bluuebunny/crossref_metadata_2025 huggingface dataset:
‘I never realised that doctors were into feelings too’: changing student perceptions through interprofessional education
Authors: Cooke Samantha , Chew‐Graham Carolyn , Boggis Caroline , Wakefield Ann
Published: August 2003

The National Health Service (NHS) has called for the ‘eradication of demarcation lines between healthcare professionals’ in the UK. Educational institutions are therefore striving to achieve this outcome through integrative interprofessional initiatives. This article discusses the effects of an integrative training course for medical and nursing students in ‘breaking bad news’ to patients. Triangulation of the qualitative methods enabled the researchers to gather student perspectives on this experience. Data analysis revealed that the 34 student volunteers challenged misconceptions of professional roles through this interprofessional programme. Questionnaires demonstrated that although most students had enrolled on the course to develop communication skills, the interprofessional aspect of the course was one of the main educational benefits. While outcomes were largely positive, some students were anxious about a holistic interprofessional curriculum. Undergraduate healthcare students may need to collaborate earlier, and for longer time‐periods, to enhance professional understanding and relationships.
Developmental differences in the immortalization of lung fibroblasts by telomerase
Authors: Forsyth Nicholas R. , Evans A. Patrice , Shay Jerry W. , Wright Woodring E.
Published: August 2003

The role of ambient (21%) and physiological oxygen (2–5%) in the immortalization of fetal vs. adult human lung fibroblasts was examined. Growth in low oxygen and antioxidants extended the lifespan of both fetal and adult strains. As the ectopic expression of telomerase could immortalize adult lung fibroblasts cultured in ambient oxygen, the lifespan‐shortening effects of 21% oxygen must have been largely limited to telomeres. By contrast, fetal lung fibroblasts could not be immortalized in ambient oxygen in spite of telomere elongation by telomerase, suggesting more widespread oxidative damage. The long‐term culture requirements for the immortalization of WI‐38 fetal lung fibroblasts included supplementation with N‐(tert) butyl hydroxylamine, dexamethasone, zinc and vitamin B12, in addition to growth in physiological oxygen. The mechanisms regulating telomere shortening remain controversial. The present results suggest that both end‐replication and oxidative damage events contribute to telomere shortening in lung fibroblasts in vitro. These observations emphasize the need for better analytical techniques to distinguish whether the correlation of short telomeres with disease and mortality in humans reflects the consequences of increased proliferation, telomere shortening as a result of oxidative damage or some combination of these processes.
Optical Generation and Detection of Ultrasound
Authors: Sorazu B. , Thursby G. , Culshaw B. , Dong F. , Pierce S. G. , Yang Y. , Betz D.
Published: August 2003

Abstract: This is a review of the optical generation and detection of ultrasound on work carried out in different optical detection techniques at the Strathclyde University. We start by pointing out some limitations of conventional ultrasonic transducers and show how the use of optical‐based transducers can overcome them. After explaining how laser generation of ultrasound works, we will describe and compare the advantages and disadvantages of three optical detection techniques. Finally, we describe applications in which optical ultrasound techniques appear to have a promising future.
Pipe Weld Investigation using Shearography
Authors: Groves R. M. , James S. W. , Tatam R. P.
Published: August 2003

Abstract: In this paper the full‐field optical technique of shearography is used to fully characterise the surface strain of the region around a welded joint in a pipe. Shearography is an interferometric optical technique sensitive to displacement gradient, a parameter that is closely related to the surface strain. The surface of the material at a welded joint is uneven, but measurements may still be performed using full‐field non‐contact optical methods. In this paper the authors present a multi‐component shearography system, which measures the in‐ and out‐of‐plane displacement gradient components by determining three non‐orthogonal displacement gradient components and performing a coordinate transformation. To compensate for non‐planar object surfaces the coordinate transformation procedure incorporates a correction for the object shape, measured using the same apparatus. The instrument was used to determine the six components of displacement gradient, thereby fully characterising the surface strain. In comparison with resistance strain gauges, an accuracy of ±11 μɛ was achieved over a limited measurement range.
Family Caregivers' Experiences with Community Services: A Qualitative Analysis
Authors: Winslow Betty Wehtje
Published: August 2003

Abstract  Researchers of family caregiving have presented mixed results in evaluating the effectiveness of community services in reducing family caregiver stress and have indicated that many caregivers use limited services or access services late in their caregiving experience. The purpose of this study was to describe the experience of the use of community services, including benefits and barriers, by family caregivers of relatives with Alzheimer's disease or a related disorder. Community services included assistance with caregiving or related tasks and educational or emotional support that was provided by health professionals or community service providers. In this qualitative descriptive study, a convenience sample of 21 family caregivers was interviewed. Open‐ended questions were used to explore the caregivers' experiences with community services. Transcribed data were analyzed using qualitative content‐analysis techniques. Results indicated that family caregivers received benefits of renewal, sense of community, and new knowledge and believed that their patient benefited from the services. Barriers to service use included care receiver resistance, reluctance of the caregiver, hassles for the caregiver, concerns over quality, and concerns over finances. These findings provide direction for community nurses and other health professionals in targeting interventions that will meet the expressed needs of caregivers.
Administrative Characteristics of Comprehensive Prenatal Case Management Programs
Authors: Issel L. Michele , Anderson Ruth A. , Kane Debra J.
Published: August 2003

Abstract  The purpose of this study was to examine comprehensive prenatal case management programs in terms of organizational, program, and process characteristics. Data from 66 program surveys of government agencies were used. Organizational capacity was measured as extent of organizational change and extent of interagency agreements. Program data included age and size of the program, reasons for having case management, and funding diversity. Process data were eight types of interventions.

The most highly rated reason for having case management was to improve client outcomes. The greatest organizational change was in the area of the organizational structure, followed by financial status and types of services provided. Contracts with other agencies were rare. Agencies with more interagency contacts reported higher levels of change in the case management department and turnover among mid‐level managers. Older programs had fewer employees. Approximately 49% of client contacts were not billed to Medicaid. Larger programs had significantly less time allocated to emotional support and coaching.

Data on organizational characteristics, program, and process variables provide insights into comprehensive case management. Relationships among these variables underscore the importance of studying client outcomes within the context of program and organizational idiosyncrasies. Future studies of comprehensive prenatal case management should focus on cross‐level questions.
Diet and Exercise in Low‐Income Culturally Diverse Middle School Students
Authors: Marilyn Frenn , Shelly Malin
Published: August 2003

Abstract  It is important to understand constructs essential to low‐fat‐diet and physical‐activity behaviors of low‐income culturally diverse middle‐school‐age students, because ethnicity and socioeconomic status influence body weight status, and these groups are most at risk for obesity later in life. In this descriptive study, constructs important in low‐fat diet and physical activity in low‐ to middle‐income, culturally diverse middle school students were examined. Revised for cultural/developmental appropriateness and reading level, instruments incorporating constructs from the Health Promotion and Transtheoretical Models were tested with 221 youth. Results demonstrated that percentage of fat in diet, total number of strategies used for a low‐fat diet, access to low‐fat food, and total number of exercise processes varied significantly (p < 0.05) across stages of change for low‐fat diet. We concluded that interventions should foster access to low‐fat foods and processes for diet and activity change. Despite significantly lower income and higher grade level (both of which are risks for poor health behaviors), students in the private school demonstrated significantly lower fat in diet, higher perception of benefits, and better access to low‐fat food. These findings warrant additional study.
Displacing the “Rule Book” in Caring for Teen Mothers
Authors: SmithBattle Lee
Published: August 2003

Abstract  Teen mothers most often appear in professional discourse as voiceless subjects who are to be “brought in line” with scientific norms. This paper challenges this scientific “rule book” and offers a corrective that recovers the practical and engaged reasoning of teen mothers and the public health nurses (PHNs) who serve them. This corrective approach validates and supports the “voices” of teen mothers and the clinical acumen of PHNs.
Using Roy's Adaptation Model When Caring for a Group of Young Women Contemplating Quitting Smoking
Authors: Villareal Ethylene
Published: August 2003

Abstract  This article provides an overview of the use of Roy's adaptation model when caring for a group of young women who were in the precontemplation phase of smoking cessation. The model served as a guide to assess each member's level of adaptation in each of the four modes to identify actual or potential adaptation problems and then examining the stimuli that influence those problems. Nursing interventions focused on approaches to the management of stimuli to promote adaptation for the group by helping the members move to the phase of thinking of quitting smoking.
Validity and Community‐Health‐Nursing Sensitivity of Six Outcomes for Community Health Nursing with Older Clients
Authors: Head Barbara J. , Maas Meridean , Marion Johnson
Published: August 2003

Abstract A survey research design was used to assess the importance, sensitivity to nursing interventions, and content validity of six client outcomes from the Nursing Outcomes Classification (NOC)). Outcomes relevant for elderly community residents and caregivers were included in a questionnaire mailed to American Nurses Credentialing Center–certified expert community health nurses. Two hundred thirty‐nine experts rated specific indicators of the six outcomes for their importance in determining the outcomes and the contribution of nursing to their achievement. Outcomes also were rated for their importance for community health nursing clients and responsiveness to community health nursing intervention.

Results strongly support the content validity and nursing sensitivity of outcomes and specific indicators. Experts judged all six outcomes to be important and 90% of indicators as important in determining the outcome. All outcomes and 78% of indicators were judged to be responsive to community health nursing intervention.

Recommendations include the testing of NOC outcomes in community health nursing clinical practice and inclusion in community health nursing curricula. Areas for further research include development and validation of community‐level outcomes, validation of outcomes with rural and home health nursing experts, and exploration of the community health nursing‐sensitivity of one study outcome.
Assessing Risk of Falling in Older Adults
Authors: Huang Hui‐Chi , Gau Meei‐Ling , Lin Wen‐Chuan , George Kernohan
Published: August 2003

Abstract  Falls by older people present serious problems in every society. The purpose of this study was to investigate the role of a checklist in estimation and reduction of the risk for falls for older adults in Taiwan. Following literature review, a purposive sample was used in a cross‐sectional design to assess risk factors using a checklist. Older adults (N = 103) were recruited from three sheltered housing projects (elderly apartments in Taipei County); 52 individuals had fallen within the past year. A set of significant risk factors was identified, including physiological, psychological, environmental, and social dimensions. Members of the fall group had shorter Functional Reach and took more time to complete the Get‐up and Go test than the control group. Some illnesses and drugs were associated with an increased risk of fall.
A Comparison Pilot Study of Public Health Field Nursing Home Visitation Program Interventions for Pregnant Hispanic Adolescents
Authors: Nguyen Jody Duong , Carson Michael L. , Parris Kathleen M. , Place Patricia
Published: August 2003

Objective:  Improve pregnancy outcomes in first‐time Hispanic adolescent mothers and their infants.

Setting:  Urban communities in Orange County, California.

Design and Methods:  A comparison of the Nurse‐Family Partnership pilot study home visitation program with traditional Public Health Field Nursing (PHFN) home visitation.

Participants:  Two hundred twenty‐five Hispanic adolescent mothers and their infants.

Interventions:  Participants in the control group received the traditional PHFN services; the intervention group received interventions from advanced trained public health nurses The control group received a minimum of three home visits: one initial client assessment and family profile, one antepartum visit, and one postpartum visit, including newborn assessment. Participants in the intervention group received weekly home visits for the first 4 weeks, followed by visits every other week until delivery, weekly visits for the next 6 weeks, visits every other week until the child was 20 months, and monthly visits until the child was 24 months of age.

Results:  Preliminary results indicate that home visitation by public health nurses (PHNs) positively affected the health of adolescents mothers and their infants. The incidence of premature births to adolescent mothers in the intervention group was lower than that found in the California population of adolescent mothers.

Conclusion:  Preliminary results from this program showed that PHN home visitation (control and intervention groups) positively affects the birth outcomes of adolescent mothers and their infants.
Does Serotonin Play a Role in Epilepsy?
Authors: Theodore William H.
Published: August 2003

Studies in experimental models have suggested a potential role for serotonergic transmission in epilepsy, and interest in this research has been increased by the development of positron emission tomography (PET) ligands that can be used to study 5-hydroxytryptamine (5-HT) receptors and transporters. The serotonergic system is very complex. At least 13 distinct G protein–coupled 5-HT receptors and one ligand-gated ion channel receptor (5-HT3) are divided into seven distinct classes (5-HT1 to 5-HT7) ( 1 ). The receptors vary widely in their distribution and effects, innervating vascular structures and gut smooth muscle as well as neuronal tissue. Several receptor subtypes may be relevant to epilepsy.
The eigenvalue equation on the Eguchi–Hanson space
Authors: Malmendier Andreas
Published: August 2003

We consider the eigenvalue equation for the Laplace–Beltrami operator acting on scalar functions on the noncompact Eguchi–Hanson space. The corresponding differential equation is reducible to a confluent Heun equation with Ince symbol [0,2,12]. We construct approximations for the eigenfunctions and their asymptotic scattering phases with the help of the Liouville–Green approximation (WKB). Furthermore, for specific discrete eigenvalues obtained by a continued T-fraction we construct the solution by the Frobenius method and determine its scattering phase by a monodromy computation.
Two choices of the gauge transformation for the AKNS hierarchy through the constrained KP hierarchy
Authors: He Jingsong , Li Yishen , Cheng Yi
Published: August 2003

On the basis of the equivalence between the AKNS hierarchy and the cKP hierarchy with the constraint k=1, we point out that there exist two choices to keep the form of the Lax operator when we perform the gauge transformation for the AKNS hierarchy, which results in two classes of functions to trigger the gauge transformation. For the second choice, two theorems for two types of gauge transformation are established. Several new and more general forms of tau-functions for the AKNS hierarchy are obtained by means of gauge transformations of both types. The union of the two choices leads to new forms of τ-functions. We generate the AKNS hierarchy from the “free” Lax operator L(0)=∂ via a chain of gauge transformations.
Anisotropic electronic structure of in-plane aligned a-axis YBa2Cu3O7−δ thin films
Authors: Luo C. W. , Chen M. H. , Liu S. J. , Wu K. H. , Juang J. Y. , Uen T. M. , Lin J.-Y. , Chen J.-M. , Gou Y. S.
Published: August 2003

Polarization-dependent x-ray absorption near-edge spectra (XANES) of the O 1s has been measured on a highly in-plane aligned a-axis YBa2Cu3O7−δ (YBCO) thin film. The in-plane XANES, with the electric field E of the linearly polarized synchrotron light being parallel to the b or c axis of YBCO films (E//b or E//c) were obtained in a normal-incidence alignment. The XANES for E//a was then calculated from the data obtained by varying the angle. The results lend strong support to those obtained by using detwinned YBCO single crystals in all crystalline orientations, including the extrapolated c-axis spectra.
Resonant electron firehose instability: Particle-in-cell simulations
Authors: Gary S. Peter , Nishimura Kazumi
Published: August 2003

Consider a collisionless, homogeneous plasma in which the electron velocity distribution is a bi-Maxwellian with T⊥<T∥, where the subscripts refer to directions relative to the background magnetic field B0. If this anisotropy is sufficiently large and the electron β∥ is sufficiently greater than one, linear dispersion theory predicts that a cyclotron resonant electron firehose instability is excited at propagation oblique to B0 with growth rates less than the electron cyclotron frequency |Ωe| and zero real frequency. This theory at constant maximum growth rate yields threshold conditions for this growing mode of the form 1−T⊥e/T∥e=Se′/β∥eαe′, where the two fitting parameters satisfy 1≲Se′≲2 and αe′≲1.0 over 2.0⩽β∥e⩽25.0. The first particle-in-cell computer simulations of the resonant electron firehose instability are described here. These simulations show that enhanced magnetic field fluctuations reach a maximum value of |δB|2/B02 which increases with β∥e. These enhanced fields scatter the electrons, reducing their anisotropy approximately to a linear theory threshold condition and yielding a dimensionless scattering rate which increases as β∥e increases. These results are consistent with the general principle that, for a given plasma species, scattering by enhanced fluctuations from anisotropy-driven electromagnetic instabilities acts to make the velocity distribution more nearly isotropic as the β∥ of that species increases.
On integrable Hamiltonians for higher spin XXZ chain
Authors: Bytsko Andrei G.
Published: August 2003

Integrable Hamiltonians for higher spin periodic XXZ chains are constructed in terms of the spin generators; explicit examples for spins up to 32 are given. Relations between Hamiltonians for some Uq(sl2)-symmetric and U(1)-symmetric universal r-matrices are studied; their properties are investigated. A certain modification of the higher spin periodic chain Hamiltonian is shown to be an integrable Uq(sl2)-symmetric Hamiltonian for an open chain.
Continuous wavelet transform on a special homogeneous space
Authors: Fashandi M. , Kamyabi Gol R. A. , Niknam A. , Pourabdollah M. A.
Published: August 2003

We consider a semidirect product of two locally compact groups S and T, with S Abelian, denoted by SσT. An action of SσT on S is introduced to make S a homogeneous space of SσT. Then we define a unitary representation from SσT into the unitary group of L2(S) which is our main tool for defining the continuous wavelet transform on L2(S). Also the main properties of the transform are discussed. We prove the Plancherel and inversion formulas and reproducing kernel’s formula for this transform. This is finally specialized to the case of the continuous wavelet transform on L2(Rd).
Nonadiabatic processes involving three electronic states. I. Branch cuts and linked pairs of conical intersections
Authors: Han Seungsuk , Yarkony David R.
Published: August 2003

The location and consequences of linked seams of conical intersections, conical intersections of states (J,K) and (K,L), are considered. We show that this class of conical intersections gives rise to the induced geometric phase effect, as a result of which the derivative couplings may be double-valued. This double-valuedness has important consequences, some limiting others not. We show, using an analysis based on branch cuts, that if the derivative coupling is double-valued, its circulation, its line integral about a closed loop, is not a unique function of the path, being starting point dependent. On the other hand the change from single-valued to double-valued derivative couplings can be used to search for linked intersections.
Global symmetries of time-dependent Schrödinger equations
Authors: Okubo Susumu
Published: August 2003

Some symmetries of time-dependent Schrödinger equations for inverse quadratic, linear, and quadratic potentials have been systematically examined by using a method suitable to the problem. Especially, the symmetry group for the case of the linear potential turns out to be a semidirect product SL(2,R) ⓈT2(R) of the SL(2,R) with a two-dimensional real translation group T2(R). Here, the time variable t transforms as t→t′=(ct+d)/(at+b) for real constants a, b, c, and d satisfying bc−ad=1 with an accompanying transformation for the space coordinate x.
Classical transport of charged particles in a magnetic field
Authors: Corngold Noel
Published: August 2003

We examine the traditional transport equation for classical, charged particles diffusing in a cold, absorbing medium subject to a uniform magnetic field and in which scattering is isotropic. Steady-state solutions in plane geometry are examined in some detail; we make no expansion about an isotropic angular distribution. Restricting the motion to two dimensions captures most of the interesting features; there is some discussion of the three-dimensional case.
Determination of quantum symmetries for higher ADE systems from the modular T matrix
Authors: Coquereaux R. , Schieber G.
Published: August 2003

We show that the Ocneanu algebra of quantum symmetries, for an ADE diagram (or for higher Coxeter–Dynkin systems, like the Di Francesco–Zuber system) can be, in most cases, deduced from the structure of the modular T matrix in the A series. We recover in this way the (known) quantum symmetries of su(2) diagrams and illustrate our method by studying those associated with the three genuine exceptional diagrams of type su(3), namely, E5, E9, and E21. This also provides the shortest way to the determination of twisted partition functions in boundary conformal field theory with defect lines.
A direct calculation of the free energy from the Bethe ansatz equation for the Heisenberg model
Authors: Kato Go , Wadati Miki
Published: August 2003

Thermodynamics of the XXX Heisenberg model is studied. The trace of the Boltzmann weight with respect to the Hilbert space is taken in the thermodynamic limit with the number of up-spins being fixed. The expression of the trace gives an explanation why the correct thermodynamic quantities are derived from the string hypothesis. A combination of this with the previous result leads to a conclusion that the free energy can be calculated only from the Bethe ansatz equation. The method is more direct than other known methods which were used to derive the free energy.
Inverse problem of scanning force microscope force measurements
Authors: Todd Brian A. , Eppell Steven J.
Published: August 2003

The Hooke’s Law model, traditionally used to determine forces from the deflection of scanning force microscope (SFM) cantilevers, restricts the bandwidth to well below the cantilever resonant frequency. The limitation imposed on measurements by Hooke’s Law can be overcome by modeling the multimodal and dynamical response of the cantilever (i.e., accounting for the viscous and inertial response) using a beam model. However, when calculating the forces on the cantilever from deflection measurements, this “inverse problem” is ill posed (i.e., it amplifies noise in the measurement, so that simple inversion produces useless solutions). Regularization techniques provide mathematical solutions to this ill-posed problem but introduce nontrivial mechanisms by which inputs to the system are propagated to outputs. In this article, we investigate the propagation of errors in the inverse problem of SFM force measurements. We first develop a noise model and validate it using experimental measurements. This is then applied to simulate a force–distance experiment with a relevant amount of noise. This provides a cantilever deflection signal based on known forces with which to evaluate the accuracy and precision of a force reconstruction algorithm. We show that Tikhonov regularized solutions obtained with an L-curve analysis reconstruct forces with an accuracy of better than 90% on average but with poor precision, yielding a signal-to-noise ratio of ∼2 for a 0.02 N/m cantilever. Ensemble averaging is recommended to improve the precision. This allows both accurate and precise force curves to be reconstructed with a high bandwidth.
Spontaneous localization of electrons in two-dimensional lattices within the adiabatic approximation
Authors: Brizhik L. S. , Eremko A. A. , Piette B. M. A. G. , Zakrzewski W. J.
Published: August 2003

The conditions for spontaneous localization of electrons in an isotropic two-dimensional electron–phonon lattice are investigated within the zero adiabatic approximation. It is shown that the localization occurs when the electron–phonon coupling takes values within certain finite interval of values gc,1<g<gc,2. At ggc,2 the strong localization on one lattice site takes place. In this paper we introduce an ansatz which, under a variational principle, allows us to describe all three regimes at the same time. The radius of the electron localization, as a function of electron–phonon coupling constant, is evaluated analytically and shown to fit well the numerical data.
Nonlinear transforms of momenta and Planck scale limit
Authors: Chakrabarti A.
Published: August 2003

Starting with the generators of the Poincaré group for arbitrary mass (m) and spin (s), a nonunitary transformation is implemented to obtain momenta with an absolute Planck scale limit. In the rest frame (for m>0) the transformed energy coincides with the standard one, both being m. As the latter tends to infinity under Lorentz transformations the former tends to a finite upper limit m coth(lm)=l−1+O(l), where l is the Planck length and the mass-dependent nonleading terms vanish exactly for zero rest mass. The invariant m2 is conserved for the transformed momenta. The speed of light continues to be the absolute scale for velocities. We study various aspects of the kinematics in which two absolute scales have been introduced in this specific fashion. The precession of polarization and transformed position operators are among them. A deformation of the Poincaré algebra to the SO(4,1) de Sitter one permits the implementation of our transformation in the latter case. A supersymmetric extension of the Poincaré algebra is also studied in this context.
Berezin transform on the quantum unit ball
Authors: Shklyarov Dmitry , Zhang Genkai
Published: August 2003

We introduce and study, in the framework of a theory of quantum Cartan domains, a q-analog of the Berezin transform on the unit ball. We construct q-analogs of weighted Bergman spaces, Toeplitz operators, and covariant symbol calculus. In studying the analytical properties of the Berezin transform we introduce also the q-analog of the SU(n,1)-invariant Laplace operator (the Laplace–Beltrami operator) and present related results on harmonic analysis on the quantum ball. These are applied to obtain an analog of one result by A. Unterberger and H. Upmeier. An explicit asymptotic formula expressing the q-Berezin transform via the q-Laplace–Beltrami operator is also derived. At the end of the article, we give an application of our results to basic hypergeometric q-orthogonal polynomials.
Momentum distribution of accelerated ions in ultra-intense laser–plasma interactions via neutron spectroscopy
Authors: Habara H. , Kodama R. , Sentoku Y. , Izumi N. , Kitagawa Y. , Tanaka K. A. , Mima K. , Yamanaka T.
Published: August 2003

The dependence of neutron spectra on the incident laser polarization has been studied to elucidate ion acceleration processes in ultra-intense laser–plasma interactions. Obliquely incident, 50–100 TW (450–800 fs) laser pulses irradiated a deuterated plastic solid target at 1019 W/cm2 with both s- and p-polarizations. Neutron spectra from the deuteron–deuteron d(d,n)3He nuclear reactions show the ion acceleration into the target in the direction of the target normal for both polarizations. The experiment and particle-in-cell simulations indicate the ions are accelerated inside the target by an intense electrostatic field created by charge displacement at the laser focus.
Evolution of photoluminescent defect clusters in proton- and copper-implanted silicon crystals during annealing
Authors: Nakamura Minoru , Murakami Susumu
Published: August 2003

Evolution of intrinsic defects (interstitials or vacancies) formed by implanting with protons and copper ions in silicon crystals and then annealing the crystals at temperatures from 100 to 800 °C was investigated by photoluminescence (PL) measurements. For samples annealed below 400 °C, only the well known W and I3 center peaks were observed for both proton and copper implantations. Several no-phonon PL peaks (at least six), that were inferred to be due to interstitial clusters, were newly evolved between 1.2 to 1.4 μm for samples heavily implanted with both protons and copper ions after annealing between 500 and 600 °C, indicating the existence of several self-interstitial clusters having a stability between that of the W center and the {311} defects. From the dependences of the PL intensities of these new peaks on the densities of the displaced atoms formed by implantations and on the annealing temperatures, these clusters were thought to be composed of larger numbers of self-interstitials than the W center. In addition to these peaks (the W, I3, and new centers), several broad peaks seemingly due to plural origins were observed after annealing the heavily implanted samples from room temperature to 600 °C, however, they completely vanished after annealing at 700 °C. Evolution of the PL peak located at 1.376 μm and known to be due to the {311} defects was not observed after the annihilation of the preceding peaks that are presumed to be the precursors of the {311} peak.
Cross-coupling in Coulomb blockade circuits: Bidirectional electron pump
Authors: Altebaeumer Thomas , Amakawa Shuhei , Ahmed Haroon
Published: August 2003

Coulomb blockade devices can circumvent some of the problems that arise from the continuing miniaturization of conventional circuits. However, device miniaturization and higher circuit integration aggravate cross-coupling phenomena in Coulomb blockade circuits. As an example, a silicon-based bidirectional electron pump was electrically characterized with emphasis on cross-coupling arising from the clock signal driving the pump. The cross-coupling alters profoundly the expected device characteristics, and the experimental data are confirmed by Monte Carlo simulations.
Current point formation and magnetic reconnection process in nonlinearly destabilized double tearing modes
Authors: Ishii Y. , Azumi M. , Kishimoto Y.
Published: August 2003

Magnetic reconnection process triggered by the nonlinearly destabilized double tearing mode (DTM) is studied in detail. A localized plasma current, which is referred as a current point, is formed at the X-type reconnection region of the outer magnetic island in the nonlinear growth phase of DTM [Phys. Rev. Lett. 89, 205002 (2002)]. Magnetic reconnection process with a current point shows new features different from those with the well-known Sweet–Parker type current sheet. In contrast to the latter one, the inverse aspect ratio of the plasma current at the reconnection region of the outer magnetic island, δ/Δ, increases in the Rutherford type phase and decreases after the nonlinear destabilization of DTM is triggered. The weak dependence of the temporal growth rate on the plasma resistivity in the explosive growth phase is due to this unique temporal evolution of the spatial structure of a current point. The simulations in toroidal geometry show that a current point with coherent character is also formed even in the stochastic magnetic field resultant from overlapping magnetic islands with different helicity.
Kinetic simulations of the stability of a plasma confined by the magnetic field of a current rod
Authors: Tonge J. , Leboeuf J. N. , Huang C. , Dawson J. M.
Published: August 2003

The kinetic stability of a plasma in the magnetic field of a current rod is investigated for various temperature and density profiles using three-dimensional particle-in-cell simulations. Such a plasma obeys similar physics to a plasma in a dipole magnetic field, while it is easier to perform computer simulations, and do theoretical analysis, of a plasma in the field of a current rod. Simple energy principle calculations and simulations with a variety of temperature and density profiles show that the plasma is stable to interchange for pressure profiles proportional to r−10/3. As predicted by theory the simulations also show that the density profile will be stationary as long as density is proportional to r−2 even though the temperature profile may not be stable.
Symmetric inertial confinement fusion capsule implosions in a high-yield-scale double-Z-pinch-driven hohlraum on Z
Authors: Bennett G. R. , Vesey R. A. , Cuneo M. E. , Porter J. L. , Adams R. G. , Aragon R. A. , Rambo P. K. , Rovang D. C. , Ruggles L. E. , Simpson W. W. , Smith I. C. , Speas C. S. , Struve K. W. , Wenger D. F. , Landen O. L.
Published: August 2003

Detailed radiation-hydrodynamics calculations indicate that the dual-63-MA Z-pinch high-yield (HY) 220-eV inertial confinement fusion concept [Phys. Plasmas 6, 2129 (1999)] may release 400 MJ of fusion yield, if pulse shaping, capsule preheat, and x-radiation drive uniformity can be acceptably controlled. Radiation symmetry is under detailed investigation in an advanced, 70-eV HY-scale scoping hohlraum [Phys. Rev. Lett. 88, 215004 (2002)] driven by the single 20-MA power feed of Sandia National Laboratories’ Z accelerator. The time-averaged polar radiation asymmetry, 〈ΔI〉/I, is inferred from direct distortion measurements of an imploding capsule’s limb-darkened (“backlit”) shell, via 6.7 keV point projection x-ray imaging. Thus far, 〈ΔI〉/I has been measured at the 3.0±1.4 (%) level, on the best shots, in hohlraums (cylindrical) with length/radius ratios L/R of 1.61 and 1.69, either side of a L/R=1.66 predicted optimum for a zeroed P2 Legendre mode. Simulations suggest that when scaled to 220 eV with zeroed odd Legendre modes, relevant to the best fraction of shots on a dual power-feed HY accelerator, the increased hohlraum wall albedo would reduce the field asymmetry to the 0.9% level; thus approaching the uniformity requirements of high-yield ignition. Future studies at L/R=1.66 will include refinements in experimental methods and image analysis techniques (denoising), and the measured symmetry is anticipated to improve further.
The 3838 Å photoluminescence line in 4H-SiC
Authors: Henry A. , Forsberg U. , Janson M. S. , Janzén E.
Published: August 2003

We report the results of a study of the origins of the peak near 3838 Å observed in the photoluminescence (PL) spectrum of 4H-SiC. For n+-doped 4H-SiC material, it appears as a broad peak that is shown to be related to high-level nitrogen doping, with an energy position depending on the nitrogen concentration. A similar band is observed for 6H material, displaced in energy position by the band-gap difference between the two polytypes. A sharp peak near 3838 Å in the 4H-SiC PL spectrum has a phonon structure containing localized modes. This recombination leading to this PL line is most likely associated with an isoelectronic complex defect. The present results allow a better understanding of the PL spectrum of a low-doped epilayer grown on a heavily doped substrate.
Effects of KrF excimer laser irradiation on metal contacts to n-type and p-type GaN
Authors: Jang Ho Won , Sands T. , Lee Jong-Lam
Published: August 2003

Electrical properties of metal contacts on laser-irradiated n-type and p-type GaN surfaces were investigated using current–voltage, capacitance–voltage, and synchrotron radiation photoemission spectroscopy. After the irradiation of a KrF excimer laser pulse (600 mJ/cm2 at 248 nm for 38 ns) onto Si-doped GaN, a nonalloyed Ti/Al metallization formed an ohmic contact with the specific contact resistivity of 1.7×10−6 Ω cm2. The laser irradiation decomposed GaN into metallic Ga and nitrogen gas. The decomposed metallic Ga reacted with oxygen in air to form a Ga oxide layer with the thickness of ∼40 Å, producing a large number of N vacancies near the surface. The formation of a degenerated n-type GaN layer resulted in the low contact resistivity. For Mg-doped GaN, the laser irradiation increased the effective acceptor concentration. Simultaneously, the activation efficiency of Mg dopants was enhanced by the photon-assisted breaking of Mg–H bonds and/or the removal of hydrogen atoms in the presence of oxygen, producing the p-type GaN with an increased hole concentration. As a result, the contact resistivity of an oxidized Ni/Au contact could be reduced from 1.3×10−3 to 3.6×10−4 Ω cm2.
Angular Gelfand–Tzetlin coordinates for the supergroup UOSp(k1/2k2)
Authors: Guhr Thomas , Kohler Heiner
Published: August 2003

We construct Gelfand–Tzetlin coordinates for the unitary orthosymplectic supergroup UOSp(k1/2k2). This extends a previous construction for the unitary supergroup U(k1/k2). We focus on the angular Gelfand–Tzetlin coordinates, i.e., our coordinates stay in the space of the supergroup. We also present a generalized Gelfand pattern for the supergroup UOSp(k1/2k2) and discuss various implications for representation theory.
Variational approach to electron-magnetohydrodynamic equilibria
Authors: Bhattacharyya R. , Janaki M. S.
Published: August 2003

Electron-magnetohydrodynamic equilibrium is studied through a variational approach. The equilibrium state is described by the Beltrami equation. Through a constrained minimization of the pseudo-resistive dissipation in the system, a variational problem is formulated to mimic the equilibrium state. It is found that a subclass of the Euler–Lagrange equations has strong morphological resemblance with the equilibrium topology of the system.
Rigorous analysis of two-level charge pumping: Application to the extraction of interface trap concentration versus energy profiles in metal–oxide–semiconductor transistors
Authors: Bauza D.
Published: August 2003

Charge pumping (CP) is the most widely used Si−SiO2 interface trap electrical characterization technique. However, several important characteristics and basic principles of this technique have not yet been rigorously defined. In this article, the onsets of nonsteady-state carrier emission and steady-state carrier capture, which occur during the transition edges of the gate signal when large gate pulses are used, are defined. The energies at the Si−SiO2 interface where these mechanisms start are calculated. Then, the case of asymmetrical or of small gate pulses, where capture of at least one carrier type cannot occur during the transition edges of the gate signal but proceeds during the following steady-state bias, is dealt with. The consequences of such a situation on the contribution of carrier emission to the CP current is studied. This allows a model which accurately describes the CP current in a large number of situations to be obtained. Using this model, it is shown that when the trap capture cross sections are small near the band edges, the energies where non-steady-state carrier emission takes place, interact with the high and/or low Fermi-level position. It is also shown that under asymmetrical biases, the energy regions in the upper and lower half of the band gap contributing to the CP current vary nearly symmetrically. This model is used for discussing the reliability of two-level CP for extracting interface trap concentration versus energy, Dit(E), profiles in metal–oxide–semiconductor devices. A comparison is carried out with the simplified extraction methods found in literature. The influence, on the Dit(E) profiles, of the trap cross sections and of the biases is discussed. The advantages of the spectroscopic CP are pointed out.
Relaxation processes of photoexcited carriers in GaAs/AlAs multiple quantum well structures grown by molecular beam epitaxy at low temperatures
Authors: Rath M. C. , Araya T. , Kumazaki S. , Yoshihara K. , Otsuka N.
Published: August 2003

The relaxation processes of photoexcited carriers in GaAs/AlAs multiple quantum well structures grown at low temperatures by molecular beam epitaxy were studied by a tunable single-beam femtosecond pump–probe method. Concentrations of singularly ionized antisite arsenic ions, AsGa+, in the quantum wells, which were considered as traps of photoexcited carriers, were estimated from flux conditions and substrate temperatures in the growth. Transient transmittivity of the structures were measured by varying the pump–probe photon energy. The trapping rate of photoexcited carriers, which corresponded to the reciprocal of the carrier lifetime, was derived from the relaxation profile at the pump–probe photon energy close to the exciton resonant excitation energy for each structure. The trapping rate was found to increase linearly with AsGa+ in a lower concentration range and superlinearly in a higher concentration range. Photoluminescence and absorption spectra were observed at room temperature and their correlation to the carrier lifetimes were investigated.
Profiling and modeling of dc nitrogen microplasmas
Authors: Wilson Chester G. , Gianchandani Yogesh B. , Arslanbekov Robert R. , Kolobov Vladimir , Wendt Amy E.
Published: August 2003

This article explores electric current and field distributions in dc microplasmas, which have distinctive characteristics that are not evident at larger dimensions. These microplasmas, which are powered by coplanar thin-film metal electrodes with 400-μm minimum separations on a glass substrate, are potentially useful for microsystems in both sensing and microfabrication contexts. Experiments in N2 ambient show that electron current favors electrode separations of 4 mm at 1.2 Torr, reducing to 0.4 mm at 10 Torr. The glow region is confined directly above the cathode, and within 200–500 μm of its lateral edge. Voltage gradients of 100 kV/m exist in this glow region at 1.2 Torr, increasing to 500 kV/m at 6 Torr, far in excess of those observed in larger plasmas. Numerical simulations indicate that the microplasmas are highly nonquasineutral, with a large ion density proximate to the cathode, responsible for a dense space-charge region, and the strong electric fields in the glow region. It is responsible for the bulk of the ionization and has a bimodal electron energy distribution function, with a local peak at 420 eV.
Preparation and structural investigation of epitaxially grown antiferromagnetic FeSn2(001) thin films on InSb(001)
Authors: Kuncser V. , Doi M. , Sahoo B. , Stromberg F. , Keune W.
Published: August 2003

Antiferromagnetic FeSn2(001) thin films with different thicknesses and relatively low Néel temperatures were grown on InSb(001)(4×2) surfaces by molecular-beam epitaxy. The Néel temperature could be increased to above room temperature by subsequent thermal annealing. In situ structural characterization was performed by high- and low-energy electron diffraction. The degree of the structural (001) texture as a function of the preparation and annealing conditions was investigated by x-ray diffractometry. The local magnetic properties and the spin structure were studied using Fe57 conversion electron Mössbauer spectroscopy (CEMS) at different temperatures. The epitaxial FeSn2(001) thin films exhibit in-plane Fe spin orientation and appear to be suitable antiferromagnets for studying the interfacial spin structure in exchange-biased bilayers by CEMS.
Quantitative comparisons of dissolved hydrogen density and the electrical and optical properties of ZnO
Authors: Seager C. H. , Myers S. M.
Published: August 2003

Recent density functional theory calculations indicate that hydrogen is soluble in ZnO, effectively forming a shallow donor state. It has been suggested that these donors are responsible for the large increases in electron concentration seen in ZnO samples annealed at elevated temperatures in H2 gas. In order to make a quantitative connection between the amount of dissolved hydrogen and any observed changes in electrical properties, we have annealed single crystal ZnO samples from several sources in H2 and D2 gas at 750 °C and compared the observed changes in carrier concentration with nuclear reaction analysis and secondary ion mass spectrometry profiles of deuterium. We find that the amount of deuterium remaining in our gas-charged samples is ∼3.6–5.5×1017 cm−3, substantially larger than the increase seen in conduction band electron densities at 350 K. Our modeling indicates that these gas treatments produce a hydrogen-related donor state at 0.036±0.004 eV below the conduction band minimum and also cause significant increases in the measured conduction band electron mobility. These mobility increases and other features of our data strongly suggest that a substantial fraction of the dissolved hydrogen forms complexes with (passivates) acceptor impurities. Analysis of optical and electrical data also indicates that, while hydrogen is present in significant amounts in as-received samples, it is not the dominant “native” donor. Several infrared absorption peaks are observed before and after H2/D2 exposure, which we identify with local O–H/D stretch modes. The most prominent of these has an asymmetric absorption peak at 3546 cm−1 arising from a c-axis oriented defect dipole, which is postulated to be hydrogen located in a bond-centered position between oxygen and zinc atoms. Comparisons are made between our experimental results and density functional theory calculations.