bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical modeling of projectile penetration into compressible rigid viscoplastic media
Authors: Cazacu Oana , Ionescu Ioan R. , Perrot Thomas
Published: October 2007

We develop computational methods for modeling penetration of a rigid projectile into porous media. Compressible rigid viscoplastic models are used to capture the solid–fluid transition in behavior at high strain rates and account for damage/plasticity couplings and viscous effects that are observed in geological and cementitious materials.

A hybrid time discretization is used to model the non‐stationary flow of the target material and the projectile–target interaction, i.e. an explicit Euler method for the projectile equation and a forward (implicit) method for the target boundary value problem. At each time step, a mixed finite element and finite‐volume strategy is
used to solve the ‘target’ boundary value problem. Specifically, the non‐linear variational inequality for the velocity field is discretized using the finite element method while a finite‐volume method is used for the hyperbolic mass conservation and damage evolution equations. To solve the velocity problem, a decomposition–coordination formulation coupled with the augmented Lagrangian method is adopted.

Numerical simulations of penetration into concrete were performed. By conducting a time step sensitivity study, it was shown that the numerical model is robust and computationally inexpensive. For the constants involved in the model (shear and volumetric viscosities, cut‐off yield limit, and exponential weakening parameter for friction) that cannot be determined from data, a parametric study was performed. It is shown that using the material model and numerical algorithms that developed the evolution of the density changes around the penetration tunnel, the shape and location of the rigid/plastic boundary, the compaction zones, and the extent of damage due to air‐void collapse are described accurately. Copyright © 2007 John Wiley & Sons, Ltd.
Poly (3,4‐ethylenedioxythiophene) γ‐Fe2O3 polymer composite–super paramagnetic behavior and variable range hopping 1D conduction mechanism–synthesis and characterization
Authors: Singh Kuldeep , Ohlan Anil , Saini Parveen , Dhawan S. K.
Published: October 2007

The present paper reports the preparation of poly (3,4‐ethylenedioxythiophene) (PEDOT) ferrimagnetic conducting polymer composite by incorporation of ferrite particles in the polymer matrix by emulsion polymerization. Synthesis of PEDOT–γ‐Fe2O3 composite was carried out by chemical oxidative polymerization of EDOT with ferrite particles in the presence of dodecylbenzenesulfonic acid (DBSA) that works as dopant as well as surfactant in aqueous medium. The resulting conducting composite possesses saturation magnetization (Ms) value of 20.56 emu/g with a conductivity of 0.4 Scm−1, which was determined by VSM and four probe technique, respectively. B‐H curve reveals that ferrimagnetic particles of γ‐Fe2O3 show super‐paramagnetic behavior at room temperature which was also observed in PEDOT–γ‐Fe2O3 composite. The resulting conducting ferrimagnetic composite shows microwave absorption loss of 18.7–22.8 dB in the frequency range of 12.4–18 GHz. Thermogravimetric analysis of the composite revealed that the composite is thermally stable up to 230°C. The characterization of the PEDOT–γ‐Fe2O3 composite was carried out using XRD and FTIR spectroscopy. Copyright © 2007 John Wiley & Sons, Ltd.
Field‐induced bending deformation of various rubber films
Authors: Watanabe Masashi
Published: October 2007

The field‐induced bending deformation of various rubber films was measured. The deformation tended to increase with the increase in the conductivity of the films. In addition, the effect of doping with tetracyanoethylene (TCNE) was also studied. This doping significantly enhanced the bending deformation and conductivity when the film was made of acrylonitrile‐butadiene rubber. The tip of the film (5 × 30 mm2, 0.28 mm thick) moved by 3 mm due to the bending deformation induced by the applied voltage (140 V). Such a rubber film may find applications as a polymer actuator. Copyright © 2007 John Wiley & Sons, Ltd.
Synthesis and characterization of dual‐responsive micrometer‐sized core‐shell composite polymer particles
Authors: Alam M. Ashraful , Miah M. A. Jalil , Ahmad Hasan
Published: October 2007

Dual‐responsive micrometer‐sized core‐shell composite polymer particles were prepared by dispersion polymerization followed by seeded copolymerization. Polystyrene (PS) particles prepared by dispersion polymerization were used as core particles. N‐isopropyl acrylamide (NIPAM) and methacrylic acid (MAA) were used to induce dual‐responsive that is thermo‐ and pH‐responsive properties in the shell layer of composite polymer particles, prepared by seeded copolymerization with PS core particles. Temperature‐ and pH‐dependent adsorption behaviors of some macromolecules on composite polymer particles indicate that produced composite polymer particles exhibit dual‐responsive surface properties. Copyright © 2007 John Wiley & Sons, Ltd.
Porous 3‐D scaffolds from regenerated Antheraea pernyi silk fibroin
Authors: Li Mingzhong , Tao Wei , Lu Shenzhou , Zhao Chunxia
Published: October 2007

In this study, porous three‐dimensional (3‐D) materials were prepared with the regenerated Antheraea pernyi (A. pernyi) silk fibroin by freeze‐drying from a lithium thiocyanate solution of its fibers. The relationship between preparation conditions and morphological structures of 3‐D materials was also studied. We concluded that with the decrease in A. pernyi silk fibroin solution concentration and the increase in the freezing temperature, the porosity and the average pore diameter of the 3‐D materials were increased while the pore density was decreased. By adjusting the freezing temperature and the silk fibroin solution concentration, the 3‐D materials having the average pore diameter of 75–260 µm and the porosity of 70–90% can efficiently be produced. As a kind of new material with excellent biocompatibility and bioactivity, the material is expected to be applied to tissue regeneration scaffolds. Copyright © 2007 John Wiley & Sons, Ltd.
ΔNp63 isoforms regulate CD44 and keratins 4, 6, 14 and 19 in squamous cell carcinoma of head and neck
Authors: Boldrup L , Coates PJ , Gu X , Nylander K
Published: October 2007

The human p63 gene codes for multiple protein isoforms and is commonly over‐expressed in squamous cell carcinoma of head and neck (SCCHN). This expression is predominantly of the ΔN‐ and β‐isoforms, the former lacking the p53‐related transactivation domain. p63 can activate or repress transcription of p53 and p73 target genes, but also has unique transcriptional targets and, unlike other p53 family members, is required for normal development and differentiation of squamous epithelia. We have identified novel targets of p63, using microarray analysis of SCCHN cells that stably over‐express individual ΔNp63 isoforms. All three isoforms induced expression of the cancer stem cell marker, CD44, with the ΔNp63β isoform showing strongest induction. Using chromatin immunoprecipitation, we were unable to show direct binding of p63 to the CD44 promoter, but found that p63 specifically increased expression of CD44 lacking variant exon 2. Each of the ΔNp63 isoforms up‐regulated expression of keratins 6A and 14 and down‐regulated expression of keratins 4 and 19, in keeping with their expression patterns in SCCHN. The data strengthen the idea that p63 has key roles in regulating normal and abnormal differentiation processes through both induction and repression of genes with opposite functions. The identification of up‐regulation and differential splicing of CD44 following p63 over‐expression indicates roles in the regulation of adhesion, metastasis and the cancer stem cell phenotype. Copyright © 2007 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Selective loss of B‐cell phenotype in lymphocyte predominant Hodgkin lymphoma
Authors: Tedoldi S , Mottok A , Ying J , Paterson JC , Cui Y , Facchetti F , van Krieken JHJM , Ponzoni M , Özkal S , Masir N , Natkunam Y , Pileri SA , Hansmann M‐L , Mason DY , Tao Q , Marafioti T
Published: October 2007

The neoplastic Reed–Sternberg cells characteristic of classical Hodgkin's lymphoma (cHL) are of B‐cell origin but they almost always show striking loss of a range of B‐cell‐associated molecules. In contrast, the neoplastic cells found in lymphocyte predominant Hodgkin's lymphoma (LPHL) (L&H cells) are traditionally thought of as possessing the full repertoire of features associated with germinal centre B cells (eg BCL‐6 expression, ‘ongoing’ Ig gene mutation). In the present paper, we report an extensive phenotypic analysis of L&H cells which revealed down‐regulation of a number of markers associated with the B‐cell lineage (eg CD19, CD37) and with the germinal centre maturation stage (eg PAG, LCK). The promoter methylation status of three of these down‐regulated genes (CD10, CD19, and LCK) was further studied in microdissected L&H cells, and this revealed that their promoters were unmethylated. In contrast, these genes showed promoter methylation in cell lines derived from CHL. Further investigation of the mechanisms responsible for the deregulation of these molecules in L&H cells may provide new insights into the genetic abnormalities underlying LPHL. Copyright © 2007 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Stress and burnout in colorectal and vascular surgical consultants working in the UK National Health Service
Authors: Sharma A. , Sharp D. M. , Walker L. G. , Monson J. R. T.
Published: October 2007

Background: It has been suggested that dealing with cancer is associated with increased stress and burnout in health‐care professionals. The aim of this study is to examine the prevalence of psychiatric morbidity and burnout in surgeons working in the National Health Service (NHS), and the putative relationship between psychiatric morbidity, burnout and the amount of cancer‐related work.

Methods: All consultant colorectal and vascular surgeons identified from their professional societies were sent a booklet consisting of questions about cancer‐related and specialty‐specific work load, job satisfaction and socio‐demographics. It also included the General Health Questionnaire (GHQ‐12), the Maslach Burnout Inventory (MBI) and the Coping Questionnaire.

Logistic regression analysis was used to identify independent predictors of psychiatric morbidity (GHQ), burnout (MBI) and retirement intentions.

Results: Five hundred and one questionnaire booklets were completed and returned (response rate 58.7%). The mean age of respondents was 47 years (range 31–65). The majority of the surgeons were male (460, 92%).

One hundred and sixty‐three (33%) surgeons scored in the positive range of the GHQ, and 154 (32%) had high burnout on at least one subscale of the MBI. Three hundred and eighty‐three (77%) surgeons stated that they intended to retire before the statutory retirement age.

Level of work satisfaction and perceived adequacy of training in communication and management skills were significantly negatively correlated with GHQ and MBI scores. Surgeons who planned to take early retirement or wished to retire as soon as they could afford to were more likely to have psychiatric morbidity and/or burnout. Surgeons who were married or cohabiting were less likely to have psychiatric morbidity, and younger surgeons were more likely to have higher levels of depersonalization (DP). Work satisfaction was negatively correlated with psychiatric morbidity and all three burnout scales.

Colorectal surgeons had a greater cancer‐related workload than vascular surgeons (48.6 vs 7.5%, respectively, U=2667, p<0.005). However, there were no significant differences between the two groups in psychiatric morbidity, personal accomplishment and emotional exhaustion. Vascular surgeons, however, had significantly higher levels of DP (p=0.04).

Conclusion: Levels of psychiatric morbidity, burnout and work dissatisfaction are worryingly high in colorectal and vascular surgeons and are likely to impact adversely on patient satisfaction and service quality. The number of surgeons intending to retire early is also a cause for concern both in terms of the overall number of trained surgeons in the NHS and in the balance between senior and junior surgeons. Apart from DP, these indicators of stress, however, were unrelated to cancer workload. Copyright © 2007 John Wiley & Sons, Ltd.
Psychosexual functioning of childhood cancer survivors
Authors: van Dijk E. M. , van Dulmen‐den Broeder E. , Kaspers G. J. L. , van Dam E. W. C. M. , Braam K. I. , Huisman J.
Published: October 2007

Purpose: The objective of the study is to explore psychosexual functioning and its relationship with quality of life in survivors of cancer in childhood.

Methods: Sixty childhood cancer survivors completed two questionnaires: psychosexual and social functioning questionnaire and MOS‐SF‐36.

Results: Psychosexual problems were frequent. About 20% of the survivors felt a limitation in their sexual life due to their illness. Older survivors (⩾25 years) had significantly less experience with sexual intercourse than their age‐matched peers in the Dutch population (p = 0.010). Survivors treated in adolescence had a delay in achieving psychosexual milestones compared with those treated in childhood: dating (p<0.025), touching under clothes (p<0.025), masturbation (female) (p<0.05) and sexual intercourse (p<0.025). No differences were found for sexual fantasies, kissing, masturbation (male) and oral sex. The total survivor group appraised their quality of life as less positive than their Dutch peers for the subscales of general and mental health (both p<0.001), physical and social functioning (p<0.01; p<0.001), bodily pain and vitality (both p<0.001). However, quality of life was not more affected adversely in survivors with psychosexual problems compared with survivors without these problems.

Conclusion: In this cohort of childhood cancer survivors, psychosexual problems were frequent. Treatment in adolescence is a risk factor for a delay in psychosexual development. Copyright © 2007 John Wiley & Sons, Ltd.
Supportive–expressive group therapy for primary breast cancer patients: a randomized prospective multicenter trial
Authors: Classen Catherine C. , Kraemer Helena C. , Blasey Christine , Giese‐Davis Janine , Koopman Cheryl , Palesh Oxana Gronskaya , Atkinson Ami , DiMiceli Sue , Stonisch‐Riggs Gail , Westendorp Joan , Morrow Gary R. , Spiegel David
Published: October 2007

Objective: The aim is to evaluate the effectiveness of a manualized 12‐week supportive–expressive group therapy program among primary breast cancer patients treated in community settings, to determine whether highly distressed patients were most likely to benefit and whether therapist's training or experience was related to outcome.

Method: Three hundred and fifty‐three women within one year of diagnosis with primary breast cancer were randomly assigned to receive supportive–expressive group therapy or to an education control condition. Participants were recruited from two academic centers and nine oncology practices, which were members of NCI's Community Clinical Oncology Program (CCOP) and were followed over 2 years.

Results: A 2×2×19 analysis of variance was conducted with main effects of treatment condition, cohort, and baseline distress and their interactions. There was no main effect for treatment condition after removing one subject with an extreme score. Highly distressed women did not derive a greater benefit from treatment. Therapist training and psychotherapy experience were not associated with a treatment effect.

Conclusions: This study provides no evidence of reduction in distress as the result of a brief supportive–expressive intervention for women with primary breast cancer. Future studies might productively focus on women with higher initial levels of distress. Copyright © 2007 John Wiley & Sons, Ltd.
Prostate cancer cells tolerate a narrow range of androgen receptor expression and activity
Authors: Tararova Natalia D. , Narizhneva Natalya , Krivokrisenko Vadim , Gudkov Andrei V. , Gurova Katerina V.
Published: October 2007

BACKGROUND

The precise role of androgen receptor (AR) in the normal development of prostate and the progression of prostate cancer (CaP) remains controversial. While AR expression and activity is associated with growth arrest and differentiation of normal prostate cells, it is maintained in CaP cells that are characterized by continued proliferation. Our objective was to determine the importance of AR signaling for survival and growth of CaP cells, particularly those with a hormone‐refractory phenotype.

METHOD

AR expression was modulated in androgen‐sensitive (AS) and androgen‐insensitive (AI) CaP cells using RNAi and cDNA transduction. Resulting changes in AR transcriptional activity and cell growth were quantified.

RESULTS

Interference with AR expression in both AS and AI CaP cells by shRNA transduction demonstrated a direct correlation between residual AR expression and cell viability. CaP cells lacking AR expression undergo apoptosis several days after AR down‐regulation. This delayed response suggests that AR regulates apoptosis likely through an indirect mechanism. Overexpression of AR or hyper‐stimulation of AR with high levels of androgen was also poorly tolerated by CaP cells. Cells with elevated AR had a growth disadvantage due to G1 cell cycle arrest and induction of p21 and GADD45 expression.

CONCLUSIONS

CaP cells expressing endogenous AR are sensitive to both increases and decreases in AR expression levels and activity. AR in CaP cells is delicately regulated to provide a balance between cell death and continued proliferation. Thus, both approaches, inhibition and over‐stimulation of AR activity, may have therapeutic value for treatment of prostate cancer. Prostate 67: 1801–1815, 2007. © 2007 Wiley‐Liss, Inc.
Establishing normal reference ranges for prostate volume change with age in the population‐based Krimpen‐study: Prediction of future prostate volume in individual men
Authors: Bosch J.L.H.R. , Tilling K. , Bohnen A.M. , Bangma C.H. , Donovan J.L.
Published: October 2007

BACKGROUND

We aim to establish the normal pattern of prostate volume change with age to provide a baseline from which accelerated prostate growth might be identified in patients with lower urinary tract symptoms/benign prostatic hyperplasia (LUTS/BPH).

METHODS

In a community‐based study, prostate volume was determined at baseline and after 2.1 and 4.2 years in men without prostate cancer. A bivariate multilevel growth curve model was used to estimate the pattern of change of prostate volume with age.

RESULTS

The average percentage increase of total prostate volume and transition zone volume per year of follow‐up was 2.2% and 3.5%, respectively. The final model showed that prostate volume was related to age only. The future prostate volume of an individual can be predicted based on his age and known history of prostate volume. The model was also used to calculate time needed for the prostate volume to increase with a certain percentage, for men with different baseline prostate volume values at different ages.

CONCLUSIONS

This method establishes normal prostate volume values by age using prostate volume history in men without prostate cancer. The model provides baseline data from which disease progression might be detected. Prostate 67: 1816–1824, 2007. © 2007 Wiley‐Liss, Inc.
Insecticidal activity of destruxin, a mycotoxin from Metarhizium anisopliae (Hypocreales), against Spodoptera litura (Lepidoptera: Noctuidae) larval stages
Authors: Sowjanya Sree K , Padmaja Vadlamani , Murthy Yellajyohula LN
Published: October 2007

BACKGROUND: The cyclodepsipeptide destruxin produced by the entomopathogen Metarhizium anisopliae (Metch.) was administered by different methods, topical application, ingestion and a combination of the two, in an attempt to minimize the mycotoxin dose for efficient management of the insect pest Spodoptera litura (Fab.).

RESULTS: The insecticidal activity of destruxin on the larval stages of S. litura showed an ascending trend in LD50 values with increasing age. The value for 12‐day‐old larvae in the combined application assay was as low as 0.045 µg g−1 body weight of crude destruxin from M‐19 strain when compared with the corresponding values of 0.17 µg g−1 body weight in the ingestion assay and 0.237 µg g−1 body weight in the topical application assay. On the other hand, values were higher in the treatments with crude destruxin from the low‐virulence M‐10 strain of M. anisopliae showing the least quantities of A and E components of destruxin.

CONCLUSION: Laboratory bioevaluation showed the combination assay of ingestion and topical application of crude destruxin to be efficient in enhancing its insecticidal properties. The adopted combination assay apparently simulates application of the insecticide at field level. Quantitative differences between destruxins from low‐ and high‐virulence strains of M. anisopliae are in accordance with its presumed role in virulence. Copyright © 2007 Society of Chemical Industry
Electrical excitation of shock and soliton‐like waves in high‐electron‐mobility transistor structures
Authors: Semenikhin Ihor , Ryzhii Victor , Vostrikova Ekaterina , Ivanov Andrej
Published: October 2007

Abstract
Population inversion of photoexcited electrons and holes in graphene and its negative terahertz conductivity
Authors: Ryzhii Victor , Ryzhii Maxim , Otsuji Taiichi
Published: October 2007

We demonstrate that sufficiently strong optical excitation may result in the population inversion in graphene, so that the real part of the ac conductivity can be negative in the terahertz range of frequencies. We study also how the heating of the electron‐hole system influences the effect of negative ac conductivity. The effect of population inversion and negative ac conductivity might be used in graphene‐based coherent sources of terahertz electromagnetic radiation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Monte Carlo simulation of surface charge effects in T‐branch nanojunctions
Authors: González T. , Iñiguez‐de‐la‐Torre I. , Pardo D. , Mateos J. , Bollaert S. , Roelens Y. , Cappy A.
Published: October 2007

We analyze the influence of the surface charge on the operation of ballistic T‐branch junctions based on InAlAs/InGaAs layers by means of a semi‐classical 2‐D Monte Carlo simulator. A new self‐consistent model in which the local value of the surface charge is dynamically adjusted depending on the surrounding carrier density is used in the calculations. The rectifying behaviour exhibited by these devices (down‐bending shape of the output voltage VC as a function of the applied voltage VR = ‐VL =V) is found to be much influenced by the surface charge. A satisfactory agreement is achieved between simulated results and experimental measurements. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Transport properties of multi‐walled carbon nanotubes grown by boron addition method
Authors: Ishii S. , Okutsu T. , Ueda S. , Takano Y.
Published: October 2007

The transport property of boron‐doped multi‐walled carbon nanotubes (MWNTs) was investigated. The boron‐doped MWNTs were grown by a novel CVD process using a methanol solution of boric acid as a source material. In order to evaluate the transport property accurately, the electrical conductivity of each individual MWNT was measured by a four‐point method. Nano‐sized four electrodes with a width of several hundred nanometers were fabricated on an individual MWNT using electron beam (EB) lithography. The conductivity of a boron‐doped MWNT was one or two orders of magnitude higher than that of a non‐doped MWNT at room temperature. Furthermore, the boron‐doped MWNT was found to maintain a high conductivity at a very low temperature of 0.6 K, while the non‐doped MWNT became an insulator. The electrical conductivity of the MWNTs was increased by boron doping. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Transient negative cyclotron absorption due to partially‐inverted distribution of photoexcited electrons
Authors: Romanets P. N. , Vasko F. T. , Ryzhii V. I.
Published: October 2007

The transient magnetoresponse of electrons with partially‐inverted distribution excited by an ultrashort optical pulse in bulk GaAs and InSb is considered. A huge transient amplification of a probe microwave or THz field due to negative cyclotron absorption is described using the kineticequation and the wave equation. A quantum picture of THz emission due to transitions between the Landau levels with different broadenings is suggested. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Feasibility of sequential multiphoton absorption for terahertz radiation detection
Authors: Castellano Fabrizio , Iotti Rita Claudia , Rossi Fausto
Published: October 2007

Multilevel architectures based on semiconductor nanostructures appear as promising designs for unipolar midinfrared detectors. In this paper we theoretically investigate their feasibility in the terahertz frequency range. Here, the performances of common quantum‐well photodetectors, based on a single bound subband, are severely hindered by high dark current and low Tblip values. We will demonstrate that, in this respect, the multi‐subband scheme represents a better alternative to the conventional design. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nonequilibrium carrier corrections to the optical gain in semiconductor quantum well structures
Authors: Weetman Philip , Wartak Marek S.
Published: October 2007

We report on the development of a novel self‐consistent nano‐scale semiconductor laser model where Wigner functions are used to model carrier dynamics and boundary conditions. The technique allows one to add a new non‐equilibrium correction term to standard formulations of optical As an example, the formalism susceptibility. is applied in the calculation of gain for a single quantum well laser. The conventional component of the gain uses a 4Ł 4 Luttinger‐Kohn bandstructure approximation and the non‐equilibrium correction term is calculated with a parabolic bandstructure approximation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Time‐resolved spectroscopy in an undoped GaN (1‐101)
Authors: Kim Eunhee , Hikosaka Toshiki , Honda Yoshio , Yamaguchi Masahito , Sawaki Nobuhiko
Published: October 2007

Time‐resolved photoluminescence spectroscopy was performed at 77 K in a GaN (1‐101) grown on a 7 degree off‐axis (001) Si substrate. The sample was grown by metal‐organic‐vapour‐phase‐epitaxy (MOVPE) and was un‐intentionally doped with O, C and Si. By using photoluminescence intensity correlation method, the energy relaxation process of the photogenerated carriers near the band edge was investigated in pico‐second regime. The correlation signal was represented by a single exponential decay curve and the energy relaxation time was determined, which depended strongly on the kinetic energy of the excess carriers. At low energies, the relaxation time was around 700 ps, while it was as short as a few ps at the highest energy under study. The correlation signals obtained for carriers of which kinetic energy was less than 80 meV showed an anti‐correlation behaviour suggesting the occurrence of carrier accumulation. The time constants for the accumulation were of several picoseconds depending on the kinetic energy, which was nearly equal to the decay time constants determined at high energies. This fact shows that the energy relaxation at high energies is controlled by the emission of an LO phonon. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Development of a measurement system for quantum shot noise at low temperatures
Authors: Hashisaka M. , Nakamura S. , Yamauchi Y. , Kasai S. , Kobayashi K. , Ono T.
Published: October 2007

The noise power spectral density of the mesoscopic devices was measured at low temperatures with two homemade systems for low‐ and high‐frequency ranges. By measuring the noise of the devices at finite bias voltages in the low‐freqiency setup, we estimated a typical cut‐off frequency to avoid the 1/f noise. We developed a high‐frequency measurement system with an cryogenic amplifier and a resonant circuit and calibrated it by measuring the Johnson‐Nyquist noise. We compare these two systems and discuss the advantage of the high‐frequency measurement system. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electron decoherence in a semiconductor due to electron‐phonon scattering
Authors: Buscemi Fabrizio , Cancellieri Emiliano , Bordone Paolo , Bertoni Andrea , Jacoboni Carlo
Published: October 2007

A quantitative analysis of the electron decoherence is performed in the case where an electron interacts with an environment consisting of a phonon bath at a given temperature T. In particular we study the decoherence in terms of the entanglement formation between the electron, initially described by a Gaussian wavepacket, and the environment by using the linear entropy written in terms of the Wigner function. In our work we evaluate, in a rigorous fully quantum mechanical approach, the electron‐phonon interaction using the Wigner‐function formalism. The problem is numerically solved for different time steps, up to the lowest order in the Neumann expansion. Our numerical procedure allows to analyze the system in different conditions and to understand the effect of the electron velocity and of the phonon momenta on the entanglement formation. Results are obtained in a one‐dimensional silicon system but they can be considered indicative of a more general behaviour. The Wigner function describing the electron and the phonon bath is evaluated by means of Neumann series, whose terms may be graphically represented by the so‐called Wigner paths. They are orbits in the Wigner phase‐space and are formed by ballistic free flights separated by scattering processes. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Transport in narrow minigap superlattices with inter‐Wannier‐Stark level tunneling
Authors: Andronov A. A. , Dodin E. P. , Nozdrin Yu. N. , Zinchenko D. I.
Published: October 2007

Low temperature electron transport under interminiband Zener tunneling and LO‐phonon scattering in the second and higher minibands in GaAs/Alx Ga1¡x As superlattices with weak barriers has been studied. At low electric fields multiple negative differential low‐frequency conductivity regions and effects of complicated electron transport have been found. In stronger fields peculiarities of current ‐ voltage curves attributed to resonant tunneling between Wannier‐Stark levels of different minibands have been separated basing on calculated wavefunctions and energies of the levels. Calculated value of optical matrix element for inter‐Wannier‐Stark transitions is promising to achieve negative conductivity at these transitions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Roughness effect on electron transport through quantum wires
Authors: Cancellieri E. , Rosini M. , Bordone P. , Jacoboni C.
Published: October 2007

In the present work we study, by means of numerical simulations, the coherent propagation of electrons in quantum wires and focus on the effect of the introduction of roughness along the channel. We study the electron evolution both in single and coupled quantum wires in the case where the electron freely move through the channel and in the case where transport is assisted by surface acoustic waves. It has been shown that systems of coupled quantum wires can realize a complete set of quantum logic gates.

However, its physical implementation is severely limited by the spreading of the wave packet and by the presence of interface roughness. Our results show that the potential of the surface acoustic wave succeeds in confining the electron wavefunction and in driving it along the channels also when interface roughness is introduced. This suggests that electron transport assisted by surface acoustic waves could be a very efficient way to realize quantum solid state devices. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Oxygen exchange between (de)nitrification intermediates and H2O and its implications for source determination of NO and N2O: a review
Authors: Kool D. M. , Wrage N. , Oenema O. , Dolfing J. , Van Groenigen J. W.
Published: October 2007

Stable isotope analysis of oxygen (O) is increasingly used to determine the origin of nitrate (NO) and nitrous oxide (N2O) in the environment. The assumption underlying these studies is that the 18O signature of NO and N2O provides information on the different O sources (O2 and H2O) during the production of these compounds by various biochemical pathways. However, exchange of O atoms between H2O and intermediates of the (de)nitrification pathways may change the isotopic signal and thereby bias its interpretation for source determination. Chemical exchange of O between H2O and various nitrogenous oxides has been reported, but the probability and extent of its occurrence in terrestrial ecosystems remain unclear. Biochemical O exchange between H2O and nitrogenous oxides, NO in particular, has been reported for monocultures of many nitrifiers and denitrifiers that are abundant in nature, with exchange rates of up to 100%. Therefore, biochemical O exchange is likely to be important in most soil ecosystems, and should be taken into account in source determination studies. Failing to do so might lead to (i) an overestimation of nitrification as NO source, and (ii) an overestimation of nitrifier denitrification and nitrification‐coupled denitrification as N2O production pathways. A method to quantify the rate and controls of biochemical O exchange in ecosystems is needed, and we argue this can only be done reliably with artificially enriched 18O compounds. We conclude that in N source determination studies, the O isotopic signature of especially N2O should only be used with extreme caution. Copyright © 2007 John Wiley & Sons, Ltd.
A new membrane inlet interface of a vacuum ultraviolet lamp ionization miniature mass spectrometer for on‐line rapid measurement of volatile organic compounds in air
Authors: Hou Keyong , Wang Junde , Li Haiyang
Published: October 2007

A novel membrane inlet interface coupled to a single‐photon ionization (SPI) miniature time‐of‐flight mass spectrometer has been developed for on‐line rapid measurement of volatile organic compounds (VOCs). The vacuum ultraviolet (VUV) light source for SPI was a commercial krypton discharge lamp with photon energy of 10.6 eV and photon flux of 1010 photons/s. The experimental results showed that the sensitivity was 5 times as high as obtained with the traditional membrane inlet. The enrichment efficiency could be adjusted in the range of 10 to 20 times for different VOCs when a buffer cell was added to the inlet interface, and the memory effect was effectively eliminated. A detection limit as low as 25 parts‐per‐billion by volume (ppbv) for benzene has been achieved, with a linear dynamic range of three orders of magnitude. The rise times were 6 s, 10 s and 15 s for benzene, toluene and p‐xylene, respectively, and the fall time was only 6 s for all of these compounds. The analytical capacity of this system was demonstrated by the on‐line analysis of VOCs in single puff mainstream cigarette smoke, in which more than 50 compounds were detected in 2 s. Copyright © 2007 John Wiley & Sons, Ltd.
Microelectrospray interface with coaxial sheath flow for high‐resolution capillary electrophoresis/mass spectrometry separation
Authors: Hashimoto Masahiko , Ishihama Yasushi , Tomita Masaru , Soga Tomoyoshi
Published: October 2007

We have fabricated a coaxial sheath liquid flow microelectrospray ionization (µESI) interface for capillary electrophoresis coupled with mass spectrometry (CE/MS). The ESI interface, which features a reduced probe diameter (130 µm i.d. × 174 µm o.d.) with a nebulizer‐free format, can relatively easily electrospray a large amount of make‐up sheath liquid (5–10 µL/min) over the long term (more than 80 runs) with a high degree of stability. The interface also provides higher separation qualities and improved detection sensitivities compared with a conventional ion spray (IS) interface. Copyright © 2007 John Wiley & Sons, Ltd.
Characterization of new phenolic compounds from leaves of Olea europaea L. by high‐resolution tandem mass spectrometry
Authors: Di Donna Leonardo , Mazzotti Fabio , Salerno Raffaele , Tagarelli Antonio , Taverna Domenico , Sindona Giovanni
Published: October 2007

A set of minor constituents of Olea europaea L. leaves have been identified and characterized by electrospray ionization tandem mass spectrometry (ESI‐MS/MS) and high‐resolution measurements (HRMS). Most of them are modified hydroxytyrosol species conjugated to a hexose unit. When possible, the structures of the new phenolic compounds present in Olea europaea L. have been confirmed by matching their MS/MS spectra with those of authentic standards isolated from other plants of the oleaceae family. The knowledge of the presence of new phenolic species in Olea europaea L. could provide tools for a full understanding of the secondary metabolism of this plant in relation to the biosynthesis of the phenolic species. Copyright © 2007 John Wiley & Sons, Ltd.
Delay‐range‐dependent robust stability and stabilization for uncertain systems with time‐varying delay
Authors: Li Tao , Guo Lei , Zhang Yuming
Published: October 2007

This paper concerns delay‐range‐dependent robust stability and stabilization for time‐delay system with linear fractional form uncertainty. The time delay is assumed to be a time‐varying continuous function belonging to a given range. On the basis of a novel Lyapunov–Krasovskii functional, which includes the information of the range, delay‐range‐dependent stability criteria are established in terms of linear matrix inequality. It is shown that the new criteria can provide less conservative results than some existing ones. Moreover, the stability criteria are also used to design the stabilizing state‐feedback controllers. Numerical examples are given to demonstrate the applicability of the proposed approach. Copyright © 2007 John Wiley & Sons, Ltd.
Adaptive designs: Looking for a needle in the haystack—A new challenge in medical research
Authors: Bauer Peter
Published: October 2007

The statistical principles of fully adaptive designs are outlined. The options of flexibility and the price to be paid in terms of statistical properties of the test procedures are discussed. It is stressed that controlled inference after major design modifications (changing hypotheses) will include a penalty: Intersections among all the hypotheses considered throughout the trial have to be rejected before testing individual hypotheses. Moreover, feasibility in terms of integrity and persuasiveness of the results achieved after adaptations based on unblinded data is considered as the crucial issue in practice. In the second part, sample size adaptive procedures are considered testing a large number of hypotheses under constraints on total sample size as in genetic studies. The advantage of sequential procedures is sketched for the example of two‐stage designs with a pilot phase for screening promising hypotheses (markers) and controlling the false discovery rate. Finally, we turn to the clinical problem how to select markers and estimate a score from limited samples, e.g. for predicting the response to therapy of a future patient. The predictive ability of such scores will be rather poor when investigating a large number of hypotheses and truly large marker effects are lacking. An obvious dilemma will show up: More optimistic selection rules may be superior if in fact effective markers exist, but will produce more nuisance prediction if no effective markers exist compared with more cautious strategies, e.g. aiming at some control of type I error probabilities. Copyright © 2007 John Wiley & Sons, Ltd.
Strategic human resource management, institutionalization, and employment modes: an empirical study in China
Authors: Li Ji , Lam Kevin , Sun James J. M. , Liu Shirley X. Y.
Published: October 2007

This study compares the predictions of institutional theory with those of the contingency perspective of strategic human resource management (SHRM) on the selection of an employment mode. Empirical data were collected from multinational enterprises, including the electronics and garment industries, that operate in China to test the relative importance of the determinants of the selection of an employment mode. The results provide greater support for the SHRM predictions than for the institutional theory predictions. The implications of the findings for researchers and practitioners are discussed. Copyright © 2007 John Wiley & Sons, Ltd.
Exploring the debate on short‐termism: a theoretical and empirical analysis
Authors: Marginson David , McAulay Laurie
Published: October 2007

The debate on short‐termism has focused on the economic factors of capital markets and performance measurement systems. Laverty (1996) has advocated the inclusion of individual and organizational dimensions to extend the debate. We reorient Laverty's extended debate by drawing upon a broad management and accounting literature and thereby develop testable theoretical explanations of short‐termism. The resulting hypotheses are tested in a telecommunications company. Our findings provide support for Laverty's (1996) argument that individual and organizational factors are important determinants of short‐termism. Copyright © 2007 John Wiley & Sons, Ltd.
Relaxor Behavior, Polarization Buildup, and Switching in Nanostructured 0.92 PbZn1/3Nb2/3O3–0.08 PbTiO3 Ceramics
Authors: Algueró Miguel , Hungría Teresa , Amorín Harvey , Ricote Jesús , Galy Jean , Castro Alicia
Published: October 2007

The relaxor‐type behavior, electrical polarization buildup, and switching in 0.92Pb(Zn1/3Nb2/3)O3–0.08PbTiO3 nanostructured ceramics with a grain size of ≈20 nm is reported for the first time. This composition presents the highest‐known piezoelectric coefficients, yet phase stability is an issue. Ceramics can only be obtained by the combination of mechanosynthesis and spark‐plasma sintering. The results raise the possibility of using nanoscale, perovskite‐relaxor‐based morphotropic‐phase‐boundary materials for sensing and actuation in nanoelectromechanical systems.
Surfactantless Synthesis of Silver Nanoplates and Their Application in SERS
Authors: Sun Yugang , Wiederrecht Gary P.
Published: October 2007

Silver nanoplates with thicknesses of 50–70 nm and edge lengths ranging from 200 nm to 1 μm have been grown on semiconductor wafers at room temperature through a simple galvanic reaction between an aqueous solution of AgNO3 and n‐type GaAs. The as‐grown Ag structures have chemically clean surfaces due to no surfactant or coordinating molecules being involved in the synthesis. Electron microscopy characterizations indicate that each Ag plate has rough surfaces and a half‐moon morphology with one straight edge and one arclike edge. Systematic studies on varying reaction conditions reveal that the oxide (i.e., Ga2O3 and As2O3) layers of GaAs, generated in situ in the reactions, play an important role in assisting the growth of anisotropic nanoplates. The cleanliness of the surfaces of the Ag nanoplates is beneficial to attachment of interesting molecules on their surfaces for various applications, such as plasmonic‐enhanced photophysical and photochemical processes and surface‐enhanced spectroscopies.
Approximate boundary conditions for diffraction by thin transmissive media
Authors: Rawlins A.D.
Published: October 2007

The object of this note is to describe a method that can be used to obtain useful boundary conditions to model various situations that arise in diffraction theory. In particular when wanting to apply the Wiener‐Hopf technique to diffraction problems that involve thin transmissive media. Transmissive here means that the thin layer medium suffers a change in the physical quantities of density, acoustic velocity, and wave number from the surrounding medium. The present approach can be used to obtain approximate boundary conditions for other physical applications where thin strata of transmissive material arise.
Individual behavioral variation in predator–prey models
Authors: Okuyama Toshinori
Published: October 2007

The role of individual behavioral variation in community dynamics was studied. Behavioral variation in this study does not refer to differences in average responses (e.g., average response between presence and absence of antipredator behavior). Rather it refers to the variation around the average response that is not explained by trivial experimental treatments. First, the effect of behavioral variation was examined based on Jensen's inequality. In cases of commonly used modeling framework with type II functional response, neglecting behavioral variation (a component of encounter rate) causes overestimation of predation effects. The effect of this bias on community processes was examined by incorporating the behavioral variation in a commonly used consumer‐resource model (Rosenzweig–MacArthur model). How such a consideration affects a model prediction (paradox of enrichment) was examined. The inclusion of behavioral variation can both quantitatively and qualitatively alter the model characteristics. Behavioral variation can substantially increase the stability of the community with respect to enrichment.
The Manifest Association Structure of the Single-Factor Model: Insights from Partial Correlations
Authors: Salgueiro Maria de Fátima , Smith Peter W. F. , McDonald John W.
Published: October 2007

The association structure between manifest variables arising from the single-factor model is investigated using partial correlations. The additional insights to the practitioner provided by partial correlations for detecting a single-factor model are discussed. The parameter space for the partial correlations is presented, as are the patterns of signs in a matrix containing the partial correlations that are not compatible with a single-factor model.
Thermal and Textural Properties of Organogels Developed by Candelilla Wax in Safflower Oil
Authors: Toro‐Vazquez J. F. , Morales‐Rueda J. A. , Dibildox‐Alvarado E. , Charó‐Alonso M. , Alonzo‐Macias M. , González‐Chávez M. M.
Published: October 2007

We investigated organogel formation in dispersions of CW in safflower oil (SFO). Candelilla wax (CW) has as its main component hentriacontane (78.9%), a n‐alkane with self assembly properties in organic solvents (i.e., vegetable oils). Results showed that, independent of the cooling rate (i.e., 1 °C/min and 10 °C/min) and gel setting temperature (Tset), the CW organogels observed a thermoreversible behavior. This was evaluated by the behavior of thermal parameters that characterized organogel formation (gelation temperature, Tg; heat of gelation, ΔHg) and melting (melting temperature, Tp; heat of melting, ΔHM) after two heating‐cooling cycles. For a given CW concentration (i.e., 0.5, 1.0, and 3%), the magnitude of ΔHM and Tp and the structural organization of the organogel, depended on the cooling rate, the thermodynamic drive force for gelation, and the annealing process occurring at high Tset (i.e., 25 °C). At Tset of 25 °C the microplatelet units that formed the organogel aggregated as a function of storage time, a process that resulted in an increase in organogel hardness. In contrast, at Tset of 5 °C annealing occurred in a limited extent, but gels had higher solid fat content and microplatelet units of a smaller size than the gels obtained at 25 °C. The result was a three‐dimensional network with greater hardness than the one obtained at 25 °C. The 3% CW organogels showed no phase separation up to 3 months at room temperature, with textures of potential use by the food industry.