bluuebunny/crossref_metadata_2025 huggingface dataset:
Predictors and outcomes of recurrent disease after a negative second look laparotomy
Authors: Ayhan Ali , Gultekin Murat , Dursun Polat , Dogan Nasuh Utku , Aksan Guldeniz , Guven Suleyman , Yuce Kunter
Published: November 2007

Background and Objectives

To analyze the predictors and outcomes of recurrent disease in patients with epithelial ovarian carcinoma (EOC) after a negative second look laparotomy (SLL).

Methods

One hundred nine EOC patients with a negative SLL treated at Hacettepe Hospital were retrospectively analyzed.

Results

Of these patients, 70 (64.2%) had no evidence of disease during follow up while remaining 39 (35.8%) had recurrence. Majority of the recurrences (82.1%) were detected within the initial 2 years of the SLL procedure. Multivariate analysis revealed stage and grade of the disease to be the significant predictors for the recurrent disease (P < 0.01 and P = 0.025, respectively). A second analysis with respect to initial metastatic sites revealed omental metastatis was significantly associated with recurrent disease (P < 0.001). Survival of patients with a recurrent disease was significantly poorer and dropped abruptly once a recurrence is developed.

Conclusions

Patients with initial omental metastasis, advanced stage and high grade tumors have highest risk for developing recurrences after a (−) SLL. Most of the recurrences develop during the initial 2 years following the (−) SLL and survival drops to less than 2 years once a recurrence is found. J. Surg. Oncol. 2008;97:226–230. © 2007 Wiley‐Liss, Inc.
Function, disability, and health‐related quality of life after allograft‐prosthesis composite reconstructions of the proximal femur
Authors: Biau David J. , Davis Aileen , Vastel Laurent , Tomeno Bernard , Anract Philippe
Published: November 2007

Background

Factors affecting function, disability and health‐related quality of life after allograft‐prosthesis composite reconstructions have been poorly studied.

Methods

Retrospective study of eighteen patients who underwent reconstruction with proximal femoral allograft‐prosthesis composites and answered questionnaires to assess hip function (Postel and Merle d'Aubigné, self‐reported Harris Hip Score), disability (Toronto Extremity Salvage Score), and health‐related quality of life (SF‐36).

Results

The median Toronto Extremity Salvage Score was 76 (IQR: 48–85), the median self‐reported Harris Hip Score was 90 (IQR: 48–95) and the median Postel and Merle d'Aubigné score was 17 (IQR: 12–17). Older age, female gender, and presentation with a pathologic fracture were associated with increased disability and poorest function. The median Physical Component Summary score was 44 (IQR: 39–45) and Mental Component Summary scores were 49 (IQR: 46–56). Male gender and recurrence of disease were associated with poorer health‐related quality of life. There was a high degree of correlation between function, disability scores and Physical Component Summary score.

Conclusions

Patients' characteristics at presentation such as age, gender, and occurrence of a pathologic fracture play an important role in determining disability, function, and health‐related quality of life after allograft‐prosthesis composite reconstruction of the proximal femur. J. Surg. Oncol. 2008;97:210–215. © 2007 Wiley‐Liss, Inc.
Extended left‐sided pancreatectomy with spleen preservation
Authors: Mohebati Arash , Schwarz Roderich E.
Published: November 2007

Background

Distal pancreatectomy (DP) is frequently performed with splenectomy, although splenectomy can be linked to various untoward effects, and sparing of the main splenic vessels (SVs) is not necessary for successful spleen preservation (SP).

Methods

We reviewed all DPs in a single‐surgeon practice to assess feasibility and outcomes of SP.

Results

Between 1997 and 2007, 41 of 177 pancreatic resections involved a DP (23%). There were 14 men (34%) and 27 women (66%), with a median age of 60 years (range: 34–86). Four procedures were en bloc resections, two total pancreatectomies, while eight of the remaining 35 DPs were performed laparoscopically. SP was accomplished in 33 of 34 possible cases (SP rate 97%), despite SV resection in 27 of these (82%). The postoperative complication rate was 24%, without death. Pancreatic fistulae occurred in two patients (5% of patients at risk), and one SPDP led to splenic infarct. No other clinically relevant problems specific to SP have become apparent.

Conclusions

Pancreatic fistula rate and other outcomes in this small DP experience compare favorably to other DP series. Few spleen‐specific complications and the radicality of resection support the liberal use of SP with SV resection, irrespective of an open or laparoscopic approach. J. Surg. Oncol. 2008;97:150–155. © 2007 Wiley‐Liss, Inc.
Multiwavelength figure-of-eight fiber laser with a nonlinear optical loop mirror
Authors: Zhang Z X , Xu K , Wu J , Hong X B , Lin J T
Published: November 2007

Multiwavelength Erbium-doped fiber laser with figure-of-eight configuration is designed and demonstrated. The intensity-depended transmission of nonlinear optical loop mirror can balance mode competition effect of homogenous broadening gain medium, and thus allows for stable room-temperature multiwavelength generation. The experiment results indicate that the wavelength numbers of attained multiwavelength spectra vary with the polarization states. Additionally, the impact of pump power on the multiwavelength is investigated.
1H and 13C NMR assignments for the sesquiterpene aldehydes, lepidozenal and isobicyclogermacrenal, from Eucalyptus dawsonii
Authors: Tucker David J. , Southwell Ian A. , Lowe Robert F. , Russell Michael F. , Brereton Ian M.
Published: November 2007

Lepidozenal and isobicyclogermacrenal were isolated from the leaves of Eucalyptus dawsonii and a complete assignment of their 1H and 13C NMR spectra was carried out using 2D NMR methods. Copyright © 2007 John Wiley & Sons, Ltd.
Disorder in condensed matter systems: proton spin lattice relaxation study of the mixed systems of betaine phosphate and glycine phosphite, BPxGPI(1−x)
Authors: Ramanuja M. N. , Ramesh K. P. , Ramakrishna J.
Published: November 2007

Proton NMR relaxation measurements have been carried out in the mixed system of antiferroelectric (AFE) betaine phosphate (BP) and ferroelectric (FE) glycine phosphite (GPI), BPxGPI(1−x), at 11.4 and 23.3 MHz from 300 to 100 K for x = 0.3, 0.4, 0.5, 0.6, 0.7 and 0.8. The temperature dependence of spin lattice relaxation (SLR) time follows the BPP model in the parent compounds, while the Larmor frequency dependence of T1 in the mixed system is rather unusual. The T1 curve exhibits different slopes for the low‐temperature wings at the two frequencies, which is a clear experimental evidence of the presence of different methyl groups with different activation energies (Ea), indicating disorder. For x = 0.3 and 0.4, biexponential recovery of magnetization has been observed below 190 K, showing that the degree of disorder varies with the concentration. The temperature dependence of relaxation time data has been interpreted in terms of NH3, trimethyl ammonium and methyl group reorientations. Copyright © 2007 John Wiley & Sons, Ltd.
Complete 1H and 13C NMR assignments of three new polyhydroxylated sterols from the South China Sea gorgonian Subergorgia suberosa
Authors: Qi Shu‐Hua , Zhang Si , Wang Yi‐Fei , Li Ming‐Yi
Published: November 2007

Three new polyhydroxylated sterols, 3β,6α,11,20β,24‐pentahydroxy‐ 9,11‐seco‐5α‐24‐ethylcholest‐7,28‐diene‐9‐one (1), 3‐(1′,2′‐ethandiol)‐24‐ methylcholest‐8(9),22E‐diene‐3β,5α,6α,7α,11α‐pentaol (2), 24‐methylcholest‐7,22 E‐diene‐3β,5α,6β,25‐tetraol (3) together with five known sterols, were isolated from the EtOH/CH2Cl2 extract of the South China Sea gorgonian Subergorgia suberosa. The complete assignments of the 1H and 13C NMR chemical shifts for these new compounds were achieved by means of 1D and 2D NMR techniques, including HSQC, HMBC, 1H1H COSY, and NOESY spectra. Copyright © 2007 John Wiley & Sons, Ltd.
Quantitative assessment of intervertebral disc glycosaminoglycan distribution by gadolinium‐enhanced MRI in orthopedic patients
Authors: Vaga Stefania , Raimondi Manuela Teresa , Caiani Enrico Gianluca , Costa Francesco , Giordano Carmen , Perona Franco , Zerbi Alberto , Fornari Maurizio
Published: November 2007

Our hypothesis was that the enhanced MRI of cartilage (dGEMRIC) imaging protocol could be used in patients to quantify the sulfated glycosaminoglycan (sGAG) in intervertebral discs (IVD). To test this hypothesis, 23 patients with degenerative disc pathology scheduled for surgery were studied by a specific dGEMRIC protocol: each patient underwent two MRI scans, before and 3.5 hr after Gd(DTPA)2‐injection of a nonconventional dose of 40 mL. Then, T1PRE‐ENH and T1POST‐ENH parametric images of the disc were obtained, from which a new index ΔT1 of the molecular status of the IVD was computed (T1PRE‐ENH − T1POST‐ENH). A total of 31 tissue samples (one or two from each patient) obtained at herniectomy were collected and biochemically analyzed for sGAG content and used as the gold standard for comparison. ΔT1 values in correspondence to degenerated sectors were higher (158 ± 36 ms) compared to normal sectors (80 ± 13 ms). Linear regression analysis between MRI‐derived and biochemistry‐derived measurements resulted in a significant correlation (r = 0.73, P < 0.0001). The ΔT1 parametric images, calculated using the modified dGEMRIC technique, provided noninvasive quantitative information about sGAG content within discal tissue in vivo, which resulted in agreement with biochemical analysis. The application of this new MRI method could provide diagnostic information for standard treatment of lumbar discopathy and for innovative therapies of regenerative medicine. Magn Reson Med, 2007. © 2007 Wiley‐Liss, Inc.
Measurement of glycine in human brain by triple refocusing 1H‐MRS in vivo at 3.0T
Authors: Choi Changho , Bhardwaj Paramjit P. , Seres Peter , Kalra Sanjay , Tibbo Philip G. , Coupland Nicholas J.
Published: November 2007

A new 1H‐MRS filtering strategy for selective measurement of glycine (Gly) in human brain in vivo at 3.0T is proposed. Investigation of multiple refocusing following a 90° excitation pulse indicated that triple refocusing is most effective for suppression of the strongly coupled resonances of myo‐inositol (mI) at the Gly 3.55‐ppm resonance. The echo times of the triple refocusing were optimized, with numerical analysis of the filtering performance, as {TE1, TE2, TE3} = {67, 62, 69} ms. Compared with the 90°‐acquired mI signal the mI suppression ratios of the filter were 170 and 1000, in terms of peak amplitude and area, respectively, between 3.51 and 3.59 ppm. From LCModel analyses, using density‐matrix calculated spectra as basis functions, the concentration of Gly in parieto‐occipital cortex of healthy adults was estimated to be 0.5 ± 0.1 mM (mean ± SD, n = 6), with reference to creatine at 8 mM. Magn Reson Med, 2007. © 2007 Wiley‐Liss, Inc.
Displacement encoding for the measurement of cartilage deformation
Authors: Neu Corey P. , Walton Jeffrey H.
Published: November 2007

Articular cartilage is a load bearing and lubricating tissue in animal joints. Heterogeneous deformations arise in the structured and zonal tissue under the application of mechanical load. The character of these deformations is altered by degenerative joint disease. Here, we document an MRI‐based technique for determining deformations throughout the volume of the tissue based on displacement encoding with stimulated echoes (DENSE) and a fast spin echo (FSE) readout. A DENSE‐FSE technique was designed to image cartilage at 9.4 Tesla in a deformed state during the application of cyclic mechanical loading. Artifact elimination arising from stimulated echoes and FSE was accomplished by radio frequency pulse phase cycling. The error of the technique was random and was quantified in terms of precision as better than 0.17% strain. Heterogeneous deformation field patterns in axial, transverse, and shear directions were quantified in a single tissue explant loaded in simple uniaxial compression. The technique is appropriate for documenting tissue deformations during applied physiologically relevant stress levels and loading rates. It may also be applied to characterize the micromechanical strain environment in normal, diseased, or regenerated cartilage in response to applied mechanical loading. Magn Reson Med, 2007. © 2007 Wiley‐Liss, Inc.
Extracellular matrix signature identifies breast cancer subgroups with different clinical outcome
Authors: Bergamaschi A , Tagliabue E , Sørlie T , Naume B , Triulzi T , Orlandi R , Russnes HG , Nesland JM , Tammi R , Auvinen P , Kosma V‐M , Ménard S , Børresen‐Dale A‐L
Published: November 2007

Prediction of the clinical outcome of breast cancer is multi‐faceted and challenging. There is growing evidence that the complexity of the tumour micro‐environment, consisting of several cell types and a complex mixture of proteins, plays an important role in development, progression, and response to therapy. In the current study, we investigated whether invasive breast tumours can be classified on the basis of the expression of extracellular matrix (ECM) components and whether such classification is representative of different clinical outcomes. We first examined the matrix composition of 28 primary breast carcinomas by morphology and gene expression profiling using 22K oligonucleotide Agilent microarrays. Hierarchical clustering of the gene expression profile of 278 ECM‐related genes derived from the literature divided the tumours into four main groups (ECM1–4). A set of selected differentially expressed genes was validated by immunohistochemistry. The robustness of the ECM classification was confirmed by studying the four ECM groups in a previously published gene expression data set of 114 early‐stage primary breast carcinomas profiled using cDNA arrays. Univariate survival analysis showed significant differences in clinical outcome among the various ECM subclasses. One set of tumours, designated ECM4, had a favourable outcome and was defined by the overexpression of a set of protease inhibitors belonging to the serpin family, while tumours with an ECM1 signature had a poorer prognosis and showed high expression of integrins and metallopeptidases, and low expression of several laminin chains. Furthermore, we identified three surrogate markers of ECM1 tumours: MARCO, PUNC, and SPARC, whose expression levels were associated with breast cancer survival and risk of recurrence. Our findings suggest that primary breast tumours can be classified based upon ECM composition and that this classification provides relevant information on the biology of breast carcinomas, further supporting the hypothesis that clinical outcome is strongly related to stromal characteristics. Copyright © 2007 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Opposite pathobiochemical fate of pyruvate kinase and adenylate kinase in aged rat skeletal muscle as revealed by proteomic DIGE analysis
Authors: Doran Philip , O'Connell Kathleen , Gannon Joan , Kavanagh Marcella , Ohlendieck Kay
Published: November 2007

Sarcopenia is the drastic loss of skeletal muscle mass and strength during ageing. In order to better understand the molecular pathogenesis of age‐related muscle wasting, we have performed a DIGE analysis of young adult versus old rat skeletal muscle. Proteomic profiling revealed that out of 2493 separated 2‐D spots, 69 proteins exhibited a drastically changed expression. Age‐dependent alterations in protein abundance indicated dramatic changes in metabolism, contractile activity, myofibrillar remodelling and stress response. In contrast to decreased levels of pyruvate kinase (PK), enolase and phosphofructokinase, the mitochondrial ATP synthase, succinate dehydrogenase, malate dehydrogenase, isocitrate dehydrogenase and adenylate kinase (AK) were increased in senescent fibres. Higher expression levels of myoglobin and fatty acid binding‐protein indicated a shift to more aerobic‐oxidative metabolism in a slower‐twitching aged fibre population. The drastic increase in αB‐crystallin and myotilin demonstrated substantial filament remodelling during ageing. An immunoblotting survey of selected muscle proteins confirmed the pathobiochemical transition process in aged muscle metabolism. The proteomic analysis of aged muscle has identified a large cohort of new biomarkers of sarcopenia including opposite changes in PK and AK, which might be useful for the design of improved diagnostic procedures and/or therapeutic strategies to counteract ageing‐induced muscle degeneration.
Corrigendum: Effect of electronic compensation on plethysmographic airway resistance measurements
Authors: Broughton Simon , Rafferty Gerrard F. , Milner Anthony D. , Greenough Anne
Published: November 2007

The original article to which this Erratum refers was published in Pediatric Pulmonology 2007;42(9):764–772/DOI 10.1002/ppul.20661. © 2007 Wiley‐Liss, Inc.
Structure‐based design of a bicyclic peptide antagonist of the vascular endothelial growth factor receptors
Authors: Goncalves Victor , Gautier Benoit , Garbay Christiane , Vidal Michel , Inguimbert Nicolas
Published: November 2007

Dysregulated angiogenesis is implicated in several pathologies, including cancer and age‐related macular degeneration. A potential antiangiogenic strategy consists in developing VEGF receptor ligands capable of preventing VEGF binding and the subsequent activation of these receptors. Herein, we describe the structure‐based design of a VEGF‐mimicking peptide, VG3F. This 25‐mer peptide was doubly cyclized, on‐resin, by formation of both a disulfide bridge and an intramolecular amide bond to constrain it to adopt a bioactive conformation. Tested on in vitro assays, VG3F was able to prevent VEGF binding to VEGF receptor 1 and inhibit both VEGF‐induced signal transduction and cell migration. Copyright © 2007 European Peptide Society and John Wiley & Sons, Ltd.
Controlled disassembly of peptide amphiphile fibres
Authors: Löwik Dennis W. P. M. , Meijer Joris T. , Minten Inge J. , van Kalkeren Henri , Heckenmüller Lisa , Schulten Ines , Sliepen Kwinten , Smittenaar Peter , van Hest Jan C. M.
Published: November 2007

In this paper, the introduction of both a methionine residue and a nitrobenzyl derivative as a labile linker between the peptide part and the hydrophobic alkyl chain of a peptide amphiphile are presented. These modifications are shown not to inhibit the formation of structured assemblies that analogous peptide amphiphiles lacking the linkers are able to form. Moreover, the introduction of either labile linker allows removal of the peptide amphiphile's stabilizing hydrophobic moieties to initiate a controlled disassembly of fibre aggregates. This is achieved by either treatment with CNBr or UV irradiation, respectively. These disassembly mechanisms could be the starting point for methodology that allows further manipulation of self‐assembled peptide amphiphile architectures. Copyright © 2007 European Peptide Society and John Wiley & Sons, Ltd.
Exact method to solve the Boltzmann equation to any order in the driving forces: Application to transport parameters
Authors: Brugger S. C. , Peikert V. , Schenk A.
Published: November 2007

In this paper a method to compute transport parameters in semiconductor devices as a function of the driving forces is presented. The method is based on an exact expansion of the distribution function (solution of the Boltzmann transport equation) in a series in the electric field and the gradient of the quasi‐Fermi potential. Eventhough this series probably diverges for high fields, it is still usable for low and moderate field intensities. Results for silicon clearly show that the usual parametrization of the mobility in TCAD models is inaccurate in pn junctions. Furthermore, it gives new insights into the form of the correct parametrization. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Coherent pseudo‐spin resonance in a laterally coupled double quantum dot
Authors: Kubo Toshihiro , Tokura Yasuhiro , Tarucha Seigo
Published: November 2007

In a laterally coupled double quantum dot (DQD), we can refer to the tunnel‐coupled symmetric (antisymmetric) state as the pseudo‐spin up (down) state. We study the coherent pseudo‐spin dynamics in a laterally coupled DQD. We propose the blockade phenomena induced by quantum interference effect through the pseudo‐spin states. Under such a blockade condition, we calculate the leakage current due to the coherent pseudospin dynamics driven by time‐varying microwave (MW) fields. When the resonant condition is satisfied, the current has a peak (right figure). Moreover, we examine the effect of the photon‐assisted‐tunneling (PAT) on pseudospin dynamics. We show that the PAT does not significantly influence the leakage current under above blockade condition. The frequency and the inter‐dot tunnel coupling dependence of the leakage current. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Energy distribution of the ballistic hot electrons and holes emitted from a quantum point contact and probed by a quantum dot
Authors: Kobayashi T. , Sasaki S. , Fujisawa T. , Tokura Y. , Akazaki T.
Published: November 2007

We present measurements on the energy distribution profile of the ballistic hot carriers emitted from a quantum point contact. The hot carriers were injected to a quantum dot using magnetic focusing technique and analyzed by measuring differential conductance of the quantum dot. We found a thermally broadened energy distribution of the hot carriers near the bias voltage applied to the quantum point contact in an otherwise uniform distribution down to the equilibrium Fermi energy. We also measured an occupation ratio of available states by the injected hot carriers, and fully characterized their energy distribution profile. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Full band Monte Carlo study of ballistic effects in nanometer‐scaled strained P channel Double Gate MOSFETs
Authors: Huet K. , Chassat C. , Nguyen D.‐P. , Galdin‐Retailleau S. , Bournel A. , Dollfus P.
Published: November 2007

Ballistic transport in a 20 nm long P type Double Gate (DG) MOSFET structure is studied using a Monte Carlo (MC) technique. Hole transport being dominated by the strong anisotropy of the valence dispersion relation, the full bandstructure obtained by a 30 band k ·p calculation is used. The valence bandstructure is shown to be highly anisotropic. The deformation induced by strain is different whether biaxial tensile or compressive strain is applied. This will have an influence on the final density of states (DOS) and scattering rates, closely related to carrier mobility. In the on‐state of the transistor, we demonstrate the out‐of‐equilibrium nature of carrier transport in the entire channel. Microscopic quantities analysis with strain shows the influence of scattering, bandstructure change and ballistic effects on hole transport. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nonequilibrium transport properties for a three‐site quantum wire model
Authors: Zheng Yangdong , Mizuta Hiroshi , Oda Shunri
Published: November 2007

We derive nonequilibrium electronic transport properties for a three‐site quantum wire model within Hartree‐Fock approximation making use of Keldysh formalism. Some rigorous formulas are provided for direct calculations when Coulomb repulsion is present. According to numerical calculations using these formulas, we investigate the conductance, transport current, and on site electronic charges of the wire in some special occasions. In noninteracting case, when site‐site couplings in the wire are tougher than wire‐electrode couplings, the resonant tunneling transport takes place and the phenomenon of conductance quantization can be easily observed. The transport properties of up‐spin are identical with those of down‐spin. When the Coulomb interaction is present, the line shapes of transport characteristics are changed because of electron‐electron repulsions. With the increase of U, the Coulomb blockade and metal‐insulator transition (Mott transition) phenomena are obvious if the self‐energies Γ have small values compared with U. The transport properties of the up‐spin also become quite different from those of the down‐spin indicating that the spin polarization takes place in the wire. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Resonant tunneling through a dilute nitride quantum well
Authors: Mori N. , Allison G. , Patanè A. , Eaves L.
Published: November 2007

We have developed a theory for resonant tunneling through a dilute nitride quantum well in the presence of a tilted magnetic field. We show that magneto‐tunneling spectroscopy provides a novel means of probing the scattering potential due to randomly distributed nitrogen impurities. This technique can be extended to probe other types and sources of disordered potential. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High‐field characteristics of ZnO and ZnO/ZnMgO heterostructures
Authors: Sasa S. , Hayafuji T. , Kawasaki M. , Nakashima A. , Koike K. , Yano M. , Inoue M.
Published: November 2007

High‐field transport properties of ZnO and ZnO/ZnMgO heterostructures were investigated. Three types of structures, a 500‐nm‐thick ZnO and ZnO/ZnMgO single‐hetero‐ (SH) and single‐quantum‐well (SQW) structures containing a thin (10‐20 nm) ZnO channel layer, were grown on a‐plane sapphire substrates by plasma‐assisted molecular beam epitaxy. The dc and pulsed I ‐V characteristics were measured at room temperature by using two‐terminal devices with the source‐to‐drain spacing of 2‐8 μm. By using the pulsed I ‐V measurements, the velocity‐field (v ‐E) characteristics were observed for electric field up to about 100 kV/cm. The v‐E characteris‐ tics revealed that no velocity saturation was observed until the velocity reached at a value of 7.6 × 106 cm/s for the thick ZnO structure while a rapid reduction of the mobility thus a saturation of the velocity at a relatively low electric field was observed for the SH structure. The reduction of the mobility was even pronounced for SQW structure. The velocity saturation might be due to the interplay between the inhomogeneities and polarization in the heterostructures. To our knowledge, this is the first experimental report on the high‐field characteristics in ZnO and ZnO/ZnMgO heterostructures. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Generation of highly circularly polarized light from uniform InAs/GaAs quantum dots
Authors: Kusunoki K. , Tsukiji N. , Umi T. , Tackeuchi A. , Yamaguchi K.
Published: November 2007

Highly circularly polarized light is generated from highly uniform InAs/GaAs quantum dots. These quantum dots allowed us to observe the spin dynamics at each energy state selectively without disturbing the inhomogeneous broadening. Time‐resolved spin‐dependent photoluminescence measurements show that the spin polarization at the second excited state reaches a maximum of 45% at 10 K, and that the spin polarization is greater at higher‐energy states. This large spin polarization is explained by the spin Pauli blocking effect. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Quantum theory of transport and optical gain in quantum cascade lasers
Authors: Kubis T. , Yeh C. , Vogl P.
Published: November 2007

We have developed a self‐consistent non‐equilibrium Green's function theory for charge transport and optical gain in quantum cascade lasers (QCL). Acoustic, polar‐optical phonon scattering, impurity, Hartree electron‐electron and interface roughness scattering within the self‐consistent Born approximation are taken into account. The incorporation of the full momentum and energy dependence of the scattering mechanisms turns out to be vital for the QCL device characteristics. The optical gain is calculated in linear optical response, taking into account the non‐equilibrium state occupations. For low‐doping THz GaAs/AlGaAs QCLs, we find the carrier transport at low bias to be dominated by multi‐barrier tunneling rather than by sequential tunneling. Importantly, interface roughness is shown to increase the current density drastically and up to a factor of 1.5 but suppress the gain by a factor of 10 for a realistic interface roughness. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Quantum optics in semiconductor microcavities
Authors: Savasta Salvatore , Di Stefano Omar , Portolan Stefano
Published: November 2007

Polaritons in semiconductor microcavities are hybrid quasiparticles consisting of a superposition of cavity photons and two‐dimensional excitons in embedded quantum wells (QWs). Owing to their exciton content, they have a strong mutual interaction which can be exploited for producing spontaneous parametric scattering of pump polaritons into signal‐idler polariton pairs. This process is able to produce polariton states exhibiting quantum correlations, and can thus be exploited for potential applications as well as to study quantum optical processes within a complex many‐body system. Here we present an overview of polariton parametric processes within a full quantum description based on the dynamics controlled truncation scheme. We also describe the results of an experiment that proves the existence of polariton pair correlations. This interpretation is confirmed by a microscopic theoretical analysis of the measured interference visibility. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Microscopic theory of spin‐filtering in non‐magnetic semiconductor nanostructures
Authors: Kubis T. , Vogl P.
Published: November 2007

In this paper, we investigate the intrinsic spin‐Hall effect in mesoscopic systems, i.e. spin‐orbit induced spin‐polarizations with and without external magnetic fields in confined two‐dimensional systems at low temperatures. We employ a non‐equilibrium Green's function approach that takes into account the coupling of non‐equilibrium spin occupancies and spin‐resolved electronic scattering states in open nanometer quantum systems. Importantly, our calculations go beyond the widely used continuum approximation of the spin‐orbit interaction in the envelope function approximation and are based on a microscopic relativistic tight‐binding approach that ensures the spin‐orbit effects to be properly taken into account for any degree of charge confinement and localization and to all orders in the electron wave vector. We show that the qualitative trends and results in spin polarizations, their dependency on charge density, spin‐orbit interaction strength, and confinement, as obtained within the envelope function approximation, agree with the results of atomistic calculations. The quantitative results, on the other hand, can differ significantly. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of hot electron effects on intersubband Raman laser in modulation‐doped GaAs/AlGaAs coupled double quantum wells
Authors: Miura M. , Katayama S.
Published: November 2007

We present a simulation of hot electron effects on inter‐subband Raman laser (IRL) consisting of modulation‐doped n‐type GaAs/AlGaAs coupled double quantum wells (CDQWs) with high 2D electron density. A time evolution for occupation number and electron temperature in each subband as well as the number of lasing Stokes photons are calculated self‐consistently for the modelled IRL. It is shown that Raman gain exhibits a characteristic reduction synchronizing an increase of Stokes photon density as time is evolved in sub‐nanosecond range. Then a saturation feature of output power is expected. The energy relaxation due to the confined LO phonons and the interface modes gives rise to interesting change of electron temperature in subband 1 and subband 2 during the Raman lasing. The threshold optical pumping intensity is estimated to be 50 kW/cm2. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Cascade optical excitation of an artificial exciton molecule in a coupled quantum dot
Authors: Goshima Keishiro , Komori Kazuhiro , Sugaya Takeyoshi , Takagahara Toshihide
Published: November 2007

We investigated the formation dynamics of the artificial exciton molecule state, which consists of two different excitons confined in each quantum dot of a pair of quantum dots, namely a coupled quantum dot (CQD). By the selective optical excitation of the inherent energy states of two different excitons using two color continuous wave (CW) and pulsed lasers, we successively created Xb excitons and an artificial exciton molecule state, and monitored the photoluminescence, namely the population, of the artificial exciton molecule states. By employing the power dependence of the two colors and the excitation energy dependence, we succeeded in controlling the cascade optical excitation of an artificial exciton molecule. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A CFL‐like constraint for the fast marching method in inhomogeneous chemical kinetics
Authors: Escobedo Ramón
Published: November 2007

Level sets and fast marching methods are a widely used technique for problems with moving interfaces. Chemical kinetics has been recently added to this family, for the description of reaction paths and chemical waves in homogeneous media, in which the velocity of the interface is described by a given field. A more general framework must consider variable velocities due to inhomogeneities induced by chemical changes. In this case, a constraint must be satisfied for the correct use of fast marching method. We deduce an analytical expression of this constraint when the Godunov scheme is used to solve the Eikonal equation, and we present numerical simulations of a case which must be enforced to obey the constraint. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Solvent effect of aqueous media on properties of glycine: Significance of specific and bulk solvent effects, and geometry optimization in aqueous media
Authors: Tiwari Saumya , Mishra P. C. , Suhai S.
Published: November 2007

Geometries of the normal (N) and zwitterionic (Z) forms of glycine (gly) and their complexes gly.(H2O)n, n = 0–2, were fully optimized in gas phase and aqueous media, and transition states located between the corresponding N and Z forms. The geometry was also optimized and vibrational spectra calculated for the gly.(H2O)3 complex of Z glycine. Density functional theory at the B3LYP/AUG‐cc‐pVDZ level was employed for the geometry optimization calculations in gas phase and aqueous media while single point energy calculations were performed at the MP2/AUG‐cc‐pVDZ level in each case. Solvation in bulk water was treated using the polarizable continuum model (PCM). Zero‐point energy correction to total energy and thermal energy correction to enthalpy were obtained at the B3LYP/AUG‐cc‐pVDZ level of theory in both gas phase and bulk aqueous media and these corrections were also considered to be valid for the corresponding single point energy calculations performed at the MP2/AUG‐cc‐pVDZ level of theory. When geometries of the complexes of glycine with water molecules are optimized in aqueous media, the calculated properties are found to be appreciably modified with respect to those obtained by gas phase geometry optimization followed by solvation in aqueous media. For several vibrational frequencies, the agreement between the calculated and experimentally observed results is improved appreciably when both the specific and bulk solvent effects are considered in combination with full geometry optimization in aqueous media. For certain vibrational frequencies, mode assignments have also been modified. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Maximum eigenvalues of the reciprocal distance matrix and the reverse Wiener matrix
Authors: Zhou Bo , Trinajstić Nenad
Published: November 2007

We report some properties of the maximum eigenvalues of the reciprocal distance matrix and the reverse Wiener matrix of a connected graph, in particular, various lower and upper bounds, and the Nordhaus–Gaddum‐type results for them. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Internal‐rotation and inversion potential energy surfaces for methylamine and methylphosphine
Authors: Kim Hae‐Won , Zeroka Daniel
Published: November 2007

Using the HF, MP2, and DFT methods with a 6‐311G** basis set, we examine the internal‐rotation and inversion of the amino and phosphino groups in methylamine and methylphosphine. The resulting energy surfaces are reported as a function of rotation and inversion descriptors. Both surfaces are characterized by several special points: three minimum energy states, three first‐order internal‐rotation transition states, six first‐order inversion transition states, and six second‐order inversion transition states. The MP2 method gave better agreement with experiment. For methylamine, the MP2 energy barrier for internal‐rotation is 8.73 kJ/mol; for first‐order inversion it is 22.80 kJ/mol and for second‐order inversion it is 22.41 kJ/mol. For methylphosphine, the MP2 energy barriers are 7.53, 149.88, and 149.65 kJ/mol, respectively. The energy barriers include ZPE correction contributions. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Characterization ofin vitrometabolites of deoxypodophyllotoxin in human and rat liver microsomes using liquid chromatography/tandem mass spectrometry
Authors: Lee Sang Kyu , Jun In Hye , Yoo Hye Hyun , Kim Ju Hyun , Seo Young Min , Kang Mi Jeong , Lee Seung Ho , Jeong Tae Cheon , Kim Dong Hyun
Published: November 2007

Thein vitrometabolism of deoxypodophyllotoxin (DPT), a medicinal herbal product isolated fromAnthriscus sylvestris(Apiaceae), was investigated in rats and human microsomes and human recombinant cDNA‐expressed CYPs. The incubation of DPT with pooled human microsomes in the presence of NADPH generated five metabolites while its incubation with dexamethasone (Dex)‐induced rat liver resulted in seven metabolites (M1–M7) with major metabolic reactions including mono‐hydroxylation,O‐demethylation and demethylenation. Reasonable structures of the seven metabolites of DPT could be proposed, based on the electrospray tandem mass spectra. Chemical inhibition by ketoconazole and metabolism studies with human recombinant cDNA‐expressed CYPs indicated that CYP 3A4 and 2C19 are the major CYP isozymes in the metabolism of DPT in human liver microsomes. Copyright © 2007 John Wiley & Sons, Ltd.
Study on the formation of an amoxicillin adduct with methanol using electrospray ion trap tandem mass spectrometry
Authors: Grujic Svetlana , Vasiljevic Tatjana , Lausevic Mila , Ast Teodor
Published: November 2007

The possibility of using the protonated methanol‐adduct of antimicrobial amoxicillin for its identification and quantification at residue levels has been investigated, since it is impossible to completely suppress the formation of these adducts when methanol is present in the solvent system. This process has been monitored over time and as a function of concentration. It was determined that adducts were instantly formed and that the abundance of the protonated methanol‐adduct at m/z 398 increased at the expense of the protonated molecule m/z 366 with storage time. The effect of several common solvents and mobile‐phase additives on the ionization efficiency of amoxicillin and the formation of the methanol adduct has also been investigated. It was shown that the mass spectra of amoxicillin were strongly influenced by the solvent in which the analyte is dissolved and by the analyte concentration, as well as by the composition of mobile phase. Methanol was determined to be the best spray solvent, as it provided spectra with the lowest abundance of dimer ions. It was also determined that acetic acid as the mobile‐phase additive provided the highest signal intensities, while ammonium acetate should not be used as an additive for the determination of amoxicillin at residue levels. Using high‐performance liquid chromatography/electrospray ionization tandem mass spectrometry (HPLC/ESI‐MS/MS), fragmentation of the protonated molecules and the protonated methanol‐adduct ions, in both positive and negative ion mode, has been performed. The fragmentation was stable and strong product ion spectra were obtained. The linearity of the MS detector response, and that of the chromatographic method, was tested. Due to the linear behaviour it was concluded that the protonated methanol‐adduct ion can be used for analytical purposes, i.e. for identification and quantification of amoxicillin at trace levels. Copyright © 2007 John Wiley & Sons, Ltd.
Neurostatistics: Applications, challenges and expectations
Authors: Georgopoulos Apostolos P. , Karageorgiou Elissaios
Published: November 2007

Brain function and its relations to cognition and behavior can be elucidated only by the use of various complementary methods. Over the past 20 years, we have been studying the brain mechanisms underlying spatial processes using different methods, including the recording of single cell activity in behaving monkeys, functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG) in human subjects, all performing the same tasks. These methods provide partially overlapping perspectives, resulting in a gain in knowledge beyond the province of the individual method. A common aspect in this endeavor is the statistical analysis of the data acquired by different methods, especially regarding the encoding of information in unitary elements (single cell activity in neurophysiology, blood oxygenation level‐dependent (BOLD) activation of voxels in fMRI, magnetic field strength in MEG) and the decoding of information from ensembles. In this paper we illustrate the various approaches, their data analysis and possible applications to medicine in the context of operations in space. Published in 2007 by John Wiley & Sons, Ltd.
Cyclotrimerization reactions of arynes and strained cycloalkynes
Authors: Peña Diego , Pérez Dolores , Guitián Enrique
Published: November 2007

The use of arynes and related species as substrates in metal‐catalyzed cycloaddition reactions leads to structurally interesting products. Palladium‐catalyzed cyclotrimerization of arynes provides a new method for the synthesis of polycyclic aromatic hydrocarbons. For instance, the chemoselective formal [2 + 2 + 2] cocycloaddition of 2,3‐triphenylynes with alkynes affords extended triphenylenes, which are good candidates to behave as liquid crystals. Cotrimerization of benzyne and electron‐deficient alkenes selectively affords dihydrophenanthrenes or ortho‐olefinated biaryls depending on the catalytic system employed. The use of 2,2′‐bis(diphenylphosphino)‐1,1′‐binophythyl (BINAP)‐based palladium(0) catalysts in the cocyclotrimerization of 7‐methoxynaphthalyne and dimethyl acetylenedicarboxylate affords an enantiomerically enriched tetrasubstituted pentahelicene, the first example of a metal‐catalyzed enantioselective reaction involving arynes. Strained cyclic alkynes can also participate in the palladium‐catalyzed cyclotrimerization reactions, which again lead to structurally interesting products. © 2007 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 7: 326–333; 2007: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.20132
Early manifestations and spectrum of recipient twin cardiomyopathy in twin–twin transfusion syndrome: relation to Quintero stage
Authors: Michelfelder E. , Gottliebson W. , Border W. , Kinsel M. , Polzin W. , Livingston J. , Khoury P. , Crombleholme T.
Published: November 2007

Objectives

To examine cardiac structural and functional changes in twin–twin transfusion syndrome (TTTS), relative to Quintero stage, as a means of evaluating the spectrum of cardiomyopathy in TTTS.

Methods

This was a cross‐sectional, retrospective study of 42 consecutive cases of TTTS referred to a single fetal therapy center. Quintero stages were assigned by standard criteria. Presence of ventricular hypertrophy, cardiomegaly, atrioventricular valve regurgitation (AVVR), ventricular systolic dysfunction and right ventricular outflow tract obstruction on fetal echocardiography were noted. The Doppler myocardial performance index (MPI), an index of global ventricular function, was calculated for both ventricles in subjects with adequate Doppler data. We compared cardiac changes across Quintero stages.

Results

There was no cardiomyopathy observed in donor twins. The majority of subjects presented at Quintero Stage I (n = 14), II (n = 14) or III (n = 11), with fewer at Stages IV (n = 2) or V (n = 1). As early as Quintero Stages I and II, a significant proportion of recipient twins had ventricular hypertrophy (17/28, 61%), AVVR (6/28, 21%) or quantitative abnormalities in either right (12/24, 50%) or left (14/24, 58%) ventricular function. Increasing prevalence of biventricular systolic dysfunction and cardiomegaly accompanied advancing Quintero stage.

Conclusions

Changes in cardiac structure and function not reflected in Quintero staging occur in recipient twins early in the evolution of TTTS. Incorporation of cardiac findings into assessment of TTTS severity may prove useful in stratification of risk and treatment selection. Copyright © 2007 ISUOG. Published by John Wiley & Sons, Ltd.
Three‐dimensional sonographic assessment of fetal urine production before and after laser surgery in twin‐to‐twin transfusion syndrome
Authors: Yamamoto M. , Essaoui M. , Nasr B. , Malek N. , Takahashi Y. , Moreira de Sa R. , Ville Y.
Published: November 2007

Objective

Fetal urine production in twin‐to‐twin transfusion syndrome (TTTS) reflects the hemodynamic imbalance between the donor and recipient twins but it has not been measured in this particular condition. The aim of this study was to measure fetal urine production using three‐dimensional (3D) ultrasound in donor and recipient twins before and after laser treatment for TTTS and to correlate this with umbilical venous volume flow (UVVF).

Methods

Urine production rate (UPR) was measured using 3D ultrasound with Virtual Organ Computer‐aided AnaLysis (VOCAL™) in 106 cases of severe TTTS. The rotation angle was set at 30°. The bladder volume was measured twice in each fetus (V1 and V2), with an interval of 5–30 min between measurements, in order to calculate the UPR. When V2 > V1, UPR was calculated using the formula: V2 − V1 /time interval. Together with UPR, UVVF was measured before and after treatment. Both parameters were corrected for fetal weight. Inter‐ and intraobserver variability were calculated in 16 cases using the intraclass correlation coefficient.

Results

Before laser treatment, UPR was significantly higher in recipients compared with donors (median, 14.8 and 0 mL/h/kg, mean 23.8 and 2.3 mL/h/kg, respectively, P < 0.001), and UPR was positively correlated with UVVF in both twins. Following laser treatment (48 h later), UPR decreased to 9 mL/h/kg (P < 0.001) in recipients, while there was no change in donors. UVVF increased significantly from a median value of 92 to 132 mL/min/kg (P < 0.01) in donors and decreased significantly from 150 to 99 mL/min/kg (P < 0.001) in recipients.

Conclusions

In TTTS UPR is correlated to UVVF and reflects the hemodynamic imbalance between donor and recipient twins. Following laser treatment, UPR decreases in recipients but is unaffected in donors. However, changes in UVVF occur in both twins. This suggests that although fetal renal function is driven by fetal hemodynamics, there may be a lag in the recovery of renal function in the donor twin. Copyright © 2007 ISUOG. Published by John Wiley & Sons, Ltd.