Research on boron filaments and boron reinforced composites

Boron filaments for use as reinforcing phase in composite materials for aerospace structure

EVALUATION OF ALTERNATIVE RISK SPECIFICATIONS IN FARM PROGRAMMING MODELS

The use of alternative probability density functions to specify risk in farm programming models is explored and compared to a traditional specification using historical data. A method is described that compares risk efficient crop mixes using stochastic dominance techniques to examine impacts of different risk specifications on farm plans. Results indicate that a traditional method using historical farm data is as efficient for risk averse producers as two other methods of incorporating risk in farm programming models when evaluated using second degree stochastic dominance. Stochastic dominance with respect to a function further discriminates among the distributions, indicating that a density function based on the historic forecasting accuracy of the futures market results in a more risk-efficient crop mix for highly risk averse producers. Results also illustrate the need to validate alternative risk specifications perceived as improvements to traditional methods.Risk and Uncertainty,

Evolution of changes in carbon monoxide transfer factor in men with chronic obstructive pulmonary disease

SummaryProgression of chronic obstructive pulmonary disease (COPD) has been studied predominantly by following change in forced expiratory volume in 1s (FEV1) which reflects both primary airway disease and associated alveolar disease. Carbon monoxide transfer (Tlco) (the product of the transfer coefficient Kco and alveolar volume Va) is the only simple, widely available test of alveolar function, but few studies have followed long-term changes in an individual.Seventeen middle-aged men with moderate chronic airflow obstruction (mean FEV1 56% of predicted values) were observed with yearly measurements of FEV1, Tlco and Kco over a mean of 18.9yr. At the end of follow-up FEV1 had fallen to 29% of predicted values. Va, measured by single breath dilution, fell in each man. Kco at recruitment ranged from 41% to 110% predicted and remained >75% predicted in eight men at the end of follow-up supporting a phenotype of COPD with predominant airway disease and little emphysema. Fall in FEV1 was faster (2.03% predicted FEV1/yr) in seven men with low initial Kco<75% pred. than in men with initial Kco>75% pred. (1.14% predicted FEV1/yr, P=0.006).Repeated measurements of CO transfer in an individual should increase the present poor knowledge of the contribution of alveolar disease to the progression of chronic airflow obstruction

Aseptic Barriers Allow a Clean Contact for Contaminated Stethoscope Diaphragms.

Objective:To determine whether a single-use stethoscope diaphragm barrier surface remains aseptic when placed on pathogen-contaminated stethoscopes. Methods:From May 31 to August 5, 2019, we tested 2 separate barriers using 3 different strains of 7 human pathogens, including extended-spectrum β-lactamase-producing Escherichia coli, methicillin-resistant Staphylococcus aureus, and vancomycin resistant Enterococcus faecium. Results:For all diaphragms with either of the 2 barriers tested, no growth was recorded for any of the pathogens. Stethoscopes with aseptic barriers remained sterile for up to 24 hours. These single-use barriers also provided aseptic surfaces when stethoscope diaphragms were inoculated with human specimens, including saliva, stool, urine, and sputum. Conclusion:Disposable aseptic diaphragm barriers may provide robust and efficient solutions to reduce transmission of pathogens via stethoscopes

Interacting damage models mapped onto Ising and percolation models

We introduce a class of damage models on regular lattices with isotropic interactions, as e.g. quasistatic fiber bundles. The system starts intact with a surface-energy threshold required to break any cell sampled from an uncorrelated quenched-disorder distribution. The evolution of this heterogeneous system is ruled by Griffith's principle which states that a cell breaks when the release in elastic energy in the system exceeds the surface-energy barrier necessary to break the cell. By direct integration over all possible realizations of the quenched disorder, we obtain the probability distribution of each damage configuration at any level of the imposed external deformation. We demonstrate an isomorphism between the distributions so obtained and standard generalized Ising models, in which the coupling constants and effective temperature in the Ising model are functions of the nature of the quenched-disorder distribution and the extent of accumulated damage. In particular, we show that damage models with global load sharing are isomorphic to standard percolation theory, that damage models with local load sharing rule are isomorphic to the standard Ising model, and draw consequences thereof for the universality class and behavior of the autocorrelation length of the breakdown transitions corresponding to these models. We also treat damage models having more general power-law interactions, and classify the breakdown process as a function of the power-law interaction exponent. Last, we also show that the probability distribution over configurations is a maximum of Shannon's entropy under some specific constraints related to the energetic balance of the fracture process, which firmly relates this type of quenched-disorder based damage model to standard statistical mechanics.Comment: 16 pages, 3 figure

Fracture of disordered solids in compression as a critical phenomenon: I. Statistical mechanics formalism

This is the first of a series of three articles that treats fracture localization as a critical phenomenon. This first article establishes a statistical mechanics based on ensemble averages when fluctuations through time play no role in defining the ensemble. Ensembles are obtained by dividing a huge rock sample into many mesoscopic volumes. Because rocks are a disordered collection of grains in cohesive contact, we expect that once shear strain is applied and cracks begin to arrive in the system, the mesoscopic volumes will have a wide distribution of different crack states. These mesoscopic volumes are the members of our ensembles. We determine the probability of observing a mesoscopic volume to be in a given crack state by maximizing Shannon's measure of the emergent crack disorder subject to constraints coming from the energy-balance of brittle fracture. The laws of thermodynamics, the partition function, and the quantification of temperature are obtained for such cracking systems.Comment: 11 pages, 2 figure

Comparative study of variable flux memory machines with parallel and series hybrid magnets

Variable flux memory (VFM) permanent magnet (PM) machines exhibit an additional degree-of-freedom for control, i.e. PM magnetization state, and thus excellent flux controllability. Moreover, the hybrid PM topologies having variable PM (VPM) with low coercive force and constant PM (CPM) with high coercive force at the same time, are employed to improve the torque density and the flux controllability. The parallel and series connections between the two different kinds of PMs are both feasible. Based on two-dimensional (2-D) finite element (FE) analysis, the VFM machines with these two connection types are investigated and compared in this paper. The results reveal that the VPM with series connected CPM is beneficial for more stable working point and better torque density. A pair of VFM prototypes with parallel and series hybrid PMs respectively are manufactured and tested to validate the analyses

A Novel Variable Flux Memory Machine With Series Hybrid Magnets

This paper proposes a novel variable flux memory (VFM) machine, in which the “constant” permanent magnet (CPM) with high coercive force and the “variable” PM (VPM) with low coercive force are alternatively located in the interior-PM rotor. Thus, the VPMs and CPMs are magnetically connected in series, with which the CPMs can assist the VPMs to withstand the unintentional demagnetization caused by armature reaction. Therefore, a high armature current can be applied to the machine. Meanwhile, the reluctance torque is retrieved. Thus, a high torque density can be obtained. Based on two-dimensional finite element analysis, first, the electromagnetic performance of the proposed VFM machine in two extreme magnetization states is evaluated in detail. Then, the demagnetization and remagnetization characteristics are investigated, in which the working points of VPMs are illustrated. Furthermore, the advantages of improved efficiency of the proposed VFM machine are demonstrated. A prototype machine is manufactured and tested to validate the predictions

Translational outcomes in a full gene deletion of ubiquitin protein ligase E3A rat model of Angelman syndrome.

Angelman syndrome (AS) is a rare neurodevelopmental disorder characterized by developmental delay, impaired communication, motor deficits and ataxia, intellectual disabilities, microcephaly, and seizures. The genetic cause of AS is the loss of expression of UBE3A (ubiquitin protein ligase E6-AP) in the brain, typically due to a deletion of the maternal 15q11-q13 region. Previous studies have been performed using a mouse model with a deletion of a single exon of Ube3a. Since three splice variants of Ube3a exist, this has led to a lack of consistent reports and the theory that perhaps not all mouse studies were assessing the effects of an absence of all functional UBE3A. Herein, we report the generation and functional characterization of a novel model of Angelman syndrome by deleting the entire Ube3a gene in the rat. We validated that this resulted in the first comprehensive gene deletion rodent model. Ultrasonic vocalizations from newborn Ube3am-/p+ were reduced in the maternal inherited deletion group with no observable change in the Ube3am+/p- paternal transmission cohort. We also discovered Ube3am-/p+ exhibited delayed reflex development, motor deficits in rearing and fine motor skills, aberrant social communication, and impaired touchscreen learning and memory in young adults. These behavioral deficits were large in effect size and easily apparent in the larger rodent species. Low social communication was detected using a playback task that is unique to rats. Structural imaging illustrated decreased brain volume in Ube3am-/p+ and a variety of intriguing neuroanatomical phenotypes while Ube3am+/p- did not exhibit altered neuroanatomy. Our report identifies, for the first time, unique AS relevant functional phenotypes and anatomical markers as preclinical outcomes to test various strategies for gene and molecular therapies in AS