Infinite barbarians

This paper discusses an infinite regress that looms behind a certain kind of historical explanation. The movement of one barbarian group is often explained by the movement of others, but those movements in turn call for an explanation. While their explanation can again be the movement of yet another group of barbarians, if this sort of explanation does not stop somewhere we are left with an infinite regress of barbarians. While that regress would be vicious, it cannot be accommodated by several general views about what viciousness in infinite regresses amounts to. This example is additional evidence that we should prefer a pluralist approach to infinite regresses

Experiments investigating the generation and transport of 10--12 MeV, 30-kA, mm-size electron beams with linear inductive voltage adders

The authors present the design, analysis, and results of the high-brightness electron beam experiments currently under investigation at Sandia National Laboratories. The anticipated beam parameters are the following: 8--12 MeV, 35--50 kA, 30--60 ns FWHM, and 0.5-mm rms beam radius. The accelerators utilized are SABRE and HERMES III. Both are linear inductive voltage adders modified to higher impedance and fitted with magnetically immersed foil less electron diodes. In the strong 20--50 Tesla solenoidal magnetic field of the diode, mm-size electron beams are generated and propagated to a beam stop. The electron beam is field emitted from mm-diameter needle-shaped cathode electrode and is contained in a similar size envelop by the strong magnetic field. These extremely space charge dominated beams provide the opportunity to study beam dynamics and possible instabilities in a unique parameter space. The SABRE experiments are already completed and have produced 30-kA, 1.5-mm FWHM electron beams, while the HERMES-III experiments are on-going

Development of a Dynamic Spot Size Diagnostic for Flash Radiographic X-Ray Sources

There has been considerable work in recent years in the development of high-brightness, high-dose flash x-ray radiographic sources. Spot size is one of several parameters that helps characterize source performance and provides a figure of merit to assess the suitability of various sources to specific experimental requirements. Time-integrated spot-size measurements using radiographic film and a high-Z rolled-edge object have been used for several years with great success. The Advanced Radiographic Technologies program thrust to improve diode performance requires extending both modeling and experimental measurements into the transient time domain. A new Time Resolved Spot Detector (TRSD) is under development to provide this information. In this paper we report the initial results of the performance of a 148-element scintillating fiber array that is fiber-optically coupled to a gated streak camera. Spatial and temporal resolution results are discussed and the data obtained from the Sand ia National Laboratories (SNL) RITS-3 (Radiographic Integrated Test Stand) accelerator are presented

The management aspect of psychotherapy with aggressive children

Psychotherapy with an aggressive child may require the imposition of rather firm limitations over aspects of the patient's aggressive behavior. The nature of this management strategy is determined by the individual child's psychopathology. The management aspects of the psychotherapy with two aggressive boys are illustrated in detail. In one case, stringent limitations were imposed when it was discovered that the boy's behavior was regressive and represented an effort to sadistically control people in his environment. In the other case, the behavior was initially left almost unchallenged; this boy's aggressive and delinquent behavior reflected an effort to achieve a sense of order in an inconsistent external and potentially chaotic internal environment.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43969/1/10578_2005_Article_BF01463450.pd

Fundamental Science Investigations to Develop a 6-MV Laser Triggered Gas Switch for ZR: First Annual Report.

In October 2005, an intensive three-year Laser Triggered Gas Switch (LTGS) development program was initiated to investigate and solve observed performance and reliability issues with the LTGS for ZR. The approach taken has been one of mission-focused research: to revisit and reassess the design, to establish a fundamental understanding of LTGS operation and failure modes, and to test evolving operational hypotheses. This effort is aimed toward deploying an initial switch for ZR in 2007, on supporting rolling upgrades to ZR as the technology can be developed, and to prepare with scientific understanding for the even higher voltage switches anticipated needed for future high-yield accelerators. The ZR LTGS was identified as a potential area of concern quite early, but since initial assessments performed on a simplified Switch Test Bed (STB) at 5 MV showed 300-shot lifetimes on multiple switch builds, this component was judged acceptable. When the Z{sub 20} engineering module was brought online in October 2003 frequent flashovers of the plastic switch envelope were observed at the increased stresses required to compensate for the programmatically increased ZR load inductance. As of October 2006, there have been 1423 Z{sub 20} shots assessing a variety of LTGS designs. Numerous incremental and fundamental switch design modifications have been investigated. As we continue to investigate the LTGS, the basic science of plastic surface tracking, laser triggering, cascade breakdown, and optics degradation remain high-priority mission-focused research topics. Significant progress has been made and, while the switch does not yet achieve design requirements, we are on the path to develop successively better switches for rolling upgrade improvements to ZR. This report summarizes the work performed in FY 2006 by the large team. A high-level summary is followed by detailed individual topical reports

Inductive voltage adder (IVA) for submillimeter radius electron beam

The authors have already demonstrated the utility of inductive voltage adder accelerators for production of small-size electron beams. In this approach, the inductive voltage adder drives a magnetically immersed foilless diode to produce high-energy (10--20 MeV), high-brightness pencil electron beams. This concept was first demonstrated with the successful experiments which converted the linear induction accelerator RADLAC II into an IVA fitted with a small 1-cm radius cathode magnetically immersed foilless diode (RADLAC II/SMILE). They present here first validations of extending this idea to mm-scale electron beams using the SABRE and HERMES-III inductive voltage adders as test beds. The SABRE experiments are already completed and have produced 30-kA, 9-MeV electron beams with envelope diameter of 1.5-mm FWHM. The HERMES-III experiments are currently underway

Core Competencies Addressed in Grand Rounds of Academic Departments

Background: The Accreditation Councils of Graduate Medical Education (ACGME) and Continuing Medical Education (ACCME) require that educational activities support professional development of health professionals. Core competencies include medical knowledge, patient care and procedural skills, practice-based learning and improvement, professionalism, systems-based practice, and interprofessional communication. Although a review of the Institute of Medicine (IOM) core competencies is a required component of graduate medical education, the frequencies in which the competencies are addressed during grand rounds is unknown. Purpose: To evaluate academic department grand rounds lecture series for content of the IOM recommended core competencies. Methods: This retrospective study involves a review of learning objectives from grand rounds lectures in the five core departments (internal medicine, pediatrics, psychiatry, obstetrics and gynecology (OB/GYN) and family medicine) between January 2014 and June 2015. Each learning objective was reviewed by a senior medical student, acting intern, and faculty member and by consensus assigned to the appropriate core competency. Results: Complete information was available for 271 grand rounds presentations, with 74% having 3 to 4 objectives per lecture. Two or more competencies were covered in 35% of all lectures. Medical knowledge was the primarily addressed core competency, regardless of specialty. About 50% or less of lectures involved solely medical knowledge. Other core competencies are not adequately covered on grand rounds. The fewest objectives were consistently dedicated to interprofessional communication, professionalism, systems-based practice, and practice-based learning. Professionalism was highlighted most by the internal medicine department (p \u3c .01), because one month of lectures was dedicated to the subject. Conclusions: Grand rounds lectures offer educational opportunities to cover the core competencies especially those that do not deal with medical knowledge. In the future, presenters will be provided information about core competencies before their lecture and as a part of their post lecture feedback

Experimental Time Resolved Electron Beam Temperature Measurements Using Bremsstrahlung Diagnostics

Electron beam temperature, {beta}{perpendicular} (= v{perpendicular}/v), is important to control for the development of high dose flash radiographic bremsstrahlung sources. At high voltage (> 5 MV) increasing electron beam temperature has a serious deleterious effect on dose production. The average and time resolved behavior of beam temperature was measured during radiographic experiments on the HERMES III accelerator (10 MV, 50 kA, 70 ns). A linear array of thermoluminescent dosimeters (TLDs) were used to estimate the time integrated average of beam temperature. On and off-axis photoconducting diamond (PCD) detectors were used to measure the time resolved bremsstrahlung dose rate, which is dependent on beam energy and temperature. The beam temperature can be determined by correlating PCD response with accelerator voltage and current and also by analyzing the ratio of PCD amplitudes on and off axis. This ratio is insensitive to voltage and current and thus, is more reliable than utilizing absolute dose rate. The data is unfolded using comparisons with Monte Carlo simulations to obtain absolute beam temperatures. The data taken on HERMES III show abrupt increases in {beta}{perpendicular} midway through the pulse indicating rapid onset of beam instability