Impedance of a Rectangular Beam Tube with Small Corrugations

We consider the impedance of a structure with rectangular, periodic corrugations on two opposing sides of a rectangular beam tube. Using the method of field matching, we find the modes in such a structure. We then limit ourselves to the the case of small corrugations, but where the depth of corrugation is not small compared to the period. For such a structure we generate analytical approximate solutions for the wave number $k$, group velocity $v_g$, and loss factor $\kappa$ for the lowest (the dominant) mode which, when compared with the results of the complete numerical solution, agreed well. We find: if $w\sim a$, where $w$ is the beam pipe width and $a$ is the beam pipe half-height, then one mode dominates the impedance, with $k\sim1/\sqrt{w\delta}$ ($\delta$ is the depth of corrugation), $(1-v_g/c)\sim\delta$, and $\kappa\sim1/(aw)$, which (when replacing $w$ by $a$) is the same scaling as was found for small corrugations in a {\it round} beam pipe. Our results disagree in an important way with a recent paper of Mostacci {\it et al.} [A. Mostacci {\it et al.}, Phys. Rev. ST-AB, {\bf 5}, 044401 (2002)], where, for the rectangular structure, the authors obtained a synchronous mode with the same frequency $k$, but with $\kappa\sim\delta$. Finally, we find that if $w$ is large compared to $a$ then many nearby modes contribute to the impedance, resulting in a wakefield that Landau damps.Comment: 18 pages, 6 figures, 1 bibliography fil

An Evaluation of a Unique Gatekeeper Training for Suicide Prevention of College Students: Demonstrating Effective Partnering within Student Affairs

For college students, suicide is the second leading cause of death. In this study, we evaluated a gatekeeper training suicide prevention program that em-phasizes emotional connectivity with students in crisis and incorporates the collaborative efforts between Housing/Residential Programs and the Counsel-ing Center. Participants consisted of graduate and resident assistants. Very significant gains were found from pre-training to post-training and from pre-training to three-month follow-up in knowledge, skills, and emotional connectivi-ty. Two years of data will be presented

Preliminary studies on 6 to 7 days old blastocysts non-surgically recovered from cattle, III. – Method for chromosome preparation

International audienc

Take Care- Use Antibiotics Responsibly Swine Practitioner Project

The Take Care - Use Antibrotics Responsibly® program is an antimicrobial resistance and use educat1on and awareness program for pork producers. The program is based on principles and guidelines intended to minimize the development of antimicrobial resistance whrle maximizing animal health The program was developed by the National Pork Board, but veterinarians are key in the delivery of the program on farm. Since there are many factors that contribute to the amounts and types of antimicrobrals used on farm it was decided that the best way to measure program effectiveness was through measurement of changes in the attitude and behaviors of program particrpants

Management factors associated with seropositivity to Lawsonia intracellularis in US swine herds.

abstract: This study was conducted to determine risk factors for Lawsonia intracellularis seropositivity in the breeding and grower-finisher units of US farrowing-to-finishing swine herds. Serum was collected from 15 breeding females and 15 grower-finisher pigs per herd in 184 farrow-to-finish herds, a subset of 405 herds in the National Animal Health Monitoring System (NAHMS) Swine 1995 Study that examined management, health and productivity in herds with at least 300 finisher pigs. Sera were tested by indirect fluorescent antibody test for L. intracellularis. Test results were linked with NAHMS questionnaire data and a logistic regression model of management factors associated with L. intracellularis serological status was developed. Separate models were used for breeding and grower-finisher units. Risk factors for seropositive breeding units were L intracellularis-seropositive status of the grower-finisher unit, use of a continuous system of management for the farrowing unit and a young parity structure (<75% multiparous sows). Risk factors for seropositive grower-finisher units were L. intracellularis-seropositive status of the breeding unit, the number of pigs entering the grower-finisher stage, raising pigs on concrete slats, and intensive management compared with raising pigs on outdoor lots. Use of all in-all out management in the farrowing house and an older parity structure in the sow herd were associated with a lower risk of L. intracellularis seropositivity in the breeding unit, and slatted concrete flooring in grower-finisher houses was associated with a greater risk. Alteration of these management factors might improve control of L. intracellularis infection in farrowing-to-finishing herds

Flame burning speeds and combustion characteristics of undiluted and nitrogen-diluted hydrogen-nitrous oxide mixtures

In the present study, some explosive properties of undiluted and nitrogen-diluted H_2–N_2O mixtures were characterized. Laminar burning speeds and the explosion-induced pressure rises were determined experimentally for a range of mixture equivalence ratios (ϕ=0.15−1.0), dilutions (0-55%N_2) and initial pressures (20-80kPa). The measured burning speeds were used to validate laminar burning speed computations using a detailed chemical kinetic mechanism. The computations were then used to estimate burning speeds at high initial pressure and low dilution conditions that could not be measured experimentally. The results demonstrate that hydrogen–nitrous oxide mixtures exhibit laminar burning speeds as large as 350 cm/s and pressure rise coefficients (K_g) as large as 35 MPa m/s. Also, flames in lean mixtures are shown to be highly unstable which can lead to flame acceleration and possible deflagration-to-detonation transition