bluuebunny/crossref_metadata_2025 huggingface dataset:
Multi-frequency ferromagnetic resonance investigation of nickel nanocubes encapsulated in diamagnetic magnesium oxide matrix
Authors: Nellutla Saritha , Nori Sudhakar , Singamaneni Srinivasa R. , Prater John T. , Narayan Jagdish , Smirnov Alex I.
Published: December 2016

Partially aligned nickel nanocubes were grown epitaxially in a diamagnetic magnesium oxide (MgO:Ni) host and studied by a continuous wave ferromagnetic resonance (FMR) spectroscopy at the X-band (9.5 GHz) from ca. 117 to 458 K and then at room temperature for multiple external magnetic fields/resonant frequencies from 9.5 to 330 GHz. In contrast to conventional magnetic susceptibility studies that provided data on the bulk magnetization, the FMR spectra revealed the presence of three different types of magnetic Ni nanocubes in the sample. Specifically, three different ferromagnetic resonances were observed in the X-band spectra: a line 1 assigned to large nickel nanocubes, a line 2 corresponding to the nanocubes exhibiting saturated magnetization even at ca. 0.3 T field, and a high field line 3 (geff ∼ 6.2) tentatively assigned to small nickel nanocubes likely having their hard magnetization axis aligned along or close to the direction of the external magnetic field. Based on the analysis of FMR data, the latter nanocubes possess an anisotropic internal magnetic field of at least ∼1.0 T in magnitude.
Microwave extraction method of radiative recombination and photon lifetimes up to 85 °C on 50 Gb/s oxide-vertical cavity surface emitting laser
Authors: Wang C. Y. , Liu M. , Feng M. , Holonyak N.
Published: December 2016

Optical modulation bandwidth for a semiconductor diode laser is governed by the thermally limited spontaneous radiative recombination lifetime, τrec, photon lifetime, τp, and cavity photon density for stimulated recombination. Thus, temperature dependent recombination lifetime is a critical parameter for the limitation of photonic device operations. Here, we develop a microwave extraction method to accurately determine the radiative recombination and photon lifetimes over a temperature range up to 85 °C through the equivalent circuit modeling based on the measured microwave scattering-parameters. For an 850 nm oxide-vertical cavity surface emitting laser with error free data transmission capability over 50 Gb/s, the extracted lifetimes are τrec = 0.1778 ns and τp = 4.2 ps at 25 °C and τrec = 0.2445 ns and τp = 4.8 ps at 85 °C.
Influence of pitch on the morphology and luminescence properties of self-catalyzed GaAsSb nanowire arrays
Authors: Ren Dingding , Huh Junghwan , Dheeraj Dasa L. , Weman Helge , Fimland Bjørn-Ove
Published: December 2016

We report on the influence of hole pattern pitch lengths in the silicon oxide mask and specific nanowire (NW) locations on the morphology and luminescence properties of self-catalyzed GaAsSb NW arrays grown by molecular beam epitaxy. Due to stronger competition for the limited amount of Ga adatoms, the GaAsSb NWs in the center of arrays with short pitch lengths possess a smaller catalyst droplet contact angle than that of the NWs at the array edge. This smaller contact angle leads to a reduction in the collection of group V flux, bringing about shorter NWs in the center. For pitch lengths beyond the diffusion length of Ga adatoms on the mask, the GaAsSb NWs are taller with larger contact angles than in the case with short pitch lengths. Considering that Sb has a longer diffusion length on the side facets of the NWs than that of As, a reduction/increase of the contact angle will bring about an increase/reduction in the Sb/As ratio of the group-V fluxes collected by the catalyst droplets. By performing micro-photoluminescence (μ-PL) measurements on the GaAsSb NW arrays at the center of the array for different pitch lengths, a red shift of the μ-PL spectra was found with a decrease in pitch length. Our findings demonstrate that the Ga diffusion-induced contact angle difference is the main cause for the variations in NW morphology and composition with different pitch lengths and NW locations in the array, which provides guidance to optimize the design of NW array devices for advanced optoelectronic applications.
Nontrivial contribution of Fröhlich electron-phonon interaction to lattice thermal conductivity of wurtzite GaN
Authors: Yang Jia-Yue , Qin Guangzhao , Hu Ming
Published: December 2016

The macroscopic thermal transport is fundamentally determined by the intrinsic interactions among microscopic electrons and phonons. In conventional insulators and semiconductors, phonons dominate the thermal transport, and the contribution of electron-phonon interaction (EPI) is negligible. However, in polar semiconductors, the Fröhlich electron-phonon coupling is strong and its influence on phononic thermal transport is of great significance. In this work, the effect of EPI on phonon dispersion and lattice thermal conductivity of wurtzite gallium nitride (GaN) is comprehensively investigated from the atomistic level by performing first-principles calculations. Due to the existence of relatively large electronegativity difference between Ga and N atoms, the Fröhlich coupling in wurtzite GaN is remarkably strong. Consequently, the lattice thermal conductivity of natural wurtzite GaN at room temperature is reduced by ∼24%–34% when including EPI, and the resulted thermal conductivity value is in better agreement with experiments. Furthermore, the scattering rate of phonons due to EPI, the intrinsic phonon-phonon interaction (PPI) as well as isotope disorder is computed and analyzed. It shows that the EPI scattering rate is comparable to PPI for low-frequency heat-carrying phonons. This work attempts to explore the mechanism of thermal transport beyond intrinsic PPI for polar semiconductors, with a great potential of thermal conductivity engineering for desired performance.
Tunneling electroresistance effect in ultrathin BiFeO3-based ferroelectric tunneling junctions
Authors: Yoong Herng Yau , Wang Han , Xiao Juanxiu , Guo Rui , Yang Ping , Yang Yi , Lim Sze Ter , Wang John , Venkatesan T. , Chen Jingsheng
Published: December 2016

Tunneling electroresistance (TER) effect has been observed in high quality ultrathin BiFeO3 thin films. The growth quality of the ultrathin BiFeO3 films was confirmed using the synchrotron high resolution X-ray diffraction techniques as well as high-resolution transmission electron microscopy. Ferroelectric-based resistive switching behavior is observed down to 2 u.c. of BiFeO3 ultrathin film, which is way below the critical thickness of BiFeO3 thin films exhibiting ferroelectricity reported in the previous research works. Upon fitting mathematically using the direct tunneling model, it could be seen that there is an increase in the change in the average potential barrier height when the barrier thickness increases from 2 u.c. to 10 u.c., which also results in an increase in the TER ratio by one order of magnitude. These results are promising and pave the way for developing ultrathin BiFeO3 films to be adopted in the non-volatile memory applications.
Localized holes and delocalized electrons in photoexcited inorganic perovskites: Watching each atomic actor by picosecond X-ray absorption spectroscopy
Authors: Santomauro Fabio G. , Grilj Jakob , Mewes Lars , Nedelcu Georgian , Yakunin Sergii , Rossi Thomas , Capano Gloria , Al Haddad André , Budarz James , Kinschel Dominik , Ferreira Dario S. , Rossi Giacomo , Gutierrez Tovar Mario , Grolimund Daniel , Samson Valerie , Nachtegaal Maarten , Smolentsev Grigory , Kovalenko Maksym V. , Chergui Majed
Published: December 2016

We report on an element-selective study of the fate of charge carriers in photoexcited inorganic CsPbBr3 and CsPb(ClBr)3 perovskite nanocrystals in toluene solutions using time-resolved X-ray absorption spectroscopy with 80 ps time resolution. Probing the Br K-edge, the Pb L3-edge, and the Cs L2-edge, we find that holes in the valence band are localized at Br atoms, forming small polarons, while electrons appear as delocalized in the conduction band. No signature of either electronic or structural changes is observed at the Cs L2-edge. The results at the Br and Pb edges suggest the existence of a weakly localized exciton, while the absence of signatures at the Cs edge indicates that the Cs+ cation plays no role in the charge transport, at least beyond 80 ps. This first, time-resolved element-specific study of perovskites helps understand the rather modest charge carrier mobilities in these materials.
Exact diagonalization of non-Hermitian so(3,2) models: Generalized two-mode boson systems
Authors: Zhang Hong-Biao , Wang Gangcheng
Published: December 2016

We propose a unified approach to exactly diagonalize generalized non-Hermitian so(3,2) models. This approach is a series of similarity transformations, which is constructed by some similarity transformation operators associated with su(1,1) and su(2) subalgebras of so(3,2) Lie algebra. During this diagonalization, it is worth noting that a key step is to get rid of the terms Eˆ± and Fˆ± together via the proper similarity transformations first. In this way, exact solutions of the non-Hermitian so(3,2) models are obtained. Meanwhile we give the corresponding eigenstates, which are regarded as Lie algebra so(3,2) coherent-like number states. The results can cover the generic form of the eigenvalues and eigenstates to the generalized non-Hermitian two-mode boson systems with the discrete spectrum, including 2D PT-symmetric and non-PT-symmetric oscillators as the special cases. Also they are true for the Hermitian case.
Modeling of mixing and interaction of multi-cathode spot vacuum arc jets
Authors: Wang Lijun , Qin Kang , Deng Jie , Jia Shenli
Published: December 2016

Vacuum arc consists of cathode spot and mixing zone, arc column and anode zone. The separate jets and the mixing zone should be considered in the model of diffuse arc. Moreover, the interaction between the plasma jets in multi-cathode spot vacuum arc also is very important. In this paper, mixing and interaction of multi-cathode spot vacuum arc jets were studied through simulation. To completely investigate the mixing and interaction of vacuum arc jets, a steady 3D Magneto-Hydro-Dynamic (MHD) modeling was established. In order to find out the influence of different parameters on mixing and interaction of vacuum arc jets, simulations with different parameters such as currents, angel of vacuum arc jets, with or without electromagnetic equations, tilted jets and different height of mixing zone were conducted. The simulation results show that the densities of ion number and plasma pressure as well as ion temperature increase with the increase of arc current, while the plasma velocity decreases. The jet center is more deviated from the cathode center with the increase of angle of tilted jets.
Stochastic chaos induced by diffusion processes with identical spectral density but different probability density functions
Authors: Lei Youming , Zheng Fan
Published: December 2016

Stochastic chaos induced by diffusion processes, with identical spectral density but different probability density functions (PDFs), is investigated in selected lightly damped Hamiltonian systems. The threshold amplitude of diffusion processes for the onset of chaos is derived by using the stochastic Melnikov method together with a mean-square criterion. Two quasi-Hamiltonian systems, namely, a damped single pendulum and damped Duffing oscillator perturbed by stochastic excitations, are used as illustrative examples. Four different cases of stochastic processes are taking as the driving excitations. It is shown that in such two systems the spectral density of diffusion processes completely determines the threshold amplitude for chaos, regardless of the shape of their PDFs, Gaussian or otherwise. Furthermore, the mean top Lyapunov exponent is employed to verify analytical results. The results obtained by numerical simulations are in accordance with the analytical results. This demonstrates that the stochastic Melnikov method is effective in predicting the onset of chaos in the quasi-Hamiltonian systems.
Optical and magnetic properties of a transparent garnet film for atomic physics experiments
Authors: Saito Mari , Tajima Ryoichi , Kiyosawa Ryota , Nagata Yugo , Shimada Hiroyuki , Ishibashi Takayuki , Hatakeyama Atsushi
Published: December 2016

We investigated the optical and magnetic properties of a transparent magnetic garnet with a particular focus on its applications to atomic physics experiments. The garnet film used in this study was a magnetically soft material that was originally designed for a Faraday rotator at optical communication wavelengths in the near infrared region. The film had a thickness of 2.1 μm and a small optical loss at a wavelength of λ=780 nm resonant with Rb atoms. The Faraday effect was also small and, thus, barely affected the polarization of light at λ=780 nm. In contrast, large Faraday rotation angles at shorter wavelengths enabled us to visualize magnetic domains, which were perpendicularly magnetized in alternate directions with a period of 3.6 μm. We confirmed the generation of an evanescent wave on the garnet film, which can be used for the optical observation and manipulation of atoms on the surface of the film. Finally, we demonstrated a magnetic mirror for laser-cooled Rb atoms using the garnet film.
‘Why didn’t you write a not-for-cardiopulmonary resuscitation order?’ Unexpected death or failure of process?
Authors: Levinson Michele , Mills Amber , Barrett Jonathan , Sritharan Gaya , Gellie Anthea
Published: December 2016

Objective
The aim of the present study was to understand the reasons for the delivery of non-beneficial cardiopulmonary resuscitation (CPR) attempts in a tertiary private hospital over 12 months. We determined doctors’ expectations of survival after CPR for their patient, whether they had considered a not-for-resuscitation (NFR) order and the barriers to completion of NFR orders.

Methods
Anonymous questionnaires were sent to the doctors primarily responsible for a given patient’s care in the hospital within 2 weeks of the unsuccessful CPR attempt. The data were analysed quantitatively where appropriate and qualitatively for themes for open-text responses

Results
Most doctors surveyed in the present study understood the poor outcome after CPR in the older person. Most doctors had an expectation that their own patient had a poor prognosis and a poor likely predicted outcome after CPR. This implied that the patient’s death was neither unexpected nor likely to be reversible. Some doctors considered NFR orders, but multiple barriers to completion were cited, including the family’s wishes, being time poor and diffusion or deferral of responsibility.

Conclusions
It is likely that futile CPR is provided contrary to policy and legal documents relating to end-of-life care, with the potential for harms relating to both patient and family, and members of resuscitation teams. The failure appears to relate to process rather than recognition of poor patient outcome.

What is known about the topic?
Mandatory CPR has been established in Australian hospitals on the premise that it will save lives. The outcome from in-hospital cardiac arrest has not improved despite significant training and resources. The outcome for those acutely hospitalised patients aged over 80 years has been repeatedly demonstrated to be poor with significant morbidity in the survivors. There is emerging literature on the extent of the delivery of non-beneficial treatments at the end of life, including futile CPR, the recognition of harms incurred by patients, families and members of the resuscitation teams and on the opportunity cost of the inappropriate use of resources.

What does this paper add?
This is the first study, to our knowledge, that has demonstrated that doctors understood the outcomes for CPR, particularly in those aged 80 years and older, and that failure to recognise poor outcome and prognosis in their own patients is not a barrier to writing NFR orders.

What are the implications for practitioners?
Recognition of the poor outcomes from CPR for the elderly patient for whom the doctor has a duty of care should result in a discussion with the patients, allowing an exploration of values and expectations of treatment. This would promote shared decision making, which includes the use of CPR. Facilitation of these discussions should be the focus of health service review.
It’s more than money: policy options to secure medical specialist workforce for regional centres
Authors: May Jennifer , Walker Judi , McGrail Mathew , Rolley Fran
Published: December 2016

Objectives Regional centres and their rural hinterlands support significant populations of non-metropolitan Australians. Despite their importance in the settlement hierarchy and the key medical services provided from these centres, little research has focused on their issues of workforce supply and long-term service requirements. In addition, they are a critical component of the recent growth of ‘regional’ hub-and-spoke specialist models of service delivery. Methods The present study interviewed 62 resident specialists in four regional centres, seeking to explore recruitment and retention factors important to their location decision making. The findings were used to develop a framework of possible evidence-informed policies. Results This article identifies key professional, social and locational factors, several of which are modifiable and amenable to policy redesign, including work variety, workplace culture, sense of community and spousal employment; these factors that can be targeted through initiatives in selection, training and incentives. Conclusions Commonwealth, state and local governments in collaboration with communities and specialist colleges can work synergistically, with a multiplicity of interdigitating strategies, to ensure a positive approach to the maintenance of a critical mass of long-term rural specialists. What is known about the topic? Rural origin increases likelihood of long-term retention to rural locations, with rural clinical school training associated with increased rural intent. Recruitment and retention policy has been directed at general practitioners in rural communities, with little focus on regional centres or medical specialists. What does this study add? Rural origin is associated with regional centre recruitment. Professional, social and locational factors are all moderately important in both recruitment and retention. Specialist medical training for regional centres ideally requires both generalist and subspecialist skills sets. Workforce policy needs to address modifiable factors with four groups, namely commonwealth and state governments, specialist medical colleges and local communities, all needing to align their activities for achievement of long-term medical workforce outcomes. What are the implications for practitioners? Modifiable factors affecting recruitment and retention must be addressed to support specialist models of care in regional centres. Modifiable factors relate to maintenance of a critical mass of practitioners, training a fit-for-purpose workforce and coordinated effort between stakeholders. Although remuneration is important, the decision to stay relates primarily to non-financial factors.
Assessing the reliability of dynamical and historical climate forecasts in simulating hindcast pasture growth rates
Authors: Harrison Matthew T. , Christie Karen M. , Rawnsley Richard P.
Published: December 2016

A priori knowledge of seasonal pasture growth rates helps livestock farmers plan with pasture supply and feed budgeting. Longer forecasts may allow managers more lead time, yet inaccurate forecasts could lead to counterproductive decisions and foregone income. By using climate forecasts generated from historical archives or the global circulation model (GCM) called the Predictive Ocean Atmosphere Model for Australia (POAMA), we simulated pasture growth rates in a whole-farm model and compared growth-rate forecasts with growth-rate hindcasts (viz. retrospective forecasts). Hindcast pasture growth rates were generated using posterior weather data measured at two sites in north-western Tasmania, Australia. Forecasts were made on a monthly basis for durations of 30, 60 and 90 days. Across sites, forecasting approaches and durations, there were no significant differences between simulated growth-rate forecasts and hindcasts when our statistical inference was conducted using either the Kolmogorov–Smirnov statistic or empirical cumulative distribution functions. However, given that both of these tests were calculated by comparing growth-rate hindcasts with monthly distributions of forecasts, we also examined linear correlations between monthly hindcast values and median monthly growth-rate forecasts. Using this approach, we found a higher correlation between hindcasts and median monthly forecasts for 30 days than for 60 or 90 days, suggesting that monthly growth-rate forecasts provide more skilful predictions than forecast durations of 2 or 3 months. The range in monthly growth-rate forecasts at 30 days was less than that at 60 or 90 days, further reinfocing the aforementioned result. The strength of the correlation between growth-rate hindcasts and median monthly forecasts from the historical approach was similar to that generated using POAMA data. Overall, the present study found that (1) statistical methods of comparing forecast data with hindcast data are important, particularly if the former is a distribution whereas the latter is a single value, (2) 1-month growth-rate forecasts have less uncertainty than forecast durations of 2 or 3 months, and (3) there is little difference between pasture growth rates simulated using climate data from either historical records or from GCMs. To test the generality of these conclusions, the study should be extended to other dairy regions. Including more regions would both enable studies of sites with greater intra-seasonal climate variability, but also better highlight the impact of seasonal and regional variation in forecast skill of POAMA as applied in our forecasting methods.
Elevated temperature increases in planta expression levels of virulence related genes in Magnaporthe oryzae and compromises resistance in Oryza sativa cv. Nipponbare
Authors: Onaga Geoffrey , Wydra Kerstin D. , Koopmann Birger , Séré Yakouba , von Tiedemann Andreas
Published: December 2016

Temperature changes have the potential to alter the incidence and severity of plant disease epidemics and pressures, as well as to reshape the co-evolutionary relationships between plants and pathogens. However, the molecular basis of temperature modulation of pathogenicity of plant pathogens is still unclear. Here, we studied the effect of temperature on biomass of Magnaporthe oryzae in planta using qPCR. Additionally, the transcriptomes of M. oryzae and rice were analysed using RNA-seq. Rice seedlings were exposed to 35°C and 28°C for 7 days before pathogen inoculation. Inoculated plants were kept in the dark at 28°C for 24 h and later re-exposed to 35°C and 28°C for an additional 24 h before sample collection. Plants grown and predisposed to 35°C prior to inoculation exhibited accelerated tissue necrosis compared with plants grown and inoculated at 28°C. In accordance with the disease severity observed on infected leaves, in planta fungal biomass was significantly higher at 35°C than 28°C. Moreover, M. oryzae exhibited increased expression levels of putative fungal effector genes in plants exposed to 35°C compared with plants exposed to 28°C. Collectively, this study revealed that temperature elevation could favour M. oryzae infection by compromising plant resistance and accelerating plant tissue colonisation with the pathogen.
Gel-coated tubes extend above-freezing storage of honey bee (Apis mellifera) semen to 439 days with production of fertilised offspring
Authors: Hopkins Brandon K. , Cobey Susan W. , Herr Charles , Sheppard Walter S.
Published: December 2016

Honey bees are an important agricultural species; however, relatively little work has been done to improve artificial reproductive technologies for this animal. The collection and distribution of germplasm for breeding and conservation is critical for improving managed honey bee populations and conserving threatened subspecies. The most efficient method of controlling breeding in honey bees is by artificial insemination. The collection of semen for insemination requires the use of antibiotics, which is especially critical if semen is to be stored for any length of time. The introduction of antibiotics is normally done through a balanced salt solution. In this study we compare, at two temperatures, the storage of undiluted semen in antibiotic–gel-coated capillary tubes with storage of semen diluted in a balanced salt solution containing antibiotics. Live–dead cell staining and artificial insemination of honey bee queens were performed at 45, 99 and 439 days after collection of the semen. In every case the antibiotic–gel-coated tube storage method at 14°C produced a higher percentage of fertilised offspring. This study demonstrates the longest period of time spermatozoa have been stored above freezing while maintaining fertilisation capacity.
Exploring the role of sex-seeking apps and websites in the social and sexual lives of gay, bisexual and other men who have sex with men: a cross-sectional study
Authors: Card Kiffer G. , Lachowsky Nathan J. , Cui Zishan , Shurgold Susan , Gislason Maya , Forrest Jamie I. , Rich Ashleigh J. , Moore David , Roth Eric , Hogg Robert S.
Published: December 2016

Background
The objective of this study was to explore the relationship between online sex-seeking, community/social attachment and sexual behaviour. Methods: Respondent-driven sampling was used to recruit 774 sexually active gay and bisexual men in Vancouver, Canada, aged ≥16 years. Multivariable logistic regression compared men who had used online sex-seeking apps/websites in the past 6 months (n = 586) with those who did not (n = 188). Results: Multivariable results showed that online sex seekers were more likely to be younger [adjusted odds ratio (aOR) = 0.95, 95% CI: (0.93–0.96)], college educated [aOR = 1.60, 95% CI: (1.07, 2.40)], have more Facebook friends [aOR = 1.07, 95% CI: (1.01, 1.13)], spend more social time with other gay men [aOR = 1.99, 95% CI: (1.33–2.97)], and were less likely to identify emotionally with the gay community [aOR = 0.93, 95% CI: (0.86–1.00)]. Further, they had displayed high sensation-seeking behaviour [aOR = 1.08, 95% CI: (1.03–1.13)], were more likely to engage in serodiscordant/unknown condomless anal sex [aOR = 2.34, 95% CI: (1.50–3.66)], use strategic positioning [aOR = 1.72, 95% CI: (1.08–2.74)], ask their partner’s HIV-status prior to sex [aOR = 2.06, 95% CI: (1.27–3.37)], and have ever been tested for HIV [aOR = 4.11, 95% CI: (2.04–8.29)]. Conclusion: These findings highlight the online and offline social behaviour exhibited by gay and bisexual men, pressing the need for pro-social interventions to promote safe-sex norms online. We conclude that both Internet and community-based prevention will help reach app/web users.
Least squares approximation of Lyapunov exponents
Authors: Berger B. S. , Rokni M.
Published: December 2016

Discrete least squares approximations are shown to converge for the Lyapunov exponents of dynamical systems. Numerical examples demonstrate the approximation’s utility.
Rotationally symmetric solutions for shallow membrane caps
Authors: Dickey R. W.
Published: December 2016

We discuss the displacements and stresses in a shallow membrane cap with either displacement or stress prescribed on the boundary and subjected to a small applied pressure. It is shown that if the prescribed boundary stress is sufficiently large there is a rotationally symmetric solution and if the applied pressure is large there is a solution to the problem with zero displacement prescribed on the boundary. However, there are situations in which there are no rotationally symmetric solutions. One case is described in which there are no rotationally symmetric solutions unless the prescribed boundary stress or prescribed boundary displacement is large.
Uncoupling the differential equations arising from a technique for evaluating indefinite integrals containing special functions or their products
Authors: Piquette Jean C.
Published: December 2016

A previous article by Piquette and Van Buren [1] described an analytical technique for evaluating indefinite integrals involving special functions or their products. The technique replaces the integral by an inhomogeneous set of coupled first-order differential equations. This coupled set does not explicitly contain the special functions of the integrand, and any particular solution of the set is sufficient to obtain an analytical expression for the indefinite integral. It is shown here that the coupled set arising from the method always occurs in normal form. Hence, it is amenable to the method of Forsyth [6] for uncoupling such a set. That is, the solution of the set can be made to depend upon the solution of a single differential equation of order equal to the number of equations in the set. Any particular solution of this single equation is then sufficient to yield the desired indefinite integral. As examples, the uncoupled equation is given here for integrals involving (i) the product of two Bessel functions, (ii) the product of two Hermite functions, or (iii) the product of two Laguerre functions, and a tabulation of integrals of these types is provided. Examples involving products of three or four special functions are also provided. The method can be used to extend the integration capabilities of symbolic-mathematics computer programs so that they can handle broad classes of indefinite integrals containing special functions or their products.
Energy balance criteria for viscoelastic fracture
Authors: Golden J. M. , Graham G. A. C.
Published: December 2016

An energy balance criterion of the Griffith type has been used to derive conditions that are valid, in the isothermal noninertial approximation, for the growth of cracks in viscoelastic bodies. These bodies are acted upon by general position and time-dependent load. The conditions have the same form as the instability conditions obtained for the corresponding problems in elasticity theory and, in particular, are independent of crack velocity. The analysis relies upon an exact calculation of the displacement and stress fields that is derived in the Appendix with the aid of extensions to viscoelasticity of the Kolosov-Muskhelishvili equations of elasticity theory.
Pseudodissipative systems. III. Global behavior
Authors: Walker J. A.
Published: December 2016

A result is presented which suggests the form of global Liapunov functions for many nonlinear mechanical systems in the “pseudodissipative” class. Consequently, this result often provides a means of “global analysis” of the overall behavior of such a system. In each of three examples, the general behavior of a mechanical system is ascertained by means of the result presented.
Symmetric finite element and boundary integral coupling methods for fluid-solid interaction
Authors: Bielak J. , MacCamy R. C.
Published: December 2016

This paper presents a coupled finite element and boundary integral method for solving the time-periodic oscillation and scattering problem of an inhomogeneous elastic body immersed in a compressible, inviscid, homogeneous fluid. By using integral representations for the solution in the infinite exterior region occupied by the fluid, the problem is reduced to one defined only over the finite region occupied by the solid, with associated nonlocal boundary conditions. This problem is then given a family of variational formulations, including a symmetric one, which are used to derive finite-dimensional Galerkin approximations. The validity of the method is established explicitly, and results of an error analysis are discussed, showing optimal convergence to a classical solution.
On two problems of electrical heating of conductors
Authors: Cimatti Giovanni
Published: December 2016

The thermal effects of the currents induced in a massive conductor by an external slowly varying magnetic field are studied with regard to existence and uniqueness of solutions. In the first part a theorem of existence of solution is also given for the thermistor problem with a current limiting device.
The development of travelling waves in quadratic and cubic autocatalysis with unequal diffusion rates. III. Large time development in quadratic autocatalysis
Authors: Billingham J. , Needham D. J.
Published: December 2016

We study the isothermal, quadratic autocatalytic reaction scheme

A
+

B
→
2
B

A + \\ B \to 2B

, where

A
A

is a reactant and

B
B

is an autocatalyst. We consider the situation when a quantity of

B
B

is introduced locally into a uniform expanse of

A
A

in one-dimensional slab geometry. By analysing the large time asymptotic solution of the resulting initial value problem we show that either a permanent form travelling wave or a phase wave develops. In the case when a travelling wave evolves we determine the first two terms in the large time asymptotic expansion of the propagation speed, which is dependent upon the asymptotic form of the initial input distribution of

B
B

far ahead of the wavefront.
Self-similar solutions of the second kind of nonlinear diffusion-type equations
Authors: Diez Javier Alberto , Gratton Julio , Minotti Fernando
Published: December 2016

We study the self-similar solutions of the problem of one-dimensional nonlinear diffusion of a passive scalar

u
u

(diffusivity

D
∞

u
m

,
m
≥
1

D \infty {u^m}, m \ge 1

) towards the centre of a cylindrical or spherical symmetry. It is shown that this problem has a self-similar solution of the second kind. The self-similarity exponent

δ
\delta

is found by solving a nonlinear eigenvalue problem arising from the requirement that the integral curve that represents the solution must join the appropriate singular points in the phase plane of the diffusion equation. In this way the integral curves that describe the solution before and after the diffusive current arrives at the centre of symmetry can be determined. The eigenvalues for different values of the nonlinearity index

m
m

and for cylindrical and spherical geometry are computed. Numerical integration of the equations allows us to determine the shape of the solution in terms of the physical variables. The application to the case

m
=
3

m = 3

, corresponding (for cylindrical symmetry) to the creeping gravity currents of a very viscous liquid, is worked out in detail.
Degenerate deformations and uniqueness in highly elastic networks
Authors: Green W. A. , Shi Jingyu
Published: December 2016

This work deals with the continuum theory for plane deformations of a network formed of two families of highly elastic cords, under the assumption of no resistance to shearing. Following Pipkin [3] it is shown that there exists a collapse mode of deformation in which a finite region of the network collapses onto a single curve and examples are exhibited which correspond to a universal deformation and to a universal state of tension. It is further shown that the assumption that the cords can withstand no compression leads to the existence of half-slack and fully-slack regions, as defined by Pipkin [5]. The most general deformation associated with a half-slack region is determined. A variational principle is established for the general boundary value problem and it is shown that, for strain-energy functions which are quadratic in the stretches of the cords, this leads to a minimum principle and a generalized uniqueness theorem. A stability and uniqueness theorem is derived for the materials with a more general strain energy function.
A Saint-Venant principle for a theory of nonlinear plane elasticity
Authors: Horgan C. O. , Payne L. E.
Published: December 2016

A formulation of Saint-Venant’s principle within the context of a restricted theory of nonlinear plane elasticity is described. The theory assumes small displacement gradients while the stress-strain relations are nonlinear. We consider plane deformations of such an elastic material occupying a rectangular region. The lateral sides are traction-free while the far end is subjected to a uniformly distributed tensile traction

τ
≥
0

\tau \ge 0

. The near end is subjected to a prescribed normal and shear traction. If this end loading were also that of uniform tension, then one possible corresponding stress state throughout the rectangle is that of uniform tension. When the near end loading is not uniform, the resulting stress field is expected to approach a uniform tensile state with increasing distance from the near end. This result is established here using differential inequality techniques for quadratic functionals. It is shown that, under certain constitutive assumptions, an energy-like quadratic functional, defined on the difference between the deformation field and the uniform tensile state, decays exponentially with distance from the near end. The estimated decay rate (which is a lower bound on the actual rate of decay) is characterized in terms of the load level

τ
\tau

, the domain geometry, and material properties. The results predict a progressively slower decay of end effects with increasing load level

τ
\tau

. The mathematical issues of concern involve spatial decay of solutions of a fourth-order nonlinear elliptic partial differential equation.
Examples of bifurcation from a continuum of eigenvalues and from the continuous spectrum
Authors: Jorge M. C. , Minzoni A. A.
Published: December 2016

In this note we consider an example arising from a caricature of a geophysical problem where we show explicitly bifurcation from a continuum of eigen-values. Also we consider an example of bifurcation from the continuous spectrum for a simple integrodifferential equation.
On objective surface rates
Authors: Stumpf H. , Badur J.
Published: December 2016

In this paper we derive objective, in the sense of surface, rates of tensors and we give a correct formulation of a two-dimensional continuum. Furthermore we present objective rates of tensors on the boundary line enclosing the surface under consideration. It can be considered as a first step to derive objective rates for generalized continua as Cosserat continua and Kirchhoff-Love type nonlinear shell theories.
Thermodynamic properties and stability for the heat flux equation with linear memory
Authors: Giorgi C. , Gentili G.
Published: December 2016

Within the linearized theory of heat conduction with fading memory, some restrictions on the constitutive equations are found as a direct consequence of thermodynamic principles. Such restrictions allow us to obtain existence, uniqueness, and stability results for the solution to the heat flux equation. Both problems, which respectively occur when the instantaneous conductivity

k
0

{k_0}

is positive or vanishes, are considered.
The effect of constitutive law perturbations on finite antiplane shear deformations of a semi-infinite strip
Authors: Horgan C. O. , Payne L. E.
Published: December 2016

This paper is concerned with assessing the effects of small perturbations in the constitutive laws on antiplane shear deformation fields arising in the theory of nonlinear elasticity. The mathematical problem is governed by a second-order quasilinear partial differential equation in divergence form. Dirichlet (or Neumann) boundary-value problems on a semi-infinite strip, with nonzero data on one end only, are considered. Such problems arise in investigation of Saint-Venant end effects in elasticity theory. The main result provides a comparison between two solutions, one of which is a solution to a simpler equation, for example Laplace’s equation. Three examples involving perturbations of power-law material models are used to illustrate the results.
Force and torque of an electromagnetically levitated metal sphere
Authors: Lohöfer G.
Published: December 2016

The Lorentz force and torque exerted on an electrically conducting sphere exposed to an external, time-varying magnetic field are analytically calculated. The external magnetic field is generated by a set of sinusoidally alternating, but otherwise arbitrary, current density fields of different frequencies and phases. Expressions for the force and torque in a laboratory frame of reference, which is more convenient for application, are also given. Finally, the special cases of rotational and mirror-symmetric external current density fields are treated in more detail.
Superimposed travelling wave solutions for nonlinear diffusion
Authors: Hill Desmond L. , Hill James M.
Published: December 2016

For one-dimensional nonlinear diffusion with diffusivity

D

(
c
)

=

c

−
1

D\left ( c \right ) = {c^{ - 1}}

, a new exact solution is noted which relates to both the well-known travelling wave solution and the source solution. The new solution can have a zero initial condition and admits essentially two distinct forms, one involving the hyperbolic tangent function and the other involving the circular tangent function. The solution involving tanh is physically meaningful and is displayed graphically while that involving the tan function is utilized together with a reciprocal Bäcklund transformation to produce a further new solution, which is physically more interesting than the tan solution, and is also displayed graphically. The basic idea used in this paper is generalized to a high-order nonlinear diffusion equation. For a third-order nonlinear diffusion-like equation, a solution reminiscent of solutions of soliton equations and involving the hyperbolic secant function is obtained and displayed graphically. The solutions investigated here are all characterized by the curious property that individually they are solutions for nonlinear diffusion and, moreover, their “sum” is also a bonafide nonlinear diffusion solution so that, for this specific solution, a nonlinear partial differential equation displays a “limited” superposition principle.
Quenching profiles for one-dimensional semilinear heat equations
Authors: Filippas Stathis , Guo Jong-Shenq
Published: December 2016

We are interested in the local behavior, near a quenching point, of a solution of a semilinear heat equation with singular powerlike absorption. Using the method of Herrero and Velazquez, we obtain a precise description of the spatial profile of the solution in a neighborhood of a quenching point at the quenching time, under certain assumptions on the initial data.
An approximation framework for equations in linear viscoelasticity with strongly singular kernels
Authors: Fabiano R. H. , Ito K.
Published: December 2016

In this paper we consider equations that arise in linear viscoelastic models. Within the context of linear semigroup theory we present an approximation framework for these equations. A relevant convergence result is proved using the Trotter-Kato theorem. This work extends previous results that did not apply to equations with strongly singular kernels.
Roots of 𝐽ᵧ(𝑧)±𝑖𝐽ᵧ₊₁(𝑧)=0 and the evaluation of integrals with cylindrical function kernels
Authors: Tadepalli Srinivas , Synolakis Costas Emmanuel
Published: December 2016

An elementary proof is presented showing that the function

f

(
z
)

=

J
γ

(
z
)

±
i

J

γ
+
1

(
z
)

f\left ( z \right ) = \\ {J_\gamma }\left ( z \right ) \pm i{J_{\gamma + 1}} \left ( z \right )

, where

γ
\gamma

is a natural number, has no zeroes in the lower and upper half-planes respectively. The roots of

f

(
z
)

f\left ( z \right )

are given for certain values of

γ
\gamma

and their locations are plotted. Cartesian maps (mappings of constant coordinate lines) of

f

(
z
)

f\left ( z \right )

are obtained, and special features of these maps are discussed. Some integrals with cylindrical kernels involving

f

(
z
)

f\left ( z \right )

are obtained in terms of the zeroes of

J
γ

(
z
)

{J_\gamma }\left ( z \right )

.
Note on the numerical construction of geodesics and ray paths
Authors: Pearson Carl E.
Published: December 2016

This note discusses the choice of parameter in the numerical construction of a geodesic, and in particular the role of arc length.
On anisotropic elastic materials that possess three identical Stroh eigenvalues as do isotropic materials
Authors: Ting T. C. T.
Published: December 2016

For anisotropic elastic materials for which the displacements

u
i

{u_i}

depend on

x
1

{x_1}

and

x
2

{x_2}

only, a general solution for

u
i

{u_i}

depends on one variable

z
=

x
1

+
p

x
2

z = {x_1} + p{x_2}

where

p
p

is an eigenvalue of the fundamental elasticity tensor of Stroh. There are six

p
p

’s which consist of three pairs of complex conjugates. For isotropic materials,

p
=
±
i

p = \pm i

are the eigenvalues of multiplicity three. We point out trivial cases in which a completely anisotropic material has the eigenvalues

p
=
±
i

p = \pm i

and has the solutions to two-dimensional elasticity problems that are identical to the solutions for isotropic materials. Excluding these trivial cases, we show that

p
=
±
i

p = \pm i

can be the eigenvalues of multiplicity three for monoclinic materials with the symmetry plane at

x
1

=
0

{x_1} = 0

, at

x
2

=
0

{x_2} = 0

, or at any plane that contains the

x
3

{x_3}

-axis. If the symmetry plane is at

x
3

=
0

{x_3} = 0

, then

p
=
±
i

p = \pm i

occur only when the material is transversely isotropic with the axis of symmetry at the

x
3

{x_3}

-axis. We also consider the general case in which the eigenvalues are arbitrary and are of multiplicity three. The eigenrelation associated with the triple eigenvalues is nonsemisimple for all cases studied here. There are only two independent eigenvectors associated with the triple eigenvalues.
Asymptotic behaviour in linear viscoelasticity
Authors: Muñoz Rivera Jaime E.
Published: December 2016

We study the asymptotic behaviour of the solution of the viscoelastic equation, and we prove for a bounded domain that the energy associated to this system approaches zero exponentially as time goes to infinity. Moreover, for the whole space

R

n

{\mathbb {R}^n}

we will prove that the displacement vector field can be decomposed into two parts, solenoidal and irrotational, whose corresponding energies decay to zero uniformly as time goes to infinity with rates that depend on the regularity of the initial data.
Intermodal interaction of internal solitary waves
Authors: Yih Chia-Shun
Published: December 2016

Interaction of internal solitary waves of different modes in an incompressible fluid with an exponential stratification in density is considered. Two such waves are considered. These waves may be going in the same direction or in opposite directions. The analysis shows that the interaction produces two pairs of waves, whose mode indices are the difference and the sum of those of the original waves, respectively. Each pair consists of a right-going wave and a left-going one, and a part that vanishes eventually everywhere. Higher-order terms affecting interaction are briefly discussed. The interaction of more than two waves can be dealt with pair by pair.
Justification of the linear long-wave approximation to viscous fluid flow down an inclined plane
Authors: Sun S. M. , Shen M. C.
Published: December 2016

The objective of this paper is to justify the linear long-wave approximation used in the derivation of approximate equations for long waves on the free surface of a two-dimensional viscous fluid flow down an inclined plane. To the first order of a small parameter, the approximate equation is a heat equation, which becomes ill-posed if a Reynolds number

R
R

is greater than some critical value

R
c

{R_c}

. To overcome this difficulty we consider a higher-order approximate equation, which is well-posed even if

R
>

R
c

R > {R_c}

, and show that the solution of the higher-order equation is an approximation to the solution of the linearized Navier-Stokes equations. The justification is based upon a set of long-wave initial conditions, and the error bounds can also be expressed in terms of pointwise estimates.