Advanced research and technology programs for advanced high-pressure oxygen-hydrogen rocket propulsion

A research and technology program for advanced high pressure, oxygen-hydrogen rocket propulsion technology is presently being pursued by the National Aeronautics and Space Administration (NASA) to establish the basic discipline technologies, develop the analytical tools, and establish the data base necessary for an orderly evolution of the staged combustion reusable rocket engine. The need for the program is based on the premise that the USA will depend on the Shuttle and its derivative versions as its principal Earth-to-orbit transportation system for the next 20 to 30 yr. The program is focused in three principal areas of enhancement: (1) life extension, (2) performance, and (3) operations and diagnosis. Within the technological disciplines the efforts include: rotordynamics, structural dynamics, fluid and gas dynamics, materials fatigue/fracture/life, turbomachinery fluid mechanics, ignition/combustion processes, manufacturing/producibility/nondestructive evaluation methods and materials development/evaluation. An overview of the Advanced High Pressure Oxygen-Hydrogen Rocket Propulsion Technology Program Structure and Working Groups objectives are presented with highlights of several significant achievements

Mercury Air/Surface Exchange Kinetics of Background Soils of the Tahquamenon River Watershed in the Michigan Upper Peninsula

Air/surface exchange of mercury was investigated over background soils at five sites in the Tahquamenon River watershed in the Michigan Upper Peninsula in the summer of 1998. Measurements of Hg fluxes were performed during middayperiods using the ORNL Teflon dynamic flux chamber. Mean Hg emission fluxes were 1.4±0.3–2.4±1.0 ng m -2 hr -1 for three shaded forest sites and 7.6±1.7 ng m -2 hr -1 for an open field site. Hg dry deposition was observed at a heavily shaded forest site overwet soils (mean = –0.3±0.2 ng m -2 hr -1 ). Theoverall mean Hg flux was 1.4±1.4 ng m -2 hr -1 for the four shaded forest sites. The Hg fluxes observed at these sites are similar to those found at other northern background sites. Significant, rapid response of Hg emission to solar radiation was observed over these background soils. Artificial irrigation over these soils induced immediate andmeasurable increases in Hg emission. Soil temperature was found to be less influential to Hg air/surface exchange over these heavily shaded forest background soils than we have seen elsewhere.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43896/1/11270_2004_Article_267454.pd

Visualizing the microscopic coexistence of spin density wave and superconductivity in underdoped NaFe1-xCoxAs

Although the origin of high temperature superconductivity in the iron pnictides is still under debate, it is widely believed that magnetic interactions or fluctuations play an important role in triggering Cooper pairing. Because of the relevance of magnetism to pairing, the question of whether long range spin magnetic order can coexist with superconductivity microscopically has attracted strong interests. The available experimental methods used to answer this question are either bulk probes or local ones without control of probing position, thus the answers range from mutual exclusion to homogeneous coexistence. To definitively answer this question, here we use scanning tunneling microscopy to investigate the local electronic structure of an underdoped NaFe1-xCoxAs near the spin density wave (SDW) and superconducting (SC) phase boundary. Spatially resolved spectroscopy directly reveal both the SDW and SC gap features at the same atomic location, providing compelling evidence for the microscopic coexistence of the two phases. The strengths of the SDW and SC features are shown to anti correlate with each other, indicating the competition of the two orders. The microscopic coexistence clearly indicates that Cooper pairing occurs when portions of the Fermi surface (FS) are already gapped by the SDW order. The regime TC < T < TSDW thus show a strong resemblance to the pseudogap phase of the cuprates where growing experimental evidences suggest a FS reconstruction due to certain density wave order. In this phase of the pnictides, the residual FS has a favorable topology for magnetically mediated pairing when the ordering moment of the SDW is small.Comment: 18 pages, 4 figure

Is the New Mayo Clinic Quadratic Equation Useful for the Estimation of Glomerular Filtration Rate in Type 2 Diabetic Patients?

OBJECTIVE—To test the Mayo Clinic Quadratic (MCQ) equation against isotopic glomerular filtration rate, compared with the Modification of Diet in Renal Disease (MDRD) and the Cockcroft-Gault formulas, in type 2 diabetes

Local terahertz field enhancement for time-resolved x-ray diffraction

We report local field strength enhancement of single-cycle terahertz (THz) pulses in an ultrafast time-resolved x-ray diffraction experiment. We show that patterning the sample with gold microstructures increases the THz field without changing the THz pulse shape or drastically affecting the quality of the x-ray diffraction pattern. We find a five-fold increase in THz-induced x-ray diffraction intensity change in the presence of microstructures on a SrTiO3 thin-film sample

Ultrafast transient generation of spin-densitywave order in the normal state of BaFe2As2 driven by coherent lattice vibrations

The interplay among charge, spin and lattice degrees of freedom in solids gives rise to intriguing macroscopic quantum phenomena such as colossal magnetoresistance, multiferroicity and high-temperature superconductivity. Strong coupling or competition between various orders in these systems presents the key to manipulate their functional properties by means of external perturbations such as electric and magnetic fields or pressure. Ultrashort and intense optical pulses have emerged as an interesting tool to investigate elementary dynamics and control material properties by melting an existing order. Here, we employ few-cycle multi-terahertz pulses to resonantly probe the evolution of the spin-density-wave (SDW) gap of the pnictide compound BaFe2As2 following excitation with a femtosecond optical pulse. When starting in the low-temperature ground state, optical excitation results in a melting of the SDW order, followed by ultrafast recovery. In contrast, the SDW gap is induced when we excite the normal state above the transition temperature. Very surprisingly, the transient ordering quasi-adiabatically follows a coherent lattice oscillation at a frequency as high as 5.5 THz. Our results attest to a pronounced spin-phonon coupling in pnictides that supports rapid development of a macroscopic order on small vibrational displacement even without breaking the symmetry of the crystal

How does study quality affect the results of a diagnostic meta-analysis?

Background: The use of systematic literature review to inform evidence based practice in diagnostics is rapidly expanding. Although the primary diagnostic literature is extensive, studies are often of low methodological quality or poorly reported. There has been no rigorously evaluated, evidence based tool to assess the methodological quality of diagnostic studies. The primary objective of this study was to determine the extent to which variations in the quality of primary studies impact the results of a diagnostic meta-analysis and whether this differs with diagnostic test type. A secondary objective was to contribute to the evaluation of QUADAS, an evidence-based tool for the assessment of quality in diagnostic accuracy studies. Methods: This study was conducted as part of large systematic review of tests used in the diagnosis and further investigation of urinary tract infection (UTI) in children. All studies included in this review were assessed using QUADAS, an evidence-based tool for the assessment of quality in systematic reviews of diagnostic accuracy studies. The impact of individual components of QUADAS on a summary measure of diagnostic accuracy was investigated using regression analysis. The review divided the diagnosis and further investigation of UTI into the following three clinical stages: diagnosis of UTI, localisation of infection, and further investigation of the UTI. Each stage used different types of diagnostic test, which were considered to involve different quality concerns. Results: Many of the studies included in our review were poorly reported. The proportion of QUADAS items fulfilled was similar for studies in different sections of the review. However, as might be expected, the individual items fulfilled differed between the three clinical stages. Regression analysis found that different items showed a strong association with test performance for the different tests evaluated. These differences were observed both within and between the three clinical stages assessed by the review. The results of regression analyses were also affected by whether or not a weighting (by sample size) was applied. Our analysis was severely limited by the completeness of reporting and the differences between the index tests evaluated and the reference standards used to confirm diagnoses in the primary studies. Few tests were evaluated by sufficient studies to allow meaningful use of meta-analytic pooling and investigation of heterogeneity. This meant that further analysis to investigate heterogeneity could only be undertaken using a subset of studies, and that the findings are open to various interpretations. Conclusion: Further work is needed to investigate the influence of methodological quality on the results of diagnostic meta-analyses. Large data sets of well-reported primary studies are needed to address this question. Without significant improvements in the completeness of reporting of primary studies, progress in this area will be limited

Oocyte and ovarian tissue cryopreservation in European countries : statutory background, practice, storage and use

STUDY QUESTION: What is known in Europe about the practice of oocyte cryopreservation (OoC), in terms of current statutory background, funding conditions, indications (medical and ‘non-medical’) and specific number of cycles? SUMMARY ANSWER: Laws and conditions for OoC vary in Europe, with just over half the responding countries providing this for medical reasons with state funding, and none providing funding for ‘non-medical’ OoC. WHAT IS ALREADY KNOWN: The practice of OoC is a well-established and increasing practice in some European countries, but data gathering on storage is not homogeneous, and still sparse for use. Ovarian tissue cryopreservation (OtC) is only practiced and registered in a few countries. STUDY DESIGN, SIZE, AND DURATION: A transversal collaborative survey on OoC and OtC, was designed, based on a country questionnaire containing information on statutory or professional background and practice, as well as available data on ovarian cell and tissue collection, storage and use. It was performed between January and September 2015. PARTICIPANTS/MATERIALS, SETTING AND METHODS: All ESHRE European IVF Monitoring (EIM) consortium national coordinators were contacted, as well as members of the ESHRE committee of national representatives, and sent a questionnaire. The form included national policy and practice details, whether through current existing law or code of practice, criteria for freezing (age, health status), availability of funding and the presence of a specific register. The questionnaire also included data on both the number of OoC cycles and cryopreserved oocytes per year between 2010 and 2014, specifically for egg donation, fertility preservation for medical disease, ‘other medical’ reasons as part of an ART cycle, as well as for ‘non-medical reasons’ or age-related fertility decline. Another question concerning data on freezing and use of ovarian tissue over 5 years was added and sent after receiving the initial questionnaire. MAIN RESULTS AND THE ROLE OF CHANCE: Out of 34 EIM members, we received answers regarding OoC regulations and funding conditions from 27, whilst 17 countries had recorded data for OoC, and 12 for OtC. The specific statutory framework for OoC and OtC varies from absent to a strict frame. A total of 34 705 OoC cycles were reported during the 5-year-period, with a continuous increase. However, the accurate description of numbers was concentrated on the year 2013 because it was the most complete. In 2013, a total of 9126 aspirations involving OoC were reported from 16 countries. Among the 8885 oocyte aspirations with fully available data, the majority or 5323 cycles (59.9%) was performed for egg donation, resulting in the highest yield per cycle, with an average of 10.4 oocytes frozen per cycle. OoC indication was ‘serious disease’ such as cancer in 10.9% of cycles, other medical indications as ‘part of an ART cycle’ in 16.1%, and a non-medical reason in 13.1%. With regard to the use of OoC, the number of specifically recorded frozen oocyte replacement (FOR) cycles performed in 2013 for all medical reasons was 14 times higher than the FOR for non-medical reasons, using, respectively, 8.0 and 8.4 oocytes per cycle. Finally, 12 countries recorded storage following OtC and only 7 recorded the number of grafted frozen/thawed tissues. LIMITATIONS, REASONS FOR CAUTION: Not all countries have data regarding OoC collection, and some data came from voluntary collaborating centres, rather than a national authority or register. Furthermore, the data related to use of OoC were not included for two major players in the field, Italy and Spain, where numbers were conflated for medical and non-medical reasons. Finally, the number of cycles started with no retrieval is not available. Data are even sparser for OtC. WIDER IMPLICATIONS OF THE FINDINGS: There is a need for ART authorities and professional bodies to record precise data for practice and use of OoC (and OtC), according to indications and usage, in order to reliably inform all stakeholders including women about the efficiency of both methods. Furthermore, professional societies should establish professional standards for access to and use of OoC and OtC, and give appropriate guidance to all involved. STUDY FUNDING/COMPETING INTEREST(S): The study was supported by ESHRE. There are no conflicts of interest.peer-reviewe