164,586 research outputs found
Sull'isomorfismo di H-anelli dotati di un modulo irriducibile e quasi fedele
No full textsi studiano gli isomorfismi di H-anelli primitivi o quasi
primitivi, nell'ambito delle loro classificazioni dovute ad A.
Caggegi ed a L. Bader e A. Franchett
Spreads of and ovoids of polar spaces
No full textTo any spread S of PG(3,q) corresponds a family of locally
hermitian ovoids of the Hermitian surface H(3, q^2), and
conversely;
if in addition S is a semifield spread, then each
associated ovoid is a translation ovoid, and conversely.
In this paper we calculate the translation group of the locally
hermitian ovoids of H(3,q^2) arising from a given semifield
spread,
and we characterize the p-semiclassical ovoid constructed by Cossidente, Ebert, Marino and Siciliano as the only translation ovoid of H(3,q^2)
whose
translation group is abelian.
If S is a spread of PG(3,q) and O(S) is one of the
associated ovoids of H(3,q^2),
then using the duality between
H(3,q^2) and Q^-(5, q) , another spread of PG(3,q) , say
S_1, can be constructed.
On the other hand, using the
Barlotti-Cofman representation of H(3,q^2), one more spread of a
3-dimensional projective space,
say S_2, arises from the
ovoid O(S). Lunardon has posed some questions on the
relations among S, S_1 and S_2;
here we prove that the
three spreads are always isomorphic
Modèles des filiations. Entretien avec Serge Lebovici mené par Michel Bader et Olivier Chouchena
No full textExplaining variation in the effectiveness of anti-corruption activism in Ukraine's regions: The role of local context, political will, institutional factors, and structural factors
No full textThe 2013-2014 Revolution has spurred a boom in civic anti-corruption initiatives across Ukraine. There is as yet little understanding of how effective these initiatives are and what explains variation in their effectiveness. Through a comprehensive study of anti-corruption activism in the regions of Ukraine,1 this paper analyzes contextual factors that shape local anticorruption initiatives. We conducted 242 semi-structured interviews with representatives of anti-corruption civic initiatives in 57 cities and towns, representing all the regions of Ukraine that are under the control of the Ukrainian government. We find that political will is an important factor supporting the effectiveness of anticorruption activism, as it creates more opportunities for impact. However, we identify a substantial number of cases of anti-corruption initiatives that were effective even though local authorities had low political will to counteract corruption
Variations on the Author
No full text“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Stem cell mechanobiology
No full textStem cells are undifferentiated cells that are capable of proliferation, self-maintenance and differentiation towards specific cell phenotypes. These processes are controlled by a variety of cues including physicochemical factors associated with the specific mechanical environment in which the cells reside. The control of stem cell biology through mechanical factors remains poorly understood and is the focus of the developing field of mechanobiology. This review provides an insight into the current knowledge of the role of mechanical forces in the induction of differentiation of stem cells. While the details associated with individual studies are complex and typically associated with the stem cell type studied and model system adopted, certain key themes emerge. First, the differentiation process affects the mechanical properties of the cells and of specific subcellular components. Secondly, that stem cells are able to detect and respond to alterations in the stiffness of their surrounding microenvironment via induction of lineage-specific differentiation. Finally, the application of external mechanical forces to stem cells, transduced through a variety of mechanisms, can initiate and drive differentiation processes. The coalescence of these three key concepts permit the introduction of a new theory for the maintenance of stem cells and alternatively their differentiation via the concept of a stem cell 'mechano-niche', defined as a specific combination of cell mechanical properties, extracellular matrix stiffness and external mechanical cues conducive to the maintenance of the stem cell population.<br/
Pressure signatures can influence tissue response for individuals supported on an alternating pressure mattress
No full textProlonged mechanical loading can lead to the breakdown of skin and underlying tissues which can, in turn, develop into a pressure ulcer. The benefits of pressure relief and/or redistribution to minimise risk have been well documented. Manufacturers have developed alternating air pressure mattresses (APAMs) to provide periodic relief for individuals on prolonged bed-rest. The present study describes the development of a control system, termed Pneumatic Manager which can vary the signature of an APAM, namely its pressure amplitude, cell profile and cycle period. An experimental array was designed to investigate the effects of varying these parameters, particularly with respect to its ability to maintain skin viability in a group of five healthy volunteers lying in a supine position. Transcutaneous gas (TcPO2/TcPCO2) tensions at the sacrum were monitored. In addition, pressures and microclimate parameters at the loaded support interface were also measured.In the majority of test conditions the alternating support produced sacral TcPO2 values, which either remained relatively high or fluctuated in concert with cycle period providing adequate viability. However, in 46% of cases at the extreme pressure amplitude of 100/0 mmHg, there was compromise to the skin viability at the sacrum, as reflected in depressed TcPO2 levels associated with an elevation of TcPCO2 levels above the normal range. In all cases, both the humidity and temperature levels increased during the test period. It is interesting to note that interface pressures at the sacrum rarely exceeded 60 mmHg. Although such studies need to be extended to involve bed-bound individuals, the results provide a design template for the optimum pressure signatures of APAM systems to ensure maintenance of skin viability during pronged loading
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Larry O. Spencer, Conference Author Presentation
No full textGen. Larry O. Spencer, USAF (Ret.), author of Dark Horse: A Journey from the Horseshoe to the Pentago
Viscoelastic Cell Mechanics and actin remodelling are dependent on the rate of applied pressure
No full textBackground: living cells are subjected to external and internal mechanical stresses. The effects of these stresses on the deformation and subsequent biological response of the cells remains unclear. This study tested the hypothesis that the rate at which pressure (or stress) is applied influence the viscoelastic properties of the cell associated with differences in the dynamics of the actin cytoskeleton.Principal finding: micropipette aspiration was used to determine the instantaneous and equilibrium moduli and the viscosity of isolated chondrocytes based on the standard linear solid (SLS) model and a variation of this incorporating Boltzmann superposition. Cells were visualised for 180 seconds following aspiration to 7 cmH2O at 0.35, 0.70 and 5.48 cmH2O/sec. Cell recovery was then examined for a further 180 seconds once the pressure had been removed. Reducing the rate of application of pressure reduced the levels of cell deformation and recovery associated with a significant increase in modulus and viscosity. Using GFP transfection and confocal microscopy, we show that chondrocyte deformation involves distortion, disassembly and subsequent reassembly of the cortical actin cytoskeleton. At faster pressure rates, cell deformation produced an increase in cell volume associated with membrane bleb formation. GFP-actin transfection inhibited the pressure rate dependent variation in cell mechanics indicating that this behaviour is regulated by GFP-sensitive actin dynamics.Conclusion: we suggest that slower rates of aspiration pressure enable greater levels of cortical actin distortion. This is partially inhibited by GFP or faster aspiration rates leading to membrane bleb formation and an increase in cell volume. Thus the rate of application of pressure regulates the viscoelastic mechanical properties of living cells through pressure rate sensitive differences in actin dynamics. Therefore cells appear softer when aspirated at a faster rate in contrast to what is expected of a normal viscoelastic materia
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