571 research outputs found
Controlled longitudinal emittance blow-up using band-limited phase noise in CERN PSB
No full textControlled longitudinal emittance blow-up (from 1 eVs to 1.4 eVs) for LHC beams in the CERN PS Booster is currently achievied using sinusoidal phase modulation of a dedicated high-harmonic RF system. In 2021, after the LHC injectors upgrade, 3 eVs should be extracted to the PS. Even if the current method may satisfy the new requirements, it relies on low-power level RF improvements. In this paper another method of blow-up was considered, that is the injection of band-limited phase noise in the main RF system (h=1), never tried in PSB but already used in CERN SPS and LHC, under different conditions (longer cycles). This technique, which lowers the peak line density and therefore the impact of intensity effects in the PSB and the PS, can also be complementary to the present method. The longitudinal space charge, dominant in the PSB, causes significant synchrotron frequency shifts with intensity, and its effect should be taken into account. Another complication arises from the interaction of the phase loop with the injected noise, since both act on the RF phase. All these elements were studied in simulations of the PSB cycle with the BLonD code, and the required blow-up was achieved
The Relevance and Challenges of an Economic Evaluation of Florida's 4-H Program
No full textFE753, a 4-page fact sheet by Alfonso Flores-Lagunes and Troy Timko, describes the 4-H program and the importance of economic evaluation of its impact, provides a primer on economic evaluation of programs, and lays out a research roadmap for accumulating the data necessary for an economic evaluation of the Florida 4-H program. Includes references. Published by the UF Department of Food and Resource Economics, October 2008
Benchmarking the Beam Longitudinal Dynamics Code BLOND
No full textThe relatively recent Beam Longitudinal Dynamics code BLonD has already been applied to a wide range of studies for all present CERN synchrotrons. Its application area ranges from studies of RF manipulations, over single and multi-bunch interactions with impedance, to the action of feedback loops and RF noise. In this paper, we present benchmarks and comparisons with measurements, theory, or other codes, which have increased greatly the trust in the code. Tests related to bunch-to-bucket transfer, feedback loops, diffusion due to noise injection, as well as collective effects, are presented
CERN PS Booster longitudinal dynamics simulations for the post-LS2 scenario
No full textThe CERN PS Booster is the first synchrotron in the LHC proton injection chain, it currently accelerates particles from 50 MeV to 1.4 GeV kinetic energy. Several upgrades foreseen by the LHC Injectors Upgrade Program will allow the beam to be accelerated from 160 MeV to 2 GeV after Long Shutdown 2 in 2021. The present RF systems will be replaced by a new one, based on Finemet technology. These and other improvements will help to increase the LHC luminosity by a factor of ten. In order to study beam stability in the longitudinal plane simulations have been performed with the CERN BLonD code, using an accurate longitudinal impedance model and a reliable estimation of the longitudinal space charge. Particular attention has been dedicated to the three main features that currently let the beam go stably through the ramp: Double RF operation in bunch-lengthening mode to reduce the transverse space charge tune spread, exploitation of feedback loops to damp dipole oscillations, and controlled longitudinal emittance blow-up. RF phase noise injection has been considered to study if it could complement or substitute the currently used method based on sinusoidal phase modulation
DNA sequence of the araBAD-araC controlling region in Salmonella typhimurium LT2
No full textThe araB and araC genes of Salmonella typhimurium have been cloned onto the plasmid pBR322. Restriction analysis and subcloning of restriction fragments localized these genes to a 4.4 kb DNA fragment. Complementation analysis revealed that the cloned araB and araC genes from S. typhimurium complemented araB and araC mutant strains of escherichia coli. Conversely, cloned araB and araC genes from E. coli complemented araB and araC mutant strains of Escherichia coli. Conversely, cloned araB and araC genes from E. coli complemented araB and ara C mutant strains of S. typhimurium. The DNA sequence was determined for the S. typhimurium araB and araC controlling region and for the initially translated portions of these genes. The nucleotide sequence of the araB promoter was 87% homologous with the same region in E. coli and contained no deletions or insertions relative to the E. coli sequence. The presumed AUG codon corresponding to the amino terminus of the S. typhimurium araC protein was in the same location as in E. coli. There was, however, considerable divergence for the E. coli sequence preceding the translation start site. The nucleotide sequence of the initial 237 bp in the open reading frame of the S. typhimurium araC gene was 78% homologous with the same sequence in E. coli. By comparison, the amino acid sequence for this region was 91% conserved
Effect of probiotics on the fecal microflora after radiotherapy: A pilot study
No full textBackground and Aim : The development of gastrointestinal symptoms following pelvic radiotherapy depends on morphological and functional modifications of the intestinal epithelium after radiation. The aim of this study was to evaluate and compare the effects of preventive administration of the preparation ′′5′′ Strain Dophilus and Hylak on the fecal microflora after radiotherapy in patients during radiotherapy. Materials and Methods : Fourteen patients were randomly selected and subdivided into two groups: The first group was administered ′′5′′ Strain Dophilus (L Group) and the second group was administered Hylak (H Group). Radiation was delivered by a Cobalt 60 unit by using the four field box technique. The doses were divided into 2 Gy per day over 5 to 7 weeks to give the total cumulative dose of 50 Gy (2 Gy/day). High risk patients (e.g., patients with prostate cancer), received dosage 65 67 Gy (2 Gy/day). Results : Both experimental and clinical studies have shown that probiotics can effectively modulate intestinal inflammation by altering the composition and the metabolic and functional properties of gut indigenous flora. Conclusions : Many bacteria were found to be sensitive to irradiation. It would be necessary to check the possible effects of cytostatics on bacteria in larger studies
Modelling intra-beam scattering in the LHC for longitudinal beam loss studies
No full textIn the Large Hadron Collider (LHC), intra-beam scattering (IBS) is one of the main drivers of longitudinal emittance growth during the long injection plateau. With the halo of the longitudinal bunch distribution being close to the separatrix, IBS consequently drives beam losses by pushing particles outside the RF bucket at the flat-bottom. As IBS and beam losses impose a requirement on the minimum RF bucket size, this mechanism has an important impact on the RF power requirements for the High Luminosity (HL-) LHC. In this contribution, the effect of IBS is introduced in the Beam Longitudinal Dynamics (BLonD) tracking code. This numerical model is then benchmarked against analytical estimates, as well as against beam measurements performed in the LHC. The impact of IBS-driven losses on the RF power requirements is discussed through the correlation between the time spent at flat-bottom and the average bunch length, which translates into start-of-ramp losses
Effects of cavity pre-detuning on RF power transients at injection into the LHC
No full textAt injection into the Large Hadron Collider (LHC), the radiofrequency (RF) system is perturbed by beam-induced voltage resultingin strong RF power transients and the instant detuning of thecavities. The automatic tuning system, however, needs time for themechanical compensation of the resonance frequency to takeplace. Acting back on the beam, the transients in RF power areexpected to limit the maximum injected intensity by generatingunacceptable beam loss. Reducing them is therefore essential toreach the target intensity during the High Luminosity (HL) LHCera. At LHC flat bottom, the cavities are operated using thehalf-detuning beam-loading compensation scheme. As implementedtoday, the tuner control algorithm starts acting only after theinjection of the first longer bunch train which causes the bunchesfor this injection to experience the largest power spikes. Thiscontribution presents an adapted detuning scheme for the RF cavitiesbefore injection. It was proposed as a path to decrease thetransients, hence increasing the available intensity margin for theavailable RF power. The expected gain is evaluated in particletracking simulations and measurements acquired during operation
Does Participation in 4-H Improve Schooling Outcomes? Evidence from Florida
No full textWe examine the effect of participation in 4-H, the largest youth development program in the United States, on standardized test scores. We do this by utilizing grade-level longitudinal data on Florida's school districts from the Florida Department of Education combined with 4-H participation statistics from Florida 4-H. Specifically, we analyze the effect of the extent of 4-H participation for third through tenth grade on the mathematics and reading subtests of the Florida Comprehensive Assessment Test (FCAT). We use a difference-in-difference-in-differences (DDD) approach to control for potential confounders of the causal relationship at the level of school districts, grades, and years. Our results indicate that the extent of 4-H participation at the district-grade-year level is positively and significantly related to several measures of performance on the FCAT test
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