bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of disjoining pressure in a thin film equation with non-uniform forcing
Authors: MOULTON D. E. , LEGA J.
Published: August 2013

We explore the effect of disjoining pressure on a thin film equation in the presence of a non-uniform body force, motivated by a model describing the reverse draining of a magnetic film. To this end, we use a combination of numerical investigations and analytical considerations. The disjoining pressure has a regularizing influence on the evolution of the system and appears to select a single steady-state solution for fixed height boundary conditions; this is in contrast with the existence of a continuum of locally attracting solutions that exist in the absence of disjoining pressure for the same boundary conditions. We numerically implement matched asymptotic expansions to construct equilibrium solutions and also investigate how they behave as the disjoining pressure is sent to zero. Finally, we consider the effect of the competition between forcing and disjoining pressure on the coarsening dynamics of the thin film for fixed contact angle boundary conditions.
Temporal Patterns of Change in Panic Disorder during Cognitive Behaviour Therapy: An Indian Study
Authors: Manjula M. , Prasadarao P.S.D.V. , Kumaraiah V. , Raguram R.
Published: August 2013

Background: CBT has been proven to be effective in the treatment of panic disorder; however, attempts to study the process of change are limited. Aim: The study evaluated the temporal patterns of change in the panic symptoms, cognitions, behaviours, and anxiety sensitivity in subjects with panic disorder being treated with CBT. Method: Thirty subjects with panic disorder were allocated to two groups: Cognitive Behaviour Therapy (CBT, n = 15) and Behaviour Therapy (BT, n = 15). Assessments were carried out weekly for five consecutive weeks using the Semi-Structured Interview Schedule, the Anxiety Sensitivity Index, the Agoraphobic Cognitions Questionnaire, and the Texas Panic Attack Record Form. The CBT group received comprehensive CBT and the BT group received psycho-education and Applied Relaxation. Results: Following intervention the change was continuous and gradual on all the variables in the CBT group and the scores reduced to a functional range after 4–5 weeks of therapy. Such a change was not evident in the BT group. Significant change was evident in cognitive domains following the introduction of the exposure and cognitive restructuring within the CBT group. Both cognitive and behavioural techniques contributed to the overall change. Conclusion: CBT had an impact on the cognitive domains and significant changes were evident corresponding to the addition of cognitive restructuring and exposure techniques in the 3rd to 5th week. Both cognitive and behavioural components are therefore crucial for overall improvement to occur.
Nurses' knowledge about palliative care in Southeast Iran
Authors: Iranmanesh Sedigheh , Razban Farideh , Tirgari Batool , Zahra Ghazanfari
Published: August 2013

Objective:

Palliative care requires nurses to be knowledgeable about different aspects of the care that they provide for dying patients. This study, therefore, was conducted to examine oncology and intensive care nurses' knowledge about palliative care in Southeast Iran.

Method:

Using the Palliative Care Quiz for Nursing (PCQN), 140 oncology and intensive care unit (ICU) nurses' knowledge about palliative care in three hospitals supervised by Kerman University of Medical Sciences was assessed.

Results:

In PCQN, the mean score was 7.59 (SD: 2.28). The most correct answers were in the category of management of pain and other symptoms (46.07%). The lowest correct answers were in the category of psychosocial and spiritual care (19.3%).

Significance of results:

These findings suggest that nurses' knowledge about palliative care can be improved by establishing specific palliative care units to focus on end-of-life care. This establishment requires incorporation of an end-of-life nursing education curriculum into undergraduate nursing studies.
A Reading of Westcott's Gospel of Creation: An Early Venture into Ecological Theology?
Authors: Reid Duncan
Published: August 2013

In response to the contemporary ecological movement, ecological perspectives have become a significant theme in the theology of creation. This paper asks whether antecedents to this growing significance might predate the concerns of our times and be discernible within the diverse interests of nineteenth-century Anglican thinking. The means used here to examine this possibility is a close reading of B. F. Westcott's ‘Gospel of Creation’. This will be contextualized in two directions: first with reference to the understanding of the natural world in nineteenth-century English popular thought, and secondly with reference to the approach taken to the doctrine of creation by three late twentieth-century Anglican writers, two concerned with the relationship between science and theology in general, and a third concerned more specifically with ecology.
Selbstkontrollstrategien bei hohem wahrgenommenem Stress und hohen Bewegungsbarrieren
Authors: Gerber Markus , Fuchs Reinhard , Pühse Uwe
Published: August 2013

Die Ressourcen der exekutiven Funktionen von Menschen sind begrenzt, weshalb nicht unbeschränkt Energie in die Selbstkontrollfunktion investiert werden kann. Aus sport- und gesundheitspsychologischer Perspektive bedeutet dies, dass chronischer Stress möglicherweise die Kapazität von Personen herabsetzt, die kognitive Kontrolle über ihr Sportverhalten aufrechtzuerhalten. Aufbauend auf den Postulaten des Strength Model of Self-Control wird in der vorliegenden Studie geprüft, ob der häufige Gebrauch spontaner Selbstkontrollstrategien bei 300 Polizeiangestellten (30 % Frauen, M = 41.8 Jahre) mit mehr Sportaktivität einhergeht, wenn sich diese hohem Stress ausgesetzt fühlen oder ein hohes Mass an sportbezogenen Barrieren wahrnehmen. Die Befunde zeigen, dass der spontane Gebrauch von Implementierungsintentionen und Strategien der Intentionsabschirmung mit erhöhter Sportaktivität assoziiert ist. Dieser Zusammenhang scheint jedoch unabhängig vom Stressniveau und den wahrgenommenen Bewegungsbarrieren zu sein. Die Studie unterstützt die Annahme, dass volitionale Selbstkontrollstrategien wie das Formulieren von Handlungsplänen und das Antizipieren von Bewegungsbarrieren und Bewältigungsstrategien bei Polizeiangestellten zur verbesserten Umsetzung gesundheitsbezogener Verhaltensziele beiträgt.
Der Weg von der Persönlichkeit zu sportlichen Leistungen
Authors: Schwinger Malte , Olbricht Stefanie , Stiensmeier-Pelster Joachim
Published: August 2013

In einer Reihe von Studien wurden bedeutsame Zusammenhänge der Big Five Persönlichkeitsfaktoren Extraversion, Neurotizismus, Gewissenhaftigkeit, Verträglichkeit und Offenheit für Erfahrungen mit sportlichen Leistungen berichtet. Gleichwohl ist bislang wenig über die genauen Wirkmechanismen der verschiedenen Persönlichkeitsmerkmale bekannt. In der vorliegenden Arbeit wurde anhand einer Stichprobe von N = 149 Wettkampfschwimmern sowie N = 79 Freizeitschwimmern die Gültigkeit eines hierarchischen Modells, in dem der Zusammenhang zwischen Big Five und sportlichen Leistungen durch habituelle Zielorientierungen sowie spezifische Verhaltensweisen mediiert wird, pfadanalytisch überprüft. Vor allem Gewissenhaftigkeit und Neurotizismus wiesen vielfältige erwartete Zusammenhänge mit Zielorientierungen, Ausdauer und Self-Handicapping auf, welche ihrerseits signifikante Prädiktoren der Schwimmleistungen darstellten. Für Wettkampf- und Freizeitschwimmer zeigten sich differenzielle Wirkmechanismen, was die Wichtigkeit der Berücksichtigung kontextueller Moderatoren in sportpsychologischen Untersuchungen unterstreicht.
Examining the Personal Experience of Aging Scale With the Three Step Test Interview
Authors: Bode Christina , Jansen Harrie
Published: August 2013

A study on aging experience in patients with rheumatic diseases showed low statistical consistency (Cronbach’s alpha) for the Physical Decline subscale of the Personal Experience of Aging Scale whereas the scale functioned very well in preceding surveys. This discrepancy led to the decision to examine the contextual validity of the subscale with a cognitive interview methodology. In the current study we applied the Three Step Test Interview as a cognitive interviewing device to explore misinterpretations and other problems in answering the PD questionnaire items, with the aim of identifying item improvements that might also be beneficial to the statistical quality of the PD subscale. Some problems were identified that were not related to the statistical inter-item correlation rates, nor to the arthritis context of this sample, but were rather due to faulty item formulation. Reformulations were designed to improve the items. The report of this study follows the Cognitive Interviewing Reporting Framework. Experiences with this new guideline are discussed.
Autophagy in Myf5+ progenitors regulates energy and glucose homeostasis through control of brown fat and skeletal muscle development
Authors: Martinez‐Lopez Nuria , Athonvarangkul Diana , Sahu Srabani , Coletto Luisa , Zong Haihong , Bastie Claire C , Pessin Jeffrey E , Schwartz Gary J , Singh Rajat
Published: August 2013

Macroautophagy (MA) regulates cellular quality control and energy balance. For example, loss of MA in aP2‐positive adipocytes converts white adipose tissue (WAT) into brown adipose tissue (BAT)‐like, enhancing BAT function and thereby insulin sensitivity. However, whether MA regulates early BAT development is unknown. We report that deleting Atg7 in myogenic Myf5+ progenitors inhibits MA in Myf5‐cell‐derived BAT and muscle. Knock out (KO) mice have defective BAT differentiation and function. Surprisingly, their body temperature is higher due to WAT lipolysis‐driven increases in fatty acid oxidation in ‘Beige’ cells in inguinal WAT, BAT and muscle. KO mice also present impaired muscle differentiation, reduced muscle mass and glucose intolerance. Our studies show that ATG7 in Myf5+ progenitors is required to maintain energy and glucose homeostasis through effects on BAT and muscle development. Decreased MA in myogenic progenitors with age and/or overnutrition might contribute to the metabolic defects and sarcopenia observed in these conditions.
Exceeding the limit of plasmonic light trapping in textured screen-printed solar cells using Al nanoparticles and wrinkle-like graphene sheets
Authors: Chen Xi , Jia Baohua , Zhang Yinan , Gu Min
Published: August 2013

The solar cell market is predominantly based on textured screen-printed solar cells. Due to parasitic absorption in nanostructures, using plasmonic processes to obtain an enhancement that exceeds 2.5% of the short-circuit photocurrent density is challenging. In this paper, a 7.2% enhancement in the photocurrent density can be achieved through the integration of plasmonic Al nanoparticles and wrinkle-like graphene sheets. For the first time, we experimentally achieve Al nanoparticle-enhanced solar cells. An innovative thermal evaporation method is proposed to fabricate low-coverage Al nanoparticle arrays on solar cells. Due to the ultraviolet (UV) plasmon resonance of Al nanoparticles, the performance enhancement of the solar cells is significantly greater than that from Ag nanoparticles. Subsequently, we deposit wrinkle-like graphene sheets over the Al nanoparticle-enhanced solar cells. Compared with planar graphene sheets, the bend carbon layer also exhibits a broadband light-trapping effect. Our results exceed the limit of plasmonic light trapping in textured screen-printed silicon solar cells.
Establishment of a human skeletal muscle-derived cell line: biochemical, cellular and electrophysiological characterization
Authors: Rokach Ori , Ullrich Nina D. , Rausch Martin , Mouly Vincent , Zhou Haiyan , Muntoni Francesco , Zorzato Francesco , Treves Susan
Published: August 2013

Excitation–contraction coupling is the physiological mechanism occurring in muscle cells whereby an electrical signal sensed by the dihydropyridine receptor located on the transverse tubules is transformed into a chemical gradient (Ca2+ increase) by activation of the ryanodine receptor located on the sarcoplasmic reticulum membrane. In the present study, we characterized for the first time the excitation–contraction coupling machinery of an immortalized human skeletal muscle cell line. Intracellular Ca2+ measurements showed a normal response to pharmacological activation of the ryanodine receptor, whereas 3D-SIM (super-resolution structured illumination microscopy) revealed a low level of structural organization of ryanodine receptors and dihydropyridine receptors. Interestingly, the expression levels of several transcripts of proteins involved in Ca2+ homoeostasis and differentiation indicate that the cell line has a phenotype closer to that of slow-twitch than fast-twitch muscles. These results point to the potential application of such human muscle-derived cell lines to the study of neuromuscular disorders; in addition, they may serve as a platform for the development of therapeutic strategies aimed at correcting defects in Ca2+ homoeostasis due to mutations in genes involved in Ca2+ regulation.
Carbamylation of LDL and its relationship with myeloperoxidase in Type 2 diabetes mellitus
Authors: Shiu Sammy W. M. , Xiao Su-Mei , Wong Ying , Chow Wing-Sun , Lam Karen S. L. , Tan Kathryn C.B.
Published: August 2013

LDL (low-density lipoprotein) is subjected to pro-atherogenic modifications in the circulation. A novel uraemia-independent mechanism of carbamylation of lipoproteins mediated by MPO (myeloperoxidase) has recently been reported. We have investigated whether carbamylation of LDL was increased in patients with Type 2 diabetes without renal impairment and the role of MPO. cLDL (carbamylated LDL) and MPO were measured by ELISA in a cross-sectional study of 198 patients and 174 non-diabetic controls. The impact of lowering MPO on plasma cLDL was determined by assaying cLDL and MPO in archived samples from a previous randomized open-label parallel group study comparing rosiglitazone (n=20) and sulfonylurea (n=24). Both plasma cLDL (P<0.05) and MPO levels (P<0.01) were higher in patients with Type 2 diabetes than controls in the cross-sectional study. Plasma cLDL correlated with MPO (r=0.42 and P<0.01) in subjects with diabetes, and plasma MPO was an independent determinant of plasma cLDL even after adjusting for age, gender, BMI (body mass index), apoB (apolipoprotein B), urea and HbA1c (glycated haemoglobin). In the randomized trial, rosiglitazone significantly lowered MPO (P<0.01) and cLDL (P<0.05), whereas no changes were observed in the sulfonylurea group despite a similar reduction in HbA1c. The magnitude of reduction in plasma cLDL correlated with changes in MPO, but not with HbA1c in the rosiglitazone group, suggesting that lowering MPO reduced plasma cLDL. Plasma cLDL is increased in patients with Type 2 diabetes even in the absence of renal impairment and carbamylation of LDL in these subjects is mainly mediated by MPO and not by urea.
Cross‐layer channel selection and reward‐based power allocation for increasing system capacity and reward in multiple‐input–multiple‐output wireless communications
Authors: Chang Ben‐Jye , Liang Ying‐Hsin , Tsai Tzung‐Shiun
Published: August 2013

For increasing network bandwidth and guaranteeing quality of service in WiMAX, IEEE 802.16 m proposes the multiple‐input–multiple‐output (MIMO) technique that offers compatible specifications with the existing IEEE 802.16 family specifications. However, the performance of the IEEE 802.16 MIMO specification is significantly degraded in the high‐mobility environment and high communication interference. As a result, a sender easily uses inaccurate modulation and coding scheme (MCS) and improper power allocation for different‐priority users having different received signal‐to‐noise ratios. The system capacity is thus affected significantly. Additionally, the multiuser MIMO systems seldom consider that different‐priority users and different‐class traffic bring different rewards to the system. This study thus proposes a cross‐layer reward‐based approach (namely CLR) that consists of three schemes: adaptive modulation and coding determination, cross‐layer dynamic channel selection, and reward‐based weighting power allocation. The proposed CLR approach achieves accurate channel state information determination, optimal channel selection, and adaptive reward power allocation. Numerical results demonstrate that the proposed approach significantly outperforms the other approaches in system reward, system capacity, and the accuracy of the MCS determination.
Modelling and simulation of a generalised vehicle‐to‐vehicle fading channel
Authors: Imran Akram Muhammad , Sheikh Asrar U.
Published: August 2013

This study presents statistical properties of the vehicle‐to‐vehicle Nakagami–Hoyt channel model with diffused line of sight (LOS) under isotropic condition. The envelope and phase probability density functions, spatial‐time autocorrelation function, the power spectral density, level crossing rate, the average duration of fade, squared time autocorrelation function and mean‐square error of time autocorrelation function of the Nakagami–Hoyt channel have been derived under the assumption that both the transmitter and receiver are mobile having omnidirectional antennas and a diffused LOS component is present. The model has been validated using the inverse fast Fourier transform‐based simulator. The simulator and analytical results corroborate.
Practical linear precoder design for finite alphabet multiple‐input multiple‐output orthogonal frequency division multiplexing with experiment validation
Authors: Zheng Yahong Rosa , Wang Mingxi , Zeng Weiliang , Xiao Chengshan
Published: August 2013

A low complexity precoding method is proposed for practical multiple‐input multiple‐output (MIMO) orthogonal frequency‐division multiplexing (OFDM) systems. Based on the two‐step optimal precoder design algorithm that maximises the lower bound of the mutual information with finite‐alphabet inputs, the proposed method simplifies the precoder design by fixing the right singular vectors of the precoder matrix, eliminating the iterative optimisation between the two steps, and discretising the search space of the power allocation vector. For a 4 × 4 channel, the computational complexity of the proposed precoder design is reduced to 3 and 6% of that required by the original two‐step algorithm with quadrature phase shift keying (QPSK) and 8 phase‐shift keying (8PSK), respectively. The proposed method achieves nearly the same mutual information as the two‐step iterative algorithm for a large range of signal‐to‐noise ratio (SNR) region, especially for large MIMO size and/or high constellation systems. The proposed precoding design method is applied to a 2 × 2 MIMO‐OFDM system with 2048 subcarriers by designing 1024 precoders for extended channel matrices of size 4 × 4. A transceiver test bed implements these precoding matrices in comparison with other existing precoding schemes. Indoor experiments are conducted for fixed‐platform non‐line‐of‐sight channels, and the data processing results show that the proposed precoding method achieves the lowest bit error rate compared with maximum diversity, classic water‐filling and channel diagonalisation methods.
Joint bit loading and power allocation for downlink minimum mean square error combining based multi‐carrier code division multiple access systems
Authors: Kuo Yaw‐Wen , Yang Chen‐Kao , Lin Jia‐Hong
Published: August 2013

The performance of a downlink multi‐carrier code‐division multiple‐access (MC‐CDMA) system heavily depends on the receiver type at the user side. The minimum mean square error‐combining scheme possesses the finest performance. However, the resource allocation problem becomes a highly complex task because of multiple access interference. This study investigates a realistic scenario, where the base station determines the bit loading and power for all downlink users with both the power and bit error rate (BER) constraints to maximise the overall system throughput. The authors first derive the instantaneous signal to interference and noise ratio (SINR) and then approximate data transmission as an equivalent M‐QAM system with a signal‐to‐noise ratio (SNR) equal to the instantaneous SINR of that user. Combined with accurate BER formulas of M‐QAM system, the authors estimate the BER for each user given a set of power and bit loading configuration. Finally, the authors develop an iterative joint bit loading and power allocation algorithm to maximise the system throughput. The simulation results show that the proposed solution achieves performance close to the optimal one and maintains the BER close to the desired target.
Performance comparison of chaotic spreading sequences generated by two different classes of chaotic systems in a chaos‐based direct sequence‐code division multiple access system
Authors: Rahnama Nazila , Talebi Siamak
Published: August 2013

In the world of wireless communications, achieving a highly secure transmission at the lowest possible performance degradation has presented a major challenge and a number of conventional direct‐sequence‐code division multiple access (DS‐CDMA)‐based solutions have been put forward that deals with the issue. This study aims to overcome the challenge by introducing a new approach that employs a chaotic sequence in DS‐CDMA system over fading channels. The proposed algorithm, which assumes a perfect sync between the transmitter and the receiver, generates a binary code by using a three‐dimensional (3D) chaotic system. Simulations based on a flat‐fading channel with additive white Gaussian noise and inter‐user interference reveal that the new approach outperforms codes generated by other classes of chaotic systems, that is, the 1D chaotic system. The results also proved the proposition's performance is comparable to conventional pseudo‐noise spreading codes, the Gold code, in several key aspects including security of transmission, bit‐error rate, code generation speed and the number of possible code sequences.
Low‐complexity channel estimation and turbo equalisation for high frequency channels
Authors: Li Qiang , Teh Kah Chan , Li Kwok Hung
Published: August 2013

A low‐complexity channel estimation algorithm is proposed to improve performance of two high frequency standardised waveforms: MIL‐STD‐188‐110B Appendix C standard and STANAG 4285. In the proposed estimation algorithm, the channel impulse response is modelled as a linear‐time function within a frame and the least square criterion is adopted. With the estimated CIRs, the authors study and compare bit‐error‐rate (BER) performance and complexity of three turbo equalisation (TEQ) schemes, including the minimum mean‐square error (MMSE), the MMSE with decision feedback equalisation (DFE) (MMSE‐DFE) and the soft‐feedback interference‐cancellation (SFIC) turbo receivers. The authors then propose a hybrid TEQ scheme that uses the MMSE‐DFE equaliser for the first iteration and the SFIC equaliser for the rest. Simulation results show that the proposed channel estimation algorithm performs well and the TEQ schemes realise a significant performance improvement as compared with a non‐iterative receiver. Moreover, the proposed hybrid TEQ scheme achieves the best trade‐off between BER and complexity for the MIL‐STD‐188‐110B Appendix C standard, whereas the SFIC‐TEQ scheme is optimal for the STANAG 4285 standard.
Proof on the maximal rates of space‐time block codes from complex orthogonal design
Authors: Chen Jun‐Sheng , Wang Jian‐Xin
Published: August 2013

In this study, the authors present a novel proof on the maximal rates of space‐time block codes from complex orthogonal design (COD). The method of the proof is derived from an observation about the CODs, which reveals some inherent laws of their structure. The proof is applicable to any CODs, rather than to some specific designs, and does not need any auxiliary matrix or matrix transformation. The conclusion in this study also indicates that the upper bound of the CODs’ rate conjectured by the authors is tight and achievable.
Maximum Euclidean distance network coded modulation for asymmetric decode‐and‐forward two‐way relaying
Authors: Chen Wei , Cao Zhigang , Hanzo Lajos
Published: August 2013

Network coding (NC) compresses two traffic flows with the aid of low‐complexity algebraic operations, hence holds the potential of significantly improving both the efficiency of wireless two‐way relaying, where each receiver is collocated with a transmitter and hence has prior knowledge of the message intended for the distant receiver. In this contribution, network coded modulation (NCM) is proposed for jointly performing NC and modulation. As in classic coded modulation, the Euclidean distance between the symbols is maximised, hence the symbol error probability is minimised. Specifically, the authors first propose set‐partitioning‐based NCM as an universal concept which can be combined with arbitrary constellations. Then the authors conceive practical phase‐shift keying/quadrature amplitude modulation (PSK/QAM) NCM schemes, referred to as network coded PSK/QAM, based on modulo addition of the normalised phase/amplitude. To achieve a spatial diversity gain at a low complexity, a NC oriented maximum ratio combining scheme is proposed for combining the network coded signal and the original signal of the source. An adaptive NCM is also proposed to maximise the throughput while guaranteeing a target bit error probability (BEP). Both theoretical performance analysis and simulations demonstrate that the proposed NCM can achieve at least 3 dB signal‐to‐noise ratio gain and two times diversity gain.
Dissociative electron attachment to DNA-diamine thin films: Impact of the DNA close environment on the OH− and O− decay channels
Authors: Boulanouar Omar , Fromm Michel , Mavon Christophe , Cloutier Pierre , Sanche Léon
Published: August 2013

We measure the desorption of anions stimulated by the impact of 0–20 eV electrons on highly uniform thin films of plasmid DNA-diaminopropane. The results are accurately correlated with film thickness and composition by AFM and XPS measurements, respectively. Resonant structures in the H−, O−, and OH− yield functions are attributed to the decay of transient anions into the dissociative electron attachment (DEA) channel. The diamine induces ammonium-phosphate bridges along the DNA backbone, which suppresses the DEA O− channel and in counter-part increases considerably the desorption of OH−. The close environment of the phosphate groups may therefore play an important role in modulating the rate and type of DNA damages induced by low energy electrons.
2D IR spectra of cyanide in water investigated by molecular dynamics simulations
Authors: Lee Myung Won , Carr Joshua K. , Göllner Michael , Hamm Peter , Meuwly Markus
Published: August 2013

Using classical molecular dynamics simulations, the 2D infrared (IR) spectroscopy of CN− solvated in D2O is investigated. Depending on the force field parametrizations, most of which are based on multipolar interactions for the CN− molecule, the frequency-frequency correlation function and observables computed from it differ. Most notably, models based on multipoles for CN− and TIP3P for water yield quantitatively correct results when compared with experiments. Furthermore, the recent finding that T1 times are sensitive to the van der Waals ranges on the CN− is confirmed in the present study. For the linear IR spectrum, the best model reproduces the full widths at half maximum almost quantitatively (13.0 cm−1 vs. 14.9 cm−1) if the rotational contribution to the linewidth is included. Without the rotational contribution, the lines are too narrow by about a factor of two, which agrees with Raman and IR experiments. The computed and experimental tilt angles (or nodal slopes) α as a function of the 2D IR waiting time compare favorably with the measured ones and the frequency fluctuation correlation function is invariably found to contain three time scales: a sub-ps, 1 ps, and one on the 10-ps time scale. These time scales are discussed in terms of the structural dynamics of the surrounding solvent and it is found that the longest time scale (≈10 ps) most likely corresponds to solvent exchange between the first and second solvation shell, in agreement with interpretations from nuclear magnetic resonance measurements.
Treatment of scalar-relativistic effects on nuclear magnetic shieldings using a spin-free exact-two-component approach
Authors: Cheng Lan , Gauss Jürgen , Stanton John F.
Published: August 2013

A cost-effective treatment of scalar-relativistic effects on nuclear magnetic shieldings based on the spin-free exact-two-component theory in its one-electron variant (SFX2C-1e) is presented. The SFX2C-1e scheme gains its computational efficiency, in comparison to the four-component approach, from a focus on spin-free contributions and from the elimination of the small component. For the calculation of nuclear magnetic shieldings, the separation of spin-free and spin-dependent terms in the parent four-component theory is carried out here for the matrix representation of the Dirac equation in terms of a restricted-magnetically balanced gauge-including atomic orbital basis. The resulting spin-free four-component matrix elements required to calculate nuclear magnetic shieldings are then used to construct the corresponding SFX2C-1e Hamiltonian and its perturbed counterpart in the context of SFX2C-1e analytic derivative theory. To demonstrate the applicability of the approach, we report coupled-cluster calculations for prototypical problems such as the 17O shieldings of transition-metal oxo complexes (\documentclass[12pt]{minimal}\begin{document}${\rm MO}_4^{2-}$\end{document} MO 42−, M = Cr, Mo, and W) and the 129Xe shieldings of xenon fluorides (XeF2, XeF4, and XeF6).
Equilibrium theory of the hard sphere fluid and glasses in the metastable regime up to jamming. I. Thermodynamics
Authors: Jadrich Ryan , Schweizer Kenneth S.
Published: August 2013

We formulate and apply a non-replica equilibrium theory for the fluid-glass transition, glass thermodynamic properties, and jamming of hard spheres in three and all higher spatial dimensions. Numerical predictions for the zero complexity glass transition and jamming packing fractions, and a “densest” equilibrium glass, are made. The equilibrium glass equation of state is regarded as the practical continuation of its fluid analog up to jamming. The analysis provides a possible resolution to the inability of any fluid virial series re-summation based equation of state to capture jamming at a reasonable volume fraction. The numerical results are quantitatively compared with various simulation data for equilibrium hard sphere glasses in 3 to 12 dimensions. Although there are uncertainties in this comparison, the predicted zero complexity or configurational entropy and corresponding jamming packing fractions do agree well with two characteristic packing fractions deduced from the dynamic simulation data. The similarities and differences of our approach compared to the replica approach are discussed. The high dimensional scaling of the equilibrium glass transition and jamming volume fractions are also derived. The developments in this paper serve as input to Paper II [R. Jadrich and K. S. Schweizer, J. Chem. Phys. 139, 054502 (2013)10.1063/1.4816276] that constructs a self-consistent integral equation theory of the 3-dimensional hard sphere pair structure, in real and Fourier space, in the metastable regime up to jamming. The latter is employed as input to a microscopic dynamical theory of single particle activated barrier hopping.
Equilibrium theory of the hard sphere fluid and glasses in the metastable regime up to jamming. II. Structure and application to hopping dynamics
Authors: Jadrich Ryan , Schweizer Kenneth S.
Published: August 2013

Building on the equation-of-state theory of Paper I, we construct a new thermodynamically consistent integral equation theory for the equilibrium pair structure of 3-dimensional monodisperse hard spheres applicable up to the jamming transition. The approach is built on a two Yukawa generalized mean spherical approximation closure for the direct correlation function (DCF) beyond contact that reproduces the exact contact value of the pair correlation function and isothermal compressibility. The detailed construction of the DCF is guided by the desire to capture its distinctive features as jamming is approached. Comparison of the theory with jamming limit simulations reveals good agreement for many, but not all, of the key features of the pair correlation function. The theory is more accurate in Fourier space where predictions for the structure factor and DCF are accurate over a wide range of wavevectors from significantly below the first cage peak to very high wavevectors. New features of the equilibrium pair structure are predicted for packing fractions below jamming but well above crystallization. For example, the oscillatory DCF decays very slowly at large wavevectors for high packing fractions as a consequence of the unusual structure of the radial distribution function at small separations. The structural theory is used as input to the nonlinear Langevin equation theory of activated dynamics, and calculations of the alpha relaxation time based on single particle hopping are compared to recent colloid experiments and simulations at very high volume fractions.
Linear stability and acoustic characteristics of compressible, viscous, subsonic coaxial jet flow
Authors: Gloor Michael , Obrist Dominik , Kleiser Leonhard
Published: August 2013

This study explores the parameter influence on the linear stability characteristics of viscous compressible coaxial jet flow at subsonic flow velocities. We study the impact of parameters on the disturbance development, such as the Reynolds number, Mach number, momentum thickness, temperature and velocity ratio between bypass flow and core stream as well as the influence of the azimuthal wavenumber. In addition to the discussion on the unstable modes, we also investigate the properties of acoustic (radiating) modes which are relevant for sound propagation to the acoustic far-field. By analyzing the eigenfunction profiles of the acoustic modes, we identify a possible interaction mechanism between the shear layer and the acoustic modes.
A convergent reaction-diffusion master equation
Authors: Isaacson Samuel A.
Published: August 2013

The reaction-diffusion master equation (RDME) is a lattice stochastic reaction-diffusion model that has been used to study spatially distributed cellular processes. The RDME is often interpreted as an approximation to spatially continuous models in which molecules move by Brownian motion and react by one of several mechanisms when sufficiently close. In the limit that the lattice spacing approaches zero, in two or more dimensions, the RDME has been shown to lose bimolecular reactions. The RDME is therefore not a convergent approximation to any spatially continuous model that incorporates bimolecular reactions. In this work we derive a new convergent RDME (CRDME) by finite volume discretization of a spatially continuous stochastic reaction-diffusion model popularized by Doi. We demonstrate the numerical convergence of reaction time statistics associated with the CRDME. For sufficiently large lattice spacings or slow bimolecular reaction rates, we also show that the reaction time statistics of the CRDME may be approximated by those from the RDME. The original RDME may therefore be interpreted as an approximation to the CRDME in several asymptotic limits.
Volume of mixing effect on fluid counter-diffusion
Authors: Orsi Gianni , Mauri Roberto
Published: August 2013

The counter-current diffusion-driven mixing process of two miscible fluids is studied in the absence of gravity, assuming that the mixture is non-regular, that is its volume is smaller than the sum of the initial volumes of the two components. Two competing effects are present in the mixing region: on one hand, the mass flow rate of each species increases, due to the larger density of the fluid; on the other hand, though, the volumetric flux is retarded by the inward convection due to volume disappearance, which opposes the outward velocity field due to diffusion. This intuition is confirmed by the analytical result of a 1D non-ideal mixing process, showing that, in the presence of the convection induced by a volume decrease: (a) the process is self-similar; (b) the mass flux of each species at the interface increases by approximately 0.8ε, where ε is the maximum relative volume decrease; and (c) the volume flux of each species decreases by approximately a 0.2ε amount. This result is further confirmed by a perturbation analysis for small ε.
Instabilities and waves on a columnar vortex in a strongly stratified and rotating fluid
Authors: Park Junho , Billant Paul
Published: August 2013

This paper investigates the effect of the background rotation on the radiative instability of a columnar Rankine vortex in a strongly stratified fluid. We show that a cyclonic background rotation strongly stabilizes the radiative instability. The modes become neutral when the Rossby number Ro is below a critical value which depends on the azimuthal wavenumber of the wave. In the limit of small Rossby number, there exist fast neutral waves that are not captured by the quasi-geostrophic theory. In the presence of anticyclonic background rotation, the centrifugal instability dominates the radiative instability only when −400 ≲ Ro < −1. The numerical stability analysis is completed by asymptotic analyses for large wavenumbers which explain the properties and mechanisms of the waves and the instabilities. The stability of a continuous smoothed Rankine vortex is also investigated. The most amplified azimuthal wavenumber is then finite instead of infinite for the Rankine vortex.
Competition between CoOx and CoPt phases in Pt/Co/AlOx semi tunnel junctions
Authors: Garad H. , Ortega L. , Ramos A. Y. , Joly Y. , Fettar F. , Auffret S. , Rodmacq B. , Diény B. , Proux O. , Erko A. I.
Published: August 2013

We report on the evolution of the structure and composition of a Pt(3 nm)/Co(0.6 nm)/AlOx(2 nm) trilayer sputtered on Si/SiO2 under oxidation and annealing processes by combined x-ray reflectivity and x-ray absorption studies. We describe the progressive and inhomogeneous oxidation of the layers by increasing the oxidation time. Before annealing, the layers have lower density than bulk samples and noticeable roughness. After thermal annealing, a significant improvement of the quality of the alumina layer goes along with the formation of a CoPt alloy that reduces the number of Co-O bonds. These structural outcomes clarify the evolution of the magnetic and transport properties reported at room temperature in these samples.
Orbital-optimized coupled-electron pair theory and its analytic gradients: Accurate equilibrium geometries, harmonic vibrational frequencies, and hydrogen transfer reactions
Authors: Bozkaya Uğur , Sherrill C. David
Published: August 2013

Orbital-optimized coupled-electron pair theory [or simply “optimized CEPA(0),” OCEPA(0), for short] and its analytic energy gradients are presented. For variational optimization of the molecular orbitals for the OCEPA(0) method, a Lagrangian-based approach is used along with an orbital direct inversion of the iterative subspace algorithm. The cost of the method is comparable to that of CCSD [O(N6) scaling] for energy computations. However, for analytic gradient computations the OCEPA(0) method is only half as expensive as CCSD since there is no need to solve the λ2-amplitude equation for OCEPA(0). The performance of the OCEPA(0) method is compared with that of the canonical MP2, CEPA(0), CCSD, and CCSD(T) methods, for equilibrium geometries, harmonic vibrational frequencies, and hydrogen transfer reactions between radicals. For bond lengths of both closed and open-shell molecules, the OCEPA(0) method improves upon CEPA(0) and CCSD by 25%–43% and 38%–53%, respectively, with Dunning's cc-pCVQZ basis set. Especially for the open-shell test set, the performance of OCEPA(0) is comparable with that of CCSD(T) (ΔR is 0.0003 Å on average). For harmonic vibrational frequencies of closed-shell molecules, the OCEPA(0) method again outperforms CEPA(0) and CCSD by 33%–79% and 53%–79%, respectively. For harmonic vibrational frequencies of open-shell molecules, the mean absolute error (MAE) of the OCEPA(0) method (39 cm−1) is fortuitously even better than that of CCSD(T) (50 cm−1), while the MAEs of CEPA(0) (184 cm−1) and CCSD (84 cm−1) are considerably higher. For complete basis set estimates of hydrogen transfer reaction energies, the OCEPA(0) method again exhibits a substantially better performance than CEPA(0), providing a mean absolute error of 0.7 kcal mol−1, which is more than 6 times lower than that of CEPA(0) (4.6 kcal mol−1), and comparing to MP2 (7.7 kcal mol−1) there is a more than 10-fold reduction in errors. Whereas the MAE for the CCSD method is only 0.1 kcal mol−1 lower than that of OCEPA(0). Overall, the present application results indicate that the OCEPA(0) method is very promising not only for challenging open-shell systems but also for closed-shell molecules.
Dynamics of the D+ + H2 → HD + H+ reaction at the low energy regime by means of a statistical quantum method
Authors: González-Lezana Tomás , Honvault Pascal , Scribano Yohann
Published: August 2013

The D+ +H2(v = 0, j = 0, 1) → HD+H+ reaction has been investigated at the low energy regime by means of a statistical quantum mechanical (SQM) method. Reaction probabilities and integral cross sections (ICSs) between a collisional energy of 10−4 eV and 0.1 eV have been calculated and compared with previously reported results of a time independent quantum mechanical (TIQM) approach. The TIQM results exhibit a dense profile with numerous narrow resonances down to Ec ∼ 10−2 eV and for the case of H2(v = 0, j = 0) a prominent peak is found at ∼2.5 × 10−4 eV. The analysis at the state-to-state level reveals that this feature is originated in those processes which yield the formation of rotationally excited HD(v′ = 0, j′ > 0). The statistical predictions reproduce reasonably well the overall behaviour of the TIQM ICSs at the larger energy range (Ec ⩾ 10−3 eV). Thermal rate constants are in qualitative agreement for the whole range of temperatures investigated in this work, 10–100 K, although the SQM values remain above the TIQM results for both initial H2 rotational states, j = 0 and 1. The enlargement of the asymptotic region for the statistical approach is crucial for a proper description at low energies. In particular, we find that the SQM method leads to rate coefficients in terms of the energy in perfect agreement with previously reported measurements if the maximum distance at which the calculation is performed increases noticeably with respect to the value employed to reproduce the TIQM results.
Mechanism of controlling supersonic cavity oscillations using upstream mass injection
Authors: Li Weipeng , Nonomura Taku , Fujii Kozo
Published: August 2013

The mechanism of controlling supersonic cavity oscillations using upstream mass injection is investigated by implicit large-eddy simulations of a turbulent flow (M∞ = 2.0, ReD = 105) past a rectangular cavity with a length-to-depth ratio of 2. The mass injection is simulated by specifying a vertical velocity profile of a jet ejecting steadily through a slot placed at the upstream of the cavity leading edge. The results show that the steady upstream mass injection produces significant attenuation of the cavity oscillations, and two primary mechanisms are demonstrated to be directly responsible for the noise suppression: lifting up of the cavity shear layer, and damping of the shear-layer instability. It is found that the case of low mass flow injection investigated is more effective in stabilizing the cavity shear layer than the high mass flow injection. A transition stage might exist between two well-developed oscillating modes, but “mode-switching” is not observed.
Molecular theory for the phase equilibria and cluster distribution of associating fluids with small bond angles
Authors: Marshall Bennett D. , Chapman Walter G.
Published: August 2013

We develop a new theory for associating fluids with multiple association sites. The theory accounts for small bond angle effects such as steric hindrance, ring formation, and double bonding. The theory is validated against Monte Carlo simulations for the case of a fluid of patchy colloid particles with three patches and is found to be very accurate. Once validated, the theory is applied to study the phase diagram of a fluid composed of three patch colloids. It is found that bond angle has a significant effect on the phase diagram and the very existence of a liquid–vapor transition.
Acidic pH retards the fibrillization of human islet amyloid polypeptide due to electrostatic repulsion of histidines
Authors: Li Yang , Xu Weixin , Mu Yuguang , Zhang John Z. H.
Published: August 2013

The human Islet Amyloid Polypeptide (hIAPP) is the major constituent of amyloid deposits in pancreatic islets of type-II diabetes. IAPP is secreted together with insulin from the acidic secretory granules at a low pH of approximately 5.5 to the extracellular environment at a neutral pH. The increased accumulation of extracellular hIAPP in diabetes indicates that changes in pH may promote amyloid formation. To gain insights and underlying mechanisms of the pH effect on hIAPP fibrillogenesis, all-atom molecular dynamics simulations in explicit solvent model were performed to study the structural properties of five hIAPP protofibrillar oligomers, under acidic and neutral pH, respectively. In consistent with experimental findings, simulation results show that acidic pH is not conducive to the structural stability of these oligomers. This provides a direct evidence for a recent experiment [L. Khemtemourian, E. Domenech, J. P. F. Doux, M. C. Koorengevel, and J. A. Killian, J. Am. Chem. Soc. 133, 15598 (2011)]10.1021/ja205007j, which suggests that acidic pH inhibits the fibril formation of hIAPP. In addition, a complementary coarse-grained simulation shows the repulsive electrostatic interactions among charged His18 residues slow down the dimerization process of hIAPP by twofold. Besides, our all-atom simulations reveal acidic pH mainly affects the local structure around residue His18 by destroying the surrounding hydrogen-bonding network, due to the repulsive interactions between protonated interchain His18 residues at acidic pH. It is also disclosed that the local interactions nearby His18 operating between adjacent β-strands trigger the structural transition, which gives hints to the experimental findings that the rate of hIAPP fibril formation and the morphologies of the fibrillar structures are strongly pH-dependent.
A variational method for density functional theory calculations on metallic systems with thousands of atoms
Authors: Ruiz-Serrano Álvaro , Skylaris Chris-Kriton
Published: August 2013

A new method for finite-temperature density functional theory calculations which significantly increases the number of atoms that can be simulated in metallic systems is presented. A self-consistent, direct minimization technique is used to obtain the Helmholtz free energy of the electronic system, described in terms of a set of non-orthogonal, localized functions which are optimized in situusing a periodic-sinc basis set, equivalent to plane waves. Most parts of the calculation, including the demanding operation of building the Hamiltonian matrix, have a computational cost that scales linearly with the number of atoms in the system. Also, this approach ensures that the Hamiltonian matrix has a minimal size, which reduces the computational overhead due to diagonalization, a cubic-scaling operation that is still required. Large basis set accuracy is retained via the optimization of the localized functions. This method allows accurate simulations of entire metallic nanostructures, demonstrated with calculations on a supercell of bulk copper with 500 atoms and on gold nanoparticles with up to 2057 atoms.