bluuebunny/crossref_metadata_2025 huggingface dataset:
An efficient energy‐aware predictive clustering approach for vehicular ad hoc networks
Authors: Bali Rasmeet S. , Kumar Neeraj , Rodrigues Joel J.P.C.
Published: January 2015

With an emergence of information and communication technologies, there is an increase in the demands of providing safety and comfort to the passengers during their mobility on the road. These demands can be fulfilled by one of the most popular networks of its type—vehicular adhoc networks (VANETs). As vehicles in VANETs are constrained with respect to the available resources such as computation and storage, lot of energy is consumed to perform a number of complex operations, which may lead to the emission of harmful CO2 emission that effect the global warming system. Moreover, because of high velocity led by constant topological changes, it is a challenging task to maintain quality of service with respect to parameters such as high throughput, and minimum end‐to‐end delay. Hence, an intelligent approach is required to optimize the various complex operations in this environment, which may led to the minimum emission of CO2 and other gasses. To address these issues, this paper proposes an efficient energy‐aware predictive clustering scheme for vehicles. Efficient algorithms are designed for future mobility predictions and average variations of vehicles on the road. The algorithms estimate the clustering duration and total vehicles in the cluster. The performance of the designed algorithms is studied using extensive simulations by varying the number of vehicles and cluster durations in comparison with existing benchmarked scheme in the literature. The results obtained show that the proposed scheme is superior in comparison with the existing scheme of its category. Copyright © 2015 John Wiley & Sons, Ltd.
Risk factors for hyperkalaemia in a cohort of patients with newly diagnosed heart failure: a nested case–control study in UK general practice
Authors: Michel Alexander , Martín‐Pérez Mar , Ruigómez Ana , García Rodríguez Luis A.
Published: January 2015

Aims

The aim of this study was to identify risk factors for hyperkalaemia in a cohort of patients with newly diagnosed heart failure in the UK.

Methods and results

A nested case–control study was conducted using data from The Health Improvement Network primary care database. A cohort of 19 194 patients aged 1–89 years between January 2000 and December 2005 with newly diagnosed heart failure was followed up and cases of hyperkalaemia identified. Cases were frequency matched to controls by age, sex, and calendar year, and information on demographics, co‐morbidities, co‐medications, and lifestyle factors was extracted from the database. Using unconditional logistic regression models, odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to identify potential risk factors. In total, 2176 hyperkalaemia cases were identified over a mean follow‐up of 3.9 years. Significant risk factors for hyperkalaemia were: renal failure (OR 3.81; 95% CI 3.29–4.42), type II diabetes (OR 1.52; 95% CI 1.31–1.75), valvular heart disease (OR 1.28; 95% CI 1.06–1.54), and current use of potassium‐sparing diuretics (OR 3.01; 95% CI 2.61–3.48), ACE inhibitors (OR 1.70; 95% CI 1.41–2.04), trimethoprim (OR 2.82; 95% CI 1.88–4.23), non‐steroidal anti‐inflammatory drugs (OR 1.41; 95% CI 1.11–1.79), and several drug combinations. The risk was highest within the first month of medication use and decreased thereafter.

Conclusion

Our findings may help to better identify patients with heart failure most likely to benefit from careful monitoring of serum potassium levels. Particular vigilance is needed during the start of treatment with certain medications.
Dune deformation in a multi‐directional wind regime: White Sands Dune Field, New Mexico
Authors: Pedersen Anine , Kocurek Gary , Mohrig David , Smith Virginia
Published: January 2015

As with most dune fields, the White Sands Dune Field in New Mexico forms in a wind regime that is not unimodal. In this study, crescentic dune shape change (deformation) with migration at White Sands was explored in a time series of five LiDAR‐derived digital elevation models (DEMs) and compared to a record of wind direction and speed during the same period. For the study period of June 2007 to June 2010, 244 sand‐transporting wind events occurred and define a dominant wind mode from the SW and lesser modes from the NNW and SSE. Based upon difference maps and tracing of dune brinklines, overall dune behavior consists of crest‐normal migration to the NE, but also along‐crest migration of dune sinuosity and stoss superimposed dunes to the SE. The SW winds are transverse to dune orientations and cause most forward migration. The NNW winds cause along‐crest migration of dune sinuosity and stoss bedforms, as well as SE migration of NE‐trending dune terminations. The SSE winds cause ephemeral dune deformation, especially crestal slipface reversals. The dunes deform with migration because of differences in dune‐segment size, and differences in the lee‐face deposition rate as a function of the incidence angle between the wind direction and the local brinkline orientation. Each wind event deforms dune shape, this new shape then serves as the boundary condition for the next wind event. Shared incidence‐angle control on dune deformation and lee‐face stratification types allows for an idealized model for White Sands dunes. Copyright © 2015 John Wiley & Sons, Ltd.
This Ad is for You: Targeting and the Effect of Alcohol Advertising on Youth Drinking
Authors: Molloy Eamon
Published: January 2015

Endogenous targeting of alcohol advertisements presents a challenge for empirically identifying a causal effect of advertising on drinking. Drinkers prefer a particular media; firms recognize this and target alcohol advertising at these media. This paper overcomes this challenge by utilizing novel data with detailed individual measures of media viewing and alcohol consumption and three separate empirical techniques, which represent significant improvements over previous methods. First, controls for the average audience characteristics of the media an individual views account for attributes of magazines and television programs alcohol firms may consider when deciding where to target advertising. A second specification directly controls for each television program and magazine a person views. The third method exploits variation in advertising exposure due to a 2003 change in an industry‐wide rule that governs where firms may advertise. Although the unconditional correlation between advertising and drinking by youth (ages 18–24) is strong, models that include simple controls for targeting imply, at most, a modest advertising effect. Although the coefficients are estimated less precisely, estimates with models including more rigorous controls for targeting indicate no significant effect of advertising on youth drinking. Copyright © 2015 John Wiley & Sons, Ltd.
Benefits and drawbacks of open partial horizontal laryngectomies, Part A: Early‐ to intermediate‐stage glottic carcinoma
Authors: Succo Giovanni , Crosetti Erika , Bertolin Andy , Lucioni Marco , Caracciolo Alessandra , Panetta Valentina , Sprio Andrea Elio , Berta Giovanni Nicolao , Rizzotto Giuseppe
Published: January 2015

Background

Laryngeal squamous cell carcinoma (SCC) accounts for 1.9% of cancers worldwide. Most of these are diagnosed in the early stages (T1–T2, and N0). For these, a larynx preserving/conserving option is preferable. Beyond transoral laser microsurgery (TLM), open partial horizontal laryngectomy is a function‐sparing surgical technique used to treat laryngeal SCC.

Methods

We retrospectively analyzed the clinical outcomes of 216 patients who underwent open partial horizontal laryngectomy for glottic cT2 laryngeal cancer.

Results

Five‐year overall survival (OS), disease‐specific survival (DFS), locoregional control, local control, laryngeal function preservation, and laryngectomy‐free survival rates were 93.1%, 98.0%, 97.1%, 97.5%, 97.8%, and 98.5%, respectively. Disease controls were significantly affected by previous treatment and type of surgery used.

Conclusion

Although TLM for cT2 laryngeal cancer with unimpaired vocal cord mobility still represents a sound option, open partial horizontal laryngectomy offers higher local control and laryngeal preservation rates for selected patients with impaired mobility of vocal cords combined with involvement of the paraglottic space. © 2015 Wiley Periodicals, Inc. Head Neck 38: E333–E340, 2016
Isoliquiritigenin as a cause of DNA damage and inhibitor of ataxia‐telangiectasia mutated expression leading to G2/M phase arrest and apoptosis in oral squamous cell carcinoma
Authors: Hsia Shih‐Min , Yu Cheng‐Chia , Shih Yin‐Hua , Yuanchien Chen Michael , Wang Tong‐Hong , Huang Yu‐Ting , Shieh Tzong‐Ming
Published: January 2015

Background

Isoliquiritigenin (ISL), a natural compound extracted from licorice, has chemopreventive and antitumor activities. The purpose of this study was to investigate the anticancer effect of ISL on human oral squamous cell carcinoma (OSCC).

Methods

The anti‐OSCC effects of ISL were evaluated using the 3‐(4,5‐dimethylthiazol‐2‐yl)−2,5‐diphenyltetrazolium bromide test, flow cytometry, reverse transcription‐polymerase chain reaction, Western blotting, promoter activity, terminal deoxynucleotidyl transferase dUTP nick‐end labeling assay, malignant phenotype analysis, microRNA, and xenografting.

Results

ISL induced OSCC cell cycle G2/M phase arrest, apoptosis, and DNA damage. However, the DNA repair‐associated ataxia telangiectasia mutated (ATM) and phospho‐ATM were downregulated, ATM mRNA remained unchanged, and the downstream signals were inhibited. ATM recovered when the caspase activity was blocked by Z‐DVED‐FMK. A low dose of ISL inhibited OSCC malignancy in vitro and reduced the tumor size in vivo.

Conclusion

ATM was cleaved by ISL‐activated caspase, thus inhibiting DNA repair in OSCC cells. Therefore, ISL is a promising chemopreventive agent against oral cancer. © 2015 Wiley Periodicals, Inc. Head Neck 38: E360–E371, 2016
How to optimize hepatitis C virus treatment impact on life years saved in resource‐constrained countries
Authors: Obach Dorothée , Yazdanpanah Yazdan , Esmat Gamal , Avihingsanon Anchalee , Dewedar Sahar , Durier Nicolas , Attia Alain , Anwar Wagida A. , Cousien Anthony , Tangkijvanich Pisit , Eholié Serge Paul , Doss Wahid , Mostafa Aya , Fontanet Arnaud , Mohamed Mostafa K. , Deuffic‐Burban Sylvie
Published: January 2015

In resource‐constrained countries where the prevalence of hepatitis C virus (HCV) disease is usually high, it is important to know which population should be treated first in order to increase treatment effectiveness. The aim was to estimate the effectiveness of different HCV treatment eligibility scenarios in three different countries. Using a Markov model, we estimated the number of life‐years saved (LYS) with different treatment eligibility scenarios according to fibrosis stage (F1‐F4 or F3‐4), compared to base case (F2‐F4), at a constant treatment rate, of patients between 18 and 60 years of age, at stages F0/F1 to F4, without liver complications or coinfections, chronically infected by HCV, and treated with pegylated interferon (IFN)/ribavirin or more‐efficacious therapies (i.e. IFN free). We conducted the analysis in Egypt (prevalence = 14.7%; 45,000 patients treated/year), Thailand (prevalence = 2.2%; 1,000 patients treated/year), and Côte d'Ivoire (prevalence = 3%; 150 patients treated/year). In Egypt, treating F1 patients in addition to ≥F2 patients (SE1 vs. SE0) decreased LYS by 3.9%. Focusing treatment only on F3‐F4 patients increased LYS by 6.7% (SE2 vs. SE0). In Thailand and Côte d'Ivoire, focusing treatment only on F3‐F4 patients increased LYS by 15.3% and 11.0%, respectively, compared to treating patients ≥F2 (ST0 and SC0, respectively). Treatment only for patients at stages F3‐F4 with IFN‐free therapies would increase LYS by 16.7% versus SE0 in Egypt, 22.0% versus ST0 in Thailand, and 13.1% versus SC0 in Côte d'Ivoire. In this study, we did not take into account the yearly new infections and the impact of treatment on HCV transmission. Conclusion: Our model‐based analysis demonstrates that prioritizing treatment in F3‐F4 patients in resource‐constrained countries is the most effective scenario in terms of LYS, regardless of treatment considered. (Hepatology 2015;62:31‐39)
Crystal structure and functional analysis of MiD49, a receptor for the mitochondrial fission protein Drp1
Authors: Losón Oliver C. , Meng Shuxia , Ngo Huu , Liu Raymond , Kaiser Jens T. , Chan David C.
Published: January 2015

Mitochondrial fission requires recruitment of dynamin‐related protein 1 (Drp1) to the mitochondrial surface, where assembly leads to activation of its GTP‐dependent scission function. MiD49 and MiD51 are two receptors on the mitochondrial outer membrane that can recruit Drp1 to facilitate mitochondrial fission. Structural studies indicated that MiD51 has a variant nucleotidyl transferase fold that binds an ADP co‐factor essential for activation of Drp1 function. MiD49 shares sequence homology with MiD51 and regulates Drp1 function. However, it is unknown if MiD49 binds an analogous co‐factor. Because MiD49 does not readily crystallize, we used structural predictions and biochemical screening to identify a surface entropy reduction mutant that facilitated crystallization. Using molecular replacement, we determined the atomic structure of MiD49 to 2.4 Å. Like MiD51, MiD49 contains a nucleotidyl transferase domain; however, the electron density provides no evidence for a small‐molecule ligand. Structural changes in the putative nucleotide‐binding pocket make MiD49 incompatible with an extended ligand like ADP, and critical nucleotide‐binding residues found in MiD51 are not conserved. MiD49 contains a surface loop that physically interacts with Drp1 and is necessary for Drp1 recruitment to the mitochondrial surface. Our results suggest a structural basis for the differential regulation of MiD51‐ versus MiD49‐mediated fission.
Aligning Policy to Promote Cascade Genetic Screening for Prevention and Early Diagnosis of Heritable Diseases
Authors: George Rani , Kovak Karen , Cox Summer L.
Published: January 2015

Cascade genetic screening is a methodology for identifying and testing close blood relatives of individuals at increased risk for heritable conditions and follows a sequential process, minimizing testing costs and the number of family members who need to be tested. It offers considerable potential for cost savings and increased awareness of heritable conditions within families. CDC‐classified Tier 1 genomic applications for hereditary breast and ovarian cancer syndrome (HBOC), Lynch Syndrome (LS), and familial hypercholesterolemia (FH) are recommended for clinical use and support the use of cascade genetic screening. Most individuals are unaware of their increased risk for heritable conditions such as HBOC, LS, and FH. Consistent implementation of cascade genetic screening could significantly increase awareness and prevention of heritable conditions. Limitations to effective implementation of cascade genetic screening include: insufficient genetic risk assessment and knowledge by a majority of healthcare providers without genetics credentials; a shortage of genetic specialists, especially in rural areas; a low rate of reimbursement for comprehensive genetic counseling services; and an individual focus on prevention by clinical guidelines and insurance coverage. The family‐centric approach of cascade genetic screening improves prevention and early diagnosis of heritable diseases on a population health level. Cascade genetic screening could be better supported and augmented through changes in health policy.
Hegemann's disease and fishtail deformity: Aetiopathogenesis, radiographic appearance and clinical outcome
Authors: Claessen Femke M. A. P. , Louwerens Jan K. G. , Doornberg Job N. , van Dijk C. Niek , van den Bekerom Michel P. J. , Eygendaal Denise
Published: January 2015

Purpose

A systematic review regarding clinical studies on Hegemann's disease and fishtail deformity was performed with the aims to: (1) formulate the most up-to-date theory on aetiology in order to better define these conditions, (2) summarise the most frequent radiographic descriptions on radiographs and (3) give an overview of different treatment options.

Methods

A systematic review of studies to date on Hegemann's disease and fishtail deformity was performed. Studies were eligible if: (1) the article provides a description of Hegemann's disease or fishtail deformity, (2) original data of at least one patient was available, (3) the article was written in English, German or Dutch and (4) a full manuscript was available. Animal studies, reviews and expert opinions were not included.

Results

We included a total of 22 articles: seven regarding Hegemann's disease including eight patients and 15 regarding fishtail deformity including 58 patients.

Conclusions

Fishtail deformity and Hegemann's disease seem to be a spectrum of vascular disorders of the distal humerus, varying from a benign mild vascular disorder to a complete avascular necrosis after fractures. Additional imaging is advised to confirm the presence of a fishtail deformity, intra-articular loose bodies and signs of osteoarthritis to decide if, and what, operative treatment is needed. As long as no clear aetiology for both diseases exist and the clinical symptoms and radiographic appearance are difficult to distinguish, both entities should preferably be named as ‘vascular disturbance of the trochlear growth plate’ to overcome confusing definitions and discussions.
Intense Sweeteners, Appetite for the Sweet Taste, and Relationship to Weight Management
Authors: Bellisle France
Published: January 2015

High intensity, low-energy sweeteners (LES) are used by many consumers in order to limit energy intake and possibly facilitate body weight control. These beneficial effects are often questioned in the scientific and lay media. LES are frequently accused of stimulating and/or maintaining a liking for sweetness which in turn would be deleterious for adequate body weight control. Evidence for the specific effects of LES use on appetite for sweet products will be extracted from observational studies, experimental laboratory studies, randomized controlled trials, and finally brain imaging studies. While many of the existing studies cannot identify any causal links between use of LES and appetite for sweetness, randomized trials in children and adults suggest that use of LES tends to reduce rather than increase the intake of sugar-containing foods and to facilitate, rather than impair, weight loss.
A Comparative Study of four Oral Contrast Agents for Small Bowel Distension with Computed Tomography Enterography
Authors: Leduc Francois , De Anirban , Rebello Ryan , Muhn Narry , Ioannidis George
Published: January 2015

Purpose

To assess the efficacy of a variety of oral contrast agents in obtaining small bowel distention for computed tomography (CT) enterography examinations.

Methods

A retrospective study was developed to quantitatively assess small bowel luminal distension during CT enterography by using 4 contrast agents, which included water, Metamucil, polyethylene glycol, and lactulose. A total of 256 patients were enrolled in the study and included 64 individuals for each oral regimen. The widest loop of small bowel in each of 4 quadrants on representative coronal images was separately measured for luminal distension. Overall distension and the greatest number of “useful” quadrants were evaluated. Overall distension was calculated by summing the 4 quadrant values into an overall luminal diameter distention score (cm). A “useful” quadrant was defined as having a measurement of ≥2 cm. Each “useful” quadrant was assigned a score of 1, with values that ranged from 0-4.

Results

For overall distension, multivariable liner regression analysis showed that the lactulose group had a significantly higher overall distension value than Metamucil, polyethylene glycol, and water by 0.88, 0.92, and 1.63 cm, respectively, with 95% confidence interval. The categorical multivariable logistic regression analysis showed that the lactulose group had greater odds of having more “useful” quadrants than the Metamucil, polyethylene glycol, and water groups, with odds ratios of 3.51, 2.68, and 9.19, respectively.

Conclusion

Lactulose achieves better small bowel distension for CT enterography studies than the other 3 agents and, therefore, is the preferred oral regimen at our institution.
Models of Artificial Neural Networks Applied to Demand Forecasting in Nonconsolidated Tourist Destinations
Authors: Berenguer Tomás Molinet , Berenguer José Antonio Molinet , García María Elena Betancourt , Pol Alfonso Palmer , Moreno Juan José Montaño
Published: January 2015

This article focuses on a new proposed artificial neural network (ANN) model for tourism demand forecasting using time-series which, unlike previous models, uses different seasons of arrivals and values of months with similar behavior as input variables and achieves a forecast up to a year in advance. We demonstrate the validity and greater precision of the proposed model in forecasting a nonconsolidated destination with marked seasonality, which has been scarcely dealt with in other research. We achieve a comparatively greater quality of results and a longer period in advance than previously used auto-regressive integrated moving average (ARIMA) and ANN models. Highly accurate results were also obtained in destinations such as Portugal, which also proves its validity for mature destinations.
How Dyads Reminiscence Moderates the Relations Between Familiarity, Trust, and Memory Conformity
Authors: Condon Candice E. , Ritchie Timothy D. , Igou Eric R.
Published: January 2015

We examined memory conformity about an experience among dyads. Specifically, we tested the extent to which interpersonal familiarity and trust among dyads predicted their memory conformity to each other, and the extent to which the reminiscence mode (verbal discussion vs. nonverbal revision) moderated these relations. Participants (N = 100) in pairs (dyads = 50) either discussed verbally (discussion dyads = 25) or exchanged their written details nonverbally (revision dyads = 25) about a novel, shared experience in the laboratory. Discussing a new, shared event with a partner (vs. comparing each other’s written testimonies) predicted corrective memory conformity (personal memory improvement) and distortive memory conformity (personal memory errors). The data did not support an alternative model. Results thus suggest that familiarity and trust predict memory conformity, corrective and distortive, but only when people directly discuss their memories about an experience. Implications of these findings are discussed in relation to the two social psychological variables familiarity and trust in the context of memory conformity.
Contact-free sheet resistance determination of large area graphene layers by an open dielectric loaded microwave cavity
Authors: Shaforost O. , Wang K. , Goniszewski S. , Adabi M. , Guo Z. , Hanham S. , Gallop J. , Hao L. , Klein N.
Published: January 2015

A method for contact-free determination of the sheet resistance of large-area and arbitrary shaped wafers or sheets coated with graphene and other (semi) conducting ultrathin layers is described, which is based on an open dielectric loaded microwave cavity. The sample under test is exposed to the evanescent resonant field outside the cavity. A comparison with a closed cavity configuration revealed that radiation losses have no significant influence of the experimental results. Moreover, the microwave sheet resistance results show good agreement with the dc conductivity determined by four-probe van der Pauw measurements on a set of CVD samples transferred on quartz. As an example of a practical application, correlations between the sheet resistance and deposition conditions for CVD graphene transferred on quartz wafers are described. Our method has a high potential as measurement standard for contact-free sheet resistance measurement and mapping of large area graphene samples.
Anisotropy of the Reynolds stress tensor in the wakes of wind turbine arrays in Cartesian arrangements with counter-rotating rotors
Authors: Hamilton Nicholas , Cal Raúl Bayoán
Published: January 2015

A 4 × 3 wind turbine array in a Cartesian arrangement was constructed in a wind tunnel setting with four configurations based on the rotational sense of the rotor blades. The fourth row of devices is considered to be in the fully developed turbine canopy for a Cartesian arrangement. Measurements of the flow field were made with stereo particle-image velocimetry immediately upstream and downstream of the selected model turbines. Rotational sense of the turbine blades is evident in the mean spanwise velocity W and the Reynolds shear stress −vw¯. The flux of kinetic energy is shown to be of greater magnitude following turbines in arrays where direction of rotation of the blades varies. Invariants of the normalized Reynolds stress anisotropy tensor (η and ξ) are plotted in the Lumley triangle and indicate that distinct characters of turbulence exist in regions of the wake following the nacelle and the rotor blade tips. Eigendecomposition of the tensor yields principle components and corresponding coordinate system transformations. Characteristic spheroids representing the balance of components in the normalized anisotropy tensor are composed with the eigenvalues yielding shapes predicted by the Lumley triangle. Rotation of the coordinate system defined by the eigenvectors demonstrates trends in the streamwise coordinate following the rotors, especially trailing the top-tip of the rotor and below the hub. Direction of rotation of rotor blades is shown by the orientation of characteristic spheroids according to principle axes. In the inflows of exit row turbines, the normalized Reynolds stress anisotropy tensor shows cumulative effects of the upstream turbines, tending toward prolate shapes for uniform rotational sense, oblate spheroids for streamwise organization of rotational senses, and a mixture of characteristic shapes when the rotation varies by row. Comparison between the invariants of the Reynolds stress anisotropy tensor and terms from the mean mechanical energy equation indicate correlation between the degree of anisotropy and the regions of the wind turbine wakes where turbulence kinetic energy is produced. The flux of kinetic energy into the momentum-deficit area of the wake from above the canopy is associated with prolate characteristic spheroids. Flux upward into the wake from below the rotor area is associated with oblate characteristic spheroids. Turbulence in the region of the flow directly following the nacelle of the wind turbines demonstrates greater isotropy than regions following the rotor blades. The power and power coefficients for wind turbines indicate that flow structures on the order of magnitude of the spanwise turbine spacing that increase turbine efficiency depending on particular array configuration.
The shapes of simple three and four junction comb polymers
Authors: von Ferber Christian , Bishop Marvin , Forzaglia Thomas , Reid Cooper , Zajac Gregory
Published: January 2015

A scheme originally proposed by G. Wei [Physica A 222, 152 (1995); Physica A 222, 155 (1995)] is redesigned to produce numerical shape parameters of arbitrary tree-branched polymers based on the Kirchhoff matrix eigenvalue spectrum. This method and two different Monte Carlo techniques (pivot and growth) are employed to investigate the asphericity of three and four junction comb polymers in both the ideal and excluded volume regimes. It is found that the extrapolated g-ratio and asphericity values obtained by all of these methods are in excellent agreement with each other and the available theory in the ideal regime and that polymers with a complete set of interior branches display a more sphere-like shape.
Correction of absorption-edge artifacts in polychromatic X-ray tomography in a scanning electron microscope for 3D microelectronics
Authors: Laloum D. , Printemps T. , Lorut F. , Bleuet P.
Published: January 2015

X-ray tomography is widely used in materials science. However, X-ray scanners are often based on polychromatic radiation that creates artifacts such as dark streaks. We show this artifact is not always due to beam hardening. It may appear when scanning samples with high-Z elements inside a low-Z matrix because of the high-Z element absorption edge: X-rays whose energy is above this edge are strongly absorbed, violating the exponential decay assumption for reconstruction algorithms and generating dark streaks. A method is proposed to limit the absorption edge effect and is applied on a microelectronic case to suppress dark streaks between interconnections.
Structural transitions and long-time self-diffusion of interacting colloids confined by a parabolic potential
Authors: Euán-Díaz Edith C. , Herrera-Velarde Salvador , Misko Vyacheslav R. , Peeters François M. , Castañeda-Priego Ramón
Published: January 2015

We report on the ordering and dynamics of interacting colloidal particles confined by a parabolic potential. By means of Brownian dynamics simulations, we find that by varying the magnitude of the trap stiffness, it is possible to control the dimension of the system and, thus, explore both the structural transitions and the long-time self-diffusion coefficient as a function of the degree of confinement. We particularly study the structural ordering in the directions perpendicular and parallel to the confinement. Further analysis of the local distribution of the first-neighbors layer allows us to identify the different structural phases induced by the parabolic potential. These results are summarized in a structural state diagram that describes the way in which the colloidal suspension undergoes a structural re-ordering while increasing the confinement. To fully understand the particle dynamics, we take into account hydrodynamic interactions between colloids; the parabolic potential constricts the available space for the colloids, but it does not act on the solvent. Our findings show a non-linear behavior of the long-time self-diffusion coefficient that is associated to the structural transitions induced by the external field.
Counting graphene layers with very slow electrons
Authors: Frank Ludĕk , Mikmeková Eliška , Müllerová Ilona , Lejeune Michaël
Published: January 2015

The study aimed at collection of data regarding the transmissivity of freestanding graphene for electrons across their full energy scale down to the lowest energies. Here, we show that the electron transmissivity of graphene drops with the decreasing energy of the electrons and remains below 10% for energies below 30 eV, and that the slow electron transmissivity value is suitable for reliable determination of the number of graphene layers. Moreover, electrons incident below 50 eV release adsorbed hydrocarbon molecules and effectively clean graphene in contrast to faster electrons that decompose these molecules and create carbonaceous contamination.
A note on a strongly damped wave equation with fast growing nonlinearities
Authors: Kalantarov Varga , Zelik Sergey
Published: January 2015

A strongly damped wave equation including the displacement depending nonlinear damping term and nonlinear interaction function is considered. The main aim of the note is to show that under the standard dissipativity restrictions on the nonlinearities involved, the initial boundary value problem for the considered equation is globally well-posed in the class of sufficiently regular solutions and the semigroup generated by the problem possesses a global attractor in the corresponding phase space. These results are obtained for the nonlinearities of an arbitrary polynomial growth and without the assumption that the considered problem has a global Lyapunov function.
A general non-Abelian density matrix renormalization group algorithm with application to the C2 dimer
Authors: Sharma Sandeep
Published: January 2015

We extend our previous work [S. Sharma and G. K.-L. Chan, J. Chem. Phys. 136, 124121 (2012)], which described a spin-adapted (SU(2) symmetry) density matrix renormalization group algorithm, to additionally utilize general non-Abelian point group symmetries. A key strength of the present formulation is that the requisite tensor operators are not hard-coded for each symmetry group, but are instead generated on the fly using the appropriate Clebsch-Gordan coefficients. This allows our single implementation to easily enable (or disable) any non-Abelian point group symmetry (including SU(2) spin symmetry). We use our implementation to compute the ground state potential energy curve of the C2 dimer in the cc-pVQZ basis set (with a frozen-core), corresponding to a Hilbert space dimension of 1012 many-body states. While our calculated energy lies within the 0.3 mEh error bound of previous initiator full configuration interaction quantum Monte Carlo and correlation energy extrapolation by intrinsic scaling calculations, our estimated residual error is only 0.01 mEh, much more accurate than these previous estimates. Due to the additional efficiency afforded by the algorithm, the excitation energies (Te) of eight lowest lying excited states: a3Πu, b3Σg−, A1Πu, c3Σu+, B1Δg, B′1Σg+, d3Πg, and C1Πg are calculated, which agree with experimentally derived values to better than 0.06 eV. In addition, we also compute the potential energy curves of twelve states: the three lowest levels for each of the irreducible representations 1Σg+, 1Σu+, 1Σg−, and 1Σu−, to an estimated accuracy of 0.1 mEh of the exact result in this basis.
A first principles approach to the electronic properties of liquid and supercritical CO2
Authors: Cabral Benedito J. Costa , Rivelino Roberto , Coutinho Kaline , Canuto Sylvio
Published: January 2015

The electronic absorption spectra of liquid and supercritical CO2 (scCO2) are investigated by coupling a many-body energy decomposition scheme to configurations generated by Born-Oppenheimer molecular dynamics. A Frenkel exciton Hamiltonian formalism was adopted and the excitation energies were calculated with time dependent density functional theory. A red-shift of ∼ 0.2 eV relative to the gas-phase monomer is observed for the first electronic absorption maximum in liquid and scCO2. The origin of this shift, which is not very dependent on deviations from the linearity of the CO2 molecule, is mainly related to polarization effects. However, the geometry changes of the CO2 monomer induced by thermal effects and intermolecular interactions in condensed phase lead to the appearance of an average monomeric electric dipole moment 〈μ〉 = 0.26 ± 0.04 D that is practically the same at liquid and supercritical conditions. The predicted average quadrupole moment for both liquid and scCO2 is 〈Θ〉 = − 5.5 D Å, which is increased by ∼ −0.9 D Å relative to its gas-phase value. The importance of investigating the electronic properties for a better understanding of the role played by CO2 in supercritical solvation is stressed.
Broadband enhanced transmission of acoustic waves through serrated metal gratings
Authors: Qi Dong-Xiang , Deng Yu-Qiang , Xu Di-Hu , Fan Ren-Hao , Peng Ru-Wen , Chen Ze-Guo , Lu Ming-Hui , Huang X. R. , Wang Mu
Published: January 2015

In this letter, we have demonstrated that serrated metal gratings, which introduce gradient coatings, can give rise to broadband transmission enhancement of acoustic waves. Here, we have experimentally and theoretically studied the acoustic transmission properties of metal gratings with or without serrated boundaries. The average transmission is obviously enhanced for serrated metal gratings within a wide frequency range, while the Fabry-Perot resonance is significantly suppressed. An effective medium hypothesis with varying acoustic impedance is proposed to analyze the mechanism, which was verified through comparison with finite-element simulation. The serrated boundary supplies gradient mass distribution and gradient normal acoustic impedance, which could efficiently reduce the boundary reflection. Further, by increasing the region of the serrated boundary, we present a broadband high-transmission grating for wide range of incident angle. Our results may have potential applications to broadband acoustic imaging, acoustic sensing, and acoustic devices.
Z-scan measurements of the nonlinear refractive index of a pumped semiconductor disk laser gain medium
Authors: Quarterman A. H. , Tyrk M. A. , Wilcox K. G.
Published: January 2015

We measure the nonlinear refractive index of an antiresonant 1050 nm semiconductor disk laser (SDL) gain medium using a reflection-type z-scan system, with a 1064 nm, 10-ps-pulse laser as a probe, and a fiber-coupled 808 nm diode pump laser for carrier injection. Empirically, the nonlinear refractive index is found to depend approximately linearly on applied pump intensity, having a value of −1.5(0.2) × 10−12 cm2/W at zero excitation but increasing to take on positive values at typical SDL operating conditions. The focal lengths of corresponding Kerr lenses calculated using typical SDL pulse intensities and spot sizes are sufficiently short to be comparable to SDL cavity mirrors, implying that Kerr lens modelocking may be responsible for the behavior described in recent reports of self-mode-locked SDLs.
Kelvin probe characterization of buried graphitic microchannels in single-crystal diamond
Authors: Bernardi E. , Battiato A. , Olivero P. , Picollo F. , Vittone E.
Published: January 2015

In this work, we present an investigation by Kelvin Probe Microscopy (KPM) of buried graphitic microchannels fabricated in single-crystal diamond by direct MeV ion microbeam writing. Metal deposition of variable-thickness masks was adopted to implant channels with emerging endpoints and high temperature annealing was performed in order to induce the graphitization of the highly-damaged buried region. When an electrical current was flowing through the biased buried channel, the structure was clearly evidenced by KPM maps of the electrical potential of the surface region overlying the channel at increasing distances from the grounded electrode. The KPM profiling shows regions of opposite contrast located at different distances from the endpoints of the channel. This effect is attributed to the different electrical conduction properties of the surface and of the buried graphitic layer. The model adopted to interpret these KPM maps and profiles proved to be suitable for the electronic characterization of buried conductive channels, providing a non-invasive method to measure the local resistivity with a micrometer resolution. The results demonstrate the potential of the technique as a powerful diagnostic tool to monitor the functionality of all-carbon graphite/diamond devices to be fabricated by MeV ion beam lithography.
Contribution of radicals and ions in catalyzed growth of single-walled carbon nanotubes from low-temperature plasmas
Authors: Marvi Z. , Xu S. , Foroutan G. , Ostrikov K.
Published: January 2015

The growth kinetics of single-walled carbon nanotubes (SWCNTs) in a low-temperature, low-pressure reactive plasma is investigated using a multiscale numerical simulation, including the plasma sheath and surface diffusion modules. The plasma-related effects on the characteristics of SWCNT growth are studied. It is found that in the presence of reactive radicals in addition to energetic ions inside the plasma sheath area, the effective carbon flux, and the growth rate of SWCNT increase. It is shown that the concentration of atomic hydrogen and hydrocarbon radicals in the plasma plays an important role in the SWCNT growth. The effect of the effective carbon flux on the SWCNT growth rate is quantified. The dependence of the growth parameters on the substrate temperature is also investigated. The effects of the plasma sheath parameters on the growth parameters are different in low- and high-substrate temperature regimes. The optimum substrate temperature and applied DC bias are estimated to maximize the growth rate of the single-walled carbon nanotubes.
Array of Cu2O nano-columns fabricated by oblique angle sputter deposition and their application in photo-assisted proton reduction
Authors: Swain S. , Thakur I. , Chatterjee S. , Kulkarni N. A. , Ayyub P. , Chaudhary Y. S.
Published: January 2015

Nano-columnar arrays of Cu2O were grown by the oblique angle sputter deposition technique based on the self-shadowing principle. The as-grown nano-columnar samples are oriented along {111} direction, and they are highly transmitting in the visible range with a low reflectance. In this work, we show the photo-electrochemical activity of nano-columnar array of Cu2O, which shows a higher (∼25%) photocurrent density and a two-fold enhancement in the incident-to-photon conversion efficiency as compared to continuous thin film of Cu2O in photo-assisted proton reduction type reaction. The improvement in electrochemical activity of nano-columnar Cu2O photocathode can be attributed to the change in morphology, crystal structure, as well as electrical property, which shows a higher degree of band bending, increased donor carrier (e−) density and lower width of space charge region as revealed by capacitance measurements and Mott-Schottky analysis.
Oxygen precipitation in 1020 cm−3 germanium-doped Czochralski silicon
Authors: Dong Peng , Zhao Jian , Liang Xingbo , Tian Daxi , Yuan Shuai , Yu Xuegong , Ma Xiangyang , Yang Deren
Published: January 2015

We have investigated the effects of germanium (Ge)-doping at the level of 1020 cm−3 on oxygen precipitation (OP) behaviors in Czochralski (CZ) silicon subjected to different low-high two-step anneals without or with prior high temperature rapid thermal processing (RTP). It is found that Ge-doping remarkably suppresses OP in CZ silicon without prior RTP. However, Ge-doping significantly enhances OP in CZ silicon with prior RTP. The suppressed OP in the case of the absence of prior RTP is primarily due to the fact that the 1020 cm−3 Ge-doping introduces compressive strain into silicon crystal lattice, which increases the critical size of oxygen precipitate nuclei for a given nucleation temperature. Moreover, it is revealed that the 1020 cm−3 Ge-doping facilitates the formation of vacancy-oxygen (V-O) complexes and may introduce Ge-V-O complexes in CZ silicon during high temperature RTP. More vacancy-related complexes in CZ silicon not only reduce the critical size of oxygen precipitate nuclei but also provide more precursors for oxygen precipitate nucleation. Therefore, the 1020 cm−3 Ge-doping enhances OP in CZ silicon subjected to the two-step anneals following high temperature RTP.
Engineering resonance dynamics of plasmon hybridized systems
Authors: Kodigala Ashok , Lepetit Thomas , Kanté Boubacar
Published: January 2015

The ability to control resonances is crucial in advancing applications of plasmonics ranging from chemical and biological sensing at the single molecule level to on-chip communication via fully optical interconnects. To this end, a method employing an effective Hamiltonian formalism is described to study and tailor resonances of plasmonic systems at optical frequencies. Using this method, we compute the complex poles of the scattering matrix and investigate resonance dynamics of coupled plasmonic bars. We show that symmetry breaking, by tailoring near-field interactions in the whole complex plane, provides a very large degree of tunability, including a controllable negative coupling regime.
Charging/discharging behavior and mechanism of silicon quantum dots embedded in amorphous silicon carbide films
Authors: Wen Xixing , Zeng Xiangbin , Zheng Wenjun , Liao Wugang , Feng Feng
Published: January 2015

The charging/discharging behavior of Si quantum dots (QDs) embedded in amorphous silicon carbide (a-SiCx) was investigated based on the Al/insulating layer/Si QDs embedded in a-SiCx/SiO2/p-Si (metal-insulator-quantum dots-oxide-silicon) multilayer structure by capacitance-voltage (C-V) and conductance-voltage (G-V) measurements. Transmission electron microscopy and Raman scattering spectroscopy measurements reveal the microstructure and distribution of Si QDs. The occurrence and shift of conductance peaks indicate the carrier transfer and the charging/discharging behavior of Si QDs. The multilayer structure shows a large memory window of 5.2 eV at ±8 V sweeping voltage. Analysis of the C-V and G-V results allows a quantification of the Coulomb charging energy and the trapped charge density associated with the charging/discharging behavior. It is found that the memory window is related to the size effect, and Si QDs with large size or low Coulomb charging energy can trap two or more electrons by changing the charging voltage. Meanwhile, the estimated lower potential barrier height between Si QD and a-SiCx, and the lower Coulomb charging energy of Si QDs could enhance the charging and discharging effect of Si QDs and lead to an enlarged memory window. Further studies of the charging/discharging mechanism of Si QDs embedded in a-SiCx can promote the application of Si QDs in low-power consumption semiconductor memory devices.
Impact of relative phase shift on inward turbulent spreading
Authors: Ma C. H. , Xu X. Q. , Xi P. W. , Xia T. Y.
Published: January 2015

The relative cross-phase between density, temperature, and potential perturbations plays a major role in turbulent spreading and transport. Nonlinear Landau-Fluid simulations show that the electron wave-particle resonances provide a relatively strong parallel damping effect on the electron temperature perturbation and can induce a relative cross-phase shift of smaller than π∕2 angle between E × B velocity and the electron temperature perturbation for large electron temperature gradient, which yields a large spreading for electron. The relative phase for ions is about π∕2 and has no turbulent spreading effect on it. The inward turbulent spreading stops at the position where the radial turbulent correlation length is shorter than the magnetic surface spacing. The temperature pedestal height determines the energy loss due to the turbulent spreading.
Electrical and structural degradation of GaN high electron mobility transistors under high-power and high-temperature Direct Current stress
Authors: Wu Y. , Chen C.-Y. , del Alamo J. A.
Published: January 2015

We have stressed AlGaN/GaN HEMTs (High Electron Mobility Transistors) under high-power and high-temperature DC conditions that resulted in various levels of device degradation. Following electrical stress, we conducted a well-established three-step wet etching process to remove passivation, gate and ohmic contacts so that the device surface can be examined by SEM and AFM. We have found prominent pits and trenches that have formed under the gate edge on the drain side of the device. The width and depth of the pits under the gate edge correlate with the degree of drain current degradation. In addition, we also found visible erosion under the full extent of the gate. The depth of the eroded region averaged along the gate width under the gate correlated with channel resistance degradation. Both electrical and structural analysis results indicate that device degradation under high-power DC conditions is of a similar nature as in better understood high-voltage OFF-state conditions. The recognition of a unified degradation mechanism provides impetus to the development of a degradation model with lifetime predictive capabilities for a broad range of operating conditions spanning from OFF-state to ON-state.