bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of the effectiveness of saturation pulses in the heart at 3T
Authors: Kim Daniel , Gonen Oded , Oesingmann Niels , Axel Leon
Published: November 2007

Cardiac MRI at 3T provides a means to increase the contrast‐to‐noise ratio (CNR) for first‐pass perfusion MRI. However, both the static magnetic field (B0) and radio frequency (RF) field (B1) variations within the heart are comparatively higher at 3T than at 1.5T. The increased field variations can degrade the performance of a single rectangular saturation pulse that is conventionally used for magnetization preparation. The accuracy of T1‐weighted signal measurement depends on the uniformity of the magnetization saturation. The purpose of this study was to assess the relative effectiveness of the rectangular, pulse train, and adiabatic composite (BIR‐4) saturation pulses in the human heart at 3T. In volunteers, after nominal saturation, the mean residual magnetization within the left ventricle (LV) was different between all three pulses (0.13 ± 0.06 vs. 0.03 ± 0.02 vs. 0.03 ± 0.01, respectively; P < 0.001). Within paired groups, the mean residual magnetization was significantly higher for the rectangular pulse than for either the pulse train and BIR‐4 pulses (P < 0.001), but not different between the pulse train and BIR‐4 pulses. The performances of all three saturation pulses were comparatively poorer in the right ventricle (RV) than in the LV, respectively. Magn Reson Med, 2007. © 2007 Wiley‐Liss, Inc.
Diffusion tensor metrics, T2 relaxation, and volumetry of the naturally aging human caudate nuclei in healthy young and middle‐aged adults: Possible implications for the neurobiology of human brain aging and disease
Authors: Hasan Khader M. , Halphen Christopher , Boska Michael D. , Narayana Ponnada A.
Published: November 2007

In this study of a cohort of 33 young and middle‐age adults (19–59 years) we report simultaneous measurements of normal age‐related changes in the caudate nuclei volume, diffusion tensor metrics, and T2 relaxation time. Both the absolute caudate volume and its ratio relative to the total intracranial volume decreased rapidly with age in both men and women (r = −0.55; P < 0.001). The fractional diffusion tensor anisotropy of the caudate nuclei increased with age in both males and females (r = 0.48; P = 0.005). The corresponding age correlations of the caudate axial (r = 0.17; P = 0.35), transverse (r = −0.12; P = 0.50), mean diffusivities (r = 0.018; P = 0.92), and T2 relaxation times (r = 0.194; P = 0.28) were weaker and did not reach statistical significance (P > 0.05). Our preliminary findings warrant further studies on the older and aging adults and indicate that caudate diffusion tensor imaging‐derived metrics can be used as surrogates in modeling the neuronal substrates of gray matter atrophy. Magn Reson Med, 2007. © 2007 Wiley‐Liss, Inc.
Imaging periodic currents using alternating balanced steady‐state free precession
Authors: Buračas Giedrius T. , Liu Thomas T. , Buxton Richard B. , Frank Lawrence R. , Wong Eric C.
Published: November 2007

Existing functional brain MR imaging methods detect neuronal activity only indirectly via a surrogate signal such as deoxyhemoglobin concentration in the vascular bed of cerebral parenchyma. It has been recently proposed that neuronal currents may be measurable directly using MRI (ncMRI). However, limited success has been reported in neuronal current detection studies that used standard gradient or spin echo pulse sequences. The balanced steady‐state free precession (bSSFP) pulse sequence is unique in that it can afford the highest known SNR efficiency and is exquisitely sensitive to perturbations in free precession phase. It is reported herein that when a spin phase‐perturbing periodic current is locked to an RF pulse train, phase perturbations are accumulated across multiple RF excitations and the spin magnetization reaches an alternating balanced steady state (ABSS) that effectively amplifies the phase perturbations due to the current. The alternation of the ABSS signal therefore is highly sensitive to weak periodic currents. Current phantom experiments employing ABSS imaging resulted in detection of magnetic field variations as small as 0.15nT in scans lasting for 36 sec, which is more sensitive than using gradient‐recalled echo imaging. Magn Reson Med, 2007. © 2007 Wiley‐Liss, Inc.
Diffusion‐weighted imaging of the fetal brain in vivo
Authors: Kim Dong‐Hyun , Chung SungWon , Vigneron Daniel B. , Barkovich A. James , Glenn Orit A.
Published: November 2007

A method of performing diffusion‐weighted imaging (DWI) and diffusion tensor imaging (DTI) of the fetal brain in utero is proposed. The major difficulty of performing diffusion imaging in utero is the presence of motion. By modifying conventional single‐shot spin‐echo echo‐planar DWI with a short repetition time sequence, a sequence that performs DWI and DTI within a breath‐hold of the mother (13 sec and 18 sec, respectively) was devised. T1 weighting caused by the use of short repetition times is compensated by interspersing diffusion imaging with additional b=0 image acquisitions. In utero fetal brain DWI and DTI were performed using this sequence. Quantitative analysis revealed minimal differences in the obtained apparent diffusion coefficient (ADC; directionally averaged ADC) values when using this sequence. The method can be readily implemented in a clinical setting and is especially useful when scanning mothers who cannot tolerate lengthier breath‐holds. Magn Reson Med, 2007. © 2007 Wiley‐Liss, Inc.
Developing multidisciplinary guidelines for the management of early rheumatoid arthritis
Authors: Hennell Sheena , Luqmani Raashid
Published: November 2007

Objective: To develop an evidence based guideline, for the multidisciplinary management of early rheumatoid arthritis (RA).

Methods: Recommendations were developed using both an evidence‐based approach and expert opinion. The scientific committee, composed of key members of the rheumatology multidisciplinary team used a Delphi approach to evaluate topics and standard statements, which formed the basis for developing recommendations for management of RA in the first 2 years of disease. Evidence taken from literature was used to support these recommendations.

Results: 24 evidence based recommendations for the management of early RA, with a grade of recommendation from A to C, were developed. In addition an algorithm of care was designed to promote a clear multidisciplinary management pathway. A mechanism for audit was also identified.

Conclusion: Involvement of the multidisciplinary rheumatology team has enabled a holistic guideline to be developed for the management of patients presenting with early RA. This guideline is based around best practice that is supported by published literature. Whilst most statements in the guideline are based on strong evidence, others have been formulated by expert consensus in the absence of data and should serve as an opportunity to improve current practice through future research and audit. The development and implementation of such a guideline should improve the care of patients with early RA. Copyright © 2007 John Wiley & Sons, Ltd.
Proteomic analysis of the proteins regulated by HrpB from the plant pathogenic bacterium Burkholderia glumae
Authors: Kang Yongsung , Kim Jinwoo , Kim Suhyun , Kim Hongsup , Lim Jae Yun , Kim Minkyun , Kwak Jangyul , Moon Jae Sun , Hwang Ingyu
Published: November 2007

Plant pathogenic bacteria transfer effector proteins into plant cells via the hypersensitive response and pathogenicity (Hrp) type III protein secretion system (T3SS) during infection. The genes encoding the Hrp T3SS are expressed only under plant apoplast‐mimicking conditions in an AraC‐type transcriptional activator HrpB‐dependent manner. To identify the proteins controlled by HrpB in Burkholderia glumae in vitro, we constitutively expressed hrpB and analyzed the proteins showing altered expression using 2‐DE and ESI‐MS/MS. Among 46 proteins exhibiting consistently altered expression, which were encoded by 34 different genes, 34 were secretory proteins and 12 were cytoplasmic. Twenty‐eight of the secreted proteins showed increased accumulation, whereas the other six showed decreased accumulation. None of the HrpB‐dependent proteins had significant homology to known T3SS‐dependent proteins, except for HrpK from Pseudomonas syringae pv. syringae and two T3SS‐associated cytoplasmic proteins from Ralstonia solanacearum. Twenty‐one of the 34 genes had putative HrpB‐binding sequences in their upstream regulatory regions. Secretion of all 34 extracellular proteins was independent of the Hrp T3SS, and 16 were secreted via a type II protein secretion system (T2SS). Mutants lacking the T2SS or Hrp T3SS produced toxoflavin but were less virulent to rice panicles, indicating the importance of these proteins in pathogenicity.
Elastic image registration of 2‐D gels for differential and repeatability studies
Authors: Sorzano Carlos O. S. , Arganda‐Carreras Ignacio , Thévenaz Philippe , Beloso Ana , Morales Gracia , Valdés Israel , Pérez‐García Carmen , Castillo Carmen , Garrido Elisa , Unser Michael
Published: November 2007

One of the main applications of electrophoretic 2‐D gels is the analysis of differential responses between different conditions. For this reason, specific spots are present in one of the images, but not in the other. In some other occasions, the same experiment is repeated between 2 and 12 times in order to increase statistical significance. In both situations, one of the major difficulties of these analysis is that 2‐D gels are affected by spatial distortions due to run‐time differences and dye‐front deformations, resulting in images that are significantly dissimilar not only because of their content, but also because of their geometry. In this technical brief, we show how to use free, state‐of‐the‐art image registration and fusion algorithms developed by us for solving the problem of comparing differential expression profiles, or computing an “average” image from a series of virtually identical gels.
Interventions to improve recall of medical information in cancer patients: a systematic review of the literature
Authors: van der Meulen Nienke , Jansen Jesse , van Dulmen Sandra , Bensing Jozien , van Weert Julia
Published: November 2007

This systematic review investigates which interventions are effective to improve recall of medical information in cancer patients. A literature research was done in PubMed, PsychINFO, CINAHL and Cochrane Library, following the guidelines of the Cochrane Collaboration. The methodological quality of selected studies was assessed independently by two reviewers. The results were synthesized with a Best Evidence Synthesis. Of initially 5173 found publications, 10 met all selection criteria. The results indicate that an audiotape of the patients' own consultation has added value upon oral information only. However, providing patients with a general audiotape does not improve recall of information and might even inhibit patients' recall. Furthermore, there is scientific evidence, although limited, that the use of a question prompt sheet (QPS) has a positive effect on recall of information, provided that the physician actively endorses this sheet. No evidence was found for an effect of providing patients with a summary letter of the consultation on recall, although research on this subject is scarce. In conclusion, the review suggests that interventions that are tailored to the individual cancer patient, such as an audiotape of the consultation or a QPS, are most effective. Further research needs to be done to establish robust results. Copyright © 2007 John Wiley & Sons, Ltd.
One‐week Short‐Term Life Review interview can improve spiritual well‐being of terminally ill cancer patients
Authors: Ando Michiyo , Morita Tatsuya , Okamoto Takuya , Ninosaka Yasuyoshi
Published: November 2007

Purpose: The primary aim of this study was to assess the efficacy of the Short‐Term Life Review on the spiritual well‐being, as well as anxiety, depression, suffering, and happiness of terminally ill cancer patients.

Method: Thirty patients reviewed their lives in the first session and they confirmed the contents in the album based on the life review in the second session. Duration of the treatment was one week. Measurement instruments included Functional Assessment Chronic Illness Therapy‐Spiritual (FACIT‐Sp), Hospital Anxiety and Depression Scale (HADS), Numeric Rating Scales of Suffering (from 0 to 6) and Happiness (from 1 to 7).

Results: After the therapy, the mean FACIT‐Sp scores increased from 16±8.2 to 24±7.1, anxiety score significantly decreased from 6.8±4.7 to 3.0±2.2, depression score significantly decreased from 10.2±4.7 to 6.6±4.1, suffering score significantly decreased from 3.4±1.9 to 1.8±1.4, and happiness score significantly increased from 4.6±1.9 to 5.6±1.6. Total HADS scores significantly decreased from 17±8.6 to 9.5±5.4.

Conclusion: The Short‐Term Life Review is feasible and may be effective in improving the spiritual and psychosocial well‐being of terminally ill cancer patients. Copyright © 2007 John Wiley & Sons, Ltd.
Do patients with schizophrenia receive state‐of‐the‐art lung cancer therapy? A brief report
Authors: Mateen Farrah J. , Jatoi Aminah , Lineberry Timothy W. , Aranguren Dawn , Creagan Edward T. , Croghan Gary A. , Jett James R. , Marks Randolph S. , Molina Julian R. , Richardson Ronald L.
Published: November 2007

Objective: Patients with schizophrenia sometimes receive substandard medical care. This study explored such disparities among lung cancer patients with underlying schizophrenia.

Methods: This retrospective study focused on patients with pre‐existing schizophrenia (or in some instances schizoaffective disorder) and a lung cancer diagnosis made between 1980 and 2004. ‘Disparity’ was defined as a patient's having been prescribed less aggressive therapy for a potentially curable cancer based on state‐of‐the‐art treatment standards for the time and for the cancer stage. Qualitative methods were used to assess healthcare providers' decision‐making.

Results: 29 patients were included. The median age was 59 years; 38% were men. Twenty‐three had non‐small cell lung cancer and 6 small cell lung cancer; 17 had potentially curable cancers. Five of 17 had a ‘disparity’ in cancer care: (1) no cancer therapy was prescribed because of chronic obstructive pulmonary disease; (2) no cancer therapy was prescribed because of infection; (3) no chemotherapy was prescribed because the patient declined it; radiation was provided; (4) no chemotherapy was prescribed because of the patient's schizophrenia symptoms; radiation was administered; and (5) no surgery was performed because of disorientation from a lobotomy; radiation was prescribed. Comments from healthcare providers suggest reflection and ethical adjudication in decision‐making.

Conclusion: Schizophrenia was never the sole reason for no cancer treatment in patients with potentially curable lung cancer. This study provides the impetus for others to begin to assess the effect of schizophrenia on lung cancer management in other healthcare settings. Copyright © 2007 John Wiley & Sons, Ltd.
Black hole attractors and the entropy function in four‐ and five‐dimensionalN= 2 supergravity
Authors: Perz J.
Published: November 2007

In this overview of selected aspects of the black hole attractor mechanism, after introducing the necessary foundations, we examine the relationship between two ways to describe the attractor phenomenon in four‐dimensionalN= 2 supergravity: the entropy function and the black hole potential. We also exemplify their practical application to finding solutions to the attractor equations for a conifold prepotential. Next we describe an extension of the original definition of the entropy function to a class of rotating black holes in five‐dimensionalN= 2 supergravity based on cubic polynomials, exploiting a connection between four‐ and five‐dimensional black holes. This link allows further the derivation of five‐dimensional first‐order differential flow equations governing the profile of the fields from infinity to the event horizon and construction of non‐supersymmetric interpolating solutions in four dimensions by dimensional reduction. Finally, since four‐dimensional extremal black holes inN= 2 supergravity can be viewed as certain two‐dimensional string compactifications with fluxes, we discuss implications of the conifold example in the context of the entropic principle, which postulates as a probability measure on the space of these string compactifications the exponentiated entropy of the corresponding black holes.
Microwave‐assisted Boc‐solid phase peptide synthesis of cyclic cysteine‐rich peptides
Authors: Čemažar Maša , Craik David J.
Published: November 2007

In this study we describe the first protocols for the synthesis of cystine‐rich peptides in the presence of microwave radiation with Boc‐solid phase peptide synthesis (SPPS). This method is exemplified for macrocyclic peptides known as cyclotides, which comprise ∼30 amino acids and incorporate a cystine knot arrangement of their three disulfide bonds. However, the method is broadly applicable for a wide range of peptides using Boc‐SPPS, especially for SPPS of large peptides via native chemical ligation. Microwave radiation produces peptides in high yield and with high purity, and we were able to reduce the time for the assembly of ∼30 mer peptide chains to an overnight reaction in the automated microwave‐assisted synthesis. Copyright © 2007 European Peptide Society and John Wiley & Sons, Ltd.
High‐field transport in semiconductors by transmission formalism
Authors: Natori K.
Published: November 2007

High field transport in semiconductor is investigated by the transmission‐reflection formalism. One‐dimensional Boltzmann transport equation (BTE) is solved, without resorting to the relaxation time approximation as well as to the perturbation expansion. In case of elastic scattering without energy relaxation, the current density is proportional to square root of the electric field for a wide range of field. By inclusion of the energy relaxation due to the optical phonon emission, the current density restored the proportionality to electric field, and showed a tendency of saturation in high‐field. The saturation in the high‐field is concluded to be due to the ballistic transmission of carriers through a specific layer located at the beginning of channel. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Observation of the second‐nearest‐neighbor Bloch oscillation in a GaAs/AlAs superlattice
Authors: Hasegawa T. , Mizoguchi K. , Nakayama M.
Published: November 2007

We have systematically investigated the quantum beat of the miniband excitons and the Bloch oscillation in the Wannier‐Stark (WS) localization as a function of applied bias voltage in a GaAs (6.8 nm)/AlAs (0.9 nm) superlattice embedded in a p ‐i ‐n diode structure. The coherent dynamics behaviors were detected with a reflection‐type pump‐probe technique. We clearly observed the transformation process from the miniband‐exciton quantum beat to the Bloch oscillation with an increase in applied bias voltage producing an internal electric field. The noteworthy finding is the fact that the Bloch oscillation with the frequency of vBO = 2eFD /h appears in a weak localization regime in addition to the usual Bloch oscillation with vBO = eFD /h in a strong localization regime, where F is the electric field, and D is the superlattice period. The frequency of 2eFD /h indicates that the newly observed Bloch oscillation is due to the wave‐packet motion in the second‐nearest‐neighbor space range. The results described above are explained by the electric‐field‐strength dependence of the envelope‐function localization, which is estimated from the envelope‐function profile calculated by a transfer‐matrix method and the excitonic transitions observed by electroreflectance spectroscopy. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ultrafast dynamics of plasmon‐phonon coupling: Estimation of electron mobility in GaAs
Authors: Hase Muneaki
Published: November 2007

Utilizing a femtosecond pump‐probe technique, ultrafast relaxation of plasmon‐like LO phonon‐plasmon coupled (LOPC) modes is studied. The time‐resolved reflectivity change exhibits strong mode beating between the LO phonon and the lower branch of the LOPC modes. It is revealed that the decay of the upper branch (or plasmon‐like mode) of the coupled modes is very rapid in time‐frequency space, explored by using wavelet analysis. The decay time of the plasmon‐like LOPC mode, which corresponds to the relaxation time τ, is obtained to be ∼ 79 fs and this time constant enables us to extract the electron mobility μ to be 2074 ± 200 cm2/Vs. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Local Hall measurement of magnetization reversal and magnetic interaction in Fe/Au/Fe trilayer rings
Authors: Miyawaki T. , Kohda M. , Fujita A. , Nitta J.
Published: November 2007

Magnetization reversal process of ring‐shaped Fe/Au/Fe pseudo‐spin valve is investigated with different Au thickness by local Hall effect (LHE) using semiconductor two dimensional electron gas. The Hall resistance shows clear hysteresis loop with four different transition fields. By comparing the single‐layer Fe rings, four steps are due to the onion (voretex)‐to‐vortex (onion) transitions both in the top and the bottom rings. The LHE measurement enables us to measure the distinct characterization of the magnetization reversal between the top and bottom Fe rings. Magnetic interactions between two Fe rings are measured as a function of Au thickness. The variation of the onion‐to‐vortex transition field is explained by the displacement of the domain walls in the onion state due to the stray field from the ring edge. The vortex‐to‐onion transition fields are shifted to the lower field in both Fe layers with decreasing Au thickness due to the reduction of entire magnetostatic energy in PSV rings. One possible explanation is the absorption of the stray field between two Fe rings. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Resonant energy transfer in electron‐driven proton pumps
Authors: Smirnov A. Yu. , Mourokh L. G. , Nori Franco
Published: November 2007

We examine proton and electron transport in living cell membranes and show that the Coulomb interaction leads to a resonant energy transfer, from the electrons to protons during their simultaneous tunnelings, which allows the proton pump to work. The proton pump efficiency is controlled by the electron voltage build‐up, external temperature, and the molecular electrostatics driving the electron and proton energies to their resonant conditions. We also show that physiological (e.g., human body) temperatures are optimal for the operation of this proton pump. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Wigner ensemble Monte‐Carlo simulation of nano‐MOSFETs in degenerate conditions
Authors: Querlioz D. , Saint‐Martin J. , Do V.‐N. , Bournel A. , Dollfus P.
Published: November 2007

Wigner quasi‐distribution function is an appropriate quantum mechanics formulation to study the transition from semi‐classical to quantum transport in nano‐devices since it can accurately describe quantum transport including the decoherence due to scatterings. We have recently developed an efficient approach to solving the Wigner transport equation using a Monte Carlo (MC) algorithm that has been applied to Resonant Tunnelling Diodes and nano‐MOSFET simulation. The approach is here extended to incorporate degeneracy effects that are important in highly doped MOSFETs. The calculation is compared with Non Equilibrium Green's Function and the semi‐classical Boltzmann equation. Relative importance of quantum transport and decoherent scattering is discussed at low and room temperatures. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Limiting factors for high temperature operation of THz quantum cascade lasers
Authors: Jirauschek C. , Lugli P.
Published: November 2007

We theoretically investigate the temperature performance of GaAs‐based resonant phonon depopulation THz quantum cascade lasers, using an ensemble Monte Carlo simulation which includes both carrier‐carrier and carrier‐phonon scattering. By evaluating the temperature dependence of the different carrier transport paths, we identify the factors restricting high temperature operation. As a major detrimental effect, a strongly increased occupation of the lower laser level is found due to a less efficient depletion at elevated temperatures, which can mainly be attributed to the resonant nature of the depletion process. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electron transport through single self‐assembled InAs quantum dots coupled to superconducting nanogap electrodes
Authors: Shibata K. , Buizert C. , Oiwa A. , Hirakawa K. , Tarucha S.
Published: November 2007

We have fabricated superconductor‐quantum dot‐superconductor (SC‐QD‐SC) junctions by using SC aluminum electrodes with narrow gaps laterally contacting a single self‐assembled InAs QD. By adopting an appropriate metal deposition sequence we avoided electrical contact through natural oxides on the Al surfaces, and fabricated SC‐QD‐SC junctions with low sample resistance of the order of 4–500 kΩ at room temperature. These junctions exhibit clear Cou‐ lomb staircases at T = 40 mK. Coulomb oscillations are also observed when the backgate voltages are swept. Furthermore, clear suppression in conductance is observed for |VSD| < 2Δ /e, where Δ is the SC energy gap of Al, reflecting the superconductivity in the Al leads. The suppressed conductance disappears at higher temperatures (T ≥ 1 K) or at high magnetic fields (B ≥ 100 mT). These results indicate that SC‐QD‐SC junctions have been successfully fabricated for the first time in the self‐assembled InAs QD system. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
3D Monte Carlo simulation of transport in electro‐statically confined silicon nanochannels
Authors: Mohamed Mohamed , Martin Pierre , Ravaioli Umberto
Published: November 2007

This study investigates transport and electrostatic behavior of quasi 1D nanowires adopting a relatively simple planar fabrication technique. The confined conduction channel is created by etching an oxide trench, realizing a T‐gate structure. Since multiple channels are normally needed to realize sufficient current drive in practical applications, the behavior of single and coupled adjacent silicon nanowires is characterized using a 3D quantum corrected Monte Carlo approach. Results indicate that a single T‐gate structure provides over 27% increase in current drive compared to conventional MOSFET at a drain voltage of 1V. In addition, design consideration and recommendation is presented. Cross section of a T‐gate MOSFET. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Phonon scattering of hot electrons in intense mid‐infrared laser fields
Authors: Furuse H. , Mori N. , Kubo H. , Momose H. , Kondow M.
Published: November 2007

We calculated intravalley and intervalley phonon scattering rates of accelerated electrons under intense midinfrared laser fields. We extended the Keldysh theory, which assumes oscillatory motion of Bloch electrons driven by intense laser fields, to phonon scattering of electrons in semiconductors. We find that phonon emission is possible even if the initial electron energy is less than the phonon energy due to multi‐photon absorption processes. We also find that the scattering rates increase with electric field strength and wavelength. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experimental and theoretical investigation of terahertz optical‐beating detection by plasma waves in high electron mobility transistors
Authors: Marinchio H. , Torres J. , Sabatini G. , Nouvel P. , Palermo C. , Chusseau L. , Varani L. , Teppe F. , Shiktorov P. , Starikov E. , Gružinskis V. , Shchepetov A. , Bollaert S. , Roelens Y.
Published: November 2007

A photomixed laser beam of two 1.55 mm cw lasers is used to obtain interband photoexcitation at the difference frequency and at room temperature in submicron gate‐length InAlAs/InGaAs transistors. Results show the clear excitation of plasma oscillation modes in the transistor channel. Fundamental plasma resonant frequency and its odd harmonics can be tuned with the applied gate voltage. Numerical simulations have also been performed using a hydrodynamic approach coupled to a pseudo‐2D Poisson equation. Numerical results are in qualitative agreement with experiments and confirm optical beating detection at terahertz frequencies. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Two level mixing effects probed by resonant tunnelling through vertically coupled quantum dots
Authors: Amaha S. , Payette C. , Gupta J. A. , Hatano T. , Ono K. , Kodera T. , Tokura Y. , Austing D. G. , Tarucha S.
Published: November 2007

We study the magnetic (B ‐) field evolution of single‐particle levels in one dot by observing resonant tunnelling (RT) between two weakly coupled vertical quantum dots in series. The B ‐field dependence of the RT current peaks in the spectrum follows closely that of the states of a circular two dimensional harmonic potential. Several prominent two‐level anti‐crossing features are revealed. The RT current changes dramatically on passing through the anti‐crossing point. This can be assigned to the nature of inter‐dot RT though intra‐dot level‐mixed states. (a) Schematic diagram of our device. (b) Measured anti‐cross in the resonant current induced by intra‐dot two level mixing. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
All‐optical injection of ballistic electrical currents in unbiased silicon
Authors: Betz M. , Costa L. , Spasenovic M. , Bristow A. D. , van Driel H. M.
Published: November 2007

The absorption of phase‐related near‐infrared fundamental (ω) and second harmonic (2ω) femtosecond pulses results in ballistic electrical currents in clean bulk silicon at room temperature. The ultrafast charge motion is directly monitored via a time‐resolved analysis of the emitted THz bursts of radiation. The vector direction of the current is precisely controlled by the polarization of the two‐color pump field and the relative phase ΔΦ = 2Φω – Φ2ω . The current generation process relies on a third order optical nonlinearity. Microscopically, current injection can be understood as arising from the quantum interference of one‐ and two‐photon absorption processes. Surprisingly, the efficiency of the current injection is relatively high despite the multitude of possible phonon‐assisted absorption channels in the multi‐valley band structure. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Carrier spin relaxation in undoped GaAs double quantum wells
Authors: Lu S. L. , Ushiyama T. , Tackeuchi A. , Muto S.
Published: November 2007

Carrier spin relaxation in undoped GaAs/AlGaAs asymmetric double quantum wells (QWs) at room temperature was studied by spin‐dependent pump and probe reflection measurements. The electron tunneling, which occurs between the two lowest conduction bands in the narrow and wide QWs, has a negligible effect on the electron spin relaxation. The most striking feature is that a long hole spin relaxation time was directly observed in the case of fast electron tunneling while it was not observed in the case of relatively slow electron tunneling. The hole that remains in the QWs due to the escape of the electron tunneling out makes the direct observation of hole spin relaxation possible. The measured hole spin relaxation time varies from 107 ps to 80 ps when the excitation power changes from 10 mW to 40 mW. This study provides direct experimental evidence of the important effect of the interaction between electrons and holes on the hole spin relaxation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamic nuclear polarization in a double quantum dot device: electrical induction and detection
Authors: Baugh Jonathan , Kitamura Yosuke , Ono Keiji , Tarucha Seigo
Published: November 2007

We quantify the magnitude, buildup and relaxation dynamics of dynamic nuclear polarization (DNP) in a vertical GaAs double quantum dot device. This is accomplished using electrical techniques in the two‐electron spin‐blockade regime. Measurements are based on realtime electrical control of the relevant two‐electron spindependent energy levels, and observation of DNPinduced current step features at finite external magnetic fields. A simple phenomenological picture is presented to discuss the factors that limit maximum polarization in this system. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of electron‐electron interaction on the diffusion current of spin‐polarized electrons
Authors: Takahashi Yutaka , Inaba Nobuyuki , Hirose Fumihiko
Published: November 2007

Electron‐electron interaction modifies carrier transport in the spin‐polarized system. The effects are investigated in the two‐dimensional electron gas in semiconductor heterostructures. We find that the diffusion currents of spin‐up and spin‐down electrons are reduced, compared to the non‐interacting values, by the momentum exchange between spin‐up and spin‐down electrons through their collisions (Spin Drag), and also by the electron energy renormalization arising from the manyparticle correlations. We numerically calculate the diffusion coefficients of spin‐up and spin‐down electrons separately in high‐quality heterostructures of GaAs at low temperatures, including the effect of finite spin life time. Our calculations show that the diffusion coefficients are reduced down to less than half of their non‐interacting values. We also find the negative diffusivity at low temperatures. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Carrier acceleration under very high fields in bulk GaAs investigated by time‐domain terahertz spectroscopy
Authors: Zhu Y. M. , Unuma T. , Shibata K. , Hirakawa K. , Ino Y. , Kuwata‐Gonokami M.
Published: November 2007

Nonequilibrium electron transport in bulk GaAs under very high electric fields up to 300 kV/cm has been investigated by time‐domain terahertz (THz) spectroscopy. It is found that when applied electric field, F, is above 50 kV/cm, the initial acceleration signal in THz emission waveforms starts decreasing with increasing F. This result suggests that the effective acceleration mass of electrons significantly increases with increasing F, most likely due to strong band mixing under very high fields. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Density functional computations of the cyclopropanation of ethene catalyzed by iron (II) carbene complexes Cp(CO)(L)FeCHR, L = CO, PMe3, R = Me, OMe, ph, CO2Me
Authors: Wang Fen , Meng Qingxi , Li Ming
Published: November 2007

Density functional theory has been used to study the Fe‐catalyzed cyclopropanation of Fe‐carbene complexes with ethene. All the intermediates and transition states were optimized completely at the B3LYP/6‐31+G(d,p) level. Calculation results confirm that the cyclopropanation of Fe‐carbene complexes with ethene involves the two reaction paths I and II. In the reaction path I, the double bond of ethene attacks directly on the carbene carbon of Fe‐carbene complexes to generate the cyclopropane. In the reaction path II, ethene substitution for PMe3 or CO in the Fe‐carbene complexes leads to the complexes M2; and the attack of one carbon of ethene on the carbene carbon results in the complexes M3 with a FeCCC four‐membered ring, and then generates the cyclopropane via the elimination reaction. For Fe‐carbene complexes A, C, D, E, and H, the main reaction mode is the reaction path I; for Fe‐carbene complexes B, F, and G, the main reaction mode is the reaction path II. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Bonding analysis for NgAuOH (Ng = Kr, Xe)
Authors: Zhang Ping Xia , Zhao Yong Fang , Hao Feng You , Li Xin Ying
Published: November 2007

Noble‐gas‐noble‐metal hydroxides NgAuOH (Ng = Kr, Xe) are investigated at the MP2 theoretical level. All species are found to be in Cs symmetry with an approximate linear NgAuO moiety. The noble‐gas‐noble‐metal bond lengths are comparable with covalent limits, and the corresponding binding energies have been computed to be 59.6 and 83.4 kJ/mol for KrAuOH and XeAuOH, respectively. Except the charge‐induced dipole contribution to the binding energies, the remainder could be ascribed to the higher‐order charge‐induction energies, dispersion energies, the contributions of multipole moments on AuOH and covalent effects. The title species are sufficiently chemical bound and are expected to be stable species theoretically. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Analysis of biologically active compounds in water by ultra‐performance liquid chromatography quadrupole time‐of‐flight mass spectrometry
Authors: Farré Marinella , Gros Meritxell , Hernández Belen , Petrovic Mira , Hancock Peter , Barceló Damià
Published: November 2007

A new method based on ultra‐performance liquid chromatography (UPLC) quadrupole time‐of‐flight mass spectrometry ((Q‐ToF)‐MS) was developed for the analysis of 32 biologically active compounds including anti‐inflammatories, analgesics, lipid regulators, psychiatric drugs, anti‐ulcer agents, antibiotics, beta‐blockers and phytoestrogens. This new method allows chromatographic analysis in 14 min, with instrumental detection limits from 2 to 84 pg, and limits of quantification ranging from 0.1 to 15 ng/L in tap water, and from 2 to 300 ng/L in wastewater.

The potential of liquid chromatography with triple quadrupole mass spectrometry (LC/QqQ‐MS) was compared with that of UPLC/(Q‐ToF)‐MS for the analysis of biologically active compounds in water samples. LC/Q‐ToF provides accurate mass information and a significantly higher mass resolution than quadrupole analyzers. The available mass resolution of ToF instruments diminishes the problem of isobaric interferences and helps the analysis of trace compounds in complex samples.

In this work UPLC/Q‐ToF chromatograms were recorded containing full scan spectral data. The m/z values of analytes were extracted from the total ion chromatogram (TIC) and the accurate masses of the compounds were obtained. In addition, to increase the selectivity of ToF measurements a narrow accurate mass interval (20 m m/z units mass window) was used to reconstruct the chromatographic traces.

However, regarding quantitative performance in terms of dynamic range and limits of detection (LODs), typical LODs achieved by QqQ instruments operating in multiple‐reaction monitoring (MRM) mode ranged from 1 to 50 ng/L in wastewater, and the linear response for QqQ instruments generally covers three orders of magnitude. This is an important advantage over ToF instruments and one of the reasons why QqQ instruments are widely used in quantitative environmental analysis. Copyright © 2007 John Wiley & Sons, Ltd.
Determination of N‐glycosylation sites and site heterogeneity in a monoclonal antibody by electrospray quadrupole ion‐mobility time‐of‐flight mass spectrometry
Authors: Olivova Petra , Chen Weibin , Chakraborty Asish B. , Gebler John C.
Published: November 2007

This paper presents an improved analytical method for glycosylation structural characterizations of a monoclonal antibody (mAb) using a newly developed quadrupole ion‐mobility time‐of‐flight (ESI‐Q‐IM‐TOF) mass spectrometer. Using this method, high‐resolution mass spectra were acquired to produce the overall glycosylation profile of the mAb. Additionally, the light and heavy chains from the reduced antibody were separated in the gas phase by the ion mobility functionality of the instrument, allowing accurate mass measurement of each subunit. Furthermore, the glycan sequences, as well as the glycosylation site, were determined by a two‐step sequential fragmentation process using the unique dual‐collision‐cell design of the instrument, thus providing detailed characterizations of the glycan structures. Copyright © 2007 John Wiley & Sons, Ltd.
A binary matrix of 2,5‐dihydroxybenzoic acid and glycerol produces homogenous sample preparations for matrix‐assisted laser desorption/ionization mass spectrometry
Authors: Soltwisch Jens , Berkenkamp Stefan , Dreisewerd Klaus
Published: November 2007

We introduce a two‐component matrix for ultraviolet matrix‐assisted laser desorption/ionization mass spectrometry (UV‐MALDI‐MS) that consists of 2,5‐dihydroxybenzoic acid (DHB) and glycerol. Upon slow evaporation of residual water/methanol solvents in a pre‐vacuum chamber sample preparations are obtained that exhibit a homogeneous morphology with analyte‐matrix crystals evenly distributed over the whole sample spot. At a molar DHB/glycerol ratio of ∼1:5, the crystals range in length from ∼100 to 300 µm and are about 15–30 µm wide. Mass spectra of peptides, proteins, and an oligosaccharide are presented and compared with those recorded from standard dried‐droplet DHB matrix. The ion signals show a reproducibility of the order of 10–15% when scanning the surface of an individual sample or even different samples that contain the same amount of peptide, A close to linear relationship between peptide concentration and the corresponding peptide ion signal is found over three orders of magnitude of sample prepared. However, when a fixed position is irradiated with a large number of laser pulses, a monotonous decay of peptide ion signal with time is observed. Potentially, the binary matrix will be especially useful for the analysis of samples that are stabilized in buffered aqueous glycerol solution and preliminary results addressing this aspect are shown. Copyright © 2007 John Wiley & Sons, Ltd.
Otter predation in a trout fish farm of Central–East Portugal: preference for ‘fast‐food’?
Authors: Marques C. , Rosalino L. M. , Santos‐Reis M.
Published: November 2007

The Eurasian otter (Lutra lutra) is a known piscivorous predator throughout its distribution range, although in some regions a more generalist behaviour emerged, such as in southern European latitudes. We evaluated otter feeding preference/avoidance towards the elements of the fish guild inhabiting a Mediterranean environment (Côa River, Central Portugal) and assessed the influence of proximity to a surplus of trophic resources (a rainbow trout production farm) on the species diet. Almost two years of collected spraints revealed that otters subsisted by consuming almost exclusively fish (94% of consumed biomass), especially the rainbow trout (87% of consumed biomass), although in summer this consumption is complemented with reptiles and amphibians. Due to the presence of the trout farm, and the consequent constancy in the availability of trout, the observed otter specialization in rainbow trout represents an extreme opportunistic behaviour. Copyright © 2007 John Wiley & Sons, Ltd.
INCA: New statistic for estimating the number of clusters and identifying atypical units
Authors: Irigoien I. , Arenas C.
Published: November 2007

This paper presents a solution to two problems that arise in the classification of data such as types of tumor, samples of gene expression profiles or general biomedical data. First, to estimate the real number of clusters in a data set and second to decide whether a new unit belongs to one of these previously identified clusters or it is an outlier or atypical unit. We propose a new statistic which allows us to solve these problems. As our approach is based on a measure of distance or dissimilarity between any pair of units, it can be applied to any kind of multivariate data (continuous, binary or multi‐attribute data) and it has applications in many biomedical fields. We validated the approach in simulated examples and applied it to the diagnosis of dermal diseases and to the analysis of lymphatic cancer data, showing the good performance of our approach. Copyright © 2007 John Wiley & Sons, Ltd.
Methodological aspects of in vitro sensing of L‐glutamate in acute brain slices
Authors: Sugawara Masao
Published: November 2007

L‐Glutamate is a major amino acid neurotransmitter in the central neuronal system of the mammalian brain and plays a vital role in brain development, synaptic plasticity, neurotoxicity, and neuropathological disorders. Despite technical limitations, progress is being made in sensing L‐glutamate in vivo and in vitro. Sophisticated microsensors with the necessary spatial and temporal resolution have recently been emerging, which enable us to discern regional distribution, concentration levels, and temporal changes of L‐glutamate in acute brain slices. The L‐glutamate sensors for in vitro sensing have different structures and sizes, such as glass capillary‐based enzyme sensors, polymer‐coated enzyme sensors, and patch sensors based on natural sensing probes. The concentration of L‐glutamate released in brain slices by chemical stimulation is markedly dependent on neuronal regions, types of stimulation, and sensing methods. Real‐ and long‐time monitoring of L‐glutamate in acute hippocampal slices is beginning to shed light on L‐glutamate release related to the molecular mechanisms of long‐term potentiation. Progress is also being made toward the visualization of L‐glutamate release in acute hippocampal slices. The methodological aspects of in vitro sensing of L‐glutamate are discussed. © 2007 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 7: 317–325; 2007: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.20126
Network Governance and Multi-level Delegation: European Networks of Regulatory Agencies
Authors: COEN DAVID , THATCHER MARK
Published: November 2007

European networks of regulators in industries such as telecommunications, securities, energy and transport have been cited as important examples of the growth of network governance in Europe. Using a principal-agent perspective as a starting point, the article examines why a double delegation to networks of regulators has taken place. It looks at how and why the European Commission, national governments and independent regulatory agencies have driven the creation of networks, their institutional character and their implications for regulatory governance in Europe. It argues that problems of co-ordination were the main factor advanced to justify establishing networks of regulators. The new networks have been given a wide range of tasks and broad membership, but enjoy few formal powers or resources. They are highly dependent on the European Commission and face rivals for the task of co-ordinating European regulators. Thus in institutional terms the spread of network governance has in fact been limited.
The Making of the European Energy Market: The Interplay of Governance and Government
Authors: EBERLEIN BURKARD
Published: November 2007

This case study asks whether delegated, sectoral governance by private actors and arm’s-length agencies enhances policy efficacy or does sectoral governance require a shadow of hierarchy cast by government actors to deliver desired policy results? EU energy market liberalisation shows that sectoral governance successfully mobilises regulatory expertise, capacity and legitimacy and delivers workable norms and rules for market transactions in a complex policy environment. However, it also finds that the efficacy of sectoral governance mechanisms is constrained by distributive conflicts between different national jurisdictions and sector interests. If deadlock occurs, the European Commission as governmental principal casts a double shadow of hierarchy over sectoral governance agents: the threat of further legislation and of EU competition law. While both instruments enhance policy efficacy, they cannot substitute for the intrinsic rule-making qualities of sectoral governance: governance and government play complementary roles in the policy process.