Trends in the incidence of physician-diagnosed post-traumatic stress disorder among active-duty U.S. military personnel between 1999 and 2008

Background: The impact of combat operations in Iraq and Afghanistan on the incidence of post-traumatic stress disorder(PTSD) in military service members has been poorly quantified. The purpose of this study was to examine trends in the incidence rate of physician-diagnosed PTSD in active-duty military personnel between 1999 and 2008.Methods: We conducted a retrospective cohort study utilizing data extracted from the Defense Medical Surveillance System to identify incident cases of PTSD within the study population. The incidence rate of physician-diagnosed PTSD was the primary outcome of interest. Multivariable Poisson regression was used to analyze the data.Results: The overall incidence rate of PTSD among all active-duty US military personnel was 3.84(95% CI: 3.81, 3.87) cases per 1000 person-years. The adjusted average annual percentage increase in the incidence rate of PTSD prior to the initiation of Operation Iraqi Freedom(OIF) was a modest 5.02%(95% CI: 1.85, 8.29%). Following the initiation of OIF, the average annual percentage increase in the rate of PTSD was 43.03%(95% CI: 40.55, 45.56%). Compared to the baseline period between 1999 and 2002, the incidence rate of PTSD in 2008 was nearly 7 times higher(RR=6.85, 95% CI: 6.49, 7.24). Significant increases in the incidence rate of PTSD were observed following the initiation of OIF regardless of sex, age, race, marital status, military rank, or branch of military service. Notably, the rate of PTSD among females was 6–7 times higher prior to OIF, but there was no difference by gender by 2008.Conclusions: Overall, these data quantify the significant increase in the incidence rate of PTSD following the initiation of combat operations in Iraq and Afghanistan within the active-duty military population during the study period.

Factors and expectations influencing concussion disclosure within NCAA DivisionⅠathletes:A mixed methodological approach

Background:Participation in sports is associated with many benefits to all aspects of health;however,it also comes with the risk of injury,particularly concussions.Self-disclosure and care seeking following a concussion are especially important because of the lack of outwardly visible signs and/or symptoms.Although recent research has explored factors affecting concussion disclosure,use of isolated methodologies limits the ability to contextualize how disclosure or nondisclosure occurs.Therefore,the purpose of this study was to describe the factors and expectations of National Collegiate Athletic Association(NCAA)athletes that may influence concussion disclosure.Methods:This mixed-methods convergent parallel research study included 25 NCAA Division I athletes representing 13 sports,all of whom completed a concussion-education session with pre-/post-test surveys and a semistructured interview.Eligible athletes were at least 18 years old and on an NCAA roster.The surveys focused on previous concussion-related disclosure behaviors,knowledge,attitudes,beliefs,norms,and intentions about disclosing concussion.Interviews focused on the athletes’experiences related to concussion disclosure.Survey data were analyzed using descriptive statistics and Mann-Whitney U tests.Interviews were analyzed using a Consensual Qualitative Research tradition.Results:Participants had good concussion knowledge(median=46.0),positive attitudes(median=38.0),strong beliefs(median=13.0),and strong intentions to disclose concussion symptoms(median=7.0).None of the constructs differed by participants’gender.Although quantitative findings were mostly positive,interview data highlighted factors that may explain why some participants are successful in disclosing concussions and why others may find disclosure difficult.Educational efforts,sport culture,and medical professional presence were the primary facilitators discussed by participants.Stigma,pressure,and a lack of team support were perceived as disclosure barriers.Conclusion:The context in which concussion disclosure occurs or does not occur is vital to the success of educational interventions.Interventions must prioritize stakeholder-and team-based perspectives on concussion to establish a network supportive to disclosure.

Detailed description of Division I ice hockey concussions:Findings from the NCAA and Department of Defense CARE Consortium

Objective:Since concussion is the most common injury in ice hockey,the objective of the current study was to elucidate risk factors,specific mechanisms,and clinical presentations of concussion in men’s and women’s ice hockey.Methods:Ice hockey players from 5 institutions participating in the Concussion Assessment,Research,and Education Consortium were eligible for the current study.Participants who sustained a concussion outside of this sport were excluded.There were 332(250 males,82 females)athletes who participated in ice hockey,and 47(36 males,11 females)who sustained a concussion.Results:Previous concussion(odds ratio(OR)=2.00;95%confidence interval(95%CI):1.02‒3.91)was associated with increased incident concussion odds,while wearing a mouthguard was protective against incident concussion(OR=0.43;95%CI:0.22‒0.85).Overall,concussion mechanisms did not significantly differ between sexes.There were specific differences in how concussions presented clinically across male and female ice hockey players,however.Females(9.09%)were less likely than males(41.67%)to have a delayed symptom onset(p=0.045).Additionally,females took significantly longer to reach asymptomatic(p=0.015)and return-to-play clearance(p=0.005).Within the first 2 weeks post-concussion,86.11%of males reached asymptomatic,while only 45.50%of females reached the same phase of recovery.Most males(91.67%)were cleared for return to play within 3 weeks of their concussion,compared to less than half(45.50%)of females.Conclusion:The current study proposes possible risk factors,mechanisms,and clinical profiles to be validated in future concussions studies with larger female sample sizes.Understanding specific risk factors,concussion mechanisms,and clinical profiles of concussion in collegiate ice hockey may generate ideas for future concussion prevention or intervention studies.

A Conceptual Numerical Model of the Wave Equation Using the Complex Variable Boundary Element Method

In this work, a conceptual numerical solution of the two-dimensional wave partial differential equation (PDE) is developed by coupling the Complex Variable Boundary Element Method (CVBEM) and a generalized Fourier series. The technique described in this work is suitable for modeling initial-boundary value problems governed by the wave equation on a rectangular domain with Dirichlet boundary conditions and an initial condition that is equal on the boundary to the boundary conditions. The new numerical scheme is based on the standard approach of decomposing the global initial-boundary value problem into a steady-state component and a time-dependent component. The steady-state component is governed by the Laplace PDE and is modeled with the CVBEM. The time-dependent component is governed by the wave PDE and is modeled using a generalized Fourier series. The approximate global solution is the sum of the CVBEM and generalized Fourier series approximations. The boundary conditions of the steady-state component are specified as the boundary conditions from the global BVP. The boundary conditions of the time-dependent component are specified to be identically zero. The initial condition of the time-dependent component is calculated as the difference between the global initial condition and the CVBEM approximation of the steady-state solution. Additionally, the generalized Fourier series approximation of the time-dependent component is fitted so as to approximately satisfy the derivative of the initial condition. It is shown that the strong formulation of the wave PDE is satisfied by the superposed approximate solutions of the time-dependent and steady-state components.

An Unsteady Two-Dimensional Complex Variable Boundary Element Method

The Complex Variable Boundary Element Method (CVBEM) procedure is extended to modeling applications of the two-dimensional linear diffusion partial differential equation (PDE) on a rectangular domain. The methodology in this work is suitable for modeling diffusion problems with Dirichlet boundary conditions and an initial condition that is equal on the boundary to the boundary conditions. The underpinning of the modeling approach is to decompose the global initial-boundary value problem into a steady-state component and a transient component. The steady-state component is governed by the Laplace PDE and is modeled using the Complex Variable Boundary Element Method. The transient component is governed by the linear diffusion PDE and is modeled by a linear combination of basis functions that are the products of a two-dimensional Fourier sine series and an exponential function. The global approximation function is the sum of the approximate solutions from the two components. The boundary conditions of the steady-state problem are specified to match the boundary conditions from the global problem so that the CVBEM approximation function satisfies the global boundary conditions. Consequently, the boundary conditions of the transient problem are specified to be continuously zero. The initial condition of the transient component is specified as the difference between the initial condition of the global initial-boundary value problem and the CVBEM approximation of the steady-state solution. Therefore, when the approximate solutions from the two components are summed, the resulting global approximation function approximately satisfies the global initial condition. In this work, it will be demonstrated that the coupled global approximation function satisfies the governing diffusion PDE. Lastly, a procedure for developing streamlines at arbitrary model time is discussed.

Resolution of the Computational Diffusion Hydrodynamic Model into Partial Differential Equation Form

Computational modeling continues to evolve in applications of hydrology and hydraulics, and the field of Computational Hydrology and Hydraulics has grown into a significant technology in both engineering and computational mathematics. In this paper, the fundamental issue of assessment of computational error is addressed by determination of an “equivalent” mathematical statement, as a partial differential equation (“PDE”) that describes the original mathematical PDE statement and computational solution of it. In other words, given that the computational model does not exactly solve the governing PDE and that the computational processes used to approximate the governing PDE further moves the computational outcome away from the exact solution, what “alternate” or “equivalent” PDE does the resulting computational model exactly solve? In this paper it is shown that development of such an equivalent PDE enables an assessment of computational error by direct comparison of the equivalent PDE to the original PDE targeted to being solved. As an example, the USGS Diffusion Hydrodynamic Model (“DHM”) is examined as to development of an equivalent PDE that describes the DHM computational modeling outcome, which is then compared to the actual outcomes resulting from application of the DHM model.

Examination of Computational Precision versus Modeling Complexity for Open Channel Flow with Hydraulic Jump

In this work, for flow with a hydraulic jump, the predictive capabilities of popular hydraulic models (HEC-RAS and WSPG) are validated with the published results from the three dimensional Computational Fluid Dynamics (CFD) model (OpenFOAM). The analysis is performed for flows with a Froude number of 6.125 and Reynolds number of 3.54 × 105. While the hydraulic models solve the one-dimensional energy equation, in the CFD model solution of the three dimensional Reynolds averaged Navier-Stokes (RANS) equations, with a turbulence model, is used. As the results indicate, although the hydraulic models can satisfactorily predict the location of the steady-state jump, the length of the hydraulic jump (i.e. distance from the toe of the jump to a location in tail water zone) and other jump characteristics are better simulated by the CFD model. The solution from hydraulic models is sensitive to the channel bottom roughness value.

On Merging Cover Inequalities for Multiple Knapsack Problems

This paper describes methods to merge two cover inequalities and also simultaneously merge multiple cover inequalities in a multiple knapsack instance. Theoretical results provide conditions under which merged cover inequalities are valid. Polynomial time algorithms are created to find merged cover inequalities. A computational study demonstrates that merged inequalities improve the solution times for benchmark multiple knapsack instances by about 9% on average over CPLEX with default settings.

Assessment of Ice Volume Changes in the Cryosphere via Simplified Heat Transport Model

In order to describe changes in ice volume in the cryosphere, a differential equation mathematical model is used in this paper. The dominating effects of freezing and thawing in the cryosphere enable simplification of the heat transport equations. This results in a mathematical model that can be solved exactly and is useful in investigating other climatic components, which in turn may be similarly analyzed for possible Global Circulation Model (GCM) validation. Data forms representing temperature and ice volume during the Pleistocene are available and can be directly compared with the exact solution of the simplified differential equation used in this paper. The model parameters may then be adjusted to approximate the effects of climate change;the adjusted model then run in reverse time, to develop an alternative history of ice volume of the cryosphere to be compared with the actual data interpretations previously published in the literature. In this fashion, an assessment may be made as to possible climate impacts in the cryosphere.

Evaluation of Doppler Radar Data for Assessing Depth-Area Reduction Factors for the Arid Region of San Bernardino County

The Doppler Radar derived rainfall data for over 150 candidate storms during 1997-2015 period, for the County of San Bernardino, California, was assessed. Eleven most significant storms were identified for detailed analysis. For these significant storms, Depth-Area Reduction Factors (“DARF”) curves were developed and compared with the published curves developed and adapted by several flood control agencies for this study area. More rainfall data need to be pursued and analyzed before any correlation hypothesis is proposed.

Rainfall Infiltration Return Frequency Estimates

Depth-duration analysis, such as accomplished for rainfall, can be useful in the analysis of infiltration of rainfall. The assessment of infiltration depth-duration in terms of return frequency is of interest. In this paper, depth-duration values of daily rainfall infiltration are estimated using the National Resources Conservation Service (NRCS) Curve Number (CN) approach for estimating daily runoff. The CN methods may be generally applicable to soils that are free draining. From the estimated history of daily infiltration, a depth-duration analysis is accomplished for all duration sizes from 1 day to 365 days. These annual outcomes are then analyzed as to a possible underlying probability distribution. For the rain gages considered, the depth-duration infiltration estimates (using the CN approach) appear to be normally distributed. From the fitted distribution, estimates of rare events of rainfall infiltration may be made, and possible linkage to earth movement events accomplished with respect to return frequency of infiltration, which in turn can aid in the design and risk assessment of fixed works involving soil water accumulation.

What Rainfall Return Frequency?

In this paper, a comparison is made of available rainfall data in a localized study area of Los Angeles County, California. This particular area has also been studied by the State of California Department of Water Resources (DWR), the National Weather Service (NWS) National Oceanographic and Atmospheric Administration (NOAA), and the Los Angeles County (LAC) Department of Public Works. All three of these cited governmental agencies independently analyzed the rainfall data to identify rainfall trends for the study area, and then prepared statistical analyses in order to develop estimates of return frequencies for various peak durations of rainfall, among other items of interest to hydrologists. Additionally, these three agencies have available two different analyses of the available data, resulting in updates to their respective published works. Consequently, six different statistical analyses are available for comparison and assessment. In this paper, an examination is made of these six statistical studies and some of the differences between the various analyses are identified and explained.

Changes in the Physical and Mechanical Properties of Human Blood with Sustained Prophylactic Use of Acetylsalicylic Acid (Aspirin)—A Rheological Study

While the prophylactic use of regular, low dosage, acetylsalicylic acid (aspirin) has been employed due to the inhibitory effect on platelet aggregation, few if any rheological studies validate the change in the physical and mechanical properties of human blood post-aspirin administration. The viscosity and yield stress of blood from eleven donors were assessed at varied shear rates before and after daily aspirin administration (81 mg) for 14 consecutive days. The findings indicate a statistically relevant aggregated decrease with respect to viscosity and yield stress within the study population.

CVBEM and FVM Computational Model Comparison for Solving Ideal Fluid Flow in a 90-Degree Bend

While finite volume methodologies (FVM) have predominated in fluid flow computations, many flow problems, including groundwater models, would benefit from the use of boundary methods, such as the Complex Variable Boundary Element Method (CVBEM). However, to date, there has been no reporting of a comparison of computational results between the FVM and the CVBEM in the assessment of flow field characteristics. In this work, the CVBEM is used to develop a flow field vector outcome of ideal fluid flow in a 90-degree bend which is then compared to the computational results from a finite volume model of the same situation. The focus of the modelling comparison in the current work is flow field trajectory vectors of the fluid flow, with respect to vector magnitude and direction. Such a comparison is necessary to validate the development of flow field vectors from the CVBEM and is of interest to many engineering flow problems, specifically groundwater modelling. Comparison of the CVBEM and FVM flow field trajectory vectors for the target problem of ideal flow in a 90-degree bend shows good agreement between the considered methodologies.

Correlating Rheological Experiments, TEVP Models, and Microstructure with Small Angle Light Scattering

The existence of an evolving microstructure in a 2.9 vol% fumed silica in paraffin oil and polyisobutylene is demonstrated experimentally and via rheological modeling during steady state and large amplitude oscillatory shear flow. The continuously evolving, rebuilding, and breaking down of the microstructure is shown, and correlated through the rheology experiments, thixo-elastovisco-plastic modeling, and small angle light scattering (SALS). All elements are then connected via a global, stochastic optimization algorithm that will provide parameter estimation with a “best-fit” of the steady state and transient data using the well-known Modified Delaware Thixotropic Model, allowing for the comparison of SALS results with experimental values.

A Model of the Universe that Can Explain Dark Matter, Dark Energy, and the Fourth Space Dimension

This paper explains how a model of the universe can be constructed by incorporating time and space into geometry in a unique way to produce a 4-space dimension/1-time dimension model. The model can then show how dark matter can be the gravity that is produced by real matter that exists throughout our entire universe. The model can also show how dark energy is not an increase in energy that is causing the accelerated expansion of the universe, but is an accelerating decrease in matter throughout the universe as the stars and galaxies in the universe continue to convert matter into energy during their life cycles. And then the model can show how a fourth space dimension must exist in our universe to locate a point in space.

DESIGNING THE OPTIMUM CONFIGURATIONS OF CIRCULAR AND SPHERICAL PRODUCT SPECIFICATIONS FOR MULTIPLE QUALITY CHARACTERISTICS

As an integral part of tolerance design in the context of design for six sigma, determining optimal product specifications has become the focus of increased activity, as manufacturing industries strive to increase productivity and improve the quality of their products. Although a number of research papers have been reported in the research community, there is room for improvement. Most existing research papers consider determining optimal specification limits for a single quality characteristic. In this paper, we develop the modeling and optimization procedures for optimum circular and spherical configurations by considering multiple quality characteristics. The concepts of multivariate quality loss function and truncated distribution are incorporated. This has never been adequately addressed, nor has been appropriately applied in industry. A numerical example is shown and comparison studies are made.