bluuebunny/crossref_metadata_2025 huggingface dataset:
2013 Alzheimer's disease facts and figures
Authors:   Alzheimer's Association, Thies William , Bleiler Laura
Published: March 2013

This report provides information to increase understanding of the public health impact of Alzheimer's disease (AD), including incidence and prevalence, mortality rates, health expenditures and costs of care, and effect on caregivers and society in general. It also explores the roles and unique challenges of long‐distance caregivers, as well as interventions that target those challenges. An estimated 5.2 million Americans have AD. Approximately 200,000 people younger than 65 years with AD comprise the younger onset AD population; 5 million comprise the older onset AD population. Throughout the coming decades, the baby boom generation is projected to add about 10 million to the total number of people in the United States with AD. Today, someone in America develops AD every 68 seconds. By 2050, one new case of AD is expected to develop every 33 seconds, or nearly a million new cases per year, and the total estimated prevalence is expected to be 13.8 million. AD is the sixth leading cause of death in the United States and the fifth leading cause of death in Americans age 65 years or older. Between 2000 and 2010, the proportion of deaths resulting from heart disease, stroke, and prostate cancer decreased 16%, 23%, and 8%, respectively, whereas the proportion resulting from AD increased 68%. The number of deaths from AD as determined by official death certificates (83,494 in 2010) likely underrepresents the number of AD‐related deaths in the United States. A projected 450,000 older Americans with AD will die in 2013, and a large proportion will die as a result of complications of AD. In 2012, more than 15 million family members and other unpaid caregivers provided an estimated 17.5 billion hours of care to people with AD and other dementias, a contribution valued at more than $216 billion. Medicare payments for services to beneficiaries age 65 years and older with AD and other dementias are three times as great as payments for beneficiaries without these conditions, and Medicaid payments are 19 times as great. Total payments in 2013 for health care, long‐term care, and hospice services for people age 65 years and older with dementia are expected to be $203 billion (not including the contributions of unpaid caregivers). An estimated 2.3 million caregivers of people with AD and other dementias live at least 1 hour away from the care recipient. These “long‐distance caregivers” face unique challenges, including difficulty in assessing the care recipient's true health condition and needs, high rates of family disagreement regarding caregiving decisions, and high out‐of‐pocket expenses for costs related to caregiving. Out‐of‐pocket costs for long‐distance caregivers are almost twice as high as for local caregivers.
The role of AV and VV optimization for CRT
Authors: Brabham William W. , Gold Michael R.
Published: March 2013

Cardiac resynchronization therapy is an effective therapy for patients with left ventricular systolic dysfunction and a ventricular conduction delay; however, approximately 30% of patients do not experience significant clinical improvement with this treatment. Modern devices allow individualized programming of the AV delay and VV offset, which offer the possibility of improving clinical response rates with optimized programming. AV and VV delay optimization techniques have included echocardiography, device‐based algorithms, and several other novel noninvasive techniques. While an acute improvement in hemodynamic function has been clearly demonstrated with optimized device settings, long‐term clinical benefit is limited. In the majority of cases, an empiric AV delay with simultaneous biventricular or left ventricular pacing is adequate. The value of optimization of these intervals in “non‐responders” still requires further investigation.
A Pelvic Floor Fitness Program for Older Women With Urinary Symptoms: A Feasibility Study
Authors: Dugan Sheila A. , Lavender Missy D. , Hebert‐Beirne Jennifer , Brubaker Linda
Published: March 2013

Objective

To determine the feasibility of an adapted pelvic fitness and educational program to control urinary incontinence (UI) and overactive bladder (OAB) symptoms in women older than 65 years.

Design

Feasibility study.

Setting

Residential independent‐living facilities.

Participants

Forty‐three study subjects, limited to women 65 years and older residing in or using an independent‐living facility, who self‐reported that they had symptoms of UI or OAB.

Methods

Study participants volunteered to participate in a 6‐week pelvic fitness class. Classes were held at 3 different independent‐living sites. Forty‐three women in 4 different treatment groups with 9‐15 women per group completed the adapted group pelvic fitness and education instruction, which was provided twice a week for 6 weeks. At one site, in addition to the treatment group, an education‐only group met; in this group, 14 women received an alternate intervention consisting of only one educational session and a booklet presenting the didactic content without specific muscle isolation or training.

Main Outcome Measurements

In addition to demographics, standardized assessments using validated instruments were obtained before the first class and after the last class, including general health, self‐reported bladder function, quality of life, and the timed up‐and‐go test.

Results

Most participants (97%) were white, with a mean age of 83 years (range, 67‐95 years). Most participants in the treatment groups (83%) reported symptom improvement. Statistically significant improvements in OAB and bladder symptoms were found after 6 weeks in the treatment groups, based on visual analog scale scores (P = .0058) for bothersomeness of bladder symptoms, the total score of the Urogenital Distress Inventory, Short Form (P ≤ .0001), and the total score of the Incontinence Impact Questionnaire, Short Form (P = .0036).

Conclusions

A group pelvic floor fitness program combined with pelvic health education is a promising approach to reduce urinary symptoms and improve the quality of life of older women living with OAB or UI symptoms.
Ultrasound Measures of the Lumbar Multifidus: Effect of Task and Transducer Position on Reliability
Authors: Larivière Christian , Gagnon Dany , De Oliveira Eros , Henry Sharon M. , Mecheri Hakim , Dumas Jean‐Pierre
Published: March 2013

Objective

To (1) assess the intra‐ and inter‐rater reliability of different ultrasound (US) measures of the lumbar multifidus muscle in subjects with and without chronic low back pain and (2) test 3 different ways to enhance reliability, that is, by testing different tasks, using a template, and averaging trials within or between days.

Design

Cross‐sectional repeated‐measures design.

Setting

Laboratory setting.

Patients

Fifteen subjects with chronic low back pain and 15 control subjects.

Methods

Subjects (n = 30) performed contralateral arm lifting and contralateral leg lifting while in the prone position. Two 7‐second videos of the lumbar multifidus (from rest to contraction) were collected with and without a template (transparency) to reposition the transducer on the skin. One of the two raters repeated the testing 7 to 14 days later to assess intrarater reliability in addition to inter‐rater reliability. Reliability was assessed with the generalizability theory as a framework.

Main outcome measurements

US imaging measures of the lumbar multifidus thickness were obtained in patients at rest and during standardized contractions (hereafter called primary measures) at 2 vertebral levels and on both sides. These primary measures were used to calculate different, potentially useful US parameters (hereafter called derived measures).

Results

Intrarater reliability was better than inter‐rater reliability, and primary measures were more reliable than derived measures. The tasks investigated showed comparable reliability results, and the use of the transducer position template was not effective to increase reliability. Averaging the measures of 3 images increased reliability substantially.

Conclusions

Optimal reliability requires the use of a single rater and the averaging of at least 3 images per visit. In these conditions, primary measures reach acceptable levels of reliability, which was more difficult to achieve for most derived measures. Arm or leg lifting tasks showed similar reliability, and thus the arm‐lifting task is recommended for comparisons with previous studies. The use of a transducer position template is not recommended.
Transparency in the reporting of in vivo pre-clinical pain research: The relevance and implications of the ARRIVE (Animal Research: Reporting In Vivo Experiments) guidelines
Authors: Rice Andrew S.C. , Morland Rosemary , Huang Wenlong , Currie Gillian L. , Sena Emily S. , Macleod Malcolm R.
Published: March 2013

Clear reporting of research is crucial to the scientific process. Poorly designed and reported studies are damaging not only to the efforts of individual researchers, but also to science as a whole. Standardised reporting methods, such as those already established for reporting randomised clinical trials, have led to improved study design and facilitated the processes of clinical systematic review and meta-analysis.

Such standards were lacking in the pre-clinical field until the development of the ARRIVE (Animal Research: Reporting In Vivo Experiments) guidelines. These were prompted following a survey which highlighted a widespread lack of robust and consistent reporting of pre-clinical in vivo research, with reports frequently omitting basic information required for study replication and quality assessment.

The resulting twenty item checklist in ARRIVE covers all aspects of experimental design with particular emphasis on bias reduction and methodological transparency. Influential publishers and research funders have already adopted ARRIVE. Further dissemination and acknowledgement of the importance of these guidelines is vital to their widespread implementation.

Conclusions and implications

Wide implementation of the ARRIVE guidelines for reporting of in vivo preclinical research, especially pain research, are essential for a much needed increased transparency and quality in publishing such research. ARRIVE will also positively influence improvements in experimental design and quality, assist the conduct of accurate replication studies of important new findings and facilitate meta-analyses of preclinical research.
Quantifying the periodicity of Heinrich and Dansgaard–Oeschger events during Marine Oxygen Isotope Stage 3
Authors: Long John A. , Stoy Paul C.
Published: March 2013

Data from multiple ice and sediment cores in the North Atlantic show that Marine Oxygen Isotope Stage 3 (MIS 3) was characterized by recurring millennial-scale variations in climate, but the periodic behavior of the well-known millennial-scale variations, Heinrich events and Dansgaard–Oeschger events, is uncertain. We use oxygen isotope values from the Greenland Ice Sheet Project 2 (GISP2) and North Greenland Ice Core Project (NGRIP) ice cores and estimated sea-surface temperature derived from a Bermuda Rise marine sediment core as climate proxies to assess the periodic behavior of Heinrich events and Dansgaard–Oeschger events using Lomb–Scargle spectral decomposition and continuous time autoregressive models. We find that continuous time autoregressive models produce less variable estimates of periodicity for Heinrich events than Lomb–Scargle methods. Heinrich events during MIS 3 are periodic with an estimated periodicity of 6.29–6.49 ka in the GISP 2 ice core, 6.71–6.76 ka in the marine sediment core, and 7.89–8.23 ka in the NGRIP core. There is insufficient evidence from these data to conclude that Dansgaard–Oeschger events exhibit a single periodicity during MIS 3. We also find that the periodic behavior of millennial-scale variations depends on the observational time frame.
Posterior maxillary alveolar vertical distraction osteogenesis by bi‐directional distractor
Authors: Ooi Kazuhiro , Inoue Nobuo , Okada Tomoyuki , Matsushita Kazuhiro , Totsuka Yasunori
Published: March 2013

A patient with severe posterior maxillary hypoplasia was simulated using a 3‐dimensional model by rapid prototyping, and segmental vertical distraction osteogenesis was planned to advance the posterior maxillary segment. The bi‐directional distractor was adapted to the alveolar ridge and zygomatic buttress. After a 7‐day latency period, we started distraction at a rate of 0.35 mm every 12 h. 12 mm of advancement of the posterior maxillary segment was achieved. This distraction osteogenesis using a bi‐directional distractor with proper therapeutic planning and good surgical technique will help ensure adequate vector control to predictably regenerate the hard and soft tissues during alveolar distraction.
Mapping the Evidence of Prevention and Intervention Studies for Suicidal and Self-Harming Behaviors in Young People
Authors: De Silva Stefanie , Parker Alexandra , Purcell Rosemary , Callahan Patrick , Liu Ping , Hetrick Sarah
Published: March 2013

Background: Suicide and self-harm (SSH) in young people is a major cause of disability-adjusted life years. Effective interventions are of critical importance to reducing the mortality and morbidity associated with SSH. Aims: To investigate the extent and nature of research on interventions to prevent and treat SSH in young people using evidence mapping. Method: A systematic search for SSH intervention studies was conducted (participant mean age between 6–25 years). The studies were restricted to high-quality evidence in the form of systematic reviews, meta-analyses, and controlled trials. Results: Thirty-eight controlled studies and six systematic reviews met the study inclusion criteria. The majority (n = 32) involved psychological interventions. Few studies (n = 9) involved treating young people with recognized mental disorders or substance abuse (n = 1) which also addressed SSH. Conclusion: The map was restricted to RCTs, CCTs, systematic reviews, and meta-analyses, and thus might have neglected important information from other study designs. The effectiveness of interventions within the trials was not evaluated. The evidence base for SSH interventions in young people is not well established, which hampers best-practice efforts in this area. Promising interventions that need further research include school-based prevention programs with a skills training component, individual CBT interventions, interpersonal psychotherapy, and attachment-based family therapy. Gaps in the research exist in evaluations of interventions for SSH in young people with identifiable psychopathology, particularly substance use disorder, and research that classifies participants on the basis of their suicidal intent.
Applying the Anderson-Darling Test to Suicide Clusters
Authors: MacKenzie Donald W.
Published: March 2013

Background: Suicide clusters at Cornell University and the Massachusetts Institute of Technology (MIT) prompted popular and expert speculation of suicide contagion. However, some clustering is to be expected in any random process. Aim: This work tested whether suicide clusters at these two universities differed significantly from those expected under a homogeneous Poisson process, in which suicides occur randomly and independently of one another. Method: Suicide dates were collected for MIT and Cornell for 1990–2012. The Anderson-Darling statistic was used to test the goodness-of-fit of the intervals between suicides to distribution expected under the Poisson process. Results: Suicides at MIT were consistent with the homogeneous Poisson process, while those at Cornell showed clustering inconsistent with such a process (p = .05). Conclusions: The Anderson-Darling test provides a statistically powerful means to identify suicide clustering in small samples. Practitioners can use this method to test for clustering in relevant communities. The difference in clustering behavior between the two institutions suggests that more institutions should be studied to determine the prevalence of suicide clustering in universities and its causes.
A Concise Total Synthesis of (±)-Asteriscunolide C
Authors: Fernandes Rodney A. , Chavan Vijay P.
Published: March 2013

This Letter has been retracted by the authors upon request of the Editorial Board for reasons of significant content overlap with a parallel submission to another journal.1

The Editorial Board recognizes that, had the submission to Chem. Commun. (submitted five weeks prior to this Synlett manuscript), been referenced and its contents disclosed, the striking similarities between the chiral (Chem. Commun.) and racemic (Synlett) syntheses would have been noted and the Synlett Letter would not have been accepted for publication.

(1) A 12-membered to a strained 11-membered ring: first stereoselective total synthesis of (−)-asteriscunolide C, Fernandes, R. A.; Chavan, V. P. Chem. Commun. 2013, 49, 3354.
Density and confinement effects of glass forming m-toluidine in nanoporous Vycor investigated by depolarized dynamic light scattering
Authors: Blochowicz Thomas , Gouirand Emmanuel , Schramm Sebastian , Stühn Bernd
Published: March 2013

We investigate the reorientational dynamics of supercooled m-toluidine contained in a matrix of nanoporous Vycor with depolarized dynamic light scattering. Under equilibrium conditions a clear sample is obtained and the dynamics of m-toluidine molecules from inside the nanopores can be accessed via light scattering. However, when supercooling the imbibed liquid at conventional cooling rates, strong non-equilibrium effects occur due to the mismatch of expansion coefficients and the sample gets turbid several tens of Kelvin above the bulk glass transition. Only at cooling rates as low as 0.02 K/min this can be avoided and the dynamics of m-toluidine in confinement can be followed even below the bulk glass transition temperature. In confinement a pronounced acceleration of the reorientational dynamics is observed and the characteristic correlation times follow an Arrhenius law close to Tg. However it seems likely that part of the observed differences to bulk behavior is due to density effects, which are reduced but cannot be fully avoided at low cooling rates.
Hydration forces between surfaces of surfactant coated single-walled carbon nanotubes
Authors: Do Changwoo , Jang Hyung-Sik , Choi Sung-Min
Published: March 2013

The interaction force between functionalized single-walled carbon nanotubes (SWNTs) plays an important role in the fabrication of self-assembled and highly ordered SWNT arrays for a wide range of potential applications. Here, we measured interaction force between SWNTs encapsulated with polymerized surfactant monolayer (p-SWNTs). The balance between the repulsion between p-SWNTs and the osmotic pressure exerted by poly(ethylene glycol) in aqueous solution results in two-dimensional hexagonal arrays of p-SWNTs with very small surface to surface distances (<1 nm). The interaction force measured by the osmotic pressure technique shows characteristic decay length of hydration force in its origin.
First-principles structural design of superhard materials
Authors: Zhang Xinxin , Wang Yanchao , Lv Jian , Zhu Chunye , Li Qian , Zhang Miao , Li Quan , Ma Yanming
Published: March 2013

We reported a developed methodology to design superhard materials for given chemical systems under external conditions (here, pressure). The new approach is based on the CALYPSO algorithm and requires only the chemical compositions to predict the hardness vs. energy map, from which the energetically preferable superhard structures are readily accessible. In contrast to the traditional ground state structure prediction method where the total energy was solely used as the fitness function, here we adopted hardness as the fitness function in combination with the first-principles calculation to construct the hardness vs. energy map by seeking a proper balance between hardness and energy for a better mechanical description of given chemical systems. To allow a universal calculation on the hardness for the predicted structure, we have improved the earlier hardness model based on bond strength by applying the Laplacian matrix to account for the highly anisotropic and molecular systems. We benchmarked our approach in typical superhard systems, such as elemental carbon, binary B-N, and ternary B-C-N compounds. Nearly all the experimentally known and most of the earlier theoretical superhard structures have been successfully reproduced. The results suggested that our approach is reliable and can be widely applied into design of new superhard materials.
Microscopic theory of singlet exciton fission. II. Application to pentacene dimers and the role of superexchange
Authors: Berkelbach Timothy C. , Hybertsen Mark S. , Reichman David R.
Published: March 2013

We apply our theoretical formalism for singlet exciton fission, introduced in the previous paper [T. C. Berkelbach, M. S. Hybertsen, and D. R. Reichman, J. Chem. Phys. 138, 114102 (2013)]10.1063/1.4794425 to molecular dimers of pentacene, a widely studied material that exhibits singlet fission in the crystal phase. We address a longstanding theoretical issue, namely whether singlet fission proceeds via two sequential electron transfer steps mediated by charge-transfer states or via a direct two-electron transfer process. We find evidence for a superexchange mediated mechanism, whereby the fission process proceeds through virtual charge-transfer states which may be very high in energy. In particular, this mechanism predicts efficient singlet fission on the sub-picosecond timescale, in reasonable agreement with experiment. We investigate the role played by molecular vibrations in mediating relaxation and decoherence, finding that different physically reasonable forms for the bath relaxation function give similar results. We also examine the competing direct coupling mechanism and find it to yield fission rates slower in comparison with the superexchange mechanism for the dimer. We discuss implications for crystalline pentacene, including the limitations of the dimer model.
Thin conductive diamond films as beam intensity monitors for soft x-ray beamlines
Authors: Kummer K. , Fondacaro A. , Yakhou-Harris F. , Sessi V. , Pobedinskas P. , Janssens S. D. , Haenen K. , Williams O. A. , Hees J. , Brookes N. B.
Published: March 2013

Quantitative analysis of X-ray absorption and dichroism data requires knowledge of the beamline photon flux during the measurements. We show that thin conductive (B-doped) diamond thin films can be an alternative to the widely used gold meshes for monitoring the beam intensity of soft X-ray beamlines in situ. Limited by the carbon extended x-ray absorption fine structure oscillations, the diamond films become applicable beginning from about 600 eV photon energy, where the important transition metal edges and the rare-earth edges are found. The 100 nm and 250 nm thick free-standing diamond films were grown and tested against standard gold meshes in real-life dichroism experiments performed at beamline ID08 of the European Synchrotron Radiation Facility, Grenoble, France. Quantitative agreement was found between the two experimental data sets. The films feature an extremely high transmission of about 90% and, at the same time, yield a sufficiently strong and clean reference signal. Furthermore, the thin films do not affect the shape of the transmitted beam. X-rays passing mesh-type monitors are subject to diffraction effects, which widen the beam and become particularly disturbing for small beamsizes in the micrometer range.
A general method for spatially coarse-graining Metropolis Monte Carlo simulations onto a lattice
Authors: Liu Xiao , Seider Warren D. , Sinno Talid
Published: March 2013

A recently introduced method for coarse-graining standard continuous Metropolis Monte Carlo simulations of atomic or molecular fluids onto a rigid lattice of variable scale [X. Liu, W. D. Seider, and T. Sinno, Phys. Rev. E 86, 026708 (2012)]10.1103/PhysRevE.86.026708 is further analyzed and extended. The coarse-grained Metropolis Monte Carlo technique is demonstrated to be highly consistent with the underlying full-resolution problem using a series of detailed comparisons, including vapor-liquid equilibrium phase envelopes and spatial density distributions for the Lennard-Jones argon and simple point charge water models. In addition, the principal computational bottleneck associated with computing a coarse-grained interaction function for evolving particle positions on the discretized domain is addressed by the introduction of new closure approximations. In particular, it is shown that the coarse-grained potential, which is generally a function of temperature and coarse-graining level, can be computed at multiple temperatures and scales using a single set of free energy calculations. The computational performance of the method relative to standard Monte Carlo simulation is also discussed.
Three-dimensional flow structure and aerodynamic loading on a revolving wing
Authors: Garmann Daniel J. , Visbal Miguel R. , Orkwis Paul D.
Published: March 2013

A numerical study is conducted to examine the vortex structure and aerodynamic loading on a revolving wing in quiescent flow. A high-fidelity, implicit large eddy simulation technique is employed to simulate a revolving wing configuration consisting of a single, aspect-ratio-one rectangular plate extended out a distance of half a chord from the rotational axis at a fixed angle relative to the axis. Shortly after the onset of the motion, the rotating wing generates a coherent vortex system along the leading-edge. This vortex system remains attached throughout the motion for the range of Reynolds numbers explored, despite the unsteadiness and vortex breakdown observed at higher Reynolds numbers. The average and instantaneous wing loading also increases with Reynolds number. At a fixed Reynolds number, the attachment of the leading-edge vortex is also shown to be insensitive to the geometric angle of the wing. Additionally, the flow structure and forcing generated by a purely translating wing is investigated and compared with that of the revolving wing. Similar features are present at the inception of the motion, however, the two flows evolve very differently for the remainder of the maneuver. Comparisons of the revolving wing simulations with recent experimental particle image velocimetry (PIV) measurements using a new PIV-like data reduction technique applied to the computational solution show very favorable agreement. The success of the data reduction technique demonstrates the need to compare computations and experiments of differing resolutions using similar data-analysis techniques.
Reorganization energy of electron transfer processes in ionic fluids: A molecular Debye-Hückel approach
Authors: Xiao Tiejun , Song Xueyu
Published: March 2013

The reorganization energy of electron transfer processes in ionic fluids is studied under the linear response approximation using a molecule Debye-Hückel theory. Reorganization energies of some model reactants of electron transfer reactions in molten salts are obtained from molecular simulations and a molecule Debye-Hückel approach. Good agreements between simulation results and the results from our theoretical calculations using the same model Hamiltonian are found. Applications of our theory to electron transfer reactions in room temperature ionic liquids further demonstrate that our theoretical approach presents a reliable and accurate methodology for the estimation of reorganization energies of electron transfer reactions in ionic fluids.
Study of nanometric superconducting multilayers for RF field screening applications
Authors: Antoine C. Z. , Villegier J.-C. , Martinet G.
Published: March 2013

Vortex penetration severely limits high field performances in bulk niobium RF cavities for accelerators. To reach higher fields, Gurevich [Appl. Phys. Lett. 88, 012511 (2006)] proposed to deposit nanometric layers (d < λ) to partially screen of the field sensed by niobium. Model (NbN/MgO)n (n = 0 to 4) samples have been deposited on thick Nb layers. This paper presents the first complete characterization set (HC1 and RF surface resistance) of a new family of composite nanostructured superconducting layers deposited on Nb, which are liable to bring a breakthrough in the technology of superconducting accelerating RF cavities.
Field-induced magnetic phase transition in Pr3+ doped Sm0.5Sr0.5MnO3 manganites
Authors: Giri S. K. , Nath T. K.
Published: March 2013

Magnetic properties of Pr3+ doped Sm0.5Sr0.5MnO3 manganite with the variation of particle size down to 30 nm have been investigated in detail. We have critically examined the magnetic field (H) dependence of the order of the ferromagnetic (FM) to paramagnetic (PM) phase transition in this Sm0.35Pr0.15Sr0.5MnO3 manganite. It has been shown that all the particle sizes (bulk to nano) exhibit first order FM → PM phase transition under low magnetic field accompanied by magnetization with thermal hysteresis in the field cooled cooling and warming cycle. However, the samples exhibit a second order magnetic phase transition above a critical field HCR. Again with decreasing the particle size, the ferromagnetic transition temperature, the thermal hysteresis width in the magnetizations, and the critical field HCR significantly decrease, which indicate that the ferromagnetism is weakened and the first-order magnetic phase transition is softened. We have also used the Banerjee criteria to distinguish the first-order magnetic phase transition from the second-order one. A detailed analysis of the magnetization measurements of this manganite reveal the disorder-induced softening of the first order phase transition in this phase separated manganite.
Effect of oxygen vacancies on the electronic structure and transport properties of SrRuO3 thin films
Authors: Lu Wenlai , He Kaihua , Song Wendong , Sun Cheng-Jun , Moog Chow Gan , Chen Jing-sheng
Published: March 2013

Epitaxial SrRuO3 films were grown under different oxygen partial pressures inducing different amounts of oxygen vacancies. In spite of microstructural disorders, a considerable improvement in the conductivity was observed at ambient temperature with increasing the oxygen vacancies. The oxygen vacancies are responsible for the conductivity improvement by enhancing the orbital overlap between Ru dz2 and O pz orbitals. The finding indicates that the oxygen vacancy plays an important role in determining the transport properties of perovskite oxides, by modifying their electronic structures.
Enhanced broad-band extraordinary optical transmission through subwavelength perforated metallic films on strongly polarizable substrates
Authors: Sun Tianyi , Metin Akinoglu Eser , Guo Chuanfei , Paudel Trilochan , Gao Jinwei , Wang Yang , Giersig Michael , Ren Zhifeng , Kempa Krzysztof
Published: March 2013

We demonstrate through simulations and experiments that a perforated metallic film, with subwavelength perforation dimensions and spacing, deposited on a substrate with a sufficiently large dielectric constant, can develop a broad-band frequency window where the transmittance of light into the substrate becomes essentially equal to that in the film absence. We show that the location of this broad-band extraordinary optical transmission window can be engineered in a wide frequency range (from IR to UV), by varying the geometry and the material of the perforated film as well as the dielectric constant of the substrate. This effect could be useful in the development of transparent conducting electrodes for various photonic and photovoltaic devices.
Nonlinear phase shifters based on forward volume spin waves
Authors: Ustinov Alexey B. , Kalinikos Boris A. , Lähderanta E.
Published: March 2013

A microwave nonlinear phase shifter based on forward volume spin waves (FVSWs) is studied. The device is fabricated with perpendicularly magnetized 5.2-μm thick single-crystal yttrium iron garnet film. The performance characteristics of the device are measured for the bias magnetic field of 1850–3700 Oe. The obtained results show that the nonlinear phase shifter produces a power-dependent phase shift of a microwave signal. The nonlinear phase shift (NLPS) appears with the signal power increasing and demonstrates almost linear rise up to 180°. With constant incident microwave power, the NLPS is a decreasing function of the bias magnetic field. A nonlinear damping of the FVSWs restricts the linear rise of the device output power with incident power increasing. The experimental data are in good agreement with theory. The phenomenological parameters describing the FVSWs nonlinear damping are determined.
Gluing bifurcations in coupled spin torque nano-oscillators
Authors: Turtle James , Beauvais Katherine , Shaffer Richard , Palacios Antonio , In Visarath , Emery Teresa , Longhini Patrick
Published: March 2013

Over the past few years, it has been shown, through theory and experiments, that the AC current produced by spin torque nano-oscillators (STNO), coupled in an array, can lead to feedback between the STNOs causing them to synchronize and that, collectively, the microwave power output of the array is significantly larger than that of an individual valve. Other works have pointed, however, to the difficulty in achieving synchronization. In particular, Persson et al. [J. Appl. Phys. 101, 09A503 (2007)] shows that the region of parameter space where the synchronization state exists for even a small array with two STNOs is rather small. In this work, we explore in more detail the nature of the bifurcations that lead into and out of the synchronization state for the two-array case. The bifurcation analysis shows bistability between in-phase and out-of-phase limit cycle oscillations. In fact, there are two distinct pairs of such cycles. But as the input current increases, the limit cycles may increase their amplitudes until they merge with one another in a gluing bifurcation. More importantly, we show that changing the direction of the applied magnetic field can, in principle, increase the region of synchronized oscillations.
Analysis and design of wire-based metamaterial absorbers using equivalent circuit approach
Authors: Pang Yongqiang , Cheng Haifeng , Zhou Yongjiang , Wang Jun
Published: March 2013

Wire-based metamaterial absorbers, as a kind of simple but versatile artificial structures, have been widely investigated from microwave to optical frequencies. In order to completely understand how the constitutive parameters affect the absorption properties, an equivalent circuit model is developed in this paper. The analytical, numerical, and experimental results show that the absorption frequency is determined by the wire length and the spacer electromagnetic parameters, whereas the absorption level by the thickness of spacers and losses which include Ohmic loss of the metal as well as dielectric loss of the spacers. It is also explained why the small losses have hardly any effect on the absorption frequency, but can result in the near-unity absorption. Based on the circuit model, some strategies for designing broadband absorbers are discussed finally.
Design of an electronic synapse with spike time dependent plasticity based on resistive memory device
Authors: Hu S. G. , Wu H. T. , Liu Y. , Chen T. P. , Liu Z. , Yu Q. , Yin Y. , Hosaka Sumio
Published: March 2013

This paper presents a design of electronic synapse with Spike Time Dependent Plasticity (STDP) based on resistive memory device. With the resistive memory device whose resistance can be purposely changed, the weight of the synaptic connection between two neurons can be modified. The synapse can work according to the STDP rule, ensuring that the timing between pre and post-spikes leads to either the long term potentiation or long term depression. By using the synapse, a neural network with three neurons has been constructed to realize the STDP learning.
Negative differential resistance and spin polarization of metal-C6H6 multidecker complexes
Authors: Zhu Si-Cong , Yao Kai-Lun , Gao Guo-Ying , Yao Wei , Ni Yun , Peng Li
Published: March 2013

We investigate the electronic properties of one-dimensional metal-C6H6 multidecker complexes: chromium(Cr)-benzene(Bz), benzene(Bz)-chromium(Cr)-benzene(Bz)-iron(Fe) wires and CrnBz2 (n = 1, 2, 3) and CrBz2Fem (m = 1, 2) clusters by applying nonequilibrium Green's functions combined with the density-functional theory. We predict that the ground state of the FeBzCrBzFe cluster is 100% spin-polarized. The density of states shows metallic for the spin-up electrons, while a semiconductor gap merges for the spin-down electrons (half-metallic). It is found that there is 92%–97% spin polarization of the electron transmission for the five sandwich molecular junctions constructed by the multilayer metal-benzene organometallic CrnBz2 (n = 1, 2, 3) and CrBz2Fem (m = 1, 2) clusters, which coupled to gold electrodes. In deed, these clusters will perform as nearly perfect spin-filters via the electron transport calculations. The current increases with the cluster length and depends on the bias and spin-up current-voltage characteristics for three kinds of sandwich molecular junctions (Bz2Cr, BzCrBzFe, and Bz2Cr3). It also shows robust negative differential resistance behavior, which is closely related with the evolution of the transmission spectrum under applied bias.
The effects of strain, current, and magnetic field on superconductivity in Pr0.5Ca0.5MnO3/YBa2Cu3O7/Pr0.5Ca0.5MnO3 trilayer
Authors: Kumar Baisnab Dipak , Janawadkar M. P. , Sharma Shilpam , Sarguna R. M. , Vaidhyanathan L. S. , Bharathi A.
Published: March 2013

Thin film trilayers of Pr0.5Ca0.5MnO3/YBa2Cu3O7/Pr0.5Ca0.5MnO3 have been deposited on MgO substrate by pulsed laser deposition technique. The film thicknesses were selected so that in one of the trilayers, the bottom Pr0.5Ca0.5MnO3 layer is thin, and hence, subjected to substrate induced strain, while in another trilayer, the bottom layer is sufficiently thick to ensure that it is not subjected to such strain. Current and magnetic field dependent resistance measurements have been carried out on the trilayers down to liquid helium temperatures to investigate the influence of charge-order melting and the consequent formation of ferromagnetic clusters in the Pr0.5Ca0.5MnO3 film on the superconducting properties of YBa2Cu3O7. These measurements show that the suppression of the superconducting transition temperature (Tc) of YBa2Cu3O7 is relatively high for the strained trilayer compared to that observed for the other. The activation energy for hopping of vortices in the sandwiched YBa2Cu3O7 film was estimated from an analysis of the data; the vortex pinning force was found to be higher for the strained trilayer. The experimental results suggest the possibility of simultaneous use of strain, current, and magnetic field to control the superconducting behavior of the sandwiched YBa2Cu3O7 layer.
Tsirelson's problem and asymptotically commuting unitary matrices
Authors: Ozawa Narutaka
Published: March 2013

In this paper, we consider quantum correlations of bipartite systems having a slight interaction, and reinterpret Tsirelson's problem (and hence Kirchberg's and Connes's conjectures) in terms of finite-dimensional asymptotically commuting positive operator valued measures. We also consider the systems of asymptotically commuting unitary matrices and formulate the Stronger Kirchberg Conjecture.
Note: A real-time beam current density meter
Authors: Liu Junliang , Yu Deyang , Ruan Fangfang , Xue Yingli , Wang Wei
Published: March 2013

We have developed a real-time beam current density meter for charged particle beams. It measures the mean current density by collimating a uniform and large diameter primary beam. The suppression of the secondary electrons and the deflection of the beam were simulated, and it was tested with a 105 keV Ar7+ ion beam.
Fermionic covariant prolongation structure theory for multidimensional super nonlinear evolution equation
Authors: Yan Zhao-Wen , Li Min-Li , Wu Ke , Zhao Wei-Zhong
Published: March 2013

The fermionic covariant prolongation structure theory is investigated. We extend the fermionic covariant prolongation structure technique to the multidimensional super nonlinear evolution equation and present the fermionic covariant fundamental equations determining the prolongation structure. Furthermore, we investigate a (2+1)-dimensional super nonlinear Schrödinger equation and analyze its integrability by means of this prolongation structure technique. We derive its Lax representation and Bäcklund transformation. Moreover, we present a solution of this multidimensional super integrable equation.
Communication: An efficient algorithm for evaluating the Breit and spin–spin coupling integrals
Authors: Shiozaki Toru
Published: March 2013

We present an efficient algorithm for evaluating a class of two-electron integrals of the form \documentclass[12pt]{minimal}\begin{document}$\mathbf {r}_{12}\otimes \mathbf {r}_{12}/r_{12}^n$\end{document}r12⊗r12/r12n over one-electron Gaussian basis functions. The full Breit interaction in four-component relativistic theories beyond the Gaunt term is such an operator with n = 3. Another example is the direct spin–spin coupling term in the quasi-relativistic Breit–Pauli Hamiltonian (n = 5). These integrals have been conventionally evaluated by expensive derivative techniques. Our algorithm is based on tailored Gaussian quadrature, similar to the Rys quadrature for electron repulsion integrals (ERIs), and can utilize the so-called horizontal recurrence relation to reduce the computational cost. The CPU time for computing all six Cartesian components of the Breit or spin–spin coupling integrals is found to be only 3 to 4 times that of the ERI evaluation.
Near-ultraviolet light-emitting diodes with transparent conducting layer of gold-doped multi-layer graphene
Authors: Cho Chu-Young , Choe Minhyeok , Lee Sang-Jun , Hong Sang-Hyun , Lee Takhee , Lim Wantae , Kim Sung-Tae , Park Seong-Ju
Published: March 2013

We report on gold (Au)-doped multi-layer graphene (MLG), which can be used as a transparent conducting layer in near-ultraviolet light-emitting diodes (NUV-LEDs). The optical output power of NUV-LEDs with thermally annealed Au-doped MLG was increased by 34% compared with that of NUV-LEDs with a bare MLG. This result is attributed to the reduced sheet resistance and the enhanced current injection efficiency of NUV-LEDs by the thermally annealed Au-doped MLG film, which shows high transmittance in NUV and UV regions and good adhesion of Au-doped MLG on p-GaN layer of NUV-LEDs.
Morphological control of GaAs/InAs radial heterostructure nanowires: From cylindrical to coherent quantum dot structure
Authors: Guo Jingwei , Huang Hui , Zhang Jianwei , Li Xiaogan , Huang Yongqing , Ren Xiaomin , Ji Zhuoyu , Liu Ming
Published: March 2013

Various surface morphologies of hierarchical GaAs/InAs core/shell heterostructure were obtained by carefully tuning the growth parameters. The growth of the InAs shell around the surface of the GaAs core could be evolved from 2D mode to 3D mode as the variation of the growth parameters. As a consequence, the morphology of the InAs shell can systematically change from the uniformly coated cylindrical to isolated islands and eventually nanorings. The isolated nanoring structure can be formed innovatively by coalescence of the islands without the assistance of twin-induced concave sites. Different types of dislocations in the shell structure, which could result from the different behaviors of misfit-stress relaxation processes, were observed during these two growth modes. The mechanisms of the morphological evolution are also discussed in detail.
High-pressure x-ray diffraction and Raman spectroscopy of phase transitions in Sm2O3
Authors: Jiang Sheng , Liu Jing , Lin Chuanlong , Li Xiaodong , Li Yanchun
Published: March 2013

The structural phase transitions in Sm2O3 with mixed phases of cubic and monoclinic as starting material were studied by in situ high-pressure synchrotron angle dispersive x-ray diffraction and Raman scattering measurements up to 40.1 GPa and 41.0 GPa, respectively. The x-ray diffraction data indicate that the monoclinic and cubic phases begin to transform to a hexagonal phase at 2.5 and 4.2 GPa, respectively. The hexagonal phase is stable up to at least 40.1 GPa and could not be quenched to ambient conditions. These phase transitions have also been confirmed by Raman spectroscopy. A third-order Birch-Murnaghan fit based on the observed pressure-volume data yields zero pressure bulk moduli B0 = 149(2), 153(7), and 155(5) GPa for cubic, monoclinic, and hexagonal phases, respectively, when their first pressure derivatives (B0′) were fixed as 4. The pressure coefficients of Raman peaks and the mode Grüneisen parameters of different Raman modes were also obtained. Coupled with previous results, we conclude that the transition pressure of medium rare-earth sesquioxides from the cubic and monoclinic to the hexagonal phase increase with the decreasing of the cation radius.
Ultra-low field magnetic resonance imaging detection with gradient tensor compensation in urban unshielded environment
Authors: Dong Hui , Qiu Longqing , Shi Wen , Chang Baolin , Qiu Yang , Xu Lu , Liu Chao , Zhang Yi , Krause Hans-Joachim , Offenhäusser Andreas , Xie Xiaoming
Published: March 2013

An ultra-low field (ULF) magnetic resonance imaging (MRI) system was set up in an urban laboratory without magnetic shielding. The measured environmental gradient fields of 1 ∼ 5 μT/m caused image distortion. We designed a gradient detection and compensation system to effectively balance the gradient tensor components. The free induction decay signal duration of tap water was thus extended from 0.3 s to 2.5 s, providing the possibility for high-resolution imaging. Two-dimensional MRI images were then obtained at 130 μT with a helium-cooled second-order superconducting quantum interference device gradiometer. This result allows us to develop an inexpensive ULF MRI system for biological studies.
Versatile graphene nanocomposite microheater patterning for various thermoplastic substrates based on capillary filling and transfer molding
Authors: Woo Kim Hyung , Jea Park Sung , Lee Bong-Kee , Sung Kim Dong
Published: March 2013

We report a fabrication method of graphene nanocomposite patterns on a thermoplastic substrate using capillary filling and transfer molding techniques. As a proof of concept, we produced microheaters using a low-viscosity graphene nanocomposite solution. After filling a microchannel on a polydimethylsiloxane (PDMS) stamp with graphene solution, the solution solvent was evaporated, leaving behind the graphene nanocomposite pattern. Subsequent embossing of the graphene nanocomposite patterns on the PDMS stamp onto a polymethylmethacrylate substrate allowed the transfer of the microheater pattern. Capillary filling was characterized analytically and experimentally. The performance and thermal response of the fabricated microheater were very promising.
Ultra-shallow quantum dots in an undoped GaAs/AlGaAs two-dimensional electron gas
Authors: Mak W. Y. , Sfigakis F. , Das Gupta K. , Klochan O. , Beere H. E. , Farrer I. , Griffiths J. P. , Jones G. A. C. , Hamilton A. R. , Ritchie D. A.
Published: March 2013

We report quantum dots fabricated on very shallow 2-dimensional electron gases, only 30 nm below the surface, in undoped GaAs/AlGaAs heterostructures grown by molecular beam epitaxy. Due to the absence of dopants, an improvement of more than one order of magnitude in mobility (at 2 × 1011 cm−2) with respect to doped heterostructures with similar depths is observed. These undoped wafers can easily be gated with surface metallic gates patterned by e-beam lithography, as demonstrated here from single-level transport through a quantum dot showing large charging energies (up to 1.75 meV) and excited state energies (up to 0.5 meV).