227 research outputs found
Travel and Parking Behavior in the United States
This paper looks at the connection between the regulation of parking by cities, transit service levels, and travel and parking behavior in the United States. Travel behavior information comes from the 1990 Nationwide Personal Transportation Survey (NPTS) and the Federal Urban Mass Transportation Administrationâs 1990 Section 15 Report. Data on the current state of parking programs in place in central business districts of the U.S. is identified through telephone interviews of local officials responsible for parking policies from the twenty cities identified in the NPTS. The travel behavior analyses and the data from the parking officials interviews were combined with data from the Federal Highway Administrationâs Journey-to-Work data to group cities according to their parking policies, transit service, and ridership levels on a continuum of âTransit-Accommodating Citiesâ and âAuto-Accomodating Citiesâ. A key finding is that cities with interventionist parking policies, high parking prices and limited supply, frequent transit service, and a high probability that travelers will pay to park are the most likely to have high transit ridership figures
Accommodation of lattice mismatch in Ge_(x)Si_(1âx)/Si superlattices
We present evidence that the critical thickness for the appearance of misfit defects in a given material and heteroepitaxial structure is not simply a function of lattice mismatch. We report substantial differences in the relaxation of mismatch stress in Ge_(0.5)Si_(0.5)/Si superlattices grown at different temperatures on (100) Si substrates. Samples have been analyzed by xâray diffraction, channeled Rutherford backscattering, and transmission electron microscopy. While a superlattice grown at 365â°C demonstrates a high degree of elastic strain, with a dislocation density <10^5 cm^(â2) , structures grown at higher temperatures show increasing numbers of structural defects, with densities reaching 2Ă10^(10) cm^(â2) at a growth temperature of 530â°C. Our results suggest that it is possible to freeze a latticeâmismatched structure in a highly strained metastable state. Thus it is not surprising that experimentally observed critical thicknesses are rarely in agreement with those predicted by equilibrium theories
Effects of Comprehensive Plan Amendments on Interchange Traffic in Oregon
In this paper we examine the effects of amendments to local comprehensive plans on interchange performance. Plan amendments over a 15-year period in Oregon resulting in changes to industrial or commercial land use were reviewed to identify those that occurred within one mile of an interchange. Regression analysis was then performed to estimate the impact of nearby plan amendments on subsequent interchange ADT. Plan amendments were found to have a substantial ADT effect on rural interchanges, but their incidence was very limited. In urban core areas, the estimated effect of plan amendments was negligible, possibly due to interchange congestion or effective land use planning. In urban fringe areas, plan amendments were estimated to account for about 5 percent of the subsequent interchange ADT, equivalent to about two years of the design life of these facilities
Review essay: Anthony Howe. Byron and the Forms of Thought (Liverpool: Liverpool UP, 2013) and Carla Pomare. Byron and the Discourse of History (Farnham and Burlington: Ashgate, 2013).
This essay is a comparative review of two recently published books in Byron studies: Anthony Howe's Byron and the Forms of Thought (Liverpool: Liverpool UP, 2013) and Carla Pomare's Byron and the Discourse of History (Farnham and Burlington: Ashgate, 2013)
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A New Method for Making Shallow P-Type Junctions
In this paper the authors present a new method for making shallow p-type junctions in silicon by molecular ion implantation. Unlike current molecular ion implantation methods which use boron and fluorine molecules, this new method uses an element which is completely miscible in silicon. Note that fluorine is an element that saturates at a very low concentration in silicon. The compounds used in this new method are boron silicides and boron germanium molecules. These compounds have several distinct advantages including the facts that the co-element silicon (or germanium) has a very high saturation value in the silicon matrix, the co-element is massive and therefore creates more damage during implantation, and the co-element has a larger projected range than the boron. Note that the Rp for fluorine is shallower than that of Boron for a BF{sub 2} implant. Recent experiments indicate that BSi ion beams can be generated in a sputter ion source with efficiencies of 0.5% with respect to the generated Si beam. A plan to develop a new ion source that is compatible with current ion implantation systems is presented
Making things happen : a model of proactive motivation
Being proactive is about making things happen, anticipating and preventing problems, and seizing opportunities. It involves self-initiated efforts to bring about change in the work environment and/or oneself to achieve a different future. The authors develop existing perspectives on this topic by identifying proactivity as a goal-driven process involving both the setting of a proactive goal (proactive goal generation) and striving to achieve that proactive goal (proactive goal striving). The authors identify a range of proactive goals that individuals can pursue in organizations. These vary on two dimensions: the future they aim to bring about (achieving a better personal fit within oneâs work environment, improving the organizationâs internal functioning, or enhancing the organizationâs strategic fit with its environment) and whether the self or situation is being changed. The authors then identify âcan do,â âreason to,â and âenergized toâ motivational states that prompt proactive goal generation and sustain goal striving. Can do motivation arises from perceptions of self-efficacy, control, and (low) cost. Reason to motivation relates to why someone is proactive, including reasons flowing from intrinsic, integrated, and identified motivation. Energized to motivation refers to activated positive affective states that prompt proactive goal processes. The authors suggest more distal antecedents, including individual differences (e.g., personality, values, knowledge and ability) as well as contextual variations in leadership, work design, and interpersonal climate, that influence the proactive motivational states and thereby boost or inhibit proactive goal processes. Finally, the authors summarize priorities for future researc
Risk-taking, delay discounting, and time perspective in adolescent gamblers: an experimental study
Previous research has demonstrated that adult pathological gamblers (compared to controls) show risk-proneness, foreshortened time horizon, and preference for immediate rewards. No study has ever examined the interplay of these factors in adolescent gambling. A total of 104 adolescents took part in the research. Two equal-number groups of adolescent non-problem and problem gamblers, defined using the South Oaks Gambling Screen-Revised for Adolescents (SOGS-RA), were administered the Balloon Analogue Risk Task (BART), the Consideration of Future Consequences (CFC-14) Scale, and the Monetary Choice Questionnaire (MCQ). Adolescent problem gamblers were found to be more risk-prone, more oriented to the present, and to discount delay rewards more steeply than adolescent non-problem gamblers. Results of logistic regression analysis revealed that BART, MCQ, and CFC scores predicted gambling severity. These novel finding provides the first evidence of an association among problematic gambling, high risk-taking proneness, steep delay discounting, and foreshortened time horizon among adolescents. It may be that excessive gambling induces shortsighted behaviors that, in turn, facilitate gambling involvement
Taxonomic and Environmental Variability in the Elemental Composition and Stoichiometry of Individual Dinoflagellate and Diatom Cells from the NW Mediterranean Sea
Here we present, for the first time, the elemental concentration, including C, N and O, of single phytoplankton cells collected from the sea. Plankton elemental concentration and stoichiometry are key variables in phytoplankton ecophysiology and ocean biogeochemistry, and are used to link cells and ecosystems. However, most field studies rely on bulk techniques that overestimate carbon and nitrogen because the samples include organic matter other than plankton organisms. Here we used X-ray microanalysis (XRMA), a technique that, unlike bulk analyses, gives simultaneous quotas of C, N, O, Mg, Si, P, and S, in single-cell organisms that can be collected directly from the sea. We analysed the elemental composition of dinoflagellates and diatoms (largely Chaetoceros spp.) collected from different sites of the Catalan coast (NW Mediterranean Sea). As expected, a lower C content is found in our cells compared to historical values of cultured cells. Our results indicate that, except for Si and O in diatoms, the mass of all elements is not a constant fraction of cell volume but rather decreases with increasing cell volume. Also, diatoms are significantly less dense in all the measured elements, except Si, compared to dinoflagellates. The N:P ratio of both groups is higher than the Redfield ratio, as it is the N:P nutrient ratio in deep NW Mediterranean Sea waters (N:P = 20â23). The results suggest that the P requirement is highest for bacterioplankton, followed by dinoflagellates, and lowest for diatoms, giving them a clear ecological advantage in P-limited environments like the Mediterranean Sea. Finally, the P concentration of cells of the same genera but growing under different nutrient conditions was the same, suggesting that the P quota of these cells is at a critical level. Our results indicate that XRMA is an accurate technique to determine single cell elemental quotas and derived conversion factors used to understand and model ocean biogeochemical cycles
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