326 research outputs found
Determination of the elastic parameters of a material from a standardized dynamic stiffness testing
Viscoelastic layers under floating floors are often used to reduce impact sound. A standardized dynamic stiffness test is routinely used to estimate the performance of a layer as an impact sound isolator. During the test, a material sample is placed between a load plate and a motionless rigid foundation. In this work, equations that provide a useful analytical description of the standardized test are derived. The new analytical approach is linked with the analysis of multilayer elastomeric bearings. The new approach leads to simpler analytical solutions as compared with those of previous studies, which makes them easy to translate into computer codes. The obtained expressions are almost independent of the shape of the boundary and are only dependent on static values such as the area and moments of inertia of the contour. Taking advantage of the new closed-form solutions, it is shown that, under certain restrictions, the analytical approach may be used to experimentally estimate the elastic parameters of a flexible material using a harmonic (frequency-dependent) analysis. It is reported that results obtained using the proposed approach are in good agreement with those obtained using a commercial finite element software.This work was supported by CONICYT–FONDECYT [grant number 1171110]
Hinge and Amino-Terminal Sequences Contribute to Solution Dimerization of Human Progesterone Receptor
We and others have shown previously that progesterone receptors (PR) form homodimers in solution in the absence of DNA and that dimers are the preferential form of receptor that binds with high affinity to target DNA. To determine the sequence regions involved in solution homodimerization, wild type PR and truncated PR proteins were expressed in an insect baculovirus system. The expression constructs included the ligand-binding domain [LBD, amino acids (aa) 688–933], the LBD plus hinge (hLBD, aa 634–933), the hLBD plus the DNA-binding domain (DhLBD, aa 538–933), and the full- length A and B isoforms of PR. PR-PR interactions were detected by three methods, coimmunoprecipitation of the PR fragments with full-length PR-A, pull-down of PR-polypeptides with polyhistidine-tagged versions of the same polypeptides immobilized to metal affinity columns and cooperative ligand-binding assays (Hill coefficient, nH \u3e 1 indicating PR-PR interaction). By all three assays, the LBD alone was not sufficient to mediate protein-protein interaction. However, the LBD did exhibit other properties ascribed to this domain, including binding to steroids with a relatively good affinity and specificity, ligand-induced conformational changes at the carboxyl terminus tail and binding of heat shock protein 90 and its dissociation in response to hormone. Thus, failure of the expressed LBD to mediate dimerization does not appear to be due to an extensively misfolded or unstable polypeptide. The minimal carboxyl-terminal fragment capable of mediating PR-PR interaction was the hLBD construct. However, by immobilized metal affinity chromatography assay, self-association of PR-A was 3.5-fold more efficient than that of either the DhLBD or hLBD constructs. An expressed amino-terminal domain (aa 165–535) lacking the DNA-binding domain, hinge, and LBD was found to physically associate with PR-A or with another amino-terminal fragment lacking the LBD, but retaining the DNA-binding domain. These results provide evidence for direct amino-terminal interactions in the more efficient PR-PR interaction exhibited by wild-type PR-A, as compared with DhLBD and hLBD constructs. The overall results of this paper are consistent with the conclusion that the carboxyl-terminal LBD is not sufficient for mediating PR dimerization and that multiple regions, including the hinge and amino-terminal sequences, contribute either directly or indirectly to homodimerization of PR
Compact x-ray source based on burst-mode inverse Compton scattering at 100 kHz
A design for a compact x-ray light source (CXLS) with flux and brilliance
orders of magnitude beyond existing laboratory scale sources is presented. The
source is based on inverse Compton scattering of a high brightness electron
bunch on a picosecond laser pulse. The accelerator is a novel high-efficiency
standing-wave linac and RF photoinjector powered by a single ultrastable RF
transmitter at x-band RF frequency. The high efficiency permits operation at
repetition rates up to 1 kHz, which is further boosted to 100 kHz by operating
with trains of 100 bunches of 100 pC charge, each separated by 5 ns. The entire
accelerator is approximately 1 meter long and produces hard x-rays tunable over
a wide range of photon energies. The colliding laser is a Yb:YAG solid-state
amplifier producing 1030 nm, 100 mJ pulses at the same 1 kHz repetition rate as
the accelerator. The laser pulse is frequency-doubled and stored for many
passes in a ringdown cavity to match the linac pulse structure. At a photon
energy of 12.4 keV, the predicted x-ray flux is
photons/second in a 5% bandwidth and the brilliance is in pulses with RMS pulse
length of 490 fs. The nominal electron beam parameters are 18 MeV kinetic
energy, 10 microamp average current, 0.5 microsecond macropulse length,
resulting in average electron beam power of 180 W. Optimization of the x-ray
output is presented along with design of the accelerator, laser, and x-ray
optic components that are specific to the particular characteristics of the
Compton scattered x-ray pulses.Comment: 25 pages, 24 figures, 54 reference
Electron beam shaping via laser heater temporal shaping
Active longitudinal beam optics can help FEL facilities achieve cutting edge
performance by optimizing the beam to: produce multi-color pulses, suppress
caustics, or support attosecond lasing. As the next generation of
superconducting accelerators comes online, there is a need to find new elements
which can both operate at high beam power and which offer multiplexing
capabilities at Mhz repetition rate. Laser heater shaping promises to satisfy
both criteria by imparting a programmable slice-energy spread on a shot-by-shot
basis. We use a simple kinetic analysis to show how control of the slice energy
spread translates into control of the bunch current profile, and then we
present a collection of start-to-end simulations at LCLS-II in order to
illustrate the technique.Comment: 12 pages, 11 figure
Environmental evolution and archaeological record of Barrancas river basin, Jujuy province, Argentina
Since 2012 our research team started the “Barrancas Archaeological Project” which main goal is to study the history of the people that dwelled this locality and neighbouring areas during the last 10000 years and yo put in value the cultural heritage of these societies. This paper have two aims: 1) to characterize the general environmental evolution of the Barrancas river basin since the end of Pleistocene and to discuss its impact on the human groups that used it: and 2) to briefly describe the archaeological record recovered in the upper and mid-section of the Barrancas river, mainly the chronology and general characteristics of the archaeological sites under study and the relative chronology and placement of the currently documented rock art. Barrancas archaeological evidence conjoined with the paleoenvironmental data obtained in this basin shows that substantial changes in local habitats have had a relevant role in the way in what human groups used this spaces through time, allowing to characterize them alternatively as a nodal or inter-nodal area through Holocene.Introducción El área de estudio - Antecedentes paleoambientales suprarregionales y regionales Evolución ambiental de Barrancas - Los registros paleoambientales de Barrancas - Tendencias paleoambientales - Evolución de la capacidad de carga en la cuenca desde los 7300 cal AP Síntesis de los sitios arqueológicos y ocupaciones humanas en Barrancas - Ocupaciones humanas del Holoceno Temprano y Medio (10.000-3750 años cal. AP) - Ocupaciones humanas entre 3500-1550 años cal. AP - Ocupaciones humanas ente 1200 y 200 cal AP - Manifestaciones rupestres Discusión y Conclusió
The first survey addressing patients with BMI over 50: a survey of 789 bariatric surgeons
Background: Bariatric surgery in patients with BMI over 50 kg/m2 is a challenging task. The aim of this study was to address main issues regarding perioperative management of these patients by using a worldwide survey. Methods: An online 48-item questionnaire-based survey on perioperative management of patients with a BMI superior to 50 kg/m2 was ideated by 15 bariatric surgeons from 9 different countries. The questionnaire was emailed to all members of the International Federation of Surgery for Obesity (IFSO). Responses were collected and analyzed by the authors. Results: 789 bariatric surgeons from 73 countries participated in the survey. Most surgeons (89.9%) believed that metabolic/bariatric surgery (MBS) on patients with BMI over 50 kg/m2 should only be performed by expert bariatric surgeons. Half of the participants (55.3%) believed that weight loss must be encouraged before surgery and 42.6% of surgeons recommended an excess weight loss of at least 10%. However, only 3.6% of surgeons recommended the insertion of an Intragastric Balloon as bridge therapy before surgery. Sleeve Gastrectomy (SG) was considered the best choice for patients younger than 18 or older than 65 years old. SG and One Anastomosis Gastric Bypass were the most common procedures for individuals between 18 and 65 years. Half of the surgeons believed that a 2-stage approach should be offered to patients with BMI > 50 kg/m2, with SG being the first step. Postoperative thromboprophylaxis was recommended for 2 and 4 weeks by 37.8% and 37.7% of participants, respectively. Conclusion: This survey demonstrated worldwide variations in bariatric surgery practice regarding patients with a BMI superior to 50 kg/m2. Careful analysis of these results is useful for identifying several areas for future research and consensus building
Karyotype characterization of wheat breeding lines carrying resistance genes from Aegilops ventricosa
We have used in situ hybridization combining genomic and repeated DNA fluorescent probes to determine the karyotype composition of two bread wheat introgression lines: H-93-33, which carries the gene H27 for resistance to the Hessian fly M. destructor (Delibes et al. 1997); and H-93-8, carrying the gene Cre2 which confers resistance to the cereal cyst nematode H. avenae (Delibes et al. 1993). Both introgression lines had been derived from an earlier cross between T. aestivum subsp. aestivum (2n=42; genome composition AABBDD) and a semi-fertile hybrid between T. turgidum subsp. turgidum (2n=28; genome composition AABB) and the wild grass Ae. ventricosa (2n=28; genome constitution DvDvN¬vNv). We also have examined several resistant advanced lines that were obtained from H-93-33 (lines ID-2151, ID-2193, Ma-1612-a and Ma-1612-b) or H-93-8 (line ID-2150) after 3 to 5 backcrosses with commercial wheats
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