University of Arkansas

About: University of Arkansas is a education organization based out in Fayetteville, Arkansas, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 17225 authors who have published 33329 publications receiving 941102 citations. The organization is also known as: Arkansas & UA.

Transforming growth factor β contributes to progressive diabetic nephropathy

Abstract: Renal failure is a common and serious complication of longstanding diabetes mellitus. Diabetes is now the most common cause of end-stage renal failure requiring dialysis in the United States, accounting for almost 40% of all new dialysis patients (1). Moreover, the incidence of renal failure caused by diabetes, particularly type II diabetes, is rising dramatically worldwide (2). Compounding the tragedy of the explosive growth in the incidence renal failure caused by diabetes is the grim reality that the survival of patients with renal failure caused by diabetes is much worse than that of patients with renal failure resulting from other causes. In Germany, for example, Koch et al. (3) reported a 5-year survival of only 5% among patients with type II diabetes undergoing dialysis. Fortunately, progress is being made in our understanding of the pathogenesis of diabetic renal disease and in our ability to delay, or even prevent, this devastating complication. Two studies appearing in this issue of PNAS (4, 5) are illustrative of this progress. Diabetic nephropathy refers to a characteristic set of structural and functional kidney abnormalities that occur in patients with diabetes. Although best described in patients with type I diabetes (6), similar findings are now known to occur in the more common type II diabetic patient (7). Structural abnormalities include hypertrophy of the kidney, an increase in the thickness of glomerular basement membranes, accumulation of extracellular matrix components in the glomerulus (nodular and diffuse glomerulosclerosis), tubular atrophy, and interstitial fibrosis (6, 7). Functional alterations include an early increase in the glomerular filtration rate with intraglomerular hypertension, subsequent proteinuria, systemic hypertension, and eventual loss of renal function (8).

An Investigation of the Dynamic Relationship between Agency Theory and Dividend Policy

Abstract: Agency theory posits that the dividend mechanism provides an incentive for managers to reduce the costs associated with the principal/agent relationship. Distributing resources in the form of cash dividends forces managers to seek outside capital, thus causing them to reduce agency costs as they subject themselves to the scrutiny of the capital marketplace. Under this scenario the optimum level of dividend payout is that which minimizes the agency cost structure relative to the cost of raising needed funds. A test of this theory employing time-series cross-sectional analysis and more direct measures of the agency cost structure shows that these tenets of agency theory may be valid. Managers do appear to adjust the dividend payout in response to the agency cost/transaction cost structure, both through time as well as across firms.

Sibling size and investment in children’s education: an asian instrument

Abstract: This study estimates the trade-off between child quantity and quality by exploiting exogenous variation in fertility under son preferences. Under son preferences, both sibling size and fertility timing are determined depending on the first child’s gender, which is random as long as parents do not abort girls at their first childbearing. For the sample South Korean households, I find strong evidence of unobserved heterogeneity in preferences for child quantity and quality across households. The trade-off is not as strong as observed cross-sectional relationships would suggest. However, even after controlling for unobserved heterogeneity, a greater number of siblings have adverse effects on per-child investment in education, in particular, when fertility is high.

Unprecedented pressure increase in deep magma reservoir triggered by lava‐dome collapse

Abstract: [1] The collapse of the Soufriere Hills Volcano lava dome on Montserrat in July 2003 is the largest such event worldwide in the historical record. Here we report on borehole dilatometer data recording a remarkable and unprecedented rapid (∼600s) pressurisation of a magma chamber, triggered by this surface collapse. The chamber expansion is indicated by an expansive offset at the near dilatometer sites coupled with contraction at the far site. By analyzing the strain data and using added constraints from experimental petrology and long-term edifice deformation from GPS geodesy, we prefer a source centered at approximately 6 km depth below the crater for an oblate spheroid with overpressure increase of order 1 MPa and average radius ∼1 km. Pressurisation is attributed to growth of 1–3% of gas bubbles in supersaturated magma, triggered by the dynamics of surface unloading. Recent simulations demonstrate that pressure recovery from bubble growth can exceed initial pressure drop by nearly an order of magnitude.

Nitrogen isotope composition of tomato (Lycopersicon esculentum Mill. cv. T‐5) grown under ammonium or nitrate nutrition

Abstract: Studies that quantify plant δ15N often assume that fractionation during nitrogen uptake and intra-plant variation in δ15N are minimal. We tested both assumptions by growing tomato (Lycopersicon esculetum Mill. cv. T-5) at NH4+ or NO−3 concentrations typical of those found in the soil. Fractionation did not occur with uptake; whole-plant δ15N was not significantly different from source δ15 N for plants grown on either nitrogen form. No intra-plant variation in δ15N was observed for plants grown with NH+4. In contrast. δ15N of leaves was as much as 5.8% greater than that of roots for plants grown with NO−3. The contrasting patterns of intra-plant variation are probably caused by different assimilation patterns. NH+4 is assimilated immediately in the root, so organic nitrogen in the shoot and root is the product of a single assimilation event. NO−3 assimilation can occur in shoots and roots. Fractionation during assimilation caused the δ15N of NO−3 to become enriched relative to organic nitrogen; the δ15N of NO−3 was 11.1 and 12.9% greater than the δ15N of organic nitrogen in leaves and roots, respectively. Leaf δ15N may therefore be greater than that of roots because the NO−3 available for assimilation in leaves originates from a NO−3 pool that was previously exposed to nitrate assimilation in the root.