bluuebunny/crossref_metadata_2025 huggingface dataset:
Delta wings with shock-free cross flow
Authors: Sritharan S. S.
Published: December 2016

It has been realized recently that in order to have a high level of maneuverability, supersonic delta wings should have a cross flow that is free of embedded shock waves. The conical cross flow sonic surface differs from that of plane transonic flow in many aspects. Well-known properties such as the monotone law are not true for conical cross flow sonic surfaces. Using a local analysis of the cross flow sonic line, relevant conditions for smooth cross flow are obtained. Using a technique to construct artificially a smooth sonic surface and an efficient numerical method to calculate the flow field, one obtains cones with smooth cross flow.
On the formulation of hyperbolic Stefan problems
Authors: Solomon A. D. , Alexiades V. , Wilson D. G. , Drake J.
Published: December 2016

The study of phase change processes governed by hyperbolic heat transfer is at an embryonic stage. We raise here some of the relevant questions and make some remarks on the formulation and qualitative behavior of hyperbolic Stefan problems. In particular, we correct an error in the interface condition appearing in two earlier studies, and present an explicit solution to a simple one-phase problem and study its behavior. Finally we describe an enthalpy (weak) formulation for a two-phase problem and report on a few numerical experiments based on it.
Asymptotic analysis of Stokes flow in a tortuous vessel
Authors: Chadwick R. S.
Published: December 2016

Steady slow viscous flow is considered inside a vessel with circular cross section. The centerline curvature is specified as a function of arc length. The Stokes equations are written in orthogonal curvilinear coordinates. The primary small parameter is the slenderness ratio

ϵ
\epsilon

, which is the ratio of vessel radius to vessel length or wavelength. The product of centerline curvature and vessel length is assumed to be of order unity. A transverse drift appears at

O

(

ϵ
2

)

O\left ( {{\epsilon ^2}} \right )

that is proportional to the rate of change of curvature. Contours of axial velocity show a primary peak shifted toward the inside wall and a secondary peak grows toward the outside wall as curvature is increased. The flux ratio or relative hydrodynamic conductance is calculated to

O

(

ϵ
4

)

O\left ( {{\epsilon ^4}} \right )

and includes the effect of variable curvature. The present calculations tend to indicate that the sinusoidal mode of buckled micro-vessel could offer substantially more resistance to flow than the helical buckled mode.
Invariant curves for numerical methods
Authors: Doan H. T.
Published: December 2016

The problem of finding periodic orbits of dynamical systems numerically is considered. It is shown that if a convergent, strongly stable, multi-step method is employed then under some suitable conditions, there exist invariant curves. The result also shows that the rates of convergence toward the invariant curves are roughly the same for different methods and different step sizes.
Heat conduction in a thin circular pipe due to a circumferentially moving heat source
Authors: Nair S.
Published: December 2016

The solution of the title problem is often approximated by the temperature distribution in a flat plate due to an array of periodically placed heat sources, where the curvature of the pipe is neglected. Here, using an asymptotic expansion in terms of the thickness to radius ratio, linear corrections to the flat plate solution are obtained explicitly. Results indicate that these corrections may be significant depending, of course, on the above small parameter and the speed of the moving source.
Translational addition theorems for prolate spheroidal vector wave functions 𝑀^{𝑟} and 𝑁^{𝑟}
Authors: Dalmas Jeannine , Deleuil Roger
Published: December 2016

The translational addition theorems for prolate spheroidal vector wave functions

M

r

{\textrm {M}^r}

and

N

r

{\textrm {N}^r}

with reference to the spheroidal coordinate system at the origin 0 are obtained in terms of spheroidal vector wave functions with reference to the translated spheroidal coordinate system at the origin

0
′

0’

. These addition theorems are absolutely necessary for the study of the multiple scattering of electromagnetic waves when the single electromagnetic scattering solution is also expressed in terms of spheroidal vector wave functions

M

r

{\textrm {M}^r}

and

N

r

{\textrm {N}^r}

.
Transient dynamic Green’s functions for a cracked plane
Authors: Brock L. M.
Published: December 2016

Closed-form solutions for the transient dynamic problems of a suddenly applied anti-plane concentrated force and concentrated impulse near a crack are obtained. The various wave signals comprising the solutions are identified, and their behavior noted. The concentrated force solution is then employed as a Green’s function to solve the important problem of arbitrary screw dislocation motion near a crack edge.
Remarks on some nonconservation problems
Authors: Sherman B.
Published: December 2016

A horizontal channel of uniform cross section has an impervious channel bed to the left of

x
=
0

x = 0

and allows infiltration at a constant rate to the right of

x
=
0

x = 0

. Initially there is water at constant depth and zero velocity. There are left and right moving interfaces and, between them, water with positive velocity. At a certain time there will be a water edge to the right of which there is no water in the channel. The time history of this water edge is a free boundary. The solution of this problem, which is nonconservation because mass and momentum are carried away by infiltration, is discussed below. A single equation, which is also nonconservation, has an explicit solution. The characteristics of this single equation have a geometry similar to that the

C
2

{C_2}

characteristics of the channel problem.
Instabilities of the Ginzburg-Landau equation. II. Secondary bifurcation
Authors: Newton Paul K. , Sirovich Lawrence
Published: December 2016

A perturbation treatment of secondary bifurcation for the Ginzburg-Landau equation is presented. An analytical form for limit cycle instability is determined. This is compared with numerical results and shown to be in good agreement over a wide parameter range.
Nonlinear focussing in magnetic fluids
Authors: Malik S. K. , Singh M.
Published: December 2016

The phenomenon of nonlinear focussing or collapse is presented for two superposed magnetic fluids subjected to a normal magnetic field. We show that the focussing is direction-dependent and is more pronounced at shorter wavelengths as well as at higher values of density ratio. Nonlinear focussing occurs if the dimensions of the system are higher than one and the magnetic field is in the subcritical regime. Because of this nonlinear effect, the regular pattern formation may develop local spots of highly irregular behaviour.
Rotational-translational addition theorems for scalar spheroidal wave functions
Authors: MacPhie R. H. , Dalmas J. , Deleuil R.
Published: December 2016

Rotational-translational addition theorems for the scalar spheroidal wave function

ψ

m
n

(
i
)

(

h
;
η
,
ξ
,
ϕ

)

\psi _{mn}^{\left ( i \right )}\left ( {h;\eta ,\xi ,\phi } \right )

, with

i
=
1
,
3
,
4

i = 1,3,4

, are deduced. This permits one to represent the

m

n

t
h

m{n^{th}}

scalar spheroidal wave function, associated with one spheroidal coordinate system

(

h
q

;

η
q

,

ξ
q

,

ϕ
q

)

\left ( {{h_q};{\eta _q},{\xi _q},{\phi _q}} \right )

centered at its local origin

O
q

{O_q}

, by an addition series of spheroidal wave functions associated with a second rotated and translated system

(

h
r

;

η
r

,

ξ
r

,

ϕ
r

)

\left ( {{h_r};{\eta _r},{\xi _r},{\phi _r}} \right )

, centered at

O
r

{O_r}

. Such theorems are necessary in the rigorous analysis of radiation and scattering by spheroids with arbitrary spacings and orientations.
On uniqueness and stability in generalized thermoelasticity
Authors: Sherief Hany H.
Published: December 2016

A uniqueness theorem for the equations of generalized thermoelasticity with one relaxation time, derived by Dhaliwal and Sherief [1], is proved. The stability of the null solution in the sense of Liapounov, measured by a suitable norm, is shown. The corresponding equations for a homogeneous isotropic material, derived by Lord and Shulman [2], are considered as a special case.
Stability of time-periodic temperature fields
Authors: Yih Chia-Shun , Shi Jinsong
Published: December 2016

The energy method developed by Joseph [4], Davis [2], and Homsy [3] is applied to the time-periodic temperature fields considered by Yih and Li [11] to obtain Rayleigh numbers below which the fluid is stable. This is done to see how far the Rayleigh numbers so determined fall below the critical Rayleigh numbers, above which the flow is unstable, as determined by the linear theory [11]. It is found that, unlike the case of classical Bénard cells, the gray area, or area of ignorance, is quite large, indicating the need for some improvement of the energy method to give sharper lower bounds on the Rayleigh number.
On the solution of integral equations with strongly singular kernels
Authors: Kaya A. C. , Erdogan F.
Published: December 2016

In this paper some useful formulas are developed to evaluate integrals having a singularity of the form

(

t
−
x

)

−
m

,
m
≥
1

{\left ( {t - x} \right )^{ - m}},m \ge 1

. Interpreting the integrals with strong singularities in the Hadamard sense, the results are used to obtain approximate solutions of singular integral equations. A mixed boundary value problem from the theory of elasticity is considered as an example. Particularly for integral equations where the kernel contains, in addition to the dominant term

(

t
−
x

)

−
m

{\left ( {t - x} \right )^{ - m}}

, terms which become unbounded at the end points, the present technique appears to be extremely effective to obtain rapidly converging numerical results.
Asymptotic behavior of periodic, periodic biharmonic and periodic harmonic functions
Authors: Howell Kenneth B.
Published: December 2016

The behavior of periodic functions defined on domains containing the upper half space,

{

(

x
1

,

x
2

,
.
.
.
,

x
n

)

:

x
n

>
0

}

\left \{ {\left ( {{x^1},{x^2},...,{x^n}} \right ):{x^n} > 0} \right \}

, is investigated as

x
n

{x^n}

approaches infinity. Bounds on some of the first order derivatives of these functions are obtained which are directly proportional to bounds on derivatives of arbitrary orders in certain directions. It is shown that a periodic biharmonic and a periodic harmonic function can be approximated, respectively, by a third degree and a first degree polynomial in the variable

x
n

{x^n}

and that, as

x
n

{x^n}

approaches infinity, the error in using this approximation vanishes faster than the reciprocal of

x
n

{x^n}

raised to any power.
Local existence of the solution to a nonlinear inverse problem in gravitation
Authors: Jorge M. C.
Published: December 2016

We consider the problem of modeling the external gravitational field of the earth from measurements of its intensity on the surface. The problem is formulated as a nonlinear oblique boundary value problem for the external gravitational potential. The equation for the potential is approximated for small anomalies and solved by a regular perturbation expansion. The convergence of the series is proved using Schauder estimates, and local existence for small anomalies is established. The technique used to prove the convergence of the series is in the same spirit as the Cauchy—Kowalewsky estimates. This study completes previous work done by Backus who proved uniqueness of the solution.
A Stokes flow model for the drag on a blood cell
Authors: Davis A. M. J. , Ranger K. B.
Published: December 2016

The geometrical inverse of a prolate ellipsoid of revolution with respect to its center is a biconcave lens for certain values of the parameters. This is used as a model for the normal shape of a red blood cell. The Stokes flow past this body is found explicitly and an expression given for the drag.
Asymptotic solutions for finite deformation of thin shells of revolution with a small circular hole
Authors: Weinitschke Hubertus J. , Lange Charles G.
Published: December 2016

The method of matched asymptotic expansions is used to describe the finite deformation of thin shells of revolution with a small circular hole at the apex. The loading is assumed to be a rotationally symmetric, smoothly varying normal pressure. The mathematical problem is of singular perturbation type characterized by a boundary layer region at the inner edge of the small hole. The analytical results are compared with numerical approximations, and formulas for the stress concentration factors at the hole are presented.
Existence globale de solutions faibles sous une hypothèse unilaterale pour un système hyperbolique non linéaire
Authors: Serre D.
Published: December 2016

We investigate a one-dimensional system of two conservation laws, cited by Leroux. The hyperbolicity region is nonconvex in the phase plane. It is a particular case of a general class studied by B. Temple.
A variational formalism for steady flow of dusty fluid problems. I
Authors: Hajj Adnan A. , Elshehawey Elsayed F.
Published: December 2016

A general variational formalism for the solution of steady flow of dusty fluids is given. The associated boundary conditions are enforced by suitable terms in a functional which is stationary at the solution of the given problem and consequently the expansion functions used need not satisfy any of the boundary conditions.
A note on solitary wave solutions of the Leibovich-Roberts equation
Authors: Bogdan T. J. , Lerche I.
Published: December 2016

The propagation of weakly nonlinear, weakly dispersive sound waves in a magnetic cylinder satisfies an equation originally discussed in a limiting form by Leibovich (1970) and in general form by Roberts (1985). We show here that the resulting Leibovich-Roberts equation possesses nonlinear solitary wave behaviors akin to Benjamin-Ono waves in a slab. We also show how the structure of the solitary waves can be determined using a variational principle.
Initial-boundary value problems for the equation 𝑢_{𝑡𝑡}=(𝜎(𝑢ₓ))ₓ+(𝛼(𝑢ₓ)𝑢_{𝑥𝑡})ₓ+𝑓
Authors: Kuttler K. , Hicks D.
Published: December 2016

Existence and uniqueness theorems are proved for global weak solutions of initial-boundary value problems corresponding to the equation
\[
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="u Subscript t t Baseline equals left-parenthesis sigma left-parenthesis u Subscript x Baseline right-parenthesis right-parenthesis Subscript x Baseline plus left-parenthesis alpha left-parenthesis u Subscript x Baseline right-parenthesis u Subscript x t Baseline right-parenthesis Subscript x Baseline plus f">

u

t
t

=

(

σ

(

u
x

)

)

x

+

(

α

(

u
x

)

u

x
t

)

x

+
f

{u_{tt}} = {\left ( {\sigma \left ( {{u_x}} \right )} \right )_x} + {\left ( {\alpha \left ( {{u_x}} \right ){u_{xt}}} \right )_x} + f

\]
under assumptions that do not require smoothness or monotonicity of

σ
\sigma

. The initial data are not assumed to be smooth, the boundary data are allowed to be time dependent, and

f
f

is only assumed to be in

L
2

{L^2}

.
A mathematical problem from detonation theory
Authors: Fickett Wildon
Published: December 2016

A simplified abstraction of a partial-differential-equation problem which appears in the study of small perturbations on a detonation wave is studied. The interesting feature of this problem is that the function representing the unknown values of the dependent variable on one boundary appears as a source term in the partial differential equation. This unknown boundary function turns out to be the solution of an ordinary differential-difference equation. We study the properties of this differential-difference equation, and also present some representative solutions of the complete problem.
The figure-of-8 librations of the gravity gradient pendulum and modes of an orbiting tether
Authors: Melvin Peter J.
Published: December 2016

An algorithm is presented for the Hill-Poincaré analytical continuation of the out-of-plane normal mode of the gravity gradient pendulum. The Poincaré-Lindstedt solution employs 17 Poisson series and 24 recursion relations and was evaluated to the 50th order on a CRAY. The trajectories of the nonlinear normal modes are figures-of-8 on the unit sphere which can be computed nearly to the orbit normal. Numerical integrations indicate further that 1) initial conditions computed at the nadir can be used to generate figures-of-8 over the pole, 2) the single hemispherical figures-of-8 appear to be stable at large amplitudes, and 3) the gravity gradient pendulum has chaotic solutions. A theory is developed for the linear normal modes of a tethered satellite, and the eigenvalues are found for the rosary tether.
Nonlinear capillary-gravity waves in magnetic fluids
Authors: Malik S. K. , Singh M.
Published: December 2016

The nonlinear wave propagation of capillary-gravity waves on the surface of a ferrofluid of finite depth is investigated by employing the method of multiple scales. The stability analysis reveals the existence of different regions of instability. We show that the nonlinear modulational instability cannot be suppressed by the application of a strong magnetic field, however strong it may be. The influence of the magnetic field is not only quite signficant but its effect is also different for different regions of stability.
Remark on existence and uniqueness for the thermistor problem under mixed boundary conditions
Authors: Cimatti Giovanni
Published: December 2016

The steady-state electrical heating of a solid conductor is studied with mixed boundary conditions. A theorem of existence, nonexistence, and uniqueness of solutions is given under general assumptions on the electrical and thermal conductivities. The basic tool of the proof is a transformation first proposed in [3] by H. Diesselhorst.
Statics, structure, and residual normal moveout: Exact mathematical solutions in simple form
Authors: Lerche I.
Published: December 2016

The separation of seismic reflection times into the component parts due to source static, receiver static, structure time, and residual normal moveout is exhibited in terms of simple differential and integral operations on the reflection time. The solution is valid for all component parts which possess an

L
2

{L_2}

norm on the open one-dimensional domain of common midpoint. The equations yield simple, explicit solutions for each separate component. Possible methods of implementing these direct solutions for real travel-time data are presented with suggestions for avoiding, or bypassing, the differential operations. These solutions are presented both to provide a novel viewpoint for examining the so-called statics equation and as an aid to those who are actively pursuing the problem of finding methods for successfully optimizing statics problems in divers and diverse situations.
Plane strain problem of two coplanar cracks in an initially stressed neo-Hookean anisotropic infinite medium
Authors: Singh Brij M. , Dhaliwal Ranjit S.
Published: December 2016

We consider the plane strain problem of determining the crack energy in an initially stressed neo-Hookean anisotropic infinite medium containing two coplanar cracks. We assume that the cracks are opened by a constant internal pressure. By using a Fourier transform solution of the equilibrium equations the problem is reduced to solving a set of triple integral equations with a cosine kernel. These integral equations are solved and a closed-form expression for the crack energy

W
W

is obtained. The numerical values of

W
W

are graphed in Figs. 1, 2.
Viscoelastic Rayleigh waves
Authors: Currie P. K. , Hayes M. A. , O’Leary P. M.
Published: December 2016

A general analysis is given of the propagation of surface waves over a half-space of homogeneous isotropic linearly-viscoelastic material. Particular emphasis is placed on the properties of the particle paths. The detailed examination of particular models shows that (in contrast with elastic materials) (i) more than one surface wave may be possible; (ii) the waves may be either direct or retrograde at the surface; (iii) the motion may change sense at many or no levels below the surface; (iv) the wave speed may be greater than the body-wave speeds.
Theory of multi-diffusion flames
Authors: Liu T. M. , Chiu H. H.
Published: December 2016

A theory which provides categorical classification and prediction of flame configurations for multi-component mixtures consisting of

N
N

species has been developed. The application of the theory of irreducible operators decouples the species equations; and the fundamental solutions, if they exist, satisfy the same equations as that of a binary mixture. The theory is applied to two flow configurations: first, the flame at the mouth of a tube in a duct, and second, the flame in an unconfined jet. The single mode flame structure is essentially the same as that of binary diffusion approximation with proper modification of the effective diffusivity. The double mode structure consists of two diffusion modes. The individual mode satisfies the diffusion equation with characteristic effective diffusivity. The theory could be easily used by experiments and designers for practical purposes such as correlating experimental data or estimating burner size.
Motion of an explosive-induced plane shock wave
Authors: Fickett W.
Published: December 2016

A plane, unsupported, Chapman-Jouguet detonation in a condensed explosive drives a decelerating shock into a semi-infinite inert of lower shock impedance. A previously reported exact solution for a portion of this one-dimensional time-dependent problem is extended to the entire flow field, and some numerical results are given. The solution has the form of a small set of first-order ordinary differential equations for the shock, and a similar set for each particle path.
On wave propagation problems in which 𝑐_{𝑓}=𝑐_{𝑠}=𝑐₂ occurs
Authors: Ting T. C. T.
Published: December 2016

The combined longitudinal and torsional plastic waves in a thin-walled tube of rate-independent isotropic work-hardening material are used to illustrate the problems involved when the situation

c
f

=

c
8

=

c
2

{c_f} = {c_8} = {c_2}

occurs. Two examples are presented. In the first example, the stress paths in the

σ
∼
τ

\sigma \sim \tau

plane for the fast and slow simple waves are examined in the region near the singular point

(

σ
∗
,
0

)

\left ( {\sigma *,0} \right )

where

c
f

=

c
8

=

c
2

{c_f} = {c_8} = {c_2}

. For

η
≥

1
2

\eta \ge \frac {1}{2}

, where

η
\eta

is a nondimensional material constant defined in the paper, there is no stress path passing through the singular point

(
σ
∗
,
0
)

(\sigma *,0)

other than the

σ
\sigma

-axis itself. For

0
>
η
>

1
2

0 > \eta > \frac {1}{2}

, there is a family of stress paths emanated from

(
σ
∗
,
0
)

(\sigma *,0)

which span an angle of

tan

−
1

(

1
−
2
η

)

1

/

2

{\tan ^{ - 1}}{\left ( {1 - 2\eta } \right )^{1/2}}

with the

σ
\sigma

-axis. In any case, the stress paths for the fast and slow simple waves are not orthogonal to each other at the singular point. In the second example, a study is made of the propagation of the plastic wave front into the tube which is initially prestressed at the stress state

(

σ
∗
,
0

)

\left ( {\sigma *,0} \right )

. It is shown that the solution in the region next to a region of constant state is not necessarily a simple wave solution. In fact, an unloading can occur at the plastic wave front which changes its speed from

c
2

{c_2}

to

c
0

{c_0}

at the onset of the unloading.
Refraction of acoustic duct waveguide modes by exhaust jets
Authors: Mani R.
Published: December 2016

The refraction of acoustic duct waveguide modes emitted from the open end of a semi-infinite rectangular duct by a jet-like exhaust flow is studied theoretically. The problem is formulated as a Wiener-Hopf problem and is ultimately solved by an approximate method due to Carrier and Koiter. Continuity of transverse acoustic particle displacement and of acoustic pressure is assumed at the jet/still-air interface. The solution exhibits several features of the acoustics of moving media such as a source convection effect, zones of relative silence, simple refraction, etc. Plots of far-field directivity patterns are presented for several cases and show refraction effects to be important even at modest exhaust Mach numbers of order 0.3. Only subsonic exhaust Mach numbers are considered. In view of the problem’s technological interest, the solution for the far-field directivity is written out in full detail in the appendices. In the low-frequency limit when only one duct waveguide mode (the plane wave mode) propagates, we also examine the reflection coefficient. It is found that this reflection coefficient, in general, considerably exceeds either the no-flow value or the value for the case with uniform flow both inside and outside the waveguide (i.e., in the whole space). Apparently the acoustic medium mismatch enhances the geometric mismatch in the jet flow case, thus producing a higher reflection coefficient.
Adventures in applied mathematics
Authors: Pekeris C. L.
Published: December 2016

A review is given of the work carried out at the Weizmann Institute during the past 25 years in the fields of terrestrial spectroscopy, the dynamo theory of the earth’s magnetic field, the tides in the world oceans, theoretical seismograms, hydrodynamic stability, atomic spectroscopy, and the Boltzmann integral equation. Some open problems in the solution of the Schrödinger wave equation are formulated.
An improved estimate for the error in the classical, linear theory of plate bending
Authors: Simmonds James G.
Published: December 2016

The relative mean square error in the three-dimensional stress field predicted by classical plate theory is shown to be

O

(

h

/

L
∗

)

2

O{\left ( {h/{L_ * }} \right )^2}

, where

h
h

is the plate thickness and

L
∗

{L_ * }

is a mean square measure of the wavelength of the midplane deformation pattern. This improves a recent result of Nordgren who obtained a relative error estimate of

O

(

h

/

L
∗

)

O\left ( {h/{L_ * }} \right )

. The improved error estimate, which, like Nordgren’s, is based on the Prager—Synge hypercircle theorem in elasticity, is obtained by constructing a kinematically admissible three-dimensional displacement field that depends on the solution of the classical plate equations but which yields an accurate, nonzero distribution of the transverse shearing strain through the thickness.
Unsteady vaporization of liquid droplet
Authors: Chiu H. H.
Published: December 2016

The development of the temperature and concentration profiles in the vicinity of a vaporizing liquid droplet exposed to a hot gas, when Soret and Dufour numbers are finite, is examined under linearized theory consisting of two coupled diffusion equations.
A class of motions with constant stretch history
Authors: Huilgol R. R.
Published: December 2016

The purpose of this paper is to examine the kinematics and dynamics of a class of motions with constant stretch history. A kinematical result is announced to indicate the velocity field such a motion may have and two examples, viz. helical-torsional flow and the helical flow combined with the axial motion of fanned planes, are discussed in detail. The helical-torsional flow is found to be experimentally realizable, albeit approximately, and it is shown how an apparatus may be built to measure the material functions occurring in such flows. Two nonlinear differential equations are derived to determine the velocity profile when the motion under study is treated as a nearly viscometric flow. In addition, restrictions on the proper numbers of the first Rivlin-Ericksen tensor are arrived at so that the motion with constant stretch history is completely determined by the first two or first three Rivlin-Ericksen tensors. This permits a reduction in the number of terms occurring in the full expansion of the constitutive equation.
Canonical approach to biharmonic variational problems
Authors: Arthurs A. M.
Published: December 2016

A canonical approach to biharmonic variational problems is presented. It provides a new form of the principle of stationary energy and a new derivation of the principle of minimum potential energy.
Singular stress concentrations in second-grade materials
Authors: Lardner R. W.
Published: December 2016

The problems of a second-grade elastic half-space deformed in plane strain and subject to a concentrated load, a discontinuous load, and a double force, acting at a point on the free surface are solved. The nature of the stress singularity is found in each case. Although the strengths of the stress singularities are the same as for both classical elasticity and conventional couple-stress materials, the detailed forms are different and depend on a certain combination of the five new elastic constants. The displacement field produced by a point load is bounded in the neighbourhood of the point of application of the force, in contrast to both earlier theories where it is singular.
Boundary shape identification problems in two-dimensional domains related to thermal testing of materials
Authors: Banks H. T. , Kojima Fumio
Published: December 2016

This paper is concerned with the identification of the geometrical structure of the system boundary for a two-dimensional diffusion system. The domain identification problem treated here is converted into an optimization problem based on a fit-to-data criterion and theoretical convergence results for approximate identification techniques are discussed. Results of numerical experiments to demonstrate the efficacy of the theoretical ideas are reported.
Note on the roots of 𝑓(𝑧)=𝐽₀(𝑧)-𝑖𝐽₁(𝑧)
Authors: Rawlins A. D.
Published: December 2016

An elementary proof is given which shows that

f

(
z
)

f\left ( z \right )

has no zeros in the upper half plane.
The starting solution for two-dimensional heat conduction problems with change of phase
Authors: Boley Bruno A. , Yagoda Harvey P.
Published: December 2016

A short-time solution for two-dimensional change-of-phase problems for a half space is developed. The problems are such that melting starts at a point of the surface and spreads both along the surface and towards the interior of the body. Heating is applied by an analytic but otherwise general heat input.
On the formulation of constitutive equations for living soft tissues
Authors: Prager William
Published: December 2016

Soft living tissues deform freely under negligible stresses until a certain strain level is reached at which their stiffness increases sharply. Constitutive equations are developed that describe this kind of mechanical behavior and include Hooke’s law as a limiting case. It is shown that, similar to Hooke’s law, these constitutive equations assure uniqueness of solution for a broad class of boundary value problems. Possible extensions of the theory are briefly indicated.
Cohomology of uniserial 𝑝-adic space groups
Authors: Díaz Ramos Antonio , Garaialde Ocaña Oihana , González-Sánchez Jon
Published: December 2016

A decade ago, J. F. Carlson proved that there are finitely many cohomology rings of finite22-groups of fixed coclass, and he conjectured that this result ought to be true for odd primes. In this paper, we prove the non-twisted case of Carlson’s conjecture for any prime and we show how to proceed in the twisted case.
GWAlpha: genome-wide estimation of additive effects (alpha) based on trait quantile distribution from pool-sequencing experiments
Authors: Fournier-Level Alexandre , Robin Charles , Balding David J
Published: December 2016

Motivation

Sequencing pools of individuals (Pool-Seq) is a cost-effective way to gain insight into the genetics of complex traits, but as yet no parametric method has been developed to both test for genetic effects and estimate their magnitude. Here, we propose GWAlpha, a flexible method to obtain parametric estimates of genetic effects genome-wide from Pool-Seq experiments.

Results

We showed that GWAlpha powerfully replicates the results of Genome-Wide Association Studies (GWAS) from model organisms. We perform simulation studies that illustrate the effect on power of sample size and number of pools and test the method on different experimental data.

Availability and Implementation

GWAlpha is implemented in python, designed to run on Linux operating system and tested on Mac OS. It is freely available at https://github.com/aflevel/GWAlpha.

Supplementary information

Supplementary data are available at Bioinformatics online.
Impact and Cost-effectiveness of Selective Human Papillomavirus Vaccination of Men Who Have Sex With Men
Authors: Lin Allen , Ong Koh J. , Hobbelen Peter , King Eleanor , Mesher David , Edmunds W. John , Sonnenberg Pam , Gilson Richard , Bains Irenjeet , Choi Yoon H. , Tanton Clare , Soldan Kate , Jit Mark
Published: December 2016

Background.

Men who have sex with men (MSM) have a high lifetime risk of anogenital warts and cancers related to infection with human papillomavirus (HPV). They also benefit less from herd protection than heterosexual males in settings with female-only HPV vaccination.

Methods.

We evaluated the potential health impact and cost-effectiveness of offering vaccination to MSM who visit genitourinary medicine (GUM) clinics. We used a mathematical model of HPV 6/11/16/18 sexual transmission within an MSM population in England, parameterized with sexual behaviour, GUM attendance, HPV prevalence, HIV prevalence, warts, and cancer incidence data. Interventions considered were offering HPV vaccination to either HIV-positive MSM or MSM regardless of HIV status, for age bands 16–25, 16–30, 16–35, and 16–40 years.

Results.

Substantial declines in anogenital warts and male HPV-related cancer incidence are projected to occur following an offer of vaccination to MSM. MSM not attending GUM clinics will partially benefit from herd protection. Offering vaccination to HIV-positive MSM up to age 40 is likely to be cost-effective if vaccine procurement and administration costs are below £96.50 a dose. At £48 a dose, offering vaccination to all MSM up to age 40 is likely to be cost-effective.

Conclusions.

Quadrivalent HPV vaccination of MSM via GUM clinics is likely to be an effective and cost-effective way of reducing the burden of HPV-related disease in MSM.
Operationalizing and implementing ecosystem-based management
Authors: Link Jason S. , Browman Howard I.
Published: December 2016

There is now a large literature on ecosystem-based management (EBM; also known as the ecosystem approach). Our sense is that EBM is moving - albeit slowly - from the “what's, why's and when's” to the “how's” of operationalization and implementation; as such it seemed timely to develop this article theme set (TS). Our objectives were to ascertain the state of the discipline and to advance EBM by offering practical examples of its implementation - or attempts at such - in a variety of incarnations and at various scales, including what has or has not worked, suggestions for best practice, and lessons learned. As exemplified by the articles in this TS, key lessons learned include the need for: constant and clear communication with all parties involved; clear objectives and governance; the distillation of complex ecosystem information into digestible indicators; the establishment of reference levels on which management decisions can be made; and clear protocols to evaluate tradeoffs. Instances of truly multisectoral EBM remain rare, with EBM having advanced farthest within specific ocean-use sectors. Although progress towards implementing operational EBM has been somewhat limited, and although EBM is by its very nature complex and difficult to operationalize, there has been progress nonetheless. We hope that this TS will encourage even further operationalization of EBM.
Emergence of Novel PathogenicStreptomycesSpecies by Site-Specific Accretion andcis-Mobilization of Pathogenicity Islands
Authors: Zhang Yucheng , Loria Rosemary
Published: December 2016

The main pathogenicity factor of Streptomyces species associated with the potato common scab disease is a nitrated diketopiperazine called thaxtomin A (ThxA). In Streptomyces scabiei (syn. S. scabies), which is thought to be the most ancient pathogenic Streptomyces species, the ThxA biosynthetic cluster is located within a mobile genomic island called the toxicogenic region (TR). Three attachment (att) sites further separate TR into two subregions (TR1 and TR2). TR1 contains the ThxA biosynthetic cluster and is conserved among several pathogenic Streptomyces species. However, TR2, an integrative and conjugative element, is missing in most pathogenic species. In our previous study, we demonstrated the mobilization of the whole TR element or TR2 alone between S. scabiei and nonpathogenic Streptomyces species. TR1 alone did not mobilize in these experiments. These data suggest that TR2 is required for the mobilization of TR1. Here, we show that TR2 can self mobilize to pathogenic Streptomyces species harboring only TR1 and integrate into the att site of TR1, leading to the tandem accretion of resident TR1 and incoming TR2. The incoming TR2 can further mobilize resident TR1 in cis and transfer to a new recipient cell. Our study demonstrated that TR1 is a nonautonomous cis-mobilizable element and that it can hijack TR2 recombination and conjugation machinery to excise, transfer, and integrate, leading to the dissemination of pathogenicity genes and emergence of novel pathogenic species. Additionally, comparative genomic analysis of 23 pathogenic Streptomyces isolates from ten species revealed that the composite pathogenicity island (PAI) formed by TR1 and TR2 is dynamic and various compositions of the island exist within the population of newly emerged pathogenic species, indicating the structural instability of this composite PAI.
United States Health Care Reform Progress to Date and Next Steps
Authors: Obama Barack
Published: December 2016

(Abstracted from JAMA 2016;316(5):525–532)

The economy, federal budgets, and the financial well-being of American families are all impacted by health care costs. To combat the issues of the rapid rise in health care costs as well as to address the issue of a significant proportion of the population being uninsured, the Affordable Care Act (ACA) was the most important health care legislation enacted in the United States since the creation of Medicare and Medicaid in 1965.
Epigenetic Germline Inheritance of Diet-Induced Obesity and Insulin Resistance
Authors: Huypens Peter , Sass Steffen , Wu Moya , Dyckhoff Daniela , Tschöp Matthias , Theis Fabian , Marschall Susan , de Angelis Martin Hrabě , Beckers Johannes
Published: December 2016

(Abstracted from Nat Genet 2016;48:497–499)

Several genetic risk factors for diabetes and obesity have been identified. In addition to genetic risk factors, it has been proposed that epigenetic alterations in gametes are another potential mechanism of disease risk inheritance.
Symptomatic Implant Removal Following Dual Mini-Fragment Plating for Clavicular Shaft Fractures
Authors: Czajka Cory M. , Kay Andrew , Gary Joshua L. , Prasarn Mark L. , Choo Andrew M. , Munz John W. , Harvin William H. , Achor Timothy S.
Published: December 2016

Objectives:

To determine the proportion of patients requiring secondary surgery for symptomatic implant removal after open reduction, internal fixation using dual mini-fragment plating technique for clavicular shaft fractures.

Design:

Retrospective observational study.

Setting:

Single university Level 1 trauma center.

Patients:

Eighty-one patients treated with open reduction, internal fixation using dual mini-fragment plating technique for clavicular shaft fractures (OTA/AO 15-B1, B2, and B3) with minimum 12-month follow-up (median 477 days; range 371–1549 days).

Intervention:

Open reduction, internal fixation using dual mini-fragment plating technique for clavicular shaft fractures.

Main Outcome Measurements:

Incidence of secondary surgery, QuickDASH (Disabilities of the Arm, Shoulder, and Hand) scores.

Results:

Six of 81 patients (7.4%) underwent secondary surgery for implant removal for any reason. Of these, 3 (3.7%) underwent symptomatic implant (soft-tissue irritation) removal, 2 (2.5%) required implant removal in the setting of infection, and 1 patient (1.2%) required revision open reduction internal fixation for early implant failure. The mean QuickDASH score in this series was 8.44 (±6.94, range 0–77.27). The associated implant cost of the typical construct utilized in this series was $1511.38. The mean surgical time was 97 minutes (range 71–143 minutes).

Conclusions:

The utilization of a dual mini-fragment plating technique in the treatment of clavicular shaft fractures results in a low rates of secondary surgery for symptomatic implant removal (3.7%) and similar QuickDASH scores when compared with historical controls treated with 3.5-mm plates placed on the superior clavicle. Potential disadvantages in using this technique include a higher surgical implant cost and length of surgery.

Level of Evidence:

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.
Advanced Imaging Lacks Clinical Utility in Treating Geriatric Pelvic Ring Injuries Caused by Low-Energy Trauma
Authors: Natoli Roman M. , Fogel Harold A. , Holt Daniel , Schiff Adam , Bernstein Mitchell , Summers Hobie D. , Lack William
Published: December 2016

Objectives:

Is advanced imaging necessary in the evaluation of pelvic fractures caused by low-energy trauma in elderly patients?

Design:

Retrospective review.

Setting:

Single institution, Level 1 Trauma Center.

Patients:

Age ≥60 years old treated for low-energy traumatic pelvic ring injuries.

Intervention:

None.

Main Outcomes:

Posterior pelvic ring injuries diagnosed on advanced imaging, radiographic displacement, admission status, hospital length of stay, change in weight-bearing status recommendations, and whether operative treatment was pursued.

Results:

Eighty-seven patients met the inclusion criteria, of which 42 had advanced imaging to evaluate the posterior pelvic ring (10 magnetic resonance imaging, 32 computed tomography). More posterior pelvic ring injuries were identified with advanced imaging compared with radiographs alone (P < 0.001). There was no statistically significant difference in rate of admission (P = 0.5) or hospital length of stay (P = 0.31) between patients with radiographs alone compared with patients evaluated with radiographs plus advanced imaging. The rate of displacement >1 cm at presentation and 6-week follow-up was unaffected by the presence of a posterior injury diagnosed on advanced imaging. Treatment for all 87 patients remained weight-bearing as tolerated with assist device irrespective of advanced imaging findings, and no patient underwent surgical intervention by 12-week follow-up.

Conclusions:

Despite frequent identification of posterior pelvic ring injuries in patients evaluated with advanced imaging, admission status, length of hospital stay, radiographic displacement, and treatment recommendations were unaffected by these findings. The use of advanced imaging in elderly patients with low-energy traumatic pelvic ring fractures may not be necessary.

Level of Evidence:

Diagnostic Level IV. See Instructions for Authors for a complete description of levels of evidence.
The Role of Computed Tomography in Surgical Planning for Trimalleolar Fracture. A Survey of OTA Members
Authors: Gibson Peter D. , Bercik Micheal J. , Ippolito Joseph A. , Didesch Jacob , Hwang John S. , Koury Kenneth L. , Sirkin Michael , Adams Mark , Reilly Mark C.
Published: December 2016

Objective:

Does the additional information provided by computed tomography (CT) alter surgeons' treatment plans for trimalleolar ankle fracture?

Design:

Prospective.

Setting:

Electronic survey.

Patients/Participants:

Members of the OTA.

Intervention:

Compare management of trimalleolar ankle fracture before and after CT.

Main Outcome Measurements:

Compare types of fixation used, indication for fixation, and approach need for fixation before and after CT.

Results:

Overall, OTA members' operative technique changed in 430 of the 1710 (25.1%) cases after review of the CT images. Of the 430 observations in which the operative technique was altered, the surgeon had initially stated that they would not have requested a CT in 51.2% incidences. When analyzing if CT affected whether or not operative fixation was indicated, a total of 16.3% responses changed. Surgeons were significantly more likely to change from no fixation to fixation (11.5%) than vice versa (4.8%) after reviewing CT imaging. A total of 17.8% of responses changed operative approach after reviewing the CT; 11.7% changed to open reduction internal fixation, whereas 6.1% changed away from open reduction internal fixation.

Conclusion:

A consensus on the ideal treatment of trimalleolar fractures remains elusive, evidenced by a high variation in treatment preference, both before and after CT review. Our results demonstrate with the additional information delineated on CT, a surgeons' operative plan, technique, and approach often change. With greater than 25% of respondents changing their treatment strategy after seeing CT imaging, radiographs alone limited surgeon understanding of fracture pattern. Because of difficulty understanding the posterior fracture fragment, we recommend preoperative CT on all trimalleolar fractures.

Level of Evidence:

Diagnostic Level V. See Instructions for Authors for a complete description of levels of evidence.
Association Between Age of Beginning Primary School and Attention Deficit Hyperactivity Disorder
Authors: Gökçe Sebla , Yazgan Yanki , Ayaz Ayşe Burcu , Kayan Esengül , Yusufoğlu Canan , Carkaxhiu Bulut Gresa , Aslan Genç Herdem , Dedeoğlu Ceyda , Demirhan Seçil , Sancak Arzu , Saridoğan Gökçe Elif
Published: December 2016

Objective:

In April 2012, the Turkish national education system was modified, and the compulsory school age of entry (first grade) was redefined as a minimum of 60 months and a maximum of 66 months (replacing the former minimum criterion of 72 months). In this study, we hypothesized that students starting school before 72 months (the previous age standard for the first grade) may experience (1) a greater number of symptoms of attention deficit hyperactivity disorder (ADHD) and (2) lower functioning in social, behavioral, and academic domains.

Method:

We performed a cross-sectional community-based study in the first and second grades of all primary schools (4356 students) located in the Kadıköy county of Istanbul, Turkey. Teachers completed Swanson, Nolan, and Pelham version IV and Conners' Teacher's report forms for symptoms of ADHD, the Perceived Competence Scale for functioning, and a sociodemographic questionnaire.

Results:

Among first graders, the group that began primary school before the age of 72 months had a higher ADHD prevalence than both of the groups that began primary school between the ages of 72 to 77 months and 78 to 83 months (p < .001 for both groups). ADHD symptoms diminished and academic, social, and behavioral functioning improved with age for the first and second grade students.

Conclusion:

The probability of displaying ADHD symptoms (and caseness) is greater among the “earlier” beginners, whereas the “conventional” classmates exhibited better academic, social, and behavioral functioning.