bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation and interpretation of residual rickets deformities in adults
Authors: Brickley M. , Mays S. , Ives R.
Published: November 2008

Recent research has considerably improved the recognition and recording of rickets and osteomalacia in archaeological human bone, but the recognition and recording of residual deformities of rickets present in adults is still limited. The aim of this study was to assist with differential diagnosis of residual rickets deformities and determine which of the deformities that are characteristic of rickets could be identified in the adult skeleton. Long bone deformities were investigated, with research focusing on deformities of the leg bones. One hundred and thirty‐five adults from the historic cemetery of St Martin's, Birmingham, where vitamin D deficiency was known to have been widespread, were analysed. Deformities of leg bones were three times as frequent as arm bone deformities, and deformity of both the femur and tibia was the most frequently recorded combination of leg bones. Medial bending of the tibiae and anterior bending of femora, both at the proximal end, were the most frequently recorded types of deformities. A review of a range of conditions that can cause bowing deformities, and comparison of bowing recorded in children with rickets and the present cases, concluded that the most likely cause of the deformities recorded was residual changes linked to rickets. In this community, bowing deformities linked to rickets were quite common amongst adults and probably did not have adverse social consequences, but further studies are required to determine whether this attitude to deformity was more widespread. Copyright © 2008 John Wiley & Sons, Ltd.
Risk assessment for Down syndrome with genetic sonogram in women at risk
Authors: Vergani Patrizia , Ghidini Alessandro , Weiner Steven , Locatelli Anna , Pozzi Elisa , Biffi Anna
Published: November 2008

Objective

To evaluate the algorithms of risk assessment for Down syndrome (DS).

Methods

Cohort study conducted in women at risk undergoing midtrimester genetic sonogram. Univariate and logistic regression analysis were used to relate findings to the occurrence of DS. The resulting model was validated in an independent population of patients.

Results

In a multivariable model adjusted for gestational age and maternal age, nuchal fold thickness (NFT) ≥ 5 mm (OR = 4.6, 95% CI 0.9‐23.9), presence of renal pelvic dilation (OR = 18.0, 95% CI 2.9‐110.5), absent mid‐phalanx of the 5th finger (OR = 29.9, 95% CI 6.1‐145.8), presence of noncardiac malformations (OR = 20.1, 95% CI 2.6‐154.7) or isolated heart defects (OR = 60.2, 95% CI 9.5‐382.8), the interactions of gestational age with NFT ≥ 5 mm (P = 0.04) and malformations with heart defects (P = 0.03) were significantly associated with DS. Utilizing this model and a risk cutoff point of 1/270, the sensitivity was 83.3% (5/6) with a false positive rate (FPR) of 28.5% (159/558).

Conclusion

Genetic sonogram has adequate accuracy to be incorporated into management algorithms for risk assessment of DS in women at risk. Copyright © 2008 John Wiley & Sons, Ltd.
Relative strength of the intramolecular hydrogen bonding in 1‐phenylazo‐naphthalen‐2‐ol and 1‐phenyliminomethyl‐naphtahlen‐2‐ol
Authors: Nedeltcheva Daniela , Antonov Liudmil
Published: November 2008

The relative strength of the intramolecular hydrogen bonding (IHB) in the title compounds has been investigated by means of ab initio quantum chemical calculations, UV–Vis spectral study and linear solvation energy relationship analysis (LSER) of the obtained tautomeric constants. It has been found that in acetone (and in all used solvents with substantial proton acceptor abilities) the tautomeric constant in the azonaphthol compound is lower than could be expected. The fact is explained with the breakage of the IHB and the coexistence of closed and open enol tautomers. Copyright © 2008 John Wiley & Sons, Ltd.
Understanding the stereo‐ and regioselectivities of the polar Diels–Alder reactions between 2‐acetyl‐1,4‐benzoquinone and methyl substituted 1,3‐butadienes: a DFT study
Authors: Soto‐Delgado Jorge , Domingo Luis R. , Araya‐Maturana Ramiro , Contreras Renato
Published: November 2008

The polar Diels–Alder (DA) reactions of 2‐acetyl‐1,4‐benzoquinone (acBQ) with methyl substituted 1,3‐butadienes have been studied using DFT methods at the B3LYP/6‐31G(d) level of theory. These reactions are characterized by a nucleophilic attack of the unsubstituted ends of the 1,3‐dienes to the β conjugated position of the acBQ followed by ring‐closure. The reactions present a total regioselectivity and large endo selectivity. The analysis based on the global electrophilicity of the reagents at the ground state, and the natural bond orbital (NBO) population analysis at the transition states correctly explain the polar nature of these cycloadditions. The large electrophilic character of acBQ is responsible for the acceleration observed in these polar DA reactions. Copyright © 2008 John Wiley & Sons, Ltd.
Responses of tropical deep convective precipitation systems and their associated convective and stratiform regions to the large‐scale forcing
Authors: Gao Shouting , Li Xiaofan
Published: November 2008

Responses of convective and stratiform rainfall to large‐scale forcing in the tropical deep convective regime are investigated by analysing data from a two‐dimensional cloud‐resolving model simulation. The model is forced by large‐scale vertical velocity, zonal wind, horizontal advection, and sea‐surface temperature observed and derived from TOGA COARE. The imposed large‐scale vertical velocity shows that the ascending motion averaged from 22–27 December 1992 is significantly stronger than that averaged from 3–8 January 1993. Thus, the periods of 22–27 December 1992 and 3–8 January 1993 are, respectively, identified as strong‐forcing (SF) and weak‐forcing (WF) phases. Although the convective rain rates are similar in the two phases, stratiform rain rate is larger in the SF phase than in the WF phase, which leads to larger time and spatial mean surface rain rate in the SF phase. Similar rates of water vapour convergence and vapour condensation and collection of cloud water by rain over water‐hydrometeor‐dominated convective regions are responsible for similar convective rain rates in the two phases. Water vapour divergence is larger in the WF phase than in the SF phase, which causes smaller vapour condensation and deposition rates in the WF phase. As a result, the collection rate of cloud water by rain and the melting rate of graupel to rain are smaller in the WF phase than in the SF phase, which accounts for the smaller stratiform rain rate in the WF phase. Copyright © 2008 Royal Meteorological Society
PC2: A prognostic cloud fraction and condensation scheme. II: Climate model simulations
Authors: Wilson Damian R. , Bushell Andrew. C. , Kerr‐Munslow Amanda M. , Price Jeremy D. , Morcrette Cyril J. , Bodas‐Salcedo Alejandro
Published: November 2008

A prognostic cloud fraction and prognostic condensate scheme (PC2) has been developed for the Met Office Unified Model. A companion paper discussed the motivation for a new scheme and described its formulation in detail. In this paper we describe the results of climate model simulations, concentrating on the mechanisms by which the cloud and condensate predicted by the model change between the Control and new scheme. We demonstrate that the detrainment of condensate from the convection scheme directly into the large scale, as parametrized in the PC2 scheme, produces improved simulations of deep tropical cloud. We also show that the unphysical strong link between cloud fraction and condensed water content that is present in the Control scheme has been broken by using PC2, but that it is still challenging to produce optically thin cloud in a large‐scale model. Shallow convection proves to be a difficult cloud type to parametrize using a prognostic scheme, although the PC2 scheme performs well. The use of increased vertical resolution, in both the Control and PC2, improved the simulation of cloud when compared to observations. © Crown Copyright 2008. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd.
Optimal foldover plans for mixed‐level fractional factorial designs
Authors: Guo Yong , Simpson James R. , Pignatiello Joseph J.
Published: November 2008

Reversing plus and minus signs of one or more factors is the traditional method to fold over two‐level fractional factorial designs. However, when factors in the original design have more than two levels, the method of ‘reversing signs’ loses its efficacy. This article develops a mechanism to foldover designs involving factors with different numbers of levels, say mixed‐level designs. By exhaustive search we identify the optimal foldover plans. The criterion used is the general balance metric, which can reveal the aberration properties of the combined designs (original design plus foldover). The optimal foldovers for some efficient mixed‐level fractional factorial designs are provided for practical use. Copyright © 2008 John Wiley & Sons, Ltd.
Establishment of a three‐dimensional culture and mechanical loading system for skeletal myoblasts
Authors: Li Yu , Song Jinlin , Yang Pu , Zou Rui , Fan Xiaofeng , Zhao Zhihe
Published: November 2008

Establishment of a three‐dimensional (3‐D) culture and mechanical loading system which simulates the in vivo environment is critical in cytomechanical studies. The present article attempts to do this by integrating porous PLGA scaffolds with a four‐point bending strain unit. Three types of PLGA scaffolds with three average pore sizes were synthesized, i.e., type I (60–88 μm), type II (88–100 μm) and type III (100–125 μm). To establish the 3‐D mechanical loading system, PLGA membrane was integrated with conventional force‐loading plates and the third passage skeletal myoblasts from neonatal Sprague–Dawley (SD) rats were seeded. Small PLGA membranes were put in 24‐well plates followed by cell implantation and MTT assay was performed on days 1, 2, 4, 6 and 8 to compare biocompatibility of the three types of scaffolds. After 3 days’ culture, many more cells had grown in type II than in type I or type III under fluorescence microscopy. In the MTT assay, OD of type II was significantly higher (P < 0.05) than the other two, especially at the early stage. As type II proved to be the best among the three, it was used as the scaffold in the preliminary mechanical loading study and 4000 μstrain cyclic uniaxial strain was imposed. The system worked well and it was found that short to median time of stretching enhances while prolonged time of stretching inhibits cell proliferative activity of the 3‐D cultured skeletal myoblasts(P < 0.05). It is concluded that the combination of PLGA scaffolds with a four‐point bending strain unit provides a satisfactory 3‐D mechanical loading system.
Usefulness of systolic time intervals in the identification of abnormal ventriculo‐arterial coupling in stable heart failure patients*
Authors: Cheng Hao‐Min , Yu Wen‐Chung , Sung Shih‐Hsien , Wang Kang‐Ling , Chuang Shao‐Yuan , Chen Chen‐Huan
Published: November 2008

Background:

The ratio of effective arterial elastance (Ea) to ventricular end‐systolic elastance (Ees) indicates the status of ventriculo‐arterial coupling.

Aims:

We investigated if systolic time intervals (pre‐ejection period, PEP; ejection time, ET; and their ratio, PEP/ET) can be used to identify heart failure patients with abnormal ventriculo‐arterial coupling.

Methods:

Age and sex‐matched study subjects included 54 apparently healthy subjects with normal left ventricular (LV) function, and stable patients with LV diastolic (n=54) and systolic dysfunction (n=54). Ees and Ea were estimated non‐invasively by echocardiography, and abnormal ventriculo‐arterial coupling was defined as Ea/Ees>1.2. PEP, ET, and PEP/ET were measured automatically using electrocardiography, phonocardiography, and brachial pulse volume recording.

Results:

Ea/Ees>1.2 was present in 48.1% of subjects with systolic dysfunction. The PEP/ET was significantly associated with most parameters of LV structure and function, and Ea/Ees (r=0.67, p<0.001). Using PEP/ET≥0.423 as cut point, the sensitivity and specificity to identify patients with Ea/Ees>1.2 were 85.7% and 84.3%, respectively for the whole population, and 84.6% and 78.6%, for patients with systolic dysfunction.

Conclusion:

Abnormal ventriculo‐arterial coupling was present in almost half of stable patients with systolic dysfunction. PEP/ET was useful in identifying such patients.
A unified degree day model describes survivorship ofCopitarsia corrudaPogue & Simmons (Lepidoptera: Noctuidae) at different constant temperatures
Authors: Gómez N.N. , Venette R.C. , Gould J.R. , Winograd D.F.
Published: November 2008

Predictions of survivorship are critical to quantify the probability of establishment by an alien invasive species, but survival curves rarely distinguish between the effects of temperature on development versus senescence. We report chronological and physiological age-based survival curves for a potentially invasive noctuid, recently described asCopitarsia corrudaPogue & Simmons, collected from Peru and reared on asparagus at six constant temperatures between 9.7 and 34.5°C.Copitarsiaspp. are not known to occur in the United States but are routinely intercepted at ports of entry. Chronological age survival curves differ significantly among temperatures. Survivorship at early age after hatch is greatest at lower temperatures and declines as temperature increases. Mean longevity was 220 (±13 SEM) days at 9.7°C. Physiological age survival curves constructed with developmental base temperature (7.2°C) did not correspond to those constructed with a senescence base temperature (5.9°C). A single degree day survival curve with an appropriate temperature threshold based on senescence adequately describes survivorship under non-stress temperature conditions (5.9–24.9°C).
Competition and intraguild predation between the braconid parasitoidBracon hylobiiand the entomopathogenic nematodeHeterorhabditis downesi, natural enemies of the large pine weevil,Hylobius abietis
Authors: Everard A. , Griffin C.T. , Dillon A.B.
Published: November 2008

In biological control programmes introduced natural enemies compete with indigenous enemies for hosts and may also engage in intraguild predation when two species competing for the same prey attack and consume one another. The large pine weevil,Hylobius abietisL. (Coleoptera: Curculionidae), is an important pest of coniferous reforestation in Europe. Among its natural enemies, the parasitoidBracon hylobiiRatz. (Hymenoptera: Braconidae) and entomopathogenic nematodes have potential as biological control agents. Both parasitoid and nematodes target the weevil larvae and, hence, there is potential for competition or intraguild predation.

In this study, we examine the interaction ofB. hylobiiwith the nematodeHeterorhabditis downesiStock, Griffin and Burnell (Nematode: Heterorhabditidae), testing the susceptibility of larvae, pupae and adults ofB. hylobiitoH. downesiand whether female parasitoids discriminate between nematode-infected and uninfected weevils for oviposition. In choice tests, when weevils were exposed to nematodes 1–7 days previously, noB. hylobiioviposited on nematode-infected weevil larvae. Up to 24 h, healthy weevils were twice as likely as nematode-infected ones to be used for oviposition.Bracon hylobiifemales did not adjust clutch size; nematode-infected hosts were either rejected or the parasitoid laid a full clutch of eggs on them.

When nematodes were applied to the parasitoid feeding on weevil larvae, the nematodes parasitized the parasitoid larvae, there was a reduction in cocoon formation and fewer cocoons eclosed. Eclosion rate was not reduced when nematodes were applied to fully formed cocoons, but nearly all of the emerging adults were killed by nematodes.
Fine-scale chemical zonation in small mafic dykes, Kestiö Island, SW Finland
Authors: CHISTYAKOVA SOFYA , LATYPOV RAIS
Published: November 2008

Detailed centimetre-scale sampling across two small dolerite dykes (7 and 21 cm wide) of Kestiö Island, SW Finland, has revealed a well-developed internal zonation, with surprisingly systematic compositional variations. From the margins inwards, the dykes exhibit a steady decrease in whole-rock MgO, Mg number (100Mg/(Mg+Fetotal)) and normative Opx (indicating a normal fractionation trend) with simultaneous increase in normative An (100An/(An+Ab)) and decrease in incompatible Zr, Y, TiO2and P2O5(indicating a reverse fractionation trend). In addition, marginal rocks of dykes contain normative corundum that is apparently associated with their significant depletion in whole-rock CaO. The extent of margin-to-centre differentiation of dykes in terms of most components is slight to modest, although in some petrochemical parameters it is quite high (e.g. 15 mol. % of normative An). The dykes are almost glassy and uncontaminated by host rocks, suggesting that their compositional profiles are primary and most likely reflect temporal changes in composition of magma filling the dykes. A mechanism responsible for the systematic changes in composition of inflowing magma remains elusive, however, since no known processes are able to force magma to evolve simultaneously along both normal and reverse fractionation trends. The study thus appears to indicate some not yet specified process of magma differentiation.
The Unit 12 allivalite, Eastern Layered Intrusion, Isle of Rum: a textural and geochemical study of an open-system magma chamber
Authors: HOLNESS MARIAN B. , WINPENNY BEN
Published: November 2008

The Eastern Layered Intrusion of the Rum Central Complex, NW Scotland, comprises 16 macro-units broadly defined by a basal peridotite body overlain by gabbros and troctolites. The local term for the upper plagioclase-bearing cumulates is ‘allivalite’. The Unit 12 allivalite contains five subsidiary peridotite horizons, each continuous on the kilometre scale. Field, textural and geochemical evidence points to the Unit 12 allivalite forming by progressive accumulation of crystals from up to seven separate magma batches, varying from picrite to basalt. The thickness of the magma lens in the sill-like chamber was as low as 30 m during a significant part of the development of the Unit 12 allivalite, and evidence supports one eruption from the chamber during its accumulation.
BRITAIN AND GLOBALISATION SINCE 1850: III. CREATING THE WORLD OF BRETTON WOODS, 1939–1958
Authors: Daunton Martin
Published: November 2008

During the Second World War, attention turned to reconstructing the world economy by moving away from competitive devaluations, protectionism and economic nationalism that had marred the 1930s. The Americans had considerable economic and political power, and they wished to restore multilateral trade, fixed exchanges and convertibility of currencies. The British government was in a difficult position, for it faced a serious balance of payments deficit and large accumulations of sterling in the Commonwealth and other countries. Multilateralism and convertibility posed serious difficulties. This address considers whether the American government had economic and financial hegemony after the war, or whether it was constrained; and asks how the British government was able to manoeuvre between America, Europe and the sterling area. The result was a new trade-off between international monetary policy, free trade, capital controls and domestic economic policy that was somewhat different from the ambitions of the American government and from British commitments made during and at the end of the war.
Supershort avalanche electron beam generation in gases
Authors: Tarasenko V.F. , Baksht E.H. , Burachenko A.G. , Kostyrya I.D. , Lomaev M.I. , Rybka D.V.
Published: November 2008

This paper reports on the properties of a supershort avalanche electron beam generated in the air or other gases under atmospheric pressure and gives the analysis of a generation mechanism of supershort avalanche electron beam, as well as methods of such electron beams registration. It is reported that in the air under the pressure of 1 atm, a supershort (<100 ps) avalanche electron beam is formed in the solid angle more than 2π steradian. The electron beam has been obtained behind a 45 µm thick Al-Be foil in SF6 and Xe under the pressure of 2 atm, and in He, under the pressure of about 15 atm. It is shown that in SF6 under the high pressure (>1 atm) duration (full width at half maximum) of supershort avalanche electron beam pulse is about 150 ps.
Fore-vacuum plasma-cathode electron sources
Authors: Burdovitsin V.A. , Oks E.M.
Published: November 2008

This paper presents a review of physical principles, design, and performances of plasma-cathode direct current (dc) electron beam guns operated in so called fore-vacuum pressure (1–15 Pa). That operation pressure range was not reached before for any kind of electron sources. A number of unique parameters of the e-beam were obtained, such as electron energy (up to 25 kV), dc beam current (up 0.5 A), and total beam power (up to 7 kW). For electron beam generation at these relatively high pressures, the following special features are important: high probability of electrical breakdown within the accelerating gap, a strong influence of back-streaming ions on both the emission electrode and the emitting plasma, generation of secondary plasma in the beam propagation region, and intense beam-plasma interactions that lead in turn to broadening of the beam energy spectrum and beam defocusing. Yet other unique peculiarities can occur for the case of ribbon electron beams, having to do with local maxima in the lateral beam current density distribution. The construction details of several plasma-cathode electron sources and some specific applications are also presented.
A singular Gierer—Meinhardt system with different source terms
Authors: Ghergu Marius , Rădulescu Vicenţiu
Published: November 2008

We study the existence and non-existence of classical solutions to a general Gierer—Meinhardt system with Dirichlet boundary condition. The main feature of this paper is that we are concerned with a model in which both the activator and the inhibitor have different sources given by general nonlinearities. Under some additional hypotheses and in the case of pure powers in nonlinearities, regularity and uniqueness of the solution in one dimension is also presented.
Introduction: The syntax of nominals and noun phrases
Authors: Börjars Kersti , Delsing Lars-Olof
Published: November 2008

The noun phrase was long a neglected area within research in modern syntactic theory. Studies tended to focus instead on the clause and less attention was paid to the internal structure of the noun phrase. The early studies would often take an interest in the properties of noun phrases only in so far as they interacted with clausal morpho-syntax. Nominalisations were then subject to some early studies, as in Chomsky (1970) and work inspired by it.
Kayne's model of Case and Finnish nominal phrases
Authors: Brattico Pauli
Published: November 2008

The standard view concerning Case assignment or valuation is that Case is valued to determiner phrases (DPs) in syntax. Recently, Kayne has proposed an alternative model, in which Case is valued to lexical elements rather than to phrases. This article cites several facts from Finnish in support of this model. A detailed Kaynean model of Case is developed. According to this model, abstract Case is valued to lexical elements by the highest ranking c-commanding Case assigner when each phase (CP,vP) is sealed, where ranking is based on a particular Case Hierarchy and a simple notion of locality. Configurations in which Case is seemingly assigned under a spec–head relation are provided with an alternative interpretation.
Syllables without vowels: phonetic and phonological evidence from Tashlhiyt Berber
Authors: Ridouane Rachid
Published: November 2008

It has been proposed that Tashlhiyt is a language which allows any segment, including obstruents, to be a syllable nucleus. The most striking and controversial examples taken as arguments in favour of this analysis involve series of words claimed to contain only obstruents. This claim is disputed in some recent work, where it is argued that these consonant sequences contain schwas that can be syllable nuclei. This article presents arguments showing that vowelless syllables do exist in Tashlhiyt, both at the phonetic and phonological levels. Acoustic, fibrescopic and photoelectroglottographic examination of voiceless words (e.g. [tkkststt]) provide evidence that such items lack syllabic vocalic elements. In addition, two types of phonological data, metrics and a spirantisation process, are presented to show that in this language schwa is not a segment which can be independently manipulated by phonological grammar and which can be referred to the syllable structure.
The 100‐ka and rapid sea level changes recorded by prograding shelf sand bodies in the Gulf of Lions (western Mediterranean Sea)
Authors: Bassetti M. A. , Berné S. , Jouet G. , Taviani M. , Dennielou B. , Flores J.‐A. , Gaillot A. , Gelfort R. , Lafuerza S. , Sultan N.
Published: November 2008

Thick forced regressive units on the wide continental shelf of the Gulf of Lions (western Mediterranean) recorded the composite effect of sea level changes during the Quaternary. They are mostly composed of coastal siliciclastic and bioclastic wedges showing clinoform geometry. These deposits have been intensively explored through high‐resolution seismic investigations, but only recently it was possible to ground truth seismic interpretations, based on a long (100 m) borehole that crossed the succession and recovered a large part of the mainly sandy deposits (∼84% recovery). A multiproxy analysis of the sedimentary succession shows that (1) the stratal architecture of the shelf margin is defined by major bounding surfaces that are polygenic erosion surfaces associated with coarse‐grained material incorporating abundant and diverse shells, including cold‐water fauna (presently absent from the Mediterranean Sea). Between each surface, coarsening upward units with steep (up to 5°) foresets are made of massive (more than 20 m thick) sands with possible swaley and hummocky cross‐stratification, passing seaward to sands with muddy intervals and, further offshore, alternating highly boiturbated sands and silts. Each prograding wedge corresponds to a forced‐regressive shoreface (or delta front/prodelta), deposited during the overall sea level falls occurring at (relatively slow) interglacial/glacial transition and therefore represents the record of 100 ka cyclicity. Higher‐frequency Milankovitch cyclicities are also probably represented by distinct shoreface/delta front wedges; (2) detailed examination of the architecture and chronostratigraphy of the most recent sequence shows that minor bounding surfaces, corresponding to abrupt shallowing of sedimentary facies, separate downward stepping parasequences within the last 100 ka sequence. These events are in phase with millennial‐scale glacial climatic and sea level variability, the downward shift surfaces corresponding to the falls during the coldest stadials. These deposits provide a comprehensive and well‐constrained Pleistocene analog to the numerous shoreface deposits attributed to falling‐stage systems tracts recognized in ancient stratigraphic records, studied at the outcrop scale.
Viral hepatitis and fatty liver disease: how an unwelcome guest makes pâté of the host
Authors: Brown Andrew J.
Published: November 2008

HBV and HCV (hepatitis B and C viruses respectively) affect hundreds of millions of people globally, and are a major cause of chronic liver disease, including NAFLD (non-alcoholic fatty liver disease). Previous work on HCV-associated fatty liver disease has implicated two transcription factors that are important in lipid metabolism, SREBP1c (sterol-regulatory-element-binding protein 1c) and the LXRα (liver X receptor α). HBV-associated fatty liver disease has been less well-studied. New work from Kim and colleagues in this issue of the Biochemical Journal has provided new insight into how HBV causes fatty liver disease. Investigating HBV's so-called X gene product (HBx), they report that this viral protein directly binds to LXRα in the host liver cells to up-regulate the lipogenic transcription factor, SREBP1c. Also discussed in this commentary is another way that viruses such as HBV and HCV could induce SREBP1c-mediated lipogenesis, via the PI3K (phosphoinositide 3-kinase)–Akt signalling pathway.
Effect of structural anisotropy on electronic conduction in delafossite tin doped copper indium oxide thin films
Authors: Singh Mandeep , Mehta B. R.
Published: November 2008

Sn doped CuInO2 thin films having a single delafossite phase have been synthesized by magnetron sputtering technique. A gradual decrease in the activation energy from 0.43 to about 0.10 eV and a large increase in conductivity are observed in Sn doped samples with increasing fraction of crystallites having (006) orientation due to an increase in substrate temperature. Due to thermally activated carrier transport along O-A-O layers and activated carrier generation along BO6 layers, crystallite orientation becomes a crucial factor in controlling the conduction in delafossite thin films.
High quality AlN grown on SiC by metal organic chemical vapor deposition
Authors: Chen Z. , Newman S. , Brown D. , Chung R. , Keller S. , Mishra U. K. , Denbaars S. P. , Nakamura S.
Published: November 2008

Growth conditions for AlN in two dimensional (2D) and three dimensional (3D) growth modes were explored on SiC using metal organic chemical vapor deposition. High quality AlN layers were obtained by alternating between 3D and 2D growth modes, referred to as modulation growth (MG). Long parallel atomic terraces without step terminations were observed in atomic force microscopy (AFM) scans of MG AlN, indicating a reduced dislocation density. X-ray diffraction rocking curves yielded full widths at half maximum (FWHM) of 86 and 363arcsec for the (002) and (102) reflections, respectively, giving further evidence of low dislocation density in the film. 3D-2D MG also releases some of the tensile strain in the AlN film, enabling the growth of thick, crack-free AlN on SiC substrates.
Analysis of efficiency characteristics of green phosphorescent organic light-emitting devices
Authors: Yoon Ji-hwan , Park Il-soo
Published: November 2008

Efficiency characteristics of green phosphorescent organic light-emitting devices (PHOLEDs) with different host materials and device structures were investigated by examining the luminance efficiency-current density curves and electroluminescence spectra. The efficiency of PHOLEDs at low current density as well as at high current density was greatly affected by energy levels and carrier transport properties of the host and hole/electron transporting materials. The devices exhibited high initial luminance efficiency when hole-electron recombination was well confined in the emitting layer (EML). Efficiency roll off with increasing current density was observed as hole-electron recombination and charge balance in EML deteriorated with current density.
Solvation of Na2+ in Arn clusters. I. Structures and spectroscopic properties
Authors: Douady J. , Jacquet E. , Giglio E. , Zanuttini D. , Gervais B.
Published: November 2008

We present a theoretical study of Na2+ solvation in an argon matrix Arn for n=1 to a few tens. We use a model based on an explicit description of valence electron interaction with Na+ and Ar cores by means of core polarization pseudopotential. The electronic structure determination is thus reduced to a one-electron problem, which can be handled efficiently. We investigate the ground state geometry and related optical absorption of Na2+Arn clusters. For n⩽5, the lowest energy isomers are obtained by aggregation of Ar atoms at one single extremity of Na2+, leading to moderate perturbation of the optical transition. For 6⩽n⩽15, the Ar atoms aggregate at both extremities. This structural change is associated with a strong blueshift of the first optical transition (XΣg+2→AΣu+2), which reveals the confinement of the excited AΣu+2 state. The Na2+ energy spectrum is so strongly perturbed that the AΣu+2 state becomes higher than the BΠu+2 states. The closure of the first solvation shell is observed at n=17. Above this size, the second solvation shell develops. Its structure is dominated by a pentagonal organization around the Na2+ molecular axis. The optical transitions vary smoothly with n and the AΣu+2 and BΠu2 states are no longer inverted, though the first optical transition remains strongly blueshifted.
Broadband Raman amplification in silicon
Authors: Solli Daniel R. , Koonath Prakash , Jalali Bahram
Published: November 2008

Raman gain is a useful nonlinear phenomenon that has made optically pumped silicon lasers and amplifiers a reality. Unfortunately, the bandwidth of Raman gain in silicon is normally rather limited, owing to the narrow Raman linewidths typical of crystalline materials. Here, we report Raman amplification in silicon with a spectrum that is modified by the simultaneous occurrence of self-phase-modulation. This combined nonlinear action produces a broad Raman gain spectrum from a narrowband pump source.
The Na+–H2 cation complex: Rotationally resolved infrared spectrum, potential energy surface, and rovibrational calculations
Authors: Poad B. L. J. , Wearne P. J. , Bieske E. J. , Buchachenko A. A. , Bennett D. I. G. , Kłos J. , Alexander M. H.
Published: November 2008

The rotationally resolved infrared spectrum of the Na+–H2 cation complex is recorded in the H–H stretch region (4067–4118 cm−1) by monitoring the production of Na+ photofragments. Altogether 42 lines are identified, 40 of which are assigned to Ka=1-1 transitions (associated with complexes containing ortho-H2) and two tentatively assigned to Ka=0-0 transitions (associated with complexes containing para-H2). The Ka=1-1 subband lines were fitted using a Watson A-reduced Hamiltonian, yielding effective spectroscopic constants. The band origin is estimated as 4094.6 cm−1, a shift of −66.6 cm−1 with respect to the Q1(0) transition of the free H2 molecule. The results demonstrate that Na+–H2 has a T-shaped equilibrium configuration with the Na+ ion attached to a slightly perturbed H2 molecule but that large-amplitude vibrational motions significantly influence the rotational constants derived from the asymmetric rigid rotor analysis. The vibrationally averaged intermolecular separation in the ground vibrational state is estimated as 2.493 Å, increasing slightly (by 0.002 Å) when the H2 subunit is vibrationally excited. A new three-dimensional potential energy surface is developed to describe the Na+–H2 complex. Ab initio points calculated using the CCSD(T) method and aug-cc-pVQZ basis set augmented by bond functions are fitted using a reproducing kernel Hilbert space method [Ho et al., J. Chem. Phys. 104, 2584 (1996)] to give an analytical representation of the potential energy surface. Ensuing variational calculations of the rovibrational energy levels demonstrate that the potential energy surface correctly predicts the frequency of the νHH transition (to within 2.9 cm−1) and the dissociation energies [842 cm−1 for Na+–H2(para) and 888 cm−1 for Na+–H2(ortho)]. The B and C rotational constants are slightly underestimated (by 1.7%), while the vibrationally averaged intermolecular separation is overestimated by 0.02 Å.
Room-temperature ferromagnetism in (Mn, N)-codoped TiO2 films grown by plasma assisted molecular beam epitaxy
Authors: Li X. Y. , Wu S. X. , Xu L. M. , Liu Y. J. , Xing X. J. , Li S. W.
Published: November 2008

(Mn, N)-codoped TiO2 films have been fabricated by plasma assisted molecular beam epitaxy. X-ray diffraction and x-ray photoelectron spectroscopy studies indicate the incorporation of both Mn and N ions into the TiO2 lattice but without Mn metal clusters. Ferromagnetism with clear hysteresis at 300 K is observed in (Mn, N)-codoped TiO2 films, whereas the films without nitrogen show paramagnetic behavior. It is demonstrated experimentally that the intentional nitrogen doping plays an important role in realizing dominant ferromagnetic ordering in Mn-doped TiO2 films.
Photodissociation of protonated tryptophan and alteration of dissociation pathways by complexation with crown ether
Authors: Kadhane Umesh , Andersen Jens Ulrik , Ehlerding Anneli , Hvelplund Preben , Kirketerp Maj-Britt S. , Lykkegaard Morten Køcks , Nielsen Steen Brøndsted , Panja Subhasis , Wyer Jean Ann , Zettergren Henning
Published: November 2008

The behavior of protonated tryptophan (TrpH+) and its complex with 18-crown-6-ether (CE) after photoexcitation has been explored based on measurements of dissociation lifetimes, fragmentation channels, and absorption spectra using an electrostatic ion storage ring. A recent implementation of pulsed power supplies for the ring elements with microsecond response times allows us to identify the daughter ion fragment masses and to disentangle fragmentation that occurs from excited states immediately after photoexcitation from that occurring on a longer time scale of several microseconds to milliseconds. We find that attachment of crown ether significantly alters the dissociation channels since it renders the πσ*(NH3) state inaccessible and hence prevents the N–H bond breakage which is an important fragmentation channel of TrpH+. As a result, on a long time scale (>10μs), photoexcited TrpH+(CE) decays exponentially whereas TrpH+ displays a power-law decay. The only ions remaining in the latter case are Trp+⋅ radical cations with a broad internal energy distribution caused by the departing hydrogen. Large changes in the fragment branching ratios as functions of excitation wavelength between 210 and 290nm were found for both TrpH+ and TrpH+(CE).
Lubrication approximation for microparticles moving along parallel walls
Authors: Ekiel-Jeżewska Maria L. , Wajnryb Eligiusz , Bławzdziewicz Jerzy , Feuillebois François
Published: November 2008

Lubrication expressions for the friction coefficients of a spherical particle moving in a fluid between and along two parallel solid walls are explicitly evaluated in the low-Reynolds-number regime. They are used to determine lubrication expression for the particle free motion under an ambient Poiseuille flow. The range of validity and the accuracy of the lubrication approximation are determined by comparing with the corresponding results of the accurate multipole procedure. The results are applicable for thin, wide, and long microchannels, or quasi-two-dimensional systems.
Electronically excited rubidium atom in a helium cluster or film
Authors: Leino Markku , Viel Alexandra , Zillich Robert E.
Published: November 2008

We present theoretical studies of helium droplets and films doped with one electronically excited rubidium atom Rb∗ (P2). Diffusion and path integral Monte Carlo approaches are used to investigate the energetics and the structure of clusters containing up to 14 helium atoms. The surface of large clusters is approximated by a helium film. The nonpair additive potential energy surface is modeled using a diatomic in molecule scheme. Calculations show that the stable structure of Rb∗Hen consists of a seven helium atom ring centered at the rubidium, surrounded by a tirelike second solvation shell. A very different structure is obtained when performing a “vertical Monte Carlo transition.” In this approach, a path integral Monte Carlo equilibration starts from the stable configuration of a rubidium atom in the electronic ground state adsorbed to the helium surface after switching to the electronically excited surface. In this case, Rb∗Hen relaxes to a weakly bound metastable state in which Rb∗ sits in a shallow dimple. The interpretation of the results is consistent with the recent experimental observations [G. Auböck et al., Phys. Rev. Lett. 101, 035301 (2008)].
High power microwave switching utilizing a waveguide spark gap
Authors: Foster J. , Edmiston G. , Thomas M. , Neuber A.
Published: November 2008

A reduction in the rise time of a 2.85 GHz high power microwave (HPM) pulse is achieved by implementing an overvoltaged spark gap inside a waveguide structure. The spark gap is oriented such that when triggered, the major electric field component of the dominant TE10 mode is shorted. The transition from a transmissive to a highly reflective microwave structure in a relatively short period of time (tens of nanoseconds) creates a means to switch multimegawatt power levels on a much faster timescale than mechanical switches. An experimental arrangement composed of the waveguide spark gap and a high power circulator is used to reduce the effective rise time of a HPM pulse from a U.S. Air Force AW/PFS-6 radar set from 600 ns down to 50 ns. The resulting HPM pulse exhibits a much more desirable excitation profile when investigating microwave induced dielectric window flashover. Since most theoretical discussions on microwave breakdown assume an ideal step excitation, achieving a “squarelike” pulse is needed if substantial comparison between experiment and theory is sought. An overview of the experimental setup is given along with relevant performance data and comparison with computer modeling of the structure.
Electric properties of soft PZT ceramics under combined electric and mechanic fields
Authors: Suchanicz J. , Sitko D. , Kim-Ngan N.-T. H. , Balogh A. G.
Published: November 2008

The effect of uniaxial pressure (0–1000 bars) applied parallel or perpendicular to the ac electric field on electric properties of soft PZT ceramics has been investigated. It was found that uniaxial pressure significantly influences these properties. With increasing pressure the peak intensity in the ε(T) curve decreases, becomes diffuse and shifts to a higher temperature, dielectric hysteresis is reduced, and dielectric dispersion decreases. It was shown that the application of pressure perpendicular to the electric poling direction improves the ferroelectric properties. It was concluded, that applied uniaxial pressure or increasing Ti-ion concentration in PZT system induces similar effects. The results were discussed in term of Cochran soft-mode model and domain switching under influence of pressure.
Modeling of spin metal-oxide-semiconductor field-effect transistor: A nonequilibrium Green’s function approach with spin relaxation
Authors: Low Tony , Lundstrom Mark S. , Nikonov Dmitri E.
Published: November 2008

A spin metal-oxide-semiconductor field-effect transistor (spin MOSFET), which combines a Schottky-barrier MOSFET with ferromagnetic source and drain contacts, is a promising device for spintronic logic. Previous simulation studies predict that this device should display a very high magnetoresistance (MR) ratio (between the cases of parallel and antiparallel magnetizations) for the case of half-metal ferromagnets (HMF). We use the nonequilibrium Green’s function formalism to describe tunneling and carrier transport in this device and to incorporate spin relaxation at the HMF-semiconductor interfaces. Spin relaxation at interfaces results in nonideal spin injection. Minority spin currents arise and dominate the leakage current for antiparallel magnetizations. This reduces the MR ratio and sets a practical limit for spin MOSFET performance. We found that MR saturates at a lower value for smaller source-to-drain bias. In addition, spin relaxation at the detector side is found to be more detrimental to MR than that at the injector side, for drain bias less than the energy difference of the minority spin edge and the Fermi level.
Fabrication of terahertz hollow-glass metallic waveguides with inner dielectric coatings
Authors: Bowden Bradley , Harrington James A. , Mitrofanov Oleg
Published: November 2008

Hollow-core glass waveguides (HCWs) with inner coatings of silver and polystyrene (PS) have been fabricated for transmission of terahertz radiation. A liquid-phase chemical deposition process was used to deposit silver and PS thin film coatings inside glass tubing. The PS dielectric layer can substantially lower the loss of the HCW compared to the metal-only waveguide. A polymer coating was chosen because it is possible to deposit the dielectric film thickness required for operation in the terahertz regime. Specifically, the dielectric film thickness is proportional to the wavelength so the PS coatings need to be on the order of 10 to 15 μm to minimize transmission losses at terahertz frequencies. This is much thicker than the submicron thick dielectric coatings needed in the IR region. The thickness of the PS film depends on the concentration of PS in the coating solution and the coating rate. Both of these parameters are studied and related to the losses in the waveguides. The lowest loss of 0.95 dB/m at 119 μm (2.5 THz) was obtained for hybrid HE mode propagation in a waveguide with a 8.2 μm thick PS film deposited inside a 2.2 mm bore, 90 cm long glass tube.
Optical coupling of core-shell quantum dots to size-selected gold clusters
Authors: Palomba S. , Palmer R. E.
Published: November 2008

We have investigated the optical properties of CdSe/ZnS core-shell quantum dots (QDs), perturbed by the presence of a patterned film of size-selected gold nanoclusters. Quenching of the fluorescence emission of the quantum emitters was observed as a function of the distance between the metal nanoparticles and the QDs. Long-range quenching was observed up to distances of ∼100 nm, which we attribute to a field-enhancement effect caused by the small size-selected clusters (<8 nm in diameter). This effect is weak relative to the dielectric damping caused by the electron-hole pair excitation in the clusters. We present experimental results that show agreement with a bulk-dielectric model implying that quantum confinement effects do not appear even at a cluster diameter of only ∼8 nm.
Effective field equations of brane-induced electromagnetism
Authors: Dahia F. , Romero C. , Cruz M. A. S.
Published: November 2008

Using a covariant embedding formalism, we find the effective field equations for the electromagnetism that emerge on branes in the context of Dvali–Gabadadze–Porrati (DGP) braneworld scenario. Our treatment is essentially geometrical. We start with Maxwell equations in five dimensions and project them into an arbitrary brane. The formalism is quite general and allows us to consider curved bulk spaces and curved branes whose tension is not necessarily null. The kinetic electromagnetic term induced on the world volume of the brane, proper of DGP models, is incorporated in this formulation by means of an appropriate match condition. We also give an estimate of each term of the effective field equations and determine the domain in which the four-dimensional Maxwell equations can be recovered in the brane.
Elasticity of amorphous zirconium tungstate at high pressure
Authors: Liu Wei , Li Baosheng
Published: November 2008

Compressional (VP) and shear wave (VS) velocities of the amorphous phase of ZrW2O8 have been measured up to 10.4 GPa at room temperature using ultrasonic interferometry in conjunction with synchrotron x radiation. The pressure-density relation is determined using the measured velocities. Both VP and VS, as well as the adiabatic bulk and shear moduli, exhibit monotonic increase with increasing pressure. The pressure derivatives of the bulk and shear moduli are determined to be KS0′=7.3(1) and G0′=1.8(1), with bulk and shear moduli KS0=61.7(5) GPa and G0=35.0(2) GPa. Comparing with the α phase, VP, VS, KS0, E, Θac, and σ of the amorphous phase decrease by 14.8%, 10.0%, 17.2%, 2.9%, 1.2%, and 15.5%, along with 28% and 3.2% increase in density and shear modulus, respectively.