Time scale Hardy-type inequalities with ‘broken’ exponent p

In this paper, some new Hardy-type inequalities involving ?broken? exponents are derived on arbitrary time scales. Our approach uses both convexity and superquadracity arguments, and the results obtained generalize, complement and provide refinements of some known results in literatur

Tubuloglomerular feedback and interstitial pressure in obstructive nephropathy

Tubuloglomerular feedback and interstitial pressure in obstructive nephropathy. The possible role of the tubuloglomerular feedback (TGF) mechanism in the altered glomerular hemodynamics and tubular reabsorption which occur with prolonged (24-hr) ureteral obstruction and the changes in renal interstitial hydrostatic and oncotic pressure which may modulate TGF sensitivity were examined. The proximal tubule stop-flow pressure (PSF) response to increased distal tubular flow rates (TGF activity) was determined in rats with sham operation, 24-hr unilateral ureteral obstruction (UUO), or 24-hr bilateral ureteral obstruction (BUO), both before and for 2 hr after relief of obstruction. Subcapsular hydrostatic pressure, lymph flow and oncotic pressure, clearance and excretory data were measured in the second series of animals. During and after release of UUO, TGF sensitivity was increased, as indicated by the marked decrease in the loop perfusion rate at which 50% of the maximum decrease in PSF occurred (the turning point of TGF activation). Interstitial oncotic pressure but not hydrostatic pressure was significantly increased in UUO kidneys. In BUO rats, the turning point for TGF activation was slightly higher than the controls and the change in PSF with maximum loop perfusion rates was reduced, indicating a blunting of the TGF response before and particularly during postobstructive diuresis after release of BUO. Interstitial hydrostatic and oncotic pressures were both slightly increased resulting in no changes in net interstitial Starling forces. We conclude that enhanced TGF sensitivity after release of prolonged UUO, associated with increased interstitial oncotic pressure, may play a role in preventing postobstructive diuresis, while the blunting of TGF sensitivity after BUO may contribute to this phenomenon.Rétrocontrôle glomérulo-tubulaire et pression interstitielle au cours de la néphropathie obstructive. Le rôle possible du mécanisme de rétrocontrôle glomérulo-tubulaire (TGF) dans l'altération de l'hémadynamique glomérulaire et la réabsorption tubulaire qui se produisent lors d'une obstruction urétérale prolongée (24 heures) et les modifications des pressions hydrostatiques et oncotiques interstitielles rénales qui pourraient moduler la sensibilité TGF ont été étudiés. La réponse de pression en flux interrompu (PSF) du tubule proximal à une augmentation des débits tubulaires distaux a été déterminée chez des rats ayant subi un simulacre d'intervention, lors d'une obstruction urétérale unilatérale de 24 heures (UUO) ou lors d'une obstruction urétérale bilatérale de 24 heures (BUO), avant et 2 heures après la levée de l'obstruction. La pression hydrostatique sous-capsulaire, le flux et la pression oncotique lymphatiques, les paramètres de clearance et d'excrétion ont été mesurés chez une deuxième série d'animaux. Pendant et après levée de l'UUO, la sensibilité TGF a augmenté, comme le montrait la diminution marquée du débit de perfusion de l'anse pour lequel 50% de la chute maximale de PSF se produisait (le point d'inflexion de l'activation TGF). La pression oncotique mais non la pression hydrostatique interstitielle était significativement accrue dans les reins UUO. Chez les rats BUO, le point d'inflexion de l'activation TGF était légèrement plus élevé que chez les contrôles, et la modification de PSF aux débits de perfusion de l'anse maxima était diminuée, indiquant une altération de la réponse TGF avant et surtout pendant la diurèse post-obstructive, après levée de la BUO. Les pressions interstitielles hydrostatiques et oncotiques légèrement augmentées, d'où l'absence de modification des forces de Starling interstitielles nettes. Nous concluons que l'augmentation de la sensibilité TGF après levée d'une UUO prolongée associée à une élévation de la pression oncotique interstitielle, pourrait jouer un rôle pour prévenir la diurèse post-obstructive, alors que l'altération de la sensibilité TGF après BUO pourrait contribuer à ce phénomène

Brownian motion with dry friction: Fokker-Planck approach

We solve a Langevin equation, first studied by de Gennes, in which there is a solid-solid or dry friction force acting on a Brownian particle in addition to the viscous friction usually considered in the study of Brownian motion. We obtain both the time-dependent propagator of this equation and the velocity correlation function by solving the associated time-dependent Fokker-Planck equation. Exact results are found for the case where only dry friction acts on the particle. For the case where both dry and viscous friction forces are present, series representations of the propagator and correlation function are obtained in terms of parabolic cylinder functions. Similar series representations are also obtained for the case where an external constant force is added to the Langevin equation.Comment: 18 pages, 13 figures (in color

Some sharp inequalities for integral operators with homogeneous kernel

One goal of this paper is to show that a big number of inequalities for functions in L-p(R+), p >= 1, proved from time to time in journal publications are particular cases of some known general results for integral operators with homogeneous kernels including, in particular, the statements on sharp constants. Some new results are also included, e.g. the similar general equivalence result is proved and applied for 0 < p < 1. Some useful new variants of these results are pointed out and a number of known and new Hardy-Hilbert type inequalities are derived. Moreover, a new Polya-Knopp (geometric mean) inequality is derived and applied. The constants in all inequalities in this paper are sharp

Model of the complex of Parathyroid hormone-2 receptor and Tuberoinfundibular peptide of 39 residues

<p>Abstract</p> <p>Background</p> <p>We aim to propose interactions between the parathyroid hormone-2 receptor (PTH2R) and its ligand the tuberoinfundibular peptide of 39 residues (TIP39) by constructing a homology model of their complex. The two related peptides parathyroid hormone (PTH) and parathyroid hormone related protein (PTHrP) are compared with the complex to examine their interactions.</p> <p>Findings</p> <p>In the model, the hydrophobic N-terminus of TIP39 is buried in a hydrophobic part of the central cavity between helices 3 and 7. Comparison of the peptide sequences indicates that the main discriminator between the agonistic peptides TIP39 and PTH and the inactive PTHrP is a tryptophan-phenylalanine replacement. The model indicates that the smaller phenylalanine in PTHrP does not completely occupy the binding site of the larger tryptophan residue in the other peptides. As only TIP39 causes internalisation of the receptor and the primary difference being an aspartic acid in position 7 of TIP39 that interacts with histidine 396 in the receptor, versus isoleucine/histidine residues in the related hormones, this might be a trigger interaction for the events that cause internalisation.</p> <p>Conclusions</p> <p>A model is constructed for the complex and a trigger interaction for full agonistic activation between aspartic acid 7 of TIP39 and histidine 396 in the receptor is proposed.</p

The FAIR Guiding Principles for scientific data management and stewardship

There is an urgent need to improve the infrastructure supporting the reuse of scholarly data. A diverse set of stakeholders—representing academia, industry, funding agencies, and scholarly publishers—have come together to design and jointly endorse a concise and measureable set of principles that we refer to as the FAIR Data Principles. The intent is that these may act as a guideline for those wishing to enhance the reusability of their data holdings. Distinct from peer initiatives that focus on the human scholar, the FAIR Principles put specific emphasis on enhancing the ability of machines to automatically find and use the data, in addition to supporting its reuse by individuals. This Comment is the first formal publication of the FAIR Principles, and includes the rationale behind them, and some exemplar implementations in the community

Predicting bee community responses to land-use changes: Effects of geographic and taxonomic biases

Land-use change and intensification threaten bee populations worldwide, imperilling pollination services. Global models are needed to better characterise, project, and mitigate bees' responses to these human impacts. The available data are, however, geographically and taxonomically unrepresentative; most data are from North America and Western Europe, overrepresenting bumblebees and raising concerns that model results may not be generalizable to other regions and taxa. To assess whether the geographic and taxonomic biases of data could undermine effectiveness of models for conservation policy, we have collated from the published literature a global dataset of bee diversity at sites facing land-use change and intensification, and assess whether bee responses to these pressures vary across 11 regions (Western, Northern, Eastern and Southern Europe; North, Central and South America; Australia and New Zealand; South East Asia; Middle and Southern Africa) and between bumblebees and other bees. Our analyses highlight strong regionally-based responses of total abundance, species richness and Simpson's diversity to land use, caused by variation in the sensitivity of species and potentially in the nature of threats. These results suggest that global extrapolation of models based on geographically and taxonomically restricted data may underestimate the true uncertainty, increasing the risk of ecological surprises