bluuebunny/crossref_metadata_2025 huggingface dataset:
Materials processing issues influencing the frequency stability of the initial magnetic permeability of MnZn ferrites
Authors: Hanuszkiewicz J. , Holz D. , Eleftheriou E. , Zaspalis V.
Published: May 2008

The frequency behavior of the initial permeability of MnZn ferrites is generally described by Snoek’s law related to gyromagnetic resonance. However, in polycrystalline systems, for the same initial permeability, the frequency stability can be tailored by modifying the specific resistivity of the grain boundaries. This is achieved through the accumulation of high resistivity doping phases along the grain boundaries. The grain boundary specific resistivity may decrease or increase with increasing the average grain size depending on the ferrite composition and the extent of dopant segregation. In order to explain the experimental results and to account for the permeability dependency on the specific resistivity, a modification of the nonmagnetic grain boundary model is proposed to a less magnetic grain boundary model, where not the thickness but the initial permeability of the grain boundary layer is the main variable that is influenced by the process parameters.
The magnetic field effect on the transport and efficiency of group III tris(8-hydroxyquinoline) organic light emitting diodes
Authors: Shakya P. , Desai P. , Somerton M. , Gannaway G. , Kreouzis T. , Gillin W. P.
Published: May 2008

Magnetoresistance and efficiency measurements of organic light emitting diode structures based on the group III hydroxyquinolates (Mq3) have been made as a function of magnetic field and Mq3 thickness, where M=Al, Ga, and In. For all quinolates, independent of thickness, we observed very similar behavior for the efficiency of the devices, with large increases in efficiency occurring at low values of applied field, which rapidly saturate as the field is increased. The current through these devices is found to be a strong function of both the device thickness and the metal ion. For Alq3 based devices, the current changes appear to correlate strongly with the triplet population in the devices. For Gaq3 and Inq3 devices, the magnetoresistance is found not to correlate with the triplet concentration and this may be evidence that there is little energetic barrier for carrier trapping in these materials. For all materials, a further dependence of the magnetoresistance on applied field was observed, which needs closer investigation.
Quintics with finite simple symmetries
Authors: Luhn Christoph , Ramond Pierre
Published: June 2008

We construct all quintic invariants in five variables with simple non-Abelian finite symmetry groups. These define Calabi–Yau threefolds which are left invariant by the action of A5, A6, or PSL2(11).
Gradiometric micro-SQUID susceptometer for scanning measurements of mesoscopic samples
Authors: Huber Martin E. , Koshnick Nicholas C. , Bluhm Hendrik , Archuleta Leonard J. , Azua Tommy , Björnsson Per G. , Gardner Brian W. , Halloran Sean T. , Lucero Erik A. , Moler Kathryn A.
Published: May 2008

We have fabricated and characterized micro-SQUID susceptometers for use in low-temperature scanning probe microscopy systems. The design features the following: a 4.6μm diameter pickup loop; an integrated field coil to apply a local field to the sample; an additional counterwound pickup-loop/field-coil pair to cancel the background signal from the applied field in the absence of the sample; modulation coils to allow setting the SQUID at its optimum bias point (independent of the applied field), and shielding and symmetry that minimizes coupling of magnetic fields into the leads and body of the SQUID. We use a SQUID series array preamplifier to obtain a system bandwidth of 1MHz. The flux noise at 125mK is approximately 0.25μΦ0∕Hz above 10kHz, with a value of 2.5μΦ0∕Hz at 10Hz. The nominal sensitivity to electron spins located at the center of the pickup loop is approximately 200μB∕Hz above 10kHz, in the white-noise frequency region.
Evidence for an indirect gap in β−FeSi2 epilayers by photoreflectance spectroscopy
Authors: Birdwell A. G. , Littler C. L. , Glosser R. , Rebien M. , Henrion W. , Stauβ P. , Behr G.
Published: May 2008

Photoreflectance spectra obtained from epitaxial films of semiconducting β−FeSi2 exhibit complex line shapes resulting from a variety of optical transitions. While we have previously established a direct gap at 0.934±0.002eV at 75K, we find an additional weak structure at a lower energy. We attribute the origin of this spectral feature to indirect transitions assisted by the emission of a phonon. From our analysis, we determine an indirect gap energy of 0.823±0.002eV at 75K.
In situ probing electrical response on bending of ZnO nanowires inside transmission electron microscope
Authors: Liu K. H. , Gao P. , Xu Z. , Bai X. D. , Wang E. G.
Published: May 2008

In situ electrical transport measurements on individual bent ZnO nanowires have been performed inside a high-resolution transmission electron microscope, where the crystal structures of ZnO nanowires were simultaneously imaged. A series of consecutively recorded current-voltage (I-V) curves along with an increase in nanowire bending show the striking effect of bending on their electrical behavior. The bending-induced changes of resistivity, electron concentration, and carrier mobility of ZnO nanowires have been retrieved based on the experimental I-V data, which suggests the applications of ZnO nanowires as nanoelectromechanical sensors.
A synthetic heterodyne interferometer for small amplitude of vibration measurement
Authors: Kang Seonggu , La Jongpil , Yoon Heesun , Park Kyihwan
Published: June 2008

The homodyne interferometer has the advantages of simple optical configuration and low cost. However, it requires a caution in using an electronic filter such as high pass filter (HPF) to get rid of low frequency electronic noises and the dc offset associated with the optical intensity in the photodiode electronic circuitry. When the vibration amplitude is smaller than at least 1∕2 of the wavelength of He–Ne laser, a problem of incorrect velocity or distorted velocity measurement can be caused since a dc value of the interference signal is eliminated by using the HPF. To solve this problem of using the HPF in the homodyne interferometer, a synthetic interferometer using a mechanical modulation method is proposed in this work by exciting a reference mirror with the displacement larger than 1∕2 of the wavelength. In this work, the analytical work is presented to show how the synthetic interferometer solves the problem of incorrect velocity measurement by using the Fourier–Bessel function description of the interference signals. Simulation and experimental works are also presented to validate the synthetic heterodyne interferometer proposed in this work.
Far infrared absorption and terahertz time domain spectroscopy of liquid CS2: Experiments and molecular dynamics simulation
Authors: Danten Y. , Besnard M. , Delagnes J. C. , Mounaix P.
Published: May 2008

The far infrared absorption spectrum of liquid CS2 has been measured up to 3.5THz by using time domain spectroscopy. The validity of the spectral features has been assessed from a comparison with experimental data reported in literature. The absorption profile has been interpreted on the ground of an induction mechanism model by using molecular dynamics simulation.
Resonant spin polarization and Hall effects in a two-dimensional electron gas
Authors: Zhang Degang , Mu Yao-Ming , Ting C. S.
Published: May 2008

We have studied transport properties in a two-dimensional electron gas with equal Rashba and Dresselhaus spin-orbit interactions under a perpendicular magnetic field. By employing the exact solution for this system, we found resonant charge and spin Hall conductances at a certain magnetic field, where all the nearest neighboring Landau levels cross. Near this value of magnetic field, there exists a resonant spin polarization, which can also induce resonant charge and spin Hall effects.
Defects limiting performance of devices fabricated on GaN/metal heterostructure
Authors: Maximenko Serguei I. , Freitas Jaime A. , Mittereder Jeffrey A. , Rowland Larry B. , Kim Jihyun
Published: May 2008

Ni Schottky barrier contacts were processed to characterize quality and suitability of GaN films grown on (111) face of titanium carbide metallic substrates for vertical device application. We found that defects such as voids (pores) in the GaN film strongly influence the optical and electrical properties of the epitaxial layers. Micro-Raman studies showed that these voids have a high concentration of free carriers. Schottky barrier contacts placed on the regions with high defect density are characterized by high leakage current. Barrier height of Schottky contacts containing smaller number of defects were typically around 0.72eV.
Effect of manganese doping on remnant polarization and leakage current in (K0.44,Na0.52,Li0.04)(Nb0.84,Ta0.10,Sb0.06)O3 epitaxial thin films on SrTiO3
Authors: Abazari M. , Akdoğan E. K. , Safari A.
Published: May 2008

Single phase, epitaxial, ⟨001⟩ oriented, undoped and 1mol% Mn-doped (K0.44,Na0.52,Li0.04)(Nb0.84,Ta0.10,Sb0.06)O3 thin films of 400nm thickness were synthesized on SrRuO3 coated SrTiO3. Such films exhibit well saturated hysteresis loops and have a spontaneous polarization (Ps) of 10μC∕cm2, which is a 150% higher over the Ps of the undoped composition. The coercive field of 1mol% Mn doped films is 13kV∕cm. Mn-doping results in three orders of magnitude decrease in leakage current above 50kV∕cm electric field, which we attribute to the suppression of intrinsic p-type conductivity of undoped films by Mn donors.
Flexible image sensor array with bulk heterojunction organic photodiode
Authors: Ng Tse Nga , Wong William S. , Chabinyc Michael L. , Sambandan Sanjiv , Street Robert A.
Published: May 2008

Thick organic bulk heterojunction photodiodes with low dark current <1nA∕cm2 and efficient charge collection are reported. An electric field >1V∕μm is sufficient to achieve >75% charge collection in films of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene-vinylene] and [6,6]-phenyl-C61-butyric acid methyl ester blends up to 4μm thick, and the rate of photocurrent decay is reduced at saturation fields. The integration of a 4μm thick sensor layer onto a flexible amorphous silicon thin-film transistor backplane gave an image sensor array with 35% external quantum efficiency and noise equivalent power of 30pW∕cm2 at reverse bias voltage of −4V.
High-dome blisters formed by deuterium-induced local superplasticity
Authors: Shu W. M.
Published: May 2008

The high-dome blisters appearing on tungsten after deuterium plasma exposure at around 500K are considered to be generated by the diffusion and agglomeration of the deuterium-vacancy clusters, and this kind of deformation is called as deuterium-induced local superplasticity. There were cavities inside the blisters smaller than a few micrometers, whereas there were no hollow lids formed for some blisters greater than a few micrometers, which is contrary to the typical feature of blisters reported before.
Achieving large macroscopic compressive plastic deformation and work-hardening-like behavior in a monolithic bulk metallic glass by tailoring stress distribution
Authors: Chen L. Y. , Ge Q. , Qu S. , Jiang Q. K. , Nie X. P. , Jiang J. Z.
Published: May 2008

The limited plastic deformation and lack of work hardening seriously restrict the applications of bulk metallic glasses (BMGs). Here, large macroscopic compressive plastic deformation (over 15%) and work-hardening-like behavior were achieved in a monolithic BMG through tailoring loading stress distribution experimentally. Numerical analysis was also carried out to investigate the stress distribution under the same mechanical condition. It is shown that loading induced stress gradient is responsible for the achievement mentioned above.
Strengthened lithium for x-ray blast windows
Authors: Pereira N. R. , Imam M. A.
Published: June 2008

Lithium’s high x-ray transparency makes it an attractive material for windows intended to protect soft x-ray diagnostics in high energy density experiments. Pure lithium is soft and weak, but lithium mixed with lithium hydride powder becomes harder and stronger, in principle without any additional x-ray absorption. A comparison with the standard material for x-ray windows, beryllium, suggests that lithium or lithium strengthened by lithium hydride may well be an excellent option for such windows.
Concentric ring pattern formation in heated chromium-gold thin films on silicon
Authors: Randhawa Jatinder S. , Bernfeld Adam , Keung Michael , Volinsky Alex A. , Gracias David H.
Published: May 2008

Patterns that formed spontaneously upon heating thermally evaporated thin films of gold (Au) and chromium (Cr) on silicon (Si) substrates to 500°C were investigated. A variety of patterns were observed. The type of pattern formed correlated with the thickness ratio of Cr to Au. The most striking pattern consisted of concentric rings spaced approximately 10–30μm apart. Each ring was composed of pits 2–5μm in length, which extended 200–400nm into the silicon substrate. While concentric patterns are widely seen in chemical reaction-diffusion systems, pattern formation in the heated Au∕Cr∕Si system has not been previously observed.
Classical Coulomb blockade of a silicon nanowire dot
Authors: Huang Shaoyun , Fukata Naoki , Shimizu Maki , Yamaguchi Tomohiro , Sekiguchi Takashi , Ishibashi Koji
Published: May 2008

Single electron transistors (SETs) have been fabricated with an individual n-type single-crystal silicon nanowire (SiNW) that was grown by a catalytic chemical vapor deposition technique, and their transport properties have been measured in low temperatures. The SiNW-SET in the present work exhibited well pronounced Coulomb oscillations in a wide gate voltage range from −10to10V, featuring in uniform peak height, uniform full width at half maximum, and equidistant peak spacing. The charging energy turned out to be 64μeV. The temperature dependence of Coulomb oscillations revealed that the dot worked within the classical Coulomb blockade model.
Effect of buffer gas ratios on the relationship between cell temperature and frequency shifts of the coherent population trapping resonance
Authors: Deng K. , Guo T. , He D. W. , Liu X. Y. , Liu L. , Guo D. Z. , Chen X. Z. , Wang Z.
Published: May 2008

We studied the relationship between pressure ratio of the buffer gases (argon and neon) and the rate of coherent population trapping resonance frequency shift with cell temperature in Rb85. We found that when the total pressure of the buffer gases varies within the range of 5–15kPa, the frequency shift rate varies along a bell shaped curve. Every curve crossed the horizontal axis at two points that are roughly symmetrical with respect to the midpoint at 1:1. This allows us to minimize the rate of frequency shift by adjusting the pressure ratio of the buffer gases to these two points.
Characteristics of HIV diagnoses in Australia, 1993-2006
Authors: Guy Rebecca J. , McDonald Ann M. , Bartlett Mark J. , Murray Jo C. , Giele Carolien M. , Davey Therese M. , Appuhamy Ranil D. , Knibbs Peter , Coleman David , Hellard Margaret E. , Grulich Andrew E. , Kaldor John M.
Published: June 2008

Objective: To describe recent trends in the diagnosis of HIV infection in Australia. Methods: National HIV surveillance data from 1993 to 2006 were analysed with a focus on geographic differences by HIV exposure route and late presentation (HIV within 3 months of a first AIDS-defining illness or a CD4 count of less than 200 cells μL–1). Results: In 1993–99, the number of HIV diagnoses declined by 32%, and then increased by 39% from 1999 to 2006. From 2000 onwards, rates increased significantly in Victoria, Queensland, South Australia and Western Australia. The most frequently reported routes of HIV exposure were male to male sex (71%) and heterosexual contact (18%), and the population rate of diagnoses have increased in both categories. Among the cases reported as heterosexually acquired (n = 2199), 33% were in people born in a high-prevalence country and 19% in those with partners from a high-prevalence country. Late presentation was most frequent in heterosexually acquired infections in persons who had a partner from a high-prevalence country: 32% compared with 20% overall. Conclusions: Recent increases in annual numbers of HIV diagnoses in Australia underline the continuing need for HIV-prevention programs, particularly among men having male to male sex. Early diagnosis and access to care and treatment should also be emphasised, as a substantial proportion of people with HIV infection are unaware of their status until late in the course of disease.
Trends in HIV prevalence among homosexual and bisexual men in eastern Australian states
Authors: Prestage Garrett , Jin Fengyi , Zablotska Iryna , Imrie John , Kaldor John M. , Grulich Andrew E.
Published: June 2008

Objectives: In Australia, HIV notification rates in homosexual men, previously much higher in New South Wales, have become similar across the eastern states. We examined whether trends in HIV prevalence in community-based samples of homosexual men were consistent with the trends in HIV notifications. Methods: We examined data on self-reported HIV status from annual cross-sectional, self-completed anonymous surveys of homosexual men conducted between 1998 and 2006 in Sydney, Melbourne and Brisbane. Men were recruited at gay community venues, clinics and large gay community events. We calculated age-specific and age-standardised HIV prevalence rates. Comparisons of HIV prevalence between the three cities and across time were carried out using age-specific rates, and using logistic regression, controlling for age. Results: Men recruited from clinics had a much higher prevalence of HIV (P < 0.001) and were excluded from further analyses. Among the 50 239 completed questionnaires obtained at non-clinic sites, there was a marked decline in aged-standardised HIV prevalence in Sydney (from 14.2 to 8.98%, P < 0.001), a small decline in Brisbane (from 8.51 to 6.94%, P = 0.012) and no change in Melbourne (from 8.35 to 8.06%, P = 0.848). There were significant declines in men aged less than 50 years in Sydney, and in men aged less than 30 years in Brisbane. In Melbourne there was no significant trend in HIV at any age. Conclusion: HIV prevalence among young homosexual men has declined in Sydney, and these data suggest that HIV incidence among homosexual men is now similar in the eastern state capitals of Australia.
Differing trends in sexual risk behaviours in three Australian states: New South Wales, Victoria and Queensland, 1998-2006
Authors: Zablotska Iryna B. , Prestage Garrett , Grulich Andrew E. , Imrie John
Published: June 2008

Background: In Australia, the HIV epidemic is concentrated among gay men. In recent years, the number of new diagnoses stabilised in New South Wales (NSW), but increased in other states. We reviewed the trends in sexual behaviours to explain this difference. Methods: We used the Gay Community Periodic Surveys in NSW, Victoria and Queensland during 1998–2006 and restricted analyses to the 30–49 year olds who contribute most of the HIV cases. We used the χ2-test for trends in unprotected anal intercourse with casual partners (UAIC) and regular partners, number of partners, type of relationships, knowledge of HIV serostatus and its disclosure. We compared behaviours of HIV-positive and -negative men and men across states using logistic regression adjusted for the year of report. Results: Trends in behaviours differed across the states: following a period of increase, UAIC prevalence declined in NSW since 2001, but continued to increase in Victoria and Queensland. There were other changes in NSW that were not observed in Victoria and Queensland: a decline in factors increasing HIV risk (the proportions of men with multiple sex partners and men engaging in UAIC and not knowing or not disclosing HIV serostatus) and an increase in behaviours reducing it (the proportions of men in monogamous relationships and men disclosing HIV serostatus while having UAIC). Conclusion: There were patterns of declining HIV risk behaviours in NSW, and increasing risk behaviours elsewhere, that mirrored recent changes in HIV case notifications in Australia. These data suggest that behavioural surveillance can predict changes in HIV epidemiology.
Trends in HIV testing among homosexual and bisexual men in eastern Australian states
Authors: Prestage Garrett , Jin Fengyi , Zablotska Iryna B. , Imrie John , Grulich Andrew E. , Pitts Marian
Published: June 2008

Objectives: We examined whether trends in HIV testing in community-based samples of homosexual men may account for the convergence in HIV notification rates in homosexual men across the eastern states of Australia. Methods: We examined data on self-reported HIV testing from annual cross-sectional, self-completed anonymous surveys of homosexual men conducted between 1998 and 2006 in Sydney, Melbourne and Brisbane. Men were recruited at gay community venues and events. Comparisons of HIV testing between the three cities and across time were carried out. We also compared reported rates of HIV testing across states in Private Lives, the 2005 online survey of health and wellbeing among non-heterosexual people. Results: Men recruited from clinics had a much higher prevalence of HIV testing and were excluded from further analyses. Among the 48 263 completed questionnaires obtained in non-clinic sites, there was a marked decline in the proportion of men who had never been tested for HIV in Sydney (from 8.1 to 5.1%, P trend < 0.001) and Brisbane (from 11.8 to 7.9%, P trend = 0.002) but no change in Melbourne. This proportion of men who had never been tested was lower in Sydney than in either Melbourne or Brisbane (P < 0.001). There were increases in the proportion of non-HIV-positive men who had been tested for HIV in the previous year across all three cities, although the proportion in Melbourne was lower than in the other two cities. Conclusion: These data suggest that changes in HIV testing rates among homosexual men are insufficient to account for the recent differences in trends in HIV notifications in eastern Australia.
Could sexually transmissible infections be contributing to the increase in HIV infections among men who have sex with men in Australia?
Authors: Middleton Melanie G. , Grulich Andrew E. , McDonald Ann M. , Donovan Basil , Hocking Jane S. , Kaldor John M.
Published: June 2008

Background: To review existing data on sexually transmissible infections (STI) in men who have sex with men in Australia in order to determine the possible contribution of STI to diverging trends in HIV notifications in different states. Methods: We reviewed data from multiple sources, including routine national surveillance data, laboratory surveillance data, self-reported information on STI testing in men who have sex with men and ad hoc reports of STI prevalence. Results: We found increasing rates of gonorrhoea and infectious syphilis notifications in urban men in Australia between 1997 and 2006, and increasing rates of chlamydia notifications in men aged 30–49 years. There was little difference in these trends by state. Differences in the population groups sampled meant we were unable to gain further information on trends in men who have sex with men from these studies. Data on STI testing showed an increase in anal STI testing between 2003 and 2006, which may have increased the number of diagnoses of chlamydia and gonorrhoea for men who have sex with men during this period. Conclusions: Over the past 10 years, there has been a substantial increase in diagnoses of gonorrhoea and infectious syphilis, and probably chlamydia, in men who have sex with men in Australia. However, it is unlikely that changes in the pattern of STI transmission are responsible for the recent divergence in HIV rates between Australian states because there is little evidence that trends in STI also differ by state.
Impact of geoengineering schemes on the global hydrological cycle
Authors: Bala G. , Duffy P. B. , Taylor K. E.
Published: May 2008

The rapidly rising CO
2
level in the atmosphere has led to proposals of climate stabilization by “geoengineering” schemes that would mitigate climate change by intentionally reducing solar radiation incident on Earth's surface. In this article we address the impact of these climate stabilization schemes on the global hydrological cycle. By using equilibrium climate simulations, we show that insolation reductions sufficient to offset global-scale temperature increases lead to a decrease in global mean precipitation. This occurs because solar forcing is more effective in driving changes in global mean evaporation than is CO
2
forcing of a similar magnitude. In the model used here, the hydrological sensitivity, defined as the percentage change in global mean precipitation per degree warming, is 2.4% K
−1
for solar forcing, but only 1.5% K
−1
for CO
2
forcing. Although other models and the climate system itself may differ quantitatively from this result, the conclusion can be understood based on simple considerations of the surface energy budget and thus is likely to be robust. For the same surface temperature change, insolation changes result in relatively larger changes in net radiative fluxes at the surface; these are compensated by larger changes in the sum of latent and sensible heat fluxes. Hence, the hydrological cycle is more sensitive to temperature adjustment by changes in insolation than by changes in greenhouse gases. This implies that an alteration in solar forcing might offset temperature changes or hydrological changes from greenhouse warming, but could not cancel both at once.
Acid sphingomyelinase involvement in tumor necrosis factor α-regulated vascular and steroid disruption during luteolysis
in vivo
Authors: Henkes Luiz E. , Sullivan Brian T. , Lynch Maureen P. , Kolesnick Richard , Arsenault Danielle , Puder Mark , Davis John S. , Rueda Bo R.
Published: May 2008

TNF is well known for its role in inflammation, including direct effects on the vasculature. TNF also is implicated in the regulation of reproduction by its actions to affect ovarian steroidogenic cells and to induce apoptosis of corpus luteum (CL)-derived endothelial cells
in vitro
. We hypothesized that the disruption of TNF signaling would postpone the regression of the highly vascularized CL
in vivo
, and this effect could be replicated in mutant mouse models lacking TNF receptor (TNFRI
−/−
) and/or a critical enzyme of TNF signaling, acid sphingomyelinase (ASMase
−/−
). In the current study, the treatment of pseudopregnant mice with the luteolytic mediator prostaglandin F2-α (PGF) significantly increased TNF in the ovaries when compared with saline-treated controls. Treatment with PGF also reduced serum progesterone (P4) concentrations and caused involution of the CL. However, pretreatment of pseudopregnant mice with Etanercept (ETA), a TNF-neutralizing antibody, inhibited the PGF-induced decrease in P4 and delayed luteal regression. A similar outcome was evident in pseudopregnant TNFRI
−/−
animals. Treatment of luteal microvascular endothelial cells (MVECs) with TNF provoked a significant increase in ASMase activity when compared with the corresponding controls. Furthermore, TNF-induced MVEC death was inhibited in the ASMase
−/−
mice. The ASMase
−/−
mice displayed no obvious evidence of luteal regression 24 h after treatment with PGF and were resistant to the PGF-induced decrease in P4. Together these data provide evidence that TNF plays an active role in luteolysis. Further studies are required to determine the deleterious effects of anti-inflammatory agents on basic ovarian processes.
Independent origins of syringyl lignin in vascular plants
Authors: Weng Jing-Ke , Li Xu , Stout Jake , Chapple Clint
Published: May 2008

Lycophytes arose in the early Silurian (≈400 Mya) and represent a major lineage of vascular plants that has evolved in parallel with the ferns, gymnosperms, and angiosperms. A hallmark of vascular plants is the presence of the phenolic lignin heteropolymer in xylem and other sclerified cell types. Although syringyl lignin is often considered to be restricted in angiosperms, it has been detected in lycophytes as well. Here we report the characterization of a cytochrome P450-dependent monooxygenase from the lycophyte
Selaginella moellendorffii
. Gene expression data, cross-species complementation experiments, and
in vitro
enzyme assays indicate that this P450 is a ferulic acid/coniferaldehyde/coniferyl alcohol 5-hydroxylase (F5H), and is capable of diverting guaiacyl-substituted intermediates into syringyl lignin biosynthesis. Phylogenetic analysis indicates that the
Selaginella
F5H represents a new family of plant P450s and suggests that it has evolved independently of angiosperm F5Hs.
Role of excited electronic states in the high-pressure amorphization of benzene
Authors: Citroni Margherita , Bini Roberto , Foggi Paolo , Schettino Vincenzo
Published: May 2008

High-pressure methods are increasingly used to produce new dense materials with unusual properties. Increasing efforts to understand the reaction mechanisms at the microscopic level, to set up and optimize synthetic approaches, are currently directed at carbon-based solids. A fundamental, but still unsolved, question concerns how the electronic excited states are involved in the high-pressure reactivity of molecular systems. Technical difficulties in such experiments include small sample dimensions and possible damage to the sample as a result of the absorption of intense laser fields. These experimental challenges make the direct characterization of the electronic properties as a function of pressure by linear and nonlinear optical spectroscopies up to several GPa a hard task. We report here the measurement of two-photon excitation spectra in a molecular crystal under pressure, up to 12 GPa in benzene, the archetypal aromatic system. Comparison between the pressure shift of the exciton line and the monomer fluorescence provides evidence for different compressibilities of the ground and first excited states. The formation of structural excimers occurs with increasing pressure involving molecules on equivalent crystal sites that are favorably arranged in a parallel configuration. These species represent the nucleation sites for the transformation of benzene into amorphous hydrogenated carbon. The present results provide a unified picture of the chemical reactivity of benzene at high pressure.
Promoter elements associated with RNA Pol II stalling in the
Drosophila
embryo
Authors: Hendrix David A. , Hong Joung-Woo , Zeitlinger Julia , Rokhsar Daniel S. , Levine Michael S.
Published: May 2008

RNA Polymerase II (Pol II) is bound to the promoter regions of many or most developmental control genes before their activation during
Drosophila
embryogenesis. It has been suggested that Pol II stalling is used to produce dynamic and rapid responses of developmental patterning genes to transient cues such as extracellular signaling molecules. Here, we present a combined computational and experimental analysis of stalled promoters to determine how they come to bind Pol II in the early
Drosophila
embryo. At least one-fourth of the stalled promoters contain a shared sequence motif, the “pause button” (PB): KCGRWCG. The PB motif is sometimes located in the position of the DPE, and over one-fifth of the stalled promoters contain the following arrangement of core elements: GAGA, Inr, PB, and/or DPE. This arrangement was used to identify additional stalled promoters in the
Drosophila
genome, and permanganate footprint assays were used to confirm that the segmentation gene
engrailed
contains paused Pol II as seen for heat-shock genes. We discuss different models for Pol II binding and gene activation in the early embryo.
Contacts between membrane proximal regions of the PDGF receptor ectodomain are required for receptor activation but not for receptor dimerization
Authors: Yang Yan , Yuzawa Satoru , Schlessinger Joseph
Published: May 2008

The mechanism of PDGF-receptor β (PDGFRβ) activation was explored by analyzing the properties of mutant receptors designed based on the crystal structure of the extracellular region of the related receptor tyrosine kinase KIT/stem cell factor receptor. Here, we demonstrate that PDGF-induced activation of a PDGFRβ mutated in Arg-385 or Glu-390 in D4 (the fourth Ig-like domain of the extracellular region) was compromised, resulting in impairment of a variety of PDGF-induced cellular responses. These experiments demonstrate that homotypic D4 interactions probably mediated by salt bridges between Arg-385 and Glu-390 play an important role in activation of PDGFRβ and all type III receptor tyrosine kinases. We also used a chemical cross-linking agent to covalently cross-link PDGF-stimulated cells to demonstrate that a Glu390Ala mutant of PDGFRβ undergoes typical PDGF-induced receptor dimerization. However, unlike WT PDGFR that is expressed on the surface of ligand-stimulated cells in an active state, PDGF-induced Glu390Ala dimers are inactive. Although the conserved amino acids that are required for mediating D4 homotypic interactions are crucial for PDGFRβ activation, these interactions are dispensable for PDGFRβ dimerization. Moreover, PDGFRβ dimerization is necessary but not sufficient for tyrosine kinase activation.
Dietary guidelines for pregnant women
Authors: Ortega Rosa M
Published: June 2008

The nutrition of pregnant women is decisive in the course of gestation and the health of both mother and child. However, in the Spanish population, clinical monitoring of nutrition is rare, the control of bodyweight receiving most attention. Many studies show that pregnant women take too much fat and too little carbohydrate, and that intakes of fibre and several trace elements are lower than recommended.

Although many people think they know what a correct (varied and balanced) diet is, the concept is often misleading. Generally, they do not match the ideal theoretical framework for achieving an adequate energy profile of the diet. Neither do they facilitate intakes of vitamins and minerals close to recommended levels. Nutrition education programmes are therefore required to explain adequate dietary guidelines to pregnant women, and indeed to all women of childbearing age.

Considering the criteria suggested by a number of researchers concerning the number of food portions from each food group that pregnant women should include in their diets, the following guidelines for daily consumption are proposed: 3–4 portions of milk products, 2–3 portions of meat, fish or eggs, and 3 portions of fruit, 4–5 portions of vegetables or greens and 7–8 portions of cereals and legumes (a portion is defined as the amount of food that would be found on an average plateful or the normal units of consumption of a food).
Variability in Vancomycin Use in Newborn Intensive Care Units Determined From Data in an Electronic Medical Record
Authors: Arnold Cody , Clark Reese , Bosco Jaclyn , Shoemaker Craig , Spitzer Alan R.
Published: June 2008

Data from an electronic medical record were used to demonstrate a large variation in the proportion of patients treated with vancomycin in 56 newborn intensive care units, which ranged from 18% to 70% . Use of oxacillin or nafcillin instead of vancomycin was rare during the first few years of the study period but was routine in 13% of the newborn intensive care units during the last fewyears of the study period. The use of electronic medical record data for studies of antibiotic use is discussed here.
Estimating dynamic models for gene regulation networks
Authors: Cao Jiguo , Zhao Hongyu
Published: May 2008

Motivation: Transcription regulation is a fundamental process in biology, and it is important to model the dynamic behavior of gene regulation networks. Many approaches have been proposed to specify the network structure. However, finding the network connectivity is not sufficient to understand the network dynamics. Instead, one needs to model the regulation reactions, usually with a set of ordinary differential equations (ODEs). Because some of the parameters involved in these ODEs are unknown, their values need to be inferred from the observed data.

Results: In this article, we introduce the generalized profiling method to estimate ODE parameters in a gene regulation network from microarray gene expression data which can be rather noisy. Because numerically solving ODEs is computationally expensive, we apply the penalized smoothing technique, a fast and stable computational method to approximate ODE solutions. The ODE solutions with our parameter estimates fit the data well. A goodness-of-fit test of dynamic models is developed to identify gene regulation networks.

Contact:  hongyu.zhao@yale.edu
Evaluation of Peripheral Vocal Cord Paralysis by Electromyography
Authors: Grosheva Maria , Wittekindt Claus , Pototschnig Claus , Lindenthaler Werner , Guntinas‐Lichius Orlando
Published: May 2008

Objective: To analyze the predictive value of electromyography (EMG) after peripheral vocal cord paralysis and to estimate regeneration time.

Study Design: Retrospective study based on electromyographic data and medical chart review of university based ENT hospitals.

Methods: EMG results of 448 patients were classified into neuropraxia, axonotmesis/neurotmesis, or not classifiable and followed until final outcome. Final outcome was classified electromyographically into restitutio ad integrum, defective healing, or not classifiable.

Results: The etiology of the paralysis was thyroid gland surgery in 42.9% and other iatrogenic lesions in 11.8%. Idiopathic paralysis was found in 20.3%. Mean follow‐up time was 4.8 months. Initial EMG findings were neuropraxia in 31.0%, axonotmesis/neurotmesis in 40.8%, and not classifiable in 28.1%. Restitutio ad integrum was detected by EMG in 17.6% and defective healing in 43.3%. In 39.1%, the outcome could not be classified. The positive predictive value of EMG was 97% and the negative predictive value 60%. The outcome depended significantly on the initial EMG result (P < .0001) but not on the etiology (P = .737) of the paresis. Regeneration time after neuropraxia was 4.0 months and after axonotmesis/neurotmesis 5.6 months.

Conclusion: Laryngeal EMG has a high predictive value for acute peripheral vocal cord paralysis. The outcome can be predicted more reliably by means of EMG than by analysis of the etiology of the lesion.
Expressions of Caspase‐14 in Human Middle Ear Cholesteatoma
Authors: Jung Myung‐Ho , Lee Jang Hyeog , Cho Jae‐Gu , Jung Hak Hyun , Hwang Soon‐Jae , Chae Sung‐Won
Published: May 2008

Objectives: Cholesteatoma is characterized by an excessive proliferation and differentiation of keratinocytes with a progressive accumulation of keratin debris. Caspase‐14 is a novel regulator of keratinocyte terminal differentiation. The purpose of this study was to investigate the expression patterns and localizations of caspase‐ 14 in cholesteatoma and in normal external auditory canal (EAC) epithelium.

Methods: The expression levels of caspase‐14 mRNA were evaluated through real‐time polymerase chain reaction (PCR) and Western blotting. Cholesteatoma and normal EAC epithelium were immunostained with a monoclonal antibody to caspase‐14. The localizations of immunoreactivity to the caspase‐14 antibody were compared between cholesteatoma and normal EAC epithelium through immunohistochemical staining.

Results: As shown by real‐time reverse‐transcription PCR, the expression level of caspase‐14 mRNA in cholesteatoma epithelium was significantly higher than in normal EAC epithelium. Caspase‐14 protein was detected in both normal EAC and cholesteatoma, but its expression was shown to be greater in cholesteatoma on Western blot analysis. As shown with immunohistochemical staining, caspase‐14 protein was primarily expressed in the granular layer and the upper parts of the spinous layer in cholesteatoma epithelium and in the superficial layer of normal EAC epithelium. The expression of caspase‐14 was more intense in cholesteatoma tissues than in normal EAC epithelium.

Conclusion: The increased level of caspase‐14 expression in cholesteatoma tissues may play a role in terminal differentiation of epithelium and accumulation of keratin debris from external matrix.
Variations in Posttonsillectomy Hemorrhage Rates Are Scale Invariant
Authors: Phillips John , Ward Thomas , Montgomery Paul Q.
Published: May 2008

Background: Scale invariance is a property of scientific laws or objects that change in a prescribed fashion if measurements are scaled, and is often represented by a power‐law relationship. Power laws suggest that events of a large magnitude will be rare, while small events will be much more common, and that a simple mathematical law relates “severity” with frequency. Scale invariance has been demonstrated in scientific fields including physics, social science, and economics. The authors use the complication of a posttonsillectomy hemorrhage to test whether this property is a feature of surgical complications.

Methods: Non‐identifiable data were obtained regarding posttonsillectomy hemorrhage and subcategorized by calendar month, and the percentage rate of posttonsillectomy hemorrhage was calculated. The data were then transformed using a logarithmic function. This transformed data were plotted and a linear regression analysis was performed.

Results: The 13‐year period studied included 6,381 tonsillectomy procedures. The logarithm of the frequency of a given rate range of posttonsillectomy hemorrhage (y) was linearly related to the logarithm of the geometric mean of the rate range (x). The best‐fit straight line was y = −1.3996× + 2.0624 with R2 = 0.851, n = 10, r = 0.922, and P < .001.

Conclusions: The authors found that the incidence of posttonsillectomy hemorrhage is scale invariant. The practical implication is that the observation of rare incidences of large hemorrhage rates may not be due to a unique circumstance or a particular operative fault. To reduce the incidence of extreme rates of postoperative hemorrhage, a review of the entire process of tonsillectomy would be required. Scale‐invariance analysis may represent a novel tool that should be considered when reviewing surgical complications.
Predictors of Reconstruction with Mohs Removal of Nonmelanoma Skin Cancers
Authors: Boyle Kristen , Newlands Shawn D. , Wagner Richard F. , Resto Vicente A.
Published: May 2008

Objectives/Hypothesis: To assess clinico‐demographic characteristics available before Mohs removal of nonmelanoma skin cancers of the head and neck as predictors of the need for extensive reconstruction.

Study Design: Retrospective chart review.

Methods: Variables examined were age, sex, race, marital status, past medical history, family history of skin cancer, use of tobacco or alcohol, history of radiation therapy, history of reconstruction, history of immunosuppression, tumor size, tumor site, histology, primary or recurrent tumor, number of tumors treated, and history and location of previous skin tumors. Univariate and multivariate analyses were performed assessing the need for extensive reconstruction after skin tumor removal as an outcome variable.

Results: Age, tumor site, and a past history of reconstruction after resection of a previous skin tumor were characteristics identified as being predictive of the need for advanced reconstruction. The most common tumor locations that required postablation reconstruction were the nose (228 tumors) and the ear (148 tumors). Thirty‐six of recurrent tumors and 32% of primary tumors were reconstructed. The odds of a female requiring reconstruction were 2:1. The mean ages were 64.3 years in the reconstruction group and 67.2 years in those not reconstructed. Size of tumor did not correlate with the need for reconstruction.

Conclusions: Patient's age, skin tumor location, and past history of extensive reconstruction after previous resection of skin tumor are patient‐specific characteristics available before tumor resection that predict the need for advanced reconstruction in patients undergoing Mohs micrographic surgery removal of skin cancers.
The Rhinology Experience in Otolaryngology Residency: A Survey of Chief Residents
Authors: Tabaee Abtin , Anand Vijay K. , Stewart Michael G. , Fried Marvin P.
Published: May 2008

Objectives: The development of rhinology as a distinct subspecialty is based on recent advances in the research, clinical, and surgical aspects of the field. The impact of this evolution on the rhinologic experience in otolaryngology residency programs is not currently understood.

Methods: An anonymous, web‐based survey of chief residents in otolaryngology residency programs was performed. Participants were asked to rate their residency experience in rhinology in terms of didactics, research opportunities, mentorship availability, clinical care, and surgical experience on an ordinal 5‐point Likert scale with higher scores representing more favorable responses.

Results: Forty‐eight respondents completed the survey, yielding a response rate of 17.6%. The overall experience in rhinology was reported as positive (4.3 points). The individual items with statistically lower scores included availability of basic science research (P = .04), comfort level with the medical management of unusual rhinologic issues (P = .0006), and comfort level with advanced sinus procedures (P < .0001). However, overall ratings were high, and even the poorer‐scoring items were still rated favorably. In programs with rhinology fellowships, basic science opportunities were reported as being higher (P = .04) than programs without fellowships. There were no other statistically significant differences in programs with rhinology fellowships. There was no correlation between responses and future career choice.

Conclusion: The overall residency training experience in rhinology appears to be positive, and presence of a rhinology fellowship appears not to have a negative impact on resident rhinologic training.