bluuebunny/crossref_metadata_2025 huggingface dataset:
Electronic and vibrational properties of nickel sulfides from first principles
Authors: Wang Jeng-Han , Cheng Zhe , Brédas Jean-Luc , Liu Meilin
Published: December 2007

We report the results of first-principles calculations (generalized gradient approximation–Perdew Wang 1991) on the electronic and vibrational properties of several nickel sulfides that are observed on Ni-based anodes in solid oxide fuel cells (SOFCs) upon exposure to H2S contaminated fuels: heazlewoodite Ni3S2, millerite NiS, polydymite Ni3S4, and pyrite NiS2. The optimized lattice parameters of these sulfides are within 1% of the values determined from x-ray diffraction. The electronic structure analysis indicates that all Ni–S bonds are strongly covalent. Furthermore, it is found that the nickel d orbitals shift downward in energy, whereas the sulfur p orbitals shift upward with increasing sulfur content; this is consistent with the decrease in conductivity and catalytic activity of sulfur-contaminated Ni-based electrodes (or degradation in SOFC performance). In addition, we systematically analyze the classifications of the vibrational modes at the Γ point from the crystal symmetry and calculate the corresponding vibrational frequencies from the optimized lattice constants. This information is vital to the identification with in situ vibrational spectroscopy of the nickel sulfides formed on Ni-based electrodes under the conditions for SOFC operation. Finally, the effect of thermal expansion on frequency calculations for the Ni3S2 system is also briefly examined.
Analysis of band broadening in vibrational high-resolution electron-energy-loss spectra of condensed methane
Authors: Swiderek P. , Burean E.
Published: December 2007

High-resolution vibrational electron-energy-loss spectra of multilayer condensed films of methane recorded at 20K show a strong tailing of the vibrational bands that clearly exceeds the instrumental resolution. At low incident electron energy, this tailing is remarkably less important for the dipole-allowed bending vibration (ν4) than for other bands. Also, the tailing becomes less pronounced with increasing size of the molecule as demonstrated by spectra of ethane and heptane recorded under the same conditions. Dipole coupling, rotational broadening, and multiple inelastic scattering have been considered as origins of this band broadening. While the first two effects can be excluded, multiple scattering involving a low-frequency phonon band provides a reasonable explanation as demonstrated by simulations of the spectrum of methane using a classical two-stream model. A lower phonon frequency in the cases of the larger molecules is held responsible for the better resolved vibrational signals in the spectra of ethane and heptane.
Hydrodynamic model for relaxation of optically injected currents in quantum wells
Authors: Abrarov R. M. , Sherman E. Ya. , Sipe J. E.
Published: December 2007

We use a hydrodynamic model to describe the relaxation of optically injected currents in quantum wells on a picosecond time scale, numerically solving the continuity and velocity evolution equations with the Hermite-Gaussian functions employed as a basis. The interplay of the long-range Coulomb forces and nonlinearity in the equations of motion leads to rather complex patterns of the calculated charge and current densities. We find that the time dependence of even the first moment of the electron density is sensitive to this complex evolution.
An exact fluid model for relativistic electron beams: The many moment case
Authors: Carrisi M. C. , Pennisi S.
Published: December 2007

An interesting and satisfactory fluid model has been proposed in literature for the description of relativistic electron beams. It was obtained with 14 independent variables by imposing the entropy principle and the relativity principle. Here the case is considered with an arbitrary number of independent variables, still satisfying the above mentioned two principles; these lead to conditions whose general solution is here found. We think that the results satisfy also a certain ordering with respect to a smallness parameter ϵ measuring the dispersion of the velocity about the mean; this ordering generalizes that appearing in literature for the 14 moments case.
Hypersonic drift-tearing magnetic islands in tokamak plasmas
Authors: Fitzpatrick R. , Waelbroeck F. L.
Published: December 2007

A two-fluid theory of long wavelength, hypersonic, drift-tearing magnetic islands in low-collisionality, low-β plasmas possessing relatively weak magnetic shear is developed. The model assumes both slab geometry and cold ions, and neglects electron temperature and equilibrium current gradient effects. The problem is solved in three asymptotically matched regions. The “inner region” contains the island. However, the island emits electrostatic drift-acoustic waves that propagate into the surrounding “intermediate region,” where they are absorbed by the plasma. Since the waves carry momentum, the inner region exerts a net force on the intermediate region, and vice versa, giving rise to strong velocity shear in the region immediately surrounding the island. The intermediate region is matched to the surrounding “outer region,” in which ideal magnetohydrodynamic holds. Isolated hypersonic islands propagate with a velocity that lies between those of the unperturbed local ion and electron fluids, but is much closer to the latter. The ion polarization current is stabilizing, and increases with increasing island width. Finally, the hypersonic branch of isolated island solutions ceases to exist above a certain critical island width. Hypersonic islands whose widths exceed the critical width are hypothesized to bifurcate to the so-called “sonic” solution branch.
A high pressure cell for small angle neutron scattering up to 500MPa in combination with light scattering to investigate liquid samples
Authors: Kohlbrecher J. , Bollhalder A. , Vavrin R. , Meier G.
Published: December 2007

We report on a high pressure cell to use with small angle neutron scattering (SANS) in a pressure range up to 500MPa. The cell offers the new possibility to investigate liquid samples by a specially designed sample chamber, which allows changing of samples relatively easily. Since the cell construction uses sapphire as window material, also light scattering investigations can be performed simultaneously to the SANS measurements. In this article we describe the construction of a high pressure cell and we demonstrate the applicability of the construction for SANS in combination with dynamic light scattering showing data on the biological molecule lysozyme.
Spatial, energy, and time-dependent study of surface charging using spectroscopy and microscopy techniques
Authors: Di Santo Giovanni , Coluzza Carlo , Flammini Roberto , Zanoni Robertino , Decker Franco
Published: December 2007

Spatial, energy, and time-dependent effects induced by surface charging of conductive and nonconductive samples have been studied by spectroscopic and microscopic techniques. Surface charging of indium-tin oxide and cesium iodide has been studied by atomic force microscopy with a conducting tip and photoemission electron microscopy. Intensity fluctuations of the photoemission spectra recorded on amorphous and crystalline silicon nitride are also presented. The consequence of such effects on the determination of local physical and chemical properties of insulating materials is discussed.
A sufficient condition for the linear stability of magnetohydrodynamic equilibria with field aligned incompressible flows
Authors: Throumoulopoulos G. N. , Tasso H.
Published: December 2007

A sufficient condition for the linear stability of three dimensional equilibria with incompressible flows parallel to the magnetic field is derived. The condition refers to internal modes and involves physically interpretable terms related to the magnetic shear and the flow shear.
Pulsed Terahertz Signal Reconstruction
Authors: Fletcher J. R. , Swift G. P. , Dai DeChang , Chamberlain J. M. , Upadhya P. C.
Published: December 2007

A procedure is outlined which can be used to determine the response of an experimental sample to a single, simple broadband frequency pulse in terahertz frequency time domain spectroscopy (TDS). The advantage that accrues from this approach is that oscillations and spurious signals (arising from a variety of sources in the TDS system or from ambient water vapor) can be suppressed. In consequence, small signals (arising from the interaction of the radiation with the sample) can be more readily observed in the presence of noise. Procedures for choosing key parameters and methods for eliminating further artifacts are described. In particular, the use of input functions which are based on the binomial distribution is described. These binomial functions are used to unscramble the sample response to a simple pulse: they have sufficient flexibility to allow for variations in the spectra of different terahertz sources, some of which have low frequency as well as high frequency cutoffs. The signal processing procedure is validated by simple reflection and transmission experiments using a gap between polytetrafluoroethylene (PTFE) plates to mimic a void within a larger material. It is shown that a resolution of 100μm is easily achievable in reflection geometry after signal processing.
Optical and electrical properties of highly nitrogen-doped ZnO thin films grown by plasma-assisted molecular beam epitaxy
Authors: Jiao Shujie , Lu Youming , Zhang Zhengzhong , Li Binghui , Yao Bin , Zhang Jiying , Zhao Dongxu , Shen Dezhen , Fan Xiwu
Published: December 2007

Nitrogen-doped ZnO thin films with different nitrogen concentrations were fabricated by plasma-assisted molecular beam epitaxy. Hall effect measurements show p-type conduction for samples with low doping concentration. In highly doped ZnO, the p-type conduction converted to high resistance or unstable p-type behavior. This result indicates that highly doped samples are heavily compensated. In the low temperature photoluminescence spectrum, a donor-acceptor pair (DAP) emission band shows a strong redshift and broadening with increasing nitrogen doping concentration. The large shift of the DAP emission is explained by the Coulomb-potential fluctuation model related to compensated semiconductors.
Random matrices, nonbacktracking walks, and orthogonal polynomials
Authors: Sodin Sasha
Published: December 2007

Several well-known results from the random matrix theory, such as Wigner’s law and the Marchenko-Pastur law, can be interpreted (and proved) in terms of nonbacktracking walks on a certain graph. Orthogonal polynomials with respect to the limiting spectral measure play a role in this approach.
Weak ferromagnetism in Cu-doped GaN
Authors: Rosa A. L. , Ahuja R.
Published: December 2007

We employ density-functional theory within the generalized-gradient approximation to study the structural and electronic properties of Cu-doped GaN. We find that spin polarization on the Cu atoms in the GaN lattice is very small, leading to rather weak ferromagnetic behavior. We therefore suggest that Cu-doped GaN is unsuitable for spintronics applications. Our results refute previous calculations, which reported robust ferromagnetism in Cu-doped GaN.
Tunable low-energy Ar fast atom source with large diameter
Authors: Hara Yasuhiro , Takashima Seigo , Yamakawa Koji , Den Shoji , Toyoda Hirotaka , Hori Masaru
Published: December 2007

We have developed a low-energy Ar fast atom source consisting of a surface wave plasma (SWP) source and two carbon electrodes with a diameter of 80mm. Ions were extracted from the SWP using two carbon electrodes, accelerated and injected to the process chamber and then neutralized by charge exchange reaction without energy loss. Characteristics of the Ar ions and Ar fast atoms were investigated using quadrupole mass spectroscopy with an energy analyzer. Energies of Ar fast atoms were successfully controlled from 20to80eV by varying the acceleration voltage applied at the carbon electrode.
Magnetic nanocheckerboards with tunable sizes in the Mn-doped CoFe2O4 spinel
Authors: Zhang C. L. , Tseng C. M. , Chen C. H. , Yeo S. , Choi Y. J. , Cheong S.-W.
Published: December 2007

Formation of magnetically ordered array of two types of rectangular nanorods, ∼300nm in length and a few nanometers in size, is achieved in the Mn-doped CoFe2O4 spinel through chemical phase separation mediated by cooperative Jahn-Teller distortions. At room temperature, the magnetic nanorods, with composition close to CoFe2O4, interlace with the paramagnetic counterparts and form a highly organized checkerboard pattern in the cross section. The checkerboard size in the range of ∼13.8×7.9–∼17.3×14.0nm2 is tunable with composition and, particularly, with the isothermal annealing time. These three-dimensional nanocheckerboards exhibit a nearly ideal configuration for the patterned perpendicular recording medium.
Evolution of phase change memory characteristics with operating cycles: Electrical characterization and physical modeling
Authors: Sarkar Joy , Gleixner Bob
Published: December 2007

The authors report an improvement in electrical characteristics with operational cycles of phase change memory cells having Ge2Sb2Te5 as the active material. An increase in amorphous-state resistance and threshold voltage and decrease in crystalline-state resistance with cycling are observed, which can be explained by gradual compositional change of the memory material driven by the energy input during programming operations. It is also found that melting of the active volume is critical for such improvement in the electrical characteristics. A physical model is proposed based on an expanding cell active volume with operating cycles to self-consistently explain the reported electrical data.
Dual broadband photodetector based on interband and intersubband transitions in InAs quantum dots embedded in graded InGaAs quantum wells
Authors: Passmore Brandon S. , Wu Jiang , Manasreh M. O. , Salamo G. J.
Published: December 2007

Two broadband photoresponse from InAs quantum dots embedded in graded InGaAs quantum well photodetectors were observed in the spectral regions of 4–12μm (midinfrared band) and 0.5–1.0μm (near-infrared-visible band). The midinfrared band is attributed to the intersubband transitions within the quantum dots and was observed at temperatures less than 80K. The near-infrared-visible band is attributed to interband transitions and is observed in the temperature range of 77–300K. The room temperature detectivity of the near-infrared-visible band is estimated to be on the order of ∼3.0×108cmHz∕W with a bias voltage less than 1.0V.
Lattice contraction and magnetic and electronic transport properties of Mn3Zn1−xGexN
Authors: Sun Ying , Wang Cong , Wen Yongchun , Zhu Kaigui , Zhao Jingtai
Published: December 2007

The lattice and electronic and magnetic transport properties of the antiperovskite structure Mn3Zn1−xGexN compounds were investigated. For Mn3ZnN, there is a magnetic transition from antiferromagnetic to paramagnetic near 185K. Correspondingly, the resistivity shows an abrupt drop, but any sudden change of lattice parameters is not found. However, it is interesting that the partial substitution of Ge for Zn induces a lattice contraction near the magnetic transition temperature, where a drop of the resistivity remain, and the transition temperature point increases and the temperature range is broadened with increasing doped Ge contents. The thermodynamics properties were also investigated.
Photovoltaic response of a polymer p-i-n junction
Authors: Zhang Yanguang , Hu Yufeng , Gao Jun
Published: December 2007

We report the photovoltaic characterization of a polymer p-i-n junction, realized by in situ electrochemical doping and thermal cycling. The planar, “frozen” p-i-n junction exhibits record-high open-circuit voltage up to 2.25V, and in-plane short-circuit current density in excess of 10mA∕cm2 under simulated sunlight (∼300mW∕cm2). Our results suggest that built-in potential close to the polymer energy gap in magnitude can be obtained in a polymer device structure without the use of dissimilar electrodes, and large short-circuit current density is possible without the use of strong electron acceptors, which limits the open-circuit voltage.
Crucial uncertainties in predicting biological control of DMS emission
Authors: Archer Stephen
Published: December 2007

Environmental context. The CLAW hypothesis, published in Nature in 1987, highlighted the important potential role in climate regulation of dimethyl sulfide (DMS) production in the oceans. Since the hypothesis was presented, it has become increasingly apparent that a complex network of biological and physicochemical processes control DMS emissions from the oceans. The present essay discusses several of the crucial biological controls on DMS production that remain major uncertainties in our ability to decipher whether DMS cycling could contribute to the regulation of a warming climate.
The CLAW hypothesis: a review of the major developments
Authors: Ayers Greg P. , Cainey Jill M.
Published: December 2007

Environmental context. Understanding the role of clouds in the warming and the cooling of the planet and how that role alters in a warming world is one of the biggest uncertainties climate change researchers face. Important in this regard is the influence on cloud properties of cloud condensation nuclei, the tiny atmospheric particles necessary for the nucleation of every single cloud droplet. The anthropogenic contribution to cloud condensation nuclei is known to be large in some regions through knowledge of pollutant emissions; however, the natural processes that regulate cloud condensation nuclei over large parts of the globe are less well understood. The CLAW hypothesis provides a mechanism by which plankton may modify climate through the atmospheric sulfur cycle via the provision of sulfate cloud condensation nuclei. The CLAW hypothesis was published over 20 years ago and has stimulated a great deal of research.
Abstract. The CLAW hypothesis has for 20 years provided the intriguing prospect of oceanic and atmospheric systems exhibiting in an intimately coupled way a capacity to react to changing climate in a manner that opposes the change. A great number of quality scientific papers has resulted, many confirming details of specific links between oceanic phytoplankton and dimethylsulfide (DMS) emission to the atmosphere, the importance of DMS oxidation products in regulation of marine atmospheric cloud condensation nucleus (CCN) populations, and a concomitant influence on marine stratocumulus cloud properties. However, despite various links in the proposed phytoplankton–DMS–CCN–cloud albedo climate feedback loop being affirmed, there has been no overall scientific synthesis capable of adequately testing the hypothesis at a global scale. Moreover, significant gaps and contradictions remain, such as a lack of quantitative understanding of new particle formation processes in the marine atmospheric boundary layer, and of the extent to which dynamical, rather than microphysical, cloud feedbacks exist. Nevertheless, considerable progress has been made in understanding ‘Earth System Science’ involving the integration of ocean and atmospheric systems inherent in the CLAW hypothesis. We present here a short review of this progress since the publication of the CLAW hypothesis.
Sexual dysfunction in men treated with depot antipsychotic drugs: a pilot study
Authors: Plevin David , Galletly Cherrie , Roughan Penny
Published: December 2007

Background: Sexual dysfunction is common, but often under-recognised, in people with schizophrenia. Many antipsychotic drugs are known to cause prolactin elevation, and it is often assumed that sexual dysfunction is a consequence of prolactin elevation. We investigated the relationship between sexual function and serum concentrations of prolactin and testosterone in men receiving regular long-acting depot injections of antipsychotic medication. Methods: Twenty-two men attending a community depot clinic participated. A structured interview was used to collect information about sexual function, and serum prolactin and testosterone concentrations were measured. Results: Sexual dysfunction was common, with 73% of men reporting problems in at least one area of sexual function. Six men had elevated serum prolactin and one had reduced serum testosterone. Antipsychotic drug dose was positively correlated with serum prolactin and negatively correlated with serum testosterone, but there was no association between serum prolactin or testosterone concentrations and any measure of sexual dysfunction. Conclusion: Sexual dysfunction is a major problem for men living with chronic schizophrenia, but our results suggest that it is not directly attributable to elevated prolactin or reduced testosterone concentrations.
Adolescent girls' communication with partners about microbicide use
Authors: Short Mary B. , Ramos Stephanie , Oakes Jennifer K. , Rosenthal Susan L.
Published: December 2007

Background: Topical microbicides could be a female-controlled method of preventing sexually transmissible infections. Despite the possibility of surreptitious use, most women report that they would tell partners, and microbicides may be detectable. The purpose of the present study was to examine communication between adolescent girls and their partners regarding microbicides. Methods: Girls (aged 14–21 years) participated in a 6-month study in which they were given vaginal moisturisers to use when they had intercourse. Data was collected about their demographics, sexual histories and conversations with mothers and partners. Both quantitative and qualitative analyses were conducted. Results: Girls (n = 171) were asked about conversations with their partners. Talking with mothers and using the product were significantly related to talking with partners. Reasons for not talking were intrapersonal or interpersonal variables, the context of the relationship did not warrant an explanation and the lack of a decision to communicate. There seemed to be no difference in conversations for those who used or did not use. Girls had conversations with their partners when deciding to be in the study, when they were engaged in study activities or when deciding to use the product. Conversations about using the product focused on needing to use the product because of study demands, the lubricating properties or wanting to experience product use. Conclusions: Most of the girls talked to their partners and had positive conversations. Girls may need help initiating conversations and managing reluctant partners.
Evaluation, using two assessment instruments, of the American and British national guidelines for the management of sexually transmissible and genital infections
Authors: Baird Aisling , Olarinde Olufunso , Talbot Martin
Published: December 2007

Background: The objective of the present study was to compare, utilising two guideline assessment instruments, six corresponding clinical practice guidelines of the British Association for Sexual Health and HIV and the Centres for Disease Control. Methods: Three raters independently assessed the recently published guidelines for gonorrhoea, chlamydial infection, early syphilis, pelvic inflammatory disease, bacterial vaginosis and HIV testing using two instruments, the Cluzeau and the AGREE (Appraisal of Guidelines for Research and Evaluation instrument). The Cluzeau scores were a simple percentage comparison; the AGREE scores were a standardised score for each guideline development domain. Differences were assessed using the Wilcoxson signed ranks test. Inter-rater variability was calculated on the Cluzeau instrument utilising the intragroup correlation method. Results: The British Association for Sexual Health and HIV guidelines scored higher than the Centres for Disease Control guidelines in many of the assessed domains. There were significant differences between the two in many of the scores (P = 0.026–0.028). Inter-rater concordance was high to very high at 0.70–0.83. Conclusions: There were often major differences in scores between the two guideline groups. It is necessary for wider discussion within the profession to consider the significance of these findings.
Young women's misperceptions about sexually transmissible infection testing: a 'clean and clear' misunderstanding
Authors: Head Sara K. , Crosby Richard A. , Shrier Lydia A. , Moore Gregory R.
Published: December 2007

Background: This exploratory study investigated young women’s perceptions of sexually transmissible infection (STI) testing received during gynaecological care. Correlates of the incorrect perception that STI testing occurred were assessed. Methods: Cross-sectional study of sexually active young women, age 18–24 years, attending a university healthcare setting for gynaecological care (n = 109). Two hundred and four women were approached and 87 were ineligible; of the remaining 117, 93.2% chose to enrol. Results: Of the women enrolled, 25.7% falsely perceived that they were STI tested (labelled ‘clean and clear’). Only approximately one in seven (14.7%) accurately understood the STI for which they were tested. In multivariate analyses, controlling for race, STI symptoms, depression, number of lifetime visits to the gynaecologist, and suspicion of current STI, three variables were significant: minority race (adjusted odds ratio (AOR) = 4.84, confidence interval (CI) = 1.38–16.96, P = 0.01), earlier age at sexual debut (AOR = 4.67, CI = 1.73–12.57, P = 0.002), and previous STI diagnosis (AOR = 3.38, CI = 1.07–10.66, P = 0.04). Comment: The findings suggest that many young women may have an inaccurate understanding of the STI testing they undergo during gynaecological care and may operate under the misperception they are ‘clean and clear’ of STI. Women with said misperception were more likely to be of minority race and report relatively earlier age of sexual debut and previous STI diagnosis. Further investigation is warranted to determine whether the ‘clean and clear’ misperception influences young women’s sexual risk behaviour.
49. SYPHILIS SCREENING PROFILE AT SEXUAL HEALTH CLINIC, ST GEORGE HOSPITAL & SUTHERLAND HOSPITAL
Authors: Tran H. , Konecny P. , Carmody C.
Published: December 2007

A retrospective analysis was conducted to describe the cases of Syphilis identified and managed at Short Street Centre and The Sutherland Sexual Health Centre, in South Eastern Sydney and Illawarra Area, from January 2000 to June 2007. Syphilis serology is routinely offered as part of an STI screen to new and follow-up patients as appropriate. Information on the diagnoses, demographic and other variables was extracted from the clinical database Sexual Health Information Program (SHIP) and analysed in SPSS v11. Information on age, gender, relationship status, country of birth, presenting symptoms, stage of Syphilis, type of treatment and subsequent RPR levels were confirmed from patient records. An analysis of the relative frequency of the stages of Syphilis from over 130 patients will be presented and their relationship to a number of demographic and behavioural factors.
54. CAPITALISING ON THE UNIQUE OPPORTUNITY OF THE HPV VACCINE, FOR A CERVICAL SCREENING PROGRAM
Authors: Rawlings L.
Published: December 2007

The medical advancement of the human papilloma virus (HPV) vaccine and it's swift addition to the National Immunisation Program, caused a sudden surge in the public's awareness and interest in HPV. The challenge for PapScreen Victoria, a state based cervical screening program, was to react quickly and strategically to ensure that this new knowledge did not prevent women from having Pap tests.
PapScreen pre-empted that the vaccine would have a huge impact on the current program, and undertook an educational journey to identify issues. The program sought expert opinions, formulated new partnerships in the immunisation sector and examined the current research.
The program identified that its role was to inform women about HPV and the importance to continue screening in this new era of HPV vaccination. In the prevention of cervical cancer, there was also a role to inform health professionals, parents and young women about the benefits of the vaccine. The challenge was capatilising on the unique opportunity that the vaccine created.
Developing and implementing strategies quickly was paramount in the program's success on capitalising this interest. Across three main areas - community, communications and research - the program implemented a range of strategies, including new resources, media opportunities, formative research and education, among others. PapScreen's aim was to remain the prime source of information for the prevention of cervical cancer in Victoria.
The success of these strategies has been profound and immunisation messages are now included in all program messages across a range of sectors. The program was able to capitalise on this unique occasion by being flexible, proactive and strategically adaptable to the public health environment.
Rapid diversification and dispersal during periods of global warming by plethodontid salamanders
Authors: Vieites David R. , Min Mi-Sook , Wake David B.
Published: December 2007

A phylogeny and timescale derived from analyses of multilocus nuclear DNA sequences for Holarctic genera of plethodontid salamanders reveal them to be an old radiation whose common ancestor diverged from sister taxa in the late Jurassic and underwent rapid diversification during the late Cretaceous. A North American origin of plethodontids was followed by a continental-wide diversification, not necessarily centered only in the Appalachian region. The colonization of Eurasia by plethodontids most likely occurred once, by dispersal during the late Cretaceous. Subsequent diversification in Asia led to the origin of
Hydromantes
and
Karsenia
, with the former then dispersing both to Europe and back to North America. Salamanders underwent rapid episodes of diversification and dispersal that coincided with major global warming events during the late Cretaceous and again during the Paleocene–Eocene thermal optimum. The major clades of plethodontids were established during these episodes, contemporaneously with similar phenomena in angiosperms, arthropods, birds, and mammals. Periods of global warming may have promoted diversification and both inter- and transcontinental dispersal in northern hemisphere salamanders by making available terrain that shortened dispersal routes and offered new opportunities for adaptive and vicariant evolution.
Environmental impacts of divorce
Authors: Yu Eunice , Liu Jianguo
Published: December 2007

Divorce is increasingly common around the world. Its causes, dynamics, and socioeconomic impacts have been widely studied, but little research has addressed its environmental impacts. We found that average household size (number of people in a household) in divorced households (households with divorced heads) was 27–41% smaller than married households (households with married heads) in 12 countries across the world around the year 2000 (between 1998 and 2002). If divorced households had combined to have the same average household size as married households, there could have been 7.4 million fewer households in these countries. Meanwhile, the number of rooms per person in divorced households was 33–95% greater than in married households. In the United States (U.S.) in 2005, divorced households spent 46% and 56% more on electricity and water per person than married households. Divorced households in the U.S. could have saved more than 38 million rooms, 73 billion kilowatt-hours of electricity, and 627 billion gallons of water in 2005 alone if their resource-use efficiency had been comparable to married households. Furthermore, U.S. households that experienced divorce used 42–61% more resources per person than before their dissolution. Remarriage of divorced household heads increased household size and reduced resource use to levels similar to those of married households. The results suggest that mitigating the impacts of resource-inefficient lifestyles such as divorce helps to achieve global environmental sustainability and saves money for households.
Exceptionally well preserved late Quaternary plant and vertebrate fossils from a blue hole on Abaco, The Bahamas
Authors: Steadman David W. , Franz Richard , Morgan Gary S. , Albury Nancy A. , Kakuk Brian , Broad Kenneth , Franz Shelley E. , Tinker Keith , Pateman Michael P. , Lott Terry A. , Jarzen David M. , Dilcher David L.
Published: December 2007

We report Quaternary vertebrate and plant fossils from Sawmill Sink, a “blue hole” (a water-filled sinkhole) on Great Abaco Island, The Bahamas. The fossils are well preserved because of deposition in anoxic salt water. Vertebrate fossils from peat on the talus cone are radiocarbon-dated from ≈4,200 to 1,000 cal BP (Late Holocene). The peat produced skeletons of two extinct species (tortoiseChelonoidisundescribed sp. and CaracaraCaracara creightoni) and two extant species no longer in The Bahamas (Cuban crocodile,Crocodylus rhombifer; and Cooper's or Gundlach's Hawk,Accipiter cooperiiorAccipiter gundlachii). A different, inorganic bone deposit on a limestone ledge in Sawmill Sink is a Late Pleistocene owl roost that features lizards (one species), snakes (three species), birds (25 species), and bats (four species). The owl roost fauna includesRallusundescribed sp. (extinct; the first Bahamian flightless rail) and four other locally extinct species of birds (Cooper's/Gundlach's Hawk,A. cooperii/gundlachii; flickerColaptessp.; Cave Swallow,Petrochelidon fulva; and Eastern Meadowlark,Sturnella magna) and mammals (Bahamian hutia,Geocapromys ingrahami; and a bat,Myotissp.). The exquisitely preserved fossils from Sawmill Sink suggest a grassy pineland as the dominant plant community on Abaco in the Late Pleistocene, with a heavier component of coppice (tropical dry evergreen forest) in the Late Holocene. Important in its own right, this information also will help biologists and government planners to develop conservation programs in The Bahamas that consider long-term ecological and cultural processes.
Runx2 deficiency and defective subnuclear targeting bypass senescence to promote immortalization and tumorigenic potential
Authors: Zaidi Sayyed K. , Pande Sandhya , Pratap Jitesh , Gaur Tripti , Grigoriu Simina , Ali Syed A. , Stein Janet L. , Lian Jane B. , van Wijnen Andre J. , Stein Gary S.
Published: December 2007

The osteogenic Runt-related (Runx2) transcription factor negatively regulates proliferation and ribosomal gene expression in normal diploid osteoblasts, but is up-regulated in metastatic breast and prostate cancer cells. Thus, Runx2 may function as a tumor suppressor or an oncogene depending on the cellular context. Here we show that Runx2-deficient primary osteoblasts fail to undergo senescence as indicated by the absence of β-gal activity and p16
INK4a
tumor suppressor expression. Primary Runx2-null osteoblasts have a growth advantage and exhibit loss of p21
WAF1/CIP1
and p19
ARF
expression. Reintroduction of WT Runx2, but not a subnuclear targeting-defective mutant, induces both p21
WAF/CIP1
and p19
ARF
mRNA and protein resulting in cell-cycle inhibition. Accumulation of spontaneous phospho-H2A.X foci, loss of telomere integrity and the Mre11/Rad50/Nbs1 DNA repair complex, and a delayed DNA repair response all indicate that Runx2 deficiency leads to genomic instability. We propose that Runx2 functions as a tumor suppressor in primary diploid osteoblasts and that subnuclear targeting contributes to Runx2-mediated tumor suppression.
Real-time observation of bacteriophage T4 gp41 helicase reveals an unwinding mechanism
Authors: Lionnet Timothée , Spiering Michelle M. , Benkovic Stephen J. , Bensimon David , Croquette Vincent
Published: December 2007

Helicases are enzymes that couple ATP hydrolysis to the unwinding of double-stranded (ds) nucleic acids. The bacteriophage T4 helicase (gp41) is a hexameric helicase that promotes DNA replication within a highly coordinated protein complex termed the replisome. Despite recent progress, the gp41 unwinding mechanism and regulatory interactions within the replisome remain unclear. Here we use a single tethered DNA hairpin as a real-time reporter of gp41-mediated dsDNA unwinding and single-stranded (ss) DNA translocation with 3-base pair (bp) resolution. Although gp41 translocates on ssDNA as fast as the
in vivo
replication fork (≈400 bp/s), its unwinding rate extrapolated to zero force is much slower (≈30 bp/s). Together, our results have two implications: first, gp41 unwinds DNA through a passive mechanism; second, this weak helicase cannot efficiently unwind the T4 genome alone. Our results suggest that important regulations occur within the replisome to achieve rapid and processive replication.
Perceptual detection as a dynamical bistability phenomenon: A neurocomputational correlate of sensation
Authors: Deco Gustavo , Pérez-Sanagustín Mar , de Lafuente Victor , Romo Ranulfo
Published: December 2007

Recent studies that combined psychophysical/neurophysiological experiments [de Lafuente V, Romo R (2005)
Nat Neurosci
8:1698–1703] analyzed the responses from single neurons, recorded in several cortical areas of parietal and frontal lobes, while trained monkeys reported the presence or absence of a mechanical vibration of varying amplitude applied to skin of one fingertip. The analysis showed that the activity of primary somatosensory cortex neurons covaried with the stimulus strength but did not covary with the animal's perceptual reports. In contrast, the activity of medial premotor cortex (MPC) neurons did not covary with the stimulus strength but did covary with the animal's perceptual reports. Here, we address the question of how perceptual detection is computed in MPC. In particular, we regard perceptual detection as a bistable neurodynamical phenomenon reflected in the activity of MPC. We show that the activity of MPC is consistent with a decision-making-like scenario of fluctuation-driven computation that causes a probabilistic transition between two bistable states, one corresponding to the case in which the monkey detects the sensory input, the other corresponding to the case in which the monkey does not. Moreover, the high variability activity of MPC neurons both within and between trials reflects stochastic fluctuations that may play a crucial role in the monkey's probabilistic perceptual reports.
Localizing frustration in native proteins and protein assemblies
Authors: Ferreiro Diego U. , Hegler Joseph A. , Komives Elizabeth A. , Wolynes Peter G.
Published: December 2007

We propose a method of quantifying the degree of frustration manifested by spatially local interactions in protein biomolecules. This method of localization smoothly generalizes the global criterion for an energy landscape to be funneled to the native state, which is in keeping with the principle of minimal frustration. A survey of the structural database shows that natural proteins are multiply connected by a web of local interactions that are individually minimally frustrated. In contrast, highly frustrated interactions are found clustered on the surface, often near binding sites. These binding sites become less frustrated upon complex formation.
How Does Being Female Assist Help-Seeking for Mental Health Problems?
Authors: Judd Fiona , Komiti Angela , Jackson Henry
Published: December 2007

Objective: In Australia the prevalence of mental health problems does not vary by gender, but help-seeking and service utilization do. The aim of the present study was to examine a number of attitudinal factors that may influence help-seeking for mental health problems.

Method: A cross-sectional community survey was conducted with a sample of 579 rural residents (57.9% female), who completed self-report measures assessing stoicism, alexithymia, perceived and personal stigma and the various facets of the personality trait of openness to experience.

Results: Men scored higher on measures of stoicism and personal stigma associated with mental health problems than women, and compared to women had lower scores on the facets of openness to experience.

Conclusions: Higher rates of help-seeking for mental health problems by women may be due to lower levels of stoicism and personal stigma related to mental health problems in women compared to men.
Searching the Internet for Drug‐Related Web Sites: Analysis of Online Available Information on Ecstasy (MDMA)
Authors: Deluca Paolo , Schifano Fabrizio ,   for the Psychonaut 2002 Research Group
Published: December 2007

Although the Internet is a growing source of information on MDMA/ecstasy, no studies so far have investigated the level and quality of ecstasy information available to the typical Web user. In the present study, 280 Web sites were identified and analyzed; 50.4% had an anti‐drug approach, 16.2% a harm reduction approach, and 24.8% a pro‐drug approach. MDMA pro‐drug Web sites appeared significantly earlier in the search engines' results list than both anti‐drug and harm reduction Web sites (F (3; 159) = 3.288; p = .022). This study represents the first systematic analysis of information available online on ecstasy. Implications for further research are discussed.
The CAGE as a Measure of Hazardous Drinking in the Homeless
Authors: Hesse Morten , Thiesen Henrik
Published: December 2007

The aim of this study was to test the validity of the CAGE questions as a measure of severe drinking in subjects at drop‐in centers for the homeless, using biological markers of acute liver reaction to alcohol as the “gold standard.” A sample of homeless men and women in Copenhagen were invited to participate in a study of health problems. Subjects were interviewed and blood samples were taken and screened for indicators of liver dysfunction (gamma‐glutamyltransferase [γGT], mean corpuscular volume [MCV], alanine aminotransferase [ALAT], and alkaline phosphatase [Alpase]), and hepatitis C [HCV]. Scores on CAGE correlated strongly with years of heavy drinking (rho = 0.43, p < 0.001), and while years of drinking did not correlate with biomarkers after controlling for multiple hypothesis testing, CAGE correlated with γGT, Alpase and ALAT, but not MCV. The correlations held even among those without HCV, but subjects with HCV + and CAGE > 1 had quite extreme values on liver markers. Findings suggested that the CAGE was able to identify homeless drinkers whose drinking was signifantly associated with increases in biomarkers associated with heavy drinking.
Perception of Smoking‐Related Health Consequences among Pregnant and Non‐Pregnant Women
Authors: Ortendahl Monica , Näsman Per
Published: December 2007

The objective was to examine the perception of smoking‐related health consequences and its relationship to pregnancy and intent to quit. Over a two‐week period, pregnant and non‐pregnant women, intending and not intending to quit smoking, rated the probability for smoking‐related health consequences to occur, given continuing to smoke and quitting smoking. Pregnant women who did not intend to quit smoking exhibited the lowest estimated probability for the smoking‐related health consequences to occur if they continued smoking. For all women, there was a statistically significant estimated effect of quitting smoking. Renewed attention needs to be given to perceptions of health risks of smoking, especially among pregnant women.
The Impact of Personality Disorders on Alcohol‐Use Outcomes in a Pharmacotherapy Trial for Alcohol Dependence and Comorbid Axis I Disorders
Authors: Ralevski Elizabeth , Ball Samuel , Nich Charla , Limoncelli Diana , Petrakis Ismene
Published: December 2007

Although antisocial and borderline personality disorders frequently co‐occur with alcohol dependence and other Axis I disorders, their effect on alcohol use outcomes in context of pharmacotherapy remains unclear. Patients with Major Axis I disorders, including alcohol dependence, and diagnosis of antisocial (ASPD) or borderline personality disorder (BPD) were enrolled in a 12‐week medication trial for treatment of their alcohol dependence. Everyone was randomized to one of four cells: naltrexone alone, placebo alone, open label disulfiram and naltrexone, or open label disulfiram and placebo. Outcome measures included scales for alcohol use and craving. Data were analyzed comparing patients with ASPD vs. those without, and patients with BPD vs. those without. Diagnosis of personality disorder did not adversely affect alcohol outcomes, and patients with ASPD or BPD did not have a poorer response to medication than patients without diagnosis of ASPD or BPD. The findings suggest that naltrexone and disulfiram can be safely and effectively used with patients who have comorbid diagnoses of Axis I and Axis II disorders.
Height 0 characters of finite groups of Lie type
Authors: Malle Gunter
Published: December 2007

We give a classification of irreducible characters of finite groups of Lie type of

p
′

p’

-degree, where

p
p

is any prime different from the defining characteristic, in terms of local data. More precisely, we give a classification in terms of data related to the normalizer of a suitable Levi subgroup, which in many cases coincides with the normalizer of a Sylow

p
p

-subgroup. The McKay conjecture asserts that there exists a bijection between characters of

p
′

p’

-degree of a group and of the normalizer of a Sylow

p
p

-subgroup. We hope that our result will constitute a major step towards a proof of this conjecture for groups of Lie type, and, in conjunction with a recent reduction result of Isaacs, Malle and Navarro, for arbitrary finite groups.
Association studies for untyped markers with TUNA
Authors: Wen Xiaoquan , Nicolae Dan L.
Published: December 2007

Summary: The software package TUNA (Testing UNtyped Alleles) implements a fast and efficient algorithm for testing association of genotyped and ungenotyped variants in genome-wide case-control studies. TUNA uses Linkage Disequilibrium (LD) information from existing comprehensive variation datasets such as HapMap to construct databases of frequency predictors using linear combination of haplotype frequencies of genotyped SNPs. The predictors are used to estimate untyped allele frequencies, and to perform association tests. The methods incorporated in TUNA achieve great accuracy in estimation, and the software is computationally efficient and does not demand a lot of system memory and CPU resources.

Availability: The software package is available for download from the website: http://www.stat.uchicago.edu/~wen/tuna/

Contact:  nicolae@galton.uchicago.edu
Guaraná′s Journey from Regional Tonic to Aphrodisiac and Global Energy Drink
Authors: Smith Nigel , Atroch André Luiz
Published: December 2007

Guaraná (Paullinia cupana H.B.K., Sapindaceae) is a rainforest vine that was domesticated in the Amazon for its caffeine‐rich fruits. Guaraná has long been used as a tonic and to treat various disorders in Brazil and abroad and became a national soda in Brazil about a century ago. In the last two decades or so, guaraná has emerged as a key ingredient in various ‘sports’ and energy drinks as well as concoctions that allegedly boost one′s libido. For some time, guaraná′s high caffeine content was thought to be a detriment because of health concerns about excessive intake of caffeine‐rich drinks. But it is precisely this quality, and the fact that it has a mysterious name and comes from an exotic land, that has propelled guaraná into a global beverage.