bluuebunny/crossref_metadata_2025 huggingface dataset:
Acquired factor VIII inhibitors in pregnancy: data from the Italian Haemophilia Register relevant to clinical practice
Authors:   Italian Association of Haemophilia Centres (AICE): Register of acquired factor VIII inhibitors (RIIA)
Published: December 2004

Objective
To review the clinical problems related to the inhibitor of factor VIII (FVIII) in pregnancy.

Design
Retrospective analysis.

Setting
Haemophilia and haemotology centres.

Population
Patients registered and followed up at the centres.

Methods
Data were collected from the Italian Haemophilia Register of acquired FVIII inhibitor.

Results
Twenty of 96 cases with FVIII inhibitor were identified postpartum. The time of appearance was 3–150 days postpartum. All but one of the cases were idiopathic; 11/20 patients required blood transfusions. In six patients, the inhibitor was identified because of surgical bleeding, four after hysterectomies carried out because of postpartum haemorrhage. A prolonged activated partial thromboplastin time was present in all women in whom the test was carried out. Nine women did not require treatment because the bleeding was mild; in 11 patients bleeding was promptly controlled by different therapeutic modalities. Immunosuppressive therapy was used to suppress the inhibitor. The majority of the patients who achieved complete remission received steroids; in 6/6 patients who relapsed, a second remission was obtained with combined therapy.

Conclusions
In a review of 20 pregnancies with FVIII inhibitor, over a 15 year period, bleeding was controlled in all cases with no fatalities. Correct evaluation of coagulation screening tests, in particular, activated partial thromboplastin time, is essential.
A randomised trial of timed delivery for the compromised preterm fetus: short term outcomes and Bayesian interpretation
Authors:   The GRIT Study Group,   participants are listed at the end of this article
Published: December 2004

Objectives To compare the effect of delivering early to pre‐empt terminal hypoxaemia with delaying for as long as possible to increase maturity.

Design A randomised controlled trial.

Setting 69 hospitals in 13 European countries.

Participants Pregnant women with fetal compromise between 24 and 36 weeks, an umbilical artery Doppler waveform recorded and clinical uncertainty whether immediate delivery was indicated.

Methods The interventions were ‘immediate delivery’ or ‘delay until the obstetrician is no longer uncertain’. The data monitoring and analysis were Bayesian.

Main outcome measures ‘Survival to hospital discharge’ and ‘developmental quotient at two years of age’, this latter to be reported later.

Results Of 548 women (588 babies) recruited, outcomes were available on 547 mothers (587 babies). The median time‐to‐delivery intervals were 0.9 days in the immediate group and 4.9 days in the delay group. Total deaths prior to discharge were 29 (10%) in the immediate group versus 27 (9%) in the delay group (odds ratio 1.1, 95% CI 0.61–1.8). Total caesarean sections were 249 (91%) in the immediate group versus 217 (79%) in the delay group: (OR 2.7; 95% CI 1.6–4.5). These odds ratios were similar for those randomised at gestational ages above or below 30 weeks.

Interpretation The lack of difference in overall mortality suggests that clinicians participating in this trial were on average prepared to randomise at about the correct equivocal threshold between delivery and delay. However, there was insufficient evidence to convince enthusiasts for either immediate or delayed delivery that they were wrong.
Exploring the role of leukotriene receptor antagonists in the management of allergic rhinitis and comorbid asthma
Authors: Pawankar R.
Published: December 2004

The links between asthma and rhinitis are well documented and are based upon epidemiological, immunological and clinical observations. Leukotriene receptor antagonists (e.g. montelukast) are an established, effective and well tolerated treatment option for asthma, and more recent evidence now demonstrates their clinical utility in the treatment of allergic rhinitis. In seasonal allergic rhinitis, montelukast monotherapy has been shown to provide relief from daytime nasal symptoms (including congestion, runny nose, nasal itching and sneezing), as well as nighttime and eye symptoms. These clinical benefits were associated with reduced eosinophil counts in the blood, suggesting an effect on the underlying mechanisms of allergic inflammation. In addition, studies that have evaluated the combination of an antileukotriene with an antihistamine have typically shown a numerical and sometimes statistical benefit of combination therapy. Given the frequent coexistence and shared pathophysiologies of asthma and allergic rhinitis, a common therapeutic approach would seem warranted. Leukotriene receptor antagonists, such as montelukast, are emerging as a rational approach to ‘one airway’ disease management.
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Authors:   Society for Conservation Biology The Editorial Office of Conservation Biology
Published: December 2004

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Society for Conservation Biology The Editorial Office of Conservation Biology
Invasiveness of Some Biological Control Insects and Adequacy of Their Ecological Risk Assessment and Regulation
Authors: Louda S. M. , Arnett A. E. , Rand T. A. , Russell F. L.
Published: December 2004

Abstract:The problem of invasive species has reignited interest in biological control as a management tool. Classical biological control involves deliberate release of exotic natural enemies into new environments in an attempt to limit the density of an invasive species. Persistent, sustained limitation of invasive species by coevolved natural enemies is a seductive concept. Evidence now suggests, however, that biological control through the release of natural enemies can carry unanticipated ecological risks. There have been ecological side effects of distributing a deliberately introduced weevil (   Rhinocyllus conicus ) and an adventitious weevil (  Larinus planus ) for the biological control of exotic thistles. Both weevils have had major direct effects on key population‐growth parameters of native thistles, andR. conicushas had an indirect effect on the interaction between a thistle and a native insect. These findings led us to review how ecological risk is evaluated, and to ask whether pre‐release tests can predict the types of ecological effects documented. We conclude that, when done thoroughly, the tests used can determine host specificity by identifying physiological host range, but the usual tests cannot be relied upon to predict the ecological host range or impact on populations of less‐preferred but accepted native species. Our data provide support for suggestions that the behavioral and developmental data now taken need to be supplemented with additional data on population parameters to better predict field‐host use, population growth, interaction strengths, and ecological outcomes for native species that are potential hosts.
Vertically segregated hybrid blends for photovoltaic devices with improved efficiency
Authors: Sun Baoquan , Snaith Henry J. , Dhoot Anoop S. , Westenhoff Sebastian , Greenham Neil C.
Published: December 2004

Solution-processed photovoltaic devices based on blends of conjugated polymers and inorganic semiconductor tetrapods show high efficiencies due to the good electron transport perpendicular to the plane of the film. Here, we show that by using a high-boiling-point solvent, 1,2,4-trichlorobenzene, instead of chloroform for spin-coating, we can typically obtain a threefold increase in solar power conversion efficiency in devices based on CdSe tetrapods and the poly(p-phenylenvinylene) derivative OC1C10-PPV. The optimized devices show AM1.5 solar power conversion efficiencies of typically 2.1% with some devices as high as 2.8%. The results can be explained by the occurrence of vertical phase separation which leads to an optimal structure for charge collection. Evidence for this structure is obtained by environmental scanning electron microscopy, photocurrent action spectra measurements, time-resolved photoluminescence, and spectroscopic measurements of exciton dissociation and charge-carrier recombination.
Carrier compensation in semiconductors with buried metallic nanoparticles
Authors: Driscoll D. C. , Hanson M. P. , Gossard A. C.
Published: December 2004

We have grown composite epitaxial materials consisting of layers of semimetallic ErAs nanoparticles embedded in a semiconducting In0.53Ga0.47As matrix. Although the addition of ErAs particles into the InGaAs matrix increases the free-electron concentration, compensation of these free electrons is possible by depleting electrons from the metal particles through Be acceptor doping of the semiconductor. The room-temperature electron concentration of an ErAs:InGaAs superlattice sample with 0.05 monolayer ErAs per layer can be reduced by >104 by delta-doping the ErAs layers with 7×1012cm−2 of Be. The highest resistivity measured for a Be-doped ErAs:InGaAs superlattice was 350Ωcm.
Nanomixing: A way to synthesize surface nanoalloys
Authors: Som T. , Satpati B. , Satyam P. V. , Kabiraj D.
Published: December 2004

We report on room-temperature synthesis of nanodimensional Au-Ge alloy on Si surface by ion-beam mixing of nanoislands of Au and Ge. Synthesis of such surface nanoalloys could be the basis of making nanodimensional contacts towards miniaturization of microelectronic devices. The nanoislands of Au and Ge were grown by UHV electron beam evaporation technique on Si (100) surface and were irradiated by 1.5MeV Au2+ ions over a fluence range of 5×1012–1×1015ionscm−2. High-resolution transmission electron microscopy has been employed to study the formation of Au-Ge alloy in the form of nanoislands. Formation of such surface alloy nanoislands has been discussed in the light of ion-matter interaction in nanometer scale regime.
Investigation of orientational dynamics in poled nonlinear optical polymers by secondary poling
Authors: Chan S. C. , Wong K. Y.
Published: December 2004

The orientational motion of molecules in a nonlinear optical polymer was studied by secondary poling at a temperature below the glass transition temperature (Tg), after initial poling at above Tg. It was found that the molecules showed asymmetric orientational response for secondary poling between directions along and opposite to the initial poling direction. The result suggests that at sub-Tg temperatures, the local environment of the molecules becomes asymmetrical after the initial above-Tg poling, in a way that is contrary to expectation.
Effect of contact angle hysteresis on thermocapillary droplet actuation
Authors: Chen Jian Z. , Troian Sandra M. , Darhuber Anton A. , Wagner Sigurd
Published: December 2004

Open microfluidic devices based on actuation techniques such as electrowetting, dielectrophoresis, or thermocapillary stresses require controlled motion of small liquid droplets on the surface of glass or silicon substrates. In this article we explore the physical mechanisms affecting thermocapillary migration of droplets generated by surface temperature gradients on the supporting substrate. Using a combination of experiment and modeling, we investigate the behavior of the threshold force required for droplet mobilization and the speed after depinning as a function of the droplet size, the applied thermal gradient and the liquid material parameters. The experimental results are well described by a hydrodynamic model based on earlier work by Ford and Nadim. The model describes the steady motion of a two-dimensional droplet driven by thermocapillary stresses including contact angle hysteresis. The results of this study highlight the critical role of chemical or mechanical hysteresis and the need to reduce this retentive force for minimizing power requirements in microfluidic devices.
The influence of the surface topography on the magnetization dynamics in soft magnetic thin films
Authors: Craus C. B. , Palasantzas G. , Chezan A. R. , De Hosson J. Th. M. , Boerma D. O. , Niesen L.
Published: December 2004

In this work we study the influence of surface roughness on the magnetization dynamics of soft magnetic nanocrystalline Fe–Zr–N thin films deposited (under identical conditions) onto a Si oxide, a thin polymer layer, and a thin Cu layer. The substrate temperature during deposition was approximately −25°C ensuring a nanocrystalline state. The demagnetizing factors due to sample roughness were calculated based on atomic force microscopy (AFM) analysis of the surface topography. A clear correlation between sample roughness and the width of the high-frequency response is observed. The local random demagnetizing field created by the nanocrystalline structure and the surface topography is responsible for the positive shift of the ferromagnetic resonance frequency. In addition, a pronounced effect of line broadening is induced by the surface topography at large wavelengths. Finally, we show a good agreement between the values of the average demagnetizing field 4πNMS as calculated from the AFM scans, and the values calculated from the frequency-dependent complex permeability measurements.
Rate enhancement in phonon-assisted resonant tunneling in quantum dots
Authors: Chan K. S.
Published: December 2004

The buildup process of an electron’s probability in a quantum dot coupled to two conducting leads is studied in the regime of strong electron–phonon interaction. Initially the electron occupies an eigenstate in one of the conducting leads. An analytical expression is obtained for the time dependence of the electron’s probability in the quantum dot using the Green’s-function technique. A significant enhancement in the buildup rate is found when there are phonons in the quantum dot at the beginning of the tunneling process. Strong enhancement is found when the electron energy equals the zero-phonon resonant tunneling peak. Speed enhancement in resonant tunneling devices can be achieved by using properly designed quantum dot structures.
Production and recovery of defects in phosphorus-implanted ZnO
Authors: Chen Z. Q. , Kawasuso A. , Xu Y. , Naramoto H. , Yuan X. L. , Sekiguchi T. , Suzuki R. , Ohdaira T.
Published: December 2004

Phosphorus ions were implanted in ZnO single crystals with energies of 50–380keV having total doses of 4.2×1013–4.2×1015cm−2. Positron annihilation measurements reveal the introduction of vacancy clusters after implantation. These vacancy clusters grow to a larger size after annealing at a temperature of 600°C. Upon further annealing up to a temperature of 1100°C, the vacancy clusters gradually disappear. Raman-scattering measurements reveal the enhancement of the phonon mode at approximately 575cm−1 after P+ implantation, which is induced by the production of oxygen vacancies (VO). These oxygen vacancies are annealed out up to a temperature of 700°C accompanying the agglomeration of vacancy clusters. The light emissions of ZnO are suppressed after implantation. This is due to the competing nonradiative recombination centers introduced by implantation. The recovery of the light emission occurs at temperatures above 600°C. The vacancy-type defects detected by positrons might be part of the nonradiative recombination centers. The Hall measurement indicates an n-type conductivity for the P+-implanted ZnO layer, suggesting that phosphorus is an amphoteric dopant.
Stress effect on magnetoimpedance in amorphous wires at gigahertz frequencies and application to stress-tunable microwave composite materials
Authors: Panina L. V. , Sandacci S. I. , Makhnovskiy D. P.
Published: December 2004

The effect of tensile stress on magnetoimpedance (MI) in CoMnSiB amorphous wires at microwave frequencies (0.5–3GHz) is investigated both experimentally and theoretically. In the presence of the dc bias magnetic field of the order of the anisotropy field, the impedance shows very large and sensitive change when the wire is subjected to a tensile stress: 100% and 60% per 180MPa for frequencies 500MHz and 2.5GHz, respectively. It is demonstrated that this behavior owes mainly to the directional change in the equilibrium magnetization caused by the applied stress and field, which agrees well with the theoretical results for the surface impedance. This stress effect on MI is proposed to be used for creating microwave stress-tunable composite materials containing short magnetic wires. The analysis of the dielectric response from such materials shows that depending on the stress level in the material, the dispersion of the effective permittivity can be of a resonant or relaxation type with a considerable change in its values (up to 100% at 600MPa). This media can be used for structural stress monitoring by microwave contrast imaging.
Detection of nanometer-sized strain fields in (GaIn)(NAs) alloys by specific dark field transmission electron microscopic imaging
Authors: Volz Kerstin , Torunski Torsten , Stolz Wolfgang
Published: December 2004

The N-induced large strain fields in metal organic vapor phase epitaxy grown (GaIn)(NAs) quantum wells are imaged using dark field imaging in a transmission electron microscope with two different reflections, from which one is sensitive to the chemical composition and the other one to the strain in the material. By comparing the images of the (GaIn)(NAs) to those of ternary (GaIn)As alloys, which have identical macroscopic compressive strain as the quaternary alloys, as well as to those of ternary Ga(NAs) with identical N content than the quaternary alloys, it can be shown that by using the presented technique, one indeed images the N-induced strain fields in the material. The density of the strain fields increases with increasing N content to a critical value above which the crystal undergoes a morphological transition. From the density of the strain fields one could speculate that they might be originated by N-III-N next-nearest neighbors or by a N-induced N-III-N ordering with a longer chain length.
Time-resolved and time-integrated photoluminescence analysis of state filling and quantum confinement of silicon quantum dots
Authors: Van Dao Lap , Wen Xiaoming , Do My Tra Thi , Hannaford Peter , Cho Eun-Chel , Cho Young H. , Huang Yidan
Published: December 2004

In this paper we report studies of the optical properties of silicon quantum dot structures. From time-resolved and time-integrated photoluminescence measurements we investigate the state-filling effect and carrier lifetime, and discuss the parabolic confinement of quantum dot structures and the large energy splitting between quantum dot levels. The photoluminescence intensities for different quantum dot levels decay with a stretched exponential function and the decay times are in the range 2–100μs depending on the observation wavelength and the dot size.
Activation and deactivation in heavily boron-doped silicon using ultra-low-energy ion implantation
Authors: Hong Won-Eui , Ro Jae-Sang
Published: December 2004

A shallow p+∕n junction was formed using an ultra-low-energy implanter. Activation annealing exhibited both solid phase epitaxy, in which the sheet resistance dropped rapidly, and reverse annealing. Deactivation phenomena were investigated for the shallow source/drain junction based on measurements of the postannealing time and temperature following the rapid thermal annealing treatments. We found that the deactivation kinetics were divided into two regions. In the first region the rate of deactivation increased exponentially with the annealing temperature of up to 850°C. In the second region it decreased as the annealing temperature exceeded 850°C. We believe that the first region is kinetically limited while the second one is thermodynamically limited. In addition, we observed “transient enhanced deactivation,” an anomalous increase in the sheet resistance during the early annealing stage where the the temperatures were higher than 800°C. The activation energy for transient enhanced deactivation was measured to be between 1.75 and 1.87eV, while that for normal deactivation was between 3.49 and 3.69eV.
Complex quantum dot arrays formed by combination of self-organized anisotropic strain engineering and step engineering on shallow patterned substrates
Authors: Mano T. , Nötzel R. , Zhou D. , Hamhuis G. J. , Eijkemans T. J. , Wolter J. H.
Published: December 2004

One-dimensional (In,Ga)As quantum dot (QD) arrays are created on planar singular, vicinal, and shallow mesa-patterned GaAs (100) substrates by self-organized anisotropic strain engineering of an (In,Ga)As∕GaAs quantum wire (QWR) superlattice template in molecular beam epitaxy. On planar singular substrates, highly uniform single QD arrays along [0−11] are formed. On shallow [0−11] and [011] stripe-patterned substrates, the generated type-A and -B steps distinctly affect the surface migration processes which are crucial for QWR template development, i.e., strain-gradient-driven In adatom migration along [011] and surface-reconstruction-induced Ga∕In adatom migration along [0−11]. In the presence of both type-A and -B steps on vicinal substrates misoriented towards [101], the direction of adatom migration is altered to rotate the QD arrays. This establishes the relationship between self-organized anisotropic strain and step engineering, which is exploited on shallow zigzag-patterned substrates for the realization of complex QD arrays and networks with well-positioned bends and branches, exhibiting high structural and optical quality.
A proposed boron-carbide-based solid-state neutron detector
Authors: Emin David , Aselage T. L.
Published: December 2004

Its large cross section for absorption of thermal neutrons has made B10 a frequent candidate for use in neutron detectors. Here a boron-carbide-based thermoelectric device for the detection of a thermal-neutron flux is proposed. The very high melting temperatures and the radiation tolerance of boron carbides make them suitable for use within hostile environments (e.g., within nuclear reactors). The large anomalous Seebeck coefficients of boron carbides are exploited in proposing a relatively sensitive detector of the local heating that follows the absorption of a neutron by a B10 nucleus in a boron carbide.
Growth modes in heteroepitaxy of InGaN on GaN
Authors: Oliver Rachel A. , Kappers Menno J. , Humphreys Colin J. , Briggs G. Andrew D.
Published: December 2004

The morphology of InGaN epilayers grown by metal-organic vapor phase epitaxy on GaN pseudosubstrates has been examined by atomic force microscopy. The composition of the epilayers has been measured using a combination of secondary ion mass spectrometry and x-ray photoelectron spectroscopy. The dependence of the growth mode on the growth conditions has been investigated. At the lowest temperatures and NH3 fluxes, a two-dimensional island nucleation growth mode is described, in which flat islands form stacks which align along underlying GaN terraces. As the growth temperature is increased a transition to a step-flow growth mode is observed. A transition from two-dimensional island nucleation to step-flow growth may also be achieved by increasing the NH3 flux, or by decreasing the trimethylindium flux. Each transition is discussed in terms of both surface kinetics and indium incorporation into the growing film. A transition from two-dimensional to three-dimensional growth may be induced by an increase in the growth rate. At high growth rates, three-dimensional nanostructures with a variety of shapes are observed suggesting that the growth is not in the Stranski-Krastanov mode. Instead, an increase in the overall reactor pressure is identified as a key factor in achieving Stranski-Krastanov growth.
Concentration dependent interdiffusion in InGaAs∕GaAs as evidenced by high resolution x-ray diffraction and photoluminescence spectroscopy
Authors: Bollet F. , Gillin W. P. , Hopkinson M. , Gwilliam R.
Published: December 2004

A high resolution x-ray diffraction (HRXRD) and photoluminescence study of a 10nm InGaAs∕GaAs quantum well structure repeatedly diffused under thermally accurate and timed annealing conditions demonstrates that the Fickian model with a constant coefficient of diffusion is inadequate and that the distribution of compositions of the diffused well cannot be fitted with error functions. A simple model, with the well retaining its square shape and homogeneity while dissolving the barriers when annealed, is successful in modelling both the HRXRD and photoluminescence data.
Polarity of anomalous Hall effect hysteresis loops in [Pt∕Co]15∕AF∕[Co∕Pt]15 (AF=FeMn, NiO) multilayers with perpendicular anisotropy
Authors: Christides C. , Speliotis Th.
Published: December 2004

The effect of the metallic antiferromagnet (AF) γ-FeMn and the AF-semiconductor NiO alloys on the polarity of anomalous Hall resistivity loops is examined in perpendicularly biased [Pt(2nm)∕Co(0.4nm)]15∕AF(3nm)∕[Co(0.4nm)∕Pt(2nm)]15 (AF=NiO, FeMn) multilayers. The Hall resistivity exhibits negative polarity for AF=NiO and positive polarity for AF=FeMn. These differences are explained by the reduced spin-diffusion-length effects and the specular reflection of electrons at FeMn and NiO interfaces, respectively. In addition, it is shown that a sandwiched AF thin layer stabilizes the exchange-bias effect via interlayer coupling between top [Co(0.4nm)∕Pt(2nm)]15 and bottom [Pt(2nm)∕Co(0.4nm)]15 structures in multilayers with strong perpendicular magnetic anisotropy.
Flexural strength of diamond: Comparison of nanocrystalline thin films, massive chemical vapor deposits, and natural single crystals
Authors: Klein Claude A.
Published: December 2004

The recently published fracture-strength data [H. Espinosa, B. Peng, B. Prorok, N. Moldovan, O. Auciello, J. Carlisle, D. Gruen, and D. Mancini, J. Appl. Phys. 94, 6076 (2003)] for ultrananocrystalline diamond (UNCD) thin films throw valuable light on the strength performance of synthetic polycrystalline diamonds. On performing a Weibull statistical analysis that takes into account the impact of the stressed area on measured stresses at fracture, we find the following. (a) The characteristic strength—the effective strength of a 1-cm2 uniformly stressed area—of microseeded UNCD membranes is σC=0.291±0.026GPa and comparable to the strength of massive chemically vapor-deposited diamonds. (b) The characteristic strength of nanoseeded UNCD membranes is σC=1.87±0.15GPa, which points to strength characteristics similar to those of single-crystal diamond.
A comparison of ionizing radiation and high field stress effects in n-channel power vertical double-diffused metal-oxide-semiconductor field-effect transistors
Authors: Park Mun-Soo , Na Inmook , Wie Chu R.
Published: December 2004

n -channel power vertical double-diffused metal-oxide-semiconductor field-effect-transistor (VDMOSFET) devices were subjected to a high electric field stress or to a x-ray radiation. The current-voltage and capacitance-voltage measurements show that the channel-side interface and the drain-side interface are affected differently in the case of high electric field stress, whereas the interfaces are nearly uniformly affected in the case of x-ray radiation. This paper also shows that for the gated diode structure of VDMOSFET, the direct-current current-voltage technique measures only the drain-side interface; the subthreshold current-voltage technique measures only the channel-side interface; and the capacitance-voltage technique measures both interfaces simultaneously and clearly distinguishes the two interfaces. The capacitance-voltage technique is suggested to be a good quantitative method to examine both interface regions by a single measurement.
Generation of uniform plasmas by crossed internal oscillating current sheets: Key concepts and experimental verification
Authors: Tsakadze E. L. , Ostrikov K. , Tsakadze Z. L. , Xu S.
Published: December 2004

The results of comprehensive experimental studies of the operation, stability, and plasma parameters of the low-frequency (0.46MHz) inductively coupled plasmas sustained by the internal oscillating rf current are reported. The rf plasma is generated by using a custom-designed configuration of the internal rf coil that comprises two perpendicular sets of eight currents in each direction. Various diagnostic tools, such as magnetic probes, optical emission spectroscopy, and an rf-compensated Langmuir probe were used to investigate the electromagnetic, optical, and global properties of the argon plasma in wide ranges of the applied rf power and gas feedstock pressure. It is found that the uniformity of the electromagnetic field inside the plasma reactor is improved as compared to the conventional sources of inductively coupled plasmas with the external flat coil configuration. A reasonable agreement between the experimental data and computed electromagnetic field topography inside the chamber is reported. The Langmuir probe measurements reveal that the spatial profiles of the electron density, the effective electron temperature, plasma potential, and electron energy distribution/probability functions feature a high degree of the radial and axial uniformity and a weak azimuthal dependence, which is consistent with the earlier theoretical predictions. As the input rf power increases, the azimuthal dependence of the global plasma parameters vanishes. The obtained results demonstrate that by introducing the internal oscillated rf currents one can noticeably improve the uniformity of electromagnetic field topography, rf power deposition, and the plasma density in the reactor.
Detailed analysis of inverse Fourier transform techniques to uniquely infer second-order nonlinearity profile of thin films
Authors: Ozcan Aydogan , Digonnet Michel J. F. , Kino Gordon S.
Published: December 2004

The mathematical details of a family of inverse Fourier transform techniques to uniquely recover the second-order optical nonlinearity profile of thin films are discussed both theoretically and numerically. These methods are all based on the Maker-fringe technique, i.e., they involve focusing a fundamental laser beam onto a nonlinear film and measuring the generated second-harmonic power as a function of the incidence angle of the fundamental beam. It is shown that each method can be treated as a special case of a general theory. An error analysis for the recovery of theoretical nonlinearity profiles is also illustrated with numerical examples.
Carrier distribution in quantum nanostructures by scanning capacitance microscopy
Authors: Giannazzo F. , Raineri V. , La Magna A. , Mirabella S. , Impellizzeri G. , Piro A. M. , Priolo F. , Napolitani E. , Liotta S. F.
Published: December 2004

Scanning capacitance microscopy (SCM) was carried out in the angle beveling configuration on B doped, very narrow quantum wells (QWs) of Si0.75Ge0.25 layers strained between Si films. The majority carrier concentration profiles were calculated from the SCM raw data measured on QWs with a minimum width of 5nm, doped with different B concentrations ranging from 2×1016to6×1018cm−3. The equilibrium carrier distribution in the heterostructures has been calculated by different simulation approaches, which will be discussed. Moreover, the effect of the biased tip-sample interaction was studied by accurate simulations of the dC∕dV vs V characteristics for different positions of the tip moving on the beveled sample surface. The agreement between the experimental and simulated SCM profiles is very good. Thus, a spatial SCM resolution of at least 5nm was demonstrated on angle beveled samples, not only in terms of signal sensitivity, but also in terms of quantitative majority carrier profiling.
Model for the voltage and temperature dependence of the soft breakdown current in ultrathin gate oxides
Authors: Avellán A. , Miranda E. , Schroeder D. , Krautschneider W.
Published: December 2004

The voltage and temperature dependence of the soft breakdown conduction mechanism in metal-oxide-semiconductor capacitors and transistors with ultrathin dielectric layers is investigated. A physical derivation of the quantum point contact model and its parameters is presented, which incorporates the smearing of the Fermi function at the electrodes as well as the effect of thermal vibrations of the constriction’s bottleneck. The model also takes into account the boundary conditions at the two ends of the breakdown path by considering the semiconductor band bending occurring in the nondamaged surrounding device area. Good agreement between model and experimental curves is found. Because of its analytical nature, the proposed model can be implemented in circuit simulators.
Pulse propagation in adiabatically coupled photonic crystal coupled cavity waveguides
Authors: Sanchis P. , García J. , Martínez A. , Martí J.
Published: December 2004

A rigorous analysis of pulse propagation in planar photonic crystal (PhC) coupled cavity waveguides (CCWs) of finite length is reported. Conventional PhC waveguides, formed by a single line defect, are used at both interfaces of the CCW. An adiabatic taper based on progressively varying the radii of the spacing defects between cavities is used to achieve flat transmission bands with respect to the butt coupling case. The influence on the main parameters of the propagated pulse such as group delay, full width at half maximum and pulse attenuation are investigated for both the adiabatic and butt coupling cases. Furthermore, the Fabry-Perot formula has been used for modeling the pulse propagation along the CCW of finite length, which permits to analyze a large range of parameters avoiding the huge computation time requirements of finite-difference time-domain simulations.
Confinement effect of laser ablation plume in liquids probed by self-absorption of C2 Swan band emission
Authors: Sakka Tetsuo , Saito Kotaro , Ogata Yukio H.
Published: December 2004

The (0,0) Swan band of the C2 molecules in a laser ablation plume produced on the surface of graphite target submerged in water was used as a probe to estimate the density of C2 molecules in the plume. Observed emission spectra were reproduced excellently by introducing a self-absorption parameter to the theoretical spectral profile expected by a rotational population distribution at a certain temperature. The optical density of the ablation plume as a function of time was determined as a best-fit parameter by the quantitative fitting of the whole spectral profile. The results show high optical densities for the laser ablation plume in water compared with that in air. It is related to the plume confinement or the expansion, which are the important phenomena influencing the characteristics of laser ablation plumes in liquids.
Observation of dislocations in diffused 4H–SiC p-i-n diodes by electron-beam induced current
Authors: Maximenko S. , Soloviev S. , Cherednichenko D. , Sudarshan T.
Published: December 2004

The electron-beam induced current (EBIC) method was employed to investigate the electrical activity of dislocations in silicon-carbide-diffused p-n diodes. It was observed that EBIC contrast depends on the type of defect (superscrew, screw, and edge dislocation). This dependence was attributed to spatial inhomogeneities in the electrical properties of the material around the dislocations due to different impurity-dislocation interactions during high-temperature (∼1900°C) diffusion. Chemical etching of the sample was used to define the nature of the defects observed by EBIC imaging. It was found that electrical breakdown of the diodes occurs at the location of superscrew dislocations.
A helix unwinding process in ferroelectric liquid crystals with fixed boundaries
Authors: Uto Sadahito
Published: December 2004

An appropriate Euler equation for the helix unwinding process in ferroelectric liquid crystals was solved under the condition of fixed boundaries. In order to solve the equation, a Taylor-series expansion and Newton’s method, which is a numerical method for finding the root of an equation, were used. The unwinding process depends on the boundary condition, and the threshold to be unwounded disappears in the case of the fixed boundary.
Kinetics of image formation in the equipotential semiconductor-thermoplastic system
Authors: Anikin Valerii I. , Zhurminsky Igor L.
Published: December 2004

The redistribution of corona current in regions with a low potential has been experimentally shown. This led to the equipotentiality of the semiconductor-thermoplastic system at charging in the field of corona discharge. The self-coordinated model of kinetics formation of electrostatic contrast in a corona discharge is proposed. The model takes into consideration a nonlinearity of current–voltage characteristics of the semiconductor, and thermoplastic and deformation of the thermoplastic layer. The moment of deformation appearance is set at random from experimental data.
Spin microscope based on optically detected magnetic resonance
Authors: Chernobrod Boris M. , Berman Gennady P.
Published: December 2004

We propose a scanning magnetic microscope which has a photoluminescence nanoprobe implanted in the tip of an atomic force microscope, (AFM) scanning tunneling microscope (STM), or near-field scanning optical microscope, and exhibits optically detected magnetic resonance. The proposed spin microscope has nanoscale lateral resolution and the single spin sensitivity for AFM and STM.
Depolarization in percussion drilling of Solenhofen limestone
Authors: Frid V. , Goldbaum J. , Rabinovitch A. , Bahat D.
Published: December 2004

In a series of measurements of electromagnetic radiation (EMR) from percussion-drilled Solenhofen limestone, nonoscillating signals (associated with electric depolarization) preceded by short oscillating signals (associated with crack propagation) were obtained. Depolarization is therefore assumed to be caused by stress relaxation around a propagating crack. Using the parameters of EMR signals, the polarization generating displacements of the Ca2+ ions in the calcite lattice caused by drilling were calculated.
Optical analysis of nanocrystalline thin layers deposited by the ion layer gas reaction method
Authors: Muffler H.-J. , Müller F. , Lux-Steiner M. C. , Fischer Ch.-H.
Published: December 2004

Nanocrystalline ZnS thin layers are prepared by ion layer gas reaction, a low cost deposition method for compound semiconductor thin films. They are investigated by optical spectroscopy, x-ray fluorescence and energy dispersive x-ray analysis. It is seen that the absorption edges are shifting towards lower photon energies with increasing layer thickness. Also, the amount of unconverted precursor salt is decreased. A simulation procedure for fitting the determined absorption edges of these layers is introduced. This leads to particle size distribution functions showing an increasing broadening with increasing layer thickness. Moreover, the distribution maximum is moving to larger crystallite radii with larger film thickness. Both results indicate a growth in crystallite size during the layer deposition. Additionally, the increase in strength of the phonon-photon-coupling confirms the conclusions of transmission electron micrographs. Later investigations show that the noncrystalline precursor matrix which surrounds the ZnS crystallites is vanishing with increasing layer thickness. Therefore, the nanocrystallites are more frequently in contact with each other. This again favors the propagation of phonons.
Determination of growth and maintenance coefficients by calorespirometry
Authors: Matheson Sannali , Ellingson Derek J. , McCarlie V. Wallace , Smith Bruce N. , Criddle Richard S. , Rodier Laurence , Hansen Lee D.
Published: December 2004

This study describes a calorespirometric method for determining the coefficients of the correlation of specific respiration and growth rates. To validate the calorespirometric method, coefficients obtained from calorespirometric data are compared with coefficients obtained from mass and elongation growth rates measured at three temperatures on oat (Avena sativa L.) shoots. Calorespirometric measurements were also made on leaf tissue of varying age from Verbascum thapsus L., Convolvulus arvensis L., and Helianthus tuberosus Nutt. Measurements on A. sativa, C. arvensis and H. tuberosus at several temperatures show maintenance coefficients generally increase with temperature, but, in disagreement with accepted theory, growth coefficients for C. arvensis and A. sativa vary with temperature. A comparison of rates expressed as intensive and extensive quantities showed that the decline in specific respiration and growth rates with age is caused by dilution-by-growth, not down-regulation of respiration rate by reduced demand. The ratio of heat rate to CO2 rate increases with leaf age, and, for fully mature leaves, exceeds the maximum possible value for carbohydrates. This shows that the catabolic substrate may vary with leaf age in immature leaves and cannot be assumed to consist only of carbohydrates in mature leaves. Dilution-by-growth, substrate variation, and inseparability of the variables in the growth-maintenance model all complicate physiological interpretation of the slope and intercept of plots of specific respiration rates v. specific growth rates.
Effects of nitrogen supply on xylem cytokinin delivery, transpiration and leaf expansion of pea genotypes differing in xylem-cytokinin concentration
Authors: Dodd Ian C. , Ngo Chuong , Turnbull Colin G. N. , Beveridge Christine A.
Published: December 2004

The rms2 and rms4 pea (Pisum sativum L.) branching mutants have higher and lower xylem-cytokinin concentration, respectively, relative to wild type (WT) plants. These genotypes were grown at two levels of nitrogen (N) supply for 18–20 d to determine whether or not xylem-cytokinin concentration (X-CK) or delivery altered the transpiration and leaf growth responses to N deprivation. Xylem sap was collected by pressurising de-topped root systems. As sap-flow rate increased, X-CK declined in WT and rms2, but did not change in rms4. When grown at 5.0 mm N, X-CKs of rms2 and rms4 were 36% higher and 6-fold lower, respectively, than WT at sap-flow rates equivalent to whole-plant transpiration. Photoperiod cytokinin (CK) delivery rates (the product of transpiration and X-CK) decreased more than 6-fold in rms4. Growth of plants at 0.5 mm N had negligible (< 10%) effects on transpiration rates expressed on a leaf area basis in WT and rms4, but decreased transpiration rates of rms2. The low-N treatment decreased leaf expansion by 20–25% and expanding leaflet N concentration by 15%. These changes were similar in all genotypes. At sap-flow rates equivalent to whole-plant transpiration, the low N treatment decreased X-CK in rms2 but had no discernible effect in WT and rms4. Since the low N treatment decreased transpiration of all genotypes, photoperiod CK delivery rates also decreased in all genotypes. The similar leaf growth response of all genotypes to N deprivation despite differences in both absolute and relative X-CKs and deliveries suggests that shoot N status is more important in regulating leaf expansion than xylem-supplied cytokinins. The decreased X-CK and transpiration rate of rms2 following N deprivation suggests that changes in xylem-supplied CKs may modify water use.
Structures of thymidine kinase 1 of human and mycoplasmic origin
Authors: Welin Martin , Kosinska Urszula , Mikkelsen Nils-Egil , Carnrot Cecilia , Zhu Chunying , Wang Liya , Eriksson Staffan , Munch-Petersen Birgitte , Eklund Hans
Published: December 2004

Cytosolic thymidine kinase 1, TK1, is a well known cell-cycle-regulated enzyme of importance in nucleotide metabolism as well as an activator of antiviral and anticancer drugs such as 3′-azido-3′-deoxythymidine (AZT). We have now determined the structures of the TK1 family, the human andUreaplasma urealyticumenzymes, in complex with the feedback inhibitor dTTP. The TK1s have a tetrameric structure in which each subunit contains an α/β-domain that is similar to ATPase domains of members of the RecA structural family and a domain containing a structural zinc. The zinc ion connects β-structures at the root of a β-ribbon that forms a stem that widens to a lasso-type loop. The thymidine of dTTP is hydrogen-bonded to main-chain atoms predominantly coming from the lasso loop. This binding is in contrast to other deoxyribonucleoside kinases where specific interactions occur with side chains. The TK1 structure differs fundamentally from the structures of the other deoxyribonucleoside kinases, indicating a different evolutionary origin.
Impaired up-regulation of CD25 on CD4+T cells in IFN-γ knockout mice is associated with progression of myocarditis to heart failure
Authors: Afanasyeva Marina , Georgakopoulos Dimitrios , Belardi Diego F. , Bedja Djahida , Fairweather DeLisa , Wang Yan , Kaya Ziya , Gabrielson Kathleen L. , Rodriguez E. Rene , Caturegli Patrizio , Kass David A. , Rose Noel R.
Published: December 2004

Inflammation has been recognized increasingly as a critical pathologic component of a number of heart diseases. A mouse model of autoimmune myocarditis was developed to study the role of immune mediators in the development of cardiac dysfunction. We have found previously that IFN-γ deficiency promotes inflammation in murine myocarditis. It has been unclear, however, how IFN-γ deficiency in myocarditis affects cardiac function and what underlying immune mechanisms are responsible for these effects. In this work, we show that IFN-γ knockout (KO) mice have more pronounced systolic and diastolic dysfunction and greater frequency of progression to dilated cardiomyopathy and heart failure compared with WT mice. Cardiac dysfunction in the KO mice is associated with the expansion of activated (CD44high) CD3+T cells due to reduced apoptosis of CD4+, but not CD8+, T cells. CD4+T cells in the KO mice show impaired up-regulation of CD25 upon activation, resulting in the expansion of CD4+CD44+CD25-T cells and their infiltration into the heart. CD4+CD25-T cells are less apoptosis-prone compared with the CD25+population, and their infiltration into the heart is associated with greater severity of myocarditis. We conclude that IFN-γ deficiency in autoimmune myocarditis is associated with preferential expansion of CD4+CD44+CD25-T cells resulting in increased cardiac inflammation. An exaggerated inflammatory response in IFN-γ KO mice causes cardiac dysfunction, leading to dilated cardiomyopathy and heart failure.
Investigation of Autofrettaged Thick-walled Cylinders with Axial Holes Machined
Authors: Venter A.M. , de Swardt R.R.
Published: December 2004

The redistribution of residual strains in autofrettaged thick-walled steel tubes resulting from the introduction of holes machined at a radial distance, 50% of the plastic boundary has been investigated with neutron diffraction and finite-elements. In the high compressive region, the redistribution is observed to be localized close to the hole. On the outer section of the hole, the redistribution is less dramatic, but extends up to the plastic boundary. A finite-element simulation of the redistribution of the residual stresses based on an equivalent thermal field approach, based on the measured residual strain values in the solid tube, is also presented.
Phase Stresses in Al/SiCp Metal Matrix Composite Determined by Modelling and Neutron Diffraction
Authors: Baczmański A. , Levy-Tubiana R. , Fitzpatrick M.E. , Lodini A.
Published: December 2004

Neutron diffraction was used to measure the lattice strains in Al/SiCp metal matrix composite under an external load applied while the sample was in situ in the neutron beam. The evolution of the internal stresses and of the critical resolved shear stress during bending were predicted by elastoplastic models. Calculations based on these models were verified by comparison with the results of the diffraction experiment.