An analysis of the Civil War in twelve high school American history textbooks

Thesis (Ed.M.)--Boston Universit

Effects of rf breakdown on the beam in the Compact Linear Collider prototype accelerator structure

Understanding the effects of RF breakdown in high-gradient accelerator structures on the accelerated beam is an extremely relevant aspect in the development of the Compact Linear Collider (CLIC) and is one of the main issues addressed at the Two-beam Test Stand at the CLIC Test Facility 3 at CERN. During a RF breakdown large electro-magnetic fields are generated and produce parasitic magnetic fields which interact with the accelerated beam affecting its orbit and energy. We discuss here measurements of such effects observed on an electron beam accelerated in a CLIC prototype structure. Measurements of the trajectory of bunch-trains on a nanosecond time-scale showed fast changes in correspondence of breakdown which we compare with measurements of the relative beam spots on a scintillating screen. We identify different breakdown scenarios for which we offer an explanation based also on measurements of the power at the input and output ports of the accelerator structure. Finally we present the distribution of the magnitude of the observed changes in the beam orbit and we discuss its correlation with RF power and breakdown location in the accelerator structure.Comment: 10 pages, 8 figures. We replace the previous version of the article with this one, in which we extend our discussion on the experimental set-up and on the interpretation of our measurements, on the basis of the inputs received during the review process for publication on Phys. Rev. Special Topics - Accelerators and Beams. The essence of our conclusions remain unchange

Monitoring cortical excitability during repetitive transcranial magnetic stimulation in children with ADHD: a single-blind, sham-controlled TMS-EEG study

Background: Repetitive transcranial magnetic stimulation (rTMS) allows non-invasive stimulation of the human brain. However, no suitable marker has yet been established to monitor the immediate rTMS effects on cortical areas in children. Objective: TMS-evoked EEG potentials (TEPs) could present a well-suited marker for real-time monitoring. Monitoring is particularly important in children where only few data about rTMS effects and safety are currently available. Methods: In a single-blind sham-controlled study, twenty-five school-aged children with ADHD received subthreshold 1 Hz-rTMS to the primary motor cortex. The TMS-evoked N100 was measured by 64-channel-EEG pre, during and post rTMS, and compared to sham stimulation as an intraindividual control condition. Results: TMS-evoked N100 amplitude decreased during 1 Hz-rTMS and, at the group level, reached a stable plateau after approximately 500 pulses. N100 amplitude to supra-threshold single pulses post rTMS confirmed the amplitude reduction in comparison to the pre-rTMS level while sham stimulation had no influence. EEG source analysis indicated that the TMS-evoked N100 change reflected rTMS effects in the stimulated motor cortex. Amplitude changes in TMS-evoked N100 and MEPs (pre versus post 1 Hz-rTMS) correlated significantly, but this correlation was also found for pre versus post sham stimulation. Conclusion: The TMS-evoked N100 represents a promising candidate marker to monitor rTMS effects on cortical excitability in children with ADHD. TMS-evoked N100 can be employed to monitor real-time effects of TMS for subthreshold intensities. Though TMS-evoked N100 was a more sensitive parameter for rTMS-specific changes than MEPs in our sample, further studies are necessary to demonstrate whether clinical rTMS effects can be predicted from rTMS-induced changes in TMS-evoked N100 amplitude and to clarify the relationship between rTMS-induced changes in TMS-evoked N100 and MEP amplitudes. The TMS-evoked N100 amplitude reduction after 1 Hz-rTMS could either reflect a globally decreased cortical response to the TMS pulse or a specific decrease in inhibition

Untersuchung einer neuen Herzklappe für Herzunterstützungssysteme

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Ein bewährtes Verfahren zur Behandlung erkrankter natürlicher Heizklappen ist die Implantation von Heizklappenprothesen. Neben diesem Einsatz entwickelt sich zur Zeit ein weiteres Anwendungsgebiet; der Einsatz von Herzklappenprothesen in Herzunterstützungssystemen. Eine häufig dabei auftretende Komplikation stellt die Thrombenbildung dar. Diese tritt insbesondere im Bereich der verwendeten Herzklappenprothesen auf. Bei einer Implantation einer Heizklappenprothese ist ihre unmittelbare Umgebung durch die Anatomie vorgegeben. Bei einem Einsatz in einem Herzunterstützungssystem dagegen kann diese Umgebung frei gestaltet werden. Mit diesem Ansatz ergeben sich für die strömungstechnische Gestaltung der Herzklappen für Blutpumpen ganz neue Möglichkeiten. Die unmittelbare Umgebung der Klappe ist der Strömungskanal. Mit dem neuen, hier vorgestellten S-förmigen Strömungskanal der Klappe scheint es möglich zu sein, die Gefahr der Thrombenbildung zu reduzieren. Insbesondere die Vermeidung von Ablösungen führt zu einer Verringerung des Risikos der Thrombenbildung und ermöglicht damit eine verminderte Dosierung von Antikoagulantien

Impact of hatchery releases on the recreational fishery for Pacific threadfin (Polydactylus sexfilis) in Hawaii

The Pacific threadfin (Polydactylus sexfilis) is considered one of the premier Hawaiian food fishes but even with catch limits, seasonal closures, and size limits, catches have declined dramatically since the 1960s. It was identified as the top candidate species for stock enhancement in Hawaii, based on the decline in stocks, high market value, and importance of the fishery. In the stock enhancement program for Pacific threadfin, over 430,000 fingerlings of various sizes were implanted with coded wire tags and released in nursery habitats along the windward coast of Oahu between 1993 and 1998. Because few Pacific threadfin were present in creel surveys conducted between 1994 and 1998, Oahu fishermen were offered a $10 reward for each threadfin that was caught (for both hatchery-reared and wild fish). A total of 1882 Pacific threadfin were recovered from the reward program between March 1998 and May 1999, including 163 hatchery-reared fish, an overall contribution of 8.7% to the fishery. Hatchery-reared fish accounted for as high as 71% of returns in the release areas. Hatchery-reared fish were recovered on average 11.5 km (SD=9.8 km) from the release site, although some had moved as far away as 42 km. Average age for recovered hatchery-reared fish was 495 days; the oldest was 1021 days. Cultured Pacific threadfin juveniles survived and recruited successfully to the recreational fishery, accounting for 10% of fishermen’s catches on the windward side of Oahu. Recruitment to the fishery was highest for the 1997 release year; few juveniles from earlier releases were observed. Presence of a few large, fully developed females in the recreational fishery suggested that hatchery-reared fish can survive, grow, and reproductively contribute to the population. Implementation of an enhancement program that is focused on juveniles and perhaps large females, as part of an integrated fishery management strategy, could speed the recovery of this fish population

Acoustic anemometry and thermometry

Acoustic travel-time measurement is a method for remote sensing of the atmosphere. The temperature-dependent sound speed as well as the flow field can be detected by measuring the travel time of a defined acoustic signal between a sound source and a receiver when the distance between them is known. In this study the properties of the flow field are reconstructed using reciprocal sound rays to separate the directionindependent sound speed from the effective sound velocity including the flow velocity component in direction of the sound path. The measurements are taken on a horizontal scale of about 2 m x 2 m. By measurements in interiors, where no flow of air exists, the temperature can be determined with an accuracy of 0.6°C and the flow component in direction of the sound path with an accuracy of 0.3 m/s. If flow of air exists the measurements gets complicated because the phase shifts, which have been detected by the receivers, cannot be corrected like it was possible without the influence of flow

Dissecting the Mechanisms Underlying Short-Interval Intracortical Inhibition Using Exercise

Recently, 2 physiologically distinct phases of short-interval intracortical inhibition (SICI) have been identified, a larger phase at interstimulus interval (ISI) 3 ms and a smaller phase at ISI 1 ms. While the former is mediated by synaptic processes, the mechanisms underlying the first phase of SICI remain a matter of debate. Separately, it is known that fatiguing hand exercise reduces SICI, a measure of cortical excitability. Consequently, the present study assessed effects of fatiguing hand exercise on the 2 SICI phases, using threshold tracking transcranial magnetic stimulation techniques, to yield further information on underlying mechanisms. Studies were undertaken on 22 subjects, with SICI assessed at baseline, after each voluntary contraction (VC) period of 120 s and 5, 10, and 20 min after last VC, with responses recorded over abductor pollicis brevis. Exercise resulted in significant reduction of SICI at ISI 1 ms (SICIbaseline 9.5 ± 2.7%; SICIMAXIMUM REDUCTION 2.5 ± 2.5%, P < 0.05) and 3 ms (SICIbaseline 16.8 ± 1.7%; SICIMAXIMUM REDUCTION 11.6 ± 2.1%, P < 0.05), with the time course of reduction being different for the 2 phases. Taken together, findings from the present study suggest that synaptic processes were the predominant mechanism underlying the different phases of SICI

Emergence of Bulk CsCl Structure in (CsCl)nCs+ Cluster Ions

The emergence of CsCl bulk structure in (CsCl)nCs+ cluster ions is investigated using a mixed quantum-mechanical/semiempirical theoretical approach. We find that rhombic dodecahedral fragments (with bulk CsCl symmetry) are more stable than rock-salt fragments after the completion of the fifth rhombic dodecahedral atomic shell. From this size (n=184) on, a new set of magic numbers should appear in the experimental mass spectra. We also propose another experimental test for this transition, which explicitely involves the electronic structure of the cluster. Finally, we perform more detailed calculations in the size range n=31--33, where recent experimental investigations have found indications of the presence of rhombic dodecahedral (CsCl)32Cs+ isomers in the cluster beams.Comment: LaTeX file. 6 pages and 4 pictures. Accepted for publication in Phys. Rev.

Enhancement of the Curie temperature in GaMnAs/InGaMnAs superlattices

We report on an enhancement of the Curie temperature in GaMnAs/InGaMnAs superlattices grown by low-temperature molecular beam epitaxy, which is due to thin InGaMnAs or InGaAs films embedded into the GaMnAs layers. The pronounced increase of the Curie temperature is strongly correlated to the In concentration in the embedded layers. Curie temperatures up to 110 K are observed in such structures compared to 60 K in GaMnAs single layers grown under the same conditions. A further increase in T$_C$ up to 130 K can be achieved using post-growth annealing at temperatures near the growth temperature. Pronounced thickness fringes in the high resolution X-ray diffraction spectra indicate good crystalline quality and sharp interfaces in the structures.Comment: 4 pages, 4 figures, submitted to Appl. Phys. Let