bluuebunny/crossref_metadata_2025 huggingface dataset:
Osteocutaneous radial forearm reconstruction of large partial cricotracheal defects
Authors: Al–Khudari Samer , Sharma Saurabh , Young William , Stapp Robert , Ghanem Tamer A.
Published: September 2012

Background

Single‐stage procedures for reconstruction of large cricotracheal defects have been limited in success and malignant immature teratomas in the larynx of an adult have never been reported.

Methods and Results

This was a case report and literature review. A 27‐year‐old man presented with 2 weeks of new‐onset stridor and was found to have a mass obstructing 80% of the subglottis and trachea. He underwent a noncircumferential partial cricotracheal resection with a resultant 7‐cm luminal defect, followed by osteocutaneous radial forearm flap semi‐rigid reconstruction. A novel technique was used to allow a functional and patent airway, which may be applied to other partial luminal reconstructive defects. Postoperatively, the patient was decannulated and has good speech quality and swallowing function. This work was performed at the Henry Ford Health System. This project was reviewed and was granted full approval by the Henry Ford Health System Institutional Review Board.

Conclusions

This is the first reported case of malignant immature teratoma to involve the larynx, trachea, and recurrent laryngeal nerve in an adult patient, and the first single‐stage technique described to use free tissue transfer without prefabrication for a 7‐cm airway defect. © 2012 Wiley Periodicals, Inc. Head Neck, 2013
Orthotopic VX rabbit tongue cancer model with FDG–PET and histologic characterization
Authors: Stack Brendan C. , Ye John , Bartel Twyla B. , Shafirstein Gal , Chen Chien , Siegel Eric , Singh Bipin , Thacker Samta , Lowe Val J. , Nagarkar Vivek
Published: September 2012

Background

We present our experience with the use of an immunocompetent medium‐sized animal model of tongue cancer that may be suitable for imaging and surgical studies.

Methods

A New Zealand white rabbit model of tongue cancer was created by injecting a VX tumor cell suspension grown in culture into the tongue of our model. The tumor was examined 7 days following implantation by physical examination, photography, and 18fluoro 2‐deoxyglucose–positron emission tomography (FDG‐PET). At 12 days postimplantation, the model was again studied as described above prior to euthanization, and then tongue excision and bilateral neck dissections were performed. All tissue was examined by histology.

Results

We confirmed a successful orthotopic tongue cancer model that resulted in cervical nodal metastases.

Conclusion

This model may be a useful model of orthotopic head and neck cancer for future surgical or imaging research. © 2012 Wiley Periodicals, Inc. Head Neck, 2013
Potential therapeutic target and independent prognostic marker of TROP2 in laryngeal squamous cell carcinoma
Authors: Wu Hao , Xu Huiming , Zhang Shu , Wang Xudong , Zhu Huijun , Zhang Huilin , Zhu Jin , Huang Jianfei
Published: September 2012

Background

The human trophoblastic cell surface antigen 2 (TROP2) gene is associated with the development of malignancies, but its expression in laryngeal squamous cell carcinoma (SCC) and its relationship with clinical characteristics of the disease remain undetermined.

Methods

Expression of TROP2 protein was detected by immunohistochemistry with a self‐made anti‐TROP2 antibody in laryngeal SCC tissue microarrays.

Results

Elevated expression of TROP2 was detected in laryngeal SCC tissues compared with adjacent noncancerous tissues. TROP2 expression in laryngeal SCC was related to tumor differentiation (p = .0001) and lymph node metastasis (p = .0352). Cox regression analyses confirmed that TROP2 expression (p = .015), lymph node metastasis (p = .001), degree of differentiation (p = .002), tumor site (p = .021), and T classification (p = .003) were independent prognostic factors.

Conclusions

TROP2 can be used as an independent prognostic indicator for laryngeal SCC. © 2012 Wiley Periodicals, Inc. Head Neck 35: 1373–1378, 2013
Multimodal nonlinear microscopic investigations on head and neck squamous cell carcinoma: Toward intraoperative imaging
Authors: Meyer Tobias , Guntinas‐Lichius Orlando , von Eggeling Ferdinand , Ernst Günther , Akimov Denis , Schmitt Michael , Dietzek Benjamin , Popp Jürgen
Published: September 2012

Background

Prognosis and appropriate treatment of head and neck squamous cell carcinoma (HNSCC) depend on the tumor type routinely derived by invasive histopathology. A promising noninvasive alternative is nonlinear optical imaging, which is capable of in vivo tissue visualization for tumor typing and grading.

Methods and Results

Thin tissue sections from 3 patients aged 56 to 60 years presenting advanced carcinoma of the hypopharynx, larynx, and left tonsil were investigated by coherent anti‐Stokes Raman scattering (CARS), second‐harmonic generation (SHG), and 2 photon excited fluorescence (TPEF) to study the morphochemistry of the tissues. Morphologic alterations of prognostic significance, such as cell density, nuclear to cytoplasm ratio, and keratinization as well as the underlying compositional changes during malignant transformation were determined, such as the distributions of lipids, collagen, and autofluorophors.

Conclusions

Nonlinear imaging provides a noninvasive optical biopsy of the epithelial layer comparable to staining microscopy. By integration into an operational microscope, routine screening of suspicious lesions and surgical guidance can be realized. © 2012 Wiley Periodicals, Inc. Head Neck, 2013
The Longitudinal Interplay of Psychopathology and Social Competence During Chinese Children's Transition to Preschool
Authors: Zhang Xiao
Published: September 2012

The present study examined the longitudinal relations between psychopathology and social competence in a sample of 115 Chinese children during the transition to preschool initiated in their third year of life. Social competence was assessed by maternal reports at three months after preschool entry (T1) and at the end of the first (T2) and second (T3) preschool years. Internalizing and externalizing symptoms were assessed by maternal reports at T1 and T2. The results showed that T1 externalizing predicted rank‐order decreases in social competence from T2 to T3. T1 Internalizing predicted rank‐order decreases in social competence from T1 to T2 but growth of competence from T1 to T3 and rank‐order increases in competence from T2 to T3. Rank‐order decreases in internalizing from T1 to T2 also predicted rank‐order increases in social competence from T2 to T3. These longitudinal relations held across gender and proved robust to the inclusion of broad individual and family process variables as covariates. Copyright © 2012 John Wiley & Sons, Ltd.
The drive to ban the NOEC/LOEC in favor of ECx is misguided and misinformed
Authors: Green John W , Springer Timothy A , Staveley Jane P
Published: September 2012

Challenges to the use of the no observed effect concentration (NOEC) in ecotoxicology have appeared over the years, with a recent call for banning its use in favor of the x% effects concentration (ECx). This article presents an opposing view, providing reasons for the continued use of the NOEC, and for hypothesis testing in general. Although the use of ECx values is appropriate in many situations, there are numerous real-world examples where it is not suitable and offers no advantage over the use of hypothesis testing. These examples are presented with recommended data analysis techniques, illustrating the variety of statistical approaches that are meaningful in analyzing ecotoxicity data. Thoughtful consideration of study design and proper analysis and interpretation of the results will go further to advance the science of ecotoxicology than attempting to implement a blanket prohibition or endorsement of any single statistical approach. Integr Environ Assess Manag 2013; 9: 12–16. © 2012 SETAC
Can peripheral blood γδ T cells predict osteonecrosis of the jaw? An immunological perspective on the adverse drug effects of aminobisphosphonate therapy
Authors: Kalyan Shirin , Quabius Elgar Susanne , Wiltfang Jörg , Mönig Heiner , Kabelitz Dieter
Published: September 2012

Nitrogen-bisphosphonates (n-BP), often referred to as aminobisphosphonates, are the most commonly prescribed drugs for the treatment of disorders of bone fragility. However, long-term continuous treatment predisposes certain individuals to serious rare side effects, such as bisphosphonate-associated osteonecrosis of the jaw (BAONJ). n-BP use is known to unintentionally activate a subset of innate T cells called Vγ9Vδ2 T cells, but the consequence of this chronic immune stimulation has remained unexplored. The primary objectives of this study were to 1) determine the fate of Vγ9Vδ2 T cells in osteoporotic patients on n-BP therapy as a function of time and type of therapy; 2) evaluate the proportion of Vγ9Vδ2 T cells in patients who had recently experienced n-BP–associated ONJ. We found there is a notable loss of Vγ9Vδ2 T cells over time in osteoporotic patients on n-BP therapy, particularly those on intravenous (iv) therapy (Spearman r = −0.55, p < 0.0001 iv; r = −0.3, p < 0.03 oral) (n = 68); no difference was observed in total T cells, monocytes, or granulocytes. Importantly, the observed negative effect on Vγ9Vδ2 T cells coincides with the reported route of administration and timing of the rare occurrence of BAONJ. Patients (n = 6) who had experienced BAONJ were all found to be significantly deficient in Vγ9Vδ2 T cells (median = 0.07%) in comparison to age- and sex-matched treatment-naïve controls (N = 11; median = 2.40%), U = 0, p = 0.001; this was the only consistent difference in the leukocytes assessed. All BAONJ cases had an underlying condition that further contributed to impaired immunity. We propose Vγ9Vδ2 T cells show a strong potential to serve as harbingers of possible adverse immune effects of n-BP therapy, particularly in those patients already having a compromised immune system as they may be most vulnerable to the development of conditions such as BAONJ. © 2013 American Society for Bone and Mineral Research.
Conflict of interests: Multiple signal peptides with diverging goals
Authors: Venuto Annunziata , de Marco Ario
Published: September 2012

Peptide signal sequences attached to or embedded into a core protein sequence control its cellular localization and several post‐translational modifications. However, misleading or cumbersome results may be generated when expressing recombinant proteins with modified signal peptides or single domains of larger proteins. J. Cell. Biochem. 114: 510–513, 2013. © 2012 Wiley Periodicals, Inc.
Alterated talar and navicular bone morphology is associated with pes planus deformity: A CT‐scan study
Authors: Peeters Koen , Schreuer Julien , Burg Fien , Behets Catherine , Van Bouwel Saskia , Dereymaeker Greta , Sloten Jos Vander , Jonkers Ilse
Published: September 2012

We compared bone and articular morphology of the talus and navicular in clinically diagnosed flatfeet and evaluated their potential contribution to talo‐navicular joint instability. We used CT images to develop 3D models of talus and navicular bones of 10 clinically diagnosed flatfeet and 15 non‐flatfeet. We quantified their global bone dimensions, inclination and dimensions of the articular surfaces and their curvatures. Additionally, ratios of six talar and navicular dimensions were calculated. The values for these parameters were then compared between both groups. In flatfeet, the talar head faced more proximal and its width was larger compared to non‐flatfeet. Also the navicular cup faced more proximal and its depth was significantly increased. Furthermore, we observed a more protruding talar head compared to the navicular cup in the control group with the articular surface depth being relatively larger for the navicular cups when compared to the talus in flatfeet. The ratio of the talar and navicular articular surface height was decreased in flatfeet, suggesting increased height of navicular cups relative to the articulating talar heads. Our results show that flatfoot deformity is associated with morphological changes of talar and navicular articular surfaces that can favor medial arch collapse and forefoot abduction. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31: 282–287, 2013
Endoscopic cricopharyngeal myotomy for management of cricopharyngeal achalasia (CA) in an 18–month–old child
Authors: Chun Robert , Sitton Mathew , Tipnis Neelesh A. , Arvedson Joan C. , Rao Aparna , Dranove Jason , Brown David J.
Published: September 2012

A 6–month–old patient presented with dysphagia and failure to thrive. Video fluoroscopic swallow study (VFSS), esophagogastroduodenoscopy, and manometry were diagnostic for CA. A gastrostomy tube was placed at 8 months. Botulinum toxin injection improved symptoms, but within 10 weeks symptoms returned.

At 18 months, an uncomplicated endoscopic CPM was performed. A postoperative VFSS demonstrated cricopharyngeal bar resolution. Within 3 months, patient was feeding orally without a G tube.

Pediatric CPA treatment options consist of dilation, botox, and transcervical CPM. To our knowledge, this is the youngest patient treated with endoscopic CPM. Intraoperative video and photographs are presented. Laryngoscope, 2013
Accuracy of fine‐needle aspiration and imaging in the preoperative workup of salivary gland mass lesions treated surgically
Authors: Tryggvason Geir , Gailey Michael P. , Hulstein Stephanie L. , Karnell Lucy H. , Hoffman Henry T. , Funk Gerry F. , Jensen Chris S. , Van Daele Douglas J.
Published: September 2012

Objectives/Hypothesis:

Fine‐needle aspiration (FNA) biopsy and imaging are commonly used in the preoperative assessment of salivary gland mass lesions. The goal of this retrospective study was to clarify the role of FNA and imaging in the workup of salivary gland masses.

Study Design:

Retrospective cohort study.

Methods:

A computer search identified patients with an FNA of a salivary gland lesion with subsequent excision during a 10‐year study period. Chart review of study patients was performed, and information on site of lesion, age, gender, radiologic diagnosis, pain in the tumor area, and facial paralysis was recorded and analyzed.

Results:

There were 543 patients who had an FNA and subsequent histopathology. The majority of the tumors were in the parotid gland (n = 492, 90.9%), followed by submandibular gland (n = 45, 8.3%). The incidence of malignancy across all sites was 29.7%. The mean patient age was 54.1 years, and 54.1% were female. The sensitivity and specificity of FNA were 85.7% and 99.5%, respectively. Positive predictive value (PPV) was 98.6%, and negative predictive value (NPV) was 94.3%. A total of 464 patients had available radiologic studies. For the radiological diagnoses, sensitivity was 81.8% and specificity was 67.3%, whereas PPV and NPV were 52.7% and 89.3%, respectively.

Conclusions:

FNA is a reliable method of preoperatively assessing both benign and malignant salivary gland lesions. Preoperative imaging has a lower sensitivity and specificity than FNA in differentiating malignant from benign tumors. Older age, pain, and facial paralysis are clinical features independently associated with malignancy. Laryngoscope, 2013
Vowel Harmony in Optimality Theory
Authors: Walker Rachel
Published: September 2012

This article reviews the analysis of vowel harmony in Optimality Theory. Vowel harmony is a phenomenon in which the vowels in a word or another domain show systematic agreement for some property, such as rounding, backness, height, or ATR quality. Optimality Theory is a framework of generative linguistics in which grammars consist of a hierarchy of constraints on outputs. The treatment of various aspects of harmony systems are discussed, including what drives harmony, directionality and trigger control, opaque and transparent segments, dominant‐recessive patterns, and variation. Data from Turkish, Igbo, Pulaar, Diola Fogny, Finnish, and Hungarian are discussed.
Multiresponsive Properties of Triple‐Shell Architectures with Poly(N,N‐diethylaminoethyl methacrylate), Poly(N‐vinylcaprolactam), and Poly(N,N‐dimethylaminoethyl methacrylate) as Building Blocks
Authors: Tian Wei , Lv Xiaoyan , Huang Longbiao , Ali Nazakat , Kong Jie
Published: September 2012

Triple‐shell architectures, consisting of poly[(N,N‐diethylaminoethyl methacrylate)‐block‐(N‐vinylcaprolactam)‐block‐(N,N‐dimethylaminoethyl methacrylate)] triblock copolymers, are obtained by sequential reversible addition–fragmentation chain transfer polymerizations, using a terminal‐modified hyperbranched poly(β‐cyclodextrin) core as a macro chain transfer agent. UV‐vis spectroscopy results indicate that the triple‐shell architectures possess one pH response at pH 12.5 in aqueous solution at room temperature, followed by double‐temperature‐ responsiveness between 33 °C and 36 °C. The special multiresponsive properties are further confirmed by investigating the controlled release behavior of the resulting polymers using metronidazole as a model drug.
Compatibilization of Immiscible Polymer Blends by Organoclay: Effect of Nanofiller or Organo‐Modifier?
Authors: Yousfi Mohamed , Soulestin Jérémie , Vergnes Bruno , Lacrampe Marie‐France , Krawczak Patricia
Published: September 2012

PET/PE blends are prepared with and without different types of organo‐modified montmorillonites (OMMT) using a extrusion process. The droplet size of PE dispersed phase decreases upon organoclays addition, however without any direct dependence on the organoclay initial surface tension. To assess the effect of the organomodifier without MMT, PET/PE blends are then compounded adding solely the surfactants (similar to those used to modify the various organoclays). Whatever the chemical nature of the surfactant, a refinement of the PE droplets is observed, interestingly similar to those previously observed in presence of clay. This shows unambiguously that the key factor for organoclay compatibilization efficiency, in the case of PET/PE blends, is the surfactant modifier itself and not the MMT platelets.

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Reliability–sensitivity analysis using dimension reduction methods and saddlepoint approximations
Authors: Huang Xianzhen , Zhang Yimin
Published: September 2012

Reliability–sensitivity, which is considered as an essential component in engineering design under uncertainty, is often of critical importance toward understanding the physical systems underlying failure and modifying the design to mitigate and manage risk. This paper presents a new computational tool for predicting reliability (failure probability) and reliability–sensitivity of mechanical or structural systems subject to random uncertainties in loads, material properties, and geometry. The dimension reduction method is applied to compute response moments and their sensitivities with respect to the distribution parameters (e.g., shape and scale parameters, mean, and standard deviation) of basic random variables. Saddlepoint approximations with truncated cumulant generating functions are employed to estimate failure probability, probability density functions, and cumulative distribution functions. The rigorous analytic derivation of the parameter sensitivities of the failure probability with respect to the distribution parameters of basic random variables is derived. Results of six numerical examples involving hypothetical mathematical functions and solid mechanics problems indicate that the proposed approach provides accurate, convergent, and computationally efficient estimates of the failure probability and reliability–sensitivity. Copyright © 2012 John Wiley & Sons, Ltd.
Structural and optoelectronic properties of selenium‐doped silicon formed using picosecond pulsed laser mixing
Authors: Hu Shaoxu , Han Peide , Wang Shuai , Mao Xue , Li Xinyi , Gao Lipeng
Published: September 2012

Microstructured silicon doped with selenium beyond the equilibrium solid solubility limit was formed by picosecond pulsed laser mixing of a 20‐nm Se film with the underlying p‐Si wafer. The effects of pulse fluence varying from 0.40 to 0.72 J cm−2 on the structural and electronic properties of this material were investigated. It was found that the surface roughness in the laser‐irradiated regions increases with increasing pulse fluence, and a phase transition from the crystalline to the amorphous occurs at a pulse fluence of 0.72 J cm−2. Silicon microstructures were doped with selenium of the order of 1018 cm−3 within a depth of 100 nm below the surface, and n+p junctions were formed between the Se‐doped layers and the silicon substrates. The current–voltage as well as spectral response characteristics of the photodiodes fabricated from microstructured silicon were also analyzed and discussed. The leakage currents and responsivities of these photodiodes strongly depend on the pulse fluence, presumably due to the effects of picosecond laser modification on the crystal structure and electronic structure of the surface Se‐doped layers.
Is family leadership always beneficial?
Authors: Miller Danny , Minichilli Alessandro , Corbetta Guido
Published: September 2012

There has been much debate concerning the performance of family firms and the drivers of their performance. Some scholars have argued that family management is to blame when family firms go wrong; others claim that family management removes costly agency problems and encourages stewardship. Our thesis is that these disagreements can only be resolved by distinguishing among different types of family firms. We argue that family CEOs will outperform in smaller firms with more concentrated ownership and underperform in larger firms with more dispersed ownership; they will do neither where firms are smaller and ownership is more dispersed or firms are larger and ownership is more concentrated. Copyright © 2012 John Wiley & Sons, Ltd.
The coconut and the peach: Understanding, establishing, and maintaining interpersonal boundaries with international students
Authors: Yamashita Miki , Schwartz Harriet L.
Published: September 2012

This chapter explores international students' perspectives of boundaries in the American graduate‐level classroom, specifically considering the culturally based essence of boundaries.
Neocortical neurogenesis and neuronal migration
Authors: Tan Xin , Shi Song‐Hai
Published: September 2012

The neocortex, the evolutionarily newest part of the cerebral cortex, controls nearly all aspects of behavior, including perception, language, and decision making. It contains an immense number of neurons that can be broadly divided into two groups, excitatory neurons and inhibitory interneurons. These neurons are predominantly produced through extensive progenitor cell divisions during the embryonic stages. Moreover, they are not randomly dispersed, but spatially organized into horizontal layers that are essential for neocortex function. The formation of this laminar structure requires exquisite control of neuronal migration from their birthplace to their final destination. Extensive research over the past decade has greatly advanced our understanding of the production and migration of both excitatory neurons and inhibitory interneurons in the developing neocortex. In this review, we aim to give an overview on the molecular and cellular processes of neocortical neurogenesis and neuronal migration. WIREs Dev Biol 2012, 2:443–459. doi: 10.1002/wdev.88

This article is categorized under:

Gene Expression and Transcriptional Hierarchies > Cellular Differentiation

Early Embryonic Development > Gastrulation and Neurulation

Nervous System Development > Vertebrates: Regional Development
Computational analysis of noncoding RNAs
Authors: Washietl Stefan , Will Sebastian , Hendrix David A. , Goff Loyal A. , Rinn John L. , Berger Bonnie , Kellis Manolis
Published: September 2012

Noncoding RNAs have emerged as important key players in the cell. Understanding their surprisingly diverse range of functions is challenging for experimental and computational biology. Here, we review computational methods to analyze noncoding RNAs. The topics covered include basic and advanced techniques to predict RNA structures, annotation of noncoding RNAs in genomic data, mining RNA‐seq data for novel transcripts and prediction of transcript structures, computational aspects of microRNAs, and database resources. These authors contributed equally WIREs RNA 2012. doi: 10.1002/wrna.1134

This article is categorized under:

RNA Structure and Dynamics > RNA Structure, Dynamics, and Chemistry

RNA Evolution and Genomics > Computational Analyses of RNA

Regulatory RNAs/RNAi/Riboswitches > Regulatory RNAs
Neutron Diffraction at Metal Borides, Ru2B3 and Os2B3
Authors: Frotscher Michael , Senyshyn Anatoliy , Albert Barbara
Published: September 2012

The structure of Ru2B3 [space group P63/mmc, no. 194, a = 290.489(1) pm, c = 1281.637(6) pm] and Os2B3 [space group P63/mmc, no. 194, a = 291.451(2) pm, c = 1292.13(1) pm] were determined using neutron diffraction and 11B‐isotopically enriched crystalline powder samples. Thus it was possible for the first time to determine accurate boron atom positions, displacement parameters and B–B distances. The compounds do not show superconductivity down to T = 1.8 K.
The interaction of dispersal and control methods for the riverine tsetse fly Glossinapalpalisgambiensis (Diptera: Glossinidae): a modelling study
Authors: Barclay Hugh J. , Vreysen Marc J. B.
Published: September 2012

We used a spatial model of a riverine tsetse fly species Glossina palpalisgambiensis life cycle to investigate the interaction between their dispersal and three control methods and to document these interactions using sensitivity analyses. The model is currently limited to gallery forest habitat inhabited by Glossina palpalisgambiensis in the dry season in the sub‐humid zone of West Africa. The control methods modelled were traps and targets (TT), insecticide‐treated livestock (ITL), and the sterile insect technique (SIT). Both distance dispersed (up to 800 m) and percent of flies dispersing each day (up to 60 %) increased the efficiency of control by TT. Most of this increase occurred for low values of both distance dispersed and percent dispersing, but the increase continued up to the limits tried. The daily movement of cattle assisted the control program and when movement was considerable (up to 600 m daily) the effects were greater than the effects of tsetse dispersal. Random dispersal decreased aggregation and equilibrium population size, and thus also increased the efficiency of SIT. Dispersal that was mostly oriented towards clumps was of much less value for SIT but acted on TT and ITL similarly to random dispersal.
Exact solutions for isotropic random flights in odd dimensions
Authors: García-Pelayo Ricardo
Published: September 2012

We give a method to solve the isotropic random flight in arbitrary dimension and show that, when the dimension is odd, it leads to a piecewise polynomial expression for the probability density. The method is based on the fact that the projection of an isotropic function has an inverse and on the fact that the convolution commutes with the projection and the inverse projection. In order to develop this method the Abel transform and its inverse are extended. By comparing with the expression for the isotropic random flight obtained using the convolution theorem, some integrals of Bessel functions can be expressed as piecewise polynomials. The expressions for the five-dimensional case for 2, 3, and 4 steps are found explicitly. Although the main result derived from this method concerns odd dimensions, it also yields an analytical result in the four-dimensional isotropic random flight, which is derived here. The results of this article can also be considered as results on the convolution with itself of an isotropic probability density whose support is the surface of a sphere.
Influence of oxidation on flow structure in laser-oxygen cutting
Authors: Hu Jun , Qiu Xianchen , Zhang Zhuoxian , Shen Hong
Published: September 2012

In this paper, a three-dimensional axial symmetrical model of laser cutting is established by adopting N–S equation and shearing-stress transport k-ω turbulent model. Numerical simulation is carried out to analyze the flow field of shield gas inside a cut kerf; the results include velocity and pressure distribution and mass flow rate. The effects of oxidation on flow field are examined, and the formation of gas flow separation and vortex are predicted. The results show that the gas flow structure in the kerf is directly affected by the reaction between iron and oxygen in the case of laser-oxygen cutting.
Thermal conductivity of nanocrystalline silicon by direct molecular dynamics simulation
Authors: Ju Shenghong , Liang Xingang
Published: September 2012

The thermal conductivity simulation of nanocrystalline silicon is conducted on a three-dimensional configuration of nanocrystalline silicon with random grain shape for molecular dynamics simulation. The configuration is formed by the Voronoi tessellation method and the thermal conductivity is calculated by the Green-Kubo method. The effects of random grain distribution, periodic boundary, and the simulation system size are examined. Their effects on the simulation results can be neglected. The conductivity at temperature range from 300 K to 1100 K is obtained. The results indicate that the nanocrystalline thermal conductivity of silicon is far below the bulk single crystal and increases quickly with increasing grain size. The average grain boundary thermal resistance varies from 1.0 × 10−9 m2 KW−1 to 1.16 × 10−9 m2 KW−1. The restrain of the phonon mean free path by the nano-grain boundary is responsible for the sharp decrease in thermal conductivity. The effective phonon mean free path plays an important role in determining the thermal conductivity of nanocrystalline materials.
Optical properties of InGaPN epilayer with low nitrogen content grown by molecular beam epitaxy
Authors: Min Kim Kang , Nonoguchi Shogo , Krishnamurthy Daivasigamani , Emura Shuichi , Hasegawa Shigehiko , Asahi Hajime
Published: September 2012

The effect of nitrogen concentration on the optical properties of InGaP(N) epilayer was investigated. The temperature dependence of the photoluminescence (PL) peak energy of InGaPN (N = 1%) epilayer around room temperature was found to be almost one-half of that of InGaP epilayer. The incorporation of N causes the reduction of the coupling constant for the electron–phonon interaction, leading to the reduced temperature dependence of the PL peak shift. Thermal activation energy, which is deduced from the Arrhenius plot of PL intensity, was decreased by N incorporation. The reduced PL quenching is discussed in terms of the changes in the band alignment at the InGaPN/GaAs heterointerface by the increase in the N concentration.
Modeling of resonant magneto-electric effect in a magnetostrictive and piezoelectric laminate composite structure coupled by a bonding material
Authors: Hasanyan D. , Wang Y. , Gao J. , Li M. , Shen Y. , Li J. , Viehland D.
Published: September 2012

The harmonic magneto-electro-elastic vibration of a thin laminated composite was considered. A theoretical model, including shear lag and vibration effects was developed for predicting the magneto-electric (ME) effect in a laminate composite consisting of magnetostrictive and piezoelectric layers. To avoid bending, we assumed that the composite was geometrically symmetric. For finite length symmetrically fabricated laminates, we derived the dynamic strain-stress field and ME coefficients, including shear lag and vibration effects for several boundary conditions. Parametric studies are presented to evaluate the influences of material properties and geometries on the strain distribution and the ME coefficient. Analytical expressions indicate that the shear lag and the vibration frequency strongly influence the strain distribution in the laminates and these effects strongly influence the ME coefficients.
Effect of A-site La and Ba doping on threshold field and characteristic temperatures of PbSc0.5Ta0.5O3 relaxor studied by acoustic emission
Authors: Dul'kin E. , Mihailova B. , Gospodinov M. , Roth M.
Published: September 2012

The structural transitions in Pb1−xLaxSc(1+x)/2Ta(1−x)/2O3, x = 0.08 (PLST) relaxor crystals were studied by means of acoustic emission (AE) under an external electric field (E) and compared with those observed in pure PbSc0.5Ta0.5O3 (PST) and Pb0.78Ba0.22Sc0.5Ta0.5O3 (PBST) [E. Dul'kin et al., EPL 94, 57002 (2011)]. Similar to both the PST and PBST compounds, in zero field PLST exhibits AE corresponding to a para-to-antiferroelectric incommensurate phase transition at Tn = 276 K, lying in the vicinity of dielectric temperature maximum (Tm). This AE signal exhibits a nontrivial behavior when applying E resembling the electric-field-dependence of Tn previously observed for both the PST and PBST, namely, Tn initially decreases with the increase of E, attains a minimum at a threshold field Eth = 0.5 kV/cm, accompanied by a pronounced maximum of the AE count rate Ṅ = 12 s−1, and then starts increasing as E enhances. The similarities and difference between PST, PLST, and PBST with respect to Tn, Eth, and Ṅ are discussed from the viewpoint of three mechanisms: (i) chemically induced random local electric field due to the extra charge on the A-site ion, (ii) disturbance of the system of stereochemically active lone-pair electrons of Pb2+ by the isotropic outermost electron shell of substituting ion, and (iii) change in the tolerance factor and elastic field to the larger ionic radius of the substituting A-site ion due to the different radius of the substituting ion. The first two mechanisms influence the actual values of Tn and Eth, whereas the latter is shown to affect the normalized Ṅ, indicating the fractions undergoing a field-induced crossover from a modulated antiferroelectric to a ferroelectric state. Creation of secondary random electric field, caused by doping-induced A-site-O ionic chemical bonding, is discussed.
Interface trap characterization and electrical properties of Au-ZnO nanorod Schottky diodes by conductance and capacitance methods
Authors: Hussain I. , Soomro M. Y. , Bano N. , Nur O. , Willander M.
Published: September 2012

Schottky diodes with Au/ZnO nanorod (NR)/n-SiC configurations have been fabricated and their interface traps and electrical properties have been investigated by current-voltage (I-V), capacitance-voltage (C-V), capacitance-frequency (C-f), and conductance-frequency (Gp/ω-ω) measurements. Detailed and systematic analysis of the frequency-dependent capacitance and conductance measurements was performed to extract the information about the interface trap states. The discrepancy between the high barrier height values obtained from the I-V and the C-V measurements was also analyzed. The higher capacitance at low frequencies was attributed to excess capacitance as a result of interface states in equilibrium in the ZnO that can follow the alternating current signal. The energy of the interface states (Ess) with respect to the valence band at the ZnO NR surface was also calculated. The densities of interface states obtained from the conductance and capacitance methods agreed well with each other and this confirm that the observed capacitance and conductance are caused by the same physical processes, i.e., recombination-generation in the interface states.
Pressure and electric field effects on piezoelectric responses of KNbO3
Authors: Liang Linyun , Li Y. L. , Xue Fei , Chen Long-Qing
Published: September 2012

The dielectric and piezoelectric properties of a KNbO3 single crystal under applied hydrostatic pressure and positive bias electric field are investigated using phenomenological Landau-Ginzburg-Devonshire thermodynamic theory. It is shown that the hydrostatic pressure effect on the dielectric and piezoelectric properties is similar to temperature, suggesting a common underlying mechanism for the piezoelectric anisotropy and its enhancement. The stable phase diagram of KNbO3 as a function of temperature and positive bias electric field is constructed. The maximum piezoelectric coefficient d33o* varying with temperature and electric field is calculated.
Electron spin relaxation in GaAs1−xBix: Effects of spin-orbit tuning by Bi incorporation
Authors: Tong H. , Marie X. , Wu M. W.
Published: September 2012

The electron spin relaxation in n-type and intrinsic GaAs1−xBix with Bi composition 0≤x≤0.1 is investigated from the microscopic kinetic spin Bloch equation approach. The incorporation of Bi is shown to markedly decrease the spin relaxation time as a consequence of the modification of the spin-orbit interaction, which shows the feasibility of GaAs1−xBix in the applications of spintronic devices. We demonstrate that the density and temperature dependences of spin relaxation time in GaAs1−xBix resemble the ones in GaAs. Meanwhile, the Bir-Aronov-Pikus mechanism is found to be negligible compared to the D'yakonov-Perel' mechanism in intrinsic sample. Due to the absence of direct measurement of the electron effective mass in the whole compositional range under investigation, we further explore the effect of a possible variation of electron effective mass on the electron spin relaxation.
Comparative study of surface recombination in hexagonal GaN and ZnO surfaces
Authors: Onuma T. , Sakai N. , Igaki T. , Yamaguchi T. , Yamaguchi A. A. , Honda T.
Published: September 2012

Surface recombination in GaN and ZnO crystals was comparatively investigated using steady-state and time-resolved photoluminescence (PL) measurements. The measurements were performed for various surface orientations (+c, −c, and m-plane surfaces), and the measured PL intensity and lifetime showed distinct dependence on the surface orientation. The dependence clearly indicates that the surface recombination rate is modified by the effects of surface band bending. The results were also verified by numerical analysis using a rate equation model considering the diffusion of photoexcited carriers and their recombination processes on the surface and inside the crystal.
Ab initio rovibrational structure of the lowest singlet state of O2-O2
Authors: Carmona-Novillo Estela , Bartolomei Massimiliano , Hernández Marta I. , Campos-Martínez José , Hernández-Lamoneda Ramón
Published: September 2012

Rovibrational bound states of the \documentclass[12pt]{minimal}\begin{document}${\rm O}_2(^3\Sigma ^-_g,v$\end{document}O2(3Σg−,v = 0)−\documentclass[12pt]{minimal}\begin{document}${\rm O}_2(^3\Sigma ^-_g,v$\end{document}O2(3Σg−,v = 0) dimer in its singlet electronic state have been obtained by solving the time-independent Schrödinger equation for the nuclear degrees of freedom. We have employed two different ab initio potential energy surfaces, based on high level multiconfigurational methods, which are expected to give upper and lower bounds for the real values of the interaction. Results are compared with spectroscopy experiments as well as with calculations using other semi ab initioand empirical interaction potentials. For the two ab initio potentials studied here, the ground vibrational state has a rectangular geometry and behaves as a semi-rigid molecule. The associated rotational constant is found in very good agreement with high resolution spectra. However, the computed dissociation energy and the frequency of the torsion mode are larger than previous experimental determinations, and possible reasons for these discrepancies are discussed. On the other hand, we have computed the splitting between the rovibrational states of the singlet and triplet electronic states and have found a fair agreement with measurements of the dimer spectra in a solid rare gas host.
Polarization induced pn-junction without dopant in graded AlGaN coherently strained on GaN
Authors: Li Shibin , Ware Morgan , Wu Jiang , Minor Paul , Wang Zhiming , Wu Zhiming , Jiang Yadong , Salamo Gregory J.
Published: September 2012

We propose a type of pn-junction not formed by impurity-doping, but rather by grading the Al composition in an AlxGa1−xN thin film, resulting in alternating p and n conducting regions due to polarization charge. By linearly grading AlxGa1−xN from 0% to x (x ≤ 30%) and back to 0% Al, a polarization induced pn-junction is formed, even in the absence of any impurity doping. X-ray diffraction reciprocal space maps are used to determine the strain state of the different graded composition samples. Polarization induced doping also provides a solution to the problem of p-type doping efficiency for III-nitrides.
Dust cluster explosion
Authors: Saxena Vikrant , Avinash K. , Sen A.
Published: September 2012

A model for the dust cluster explosion where micron/sub-micron sized particles are accelerated at the expense of plasma thermal energy, in the afterglow phase of a complex plasma discharge is proposed. The model is tested by molecular dynamics simulations of dust particles in a confining potential. The nature of the explosion (caused by switching off the discharge) and the concomitant dust acceleration is found to depend critically on the pressure of the background neutral gas. At low gas pressure, the explosion is due to unshielded Coulomb repulsion between dust particles and yields maximum acceleration, while in the high pressure regime it is due to shielded Yukawa repulsion and yields much feebler acceleration. These results are in agreement with experimental findings. Our simulations also confirm a recently proposed electrostatic (ES) isothermal scaling relation, PE∝Vd−2 (where PE is the ES pressure of the dust particles and Vd is the confining volume).
Dual-purpose use of winter wheat in western China: cutting time and nitrogen application effects on phenology, forage production, and grain yield
Authors: Tian L. H. , Bell L. W. , Shen Y. Y. , Whish J. P. M.
Published: September 2012

Conventional rainfed mixed crop–livestock systems of western China lack high-quality forage and restrict livestock production. This study explored the forage potential from wheat and its effects on subsequent grain yield. Different cutting times were imposed on winter wheat (Triticum aestivum) at Qingyang, Gansu Province, in two growing seasons, and the effect of nitrogen (N) topdressing rates (0, 60, and 120 kg N/ha) on grain yield recovery was explored. Results showed the potential to produce 0.8–1.6 t DM/ha of wheat forage with high nutritive value when cut before stem elongation (GS 30). In the wetter year, cutting before stem elongation did not delay crop development significantly (<3 days at anthesis and 5 days at maturity), but grain yields were reduced by 17–28% compared with the uncut crop (5.8 t DM/ha), mainly due to reductions in number of spikes per m2 and, consequently, number of grains per m2. In both seasons, more forage biomass was available if crops were cut later than GS 32, but this came with large reductions (>62%) in grain yield and delays in crop development (>9 days or 131 degree-days). Crops cut later than GS 30 had greatly reduced harvest index, tillers per m2, and total N uptake but higher grain protein content. There was no significant effect of N topdressing rate on grain yield, although provided the crop was cut before GS 30, higher rates of N increased maturity biomass and crop N uptake by replacing N removed in cut biomass. This study showed that physiological delay of wheat due to cutting was not significant. The forage harvested from winter wheat before stem elongation could be a valuable feed resource to fill the feed gap in western China.
Models for estimation of hourly soil temperature at 5cm depth and for degree-day accumulation from minimum and maximum soil temperature
Authors: Horton Brian
Published: September 2012

A model has been developed for the daily variation in soil temperature at 5 cm depth, for use where both the minimum and maximum temperatures are known or can be estimated. The model is based on data from three Australian sites with minute-by-minute data over 3–7 years. The model uses two sine curves; one for the increase from minimum to maximum and another for the relatively rapid decrease in temperature immediately after the maximum. An exponential decay function is used for the slower decrease in temperature until the minimum is reached.
The time of the minimum soil temperature is primarily determined by the time of sunrise and therefore varies depending on the day of the year, whereas the time of the maximum temperature is influenced primarily by the time of the middle of the day (midpoint between sunrise and sunset). The time of the transition point between the maximum and the next minimum is related to the time of sunset. Therefore, the model uses latitude, longitude, and the day of the year to determine the time of sunrise and sunset to adjust the shape of the temperature profile throughout the day.
The model has been validated using 3-hourly soil temperature data for 35 other sites in Australia, with a correlation of 0.993 between actual 3-hourly temperatures and those predicted. Its use for degree-day calculations has been validated using hourly data from a site in Victoria, where the model’s estimates of degree-days differ <0.7% from the value based on individual hourly temperatures, whereas methods that assume a symmetrical change from maximum to minimum temperature overestimate degree-days by 6–7%.
Regulation of the H4 tail binding and folding landscapes via Lys-16 acetylation
Authors: Potoyan Davit A. , Papoian Garegin A.
Published: September 2012

Intrinsically disordered proteins (IDP) are a broad class of proteins with relatively flat energy landscapes showing a high level of functional promiscuity, which are frequently regulated through posttranslational covalent modifications. Histone tails, which are the terminal segments of the histone proteins, are prominent IDPs that are implicated in a variety of signaling processes, which control chromatin organization and dynamics. Although a large body of work has been done on elucidating the roles of posttranslational modifications in functional regulation of IDPs, molecular mechanisms behind the observed behaviors are not fully understood. Using extensive atomistic molecular dynamics simulations, we found in this work that H4 tail mono-acetylation at LYS-16, which is a key covalent modification, induces a significant reorganization of the tail’s conformational landscape, inducing partial ordering and enhancing the propensity for alpha-helical segments. Furthermore, our calculations of the potentials of mean force between the H4 tail and a DNA fragment indicate that contrary to the expectations based on simple electrostatic reasoning, the Lys-16 mono-acetylated H4 tail binds to DNA stronger than the unacetylated protein. Based on these results, we propose a molecular mechanism for the way Lys-16 acetylation might lead to experimentally observed disruption of compact chromatin fibers.