134 research outputs found
Experimental evidence of intrabeam scattering in a free-electron laser driver
Abstract
The effect of multiple small-angle Coulomb scattering, or intrabeam scattering (IBS) is routinely observed in electron storage rings over the typical damping time scale of milliseconds. So far, IBS has not been observed in single pass electron accelerators because charge density orders of magnitude higher than in storage rings would be needed. We show that such density is now available at high brightness electron linacs for free-electron lasers (FELs). We report measurements of the beam energy spread in the FERMI linac in the presence of the microbunching instability, which are consistent with a revisited IBS model for single pass systems. We also show that neglecting the hereby demonstrated effect of IBS in the parameter range typical of seeded VUV and soft x-ray FELs, results in too conservative a facility design, or failure to realise the accessible potential performance. As an example, an optimization of the FERMI parameters driven by an experimentally benchmarked model, opens the door to the extension of stable single spectral line emission to the water window (2.3–4.4 nm), with far-reaching implications for experiments in a variety of disciplines, ranging from physics and chemistry to biology and material sciences, and including nonlinear x-ray optics based on the four-wave-mixing approach.</jats:p
Yield genetic gain at national level of carioca common beans from the Embrapa Breeding Program - 1993 to 2008.
The objective of this work was to estimate the genetic gain of the commercial type carioca dry beans breeding program carried out by Embrapa Rice and Beans Research Center in a period of 16 years, from 1993 to 2008
Prostate Cancer Treatment-Related Toxicity: Comparison between 3D-Conformal Radiation Therapy (3D-CRT) and Volumetric Modulated Arc Therapy (VMAT) Techniques
Objective: This paper illustrates the results of a mono-institutional registry trial, aimed to test whether gastrointestinal (GI) and genitourinary (GU) toxicity rates were lower in localized prostate cancer patients treated with image-guided volumetric modulated arc therapy (IG-VMAT) compared to those treated with IG-3D conformal radiation therapy (IG-3DCRT). Materials and Methods: Histologically proven prostate cancer patients with organ-confined disease, treated between October 2008 and September 2014 with moderately hypofractionated radiotherapy, were reviewed. Fiducial markers were placed in the prostate gland by transrectal ultrasound guide. The prescribed total dose was 70 Gy in 28 fractions. The mean and median dose volume constraints for bladder and rectum as well as total volume of treatment were analyzed as potentially prognostic factors influencing toxicity. The Kaplan–Meier method was applied to calculate survival. Results: Overall, 83 consecutive patients were included. Forty-two (50.6%) patients were treated with 3D-CRT and 41 (49.4%) with the VMAT technique. The median follow-up for toxicity was 77.26 months for the whole cohort. The VMAT allowed for a dose reduction to the rectum and bladder for the large majority of the considered parameters; nonetheless, the only parameter correlated with a clinical outcome was a rectal dose limit V66 > 8.5% for late GI toxicity G ≥ 2 (p = 0.045). Rates of G ≥ 2 toxicities were low among the whole cohort of these patients treated with IGRT. The analysis for rectum dose volume histograms (DVHs) showed that a severe (grade ≥ 2) late GI toxicity was related with the rectal dose limit V66 > 8.5% (p = 0.045). Conclusions: This study shows that moderate hypofractionation is feasible and safe in patients with intermediate and high-risk prostate cancer. Daily IGRT may decrease acute and late toxicity to organs at risk and improve clinical benefit and disease control rate, cutting down the risk of PTV geographical missing. The adoption of VMAT allows for promising results in terms of OAR sparing and a reduction in toxicity that, also given the small sample, did not reach statistical significance
Physician Attitudes and Perceptions of Complementary and Alternative Medicine (CAM): A Multicentre Italian Study
Purpose: Complementary and Alternative Medicine (CAM) interventions are widely used by patients with chronic disorders, including cancer, and may interact with cancer treatment. Physicians are often unaware of this, probably due to poor patient-physician communication on CAM. The purpose of this study was to evaluate physicians' knowledge, attitudes and practice patterns regarding CAM in a survey conducted in Italy. Methods: A questionnaire was administered to 438 physicians (11 Italian hospitals) who predominantly treat patients with chronic disease, to collect personal and professional data and information on attitudes toward CAM and its possible role in Conventional Medicine (CM). Results: Of the 438 participants, most were specialists in oncology (18%), internal medicine (17%), surgery (15%), and radiotherapy (11%). Most worked at university (44%) or research hospitals (31%). Forty-two percent of participants believed that CAM could have an integrative role within CM. Oncologists were the physicians who were best informed on CAM (58%). Physicians working at research institutes or university hospitals had a greater knowledge of CAM than those employed at general hospitals (p < 0.0001), and those who were also involved in research activity had a greater knowledge of CAM than those who were not (p < 0.003). Length of work experience was significantly related to CAM knowledge. Moreover, 55% of participants suggest CAM interventions to their patients and 44% discuss CAM with them. The best-known interventions were acupuncture, Aloe vera and high-dose vitamin C. Conclusion: CAM use by patients with chronic disease and/or cancer has become a topical issue for the scientific community and for physicians. Knowing the reasons that prompt these patients to use CAM and guiding them in their decisions would improve treatment and outcomes and also benefit healthcare systems. Our findings contribute to a greater understanding of CAM knowledge, attitudes, and practice among Italian physicians. Further research is needed to identify the more effective CAM treatments and to work toward an integrated healthcare model
Estabilidade de linhagens de feijoeiro comum de grão preto no ensaio intermediário/2005 da Embrapa Arroz e Feijão.
O objetivo foi avaliar a estabilidade e adaptabilidade de linhagens de grão preto no ensaio intermediário/2005 do programa de melhoramento genético do feijoeiro comum da Embrapa Arroz e Feijão e identificar as mais promissoras para ambientes favoráveis e desfavoráveis
Estabilidade de linhagens de feijoeiro comum de grão carioca no ensaio intermediário/2005 da Embrapa Arroz e Feijão.
O objetivo foi avaliar a estabilidade e adaptabilidade de linhagens de grão carioca no ensaio intermediário/2005 do programa de melhoramento genético do feijoeiro comum da Embrapa Arroz e Feijão e identificar as mais promissoras para ambientes favoráveis e desfavoráveis
Evaluation of Nelore, Canchim, Santa Gertrudis, Holstein, Brown Swiss and Caracu as Sire Breeds in Matings with Nelore Cows. Effects on Progeny Growth, Carcass Traits and Crossbred Productivity
Over three calf crops, 1096 exposures of 380 Nelore (a Zebu breed) cows to 6 sire breeds Nelore (N), Canchim (C), Santa Gertrudis (G), Holstein (H), Brown Swiss (S), and Caracu (K), resulted in 644 calves weaned for a 63% calving rate. Sire breed effect was significant for birth weight, weaning weight, 13 mo weight and 18 mo weight. HN and SN calves were the heaviest at all weight periods wile CN, GN, and KN calves were the intermediates. Average daily gain from 18 mo to slaughter age was measured in 125 males finished in feed lot and 116 on pasture. A significant breed of sire × finishing system interaction was observed. Under feed lot, HN and SN had higher daily gain and dry matter intake per kg of metabolic weight than the other ones. HN calves showed the worst feed conversion. The average slaughter age was 788 d for feed lot and 989 d for pasture finished steers. Carcass traits were evaluated in 241 slaughtered animals. CN calves had the highest dressing % and edible portion % under both finishing conditions. Crossbred group productivity (calculated as 18 mo weight times the weaning rate %) was greater for locally adapted breeds of sire
Active Site Design in a Chemzyme: Development of a Highly Asymmetric and Remarkably Temperature-Independent Catalyst for the Imino Aldol Reaction**
The asymmetric aldol reaction of an enolate or enolate equivalent with an imine is a reaction of established synthetic importance for the synthesis of chiral amines in general and bamino esters in particular. [1] The development of chiral catalysts for this reaction has proven to be a difficult task and had eluded all attempts until recently when Kobayashi and co-workers examined imines derived from o-aminophenol. [2±4] Their method involves the catalysis of the reactions of these imines and ketene acetals with a catalyst generated from zirconium(iv) tert-butoxide and two equivalents of (R)-6,6'-dibromoBINOL (BINOL 1,1'-binaphth-2-ol). Our interest in the synthesis of chiral amines led us to investigate the use of VAPOL-derived catalysts A comparison of catalysts prepared from BINOL, 6,6'-dibromoBINOL and VAPOL ligands on the asymmetric induction in the reaction of the phenyl-substituted imine 1 and acetal 2 is summarized in [2] The VAPOL catalyst could be prepared in either methylene chloride or toluene, but for solubility reasons, the BINOL catalysts were prepared in methylene chloride. The VAPOL and Br 2 BINOL catalysts were superior to the BINOL catalyst at À 45 8C. The asymmetric induction dropped for the Br 2 BINOL catalyst when the temperature was raised from À 45 8C to room temperature, but curiously, the asymmetric induction for the VAPOL catalyst was essentially unchanged over this same temperature range. Only a small drop-off is noted (85 % ee) when the temperature is raised to 41 8C and the substrate-to-catalyst ratio is raised to 200:1 (entry 5). Both the R enantiomers of BINOL and Br 2 BINOL ligands give the R enantiomer of the product 3, whereas with the VAPOL ligand, it is the S enantiomer that gives the R product. This reversal is not unexpected given the structures of the ligands where the zirconium is in the minor groove of the BINOL ligands and in the major groove of the VAPOL ligand. [2g] It is clear from the examination of space-filling CPK models that it is possible to bind two VAPOL ligands to one zirconium atom but only with a facial arrangement of the four oxygen atoms as is illustratred by structure 6 in Scheme 1. This is supported by 1 H NMR experiments on a catalyst generated from zirconium tetraisopropoxide and VAPOL in the presence of two equivalents of N-methyl imidiazole. A clean spectrum is only observed with two equivalents of VAPOL relative to zirconium and the spectrum is consistent with a single C 2 -symmetrical species were performed by using the TEXSAN [13] crystallographic software package. Crystallographic data (excluding structure factors) for the structure reported in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication no. CCDC-153832. Copies of the data can be obtained free of charge on application to CCDC
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