bluuebunny/crossref_metadata_2025 huggingface dataset:
An inducible model of abacterial prostatitis induces antigen specific inflammatory and proliferative changes in the murine prostate
Authors: Haverkamp Jessica M. , Charbonneau Bridget , Crist Scott A. , Meyerholz David K. , Cohen Michael B. , Snyder Paul W. , Svensson Robert U. , Henry Michael D. , Wang Hsing‐Hui , Ratliff Timothy L.
Published: January 2011

BACKGROUND

Prostatitis is a poorly understood disease and increasing evidence suggests inflammation is involved in other prostatic diseases including prostate cancer.

METHODS

The ability of pre‐activated CD8 T cells to induce prostatitis was examined by adoptive transfer of prostate antigen specific CD8 T cells into POET‐3 mice or POET‐3/Luc/Pten−/+ mice. Characterization of the inflammatory response was determined by examining leukocyte infiltration by histological analysis, flow cytometry and by evaluating cytokine and chemokine levels in prostate tissue. The impact of inflammation on the prostate was evaluated by monitoring epithelial cell proliferation over time.

RESULTS

Initiation of inflammation by ovalbumin specific CD8+ T cells (OT‐I cells) resulted in development of acute prostatitis in the anterior, dorsolateral and ventral prostate of POET‐3 and POET‐3/Luc/Pten−/+ mice. Acute prostatitis was characterized by recruitment of adoptively transferred OT‐I cells and importantly, autologous CD4+ and CD8+ T cells, myeloid‐derived suppressor cells (MDSC) and regulatory T cells (Treg). In concert with leukocyte infiltration elevated levels of pro‐inflammatory cytokines and chemokines were observed. Inflammation also resulted in marked epithelial cell proliferation that was sustained up to 80 days post adoptive transfer of OT‐I cells.

CONCLUSIONS

The POET‐3 model represents a novel mouse model to study both acute and chronic prostate inflammation in an antigen‐specific system. Further, the POET‐3 mouse model can be crossed with other genetic models of disease such as the C57/Luc/Pten−/− model of prostate cancer, allowing the impact of prostatitis on other prostatic diseases to be evaluated. Prostate 71:1139–1150, 2011. © 2011 Wiley‐Liss, Inc.
Functional polymorphisms in cell death pathway genes FAS and FAS ligand and risk of prostate cancer in a Chinese population
Authors: Shao Pengfei , Ding Qi , Qin Chao , Wang Meilin , Tang Jialin , Zhu Jian , Chen Jiawei , Cao Qiang , Li Jie , Xu Bin , Zhang Zhengdong , Zhang Wei , Yin Changjun
Published: January 2011

BACKGROUND

Apoptosis is the physiological mechanism of programmed cell death and abnormal regulation of this pathway can lead to carcinogenesis. We hypothesized that the FAS −1377G>A, −670A>G, and FASL −844T>C polymorphisms are associated with risk of prostate cancer (PCa).

MATERIALS AND METHODS

We genotyped polymorphisms in a hospital‐based case–control study of 602 patients diagnosed with PCa and 703 cancer‐free controls in a Chinese population using polymerase chain reaction‐restriction fragment length polymorphism method.

RESULTS

We found a significantly decreased risk associated with FAS −1377GA [adjusted odds ratio (OR) = 0.71, 95% confidence interval (CI) = 0.56–0.90] genotype compared with the −1377GG genotype and decreased risk associated with FAS −670AG and −670GG genotypes (OR 0.75, 95% CI: 0.59–0.95; OR 0.70, 95% CI: 0.50–0.96) compared with the −670AA genotype. Consistently, we found that individuals carrying haplotype genotype with 0 or 1 risk allele (−1377G and −670A) had a lower risk of PCa than those with two risk alleles (OR 0.48, 95% CI: 0.28–0.80; OR 0.60, 95% CI: 0.41–0.87; OR 0.82, 95% CI: 0.69–0.97 for the AA, GG, and AG haplotype, respectively). In addition, when we evaluated these two FAS polymorphisms together, we found that the combined genotype with 4 risk alleles was associated with a significantly increased risk of PCa compared with those with 0–3 variants (OR 1.51, 95% CI: 1.19–1.91), and this increased risk was more pronounced among subgroups of Gleason score <7 and >7, and PSA > 20 ng/ml (OR 1.49, 95% CI: 1.08–2.04; OR 1.72, 95% CI: 1.25–2.44; OR 1.61, 95% CI: 1.23–2.13, respectively).

CONCLUSIONS

These results suggested that the FAS polymorphisms may contribute to PCa risk in a Chinese population. Prostate 71:1122–1130, 2011. © 2011 Wiley‐Liss, Inc.
Resistance to docetaxel‐induced apoptosis in prostate cancer cells by p38/p53/p21 signaling
Authors: Gan Lu , Wang Jianlin , Xu Huibi , Yang Xiangliang
Published: January 2011

BACKGROUND

Taxane chemotherapy is one of the few therapeutic options for men with castration‐resistant prostate cancer. However, the working mechanisms are not fully understood. We aimed to investigate the possible molecular mechanism of apoptosis induced by taxanes in prostate cancer.

METHODS

The human LNCaP cells (bearing wild‐type p53), DU145 cells (bearing mutant p53) and PC3 cells (lacking p53) were used. The expression levels of protein were determined by Western blot and the mRNA levels were determined by reverse transcriptase PCR. The apoptosis was measured by propidium iodide (PI) staining and flow cytometric analysis.

RESULTS

LNCaP cells are more resistant to docetaxel than DU145 and PC3 cells. Knocking down p53 by small interference RNA (siRNA) sensitizes LNCaP cells to docetaxel treatment. Docetaxel stabilizes p53 protein level and upregulates p21 in a p53‐dependent manner in LNCaP cells. Docetaxel increases p38 phosphorylation in LNCaP cells. Treatment with p38‐specific inhibitor SB203580 or knocking down p38 by siRNA significantly impaired the upregulation of p53 and p21 by docetaxel. Knocking down p38 or p21 sensitizes LNCaP cells to docetaxel treatment and the antiapoptotic effect of p21 can be reversed by p38 siRNA in LNCaP cells.

CONCLUSIONS

Stimulation of the p38/p53/p21 signaling axis could be important for regulating the susceptibility towards docetaxel in prostate cancer. Prostate 71:1158–1166, 2011. © 2011 Wiley‐Liss, Inc.
CYP17 gene polymorphisms and prostate cancer risk: A meta‐analysis based on 38 independent studies
Authors: Wang Fang , Zou Yan‐Feng , Feng Xiao‐Liang , Su Hong , Huang Fen
Published: January 2011

BACKGROUND

The results of recent published studies focusing on CYP17 polymorphisms in prostate cancer (PCa) susceptibility are often conflicting. We performed a meta‐analysis based on 38 independent studies to evaluate the association.

METHODS

Data were collected from the following electronic databases: PubMed, Excerpta Medica Database, and Chinese Biomedical Literature Database, with the last report up to September 2010. Meta‐analysis was conducted in a fixed/random effect model.

RESULTS

Thirty‐eight independent studies including 34,782 cases and 38,626 controls on the association of CYP17 gene polymorphisms with PCa risk in different ethnic groups were identified. The meta‐analysis was performed for five polymorphisms: rs743572 (A1/A2, 38 studies), rs6162 (C/T, 3 studies), rs619824 (C/A, 4 studies), rs2486758 (T/C, 4 studies), and rs10883782 (A/G, 4 studies). When all groups were pooled, we did not detect the association of rs743572 polymorphism with PCa risk. In the subgroup analysis, a significant association of rs743572 polymorphism and PCa was found in Black population (A2/A2 vs. A1/A1 + A2/A1: OR = 1.70, 95% CI = 1.08–2.69, P = 0.02), but not in Caucasian or Asian population. For other polymorphisms, we found that rs619824 polymorphism was associated with a significant decreased risk of PCa (A vs. C: OR = 0.95, 95% CI = 0.92–0.99, P = 0.01), and rs2486758 polymorphism was associated with a significant increased risk of PCa (C vs. T: OR = 1.07, 95% CI = 1.03–1.12, P = 0.002).

CONCLUSION

This meta‐analysis suggests that rs743572 polymorphism is associated with PCa risk in Black population, but not in Caucasian or Asian population. Moreover, our study suggests that rs619824 and rs2486758 polymorphisms are associated with PCa risk. Prostate 71:1167–1177, 2011. © 2011 Wiley‐Liss, Inc.
Impact of prostate‐specific antigen (PSA) nadir and time to PSA nadir on disease progression in prostate cancer treated with androgen‐deprivation therapy
Authors: Huang Shu‐Pin , Bao Bo‐Ying , Wu Ming‐Tsang , Choueiri Toni K. , Goggins William B. , Huang Chao‐Yuan , Pu Yeong‐Shiau , Yu Chia‐Cheng , Huang Chun‐Hsiung
Published: January 2011

BACKGROUND

The influence of PSA kinetics on the outcome of metastatic prostate cancer after androgen deprivation therapy (ADT) is not well understood. We evaluated the prognostic significance of PSA nadir and time to PSA nadir as well as their potential interactive effect on the progression of disease after ADT.

METHODS

A total of 650 men with advanced or metastatic prostate cancer treated with ADT were studied. The prognostic significance of PSA nadir and time to PSA nadir on disease progression were analyzed using Kaplan–Meier analysis and the Cox regression model.

RESULTS

We found that both PSA nadir and time to PSA nadir were independent and significant predictors of disease progression. Patients with higher PSA nadir (≥0.2 ng/ml) and shorter time to PSA nadir (<10 months) had significant shorter time to disease progression after adjusting for other covariates. The combined analyses showed a potential synergistic effect of these two variables on disease progression. Patient with higher PSA nadir and shorter time to PSA nadir had significantly higher risk for disease progression compared to those with lower PSA nadir and longer time to PSA nadir (Hazard Ratios (HR) = 3.11, P < 0.001).

CONCLUSIONS

We concluded that both PSA nadir and time to PSA nadir are significant predictors of disease progression for prostate cancer patients receiving ADT. Prostate 71:1189–1197, 2011. © 2011 Wiley‐Liss, Inc.
Parathyroid hormone is not involved in prostate growth in patients with benign prostatic hyperplasia
Authors: Kim Won Tae , Choi Young Deuk , Park Cheol , Kim Young‐Won , Yun Seok Joong , Kim Isaac Yi , Kim Wun‐Jae
Published: January 2011

BACKGROUND

A recent population‐based study reported that serum calcium and parathyroid hormone stimulate prostate growth. We evaluated whether serum PTH, vitamin D, and calcium levels correlate with prostate size, PSA levels, and obesity in Korean patients with histologically proven BPH.

METHODS

Patients with histopathologically proven BPH who underwent transurethral resection of the prostate were enrolled (n = 289). Patients with PSA levels of ≥3 ng/ml underwent multicore transrectal prostate biopsy before TURP to rule out prostate cancer. Patients with serum creatinine levels >1.4 mg/dl, PSA levels >20 ng/ml, and/or PTH levels <10 pg/ml were excluded. Correlations between serum parameters and clinical data were determined. After adjustment for potential confounders, including age and body mass index, multiple linear regression served to compute associations.

RESULTS

The mean age, serum PSA level, PTH level, and prostate size were 68.13 ± 7.15 years, 4.10 ± 3.88 ng/ml, 24.33 ± 12.52 pg/ml, and 44.27 ± 24.15 g, respectively. Prostate size correlated positively with age (r = 0.209, P < 0.001) and PSA levels (r = 0.481, P < 0.001), and PSA levels correlated positively with age (r = 0.226, P < 0.001) and prostate size (r = 0.481, P < 0.001), but neither variable correlated with PTH, vitamin D, calcium levels, or BMI. Upon multiple adjusted linear regression analysis, prostate size correlated with BMI and serum PSA (both P < 0.001), and serum PSA levels correlated with BMI and prostate size (P = 0.007, P < 0.001, respectively), but neither variable correlated with PTH, vitamin D, or serum calcium levels.

CONCLUSIONS

In Korean patients with histopathologically proven BPH, high PTH, vitamin D, and calcium levels do not stimulate prostate growth. Prostate 71:1210–1215, 2011. © 2011 Wiley‐Liss, Inc.
Long‐term cryopreservation of pyramidalis muscle specimens as a source of striated muscle stem cells for treatment of post‐prostatectomy stress urinary incontinence
Authors: Sumino Yasuhiro , Hirata Yuji , Hanada Mari , Akita Yasuyuki , Sato Fuminori , Mimata Hiromitsu
Published: January 2011

BACKGROUND

Stem‐cell injection into the degenerated external urethral sphincter is a new treatment modality for stress urinary incontinence (SUI). We examined the possibility of long‐term cryopreserved pyramidalis muscle (PM) specimens as a source of striated muscle stem cells for the treatment of post‐prostatectomy SUI.

METHODS

PM specimens were obtained from five male patients (mean age, 61–70 years) who underwent radical prostatectomy for prostate cancer. Specimens (volume, approximately 125 mm3) were obtained from the incisional edge, minced, and stored at −80°C in a freezing medium (Cell Banker 1®). After 24–60 months, the specimens were thawed and directly incubated at 37°C. Satellite cells were selectively cultured by magnetic affinity cell sorting using an anti‐neural cell adhesion molecule (NCAM) antibody. Osteogenic and adipogenic differentiation were induced by bone morphogenic protein‐7 (BMP‐7) and γ‐linolenic acid, respectively.

RESULTS

NCAM‐positive cells (>99% purity) were selectively cultured from all cryopreserved PM specimens and confirmed as being of striated muscle origin by the expression of desmin and MyoD. They fused and differentiated into multinucleated myotubes 7 days after incubation in a differentiation induction medium. Stimulation by BMP‐7 and γ‐linolenic acid induced expression of alkaline phosphatase (osteoblast marker) and lipid deposition within the cytoplasm (adipocyte characteristic), respectively.

CONCLUSIONS

Long‐term cryopreserved PM specimens can be used to culture muscle stem cells. Therefore, this method may be utilized for SUI treatment when necessary. Moreover, complete remove of the prostate gland without fear of injury to the urethral sphincter may be possible in patients with apical cancer or T3 prostate cancer. Prostate 71:1225–1230, 2011. © 2011 Wiley‐Liss, Inc.
TM4SF1, a novel primary androgen receptor target gene over‐expressed in human prostate cancer and involved in cell migration
Authors: Allioli Nathalie , Vincent Séverine , Vlaeminck‐Guillem Virginie , Decaussin‐Petrucci Myriam , Ragage Florence , Ruffion Alain , Samarut Jacques
Published: January 2011

BACKGROUND

The Androgen Receptor (AR) plays a key role in controlling prostate gland homeostasis and contributes to prostate carcinogenesis. The identification of its target genes should provide new candidates that may be implicated in cancer initiation and progression.

METHODS

Transcriptomic experiments and chromatin immunoprecipitation were combined to identify direct androgen regulated genes. Real‐time quantitative PCR (RT‐qPCR) analyses were performed to measure TM4SF1 mRNA levels in prostate cancer and benign prostatic hyperplasia (BPH) specimens. Immunohistochemical methods were used to compare TM4SF1 protein expression profiles in the same cohort. A targeted siRNAs knockdown strategy was used, prior to wound healing assays, to analyze the role of TM4SF1 in cell migration in vitro.

RESULTS

We demonstrate for the first time that TM4SF1 is a direct target gene of the AR, a transcription factor of the steroid nuclear receptor family. A functional androgen response element was identified in the promoter region of the gene. In addition, TM4SF1 mRNA expression was higher in cancer samples compared to BPH tissues. The TM4SF1 protein mediates cell motility of prostate cancer cells where it is predominantly localized in the cytoplasm, in contrast to its apical membrane localization in normal prostate epithelial cells.

CONCLUSIONS

Our results reveal a novel function for TM4SF1 in AR signaling. The TM4SF1 mRNA expression is higher in prostate cancer tissues as compared to BPH samples. Inhibition of cell migration after targeted knockdown of TM4SF1 protein expression suggests its contribution to prostate cancer cell metastasis. Prostate 71:1239–1250, 2011. © 2011 Wiley‐Liss, Inc.
Epitope motif of an anti‐nitrotyrosine antibody specific for tyrosine‐nitrated peptides revealed by a combination of affinity approaches and mass spectrometry
Authors: Drǎguşanu Mihaela , Petre Brînduşa‐Alina , Przybylski Michael
Published: January 2011

Nitration of tyrosine residues has been shown to be an important oxidative modification in proteins and has been suggested to play a role in several diseases such as atherosclerosis, asthma, lung and neurodegenerative diseases. Detection of nitrated proteins has been mainly based on the use of nitrotyrosine‐specific antibodies. In contrast, only a small number of nitration sites in proteins have been unequivocally identified by MS. We have used a monoclonal 3‐NT‐specific antibody, and have synthesized a series of tyrosine‐nitrated peptides of prostacyclin synthase (PCS) in which a single specific nitration site at Tyr‐430 had been previously identified upon reaction with peroxynitrite17. The determination of antibody‐binding affinity and specificity of PCS peptides nitrated at different tyrosine residues (Tyr‐430, Tyr‐421, Tyr‐83) and sequence mutations around the nitration sites provided the identification of an epitope motif containing positively charged amino acids (Lys and/or Arg) N‐terminal to the nitration site. The highest affinity to the anti‐3NT‐antibody was found for the PCS peptide comprising the Tyr‐430 nitration site with a KD of 60 nM determined for the peptide, PCS(424‐436‐Tyr‐430NO2); in contrast, PCS peptides nitrated at Tyr‐421 and Tyr‐83 had substantially lower affinity. ELISA, SAW bioaffinity, proteolytic digestion of antibody‐bound peptides and affinity‐MS analysis revealed highest affinity to the antibody for tyrosine‐nitrated peptides that contained positively charged amino acids in the N‐terminal sequence to the nitration site. Remarkably, similar N‐terminal sequences of tyrosine‐nitration sites have been recently identified in nitrated physiological proteins, such as eosinophil peroxidase and eosinophil‐cationic protein. Copyright © 2011 European Peptide Society and John Wiley & Sons, Ltd.
Analysis of the interacting surface of maurotoxin with the voltage‐gated Shaker B K+ channel
Authors: Fajloun Ziad , Andreotti Nicolas , Fathallah Mohamed , Sabatier Jean‐Marc , De Waard Michel
Published: January 2011

Maurotoxin (MTX) is a 34‐residue toxin that was isolated initially from the venom of the scorpion Scorpio maurus palmatus. Unlike the other toxins of the α‐KTx6 family (Pi1, Pi4, Pi7, and HsTx1), MTX exhibits a unique disulfide bridge organization of the type C1C5, C2C6, C3C4, and C7C8 (instead of the conventional C1C5, C2C6, C3C7, and C4C8, herein referred to as Pi1‐like) that does not prevent its folding along the classic α/β scaffold of scorpion toxins. MTXPi1 is an MTX variant with a conventional pattern of disulfide bridging without any primary structure alteration of the toxin. Here, using MTX and/or MTXPi1 as models, we investigated how the type of folding influences toxin recognition of the Shaker B potassium channel. Amino acid residues of MTX that were studied for Shaker B recognition were selected on the basis of their homologous position in charybdotoxin, a three disulfide‐bridged scorpion toxin also active on this channel type. These residues favored either an MTX‐ or MTXPi1‐like folding. Our data indicate clearly that Lys23 and Tyr32 (two out of ten amino acid residues studied) are the most important residues for Shaker B channel blockage by MTX. For activity on SKCa channels, the same amino acid residues also affect, directly or indirectly, the recognition of SK channels. The molecular modeling technique and computed docking indicate the existence of a correlation between the half cystine pairings of the mutated analogs and their activity on the Shaker B K+ channel. Overall, mutations in MTX could, or could not, change the reorganization of disulfide bridges of this molecule without affecting its α/β scaffold. However, changing of the peptide backbone (cross linking disulfide bridges from MTX‐like type vs MTXPi1‐like type) appears to have less impact on the molecule activity than mutation of certain key amino acids such as Lys23 and Tyr32 in this toxin. Copyright © 2011 European Peptide Society and John Wiley & Sons, Ltd.
Single‐photon detection by Si single‐electron FETs
Authors: Tabe Michiharu , Udhiarto Arief , Moraru Daniel , Mizuno Takeshi
Published: January 2011

We have demonstrated that Si single‐electron SOI‐MOSFETs with multidots channel have attractive new functions such as single‐photon detection. Multidots formed by nanoscale selective oxidation of thin SOI layer have been used for photon detection. Most recently, we have investigated photon detection capabilities of FETs having phosphorus (P)‐doped channel. In such P‐doped FETs, each P donor works as a quantum dot for electrons and single‐electron transport is achieved by tunnelling through donor potentials. Using such P‐doped FETs, single‐photon detection has been demonstrated. Furthermore, in order to directly observe the spatial landscape of even a single‐dopant potential, we have developed low‐temperature‐Kelvin probe force microscopy (LT‐KFM) and succeeded in detecting a single‐dopant potential in the channel region. In this paper, we present results of photon‐induced random telegraph signals in crystalline‐dot‐type and donor‐dot‐type multidot single‐electron SOI‐MOSFETs, and direct observation of a single‐dopant potential by LT‐KFM.
Interdependency of surface morphology and wavelength fluctuations of indium‐rich InGaN/GaN quantum wells
Authors: Lermer Teresa , Pietzonka Ines , Avramescu Adrian , Brüderl Georg , Müller Jens , Lutgen Stephan , Strauss Uwe
Published: January 2011

The origin of indium fluctuations in indium‐rich quantum wells (QWs) is of high interest for direct green laser diodes. We present the correlation of morphological features such as macrosteps investigated by AFM measurements and wavelength fluctuations seen in cathodoluminescence images of InGaN/GaN QWs grown by metal organic vapor phase epitaxy. We observe an opposed wavelength shift of 5 nm in the vicinity of macrosteps for the investigated UV and green InGaN QW samples. We present a growth model taking adsorption, desorption, and migration processes into account to explain this difference via a temperature dependent change in indium incorporation in the vicinity of the observed macrostep edges.
A novel substrate LaBGeO5 lattice‐matched to InN
Authors: Miyazawa Shintaro , Ichikawa Satoru , Liu Yuhuai , Ji Shiyang , Matsuoka Takashi , Nakae Hideo
Published: January 2011

As a novel substrate with a lattice‐mismatch of only 0.8% along the a‐axis to InN thin films, we propose LaBGeO5 (LBGO) with a trigonal symmetry for the first time. A single crystal growth of LBGO by Czochralski (Cz)‐pulling was investigated, and c‐axis‐oriented LBGO single crystals with high crystallinity were successfully grown with a pulling rate of 0.5 mm/h in O2‐atomosphere. c‐axis oriented InN film was subsequently grown on the obtained LBGO {001} substrate by metalorganic vapor epitaxy (MOVPE), and it was verified that InN film on LBGO was less‐strained as compared with that on {001} sapphire substrate. It is stressed to say that LBGO can be expected as a lattice‐matching substrate for the epitaxial growth of InN.
Kelvin probe force microscopy in the presence of intrinsic local electric fields
Authors: Baumgart Christine , Müller Anne‐Dorothea , Müller Falk , Schmidt Heidemarie
Published: January 2011

Kelvin probe force microscopy (KPFM) is used to investigate the electrostatic force between a conductive probe and doped semiconductors. The observed frequency dependence of the probed KPFM bias is strongly related to sample‐specific intrinsic local electric fields. Equilibrium drift and diffusion of excess charge carriers at low operation frequencies influence the characteristics of the asymmetric electric dipole in the surface region of the investigated semiconductors during the KPFM measurement. The sample‐specific KPFM background signal does not influence the frequency‐dependent lateral variation of the electrical signal. The KPFM bias probed on doped semiconductor nanostructures with high or small enough operation frequencies allows for quantitative dopant profiling or investigation of diffusion processes in internal electric fields, respectively.
Coherent growth of r‐plane GaN films on ZnO substrates at room temperature
Authors: Kobayashi Atsushi , Ueno Kohei , Ohta Jitsuo , Fujioka Hiroshi
Published: January 2011

We grew semipolar r‐plane GaN films on ZnO substrates at room temperature (RT) by pulsed laser depositon (PLD). The structural characteristics of r‐plane GaN films grown on nearly lattice‐matched ZnO substrates at RT were investigated by X‐ray diffraction and reciprocal space mapping (RSM). The r‐plane GaN films grown on ZnO exhibited the narrowest X‐ray rocking curves of any heteroepitaxial semipolar GaN films. The improvement in crystalline quality achieved by the use of ZnO substrates was attributed to the coherent growth of r‐plane GaN under non‐equilibrium conditions by PLD. Symmetric RSM revealed that r‐plane GaN grows on ZnO substrates without the tilting of the r‐plane that was often observed in lattice‐mismatched semipolar growth. These results indicated that the formation of misfit dislocations at the GaN/ZnO interface is suppressed by coherent growth at RT.
Structure characterization of spark plasma sintered alumina by positron annihilation lifetime spectroscopy
Authors: Djourelov Nikolay , Aman Yann , Berovski Kalin , Nédélec Patrick , Charvin Nicolas , Garnier Vincent , Djurado Elisabeth
Published: January 2011

Positron annihilation lifetime spectroscopy (PALS) measurements were performed to study the influence of the sintering temperature, heating rate and dwell time on the porosity and on the defect concentration on series of spark plasma sintered alumina samples. Two long‐lived components were found in the PALS spectra and were associated to pick‐off annihilation of ortho‐positronium localized in two types of pores. The same spectra were analysed in the frame of the three‐state‐trapping model and information for the intragranular and at grain boundary defect concentration was extracted. At sintering temperatures below 1200 °C the regime of the high (600 °C/min) heating rate leaded to more efficient defect annealing compared to the regime of the low (8 °C/min) heating rate, while at higher temperatures this difference disappeared. The low heating rate at high temperatures leaded to more compact samples compared to these sintered at the high heating rate as a result of intergranular pore concentration decrease.
Growth temperature altered morphology of Ge nanocolumns
Authors: Khare Chinmay , Gerlach Jürgen W. , Weise Michael , Bauer Jens , Höche Thomas , Rauschenbach Bernd
Published: January 2011

Germanium nanocolumns grown by glancing angle deposition on Si(100) substrates and prepatterned substrates comprising of SiO2 nanospheres demonstrated an altered morphology that is greatly influenced by the substrate temperature (TS). Surface diffusion‐driven mass transport and increased adatom mobility at homologous temperatures TS/TM ≈ 0.34 and 0.39 (TM melting temperature of Ge) augmented fibrous‐columnar and intracolumnar growth, respectively. Further increment of the substrate temperature provoked column merging and column broadening. The degree of film crystallinity increased while TS increased from 200 to 340 °C, shifting the preferential crystallite orientation from (111) to (220).
Nonalloyed ohmic contact of AlGaN/GaN HEMTs by selective area growth of single‐crystal n+‐GaN using plasma assisted molecular beam epitaxy
Authors: Zheng Zhi , Seo Huichan , Pang Liang , Kim Kyekyoon (Kevin)
Published: January 2011

Selective area growth (SAG) based on plasma assisted molecular beam epitaxy (PAMBE) was demonstrated to be effective to achieve low contact resistance for nonalloyed ohmic metals. An AlGaN/GaN high‐electron mobility transistor (HEMT) using SAG by PAMBE with nonalloyed ohmic metals and recessed drain/source structure exhibited a low specific contact resistance of 3.7 × 10−5 Ω cm2, high‐peak drain current of 604 mA/mm, and small gate leakage current of 3.4 µA. These results demonstrate that SAG by PAMBE produces nonalloyed HEMT with comparable or more favorable electric performance versus conventional alloyed counterpart while avoiding problems of the latter resulting from high‐temperature annealing.
Characteristics of undoped and Sb‐doped ZnO thin films prepared in different atmospheres by pulsed laser deposition
Authors: Zhu B. L. , Zhu S. J. , Zhao X. Z. , Su F. H. , Li G. H. , Wu X. G. , Wu J.
Published: January 2011

Undoped and 0.56 at.% Sb‐doped ZnO thin films were prepared by pulsed laser deposition (PLD) under vacuum and an oxygen pressure of 0.2 Pa with sintered ceramic as targets. The effects of Sb doping and deposition atmosphere on structure and optical–electrical properties of the films were studied by X‐ray diffraction (XRD), scanning probe microscopy (SPM), Hall Effect measurement, transmittance spectra, and photoluminescence (PL) spectra. The results showed that undoped and Sb‐doped films deposited under vacuum had better crystallinity, higher carrier concentration, lower bandgap (Eg), and single violet emission as compared with the films deposited in an oxygen pressure of 0.2 Pa. Compared with undoped ZnO film, Sb‐doped ZnO film had higher carrier concentration and almost uniform Eg in both atmospheres, and it exhibited obviously improved crystallinity and green emission under an oxygen pressure of 0.2 Pa. The results implied that the deposition atmosphere strongly affected the growth kinetics of the films and intrinsic defect in the films, and Sb doping seemed also to affect the growth kinetics of the films under certain conditions and introduced SbZn defects and possibly SbZn‐2VZn defects, thus the structure and optical–electrical properties of the films were modified by the deposition atmosphere and Sb doping.
Effective control of polarity in Bi0.9La0.1FeO3 thin films by dopant‐related internal bias
Authors: Wang Yang , Chen Weigang , Chen Zuhuang , Rami Naidu Chukka , Wang Junling , Wang John , Chen Lang
Published: January 2011

The as‐grown polarizations of Mn‐ and Ti‐doped Bi0.9La0.1FeO3 thin films (BLFMn and BLFTi) are demonstrated to align in an upward direction due to the occurrence of an internal bias field Ei that points up. On the basis of the conductivity and XPS as well as leakage current measurements, Ei in BLFMn is attributed to an asymmetric distribution of charged defects, while the elevated Fermi level and broadened positively charged depletion zone are supposed to induce Ei in BLFTi. The different physical origins of Ei are intimately connected with the nature of aliovalent acceptor and donor dopants of Mn and Ti ions, which is further verified by the consistent voltage offsets in the piezoelectric hysteresis loops. This suggests an effective way to control the polarity of ferroelectric thin films through the tuning of chemical doping levels.
Fluctuation‐induced conductivity of melt‐textured Y0.95Er0.05Ba2Cu3O7−δ superconductor prepared in air
Authors: Pinheiro Lincoln Brum de Leite Gusmão , Costa Rosângela Menegotto , Júnior Pedro Rodrigues , da Cruz Gerson Kniphoff , Jurelo Alcione Roberto
Published: January 2011

Systematic conductivity measurements near TC in melt‐textured Y0.95Er0.05Ba2Cu3O7−δ superconductors, prepared using the top‐seeding growth technique, are presented. Measurements were performed both for current applied parallel and perpendicular to the c‐axis. Samples with different disorder states were studied and the influences of the erbium addition on conductivity fluctuations are discussed. The microstructural characteristics of samples were analyzed by scanning electron microscopy and X‐ray diffraction, while the superconducting properties were determined by resistivity and dc magnetization measurements. To identify power‐law divergences of the conductivity, the results were analyzed in terms of the temperature derivative of the resistivity (${\rm d}{\rho} /{\rm d}T$) and of the logarithmic temperature derivative of the conductivity (${-} {\rm d(ln}{\Delta} {\sigma} {\rm )}/{\rm d}T$). The fluctuations above the critical temperature are highly anisotropic: Gaussian regimes were observed for the $J//a(b)c$ configuration and critical regimes for the $J//ab$ configuration. Also, for the more disordered state, the data evidenced a two‐stage transition.
Lateral IBIC characterization of single crystal synthetic diamond detectors
Authors: Lo Giudice Alessandro , Olivero Paolo , Manfredotti Claudio , Marinelli Marco , Milani Enrico , Picollo Federico , Prestopino Giuseppe , Re Alessandro , Rigato Valentino , Verona Claudio , Verona‐Rinati Gianluca , Vittone Ettore
Published: January 2011

In order to evaluate the charge collection efficiency (CCE) profile of single‐crystal diamond devices based on a p‐type/intrinsic/metal configuration, a lateral Ion Beam Induced Charge (IBIC) analysis was performed over their cleaved cross sections using a 2 MeV proton microbeam. CCE profiles in the depth direction were extracted from the cross‐sectional maps at variable bias voltage. IBIC spectra relevant to the depletion region extending beneath the frontal Schottky electrode show a 100% CCE, with a spectral resolution of about 1.5%. The dependence of the width of the high efficiency region from applied bias voltage allows the constant residual doping concentration of the active region to be evaluated. The region where the electric field is absent shows an exponentially decreasing CCE profile, from which it is possible to estimate the diffusion length of the minority carriers by means of a drift–diffusion model. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of III‐nitride polarization on VOC in p–i–n and MQW solar cells
Authors: Namkoong Gon , Boland Patrick , Bae Si‐Young , Shim Jae‐Phil , Lee Dong‐Seon , Jeon Seong‐Ran , Foe Kurniawan , Latimer Kevin , Doolittle W. Alan
Published: January 2011

We performed detailed studies of the effect of polarization on III‐nitride solar cells. Spontaneous and piezoelectric polarizations were assessed to determine their impacts upon the open circuit voltages (VOC) in p–i(InGaN)–n and multi‐quantum well (MQW) solar cells. We found that the spontaneous polarization in Ga‐polar p–i–n solar cells strongly modifies energy band structures and corresponding electric fields in a way that degrades VOC compared to non‐polar p–i–n structures. In contrast, we found that piezoelectric polarization in Ga‐polar MQW structures does not have a large influence on VOC compared to non‐polar MQW structures. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Annual cycle of the West African monsoon: regional circulations and associated water vapour transport
Authors: Thorncroft Chris D. , Nguyen Hanh , Zhang Chidong , Peyrillé Philippe
Published: January 2011

Analysis of the annually varying regional circulations and their relationship to surface conditions and water vapour transport in the West African region is presented. The progression of the West African monsoon is described in terms of four key phases: (i) an oceanic phase between November and mid‐April when the rain band is broad with peak values just north of the Equator (∼1°N); (ii) a coastal phase between mid‐April and the end of June when the rainfall peak is in the coastal region around 4°N (over the ocean); (iii) a transitional phase during the first half of July when the rainfall peak decreases; and (iv) a Sahelian phase between mid‐July and September when the rainfall peak is more intense and established in the Sahelian region around 10°N. The annual evolution of the moisture fluxes, associated convergence, and rainfall is strongly impacted by the Atlantic cold tongue (cool water close to the Equator between boreal spring and summer) and the Saharan heat‐low. The cold tongue strongly regulates the timing and intensity of the coastal rainfall in spring. The heat‐low and its associated shallow meridional circulation strongly affect the profile in moisture flux convergence north of the main rain‐band maximum; in particular it is responsible for the establishment of a second peak in column moisture flux convergence there (approximately 8° poleward of the rainfall peak).

Particular emphasis is given to the coastal rainfall onset in April. A key aspect of this onset is acceleration of low‐level cross‐equatorial southerly winds, important for establishing the cold tongue, discouraging convection near the Equator and transporting moisture towards the coast. We argue that the rainfall peak is maintained at the coast, rather than steadily moving inland with the solar insolation, due to persistent warm water in the coastal region together with frictionally induced moisture convergence there. Copyright © 2011 Royal Meteorological Society
The use of potential vorticity inversion to evaluate the effect of precipitation on downstream mesoscale processes
Authors: Baxter Martin A. , Schumacher Philip N. , Boustead Joshua M.
Published: January 2011

The influence of precipitation near the surface warm front on precipitation downstream is evaluated. A two‐way nested simulation is computed for two selected cases: 13–15 February 2003 and 3–5 January 2005. The results of the simulation are compared with output from the North American Regional Reanalysis dataset, which is used as a high‐resolution proxy for true atmospheric conditions. The relevant physical processes in the generation and maintenance of precipitation poleward of other precipitation areas are analysed, along with perturbation potential vorticity (PV) fields. Piecewise PV inversion is used to determine height and wind fields associated with the perturbation PV. These height and flow fields are used to compute derived quantities such as balanced deformation, balanced temperature perturbation, and balanced moisture flux. Both cases illustrate that the role of rainfall near surface warm fronts on precipitation downstream is complex, and is associated with more than just moisture flux. The strength, depth and orientation of diabatically generated PV anomalies within these areas of rainfall are associated with mesoscale processes relevant to the maintenance of downstream precipitation. Lastly, this work presents a methodology for analysing the role of precipitation in individual events. Copyright © 2011 Royal Meteorological Society
The dynamics of heat lows over elevated terrain
Authors: Smith Roger K. , Spengler Thomas
Published: January 2011

Orographic effects on the dynamics of heat lows are investigated in an idealized flow configuration using a hydrostatic numerical model. The behaviour of the heat low that forms over a plateau‐like orography on a circular island is compared with that when the island is flat, and that when the plateau is surrounded by land instead of sea. In all cases, a broad‐scale, negative radial gradient of potential temperature forms in the daytime mixed layer over land. The presence of orography enhances the broad‐scale baroclinicity over the orographic slope due to the identical heating of a column of air with a reduced mass, i.e. lower surface pressure. In the absence of sea, the baroclinicity is solely confined to the slope of the orography. The broad‐scale potential temperature gradient results in an overturning circulation in the lowest few kilometres, which is separate from the shallower and more intense sea breeze circulation in the island cases. The presence of orography leads to a stronger overturning circulation via enhanced baroclinicity. In the case without sea, both the overturning circulation and tangential circulation are closely tied to the orography. The overturning circulation advects absolute angular momentum inwards to spin up the low‐level circulation, despite some frictional loss of angular momentum en route. During the night, radiative cooling over the land leads to a strong nocturnal low‐level jet that amplifies the spin‐up process. During the daytime, the cyclone weakens as the angular momentum is convectively mixed through a deep layer. The study extends an earlier one of Reichmann and Smith and corrects some details in their model. The results offer a refined interpretation of the Atlantic inflow to the Saharan heat low, described recently by Grams et al., and emphasize the role of orography in the formation of the inland baroclinic zone, which is a feature thereof. Copyright © 2011 Royal Meteorological Society
The definition of ‘truth’ for Numerical Weather Prediction error statistics
Authors: Frehlich Rod
Published: January 2011

A consistent definition of ‘truth’ is presented to define the errors in a numerical weather prediction (NWP) forecast, analysis and observations resulting from the unresolved turbulent field. ‘Truth’ is defined as the convolution of the continuous atmospheric variables by the effective spatial filter of an NWP model. Direct measurements of atmospheric variables are represented as an instrument error and a convolution of the continuous atmospheric variables by the observation sampling function. This clearly separates the instrument error from the observation sampling error that describes the mismatch between the NWP model effective spatial filter and the observation sampling function. The ensemble average that defines error statistics is defined by an infinite number of atmospheric realizations with statistically similar random fluctuations in the unresolved model field. This results in large spatial variations in the observation sampling errors due to the atmospheric variations in turbulence statistics. Two approaches are discussed to describe these spatial variations: one that defines observation error referenced to each model coordinate and one that assigns observation error referenced to each observation coordinate. The observation‐error statistics depend on the observation sampling function, the local spatial statistics of the turbulence field and the NWP model filter. The effects of imprecise knowledge of the shape of the model filter on observation sampling error are small for rawinsonde measurements and for observations that produce a linear average along a track. The modifications to data‐assimilation algorithms (the maximum‐likelihood (ML) method, minimum mean‐square‐error algorithms, Kalman filtering, variational data assimilation and ensemble data assimilation) to include the spatial variations in observation‐error statistics are discussed. In addition, the generation of ensemble forecast members should be consistent with the spatial variations in total observation error. A rigorous definition of error statistics is essential for evaluating the many different types of current and future observing systems. Copyright © 2010 Royal Meteorological Society
A case‐study of mesoscale spectra of wind and temperature, observed and simulated
Authors: Larsén Xiaoli Guo , Larsen Søren , Badger Merete
Published: January 2011

The spectra of the zonal and meridional winds and temperature over the mesoscale range of length‐scales (10−5<k<10−3rad m−1, with k the radian wave number) are examined through a case‐study using measurements and simulations. The measurements include 1 s and 10 min average winds and temperature, from which the temporal spectra are obtained by Fourier transform. The mesoscale Weather Research and Forecasting (WRF) model is used to simulate the weather for four days when gravity waves are observed. The four‐day dataset also includes a period with unstable conditions and free of gravity waves. The simulation provides a possibility to study the spatial spectra and, together with the measurements, it provides an opportunity to examine the validity of the Taylor hypothesis for transforming between temporal and spatial spectra. We examined these issues under stable and unstable conditions, both in the absence and presence of gravity waves. It was found that, in the absence of gravity waves, the spectral behaviour of wind and temperature (in terms of the form of the spectra and the energy distribution) is similar to the literature, and the Taylor hypothesis is valid. When the gravity waves are present, it was found that the Doppler‐shifted frequency has to be taken into account when converting the spectra between time and space. The simulation suggests that, in the presence of gravity waves, the kinetic energy is not evenly distributed between the zonal and meridional winds, rather the wind component along the main wave propagation direction contains larger variance. Copyright © 2011 Royal Meteorological Society
Classifying severe rainfall events over Italy by hydrometeorological and dynamical criteria
Authors: Molini L. , Parodi A. , Rebora N. , Craig G. C.
Published: January 2011

Raingauge data over Italy for the period January 2006–February 2009 have been used to classify severe rainfall events into two types using a recently developed methodology. The types are defined as either long‐lived and spatially distributed (Type I) if lasting more than 12 h and larger than 50 × 50 km2or brief and localized (Type II) if having shorter duration or smaller spatial extent. A total of 81 events were identified, with 51 classified as Type I and 30 as Type II. The work presented here examines the hypothesis that the two types of event are associated with different dynamical regimes distinguished by differing degrees of control of convective precipitation by the synoptic‐scale flow. For each of the 81 events, a time‐scale for convective adjustment is computed, based on gridded hourly precipitation rates derived from rain‐gauge data and ECMWF analysis (ERA‐Interim) of convective available potential energy (CAPE). Values of the convective adjustment time‐scale,τc, shorter than 6 h indicate convection that is responding rapidly to to the synoptic environment (equilibrium), while slower time‐scales indicate that other, presumably local, factors dominate. It was anticipated thatτc> 6 h would correspond to brief and localized Type II events, whileτc< 6 h would indicate Type I events. This hypothesis was largely confirmed, with 45 of the 51 Type I events having time‐scales shorter than 6 h and 20 of the 30 Type II events having time‐scales longer than 6 h. Copyright © 2011 Royal Meteorological Society
Improving the use of observations to calibrate ensemble spread
Authors: Flowerdew Jonathan , Bowler Neill E.
Published: January 2011

The Met Office Global and Regional Ensemble Prediction System (MOGREPS) uses an online inflation factor calculation to calibrate the spread of the ensemble in space and time and counteract the tendency of the Ensemble Transform Kalman Filter (ETKF) to underestimate analysis uncertainty. Until 2008, this calibration mechanism relied entirely on sonde and wind profiler data, and was only applied locally in the Extratropics. By producing more appropriate estimates of the error variance of ATOVS brightness temperature observations, it has become possible to include these in the inflation factor calculation. This in turn provides sufficient data to apply localisation uniformly over the globe. The new scheme improves the latitudinal distribution of spread in comparison to forecast error, especially in the Tropics. Issues remain with the vertical distribution of spread, which are addressed by work to be reported in a future paper. © 2011 Crown Copyright, the Met Office. Published by John Wiley & Sons, Ltd.
End‐to‐end protocol to secure ad hoc networks against wormhole attacks
Authors: Khurana Sandhya , Gupta Neelima
Published: January 2011

Most of the protocols to defend ad hoc networks against wormhole attacks rely on ‘trust your neighbor’ relationship. In this paper, we present an end‐to‐end algorithm which is more efficient than the existing algorithm both in terms of space and time. As our algorithm does not require speed and time, we do not need clock synchronization.

We prove that our algorithm is able to detect wormholes with tunnel length greater than or equal to $ \left[\{({2p-1})/{2p}\}k+{2}/{p}\right]r_{\rm max}$, where $p ={r_{\rm max}}/{r_{\rm min}}$ , $r_{\rm min}$ is the minimum communication range, $r_{\rm max}$ is the maximum communication range between any two nodes, and $k$ is path length in terms of the number of hop‐counts. However, with the help of simulations we show that we are able to detect wormholes even when tunnel length is much less than $\left[\{({2p-1})/{2p}\}k+{2}/{p}\right]r_{\rm max}$. We also studied the effect of error in the positions of the node on the wormhole detection capability. In the absence of any error in the location, there are no false alarms and in the presence of error the effect on detection capability is negligible. Copyright © 2011 John Wiley & Sons, Ltd.