bluuebunny/crossref_metadata_2025 huggingface dataset:
Tetrel bond of pseudohalide anions with XH3F (X = C, Si, Ge, and Sn) and its role in SN2 reaction
Authors: Liu Mingxiu , Li Qingzhong , Cheng Jianbo , Li Wenzuo , Li Hai-Bei
Published: December 2016

The complexes of XH3F⋯N3−/OCN−/SCN− (X = C, Si, Ge, and Sn) have been investigated at the MP2/aug-cc-pVTZ(PP) level. The σ-hole of X atom in XH3F acts as a Lewis acid forming a tetrel bond with pseudohalide anions. Interaction energies of these complexes vary from −8 to −50 kcal/mol, mainly depending on the nature of X and pseudohalide anions. Charge transfer from N/O/S lone pair to X–F and X–H σ* orbitals results in the stabilization of these complexes, and the former orbital interaction is responsible for the large elongation of X–F bond length and the remarkable red shift of its stretch vibration. The tetrel bond in the complexes of XH3F (X = Si, Ge, and Sn) exhibits a significant degree of covalency with XH3F distorted significantly in these complexes. A breakdown of the individual forces involved attributes the stability of the interaction to mainly electrostatic energy, with a relatively large contribution from polarization. The transition state structures that connect the two minima for CH3Br⋯N3− complex have been localized and characterized. The energetic, geometrical, and topological parameters of the complexes were analyzed in the different stages of the SN2 reaction N3− + CH3Br → Br− + CH3N3.
Dynamics of single semiflexible polymers in dilute solution
Authors: Nikoubashman Arash , Milchev Andrey , Binder Kurt
Published: December 2016

We study the dynamics of a single semiflexible chain in solution using computer simulations, where we systematically investigate the effect of excluded volume, chain stiffness, and hydrodynamic interactions. We achieve excellent agreement with previous theoretical considerations, but find that the crossover from the time τb, up to which free ballistic motion of the monomers describes the chain dynamics, to the times W−1 or τ0, where anomalous monomer diffusion described by Rouse-type and Zimm-type models sets in, requires two decades of time. While in the limit of fully flexible chains the visibility of the anomalous diffusion behavior is thus rather restricted, the t3/4 power law predicted for stiff chains without hydrodynamic interactions is verified. Including hydrodynamics, evidence for the predicted [tln(t)]3/4 behavior is obtained. Similar good agreement with previous theoretical predictions is found for the decay of the bond autocorrelation functions and the end-to-end vector correlation. Finally, several predictions on the variation of characteristic relaxation times with persistence length describing the chain stiffness are tested.
Resonantly induced transparency for metals with low angular dependence
Authors: Camacho Miguel , Hibbins Alastair P. , Sambles J. Roy
Published: December 2016

Thin (sub skin-depth) metal layers are known to almost completely reflect radiation at microwave frequencies. It has previously been shown that this can be overcome at resonance via the addition of closely spaced periodic structures on either side of the film. In this work, we have extended the original one-dimensional impedance mechanism to the use of two-dimensional periodic structures both experimentally and analytically using an equivalent circuit approach. The resulting device shows experimentally a low (<5% relative frequency shift) dependence in both angle of incidence and polarisation. We also show that the same principle can be used to transmit through a thicker (∼μm) perfectly conducting film perforated with a non-diffracting (short pitch) array of subwavelength holes with the cut-off frequency above 900 GHz showing resonant transmissivities in the 20–30 GHz range above 40%.
Perspective: Methods for large-scale density functional calculations on metallic systems
Authors: Aarons Jolyon , Sarwar Misbah , Thompsett David , Skylaris Chris-Kriton
Published: December 2016

Current research challenges in areas such as energy and bioscience have created a strong need for Density Functional Theory (DFT) calculations on metallic nanostructures of hundreds to thousands of atoms to provide understanding at the atomic level in technologically important processes such as catalysis and magnetic materials. Linear-scaling DFT methods for calculations with thousands of atoms on insulators are now reaching a level of maturity. However such methods are not applicable to metals, where the continuum of states through the chemical potential and their partial occupancies provide significant hurdles which have yet to be fully overcome. Within this perspective we outline the theory of DFT calculations on metallic systems with a focus on methods for large-scale calculations, as required for the study of metallic nanoparticles. We present early approaches for electronic energy minimization in metallic systems as well as approaches which can impose partial state occupancies from a thermal distribution without access to the electronic Hamiltonian eigenvalues, such as the classes of Fermi operator expansions and integral expansions. We then focus on the significant progress which has been made in the last decade with developments which promise to better tackle the length-scale problem in metals. We discuss the challenges presented by each method, the likely future directions that could be followed and whether an accurate linear-scaling DFT method for metals is in sight.
Conformational analysis of ethyl-substituted Criegee intermediate by FTMW spectroscopy
Authors: Cabezas Carlos , Guillemin Jean-Claude , Endo Yasuki
Published: December 2016

Ethyl-substituted Criegee intermediate, C2H5CHOO, has been generated in the discharged plasma of a 1,1-diiodopropane/O2 gas mixture and spectroscopically characterized by Fourier transform microwave spectroscopy in a pulsed supersonic jet. The comparison between the experimental rotational constants and those calculated ab initio unambiguously confirms the identification of three conformers, providing the definitive probe for their molecular structures. Some of the observed pure rotational transitions show small splittings corresponding to the A/E components due to the threefold methyl internal rotation, which made it possible to determine the barrier heights of the hindered methyl rotation. The conformational abundances as well as the non observation of a plausible fourth conformer have been rationalized in terms of interconversion processes between conformers and interactions between the terminal oxygen and the protons of the ethyl moiety.
KP flows and quantization
Authors: Luu Martin T.
Published: December 2016

The quantization of a pair of commuting differential operators is a pair of non-commuting differential operators. Both at the classical and quantum levels, the flows of the Kadomtsev-Petviashvili (KP) hierarchy are defined and further one can consider switching, up to a sign, the ordering of the operators. We discuss the interaction of these operations with the quantization.
A simple method for activating the platelets used in microfluidic platelet aggregation tests: Stirring-induced platelet activation
Authors: Lee Hoyoon , Kim Gyehyu , Lim Chaeseung , Lee ByoungKwon , Shin Sehyun
Published: December 2016

High-shear stimulation is well known as one of the key factors affecting platelet activation and aggregation, which can lead to the formation of a thrombus. In one of our previous studies, we introduced migration distance-based platelet function analysis in a microfluidic system. In this study, we set out to examine the effects of stirring on shear-induced platelet activation and aggregation in a chamber system by using a rotating stirrer. We found that the rotating stirrer caused not only rotational shear flow but also a strong radial secondary flow. The latter flow led to efficient mixing in the chamber. Moreover, the rotational flow led to the generation of shear stress, the magnitude of which can be controlled to activate the platelets. Activated platelets tend to aggregate themselves. The maximum platelet aggregation was observed at a critical shear rate of 3100 s−1, regardless of the stirrer shape. Furthermore, the time taken to attain maximum aggregation was significantly shortened when using a wide stirrer (30 s) instead of a narrow one (180 s). When using a flat stirrer, the non-uniform shear field in the chamber system was resolved with the radial secondary flow-induced mixing; thus, most of the platelets were homogenously activated. The stirring-induced platelet activation mechanism was experimentally confirmed in a microfluidic system for a platelet aggregation test while monitoring the migration distance until the microfluidic channel is occluded. Our findings indicate that the present system, consisting of a rotating stirrer and a confined chamber, provides effective shear stimulation for activating platelets and inducing platelet aggregates.
Parallel electric fields are inefficient drivers of energetic electrons in magnetic reconnection
Authors: Dahlin J. T. , Drake J. F. , Swisdak M.
Published: December 2016

We present two-dimensional kinetic simulations, with a broad range of initial guide fields, which isolate the role of parallel electric fields (E∥) in energetic electron production during collisionless magnetic reconnection. In the strong guide field regime, E∥ drives essentially all of the electron energy gains, yet fails to generate an energetic component. We suggest that this is due to the weak energy scaling of particle acceleration from E∥ compared to that of a Fermi-type mechanism responsible for energetic electron production in the weak guide-field regime. This result has important implications for energetic electron production in astrophysical systems and reconnection-driven dissipation in turbulence.
Diffraction studies for stoichiometry effects in BaTiO3 grown by molecular beam epitaxy on Ge(001)
Authors: Hsu Min-Hsiang Mark , Merckling Clement , El Kazzi Salim , Pantouvaki Marianna , Richard Oliver , Bender Hugo , Meersschaut Johan , Van Campenhout Joris , Absil Philippe , Van Thourhout Dries
Published: December 2016

In this work, we present a systematic study of the effect of the stoichiometry of BaTiO3 (BTO) films grown on the Ge(001) substrate by molecular-beam-epitaxy using different characterization methods relying on beam diffraction, including reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD), and selected-area electron diffraction in transmission electron microscopy. Surprisingly, over a wide range of [Ba]/[Ti] ratios, as measured by the Rutherford backscattering spectrometry, all the BTO layers exhibit the same epitaxial relationship 〈100〉BTO(001)//〈110〉Ge(001) with the substrate, describing a 45° lattice rotation of the BTO lattice with respect to the Ge lattice. However, varying the [Ba]/[Ti] ratio does change the diffraction behavior. From RHEED patterns, we can derive that excessive [Ba] and [Ti] generate twinning planes and a rougher surface in the non-stoichiometric BTO layers. XRD allows us to follow the evolution of the lattice constants as a function of the [Ba]/[Ti] ratio, providing an option for tuning the tetragonality of the BTO layer. In addition, we found that the intensity ratio of the 3 lowest-order Bragg peaks I(001)/I(002), I(101)/I(002), and I(111)/I(002) derived from ω − 2θ scans characteristically depend on the BTO stoichiometry. To explain the relation between observed diffraction patterns and the stoichiometry of the BTO films, we propose a model based on diffraction theory explaining how excess [Ba] or [Ti] in the layer influences the diffraction response.
A metamaterial electromagnetic energy rectifying surface with high harvesting efficiency
Authors: Duan Xin , Chen Xing , Zhou Lin
Published: December 2016

A novel metamaterial rectifying surface (MRS) for electromagnetic energy capture and rectification with high harvesting efficiency is presented. It is fabricated on a three-layer printed circuit board, which comprises an array of periodic metamaterial particles in the shape of mirrored split rings, a metal ground, and integrated rectifiers employing Schottky diodes. Perfect impedance matching is engineered at two interfaces, i.e. one between free space and the surface, and the other between the metamaterial particles and the rectifiers, which are connected through optimally positioned vias. Therefore, the incident electromagnetic power is captured with almost no reflection by the metamaterial particles, then channeled maximally to the rectifiers, and finally converted to direct current efficiently. Moreover, the rectifiers are behind the metal ground, avoiding the disturbance of high power incident electromagnetic waves. Such a MRS working at 2.45 GHz is designed, manufactured and measured, achieving a harvesting efficiency up to 66.9% under an incident power density of 5 mW/cm2, compared with a simulated efficiency of 72.9%. This high harvesting efficiency makes the proposed MRS an effective receiving device in practical microwave power transmission applications.
Cooling achieved by rotating an anisotropic superconductor in a constant magnetic field: A new perspective
Authors: Phan Manh-Huong , Mandrus David
Published: December 2016

A new type of rotary coolers based on the temperature change (ΔTrot) of an anisotropic superconductor when rotated in a constant magnetic field is proposed. We show that at low temperature the Sommerfeld coefficient γ(B,Θ) of a single crystalline superconductor, such as MgB2 and NbS2, sensitively depends on the applied magnetic field (B) and the orientation of the crystal axis (Θ), which is related to the electronic entropy (SE) and temperature (T) via the expression: SE=γT. A simple rotation of the crystal from one axis to one another in a constant magnetic field results in a change in γ and hence SE: ΔSE=ΔγT. A temperature change −ΔTrot ∼ 0.94 K from a bath temperature of 2.5 K is achieved by simply rotating the single crystal MgB2 by 90° with respect to the c-axis direction in a fixed field of 2 T. ΔTrot can be tuned by adjusting the strength of B within a wide magnetic field range. Our study paves the way for development of new materials and cryogenic refrigerators that are potentially more energy-efficient, simplified, and compact.
Enhanced temperature stability and quality factor with Hf substitution for Sn and MnO2 doping of (Ba0.97Ca0.03)(Ti0.96Sn0.04)O3 lead-free piezoelectric ceramics with high Curie temperature
Authors: Tsai Cheng-Che , Chao Wei-Hsiang , Chu Sheng-Yuan , Hong Cheng-Shong , Weng Chung-Ming , Su Hsiu-Hsien
Published: December 2016

In this work, the process of two-stage modifications for (Ba0.97Ca0.03)(Ti0.96Sn0.04-xHfx)O3 (BCTS4-100xH100x) ceramics was studied. The trade-off composition was obtained by Hf substitution for Sn and MnO2 doping (two-stage modification) which improves the temperature stability and piezoelectric properties. The phase structure ratio, microstructure, and dielectric, piezoelectric, ferroelectric, and temperature stability properties were systematically investigated. Results showed that BCTS4-100xH100x piezoelectric ceramics with x=0.035 had a relatively high Curie temperature (TC) of about 112 °C, a piezoelectric charge constant (d33) of 313 pC/N, an electromechanical coupling factor (kp) of 0.49, a mechanical quality factor (Qm) of 122, and a remnant polarization (Pr) of 19μC/cm2. In addition, the temperature stability of the resonant frequency (fr), kp, and aging d33 could be tuned via Hf content. Good piezoelectric temperature stability (up to 110 °C) was found with x =0.035. BCTS0.5H3.5 + a mol% Mn (BCTSH + a Mn) piezoelectric ceramics with a = 2 had a high TC of about 123 °C, kp ∼ 0.39, d33 ∼ 230 pC/N, Qm ∼ 341, and high temperature stability due to the produced oxygen vacancies. This mechanism can be depicted using the complex impedance analysis associated with a valence compensation model on electric properties. Two-stage modification for lead-free (Ba0.97Ca0.03)(Ti0.96Sn0.04)O3 ceramics suitably adjusts the compositions for applications in piezoelectric motors and actuators.
Stability, sub-gap current, 1/f-noise, and elemental depth profiling of annealed Al:Mn-AlOX-Al normal metal-insulator-superconducting tunnel junctions
Authors: Julin J. K. , Chaudhuri S. , Laitinen M. , Sajavaara T. , Maasilta I. J.
Published: December 2016

In this paper we report a study of the effect of vacuum annealing at 400°C on the properties of normal metal-insulator-superconductor (NIS) tunnel junctions, with manganese doped aluminium (Al:Mn) as the normal metal, aluminum as the superconductor and amorphous aluminum oxide as the tunneling barrier (Al:Mn-AlOx-Al). The annealing treatment improves the stability of the junctions, increases their tunneling resistance and does not have a negative impact on the low-temperature current-voltage characteristics. The measured 1/f resistance noise of the junctions also changes after annealing, in the best case decreasing by over an order of magnitude. All these observations show that annealing is a viable route to improve NIS junction devices after the sample has been fabricated.
General practitioner management of chronic diseases in adults with severe mental illness: a community intervention trial
Authors: Cameron Cate M. , Cumsille Nazar Jose , Ehrlich Carolyn , Kendall Elizabeth , Crompton David , Liddy Ann Maree , Kisely Steve
Published: December 2016

Objective The aim of the present study was to assess the effects of a community intervention aimed at general practitioners (GPs) by comparing Medicare claims data from patients with severe mental illness (SMI) of GPs exposed to the intervention and controls that were not. Methods A comparison was made of primary care consultation and pathology data of people with SMI from intervention and control areas. Negative binomial regression models were used to compare the frequency and length of GP consultations, as well as the number and type of pathology examinations. Results Records of 103 people from intervention area and 98 controls were obtained. Intervention and control areas were not different at baseline in terms of age and claims data, but females had higher consultation rates. After adjusting for gender, people from intervention areas had more GP consultations, especially long consultations (adjusted incidence rate ratio 1.56; 95% confidence interval 1.28–1.91). They also had more pathology screening for chronic diseases, in accordance with implemented guideline recommendations. These benefits persisted after the end of the intervention. Conclusion These findings suggest that the ACTIVATE program aimed at training GPs to screen and better manage chronic diseases in adults with SMI had a positive effect up to 6 months after the trial, with demonstrated desired changes in medical management practices by GPs in the intervention area during that time. What is known about the topic? People with an SMI have higher mortality and poorer physical health than the general population. What does this paper add? The community intervention had a significant and sustained effect, with demonstrated desired changes in screening and medical management by GPs for adults with SMI in the intervention area. What are the implications for practitioners? GPs are ideally placed to assist in the prevention and better management of health conditions, thereby reducing avoidable illness and deaths in vulnerable populations, such as adults with SMI. Ongoing professional training and dissemination of clinical guidelines are critical for raising awareness about the physical and oral health care needs of people with SMI.
Corrigendum to: Medication-taking behaviour in New South Wales patients with type 2 diabetes: an observational study
Authors: Dhippayom Teerapon , Krass Ines
Published: December 2016

This study aimed to (1) determine adherence to diabetes medication in type 2 diabetes (T2D) patients; (2) describe respondents' attitudes and beliefs about medications, and barriers to adherence; and (3) to model predictors of non-adherence. Data were collected using online and postal surveys. Diabetes patients aged ?18 years who were members of the Australian Diabetes Council were invited to participate. Main outcome measures were adherence to diabetes medication using 8-item Morisky Medication Adherence Score (MMAS-8) and beliefs about medication using the Beliefs about Medicines Questionnaire. A total of 543 T2D patients responded to the survey. The median (interquartile range) MMAS-8 score was 6.8 (5.0–7.0). The prevalence of adherence (MMAS-8 score ?6) was 64.6%. The proportion of respondents who expressed concern about taking medications was 53.6%. Potential predictors of adherence included age (OR, 1.83; 95% CI, 1.19–2.82), concern about medication (OR, 0.91; 95% CI, 0.87–0.96), knowledge of diabetes (OR, 0.85, 95% CI, 0.73–0.99), having difficulty in paying for medication (OR, 0.51; 95% CI ,0.33–0.79), having more than one regular pharmacy (OR, 0.59; 95% CI, 0.36–0.95), and using insulin (OR, 0.49; 95% CI, 0.30–0.81). Adherence to taking diabetes medication in a sample of the Australian T2D patient population was suboptimal. An understanding of medication-taking behaviour will assist health-care professionals to deliver appropriate and effective interventions to enhance adherence and optimise diabetes control in T2D patients.
Stigma, gay men and biomedical prevention: the challenges and opportunities of a rapidly changing HIV prevention landscape
Authors: Brown Graham , Leonard William , Lyons Anthony , Power Jennifer , Sander Dirk , McColl William , Johnson Ronald , James Cary , Hodson Matthew , Carman Marina
Published: December 2016

Improvements in biomedical technologies, combined with changing social attitudes to sexual minorities, provide new opportunities for HIV prevention among gay and other men who have sex with men (GMSM). The potential of these new biomedical technologies (biotechnologies) to reduce HIV transmission and the impact of HIV among GMSM will depend, in part, on the degree to which they challenge prejudicial attitudes, practices and stigma directed against gay men and people living with HIV (PLHIV). At the structural level, stigma regarding gay men and HIV can influence the scale-up of new biotechnologies and negatively affect GMSM’s access to and use of these technologies. At the personal level, stigma can affect individual gay men’s sense of value and confidence as they negotiate serodiscordant relationships or access services. This paper argues that maximising the benefits of new biomedical technologies depends on reducing stigma directed at sexual minorities and people living with HIV and promoting positive social changes towards and within GMSM communities. HIV research, policy and programs will need to invest in: (1) responding to structural and institutional stigma; (2) health promotion and health services that recognise and work to address the impact of stigma on GMSM’s incorporation of new HIV prevention biotechnologies; (3) enhanced mobilisation and participation of GMSM and PLHIV in new approaches to HIV prevention; and (4) expanded approaches to research and evaluation in stigma reduction and its relationship with HIV prevention. The HIV response must become bolder in resourcing, designing and evaluating programs that interact with and influence stigma at multiple levels, including structural-level stigma.
Unfolding the Grammar of Bayesian Confirmation: Likelihood and Antilikelihood Principles
Authors: Festa Roberto , Cevolani Gustavo
Published: December 2016

We explore the grammar of Bayesian confirmation by focusing on some likelihood principles, including the Weak Law of Likelihood. We show that none of the likelihood principles proposed so far is satisfied by all incremental measures of confirmation, and we argue that some of these measures indeed obey new, prima facie strange, antilikelihood principles. To prove this, we introduce a new measure that violates the Weak Law of Likelihood while satisfying a strong antilikelihood condition. We conclude by hinting at some relevant links between the likelihood principles considered here and other properties of Bayesian confirmation recently explored in the literature.
Uniqueness result for an unknown coefficient in a nonlinear diffusion problem
Authors: Choulli M.
Published: December 2016

In this article we develop a number of monotonicity estimates of the solution to certain nonlinear diffusion equations. These estimates are then applied to prove a uniqueness result for an unknown diffusion coefficient from overspecified data measured on the boundary. Techniques presented here are based on arguments using the maximum principle.
Geometric nonlinearity: potential energy, complementary energy, and the gap function
Authors: Gao Yang , Strang Gilbert
Published: December 2016

Dual minimum principles for displacements and stresses are well established for linear variational problems and also for nonlinear (and monotone) constitutive laws. This paper studies the problem of geometric nonlinearity. By introducing a gap function, we recover complementary variational principles in the equilibrium problems of mathematical physics. When the gap function is nonnegative those become minimum principles. The theory is based on convex analysis, and the applications made here are to nonlinear mechanics.
A hodograph approach to the rotational compressible flow of an ideal fluid
Authors: Chiocchia Gianfranco
Published: December 2016

The classical hodograph equation for the study of the irrotational compressible flow of an ideal gas is here extended to the rotational case in which an entropy gradient normal to the streamlines is present. The formulation is in terms of Crocco’s stream function and leads to an equation differing from that valid for the irrotational case because of an additional nonlinear te[ill]m. In spite of this nonlinearity an exact solution can be found, describing a class of rotational vortices. Moreover, perturbative solutions can be found for the case in which the entropy gradient and the vorticity are small: one of these is here presented and describes the superposition of a constant vorticity distribution to the transonic region of the Ringleb flow.
Uniform 𝐿¹ behavior in a class of linear Volterra equations
Authors: Noren Richard
Published: December 2016

We find sufficient conditions for the solution of the equation
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="u prime left-parenthesis t right-parenthesis plus integral Subscript 0 Superscript t Baseline sigma-summation Underscript i equals 1 Overscript n Endscripts lamda Subscript i Baseline a Subscript i Baseline left-parenthesis t minus s right-parenthesis u left-parenthesis s right-parenthesis d s equals 0 comma u left-parenthesis 0 right-parenthesis equals 1">

u
′

(
t
)

+

∫
0
t

∑

i
=
1

n

λ
i

a
i

(

t
−
s

)

u

(
s
)

d
s
=
0
,
u

(
0
)

=
1

u’\left ( t \right ) + \\ \int _0^t {\sum \nolimits _{i = 1}^n {{\lambda _i}{a_i}\left ( {t - s} \right )u\left ( s \right )ds = 0, u\left ( 0 \right ) = 1} }

, to satisfy
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="integral Subscript 0 Superscript normal infinity Baseline sup Underscript lamda 1 comma period period period comma lamda Subscript n Baseline greater-than-or-equal-to 1 Endscripts left-parenthesis lamda 1 plus dot dot dot plus lamda Subscript n Baseline right-parenthesis Superscript negative 1 slash 2 Baseline times u prime left-parenthesis t comma lamda 1 comma period period period comma lamda Subscript n Baseline right-parenthesis d t greater-than normal infinity">

∫
0
∞

sup

λ
1

,
.
.
.
,

λ
n

≥
1

(

λ
1

+
⋅
⋅
⋅
+

λ
n

)

−
1

/

2

×

u
′

(

t
,

λ
1

,
.
.
.
,

λ
n

)

d
t
>
∞

\int _0^\infty {{{\sup }_{{\lambda _1},...,{\lambda _n} \ge 1}}{{\left ( {{\lambda _1} + \cdot \cdot \cdot + {\lambda _n}} \right )}^{ - 1/2}} \times \\ u’\left ( {t, {\lambda _1},...,{\lambda _n}} \right )dt > \infty }

. Our results generalize the case

n
=
1

n = 1

. Applications to a related equation in Hilbert space are given.
Changing domains and a solidification problem with void
Authors: Lenhart S. M. , Wilson D. G.
Published: December 2016

We consider Laplace’s equation posed in a region with a hole. The exact location and shape of this hole is not specified a priori. Dirichlet data are specified on the exterior boundary of the region and a Robin boundary condition holds on the edge of the hole. The problem represents a mathematical model of an equilibrium thermal state following a phase change process in which a denser solid has frozen out of its less dense liquid with the formation of a void. Since the solid is more dense that the liquid, the combined volume of frozen solid and remaining liquid is less than that of the initial liquid (which is assumed to have filled a finite container) and a vapor bubble or void results. Energy balance considerations impose two auxiliary conditions to be satisfied. We establish the existence of admissible holes, i.e., voids, for which a solution to the problem exists and, in addition, the existence of an admissible void with minimal circumference.
Semicoercive hemivariational inequalities. On the delamination of composite plates
Authors: Panagiotopoulos P. D.
Published: December 2016

In this paper semicoercive hemivariational inequalities are studied in the framework of a concrete mechanical problem: the delamination effect of laminated plates. The interlaminar bonding forces are described by a nonmonotone multivalued law which may be written as the generalized gradient of a nonconvex superpotential in the sense of F. H. Clarke. Then necessary conditions are proved for the existence of the solution, as well as sufficient conditions using compactness and average value arguments.
Linear stability analysis of cylindrical flames
Authors: Garbey Marc , Kaper Hans G. , Leaf Gary K. , Matkowsky Bernard J.
Published: December 2016

This article is concerned with the linear stability of cylindrical flames in a velocity field generated by a line source of fuel of constant strength

2
π
κ

2\pi \kappa

per unit length. The mathematical model involves the equations of mass and heat transfer in the regions on either side of the flame sheet and a set of jump conditions across the flame sheet. It admits a basic solution representing a stationary flame front in the shape of a circular cylinder at a radial distance

κ
\kappa

from the line source. The circular front loses stability if either (i) the Lewis number of the reaction-limiting component is less than some critical value less than 1 and

κ
\kappa

is greater than a critical value, or (ii) the Lewis number is greater than a critical value greater than 1. In the former case the circular front evolves into a steady cellular front, in the latter into a pulsating front, which may also be cellular. The WKB method is employed to derive approximations for the pulsating and cellular branches of the neutral stability curve.
Explicit expressions of Barnett-Lothe tensors and their associated tensors for orthotropic materials
Authors: Dongye Changsong , Ting T. C. T.
Published: December 2016

The three Barnett-Lothe tensors S, H, L, appear very often in the solutions to two-dimensional anisotropic elasticity problems. So do their associated tensors
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="ModifyingAbove upper S With caret left-parenthesis theta right-parenthesis comma ModifyingAbove upper H With caret left-parenthesis theta right-parenthesis comma ModifyingAbove upper L With caret left-parenthesis theta right-parenthesis">

S
^

(
θ
)

,

H
^

(
θ
)

,

L
^

(
θ
)

\hat S\left ( \theta \right ), \hat H\left ( \theta \right ), \hat L\left ( \theta \right )

for line forces and dislocations and

S

(
υ
)

,
H

(
υ
)

,
L

(
υ
)

S\left ( \upsilon \right ), H\left ( \upsilon \right ), L\left ( \upsilon \right )

in the problem of surface waves. Explicit expressions of the components of these tensors are derived and presented for orthotropic materials in which the planes of material symmetry coincide with the coordinate planes. With minor modifications, the results for S, H, L and
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="ModifyingAbove upper S With caret left-parenthesis theta right-parenthesis comma ModifyingAbove upper H With caret left-parenthesis theta right-parenthesis comma ModifyingAbove upper L With caret left-parenthesis theta right-parenthesis">

S
^

(
θ
)

,

H
^

(
θ
)

,

L
^

(
θ
)

\hat S\left ( \theta \right ), \hat H\left ( \theta \right ), \hat L\left ( \theta \right )

can be applied to orthotropic materials in which only the

x
3

=
0

{x_3} = 0

plane coincides with one of the planes of material symmetry.
Stabilization of adiabatic Couette-Poiseuille flow by temperature dependent viscosity
Authors: Boudourides Moses A. , Charalambakis Nicolas Ch.
Published: December 2016

We consider the adiabatic plane Couette-Poiseuille flow of a viscous incompressible fluid between two parallel planes driven by the shearing of the upper plane and a pressure gradient. The viscosity is assumed to depend on the temperature in an appropriate way to insure that every classical solution of the governing equations is asymptotically attracted by the steady Couette-Poiseuille flow profile with the temperature increasing unlimitedly. The proof is based on a priori estimates, obtained by the help of certain identities for solutions of the governing equations.
On the solvability of a two-dimensional wave-body interaction problem
Authors: Athanassoulis G. A. , Politis C. G.
Published: December 2016

The two-dimensional, deep-water, wave-body interaction problem for a single-hulled body, floating on the free surface of an ideal liquid, is considered. The body boundary may be nonsmooth and may intersect the free surface at arbitrary angles. The existence of a unique solution representable by a multipole-series expansion is proved for all but a discrete set of oscillation frequencies. The proof is based on the property of the associated multipoles to be a basis of the space

L
P

(

−
π
,
0

)

{L^P}\left ( { - \pi , 0} \right )

,

1
>
p
≤
2

1 > p \le 2

. Strict estimates of the form

D
n

=
O

(

n

−
α

)

{D_n} = O\left ( {n^{ - \alpha }} \right )

are also obtained for the coefficients of the multipole-series expansion for piecewise smooth

(

0
>
α
>
2

)

\left ( {0 > \alpha > 2} \right )

and smooth

(

α
=
2

)

\left ( {\alpha = 2} \right )

body boundaries.
On the everted state of spherical and cylindrical shells
Authors: Szeri Andrew J.
Published: December 2016

The existence, uniqueness, and qualitative nature of the everted state of spherical and cylindrical shells is examined for elastic materials with stress functions satisfying relatively simple restrictions. Qualitative analysis of the governing nonlinear ordinary differential equation is facilitated by recasting it in stress-stretch coordinates. One finds a continuum of solutions which meet the boundary conditions. Each corresponds uniquely to a shell of a particular thickness. We present numerical solutions which demonstrate the claims of the analysis.
An internal variable theory of elastoplasticity based on the maximum plastic work inequality
Authors: Eve R. A. , Reddy B. D. , Rockafellar R. T.
Published: December 2016

The methods of convex analysis are used to explore in greater depth the nature of the evolution equation in internal variable formulations of elastoplasticity. The evolution equation is considered in a form in which the thermodynamic force belongs to a set defined by a multi-valued map

G
G

. It is shown that the maximum plastic work inequality together with the assumption that

G
G

is maximal responsive (a term defined in Sec. 4), is necessary and sufficient to give a theory equivalent to that proposed by Moreau. Further consequences are investigated or elucidated, including the relationship between the yield function and the dissipation function; these functions are polars of each other. Examples are given to illustrate the theory.
A singular asymptotic expansion for the field near a moving dislocation loop
Authors: Callias Constantine , Markenscoff Xanthippi , Ni Lu Qun
Published: December 2016

The coefficients of the

1

/

ε

1/\varepsilon

and ln

ε
\varepsilon

singular terms in the field quantities near an arbitrarily moving dislocation loop are obtained by singular asymptotic expansion of integrals.
A uniqueness theorem for incompressible micropolar flows
Authors: Easwaran C. V. , Majumdar S. R.
Published: December 2016

It is proved that subject to certain regularity assumptions on velocity and microrotation and a certain convergence condition on pressure, the flow of an incompressible micropolar fluid around a finite solid body is uniquely determined by the motion of the body.
Instability of periodic states for the Sivashinsky equation
Authors: Novick-Cohen A.
Published: December 2016

The Sivashinsky equation is an asymptotically derived model equation for evolution of the solid-liquid interface which occurs during directional solidification of dilute binary alloys. During the solidification process interfaces are known experimentally to yield planar, cellular, cusped, or dendritic structures. Cellular structures, interpreted here as periodic one dimensional nontrivial steady states, are shown in this paper to be unstable, if they exist, within the context of the Sivashinsky equation. Symmetric nontrivial steady states are likewise shown to be unstable.
Asymptotic solution of a crack in a vanishingly thin elliptic inhomogeneity
Authors: Wu Chien H.
Published: December 2016

When a crack of finite size is wholly surrounded by a thin inhomogeneity, the behavior of the solution near a crack tip is the same as that of a semi-infinite crack surrounded by a semi-infinite inhomogeneity. The analytical structure of the solution for the latter problem is established via the consideration of the title problem. It is shown that the standard Fast Fourier Transform Algorithm may be applied for the determination of the coefficients involved in the analytically structured series solution. An approximate but explicit solution is also derived for the title problem.
Boundary-initiated wave phenomena in thermoelastic materials
Authors: Öncü T. S. , Moodie T. B.
Published: December 2016

The linear theory of Gurtin and Pipkin, and Chen and Gurtin is adopted to study one-dimensional progressive waves generated by thermal and mechanical disturbances applied at the boundary of a circular hole in an unbounded homogeneous thermoelastic medium. A ray-series approach is employed to generate asymptotic wavefront expansions for the field variables. The characteristics of the propagation process are obtained simply and directly. The solution is then specialized to the case where this theory reduces to the linearized theory of Lord and Shulman, and numerical results for various values of material parameters obtained from the ray-series solution in conjunction with the use of Padé approximants are displayed graphically.
Existence, uniqueness, and decay estimates for solutions in the nonlinear theory of elastic, edge-loaded, circular tubes
Authors: Horgan C. O. , Payne L. E. , Simmonds J. G.
Published: December 2016

Solutions to the two, coupled, ordinary nonlinear differential equations for a semi-infinite circular elastic tube subjected to edge loads and undergoing small axisymmetric strains, but arbitrarily large axisymmetric rotations—the simplified Reissner equations—are analyzed. First, with the aid of a Green’s function, the differential equations and boundary conditions are transformed to a complex-valued integral equation. From this equation existence, uniqueness, boundedness, and rate of decay are extracted for a dimensionless stress function,

f
f

, and an angle of rotation,

β
\beta

, for sufficiently small edge data. It is shown that these unique solutions must decay at least as fast as the linear solution. Second, it is shown that any solution that decays to zero must, at a sufficiently large distance from the edge, decay at the linear rate. Third, rates of decay are established for any solution for which the

L
2

{L_2}

or the sup norm of

β
\beta

has certain bounds. Finally, an energy (or Lyapunov) function

E
E

, defined on solutions of the differential equations, is constructed and under certain a priori restrictions on the angle of rotation, three different upper bounds on

E
E

are obtained. These also provide exponential decay estimates for solutions. The energy approach is examined with a view to more general shells where a Green’s function may not be readily available.
On the extreme variational principles for nonlinear elastic plates
Authors: Gao Yang
Published: December 2016

The min-maximum variational principles for Von Karman plates are formulated by using the theory of convex analysis. It is shown that the global extremum criteria for both the total potential and complementary variational functional is directly related to a so-called dual gap function. The existence and uniqueness of the variational solutions are proved. And the saddle point condition of the generalized variational principle is also discussed.
Parameter estimation problems for distributed systems using a multigrid method
Authors: Ta’asan Shlomo , Dutt Pravir
Published: December 2016

We consider the problem of estimating spatially varying coefficients of partial differential equations from observation of the solution and of the right-hand side of the equation. We assume that the observations are distributed in the domain and that enough observations are given. A method of discretization and an efficient multigrid method for solving the resulting discrete systems are described. Numerical results are presented for estimation of coefficients in an elliptic and a parabolic partial differential equation.
Nonlinear evolution of wave packets in magnetic fluids
Authors: Malik S. K. , Singh M.
Published: December 2016

The propagation of wave packets on the surface of a magnetic fluid of finite depth is considered in

(

2
+
1

)

\left ( {2 + 1} \right )

dimensions. It is shown that the evolution of the envelope is governed by two coupled partial differential equations with cubic nonlinearity. The stability analysis reveals the existence of more than one region of instability. The enveloping soliton and the “waveguide” solutions are derived in the regions of instability wherever they exist in one space dimension. The instability regions are sensitive to the applied magnetic field strength. The evolution of the envelope is governed by a

(

2
+
1

)

\left ( {2 + 1} \right )

-dimensional nonlinear equation which leads to a self-focussing singularity. Examined also is the long wave/short wave resonant interaction in magnetic fluids. Our study shows that the application of the magnetic field decreases the region of instability where this resonance occurs.
Persistence in dynamical systems
Authors: Teng Zhi Dong , Duan Kui Chen
Published: December 2016

In this paper, we study persistence and uniform persistence in dynamical systems. Necessary and sufficient conditions are given. These results are an extension of G. Butler, H. Freedman, and P. Waltman’s discussions. Applying these results to two- and three-dimensional ecosystems, we obtain necessary and sufficient conditions about persistence and uniform persistence of these systems.
Instability of a surface elastic line on an unnatural ramp
Authors: Manning Gerald S.
Published: December 2016

A line with bending resilience (Hooke’s Law constant

b
b

) but invariant length

l
l

(elastic line) is confined to a cylindrical surface of radius

R
R

. A clamp at its starting point requires its initial direction always to lie along the base circle, but its end point and direction are not constrained. The trajectory in which the elastic line lies for its entire length along the circle is then an equilibrium path. Since the elastic line can straighten by swerving toward the generators of the cylinder, however, the circumferential trajectory is unstable if

l

/

R

l/R

exceeds the critical value

π

/

2

3

/

2

(

≈
1.1107

)

\pi /{2^{3/2}}\left ( { \approx 1.1107} \right )

. To improve stability, we have constructed a ramp along the circle in the form of a potential energy trough (depth

γ
\gamma

, width

δ
\delta

), which, by means of surface forces, acts to attract the elastic line toward the circle. When the ramp strength is built up to a level

γ
δ

R
4

/

b
≈
5.1743

\gamma \delta {R^4}/b \approx 5.1743

, the stability of the circumferential trajectory is somewhat improved, lengths in excess of

l

/

R
≈
1.4178

l/R \approx 1.4178

now being unstable. But if the ramp strength is increased above this critical value, even if only slightly, the circumferential trajectory for arbitrarily long elastic lines abruptly becomes stable.
Lyapunov exponents for discontinuous differential equations
Authors: Berger B. S. , Rokni M.
Published: December 2016

The vector field associated with a dynamical system is assumed to be piecewise continuously differentiable. The gradient of the vector field, entering into integral expressions for the Lyapunov exponents, may therefore contain derivatives of step functions. Results from the theory of distributions are used in the integrals’ evaluation.
Upper and lower bounds for eigenvalues of the Laplacian on a spherical cap
Authors: Baginski Frank E.
Published: December 2016

In the following, we derive upper and lower bounds for eigenvalues of the Laplacian on a domain that is a spherical cap whose angular width

2

ϑ
0

2{\vartheta _0}

is less than

π
\pi

. While previous work of this nature seems to focus on the principle eigenvalue, our results apply to any eigenvalue when

0
>

ϑ
0

>
π

/

2

0 > {\vartheta _0} > \pi /2

. In addition, some of our results also apply to spherical caps for which

0
>

ϑ
0

>
π

0 > {\vartheta _0} > \pi

. When our estimates for the principle eigenvalue are compared to the results of [4, 8], we find that our upper and lower bounds are sharper.
A note on some qualitative results for beams and rods
Authors: Spillers W. R.
Published: December 2016

The small parameter technique of perturbation theory is used to argue that torsional buckling effects are of the same order of magnitude as beam column effects in the analysis of three-dimensional frames. Applications to the computer analysis of nonlinear structures are discussed.
Liquid film on an unsteady stretching surface
Authors: Wang C. Y.
Published: December 2016

A fluid film lies on an accelerating stretching surface. A similarity transform reduces the unsteady Navier-Stokes equations to a nonlinear ordinary differential equation governed by a nondimensional unsteady parameter. Asymptotic and numerical solutions are found. The results represent rare exact similarity solutions of the unsteady Navier-Stokes equations.
Long wavelength instability of the ABC-flows
Authors: Libin A. , Sivashinsky G.
Published: December 2016

Multiple-scale and spectral (Galerkin) techniques are employed to analyze the long-wave stability of a simple periodic helical flow at large Reynolds numbers. For a certain class of long-wave perturbations the corresponding mathematical problem admits an exact asymptotic solution, showing that the helical flow is always unstable.
An internal variable finite-strain theory of plasticity within the framework of convex analysis
Authors: Eve R. A. , Gültop T. , Reddy B. D.
Published: December 2016

An internal variable constitutive theory for elastic-plastic materials undergoing finite strains is presented. The theory is based on a corresponding study in the context of small strains [6], and has the following features: first, with a view to embracing the classical notions of convex yield surfaces and the normality law, the evolution law is developed within the framework of nonsmooth convex analysis, which proves to be a powerful unifying tool; secondly, the special case of elastic materials is recovered from the theory in a natural manner. After presentation of the theory a concrete example is discussed in detail.