bluuebunny/crossref_metadata_2025 huggingface dataset:
Fractionated crystallization of polypropylene droplets produced by nanolayer breakup
Authors: Jin Y. , Hiltner A. , Baer E.
Published: April 2007

Layer‐multiplying coextrusion was used to fabricate assemblies of 257 layers, in which polypropylene (PP) nanolayers alternated with thicker polystyrene (PS) layers. The PP layer thickness was varied from 12 to 200 nm. When the assembly was heated into the melt, interfacial instability‐driven breakup of the thin PP layers produced a dispersion of PP particles in a PS matrix. Particle size analysis indicated that breakup of PP microlayers produced a bimodal particle size distribution. A population of submicron particles formed because of the Rayleigh instability, and a second population of large particles formed by relaxation. Breakup of 12‐nm layers resulted in primarily submicron particles. The fraction of PP as submicron particles dropped dramatically as the layer thickness increased to 40 nm. The particle dispersion was characterized by thermal analysis and wide angle X‐ray diffraction. Fractionated crystallization gave rise to four crystallization exotherms at 40, 60, 85, and 100 °C. The exotherm at 40 °C was identified with homogeneous nucleation of the submicron particles in the smectic form. Exotherms at higher temperatures represented fractionated crystallization of the large micron‐sized particles in the PP α‐form. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1138–1151, 2007
Supportive care of rural women with breast cancer in Tasmania, Australia: changing needs over time
Authors: Minstrell Melinda , Winzenberg Tania , Rankin Nicole , Hughes Clarissa , Walker Judi
Published: April 2007

Providing for patients' psychosocial needs is a potential means of minimising cancer morbidity. Needs assessments can guide responsive patient‐centred care. A longitudinal survey of women with early breast cancer consulting a breast nurse in a primarily rural state of Australia was undertaken to measure unmet supportive care needs, identify changes in unmet needs across time and compare results with previous studies. Needs assessments were completed with the Supportive Care Needs Survey (SCNS) at 1 month (n = 74) and 3 months (n = 83) post‐diagnosis. Access to services was also examined. High levels of psychological and health system and information needs were identified at 1 month post‐diagnosis, but these decreased significantly at 3 months post‐diagnosis. Sexuality domain needs increased significantly during the same time. Compared to a previous SCNS study of rural women with breast cancer, unmet supportive care needs in this study were significantly lower than previously reported, although assistance with energy levels (i.e. fatigue) continues to be an unmet need for women with breast cancer. Results suggest there have been positive cultural changes within healthcare systems, specifically in better informing patients and providing support. Although services appear to be more responsive to breast cancer patients, significant unmet needs still exist. Copyright © 2007 John Wiley & Sons, Ltd.
Vascular endothelial growth factor and psychosocial factors in colorectal cancer
Authors: Sharma A. , Greenman J. , Sharp D. M. , Walker L. G. , Monson J. R. T.
Published: April 2007

Background: Vascular endothelial growth factor (VEGF) and psychosocial factors have both been shown to have independent prognostic value in colorectal cancer. Recently, an association between VEGF and psychosocial factors has been reported in patients with ovarian cancer.

Methods: A consecutive series of eligible patients undergoing elective resection for colorectal cancer were invited to participate. Standardized measures of various aspects of quality of life (QoL) were administered 5–12 days before surgery, and again 6–8 weeks after the operation, blood samples were obtained at the same times. Solid phase ELISA was used for VEGF‐A analysis using serum samples. Correlations and multiple regression analysis were used to examine the relationship between VEGF and psychosocial factors.

Results: One hundred and four patients with colorectal cancer were recruited. Seventy (67%) were male and the mean age was 67.6 years.

A significant positive correlation was found between preoperative VEGF level and preoperative depression (r=0.227, p=0.03). Preoperative VEGF was negatively correlated with preoperative cancer‐related concerns (r=−0.273, p=0.009) and positive affectivity (r=−0.219, p=0.05). Linear regression using TNM stage as a covariate showed that cancer‐related concerns were an independent predictor of preoperative VEGF levels (p=0.02).

Preoperative cancer‐related concerns and global QoL were negatively correlated with postoperative VEGF (r=−0.381, p=0.001, r=−0.264, p=0.005), whereas preoperative depression correlated positively with postoperative VEGF (r=0.333, p=0.003). Linear regression analysis showed that preoperative HADS depression (p=0.005) and cancer‐related concerns (p=0.002) were independent predictors of postoperative VEGF levels.

Postoperative VEGF was significantly correlated with postoperative anxiety (r=0.249, p=0.02), depression (r=0.289, p=0.01), and functional well‐being (r=−0.242, p=0.03). Linear regression analysis showed that postoperative anxiety (p=0.048), depression (p=0.013) and functional well‐being (p=0.046) independently predicted postoperative VEGF‐A levels.

Conclusion: Various psychosocial factors, particularly cancer‐related concerns and depression, appear to be related to preoperative and postoperative VEGF level in patients with newly diagnosed colorectal cancer. However, the clinical significance of these findings needs to be addressed in longitudinal follow‐up studies of recurrence and survival. Future prognostic studies involving VEGF and related cytokines should assess psychosocial variables at various time points and include these in a multivariate analysis of outcomes. Copyright © 2007 John Wiley & Sons, Ltd.
The use and perceived benefit of complementary and alternative medicine among Californians with cancer
Authors: Goldstein Michael S. , Lee Jennifer H. , Ballard‐Barbash Rachel , Brown E. Richard
Published: April 2007

Population‐based data on complementary and alternative medicine (CAM) use among cancer sufferers is lacking. In a telephone survey representative of California households (response rate = 68.9%, N = 1845) those who reported a diagnosis of cancer (excluding non‐melanoma skin cancers) were asked about CAM use. CAM use is substantial, although with few exceptions, it is approximately that found among those with non‐malignant chronic conditions. Those with cancer are more likely to report praying for their health, using support groups, and taking multiple dietary supplements. They are less apt to use CAM providers or special diets. Socio‐demographic factors associated with CAM use vary by specific CAM modality. Site of the cancer was not associated with any particular CAM modality. The use of CAM therapies specifically promoted as cancer therapies was not common, especially among those diagnosed recently. The use of CAM providers and mind–body techniques specifically for the purpose of treating cancer is unusual (<10%), while special diets are more frequently employed for the purpose of treatment and/or prevention of the cancer itself. A clear majority of those who do use CAM for treating cancer report at least some benefit from the treatment, and are likely to inform their physicians of such use. Copyright © 2007 John Wiley & Sons, Ltd.
Factors associated with breast cancer‐specific distress in younger women participating in a family history mammography screening programme
Authors: Henderson B. J. , Tyndel S. , Brain K. , Clements A. , Bankhead C. , Austoker J. , Watson E. ,   on behalf of the PIMMS Study Management Group
Published: April 2007

This multi‐centre study examined factors associated with breast cancer‐specific distress in 2321 women under 50 who are on a mammographic screening programme on account of their family history. Women were recruited from 21 UK centres, and completed a questionnaire one month before their screening appointment. The transactional theory of stress, appraisal, and coping provided the theoretical framework for the study. Factors measured included screening history, family history, perceived risk, cognitive appraisals, coping, optimism, and cancer worry. The findings indicate that the majority of women appraise their family history as being relevant and somewhat threatening to personal well‐being, but something they can deal with emotionally. Acceptance was the most commonly used coping strategy. Hierarchical regression analysis identified that the factors most significantly associated with distress were an appraisal of high relevance and threat, increased risk perception, low dispositional optimism, and the use of both avoidant and task‐orientated coping strategies. Women with children and those with relatives who have died from breast cancer were also more distressed. To conclude, most women appraised their situation positively but there is a potential profile of risk factors which may help clinicians identify those women who need extra psychological support as they progress through screening. Copyright © 2007 John Wiley & Sons, Ltd.
Protein profiling of oral brush biopsies: S100A8 and S100A9 can differentiate between normal, premalignant, and tumor cells
Authors: Driemel Oliver , Murzik Ulrike , Escher Niko , Melle Christian , Bleul Annett , Dahse Regine , Reichert Torsten Eugen , Ernst Günter , von Eggeling Ferdinand
Published: April 2007

In oral mucosa lesions it is frequently difficult to differentiate between precursor lesions and already manifest oral squamous cell carcinoma. Therefore, multiple scalpel biopsies are necessary to detect tumor cells already in early stages and to guarantee an accurate follow‐up. We analyzed oral brush biopsies (n = 49) of normal mucosa, inflammatory and hyperproliferative lesions, and oral squamous cell carcinoma with ProteinChip Arrays (SELDI) as a non‐invasive method to characterize putative tumor cells. Three proteins were found that differentiated between these three stages. These three proteins are able to distinguish between normal cells and tumor cells with a sensitivity of 100% and specificity of 91% and can distinguish inflammatory/hyperproliferative lesions from tumor cells with a sensitivity of up to 91% and specificity of up to 90%. Two of these proteins have been identified by immunodepletion as S100A8 and S100A9 and this identification was confirmed by immunocytochemistry. For the first time, brush biopsies have been successfully used for proteomic biomarker discovery. The identified protein markers are highly specific for the distinction of the three analyzed stages and therewith reflect the progression from normal to premalignant non‐dysplastic and finally to tumor tissue. This knowledge could be used as a first diagnostic step in the monitoring of mucosal lesions.
Formation of 3‐nitrotyrosines in carbonic anhydrase III is a sensitive marker of oxidative stress in skeletal muscle
Authors: Vasilaki Aphrodite , Simpson Deborah , McArdle Francis , McLean Lynne , Beynon Robert J. , Van Remmen Holly , Richardson Arlan G. , McArdle Anne , Faulkner John A , Jackson Malcolm J.
Published: April 2007

Oxidation of skeletal muscle proteins has been reported to occur following contractions, with ageing, and with a variety of disease states, but the nature of the oxidised proteins has not been identified. A proteomics approach was utilised to identify major proteins that contain carbonyls and/or 3‐nitrotyrosine (3‐NT) groups in the gastrocnemius (GTN) muscles of adult (5–11 months of age) and old (26–28 months of age) wild type (WT) mice and adult mice lacking copper, zinc superoxide dismutase (Sod1−/− mice), manganese superoxide dismutase (Sod2+/− mice) or glutathione peroxidase 1 (GPx1−/− mice). In quiescent GTN muscles of adult and old WT mice, protein carbonylation and/or formation of 3‐NT occurred in several proteins involved in glycolysis, as well as creatine kinase and carbonic anhydrase III. Following contractions, the 3‐NT intensity was increased in specific protein bands from GTN muscles of both adult and old WT mice. In quiescent GTN muscles from adult Sod1−/−, Sod2+/− or GPx1−/− mice compared with age‐matched WT mice only carbonic anhydrase III showed a greater 3‐NT content. We conclude that formation of 3‐NT occurs readily in response to oxidative stress in carbonic anhydrase III and this may provide a sensitive measure of oxidative damage to muscle proteins.
Differences in the proteome profile in placenta from normal term and preeclamptic preterm pregnancies
Authors: Webster Rose P. , Pitzer Brad A. , Roberts Victoria H. J. , Brockman Diane , Myatt Leslie
Published: April 2007

The aim of this study was to use proteomic approaches to examine differences in protein expression in placentae from normal term and preterm preeclamptic pregnancies and to validate the data thus obtained by other independent methods. Using 2‐DE we found that 80% of the proteins were present in both normal and preeclamptic placentae. However, 26 proteins in the normal term placentae were not matched in the preterm preeclamptic group. Six proteins showed increased intensity and one protein was down‐regulated in preeclampsia. Four of the seven proteins that were altered in preeclampsia were further analyzed by Western blot and immunohistochemistry. Identification by MS techniques revealed these proteins to be involved in regulatory pathways activated by stress. This is significant because preeclampsia is a multisystem disorder in human pregnancies that results in considerable oxidative and nitrative stress. Three proteins identified by MS to be Hsp27, catalase, and glucose‐regulated protein were confirmed by Western blot analysis to be significantly up‐regulated in preeclampsia. Endothelial monocyte‐activating polypeptide was shown to be down‐regulated in preeclampsia by 2‐DE and MS.
Proton pathways and H+/Cl− stoichiometry in bacterial chloride transporters
Authors: Kuang Zhifeng , Mahankali Uma , Beck Thomas L.
Published: April 2007

H+/Cl− antiport behavior has recently been observed in bacterial chloride channel homologs and eukaryotic CLC‐family proteins. The detailed molecular‐level mechanism driving the stoichiometric exchange is unknown. In the bacterial structure, experiments and modeling studies have identified two acidic residues, E148 and E203, as key sites along the proton pathway. The E148 residue is a major component of the fast gate, and it occupies a site crucial for both H+ and Cl− transport. E203 is located on the intracellular side of the protein; it is vital for H+, but not Cl−, transport. This suggests two independent ion transit pathways for H+ and Cl− on the intracellular side of the transporter. Previously, we utilized a new pore‐searching algorithm, TransPath, to predict Cl− and H+ ion pathways in the bacterial ClC channel homolog, focusing on proton access from the extracellular solution. Here we employ the TransPath method and molecular dynamics simulations to explore H+ pathways linking E148 and E203 in the presence of Cl− ions located at the experimentally observed binding sites in the pore. A conclusion is that Cl− ions are required at both the intracellular (Sint) and central (Scen) binding sites in order to create an electrostatically favorable H+ pathway linking E148 and E203; this electrostatic coupling is likely related to the observed 1H+/2Cl− stoichiometry of the antiporter. In addition, we suggest that a tyrosine residue side chain (Y445), located near the Cl− ion binding site at Scen, is involved in proton transport between E148 and E203. Proteins 2007. © 2007 Wiley‐Liss, Inc.
Short‐period InAs/GaSb superlattices for mid‐infrared photodetectors
Authors: Haugan H. J. , Szmulowicz F. , Brown G. J. , Ullrich B. , Munshi S. R. , Wickett J. C. , Stokes D. W.
Published: April 2007

Using a newly developed envelope function approximation model that includes interface effects, several InAs/GaSb type‐II superlattices (SLs) were designed for uncooled mid‐infrared detector applications. The 4 micron cutoff could be achieved with several SL designs. Superlattices with shorter periods have larger intervalence band separations than larger‐ones, which could increase the optical signal and reduce the detector noise, thus making room temperature operation possible. To test these possibilities, several short‐period SLs were grown by molecular‐beam epitaxy and their optical properties with reducing SL period were studied by band‐edge absorption, photoconductivity and photoluminescence measurements. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ir/Pt Schottky contact oxidation for nitride‐based Schottky barrier diodes
Authors: Chang P. C. , Yu C. L. , Liu C. H. , Chang S. J. , Su Y. K. , Chuang R. W. , Chiu Y. J.
Published: April 2007

We have fabricated Schottky diodes on GaN epitaxial wafer by using Ir/Pt Schottky contacts. After oxidation, the measured leakage current was decreased from 116 nA to 17.8 pA. In other words, the leakage current after annealing in O2 was shown to be about four orders of magnitude smaller than that before annealing. These improvements may be attributed to IrOx formation of the metal layer, improvement of interface between the Schottky contact and the GaN layer and curing of defects due to oxidation. We also found that the Schottky barrier height and thermal stability after annealing is better than without annealing. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High responsivity ultraviolet photodetector based on crack‐free GaN on Si (111)
Authors: Wang Xiaoyan , Wang Xiaoliang , Wang Baozhu , Xiao Hongling , Liu Hongxin , Wang Junxi , Zeng Yiping , Li Jinmin
Published: April 2007

A Schottky‐based metal‐semiconductor‐metal photodetector is fabricated on 1µm‐thick, crack‐free GaN on Si (111) substrate using an optimized AlxGa1–xN/AlN complex buffer layer. It exhibits a high responsivity of 4600A/W at 366nm which may be due to both a crack‐free sample and high internal gain. The relationship between responsivity and bias voltage is also investigated. The experiment results indicate that the responsivity increases with the bias voltage and shows a tendency to saturate. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Vertical PIN ultraviolet photodetectors based on 4H‐SiC homoepilayers
Authors: Liu X. F. , Sun G. S. , Li J. M. , Ning J. , Zhao Y. M. , Luo M. C. , Wang L. , Zhao W. S. , Zeng Y. P.
Published: April 2007

Vertical PIN ultraviolet photodetectors based on 4H‐SiC homoepilayers are presented. The growth of the 4H‐SiC homoepilayers was carried out in a LPCVD system. The size of the active area of the photodetector was 300 × 300 µm2. The dark and illuminated I‐V characteristics were measured at reverse biases from 0 V to 30 V at room temperature. The illuminated current was at least two orders of magnitude higher than the dark current at a bias of below 12 V. The photoresponse was measured from 200 nm to 400 nm at different reverse biases and the peak values of the photo response were located at 310 nm. The calculated spectral detectivity D* was shown to be higher than 1013 cmHz1/2/W from 260 to 360 nm with a peak value of 5.9 × 1013 cmHz1/2/W at 310 nm. The peak value of the photoresponse was hundreds of times higher than the response at 400 nm, which showed the device had good visible blind performance. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Understanding quantum dots: overheating of the LO‐phonon modes
Authors: Král K.
Published: April 2007

Longitudinal optical phonons have been used recently to explain the electronic energy relaxation in quantum dots. In this theory they served as a reservoir, on which the electron executes multiple scattering acts. Rather naturally such a phonon subsystem is expected to be passive, namely, in a long‐time limit of development the whole system should be able to achieve such a stationary state in which statistical distributions of both subsystems, electron and phonons, do not change in time. Here we remind briefly that the recent approach to the relaxation theory in quantum dots displays a non‐passivity of such a reservoir. We remind briefly the method of a partial elimination of this phonon overheating effect by using the Lang‐Firsov transformation. We apply the modified relaxation theory to the electronic relaxation at low electronic densities in quantum dot systems and come to conclusions about the role of e‐LO scattering mechanism in these situations. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Homogeneity assessment of large‐diameter III‐V compound semiconductor substrates by near‐infrared transmittance measurement
Authors: Inoue Yusuke , Kitamoto Takuya , Yamada Masayoshi , Kawase Tomohiro
Published: April 2007

The light absorption mechanisms below the fundamental energy gap in undoped and Si‐doped GaAs crystals have been investigated to assess EL2 defects and the carrier concentration distribution in III‐V compound semiconductor substrates. It is demonstrated, that the near‐infrared transmittance mapping equipment consisting of a high‐brigthness LED, a high‐sensitivity CCD camera, and a digital image processing system is capable to reveal surface scratches and local crystal imperfections such as inclusions, voids, and twining inside the substrate, besides EL2 defects and the carrier concentration distribution. Hence, the homogeneity of III‐V compound semiconductor substrates with diameter up to 6 inches can be assessed in less than several seconds with high spatial resolution of 640×480 pixels. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Performance comparison of Cu and Ni gates for deep submicrometer AlGaN/GaN HFETs
Authors: Sun H. F. , DiSanto D. W. , Bolognesi C. R.
Published: April 2007

Copper (Cu) was investigated as the gate contact metallization in AlGaN/GaN heterostructure field‐effect transistors (HFETs). For comparison, Nickel/Gold (Ni/Au) gate devices were fabricated on the same sample using electron beam lithography. Both metallization schemes yielded comparable transconductance characteristics: the maximum extrinsic transconductance reached 290 mS/mm. At gate voltage of ‐20 V, the reverse current for the Cu Schottky contact was roughly one to two orders of magnitude lower than that of Ni/Au contact. For Cu/Au gate devices, the product of current gain cut‐off frequency (fT) and gate length LG improved by 15% compared to Ni/Au gate devices. The power gain cut‐off frequency (fmax) also improved by at least 15%. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Blue‐shift of phosphorous‐implanted InGaAs/InGaAsP MQW laser structures by two‐step anneals
Authors: Byun Young Tae , Choi Kyoung Sun , Kim Sun Ho
Published: April 2007

We describe studies of implantation‐enhanced quantum‐well intermixing in a lattice‐matched InGaAs/InGaAsP multiple quantum well p‐i‐n heterostructure. Samples were implanted with a dose of 5×1014 P+ ions /cm2 at high energy of 1 MeV. The band gap for the samples was determined from photoluminescence at room temperature. The maximum blue‐shift of the band gap was 107 nm after the RTA process at 675 °C for 9 minutes. However, it was improved to 140 nm after two‐step anneals. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characteristics of electron beam‐evaporated high k ‐TiOx thin films on n‐GaAs
Authors: Oyama Yutaka , Ohno Takeo , Sato Taiji , Nishizawa Jun‐ichi
Published: April 2007

Electrical and structural evaluations have been performed on high‐k TiOx dielectrics which had been de‐posited on {001} oriented n‐GaAs at 100 °C by electron beam evaporation of TiO2 in a mixed atmosphere of O2/Ar. A permittivity, εs, as high as 100 has been achieved, and a breakdown field strength of 0.5 MV/cm has been obtained. Room temperature transistor action was realized utilising a p+n+ tunnel transistor with TiOx gate dielectric, both in enhancement and depletion mode operation. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Room temperature Sb‐based mid‐infrared VCSELs
Authors: Genty F. , Cerutti L. , Garnache A. , Ouvrard A. , Pérona A. , Grech P. , Romanini D. , Chevrier F.
Published: April 2007

The fabrication and the characterization of Sb‐based Mid‐Infrared emitting VCSELs are described in this paper. Both external‐cavity and microcavity optically‐pumped devices exhibit very high performances particularly well‐adapted for trace gas detection by laser spectroscopy. Concerning electrically‐pumped Sb‐based VCSELs, the first results obtained with an hybrid dielectric‐semiconductor structure are presented. However, such devices remain less mature than similar optically‐pumped laser and only microcavity‐enhanced electroluminescence could be observed near 2.3 µm at room temperature. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Reflectivity of deep‐etched InGaAs‐InP waveguide Bragg reflectors
Authors: Chong H. M. H. , Tan W. K. , Bryce A. C.
Published: April 2007

Deep etched Bragg reflector gratings in InGaAs‐InP waveguide structures have been realized. The width of the waveguide was 2 µm and was dry etched to a depth of more than 1.5 μm using CH4/H2‐based chemistry. The Bragg reflectors were designed to be first order and to have a large bandwidth – with one to three slots in the waveguide structure. The single slot reflector has a width of 190 nm and the period of other two‐slots grating is 420 nm and slot width of ∼200 nm. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Two‐dimensional simulation of type‐II InP/GaAsSb/InP double heterojunction bipolar transistors
Authors: Tao N. G. M. , Liu H. G. , Bolognesi C. R.
Published: April 2007

Two‐dimensional (2D) numerical simulations of self‐aligned sub‐micron InP/GaAsSb double heterojunction bipolar transistors (DHBTs) were performed to investigate the effects of base band gap narrowing and surface recombination. Base energy band gaps of 0.72 eV and 0.67 eV for GaAs0.51Sb0.49 bases with doping levels of 5×1018 and 5×1019 cm–3 were extracted from the comparison between the measurement data and simulation results. We took into account the surface Fermi level pinning and introduced a surface state model for the emitter side wall and extrinsic base surface. To the best of our knowledge, a good match between measured and simulated InP/GaAsSb DHBTs characteristics, from low to high current densities has not been achieved prior to the present work. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Micromagnetic properties of epitaxial MnAs films on GaAs surfaces
Authors: Hesjedal Thorsten , Engel‐Herbert Roman , Schaadt Daniel M. , Ploog Klaus H.
Published: April 2007

We present a systematic study of the micromagnetic properties of MnAs deposited by molecular‐beam epitaxy on GaAs(001) and GaAs(111)B surfaces. In epitaxial MnAs films, the strain state in MnAs‐on‐GaAs(001) (anisotropic) and MnAs‐on‐GaAs(111)B (isotropic) has a strong influence on the magnetostructural phase transition and thus the micromagnetic properties. The ferromagnetic α and the β phase coexist over a wide temperature range exhibiting self‐organized, magnetically coupled nanostructures. Independent of the substrate orientation, magnetic flux‐closure domain patterns are formed in the basal plane of MnAs. The spatial distribution of the phases in equilibrium (stripes and quasi‐hexagonal islands, respectively) stabilizes various magnetic states, which were found experimentally and confirmed by micromagnetic simulations. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comprehensive modelling of resonant‐cavity light‐emitting diode
Authors: Li Z. Q. , Li Z. M. Simon
Published: April 2007

We extended the theory by Henry (J. Lightwave Technol. LT‐4, 288 (1986) [1]) to accurately treat the coupling of spontaneous emission noise with microcavity modes. The Green's function method is employed to solve the inhomogeneous wave equation including a Langevin force Fω which accounts for spontaneous emission by carriers at angular frequency ω. The optical wave equation is coupled with the self‐consistent calculations of the material spontaneous emission rate of quantum well/dot using envelope wavefunction method. Finally the carrier transport equations are solved within the framework of 2D/3D drift‐diffusion model implemented in the Crosslight Software package APSYS (Crosslight APSYS User's Manuals, Copyright © Crosslight Software Inc. (version 2005. 11) [2]). (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
GaN/AlN electro‐optical modulator prototype at telecommunication wavelengths
Authors: Baumann E. , Giorgetta F. R. , Hofstetter D. , Guillot F. , Leconte S. , Bellet‐Amalric E. , Monroy E.
Published: April 2007

We report on a prototype electro‐optical modulator at telecommunication wavelength based on intersubband (ISB) transitions in a short‐period GaN/AlN superlattice (SL). The device has a vertical architecture resembling a nitride‐based high‐electron mobility transistor, whose barrier layer has been replaced by a 5 period SL. By applying an electrical field, we were able to influence the bandstructure and as a consequence to quench the ISB absorption peak originating from the SL. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A study on influence of micropipes in SiC substrate on overgrown AlGaN/GaN HEMT DC characteristics
Authors: Bang Hyungjin , Mitani Takeshi , Sazawa Hiroyuki , Nakashima Shinichi , Hirata Koji , Kosaki Masayoshi , Okumura Hajime
Published: April 2007

A deterioration mechanism of DC characteristics of AlGaN/GaN high‐electron mobility transistors (HEMTs) fabricated around hollow cores that extend from micropipes in SiC substrates was studied. Various sizes of hollow cores were investigated to study the influence of size dependence. Prominent deterioration of the DC characteristics of HEMTs fabricated in the vicinity of hollow cores with a diameter of 5 μm was observed, while no major deterioration was observed for HEMTs fabricated around hollow cores whose diameters were 1.5 and 3 μm. Clear correlation between the size of hollow cores and free carrier densities at the peripheries of the cores was observed using micro‐Raman imaging. The high density of free carriers around relatively large hollow cores causes deterioration of the DC characteristics of HEMTs fabricated in the vicinity of hollow cores. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fabrication of porous ZnO nanostructures and morphology control
Authors: Lee Sang Hyun , Lee Hyun Jung , Goto Hiroki , Cho Meong‐whan , Yao Takafumi
Published: April 2007

Porous ZnO nanostructures were easily fabricated by annealing and etching of as‐grown ZnO nanorods using an aqueous solution method at low temperature. The density of ZnO nanorods was changed by repetition of coating and drying of zinc acetate hydrate in ethanol. The annealing process is a very critical step to make porous ZnO nanorods because nano‐sized pore are formed at this step. Without annealing, pores could not be observed at the surface of ZnO nanorods. Furthermore, pore the size gets larger in etching steps following the annealing. The structural and optical properties for porous ZnO nanostructures were investigated using TEM and PL. Porous ZnO nanostructures were grown along the c‐axis and pores were distributed in the whole body. PL intensity was increased by annealing and etching. This is ascribed to the improved crystallinity and large surface area. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Study of nuclear quadrupolar interaction using a novel all‐electrical GaAs NMR device
Authors: Ota T. , Kumada N. , Yusa G. , Miyashita S. , Hirayama Y.
Published: April 2007

We study the nuclear quadrupolar interaction using a resistively‐detected NMR device. The nuclear spins are dynamically polarized in a sub‐micron scale region defined by split gates. In pulsed NMR spectra for 69Ga and 75As nuclei, three distinct peaks are observed. The peak splitting depends on the electric quadrupolar coupling constant EQ. By comparing the spectra of both nuclei, we find that the relative peak intensity is opposite, which is independent of the condition for the dynamic nuclear spin polarization. This result indicates that the electric‐field gradient in EQ has opposite sign at 69Ga and 75As nuclear site. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hydrogen‐assisted molecular‐beam epitaxy of ZnO layers on Zn‐polar ZnO
Authors: Suzuki H. , Minegishi T. , Park S. H. , Cho M. W. , Yao T.
Published: April 2007

Hydrogen‐assisted molecular beam epitxy of ZnO on Zn‐polar ZnO is achieved using atomic hydrogen. Exposure of atomic H helps to grow high‐quality ZnO layers on Zn‐polar ZnO substrates even at a low temperature of 400 °C. The full width at half maximum values of X‐ray rocking curves for ZnO epilayers are as narrow as 64 arcsec and 60 arcsec for (0002) and (10‐11) diffractions. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Increased power conversion efficiency through photon recycling in quantum well lasers
Authors: Wang J.‐B. , Zhang Y.‐H.
Published: April 2007

This paper reports a study of the photon recycling effect in semiconductor quantum well (QW) lasers and how to enhance such an effect to reduce threshold current density and to increase power conversion (wall‐plug) efficiency. To maximize the enhancement of the spontaneous emission recycling, it is necessary to use metal contacts with high reflectivity, to remove the substrate, and to optimize the overall doping profile design. The modeling results have also shown that the threshold current density in a multiple quantum well laser has a weak dependence on the number of QWs when the photon recycling effect is strong. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth of non‐polar (11$ \bar 2 $0) and semi‐polar (11$ \bar 2 $6) AlN and GaN films on the R‐plane sapphire
Authors: Chandrasekaran R. , Ozcan A. S. , Deniz D. , Ludwig K. F. , Moustakas T. D.
Published: April 2007

In this paper, we present detailed studies of growth of AlN and GaN films on R‐plane sapphire substrates. Contrary to previously reported work that GaN grows with its A‐plane (11$ \bar 2 $0) parallel to the R‐plane (1$ \bar 1 $02) of sapphire, our studies indicate that the crystallographic orientation of the III‐nitride films grown on such substrates depends strongly on the kinetic conditions of growth of the AlN buffer. Specifically, the group III‐rich conditions of growth of AlN buffer lead to nitride films having the (11$ \bar 2 $0) planes parallel to the sapphire surface, while growth of the buffer under N rich conditions leads to nitride films with the (11$ \bar 2 $6) planes parallel to the sapphire surface. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Process simulation of p ‐doping in GaN and related group III nitrides
Authors: Zhou Y. J. , Li Z. Q. , EL Boukili A. , Li Z. M. Simon
Published: April 2007

In this work we use the PROCOM sofware to model Mg doped GaN film growth by MOCVD. The 2/3D conservation equations of mass, energy, momentum and species are solved by the nonsymmetric conjugate gradient method with block preconditioning (H. C. Elman, Preconditioned conjugate gradient methods for nonsymmetric systems of linear equations (Yale University Research Report, 1981) [5]). A kinetics model with gas/surface adduct formation has been incorporated with detailed Mg dopant reaction mechanism. We reproduced broad doping profiles caused by memory effects and verified that the formation of (NH3)2‐MgCp2 and NH3‐MgCp2 adducts play an important role in p‐doping of GaN and related Group III nitrides. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bismuth incorporation in GaAs1–xBix grown by molecular beam epitaxy with in‐situ light scattering
Authors: Young E. C. , Whitwick M. B. , Tiedje T. , Beaton D. A.
Published: April 2007

The dilute bismide semiconductor GaAs1–xBix is an interesting new semiconductor alloy with novel properties and potential device applications. Like the dilute nitride alloy GaAs1–xNx, the dilute bismide shows a giant bandgap bowing effect. Bi alloying primarily affects the states in the vicinity of the top of the valence band rather than the bottom of the conduction band as in the case of N alloying. MBE growth of dilute bismides requires low growth temperatures (320‐390 °C) and near stochiometric group III/V ratios, due to the strong tendency of Bi to surface segregate under usual GaAs growth conditions. Optimal growth conditions are close to conditions that produce Bi and/or Ga droplets. In‐situ light scattering is found to be a useful tool for defining growth conditions that do not produce droplets on the surface. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
InGaN/GaN nanopillar‐array light emitting diodes
Authors: Neufeld C. J. , Schaake C. , Grundmann M. , Fichtenbaum N. A. , Keller S. , Mishra U. K.
Published: April 2007

GaN light emitting diodes were fabricated from arrays of nanopillars with embedded InGaN quantum wells. InGaN heterostructures were grown by MOCVD on n‐type GaN templates and pillars were fabricated by laser interference lithography and subsequent reactive ion etching and annealing. The tops of the pillars were coalesced by lateral growth of p‐type GaN by MBE forming a planar contact layer. This structure enables integration with standard planar processing while taking advantage of the nanopillar structure. LEDs were fabricated and characterized by electroluminescence, current‐voltage, and output power vs. current measurements. The devices showed rectifying behavior with a turn‐on voltage of 3 V and electroluminescence peak at 400 nm. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Enthalpy of Solvation Correlations for Gaseous Solutes Dissolved in Benzene and in Alkane Solvents Based on the Abraham Model
Authors: Mintz Christina , Clark Michael , Burton Katherine , Acree William E. , Abraham Michael H.
Published: April 2007

Data have been assembled from the published literature on the enthalpies of solvation for more than 100 compounds in heptane, hexadecane, cyclohexane, and benzene. It is shown that an Abraham solvation equation with five descriptors can be used to correlate the experimental solvation enthalpies to within standard deviations of 1.85 kJ/mol (heptane), 1.84 kJ/mol (hexadecane), 1.66 kJ/mol (cyclohexane), and 2.08 kJ/mol (benzene). The derived correlations provide very accurate mathematical descriptions of the measured enthalpy of solvation data, which in the case of benzene span a range of 111 kJ/mol. Division of the experimental values into a training set and a test set shows that there is no bias in predictions, and that the predictive capability of the correlations is better than 2.63 kJ/mol.
Computed structures and relative stabilities of Be@C74
Authors: Slanina Zdeněk , Uhlík Filip , Lee Shyi‐Long , Adamowicz Ludwik , Nagase Shigeru
Published: April 2007

The paper presents computations for a C74‐based endohedral – Be@C74. A set of four C74 cages is considered, namely one cage with isolated pentagons and three isomers with a pentagon–pentagon junction. The computations are carried out with a newly suggested functional, viz. MPWB1K, which has never been applied to metallofullerenes. Special interest is paid to the Gibbs‐energy supported relative‐stability evaluations. Although the endohedral based on the cage with isolated pentagons is the most important species at lower temperatures, at higher temperatures a cage with pentagon–pentagon junction prevails. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007
Stable strontium isotopic ratios from archaeological organic remains from the Thorsberg peat bog
Authors: von Carnap‐Bornheim Claus , Nosch Marie‐Louise , Grupe Gisela , Mekota Anna‐Maria , Schweissing Mike M.
Published: April 2007

Stable strontium isotope ratios in archaeological finds have frequently been used to determine their place of origin, in order to reconstruct migration and trade. Peat bogs offer favourable burial conditions for the preservation of organic remains such as woollen textiles and leather by a natural tanning process. However, these finds are impregnated by peat substances including contaminant strontium which is likely to mask the original 87Sr/86Sr isotopic ratio of the specimens. In this paper, we present a pilot study analysing stable strontium isotopic ratios from Iron Age textile and leather finds from the Thorsberg peat bog, focusing on a sample processing method which permits the quantitative removal of contaminating strontium from the specimens. Copyright © 2007 John Wiley & Sons, Ltd.
Bayesian generalized monotonic functional mixed models for the effects of radiation dose histograms on normal tissue complications
Authors: Schipper Matthew , Taylor Jeremy M. G. , Lin Xihong
Published: April 2007

When treating cancer patients with radiation therapy, the normal tissue in an organ close to the tumour usually receives some dose of radiation. The dose is not of the same intensity throughout the organ. This radiation can cause normal tissue complications, so for treatment planning purposes, it is important to understand the relationship between the distribution of dose intensities in the organ and the occurrence of complications. One general summary measure of the dose effect is obtained by integrating a weighting function (w(d)) over the dose distribution. The weighting function w(d) should be monotone for biological reasons. Because the true shape of w(d) is not known, we estimate it non‐parametrically subject to the monotonicity constraint. In our approach w(d) is written as a weighted sum of monotone basis functions. The weights in this sum are formulated as a mixture of point mass at zero and a Gamma random variable. A key feature of our method is that it allows for flat regions through the use of this mixture prior. The model is estimated using a Markov Chain Monte Carlo algorithm. We illustrate our method with data from a head and neck cancer study in which the irradiation of the parotid gland results in loss of saliva flow. Copyright © 2007 John Wiley & Sons, Ltd.
Integrin signaling in early sea urchin development
Authors: Burke Robert Douglas , Brothers Elizabeth , Matviw Andrea
Published: April 2007

The eggs and cleavage stage embryos of many animals express integrins and signal transduction components, yet comparatively little is known of the signaling complexes formed or the role of integrin signaling in early development. Genomic approaches have revealed the complement of integrin signaling components expressed in early sea urchin development. We review what is known about the distribution and function of integrins, integrin ligands, and integrin signal transduction proteins expressed during this critical phase of development. Immediately after fertilization integrins are expressed on the apical surface of the egg where the receptors interact with several potential ligands in the hyaline layer. The apical integrin complex is essential for reorganization of the egg cortex. During cleavage the blastocoel forms and a second integrin complex forms on the basal surface of blastomeres interacting with basal lamina components of the extracellular matrix. The integrin subunits of the apical and basal complexes differ and localization data indicate the apical and basal complexes may contain different scaffolding proteins and different kinases. We propose that there are two independent integrin‐based signaling complexes formed during cleavage and blastula formation that may have distinct and essential functions in early development. The sea urchin is an excellent model for studies of these pathways and a number of approaches are available to determine their roles in early development.
“Birth of the cool”: Using sea urchin zygotes to study centrosome duplication, cell division, and cytokinesis
Authors: Halpin Elizabeth S. , Hinchcliffe Edward H.
Published: April 2007

The successful division of the cell depends on several morphological events that must be coordinated in a cell cycle dependent fashion. Crucial to this process is the remodeling of the cytoskeleton to both establish the bipolar spindle during mitosis, and cleave the cell into two daughters during cytokinesis. From the standpoint of the cytoskeleton, this process begins during interphase with the duplication of the centrosome; it is the two daughter centrosomes that will assemble the poles of the mitotic spindle and establish its necessary bipolarity. Following the cell cycle transition into mitosis, the spindle must assemble in order to properly align the sister chromatids at the center of the cell, and release the “wait anaphase checkpoint”. As the spindle transports the disjoined sister chromatids to the spindle poles, the cell must rapidly undergo cytokinesis, cleaving the cell into two – the plane of cleavage being established by the spindle itself. Understanding the temporal regulation and molecular basis for these events has come from extensive experiments using a variety of model systems, and has benefited from cell biological, molecular genetic, and biophysical approaches. One of the earliest and most important model systems for studying mitosis is the sea urchin zygote. With their large size, rapid/synchronous cell cycles, and advantages for conduct of biochemical and cytological investigations on the same system, fertilized sea urchin eggs have revealed many of the fundamental properties of centrosome duplication, cell division and cytokinesis. Here we review several key studies that have utilized the sea urchin zygote to explore mechanisms that coordinate and drive two of the major cytoskeletal events of mitotic division – centrosome duplication and cytokinesis.
Protein and lipid signaling in membrane fusion: nuclear envelope assembly
Authors: Larijani Banafshé , Poccia Dominic
Published: April 2007

Membrane fusion is important in many cell processes including membrane trafficking, mitotic reconstitution of organelles, viral infection and fertilization. Several fusion events occur just prior and subsequent to fertilization in the sea urchin, including the sperm acrosomal reaction, fusion of sperm and egg plasma membranes, exocytosis of cortical granules, reassembly of the sperm nuclear envelope and fusion of the male and female pronuclear envelopes leading to the zygote nucleus of the one‐cell embryo. The study of male pronuclear membrane dynamics with cell‐free extracts of fertilized sea urchin eggs has revealed several novel features, in particular a structural role arising from altering phospholipids prior to nuclear membrane formation. Fusion of chromatin‐bound membrane vesicles in vitro can be triggered by either GTP hydrolysis or exogenous phosphatidyl inositol phospholipase C (PI‐PLC). Recent data strongly implicate a role for diacylglycerol in nuclear envelope formation as a structural destabilizing lipid in membrane fusion. Moreover, the endogenous enzyme, PI‐PLCγ, is >100‐fold enriched in a nuclear envelope precursor vesicle population (MV1) that is required for nuclear envelope assembly. NMR and mass spectrometry analyses show that MV1 contains high levels of phosphoinositides, including the substrate of PLCγ, compared to the other nuclear envelope precursor membranes. MV1 exists in eggs as vesicles in the cortex distinct from the endoplasmic reticulum which contributes most of the nuclear envelope membrane. PLCγ is activated by a tyrosine kinase in response to GTP hydrolysis at an early stage of nuclear envelope formation suggesting a role in initiation of fusion and revealing aspects of a signaling mechanism leading to fusion. The binding of MV1 to two poles of the sperm nucleus offers spatial as well as temporal control of the initiation phase.
Control of intelligent nonlinear adaptive systems under earthquake excitation
Authors: Masri S. F. , Chavakula S. , Caughey T. K.
Published: April 2007

A semi‐active control procedure which utilizes a class of nonlinear auxiliary mass dampers with adaptive parameters is presented. Among the major features of this approach is its simplicity, robustness, and lack of need of a mathematical model of the structure whose motion is to be controlled. Numerical simulation results as well as experimental studies with a simple laboratory test structure (reported in a cited reference) demonstrate the feasibility of the proposed approach.