bluuebunny/crossref_metadata_2025 huggingface dataset:
Prediction of UV spectra and UV-radiation damage in actual plasma etching processes using on-wafer monitoring technique
Authors: Jinnai Butsurin , Fukuda Seiichi , Ohtake Hiroto , Samukawa Seiji
Published: February 2010

UV radiation during plasma processing affects the surface of materials. Nevertheless, the interaction of UV photons with surface is not clearly understood because of the difficulty in monitoring photons during plasma processing. For this purpose, we have previously proposed an on-wafer monitoring technique for UV photons. For this study, using the combination of this on-wafer monitoring technique and a neural network, we established a relationship between the data obtained from the on-wafer monitoring technique and UV spectra. Also, we obtained absolute intensities of UV radiation by calibrating arbitrary units of UV intensity with a 126 nm excimer lamp. As a result, UV spectra and their absolute intensities could be predicted with the on-wafer monitoring. Furthermore, we developed a prediction system with the on-wafer monitoring technique to simulate UV-radiation damage in dielectric films during plasma etching. UV-induced damage in SiOC films was predicted in this study. Our prediction results of damage in SiOC films shows that UV spectra and their absolute intensities are the key cause of damage in SiOC films. In addition, UV-radiation damage in SiOC films strongly depends on the geometry of the etching structure. The on-wafer monitoring technique should be useful in understanding the interaction of UV radiation with surface and in optimizing plasma processing by controlling UV radiation.
Cryogenic temperatures as a path toward high-Q terahertz metamaterials
Authors: Singh Ranjan , Tian Zhen , Han Jiaguang , Rockstuhl Carsten , Gu Jianqiang , Zhang Weili
Published: February 2010

Optical properties of planar thin film metamaterials were measured at room and liquid nitrogen temperatures using terahertz time-domain spectroscopy. The operation of metamaterials at cryogenic temperatures is anticipated to be a promising path toward low-loss metamaterials since nonradiative losses are strongly suppressed due to higher charge mobility. A 14% increase in the quality factor of the resonances was experimentally observed. It was limited by the high electron scattering rate due to defects in thin films. Supplementary simulations assuming metamaterials made of thick films reveal a temperature controlled behavior and a 40% increase in the quality factor at 10 K.
Thermal nanostructure: An order parameter multiscale ensemble approach
Authors: Cheluvaraja S. , Ortoleva P.
Published: February 2010

Deductive all-atom multiscale techniques imply that many nanosystems can be understood in terms of the slow dynamics of order parameters that coevolve with the quasiequilibrium probability density for rapidly fluctuating atomic configurations. The result of this multiscale analysis is a set of stochastic equations for the order parameters whose dynamics is driven by thermal-average forces. We present an efficient algorithm for sampling atomistic configurations in viruses and other supramillion atom nanosystems. This algorithm allows for sampling of a wide range of configurations without creating an excess of high-energy, improbable ones. It is implemented and used to calculate thermal-average forces. These forces are then used to search the free-energy landscape of a nanosystem for deep minima. The methodology is applied to thermal structures of Cowpea chlorotic mottle virus capsid. The method has wide applicability to other nanosystems whose properties are described by the CHARMM or other interatomic force field. Our implementation, denoted SIMNANOWORLD™, achieves calibration-free nanosystem modeling. Essential atomic-scale detail is preserved via a quasiequilibrium probability density while overall character is provided via predicted values of order parameters. Applications from virology to the computer-aided design of nanocapsules for delivery of therapeutic agents and of vaccines for nonenveloped viruses are envisioned.
Combining ab initio quantum mechanics with a dipole-field model to describe acid dissociation reactions in water: First-principles free energy and entropy calculations
Authors: Maurer Patrick , Iftimie Radu
Published: February 2010

We introduce a novel approach to compute dissociation free energy and entropy values in simulations that employ a density functional theory description of the acidic moiety and of the solvent. The approach consists of utilizing an alchemical transformation of a weak acid A-COOH into the strong acid B-COOH, which makes it practical to employ alchemical free energy perturbation methods in the context of ab initio molecular dynamics simulations. The present alchemical transformation circumvents the need to tackle changes in the total number of electrons and atoms by replacing the chemical residue responsible for the change in acidity with an easily tunable external effective potential. Our investigation demonstrates that (1) a simple but effective class of external potentials that control acidity changes in the acetic/trifluoroacetic acid series can be achieved by replacing the methyl and trifluoromethyl substituents by screened dipoles. Using this dipole-field/quantum-mechanics (DF/QM) approach one can predict gas-phase geometries, proton dissociation energies, total dipole moments, and water binding energies in good agreement with full-QM values. (2) The resulting alchemical perturbation calculations are stable and well converged and allow one to compute absolute pKa values whose accuracy is limited primarily by the exchange-correlation functional employed: H–COOH=2.5±0.6 (full-QM calculation), 3.7 (exp); F3C–COOH=0.4±0.6 (DF/QM calculation), 0.5 (exp); H3C–COOH=3.1±0.7 (DF/QM calculation), 4.7 (exp); 3) Our DF/QM model predicts that the difference in acidity between H–COOH and H3C–COOH is dominated by solvent entropy effects, in excellent agreement with experimental observations. The calculated difference between the dissociation energies of these acids is ΔΔdU=0.0±0.26 kcal/mol while the experimental value is 0.0±0.1 kcal/mol.
Calculations of vibrationally resonant sum- and difference-frequency-generation spectra of chiral molecules in solutions: Three-wave-mixing vibrational optical activity
Authors: Choi Jun-Ho , Cheon Sangheon , Cho Minhaeng
Published: February 2010

Determining absolute configuration of chiral molecule can be achieved by using vibrational optical activity (VOA) measurement methods, such as vibrational circular dichroism and Raman optical activity (ROA). Recently, vibrationally resonant sum frequency generation and difference frequency generation utilizing circularly polarized beams were theoretically studied and shown that they can be alternative and complementary VOA measurement techniques [S. Cheon and M. Cho, Phys. Rev. A 71, 013808 (2005); J. Phys. Chem. A 113, 2438 (2009)]. Even for randomly oriented chiral molecules in solutions, the sum- and difference-frequency-generation signals induced by linearly polarized incident beams with mutually perpendicular polarization directions can be nonzero and are determined by the optical activity hyperpolarizability given by a product of antisymmetric Raman tensor and vibrational transition dipole. If one of the beams involved in the three-wave-mixing processes is circularly polarized and if the difference signal is measured, not only the same optical activity hyperpolarizability but also that including electric quadrupole-ROA tensor are required to determine the signals. Here, we carried out quantum chemistry calculations to obtain these quantities for a representative chiral molecule, (S)-methyl lactate, and numerically simulated the corresponding spectra. It is shown that the circular polarization three-wave-mixing signal intensities are quantitatively similar to those of the linear polarization three-wave-mixing signals, respectively, and that they are sensitive to the absolute configuration of chiral molecule. The calculation results thus suggest that these two novel techniques will be of use in studying molecular chirality even in time domain, once polarization-modulated ultrashort pulses are used to carry out circular polarization three-wave-mixing experiments.
Submegahertz frequency stabilization of a terahertz quantum cascade laser to a molecular absorption line
Authors: Richter H. , Pavlov S. G. , Semenov A. D. , Mahler L. , Tredicucci A. , Beere H. E. , Ritchie D. A. , Hübers H.-W.
Published: February 2010

The frequency of a terahertz quantum-cascade laser is stabilized to the absorption line of methanol gas at a frequency of 2.55 THz. The method is based on frequency modulation of the laser emission across the absorption line. The resulting derivativelike signal is used as an error signal for a control loop that keeps the laser frequency at maximum absorption. The unstabilized laser that is operated in a pulse tube cooler has frequency fluctuations of 15 MHz, which are reduced to 300 kHz with the control loop in action. The line shape of the locked signal is Gaussian.
Supermolecular switches based on multiwalled carbon nanotubes
Authors: Subramanian A. , Dong L. X. , Nelson B. J. , Ferreira A.
Published: February 2010

Electrostatically actuated nanoelectromechanical switches based on intershell displacement mechanisms within batch fabricated, bidirectional multiwalled carbon nanotube (MWNT) bearings are reported. Multiple devices with a 220 nm pitch are constructed within individual MWNT supermolecules. Experimental results on performance metrics including low switching voltages (0.8 to 6 V), repeatability, hysteresis, and failure modes are presented.
Exploring Ambiguity: Aboriginal Identity Negotiation in Southwestern Sydney
Authors: Yamanouchi Yuriko
Published: February 2010

There has been little discussion on urban Indigenous identity in post-settler societies. However, in the scarce works which exist on this issue there are some remarkably common traits. For most Indigenous people, identity has primarily involved kinship ties associated with their perceived place of origin. In the city, Indigenous people encounter other Indigenous people who cannot be identified through kinship ties; in this situation, organizations dealing with Indigenous issues provide ways of connecting nonrelated Indigenous people, in line with a notion of ‘pan-Indigeneity’. This pan-Indigeneity is not only based on their experience in the city, but also is influenced by the ‘antique’ image of Indigenous people created through contact with European settlers as well as the common cultural mores and traits which Indigenous people share. With these different kinds of identities, urban Indigenous identity has been described as ‘fluid’ or ‘ambiguous’. The relationship between these identities has not been much examined. This paper explores the ambiguous and dynamic nature of Aboriginal identity in southwestern Sydney. Even though they are not related, Aboriginal people can usually recognize each other as ‘Aboriginal’ through certain cultural mores and traits. However, there are some who, although claiming to be Aboriginal, who do not share these cultural mores and traits. Their presence gives rise to tension and conflict revolving around the concept of Aboriginality. Through an ethnographical examination of the process of accommodating nonrelated Aboriginal people, this paper reveals how different kinds of identities are related to each other in urban situations.
The Relative Efficiency of Automatic and Discretionary Regional Aid
Authors: Swales J Kim
Published: February 2010

Discretionary subsidies are the primary instruments for regional policy in Europe. Such aid is typically targeted at ‘additional’ projects: that is, projects that would not have been implemented without the subsidy, with the subsidy set at the minimum for the project to be implemented. This contrasts to automatic subsidies, where many of the aided projects are nonadditional and all eligible projects receive the same subsidy rate. The present paper builds on previous studies to compare three subsidy schemes: an automatic scheme and two types of discretionary scheme, one with accurate appraisal and the other with appraisal error. These schemes are assessed on their expected welfare impacts. The particular focus is the reduction in welfare gain imposed by the interaction of appraisal error and the requirements for accountability. This is potentially substantial and difficult to detect with conventional evaluation techniques.
Assessment of Regeneration Projects in Urban Areas of Environmental Interest: A Stated Choice Approach to Estimate Use and Quasi-Option Values
Authors: Strazzera Elisabetta , Cherchi Elisabetta , Ferrini Silvia
Published: February 2010

We adopt an attribute-based stated choice approach to evaluate public preferences over planning alternatives for an urban site of environmental interest. Since such projects involve some uncertainty and irreversibility, special attention is devoted to the estimation of quasi-option values associated with project development. Two distinct measures for the quasi-option value are estimated, and both coefficients indicate that the public place significant value on the reduction of the possibility of adverse irreversible effects: a more prudent development strategy is valued at about four times greater than a procedure that provides a greater chance of an undesired outcome. Furthermore, the study involves elicitation of intertemporal preferences over projects with different time spans, and estimation of the implicit discount rates: the values obtained seem high if compared with standard discount rates applied to public projects, but not far from interest rates on consumption found in the market.
Effects of Built Environments on Vehicle Miles Traveled: Evidence from 370 US Urbanized Areas
Authors: Cervero Robert , Murakami Jin
Published: February 2010

Concerns over rising fuel prices and greenhouse-gas emissions have prompted research into the influences of built environments on travel, notably vehicle miles traveled (VMT). On the basis of data from 370 US urbanized areas and using structural equation modeling, population densities are shown to be strongly and positively associated with VMT per capita (direct effect elasticity = ⊟0.604); however, this effect is moderated by the traffic-inducing effects of denser urban settings having denser road networks and better local-retail accessibility (indirect effect elasticity = 0.223, yielding a net effect elasticity = ⊟0.381). Accessibility to basic employment has comparatively modest effects, as do size of urbanized area, and rail-transit supplies and usage. Nevertheless, urban planning and city design should be part of any strategic effort to shrink the environmental footprint of the urban transportation sector.
Geographic Variations in the Early Diffusion of Corporate Voluntary Standards: Comparing ISO 14001 and the Global Compact
Authors: Perkins Richard , Neumayer Eric
Published: February 2010

Despite their availability to firms across the world, uptake of global voluntary standards has proceeded unevenly across countries over time. In this paper we seek to provide new insights into how geography shapes these spatiotemporal variations, focusing on two leading examples of codified voluntarism: ISO 14001 and the Global Compact (GC). In an advance on previous quantitative studies, which have analyzed domestic and nondomestic influences separately, we examine how the internal attributes of place ‘condition’ the influence of transnational spatial dependencies. We find that higher levels of ISO 14001 certification in other economies are more likely to spill over (via transnational linkages) into higher domestic uptake of the standard in wealthier economies, while domestic receptivity to the influence of higher GC adoptions abroad is greater in more democratic countries. Another important advance on previous studies is that we examine the influence of a larger number of measures of transnational economic linkage. Providing evidence of ‘trading-up’ and ‘investing-up’ dynamics, we show that higher densities of ISO 14001 certificates and GC participants in a country's export and inward foreign direct investment partners are associated with higher levels of domestic uptake of the respective standard. We also find tentative evidence of ‘visiting-up’ dynamics associated with the cross-border movement of businesspeople.
Exploring Causal Effects of Neighborhood Type on Walking Behavior Using Stratification on the Propensity Score
Authors: Cao Xinyu (Jason)
Published: February 2010

The causality issue has become one of the key questions in the debate over the relationship between the built environment and travel behavior. To ascertain whether changes to the built environment are a cost-effective way to change travel behavior, it is necessary to determine the magnitude of the effect. Further, it is important to understand whether the observed influence of the built environment on travel behavior diminishes substantially once we control for self-selection. Using 1553 residents living in four traditional and four suburban neighborhoods in Northern California, this study explores the causal effect of neighborhood type on walking behavior and the relationship between this effect and the observed influence of neighborhood type on walking behavior. Specifically, propensity score stratification, which has been widely used to reduce selection bias, was applied. The results showed that, on average, the causal influences of neighborhood type are likely to be overstated by 64% for utilitarian walking frequency and 16% for recreational walking frequency, if residential self-selection is not controlled for. However, neighborhood type still plays a more important role in affecting walking behavior than does self-selection. This study also offers a basic tutorial for the propensity score stratification approach and discusses its strengths and weaknesses for applications in the field of land use and travel behavior.
A Postsuburban World? An Outline of a Research Agenda
Authors: Phelps Nicholas A , Wood Andrew M , Valler David C
Published: February 2010

The emergence over the last 30–40 years of what is variously termed edge city, edgeless, and postsuburban development in North America and elsewhere raises a set of challenges for urban theory and existing ways of understanding the politics of urban growth and management. These challenges and their global import have been outlined in their broadest terms by members of a ‘Los Angeles School’. In this paper we try to develop the detail of some of these challenges in ways that might allow for comparative analysis. We begin by considering three analytical dimensions along which distinctively postsuburban settlements might be identified. These dimensions are not without their limitations but we regard them as a heuristic device around which to centre ongoing comparative research. We then go on to highlight three political contradictions attending postsuburban growth which appear to flow from some of these defining dimensions. To the extent that such postsuburban growth and politics are distinctive, they pose important challenges to established theories of urban politics. We briefly consider these challenges in the conclusion of the paper.
The Craft of Scalar Practices
Authors: Fraser Alistair
Published: February 2010

Despite recent controversies over the ontological status of scale, geographers have continued to interrogate so-called ‘scalar practices’. But not enough has been said about the skill involved in making these practices successful. Geographers have overlooked the potential for thinking through the craft of scalar practices. I therefore introduce ‘scalecraft’, a concept which builds upon existing work and is intended to draw attention to and elaborate upon the skills, aptitudes, and experiences at issue in working with scale. A relatively diverse set of secondary materials selected from recent academic literature is used first to demonstrate how scalar practices entail failures, learning, complex machinations, and innovations. I then use materials from my own research in South Africa into white farmers' practices which fashion an organic scale of action amidst a space–time of uncertainty and insecurity.
Visual Expertise with Pictures of Cars Correlates with RT Magnitude of the Car Inversion Effect
Authors: Rossion Bruno , Curran Tim
Published: February 2010

In their seminal study Diamond and Carey (1986, Journal of Experimental Psychology: General115 107–117) found a larger inversion effect for dog pictures in dog experts than novices, supporting a role of visual expertise in the observation of particularly large inversion effects for faces. However, subsequent studies have provided mixed results, and very few have compared the inversion effects for faces and familiar non-face object categories. Here we tested the effect of inversion on faces and cars in car experts and novices, using a delayed matching task across viewpoint changes. Inversion affected accuracy much more for pictures of faces than of cars for both groups, with no interaction between expertise and category. However, for car experts only there was a significant correlation between the magnitude of the inversion cost in RT for car pictures and the level of expertise as measured in an independent task. These observations support the view that the particularly large inversion effect found for faces is related to expert visual processes which can be at least partially recruited to process other non-face object categories.
Draughtsmen at Work
Authors: Parlangeli Oronzo , Roncato Sergio
Published: February 2010

To obtain the representation of a contour, the visual system integrates fragments of a pattern. One of the ‘binding rules’ governing this process requires that a path of conjunction in which contrast polarity is preserved be followed. Here we show that this rule has a corollary: where two alternative paths compete to emerge in opposite directions, the one with greater contrast luminance is likely to prevail.
Haptic Recognition of Two-Dimensional Raised-Line Patterns by Early-Blind, Late-Blind, and Blindfolded Sighted Adults
Authors: Picard Delphine , Lebaz Samuel , Jouffrais Christophe , Monnier Catherine
Published: February 2010

We investigated the role of visual experience and visual imagery in the processing of two-dimensional (2-D) tactile patterns. The performance of early-blind (EB), late-blind (LB), and blindfolded sighted (S) adults in the recognition of 2-D raised-line patterns was compared. We also examined whether recognition of 2-D tactile patterns depends on the type of memory strategy (eg spatial, visuo-spatial, verbal, and kinesthetic) used by EB, LB, and S participants to perform the task. Significant between-group differences in the recognition performance have not been found despite significant between-group differences in self-reported memory strategies. Recognition performance does not vary significantly with the strategy, but correlates positively with visuo-spatial imagery abilities in the S participants. These findings may be taken to suggest that the difficulties some blind people experience with tactile pictures are not due to difficulties in processing 2-D tactile patterns.
Influence of Make-up on Facial Recognition
Authors: Ueda Sayako , Koyama Takamasa
Published: February 2010

Make-up may enhance or disguise facial characteristics. The influence of wearing make-up on facial recognition could be of two kinds: (i) when women do not wear make-up and then are seen with make-up, and (ii) when women wear make-up and then are seen without make-up. A study is reported which shows that light make-up makes it easier to recognise a face, and heavy make-up makes it more difficult. Seeing initially a made-up face makes any subsequent facial recognition more difficult than initially seeing that face without make-up.
Effect of ash from forest fires on phosphorus availability, transport, chemical forms, and content in volcanic soils
Authors: Escudey Mauricio , de la Fuente Pamela , Antilén Mónica , Molina Mauricio
Published: February 2010

Environmental context. Intensive fertilisation and the availability of phosphorus species (less than 10%) in cultivable soils of volcanic origin are causing the accumulation of P in these soils. Phosphorus is a macronutrient that severely limits good agricultural development, so knowledge of the distribution and the different forms of P present in soils is fundamental for sustainable agricultural practice. This novel study reports the existence of increased available P in all the soils that received a load of plant ash from different tree species.
Abstract. The effect associated with the distribution of ash from plantations of native, pine, and eucalyptus forests over five soils of volcanic origin was studied by means of column leaching experiments. The results show a clear increase of pH (up to 4.4 units) and of the soil’s electric conductivity (up to 21 times), whereas total extractable P content increased 3 to 10 times with respect to the control. These effects follow a sequence depending on the origin of the ash (native forest, pine, eucalyptus), concentrated in the 0.0–10.0-cm section from the top of the columns. The observed alkalinity caused an increase of available P (from 21 to 72 times with respect to the control), in addition to decreasing residual P and increasing the extraction efficiency of the method used, discarding a transformation of inorganic P into organic P. Finally, the results show that the addition of ash is a valid and complementary alternative to phosphate fertilisation.
Roles of dissolved organic matter in the speciation of mercury and methylmercury in a contaminated ecosystem in Oak Ridge, Tennessee
Authors: Dong Wenming , Liang Liyuan , Brooks Scott , Southworth George , Gu Baohua
Published: February 2010

Environmental context. Mercury (Hg) presents an environmental concern owing to its transformation to the potent neurotoxin methylmercury (CH3Hg+). The environmental factors that control bacterial methylation of mercury are poorly understood, but we know that methylmercury is bioaccumulated and biomagnified in aquatic food webs. We show that, even at low concentrations (~3 mg L–1), natural dissolved organic matter strongly complexes with ionic Hg2+ and CH3Hg+, thereby influencing biological uptake and methylation of Hg in aquatic environments. Abstract. Complexation of the mercuric ion (Hg2+) and methylmercury (CH3Hg+) with organic and inorganic ligands influences mercury transformation and bioaccumulation in aquatic environments. Using aqueous geochemical modelling, we show that natural dissolved organic matter (DOM), even at low concentrations (~3 mg L–1), controls the Hg speciation by forming strong Hg-DOM and CH3Hg-DOM complexes through the reactive sulfur or thiol-like functional groups in DOM in the contaminated East Fork Poplar Creek at Oak Ridge, Tennessee. Concentrations of neutral Hg(OH)2, Hg(OH)Cl, CH3HgCl, and CH3HgOH species are negligible. Of the coexisting metal ions, only Zn2+, at concentrations of 1.6–2.6 × 10–7 M, competes with Hg2+ for binding with DOM, causing decrease in Hg-DOM complexation but having little impact on CH3Hg-DOM complexation. DOM may thus play a dominant role in controlling the transformation, biological uptake, and methylation of Hg in this contaminated ecosystem.
Phase II pharmaceutical metabolites acetaminophen glucuronide and acetaminophen sulfate in wastewater
Authors: Sunkara Manjula , Wells Martha J. M.
Published: February 2010

Environmental context. Excretion of pharmaceuticals and their metabolites by humans and animals, flushing unused pharmaceuticals and inadequate water treatment result in the occurrence of these chemicals as pollutants in wastewater, surface water and drinking water. In this research, the pharmaceutical agent acetaminophen (paracetamol, Tylenol) and its glucuronide and sulfate metabolites were examined as a model system for monitoring wastewater influent and effluent. The true risk to ecosystems and humans from the occurrence of pharmaceuticals in our water supply can only be estimated if accurate concentrations of parent pharmaceutical chemicals as well as their metabolites are measured. Abstract. An analytical method was developed to separately determine acetaminophen and its Phase II metabolites, acetaminophen glucuronide and acetaminophen sulfate, from wastewater in a single extract. The method developed will serve as a model for screening for the presence of other non-steroidal pharmaceutical compounds and their Phase II metabolites in wastewater. Acetaminophen glucuronide was not present in the wastewater influent tested to verify the analytical protocol, whereas concentrations of acetaminophen and acetaminophen sulfate in the influent were reproducible over time. A Phase I metabolite, p-aminophenol, was also determined to occur in the wastewater influent. Concentrations of the analytes-of-interest, detected in effluent samples collected after secondary treatment, but before UV treatment, were highly variable and were undetectable after UV treatment before release to surface water.
Interaction of CdSe/CdS core-shell quantum dots and Pseudomonas aeruginosa
Authors: Aruguete Deborah M. , Guest Jeremy S. , Yu William W. , Love Nancy G. , Hochella Michael F.
Published: February 2010

Environmental context. The growing use of nanotechnology means that nanomaterials are likely to be released into the environment, and their impact upon microbes, which form the biological foundation of all ecosystems, remains unclear. To understand how nanomaterials might affect bacteria in the environment, the interactions between a commercially-relevant quantum dot and a common soil and water bacterium was investigated. In this case, it was found that these quantum dots are non-toxic to these bacteria, and also that these bacteria do not cause degradation of the quantum dots. This study also has implications related to the environmental fate of quantum dots. Abstract. Polymer-encapsulated CdSe/CdS core-shell quantum dots, which closely model commercially-available quantum dots, were tested for toxic effects on Pseudomonas aeruginosa. The size, aggregation state, and dissolution of the quantum dots were characterised before and after exposure to bacteria. The physical association of quantum dots with bacterial cells was also examined. The quantum dots were found to have no effect upon bacterial viability. They remained chemically stable and dispersed in solution even with bacterial exposure. It is suggested that the absence of toxicity is the result of the stability of the quantum dots due to their protective polymer coatings, and their apparent lack of association with bacterial cells. The stability of the quantum dots, even in the presence of the bacteria, as well as their non-toxicity has implications for their environmental behaviour and ultimate fate.
Aggregation of titanium dioxide nanoparticles: role of calcium and phosphate
Authors: Domingos Rute F. , Peyrot Caroline , Wilkinson Kevin J.
Published: February 2010

Environmental context. The increasing use of nanomaterials in consumer products has led to increased concerns about their potential environmental and health impacts. TiO2 is a widely used nanoparticle found in sunscreens and electronic products. In order to understand and predict the mobility of TiO2 in the natural environment, it is essential to determine its state of aggregation under environmentally relevant conditions of pH, ionic strength, ion and natural organic matter content. Aggregation is likely to lead to both reduced mobility and bioavailability in soils and natural waters.
Abstract. The physicochemical characterisation of nanomaterials is crucial to predict their environmental and health impacts. Ion adsorption is known to influence the surface properties of nano-metal oxides in natural systems. The role of calcium and phosphate adsorption on aggregation was examined in the presence and absence of natural organic matter. Fluorescence correlation spectroscopy (FCS) was performed in order to determine the diffusion coefficients of TiO2 nanoparticles having a nominal size between 3 to 5 nm. Based upon FCS and electrophoretic mobility measurements, the presence of calcium resulted in a destabilisation and aggregation of the TiO2 nanoparticles, even in presence of Suwannee River fulvic acid (SRFA). Conditions which favoured phosphate adsorption also resulted in a destabilisation of the TiO2 sample but for low SRFA concentrations only.
Using FlFFF and aTEM to determine trace metal–nanoparticle associations in riverbed sediment
Authors: Plathe K. L. , von der Kammer F. , Hassellöv M. , Moore J. , Murayama M. , Hofmann T. , Hochella M. F.
Published: February 2010

Environmental context. Determining associations between trace metals and nanoparticles in contaminated systems is important in order to make decisions regarding remediation. This study analysed contaminated sediment from the Clark Fork River Superfund Site and discovered that in the <1-μm fraction the trace metals were almost exclusively associated with nanoparticulate Fe and Ti oxides. This information is relevant because nanoparticles are often more reactive and show altered properties compared with their bulk equivalents, therefore affecting metal toxicity and bioavailability.
Abstract. Analytical transmission electron microscopy (aTEM) and flow field flow fractionation (FlFFF) coupled to multi-angle laser light scattering (MALLS) and high-resolution inductively coupled plasma mass spectroscopy (HR-ICPMS) were utilised to elucidate relationships between trace metals and nanoparticles in contaminated sediment. Samples were obtained from the Clark Fork River (Montana, USA), where a large-scale dam removal project has released reservoir sediment contaminated with toxic trace metals (namely Pb, Zn, Cu and As) which had accumulated from a century of mining activities upstream. An aqueous extraction method was used to recover nanoparticles from the sediment for examination; FlFFF results indicate that the toxic metals are held in the nano-size fraction of the sediment and their peak shapes and size distributions correlate best with those for Fe and Ti. TEM data confirms this on a single nanoparticle scale; the toxic metals were found almost exclusively associated with nano-size oxide minerals, most commonly brookite, goethite and lepidocrocite.
Bacteria - nanoparticle interactions and their environmental implications
Authors: Aruguete Deborah M. , Hochella Michael F.
Published: February 2010

Environmental context. The advent of nanotechnology means that the release of nanomaterials into the environment is very likely, if not inevitable, and knowing the environmental impact of such nanomaterials is important. A key aspect of understanding this impact is to learn how nanomaterials affect microorganisms, a critical part of the environment; this topic is addressed in this review, which specifically concerns nanoparticle–bacteria interactions. Current studies show that nanoparticles have the potential to impact bacterial viability, although a great deal remains to be understood concerning nanoparticle–bacteria interactions. Abstract. Part of the responsible use of nanotechnology will be to better delineate the potential impact of nanomaterials released into the environment. A key aspect of understanding this impact is to examine the interaction between nanomaterials and microorganisms, which are not only highly abundant in nature but critical for global environmental processes. In this Highlight, current knowledge about the interaction between bacteria and industrially-relevant nanoparticles is reviewed. Important areas for further study are discussed.
Condensin complexes regulate mitotic progression and interphase chromatin structure in embryonic stem cells
Authors: Fazzio Thomas G. , Panning Barbara
Published: February 2010

In an RNA interference screen interrogating regulators of mouse embryonic stem (ES) cell chromatin structure, we previously identified 62 genes required for ES cell viability. Among these 62 genes were Smc2 and -4, which are core components of the two mammalian condensin complexes. In this study, we show that for Smc2 and -4, as well as an additional 49 of the 62 genes, knockdown (KD) in somatic cells had minimal effects on proliferation or viability. Upon KD, Smc2 and -4 exhibited two phenotypes that were unique to ES cells and unique among the ES cell–lethal targets: metaphase arrest and greatly enlarged interphase nuclei. Nuclear enlargement in condensin KD ES cells was caused by a defect in chromatin compaction rather than changes in DNA content. The altered compaction coincided with alterations in the abundance of several epigenetic modifications. These data reveal a unique role for condensin complexes in interphase chromatin compaction in ES cells.
Automated microscopy for high-content RNAi screening
Authors: Conrad Christian , Gerlich Daniel W.
Published: February 2010

Fluorescence microscopy is one of the most powerful tools to investigate complex cellular processes such as cell division, cell motility, or intracellular trafficking. The availability of RNA interference (RNAi) technology and automated microscopy has opened the possibility to perform cellular imaging in functional genomics and other large-scale applications. Although imaging often dramatically increases the content of a screening assay, it poses new challenges to achieve accurate quantitative annotation and therefore needs to be carefully adjusted to the specific needs of individual screening applications. In this review, we discuss principles of assay design, large-scale RNAi, microscope automation, and computational data analysis. We highlight strategies for imaging-based RNAi screening adapted to different library and assay designs.
A Time-Series Analysis of Clostridium difficile and Its Seasonal Association with Influenza
Authors: Polgreen Philip M. , Yang Ming , Bohnett Lucas C. , Cavanaugh Joseph E.
Published: February 2010

Objective.

To characterize the temporal progression of the monthly incidence of Clostridium difficile infections (CDIs) and to determine whether the incidence of CDI is related to the incidence of seasonal influenza.

Design.

A retrospective study of patients in the Nationwide Inpatient Sample during the period from 1998 through 2005.

Methods.

We identified all hospitalizations with a primary or secondary diagnosis of CDI with use of International Classification of Diseases, 9th Revision, Clinical Modification codes, and we did the same for influenza. The incidence of CDI was modeled as an autoregression about a linear trend. To investigate the association of CDI with influenza, we compared national and regional CDI and influenza series data and calculated cross-correlation functions with data that had been prewhitened (filtered to remove temporal patterns common to both series). To estimate the burden of seasonal CDI, we developed a proportional measure of seasonal CDI.

Results.

Time-series analysis of the monthly number of CDI cases reveals a distinct positive linear trend and a clear pattern of seasonal variation (R2 = 0.98). The cross-correlation functions indicate that influenza activity precedes CDI activity on both a national and regional basis. The average burden of seasonal (ie, winter) CDI is 23%.

Conclusions.

The epidemiologic characteristics of CDI follow a pattern that is seasonal and associated with influenza, which is likely due to antimicrobial use during influenza seasons. Approximately 23% of average monthly CDI during the peak 3 winter months could be eliminated if CDI remained at summer levels.
Use of Central Venous Catheter and Peripheral Venous Catheter as Risk Factors for Nosocomial Bloodstream Infection in Very-Low-Birth-Weight Infants
Authors: Geffers Christine , Gastmeier Anne , Schwab Frank , Groneberg Katrin , Rüden Henning , Gastmeier Petra
Published: February 2010

Objective.

To describe the relationship between the use of central and peripheral venous catheters and the risk of nosocomial, primary, laboratory-confirmed bloodstream infection (BSI) for neonates with a birth weight less than 1,500 g (very-low-birth-weight [VLBW] infants).

Methods.

Cox proportional hazard regression analysis with time-dependent variable was used to determine the risk factors for the occurrence of BSI in a cohort of VLBW infants. We analyzed previously collected surveillance data from the German national nosocomial surveillance system for VLBW infants. All VLBW infants in 22 participating neonatal departments who had a complete daily record of patient information were included.

Results.

Of 2,126 VLBW infants, 261 (12.3%) developed a BSI. The incidence density for BSI was 3.3 per 1,000 patient-days. The multivariate analysis identified the following significant independent risk factors for BSI: lower birth weight (hazard ratio [HR], 1.1–2.2), vaginal delivery (HR, 1.5), central venous catheter use (HR, 6.2) or peripheral venous catheter use (HR, 6.0) within 2 days before developing BSI, and the individual departments (HR, 0.0–4.6).

Conclusions.

After adjusting for other risk factors, use of peripheral venous catheter and use of central venous catheter were significantly related to occurrence of BSI in VLBW infants.
Natural History of Colonization with Gram-Negative Multidrug-Resistant Organisms among Hospitalized Patients
Authors: Weintrob Amy C. , Roediger Mollie P. , Barber Melissa , Summers Amy , Fieberg Ann M. , Dunn James , Seldon Venus , Leach Fluryanne , Huang Xiao-Zhe , Nikolich Mikeljon P. , Wortmann Glenn W.
Published: February 2010

Objective.

To determine the anatomic sites and natural history of colonization with gram-negative multidrug-resistant organisms (MDROs).

Design.

Prospective, longitudinal cohort study.

Setting.

Walter Reed Army Medical Center, a 236-bed tertiary care center in Washington, DC.

Patients.

Deployed subjects (ie, inpatients medically evacuated from Iraq or Afghanistan) or nondeployed subjects admitted to the same hospital.

Methods.

Consenting patients had 6 anatomic sites cultured every 3 days for 2 weeks and then weekly. Gram-negative organisms resistant to 3 or more classes of antibiotics were considered MDROs. Isolates were genotyped using pulsed-field gel electrophoresis. Clinical data, data on antibiotic use, and clinical culture results were collected.

Results.

Of 60 deployed subjects, 14 (23%) were colonized with an MDRO at admission, and 13 (22%) had incident colonization during hospitalization. The groin was the most sensitive anatomic site for detecting MDRO colonization, and all but one subject remained colonized for the duration of their hospitalization. Sixty percent of subjects with incident Acinetobacter colonization and 25% of subjects with incident Klebsiella colonization had strains that were related to those isolated from other subjects. Of 60 nondeployed subjects, 5 (8%) were colonized with an MDRO at admission; all had recent healthcare contact, and 1 nondeployed subject had an isolate related to a strain recovered from a deployed subject.

Conclusions.

Colonization with gram-negative MDROs is common among patients with war-related trauma admitted to a military hospital and also occurs among nondeployed patients with recent healthcare contact. The groin is the most sensitive anatomic site for active surveillance, and spontaneous decolonization is rare.
Signaling and ligand interaction of ILT7: receptor‐mediated regulatory mechanisms for plasmacytoid dendritic cells
Authors: Cao Wei , Bover Laura
Published: February 2010

Summary:  Plasmacytoid dendritic cells (pDCs) are specialized dendritic cells (DCs) that produce large amounts of type I interferon (IFN) after Toll‐like receptor (TLR) activation. Human pDCs preferentially express immunoglobulin‐like transcript 7 (ILT7; LILRA4), which couples with a signaling adapter to activate a prominent immunoreceptor tyrosine‐based activation motif (ITAM)‐mediated signaling pathway. ILT7 protein directly binds to and can be activated by bone marrow stromal cell antigen 2 (BST2; CD317) protein, the expression of which is found on cells pre‐exposed to IFN or on the surface of human cancer cells. The interaction between ILT7 and BST2 functions to assure an appropriate TLR response by pDCs during viral infection and likely participates in pDC‐tumor crosstalk. Two opposing modes of receptor‐mediated regulatory mechanisms work jointly to fine tune the innate immunity of pDCs.
Regulation of intestinal homeostasis by dendritic cells
Authors: Tezuka Hiroyuki , Ohteki Toshiaki
Published: February 2010

Summary:  The healthy gut consists of the commensal flora, the epithelial layer, and the gut‐associated lymphoid tissues (GALT). The GALT need to be hyporesponsive to commensal and dietary antigens while possessing the capacity to detect and attack pathogens. Accumulating evidence suggests that dendritic cells (DCs) play integral roles in managing this paradoxical situation and maintaining the complex homeostasis in the gut, which includes the induction of immunoglobulin A (IgA) synthesis. This review outlines the roles of the commensal flora, epithelial layer, and GALT in mucosal homeostasis and inflammatory conditions and highlights recent progress in our understanding of how DCs are involved in IgA synthesis in the gut.
Differentiation and function of mouse monocyte‐derived dendritic cells in steady state and inflammation
Authors: Domínguez Pilar M. , Ardavín Carlos
Published: February 2010

Summary:  Although monocytes were originally described as precursors to all the different subpopulations of macrophages found in the steady state and formed under inflammatory and infectious conditions, recent data have demonstrated conclusively that monocytes can also differentiate into dendritic cells (DCs). Monocytes are the precursors to different subsets of DCs, such as Langerhans cells and DCs found in the lamina propria of the gastrointestinal, respiratory, and urogenital tracts. In addition, monocyte‐derived DCs (moDCs), newly formed during inflammatory reactions, appear to fulfill an essential role in defense mechanisms against pathogens by participating in the induction of both adaptive and innate immune responses. In this regard, moDCs have the capacity to activate antigen‐specific CD4+ T‐cell responses and to cross‐prime CD8+ T cells, during viral, bacterial, and parasitic infections. In addition, monocytes have been recently described as the precursors to a subset of DCs specialized in innate immunity against pathogens, named TipDCs [for TNF‐α (tumor necrosis factor‐α)‐iNOS (inducible nitric oxide synthase)‐producing DCs] that display a remarkable microbicidal activity and also provide iNOS‐dependent help for antibody production by B cells. Importantly, in contrast to DCs developing in the steady state, moDCs formed during inflammatory and infectious processes are subjected to diverse soluble mediators that determine the multiple functional specificities displayed by moDCs, as a result of the remarkable developmental plasticity of monocytes. In this review, we discuss recent findings dealing with the differentiation and functional relevance of moDCs that have widened the frontiers of DC immunobiology in relation to innate and adaptive immunity and the etiology of chronic inflammatory diseases.
Microbe–dendritic cell dialog controls regulatory T‐cell fate
Authors: Grainger John R. , Hall Jason A. , Bouladoux Nicolas , Oldenhove Guillaume , Belkaid Yasmine
Published: February 2010

Each microenvironment is controlled by a specific set of regulatory elements that have to be finely and constantly tuned to maintain local homeostasis. These environments could be site specific, such as the gut environment, or induced by chronic exposure to microbes. Various populations of dendritic cells are central to the orchestration of this control. In this review, we discuss some new findings associating dendritic cells from defined compartments with the induction and control of regulatory T cells in the context of exposure to both commensal and pathogenic microbes.