3,024 research outputs found
A risk forecasting process for nanostructured materials, and nanomanufacturing
International audienceNanomaterials exhibit novel properties that enable new applications ranging from molecular electronics to energy production. Proactive consideration of the potential impacts on human health and the environment resulting from nanomaterial production and use requires methods for forecasting risk associated with of these novel materials. However, the potential variety of nanomaterials is virtually infinite and a case-by-case analysis of the risks these materials may pose is not possible. The challenge of forecasting risk for a broad number of materials is further complicated by large degrees of uncertainty concerning production amounts, the characteristics and uses of these materials, exposure pathways, and a scarcity of data concerning the relationship between nanomaterial characteristics and their effects on organisms and ecosystems. A traditional risk assessment on nanomaterials is therefore not possible at this time. In its place, an evolving process is needed for analyzing the risks associated with emerging nanomaterials-related industries. In this communication, we propose that such a process should include the following six key features: 1) the ability to generate forecasts and associated levels of uncertainty for questions of immediate concern, 2) a consideration of all pertinent sources of nanomaterials, 3) an inclusive consideration of the impacts of activities stemming from nanomaterial use and production that extends beyond the boundaries of toxicology and include full life cycle impacts, 4) the ability to adapt and update risk forecasts as new information becomes available, 5) feedback to improve information gathering and, 6) feedback to improve nanomaterial design. Feature #6 implies that the potential risks of nanomaterials must ultimately be determined as a function of fundamental, quantifiable properties of nanomaterials, so that when these properties are observed in a new material, they can be recognized as indicators of risk. Thus, the required risk assessment process for nanomaterials addresses needs that span urgent, short-term questions dealing with nanomaterials currently in commerce, to longer-term issues that will require basic research and advances in theory. In the following sections we outline issues surrounding each of these six features ad discuss
Titan cell production in Cryptococcus neoformans reshapes the cell wall and capsule composition during infection
This work was supported by the National Institutes of Health (R01AI080275 and R21AI22352), the NIH Fogarty International Center (R25TW009345), the University of Minnesota Center for Translational Science Institute (UL1TR000114), Wellcome Trust (086827, 075470, 097377, 101873 & 200208) and MRC Centre for Medical Mycology (N006364/1). The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.Peer reviewedPublisher PD
Evaluation of Ultrafiltration for Spacecraft Water Reuse
Ultrafiltration is examined for use as the first stage of a primary treatment process for spacecraft wastewater. It is hypothesized that ultrafiltration can effectively serve as pretreatment for a reverse osmosis system, removing the majority of organic material in a spacecraft wastewater. However, it is believed that the interaction between the membrane material and the surfactant found in the wastewater will have a significant impact on the fouling of the ultrafiltration membrane. In this study, five different ultrafiltration membrane materials are examined for the filtration of wastewater typical of that expected to be produced onboard the International Space Station. Membranes are used in an unstirred batch cell. Flux, organic carbon rejection, and recovery from fouling are measured. The results of this evaluation will be used to select the most promising membranes for further study
Shot noise and conductivity at high bias in bilayer graphene: Signatures of electron-optical phonon coupling
We have studied electronic conductivity and shot noise of bilayer graphene
(BLG) sheets at high bias voltages and low bath temperature K. As a
function of bias, we find initially an increase of the differential
conductivity, which we attribute to self-heating. At higher bias, the
conductivity saturates and even decreases due to backscattering from optical
phonons. The electron-phonon interactions are also responsible for the decay of
the Fano factor at bias voltages V. The high bias electronic
temperature has been calculated from shot noise measurements, and it goes up to
K at V. Using the theoretical temperature dependence of BLG
conductivity, we extract an effective electron-optical phonon scattering time
. In a 230 nm long BLG sample of mobility
cmVs, we find that decreases with increasing
voltage and is close to the charged impurity scattering time fs
at V.Comment: 7 pages, 7 figures. Extended version of the high bias part of version
1. The low bias part is discussed in arXiv:1102.065
Optimum design for BB84 quantum key distribution in tree-type passive optical networks
We show that there is a tradeoff between the useful key distribution bit rate
and the total length of deployed fiber in tree-type passive optical networks
for BB84 quantum key distribution applications. A two stage splitting
architecture where one splitting is carried in the central office and a second
in the outside plant and figure of merit to account for the tradeoff are
proposed. We find that there is an optimum solution for the splitting ratios of
both stages in the case of Photon Number Splitting (PNS) attacks and Decoy
State transmission. We then analyze the effects of the different relevant
physical parameters of the PON on the optimum solution.Comment: Published in the Journal of the Optical Society of America
Influence of anodizing process on fatigue life of a machined aluminium alloy
In order to investigate the coupled effects of machining and anodizing processes on fatigue life of alloy 7010-T7451, a series of rotating bending fatigue tests were conducted at 60Hz. In the as machined condition, test results showed that fatigue life is surface roughness dependent and that fatigue life decreases with an increase in surface roughness and this effect is found to be more pronounced in high cycle fatigue where major portion of fatigue life is consumed in nucleating the cracks. Effects of pretreatments, like degreasing and pickling employed prior to anodizing, on fatigue life of the given alloy were also studied. Results demonstrated that degreasing showed no change in fatigue life while pickling had negative impact on fatigue life of specimens. The small decrease in fatigue life of anodized specimens as compare to pickled specimens is attributed to brittle and microcracking of the coating. Scanning electron microscopic (SEM) examination revealed multi-site crack initiation for the pickled and anodized specimens. SEM examination showed that pickling solution attacked the grain boundaries and intermetallic inclusions present on the surface resulting in pits formation. These pits are of primary concern with respect to accelerated fatigue crack nucleation and subsequent anodized coating formation
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