Silicon-on-insulator MOSFETS: Material, process and device characteristics

NMOS and PMOS Single-crystal-silicon-on-insulator (SOI) MOSFETs have been fabricated at RIT using a Bonded and Etched-back process for substrate formation. A test chip, containing inverters, contact and sheet resistance structures, and various NMOS and PMOS transistors, was fabricated on a 2000A SOI substrate formed by a Bonded and Etched-back technique. Effective mobilities, subthreshold swings, and threshold voltages of the fabricated devices were extracted to investigate the impact of a Bonded and Etched-back process on device performance. A hole mobility of 486 cm2/V-s was obtained in PMOS SOI, comparable to state-of-the-art, and exceeding any mobility previously reported at RIT. A subthreshold swing of 11OmV/decade was observed in PMOS SOI. The NMOS devices were found to be inferior to those fabricated external to RIT using this SOI process. It was found that hole mobility increased by 14% on average and electron mobility increased by 6% on average for SOI devices compared to similar conventional devices fabricated in bulk silicon. Subthreshold swing decreased 93% on average for SOI devices compared to conventional bulk-silicon devices. SOI is identified as an attractive process, having significant performance advantages over bulk-silicon devices

The Emergence Of The American Agriculture Movement, 1977-1979

Beginning in late 1977, the media, television in particular, portrayed as a unique cultural phenomenon an emerging American Agriculture Movement (AAM), a pending farm strike, and a depressed farm economy that had caused this mobilization. Much was indeed unique, especially to the individual farmers and the specific manner in which they were attempting to apply political pressures, but the American Agriculture Movement itself was similar to other organizational attempts that have taken place in rural America. In the following paper we chronicle the emergence of the American Agriculture Movement as a distinct entity, identify the common features in the emergence of new farm organizations, and examine the conditions of modern society and technology that affect group formation. AN ORGANIZATION DEVELOPS Despite impressions left from journal and media accounts that portrayed a grass roots insurgency, the emergence of AAM must be seen in terms of an active leadership directing organizing efforts to a relatively inactive constituency.1 These leaders encouraged activism through a concerted strategy of mobilization with an emphasis on the national issue of a farm strike, the reintroduction of a traditional farm movement ideology, and the skillful use of public relations.2 AAM began in mid-summer· 1977 in Campo, Colorado, as an outgrowth of those enduring cafe conversations typical in all farm communities. However, Bud Bitner, George Bitner, Alvin Jenkins, Darrel Schroeder, Gene Schroeder, Van Stafford, and a few regular listeners talked mostly about a new political spokesman for farm interests during this particular summer.3 They saw a gloomy farm economy beset by both low prices and high costs, by an unresponsive government, and by an array of farm interest groups who were out of touch with real farm needs. Their immediate reaction to the 1977 Farm Bill, a piece of legislation that confirmed incentives for large-scale production without high supports, intensified their frustrations about each of these conditions and precipitated a decision to protest. Encouraged by the reception their ideas found in their own community, these locally respected larger-scale farmers and farmrelated businessmen proceeded to develop an organization based on rallies and protests against the political system.4 They would prompt and assist farmers throughout the country to organize as local groups, much along the lines of Farm Bureau county chapters, but without Bureau-related emphasis on nonpolitical services. AAM locals would be pockets of farmer interaction and discussion that would inspire political activism instead of emphasizing individual income.5 The local organizations would Jom in statewide and, finally, national demonstrations of movement support. Farmers, the initial organizers believed, were widely concerned about their weakened economic status but politically lethargic because they lacked inspired leadership

Cortical topography of intracortical inhibition influences the speed of decision making

The neocortex contains orderly topographic maps; however, their functional role remains controversial. Theoretical studies have suggested a role in minimizing computational costs, whereas empirical studies have focused on spatial localization. Using a tactile multiple-choice reaction time (RT) task before and after the induction of perceptual learning through repetitive sensory stimulation, we extend the framework of cortical topographies by demonstrating that the topographic arrangement of intracortical inhibition contributes to the speed of human perceptual decision-making processes. RTs differ among fingers, displaying an inverted U-shaped function. Simulations using neural fields show the inverted U-shaped RT distribution as an emergent consequence of lateral inhibition. Weakening inhibition through learning shortens RTs, which is modeled through topographically reorganized inhibition. Whereas changes in decision making are often regarded as an outcome of higher cortical areas, our data show that the spatial layout of interaction processes within representational maps contributes to selection and decision-making processes

High-frequency electron paramagnetic resonance investigation of the Fe3+ impurity center in polycrystalline PbTiO3 in its ferroelectric phase

The intrinsic iron(III) impurity center in polycrystalline lead titanate was investigated by means of high-frequency electron paramagnetic resonance (EPR) spectroscopy in order to determine the local-environment sensitive fine structure parameter D. At a spectrometer frequency of 190 GHz, spectral analysis of a powder sample was unambiguously possible. The observed mean value D = +35.28 GHz can be rationalized if Fe3+ ions substitute for Ti4+ at the B-site of the perovskite ABO3 lattice forming a directly coordinated iron - oxygen vacancy defect associate. A consistent fit of the multi-frequency data necessitated use of a distribution of D values with a variance of about 1 GHz. This statistical distribution of values is probably related to more distant defects and vacancies.Comment: 6 pages, 3 figures, 1 table, to appear in J. App. Phys, 96 (2004

Opposing effects of dopamine antagonism in a motor sequence task—tiapride increases cortical excitability and impairs motor learning

The dopaminergic system is involved in learning and participates in the modulation of cortical excitability (CE). CE has been suggested as a marker of learning and use-dependent plasticity. However, results from separate studies on either motor CE or motor learning challenge this notion, suggesting opposing effects of dopaminergic modulation upon these parameters: while agonists decrease and antagonists increase CE, motor learning is enhanced by agonists and disturbed by antagonists. To examine whether this discrepancy persists when complex motor learning and motor CE are measured in the same experimental setup, we investigated the effects of dopaminergic (DA) antagonism upon both parameters and upon task-associated brain activation. Our results demonstrate that DA-antagonism has opposing effects upon motor CE and motor sequence learning. Tiapride did not alter baseline CE, but increased CE post training of a complex motor sequence while simultaneously impairing motor learning. Moreover, tiapride reduced activation in several brain regions associated with motor sequence performance, i.e. dorsolateral PFC, supplementary motor area, Broca's area, cingulate and caudate body. Blood-oxygenation-level-dependent ( BOLD) intensity in anterior cingulate and caudate body, but not CE, correlated with performance across groups. In summary, our results do not support a concept of CE as a general marker of motor learning, since they demonstrate that a straightforward relation of increased CE and higher learning success does not apply to all instances of motor learning. At least for complex motor tasks that recruit a network of brain regions outside motor cortex, CE in primary motor cortex is probably no central determinant for learning success

A Map of Periodicity Orthogonal to Frequency Representation in the Cat Auditory Cortex

Harmonic sounds, such as voiced speech sounds and many animal communication signals, are characterized by a pitch related to the periodicity of their envelopes. While frequency information is extracted by mechanical filtering of the cochlea, periodicity information is analyzed by temporal filter mechanisms in the brainstem. In the mammalian auditory midbrain envelope periodicity is represented in maps orthogonal to the representation of sound frequency. However, how periodicity is represented across the cortical surface of primary auditory cortex (AI) remains controversial. Using optical recording of intrinsic signals, we here demonstrate that a periodicity map exists in primary AI of the cat. While pure tone stimulation confirmed the well-known frequency gradient along the rostro-caudal axis of AI, stimulation with harmonic sounds revealed segregated bands of activation, indicating spatially localized preferences to specific periodicities along a dorso-ventral axis, nearly orthogonal to the tonotopic gradient. Analysis of the response locations revealed an average gradient of − 100° ± 10° for the periodotopic, and −12° ± 18° for the tonotopic map resulting in a mean angle difference of 88°. The gradients were 0.65 ± 0.08 mm/octave for periodotopy and 1.07 ± 0.16 mm/octave for tonotopy indicating that more cortical territory is devoted to the representation of an octave along the tonotopic than along the periodotopic gradient. Our results suggest that the fundamental importance of pitch, as evident in human perception, is also reflected in the layout of cortical maps and that the orthogonal spatial organization of frequency and periodicity might be a more general cortical organization principle