bluuebunny/crossref_metadata_2025 huggingface dataset:
Derivation of the dispersion energy as an explicit density- and exchange-hole functional
Authors: Heßelmann Andreas
Published: February 2009

Through some simple derivations, it is shown that the nonexpanded dispersion interaction energy between two molecules can entirely be written in terms of the densities and the exchange-holes of the monomers. Thus the suspicion of Becke and Johnson [J. Chem. Phys. 122, 154104 (2005)] that the dispersion energy might be related to fluctuating dipoles produced by the electrons and their accompanying exchange-holes is confirmed. However, it will be shown that the current asymptotic result for the dispersion energy is different from the Becke–Johnson model. Some preliminary results for the polarizabilities and dispersion coefficients of a few atoms and small molecules demonstrate that the approach described in this work might be useful to estimate response properties and long-range correlation energies of molecular systems in general.
Particle-in-cell simulations of tearing modes in reversed-field-pinch-like plasma
Authors: Svidzinski V. A. , Li H. , Albright B. J. , Bowers K. J.
Published: February 2009

Fully electromagnetic particle-in-cell simulations of tearing modes in two-dimensional plane geometry in a force-free reversed field pinch (RFP)-like plasma equilibrium are performed to study possible kinetic effects on these modes in RFPs. Linear tearing modes are compared in the kinetic and two fluid models. The results showed that the growth rates and the profiles of magnetic field components in the two models are very similar, indicating that the kinetic effects on the studied tearing modes are weak such that the two fluid approximation is rather accurate for modeling these instabilities in RFPs. During the nonlinear evolution of the tearing mode in this geometry, small scale secondary instabilities located near the internal layer of the primary tearing instability are excited. These secondary instabilities appear to be driven by the nonlinearly induced local pressure gradient in the regions of unfavorable curvature of the nonlinearly evolved magnetic field. They could also appear in a realistic RFP geometry and play a role during sawtooth crashes in these machines.
Pulse stress frequency dependence of negative bias temperature instability in SiON gate transistors
Authors: Yang Jingfeng , Yang Jiaqi , Yan Baoguang , Du Gang , Liu Xiaoyan , Han Ruqi , Kang Jinfeng , Liao C. C. , Gan Z. H. , Liao M. , Wang J. P. , Wong W.
Published: February 2009

Dependence of negative bias temperature instability (NBTI) on the frequency of the pulsed stress applied on p-channel transistors with plasma nitrided SiON gate dielectrics is studied. The threshold voltage shift (ΔVth) decrease is observed with increase in frequency. The fractional relaxation is found to be more remarkable after a pulse stress with higher frequency. A phenomenological model based on the dispersive transport of hydrogen in the gate dielectrics is proposed to explain the pulse based NBTI characteristics. The frequency dependence of NBTI is attributed to the existence of deep level hydrogen traps in the gate dielectrics. The model predicts reduced frequency dependence in the ultrahigh frequency range. The results and discussion also confirm the overall correctness of the dispersive transport framework in interpreting the NBTI mechanisms.
Rotor in a cage: Infrared spectroscopy of an endohedral hydrogen-fullerene complex
Authors: Mamone S. , Ge Min , Hüvonen D. , Nagel U. , Danquigny A. , Cuda F. , Grossel M. C. , Murata Y. , Komatsu K. , Levitt M. H. , Rõõm T. , Carravetta M.
Published: February 2009

We report the observation of quantized translational and rotational motion of molecular hydrogen inside the cages of C60. Narrow infrared absorption lines at the temperature of 6 K correspond to vibrational excitations in combination with translational and rotational excitations and show well-resolved splittings due to the coupling between translational and rotational modes of the endohedral H2 molecule. A theoretical model shows that H2 inside C60 is a three-dimensional quantum rotor moving in a nearly spherical potential. The theory provides both the frequencies and the intensities of the observed infrared transitions. Good agreement with the experimental results is obtained by fitting a small number of empirical parameters to describe the confining potential, as well as the relative concentration of ortho- and para-H2.
Hydrostatic pressure induced structural instability and dielectric property of cubic BaZrO3
Authors: Zhu C. , Xia K. , Qian G. R. , Lu C. L. , Luo W. Z. , Wang K. F. , Liu J.-M.
Published: February 2009

Using the first-principle calculations, we investigate in detail the structure instability resulting from softening of the polar zone-center phonon mode [ferroelectric (FE) instability] and nonpolar zone-boundary mode [antiferrodistortive (AFD) instability] in cubic BaZrO3 (BZO) under hydrostatic pressure P from −20 to 90 GPa. The hydrostatic pressure enhances the AFD instability, while it suppresses and then enhances the FE instability. A sequence of FE→cubic→AFD→AFD/FE phase transitions with increasing P is predicted. A careful examination of the pressure dependence of full phonon dispersions and interatomic force constants in real space reveals the microscopic key interactions in driving the transitions. With increasing pressure P, the drastically evolving short-range forces suppress the FE instability induced by the long-range dipole-dipole forces under low pressure, and enhance both the AFD and FE instability under high pressure. We investigate the dielectric properties of cubic BZO under hydrostatic pressure. The dielectric constant as a function of pressure shows a minimum contributed from the TO1 mode with the lowest frequency. We argue that this pressure dependence of the dielectric constant mainly originates from fluctuations of the SR forces.
Low temperature perovskite crystallization of highly tunable dielectric Ba0.7Sr0.3TiO3 thick films deposited by ion beam sputtering on platinized silicon substrates
Authors: Zhu X. H. , Guigues B. , Defaÿ E. , Dubarry C. , Aïd M.
Published: February 2009

Ba 0.7 Sr 0.3 TiO 3 (BST) thick films with thickness up to 1 μm were deposited on Pt-coated silicon substrates by ion beam sputtering, followed by an annealing treatment. It is demonstrated that pure well-crystallized perovskite phase could be obtained in thick BST films by a low temperature process (535 °C). The BST thick films show highly tunable dielectric properties with tunability (at 800 kV/cm) up to 51.0% and 66.2%, respectively, for the 0.5 and 1 μm thick films. The relationship between strains and dielectric properties was systematically investigated in the thick films. The results suggest that a comparatively larger tensile thermal in-plane strain (0.15%) leads to the degradation in dielectric properties of the 0.5 μm thick film; besides, strong defect-related inhomogeneous strains (∼0.3%) make the dielectric peaks smearing and broadening in the thick films, which, however, preferably results in high figure-of-merit factors over a wide operating temperature range. Moreover, the leakage current behavior in the BST thick films was found to be dominated by the space-charge-limited-current mechanism, irrespective of the film thickness.
High efficiency electroluminescence devices using a series of Ir(III)-tetrazolate phosphors: Mechanisms for the drive current evolution of quantum yield
Authors: Cocchi Massimo , Kalinowski Jan , Stagni Stefano , Muzzioli Sara
Published: February 2009

We demonstrate high-brightness and high-efficiency blue-green to yellow-green electrophosphorescent organic light-emitting diodes employing a series of organic Ir complexes [Ir-(C∧N)2(N∧N)]. Three different complexes have been synthesized showing high photoluminescence solid blend efficiencies up to 44%. A low current density increase of the electroluminescence (EL) external quantum efficiency (φEL(ext)) is observed and a maximum of φEL(ext)=10.6%±0.8% photon/e and power efficiency η=27±2 lm/W are achieved at a current density of j=0.01 mA/cm2. We examine various electronic processes that underlie a nonmonotonous current density dependence of the EL quantum efficiency of electrophosphorescent light-emitting diodes. The shape of φEL(ext) versus j is shown to reflect a trade off between electron-hole encounter and charge carrier transit times, electric field effect on electron-hole pair dissociation time, and current driven triplet molecular exciton lifetime.
Current-voltage relation for a field ionizing He beam detector
Authors: DePonte D. P. , Elliott Greg S. , Kevan S. D.
Published: February 2009

Emerging interest in utilizing the transverse coherence properties of thermal energy atomic and molecular beams motivates the development of ionization detectors with near unit detection efficiency and adequate spatial resolution to resolve interference fringes of submicron dimension. We demonstrate that a field ionization tip coupled to a charged particle detector meets these requirements. We have systematically studied the current-voltage relationship for field ionization of helium using tungsten tips in diffuse gas and in a supersonic helium beam. For all 16 tips used in this study, the dependence of ion current on voltage for tips of fixed radius was found to differ from that for tips held at constant surface electric field. A scaling analysis is presented to explain this difference. Ion current increased on average to the 2.8 power of voltage for a tip at fixed field and approximately fifth power of voltage for fixed radius for a liquid nitrogen cooled tip in room temperature helium gas. For the helium beam, ion current increased as 2.2 power of voltage with constant surface field. The capture region of the tips was found to be up to 0.1 μm2 for diffuse gas and 0.02 μm2 in the beam. Velocity dependence and orientation of tip to beam were also studied.
Influence of target material on structure of the plasma outflow produced by a partly defocused laser beam
Authors: Kasperczuk A. , Pisarczyk T. , Kalal M. , Ullschmied J. , Krousky E. , Masek K. , Pfeifer M. , Rohlena K. , Skala J. , Pisarczyk P.
Published: February 2009

This paper is aimed at the explanation of mechanisms responsible for plasma jet formation: the radiative cooling of ablative plasma and the influence of target irradiation geometry. The experiment was carried out with the Prague Asterix Laser System (PALS) iodine laser. A three-frame laser interferometer and an x-ray streak camera were used as two main diagnostic tools. These investigations have shown that the geometry of target irradiation is crucial, an annular target irradiation being necessary for plasma jet formation. Thus the role of radiative cooling in the plasma jet forming seems to be negligible.
Microstructural imaging of high repetition rate ultrafast laser written LiTaO3 waveguides
Authors: McMillen Ben , Chen Kevin P. , Jaque Daniel
Published: February 2009

The microstructural changes associated with the formation of lithium tantalate waveguides after high repetition rate ultrafast laser inscription has been investigated by confocal micro-Raman experiments. While the laser beam focal volume is characterized by significant lattice damage, no reduction of Raman mode strength has been observed at the guiding region, suggesting the preservation of the nonlinear optical coefficient in the waveguide. A general blueshift of the Raman modes has been observed at the guiding region, suggesting lattice compression as the dominant mechanism of waveguide formation.
To change transport gap of semiconducting nanoparticles without disturbing the optical one: Core-shell approach
Authors: Das Bikas C. , Pal Amlan J.
Published: February 2009

We show that transport gap of semiconducting nanoparticles can be changed without disturbing the optical gap. This is achieved through inorganic-organic hybrid core-shell approach. Different inorganic nanoparticles with a bandgap in the UV to NIR range are used as the core; as a shell to the nanoparticles, a monolayer of different organic molecules is used. With the inclusion of the shell layer, optical gap of the nanoparticles does not change. Transport gap, as obtained from current-voltage characteristics of a single nanoparticle with scanning tunneling microscope tip, changes to that of the shell-material irrespective of the bandgap of core nanoparticles.
On resonant optical excitation and carrier escape in GaInN/GaN quantum wells
Authors: Schubert Martin F. , Xu Jiuru , Dai Qi , Mont Frank W. , Kim Jong Kyu , Schubert E. Fred
Published: February 2009

Recently, photoluminescence studies using resonant optical excitation in GaInN layers have been used to investigate the physical origin of efficiency droop in GaInN/GaN light-emitting diodes. In these studies, it has been assumed that in the case of resonant excitation, where electron-hole pairs are generated in the GaInN layers only, carrier transport effects play no role. We report that in contrast to this assumption, carrier escape from quantum wells does take place and shows strong dependence upon the duration of excitation and bias conditions. We also discuss the time scales required to reach steady-state conditions under pulsed optical excitation.
SiGe quantum well infrared photodetectors on pseudosubstrate
Authors: Rauter P. , Fromherz T. , Falub C. , Grützmacher D. , Bauer G.
Published: February 2009

In the SiGe system, freedom in the design of quantum well (QW) devices is constrained by the 4.2% lattice mismatch between silicon and germanium. The substitution of the Si substrate by a SiGe pseudosubstrate customized to the respective QW structure’s requirements enables the growth of a p-type SiGe QW infrared photodetector featuring interfaces between pure Si and SiGe layers of ultrahigh Ge content for a full exploitation of the band offset between the two materials. Our presented device realizes design concepts for narrowing the spectral response and reducing the noise gain made feasible by the utilization of a Si0.5Ge0.5 pseudosubstrate.
Rectifying junctions of tin oxide and poly(3-hexylthiophene) nanofibers fabricated via electrospinning
Authors: Pinto Nicholas J. , Carrasquillo Katherine V. , Rodd Christopher M. , Agarwal Ritesh
Published: February 2009

A fast, simple, and inexpensive method to fabricate in air, p-n diodes using electrospun tin oxide nanoribbons and regioregular poly(3-hexylthiophene) nanofibers is described. In addition to being a rectifier under ambient illumination or in the dark, the advantage of our design is the complete exposure of the rectifying nanojunction to the surrounding environment, making them attractive candidates in the potential fabrication of low power consumption diodes and sensors. The diode characteristics were analyzed using the standard diode equation and its use as a UV light sensor was examined.
The primary signaling outputs of brassinosteroids are regulated by abscisic acid signaling
Authors: Zhang Shanshan , Cai Zhenying , Wang Xuelu
Published: February 2009

Phytohormones have essential roles in coordinately regulating a large array of developmental processes. Studies have revealed that brassinosteroids (BRs) and abscisic acid (ABA) interact to regulate hundreds of expression in genes, governing many biological processes. However, whether their interaction is through modification or intersection of their primary signaling cascades, or by independent or parallel pathways remains a big mystery. Using biochemical and molecular markers of BR signaling and ABA biosynthetic mutants, we demonstrated that exogenous ABA rapidly inhibits BR signaling outputs as indicated by the phosphorylation status of BES1 and BR-responsive gene expression. Experiments using abri1null-allele,bri1-116, and analysis of subcellular localization of BKI1-YFP further revealed that the BR receptor complex is not required for ABA to act on BR signaling outputs. However, when the BR downstream signaling component BIN2 is inhibited by LiCl, ABA failed to inhibit BR signaling outputs. Also, using a set of ABA insensitive mutants, we found that regulation of ABA on the BR primary signaling pathway depends on the ABA early signaling components, ABI1 and ABI2. We propose that the signaling cascades of ABA and BR primarily cross-talk after BR perception, but before their transcriptional activation. This model provides a reasonable explanation for why a large proportion of BR-responsive genes are also regulated by ABA, and provides an insight into the molecular mechanisms by which BRs could interact with ABA.
Access to artificial reproduction technology in the Nordic countries in 2004
Authors: OLAFSDOTTIR HELGA SOL , MATTS WIKLAND , ANDERS MÖLLER
Published: February 2009

Objective. To survey access to Artificial Reproduction Technology (ART) treatments in 2004 with regard to legislation, geographical location, financing and the kind of ART treatments provided in the Nordic countries. Design. Retrospective descriptive survey of practice at ART clinics and legislation. Setting. Denmark, Finland, Iceland, Norway and Sweden. Sample. Sixty‐six ART clinics registered with the Nordic Fertility Society in autumn 2005. Methods. A questionnaire was sent to all ART clinics and a survey of legislation concerning ART treatments and public statistics was performed. The response rate was 79%. Main outcome measures. Access to ART treatments. Results. The differences in legislation among the countries mainly concerns gamete donation. Couples living in larger cities or densely populated areas have best access to ART treatments. With regard to subsidizing of treatment costs, Finland and Denmark seem to be the best of the Nordic countries. Conclusions. The main differences among the countries concern the legislation, the cost of the treatments and how those are subsidized.
Prevalence and correlates of substance use among school children in six African countries
Authors: Peltzer Karl
Published: February 2009

An increasing trend of noncommunicable diseases is a worldwide phenomenon, also including the developing countries. Few studies focus on adolescents' substance use in relation to mental distress and protective factors in African countries. The purpose of this study was to assess the prevalence and correlates (mental distress and protective factors) of substance use among school‐going adolescents in six African countries. The sample included 20,765 students aged from 13 to 15 years from six African countries (Kenya, Namibia, Swaziland, Uganda, Zambia, Zimbabwe), chosen by a two‐stage cluster sample design to represent all students in grades 6, 7, 8, 9, and 10 in each country. The measure used was part of the Global School‐Based Health Survey (GSHS) questionnaire, including various domains of health behaviour. Results indicate a prevalence of 12.6% tobacco use (past month), 6.6% risky alcohol use (two or more per day for at least 20 days or more in the past month), and 10.5% of illicit drug use (three or more times ever) in school‐going adolescents in six African countries. School truancy, loneliness, sleeping problems, sadness, suicidal ideation, suicide plans, and poverty were associated with substance use (tobacco, alcohol, illicit drugs), while school attendance and parental supervision and connectedness were protective factors for substance use, and peer support protective for tobacco use. It is concluded that tobacco use, risky drinking and illicit drug use were common, clustered together and were associated with school truancy, mental distress, and lack of parental and peer support among adolescent African school children. These findings stress the need for early and integrated prevention programmes.
Brain magnetic resonance elastography on healthy volunteers: A safety study
Authors: Liu Guang-Rui , Gao Pei-Yi , Lin Yan , Xue Jing , Wang Xiao-Chun , Sui Bin-Bin , Ma Li , Xi Zhi-Nong , Bai Qin , Shen Hao
Published: February 2009

Background: Magnetic resonance elastography (MRE) is a recently developed imaging technique that can directly visualize and quantitatively measure tissue elasticity.

Purpose: To evaluate the safety of brain MRE on human subjects.

Material and Methods: The study included 20 healthy volunteers. MRE sequence scan (drive signal not applied to external force actuator) and MRE study were separately performed on each volunteer at an interval of more than 24 hours. The heart rate and blood pressure of each volunteer were measured immediately before and after MRE sequence scan and MRE study. Electroencephalography (EEG) was also performed within 2 hours after each scan. The volunteers were asked about their experience of the two scans. Randomized-block analysis of variance (ANOVA) was used to analyze the data of blood pressure and heart rate. Paired t test was used to analyze the data of the two EEG examinations. The volunteers were followed up 1 week after the examination.

Results: All procedures were performed on each volunteer, and no one complained of obvious discomfort. No related adverse events were reported during follow-up. There was no statistically significant difference in heart rate or blood pressure. There was a statistically significant difference ( P<0.05) in EEG results in the right temporoparietal region. Increased power was found in the theta, delta, alpha, and beta2 bands. No brain injury was detected by the EEG examinations.

Conclusion: Based on the study results, brain MRE examinations are safe to perform on human subjects.
Outbreak of Vancomycin-ResistantEnterococcusColonization Among Pediatric Oncology Patients
Authors: Nolan Sheila M. , Gerber Jeffrey S. , Zaoutis Theoklis , Prasad Priya , Rettig Susan , Gross Kimberly , McGowan Karin L. , Reilly Anne F. , Coffin Susan E.
Published: February 2009

Objective.

To detect the burden of vancomycin-resistantEnterococcus(VRE) colonization among pediatric oncology patients and to determine risk factors for VRE acquisition.

Design.

Retrospective case-control study.

Setting.

The Children's Hospital of Philadelphia.

Patients.

Pediatric oncology patients hospitalized from June 2006 through December 2007.

Methods.

Prevalence surveys revealed an increased VRE burden among pediatric oncology patients. For the case-control study, the 16 case patients were pediatric oncology patients who had 1 stool sample negative for VRE at screening before having a stool sample positive for VRE at screening; the 62 control patients had 2 consecutive screenings in which stool samples were negative for VRE. Case and control patients were matched on the duration of the interval between screens. Analyses were performed to determine the association between multiple exposures and VRE acquisition.

Results.

The prevalence survey revealed that 5 (9.6%) of 52 patients had unsuspected VRE colonization at the time of hospitalization. Multivariate analysis identified a lack of empirical contact precautions (odds ratio [OR], 17.16 [95% confidence interval {CI}, 1.49–198.21];P= .02) and the presence of a gastrointestinal device (OR, 4.03 [95% CI, 1.04–15.56];P= .04) as significant risk factors for acquisition of VRE. Observations in the interventional radiology department revealed that staff could not access the portions of the electronic medical record in which isolation precautions were documented. Simple interventions that granted access and that trained interventional radiology staff to review the need for precautions, coupled with enhanced infection control practices, interrupted ongoing transmission and reduced the proportion of VRE screens that were positive to 15 (1.2%) of 1,270.

Conclusions.

Inadequate communication with regard to infection control precautions can increase the risk of transmission of epidemiologically important organisms, particularly when patients receive care at multiple clinic locations. Adherence to infection control practices across the spectrum of care may limit the spread of resistant organisms.
Modeling the role of competition and cooperation in the evolution of katydid acoustic synchrony
Authors: Nityananda Vivek , Balakrishnan Rohini
Published: February 2009

The precise timing of individual signals in response to those of signaling neighbors is seen in many animal species. Synchrony is the most striking of the resultant timing patterns. One of the best examples of acoustic synchrony is in katydid choruses where males produce chirps with a high degree of temporal overlap. Cooperative hypotheses that speculate on the evolutionary origins of acoustic synchrony include the preservation of the species-specific call pattern, reduced predation risks, and increased call intensity. An alternative suggestion is that synchrony evolved as an epiphenomenon of competition between males in response to a female preference for chirps that lead other chirps. Previous models investigating the evolutionary origins of synchrony focused only on intrasexual competitive interactions. We investigated both competitive and cooperative hypotheses for the evolution of synchrony in the katydid Mecopoda “Chirper” using physiologically and ecologically realistic simulation models incorporating the natural variation in call features, ecology, female preferences, and spacing patterns, specifically aggregation. We found that although a female preference for leading chirps enables synchronous males to have some selective advantage, it is the female preference for the increased intensity of aggregations of synchronous males that enables synchrony to evolve as an evolutionarily stable strategy.
Lenalidomide oral monotherapy produces a high response rate in patients with relapsed or refractory mantle cell lymphoma
Authors: Habermann Thomas M. , Lossos Izidore S. , Justice Glen , Vose Julie M. , Wiernik Peter H. , McBride Kyle , Wride Kenton , Ervin‐Haynes Annette , Takeshita Kenichi , Pietronigro Dennis , Zeldis Jerome B. , Tuscano Joseph M.
Published: February 2009

Mantle cell lymphoma (MCL) is an aggressive non‐Hodgkin lymphoma with a poor prognosis following first relapse. We present a subgroup analysis of an open‐label phase II trial investigating the efficacy and safety of lenalidomide in patients with relapsed or refractory MCL. Oral lenalidomide 25 mg was self‐administered once daily on days 1–21 every 28 d for up to 52 weeks, according to tolerability or until disease progression. The primary endpoint was overall response rate (ORR) and secondary endpoints were duration of response, progression‐free survival (PFS) and safety. Among 15 patients with MCL with a median disease duration of 5·1 years and a median of four prior treatments, the ORR was 53%. Three patients (20%) had a complete response and 5 (33%) had a partial response. The median duration of response was 13·7 months and median PFS was 5·6 months. Four of five patients who relapsed after transplantation and two of five patients who previously received bortezomib responded to lenalidomide. The most common grade 4 adverse event was thrombocytopenia (13%) and the most common grade 3 adverse events were neutropenia (40%), leucopenia (27%) and thrombocytopenia (20%). In conclusion, oral lenalidomide monotherapy is well tolerated and active in relapsed or refractory MCL.
Globalization and international adoption from China
Authors: Dowling Monica , Brown Gill
Published: February 2009

Since the mid‐1990s, China has become one of the major countries from which children are adopted overseas. This paper examines ways in which globalization has contributed to the development of international adoption from China and explores cultural and historical attitudes to population growth, child abandonment and adoption. How China's social, economic and welfare policies have affected adoption policies and practices are discussed, with reference to ethnographic fieldwork undertaken by the authors between 2001 and 2007. Interviews and group discussions were conducted with UK, Chinese and American adoptive parents, directors of social welfare institutes, Chinese welfare officials and staff of non‐government organizations working in the area of adoption and fostering in China. While globalization has affected, and continues to affect inter‐country adoption, its influence in China is analysed using Masson's value positions on international adoption – abolitionists, promoters and pragmatists. China's pragmatic approach to international adoption is considered in relation to policies that reflect the best interests of children in China and overseas.
After bariatric surgery, what vitamins should be measured and what supplements should be given?
Authors: Pournaras Dimitrios J. , Le Roux Carel W.
Published: February 2009

Bariatric surgery is the most effective treatment for morbid obesity. Although calorie malabsorption does not occur in most bariatric procedures, micronutrient deficiencies are possible. Multivitamin supplementation is essential following bariatric surgery. The recommendation would be to screen for multivitamin deficiencies prior to surgery and to monitor vitamin levels postoperatively at regular intervals. In this paper, we review the data for screening and supplementation after bariatric procedures for different vitamins.
Radioactive iodine for hyperthyroidism in children and adolescents: referral rate and response to treatment
Authors: McCormack Shana , Mitchell Deborah M. , Woo Melissa , Levitsky Lynne L. , Ross Douglas S. , Misra Madhusmita
Published: February 2009

Objectives  Radioactive iodine (131I) therapy is increasingly viewed as a safe and effective treatment for paediatric and adolescent hyperthyroidism. Our objective was to estimate treatment response and its predictors and describe current referral practices for 131I therapy.

Design  Retrospective study.

Patients  One hundred and thirty‐one children 30 days–21 years old with laboratory evidence of hyperthyroidism, seen in an academic paediatric and adolescent endocrinology practice.

Measurements  Rate of referral, indications for 131I, predictors of poor treatment response.

Results  Thirty‐eight of 102 patients with persistent hyperthyroidism (37%) received 131I (160 μCi/g thyroid tissue/131I uptake), as did an additional 10 patients initially evaluated by adult thyroidologists. Primary indications were intolerance to (29%) or poor control on (19%) antithyroid drugs, patient preference (50%) and unknown (2%). Of 48 patients treated with 131I, 89% and 11% became hypothyroid after one and two 131I doses, respectively. The goal of 131I therapy was attainment of hypothyroidism. ‘Poor treatment response’ (seen in 27%) was defined as requirement for a second 131I dose or failure to achieve hypothyroidism after 6 months. Predictors of poor treatment response included: previous use of antithyroid drugs (37%vs. 0%, P = 0·02), ophthalmopathy (58%vs. 8%, P = 0·002), and an interval of ≥12 months from diagnosis to 131I (50%vs. 10%, P = 0·003). A very elevated free T4 tended to be more prevalent in those with poor response.

Conclusions  In children and adolescents with hyperthyroidism, high rates of success after 131I are achievable. Use of antithyroid drugs, pre‐existing eye disease and prolonged time to 131I may confer relative resistance to 131I.
Short‐term overt hypothyroidism induces discrete diastolic dysfunction in patients treated for differentiated thyroid carcinoma
Authors: Hoftijzer H. C. , Bax J. J. , Heemstra K. A. , Bleeker G. B. , Delgado V. , Van der Klaauw A. A. , Romijn J. A. , Smit J. W. A. , Corssmit E. P. M.
Published: February 2009

Background  Thyroid hormone has important effects on the cardiovascular system. The consequences of episodes of acute hypothyroidism on cardiac function have been investigated in only a few studies, and their results are inconclusive. Our objective was to investigate the effects of acute hypothyroidism on cardiac function in patients with iatrogenically induced subclinical hyperthyroidism after treatment for differentiated thyroid carcinoma.

Material and methods  Fourteen patients with a history of differentiated thyroid carcinoma on thyroid‐stimulating hormone (TSH)‐suppressive thyroxine replacement therapy were studied. We assessed cardiac function before, and 1 and 4 weeks after withdrawal of thyroxine substitution. We measured serum levels of free thyroxine, triiodothyronine and TSH and used a new sophisticated Doppler echocardiography technique, tissue Doppler imaging (TDI), to assess detailed and quantitative assessment of systolic and diastolic cardiac function. Echocardiographic parameters in patients were compared to controls.

Results  Compared to controls, patients had higher left ventricular mass and wall thickness and decreased diastolic function during TSH‐suppressive l‐thyroxine substitution therapy. Thyroxine withdrawal resulted in a decrease in both early (E) and late (A) diastolic mitral inflow velocities, without impact on E/A ratio. Using TDI, late diastolic velocity (A′) decreased without impact on E′/A′ ratio. Left ventricular dimensions, wall thickness and mass did not change during thyroxine withdrawal.

Conclusions  Subclinical hyperthyroidism is accompanied by diastolic dysfunction. Subsequent acute hypothyroidism induces only subtle changes in diastolic function.
Long‐term management effects on soil organic matter in two cold, high‐elevation grasslands: clues from fractionation and radiocarbon dating
Authors: Leifeld J. , Fuhrer J.
Published: February 2009

Grassland covers large areas at the treeline of the Alps, but management effects on the amount, distribution and turnover of soil organic matter (SOM) in this region are largely unknown. Our aim was to elucidate such effects for two management types using soil fractionation in combination with radiocarbon dating. Two Swiss grasslands sites at approximately 2020 m elevation (MAT +2.2°C, MAP 1050 mm) were used, which were hay meadows until 60 years ago when one was changed to grazed pasture. The sites are located in close vicinity to each other and have similar climate and parent material. Soils at each site were shallow (maximum 20 cm) and had high stone contents and thus a limited carbon (C) storage capacity. Total soil organic carbon (SOC) stocks in the two soils were similar (6.11 ± 0.69 and 6.07 ± 0.91 kg C m−2, respectively), as were proportions of readily available SOC and Q10 values measured by means of respiration in the laboratory. Grazing caused lower soil nutrient contents and slight soil compaction. Carbon in labile fractions and its radiocarbon age were particularly useful to distinguish management effects. Significantly more SOC was located in the pasture topsoil (0–4 cm) with a higher share of particulate organic C. Particulate and microaggregate‐associated C was slightly younger under pasture, indicating incorporation of recent plant tissue by cattle. At both sites, 14C‐derived mean residence times of SOC increased in the order particulate < micro‐aggregate < silt and clay‐associated matter and were greater below 4 cm than in the topsoil. Age differences in old silt and clay C could not be attributed entirely to management effects. We discuss pitfalls for turnover estimates of bulk soils introduced by choosing non‐unique fractions. Together, the data suggest that a change from haying to cattle grazing may cause a strong decoupling of microbial processes within the soil’s architecture and that in such ecosystems SOM under pastures may be more vulnerable to environmental disturbances.
Population genetic structure of diploid sexual and polyploid apomictic hawthorns (Crataegus; Rosaceae) in the Pacific Northwest
Authors: LO EUGENIA Y. Y. , STEFANOVIĆ SAŠA , DICKINSON TIMOTHY A.
Published: February 2009

Polyploidy and gametophytic apomixis are two important and associated processes in plants. Many hawthorn species are polyploids and can reproduce both sexually and apomictically. However, the population genetic structure of these species is poorly understood. Crataegus douglasii is represented exclusively by self‐compatible tetraploid pseudogamous apomicts across North America, whereas Crataegus suksdorfii found in the Pacific Northwest is known to include self‐incompatible diploid sexuals as well as polyploid apomicts. We compare population structure and genetic variability in these two closely related taxa using microsatellite and chloroplast sequence markers. Using 13 microsatellite loci located on four linkage groups, 251 alleles were detected in 239 individuals sampled from 15 localities. Within‐population multilocus genotypic variation and molecular diversity are greatest in diploid sexuals and lowest in triploid apomicts. Apart from the isolation of eastern North American populations of C. douglasii, there is little evidence of isolation by distance in this taxon. Genetic diversity in western populations of C. douglasii suggests that gene flow is frequent, and that colonization and establishment are often successful. In contrast, local populations of C. suksdorfii are more markedly differentiated. Gene flow appears to be limited primarily by distance in diploids and by apomixis and self‐compatibility in polyploids. We infer that apomixis and reproductive barriers between cytotypes are factors that reduce the frequency of gene flow among populations, and may ultimately lead to allopatric speciation in C. suksdorfii. Our findings shed light on evolution in woody plants that show heterogeneous ploidy levels and reproductive systems.
Ground displacement data around the city of Ravenna do not support uplifting Venice by water injection
Authors: Schrefler B. A. , Ricceri G. , Achilli V. , Menin A. , Salomoni V. A.
Published: February 2009

The proposed injection of seawater in a brackish, sandy aquifer lying 600–800 m under the lagoon of Venice to lift Venice itself uniformly up to 30 cm in 10 years raises many problems. We discuss here whether a smooth uplift can be obtained as claimed by the proponents. We first underline the similarities between the Ravenna and Venice case. We then examine the subsidence around Ravenna because of fluid extraction and the measured surface displacements for the period when there is pressure recovery both in the depleted gas reservoir close to Ravenna and in the upper aquifer system. Uniform surface settlements are nowhere observed and strong influence of local heterogeneities cannot be ruled out. The whole picture suggests great caution and the need for much more investigation before undertaking such an injection.
Distribution of insensitive acetylcholinesterase (ace‐1R) in Anopheles gambiae s.l. populations from Burkina Faso (West Africa)
Authors: Dabiré K. R. , Diabaté A. , Namontougou M. , Djogbenou L. , Kengne P. , Simard F. , Bass C. , Baldet T.
Published: February 2009

Objective  To investigate through countrywide sampling at 20 localities across the three different agro‐climatic zones of Burkina Faso, the distribution of the acetylcholinesterase insensitive mutation ace‐1R, which confers resistance to organophosphates (OP) and carbamates (CM) insecticides in An. gambiae s.l.

Methods  Adult mosquitoes were collected by indoor aerosol spraying from August to October 2006. Specimens were identified to species by polymerase chain reaction (PCR) assay and characterized for the ace‐1R mutation using a PCR‐restriction fragment length polymorphism diagnostic.

Results  Collected mosquitoes were a mixture of An. gambiae s.s. and An. arabiensis across the Sudan (98.3%vs. 1.7%), Sudan‐sahelian (78.6%vs. 21.4%) and the Sahel (91.5%vs. 8.5%) ecotypes. The An. gambiae S‐form predominated in the Sudan sites from the West (69%vs. 31% for the M form) but was not found in the Sahel (100% M form). The ace‐1R mutation was dispersed throughout the Sudan and Sudan‐sahelian localities at moderate frequency (<50%) but was absent in the Sahel. It was far more prevalent in S form than M form mosquitoes (0.32 for the S form vs. 0.036 for the M form). No An. arabiensis was detected carrying the mutation. The geographic distribution of ace‐1R in the Sudan and Sudan‐sahelian correlated with the cotton growing areas dispersed throughout the two climatic zones.

Conclusions  These results have special significance as OP and CM insecticides have been proposed as alternatives or additions to pyrethroids which are currently used exclusively in many vector control programmes.
Effects of pets on asthma development up to 8 years of age: the PIAMA study
Authors: Kerkhof M. , Wijga A. H. , Brunekreef B. , Smit H. A. , De Jongste J. C. , Aalberse R. C. , Hoekstra M. O. , Gerritsen J. , Postma D. S.
Published: February 2009

Background:  Recall bias may provide discrepant relationships of pet exposure with sensitization and asthma development. We studied prospectively effects of pets at home on development of sensitization, asthma and respiratory symptoms from birth up to age 8 years.

Methods:  Event history analysis was performed on annually registered data of 2951 children, participating in the PIAMA birth cohort study.

Results:  Children with a cat or dog at home at 3 months of age had a significantly lower prevalence of sensitization to inhalant allergens at age 8, but not of asthma. A cat decreased the risk of house dust mite sensitization at age 8 [odds ratio (OR) = 0.68, 95% confidence interval (CI) 0.49–0.95], a dog of pollen sensitization (OR = 0.49, 95% CI: 0.29–0.83). A cat or dog at home did not significantly affect asthma incidence in each subsequent year. From 2 years of age onwards, the incidence of wheeze (OR = 1.52, 95% CI: 1.12–2.05) and a dry cough at night (OR = 1.28, 95% CI: 1.05–1.57) was higher in children with a dog, whereas removal of a dog increased the risk of developing asthma symptoms. Comparing analyses using prospectively and retrospectively collected data on diagnosed asthma showed important recall bias.

Conclusions:  Our prospective study shows a protective effect of early presence of pets at home on sensitization to inhalant allergens, but no prevention of asthma development. Furthermore, children with pets had more frequent transient or intermittent asthma symptoms. Parental report of asthma by recall may provide spurious results of these associations.
Orbitofrontal cortex gray matter volumes in bipolar disorder patients: a region‐of‐interest MRI study
Authors: Nery Fabiano G , Chen Hua‐Hsuan , Hatch John P , Nicoletti Mark A , Brambilla Paolo , Sassi Roberto B , Mallinger Alan G , Keshavan Matcheri S , Soares Jair C
Published: February 2009

Objectives:  Functional and postmortem studies suggest that the orbitofrontal cortex (OFC) is involved in the pathophysiology of bipolar disorder (BD). This anatomical magnetic resonance imaging (MRI) study examined whether BD patients have smaller OFC gray matter volumes compared to healthy comparison subjects (HC).

Methods:  Twenty‐eight BD patients were compared to 28 age‐ and gender‐matched HC. Subjects underwent a 1.5T MRI with 3D spoiled gradient recalled acquisition. Total OFC and medial and lateral subdivisions were manually traced by a blinded examiner. Images were segmented and gray matter volumes were calculated using an automated method.

Results:  Analysis of covariance, with intracranial volume as covariate, showed that BD patients and HC did not differ in gray matter volumes of total OFC or its subdivisions. However, total OFC gray matter volume was significantly smaller in depressed patients (n = 10) compared to euthymic patients (n = 18). Moreover, total OFC gray matter volumes were inversely correlated with depressive symptom intensity, as assessed by the Hamilton Depression Rating Scale. OFC gray matter volumes were not related to lithium treatment, age at disease onset, number of episodes, or family history of mood disorders.

Conclusions:  Our results suggest that abnormal OFC gray matter volumes are not a pervasive characteristic of BD, but may be associated with specific clinical features of the disorder.
Insect and wind pollination of an alpine biennial Aconitum gymnandrum (Ranunculaceae)
Authors: Duan Y. W. , Zhang T. F. , He Y. P. , Liu J. Q.
Published: February 2009

Wind pollination can provide reproductive insurance for animal‐pollinated dioecious plants in the absence of available pollinators, but combinations of insect and wind pollination (ambophily) have rarely been studied in hermaphrodite herbs. We examined the stable occurrence of insect pollination and wind pollination over 4 years in a population of a biennial Aconitum species (A. gymnandrum) with actinomorphic and degenerate sepals. The total frequency of visits of two bumblebee species showed no distinct fluctuations in the studied population among the 4 years. However, seed production of netted flowers after emasculation indicated wind pollination had occurred. The seed number of bagged flowers with one visit by bumblebees was significantly less than that of netted flowers after one visit, or in control flowers. Both seed number and fruit set of netted flowers were significantly lower than in control flowers. These results suggest that wind pollination provides supplementary pollen to unvisited and/or once‐visited flowers, but accounts for only a small amount of seed production compared to bumblebee pollination in natural conditions. Such a combination of insect and wind pollination might play an important role in maintaining sexual reproduction of this biennial herb, allowing it to persist in arid habitats on the Qinghai‐Tibetan Plateau, especially during Quaternary glacial periods when pollinator populations oscillated extensively.
REDOX MODULATION AT THE PERIPHERAL SITE ALTERS NOCICEPTIVE TRANSMISSION IN VIVO
Authors: Meotti Flavia C , Coelho Igor S , Franco Jeferson L , Dafre Alcir L , Rocha João BT , Santos Adair RS
Published: February 2009

The aim of the present study was to investigate the role of redox modulation during the peripheral nociceptive transmission in vivo. The nociceptive response was evaluated by the amount of time that mice spent licking the footpad injected with glutamate (20 µmol/paw). Thiol groups in footpad tissue were quantified using a colourimetric reaction with 5,5′‐dithio‐bis‐2‐nitrobenzoic acid (DTNB).

When coadministered with glutamate, the thiol alkylating agent iodoacetate (200 nmol/paw) caused significant antinociception in footpad tissue, in parallel with a decrease in free thiol groups. Treatment with the reducing agent dithiothreitol (200 nmol/paw) 5 min before glutamate and iodoacetate prevented the antinociception and thiol loss caused by iodoacetate. Injection of 100 nmol/paw ebselen (2‐phenyl‐1,2‐benzisoselenazol‐3[2H]‐one), an in vitro redox modulator of the N‐methyl‐d‐aspartate (NMDA) receptor, also prevented iodoacetate‐induced antinociception. However, ebselen did not prevent thiol loss in the footpad. Dithiothreitol and ebselen had a synergic nociceptive effect with glutamate.

Alone, ebselen (100 nmol/paw) exhibited a pronociceptive effect. The nociception induced by ebselen was blocked by glutathione depletion induced by buthionine‐sulphoximine (BSO; 2.5 µmol/paw). In addition, ebselen‐induced nociception was prevented by 75 ± 2% following injection of 5 nmol/paw MK‐801 (an NMDA receptor antagonist). The nitric oxide synthase inhibitor NG‐nitro‐l‐arginine (250 nmol/paw) had no effect on the nociception produced by ebselen.

In conclusion, the present paper reports on the effect of redox modulation on the glutamatergic system during peripheral nociceptive transmission in vivo. Antinociception was directly correlated with the availability of thiol groups, whereas the pronociceptive response of the reducing agents likely occurs via positive modulation of the NMDA receptor.