Estimating the Effects of Covariates on Health Expenditures

This paper addresses estimation of an outcome characterized by mass at zero, significant skewness, and heteroscedasticity. Unlike other approaches suggested recently that require retransformations or arbitrary assumptions about error distributions, our estimation strategy uses sequences of conditional probability functions, similar to those used in discrete time hazard rate analyses, to construct a discrete approximation to the density function of the outcome of interest conditional on exogenous explanatory variables. Once the conditional density function has been constructed, we can examine expectations of arbitrary functions of the outcome of interest and evaluate how these expectations vary with observed exogenous covariates. This removes a researcher's reliance on strong and often untested maintained assumptions. We demonstrate the features and precision of the conditional density estimation method through Monte Carlo experiments and an application to health expenditures using the RAND Health Insurance Experiment data. Overall, we find that the approximate conditional density estimator that we propose provides accurate and precise estimates of derivatives of expected outcomes for a wide range of types of explanatory variables. We find that two-part smearing models often used by health economists do not perform well. Our results, both in Monte Carlo experiments and in our real application, also indicate that simple one-part OLS models of level health expenditures can provide more accurate estimates than commonly used two-part models with smearing, provided one uses enough expansion terms in the one-part model to fit the data well.

Cell Death Pathways in Photodynamic Therapy of Cancer

Photodynamic therapy (PDT) is an emerging cancer therapy that uses the combination of non-toxic dyes or photosensitizers (PS) and harmless visible light to produce reactive oxygen species and destroy tumors. The PS can be localized in various organelles such as mitochondria, lysosomes, endoplasmic reticulum, Golgi apparatus and plasma membranes and this sub-cellular location governs much of the signaling that occurs after PDT. There is an acute stress response that leads to changes in calcium and lipid metabolism and causes the production of cytokines and stress response mediators. Enzymes (particularly protein kinases) are activated and transcription factors are expressed. Many of the cellular responses center on mitochondria and frequently lead to induction of apoptosis by the mitochondrial pathway involving caspase activation and release of cytochrome c. Certain specific proteins (such as Bcl-2) are damaged by PDT-induced oxidation thereby increasing apoptosis, and a build-up of oxidized proteins leads to an ER-stress response that may be increased by proteasome inhibition. Autophagy plays a role in either inhibiting or enhancing cell death after PDT

Cell Death Pathways in Photodynamic Therapy of Cancer

Photodynamic therapy (PDT) is an emerging cancer therapy that uses the combination of non-toxic dyes or photosensitizers (PS) and harmless visible light to produce reactive oxygen species and destroy tumors. The PS can be localized in various organelles such as mitochondria, lysosomes, endoplasmic reticulum, Golgi apparatus and plasma membranes and this sub-cellular location governs much of the signaling that occurs after PDT. There is an acute stress response that leads to changes in calcium and lipid metabolism and causes the production of cytokines and stress response mediators. Enzymes (particularly protein kinases) are activated and transcription factors are expressed. Many of the cellular responses center on mitochondria and frequently lead to induction of apoptosis by the mitochondrial pathway involving caspase activation and release of cytochrome c. Certain specific proteins (such as Bcl-2) are damaged by PDT-induced oxidation thereby increasing apoptosis, and a build-up of oxidized proteins leads to an ER-stress response that may be increased by proteasome inhibition. Autophagy plays a role in either inhibiting or enhancing cell death after PDT.National Institutes of Health (U.S.) (NIH grant R01AI050875)Center for Integration of Medicine and Innovative Technology (DAMD17-02-2-0006)United States. Dept. of Defense. Congressionally Directed Medical Research Programs (CDMRP Program in TBI (W81XWH-09-1-0514))United States. Air Force Office of Scientific Research (FA9950-04-1-0079)National Institutes of Health (U.S.) (NIH Dermatology training grant

Tuning of a hypersonic surface phononic band gap using a nanoscale two-dimensional lattice of pillars

We present experimental and theoretical evidence of a phononic band gap in a hypersonic range for thermally activated surface acoustic waves in two-dimensional (2D) phononic crystals. Surface Brillouin light scattering experiments were performed on the (001) surface of silicon, loaded with a 2D square lattice of 100- or 150-nm-high aluminum pillars with a spacing of 500nm. The surface Brillouin light scattering spectra revealed a different type of surface mode, related to the modulation of the lattice structure and the mechanical eigenmodes of the pillars. The experimental data were in excellent agreement with theoretical calculations performed using the finite-element method.Peer reviewe

Dispersion of the surface phonons in semiconductor/topological insulator Si/Bi2Te3 heterostructure studied by high resolution Brillouin spectroscopy

The dynamics and dispersion of surface phonons in heterostructure semiconductor/ topological insulator Si/Bi2Te3 was investigated using high resolution Brillouin light scattering method in the GHz frequency range. Both Rayleigh and Sezawa surface acoustic waves have been observed for wave vectors ranging from 0.006 to 0.023 nm−1. Anomaly in dispersion relations ω(q) for both surface waves were detected for the wave vector q = 0.016 nm−1. The finite element method (FEM) was used to simulate the observed shapes of ω(q) and to find the deformation profiles of surface acoustic waves. We attribute the observed changes to the coupling between low energy electrons and surface phonons. The coupling between helical Dirac states and surface phonons is discussed in the frame of accessible theoretical models

Bony ingrowth potential of 3D-printed porous titanium alloy: a direct comparison of interbody cage materials in an in vivo ovine lumbar fusion model.

Background contextThere is significant variability in the materials commonly used for interbody cages in spine surgery. It is theorized that three-dimensional (3D)-printed interbody cages using porous titanium material can provide more consistent bone ingrowth and biological fixation.PurposeThe purpose of this study was to provide an evidence-based approach to decision-making regarding interbody materials for spinal fusion.Study designA comparative animal study was performed.MethodsA skeletally mature ovine lumbar fusion model was used for this study. Interbody fusions were performed at L2-L3 and L4-L5 in 27 mature sheep using three different interbody cages (ie, polyetheretherketone [PEEK], plasma sprayed porous titanium-coated PEEK [PSP], and 3D-printed porous titanium alloy cage [PTA]). Non-destructive kinematic testing was performed in the three primary directions of motion. The specimens were then analyzed using micro-computed tomography (µ-CT); quantitative measures of the bony fusion were performed. Histomorphometric analyses were also performed in the sagittal plane through the interbody device. Outcome parameters were compared between cage designs and time points.ResultsFlexion-extension range of motion (ROM) was statistically reduced for the PTA group compared with the PEEK cages at 16 weeks (p-value=.02). Only the PTA cages demonstrated a statistically significant decrease in ROM and increase in stiffness across all three loading directions between the 8-week and 16-week sacrifice time points (p-value≤.01). Micro-CT data demonstrated significantly greater total bone volume within the graft window for the PTA cages at both 8 weeks and 16 weeks compared with the PEEK cages (p-value<.01).ConclusionsA direct comparison of interbody implants demonstrates significant and measurable differences in biomechanical, µ-CT, and histologic performance in an ovine model. The 3D-printed porous titanium interbody cage resulted in statistically significant reductions in ROM, increases in the bone ingrowth profile, as well as average construct stiffness compared with PEEK and PSP

Disaster Operations Management: an Empirical Study from Thailand

Disasters have unpredictable and deleterious impacts on modern societies. While recent operations management research has increasingly focused on disaster operations, only a few studies have examined the recovery phase of post-disaster operations. This research presents an overview of Disaster Operations Management as well as an empirical study using econometrics analysis to examine the recovery phase of post-disaster operations. The results suggest that when resources are scarce, at a strategic level we need to understand where to begin when planning the recovery process. This study is an exploratory analysis of the question of how flooding affects per capita income in areas with different levels of industrialization. We developed multiple regression models using panel data from Thailand to examine this effect, finding that flooding in a previous year has a positive effect on areas with a low level of industrialization, but a negative one on highly industrialized areas, meaning the residents of the latter are affected differently. Our results suggest the level of industrialization impacts the effectiveness of the recovery process. Finally, we discuss the implications of the study as well as suggestions for future research

Numerical and Experimental Analysis of the Influence of Assembling Conditions and the Tolerance of Adapted Implantological Components on the Durability of the Prosthetic Construction

Durable fastening of implant retained prosthetic restorations, consisting of a series of elements, is one of the main factors of successful prosthetic rehabilitation. Clinically observed mechanical problems concerning the above mentioned components are complications that occur most often in the loading phase. The aim of this research was evaluation of the suppleness of the implant- -anti-rotary abutment construction to loosening under the influence of labile mechanical stress. Numerical analysis of resistance based on the finite element analysis (FEA) was used in the initial phase of this research. The actual tests were done with the use of a dynamic mechanical analyser Netzsch DMA 242 and a polarisation microscope equipped with a CCD camera. A series of implants connected with abutments composed of two parts were analysed. The results of initial studies utilizing the finite element analysis (FEA) allowed definition of the spheres of stress concentration. On the basis of in vitro experiments, the investigators evaluated the influence of tolerance of adapted implant-abutment interface fit, as well as the torque used in the assembly of the abutment, on the occurrence of micromovements and loosening of components. The results strongly indicate correlation between the chosen variables and the risk of occurrence of mechanical complications

Impact of Oportunidades on skilled attendance at delivery in rural areas.

Oportunidades (formerly PROGRESA) is a conditional cash transfer program ran by the Mexican federal government designed to break the intergenerational cycle of poverty. Among other activities, it provides free delivery attendance for women enrolled in the program. Skilled attendance at delivery has been identified as an effective strategy to reduce maternal mortality, an important health problem in Mexico. In this paper we assess the impact of Oportunidades on skilled attendance at delivery taking advantage of the experimental design implemented for the evaluation of this program in rural areas and using a variety of analytical techniques. The main results of the study indicate that Oportunidades had, at best, only a small effect on skilled attendance at delivery in treatment communities. The program had larger effects on those women who had one birth just prior to the experimental treatment and another birth subsequent to the experimental treatment. These results should lead to a review about the strategies used by Oportunidades to increase skilled attendance at delivery