Using Liquid Natural Gas Fuel to Cryogenically Cool and Enhance a Hybrid Electric Aircraft Power System

A previous system study identified significant increases in range and number of urban air mobility (UAM) missions by replacing the all battery power system of a notional UAM vehicle with an advanced diesel hybrid using conventional diesel or liquid natural gas (LNG) fuels (at constant vehicle design gross weight). Some benefits were realized using the LNG's cryogenic properties to reduce some electrical component losses and cooling requirements. Significant questions were raised concerning volume and thermal management considerations for all studied systems. The notional, baseline vehicle was a hybrid helicopter / airplane design capable of vertical take-off and landing (VTOL), balancing high cruise efficiency with reasonable hover capability. A subsequent power system assessment using the same notional vehicle and mission was performed that identified increased volume and power requirements for the active cooling required. The cooling airflow could also generate additional drag on the vehicle during operation. For the notional vehicle studied, the additional volume identified by the subsequent study would not affect vehicle mold line and therefore drag. However, the additional drag from cooling airflow and the power to circulate it as needed would impact power system and vehicle mission performance. Vehicle and mission models were updated and rerun. Updated results still indicated significant benefits in range and number of UAM missions, but reduced the benefit by 12-15%. Hold time for the hybrid systems also generally increased a few minutes because of reduced power available for charging from the power for required cooling flows. Vehicle weights, thermal loads, and cooling airflows from the updated analyses were similar to previous results

Preliminary Assessment of Variable Speed Power Turbine Technology on Civil Tiltrotor Size and Performance

A Large Civil Tiltrotor (LCTR) conceptual design was developed as part of the NASA Heavy Lift Rotorcraft Systems Investigation in order to establish a consistent basis for evaluating the benefits of advanced technology for large tiltrotors. The concept has since evolved into the second-generation LCTR2, designed to carry 90 passengers for 1,000 nm at 300 knots, with vertical takeoff and landing capability. This paper performs a preliminary assessment of variable-speed power turbine technology on LCTR2 sizing, while maintaining the same, advanced technology engine core. Six concepts were studied; an advanced, single-speed engine with a conventional power turbine layout (Advanced Conventional Engine, or ACE) using a multi-speed (shifting) gearbox. There were five variable-speed power turbine (VSPT) engine concepts, comprising a matrix of either three or four turbine stages, and fixed or variable guide vanes; plus a minimum weight, twostage, fixed-geometry VSPT. The ACE is the lightest engine, but requires a multi-speed (shifting) gearbox to maximize its fuel efficiency, whereas the VSPT concepts use a lighter, fixed-ratio gearbox. The NASA Design and Analysis of Rotorcraft (NDARC) design code was used to study the trades between rotor and engine efficiency and weight. Rotor performance was determined by Comprehensive Analytical Model of Rotorcraft Aerodynamics and Dynamics (CAMRAD II), and engine performance was estimated with the Numerical Propulsion System Simulation (NPSS). Design trades for the ACE vs. VSPT are presented in terms of vehicle gross and empty weight, propulsion system weight and mission fuel burn for the civil mission. Because of its strong effect on gearbox weight and on both rotor and engine efficiency, rotor speed was chosen as the reference design variable for comparing design trades. Major study assumptions are presented and discussed. Impressive engine power-to-weight and fuel efficiency reduced vehicle sensitivity to propulsion system choice. The 10% weight penalty for multi-speed gearbox was more significant than most engine technology weight penalties to the vehicle design because drive system weight is more than two times engine weight. Based on study assumptions, fixed-geometry VSPT concept options performed better than their variable-geometry counterparts. Optimum design gross weights varied 1% or less and empty weights less than 2% among the concepts studied, while optimum fuel burns varied up to 5%. The outcome for some optimum configurations was so unexpected as to recommend a deeper look at the underlying technology assumptions

Paediatric trauma on the Last Frontier: an 11-year review of injury mechanisms, high-risk injury patterns and outcomes in Alaskan children

Background: Paediatric trauma system development in Alaska is complicated by a vast geographic coverage area, wide regional variations in environment and culture, and a lack of available published data. Objective: To provide a detailed description of paediatric trauma mechanisms, high-risk injury patterns and outcomes in Alaska. Design: This retrospective study included all children aged 17 years or younger in the State of Alaska Trauma Registry database admitted with traumatic injury between 2001 and 2011. Each injury record was reviewed individually and assigned a mechanism based on Centers for Disease Control E-codes. Geographic definitions were based on existing Emergency Medical Services regions. Mechanisms were compared by geographic region, patient demographics, injury characteristics and outcome. Subgroup analysis of fatal injuries was performed to identify causes of death. Results: Of 5,547 patients meeting inclusion criteria, the most common mechanisms of injury were falls (39%), motor vehicle collisions (10%) and all-terrain vehicle (ATV) accidents (9%). The overall case fatality rate was 2%. Mechanisms with the greatest risk of death were gunshot wounds (21%), pedestrians struck by motorized vehicles (9%) and motor vehicle collisions (5%). These 3 mechanisms accounted for 15% of injuries but 60% of deaths in the overall cohort. Injury patterns involving combined central nervous system (CNS) and torso injuries were unusual but especially lethal, occurring in 3% of patients but carrying a case fatality rate of 18%. Although the distribution of mechanisms was generally similar for each geographic region, ATV and snowmobile injuries were significantly more common in remote areas (23% remote vs. 7% non-remote, p < 0.0001). Conclusions: Mechanisms of paediatric trauma in Alaska have widely varying impacts on outcome and show some variation by region. Highest-risk mechanisms include gunshot wounds and motorized vehicle-related accidents. Prevention efforts should give special attention to CNS injury prevention, ATV and snowmobile safety in remote areas, and optimization of management of multisystem trauma. Further studies should investigate predictors of outcome in greater detail

Development of the Central Dogma Concept Inventory (CDCI) Assessment Tool

Scientific teaching requires scientifically constructed, field-tested instruments to accurately evaluate student thinking and gauge teacher effectiveness. We have developed a 23-question, multiple select–format assessment of student understanding of the essential concepts of the central dogma of molecular biology that is appropriate for all levels of undergraduate biology. Questions for the Central Dogma Concept Inventory (CDCI) tool were developed and iteratively revised based on student language and review by experts. The ability of the CDCI to discriminate between levels of understanding of the central dogma is supported by field testing (N = 54), and large-scale beta testing (N = 1733). Performance on the assessment increased with experience in biology; scores covered a broad range and showed no ceiling effect, even with senior biology majors, and pre/posttesting of a single class focused on the central dogma showed significant improvement. The multiple-select format reduces the chances of correct answers by random guessing, allows students at different levels to exhibit the extent of their knowledge, and provides deeper insight into the complexity of student thinking on each theme. To date, the CDCI is the first tool dedicated to measuring student thinking about the central dogma of molecular biology, and version 5 is ready to use

Giant Enhancement of Surface Second Harmonic Generation in BaTiO_3 due to Photorefractive Surface Wave Excitation

We report observation of strongly enhanced surface SHG in BaTiO_3 due to excitation of a photorefractive surface electromagnetic wave. Surface SH intensity may reach 10^{-2} of the incident fundamental light intensity. Angular, crystal orientation and polarization dependencies of this SHG are presented. Possible applications of this effect in nonlinear surface spectroscopy are discussed.Comment: 5 pages, 6 figures, submitted to Physical Review Letters on the 3/29/199

Prosthetic thigh arteriovenous access: outcome with SVS/AAVS reporting standards

AbstractPurposeDifferences in the reporting methods of results for arteriovenous (AV) access can dramatically affect apparent outcome. To enable meaningful comparisons in the literature, the Society for Vascular Surgery and the American Association for Vascular Surgery (SVS/AAVS) recently published reporting standards for dialysis access. The purpose of the present study was to determine infection rates, patency rates, and possible predictive factors for prosthetic thigh AV access outcomes with the reporting standards of the SVS/AAVS.MethodsA retrospective analysis was performed of all patients who underwent placement of thigh AV access by the Surgical Teaching Service at Greenville Memorial Hospital between 1989 and 2001. Outcomes were determined based on SVS/AAVS Standards for Reports Dealing with AV Accesses. The rate of revision per year of access patency was also determined; this end point more accurately reflects the true cost and morbidity associated with AV access than do patency or infection rates alone.ResultsOne hundred twenty-five polytetrafluoroethylene thigh AV accesses were placed in 100 patients. Nine accesses were excluded from the study, six because there was no patient follow-up and 3 as a result of deaths unrelated to the access procedure and which occurred less than 30 days after access placement. There were six (4%) late access-related deaths. There were 18 (15%) early access failures, related to infection in 14 cases (12%), thrombosis in three cases (2%), and steal in one case (1%). Early failure was more common in patients with diabetes mellitus (P = .036). The primary and secondary functional patency rates were 19% and 54%, respectively, at 2 years. Infection occurred in 48 (41%) accesses. The patency and infection rates were not influenced by patient age, gender, body mass index, or diabetes mellitus. The median number of interventions per year of access patency was 1.68, and this outcome was positively correlated with body mass index (P < .001).ConclusionsProsthetic AV access in the thigh is associated with higher morbidity compared with that reported for the upper extremity, and should be considered only if no upper extremity AV access option is available. Early access failure and the requirement for an increased number of interventions to reestablish and maintain access patency are more common in patients with diabetes mellitus and obesity. The number of interventions per year of access patency is a valuable end point when assessing the outcome of AV access procedures

WHOI Hawaii Ocean Timeseries Station (WHOTS) : WHOTS-6 2009 mooring turnaround cruise report

The Woods Hole Oceanographic Institution (WHOI) Hawaii Ocean Timeseries Site (WHOTS), 100 km north of Oahu, Hawaii, is intended to provide long-term, high-quality air-sea fluxes as a part of the NOAA Climate Observation Program. The WHOTS mooring also serves as a coordinated part of the Hawaiian Ocean Timeseries (HOT) program, contributing to the goals of observing heat, fresh water and chemical fluxes at a site representative of the oligotrophic North Pacific Ocean. The approach is to maintain a surface mooring outfitted for meteorological and oceanographic measurements at a site near 22.75°N, 158°W by successive mooring turnarounds. These observations will be used to investigate air–sea interaction processes related to climate variability. The first WHOTS mooring (WHOTS-1) was deployed in August 2004. Turnaround cruises for successive moorings (WHOTS-2 through WHOTS-5) have typically been in either June or July. This report documents recovery of the WHOTS-5 mooring and deployment of the sixth mooring (WHOTS-6). The moorings utilize Surlyn foam buoys as the surface element and are outfitted with two Air–Sea Interaction Meteorology (ASIMET) systems. Each ASIMET system measures, records, and transmits via Argos satellite the surface meteorological variables necessary to compute air–sea fluxes of heat, moisture and momentum. The upper 155 m of the mooring is outfitted with oceanographic sensors for the measurement of temperature, conductivity and velocity in a cooperative effort with R. Lukas of the University of Hawaii (UH). A pCO2 system is installed on the buoy in a cooperative effort with Chris Sabine at the Pacific Marine Environmental Laboratory. Dr. Frank Bradley, CSIRO, Australia, assisted with meteorological sensor comparisons. A NOAA “Teacher at Sea” and a NOAA “Teacher in the Lab” participated in the cruise. The WHOTS mooring turnaround was done on the University of Hawaii research vessel Kilo Moana, Cruise KM-09-16, by the Upper Ocean Processes Group of the Woods Hole Oceanographic Institution in cooperation with UH and NOAA’s Earth System Research Laboratory, Physical Sciences Division (ESRL/PSD). The cruise took place between 9 and 17 July 2009. Operations began with deployment of the WHOTS-6 mooring on 10 July at approximately 22°40.0'N, 157°57.0'W in 4758 m of water. This was followed by meteorological intercomparisons and CTDs at the WHOTS-6 and WHOTS-5 sites. The WHOTS-5 mooring was recovered on 15 July 2009. The Kilo Moana then moved to the HOT central site (22°45.0'N, 158°00.0'W) for CTD casts. This report describes the cruise operations in more detail, as well as some of the in-port operations and pre-cruise buoy preparations.Funding was provided by the National Oceanic and Atmospheric Administration under Grant No. NA17RJ1223 for the Cooperative Institute for Climate and Ocean Research (CICOR)

Preoperative clinical factors predict postoperative functional outcomes after major lower limb amputation: An analysis of 553 consecutive patients

BackgroundDespite being a major determinant of functional independence, ambulation after major limb amputation has not been well studied. The purpose, therefore, of this study was to investigate the relationship between a variety of preoperative clinical characteristics and postoperative functional outcomes in order to formulate treatment recommendations for patients requiring major lower limb amputation.MethodsFrom January 1998 through December 2003, 627 major limb amputations (37.6% below knee amputations, 4.3% through knee amputations, 34.5% above knee amputations, and 23.6% bilateral amputations) were performed on 553 patients. Their mean age was 63.7 years; 55% were men, 70.2% had diabetes mellitus, and 91.5% had peripheral vascular disease. A retrospective review was performed correlating various preoperative presenting factors such as age at presentation, race, medical comorbidities, preoperative ambulatory status, and preoperative independent living status, with postoperative functional endpoints of prosthetic usage, survival, maintenance of ambulation, and maintenance of independent living status. Kaplan-Meier survival curves were constructed and compared by using the log-rank test. Odds ratios (OR) and hazard ratios (HR) with 95% confidence intervals were constructed by using multiple logistic regressions and Cox proportional hazards models.ResultsStatistically significant preoperative factors independently associated with not wearing a prosthesis in order of greatest to least risk were nonambulatory before amputation (OR, 9.5), above knee amputation (OR, 4.4), age >60 years (OR, 2.7), homebound but ambulatory status (OR, 3.0), presence of dementia (OR, 2.4), end-stage renal disease (OR, 2.3), and coronary artery disease (OR, 2.0). Statistically significant preoperative factors independently associated with death in decreasing order of influence included age ≥70 years (HR, 3.1), age 60 to 69 (HR, 2.5), and the presence of coronary artery disease (HR, 1.5). Statistically significant preoperative factors independently associated with failure of ambulation in decreasing order of influence included age ≥70 years (HR, 2.3), age 60 to 69 (HR, 1.6), bilateral amputation (HR, 1.8), and end-stage renal disease (HR, 1.4). Statistically significant preoperative factors independently associated with failure to maintain independent living status in decreasing order of influence included age ≥70 years (HR, 4.0), age 60 to 69 (HR, 2.7), level of amputation (HR, 1.8), homebound ambulatory status (HR, 1.6), and the presence of dementia (HR, 1.6).ConclusionsPatients with limited preoperative ambulatory ability, age ≥70, dementia, end-stage renal disease, and advanced coronary artery disease perform poorly and should probably be grouped with bedridden patients, who traditionally have been best served with a palliative above knee amputation. Conversely, younger healthy patients with below knee amputations achieved functional outcomes similar to what might be expected after successful lower extremity revascularization. Amputation in these instances should probably not be considered a failure of therapy but another treatment option capable of extending functionality and independent living

A review of polymeric membranes and processes for potable water reuse

Conventional water resources in many regions are insufficient to meet the water needs of growing populations, thus reuse is gaining acceptance as a method of water supply augmentation. Recent advancements in membrane technology have allowed for the reclamation of municipal wastewater for the production of drinking water, i.e., potable reuse. Although public perception can be a challenge, potable reuse is often the least energy-intensive method of providing additional drinking water to water stressed regions. A variety of membranes have been developed that can remove water contaminants ranging from particles and pathogens to dissolved organic compounds and salts. Typically, potable reuse treatment plants use polymeric membranes for microfiltration or ultrafiltration in conjunction with reverse osmosis and, in some cases, nanofiltration. Membrane properties, including pore size, wettability, surface charge, roughness, thermal resistance, chemical stability, permeability, thickness and mechanical strength, vary between membranes and applications. Advancements in membrane technology including new membrane materials, coatings, and manufacturing methods, as well as emerging membrane processes such as membrane bioreactors, electrodialysis, and forward osmosis have been developed to improve selectivity, energy consumption, fouling resistance, and/or capital cost. The purpose of this review is to provide a comprehensive summary of the role of polymeric membranes and process components in the treatment of wastewater to potable water quality and to highlight recent advancements and needs in separation processes. Beyond membranes themselves, this review covers the background and history of potable reuse, and commonly used potable reuse process chains, pretreatment steps, and advanced oxidation processes. Key trends in membrane technology include novel configurations, materials, and fouling prevention techniques. Challenges still facing membrane-based potable reuse applications, including chemical and biological contaminant removal, membrane fouling, and public perception, are highlighted as areas in need of further research and development. Keywords: Potable reuse; Polymeric membranes; Reverse osmosis; Filtration; Fouling; Revie