomaterial-bearing waste streams consisting of:

Pure nanomaterials (e.g., carbon nanotubes)
Items contaminated with nanomaterials (e.g., wipes/PPE)
Liquid suspensions containing nanomaterials
Solid matrixes with nanomaterials that are friable or have a nanostructure loosely attached to the surface such that they can reasonably be expected to break free or leach out when in contact with air or water, or when subjected to reasonably foreseeable mechanical forces.
The guidance does not apply to nanomaterials embedded in a solid matrix that cannot reasonably be expected to break free or leach out when they contact air or water, but would apply to dusts and fines generated when cuttting or milling such materials.

DO NOT put material from nanomaterial – bearing waste streams into the regular trash or down the drain. Before disposal of any waste contaminated with nanomaterial, call the EHS Office (452-3477) for a waste determination.

Collect paper, wipes, PPE and other items with loose contamination in a plastic bag or other sealing container stored in the laboratory hood. When the bag is full, close it, take it out of the hood and place it into a second plastic bag or other sealing container. Label the outer bag with the laboratory’s proper waste label. On the content section note that it contains nano sized particles and indicate what they are.

Currently the disposal requirements for the base materials should be considered first when characterizing these materials. If the base material is toxic, such as silver or cadmium, or the carrier is a hazardous waste, such as a flammable solvent or acid, clearly they should carry those identifiers. Many nanoparticles may also be otherwise joined with toxic metals of chemicals. Bulk carbon is considered a flammable solid, so even carbon based nanomaterials should be collected for determination as hazardous waste characteristics.
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Additional Sources of Information

Below are additional information sources for nanomaterials (web sites, review articles, and individual research articles). The EHS Office plans to screen new information regularly and alert the MIT community about additional toxicology studies as they become available. We also request that MIT researchers alert us about studies that they learn of so we can distribute them to the MIT community. We would like to observe handling procedures in different labs so we can share good practice information within the MIT community. Many of the articles listed below can be accessed electronically through the MIT Libraries if an electronic subscription is available. Web sites are also provided where available.

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Web Sites that Post Current Information about Nanotoxicology

Gradient Corp. Monthly EH&S Nano News at

International Council on Nanotechnology at: Up-to-date postings on nanotoxicology worldwide.

National Institute for Occupational Safety and Health (NIOSH) Nanotechnology Topic Page at

National Nanotechnology Infrastructure Network (NNIN) at:

National Center for Biotechnology Information (NCBI) Pub Med at: [Can search for articles on nanoparticle toxicity.]

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Review Articles or Reports About Nanotoxicology

Borm P JA, Robbins D, Haubold S et al. The potential risks of nanomaterials: a review carried out for ECETOC. Part Fiber Toxicol 3:11-35 2006.

Colvin VL. The potential environmental impact of engineered nanmoaterials. Nature Biotechnology 21:1166-1170 2003. [Note: Excellent and succinct overview of nanotoxicology.

Oberdorster G, Oberdorster E, Oberdorster J. Nanotoxicology: An Emrging Discipline Evolving from Studies of Ultrafine Particles. Environmental Health Perspectives 113:823-839 2005.

Health and Safety Executive (UK). Health effects of particles produced for nanotechnologies. Document EH75/6. 35 pp. December 2004. Available at: [Search for EH75/6]

Health and Safety Executive (UK). Nanoparticles: an occupational hygiene review. Research Report 274. 100 pp. 2004. Available at: [Search for RR274]

BIA. Workshop on ultrafine aerosols at workplaces. Held August 2002 in Germany. 208 pp. Available at: [Go to Nanotechnology Topic Page. Report is listed in section Non-US Governmental Resources]

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Research Articles on Nanotoxicology
[Many articles are available electronically through MIT Libraries]

Chen HH, Yu C, Ueng TH, Chen S et al. Acute and subacute toxicity study of water soluble polyalkylsulfonated C60 in rats. Toxicol Pathol 26:143-151 1998.

Cui D, Tian F, Ozkan CS, Wang M, Gao H. Effect of single wall carbon nanotubes on human HEK293 cells. Toxicol Lett 155:73-85 2005.

Derfus AM, Chan WC, Bhatia SN. Probing the cytotoxicity of semiconductor quantum dots. Nano Lett 4:11-18 2004.

Donaldson K, Aitken R, Tran L, et al. Carbon nanotubes: a review of their properties in relation to pulmonary toxicology and workplace safety. Toxicol Sci 92:5-22 2006.

Goodman CM, McCusker CD, Yilmaz T, Rotello VM. Toxicity of gold nanoparticles functionalized with cationic and anionic side chains. Bioconjugate Chem 15:897-900 2004.

Helland A, Wick, P, Koehler A, Schmid K, Som, C. Reviewing the Environmental and Human Health Knowledge Base of Carbon Nanotubes. Env Hlth Perspec 115:1125-1131 2007

Lademann J, Weigmann HJ, Rickmeyer C, Barthelmes H et al. Penetration of titanium dioxide microparticles in a sunscreen formulation into the horny layer and the follicular orifice. Skin Parmacol Appl Skin Physiol 12:247-256 1999.

Lam CW, James JT, McCluskey R, Hunter RL Pulmonary toxicity of single-wall carbon nanotubes in mice 7 and 90 days after intratracheal instillation. Toxicol Sci 77:126-134 2004.

Li Z, Hulderman T, Salmen R, Chapman R, et al. Cardiovascular effects of pulmonary exposure to single-wall carbon nanotubes. Environ Hlth Perspec 115:377-382 2007.

Maynard AD, Baron PA, Foley M, Shvedova AA et al. Exposure to carbon nanotube material: aerosol release during the handling of unrefined single-walled carbon nanotube material. J Toxicol Environ Hlth, Part A, 67:87-107 2004.

Monteiro-Riviere NA, Nemanich RJ, Inman AO, Wang YY et al. Multi-walled carbon nanotube interactions with human epidermal keratinocytes. Toxicol Lett 155:377-384 2005.

Oberdorster E. Manufactured nanomaterials (fullerenes) induce oxidative stress in the brain of juvenile largemouth bass. Enn Hlth Perspec 112:1058-1062 2004.

Oberdorster G, Ferin J, Lehnert BE. Correlation between particle size, in vivo particle persistence and lung injury. Env Hlth Perspec 102 (suppl 5):173-179 2004a.

Oberdorster G, Sharp Z, Atudorei V, Elder A et al. Extrapulmonary translocation of ultrafine carbon particles following whole-body inhalation exposure of rats. J Toxicol Environ Hlth Part A 65:1531-1543 2002.

Oberdorster G, Sharp Z, Atudonrei V, Elder A et al. Translocation of inhaled ultrafine particles to the brain. Inhal Toxicol 16:453-459 2004b.

Rymen-Rasmussen JP, Riviere JE, Monteiro-Riviere NA. Penetration of intact skin by quantum dots with diverse physicochemical properties. Toxicol Sci 91:159-165 2006.

Sayes CM, Fortner JD, Guo W, Lyon D et al. The differential cytotoxicity of water-soluble fullerenes. Nano Lett 4:1881-1887 2004

Sayes CM, Liang F, Hudson JL et al. Functionalization density dependence of single-walled carbon nanotubes cytotoxicity in vitro. Toxicol Lett 161:135-142 2006

Shvedova AA, Kisin ER, Mercer R, Murray AR, et al. Unusual inflammatory and fibrogenic pulmonary responses to single-walled carbon nanotubes in mice. Am J Physiol Lung Cell Mol Physiol 289:L698-L708 2005.

Shiohara A, Hshino A, Hanaki K, Suzuki K, et al. On the cyto-toxicity caused by quantum dots. Microbiol Immunol 48:669-675 2004.

Tinkle SS, Antonini JM, Rich BA, Roberts JR et al. Skin as a route of exposure and sensitization in chronic beryllium disease. Env Hlth Perspec 111:1202-1208 2003.

Warheit DB, Laurence BR, Reed KL, Roach DH, et al. Comparative pulmonary toxicity assessment of single-wall carbon nanotubes in rats. Toxicol Sci 77:117-125 (2004)

Warheit DB, Webb TR, Colvin VC, et al. Pulmonary bioassay studies with nanoscale and fine-quartz particles in rats: toxicity is not dependent upon particle size but on surface characteristics. Toxicol Sci 95:270-280 2007.

Warheit DB, Webb TR, Sayes CM et al. Pulmonary instillation studies with nanoscale TiO2 rods and dots in rats: toxicity is not dependent upon particle size and surface area. Toxicol Sci 91:227-236 2006.
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Science Lessons Come in Handy To Get Glassware Unstuck

Science Lessons Come in Handy To Get Glassware Unstuck

Mary Hunt
Dear Mary: I inadvertently placed a glass mixing bowl in another bowl of a similar size that was still damp. Now I can't get them apart. Do you have any ideas how to get these two bowls apart? -- Sarma R., e-mail

Dear Sarma: Gather the kids around because you have the perfect opportunity to show them how to use science in everyday life -- specifically the way that heat causes things to expand and cold makes them contract.

First, fill the inner bowl with cold water. Now fill your kitchen sink (or a larger bowl that is big enough to accommodate the glass bowls) with hot water. Float the stuck bowls in the hot water, and press down so that as much of the outer bowl is submerged as possible without getting any hot water between the bowls. This should release the seal between the bowls.

Make sure the two temperatures are not too extreme, or the bowls could break -- unless you are dealing with Pyrex or similar types of bowls that have been tempered and will not break under extreme temperature changes.


Dear Mary: We have just built a new home and got our loan through a local bank. They say they don't report our loans. Is there anything bad about that? -- Bettina A., South Carolina

Dear Bettina: I assume you mean this lender does not report its customers' loan activities to credit bureaus, such as Experian or Equifax. This is not all that unusual because they are not required by any law to do so. The only reason this might be of concern to you is if you will be relying on your payment history with this company to improve your credit score. Because you got this loan, I am going to assume that your credit score was satisfactory, so you don't need to worry at all that they will not be reporting your activity in the future.


Dear Mary: Is there any way we can do dry cleaning at home? -- Vici, e-mail

Dear Vici: There are several home dry cleaning kits currently available for purchase in most groceries and discount stores, including FreshCare from Clorox, Dryel by Procter & Gamble and Dry Cleaner's Secret. At about $10 per kit, all of these promise to clean and/or freshen dry-clean-only or hand-wash-only fabrics without using industrial solvents used by dry cleaners. These kits' basic steps mirror those of commercial dry cleaning, without immersion in a solvent or the need for specialized machinery.

While these kits are not good substitutes for actual dry cleaning, they may be useful for removing spots and freshening dry-clean-only garments, extending the time between professional cleanings. But if you are looking for the crisp, freshly pressed look from the dry cleaner, you will be disappointed. User reviews often say the kits don't remove most stains well and often leave circles around the stains.

Your best bet, in my opinion, is to avoid buying garments that require dry cleaning. And for those that you cannot avoid, make sure you treat spots immediately with a solvent-type cleaner, such as Afta or EverBlum. Then be sure to air out wool, linen and silk garments after you wear them to increase the time between professional cleanings.


Do you have a question for Mary? E-mail her at, or write to Everyday Cheapskate, P.O. Box 2135, Paramount, CA 90723. Mary Hunt is the founder of and author of 17 books, including "Debt-Proof Living." To find out more about Mary and read her past columns, please visit the Creators Syndicate Web page at

Copyright 2008 Creators Syndicate Inc.

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CPSC: Wal-Mart Recalls Additional Charm Key Chains Due to Risk of Lead Exposure

WASHINGTON, D.C. - The U.S. Consumer Product Safety Commission, in cooperation with the firm named below, today announced a voluntary recall of the following consumer product. Consumers should stop using recalled products immediately unless otherwise instructed.

Name of Product: "Hip Charm" Key Chains

Units: About 39,000 (firm previously recalled 12,000 key chains in April 2008)

Distributor: Wal-Mart Stores Inc., of Bentonville, Ark.

Importer: FGX International Inc., of Smithfield, R.I.

Hazard: The charms on the key chain can contain high levels of lead, which is toxic if ingested and can cause adverse health effects.

Incidents/Injuries: There have been no injuries reported with the additional key chains included in this recall. The Illinois Attorney General informed Wal-Mart and CPSC in April that the previously recalled key chain was found in the home of a 9-month-old child who was discovered to have high blood levels of lead. The child was observed mouthing this key chain.

Description: The recalled key chains have several charms including a button, clover, leaf, and heart. The charms hang from a silver-colored chain. The words "Hip charm" and the following UPC numbers are printed on the products packaging: 03156811032, 03156811029, 03156811019, 03156811016, 03156811018, 03156811028, and 03156811030.

Sold at: Wal-Mart stores nationwide from April 2005 through June 2008 for between $ .50 and $6.

Manufactured in: China

Remedy: Consumers should not allow children to handle the key chain and return it to any Wal-Mart store for a full refund.

Consumer Contact: For further information, contact Wal-Mart at (800) 925-6278 between 7 a.m. and 9 p.m. CT Monday through Friday, or visit the firm's Web site at

To see this recall on CPSC's web site, including pictures of the recalled product, please go to:

Sunday, June 29, 2008


IUPAC 2007

Question: Who named Element 110 and Element 111?

Answer: Sigurd Hofmann

Answer: Darmstadtium 110

Roentgenium 111

Question: How was Element 117 formed?

Answer: by the alpha decay of Element 118 not proton


to be place in

translations by Google

present in

Saturday, June 28, 2008 and and

Friday, June 27, 2008


MONDAY, JUNE 23, 2008

Google Translations of























Tuesday, June 24, 2008

more Science Lessons Blogs

Tuesday, May 27, 2008

Muroroa and Fangataufa Atoll

Monday, May 26, 2008

Nuclear Explosions and Earthquakes

Lop Nor and Earthquakes?

Monday, May 19, 2008


Job Opportunities at Penn State U

perhaps we can learn from job opportunities descriptions

Sunday, May 18, 2008






Saturday, May 17, 2008

Laser Flash Photolysis NASA studies -literature review|1&N=0&Ntk=all&Ntx=mode%20matchall&Ntt=laser%2Bflash%2Bphotolysis


On Propylene Glycol in Ubod-Pandan and Langka Extracts

On Sulfur Dioxide in Tropical Trail Mix

More on BioChips 5/17/08

Friday, May 16, 2008

BIOCHIPS --read up on it

Wednesday, May 14, 2008

Radiophotoluminescence 5/14/08;jsessionid=LvwdHpHW9s2nnvy2d12sGZTWDZrF22dblLD31yRTphsZSJxjgy8r!-1696092046!181195628!8091!-1




Current Issue


Operational Radiation Safety

February 1969, 16:2 > Silver-activated Lithium Borate...
< Previous | Next >
Silver-activated Lithium Borate Glasses As Radiophotoluminescence Dosimeters with Low Energy Dependence.

Health Physics. 16(2):125-133, February 1969.
Becker, K.; Cheka, J. S.
A radiophotoluminescent silver-activated glass based on the (Li2O, B2O3) system instead of the usual metaphosphate matrix has been studied. By reduction of the amount of silver activator, glasses with an energy dependence comparable to LiF (sensitivity variation within +/-10 to 30% between 10 keV and several MeV) have been prepared. Their weathering resistance has been unproved by additions of BeO. Maximum radiophotoluminescence (RPL) is developed by a heat treatment. More unusual dosimetric properties of such glasses are good stability even at high temperatures (up to 300-350[degrees]C), and a remarkable difference between the RPL and the absorption spectra obtained by the thermal neutron and gamma radiation. Also, the neutron induced RPL centers are less stable than the gamma radiation induced ones. RPL and absorption spectra as well as some other properties of these glasses have been studied in comparison with a conventional metaphosphate glass.

(C)1969Health Physics Society

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Release 4.7.0

Begin forwarded message:
From: Florence T. Cua
Date: May 8, 2008 8:11:32 AM EDT
Cc: Leah Tolosa , j gan
Subject: Fwd: Title: Radiophotoluminescent Dosimetry J, in;jsessionid=LvtCLDtGgxFDtNJtZCypbhyvKW68Q2xyJsNCH7QNbppLTr1CJ807!-341159882!181195629!8091!-1




Current Issue


Operational Radiation Safety

June 1975, 28:6 > Intercomparison Between Photographic,...
< Previous | Next >
Intercomparison Between Photographic, Thermoluminescent and Radiophotoluminescent Dosimeters.

Health Physics. 28(6):793-799, June 1975.
Deus, Sudernaique F.; Watanabe, Shigueo
A comparison has been made between the responses of three different dosimetric systems, namely, photographic, thermoluminescent (TL) and radiophotoluminescent (RPL) dosimetry. The comparison was divided into two parts. The first one was carried out with known radiation conditions (exposure, normal incidence, energy) in a controlled environment (~27[degrees]C temperature, ~70% r.h.). Under these conditions, the response as a function of exposure and energy, the relation of the linearity to the energy, the lowest detectable exposure, and the reproducibility were studied. Response as a function of the exposure at 37 keVeff and at 1 MeV was found to be linear in the region of interest to routine personnel dosimetry for all dosimeters except the films. Although the film response is not linear with exposure, the ratio between the response at 37 keVeff and at 1 MeV does not depend on the exposure, and this allows the determination of a simple correction factor for the radiation energy. Such energy corrections are usually necessary, since all the dosimeters, except the LiF TL dosimeters are strongly energy dependent. In the second part, the relative response of the dosimeters was measured under the uncontrolled condition in personnel dosimetry. Because the CaSO4: Dy is the most sensitive dosimeter, comparisons were made using this dosimeter as the standard, in which case it was found that 20 out of 29 TLD-100 dosimeters gave the same reading within 30%, 13 out of 29 RPL dosimeters agreed within 30%, and only 3 out of 29 films fell within 30%.

(C)1975Health Physics Society

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Begin forwarded message:
From: "Florence T. Cua"
Date: May 8, 2008 8:06:50 AM EDT
Cc: Leah Tolosa , j gan
Subject: Title: Radiophotoluminescent Dosimetry J, in

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Radiation Protection Dosimetry
Radiation Protection Dosimetry Advance Access

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Radiation Protection Dosimetry Advance Access published online on April 10, 2006
Radiation Protection Dosimetry, doi:10.1093/rpd/nci663
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© The Author 2006. Published by Oxford University Press. All rights reserved. For Permissions, please email:

SSD 2004 Special Issue Articles


Mark S. Akselrod 1 * and Anna E. Akselrod 1
1 Landauer, Stillwater Crystal Growth Division, 723 1/2 Eastgate Road Stillwater OK, 74074, USA

* To whom correspondence should be addressed.
Mark S. Akselrod, E-mail:


Optical and dosimetric properties of a new radiophotoluminescent material based on aluminum oxide doped with carbon and magnesium (Al2O3:C,Mg) and having aggregate oxygen vacancy defects are presented. The Al2O3:C,Mg crystals are characterized by several new optical absorption and emission bands. It is suggested that the main optical properties of this material are due to the formation of aggregate defects composed of two oxygen vacancies and two Mg-impurity atoms. Radiation-induced optical absorption bands are centered at 335 and 620 nm and produce fluorescent emission at 750 nm with a 75 ± 5 ns lifetime. The dose measurements are performed by illumination of the Al2O3:C,Mg crystal with 335 nm or 650 nm light and by measuring the intensity of the 750 nm fluorescence. The detector material is insensitive to room light before and after the irradiation and the traps are stable up to 600°C. A dose measurement range between 5 mGy and 200 Gy, suitable for therapeutic radiology applications, was demonstrated. The short luminescent lifetime and nondestructive readout is favorable for imaging applications.

CiteULike Connotea What's this?

This article has been cited by other articles:

G. J. Sykora, M. S. Akselrod, M. Salasky, and S. A. Marino
Novel Al2O3:C,Mg fluorescent nuclear track detectors for passive neutron dosimetry
Radiat Prot Dosimetry, August 1, 2007; 126(1-4): 278 - 283.
[Abstract] [Full Text] [PDF]

M. S. Akselrod, R. C. Yoder, and G. M. Akselrod
Confocal fluorescent imaging of tracks from heavy charged particles utilising new Al2O3:C,Mg crystals
Radiat Prot Dosimetry, September 1, 2006; 119(1-4): 357 - 362.
[Abstract] [Full Text] [PDF]

Please note that abstracts for content published before 1996 were created through digital scanning and may therefore not exactly replicate the text of the original print issues. All efforts have been made to ensure accuracy, but the Publisher will not be held responsible for any remaining inaccuracies. If you require any further clarification, please contact our Customer Services Department.

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Tuesday, April 29, 2008

NanoTX USA 2008

is the latest

you may also check up on

Begin forwarded message:
From: "nanoTX USA - Info"
Date: April 29, 2008 10:51:06 AM EDT
Subject: nanoTX USA - Call for Papers, ABSTRACTS DUE APRIL 30

nanoTX USA’08

International Nanotechnology Conference & Trade Expo

Hyatt Regency Dallas Convention Hotel, Dallas, Texas, USA, October 2-3, 2008

Call for Papers: Abstracts due April 30, 2008

Conference topics include (but are not limited to):

Track 1: Electronics & Materials

Advanced materials

Track 2: Biology & Medicine


Track 3: Energy & Environment

Solar technologies
Architecture and Smart buildings
Energy conversion and storage (fuel cells, batteries)
Environmental Health & Safety
Green nanotech

Track 4: Transportation & Security

Ground transportation
Space applications
Homeland Security

Track 5: Business & Economic Development

Commercialization issues
Growth areas/trends
Science education
Workforce development
Government regulations

Presentations should contain current results from investigations, new theories and planned investigations and be 20 minutes in length including Q&A. Additional papers may be selected for the poster session. Each confirmed speaker will receive a complimentary full conference pass (including the trade expo) and an invitation to the Nobel Laureates Legends Reception held on October 2, 2008.

To apply for the nanoTX USA’08 Call for Papers, candidates will need to submit the following information by email to .

Color photograph (headshot) for the website
100 word maximum biography of presenter for the website
10 word maximum speech title for the website
100 word maximum speech topic summary for the website
One page abstract (please indicate appropriate track)
Full contact information including work postal address

The nanoTX USA'08 Speaker Selection Committee will notify confirmed speakers and poster session participants by May 31, 2008.

This is information you requested. Please help us circulate where possible.
If you received this in error we are most sorry, and we sincerely believed you
wished to receive the important information. To be removed from this list, just return email and request.

Saturday, April 26, 2008

Earthquake 4/26/08

Today's Earthquake Fact
The core of the earth was the first internal structural element to be identified. In 1906 R.D. Oldham discovered the core from his studies of earthquake records. The inner core is solid, and the outer core is liquid and does not transmit the shear wave energy released during an earthquake.

You Tube

Magnetic Reversal 4/26/08





Thursday, April 24, 2008

Dr. Daniel Dingel, Engineer

Back to Earthquakes and EM Fields

Is there any relations between Earthquakes and Electromagnetic Anomalies? READ UP and We need more R&D
This is one example of agreeing to disagree.

186 Proc. Japan Acad., 75, Ser. B (1999)
Vol. 75(B),
Plasmon model for origin of earthquake related electromagnetic wave noises
By MasaShi KAMOGAWA*~'**~'t~ and Yoshi-Hiko OHTSUKI*~
(Communicated by Seiya UYEDA, M. J. A., Sept. 13, 1999)
Abstract: A theory is proposed to explain how the electromagnetic waves are created from the epi-
center of large earthquakes. By the increase of strong stress in the rock, exo-electrons are excited and emit-
ted, and bulk plasmon can be produced. They propagate to the earth surface, and transform into
electromagnetic waves. Simple order-estimation shows that the electromagnetic waves of the frequency
range 10 MHz-1 GHz may be observed. Some characteristics of observed earthquake related electromagnetic
waves may be interpreted by our plasmon model.
Key words: Earthquake; plasmon; electromagnetic wave.

Question: Where would electromagnetic reversal originate: down under in the core of the earth or up there in outer space?

Question: Is there any relationship between the incidence of solar flares and electromagnetic radiation?

Question: What type solar flares would result in electromagnetic reversal?|1035579925

Friday, April 18, 2008

Scientific American, April 2008

Comb Technologies

Optical Atomic Clocks
Chemical Sensors
Designer Chemistry

Optical Frequency Combs
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Global Waste Management

Begin forwarded message:

From: "The Global Waste Management Symposium"
Date: April 18, 2008 10:12:27 AM EDT
Subject: Announcing the Keynote Presenter

Announcing the Keynote Speaker for the 2008 Global Waste Management Symposium: Dr. Michael J. Walsh, Executive Vice President, Chicago Climate Exchange

The Potential for National Carbon Emissions Trading to Reduce Greenhouse Gas Emissions
Monday, September 8

Michael J. Walsh, Ph.D., is an Executive Vice President of Chicago Climate Exchange, Inc., a self-regulatory exchange that administers a voluntary, legally binding greenhouse gas reduction and trading program for North America. Dr. Walsh also serves on the Board of Directors of the Montreal Climate Exchange.

In his prior position with Environmental Financial Products (the predecessor company to CCX), Dr. Walsh arranged several international carbon credit transactions and served as liaison and lead writer for a series of technical papers on international emissions trading prepared for the Government of Canada. As a consultant to the U.S. Agency for International Development, Dr. Walsh provided instructional seminars on emissions trading for industry and government officials from several European countries. He has been a speaker at United Nations climate conferences at Geneva, Kyoto, Buenos Aires, Bonn and The Hague, and has been a keynote speaker at industry conferences and educational workshops around the world.

For more information on Michael J. Walsh, Ph.D., please click here.

The Global Waste Management Symposium (GWMS) will serve as a forum for the presentation of both applied and fundamental research and case studies on waste management. The GWMS will include both oral presentations and posters as well as special events to provide opportunities to share ideas and problem solve.

For more information on the Global Waste Management Symposium or to register, visit Both the pre-registration deadline and hotel reservation deadline are August 11, 2008.

To date, this year’s sponsors include:



With additional support from:
Geotech Environmental Equipment, Inc.
SCS Engineers
Shaw Environmental, Inc.
Weaver Boos Consultants, LLC

View the list of tabletop sponsors

The Global Waste Management Symposium…Promoting Technology and Scientific Innovation in the Management of Solid Waste.

GWMS 2008 Strategic Partners & Media Partners
Strategic Partners:
Chicago Climate

Media Partners:

11 Riverbend Drive, Stamford, CT 06907
You received this email because you have an existing business relationship with Waste Age, WasteExpo and/or The Global Waste Management Symposium, divisions of Penton Media. Periodically, we will inform you of special Penton-related shows, products and other offers that we believe you will find helpful in your business or career. To STOP receiving promotional e-mails from The Global Waste Management Symposium and Waste Tech Landfill Technology Conference, please click here to opt-out.

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Environmental Health and Safety of Different Energy Sources

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From Wikipedia, the free encyclopedia

This article may require cleanup to meet Wikipedia's quality standards.
Please improve this article if you can. (September 2006)
Not to be confused with censure, censer, or censor.
"Detector" redirects here. For the radio electronics component, see Detector (radio).
"Detector" redirects here. For detector in particle physics, see Particle detector.
A sensor is a device which measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument. For example, a mercury thermometer converts the measured temperature into expansion and contraction of a liquid which can be read on a calibrated glass tube. A thermocouple converts temperature to an output voltage which can be read by a voltmeter. For accuracy, all sensors need to be calibrated against known standards.
Sensors are used in everyday objects such as touch-sensitive elevator buttons and lamps which dim or brighten by touching the base. There are also innumerable applications for sensors of which most people are never aware. Applications include automobiles, machines, aerospace, medicine, industry, and robotics.
A sensor's sensitivity indicates how much the sensor's output changes when the measured quantity changes. For instance, if the mercury in a thermometer moves 1cm when the temperature changes by 1°, the sensitivity is 1cm/1°. Sensors that measure very small changes must have very high sensitivities.
Technological progress allows more and more sensors to be manufactured on a microscopic scale as microsensors using MEMS technology. In most cases, a microsensor reaches a significantly higher speed and sensitivity compared with macroscopic approaches. See also MEMS sensor generations.
Contents [hide]
1 Types
1.1 Thermal
1.2 Electromagnetic
1.3 Mechanical
1.4 Chemical
1.5 Optical radiation
1.6 Ionising radiation
1.7 Acoustic
1.8 Other types
1.8.1 Non Initialized systems
1.8.2 Initialized systems
2 Classification of measurement errors
2.1 Resolution
3 Biological sensors
4 Geodetic sensors
5 See also
6 External links

Because sensors are a type of transducer, they change one form of energy into another. For this reason, sensors can be classified according to the type of energy transfer that they detect.
temperature sensors: thermometers, thermocouples, temperature sensitive resistors (thermistors and resistance temperature detectors), bi-metal thermometers and thermostats
heat sensors: bolometer, calorimeter, heat flux sensor
electrical resistance sensors: ohmmeter, multimeter
electrical current sensors: galvanometer, ammeter
electrical voltage sensors: leaf electroscope, voltmeter
electrical power sensors: watt-hour meters
magnetism sensors: magnetic compass, fluxgate compass, magnetometer, Hall effect device
metal detectors
pressure sensors: altimeter, barometer, barograph, pressure gauge, air speed indicator, rate-of-climb indicator, variometer
gas and liquid flow sensors: flow sensor, anemometer, flow meter, gas meter, water meter, mass flow sensor
gas and liquid viscosity and density: viscometer, hydrometer, oscillating U-tube
mechanical sensors: acceleration sensor, position sensor, selsyn, switch, strain gauge
humidity sensors: hygrometer
Chemical proportion sensors: oxygen sensors, ion-selective electrodes, pH glass electrodes, redox electrodes, and carbon monoxide detectors.
[edit]Optical radiation
light time-of-flight. Used in modern surveying equipment, a short pulse of light is emitted and returned by a retroreflector. The return time of the pulse is proportional to the distance and is related to atmospheric density in a predictable way - see LIDAR.
light sensors, or photodetectors, including semiconductor devices such as photocells, photodiodes, phototransistors, CCDs, and Image sensors; vacuum tube devices like photo-electric tubes, photomultiplier tubes; and mechanical instruments such as the Nichols radiometer.
infra-red sensor, especially used as occupancy sensor for lighting and environmental controls.
proximity sensor- A type of distance sensor but less sophisticated. Only detects a specific proximity. May be optical - combination of a photocell and LED or laser. Applications in cell phones, paper detector in photocopiers, auto power standby/shutdown mode in notebooks and other devices. May employ a magnet and a Hall effect device.
scanning laser- A narrow beam of laser light is scanned over the scene by a mirror. A photocell sensor located at an offset responds when the beam is reflected from an object to the sensor, whence the distance is calculated by triangulation.
focus. A large aperture lens may be focused by a servo system. The distance to an in-focus scene element may be determined by the lens setting.
binocular. Two images gathered on a known baseline are brought into coincidence by a system of mirrors and prisms. The adjustment is used to determine distance. Used in some cameras (called range-finder cameras) and on a larger scale in early battleship range-finders
interferometry. Interference fringes between transmitted and reflected lightwaves produced by a coherent source such as a laser are counted and the distance is calculated. Capable of extremely high precision.
scintillometers measure atmospheric optical disturbances.
fiber optic sensors.
short path optical interception - detection device consists of a light-emitting diode illuminating a phototransistor, with the end position of a mechanical device detected by a moving flag intercepting the optical path, useful for determining an initial position for mechanisms driven by stepper motors.
[edit]Ionising radiation
radiation sensors: Geiger counter, dosimeter, Scintillation counter, Neutron detection
subatomic particle sensors: Particle detector, scintillator, Wire chamber, cloud chamber, bubble chamber. See Category:Particle detectors
acoustic : uses ultrasound time-of-flight echo return. Used in mid 20th century polaroid cameras and applied also to robotics. Even older systems like Fathometers (and fish finders) and other 'Tactical Active' Sonar (Sound Navigation And Ranging) systems in naval applications which mostly use audible sound frequencies.
sound sensors : microphones, hydrophones, seismometers.
[edit]Other types
motion sensors: radar gun, speedometer, tachometer, odometer, occupancy sensor, turn coordinator
orientation sensors: gyroscope, artificial horizon, ring laser gyroscope
distance sensor (noncontacting) Several technologies can be applied to sense distance: magnetostriction
[edit]Non Initialized systems
Gray code strip or wheel- a number of photodetectors can sense a pattern, creating a binary number. The gray code is a mutated pattern that ensures that only one bit of information changes with each measured step, thus avoiding ambiguities.
[edit]Initialized systems
These require starting from a known distance and accumulate incremental changes in measurements.
Quadrature wheel- A disk-shaped optical mask is driven by a gear train. Two photocells detecting light passing through the mask can determine a partial revolution of the mask and the direction of that rotation.
whisker sensor- A type of touch sensor and proximity sensor.
[edit]Classification of measurement errors

A good sensor obeys the following rules:
the sensor should be sensitive to the measured property
the sensor should be insensitive to any other property
the sensor should not influence the measured property
Ideal sensors are designed to be linear. The output signal of such a sensor is linearly proportional to the value of the measured property. The sensitivity is then defined as the ratio between output signal and measured property. For example, if a sensor measures temperature and has a voltage output, the sensitivity is a constant with the unit [V/K]; this sensor is linear because the ratio is constant at all points of measurement.
If the sensor is not ideal, several types of deviations can be observed:
The sensitivity may in practice differ from the value specified. This is called a sensitivity error, but the sensor is still linear.
Since the range of the output signal is always limited, the output signal will eventually reach a minimum or maximum when the measured property exceeds the limits. The full scale range defines the maximum and minimum values of the measured property.
If the output signal is not zero when the measured property is zero, the sensor has an offset or bias. This is defined as the output of the sensor at zero input.
If the sensitivity is not constant over the range of the sensor, this is called nonlinearity. Usually this is defined by the amount the output differs from ideal behavior over the full range of the sensor, often noted as a percentage of the full range.
If the deviation is caused by a rapid change of the measured property over time, there is a dynamic error. Often, this behaviour is described with a bode plot showing sensitivity error and phase shift as function of the frequency of a periodic input signal.
If the output signal slowly changes independent of the measured property, this is defined as drift.
Long term drift usually indicates a slow degradation of sensor properties over a long period of time.
Noise is a random deviation of the signal that varies in time.
Hysteresis is an error caused by when the measured property reverses direction, but there is some finite lag in time for the sensor to respond, creating a different offset error in one direction than in the other.
If the sensor has a digital output, the output is essentially an approximation of the measured property. The approximation error is also called digitization error.
If the signal is monitored digitally, limitation of the sampling frequency also can cause a dynamic error.
The sensor may to some extent be sensitive to properties other than the property being measured. For example, most sensors are influenced by the temperature of their environment.
All these deviations can be classified as systematic errors or random errors. Systematic errors can sometimes be compensated for by means of some kind of calibration strategy. Noise is a random error that can be reduced by signal processing, such as filtering, usually at the expense of the dynamic behaviour of the sensor.
The resolution of a sensor is the smallest change it can detect in the quantity that it is measuring. Often in a digital display, the least significant digit will fluctuate, indicating that changes of that magnitude are only just resolved. The resolution is related to the precision with which the measurement is made. For example, a scanning probe (a fine tip near a surface collects an electron tunnelling current) can resolve atoms and molecules.
[edit]Biological sensors

All living organisms contain biological sensors with functions similar to those of the mechanical devices described. Most of these are specialized cells that are sensitive to:
light, motion, temperature, magnetic fields, gravity, humidity, vibration, pressure, electrical fields, sound, and other physical aspects of the external environment;
physical aspects of the internal environment, such as stretch, motion of the organism, and position of appendages (proprioception);
an enormous array of environmental molecules, including toxins, nutrients, and pheromones;
many aspects of the internal metabolic milieu, such as glucose level, oxygen level, or osmolality;
an equally varied range of internal signal molecules, such as hormones, neurotransmitters, and cytokines;
and even the differences between proteins of the organism itself and of the environment or alien creatures.
Artificial sensors that mimic biological sensors by using a biological sensitive component, are called biosensors.
The human senses are examples of specialized neuronal sensors. See Sense.
[edit]Geodetic sensors

Geodetic measuring devices measure georeferenced displacements or movements in one, two or three dimensions. It includes the use of instruments such as total stations, levels and global navigation satellite system receivers.
[edit]See also

Car sensor: reversing sensor and rain sensor.
Data acquisition
Data acquisition system
Data logger
Detection theory
Fully Automatic Time
Hydrogen microsensor
Lateral line
List of sensors
Machine olfaction
Receiver operating characteristic
Sensor network
Sensor Web
[edit]External links

Look up Sensor in
Wiktionary, the free dictionary.
Capacitive Position/Displacement Sensor Theory/Tutorial
Capacitive Position/Displacement Overview
M. Kretschmar and S. Welsby (2005), Capacitive and Inductive Displacement Sensors, in Sensor Technology Handbook, J. Wilson editor, Newnes: Burlington, MA.
C. A. Grimes, E. C. Dickey, and M. V. Pishko (2006), Encyclopedia of Sensors (10-Volume Set), American Scientific Publishers. ISBN 1-58883-056-X
SensEdu; how sensors work
Clifford K. Ho, Alex Robinson, David R. Miller and Mary J. Davis. Overview of Sensors and Needs for Environmental Monitoring. Sensors 2005, 5, 4-37
Wireless hydrogen sensor
Sensor circuits
Categories: Measuring instruments | Sensors | Transducers
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Image sensor
From Wikipedia, the free encyclopedia

A CCD-sensor on a flexible circut board
An image sensor is a device that converts an optical image to an electric signal. It is used mostly in digital cameras and other imaging devices. It is a set of charge-coupled devices (CCD) or CMOS sensors such as active-pixel sensors.
There are several main types of color image sensors, differing by the means of the color separation mechanism:
Bayer sensor, low-cost and most common, using a Bayer filter that passes red, green, or blue light to selected sensels, or pixels, forming interlaced grids sensitive to red, green, and blue. The image is then interpolated using a demosaicing algorithm.
Foveon X3 sensor, using an array of layered sensors where every pixel contains three stacked sensors sensitive to the individual colors.
3CCD, using three discrete image sensors, with the color separation done by a dichroic prism. Considered the best quality, and generally more expensive than single-CCD sensors.
Contents [hide]
2 Performance
3 Specialty sensors
4 See also
5 References
[edit]CCD Vs CMOS

Today, most digital still cameras use either a CCD images sensor or a CMOS sensor. Both types of sensor accomplish the same task of capturing light and converting it into electrical signals.
A CCD is an analog device. When light strikes the chip it is held as a small electrical charge in each photo sensor. The charges are converted to voltage one pixel at a time as they are read from the chip. Additional circuitry in the camera converts the voltage into digital information.
A CMOS chip is a type of active pixel sensor made using the CMOS semiconductor process. Extra circuitry next to each photo sensor converts the light energy to a voltage. Additional circuitry on the chip converts the voltage to digital data.
Neither technology has a clear advantage in image quality. CMOS can potentially be implemented with fewer components, use less power and provide data faster than CCDs. CCD is a more mature technology and is in most respects the equal of CMOS.[1] [2]

There are many parameters that can be used to evaluate the performance of an image sensor, including its dynamic range, its signal-to-noise ratio, its low-light sensitivity, etc. For a detailed guide to digital sensor performance, see Roger Clark's article.
[edit]Specialty sensors

Special sensors are used for various applications. The most important are the sensors for thermal imaging, creation of multi-spectral images, gamma cameras, sensor arrays for x-rays, IR Rays Infrared Rays and other highly sensitive arrays for astronomy.
[edit]See also

Video camera tube
Semiconductor detector
Contact Image Sensor (CIS)
Charge-coupled device (CCD)
Active pixel sensor (MOS, CMOS)
Image sensor format: discusses the sizes and shapes of common image sensors
This photography-related article is a stub. You can help Wikipedia by expanding it.

^ [1] CCD Vs CMOS from Photonics Spectra 2001
^ [2] Sensors By Vincent Bockaert
Categories: Photography stubs | Digital photography | Image sensors
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This page was last modified on 27 March 2008, at 19:15. All text is available under the terms of the GNU Free Documentation License. (See Copyrights for details.)
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