bluuebunny/crossref_metadata_2025 huggingface dataset:
Cherenkov radiation by an electron bunch moving in Hermitian medium
Authors: Liu Shenggang , Zhang Yaxin , Yan Yang , Hu Min , Zhong Renbin
Published: August 2007

Detailed theoretical investigation and computer calculations on Cherenkov radiation (CR) by an electron bunch moving uniformly in Hermitian medium (CRH) with and without absorption are presented in the paper. The theory shows that in the CRH, not only the current density but also the charge density of the particle contribute to the Cherenkov radiation. It has been found that there are two modes in the CRH; in general, only one of them is radiative mode and another one is local field. The frequency area where both of these two modes are radiative modes simultaneously is studied. The comparison of the two modes is given in the paper and the relation of the existence of these two modes is improved. The comparison of the calculations shows that the radiation power of mode “o” is larger than that of mode “e.” It indicates that the group velocity in the CRH is slower than the phase velocity. Detailed computer calculations are given in the paper, and some interesting physical phenomena of CR are revealed. The theory gives a simple physical interpretation of the inner fine structure of the CRH; it is concluded that the mechanism of the appearance of the inner fine structure of CR is that in a dispersive medium the group velocity is less than the phase velocity. Possible applications of this theory are also discussed.
C
O
2
laser rapid-thermal-annealing SiOx based metal-oxide-semiconductor light emitting diode
Authors: Lin Gong-Ru , Lin Chun-Jung
Published: August 2007

Structural damage enhanced near-infrared electroluminescence (EL) of a metal-oxide-semiconductor light emitting diode (MOSLED) made on SiOx film with buried nanocrystallite Si after CO2 laser rapid thermal annealing (RTA) at an optimized intensity of 6kW∕cm2 for 1ms is demonstrated. CO2 laser RTA induced oxygen-related defects are capable of improving Fowler-Nordheim tunneling mechanism of carriers at metal/SiOx interface. The CO2 laser RTA SiOx film reduces Fowler-Nordheim tunneling threshold to 1.8MV∕cm, facilitating an enhanced EL power of an indium tin oxide/SiOx∕p-Si∕Al MOSLED up to 50nW at a current density of 2.3mA∕cm2.
Use of ZnO thin films as sacrificial templates for metal organic vapor phase epitaxy and chemical lift-off of GaN
Authors: Rogers D. J. , Hosseini Teherani F. , Ougazzaden A. , Gautier S. , Divay L. , Lusson A. , Durand O. , Wyczisk F. , Garry G. , Monteiro T. , Correira M. R. , Peres M. , Neves A. , McGrouther D. , Chapman J. N. , Razeghi M.
Published: August 2007

Continued development of GaN-based light emitting diodes is being hampered by constraints imposed by current non-native substrates. ZnO is a promising alternative substrate but it decomposes under the conditions used in conventional GaN metal organic vapor phase epitaxy (MOVPE). In this work, GaN was grown on ZnO∕c-Al2O3 using low temperature/pressure MOVPE with N2 as a carrier and dimethylhydrazine as a N source. Characterization confirmed the epitaxial growth of GaN. The GaN was lifted-off the c-Al2O3 by chemically etching away the ZnO underlayer. This approach opens up the way for bonding of the GaN onto a support of choice.
Organic thin film transistors with ink-jet printed metal nanoparticle electrodes of a reduced channel length by laser ablation
Authors: Kim Dongjo , Jeong Sunho , Moon Jooho , Han Sewoon , Chung Jaewon
Published: August 2007

The authors have demonstrated organic thin film transistors (OTFTs) based on the ink-jet printed electrodes in which a reduced channel length is accomplished by laser ablation. Laser ablation on the dried silver nanoparticle electrode formed by ink-jet printing effectively shortened the channel length down to 5μm, which is difficult to achieve by ink-jet printing alone. Reducing the channel length using this hybrid technique also allows them to observe the contact resistance effect in the OTFTs, which involves the printed silver nanoparticle electrode of a lower work function with respect to the ionization energy of the organic semiconductor.

At the request of the authors and editor, this article is being retracted effective 8 February 2008.
Dipole-induced magnetic anisotropy in γ-Fe2O3(001) epitaxial films
Authors: Yanagihara H. , Hagiwara J. , Nakazumi M. , Kita Eiji , Furubayashi T.
Published: August 2007

The authors investigated the magnetic anisotropy of epitaxial films of γ-Fe2O3(001) composed entirely of Fe3+. The cubic anisotropy term (K1) was negligibly small (K1≈−2.7×104erg∕cm3), as expected for L≈0 systems; however, substantially large uniaxial anisotropy energy (Ku≈6.1×105erg∕cm3) was found as the thickness reached the bulk limit. A detailed characterization of both the in-plane and out-of-plane lattice parameters revealed that the c∕a ratio of the unit cell was intrinsically elongated due to its vacancy-ordered supercell. This unexpectedly large Ku is reasonably explained by simple dipole sums if the authors take into account the slightly stretched unit cell (c′∕a=1.03) in the growth direction even without the spin-orbit interaction.
Thick Pb(Zr,Ti)O3 film without substrate
Authors: Lee Jae-Wung , Park Chee-Sung , Jo Ji-Hoon , Kim Hyoun-Ee
Published: August 2007

In order to fabricate thick PbZrxTi1−xO3 (PZT) films for microelectromechanical system applications, the authors introduce a concept of freestanding film without a substrate. PZT films with a thickness of up to 20μm were deposited on a very thin Pt layer without a substrate by the rf-magnetron sputtering method using a single oxide target. The Pt layer (thickness <1μm) was obtained by sputtering the Pt on a Si substrate with a carbon layer between them, and subsequently removing the carbon layer by oxidation in air at 400°C. Piezoelectric properties of the film were comparable to those of bulk PZT as a result of the removal of clamping effect of the substrate.
Comment on “Pointwise analysis of scalar fields: A nonstandard approach” [J. Math. Phys. 47, 092301 (2006)]
Authors: Yamashita Hideyasu
Published: August 2007

We add a bibliography of the literature on the nonstandard treatments of Schwartz distributions to the “Pointwise analysis of scalar fields: A nonstandard approach.”
Probing fatigue in ferroelectric thin films with subnanometer depth resolution
Authors: Cao Jiang-Li , Solbach Axel , Klemradt Uwe , Weirich Thomas , Mayer Joachim , Schorn Peter J. , Böttger Ulrich
Published: August 2007

The authors report the study of polarization fatigue in Pb(Zr,Ti)O3 (PZT) ferroelectric thin films using in situ high-resolution grazing incidence x-ray specular reflectivity of synchrotron radiation. The results demonstrate that there is no formation of a region of different electron densities in the film growth direction with subnanometer depth resolution during fatigue. The upper bounds on the theoretically predicted interfacial accumulation of oxygen vacancies at the interfaces between PZT and Pt electrodes are determined by the comparison of experimental results and theoretical simulations.
Origin of the efficiency improvement in all-polymer solar cells upon annealing
Authors: Mandoc M. M. , Veurman W. , Sweelssen J. , Koetse M. M. , Blom P. W. M.
Published: August 2007

The origin of the enhanced efficiency upon annealing in solar cells based on blends of poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylene vinylene] and poly{9,9-dioctylfluorene-2,7-diyl-alt-1,4-bis[2-(5-thienyl)-1-cyanovinyl]-2-methoxy-5-(3,7-dimethyl-octyloxy)benzene} is investigated. Current-voltage measurements on solar cells and single-carrier diodes reveal that the electron and hole transport is not improved for thermally treated devices. From the analysis of the photocurrent, the authors show that the dissociation efficiency of the bound electron-hole pairs increases upon annealing, due to an increase of the initial electron-hole separation distance.
Spatial investigation of the electron energy distribution function of the high-energy electron beam sustained in the low-pressure microwave surface-wave plasma
Authors: Širý Milan , Husárik Jan , Kando Masashi
Published: August 2007

The electron energy distribution functions are studied in low-pressure microwave surface-wave sustained plasma using retarding field analyzer. Sustained discharge can be considered as superposition of the bulk plasma and the high-energy electron beamlike part. The beam component energy is pronounced up to 40eV. Beam population reaches the maximum at energy of 16eV with amount of 4% of the bulk plasma population.
Highly efficient organic tandem solar cells using an improved connecting architecture
Authors: Janssen A. G. F. , Riedl T. , Hamwi S. , Johannes H.-H. , Kowalsky W.
Published: August 2007

Tandem solar cells based on the combination of a poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl-C61-butyric acid methyl ester and a copper phthalocyanine:fullerene subcell are reported. By using a highly transparent, high-work function WO3 layer as part of the interconnecting system for the two subcells, the authors demonstrate stacked devices with power conversion efficiencies as high as 4.6%. The efficiency of the stacked devices is close to the sum of the efficiencies of the individual subcells.
Investigation of the transient symmetric H state in a pi cell
Authors: Yang Bo-Ru , Elston Steve J. , Raynes Peter , Shieh Han-Ping D.
Published: August 2007

The so-called symmetric H (Hs) state has been reported to have submillisecond response times, which results from the symmetric profile of the liquid crystal director; however, no direct evidence has been obtained to show the profile symmetry. The difficulty in proving this symmetric structure by direct observation results from the short lifetime of Hs state (typically around a few tens of milliseconds). In the work reported here, the authors utilize a burst driving method along with stroboscopic illumination from blue and red light emitting diodes to capture conoscopic images for the Hs director profile; these showed good agreement with their modeling.
Effect of aspect ratio of multiwall carbon nanotubes on resistance-pressure sensitivity of rubber nanocomposites
Authors: Jiang Mei-Juan , Dang Zhi-Min , Xu Hai-Ping , Yao Sheng-Hong , Bai Jinbo
Published: August 2007

To explore the effect of aspect ratio (AR) of nanotubes on conductivity and resistance-pressure sensitivity, four kinds of multiwall carbon nanotubes (MWNT) with different aspect ratios (AR=50, 75, 333, and 500) were dispersed into methylvinyl silicone rubber (VMQ) to fabricate the MWNT/VMQ nanocomposites. Results show that the composites with low concentration nanotubes at low AR value show great resistance-pressure sensitivity. High AR is not beneficial for the improvement of conductivity, and at the same concentration of MWNT, the composites with high AR tubes display large resistance-pressure sensitivity. The sensitivity is dependent on the quantity of conductive channels formed in the composites.
Reducing Inequalities in Health and Diet: Findings from a Study on the Impact of a Food Retail Development
Authors: Cummins Steven , Findlay Anne , Higgins Cassie , Petticrew Mark , Sparks Leigh , Thomson Hilary
Published: August 2007

The health and diet impacts of a large-scale food retail development within a deprived area of Glasgow (Springburn) are reported. The study used a prospective quasi-experimental design which compared changes in diet and psychological health in an area where a new hypermarket was built (the intervention area) with a similarly deprived comparison area in Glasgow (Shettleston). A postal survey was undertaken both before and one year after the hypermarket was built, to assess changes in diet, self-reported health, and perceptions of neighbourhood. Changes in the retail structure of both areas were assessed through a ‘before-and-(repeated)-after’ intervention shop count survey. Qualitative data on diet, the neighbourhood, and the impact of the store were collected through focus groups. The quantitative study found limited improvements in diet and health. There was weak evidence for the impact of the hypermarket on population diet. There was weak evidence that poor psychological health in the intervention area reduced. Amongst those who ‘switched’ to the new hypermarket there was weak evidence of a small improvement in mean fruit and vegetable consumption but good evidence of psychological health improvement. Qualitative and retail survey results reinforce this, identifying perceptions of areal improvement through redevelopment and a small positive impact of the new store on the retail structure of the intervention area.
Energy Consumption and Work-Travel Trips: London, Birmingham, and Manchester, 1981–2001
Authors: Frost Martin , Spence Nigel
Published: August 2007

The changing modal composition and volume of work travel in London, Birmingham, and Manchester and their resultant energy consumption implications are considered in this research. Essentially, the mechanism is to calculate the passenger km travelled by mode and then to apply mode-specific energy consumption parameters to calculate energy consumption. By classifying work-travel trips according to their travel mode and their location and orientation (within, out of, and into town) it is possible to determine where the major forces for commuting change are and, more important, assess the implications of these forces for energy consumption. Average energy intensities per person trip are not the same everywhere or for every energy-consuming mode; furthermore, the magnitude and direction of change in average energy intensities are not the same either. Many of the trends seem to be moving rapidly away from positions of energy sustainability. The data are derived from the 1981 and 2001 special workplace statistics of the Population Census for small areas, and from fuel consumption technical parameters calibrated by engineers. One important objective of the paper is to understand the relative importance for energy consumption of changing travel modes for work journeys and changing trip orientation caused by urbanisation trends.
Neoliberalising Nature: The Logics of Deregulation and Reregulation
Authors: Castree Noel
Published: August 2007

This and a companion paper examine a new and fast-growing geographical research literature about neoliberal approaches to governing human interactions with the physical environment. This literature, authored by critical geographers for the most part, is largely case study based and focuses on a range of biophysical phenomena in different parts of the contemporary world. In an attempt to take stock of what has been learnt and what is left to do, the two papers survey the literature theoretically and empirically, cognitively and normatively. They are written for the benefit of readers trying to make some sense of this growing literature and for future researchers of the topic. Specifically, they aim to parse the critical studies of nature's neoliberalisation with a view to answering four key questions posed, variously, in many or most of them: what are the main reasons why all manner of qualitatively different nonhuman phenomena in different parts of the world are being ‘neoliberalised’? what are the principal ways in which nature is neoliberalised in practice? what are the effects of nature's neoliberalisation? and how should these effects be evaluated? Without such an effort of synthesis, this literature could remain a collection of substantively disparate, theoretically informed case studies unified only in name (by virtue of their common focus on ‘neoliberal’ policies). Though all four questions posed are answerable in principle, in practice the existing research literature makes questions two, three, and four difficult to address substantively and coherently between case studies. While the first question can, from one well-established theoretical perspective, be answered with reference to four ‘logics’ at work in diverse contexts (the focus of this paper), the issues of process, effects, and evaluations are currently less tractable (and are the focus of the next paper). Together, the two pieces conclude that critical geographers interrogating nature's neoliberalisation will, in future, need to define their objects of analysis more rigorously and/or explicitly, as well as their evaluative Schemas. If the new research into neoliberalism and the nonhuman world is to realise its full potential in the years to come, then some fundamental cognitive and normative issues must be addressed. These issues are not exclusive to the literature surveyed and speak to the ‘wider’ lessons that can be drawn from any body of case study research that focuses on an ostensibly ‘general’ phenomena like neoliberalism.
Structural Salience of Elements of the City
Authors: Claramunt Christophe , Winter Stephan
Published: August 2007

People experience and memorize space primarily with the help of landmarks. These landmarks have structural salience, besides visual and semantic salience. When people move in urban space they perceive first the street network as structuring this space. Therefore, streets are a good candidate for investigating structural salience. This paper investigates different structural representations of the urban fabric, and measures to describe the structural salience especially of elements of the street network and dependent elements. The measures are taken from topology and network analysis. The goal is to identify a generic model of structural salience for urban elements that favors the automatic identification of references for route directions. The proposed model is illustrated by a case study applied to a small city in northern France.
Land-Use Policy and Planning, Theorizing, and Modeling: Lost in Translation, Found in Complexity?
Authors: Briassoulis Helen
Published: August 2007

This paper ventures an examination of the linkages among three worlds—those of land-use theorizing and modeling, and that of policy making and planning—which, despite historical and recent advances, remain comparatively poor and haunted by defective communication and problematic translation between them. It is motivated by shifts that have taken place since the late 1980s in all three worlds, away from ‘classical’ thinking (positivism, reductionism, and linear and static worldviews) and towards complex systems (CS) thinking (alternative epistemologies, holism, and nonlinear and dynamic worldviews). The principal question is whether or not CS thinking, compared to classical thinking, addresses more satisfactorily key policy and planning issues, thus holding the potential to improve communication and bridge the gaps between the three worlds. The issues examined are the representation of the sociospatial system, the land-use change process, and policy and planning intervention. After delimiting each world and the diffusion of CS thinking, the paper investigates how the classical approach and the CS approach fare in handling these issues. The analysis suggests that it is not yet possible to determine which approach is superior. The main points are summarized and CS specific and more general future research directions are indicated.
Tackling the NEET Generation and the Ability of Policy to Generate a ‘NEET’ Solution—Evidence from the UK
Authors: Pemberton Simon
Published: August 2007

Both within the UK and in a wider international context, there is an increasing concern with young people who are not in education, employment, or training (NEET). The author details research undertaken within Greater Merseyside (UK), which has relatively high levels of young NEET and where a ‘culture of worklessness’ has developed within the poorest areas. A focus is placed on the degree to which intergenerational factors influence NEET status, as opposed to peer influence, (low) educational attainment/disaffection, poor labour-market experience, or a lack of (place-specific) employment/education or training opportunities. Through reference to Hodkinson's pragmatic rational decision-making model, it is suggested that the success of policy interventions has been limited because of the diversity of influences on an individual's NEET status. However, a greater emphasis on addressing intergenerational issues through a focus on activities such as positive parenting, raising aspirations, and addressing family breakdown would make a greater impact, in conjunction with addressing disaffection through the provision of alternative forms of education, removing barriers to employment, and subsidising involvement in further/higher education.
A Very Modern Ghost: Postcolonialism and the Politics of Enchantment
Authors: McEwan Cheryl
Published: August 2007

Ghosts, spectres, and spirits and the stories told about them have long been a source of intellectual inquiry; they appear to be everywhere in scholarly discourse yet are largely absent from many recent debates about enchantment and modernity. This paper speculates on what happens to cultural politics when enchanted modernities are seen to encompass ghosts and ghost stories, and considers the political possibilities of specifically modern enchantments that have the power to enchant and disenchant simultaneously. The paper first examines the ways in which understandings of both enchantment and modernity have changed over time and, in particular, the impact of postcolonial theory on reconceptualising the relationship between the two. It then uses a ghost story encountered in fieldwork in South Africa to illustrate how the figures of ghosts and spirits can cast light on the lived experiences of postcolonial modernities. The paper contends that while ghost stories do not necessarily fit with more optimistic politics of enchantment, in the South African context they can represent active political engagement and produce positive political effect, rather than simply disenchanting those modernities that produce them. The paper concludes that an alternative approach is required to navigate between an overly cynical politics that works to disenchant the world and more optimistic accounts that focus on the ethical possibilities of enchantment. This necessitates a close reading of how modernities are enchanted in particular places and to what political effect.
Iron-binding ligands and their role in the ocean biogeochemistry of iron
Authors: Hunter Keith A. , Boyd Philip W.
Published: August 2007

Environmental context. It is now well accepted that iron is an essential micronutrient for phytoplankton growth in many areas of the global ocean, even though this element is present in seawater in extremely low abundance. It is also known that most of the iron in seawater is present as complexes formed with ligands of natural organic matter whose nature and origin remain largely unknown. Here we consider how these iron-complexing ligands might have evolved during geological time, what factors may have given rise to their presence and the possible roles that they play in iron biogeochemistry.

Abstract. Current knowledge about the role of iron-binding organic ligands in the ocean and their role in determining the biogeochemistry of this biologically active element has been summarised. Some electrochemical measurements suggest the presence of at least two ligand types, a strong binding ligand L1 found mainly in the mixed layer and a weaker ligand L2 found mainly in deep water. Speciation of FeIII is dominated by L1 in the mixed layer and L2 in the deep ocean. There is some evidence that L1 is siderophore-like and is specifically generated by marine microbes (i.e. heterotropic bacteria and cyanobacteria). We suggest that this is a specific biological mechanism for sequestering iron in the mixed layer that developed early in the ocean’s history (Archaean period, 2500–3500 million years BP), whereas the more ubiquitous L2 ligand only arose at the close of the Proterozoic (500–2500 million years BP) when eukaryotic organisms evolved to switch on the ocean’s biological pump, allowing L2 ligands to form from the oxidation of sinking biological particles. This development coincided with the complete oxygenation of the ocean’s interior which removed the iron-binding sulfide ion and allowed maintenance of the ocean’s iron inventory. These speculations are accompanied by various suggestions about avenues for future research to better understand iron biogeochemistry.
Comparing bulk extraction methods for chemically available polycyclic aromatic hydrocarbons with bioaccumulation in worms
Authors: Barthe Mickael , Pelletier Émilien
Published: August 2007

Environmental context. Determining the bioavailability of organic contaminants in sediments is a critical step in assessing the ecological risks of contamination in aquatic ecosystems. Standardised sediment bioaccumulation tests using benthic organisms are often performed to determine the relative bioavailability of sediment contamination. Unfortunately biological methods are time consuming, expensive and organisms are often difficult to maintain in good health in a laboratory exposure system. Contradictory results have been reported in the last decade and factors that affect the behaviour of extractants need to be examined for a large range of sediments. A study was conducted to determine the bioavailability of polycyclic aromatic hydrocarbons (PAHs) in sediment using worms and to compare the uptake by the biological samplers with mild solid/liquid extractions when exposed to unspiked low and highly contaminated marine and freshwater sediments. Abstract. The purpose of this study is to evaluate different techniques for assessing the availability of polycyclic aromatic hydrocarbons (PAHs) in contaminated sediments. This goal was achieved by comparing results from 28-day uptake experiments by Nereis virens and Lumbriculus variegatus with PAHs extracted by three non-exhaustive extraction methods using: n-Butanol (BuOH, 100%), an aqueous solution of hydroxypropyl-β-cyclodextrin (HPCD) and a surfactant solution of Brij700 (B700). Our results highlight the importance of considering both the PAH level in sediments and the molecular size of PAHs when attempting to predict their bioaccumulation in a biological sampler like worms using a solid/liquid extraction method. The surfactant B700 solution was quite successful to predict PAH bioaccumulation when exposed to unspiked highly contaminated sediments (25–5700 μg g–1). When low contaminated sediments (0.06–11 μg g–1) were used, HPCD and BuOH were better extractants for estimating bioaccumulation whereas B700 appeared to be too mild an extractant for most samples. Our results illustrate the interest and difficulties in finding an adequate chemical predictor for PAH bioavailabilty, particularly because PAH concentrations and sequestration processes play a determining role in the quality of results. Because B700 is not expansive and extraction solutions are easy to prepare, an extraction procedure involving this surfactant is proposed as a reliable predictor for aged highly contaminated sediments.
Omnipresence of biological material in the atmosphere
Authors: Jaenicke Ruprecht , Matthias-Maser Sabine , Gruber Sabine
Published: August 2007

Environmental context. Atmospheric biological particles have been largely overlooked in the past. While some microorganisms have been studied, the majority of other biological particles have not. The presence of these particles might force us to view the atmospheric aerosol differently.
Abstract. Measurements of biological particles in the atmosphere during the last decade indicate that the presence of these particles seems to have been underestimated by atmospheric scientists. On the average these primary aerosol particles might be present as much as 25% of the total mass (or number for particles with radius greater than 0.2 µm) concentration of the atmospheric aerosol. Such a large fraction certainly plays a major role in all processes affected by atmospheric aerosols, such as cloud and precipitation formation, climate forcing, visibility, turbidity, and so on. This disregard of the biological particles requires a new attitude in our opinion.
Past atmospheric composition and chemistry from ice cores - progress and prospects
Authors: Wolff Eric W. , Hutterli Manuel A. , Jones Anna E.
Published: August 2007

Environmental context. Investigating the past is often the only way we have of determining whether we have included all processes correctly into models, and then of verifying their behaviour. Ice cores provide an excellent way of finding out about the past. Air bubbles trapped in the ice allow us to directly access the concentration of stable trace gases, including important greenhouse gases. However, there are also tantalising possibilities to learn about aerosols and shorter-lived gases. This article describes some of the information we have already learnt from ice cores, but also describes the challenges that require understanding of atmospheric chemistry in the polar regions today in order to extract the full value of the records of the past trapped in the ice sheet.
Abstract. Ice cores provide the most direct evidence available about the past atmosphere. For long-lived trace gases, ice cores have provided clear evidence that in the last two centuries, concentrations of several greenhouse gases have risen well outside the natural range observed in the previous 650000 years. Major natural changes are also observed between cold and warm periods. Aerosol components have to be interpreted in terms of changing sources, transport and deposition. When this is done, they can also supply evidence about crucial aspects of the past environment, including sea ice extent, trace element deposition to the ocean, and about the aerosols available for cloud nucleation, for example. It is much more difficult to extract information about shorter-lived chemical species. Information may be available in components such as nitrate and formaldehyde, but to extract that information, detailed modern atmospheric studies about air to snow transfer, preservation in the ice, and the link between the polar region boundary layer and other parts of the atmosphere are urgently required.
A nonmineralized approach to abrasion-resistant biomaterials
Authors: Pontin Michael G. , Moses Dana N. , Waite J. Herbert , Zok Frank W.
Published: August 2007

The tooth-like mouthparts of some animals consist of biomacromolecular scaffolds with few mineral components, making them intriguing paradigms of biostructural materials. In this study, the abrasion resistance of the jaws of one such animal, the bloodworm
Glycera dibranchiata
, has been evaluated by nanoindentation, nanoscratching, and wear testing. The hardest, stiffest, and most abrasion-resistant materials are found within a thin (<3 μm) surface layer near the jaw tip and a thicker (10–20 μm) subsurface layer, both rich in unmineralized Cu. These results are consistent with the supposition that Cu ions are involved in the formation of intermolecular coordination complexes between proteins, creating a highly cross-linked molecular network. The intervening layer contains aligned atacamite [Cu
2
(OH)
3
Cl] fibers and exhibits hardness and stiffness (transverse to the alignment direction) that are only slightly higher than those of the bulk material but lower than those of the two Cu-rich layers. Furthermore, the atacamite-containing layer is the least abrasion-resistant, by a factor of ≈3, even relative to the bulk material. These observations are broadly consistent with the behavior of engineering polymer composites with hard fiber or particulate reinforcements. The alignment of fibers parallel to the jaw surface, and the fiber proximity to the surface, are both suggestive of a natural adaptation to enhance bending stiffness and strength rather than to endow the surface regions with enhanced abrasion resistance.
Norepinephrine loss produces more profound motor deficits than MPTP treatment in mice
Authors: Rommelfanger K. S. , Edwards G. L. , Freeman K. G. , Liles L. C. , Miller G. W. , Weinshenker D.
Published: August 2007

Although Parkinson's disease (PD) is characterized primarily by loss of nigrostriatal dopaminergic neurons, there is a concomitant loss of norepinephrine (NE) neurons in the locus coeruleus. Dopaminergic lesions induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) are commonly used to model PD, and although MPTP effectively mimics the dopaminergic neuropathology of PD in mice, it fails to produce PD-like motor deficits. We hypothesized that MPTP is unable to recapitulate the motor abnormalities of PD either because the behavioral paradigms used to measure coordinated behavior in mice are not sensitive enough or because MPTP in the absence of NE loss is insufficient to impair motor control. We tested both possibilities by developing a battery of coordinated movement tests and examining motor deficits in dopamine β-hydroxylase knockout (Dbh−/−) mice that lack NE altogether. We detected no motor abnormalities in MPTP-treated control mice, despite an 80% loss of striatal dopamine (DA) terminals.Dbh−/− mice, on the other hand, were impaired in most tests and also displayed spontaneous dyskinesias, despite their normal striatal DA content. A subset of these impairments was recapitulated in control mice with 80% NE lesions and reversed inDbh−/− mice, either by restoration of NE or treatment with a DA agonist. MPTP did not exacerbate baseline motor deficits inDbh−/− mice. Finally, striatal levels of phospho-ERK-1/2 and ΔFosB/FosB, proteins which are associated with PD and dyskinesias, were elevated inDbh−/− mice. These results suggest that loss of locus coeruleus neurons contributes to motor dysfunction in PD.
Binomial parameters differ across neocortical layers and with different classes of connections in adult rat and cat neocortex
Authors: Brémaud Antoine , West David C. , Thomson Alex M.
Published: August 2007

Binomial model-based analysis compared excitatory connections involving different classes of neurons in different neocortical layers. Single-sweep excitatory postsynaptic potentials (EPSPs) from dual intracellular recordings in adult cat and rat slices were measured. For data subsets corresponding to first EPSPs exhibiting different degrees of posttetanic potentiation and second, third etc. EPSPs in trains at different interspike intervals, coefficient of variation (
CV
), transmission failure rates (
F
), variance (
V
), and
V/M
were plotted against mean EPSP amplitude (
M
). Curves derived from binomial models in which subsets varied only in
p
(release probability) were fit and parameters
q
(quantal amplitude), and
n
(number of release sites) were estimated. Estimates for
q
and
n
were similar for control subsets and subsets recorded during Ca
2+
channel blockade, only
p
varied. Estimates from the four methods were powerfully correlated, but when
CV
,
F
,
V
, and
V/M
were plotted against
M
, different types of connections occupied different regions of parameter space. Comparisons of linear fits to
V/M
against
M
plots and of parameter estimates indicated that these differences were significant. Connections between pyramids in different layers and inputs to different cell classes in the same layer differed markedly. Monte Carlo simulations of more complex models subjected to simple binomial model-based analysis confirmed the significance of these differences. Binomial models, either simple, in which
p
and
q
are identical at all terminals involved, or more complex, in which they differ, adequately describe many neocortical connections, but each class uses different combinations of
n
, mean
p
,
and mean q
.
Theoretical Study of Decomposition Mechanism of Azoisobutyronitrile
Authors: Lin Xue-fei , Sun Cheng-ke , Yang Si-ya , Li Zong-he
Published: August 2007

The decomposition mechanisms of azoisobutyronitrile were systematically investigated. Density function theory B3LYP/6-311G*, B3LYP/6-311+G* and BHandH/6-31+G** methods were employed to optimize the geometry parameters of the reactants, transition states, possible intermediates and products based on the detailed potential energy surfaces scanned with AM1. The reaction mechanisms were also analyzed theoretically. The results indicate that the decomposition of azoisobutyronitrile is a two-bond (three body) synchronous cleavage process in the ground state (CH3)2CNC-N=N-CCN(CH3)2 2(CH3)2CNC+N2; and is a two-bond asynchronous cleavage process while in the triple state (CH3)2CNCN=N-CCN(CH3)2 (CH3)2CNCN=N CCN(CH3)2 2(CH3)2CNC+N2. The calculations rationalize and verify all experimental facts.
Characterization of V5+/TiO2-Rutile Using Molecular Dynamics Simulations
Authors: Zhang Li-pen , Pan Hai-bo , Huang Jin-ling
Published: August 2007

Molecular dynamics (MD) simulations with a quantum correction were used to study the 0.5 mol% V5+/TiO2 rutile under conditions of 300 K and 101 kPa. The interatomic potential function in MD simulations is composed of Coulomb, short-range repulsion, van der Waals, and Morse interactions. The topology of rutile was found to undergo a large deformation when Ti4+ is replaced by V5+, which can be related to the difference of valence and ionic radius between V5+ and Ti4+. The graphed distributions of Ti-O and O-O bond lengths, and O-Ti-O angles are all broaden. The simulations showed that when Ti4+ is replaced by V5+, the V5+ moves out of the O6 polyhedron and toward the interstice between TiO6 octahedra, which results in serious distortion of the octahedra near the interstice, but the phase with 0.5 mol% V5+ doping still remains in rutile. The structural features, such as the bond lengths, migration of the dopant, and crystal phase in the MD simulation are consistent with the experimental observations by FTIR, Raman, XRD and ESR.
Theoretical Study on Mechanism of C5H7 +O2 Reaction
Authors: Tan Wei , He Tian-jing , Liu Fan-chen , Chen Dong-ming
Published: August 2007

The potential energy surface (PES) for the reaction of E,E-pentadienyl with molecular oxygen was theoretically studied at the G3B3//B3LYP/6-311G(d,p) level of theory. The first step of the reaction was found to be the direct adduction of molecular O2 on either the C1 or the C3 atoms of E,E-pentadienyl, forming two C5H7O2 isomers. These two C5H7O2 isomers undergo a series of isomerization processes through either the hydrogen-transfer or cyclization pathway. In the final step, the hydrogen-transferred and cyclized isomers decompose into unsaturated aldehydes, unsaturated ketones, and hydroxyl radicals. Involves 20 stable species and 14 transition states, and the energies and structures of all reactants, products and transition states were calculated. Based on the calculated barriers and heats of formation, the authors suggest that the C2H3O+C3H4O formation channel is the dominant channel for the C5H7 +O2 reaction. The possible existence of C5H7O2 radicals as long lifetime intermediates is also proposed, which is consistent with the recent photoionization mass spectrometric experiments by Zils et al.
Calculations for Spin-allowed Transitions Between Energy Levels Above the 3s3p State in Si III
Authors: Fan Jing , Zhang Tian-yi , Zheng Neng-wu , Ma Dong-xia , Wang Tao
Published: August 2007

Spin-allowed transition probabilities between energy levels above the 3s3p state of Si III are reported by employing a coupled equation within WBEPM theory. The results show a good agreement with critical values, with the derivations mostly less than 15%. The method can readily be applied to highly excited states without any extra effort.
Gas Sensing Properties of Co3O4-loaded SnO2 to Ethanol and Acetone
Authors: Zhang Ming-ming , Jiang Guo-shun
Published: August 2007

A series of Co3O4-loaded SnO2 nanocomposite thick films were prepared by grinding, screen-printing and sintering at 700 C for 3 h. XRD data showed the nanocomposite thick films were rutile structure of SnO2 and cubic Co3O4. The composite films were found to exhibit good response to alcohol and acetone at 300 C. The film went through a sharp sensitivity maximum at 5 mol%CoO4/3 with a change in Co3O4 content. At 300 C, the maximum sensor response to alcohol and acetone, each 1000 ppm in air, was 301 and 235, respectively, which was about 7 and 5 times as large as that of the pure SnO2 respectively. The selectivity to alcohol and acetone over H2 and CO also was promoted by the addition of Co3O4 to SnO2. The mechanism of such strong promotion of sensor response (electronic sensitization) is discussed.
Synthesis and Electrorheological Properties of LTNO-PS Composites
Authors: Hou Jia-xiang , Shi Lei , Zhou Shi-ming , Zhu Qing-ren
Published: August 2007

Core-shell structural Li and Ti co-doped NiO/polystyrene samples (LTNO/PS) were synthesized by a sol-gel method and studied by TEM, X-ray diffraction, IR spectroscopy and LCR meter. It was found that the core-shell LTNO/PS particles are nearly smooth spheres with an average size of around 4.0 m, while the LTNO particles alone have a size of around 3.5 m. The electrorheological activity of LTNO particles with PS coating is larger than that of the bare ones with the same components. This research reveals that the high dielectric constant and corresponding dielectric loss of the LTNO is related to the Li and Ti contents. The increase of electrorheological activity of LTNO particles with PS coating is caused by the increase of dielectric permittivity, the surface structural change, and the reduction of leakage current of PS-coated samples due to the high resistivity and soft contacting of PS shell. By the preparation of core/shell structural materials and taking the advantage of the shell to reduce the leakage current between the particles, the electrorheological effect can be effectively increased.
Enhanced adhesion and compliance of film-terminated fibrillar surfaces
Authors: Noderer W.L , Shen L , Vajpayee S , Glassmaker N.J , Jagota A , Hui C.-Y
Published: August 2007

We present studies of a bio-inspired film-terminated fibrillar surface that has significantly enhanced adhesion and contact compliance compared with a flat control. We show that adhesion hysteresis arises from the architecture of the interfacial region. Measured in cyclic indentation experiments, it can be nearly five times the absolute work of adhesion for a flat control. Using a two-dimensional model, we propose that hysteresis develops as a result of crack trapping by fibril edges. The crack propagation mode is consistent with this model, as is the observation that with increasing hysteresis crack opening adhesion energy increases whereas crack closing adhesion energy decreases compared with a flat control. Contact compliance of the fibrillar structure is up to seven times more than that of a flat control. We present a model for the contact compliance of such structures which is in good agreement with measurements.
The Maxwell field on the Schwarzschild space–time: behaviour near spatial infinity
Authors: Valiente Kroon Juan Antonio
Published: August 2007

The behaviour of the Maxwell field near one of the spatial infinities of the Schwarzschild solution is analysed by means of the transport equations implied by the Maxwell equations on the cylinder at spatial infinity. Initial data for the Maxwell equations will be assumed to be expandable in terms of powers of a coordinate
ρ
measuring the geodesic distance to spatial infinity (in the conformal picture) and such that the highest possible spherical harmonics at order
p
are 2

p

-polar ones. It is shown that if the 2

p

-polar harmonics at order
p
in the initial data satisfy a certain regularity condition, then the solutions to the transport equations at orders
p
and
p
+1 are completely regular at the critical sets where null infinity touches spatial infinity. On the other hand, the solutions to the transport equations of order
p
+2 contain, in general, logarithmic singularities at the critical sets.
Role of modern chemistry in sustainable arable crop protection
Authors: Smith Keith , Evans David A , El-Hiti Gamal A
Published: August 2007

Organic chemistry has been, and for the foreseeable future will remain, vitally important for crop protection. Control of fungal pathogens, insect pests and weeds is crucial to enhanced food provision. As world population continues to grow, it is timely to assess the current situation, anticipate future challenges and consider how new chemistry may help meet those challenges. In future, agriculture will increasingly be expected to provide not only food and feed, but also crops for conversion into renewable fuels and chemical feedstocks. This will further increase the demand for higher crop yields per unit area, requiring chemicals used in crop production to be even more sophisticated. In order to contribute to programmes of integrated crop management, there is a requirement for chemicals to display high specificity, demonstrate benign environmental and toxicological profiles, and be biodegradable. It will also be necessary to improve production of those chemicals, because waste generated by the production process mitigates the overall benefit. Three aspects are considered in this review: advances in the discovery process for new molecules for sustainable crop protection, including tests for environmental and toxicological properties as well as biological activity; advances in synthetic chemistry that may offer efficient and environmentally benign manufacturing processes for modern crop protection chemicals; and issues related to energy use and production through agriculture.
Is Severity of Chest Pain a Cue for Women and Men to Recognize Acute Myocardial Infarction Symptoms as Cardiac in Origin?
Authors: Fukuoka Yoshimi , Dracup Kathleen , Moser Debra K. , McKinley Sharon , Ball Carol , Yamasaki Keiko , Kim Cho‐Ja
Published: August 2007

Recognizing symptoms as cardiac in origin is associated with the prompt seeking of medical care in patients with acute myocardial infarction (AMI). Therefore, the authors compared the symptom attribution of men and women experiencing AMI and examined factors associated with cardiac attribution by sex. In a cross‐sectional study, a total of 1059 AMI patients were consecutively recruited across 5 countries. A structured interview was performed during hospitalization. Approximately 40% of both men and women interpreted their symptoms as cardiac in origin. In men, a history of coronary heart disease (CHD) and chest pain severity were significantly associated with symptom interpretation as cardiac in origin (odds ratio [OR], 4.0; 95% confidence interval [CI], 2.9–5.6; OR, 2.0; 95% CI, 1.4–2.7,respectively). In women, a history of CHD was also significantly associated with symptom interpretation as cardiac in origin (OR, 4.95; 95% CI, 2.39–10.25),but not severity of chest pain. As opposed to men, severe chest pain may not be a cue for women to interpret their symptom as cardiac in origin. Education and counseling must take sex differences into account to be effective.