Loss of stem cell regenerative capacity within aged niches.

This work uncovers novel mechanisms of aging within stem cell niches that are evolutionarily conserved between mice and humans and affect both embryonic and adult stem cells. Specifically, we have examined the effects of aged muscle and systemic niches on key molecular identifiers of regenerative potential of human embryonic stem cells (hESCs) and post-natal muscle stem cells (satellite cells). Our results reveal that aged differentiated niches dominantly inhibit the expression of Oct4 in hESCs and Myf-5 in activated satellite cells, and reduce proliferation and myogenic differentiation of both embryonic and tissue-specific adult stem cells (ASCs). Therefore, despite their general neoorganogenesis potential, the ability of hESCs, and the more differentiated myogenic ASCs to contribute to tissue repair in the old will be greatly restricted due to the conserved inhibitory influence of aged differentiated niches. Significantly, this work establishes that hESC-derived factors enhance the regenerative potential of both young and, importantly, aged muscle stem cells in vitro and in vivo; thus, suggesting that the regenerative outcome of stem cell-based replacement therapies will be determined by a balance between negative influences of aged tissues on transplanted cells and positive effects of embryonic cells on the endogenous regenerative capacity. Comprehensively, this work points toward novel venues for in situ restoration of tissue repair in the old and identifies critical determinants of successful cell-replacement therapies for aged degenerating organs

On the Gauss map of embedded minimal tubes

A surface is called a tube if its level-sets with respect to some coordinate function (the axis of the surface) are compact. Any tube of zero mean curvature has an invariant, the so-called flow vector. We study how the geometry of the Gaussian image of a higher-dimensional minimal tube M is controlled by the angle alpha(M) between the axis and the flow vector of M. We prove that the diameter of the Gauss image of M is at least 2alpha(M). As a consequence we derive an estimate on the length of a two-dimensional minimal tube M in terms of alpha(\M) and the total Gaussian curvature of M

Systemic Problems: A perspective on stem cell aging and rejuvenation.

This review provides balanced analysis of the advances in systemic regulation of young and old tissue stem cells and suggests strategies for accelerating development of therapies to broadly combat age-related tissue degenerative pathologies. Many highlighted recent reports on systemic tissue rejuvenation combine parabiosis with a silver bullet putatively responsible for the positive effects. Attempts to unify these papers reflect the excitement about this experimental approach and add value in reproducing previous work. At the same time, defined molecular approaches, which are beyond parabiosis for the rejuvenation of multiple old organs represent progress toward attenuating or even reversing human tissue aging

Correlation Between Intensity and Recovery in Credit Risk Models

We start by presenting a reduced-form multiple default type of model and derive abstract results on the influence of a state variable X on credit spreads, when both the intensity and the loss quota distribution are driven by X. The aim is to apply the results to a concrete real life situation, namely, to the influence of macroeconomic risks on credit spreads term structures. There has been increasing support in the empirical literature that both the probability of default (PD) and the loss given default (LGD) are correlated and driven by macroeconomic variables. Paradoxically, there has been very little effort from the theoretical literature to develop credit risk models that would include this possibility. A possible justification has to do with the increase in complexity this leads to, even for the "treatable" default intensity models. The goal of this paper is to develop the theoretical framework needed to handle this situation and, through numerical simulation, understand the impact on credit risk term structures of the macroeconomic risks. In the proposed model the state of the economy is modeled trough the dynamics of a market index, that enters directly on the functional form of both the intensity of default and the distribution of the loss quota given default. Given this setup, we are able to make periods of economic depression, periods of higher default intensity as well as periods where low recovery is more likely, producing a business cycle effect. Furthermore, we allow for the possibility of an index volatility that depends negatively on the index level and show that, when we include this realistic feature, the impacts on the credit spread term structure are emphasized.Credit risk; sistematic risk; intensity models; recovery; credit spreads

Approaching the losses caused by imperfect short-term financing at the Russian farms

This study investigates whether an insufficient short-term financing causes losses for Russian agricultural farm and what is their upper boundary. The modified Bayesian formalism provides a workaround for scarce and in-complete data in our data set. This formalism is incorporated into the objective function of an optimisation model so that this function expresses the empirical dependence of profit on cash flow and debts. The model seeks for the optimal quarterly cash flow distribution within a year. Empirical application employs the data from 60 quarterly reports of six agricultural enterprises in the Moscow Region in 1995-1998. The losses per total farm expenses vary from 2.2 to 42.6% depending on a farm and a year. In more than a half of cases they are greater than 10%. The opportunities to improve farm financial performance can be revealed from individual changes in the quarterly cash flow distribution.imperfect short-term financing losses Russian agriculture Bayesian scarce missed data

Some Characteristics of the New Enterprises and the Profile of New Entrepreneurs

The implementation of a scientific management generating performances that can lead the sector of SMEs to the requests of the Lisbon Strategy, cannot be completed without the existence of well-trained entrepreneurs, capable to improve their skills in modern management, thus leading to competitive results in a highly competitive market. The analysis performed by this research allows us to formulate, synthetically, strengths and weaknesses in the entrepreneurial evolution during the 1995-2007period.new enterprise; entrepreneur; new enterprise foundation rate; the entrepreneur’s socio-professional profile; the entrepreneur’s level of education.

Possible errors in establishing the sample dimensions of survey investigations

Starting from the „rough” use of 1,500-1,800 subject samples in field researches with populations of the dimensions of a medium town, a capital or an entire country, which generates doubts and possible questions related to the representativeness of the investigated samples as well as to the conclusions of these researches, we developed the reconstruction of the necessary interactions in determining the sample volume, and also identified some inadvertencies. Some improvements solutions were also recommended.confidence interval, distribution laws, probable error, representativeness, sample volume.

Nanotube-based scanning rotational microscope

A scheme of the scanning rotational microscope is designed. This scheme is based on using carbon nanotubes simultaneously as a probe tip and as a bolt/nut pair which converts translational displacements of two piezo actuators into pure rotation of the probe tip. First-principles calculations of the interaction energy between movable and rotational parts of the microscope confirms the capability for its operation. The scanning rotational microscope with a chemically functionalized nanotube-based tip can be used to study how the interaction between individual molecules or a molecule and a surface depends on their relative orientation.Comment: 4 pages, 3 figure