11 resultados para function space

em BORIS: Bern Open Repository and Information System - Berna - Suiça


Relevância:

60.00% 60.00%

Publicador:

Resumo:

We quantify the extent to which a supercritical Sobolev mapping can increase the dimension of subsets of its domain, in the setting of metric measure spaces supporting a Poincaré inequality. We show that the set of mappings that distort the dimensions of sets by the maximum possible amount is a prevalent subset of the relevant function space. For foliations of a metric space X defined by a David–Semmes regular mapping Π : X → W, we quantitatively estimate, in terms of Hausdorff dimension in W, the size of the set of leaves of the foliation that are mapped onto sets of higher dimension. We discuss key examples of such foliations, including foliations of the Heisenberg group by left and right cosets of horizontal subgroups.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Mitochondrial translation in the parasitic protozoan Trypanosoma brucei relies on imported eukaryotic-type tRNAs as well as on bacterial-type ribosomes that have the shortest known rRNAs. Here we have identified the mitochondrial translation elongation factors EF-Tu, EF-Ts, EF-G1 and release factor RF1 of trypanosomatids and show that their ablation impairs growth and oxidative phosphorylation. In vivo labelling experiments and a SILAC-based analysis of the global proteomic changes induced by EF-Tu RNAi directly link EF-Tu to mitochondrial translation. Moreover, EF-Tu RNAi reveals downregulation of many nuclear encoded subunits of cytochrome oxidase as well as of components of the bc1-complex, whereas most cytosolic ribosomal proteins were upregulated. Interestingly, T. brucei EF-Tu has a 30-amino-acid-long, highly charged subdomain, which is unique to trypanosomatids. A combination of RNAi and complementation experiments shows that this subdomain is essential for EF-Tu function, but that it can be replaced by a similar sequence found in eukaryotic EF-1a, the cytosolic counterpart of EF-Tu. A recent cryo-electron microscopy study revealed that trypanosomatid mitochondrial ribosomes have a unique intersubunit space that likely harbours the EF-Tu binding site. These findings suggest that the trypanosomatid-specific EF-Tu subdomain serves as an adaption for binding to these unusual mitochondrial ribosomes.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Given its origins in traditional dialectology, and given advances in our understanding of the social embedding of language variation, it is paradoxical that space should be one of the categories that has received least attention of all in variationist sociolinguistics. Until recently, space has largely been treated as an empty stage on which sociolinguistic processes are enacted. It has been unexamined, untheorized, and its role in shaping and being shaped by variation and change untested. One function of this chapter, therefore, is to assert that space makes a difference, and to begin, in a very hesitant way, to map out what a geographically informed variation analysis might need to address. It also examines variationist interactions with the related concept of mobility. It might be reasonable to think that human geographers would provide some clues on how to proceed. As we will see, they have engaged in a great deal of soul searching about the goals of their discipline, its very existence as a separate field of enquiry, and the directions it should take. Indeed there are remarkable parallels between the recent history of human geographic thought, and interest in language variation across space. Although space has been undertheorized in variation studies, a number of researchers, from the traditional dialectologists through to those interested in the dialectology of mobility and contact, have, of course, been actively engaged in research on geographical variation and language use. Their work will be contextualized here to highlight both the parallels with theory-building in human geography, but also some of the criticisms of earlier approaches which have fed through to human geography, but remain largely unquestioned in variationist practice. The chapter therefore presents a brief theoretical background to space and mobility, before exemplifying these concepts in variationist research through an examination of, for example, the spatial diffusion of linguistic innovations, the spatial configuration of linguistic boundaries and initial steps to examine the consequences of mobility for variationist research.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

The Imager for Low Energetic Neutral Atoms test facility at the University of Bern was developed to investigate, characterize, and quantify physical processes on surfaces that are used to ionize neutral atoms before their analysis in neutral particle-sensing instruments designed for space research. The facility has contributed valuable knowledge of the interaction of ions with surfaces (e.g., fraction of ions scattered from surfaces and angular scattering distribution) and employs a novel measurement principle for the determination of secondary electron emission yields as a function of energy, angle of incidence, particle species, and sample surface for low particle energies. Only because of this test facility it was possible to successfully apply surface-science processes for the new detection technique for low-energetic neutral particles with energies below about 1 keV used in space applications. All successfully flown spectrometers for the detection of low-energetic neutrals based on the particle–surface interaction process use surfaces evaluated, tested, and calibrated in this facility. Many instruments placed on different spacecraft (e.g., Imager for Magnetopause-to-Aurora Global Exploration, Chandrayaan-1, Interstellar Boundary Explorer, etc.) have successfully used this technique.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Most available studies of interconnected matrix porosity of crystalline rocks are based on laboratory investigations; that is, work on samples that have undergone stress relaxation and were affected by drilling and sample preparation. The extrapolation of the results to in situ conditions is therefore associated with considerable uncertainty, and this was the motivation to conduct the ‘in situ Connected Porosity’ experiment at the Grimsel Test Site (Central Swiss Alps). An acrylic resin doped with fluorescent agents was used to impregnate the microporous granitic matrix in situ around an injection borehole, and samples were obtained by overcoring. The 3-D structure of the porespace, represented by microcracks, was studied by U-stage fluorescence microscopy. Petrophysical methods, including the determination of porosity, permeability and P -wave velocity, were also applied. Investigations were conducted both on samples that were impregnated in situ and on non-impregnated samples, so that natural features could be distinguished from artefacts. The investigated deformed granites display complex microcrack populations representing a polyphase deformation at varying conditions. The crack population is dominated by open cleavage cracks in mica and grain boundary cracks. The porosity of non-impregnated samples lies slightly above 1 per cent, which is 2–2.5 times higher than the in situ porosity obtained for impregnated samples. Measurements of seismic velocities (Vp ) on spherical rock samples as a function of confining pressure, spatial direction and water saturation for both non-impregnated and impregnated samples provide further constraints on the distinction between natural and induced crack types. The main conclusions are that (1) an interconnected network of microcracks exists in the whole granitic matrix, irrespective of the distance to ductile and brittle shear zones, and (2) conventional laboratory methods overestimate the matrix porosity. Calculations of contaminant transport through fractured media often rely on matrix diffusion as a retardation mechanism.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

From early colonial encounters to the ecological disasters of the twenty-first century, the performativity of contact has been a crucial element in the political significance of the beach. Conceptualising the beach as a creative trope and as a socio-cultural site, as well as an aesthetically productive topography, this collection examines its multiplicity of meanings and functions as a natural environment engendering both desire and fear in the human imagination from the Victorian period to the present. The contributors examine literature, film, and art, in addition to moments of encounter and environmental crisis, to highlight the beach as a social space inspiring particular codes of behaviour and specific discourses, as a geographical frontier between land and water, as an historical site of contact and conflict, and as a vacationscape promising regeneration and withdrawal from everyday life. The diversity of the beach is reflected in the geographical range, with essays on locales and texts from Britain, Ireland, the Caribbean, South Africa, the United States, Polynesia, and New Zealand. Focusing on the changed function of the beach as a result of processes of industrialisation and the rise of a modern leisure and health culture, this interdisciplinary volume theorises the beach as a demarcater of the precarious boundary between land and the sea, as well as between nature and culture.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

BACKGROUND During threat, interpersonal distance is deliberately increased. Personal space regulation is related to amygdala function and altered in schizophrenia, but it remains unknown whether it is particularly associated with paranoid threat. METHODS We compared performance in two tests on personal space between 64 patients with schizophrenia spectrum disorders and 24 matched controls. Patients were stratified in those with paranoid threat, neutral affect or paranoid experience of power. In the stop-distance paradigm, participants indicated the minimum tolerable interpersonal distance. In the fixed-distance paradigm, they indicated the level of comfort at fixed interpersonal distances. RESULTS Paranoid threat increased interpersonal distance two-fold in the stop-distance paradigm, and reduced comfort ratings in the fixed-distance paradigm. In contrast, patients experiencing paranoid power had high comfort ratings at any distance. Patients with neutral affect did not differ from controls in the stop-distance paradigm. Differences between groups remained when controlling for gender and positive symptom severity. Among schizophrenia patients, the stop-distance paradigm detected paranoid threat with 93% sensitivity and 83% specificity. CONCLUSIONS Personal space regulation is not generally altered in schizophrenia. However, state paranoid experience has distinct contributions to personal space regulation. Subjects experiencing current paranoid threat share increased safety-seeking behavior.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

A bitopic ligand, 4-(3,5-dimethylpyrazol-4-yl)-1,2,4-triazole (Hpz-tr) (1), containing two different heterocyclic moieties was employed for the design of copper(II)–molybdate solids under hydrothermal conditions. In the multicomponent CuII/Hpz-tr/MoVI system, a diverse set of coordination hybrids, [Cu(Hpz-tr)2SO4]·3H2O (2), [Cu(Hpz-tr)Mo3O10] (3), [Cu4(OH)4(Hpz-tr)4Mo8O26]·6H2O (4), [Cu(Hpz-tr)2Mo4O13] (5), and [Mo2O6(Hpz-tr)]·H2O (6), was prepared and characterized. A systematic investigation of these systems in the form of a ternary crystallization diagram approach was utilized to show the influence of the molar ratios of starting reagents, the metal (CuII and MoVI) sources, the temperature, etc., on the reaction products outcome. Complexes 2–4 dominate throughout a wide crystallization range of the composition triangle, while the other two compounds 5 and 6 crystallize as minor phases in a narrow concentration range. In the crystal structures of 2–6, the organic ligand behaves as a short [N–N]-triazole linker between metal centers Cu···Cu in 2–4, Cu···Mo in 5, and Mo···Mo in 6, while the pyrazolyl function remains uncoordinated. This is the reason for the exceptional formation of low-dimensional coordination motifs: 1D for 2, 4, and 6 and 2D for 3 and 5. In all cases, the pyrazolyl group is involved in H bonding (H-donor/H-acceptor) and is responsible for π–π stacking, thus connecting the chain and layer structures in more complicated H-bonding architectures. These compounds possess moderate thermal stability up to 250–300 °C. The magnetic measurements were performed for 2–4, revealing in all three cases antiferromagnetic exchange interactions between neighboring CuII centers and long-range order with a net moment below Tc of 13 K for compound 4.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

OBJECTIVES This clinical study measured the dimensional changes of existing lower complete dentures due to the integration of a prefabricated implant bar. Additionally, the impact of this dimensional change on patient satisfaction and oral function was analyzed. METHODS Twenty edentulous patients (10 men/10 women; aged 65.9 ± 11.8 years) received two interforaminal implants. Subsequent to surgery, a chair side adapted, prefabricated bar (SFI Bar(®), C+M, Biel, Switzerland) was inserted, and the matrix was polymerized into the existing lower denture. The change of the denture's lingual dimension was recorded by means of a bicolored, silicone denture duplicate that was sectioned in the oro-vestibular direction in the regions of the symphysis (S) and the implants (I-left, I-right). On the sections, the dimensional increase was measured using a light microscope. Six months after bar insertion, patients answered a standardized questionnaire. RESULTS All dentures exhibited increased lingual volume, more extensively at S than at I (P = 0.001). At S, the median diagonal size of the denture was doubled (+4.33 mm), and at I, the median increase was 50% (I-left/-right = +2.66/+2.62 mm). The original denture size influenced the volume increase (P = 0.024): smaller dentures led to a larger increase. The amount of denture increase did not have negative impact on either self-perceived oral function or patient satisfaction. Approximately, 95% of the patients were satisfied with the treatment results. CONCLUSIONS The lingual size of a lower denture was enlarged by the integration of a prefabricated bar without any negative side effects. Thus, this attachment system is suitable to convert an existing full denture into an implant-supported overdenture.