Fabrication and Testing of Catalyst-Infused Filament for 3D Printing of Ignition-Augmented Hybrid Rocket Fuels

This thesis describes and addresses the need for reliable ignition in small satellite hybrid propulsion systems using higher density oxidizers. It describes methods of creating custom 3D printing ABS plastic based filaments that contain small amounts of catalysts. These catalysts lead to a more reliable and energy-efficient ignition of a hybrid rocked propulsion system using catalyst-infused ABS and nitrous oxide and oxygen blend called Nytrox, commonly known as ”laughing gas.” The ”laughing gas” has a higher density and can therefore provide more ”miles per gallon” in a hybrid propulsion system on a small satellite when compared to gaseous oxygen (GOX). The ignition methods of hybrid rocket propulsion systems using Nytrox are compared and contrasted, and the ignition using catalyst-infused ABS as the fuel is tested. The data from these tests are presented and indicate an improvement in ignition energy and latency compared to pure ABS fuel

Investigation of high efficiency GaAs solar cells

Investigations of basic mechanisms which limit the performance of high efficiency GaAs solar cells are discussed. P/N heteroface structures have been fabricated from MOCVD epiwafers. Typical AM1 efficiencies are in the 21 to 22 percent range, with a SERI measurement for one cell being 21.5 percent. The cells are nominally 1.5 x 1.5 cm in size. Studies have involved photoresponse, T-I-V analyses, and interpretation of data in terms of appropriate models to determine key cell parameters. Results of these studies are utilized to determine future approaches for increasing GaAs solar cell efficiencies

Fabrication of Catalyst Infused Filament for 3-D Printing of Hybrid Rocket Fuels

Additive manufacturing changes the electrical breakdown properties of certain 3D-printed thermoplastics like Acrylonitrile Butadiene Styrene (ABS), and when printed materials are presented with a high-voltage electrical potential, electrical-arcing along the layered surface pyrolizes the material. This electrostatic property has been harnessed to develop a High-Performance Green Hybrid Propulsion (HPGHP) technology that has capability for reliable start, stop, and re-ignition. HPGHP operates reliably using gaseous oxygen (GOX) as the complementing oxidizer; but has experienced reliability and ignition latency issues when GOX is replaced by Nytrox, a higher-density blend of nitrous oxide and GOX. Ignition issues are overcome by infusing small amounts of ruthenium catalyst into the base print feedstock. Catalytic-assist works by partially decomposing the incoming oxidizer to release free oxygen in the upper section of the combustion chamber. This paper describes the catalyst infusion process and filament production details. Results from static hot-fire tests are presented with baseline GOX/ABS propellant tests being compared against Nytrox/ABS tests with and without catalytic additives. The catalyst additive significantly increases ignition reliability, reduces ignition latency, and lowers the required ignition energy. The catalyst-infused ABS fuels exhibit a slightly reduced performance level, as compared to GOX/ABS, but with significantly increased system volumetric efficiency

Cu-Enhanced 3-D Printed Fuels for Green SmallSat Propulsion

The Propulsion Research Laboratory at Utah State University (USU) has recently developed a promising High-Performance Green Hybrid Propulsion (HPGHP) technology that derives from the novel electrical breakdown property of certain 3-D printed like acrylonitrile butadiene styrene (ABS). This electrical breakdown property has been engineered into a proprietary, power-efficient system that can be cold-started and restarted with a high degree of reliability. One of the issues associated with ABS as a propellant is its low burn rate. It is well documented in technical literature that hybrid rocket systems generally have fuel regression rates that are typically 25-30% lower than solid fuel motors in the same thrust and impulse class. Lowered fuel regression rates tend to produce unacceptably low equivalence ratios that lead to poor mass-impulse performance, erosive fuel burning, nozzle erosion, reduced motor duty cycles, and the potential for combustion instability. To achieve equivalence ratios that produce acceptable combustion characteristics, hybrid fuel ports are often fabricated with large length-to-diameter ratios. The resulting poor volumetric efficiency is incompatible with Small Satellite (SmallSat) applications. This paper presents preliminary results from a collaborative development program between the University of Miami (UM) and USU. In this reported work, modern extrusion and 3-D printing techniques are used to fabricate sample ABS fuel grains with varying levels of copper-metallization. Hybrid-ABS fuel grains were printed from Cu-infused feed stock with 2%, 4%, and 6% Cu-mass concentrations. As baseline control, 100% pure ABS fuel grains (0% Cu) were also printed. Heat conduction via the additive copper (Cu) provides an efficient heat transfer mechanism that augments surface convection from the flame zone. Forced convection, the primary mechanism for pyrolysis for hybrid fuels, is generally inefficient due to wall-blowing associated with the radially emanating mass flow from fuel pyrolysis. Wall-blowing pushes the flame zone away from the fuel surface and significantly reduces the rate of enthalpy exchange. Homogeneously mixing a high conductivity metal such as Cu into the ABS fuel provides an efficient heat transfer mechanism, and allows radiant heat from the flame zone to be transferred deep into the fuel material. This process significantly increases the pyrolytic efficiency of the fuels. The Cu-infused fuels were tested at USU using a legacy 12-N hybrid thruster system. Fabrication and manufacturing methods are described, and results of hot fire tests are presented. The top-level conclusion is that Cu-infusion of the printed fuels measurably increases the fuel regression rate, allowing for a higher thrust level with no increase in the required volume. The Cu-infusion has negligible impact on the propellant characteristic velocity and the overall system specific impulse. The increased burn rate and overall increase in solid-fuel density resulting from Cu-infusion allows a measurable increase in the propellant impulse-density. This increase in volumetric efficiency is potentially significant for small spacecraft applications where available space has a premium value. Follow-on methods that infuse lower-molecular weight and higher thermal conductivity materials like graphene and carbon-nanotubes are proposed

High-impact animal health research conducted at the USDA’s National Animal Disease Center

Commissioned by President Dwight Eisenhower in 1958 and opened with a dedication ceremony in December 1961, the USDA, Agricultural Research Service (ARS), National Animal Disease Center (NADC) celebrated its 50-year anniversary in November 2011. Over these 50 years, the NADC established itself among the world’s premier animal health research centers. Its historic mission has been to conduct basic and applied research on selected endemic diseases of economic importance to the U.S. livestock and poultry industries. Research from NADC has impacted control or management efforts on nearly every major animal disease in the United States since 1961. For example, diagnostic tests and vaccines developed by NADC scientists to detect and prevent hog cholera were integral in the ultimate eradication of this costly swine disease from the U.S. Most major veterinary vaccines for critical diseases such as brucellosis and leptospirosis in cattle, porcine respiratory and reproductive syndrome (PRRS), porcine parvovirus and influenza in swine had their research origins or were developed and tested at the NADC. Additional discoveries made by NADC scientists have also resulted in the development of a nutritional approach and feed additives to prevent milk fever in transition dairy cattle. More recently, NADC’s archive of historic swine influenza viruses combined with an established critical mass of influenza research expertise enabled NADC researchers to lead an effective national research response to the pandemic associated with the novel 2009 H1N1 influenza virus. This review commemorates some of the key animal health contributions in NADC’s first 50 years, recaps the newly completed modernization of the center into new facilities, and offers highlights of the ongoing research that will define NADC’s mission going forward

Enhanced surgical site infection surveillance following hysterectomy, vascular, and colorectal surgery

Objective.To evaluate the use of inpatient pharmacy and administrative data to detect surgical site infections (SSIs) following hysterectomy and colorectal and vascular surgery.Design.Retrospective cohort study.Setting.Five hospitals affiliated with academic medical centers.Patients.Adults who underwent abdominal or vaginal hysterectomy, colorectal surgery, or vascular surgery procedures between July 1, 2003, and June 30, 2005.Methods.We reviewed the medical records of weighted, random samples drawn from 3,079 abdominal and vaginal hysterectomy, 4,748 colorectal surgery, and 3,332 vascular surgery procedures. We compared routine surveillance with screening of inpatient pharmacy data and diagnosis codes and then performed medical record review to confirm SSI status.Results.Medical records from 823 hysterectomy, 736 colorectal surgery, and 680 vascular surgery procedures were reviewed. SSI rates determined by antimicrobial- and/or diagnosis code-based screening followed by medical record review (enhanced surveillance) were substantially higher than rates determined by routine surveillance (4.3% [95% confidence interval, 3.6%—5.1%] vs 2.7% for hysterectomies, 7.1% [95% confidence interval, 6.7%–8.2%] vs 2.0% for colorectal procedures, and 2.3% [95% confidence interval, 1.9%–2.9%] vs 1.4% for vascular procedures). Enhanced surveillance had substantially higher sensitivity than did routine surveillance to detect SSI (92% vs 59% for hysterectomies, 88% vs 22% for colorectal procedures, and 72% vs 43% for vascular procedures). A review of medical records confirmed SSI for 31% of hysterectomies, 20% of colorectal procedures, and 31% of vascular procedures that met the enhanced screening criteria.Conclusion.Antimicrobial- and diagnosis code-based screening may be a useful method for enhancing and streamlining SSI surveillance for a variety of surgical procedures, including those procedures targeted by the Centers for Medicare and Medicaid Services.</jats:sec

Use of Medicare diagnosis and procedure codes to improve detection of surgical site infections following hip arthroplasty, knee arthroplasty, and vascular surgery

ObjectiveTo evaluate the use of routinely collected electronic health data in Medicare claims to identify surgical site infections (SSIs) following hip arthroplasty, knee arthroplasty, and vascular surgery.DesignRetrospective cohort study.SettingFour academic hospitals that perform prospective SSI surveillance.MethodsWe developed lists of International Classification of Diseases, Ninth Revision, and Current Procedural Terminology diagnosis and procedure codes to identify potential SSIs. We then screened for these codes in Medicare claims submitted by each hospital on patients older than 65 years of age who had undergone 1 of the study procedures during 2007. Each site reviewed medical records of patients identified by either claims codes or traditional infection control surveillance to confirm SSI using Centers for Disease Control and Prevention/National Healthcare Safety Network criteria. We assessed the performance of both methods against all chart-confirmed SSIs identified by either method.ResultsClaims-based surveillance detected 1.8-4.7-fold more SSIs than traditional surveillance, including detection of all previously identified cases. For hip and vascular surgery, there was a 5-fold and 1.6-fold increase in detection of deep and organ/space infections, respectively, with no increased detection of deep and organ/space infections following knee surgery. Use of claims to trigger chart review led to confirmation of SSI in 1 out of 3 charts for hip arthroplasty, 1 out of 5 charts for knee arthroplasty, and 1 out of 2 charts for vascular surgery.ConclusionClaims-based SSI surveillance markedly increased the number of SSIs detected following hip arthroplasty, knee arthroplasty, and vascular surgery. It deserves consideration as a more effective approach to target chart reviews for identifying SSIs

Properties and Origin of the High-Velocity Gas Toward the Large Magellanic Cloud

In the spectra of 139 early-type Large Magellanic Cloud (LMC) stars observed with FUSE and with deep radio Parkes HI 21-cm observations along those stars, we search for and analyze the absorption and emission from high-velocity gas at +90<v<+175 km/s. The HI column density of the high-velocity clouds (HVCs) along these sightlines ranges from <10^18.4 to 10^19.2 cm^-2. The incidence of the HVC metal absorption is 70%, significantly higher than the HI emission occurrence of 32%. We find that the mean metallicity of the HVC is [OI/HI] = -0.51 (+0.12,-0.16). There is no strong evidence for a large variation in the HVC metallicity, implying that thes e HVCs have a similar origin and are part of the same complex. The mean and scatter of the HVC metallicities are more consistent with the present-day LMC oxygen abundance than that of the Small Magellanic Cloud or the Milky Way. We find that on average [SiII/OI] = +0.48 (+0.15,- 0.25) and [FeII/OI] = +0.33 (+0.14,-0.21), implying that the HVC complex is dominantly ionized. The HVC complex has a multiphase structure with a neutral (OI, FeII), weakly ionized (FeII, NII), and highly ionized (OVI) components, and has evidence of dust but no molecules. All the observed properties of the HVC can be explained by an energetic outflow from the LMC. This is the first example of a large (>10^6 M_sun) HVC complex that is linked to stellar feedback occurring in a dwarf spiral galaxy.Comment: Accepted for publication in the Ap

Single-molecule detection of dihydroazulene photo-thermal reaction using break junction technique

基于隧穿机制的电输运是物质世界的基本过程之一。在单分子尺度，分子结构的细微变化足以导致电学性质的显著区别，这也使通过单分子电学检测方法研究化学反应过程成为可能。在这一研究工作中，课题组将通常用于单分子电学测量的裂结技术用于单分子尺度反应动力学的表征。这一工作也为未来的合成化学和化学工程研究提供了一种新思路，即通过纳米技术构造反应微环境，可以实现化学反应速率、产物和产率的优化。 该研究工作是在洪文晶教授和丹麦哥本哈根大学Mogens B. Nielsen教授的共同指导下，通过跨学科的国际合作所完成的。其中洪文晶教授课题组负责该研究工作的实验表征和统计分析，丹麦哥本哈根大学Mogens B. Nielsen教授课题组负责分子体系的合成，Kurt V. Mikkelsen教授和Gemma C. Solomon教授课题组分别负责了该研究工作的反应动力学和电输运理论计算，这也是洪文晶教授课题组与上述研究团队的首次科研合作。我校萨本栋微纳研究院的杨扬助理教授也参与了数据分析和机理讨论的部分工作。 洪文晶教授课题组长期致力于单分子尺度下的化学反应、分子组装、分子器件电输运等方面的相关研究，开发了一系列能够在单分子尺度实现精密控制和精确测量的科学仪器。以此为基础，课题组与国内外材料化学和理论研究团队密切合作，在单分子尺度电输运的量子干涉效应、电化学调控和化学反应表征等领域进行了一系列探索。【Abstract】Charge transport by tunnelling is one of the most ubiquitous elementary processes in nature. Small structural changes in a molecular junction can lead to significant difference in the single-molecule electronic properties, offering a tremendous opportunity to examine a reaction on the single-molecule scale by monitoring the conductance changes. Here, we explore the potential of the single-molecule break junction technique in the detection of photo-thermal reaction processes of a photochromic dihydroazulene/vinylheptafulvene system. Statistical analysis of the break junction experiments provides a quantitative approach for probing the reaction kinetics and reversibility, including the occurrence of isomerization during the reaction. The product ratios observed when switching the system in the junction does not follow those observed in solution studies (both experiment and theory), suggesting that the junction environment was perturbing the process significantly. This study opens the possibility of using nano-structured environments like molecular junctions to tailor product ratios in chemical reactions.This work was generously supported by the University of Copenhagen, the Danish e-Infrastructure Cooperation, the European Union Seventh Framework Programme (FP7/2007-2013) under the ERC grant agreement no.258806, the Danish Council for Independent Research—Natural Sciences, the Carlsberg foundation, NSFC (21673195,21503179), EC FP7 ITNs ‘MOLESCO’ project numbers 606728, and the Young Thousand Talent Project of China. 研究工作得到了国家自然科学基金（21673195，21503179）、固体表面物理化学国家重点实验室、能源材料化学协同创新中心（2011-iChEM）的大力资助与支持

The prognosis for individuals on disability retirement An 18-year mortality follow-up study of 6887 men and women sampled from the general population

BACKGROUND: Several studies have shown a markedly higher mortality rate among disability pensioners than among non-retired. Since most disability pensions are granted because of non-fatal diseases the reason for the increased mortality therefore remains largely unknown. The aim of this study was to evaluate potential explanatory factors. METHODS: Data from five longitudinal cohort studies in Sweden, including 6,887 men and women less than 65 years old at baseline were linked to disability pension data, hospital admission data, and mortality data from 1971 until 2001. Mortality odds ratios were analyzed with Poisson regression and Cox's proportional hazards regression models. RESULTS: 1,683 (24.4%) subjects had a disability pension at baseline or received one during follow up. 525 (7.6%) subjects died during follow up. The subjects on disability pension had a higher mortality rate than the non-retired, the hazards ratio (HR) being 2.78 (95%CI 2.08–3.71) among women and 3.43 (95%CI 2.61–4.51) among men. HR was highest among individuals granted a disability pension at young ages (HR >7), and declined parallel to age at which the disability pension was granted. The higher mortality rate among the retired subjects was not explained by disability pension cause or underlying disease or differences in age, marital status, educational level, smoking habits or drug abuse. There was no significant association between reason for disability pension and cause of death. CONCLUSION: Subjects with a disability pension had increased mortality rates as compared with non-retired subjects, only modestly affected by adjustments for psycho-socio-economic factors, underlying disease, etcetera. It is unlikely that these factors were the causes of the unfavorable outcome. Other factors must be at work