835 resultados para Proton Distance Constraints


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This paper shows that value creation by multinational enterprises (MNEs) is the result of activities where geographic distance effects can be overcome. We submit that geographic distance has a relatively low impact on international research and development (R&D) investments, owing to the spiky nature of innovation, and to the unique ability of MNEs to absorb and transfer knowledge on a global scale. On the one hand, MNEs need to set up their labs as close as possible to specialized technology clusters where valuable knowledge is concentrated, largely regardless of distance from their home base. On the other, MNEs have historically developed technical and organizational competencies that enable them to transfer knowledge within their internal networks and across technology clusters at relatively low cost. Using data on R&D and manufacturing investments of 6320 firms in 59 countries, we find that geographic distance has a lower negative impact on the probability of setting up R&D than manufacturing plants. Furthermore, once measures of institutional proximity are accounted for, MNEs are equally likely to set up R&D labs in nearby or in more remote locations. This result is driven by MNEs based in Triad countries, whereas for non-Triad MNEs the effect of geographic distance on cross-border R&D is negative and significant.

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Earth hummocks (also termed pounus or thúfur) are a common form of periglacial non-sorted patterned ground. The study objectives were to determine the morphology, distribution and development on slopes of earth hummocks in north-east Okstindan, Norway, an area with many hummocks but few documented accounts. The methodology involved detailed geomorphological mapping and precise measurement with a profileometer. The internal structure of the hummocks was investigated through excavations and sediment sample analyses. Fourteen sites with well-developed earth hummocks (accounting for over 650 individual hummock forms) were investigated. The sites have an average altitude of 750 m and occur on slopes with an average gradient of 7°. The hummock heights are in the range 0.11–0.52 m and their diameters 0.7–1.5 m, although coalescent forms are up to 5 m in length. The hummock morphology is characterised by a variable plan form, asymmetry with respect to upslope and downslope forms, downslope elongation, coalescence, and superimposed microtopography. The hummocks’ distribution appeared to have been controlled by the existence of a frost-susceptible ‘host’ sediment, but moisture availability and topographic position played a role. The authors conclude that differential frost heave and vegetation cover stability are critical for the hummocks’ longevity in the studied landscape.

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Datasets containing information to locate and identify water bodies have been generated from data locating static-water-bodies with resolution of about 300 m (1/360 deg) recently released by the Land Cover Climate Change Initiative (LC CCI) of the European Space Agency. The LC CCI water-bodies dataset has been obtained from multi-temporal metrics based on time series of the backscattered intensity recorded by ASAR on Envisat between 2005 and 2010. The new derived datasets provide coherently: distance to land, distance to water, water-body identifiers and lake-centre locations. The water-body identifier dataset locates the water bodies assigning the identifiers of the Global Lakes and Wetlands Database (GLWD), and lake centres are defined for in-land waters for which GLWD IDs were determined. The new datasets therefore link recent lake/reservoir/wetlands extent to the GLWD, together with a set of coordinates which locates unambiguously the water bodies in the database. Information on distance-to-land for each water cell and the distance-to-water for each land cell has many potential applications in remote sensing, where the applicability of geophysical retrieval algorithms may be affected by the presence of water or land within a satellite field of view (image pixel). During the generation and validation of the datasets some limitations of the GLWD database and of the LC CCI water-bodies mask have been found. Some examples of the inaccuracies/limitations are presented and discussed. Temporal change in water-body extent is common. Future versions of the LC CCI dataset are planned to represent temporal variation, and this will permit these derived datasets to be updated.

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Horticultural knowledge and skills training have been with humankind for some 10,000 to 20,000 years. With permanent settlement and rising wealth and trade, horticulture products and services became a source of fresh food for daily consumption, and a source of plant material in developing a quality environment and lifestyle. The knowledge of horticulture and the skills of its practitioners have been demonstrated through the advancing civilizations in both eastern and western countries. With the rise of the Agricultural Revolutions in Great Britain, and more widely across Continental Europe in the 17th and 18th centuries, as well as the move towards colonisation and early migration to the New Worlds, many westernised countries established the early institutions that would provide education and training in agriculture and horticulture. Today many of these colleges and universities provide undergraduate, postgraduate and vocational and technical training that specifically targets horticulture and/or horticultural science with some research and teaching institutions also providing extension and advisory services to industry. The objective of this chapter is to describe the wider pedagogic and educational context in which those concerned with horticulture operate, the institutional structures that target horticulture and horticultural science education and training internationally; examine changing educational formats, especially distance education; and consider strategies for attracting and retaining young people in the delivery of world-class horticultural education. In this chapter we set the context by investigating the horticultural education and training options available, the constraints that prevent young people entering horticulture, and suggest strategies that would attract and retain these students. We suggest that effective strategies and partnerships be put in place by the institution, the government and most importantly the industry to provide for undergraduate and postgraduate education in horticulture and horticultural science; that educational and vocational training institutions, government, and industry need to work more effectively together to improve communication about horticulture and horticultural science in order to attract enrolments of more and talented students; and that the horticulture curriculum be continuously evaluated and revised so that it remains relevant to future challenges facing the industries of horticulture in the production, environmental and social spheres. These strategies can be used as a means to develop successful programs and case studies that would provide better information to high school career counsellors, improve the image of horticulture and encourage greater involvement from alumni and the industries in recruitment, provide opportunities to improve career aspirations, ensure improved levels of remuneration, and promote the social features of the profession and greater awareness and recognition of the profession in the wider community. A successful career in horticulture demands intellectual capacities which are capable of drawing knowledge from a wide field of basic sciences, economics and the humanities and integrating this into academic scholarship and practical technologies.

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Improved understanding and prediction of the fundamental environmental controls on ecosystem service supply across the landscape will help to inform decisions made by policy makers and land-water managers. To evaluate this issue for a local catchment case study, we explored metrics and spatial patterns of service supply for water quality regulation, agriculture production, carbon storage, and biodiversity for the Macronutrient Conwy catchment. Methods included using ecosystem models such as LUCI and JULES, integration of national scale field survey datasets, earth observation products and plant trait databases, to produce finely resolved maps of species richness and primary production. Analyses were done with both 1x1 km gridded and subcatchment data. A common single gradient characterised catchment scale ecosystem services supply with agricultural production and carbon storage at opposing ends of the gradient as reported for a national-scale assessment. Species diversity was positively related to production due to the below national average productivity levels in the Conwy combined with the unimodal relationship between biodiversity and productivity at the national scale. In contrast to the national scale assessment, a strong reduction in water quality as production increased was observed in these low productive systems. Various soil variables were tested for their predictive power of ecosystem service supply. Soil carbon, nitrogen, their ratio and soil pH all had double the power of rainfall and altitude, each explaining around 45% of variation but soil pH is proposed as a potential metric for ecosystem service supply potential as it is a simple and practical metric which can be carried out in the field with crowd-sourcing technologies now available. The study emphasises the importance of considering multiple ecosystem services together due to the complexity of covariation at local and national scales, and the benefits of exploiting a wide range of metrics for each service to enhance data robustness.

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The microstructure of the crestal alveolar bone is important for both the maintenance of osseointegration and the location of the gingival soft tissues. The aim of this study was to evaluate and compare the bone microstructure of the alveolar bone and of the interimplant bone in implants inserted at different interimplant distances. The mandibular bilateral premolars of six dogs were extracted, and after 12 weeks, each dog received eight implants, for a total of 48 implants. Two pairs of implants, one for each hemiarch, were separated by 2 mm (group 1) and by 3 mm (group 2). After 12 weeks, the implants received temporary acrylic prostheses. After four more weeks, metallic crowns substituted the temporary prostheses. After an additional 8 weeks the animals were sacrificed and the hemimandibles were removed, dissected, and processed. The longitudinal collagen fiber orientation was 43.2% for the alveolar bone; it was 30.3% for the 2-mm group and 43.9% for the 3-mm group. There was a statistically significant difference between the 2-mm and 3-mm groups (p < .05). The orientation of transverse collagen fibers was 47.8% for the alveolar bone; it was 37.3% for the 2-mm group and 56.3% for the 3-mm group. There was a statistically significant difference between the 2-mm and 3-mm groups (p < .05). The marrow spaces were 34.87% for the alveolar bone, 52.3% for the 2-mm group, and 59.9% for the 3-mm group. There was a statistically significant difference between the alveolar bone and the 3-mm group (p < .05). The low mineral density index was 36.29 for the alveolar bone, 46.76 for the 2-mm group, and 17.91 for the 3-mm group. There was a statistically significant difference between the 2-mm and 3-mm groups (p < .05). The high mineral density was 87.57 for the alveolar bone, 72.58 for the 2-mm group, and 84.91 for the 3-mm group. There was a statistically significant difference between the alveolar bone and the 2-mm group (p < .05). The collagen fiber orientation resulted in statistically significant differences in both the 2-mm and 3-mm groups compared with the alveolar bone. The marrow spaces appeared significantly increased in the 3-mm group compared with the alveolar bone. The low mineral density index was significantly higher in the 2-mm group, while the high mineral density index was significantly higher in the alveolar bone. In conclusion, the interimplant distance should not be less than 3 mm.

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Background: Depending on the distance of laser tip to dental surface a specific morphological pattern should be expected. However, there have been limited reports that correlate the Er:YAG irradiation distance with dental morphology. Purpose: To assess the influence of Er:YAG laser irradiation distance on enamel morphology, by means of scanning electron microscopy (SEM). Methods: Sixty human third molars were employed to obtain discs (congruent to 1 mm thick) that were randomly assigned to six groups (n = 10). Five groups received Er:YAG laser irradiation (80 mJ/2 Hz) for 20 s, according to the irradiation distance: 11, 12, 14, 16, or 17 mm. and the control group was treated with 37% phosphoric acid for 15 s. The laser-irradiated discs were bisected. One hemi-disc was separated for superficial analysis without subsequent acid etching, and the other one, received the phosphoric acid for 15 s. Samples were prepared for SEM. Results: Laser irradiation at 11 and 12 min provided an evident ablation of enamel, with evident fissures and some fused areas. At 14, 16 and 17 mm the superficial topography was flatter than in the other distances. The subsequent acid etching on the lased-surface partially removed the disorganized tissue. Conclusions: Er:YAG laser in defocused mode promoted slight morphological alterations and seems more suitable for enamel conditioning than focused irradiation. The application of phosphoric acid on lased-enamel surface, regardless of the irradiation distance, decreased the superficial irregularities.

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The aim of this study was to assess in vitro the influence of Er:YAG laser irradiation distance on the shear strength of the bond between an adhesive restorative system and primary dentin. A total of 60 crowns of primary molars were embedded in acrylic resin and mechanically ground to expose a flat dentin surface and were randomly assigned to six groups (n = 10). The control group was etched with 37% phosphoric acid. The remaining five groups were irradiated (80 mJ, 2 Hz) at different irradiation distances (11, 12, 16, 17 and 20 mm), followed by acid etching. An adhesive agent (Single Bond) was applied to the bonding sites, and resin cylinders (Filtek Z250) were prepared. The shear bond strength tests were performed in a universal testing machine (0.5 mm/min). Data were submitted to statistical analysis using one-way ANOVA and the Kruskal-Wallis test (p < 0.05). The mean shear bond strengths were: 7.32 +/- 3.83, 5.07 +/- 2.62, 6.49 +/- 1.64, 7.71 +/- 0.66, 7.33 +/- 0.02, and 9.65 +/- 2.41 MPa in the control group and the groups irradiated at 11, 12, 16, 17, and 20 mm, respectively. The differences between the bond strengths in groups II and IV and between the bond strengths in groups II and VI were statistically significant (p < 0.05). Increasing the laser irradiation distance resulted in increasing shear strength of the bond to primary dentin.

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The study of old open clusters outside the solar circle can bring constraints on formation scenarios of the outer disc. In particular, accretion of dwarf galaxies has been proposed as a likely mechanism in the area. We use BVI photometry for determining fundamental parameters of the faint open cluster ESO 92-SC05. Colour-magnitude diagrams are compared with Padova isochrones, in order to derive age, reddening and distance. We derive a reddening E(B - V) = 0.17, and an old age of similar to 6.0 Gyr. It is one of the rare open clusters known to be older than 5 Gyr. A metallicity of Z similar to 0.004 or [M/H] similar to -0.7 is found. The rather low metallicity suggests that this cluster might be the result of an accretion episode of a dwarf galaxy.

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A new method to measure the epicycle frequency kappa in the Galactic disc is presented. We make use of the large data base on open clusters completed by our group to derive the observed velocity vector (amplitude and direction) of the clusters in the Galactic plane. In the epicycle approximation, this velocity is equal to the circular velocity given by the rotation curve, plus a residual or perturbation velocity, of which the direction rotates as a function of time with the frequency kappa. Due to the non-random direction of the perturbation velocity at the birth time of the clusters, a plot of the present-day direction angle of this velocity as a function of the age of the clusters reveals systematic trends from which the epicycle frequency can be obtained. Our analysis considers that the Galactic potential is mainly axis-symmetric, or in other words, that the effect of the spiral arms on the Galactic orbits is small; in this sense, our results do not depend on any specific model of the spiral structure. The values of kappa that we obtain provide constraints on the rotation velocity of the in particular, V(0) is found to be 230 +/- 15 km s(-1) even if the scale (R(0) = 7.5 kpc) of the Galaxy is adopted. The measured kappa at the solar radius is 43 +/- 5 km s(-1) kpc(-1). The distribution of initial velocities of open clusters is discussed.

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A new inflationary scenario whose exponential potential V (Phi) has a quadratic dependence on the field Phi in addition to the standard linear term is confronted with the five-year observations of the Wilkinson-Microwave Anisotropy Probe and the Sloan Digital Sky Survey data. The number of e-folds (N), the ratio of tensor-to-scalar perturbations (r), the spectral scalar index of the primordial power spectrum (n(s)) and its running (dn(s)/d ln k) depend on the dimensionless parameter a multiplying the quadratic term in the potential. In the limit a. 0 all the results of the exponential potential are fully recovered. For values of alpha not equal 0, we find that the model predictions are in good agreement with the current observations of the Cosmic Microwave Background (CMB) anisotropies and Large-Scale Structure (LSS) in the Universe. Copyright (C) EPLA, 2008.

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A possible slowing down of the cosmic expansion is investigated through a cosmographic approach. By expanding the luminosity distance to fourth order and fitting the SN Ia data from the most recent compilations (Union, Constitution and Union 2), the marginal likelihood distributions for the deceleration parameter today suggest a recent reduction of the cosmic acceleration and indicate that there is a considerable probability for q(0) > 0. Also in contrast to the prediction of the Lambda CDM model, the cosmographic q(z) reconstruction permits a cosmic expansion history where the cosmic acceleration could already have peaked and be presently slowing down, which would imply that the recent accelerated expansion of the universe is a transient phenomenon. It is also shown that to describe a transient acceleration the luminosity distance needs to be expanded at least to fourth order. The present cosmographic results depend neither on the validity of general relativity nor on the matter-energy contents of the universe.

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The dynamical processes that lead to open cluster disruption cause its mass to decrease. To investigate such processes from the observational point of view, it is important to identify open cluster remnants (OCRs), which are intrinsically poorly populated. Due to their nature, distinguishing them from field star fluctuations is still an unresolved issue. In this work, we developed a statistical diagnostic tool to distinguish poorly populated star concentrations from background field fluctuations. We use 2MASS photometry to explore one of the conditions required for a stellar group to be a physical group: to produce distinct sequences in a colour-magnitude diagram (CMD). We use automated tools to (i) derive the limiting radius; (ii) decontaminate the field and assign membership probabilities; (iii) fit isochrones; and (iv) compare object and field CMDs, considering the isochrone solution, in order to verify the similarity. If the object cannot be statistically considered as a field fluctuation, we derive its probable age, distance modulus, reddening and uncertainties in a self-consistent way. As a test, we apply the tool to open clusters and comparison fields. Finally, we study the OCR candidates DoDz 6, NGC 272, ESO 435 SC48 and ESO 325 SC15. The tool is optimized to treat these low-statistic objects and to separate the best OCR candidates for studies on kinematics and chemical composition. The study of the possible OCRs will certainly provide a deep understanding of OCR properties and constraints for theoretical models, including insights into the evolution of open clusters and dissolution rates.

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We present mid-infrared (mid-IR) spectra of the Compton-thick Seyfert 2 galaxy NGC 3281, obtained with the Thermal-Region Camera Spectrograph at the Gemini-South telescope. The spectra present a very deep silicate absorption at 9.7 mu m, and [S IV] 10.5 mu m and [Ne II] 12.7 mu m ionic lines, but no evidence of polycyclic aromatic hydrocarbon emission. We find that the nuclear optical extinction is in the range 24 mag <= A(V) <= 83 mag. A temperature T = 300 K was found for the blackbody dust continuum component of the unresolved 65 pc nucleus and the region at 130 pc SE, while the region at 130 pc NW reveals a colder temperature (200 K). We describe the nuclear spectrum of NGC 3281 using a clumpy torus model that suggests that the nucleus of this galaxy hosts a dusty toroidal structure. According to this model, the ratio between the inner and outer radius of the torus in NGC 3281 is R(0)/R(d) = 20, with 14 clouds in the equatorial radius with optical depth of tau(V) = 40 mag. We would be looking in the direction of the torus equatorial radius (i = 60 degrees), which has outer radius of R(0) similar to 11 pc. The column density is N(H) approximate to 1.2 x 10(24) cm(-2) and the iron K alpha equivalent width (approximate to 0.5-1.2 keV) is used to check the torus geometry. Our findings indicate that the X-ray absorbing column density, which classifies NGC 3281 as a Compton-thick source, may also be responsible for the absorption at 9.7 mu m providing strong evidence that the silicate dust responsible for this absorption can be located in the active galactic nucleus torus.

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Oscillating biochemical reactions are common in cell dynamics and could be closely related to the emergence of the life phenomenon itself. In this work, we study the dynamical features of some classical chemical or biochemical oscillators where the effect of cell volume changes is explicitly considered. Such analysis enables us to find some general conditions about the cell membrane to preserve such oscillatory patterns, of possible relevance to hypothetical primitive cells in which these structures first appeared.