Renal handling of beta-2-microglobulin in the human neonate

Renal handling of beta-2-microglobulin in the human neonate. Glomerulotubular balance for beta-2-microglobulin (β2M) in the human kidney has been reported to occur after 34 weeks conceptional age (CA), and fractional tubular reabsorption of β2M (Tβ2M) has been suggested as a useful index of renal tubular maturation. To confirm and extend these observations to include still less mature infants, renal handling of β2M was investigated during timed-urine collections with corresponding blood samples obtained from 57 infants with CA of 26 to 43 weeks and postnatal ages (PNA) 0.2 to 12 days (study 1); 18 infants were studied a second time 5 to 17 days later (study 2). GFR was measured by endogenous creatinine clearance (CCr). Tβ2M and fractional reabsorption of sodium (TNa) were calculated. Results indicated that while both increased with CA, Tβ2M (r = -0.69, P < 0.0001) and TNa (r = -0.79, P < 0.0001) varied inversely with fractional urine flow rate (V/CCr). Moreover, an inverse relationship between changes in Tβ2M and V/Ccr was observed in the same infant between study 1 and study 2 (r = -0.47, P < 0.05). These data suggest that the renal handling of β2M in the human neonate is influenced by physiologic variables that are independent of CA, and thus Tβ2M may not be a reliable predictor of renal tubular maturation in the human neonate.Elimination rénale de la béta-2-microglobuline chez le nouveau-né humain. Il a été rapporté que la balance glomérulo-tubulaire pour la béta-2-microglobuline (β2M) dans le rein humain apparait au bout de 34 semaines d'âge conceptionnel (CA), et il a été suggéré que la réabsorption tubulaire fractionnelle de la β2M (Tβ2M) est un index utile de maturation tubulaire rénale. Afin de confirmer et d'étendre ces observations en incluant des nouveau-nés encore moins matures, l'élimination rénale de β2M a été étudiée pendant des recueils d'urines minutés, avec les échantillons sanguins correspondants chez 57 nouveau-nés avec un CA de 26 à 43 semaines et des âges postnataux (PNA) de 0.2 à 12 jours (étude 1); 18 nouveau-nés ont été étudiés dans un second temps, 5 à 17 jours plus tard (étude 2). Le débit de filtration glomérulaire a été mesuré par la clearance de la créatinine endogène (CCr). Tβ2M et la réabsorption fractionnelle du sodium (TNa) ont été calculées. Les résultats ont montré que tout en augmentant avec CA, Tβ2M (r = -0.69, P < 0.0001) et TNa (r = -0.79, P < 0.0001) variaient inversement avec le débit fractionnel urinaire (V/CCr). En outre, une relation inverse entre les modifications de Tβ2M et les modifications de V/CCr a été observée chez le même nouveau-né entre l'étude 1 et l'étude 2 (r = -0.47, P < 0.05). Ces données suggèrent que l'élimination rénale de la β2M chez le nouveau-né humain est influencée par des variables physiologiques qui sont indépendantes de CA, et donc Tβ2M pourrait ne pas être un index prédictif fiable de la maturation tubulaire rénale chez le nouveau-né humain

The Price Impact of Order Book Events

We study the price impact of order book events - limit orders, market orders and cancelations - using the NYSE TAQ data for 50 U.S. stocks. We show that, over short time intervals, price changes are mainly driven by the order flow imbalance, defined as the imbalance between supply and demand at the best bid and ask prices. Our study reveals a linear relation between order flow imbalance and price changes, with a slope inversely proportional to the market depth. These results are shown to be robust to seasonality effects, and stable across time scales and across stocks. We argue that this linear price impact model, together with a scaling argument, implies the empirically observed "square-root" relation between price changes and trading volume. However, the relation between price changes and trade volume is found to be noisy and less robust than the one based on order flow imbalance

Value at Risk models with long memory features and their economic performance

We study alternative dynamics for Value at Risk (VaR) that incorporate a slow moving component and information on recent aggregate returns in established quantile (auto) regression models. These models are compared on their economic performance, and also on metrics of first-order importance such as violation ratios. By better economic performance, we mean that changes in the VaR forecasts should have a lower variance to reduce transaction costs and should lead to lower exceedance sizes without raising the average level of the VaR. We find that, in combination with a targeted estimation strategy, our proposed models lead to improved performance in both statistical and economic terms

Coherent states, constraint classes, and area operators in the new spin-foam models

Recently, two new spin-foam models have appeared in the literature, both motivated by a desire to modify the Barrett-Crane model in such a way that the imposition of certain second class constraints, called cross-simplicity constraints, are weakened. We refer to these two models as the FKLS model, and the flipped model. Both of these models are based on a reformulation of the cross-simplicity constraints. This paper has two main parts. First, we clarify the structure of the reformulated cross-simplicity constraints and the nature of their quantum imposition in the new models. In particular we show that in the FKLS model, quantum cross-simplicity implies no restriction on states. The deeper reason for this is that, with the symplectic structure relevant for FKLS, the reformulated cross-simplicity constraints, in a certain relevant sense, are now \emph{first class}, and this causes the coherent state method of imposing the constraints, key in the FKLS model, to fail to give any restriction on states. Nevertheless, the cross-simplicity can still be seen as implemented via suppression of intertwiner degrees of freedom in the dynamical propagation. In the second part of the paper, we investigate area spectra in the models. The results of these two investigations will highlight how, in the flipped model, the Hilbert space of states, as well as the spectra of area operators exactly match those of loop quantum gravity, whereas in the FKLS (and Barrett-Crane) models, the boundary Hilbert spaces and area spectra are different.Comment: 21 pages; statements about gamma limits made more precise, and minor phrasing change

Entropy of generic quantum isolated horizons

We review our recent proposal of a method to extend the quantization of spherically symmetric isolated horizons, a seminal result of loop quantum gravity, to a phase space containing horizons of arbitrary geometry. Although the details of the quantization remain formally unchanged, the physical interpretation of the results can be quite different. We highlight several such differences, with particular emphasis on the physical interpretation of black hole entropy in loop quantum gravity.Comment: 4 pages, contribution to loops '11 conference proceedings; 2 references added, a sentence remove

To Lend A Hand: A History and Analysis of the Lend-A-Hand Center in the Stinking Creek Community of Knox County, Kentucky

This thesis documents the history of the Lend-A-Hand Center, Inc., a nonprofit community service provider in Knox County, Kentucky, that has served the Stinking Creek watershed since 1958. The brainchild and lifework oftwo women from the North, Irma Gall and Peggy Kemner, the Center has had a significant impact on the Stinking Creek community. With an original mission "to lend a hand," the Center provided a wide variety of services-ranging from medical to agricultural and beyond-including Sunday school services, volunteer opportunities, and programs for both children and adults. The Center has made an important contribution to the discourse on the history of nonprofits in eastern Kentucky. The rich history of the Center demonstrates how service providers can impact local communities. The exemplary work ofthe Center and its impact on the local community, the influence of a particular philosophy about poverty and uplift work, the web of affiliations that affected the work ofthe Center, the central role of women and women's empowerment in the history of the organization, and the great potential for the future of the Center and organizations like it in Appalachia are explored through this analysis

Excitation functions for (p,x) reactions of niobium in the energy range of Ep_{\text{p}} = 40-90 MeV

A stack of thin Nb foils was irradiated with the 100 MeV proton beam at Los Alamos National Laboratory's Isotope Production Facility, to investigate the $^{93}$Nb(p,4n)$^{90}$Mo nuclear reaction as a monitor for intermediate energy proton experiments and to benchmark state-of-the-art reaction model codes. A set of 38 measured cross sections for $^{\text{nat}}$Nb(p,x) and $^{\text{nat}}$Cu(p,x) reactions between 40-90 MeV, as well as 5 independent measurements of isomer branching ratios, are reported. These are useful in medical and basic science radionuclide productions at intermediate energies. The $^{\text{nat}}$Cu(p,x)$^{56}$Co, $^{\text{nat}}$Cu(p,x)$^{62}$Zn, and $^{\text{nat}}$Cu(p,x)$^{65}$Zn reactions were used to determine proton fluence, and all activities were quantified using HPGe spectrometry. Variance minimization techniques were employed to reduce systematic uncertainties in proton energy and fluence, improving the reliability of these measurements. The measured cross sections are shown to be in excellent agreement with literature values, and have been measured with improved precision compared with previous measurements. This work also reports the first measurement of the $^{\text{nat}}$Nb(p,x)$^{82\text{m}}$Rb reaction, and of the independent cross sections for $^{\text{nat}}$Cu(p,x)$^{52\text{g}}$Mn and $^{\text{nat}}$Nb(p,x)$^{85\text{g}}$Y in the 40-90 MeV region. The effects of $^{\text{nat}}$Si(p,x)$^{22,24}$Na contamination, arising from silicone adhesive in the Kapton tape used to encapsulate the aluminum monitor foils, is also discussed as a cautionary note to future stacked-target cross section measurements. \emph{A priori} predictions of the reaction modeling codes CoH, EMPIRE, and TALYS are compared with experimentally measured values and used to explore the differences between codes for the $^{\text{nat}}$Nb(p,x) and $^{\text{nat}}$Cu(p,x) reactions.Comment: 34 pages, submitted to NIM-