bluuebunny/crossref_metadata_2025 huggingface dataset:
Prescribing practices of selective serotonin reuptake inhibitors (SSRIs) among pediatric oncologists: A single institution experience
Authors: Kersun Leslie S. , Kazak Anne E.
Published: July 2005

Although children and adolescents with cancer often experience symptoms of anxiety and depression, there are no published data regarding the use of selective serotonin reuptake inhibitors (SSRIs) for treating depression in the pediatric oncology population. The goal of this study was to characterize SSRI prescribing practices among pediatric oncologists. A brief (14 item) written survey was distributed to all attending and fellow physicians at a large center with an 85% response rate (N = 40). Half of the respondents prescribed SSRIs for patients, and the most common triggers for prescription include oncologist perceptions of the patient's general sadness, major depressive disorder, and anxiety. The majority of oncologists in the sample (70%) used more than one SSRI. Most physicians prescribe during the first year of therapy and 50% feel that their practice will be influenced by the Federal Drug Administration (FDA) warnings governing the use of SSRIs in the pediatric population. Some physicians consult hospital psychologists, while fewer consult psychiatrists prior to prescribing for these patients. The information gathered from this survey demonstrates that pediatric oncologists are prescribing SSRIs for their patients for a variety of indications. Prospective clinical trials that involve screening patients for depression and anxiety prior to and following SSRI therapy may be helpful in determining whether they result in amelioration of symptoms. It would also be important to evaluate the benefits of a concurrent psychological intervention with medication. Pediatr Blood Cancer 2006;47:339–342. © 2005 Wiley‐Liss, Inc.
Prognostic factors and treatment outcome in childhood hodgkin disease
Authors: Oguz Aynur , Karadeniz Ceyda , Okur F. Visal , Cıtak E. Caglar , Pınarlı F. Guçlu , Bora Huseyin , Akyurek Nalan
Published: July 2005

Background

The goals of this study included: (1) Identification of factors prognostic for event‐free survival (EFS) and overall survival (OS), and (2) Definition of risk groups for risk adapted therapy in children with Hodgkin disease (HD).

Procedure

From 1991 to 2003, 69 children with newly diagnosed, untreated biopsy‐proven stage I–IV HD were treated with chemotherapy (CT) and low‐dose involved field radiotherapy (LD‐IFRT). The relationship of pretreatment factors to EFS and OS was analyzed by univariate and multivariate analysis.

Results

The 5‐year EFS and OS for all patients were 90.77% and 96.22%, respectively with a median follow‐up of 73 months (3–137 months). Male to female ratio was 3:1 and 21 children (32.3%) were less than 7 years of age. Mixed cellularity was the predominant histologic subtype (38.5%). Factors associated with inferior EFS by univariate analysis were extranodal disease, hemoglobin level <11 g/dl, number of involved lymph node regions and stage. By multivariate analysis only stage IV disease was significant.

Conclusion

Our study confirms that excellent results are achievable with combined modality therapy in childhood HD. In order to use risk‐adapted therapy in children with HD, clinical prognostic factors should be validated with large, multicentered prospective clinical studies. © 2005 Wiley‐Liss, Inc.
Pelger–Huët anomaly in a child with 1q42.3‐44 deletion
Authors: Kalfa Theodosia A. , Zimmerman Sherri A. , Goodman Barbara K. , McDonald Marie T. , Ware Russell E.
Published: July 2005

Congenital Pelger–Huët anomaly (PHA) is an autosomal dominant disorder characterized by hypolobulated neutrophils with coarse clumping of the nuclear chromatin. PHA has been recently linked to the gene encoding the lamin B receptor, located at chromosome 1q41‐43. The authors report a case of PHA in a child with interstitial deletion of the 1q subtelomeric region (1q42.3‐44), providing supportive evidence to this linkage. All neutrophils in the peripheral blood smear had the characteristic unsegmented or bilobed appearance. Additional features in this child included failure to thrive, developmental delay, cleft palate, seizure disorder, and dysmorphic facial features. © 2005 Wiley‐Liss, Inc.
Thermomechanical behaviour of poly[acrylonitrile‐co‐(methyl acrylate)] fibres oxidatively treated at temperatures up to 180 °C
Authors: Soulis Spyridon , Simitzis Johannis
Published: July 2005

PAN fibres, consisting of poly[acrylonitrile‐co‐(methyl acrylate)], were oxidatively heat treated at low temperatures (up to 180 °C), during which the basic macromolecular backbone was not cyclized. The change of length of the fibres was determined under various treatment conditions (ie temperature, time, stress applied). Prolonged heat treatment resulted in lower tensile strength of the fibres. The pristine and treated fibres were characterized by Fourier‐transform infrared (FTIR), NMR and UV‐visible spectroscopy and by TGA, and the results were used for representing the different regions according to chemical aspects in a plot of temperature versus time; this is very important for the whole treatment process. A shrinkage model was proposed, having both scientific and technical importance. The change in activation volume of shrinkage of fibres with temperature, calculated from this model, is indicative of the physical transitions taking place at the molecular scale. Copyright © 2005 Society of Chemical Industry
Proteomic identification of differentially‐expressed genes in human gastric carcinomas
Authors: Nishigaki Ryuichi , Osaki Mitsuhiko , Hiratsuka Masaharu , Toda Tosifusa , Murakami Kaori , Jeang Kuan‐Teh , Ito Hisao , Inoue Toshiaki , Oshimura Mitsuo
Published: July 2005

Although genetic alterations in proto‐oncogenes, tumor‐suppressor genes, cell cycle regulators, and cell growth factors have been implicated in the process of human gastric carcinogenesis, the principle carcinogenic mechanisms are not fully understood. In this study, we used a proteomic approach to search for genes that may be involved in gastric carcinogenesis and that might serve as diagnostic markers. We identified nine proteins with increased expression and 13 proteins with decreased expression in gastric carcinomas. The two most notable groups included proteins involved in mitotic checkpoint (MAD1L1 and EB1) and mitochondrial functions (CLPP, COX5A, and ECH1). This suggested that there are links between dysfunctions in these processes and gastric carcinogenesis. We also observed the differential expression of HSP27 and CYR61 proteins in gastric carcinoma, whose expression is known to be altered in other types of tumors. Furthermore, the study identified proteins whose function in gastric carcinomas was previously unsuspected and that may serve as new molecular markers for gastric carcinomas. Importantly, immunohistochemical analyses confirmed that the levels of expression of MAD1L1, HSP27, and CYR61 were altered in gastric carcinoma tissues. Therefore, our study suggested not only that the proteins identified in this study can be useful diagnostic markers but also that a proteomics‐based approach is useful for developing a more complete picture of the pathogenesis and function of gastric carcinomas.
Spatial variability in14C‐herbicide degradation in surface and subsurface soils
Authors: Charnay Marie‐Paule , Tuis Sébastien , Coquet Yves , Barriuso Enrique
Published: July 2005

The spatial variability in mineralization of atrazine, isoproturon and metamitron in soil and subsoil samples taken from a 135‐ha catchment in north France was studied. Fifty‐one samples from the top layer were taken to represent exhaustively the 31 agricultural fields and 21 soil types of the catchment. Sixteen additional samples were collected between depths of 0.7 and 10 m to represent the major geological materials encountered in the vadose zone of the catchment. All these samples were incubated with14C‐labelled atrazine under laboratory conditions at 28 °C. Fourteen selected surface samples which exhibited distinctly different behaviour for atrazine dissipation (including sorption and mineralization) were incubated with14C‐isoproturon and14C‐metamitron. Overall soil microbial activity and specific herbicide degradation activities were monitored during the incubations through measurements of total carbon dioxide and14C‐carbon dioxide respectively. At the end of the incubations, extractable and non‐extractable (bound) residues remaining in soils were measured. Variability of herbicide dissipation half‐life in soil surface samples was lower for atrazine and metamitron (CV < 12%) than for isoproturon (CV = 46%). The main contributor to the isoproturon dissipation variability was the variability of the extractable residues. For the other herbicides, spatial variability was mainly related to the variability of their mineralization. In all cases, herbicide mineralization half‐lives showed higher variability than those of dissipation. Sorption or physicochemical soil properties could not explain atrazine and isoproturon degradation, whose main factors were probably directly related to the dynamics of the specific microbial degradation activity. In contrast, variability of metamitron degradation was significantly correlated to sorption coefficient (Kd) through correlation with the sorptive soil components, organic matter and clay. Herbicide degradation decreased with depth as did the overall microbial activity. Atrazine mineralization activity was found down to a depth of 2.5 m; beyond that, it was negligible. Copyright © 2005 Society of Chemical Industry
Degradation of simazine by microorganisms isolated from soils of Spanish olive fields
Authors: Santiago‐Mora Raquel , Martin‐Laurent Fabrice , de Prado Rafael , Franco Antonio R
Published: July 2005

The capability of the microbial flora isolated from an olive field soil from Andalusia to mineralize simazine has been analyzed. From this soil, a group of bacteria capable of degrading 60 mg simazine litre−1 in less than a week has been isolated. These microorganisms showed a low capacity for degrading this herbicide to carbon dioxide. When total DNA was isolated from this group of bacteria, we were able to detect by PCR the presence of only the atzC and the trzN genes. Some components of this bacterial population have been identified by sequencing of specific fragments from bacterial 16S rDNA, including Variovorax sp, Pseudoxanthomonas mexicana Thierry et al, Acidovorax sp and Methylopila capsulata Doronina et al. These data suggest that this consortium of bacteria performs an incomplete degradation of the simazine Copyright © 2005 Society of Chemical Industry
Temperature behavior of piezoelectric gadolinium calcium oxoborate GdCa4O(BO3)3 crystal
Authors: Markiewicz E. , Pawlaczyk C. , Kłos A. , Hofman W. , Pajączkowska A.
Published: July 2005

Temperature characteristics of the piezoelectric resonance frequencies of gadolinium calcium oxoborate (GdCOB) were studied for the following crystal cuts and vibration modes: (XYt)ϕ (ϕ = 0°, 22.5°, 67.5°) bars vibrating in longitudinal mode, (XYt)45° bar vibrating in face‐shear mode and (ZXt)0° bar vibrating in longitudinal mode and the temperature/frequency coefficients were estimated. GdCOB crystal of the orientation (XYt)45° exhibited properties most suitable for the application in temperature measuring devices in a wide temperature range (70–450 K). GdCOB crystal of the orientation (ZXt)0° exhibited zero temperature/frequency coefficient with the turning point set in the temperature range 180–210 K depending on the width‐to‐length ratio of the bar. It was found that the temperature behavior of the crystal is very similar to that of the other well known piezoelectric crystals. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Polariton squeezing in microcavities
Authors: Quattropani Antonio , Schwendimann Paolo
Published: July 2005

Squeezed states may be found in solids when considering solid state excitations like polaritons, which are mixed states of radiation and excitons or phonons. Squeezing may be observed through the polariton radiation field component, whose statistics reproduces the statistics of the polaritons. The squeezing of polaritons in different semiconductor systems and excitations regimes is discussed. For a sufficiently low density of excitation, an intrinsic but very small squeezing is found for bulk as well as for quantum well and microcavity polaritons. When the density of excitation becomes larger, a large amount of squeezing of microcavity polaritons induced by polariton–polariton scattering is demonstrated both in theory and in experiment. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Chance Correlation in Variable Subset Regression: Influence of the Objective Function, the Selection Mechanism, and Ensemble Averaging
Authors: Baumann Knut
Published: July 2005

Cross‐validation is often used to guide variable selection algorithms. While cross‐validation almost unbiasedly estimates the prediction error when no model selection (such as variable selection) is involved, it is heavily biased when a large amount of model selection is applied (i.e. sifting through thousands of models). In the latter case, the internal figures of merit such asR$ {_{{ CV}}^{2}}$orRMSEPCVcan be deceptively overoptimistic. The extent of this inflation (overoptimism) and the influence factors for the degree of inflation are studied here. It turns out, that the extent of inflation is extremely large for small data sets. The main influence factors for the degree of inflation are data set size, the size of the variable pool, the allowed object variable ratio, the objective function for guiding an stepwise selection technique, and the correlation structure of the data matrix. Moreover, changing the selection mechanism from the commonly applied stepwise procedures to the more stable shrinking and selection technique LASSO eliminates the inflation largely. No inflation is observed when ensemble averaging is used to estimate the prediction error. The latter property combined with the potential of ensemble averaging to improve the predictivity and the possibility to use the information of the single models of the ensemble for validation tasks, renders ensemble averaging an attractive tool if prediction is the primary goal of the analysis.
Pseudo cluster randomization: a treatment allocation method to minimize contamination and selection bias
Authors: Borm George F. , Melis René J. F. , Teerenstra Steven , Peer Petronella G.
Published: July 2005

In some clinical trials, treatment allocation on a patient level is not feasible, and whole groups or clusters of patients are allocated to the same treatment. If, for example, a clinical trial is investigating the efficacy of various patient coaching methods and randomization is done on a patient level, then patients who are receiving different methods may come into contact with each other and influence each other. This would create contamination of the treatment effects. Such bias might be prevented by randomization on the coaches level. The patients of a coach constitute a cluster and all the subjects in that cluster receive the same treatment. Disadvantages of this approach may be reduced statistical efficiency and recruitment bias, as the treatment that a subject will receive is known in advance. Pseudo cluster randomization avoids this, because in pseudo cluster randomization, not everybody in a certain cluster receives the same treatment, just the majority. There are two groups of clusters: in one group the majority of subjects receive treatment A, while a limited number receive treatment B. In the other group of clusters the proportions are reversed. The statistical properties of this method are described. When contamination is present, the method appears to be more efficient than randomization on a patient level or on a cluster level. Copyright © 2005 John Wiley & Sons, Ltd.
Erosion of the inner magnetosphere during geomagnetic storms
Authors: Feshchenko E. Y. , Maltsev Y. P.
Published: July 2005

Abstract. Using the empirical magnetic field model dependent on the Dst index and solar wind dynamic pressure, we calculated the behaviour of the contour B = Bs in the equatorial plane of the magnetosphere where Bs is the magnetic field in the subsolar point at the magnetopause. The inner domain of the magnetosphere outlined by this contour contains the bulk of geomagnetically trapped particles. During quiet time the boundary of the inner magnetosphere passes at the distance ~10 RE at noon and at ~7 RE at midnight. During very intense storms this distance can be reduced to 4–5 RE for all MLT. The calculation results agree well with the satellite measurements of the magnetopause location during storms. The ionospheric projection of the B = Bs contour calculated with the Euler potential technique is close to the equatorward edge of the auroral oval.
Deriving the normalised ion-neutral collision frequency from EISCAT observations
Authors: Davies J. A. , Lester M. , Robinson T. R.
Published: July 2005

Abstract. Common programme observations by the EISCAT UHF radar revealed an extended interval, post geomagnetic local noon on 03 April 1992, during which the F-region ion velocity orthogonal to the geomagnetic field was significantly enhanced, to values exceeding 2 km s–1 corresponding to a perpendicular electric field of some 100 mV m–1. Observations from this interval are used to illustrate a method by which estimates of the E-region ion-neutral collision frequency may be derived in the presence of enhanced electric field. From both the rotation of the ion velocity vector and the reduction in the ion velocity magnitude relative to that in the F-region, independent estimates of the normalised ion-neutral collision frequency are made at the UHF E-region tristatic altitudes; the derived values are, in general, lower than model predictions. Although initial calculations assume a stationary neutral atmosphere, first-order estimates of the E-region neutral wind are subsequently employed to calculate revised estimates of the normalised ion-neutral collision frequency; these neutral winds are derived by attributing the difference between predicted and observed enhancements in field-parallel ion temperature to thermospheric motion. The inclusion of neutral winds, which are themselves not inconsiderable, appears to have only a limited effect on the normalised collision frequencies derived.
Quasi-biennial and quasi-triennial oscillations in geomagnetic activity indices
Authors: Kane R. P.
Published: July 2005

Abstract. Data for geomagnetic activity index aa for 1868–1994 were subjected to spectral analysis for 12 intervals each of 11 consecutive years. In each interval, QBO and QTO (quasi-biennial and quasi-triennial oscillations) were observed at ~2.00, 2.15, 2.40, 2.70 y and ~3.20, 3.40 y, but not all in all intervals. These fluctuations are absent near (2–3 y before and after) the sunspot minima and are present only as 2 or 3 peaks in aa indices, one near or before the sunspot maximum and the other (one or two, generally the larger ones) in the declining phase of the sunspot cycle. Comparison with the solar wind (1965 onwards) showed a fairly good match, indicating that the aa variations were mostly due to similar variations in the solar wind, which must have their origin in solar physical processes. A few aa variations did not match with solar wind. When compared with terrestrial phenomena, no match was found with stratospheric low-latitude zonal wind QBO; but some QTO in aa matched QTO in ENSO (El Nino/Southern Oscillation). This may or may not be a chance coincidence and needs further exploration.
The sunspot cycle, the QBO, and the total ozone over Northeastern Europe: a connection through the dynamics of stratospheric circulation
Authors: Soukharev B.
Published: July 2005

Abstract. The interaction between the factors of the quasi-biennial oscillation (QBO) and the 11-year solar cycle is considered as an separate factor influencing the interannual January-March variations of total ozone over Northeastern Europe. Linear correlation analysis and the running correlation method are used to examine possible connections between ozone and solar activity at simultaneous moment the QBO phase. Statistically significant correlations between the variations of total ozone in February and, partially, in March, and the sunspot numbers during the different phases of QBO are found. The running correlation method between the ozone and the equatorial zonal wind demonstrates a clear modulation of 11-y solar signal for February and March. Modulation is clearer if the QBO phases are defined at the level of 50 hPa rather than at 30 hPa. The same statistical analyses are conducted also for possible connections between the index of stratospheric circulation C1 and sunspot numbers considering the QBO phase. Statistically significant connections are found for February. The running correlations between the index C1 and the equatorial zonal wind show the clear modulation of 11-y solar signal for February and March. Based on the obtained correlations between the interannual variations of ozone and index C1, it may be concluded that a connection between solar cycle – QBO – ozone occurs through the dynamics of stratospheric circulation.
Molecular and morphological supertree of stony corals (Anthozoa: Scleractinia) using matrix representation parsimony
Authors: Kerr Alexander M.
Published: July 2005

The supertree algorithm matrix representation with parsimony was used to combine existing hypotheses of coral relationships and provide the most comprehensive species‐level estimate of scleractinian phylogeny, comprised of 353 species (27% of extant species), 141 genera (63%) and 23 families (92%) from all seven suborders. The resulting supertree offers a guide for future studies in coral systematics by highlighting regions of concordance and conflict in existing source phylogenies. It should also prove useful in formal comparative studies of character evolution. Phylogenetic effort within Scleractinia has been taxonomically uneven, with a third of studies focussing on the Acroporidae or its most diverse genera. Sampling has also been geographically non‐uniform, as tropical, reef‐forming taxa have been considered twice as often as non‐reef species. The supertree indicated that source trees concur on numerous aspects of coral relationships, such as the division between robust versus complex corals and the distant relationship between families in Archaeocoeniina. The supertree also supported the existence of a large, taxonomically diverse and monophyletic group of corals with many Atlantic representatives having exsert corallites. Another large, unanticipated clade consisted entirely of solitary deep‐water species from three families. Important areas of ambiguity include the relationship of Astrocoeniidae to Pocilloporidae and the relative positions of several, mostly deep‐water genera of Caryophylliidae. Conservative grafting of species at the base of congeneric groups with uncontroversial monophyletic status resulted in a more comprehensive, though less resolved tree of 1016 taxa.
The role of eyespots as anti‐predator mechanisms, principally demonstrated in the Lepidoptera
Authors: Stevens Martin
Published: July 2005

Eyespots are found in a variety of animals, in particular lepidopterans. The role of eyespots as antipredator mechanisms has been discussed since the 19th Century, with two main hypotheses invoked to explain their occurrence. The first is that large, centrally located eyespots intimidate predators by resembling the eyes of the predators’ own enemies; the second, though not necessarily conflicting, hypothesis is that small, peripherally located eyespots function as markers to deflect the attacks of predators to non‐vital regions of the body. A third possibility is also proposed; that eyespots intimidate predators merely because they are novel or rarely encountered salient features. These hypotheses are reviewed, with special reference given to avian predators, since these are likely to be the principal visually hunting predators of the lepidopterans considered. Also highlighted is the necessity to consider the potential influence of sexual selection on lepidopteran wing patterns, and the genetics and development of eyespot formation.
Spinodal for the solution-to-crystal phase transformation
Authors: Filobelo Luis F. , Galkin Oleg , Vekilov Peter G.
Published: July 2005

The formation of crystalline nuclei from solution has been shown for many systems to occur in two steps: the formation of quasidroplets of a disordered intermediate, followed by the nucleation of ordered crystalline embryos within these droplets. The rate of each step depends on a respective free-energy barrier and on the growth rate of its near-critical clusters. We address experimentally the relative significance of the free-energy barriers and the kinetic factors for the nucleation of crystals from solution using a model protein system. We show that crystal nucleation is 8–10 orders of magnitude slower than the nucleation of dense liquid droplets, i.e., the second step is rate determining. We show that at supersaturations of three or four kBT units, crystal nuclei of five, four, or three molecules transform into single-molecule nuclei, i.e., the significant nucleation barrier vanishes below the thermal energy of the molecules. We show that the main factor, which determines the rate of crystal nucleation, is the slow growth of the near-critical ordered clusters within the quasidroplets of the disordered intermediate. Analogous to the spinodal in supersaturated fluids, we define a solution-to-crystal spinodal from the transition to single-molecule crystalline nuclei. We show that heterogeneous nucleation centers accelerate nucleation not only because of the wettinglike effects that lower the nucleation barrier, as envisioned by classical theory, but by helping the kinetics of growth of the ordered crystalline embryos.
Accurate intermolecular ground-state potential-energy surfaces of the HCCH–He, Ne, and Ar van der Waals complexes
Authors: Munteanu Cristian Robert , Fernández Berta
Published: July 2005

Accurate ground-state intermolecular potential-energy surfaces are obtained for the HCCH–He, Ne, and Ar van der Waals complexes. The interaction energies are calculated at the coupled cluster singles and doubles including connected triple excitations level and fitted to analytic functions. For the three complexes we start with systematic basis set studies carried out at several intermolecular geometries, and using augmented correlation consistent polarized valence basis sets x-aug-cc-pVXZ (x=−,d;X=D,T,Q,5), also extended with a set of 3s3p2d1f1g midbond functions. The aug-cc-pVQZ-33211 surfaces of HCCH–He, Ne, and Ar complexes are characterized by absolute minima of −24.22, −50.20, and −122.17cm−1 at distances R between the rare-gas atom and the HCCH centers of mass of 4.35, 3.95, and 3.99Å, respectively; and at angles between the vector R and the HCCH main symmetry axis of 0°, 43.3°, and 60.6°. The results are compared and considerably improve those previously available.
High-injection carrier dynamics generated by MeV heavy ions impacting high-speed photodetectors
Authors: Laird Jamie Stuart , Hirao Toshio , Onoda Shinobu , Itoh Hisayoshi
Published: July 2005

The generation of single event transients generated by the impact of high-energy ions in high-speed photodetectors leads to bit error rate degradation in optical communications in radiation hard environments such as space. High-energy heavy ions, in particular, generate a submicron electron-hole pair plasma with a picosecond temporal profile that results in ultrahigh-injection carrier dynamics which induce large space-charge effects. These space-charge effects disturb the local electric field, thereby determining the peak and duration of a single event transient. In this paper, we examine the transient response of Si p-i-n photodetectors irradiated with focused single MeV heavy ions for a range of ion energies chosen to ensure the same end of range but different average plasma densities. We discuss the role of high-injection effects on the evolving spatiotemporal response with the aid of three-dimensional technology computer-aided design software. The result of both measurement and simulation points to charge collection being dominated by three clearly separable phases: (a) an ultrafast bandwidth-limited response which follows the excitation function, (b) an ambipolar diffusion-dominated expansion phase where space-charge screening limits the extracted current, and (c) a bipolar phase where the external field penetrates the electron-hole pair plasma resulting in rapid collection by drift.
A method for the experimental determination of surface photoemission core-level shifts for 3d transition metals
Authors: Shamsutdinov N. R. , Sloof W. G. , Böttger A. J.
Published: July 2005

A method is presented to determine the photoelectron surface core-level shift (SCLS) of 3d transition metals using x-ray photoelectron spectroscopy. The experimental difficulties arising from the relatively large broadening of photoemission lines in the 3d transition series can be overcome by the analysis of the angular dependence of photoemission spectra. The proposed method has been demonstrated using well-defined single-crystal surfaces of copper. The observed values of the SCLS for copper are compared with those predicted by both ab initio calculations and a macroscopic atom model. The experimental determination of SCLSs opens alternative routes for collecting thermochemical data for surfaces/interfaces.
Lateral quantum-dot replication in three-dimensional quantum-dot crystals
Authors: Kiravittaya S. , Heidemeyer H. , Schmidt O. G.
Published: July 2005

Single quantum dots (QDs) reproduce into pairs of QDs with increasing separation distance during the growth of a three-dimensional QD crystal. Kinetic Monte Carlo simulations—that rely on strain profiles deduced from experiment—can describe this lateral replication process, which is triggered by a distinct ridge structure that evolves during the overgrowth of two-dimensional periodic QD arrays.
Monte Carlo study of vertical electron transport in GaN∕AlGaN heterostructures
Authors: Reklaitis A.
Published: July 2005

The dc and large-signal ac vertical electron transport in the double-barrier GaN∕AlGaN heterostructures are studied by Monte Carlo simulations. It is found that the current-voltage characteristic of the GaN∕AlGaN diode is asymmetric due to polarization charges at GaN∕AlGaN interfaces. On the contrary, the calculated capacitance-voltage characteristic is nearly symmetric in respect to the shifted bias voltage. The capacitance-voltage characteristic shows that GaN∕AlGaN heterostructures are promising candidates for the design of efficient varactor diodes. Study of the large-signal ac electron transport predicts that GaN∕AlGaN varactors are capable to operate as frequency triplers in the near-terahertz frequency range.
Effects of in situ vacuum annealing on the surface and luminescent properties of ZnS nanowires
Authors: Rosenberg R. A. , Shenoy G. K. , Heigl F. , Lee S.-T. , Kim P.-S. G. , Zhou X.-T. , Sham T. K.
Published: July 2005

We have monitored the changes that occur in the x-ray-excited optical luminescence, absorption, and photoemission spectra as a function of vacuum annealing time and temperature for ZnS nanowires. All measurements were done in situ. Initial heating causes desorption of surface oxides and a concurrent reduction in the intensity of all the luminescence peaks, which we attribute to the creation of surface states that quench the luminescence. Extended annealing causes diffusion of Au from the particle used to nucleate the wire growth, which results in an increase in intensity of its associated luminescent band at 520nm. Changes were also observed in the ZnL- and SK-edge x-ray absorption spectra, which are consistent with this interpretation.
Room-temperature semiconductor heterostructure refrigeration
Authors: Chao K. A. , Larsson Magnus , Mal’shukov A. G.
Published: July 2005

With the proper design of semiconductor tunneling barrier structures, we can inject low-energy electrons via resonant tunneling, and take out high-energy electrons via a thermionic process. This is the operation principle of our semiconductor heterostructure refrigerator (SHR) without the need of applying a temperature gradient across the device. Even for the bad thermoelectric material AlGaAs, our calculation shows that at room temperature, the SHR can easily lower the temperature by 5–7K. Such devices can be fabricated with the present semiconductor technology. Besides its use as a kitchen refrigerator, the SHR can efficiently cool microelectronic devices.
Tunable 30-femtosecond pulses across the deep ultraviolet
Authors: Jailaubekov Askat E. , Bradforth Stephen E.
Published: July 2005

Intense femtosecond pulses in the deep ultraviolet are generated by phase-matched four-wave mixing in an argon-filled hollow waveguide using 100-fs pulses from a commercial Ti:sapphire regenerative amplifier. Despite the long duration driving pulses, pulses as short as 25fs with energies of >5μJ at 266nm are produced after a simple double-pass prism compressor. In combination with an infrared optical parametric amplifier, tunable pulses are obtained over the 224–240nm range with energies exceeding 1μJ, bandwidths of 5nm and typical compressed pulsewidths of 31fs. Excellent mode and stability make this a promising source for deep ultraviolet pump-probe experiments.
Tuning photonic crystal nanocavity modes by wet chemical digital etching
Authors: Hennessy K. , Badolato A. , Tamboli A. , Petroff P. M. , Hu E. , Atatüre M. , Dreiser J. , Imamoğlu A.
Published: July 2005

We have developed a wet chemical digital etching technique for tuning the resonant wavelengths of photonic crystal (PC) nanocavities over a wide range of 80nm in precise 2–3nm steps while preserving high cavity quality factors. In one tuning step, a few monolayers of material are removed from the cavity surface by etching a self-formed native oxide in 1mol citric acid. Due to the self-limiting oxide thickness, total tuning range is based only on the number of etch steps, resulting in a highly controlled, digital tuning ability. We have characterized the tuning behavior of GaAs PC defect cavities of both square and triangular lattice symmetry and proven the effectiveness of this method by tuning a mode into resonance with the charged exciton, and then later the biexciton, transition of a single InAs∕GaAs self-assembled quantum dot.
Spin-cast thin semiconducting polymer interlayer for improving device efficiency of polymer light-emitting diodes
Authors: Kim Ji-Seon , Friend Richard H. , Grizzi Ilaria , Burroughes Jeremy H.
Published: July 2005

We report that adding a thin (∼10nm) semiconducting polymer interlayer between apoly(styrenesulphonate)-doped poly(3,4-ethylenedioxythiophene) (PEDT:PSS) hole transporter and an emissive semiconductor significantly improves the device efficiency of polymer light-emitting diodes (LEDs). With the interlayer, the external quantum efficiency (EQE) increases from 0.7%(0.4cd∕A at 3.7V) to 1.9% (1.0cd∕A at 3.3V) at 100cd∕m2 for red LEDs and from 1.9%(6.2cd∕A at 3.4V) to 3.0% (10.1cd∕A at 3.0V) at 1000cd∕m2 for green LEDs. An EQE of 4.0% is also observed in blue LEDs (35% increase). The interlayer is spin-coated directly on top of the PEDT:PSS layer from a poly(2,7-(9,9-di-n-octylfluorene)-alt-(1,4-phenylene-((4-sec-butylphenyl)imino)-1,4-phenylene)) (TFB) solution. This interlayer prevents significant quenching of radiative excitons at the PEDT:PSS interface by acting as an efficient exciton blocking layer.
Titania bicontinuous network structures for solar cell applications
Authors: Wang H. , Oey C. C. , Djurišić A. B. , Xie M. H. , Leung Y. H. , Man K. K. Y. , Chan W. K. , Pandey A. , Nunzi J.-M. , Chui P. C.
Published: July 2005

We report fabrication of a TiO2 interconnected network structure for photovoltaic applications, which was obtained using polystyrene-block-polyethylene oxide diblock copolymer as the templating agent. The synthetic method is simple and highly reproducible. The pore size of the structure is controlled by the amount of Ti precursor provided. The heterojunction solar cells consisting of a TiO2 porous network structure and poly (2-methoxy-5-(2′-ethyl-hexyloxy)-p-phenylene vinylene) (MEH-PPV) showed improved performance with a short circuit current of 3.25mA∕cm2 under AM 1.5 solar illumination. The achieved maximum external quantum efficiency for optimum MEH-PPV thickness was 34%.
Nanopatterning of a thin ferromagnetic CoFe film by focused-ion-beam irradiation
Authors: McGrouther D. , Chapman J. N.
Published: July 2005

High-resolution magnetic patterning of a thin CoFe layer has been performed by irradiation using a focused-ion-beam system. Features <50nm wide were formed reproducibly. The irradiated pattern comprised sets of alternating 3.0- and 1.0-μm-long magnetic wires, 100 nm wide. During magnetization reversal, the longer wires reversed at a lower field resulting in the formation of an ordered array of domains with density 10μm−1 supporting antiparallel magnetization. The ability to create domains at predefined locations is important both for fundamental studies and technological applications.
Control of threshold voltage of organic field-effect transistors with double-gate structures
Authors: Iba Shingo , Sekitani Tsuyoshi , Kato Yusaku , Someya Takao , Kawaguchi Hiroshi , Takamiya Makoto , Sakurai Takayasu , Takagi Shinichi
Published: July 2005

We fabricated pentacene field-effect transistors with planar-type double-gate structures, where the top- and bottom-gate electrodes can independently apply voltage biases to channel layers. The threshold voltage of organic transistors is changed systematically in a wide range from −16to−43V when the voltage bias of the top-gate electrode is changed from 0to+60V. The mobility in the linear regime is almost constant (0.2cm2∕Vs) at various voltage biases of the top-gate electrode and the on/off ratio is 106.
Hydrogen as origin of compressive intrinsic stress in hydrogenated amorphous silicon: The contribution of clustered forms
Authors: Pantchev B. , Danesh P. , Schmidt B.
Published: July 2005

The role of hydrogen in hydrogenated amorphous silicon (a-Si:H) has been studied from the viewpoint of its specific contribution to mechanical stress in the material. Hydrogen ion implantation has been used to increase the hydrogen concentration. In order to distinguish the effect of the changed hydrogen concentration∕bonding configuration from the accompanying implantation-induced defects, a-Si:H samples with corresponding number of displacements have been studied, created using proper doses of silicon ion implantation. The experimental results have shown that it is the silicon-bonded hydrogen that essentially affects the stress, as the major contribution has its clustered bonding configuration.
Parkin negatively regulates JNK pathway in the dopaminergic neurons ofDrosophila
Authors: Cha Guang-Ho , Kim Sunhong , Park Jeehye , Lee Eunji , Kim Myungjin , Lee Sung Bae , Kim Jin Man , Chung Jongkyeong , Cho Kyoung Sang
Published: July 2005

Parkin, an E3 ubiquitin ligase, has been found to be responsible for autosomal recessive juvenile parkinsonism characterized primarily by selective loss of dopaminergic neurons with subsequent defects in movements. However, the molecular mechanisms underlying this neuron loss remain elusive. Here, we characterizedDrosophila parkinloss-of-function mutants, which exhibit shrinkage of dopaminergic neurons with decreased tyrosine hydroxylase level and impaired locomotion. The behavioral defect ofparkinmutant flies was partially restored by administering L-DOPA, and the dopamine level in the brains of parkin mutant flies was highly decreased. Intriguingly, we found that c-Jun N-terminal kinase (JNK) is strongly activated in the dopaminergic neurons ofparkinmutants and that impaired dopaminergic neuron phenotypes are dependent on the activation of the JNK signaling pathway. In consistent with this, our epistatic analysis and mammalian cell studies showed that Parkin inhibits the JNK signaling pathway in an E3 activity-dependent manner. These results suggest that loss of Parkin function up-regulates the JNK signaling pathway, which may contribute to the vulnerability of dopaminergic neurons inDrosophila parkinmutants and perhaps autosomal recessive juvenile parkinsonism patients.
SyrB2 in syringomycin E biosynthesis is a nonheme Fe
II
α-ketoglutarate- and O
2
-dependent halogenase
Authors: Vaillancourt Frédéric H. , Yin Jun , Walsh Christopher T.
Published: July 2005

The nine-residue lipodepsipeptide syringomycin E, elaborated as a phytotoxin by
Pseudomonas syringae
pv.
syringae
B301D contains a 4-Cl-
l
-Thr-9 moiety where failure to chlorinate results in a 3-fold drop in biological activity. The proteins SyrB1 and SyrB2 encoded by the biosynthetic cluster are shown to act as a substrate and enzyme pair for SyrB2-mediated chlorination of the aminoacyl-
S
-enzyme
l
-Thr-
S
-SyrB1. SyrB2 is a member of the nonheme Fe
II
α-ketoglutarate-dependent enzyme superfamily, and requires O
2
and α-ketoglutarate as well as chloride ion to carry out monochlorination of the -CH
3
group of
l
-Thr-
S
-SyrB1. Chlorination of
l
-Thr-
S
-SyrB1 was validated by thioesterase-mediated release of
l
-Thr and 4-Cl-
l
-Thr,
N
-derivatization as fluorescent isoindoles, and HPLC separation compared with authentic standards. Incubations with
l
-[
14
C]Thr and [
36
Cl
-
] as well as MS of the released products further validated identification. Enzymatic oxidative halogenation is a previously uncharacterized reaction type for nonheme Fe
II
enzymes and may be the general mode for biosynthetic halogenation of aliphatic carbons of natural products.
Identification of mammalian arginyltransferases that modify a specific subset of protein substrates
Authors: Rai Reena , Kashina Anna
Published: July 2005

Posttranslational N-terminal protein arginylation, mediated by Arg-tRNA-protein transferase 1 (ATE1), is essential for cardiovascular development and angiogenesis in mammals but is nonessential in yeast. Evidence suggests that many proteins are arginylated
in vivo
in both mammals and yeast; however, in yeast, N-terminal arginylation can occur only on proteins bearing an N-terminal Asp or Glu, whereas in mammals, N-terminal Cys residues are also arginylation targets, suggesting that Cys arginylation contributes to the essential role of ATE1 in mammals. To date, all of the characterized forms of ATE1 in yeast and mammals have been shown to arginylate only Asp and Glu, leaving open to speculation whether Cys arginylation is possible only through other components of mammalian arginylation machinery and whether Cys-specific forms of Arg-transferase exist in mammals. Here, we report the identification of two forms of Arg-transferase in mice that are specific for N-terminal Cys. We also show that the two previously identified mammalian forms of ATE1 can arginylate Cys-containing substrates in addition to Asp- and Glu-containing substrates. This finding provides insights into the significance of Cys-specific protein arginylation in mammals and suggests possibilities of the determinants of substrate specificity within the ATE1 molecule.
THE DETERMINANTS OF FIRM PERFORMANCE: UNIONS, WORKS COUNCILS, AND EMPLOYEE INVOLVEMENT/HIGH‐PERFORMANCE WORK PRACTICES
Authors: Addison John T.
Published: July 2005

Drawing on evidence from the United States and Germany, this paper offers a survey of the effects of worker representation (in unions and works councils) and innovative work practices on firm performance. The focus is on the growing links between these two historically separate literatures. The interaction between worker representation and high‐performance work practices provides a practical means of peering inside the black box of collective voice, even if there is as yet no well‐determined hierarchy for productivity performance and certainly no blueprint for the future of unions.
HIGH‐INVOLVEMENT MANAGEMENT PRACTICES, TRADE UNION REPRESENTATION AND WORKPLACE PERFORMANCE IN BRITAIN
Authors: Bryson Alex , Forth John , Kirby Simon
Published: July 2005

Debates about Britain's productivity performance have often drawn attention to the roles played by working practices and employment relations. In the 1980s and 1990s, trade unions were a prime focus; more recently, attention has turned to high‐involvement management (HIM) practices (also referred to as ‘high‐performance work systems’). We combine the two to investigate the relationships between work organisation, trade union representation and workplace performance. We find that HIM has a positive impact on labour productivity. However, this effect is restricted to unionised workplaces, and seems more readily explained by concessionary wage bargaining than ‘mutual gains’, given the absence of any association with financial performance. These findings raise questions about the universal applicability of HIM as a route to improved workplace performance.
SACRED GROVES FOR FOREST CONSERVATION IN GHANA'S COASTAL SAVANNAS: ASSESSING ECOLOGICAL AND SOCIAL DIMENSIONS
Authors: Campbell Michael O'Neal
Published: July 2005

Despite recent interest in sacred (fetish) groves as remnant forests, few studies have investigated their sustainability and conservation role in West Africa. This article employs a Geographical Information Systems (GIS) analysis of time series images (1960‐98), comprehensive social surveys and ecological field methods to evaluate four sacred groves and eight unprotected tree stands in the coastal savanna of Ghana and compare these with vegetation in the distant forested hinterland. There were strong similarities and substantial differences in tree species between different sacred groves, and between these and the unprotected stands and proximate deciduous forests. In addition, far fewer tree losses were documented in the sacred groves than in the local unprotected stands. Although these sacred groves were on average only partially representative of deciduous forest vegetation, their stronger sustainability compared with unprotected tree stands may be important to consider in detail for conservation.
GEOPOLITICS AND HUMAN RIGHTS: UNPACKING AUSTRALIA'S BURMA1
Authors: McGregor Andrew
Published: July 2005

This paper adopts ideas from critical geopolitics to explore how Western human rights discourses have been enabled and used to construct Myanmar by Australian governments and nongovernmental aid organisations. Three distinct human rights scripts are observed that position donors as either punishers, saviours or partners. It is argued that the scripts are enabled by factors external to the actual abuses themselves, including the traditional scripting of Burma within Australian geopolitical memories; the feminine Burmese identity and the networks embodied by the opposition leader, Daw Suu Kyi; and Australia's shifting geopolitical interests in the Southeast Asia region. The case study is used to argue for a broader geography of human rights that recognises their spatiality. Such geographies can improve and broaden human rights politics and debates beyond state‐based campaigning, ensuring that campaigns are in the interests of the most marginalised, rather than the most vocal.