954 research outputs found

    About the parabolic relation existing between the skewness and the kurtosis in time series of experimental data

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    In this work we investigate the origin of the parabolic relation between skewness and kurtosis often encountered in the analysis of experimental time-series. We argue that the numerical values of the coefficients of the curve may provide informations about the specific physics of the system studied, whereas the analytical curve per se is a fairly general consequence of a few constraints expected to hold for most systems.Comment: To appear in Physica Script

    Design Concept for a Reusable/Propellantless MXER Tether Space Transportation System

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    The Momentum Exchange/Electrodynamic Reboost (MXER) tether facility is a transformational concept that significantly reduces the fuel requirements (and associated costs) in transferring payloads above low earth orbit (LEO). Facility reboost is accomplished without propellant by driving current against a voltage created by a conducting tether's interaction with the Earth's magnetic field (electrodynamic reboost). This system can be used for transferring a variety of payloads (scientific, cargo, and human space vehicles) to multiple destinations including geosynchronous transfer orbit, the Moon or Mars. MXER technology advancement requires development in two key areas: survivable, high tensile strength non-conducting tethers and reliable, lightweight payload catch/release mechanisms. Fundamental requirements associated with the MXER non-conducting strength tether and catch mechanism designs will be presented. Key requirements for the tether design include high specific-strength (tensile strength/material density), material survivability to the space environment (atomic oxygen and ultraviolet radiation), and structural survivability to micrometeoroid/orbital debris (MM/OD) impacts. The driving mechanism key,gequirements include low mass-to-capture-volume ratio, positional and velocity error tolerance, and operational reliability. Preliminary tether and catch mechanism design criteria are presented, which have been used as guidelines to "screen" and down-select initial concepts. Candidate tether materials and protective coatings are summarized along with their performance in simulated space environments (e.g., oxygen plasma, thermal cycling). A candidate catch mechanism design concept is presented along with examples of demonstration hardware

    HCV IRES manipulates the ribosome to promote the switch from translation initiation to elongation.

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    The internal ribosome entry site (IRES) of the hepatitis C virus (HCV) drives noncanonical initiation of protein synthesis necessary for viral replication. Functional studies of the HCV IRES have focused on 80S ribosome formation but have not explored its role after the 80S ribosome is poised at the start codon. Here, we report that mutations of an IRES domain that docks in the 40S subunit's decoding groove cause only a local perturbation in IRES structure and result in conformational changes in the IRES-rabbit 40S subunit complex. Functionally, the mutations decrease IRES activity by inhibiting the first ribosomal translocation event, and modeling results suggest that this effect occurs through an interaction with a single ribosomal protein. The ability of the HCV IRES to manipulate the ribosome provides insight into how the ribosome's structure and function can be altered by bound RNAs, including those derived from cellular invaders

    Deconstructing interventions: approaches to studying behavior change techniques across obesity interventions

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    Deconstructing interventions into the specific techniques that are used to change behavior represents a new frontier in behavioral intervention research. This paper considers opportunities and challenges in employing the Behavior Change Techniques Taxonomy (BCTTv1) developed by Michie and colleagues, to code the behavior change techniques (BCTs) across multiple interventions addressing obesity and capture dose received at the technique level. Numerous advantages were recognized for using a shared framework for intervention description. Coding interventions at levels of the social ecological framework beyond the individual level, separate coding for behavior change initiation vs. maintenance, fidelity of BCT delivery, accounting for BCTs mode of delivery, and tailoring BCTs, present both challenges and opportunities. Deconstructing interventions and identifying the dose required to positively impact health-related outcomes could enable important gains in intervention science

    High Fat Relative to Low Fat Ground Beef Consumption Lowers Blood Pressure and Does Not Negatively Alter Arterial Stiffness

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    Beef consumption has been stigmatized as an unhealthy dietary choice. However, randomized control trials to support this claim are lacking. PURPOSE: To examine the effect of low-fat (5%) and high-fat (25%) ground beef consumption on blood pressure (BP) and carotid-femoral pulse wave velocity (PWV).METHODS: Twenty-three male subjects (age 40±11 yrs, height 177.4±6.7 cm, weight 97.3±25.0 kg, lean mass 64.5±9.5 kg, fat mass 30.6±19.1 kg) volunteered to participate in this cross-over design study. Each participant completed two, 5-week ground beef interventions in a randomized order with a 4-week washout period in-between. All participants visited the lab four times after an overnight fast. Each visit to the lab consisted of supine BP, dual energy x-ray absorptiometry (DXA) scan to assess body composition, and PWV analysis. The PWV recording was assessed on the right carotid and femoral arteries. The distance used for the PWV calculation was 80% of the actual distance between carotid and femoral sites. All PWV measures were completed according to previously published procedures (Van Bortel, 2011). BP and PWV results were analyzed separately via 2x2 repeated measures ANOVA. RESULTS: Our results indicate there was a significant decrease in systolic BP (p=0.01) following the high-fat ground beef intervention compared to the low-fat. The BP values for low-fat beef and high-fat beef are 120/74 and 116/73 mmHg, respectively. Further, there were no significant differences between the PWV measures. CONCLUSION: Based on our results, high fat ground beef favorably alters systolic BP and does not negatively affect PWV measures

    Age as a Predictor for Complications and Patient-reported Outcomes in Multilevel Transforaminal Lumbar Interbody Fusions: Analyses From the Michigan Spine Surgery Improvement Collaborative (MSSIC)

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    STUDY DESIGN: Retrospective review of a multi-institutional data registry. OBJECTIVE: The authors sought to determine the association between age and complications & patient-reported outcomes (PRO) in patients undergoing multilevel transforaminal interbody lumbar fusion (MTLIF). SUMMARY OF BACKGROUND DATA: Elderly patients undergoing MTLIF are considered high risk. However, data on complications and PRO are lacking. Additionally, safety of multilevel lumbar fusion in the elderly remains uncertain. METHODS: Patients ≥50-year-old who underwent MTLIF for degenerative lumbar spine conditions were analyzed. Ninety-day complications and PROs (baseline, 90-d, 1-y, 2-y) were queried using the MSSIC database. PROs were measured by back & leg visual analog scale (VAS), Patient-reported Outcomes Measurement Information System (PROMIS), EuroQol-5D (EQ-5D), and North American Spine Society (NASS) Patient Satisfaction Index. Univariate analyses were used to compare among elderly and complication cohorts. Generalized estimating equation (GEE) was used to identify predictors of complications and PROs. RESULTS: A total of 3120 patients analyzed with 961 (31%) ≥ 70-y-o and 2159 (69%) between 50-69. A higher proportion of elderly experienced postoperative complications (P = .003) including urinary retention (P = \u3c.001) and urinary tract infection (P = .002). Multivariate analysis demonstrated that age was not independently associated with complications. Number of operative levels was associated with any (P = .001) and minor (P = .002) complication. Incurring a complication was independently associated with worse leg VAS and PROMIS scores (P = \u3c.001). Preoperative independent ambulation was independently associated with improved PROMIS, and EQ5D (P = \u3c.001). Within the elderly, preoperative independent ambulation and lower BMI were associated with improved PROMIS (P = \u3c.001). Complications had no significant effect on PROs in the elderly. CONCLUSIONS: Age was not associated with complications nor predictive of functional outcomes in patients who underwent MTLIF. Age alone, therefore, may not be an appropriate surrogate for risk. Furthermore, baseline preoperative independent ambulation was associated with better clinical outcomes and should be considered during preoperative surgical counseling. Level of Evidence: 3

    Evidence for short range orbital order in paramagnetic insulating (Al,V)_2O_3

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    The local structure of (Al_0.06V_0.94)_2O_3 in the paramagnetic insulating (PI) and antiferromagnetically ordered insulating (AFI) phase has been investigated using hard and soft x-ray absorption techniques. It is shown that: 1) on a local scale, the symmetry of the vanadium sites in both the PI and the AFI phase is the same; and 2) the vanadium 3d - oxygen 2p hybridization, as gauged by the oxygen 1s absorption edge, is the same for both phases, but distinctly different from the paramagnetic metallic phase of pure V_2O_3. These findings can be understood in the context of a recently proposed model which relates the long range monoclinic distortion of the antiferromagnetically ordered state to orbital ordering, if orbital short range order in the PI phase is assumed. The measured anisotropy of the x-ray absorption spectra is discussed in relation to spin-polarized density functional calculations.Comment: 8 pages, 5 figure

    The Rachel Carson Letters and the Making of Silent Spring

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    Environment, conservation, green, and kindred movements look back to Rachel Carson’s 1962 book Silent Spring as a milestone. The impact of the book, including on government, industry, and civil society, was immediate and substantial, and has been extensively described; however, the provenance of the book has been less thoroughly examined. Using Carson’s personal correspondence, this paper reveals that the primary source for Carson’s book was the extensive evidence and contacts compiled by two biodynamic farmers, Marjorie Spock and Mary T. Richards, of Long Island, New York. Their evidence was compiled for a suite of legal actions (1957-1960) against the U.S. Government and that contested the aerial spraying of dichlorodiphenyltrichloroethane (DDT). During Rudolf Steiner’s lifetime, Spock and Richards both studied at Steiner’s Goetheanum, the headquarters of Anthroposophy, located in Dornach, Switzerland. Spock and Richards were prominent U.S. anthroposophists, and established a biodynamic farm under the tutelage of the leading biodynamics exponent of the time, Dr. Ehrenfried Pfeiffer. When their property was under threat from a government program of DDT spraying, they brought their case, eventually lost it, in the process spent US$100,000, and compiled the evidence that they then shared with Carson, who used it, and their extensive contacts and the trial transcripts, as the primary input for Silent Spring. Carson attributed to Spock, Richards, and Pfeiffer, no credit whatsoever in her book. As a consequence, the organics movement has not received the recognition, that is its due, as the primary impulse for Silent Spring, and it is, itself, unaware of this provenance
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