bluuebunny/crossref_metadata_2025 huggingface dataset:
Study on aging characteristics and mechanism of high-dielectric aromatic polyureas involving trap evolutions
Authors: FENG Yang  , ZHANG Shuo  , ZHOU Bin  , LIU Peiyan  , YANG Xinru  , LI Shengtao  ,   State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, Xi'an 710049, China
Published: February 2025

Dielectric capacitors are essential energy storage devices with high power density. The dielectric films of capacitors will undergo aging at working temperatures and cause performance degradation. Polyurea (PU) is a potential working dielectric for capacitors with high energy density and low dielectric loss. However, the aging characteristics and underlying mechanism of PU has never been discussed. Given the operating temperature for commercially available dielectric capacitors, PU is exposed to 80℃ for different durations to investigate its aging characteristics. Compared with dielectric constant, breakdown strength changes significantly with aging time, which can be used as a characteristic parameter to evaluate the aging degree of PU. Combing the experimental and simulation methods, the correlation between molecular structure, trap properties and breakdown strength during thermo-oxidative aging has been studied and established. The results show that: the thermal-oxidative aging of PU can be divided into three stages. In the early stage, the bridging effect of oxygen promotes the order arrangement of molecular chains, which is shown in Fig. (a). It not only reduces the molecular chain spacing, but also slightly enhances the H-bonding interaction between adjacent urea groups. As a result, the dielectric constant decreases, while the breakdown strength are almost unchanged. In the middle stage, ether bond cleavage induces the formation of biphenyl structures, leading to a disordered structure, which is illustrated in Fig. (b). The enhanced mobility effect increases the dielectric constant. Meanwhile, the biphenyl structures deepen the trap depth, reduce carrier mobility and increase the breakdown strength. In the late stage, oxygen promotes the decomposition of urea groups, which reduces the number of urea groups that contributes to deep traps. At the same time, the main chain undergoes cleavage, releasing small molecules such as CO2 and H2O, which is revealed in Fig. (c). These factors collectively lead to a significant reduction in the breakdown strength of PU. In addition, the variation of dielectric constant, breakdown strength and energy density in the three stages is summarized, which is shown in Fig. (d).
Applications of B-spline method in precise structure calculation of few-electron atoms
Authors: ZHANG Yonghui  , SHI Tingyun  , TANG Liyan  ,   Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China
Published: February 2025

The precise spectroscopy of few-electron atoms plays a pivotal role in advancing fundamental physics, encompassing the verification of quantum electrodynamics (QED) theory, the determination of finestructure constants, and the exploration of nuclear properties. With the rapid development of precision measurement techniques, the demand for atomic structure data has evolved from mere confirmation of existence to the pursuit of unprecedented accuracy. To meet the growing needs for precision spectroscopy experiments, we have developed a series of high-precision theoretical methods based on B-spline basis sets, including the non-relativistic configuration interaction (B-NRCI) method, the correlated B-spline basis functions (C-BSBFs) method, and the relativistic configuration interaction (B-RCI) method. These methods leverage the unique properties of B-spline functions, such as locality, completeness, and numerical stability, to accurately solve the Schrödinger and Dirac equations for few-electron atoms.
Our methods have yielded significant results, particularly for helium and helium-like ions. Using these methods, we have obtained accurate energies, polarizabilities, tune-out wavelengths, and magic wavelengths. Specifically, we have achieved high-precision determinations of the energy spectra of helium, providing vital theoretical support for related experimental research. Additionally, we have made highprecision theoretical predictions of tune-out wavelengths, paving the way for new tests of QED theory. Furthermore, we have proposed effective theoretical schemes to suppress Stark shifts, thereby facilitating high-precision spectroscopy experiments of helium.
The B-spline-basis methods reviewed in this paper have proven exceptionally effective in highprecision calculations for few-electron atoms. These methods have not only provided crucial theoretical support for precision spectroscopy experiments but have also paved new avenues for testing QED. Their ability to handle large-scale configuration interactions and incorporate relativistic and QED corrections makes them versatile tools for advancing atomic physics research. In the future, the high-precision theoretical methods grounded in B-spline basis sets are poised to expand into frontier areas, including quantum state manipulation, nuclear structure property determination, ultracold molecule formation, and new physics exploration, thereby continuously driving the progress of precision measurement physics.
Afadin Sorts Different Retinal Neuron Types into Accurate Cellular Layers
Authors: Lum Matthew R , Patel Sachin H , Graham Hannah K , Zhao Mengya , Yi Yujuan , Li Liang , Yao Melissa , La Torre Anna , Santina Luca Della , Han Ying , Hu Yang , Welsbie Derek S , Duan Xin
Published: February 2025

Neurons use cell-adhesion molecules (CAMs) to interact with other neurons and the extracellular environment: the combination of CAMs specifies migration patterns, neuronal morphologies, and synaptic connections across diverse neuron types. Yet little is known regarding the intracellular signaling cascade mediating the CAM recognitions at the cell surface across different neuron types. In this study, we investigated the neural developmental role of Afadin
1–4
, a cytosolic adapter protein that connects multiple CAM families to intracellular F-actin. We introduced the conditional Afadin mutant
5
to an embryonic retinal Cre, Six3-Cre
6–8
. We reported that the mutants lead to the scrambled retinal neuron distribution, including Bipolar Cells (BCs), Amacrine Cells (ACs), and retinal ganglion cells (RGCs), across three cellular layers of the retina. This scrambled pattern was first reported here at neuron-type resolution. Importantly, the mutants do not display deficits for BCs, ACs, or RGCs in terms of neural fate specifications or survival. Additionally, the displayed RGC types still maintain synaptic partners with putative AC types, indicating that other molecular determinants instruct synaptic choices independent of Afadin. Lastly, there is a significant decline in visual function and mis-targeting of RGC axons to incorrect zones of the superior colliculus, one of the major retinorecipient areas. Collectively, our study uncovers a unique cellular role of Afadin in sorting retinal neuron types into proper cellular layers as the structural basis for orderly visual processing.
Factors influencing nursing students' attitudes toward autopsies in South Korea: a cross-sectional descriptive study
Authors: Nho Seonmi , Choi Hanna
Published: February 2025

Purpose: The purpose of this study was to investigate nursing students’ perceptions of and attitudes toward autopsies and to identify factors influencing their attitudes. Methods: This study was a descriptive survey, and the participants were 183 nursing students enrolled at Nambu University. Data were collected through an online survey conducted from September 2 to October 4, 2024 and analyzed using SPSS version 28.0, employing descriptive statistics, the t-test, one-way analysis of variance, the Scheffé test, the Pearson correlation coefficient, and multiple regression analysis. Results: Nursing students’ attitudes toward autopsies showed significant correlations with their awareness of autopsies (β = .29, p < .001), awareness of local installation of autopsy facilities (β = .16, p = .030), the perceived necessity of forensic medicine (forensic nursing) (β = .16, p = .290), and age (β = .12, p = .100), explaining a total of 17% of the variance. Conclusion: These findings underscore the need to develop and implement a systematic forensic education program to improve nursing students’ perceptions of autopsies and facilitate informed decision-making.
Space, Structure, and Refuge from Predation: Artificial Habitat for Ground-Dwelling Wildlife
Authors: Carthey Alexandra J. R.
Published: February 2025

Artificial habitat holds broad appeal as a tangible and seemingly direct ‘fix’ for the ongoing loss and fragmentation of wildlife habitat, despite a lack of sufficiently rigorous evidence demonstrating benefit for target wildlife. The common focus on replacement of hollows for hollow-dependent arboreal fauna has overlooked other potential uses of artificial habitat for ground-dwelling fauna – particularly ground-dwelling small to medium-sized mammals – based on the provision of space, structure, and refuge from predation. Here, I briefly summarize the state of the science in artificial habitat research across terrestrial and marine systems, noting that artificial marine habitat research sets good precedent for development and use of artificial habitat that provides space, structure, and refuge from predation. I encourage ecologists and conservation practitioners to collaborate closely with industrial designers, and I also make the case for species- and context-specific design and development for new artificial habitat projects. I end with a brief review of design and monitoring and evaluation principles for artificial habitat projects. I aim to encourage a broader conceptualization of potential roles for artificial habitat use in terrestrial wildlife conservation, whilst emphasizing rigorous design and evaluation practices.
Effect of Eucalyptus Based Agroforestry Systems on Soil Properties in Different Land Use Patterns in Upper-gangetic Plains of Uttar Pradesh, India
Authors: Beauty Kumari , Tomar Anita , Singh Bijay Kumar
Published: February 2025

The present study was conducted during kharif season 2022 and 2023 at the Padila Nursery, Indian Council of Forestry Research and Education, Eco-Rehabilitation Centre, Prayagraj, U.P. to compare the distribution of chemical properties and nutrient status of soil in two different depths under seven land use systems viz., T1:Eucalyptus+Mentha+Tulsi, T2:Eucalyptus+Mentha, T3:Eucalyptus+Tulsi, T4:Eucalyptus Sole, T5:Mentha+ Tulsi Sole, T6:Mentha Sole and T7:Tulsi sole. Before transplanting of the medicinal plants (mentha and tulsi) and after harvesting, the soil sampling was performed to determine the soil parameters like organic carbon and the minerals content. Eucalyptus based agroforestry system performed better as compared to sole crop in respect of various soil chemical properties and available nutrients status in soil at different soil depths. Nitrogen, phosphorus, potassium content and organic carbon were higher in the agroforestry system as compared to the open farming system. In both experimental year, the average maximum available N, P, K and organic carbon at 0-15 cm (240.23 kg/ha, 28.85 kg/ha, 135.53 kg/ha and 0.88 gm/kg respectively) and 15-30 cm (227.07 kg/ha, 25.35 kg/ha, 125.52 kg/ha and 0.55 gm/kg respectively) was observed in T3: Eucalyptus + Tulsi. A high soil pH was found in an open farming system and lower pH in an agroforestry system. The maximum soil pH for both experimental year was found in the T5: Mentha + Tulsi Sole with the average value of 7.62 in 0-15cm depth and 7.67 in 15-30 cm depth. Overall, this study determines the effect of eucalyptus based agroforestry systems on soil nutrients.
Fraser syndrome
Authors: Özgünen T. , Evrüke C. , Kadayifçi O. , Demir C. , Aridoǧan N. , Vardar M.A.
Published: July 2002

In a consanguineous marriage, a woman at 32 weeks' pregnancy presented with intrauterine growth retardation and bilateral renal agenesis. Fraser syndrome (cryptophthalmus syndactyly syndrome) was diagnosed based on cryptophthalmos, atresia of meatus acusticus externus in auricula, syndactyly, hypoplastic larynx, hypoplastic left lung, agenesis of urinary system and aberrant pancreas in duodenum. The syndrome is inherited as a recessive trait and the risk of recurrence is 25%.
Na, K‐ATPase and V‐ATPase in ovarian follicles of Drosophila melanogaster
Authors: Bohrmann Johannes , Braun Barbara
Published: July 2002

Uncovering the cause and meaning of bioelectric phenomena in developing systems requires investigations of the distribution and activity of ion‐transport mechanisms. In order to identify and localize ion pumps in ovarian follicles of Drosophila, we used immunofluorescence microscopy, immunoelectron microscopy, subcellular fractionation, immunoblots, and acridine‐orange staining. We applied various antibodies directed against the Na, K‐pump (Na, K‐ATPase) and against vacuolar‐type proton pumps (V‐ATPases). During all phases of oogenesis, Na, K‐ATPases were found in apical and lateral follicle‐cell membranes and, during rapid follicle growth (beginning with stage 10), also in nurse‐cell membranes and in the oolemma. V‐ATPases were detected in various cytoplasmic vesicles and in yolk spheres and, beginning with stage 10, also in apical follicle‐cell membranes and in the oolemma. Given these and earlier results, we propose that: 1) V‐ATPases coupled to secondary active antiporters represent the ouabain‐insensitive potassium pumps described previously; 2) both Na, K‐ATPases and V‐ATPases are involved in bioelectric phenomena as well as in osmoregulation and follicle growth, especially during stages 10–12; 3) organelle‐associated V‐ATPases play a role in vesicle acidification and in yolk processing; and 4) the channel‐forming protein ductin is a component of both V‐ATPases and gap junctions in ovarian follicles of Drosophila.
Neuroleptic malignant syndrome during olanzapine and levomepromazine treatment
Authors: Järventausta K. , Leinonen E.
Published: July 2002

Objective: To date only five reports of neuroleptic malignant syndrome (NMS) related to olanzapine exist. The first case report was published in November 1998.

Method: We report the case of a 78‐year‐old woman suffering from chronic schizophrenia who developed a NMS while being treated with olanzapine and levomepromazine. Before this her medication had been unchanged for more than 2 years.

Results: When treated with olanzapine and levomepromazine, the patient had a fulminant NMS which was complicated with pneumonia. When the neuroleptic drug treatment was discontinued, the patient recovered. However, when this combination was restarted later due to severe agitation and hallucinations, the symptoms of NMS reappeared.

Conclusion: This case report shows that the neuroleptic malignant syndrome can occur during olanzapine treatment as well as during treatment with conventional neuroleptics. This syndrome may develop even after a long and stable neuroleptic treatment.
A controlled evaluation of a national continuing medical education programme designed to improve family physicians’ implementation of diabetes‐specific clinical practice guidelines
Authors: Gerstein H. C. , Reddy S. S. K. , Dawson K. G. , Yale J. F. , Shannon S. , Norman G.
Published: July 2002

Aims New approaches to continuing medical education will facilitate the implementation of clinical practice guidelines. This study assessed the short and long‐term impact of a 7‐h, small group workshop on family physicians’ attitude, knowledge and self‐reported practice patterns regarding diabetes mellitus.

Methods One hundred and seventy‐seven of 1807 family physicians who participated in this nationwide workshop, and 113 non‐participant controls completed two validated questionnaires. Participants completed one questionnaire before the workshop and a second equivalent questionnaire 1 month later. Non‐participant controls also completed the two questionnaires 1 month apart. Between 8 and 24 months later, these individuals were mailed the same questionnaire they completed on the first occasion; 143 participants and 50 controls returned this third questionnaire.

Results Participants were more likely to be female (P = 0.03), not certified in family practice (P = 0.02), in a smaller centre (P = 0.0005), recent medical graduates (P = 0.001) and seeing fewer patients per month (P = 0.01) than controls. Compared to controls, participants had improved their attitude (P < 0.0001), knowledge (P = 0.04) and self‐reported practice patterns (P < 0.002) regarding diabetes after 1 month but not after 1 year.

Conclusions An interactive, small group, diabetes continuing education programme effectively disseminates practice guidelines to family physicians. The impact of such a programme declines after 1 year.

Keywords clinical practice guidelines, continuing medical education, diabetes mellitus, primary care
Cardiovascular Disease Risk Factors Among Older Black, Mexican‐American, and White Women and Men: An Analysis of NHANES III, 1988–1994
Authors: Sundquist Jan , Winkleby Marilyn A. , Pudaric Sonja
Published: July 2002

CONTEXT: There are few studies of ethnic differences in cardiovascular disease (CVD) risk factors in older populations.

OBJECTIVES: To examine the association of ethnicity on CVD risk factors, after accounting for socioeconomic status (SES), and to examine health behaviors among those with CVD risk factors.

DESIGN: Third National Health and Nutrition Examination Survey, 1988–1994.

SETTING: Eighty‐nine mobile examination centers.

PARTICIPANTS: 700 black, 628 Mexican‐American, and 2192 white women and men age 65 to 84 years.

MEASUREMENTS: Ethnicity in relation to type II diabetes mellitus, physical inactivity, abdominal obesity, hypertension, cigarette smoking and non‐high‐density lipoprotein cholesterol (non‐HDL‐C).

RESULTS: After accounting for age and SES, both black and Mexican‐American women had significantly higher prevalences of type II diabetes than white women. In addition, black women were significantly more likely to have abdominal obesity and hypertension and to be physically inactive than white women. Black men had significantly higher prevalences of hypertension and physical inactivity than white men. However, black men had lower prevalences of abdominal obesity than white men, and black women had lower prevalences of high non‐HDL‐C than white women. Among those with CVD risk factors, health behaviors were in need of improvement, especially among Mexican‐American women whose primary language was Spanish.

CONCLUSIONS: In this national sample of older women and men, black and Mexican American women and black men were at the greatest risk for CVD. These findings parallel the heightened risk of CVD among younger ethnic minority populations and argue for appropriate primary and secondary prevention programs, modified for the language, cultural, and medical needs of older ethnic minorities.
State Practice Variations in the Use of Tube Feeding for Nursing Home Residents with Severe Cognitive Impairment
Authors: Ahronheim Judith C. , Mulvihill Michael , Sieger Carol , Park Pil , Fries Brant E.
Published: July 2002

OBJECTIVE: To describe the differences in prevalence of tube feeding among states and to examine possible factors that could explain practice patterns.

DESIGN: Analysis of random samples from an interstate data bank comprised of the Minimum Data Set (MDS), a standardized, federally mandated assessment instrument for nursing home residents.

SETTING: Nursing homes in four states participating in a federal demonstration project of case mix payment plus five others with existing MDS data systems.

PARTICIPANTS: Individuals 65 years of age and older (N = 57,029), who had very severe cognitive impairment, including total dependence in eating, and who resided in nursing homes during 1994, the most recent year for which uniform data were available.

MEASUREMENTS: State‐by‐state differences in prevalence of tube feeding, controlling for demographic and clinical variables.

RESULTS: The prevalence of tube feeding ranged from 7.5% in Maine to 40.1% in Mississippi. Each state had a significantly elevated prevalence of tube feeding compared with Maine, with odds ratios (ORs) ranging from 1.50 to 5.83, P < .001. Specific directives not to provide tube feeding (OR 0.41, P < .001), and white race (OR 0.45, P < .001) were strongly and negatively associated with tube feeding.

CONCLUSIONS: Wide regional variations exist in the use of tube feeding of nursing home residents with equivalent impairments. Sociodemographic factors could be important, but more study is needed to determine whether physician characteristics, such as race, attitudes, or knowledge, have an impact and to clarify medical standards for the use of tube feeding in this population.
Relationship of Race/Ethnicity and Blood Pressure to Change in Cognitive Function
Authors: Bohannon Arline D. , Fillenbaum Gerda G. , Pieper Carl F. , Hanlon Joseph T. , Blazer Dan G.
Published: July 2002

OBJECTIVES:

To determine whether there are racial/ethnic differences regarding the relationship of level of blood pressure to change in cognitive function in older people.

DESIGN:

Longitudinal data 1986 to 1989 on representative, older, community‐residing African Americans and whites. Blood pressure levels were assessed and a brief screen of cognitive functioning, the Short Portable Mental Status Questionnaire (SPMSQ), was performed at baseline and 3 years later.

SETTING:

Five contiguous counties in the Piedmont area of North Carolina.

PARTICIPANTS:

African‐American (n = 2,260) and white (n = 1,876) participants in the Duke Established Populations for Epidemiologic Studies of the Elderly, aged 65 to 105 at baseline.

MEASUREMENTS:

The outcome measure was change in SPMSQ score over 3 years. Covariates included age; education; gender; self‐reported diabetes mellitus, stroke, heart attack, current smoking, and depressive symptomatology; and use of antihypertensive medication. The primary independent variable was measured blood pressure.

RESULTS:

In unadjusted analyses, a statistically significant U‐shaped relationship was found between systolic (but not diastolic) blood pressure levels and change in SPMSQ score over a 3‐year period for older white men and women. No such relationships were found between these blood pressure measurements and change in SPMSQ score in older African Americans. These findings remained after adjustment for initial SPMSQ score, demographic characteristics, and use of antihypertensive medication. There were no significant interactions between race and blood pressure on change in cognitive function.

CONCLUSION:

Decline in cognitive function was associated with extremes of systolic blood pressure in older white people. Although a similar but muted nonsignificant association was found in older African Americans, the curves for the two groups were not significantly different. Further studies in older African Americans are needed. J Am Geriatr Soc 50:424–429, 2002.
Wind‐up and the NMDA receptor complex from a clinical perspective
Authors: Eide Per K.
Published: July 2002

More rational treatment of chronic pain depends on increased understanding of the pathophysiological mechanisms underlying the various symptoms and characteristics of chronic pain. Central sensitization of pain represents an important pathophysiological mechanism that has received great attention in recent years. The experimental models used to explore mechanisms of central sensitization include the study of wind‐up in animals and temporal summation of pain in humans. Wind‐up was described more than 30 years ago as progressively increasing activity in dorsal horn cells following repetitive activation of primary afferent C‐fibres. In humans, temporal summation of repeated painful stimuli has been regarded as a psychophysical correlate of wind‐up. This review focuses on the relationship between wind‐up, temporal summation and central sensitization. In particular, the role of NMDA receptor mechanisms in the modulation of wind‐up/temporal summation is discussed. The data presented here indicate that the study of wind‐up and temporal summation has given information about some of the complex mechanisms underlying central sensitization. Both wind‐up and temporal summation appear to be dependent on NMDA receptor activation. The results of clinical trials in patients with chronic pain suggest that the NMDA receptor may represent a new target for modulation of abnormal temporal summation of pain, as well as other characteristics of chronic pain. Copyright 2000 European Federation of Chapters of the International Association for the Study of Pain
Cooling of a carrier plasma in germanium investigated with subpicosecond infrared pulses
Authors: Roskos H. , Rieck B. , Seilmeier A. , Kaiser W.
Published: July 2002

An intense light pulse of 1.0 eV photons generates a hot-carrier plasma in germanium with a density of several 1017 cm−3. Cooling of the carriers results in a rise of the transmission at ℏω=1.0 eV within a few picoseconds. Three carrier-phonon interactions based on deformation potential scattering contribute to the carrier relaxation: electron and hole intravalley scattering and intervalley electron scattering. The interaction constants for carrier cooling do not depend on lattice temperature between 30 and 300 K.
Femtosecond dynamics of semiconductor-doped glasses using a new source of incoherent light
Authors: Acioli L. H. , Gomes A. S. L. , Hickmann J. Miguel , de Araujo Cid B.
Published: July 2002

The characterization and application of a new source of incoherent light for studies of ultrafast processes in condensed matter is described. It is based on the stimulated Raman effect in monomode optical fibers and has a coherence time of ∼80 fs. As an application, we have measured the homogeneous dephasing time of CdSxSe1−x-doped glasses and obtained a value of 14±4 fs for above-gap excitation at room temperature.
Fractals and quantum mechanics
Authors: Laskin Nick
Published: July 2002

A new application of a fractal concept to quantum physics has been developed. The fractional path integrals over the paths of the Lévy flights are defined. It is shown that if fractality of the Brownian trajectories leads to standard quantum mechanics, then the fractality of the Lévy paths leads to fractional quantum mechanics. The fractional quantum mechanics has been developed via the new fractional path integrals approach. A fractional generalization of the Schrödinger equation has been discovered. The new relationship between the energy and the momentum of the nonrelativistic fractional quantum-mechanical particle has been established, and the Lévy wave packet has been introduced into quantum mechanics. The equation for the fractional plane wave function has been found. We have derived a free particle quantum-mechanical kernel using Fox’s H-function. A fractional generalization of the Heisenberg uncertainty relation has been found. As physical applications of the fractional quantum mechanics we have studied a free particle in a square infinite potential well, the fractional “Bohr atom” and have developed a new fractional approach to the QCD problem of quarkonium. We also discuss the relationships between fractional and the well-known Feynman path integral approaches to quantum mechanics.
Method for the measurement of long minority carrier diffusion lengths exceeding wafer thickness
Authors: Lagowski J. , Kontkiewicz A. M. , Jastrzebski L. , Edelman P.
Published: July 2002

A procedure is presented for determining long minority carrier diffusion lengths, L, from the measurement of the surface photovoltage (SPV) as a function of the light penetration depth. The procedure uses explicit SPV formulas adopted for diffusion lengths longer than the light penetration depths. Results obtained on high-purity silicon demonstrate new capability for noncontact wafer-scale measurement of L values in a mm range, exceeding the wafer thickness by as much as a factor of 2.5. This factor can be increased by increasing the accuracy of SPV signal measurement. The procedure does not have the fundamental limitations of previous SPV methods in which the diffusion lengths were limited to about 70% of the wafer thickness.
Scanning electron microscopy with polarization analysis (SEMPA)
Authors: Scheinfein M. R. , Unguris J. , Kelley M. H. , Pierce D. T. , Celotta R. J.
Published: July 2002

The high spatial resolution imaging of magnetic microstructure has important ramifications for both fundamental studies of magnetism and the technology surrounding the magnetic recording industry. One technique for imaging surface magnetic microstructure on the 10-nm-length scale is scanning electron microscopy with polarization analysis (SEMPA). This technique employs a scanning electron microscope (SEM) electron optical column to form a medium energy (10–50 keV), small probe (<50 nm) of high current (>1 nA) on a ferromagnetic specimen. Secondary electrons excited in the ferromagnet by the high spatial resolution probe retain their spin-polarization orientation as they leave the sample surface. The spin polarization of the emitted secondary electrons can be related directly to the local magnetization orientation. A surface magnetization map is generated when the spin polarization of the secondary electrons is analyzed as the electron beam is rastered point-by-point across the ferromagnet’s surface. In this review article we review the important instrumental components characterizing the SEMPA system. Characteristics of the electron probe forming optics, electron spin-polarization analyzers with associated transport optics, and signal processing electronics will be described. Emphasis on the fundamental design requirements will be stressed. Data acquisition, storage, and processing, as it applies specifically to SEMPA, will be reviewed. Instrumental artifacts specific to SEMPA will be outlined and techniques for their correction given. Examples of magnetic images at high spatial resolution will be shown.
S-band (2–4 GHz) pulse electron paramagnetic resonance spectrometer: Construction, probe head design, and performance
Authors: Willer Michael , Forrer Jörg , Keller Jürg , Van Doorslaer Sabine , Schweiger Arthur , Schuhmann Rolf , Weiland Thomas
Published: July 2002

The design and construction of a combined pulse/continuous wave electron paramagnetic resonance (EPR) spectrometer operating in the 2–4 GHz frequency range (S band) are presented. Details of the microwave bridge are described including a Q-tune arm for adjustments of the microwave coupling during high-power pulse excitation. Factors affecting the microwave resonator construction and the frequency and Q tuning are discussed. The distribution of the electromagnetic field in a bridged loop-gap resonator with a large sample volume for EPR and electron-nuclear double resonance experiments and experiments with B0-field steps are determined using numerical calculations. One- and two-dimensional pulse echo experiments are presented and compared with the results obtained with a pulse X-band (8–10 GHz) spectrometer. For weakly coupled nuclei the echo modulation depth increases by about one order of magnitude when lowering the microwave frequency from X band to S band.
Thin-film channel waveguide electro-optic modulator in epitaxial BaTiO3
Authors: Gill D. M. , Conrad C. W. , Ford G. , Wessels B. W. , Ho S. T.
Published: July 2002

We report on a thin-film channel waveguide electro-optic modulator fabricated in epitaxial BaTiO3 on MgO. Films had an effective dc electro-optic coefficient of reff∼50±5 pm/V and reff∼18±2 pm/V at 5 MHz for λ∼1.55 μm light. Extinction ratios of 14 dB were obtained. The electro-optic effect decreases to ∼60% of the dc value at 1 Hz, 50% of the dc value at 20 kHz, and ∼37% of the dc value at 5 MHz.
Dynamic behavior of tuning fork shear-force feedback
Authors: Ruiter A. G. T. , Veerman J. A. , van der Werf K. O. , van Hulst N. F.
Published: July 2002

The dynamics of a tuning fork shear-force feedback system, used in a near-field scanning optical microscope, have been investigated. Experiments, measuring amplitude and phase of the tuning fork oscillation as a function of driving frequency and tip-sample distance, reveal that the resonance frequency of the tuning fork changes upon approaching the sample. Either amplitude or phase of the tuning fork can be used as distance control parameter in the feedback system. Using amplitude a second-order behavior is observed while with phase only a first-order behavior is observed, and confirmed by numerical calculations. This first-order behavior results in an improved stability of our feedback system. A sample consisting of DNA strands on mica was imaged which showed a height of the DNA of 1.4 nm.
Effects of rapid thermal annealing on structure and luminescence of self-assembled InAs/GaAs quantum dots
Authors: Xu S. J. , Wang X. C. , Chua S. J. , Wang C. H. , Fan W. J. , Jiang J. , Xie X. G.
Published: July 2002

Postgrowth rapid thermal annealing was used to modify the structural and optical properties of the self-assembled InAs quantum dots grown on GaAs substrates by molecular beam epitaxy. It is found that significant narrowing of the luminescence linewidth (from 78.9 to 20.5 meV) from the InAs dot layer occurs together with about 260 meV blueshift at annealing temperatures up to 850 °C. Observation of high-resolution transmission electron microscopy shows the existence of the dots under lower annealing temperatures but disappearance of the dots annealed at 850 °C. The excited-state-filling experiments for the samples show that the luminescence of the samples annealed at 850 °C exhibits quantum well-like behavior. Comparing with the reference quantum well, we demonstrate significant enhancement of the interdiffusion in the dot layer.
Reduction of interface-state density in 4H–SiC n-type metal–oxide–semiconductor structures using high-temperature hydrogen annealing
Authors: Fukuda K. , Suzuki S. , Tanaka T. , Arai K.
Published: July 2002

The effects of hydrogen annealing on capacitance–voltage (C–V) characteristics and interface-state density (Dit) of 4H–SiC metal–oxide–semiconductor (MOS) structures have been investigated. The Dit was reduced to as low as 1×1011 eV−1 cm−2 at Ec−E=0.6 eV using hydrogen annealing above 800 °C, where Ec−E is the energy level from the conduction-band edge. Secondary ion mass spectroscopy and Dit analysis revealed that Dit decreased with the increase of hydrogen concentration accumulated at the SiO2/4H–SiC interface. The interface states at SiO2/4H–SiC are thought to be originated from the dangling bonds of C atoms as well as Si atoms, because Dit decreases as the hydrogen annealing temperature increases and saturates around 800 °C. This high-temperature hydrogen annealing is useful for accumulation-type SiC metal–oxide–semiconductor field-effect transistors, which have n-type MOS structures to reduce the Dit.
Approximate relativistic electronic structure methods based on the quaternion modified Dirac equation
Authors: Visscher Lucas , Saue Trond
Published: July 2002

New implementations of the Lévy–Leblond, zeroth-order regular approach (ZORA) and spin-free Dirac equation are presented within the framework of the four-component relativistic program system DIRAC. This implementation allows systematic incorporation of relativistic effects at different levels of theory and corresponding computational cost. One of the possibilities of the new code is to neglect the effect of spin–orbit coupling in the orbital optimization process and introduce it in a later stage of the calculation. This method is shown to be unstable despite the boundedness of the spin–orbit operator itself. © 2000 American Institute of Physics.
Time dependent quantum propagation in phase space
Authors: Shalashilin Dmitrii V. , Child Mark S.
Published: July 2002

Numerical solutions of the quantum time-dependent integro-differential Schrödinger equation in a coherent state Husimi representation are investigated. Discretization leads to propagation on a grid of nonorthogonal coherent states without the need to invert an overlap matrix, with the further advantage of a sparse Hamiltonian matrix. Applications are made to the evolution of a Gaussian wave packet in a Morse potential. Propagation on a static rectangular grid is fast and accurate. Results are also presented for a moving rectangular grid, guided at its center by a mean classical path, and for a classically guided moving grid of individual coherent states taken from a Monte Carlo ensemble.
Design principles for elementary gene circuits: Elements, methods, and examples
Authors: Savageau Michael A.
Published: July 2002

The control of gene expression involves complex circuits that exhibit enormous variation in design. For years the most convenient explanation for these variations was historical accident. According to this view, evolution is a haphazard process in which many different designs are generated by chance; there are many ways to accomplish the same thing, and so no further meaning can be attached to such different but equivalent designs. In recent years a more satisfying explanation based on design principles has been found for at least certain aspects of gene circuitry. By design principle we mean a rule that characterizes some biological feature exhibited by a class of systems such that discovery of the rule allows one not only to understand known instances but also to predict new instances within the class. The central importance of gene regulation in modern molecular biology provides strong motivation to search for more of these underlying design principles. The search is in its infancy and there are undoubtedly many design principles that remain to be discovered. The focus of this three-part review will be the class of elementary gene circuits in bacteria. The first part reviews several elements of design that enter into the characterization of elementary gene circuits in prokaryotic organisms. Each of these elements exhibits a variety of realizations whose meaning is generally unclear. The second part reviews mathematical methods used to represent, analyze, and compare alternative designs. Emphasis is placed on particular methods that have been used successfully to identify design principles for elementary gene circuits. The third part reviews four design principles that make specific predictions regarding (1) two alternative modes of gene control, (2) three patterns of coupling gene expression in elementary circuits, (3) two types of switches in inducible gene circuits, and (4) the realizability of alternative gene circuits and their response to phased environmental cues. In each case, the predictions are supported by experimental evidence. These results are important for understanding the function, design, and evolution of elementary gene circuits.
Kinetics of one-dimensional swelling and shrinking of polymer gels under mechanical constraint
Authors: Suzuki Atsushi , Hara Taku
Published: July 2002

The swelling and shrinking kinetics of thin-plate poly(N-isopropylacrylamide) gels with rectangular surfaces under mechanical constraint was investigated. The top and bottom surfaces were chemically clamped on the glass plates, and the gel could swell and shrink only along the thickness direction between two swollen states by the temperature jumps. The time evolution of the thickness was well described by a single exponential except immediately after the temperature change. The characteristic time was found to depend on the lengths of the constrained surfaces and not on the thickness at the time of sample preparation. The swelling and shrinking kinetics of the one-dimensional thickness direction is essentially governed by the relaxation of the polymer network in the two-dimensional direction along the surface.
Stress fields around defects and fibers in a polymer using carbon nanotubes as sensors
Authors: Zhao Qing , Wood Jonathan R. , Wagner H. Daniel
Published: July 2002

Raman spectroscopy was used to map the stress distribution in the vicinity of discontinuities in a polymer using single-wall nanotubes seeded in the specimen. In the case of a hole in a polymer matrix subjected to unidirectional stress, the experimental stress field compared well with the classical linear elasticity solution. For a single glass fiber embedded in a polymer, the tangential thermal residual stress in the vicinity of the fiber was picked up by Raman spectroscopy and is in satisfactory agreement with a standard two-phase concentric cylinder model.
Amorphous carbon nanowires investigated by near-edge-x-ray-absorption-fine-structures
Authors: Tang Y. H. , Zhang P. , Kim P. S. , Sham T. K. , Hu Y. F. , Sun X. H. , Wong N. B. , Fung M. K. , Zheng Y. F. , Lee C. S. , Lee S. T.
Published: July 2002

The structure and bonding of amorphous carbon nanowires and amorphous carbon nanowires-converted multiwalled carbon nanotubes have been investigated with carbon K-edge near-edge x-ray absorption fine structure using surface-sensitive total electron yield, and bulk-sensitive fluorescence yield. The results strongly support that amorphous carbon nanowire is a precursor to multiwalled carbon nanotubes.
Viscoelastic effects on the stability of wall-bounded shear flows
Authors: Sadanandan B. , Sureshkumar R.
Published: July 2002

The dissolution of high molecular weight polymers and surfactants to wall-bounded shear flows of Newtonian liquids significantly modifies their stability characteristics. The critical Reynolds number Rec first decreases with increasing flow elasticity E until a critical value E=E* is reached and increases back again for E>E*. We explore the mechanisms that cause this behavior in the viscoelastic plane Poiseuille flow of an Oldroyd-B liquid. The minimum in the Rec−E curve arises from two competing contributions to the perturbation vorticity transport: The contribution from the viscoelastic shear stress perturbations that becomes more dissipative with increasing E and that from the viscoelastic normal stress perturbations that becomes more destabilizing with increasing E. Similar behavior is also exhibited by the contributions of the normal and the shear stress perturbations to the kinetic-energy budget. When a Deborah number based on the time scale of the critical disturbance becomes O(1) (≈1.6±0.1, irrespective of the solvent to total viscosity ratio), the dissipative influence of the shear stress perturbations becomes dominant. The elasticity value EC at which this occurs is approximately equal to E*. Moreover, both E* and EC exhibit similar asymptotic dependence on the solvent to total viscosity ratio. Furthermore, E* and EC are of the same order of magnitude as the elasticity values for which the onset of polymer-induced drag reduction is predicted by direct numerical simulations. Finally, we show that the perturbation velocity vector aligns progressively closer with the base flow velocity as E is increased for E<E*, contributing to the initial destabilization.
ac field-induced actuation of single crystal Ni–Mn–Ga
Authors: Henry C. P. , Bono D. , Feuchtwanger J. , Allen S. M. , O’Handley R. C.
Published: July 2002

Single crystals of Ni–Mn–Ga have shown 6% field induced strain in quasistatic actuation against an applied load. Here we report the ac actuation response and a magnetostrictivity constant of an off-stoichiometry single crystal of Ni–Mn–Ga measuring approximately 14×5.6×1 mm. This sample shows a maximum 3% strain under a bias stress of 1.1–1.5 MPa. The deficit between the low-frequency ac field-induced strain and the 6% dc results are discussed. Additionally, the ε–H indicate a peak differential value for d13 of 1%/kOe (13×10−8 m/A) which is about two times that of Terfenol-D.
Regularization of the Chapman–Enskog expansion and its description of shock structure
Authors: Xu Kun
Published: July 2002

In the continuum transition flow regime, we propose to truncate the Chapman–Enskog expansion of the Boltzmann equation to the Navier–Stokes order without going to the Burnett or super Burnett orders. However, the particle collision time has to be generalized to depend not only on the local macroscopic flow variables, but also their gradients in the rarefied gas regime. In other words, a generalized constitutive relation for the stress and heat flux is proposed. This new model is applied to the study of argon gas shock structure. There is good agreement between the predicted shock structure and experimental results for a wide range of Mach numbers.
Energetic particles from three-dimensional magnetic reconnection events in the Swarthmore Spheromak Experiment
Authors: Brown M. R. , Cothran C. D. , Landreman M. , Schlossberg D. , Matthaeus W. H. , Qin G. , Lukin V. S. , Gray T.
Published: July 2002

Measurements are presented from the Swarthmore Spheromak Experiment (SSX) [M. R. Brown, Phys. Plasmas 6, 1717 (1999)] showing a population of superthermal, super-Alfvénic ions with Ē≅90 eV and Emax⩾200 eV accelerated by reconnection activity in three-dimensional magnetic structures. These energetic ions are temporally and spatially correlated with three-dimensional magnetic reconnection events (measured with a 3D probe array) and are accelerated along the X-line normal to the local 2D plane of reconnection. In a typical SSX discharge, the peak reconnection electromotive force E=vBL⩽(105 m/s)(0.05 T)(0.1 m)=500 V consistent with our observations. In addition, test particle simulations using magnetohydrodynamic (MHD) data from SSX simulations and run with dimensionless parameters similar to the experiment (S=1000, β=0.1) show acceleration of ions up to 2vAlf in a few Alfvén times consistent with the measurement. The process includes two phases—a strong but short duration direct acceleration in the quasi-steady reconnection electric field, and a weaker longer lived sub-diffusive component associated with turbulence.
Chaotic granular mixing
Authors: Shinbrot Troy , Alexander Albert , Moakher Maher , Muzzio Fernando J.
Published: July 2002

Several models for convective mixing of coarse, freely flowing in granular tumblers have been proposed over the past decade. Powders of practical interest, by contrast, are frequently fine and cohesive, and cannot be analyzed with these models. Moreover, even in the freely flowing regime, mixing transverse to the dominant, convective, direction is typically slow and inefficient. In this paper, we examine two chaotic mixing mechanisms, the first of which can be intentionally applied to increase transverse mixing rates severalfold, with new prospects for further improvements in three-dimensional mixing through judicious process design. The second mechanism occurs spontaneously in fine grains, resulting in mixing rates overwhelmingly exceeding what would be possible in freely flowing grains. Finally, we show that the same chaotic mixing mechanisms seen in simple drum mixers are also found to be at work in more complex blender configurations widely used in batch industrial operations.
A Mössbauer study of Al and Ga substituted magnetite
Authors: Rosenberg M. , Deppe P. , Janssen H. U. , Brabers V. A. M. , Li F. S. , Dey S.
Published: July 2002

A Mössbauer study of Fe3−xAlxO4 and Fe3−xGaxO4 has been undertaken. Measurements at low temperatures in magnetic fields enabled us to better separate the Fe(A) and Fe(B) subspectra and to determine the cation distribution on tetrahedral and octahedral sites. Whereas Al up to x=1.4 shows a strong preference for B sites, giving rise to a normalization of the spinel structure with Fe2+ located mainly in tetrahedral sites, Ga distributes over both A and B places without tendency towards normalization at least below x≲1.2.
Tomography of m=1 mode structure in tokamak plasma using least-square-fitting method and Fourier–Bessel expansions
Authors: Nagayama Yoshio
Published: July 2002

A method is discussed for reconstruction of the emissivity profile from projections. The emissivity profile is expanded into Fourier–Bessel expansions, of which coefficients are determined by the use of least-square-fitting method with the help of the Akaike information criterion. Tomographic reconstruction of the m=1 mode structure is obtained in JIPP T-II tokamak during the precursor oscillation of the sawtooth crash. The m=1 mode structure fits Wesson model rather than the Kadomtsev model.