Diabetes Alters Diurnal Rhythm of Electroretinogram in db/db Mice

Diabetic retinopathy (DR) is the most common complications of diabetes and a leading cause of blindness in the United States. The retinal neuronal changes precede the vascular dysfunction observed in DR. The electroretinogram (ERG) determines the electrical activity of retinal neural and non-neuronal cells. The retinal ERG amplitude is reduced gradually on the progression of DR to a more severe form. Circadian rhythms play an important role in the physiological function of the body. While ERG is known to exhibit a diurnal rhythm, it is not known whether a progressive increase in the duration of diabetes affects the physiological rhythm of retinal ERG. To study this, we determined the ERG rhythm of db/db mice, an animal model of type 2 diabetes at 2, 4, and 6 months of diabetes under a regular light-dark cycle and constant dark. Our studies demonstrate that the diurnal rhythm of ERG amplitude for retinal a-wave and b-wave was altered in diabetes. The implicit time was increased in db/db mice while the oscillatory potential was reduced. Moreover, there was a progressive decline in an intrinsic rhythm of ERG upon an increase in the duration of diabetes. In conclusion, our studies provide novel insights into the pathogenic mechanism of DR by showing an altered circadian rhythm of the ERG

Simple model of bouncing ball dynamics: displacement of the table assumed as quadratic function of time

Nonlinear dynamics of a bouncing ball moving in gravitational field and colliding with a moving limiter is considered. Displacement of the limiter is a quadratic function of time. Several dynamical modes, such as fixed points, 2 - cycles and chaotic bands are studied analytically and numerically. It is shown that chaotic bands appear due to homoclinic structures created from unstable 2 - cycles in a corner-type bifurcation.Comment: 11 pages, 6 figure

School Dropouts and Conditional Cash Transfers: Evidence from a Randomized Controlled Trial in Rural China’s Junior High Schools.

Recent anecdotal reports suggest that dropout rates may be higher and actually increasing over time in poor rural areas. There are many reasons not to be surprised that there is a dropout problem, given the fact that China has a high level of poverty among the rural population, a highly competitive education system and rapidly increasing wages for unskilled workers. The overall goal of this study is to examine if there is a dropout problem in rural China and to explore the effectiveness that a Conditional Cash Transfer (CCT) program could have on dropouts (and mechanism by which the CCT might affect drop outs). To meet this objective, we conducted a randomized controlled trial (RCT) of a CCT using a sample of 300 junior high school students in a nationally-designated poor county in Northwest China. Using our data, we found that the annual dropout rate in the study county was high, about 7%. We find, however, that a CCT program reduces drop outs by 60%; the dropout rate is 13.3% in the control group and 5.3 % in the treatment group. The program is most effective in the case of girls, younger students and the poorest performing students.

School dropouts and conditional cash transfers: evidence from a randomized controlled trial in rural China's junior high schools.

Recent anecdotal reports suggest that dropout rates may be higher and actually increasing over time in poor rural areas. There are many reasons not to be surprised that there is a dropout problem, given the fact that China has a high level of poverty among the rural population, a highly competitive education system and rapidly increasing wages for unskilled workers. The overall goal of this study is to examine if there is a dropout problem in rural China and to explore the effectiveness that a Conditional Cash Transfer (CCT) program could have on dropouts (and mechanism by which the CCT might affect drop outs). To meet this objective, we conducted a randomized controlled trial (RCT) of a CCT using a sample of 300 junior high school students in a nationally-designated poor county in Northwest China. Using our data, we found that the annual dropout rate in the study county was high, about 7.0%. We find, however, that a CCT program reduces drop outs by 60%; the dropout rate is 13.3% in the control group and 5.3 % in the treatment group. The program is most effective in the case of girls, younger students and the poorest performing students.

Investor sentiment, limited arbitrage and the cash holding effect

We examine the investor sentiment and limits-to-arbitrage explanations for the positive cross-sectional relation between cash holdings and future stock returns. Consistent with the investor sentiment hypothesis, we find that the cash holding effect is significant when sentiment is low, and it is insignificant when sentiment is high. In addition, the cash holding effect is strong among stocks with high transaction costs, high short selling costs, and large idiosyncratic volatility, indicating that arbitrage on the cash holding effect is costly and risky. In line with the limits-to-arbitrage hypothesis, high costs and risk prevent rational investors from exploiting the cash holding effect

Simple model of bouncing ball dynamics. Displacement of the limiter assumed as a cubic function of time

Nonlinear dynamics of a bouncing ball moving vertically in a gravitational field and colliding with a moving limiter is considered and the Poincare map, describing evolution from an impact to the next impact, is described. Displacement of the limiter is assumed as periodic, cubic function of time. Due to simplicity of this function analytical computations are possible. Several dynamical modes, such as fixed points, 2 - cycles and chaotic bands are studied analytically and numerically. It is shown that chaotic bands are created from fixed points after first period doubling in a corner-type bifurcation. Equation for the time of the next impact is solved exactly for the case of two subsequent impacts occurring in the same period of limiter's motion making analysis of chattering possible.Comment: 8 pages, 1 figure, presented at the DSTA 2011 conference, Lodz, Polan

Rising phenomena and the multi-sliding bifurcation in a two-degree of freedom impact oscillator

We consider the rising phenomena which occur in sticking solutions of a two-degree of freedom impact oscillator. We describe a mathematical formulation for modelling such a systems during both free flight and during sticking solutions for each of the masses in the system. Simulations of the sticking solutions are carried out, and rising events are observed when the forcing frequency parameter is varied. We show how the time of sticking reduces significantly as a rising event occurs. Then within the sticking region we show how rising is qualitatively similar to the multi-sliding bifurcation for sliding orbits

New Method for Dynamical Fermions and Chiral-Symmetry Breaking

The reasons for the feasibility of the Microcanonical Fermionic Average ($MFA$) approach to lattice gauge theory with dynamical fermions are discussed. We then present a new exact algorithm, which is free from systematic errors and convergent even in the chiral limit.Comment: 3 pages, DFTUZ 93/20, to appear in the Proceedings of Lattice 93, Dalla