bluuebunny/crossref_metadata_2025 huggingface dataset:
Synchronization of traffic lights for high flow
Authors: Newell G. F.
Published: December 2016

It is assumed here that the flow of traffic is so heavy that it can be described qualitatively by existing theories wherein each car follows another with no passing and that platoons formed by traffic lights spread so much between lights that the time between the arrival of the first and last cars of a platoon at a light exceeds the green period. Under such conditions it is shown that the best pairwise synchronization of lights gives the best overall synchronization for one-directional traffic. The synchronization which minimizes the total delay for all cars is one for which the tail car of a platoon suffers no delay but the lead car is stopped. For two-directional traffic, heavy in both directions, the best synchronization is very likely to be that which is optimal for the direction of traffic with the lower flow.
On variational principles in thermoelasticity and heat conduction
Authors: Herrmann G.
Published: December 2016

The variational principles for displacements, for stresses and for both displacements and stresses in isothermal elasticity are extended to the coupled processes of thermoelasticity and heat conduction in a three-dimensional, anisotropic body. The character of these principles is examined and it is established that in a stable system one is concerned with a minimum, a maximum and a stationary value problem, respectively.
On solving second order nonlinear differential equations
Authors: Zee Chong-Hung
Published: December 2016

A direct power series substitution technique is proposed to solve second order nonlinear differential equations. The errors in truncated power series are estimated to determine the significance of the result.
The maximum-minimum principles for a quasi-linear parabolic finite difference equation
Authors: Ting Thomas C. T.
Published: December 2016

A strong maximum principle for second order parabolic equations has been introduced by L. Nirenberg. The present paper contains both strong and weak maximum-minimum principles for various finite difference equations which approximate a quasi-linear parabolic differential equation. A proof of the existence and uniqueness of the solution of the finite difference equations is also presented.
A theory of nonlinear networks. I
Authors: Brayton R. K. , Moser J. K.
Published: December 2016

This report describes a new approach to nonlinear RLC-networks which is based on the fact that the system of differential equations for such networks has the special form
\[
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="upper L left-parenthesis i right-parenthesis StartFraction d i Over d t EndFraction equals StartFraction partial-differential upper P left-parenthesis i comma v right-parenthesis Over partial-differential i EndFraction comma upper C left-parenthesis v right-parenthesis StartFraction d v Over d t EndFraction equals minus StartFraction partial-differential upper P left-parenthesis i comma v right-parenthesis Over partial-differential v EndFraction period">

L

(
i
)

d
i

d
t

=

∂
P

(

i
,
v

)

∂
i

,
C

(
v
)

d
v

d
t

=
−

∂
P

(

i
,
v

)

∂
v

.

L\left ( i \right )\frac {{di}}{{dt}} = \frac {{\partial P\left ( {i,v} \right )}}{{\partial i}},C\left ( v \right )\frac {{dv}}{{dt}} = - \frac {{\partial P\left ( {i,v} \right )}}{{\partial v}}.

\]
The function,

P

(

i
,
v

)

P\left ( {i,v} \right )

, called the mixed potential function, can be used to construct Liapounov-type functions to prove stability under certain conditions. Several theorems on the stability of circuits are derived and examples are given to illustrate the results. A procedure is given to construct the mixed potential function directly from the circuit. The concepts of a complete set of mixed variables and a complete circuit are defined.
Distance matrix of a graph and its realizability
Authors: Hakimi S. L. , Yau S. S.
Published: December 2016

The distances in a linear graph are described by a distance matrix

D
D

. The realizability of a given

D
D

by a linear graph is discussed and conditions under which the realization of

D
D

is unique are established. The optimum realization of

D
D

, (i.e., the realization of

D
D

with “minimum total length"), is investigated. A procedure is given by which a tree realization of

D
D

can be found, if such a realization exists. Finally, it is shown that a tree realization, if it exists, is unique and is the optimum realization of

D
D

.
Formal equivalence of the nonlinear string and one-dimensional fluid flow
Authors: Rosen Gerald
Published: December 2016

By applying transformations to the dynamical equation for the longitudinal vibrations of a nonlinear model string, we obtain a set of equations which describes the one-dimensional flow of an ideal compressible polytropic fluid. Thus it is shown that the nonlinear string problem is formally equivalent to the classical problem of fluid flow analyzed by Riemann and by others.
A note on the integral equation methods in potential theory
Authors: Maiti M.
Published: December 2016

This note defines the kernel functions for the generation of conjugate harmonic functions in the theory of singular integral equations adapted to the boundary value problems of potential theory and elastostatics.
An application of the method of moments to stochastic equations
Authors: McCoy John J.
Published: December 2016

A modified form of Galerkin’s method is formally applied to an equation involving a stochastic bounded linear operator. The result, in general, is a sequence of stochastic linear algebraic equations. In the case of a statistically homogeneous operator, however, it is possible to obtain a sequence of deterministic linear algebraic equations. The formalism is applied to determining the electric field in a dielectric with a statistically homogeneous random permittivity.
Some implications of work hardening and ideal plasticity
Authors: Drucker D. C.
Published: December 2016

The purpose of this note is to point out the severe restriction imposed on possible stress-strain relations by a mathematical formulation of the concepts of work hardening and ideal plasticity. Using this condition, an algebraic derivation and extension is given of Prager’s extension of the Mises plastic potential function. A brief discussion is also given of the meaning of stability of plastic deformation as contrasted with stability of non-conservative systems in general.
Quasi-stationary airfoil theory in subsonic compressible flow
Authors: Miles John W.
Published: December 2016

A solution of the integral equation for an oscillating, two-dimensional, thin airfoil in a compressible flow (subsonic and inviscid) is obtained by retaining only first order terms in frequency. The results are applied to the calculation of the damping derivative of a tail in rotary motion about a forward center, and it is shown that the damping is considerably less than that calculated on the basis of stationary airfoil theory. A brief investigation of induction effects shows this reduction to be considerably less for a wing of finite aspect ratio.
Minimal problems in airplane performance
Authors: Garfinkel Boris
Published: December 2016

We develop here the theory of operating an airplane so as to minimize an arbitrary function of the end-values of the generalized coordinates. A propeller-driven airplane is treated as a particle in equilibrium, subject to the forces of drag, lift, thrust, and gravity. We assume that the specific fuel consumption is a function of the power only, and that the available power is independent of the altitude. The problem is shown to be of the Bolza type in the Calculus of Variations, with the complications arising from the presence of inequalities, discontinuities, and variables whose derivatives do not enter the problem explicitly. The Euler-Lagrange equations are derived and discussed.
Extended limit design theorems for continuous media
Authors: Drucker D. C. , Prager W. , Greenberg H. J.
Published: December 2016

Earlier results [1,2]

2

^{2}

on safe loads for a Prandtl-Reuss material subject to surface tractions or displacements which increase in ratio are here extended to any perfectly plastic material and any history of loading.
On Brownian motion, Boltzmann’s equation, and the Fokker-Planck equation
Authors: Keilson Julian , Storer James E.
Published: December 2016

In order to describe Brownian motion rigorously, Boltzmann’s integral equation must be used. The Fokker-Planck type of equation is only an approximation to the Boltzmann equation and its domain of validity is worth examining. A treatment of the Brownian motion in velocity space of a particle with known initial velocity based on Boltzmann’s integral equation is given. The integral equation, which employs a suitable scattering kernel, is solved and its solution compared with that of the corresponding Fokker-Planck equation. It is seen that when

M

/

m

M/m

, the mass ratio of the particles involved, is sufficiently high and the dispersion of the velocity distribution sufficiently great, the Fokker-Planck equation is an excellent description. Even when the dispersion is small, the first and second moments of the Fokker-Planck solution are reliable. The higher moments, however, are then in considerable error—an error which becomes negligible as the dispersion increases.
On the numerical integration of ordinary differential equations of the first order
Authors: Löwdin Per-Olov
Published: December 2016

The difference methods for the numerical integration of ordinary differential equations of the first order are discussed by using operator calculus and symbolic expansions. A new straightforward central difference method is developed, which is based on a formula closely associated with Simpson’s rule. The main features of the method are that, for each step of integration, the largest unknown term is determined by an algebraic equation and that the remaining difference correction is extremely small. The method can directly be applied even to systems of the first order with one-point boundary conditions. A numerical example is given.
An iterative solution to the effects of concentrated loads applied to long rectangular beams
Authors: Gray C. A. M.
Published: December 2016

The analysis of the bending of thin deep rectangular beams by concentrated loads has already been treated by L.N.G. Filon and Th. v. Kármán. These authors consider an infinitely long beam and express the load as a Fourier integral, obtaining integral solutions for the stresses and displacements. In their integral form, these results are rather difficult to interpret, although F. Seewald, using Kármán’s analysis, has calculated numerical values for the case of a single concentrated load.
Similarity laws for supersonic flows
Authors: Pack D. C. , Pai S. I.
Published: December 2016

The non-linear differential equation for the velocity potential of three-dimensional steady irrotational supersonic flow past wings of finite span has been investigated. It is found that the whole Mach number range from 1 to

∞
\infty

may be divided into two regions (not strictly divided), in each of which similarity laws are obtained, with two parameters

K
1

=

(

M
2

−
1

)

1

/

2

/

τ
n

{K_1} = {\left ( {{M^2} - 1} \right )^{1/2}}/{\tau ^n}

and

K
2

=
A

(

M
2

−
1

)

1

/

2

{K_2} = A{\left ( {{M^2} - 1} \right )^{1/2}}

;

τ
\tau

is the non-dimensional thickness ratio,

A
A

the aspect ratio of the wing,

M
M

the Mach number of the uniform stream in which the wing is placed. The factor

n
n

is given explicitly as a function of

M
M

and

τ
\tau

; in the lower region of Mach numbers it tends to

1

/

3

1/3

as

M
→
1

M \to 1

, for all

τ
\tau

, giving the ordinary transonic rule, and in the upper region it tends to

−
1

- 1

as

M
→
∞

M \to \infty

, for all

τ
\tau

, as in the ordinary hypersonic rule.
On the theory of the bulge test
Authors: Ross E. W. , Prager W.
Published: December 2016

It is shown that the use of Tresca’s yield condition and the associated low rule leads to a simple theory for the bulge test for perfectly plastic or strain-hardening materials. The basic equations can be integrated in closed form even for finite deflections.
On diffusion in an external field and the adjoint source problem
Authors: Keilson Julian
Published: December 2016

If diffusion in an external field is described by

∂
ρ

/

∂
t
=
D

∇
2

ρ
−
ρ

/

τ
−
∇
⋅

(

F

(
r
)

ρ

)

\partial \rho /\partial t = D{\nabla ^2}\rho - \rho /\tau - \nabla \cdot \left ( {F\left ( r \right )\rho } \right )

, the function

γ

(

r
0

)

\gamma \left ( {{r_0}} \right )

describing the probability that a particle at

r
0

{r_0}

will reach a collector surface before decaying or being absorbed by other surfaces satisfies the equation

D

∇
2

γ
−
γ

/

τ
+
F

(
r
)

⋅
∇
γ
=
0

D{\nabla ^2}\gamma - \gamma /\tau + F\left ( r \right ) \cdot \nabla \gamma = 0

. This equation has no singularity to disturb any geometric symmetry available. Boundary conditions on

γ

(
r
)

\gamma \left ( r \right )

at the collector surface and other influencing surfaces are derived and shown to be independent of the external field. The boundary conditions at the secondary surfaces are homogeneous. The collector surface boundary condition is inhomogeneous.
Indentation pressure of a smooth circular punch
Authors: Levin E.
Published: December 2016

A smooth, flat, rigid punch under increasing normal load presses against a half space of a perfectly plastic material which obeys Tresca’s yield criterion. An admissible velocity field is constructed for an arbitrary smooth punch hence, for any particular case, a limit design theorem of Drucker, Prager and Greenberg may be used to compute an upper bound for the punch indentation pressure. A lower bound for any convex area of indentation has been given by Shield and Drucker. The results of the present paper are used to compute an upper bound for a punch with circular cross section. It is conjectured that this is an upper bound for an arbitrary punch.
The stability of viscous flow between rotating cylinders
Authors: Steinman H.
Published: December 2016

In this paper Chandrasekhar’s method of solving the characteristic value problem in the theory of the stability of viscous flow between rotating cylinders is carried to a higher approximation. A comparison between the results of the various calculations among themselves and with the experiments confirms the greater feasibility of the present method.
On the growth of Taylor-Görtler vortices along highly concave walls
Authors: Smith A. M. O.
Published: December 2016

The primary objective of this study has been to prepare a chart for computing the growth of Taylor-Görtler vortices in laminar flow along walls of both high and low concave curvature. Taylor-Görtler vortices are streamwise vortices having alternate right- and left-hand rotation that may develop in the laminar boundary layer along a concave surface.
Intermodulation products for 𝜈-law biased wave rectifier for multiply frequency input
Authors: Feuerstein E.
Published: December 2016

The intermodulation products obtained by passing the sum of

N
+
1

N + 1

sinusoids of amplitudes

P
1

,
⋅
⋅
⋅

P
N

{P_1}, \cdot \cdot \cdot {P_N}

through a power rectifier of characteristic
\[
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="upper I equals left-brace StartLayout 1st Row 0 2nd Row alpha left-parenthesis upper V minus upper B right-parenthesis Superscript v Baseline EndLayout StartLayout 1st Row upper V greater-than upper B 2nd Row upper V greater-than upper B v greater-than 0 EndLayout">

I
=

{

0

α

(

V
−
B

)

v

V
>
B

V
>
B

v
>
0

I = \left \{ {\begin {array}{*{20}{l}}0\\{\alpha {{\left ( {V - B} \right )}^v}} \qquad \end {array}\begin {array}{*{20}{l}} {V > B}\\ {V > B \qquad v > 0} \end {array}} \right .

\]
have been expressed by S. O. Rice and W. R. Bennett in terms of contour integrals involving products of Bessel functions. In this paper these integrals are rewritten as improper integrals on the real line plus constant terms. These integrals converge fast enough in many cases to be useful in numerical integration.
On the motion of a simple pendulum
Authors: Garfinkel Boris
Published: December 2016

The vanishing of the tension in a simple pendulum supported by a flexible cord causes the particle to pass from the circular to a parabolic trajectory. The number and the nature of such transitions are related here to the value of the initial energy.
Air drag effect on a satellite orbit described by difference equations in the revolution number
Authors: Roberson Robert E.
Published: December 2016

For a satellite on an orbit which is affected by air drag, difference equations are derived whose solutions express changes in orbital size and shape and give the satellite’s time behavior as functions of revolution number. The results are obtained from a first order perturbation theory using a small air drag parameter.
The Blasius equation with three-point boundary conditions
Authors: Napolitano L. G.
Published: December 2016

The Blasius equation subject to three-point boundary conditions, describing the interaction between two parallel streams, is solved by way of a series in terms of ascending powers of the ratio

λ
=
(

u
1

−

u
2

)

/

u
1

\lambda = ({u_1} - {u_2})/{u_1}

, where the

u
i

′

s

{u_i}’s

are the outer streams’ velocities.
An extension of the Kantorovich method
Authors: Kerr Arnold D.
Published: December 2016

An extension of the Kantorovich method is discussed. The suggested method is demonstrated on the torsion problem of a beam of rectangular cross section. It is found that even when the solution is restricted to a one-term approximation, the method generates very good results also for stresses which are obtained as derivatives of the solution. It is shown that the final form of the generated solution is unique and that the convergence of the iterative process is very rapid. The obtained results indicate that the proposed method is a convenient tool to generate close approximate solutions, thus eliminating the arbitrariness in the choice of coordinate functions, which is a serious shortcoming inherent in the Ritz and Galerkin methods.
General solutions for plane extensible elasticae having nonlinear stress-strain laws
Authors: Antman Stuart
Published: December 2016

A general finite deformation solution is obtained for the equilibrium of hydrostatically loaded elasticae whose underformed shapes are circular arcs. The nonlinear stress-strain relations employed give the bending moment and the axial force as derivatives of a strain energy function with respect to suitable strain measures. The representation of the solution involves arbitrary constants of integration which can accommodate any end conditions consistent with equilibrium. Examples are given. The constraint of inextensibility is examined and a perturbation procedure for small extension is developed. In an appendix, the stress-strain laws are derived by an appropriate reduction of the equations for three-dimensional hyperelasticity.
The effective bandwidth of a system
Authors: Chirlian Paul M.
Published: December 2016

Bounds on the effective bandwidth, based upon transient response are obtained.
On uniqueness in general linear viscoelasticity
Authors: Lubliner J. , Sackman J. L.
Published: December 2016

On the basis of two theorems pertaining to the asymptotic behavior of certain Laplace transforms, the uniqueness of the displacement field in a general linear viscoelastic body (i.e., one with time-variable properties) throughout a time interval is demonstrated, provided the instantaneous elasticity tensor (or, in the case of a generalized Kelvin—Voigt material, the instantaneous viscosity tensor) is positive definite and a continuous function of time, and provided the following information is specified: the displacement field, to within a rigid-body motion, throughout the body and at all times before the given interval; the displacement and velocity fields throughout the body at the beginning of the interval (initial conditions); the body force throughout the body and throughout the interval; and, at each point of the boundary, in each of three orthogonal directions, a component of the traction or of the displacement throughout the time interval. If inertia is neglected, the initial conditions may be dispensed with, but the displacement field is unique only to within a rigid-body motion.
Continuity conditions at wave fronts in coupled thermoplasticity
Authors: Fine A. D.
Published: December 2016

The mass, momentum, and energy conservation requirements at wave fronts (or surfaces of discontinuity) are reduced to a form suitable for use in the coupled thermoplastic analysis. Constitutive equations are introduced in these relations, and, for one-dimensional situations, it is shown that an isothermal (or adiabatic) wave front separating regions of elastic and plastic behavior will propagate with the same speed as an isothermal (or adiabatic) surface of discontinuity lying completely inside a domain of plastic deformation. A new thermoplastic coupling parameter is obtained from an example involving spherical symmetry.
Phenomenological theory of multimode surface waves for plane structures
Authors: Karp Samuel N. , Karal Jr.
Published: December 2016

The notion of impedance boundary condition is generalized and illustrated by the discussion of the electromagnetic field arising from a magnetic line dipole source located above a plane structure. The generalized impedance boundary condition contains a set of parameters whose totality offers a physical description of the configuration. By suitably selecting these parameters, the configuration may be made to correspond to a structure that supports surface waves. We give an exact solution for a plane structure that supports one, two and three surface waves. The magnitudes of the surface waves are obtained and simple formulas for the radiated far field patterns are given. We also show how the methods employed can be extended to the case of any number of surface waves. This involves an

n
n

th order mixed boundary condition for a second order partial differential equation.
On the formulation and iterative solution of small strain plasticity problems
Authors: Havner Kerry S.
Published: December 2016

This paper is concerned with a general method of formulation and iterative solution of small displacement plasticity problems, using the Hencky-Nadai hardening law as mathematical model for the material behavior. Beginning with a minimum energy principle for small thermal-mechanical strains under simple external loading, quasi-linear partial differential equations are formulated and a method of iteration by successive solutions is proposed. A finite-difference discretization of the equations (in two dimensions) is obtained through minimization of the total potential energy function, leading to positive definite symmetric matrices for general boundary configurations.
Nonaxisymmetric punch and crack problems for initially stressed bodies
Authors: Keer Leon M.
Published: December 2016

Using the theory developed by England and Green [1] for thermoelastic problems for initially stressed bodies and a certain class of potential functions, a group of punch and crack problems are solved. The requirement for solution is that the boundary data be expressible as a trignometric series with the coefficient of each term of the series a function of radial distance from the center of the punch or crack. The solutions are obtained by inversion of Abel’s integral equation.
The vibrations of a random elastic string: the method of integral equations
Authors: Goodwin Bruce E. , Boyce William E.
Published: December 2016

The theory of Fredholm integral equations is applied to the problem of determining the natural frequencies of transverse vibrations of a tightly stretched elastic string whose mass per unit length varies with position in a stationary random manner. Upper and lower bounds for the statistical moments of the frequencies are given in terms of corresponding moments and appropriate correlation functions for the random linear density. The adequacy of the bounds decreases for the higher frequencies. Extensions to more general random boundary value problems are also indicated.
On the existence of normal mode of vibrations of nonlinear systems with two degrees of freedom
Authors: Rosenberg R. M.
Published: December 2016

A nonlinear, conservative system having two degrees of freedom is considered. The potential energy is subject to certain restrictions which are consistent with the strain energy of springs. Then, the notion of transversals; i.e., of curves orthogonal to equipotential lines, is introduced in order to prove the existence of an in-phase and of an out-of-phase normal mode of vibration, no matter how nonlinear the springs. It is shown, that the transversals are also very helpful in the discussion of general motions of the system.
On the time dependence of viscoelastic variational solutions
Authors: Schapery R. A.
Published: December 2016

Thermodynamic operational-variational principles are employed in a study of the transient response of linear viscoelastic media with an arbitrary degree of anisotropy. Assuming displacements in the form of a series of products of space-dependent functions and time-dependent generalized coordinates, the (approximate) response is calculated by minimizing a functional which is analogous to the potential energy of an elastic body. Similarly, a principle analogous to the principle of minimum complementary energy of elasticity is used to deduce transient behavior of (approximate) stresses. The displacements are not required to satisfy equilibrium or stress boundary conditions, nor are stresses calculated from the complementary principle required to satisfy compatibility or displacement boundary conditions. It is found that when applied loads and displacements are step-functions of time, the transient component of stresses and displacements is given in most cases by a series of exponentials with negative, real arguments.
The nanoscale spatial organization of B-cell receptors on immunoglobulin M– and G–expressing human B-cells
Authors: Lee Jinmin , Sengupta Prabuddha , Brzostowski Joseph , Lippincott-Schwartz Jennifer , Pierce Susan K.
Published: December 2016

B-cell activation is initiated by the binding of antigen to the B-cell receptor (BCR). Here we used dSTORM superresolution imaging to characterize the nanoscale spatial organization of immunoglobulin M (IgM) and IgG BCRs on the surfaces of resting and antigen-­activated human peripheral blood B-cells. We provide insights into both the fundamental process of antigen-driven BCR clustering and differences in the spatial organization of IgM and IgG BCRs that may contribute to the characteristic differences in the responses of naive and memory B-cells to antigen. We provide evidence that although both IgM and IgG BCRs reside in highly heterogeneous protein islands that vary in size and number of BCR single-molecule localizations, both resting and activated B-cells intrinsically maintain a high ­frequency of single isolated BCR localizations, which likely represent BCR monomers. IgG BCRs are more clustered than IgM BCRs on resting cells and form larger protein islands after antigen activation. Small, dense BCR clusters likely formed via protein–protein interactions are present on the surface of resting cells, and antigen activation induces these to come together to form less dense, larger islands, a process likely governed, at least in part, by protein–lipid interactions.
Re‐Examining the Reported Rates of Return to Food and Agricultural Research and Development: Reply
Authors: Hurley Terrance M. , Rao Xudong , Pardey Philip G.
Published: December 2016

Hurley, Rao and Pardey (2014) analytically and empirically evaluate the internal rate of return (IRR) vis a vis the modified internal rate of return (MIRR) for investments in agricultural research and development (R&D). They find that estimates of the IRR are 2.5 to 5 times larger than the MIRR for a wide range of assumptions, leading them to question the value of the IRR as a metric to represent the rate of return to agricultural R&D. Oehmke (2016) defends the IRR by arguing that it has important properties that the MIRR does not possess. In this article, we critically examine these properties demonstrating that some are not inherent to the MIRR. For other properties, we simply disagree with Oehmke's assessment of their desirability. Therefore, we are not compelled to change our original recommendation.
Historian: accurate reconstruction of ancestral sequences and evolutionary rates
Authors: Holmes Ian H
Published: December 2016

Motivation

Reconstruction of ancestral sequence histories, and estimation of parameters like indel rates, are improved by using explicit evolutionary models and summing over uncertain alignments. The previous best tool for this purpose (according to simulation benchmarks) was ProtPal, but this tool was too slow for practical use.

Results

Historian combines an efficient reimplementation of the ProtPal algorithm with performance-improving heuristics from other alignment tools. Simulation results on fidelity of rate estimation via ancestral reconstruction, along with evaluations on the structurally informed alignment dataset BAliBase 3.0, recommend Historian over other alignment tools for evolutionary applications.

Availability and Implementation

Historian is available at https://github.com/evoldoers/historian under the Creative Commons Attribution 3.0 US license.
Five MDROs you need to know
Authors: Short Pamela A. , Antonini Tami L. , Brennan Jean M. , Hobbs Melissa , Mauk Tina
Published: December 2016

Get fast facts about the multidrug-resistant organisms you may encounter in the healthcare setting.
A Feedback and Evaluation System That Provokes Minimal Retaliation by Trainees
Authors: Baker Keith , Haydar Bishr , Mankad Shawn
Published: December 2016

Background

Grade inflation is pervasive in educational settings in the United States. One driver of grade inflation may be faculty concern that assigning lower clinical performance scores to trainees will cause them to retaliate and assign lower teaching scores to the faculty member. The finding of near-zero retaliation would be important to faculty members who evaluate trainees.

Methods

The authors used a bidirectional confidential evaluation and feedback system to test the hypothesis that faculty members who assign lower clinical performance scores to residents subsequently receive lower clinical teaching scores. From September 1, 2008, to February 15, 2013, 177 faculty members evaluated 188 anesthesia residents (n = 27,561 evaluations), and 188 anesthesia residents evaluated 204 faculty members (n = 25,058 evaluations). The authors analyzed the relationship between clinical performance scores assigned by faculty members and the clinical teaching scores received using linear regression. The authors used complete dyads between faculty members and resident pairs to conduct a mixed effects model analysis. All analyses were repeated for three different epochs, each with different administrative attributes that might influence retaliation.

Results

There was no relationship between mean clinical performance scores assigned by faculty members and mean clinical teaching scores received in any epoch (P ≥ 0.45). Using only complete dyads, the authors’ mixed effects model analysis demonstrated a very small retaliation effect in each epoch (effect sizes of 0.10, 0.06, and 0.12; P ≤ 0.01).

Conclusions

These results imply that faculty members can provide confidential evaluations and written feedback to trainees with near-zero impact on their mean teaching scores.
Clavicular Refracture at the Site of Angular Malunion in Young Athletes
Authors: Furey Matthew J. , Zdero Radovan , McKee Michael D.
Published: December 2016

Objective:

The treatment of midshaft clavicle fractures has, in the last 2 decades, shifted markedly towards operative management. Prospective trials have defined accepted clinical and radiographic indications for the surgical management of clavicle fractures. This report documents 3 cases of clinically united angular malunion of the midshaft clavicle in young athletes that subsequently refractured to highlight angular deformity in the absence of displacement as a potential indication for surgical fixation.

Design:

Case series.

Setting:

A level 1 trauma centre.

Patients/Participants:

Three young athletic patients with angular malunion of the midshaft clavicle who experienced refracture, requiring surgical fixation.

Intervention:

Surgical fixation of midshaft clavicle fracture, as treatment for refracture after angular malunion.

Results:

All 3 patients required subsequent surgical fixation of their midshaft clavicle fracture, correcting the angular malunion and restoring shoulder function.

Conclusions:

Midshaft clavicular fractures that malunite with significant angulation in the absence of displacement represent a risk for subsequent refracture. For this reason, angular deformity should be considered as a potential indication for surgical fixation in acute clavicular fractures.

Level of Evidence:

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.
Survival Benefit and Cost Savings From Compliance With a Simplified 3-Hour Sepsis Bundle in a Series of Prospective, Multisite, Observational Cohorts
Authors: Leisman Daniel E. , Doerfler Martin E. , Ward Mary Frances , Masick Kevin D. , Wie Benjamin J. , Gribben Jeanie L. , Hamilton Eric , Klein Zachary , Bianculli Andrea R. , Akerman Meredith B. , D’Angelo John K. , D’Amore Jason A.
Published: December 2016

Objectives:

To determine mortality and costs associated with adherence to an aggressive, 3-hour sepsis bundle versus noncompliance with greater than or equal to one bundle element for severe sepsis and septic shock patients.

Design:

Prospective, multisite, observational study following three sequential, independent cohorts, from a single U.S. health system, through their hospitalization.

Setting:

Cohort 1: five tertiary and six community hospitals. Cohort 2: single tertiary, academic medical center. Cohort 3: five tertiary and four community hospitals.

Patients:

Consecutive sample of all severe sepsis and septic shock patients (defined: infection, ≥ 2 systemic inflammatory response syndrome, and hypoperfusive organ dysfunction) identified by a quality initiative. The exposure was full 3-hour bundle compliance. Bundle elements are as follows: 1) blood cultures before antibiotics; 2) parenteral antibiotics administered less than or equal to 180 minutes from greater than or equal to two systemic inflammatory response syndrome “and” lactate ordered, or less than or equal to 60 minutes from “time-zero,” whichever occurs earlier; 3) lactate result available less than or equal to 90 minutes postorder; and 4) 30 mL/kg IV crystalloid bolus initiated less than or equal to 30 minutes from “time-zero.” Main outcomes were in-hospital mortality (all cohorts) and total direct costs (cohorts 2 and 3).

Measurements and Main Results:

Cohort 1: 5,819 total patients; 1,050 (18.0%) bundle compliant. Mortality: 604 (22.6%) versus 834 (26.5%); CI, 0.9–7.1%; adjusted odds ratio, 0.72; CI, 0.61–0.86; p value is less than 0.001. Cohort 2: 1,697 total patients; 739 (43.5%) bundle compliant. Mortality: 99 (13.4%) versus 171 (17.8%), CI, 1.0–7.9%; adjusted odds ratio, 0.60; CI, 0.44–0.80; p value is equal to 0.001. Mean costs: $14,845 versus $20,056; CI, –$4,798 to –5,624; adjusted β, –$2,851; CI, –$4,880 to –822; p value is equal to 0.006. Cohort 3: 7,239 total patients; 2,115 (29.2%) bundle compliant. Mortality: 383 (18.1%) versus 1,078 (21.0%); CI, 0.9–4.9%; adjusted odds ratio, 0.84; CI, 0.73–0.96; p value is equal to 0.013. Mean costs: $17,885 versus $22,108; CI, –$2,783 to –5,663; adjusted β, –$1,423; CI, –$2,574 to –272; p value is equal to 0.015.

Conclusions:

In three independent cohorts, 3-hour bundle compliance was associated with improved survival and cost savings.
Pulmonary Arterial Compliance in Acute Respiratory Distress Syndrome: Clinical Determinants and Association With Outcome From the Fluid and Catheter Treatment Trial Cohort*
Authors: Metkus Thomas S. , Tampakakis Emmanouil , Mullin Christopher J. , Houston Brian A. , Kolb Todd M. , Mathai Stephen C. , Damico Rachel , Maron Bradley A. , Hassoun Paul M. , Brower Roy G. , Tedford Ryan J.
Published: December 2016

Objectives:

Pulmonary vascular dysfunction is associated with adverse prognosis in patients with the acute respiratory distress syndrome; however, the prognostic impact of pulmonary arterial compliance in acute respiratory distress syndrome is not established.

Design, Setting, Patients:

We performed a retrospective analysis of 363 subjects with acute respiratory distress syndrome who had complete baseline right heart catheterization data from the Fluid and Catheter Treatment Trial to test whether pulmonary arterial compliance at baseline and over the course of treatment predicted mortality.

Main Results:

Baseline pulmonary arterial compliance (hazard ratio, 1.18 per interquartile range of 1/pulmonary arterial compliance; 95% CI, 1.02–1.37; p = 0.03) and pulmonary vascular resistance (hazard ratio, 1.28 per interquartile range; 95% CI, 1.07–1.53; p = 0.006) both modestly predicted 60-day mortality. Baseline pulmonary arterial compliance remained predictive of mortality when pulmonary vascular resistance was in the normal range (p = 0.02). Between day 0 and day 3, pulmonary arterial compliance increased in acute respiratory distress syndrome survivors and remained unchanged in nonsurvivors, whereas pulmonary vascular resistance did not change in either group. The resistance-compliance product (resistance-compliance time) increased in survivors compared with nonsurvivors, suggesting improvements in right ventricular load.

Conclusions:

Baseline measures of pulmonary arterial compliance and pulmonary vascular resistance predict mortality in acute respiratory distress syndrome, and pulmonary arterial compliance remains predictive even when pulmonary vascular resistance is normal. Pulmonary arterial compliance and right ventricular load improve over time in acute respiratory distress syndrome survivors. Future studies should assess the impact of right ventricular protective acute respiratory distress syndrome treatment on right ventricular afterload and outcome.
Developmental Trajectories of Bottle-Feeding During Infancy and Their Association with Weight Gain
Authors: Ventura Alison K.
Published: December 2016

Objective:

To describe patterns of bottle-feeding across the first year postpartum and explore whether bottle-feeding trajectories are differentially associated with infant weight gain.

Method:

Data came from 1291 mothers who participated in the Infant Feeding Practices Study 2. Mothers completed a prenatal questionnaire and monthly surveys of infant feeding and growth between birth and 12 months. Group-based trajectory mixture modeling was used to describe developmental trajectories of bottle-feeding intensities across the first year. Growth curve modeling was used to explore associations between bottle-feeding intensity trajectory group membership and weight-for-age z-score (WAZ) trajectories from birth to 12 months.

Results:

Four qualitatively distinct trajectories of bottle-feeding were identified: (1) High-Stable: ∼100% of feeds from bottles across infancy; (2) Rapid-Increase: <30% of feeds from bottles during the neonatal assessment, increasing to ∼100% by 6 months; (3) Gradual-Increase: <10% of feeds from bottles during the neonatal assessment, gradually increasing to ∼100% by 12 months; and (4) Low-Stable: <5% of feeds from bottles across the majority of infancy. Bottle-feeding groups had significantly different WAZ trajectories across infancy; by 12 months, the High-Stable and Rapid-Increase groups had significantly higher WAZs compared with the Gradual-Increase and Low-Stable groups (p < .001). The association between bottle-feeding group membership and WAZ trajectories was not confounded by sociodemographic characteristics or the extent to which infants received breast milk.

Conclusion:

High-intensity bottle use during early infancy may place infants at higher risk for excess weight gain. Supports and policies that help mothers delay high-intensity bottle use until later infancy are warranted.
An Appraisal of Internal Mammary Artery Perforators as Recipient Vessels in Microvascular Breast Reconstruction—An Analysis of 515 Consecutive Cases
Authors: Vollbach Felix H. , Heitmann Christoph D. , Fansa Hisham
Published: December 2016

Background:

The usage of internal mammary artery perforators (IMAPs) has been described in autologous breast reconstruction although IMAPS are not yet considered standard recipient vessels. It remains unclear if these vessels can be safely used in large flaps after radiation therapy or in delayed breast reconstruction.

Methods:

Over a 2-year period, 515 free flaps for autologous breast reconstruction were performed on 419 patients by 2 surgeons (S1 and S2). In a retrospective analysis, time of reconstruction, ischemia time, flap weight, diameter of couplers, and complications were analyzed. All 515 flaps were compared in a subset with regard to the 2 surgeons: S1 who always used the IMA as a recipient vessel and S2 who attempted IMAP use if possible.

Results:

Of all 515 flaps, 424 were abdominal flaps and 91 flaps were from the upper thigh. Three hundred six cases were immediate reconstructions, and 112 were delayed reconstructions. In 97 cases, implants were converted to autologous tissue. In 112 cases, the IMAPs were used; of these, 82 were immediate and 17 were delayed reconstructions, and in 13 cases, implants were removed. Thirty-five percent of all anastomoses to IMAPs had previous radiation therapy. The flap failure rate was 1.9%. In none of these cases, the IMAPs were used. S1 never used the IMAP, and S2 used the IMAP in 37% of all of his flaps.

Conclusions:

IMAPs were safely used in all kinds of reconstructions and after radiation therapy, with no flap failure or negative effects on mastectomy skin flap perfusion. Using the IMAPs as recipient vessels is a further step toward simplifying microsurgical breast reconstruction.
CHANGE OF CHOROIDAL VOLUME IN UNTREATED CENTRAL SEROUS CHORIORETINOPATHY
Authors: Pertl Laura , Haas Anton , Hausberger Silke , Pichler Tamara , Rabensteiner Dieter F. , Seidel Gerald , Malle Eva M. , Weger Martin
Published: December 2016

Purpose:

Choroidal hyperpermeability plays a central role in the pathophysiology of central serous chorioretinopathy (CSC). In active CSC undergoing treatment, choroidal thickness decreases if subretinal fluid (SRF) resolves. This study aimed to investigate the change in choroidal thickness and volume in eyes with untreated CSC.

Methods:

The authors retrospectively analyzed 27 eyes with treatment-naïve CSC (25 patients), who had a follow-up of 4 to 6 weeks. Retinal and choroidal volume and SRF were segmented manually and calculated using the Spectralis OCT built-in software (Spectralis; Heidelberg Engineering).

Results:

In treatment-naïve eyes with CSC, an increase in SRF was significantly associated with an increase in choroidal thickness and volume (rho = 0.93, P < 0.01). Eyes with greater baseline choroidal volume showed a significantly greater decrease in SRF during follow-up (rho = −0.47, P = 0.03).

Conclusion:

In this study, an increase in SRF was associated with an increase in both choroidal thickness and volume in eyes with treatment-naïve CSC. Eyes with thicker baseline choroidal volume showed a greater reduction in SRF.
SHORT-TERM EFFECTS OF EXERCISE ON OPTIC NERVE AND MACULAR PERFUSION MEASURED BY OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY
Authors: Alnawaiseh Maged , Lahme Larissa , Treder Maximilian , Rosentreter André , Eter Nicole
Published: December 2016

Purpose:

To evaluate the effects of exercise on optic nerve and macular perfusion using optical coherence tomography angiography.

Methods:

Thirteen eyes of 13 healthy volunteers were examined using a high-speed and high-resolution spectral-domain optical coherence tomography XR Avanti with a split-spectrum amplitude-decorrelation angiography algorithm. Blood pressure, heart rate, the mean area of the foveal avascular zone , and flow density on the optic nerve head and macula, before and after exercise were measured and analyzed.

Results:

Mean patient age was 27.3 ± 3.5 years. Heart rate, systolic and diastolic blood pressure increased significantly after exercise (P < 0.001). The mean area of the foveal avascular zone did not change significantly after exercise (before: 0.27 ± 0.07 mm2; after: 0.26 ± 0.07 mm2; P = 0.10). The peripapillary and the parafoveal flow density decreased significantly after exercise (peripapillary: before: 65.1 ± 2.1; after: 62.3 ± 3.0; P < 0.001 and parafoveal: before: 56.7 ± 1.3; after: 55.6 ± 1.5; P = 0.007).

Conclusion:

Increased physical activity induced significant changes in optic nerve and macular perfusion, which were measured using split-spectrum amplitude-decorrelation angiography optical coherence tomography angiography. In studies that aim to evaluate optic nerve and macular perfusion using optical coherence tomography angiography, it should be strongly recommended that patients rest before imaging is performed and that data concerning systemic circulation including blood pressure and pulse is included within the evaluation.
A CASE OF FULL-THICKNESS MACULAR HOLE IN EYE WITH FOCAL CHOROIDAL EXCAVATION
Authors: Fayyad Omar Faisal , Al-Hashimi Mustafa Raad , Fayyad Faisal Tawfeeq
Published: December 2016

Purpose:

To report an association between a Stage 4 full-thickness macular hole and focal choroidal excavation.

Methods:

Case report.

Results:

A 46-year-old male patient with high myopia was referred for macular hole surgery and found to have an associated focal choroidal excavation. The patient underwent uneventful combined procedure with closure of macular hole.

Conclusion:

Successful macular hole surgery can be achieved even in the presence of focal choroidal excavation.