117,770 research outputs found
Spin fluids in Bianchi-I f(R)-cosmology with torsion
No full textWe study Weyssenhoff spin fluids in Bianchi type-I cosmological models, within the framework of torsional f(R)-gravity; the resulting field equations are derived and discussed in both Jordan and Einstein frames, clarifying the role played by the spin and the non-linearity of the gravitational Lagrangian f(R) in generating the torsional dynamical contributions. The general conservation laws holding for f(R)-gravity with torsion are employed to provide the conditions needed to ensure the preservation of the Hamiltonian constraint and the consequent correct formulation of the associated initial value problem. Examples are eventually given
The most general ELKO matter in torsional f(R)-theories
No full textWe study f(R)-gravity with torsion in presence of the most general ELKO matter, checking the consistency of the conservation laws with the matter field equations; we discuss some mathematical features of the field equations in connection with a cosmological application
Dirac spinors in Bianchi-I f(R)-cosmology with torsion
No full textWe study Dirac spinors in Bianchi type-I cosmological models, within the framework of torsional f(R)-gravity. We find four types of results: the resulting dynamic behavior of the universe depends on the particular choice of function f(R); some f(R) models do not isotropize and have no Einstein limit, so that they have no physical significance, whereas for other f(R) models isotropization and Einsteinization occur, and so they are physically acceptable, suggesting that phenomenological arguments may select f(R) models that are physically meaningful; the singularity problem can be avoided, due to the presence of torsion; the general conservation laws holding for f(R)-gravity with torsion ensure the preservation of the Hamiltonian constraint, so proving that the initial value problem is well-formulated for these models
A square-torsion modification of Einstein-Cartan theory
No full textIn the present paper we consider a theory of gravity in which not only curvature but also torsion is explicitly present in the Lagrangian, both with their own coupling constant. In particular, we discuss the couplings to Dirac fields and spin fluids: in the case of Dirac fields, we discuss how in our approach, the Dirac self-interactions depend on the coupling constant as a parameter that may even make these non-linearities manifest at subatomic scales, showing different applications according to the value of the parameter we have assigned; in the case of spin fluids, we discuss FLRW cosmological models arising from the proposed theory
Influence of rehabilitation on language skills in aphasic patients
No full textThe influence of language rehabilitation on specific language skills (speaking, understanding, writing, and reading) was investigated in 281 aphasic patients (162 reeducated and 119 controls) who were subjected to a second examination no less than six months after the first. The relationship of the following factors to improvement was studied: (a) time between onset of aphasia and first examination; (b) type of aphasia; (c) overall severity of aphasia on first examination; (d) presence or absence of rehabilitation between first and subsequent examination. It was found that rehabilitation had a significant positive effect on improvement in all language skills. Time between onset and first examination and overall severity of aphasia were negatively related to improvement. The relationship of type of aphasia to improvement was not significant. Additional evidence of the efficacy of rehabilitation is provided by experience with patients who began language therapy several months or years after the onset of their language disorder
High Resolution XPS of the S2p core level region of the L-Cysteine/gold interface
No full textL-cysteine self-assembled monolayers (SAMs) have been deposited on gold from the liquid and vapour phase. Synchrotron based high resolution x-ray photoemission spectroscopy has been used to characterize the sulfur chemical states at the SAM/gold interface. Results obtained from pristine and x-ray irradiated samples, prepared with both as-received and purified L-cysteine, are reported. Pristine samples prepared with purified cysteine are characterized by an intense, largely dominant S 2p state at a binding energy around 162 eV (2p(3/2) level) assigned to thiolates. A second doublet around 161 eV develops during irradiation. By comparison with the literature, this doublet is assigned to atomic sulfur present either as impurity or generated by S-C bond scission. Comparative measurements performed, under similar experimental conditions, on pristine 3-mercaptopropionic acid [HS(CH2)(2)COOH] layers deposited from the liquid phase are also presented and discussed
Occurrence of antilisterial structural bacteriocins genes in meat borne lactic acid bacteria
No full textThe ability to inhibit the growth of Listeria cells and the presence of bacteriocin encoding genes was examined in 115 LAB strains isolated from Argentinean vacuum-packaged beef and different traditional fermented sausages. Lactobacillus (L) sakei, Lactobacillus (L) curvatus and Enterococcus (E) faecium showed a great inhibition of all Listeria strains evaluated while Pediococcus (P) acidilactici and Lactobacillus (L) plantarum demonstrated a limited or absent antilisterial activity. Both L. curvatus and L. sakei carried the sppA, sppQ and sapA structural genes, encoding for sakacin P, sakacin Q and curvacin A bacteriocins, respectively. Whilst L. curvatus exhibited a higher occurrence of these genes, L. sakei strains were more effective at inhibiting Listeria (L) strains, Listeria monocytogenes UC8159 and Listeria innocua 7 being the most sensitive to these bacteriocins. Among analyzed E. faecium strains, the wide distribution of entA, entB and entP genes accounted for the high antilisterial activity particularly observed against L. monocytogenes FBUNT. The structural gene plantEF was mostly present in Lactobacillus plantarum strains and no pedA gene was found in P. acidilactici evaluated strains. The antilisterial potential of L. sakei and E. faecium offers great possibilities for the meat industry as biopreservative cultures, although more studies are needed in order to conclude about this issue
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