The changes in chemical composition during development of the bovine nuchal ligament

Whole bovine nuchal ligaments, or portions thereof (in the case of commercially valuable animals), were obtained from 45 animals (28 fetal and 17 postnatal) ranging in age from 110 days of gestation to 10 yr. Insoluble elastin was quantitatively prepared from the fresh ligaments by extraction with hot alkali and by a combination of multiple extractions with alkaline buffer and then repeated autoclaving. When adult samples were examined, the yields of insoluble residue by these two methods were very similar, but with young fetal samples the second method gave significantly higher values, because of incomplete purification of the elastin residue. The changes in the concentration of collagen, alkali-insoluble elastin, and DNA have been examined. DNA concentration, and, thus, cell population density, fell progressively during the fetal period of development, to reach a steady value soon after birth. Collagen appeared in appreciable quantities before elastin, but its concentration was rapidly halved at about the time of birth. Insoluble elastin concentration was low until the end of the 7th fetal month, at which time it began to rise rapidly. The rate of increase in elastin concentration remained high throughout the next 10–12 wk, by which time the adult value had been reached. Quantitative studies, on the basis of the whole ligament, showed that the total cell content rises to a maximum at birth, but falls soon after to a level about half that at birth. Total collagen production and elastin deposition continue at a steady, maximal rate over the interval from 235 days of gestation to the end of the 1st postnatal month. It is concluded that the immediate postnatal period would be the most favorable phase in which to attempt the isolation of the soluble precursor elastin

Venturi Flowmeter Performance Installed Downstream of the Branch of a Tee Junction

The purpose of this research was to evaluate the influence of a tee junction on flow rate measurement of a Venturi flowmeter installed downstream of the branch of a tee. Accuracy in flow measurement is important to organizations where miscalculated flow rates can add up to be millions of dollars in either lost revenue, overcharges to the client, or improper system operation. This research used Computational Fluid Dynamics (CFD) to determine ratios by which the manufacturer’s straight-line calibrated Cd (discharge coefficient) can be adjusted to improve the accuracy of the flow measurement when the Venturi is installed on the branch of a tee. Physical laboratory data was obtained for a 6-in. Venturi in a straight-line, followed by installation on the branch of a tee at zero pipe diameters and five pipe diameters downstream. CFD modeling was then used. Results show the flow rate measurement was less affected when all flow was entering the tee branch and more affected when less flow was entering the tee branch. While physical laboratory calibration is still the best way to get the most accurate flow measurement performance for a Venturi, using CFD to create contour plots of Cd ratios to adjust manufacturer given Cds over a range of Reynolds numbers and flow splits entering the tee could be an option

Trident: A three-pronged galaxy survey. I. Lyman alpha emitting galaxies at z~2 in GOODS North

Context. Lyman alpha emitting galaxies (LAEs) are used to probe the distant universe and are therefore important for galaxy evolution studies and for providing clues to the nature of the epoch of reionization, but the exact circumstances under which Lyman alpha escapes a galaxy are still not fully understood. Aims. The Trident project is designed to simultaneously examine Lyman alpha, H-alpha and Lyman Continuum emission from galaxies at redshift z~2, thus linking together these three aspects of ionising radiation in galaxies. In this paper, we outline the strategy of this project and examine the properties of LAEs in the GOODS North field. Methods. We performed a narrowband LAE survey in GOODS North using existing and two custom made filters at the Nordic Optical Telescope with MOSCA. We use complementary broad band archival data in the field to make a careful candidate selection and perform optical to near-IR SED fitting. We also estimate far-infrared luminosities by matching our candidates to detections in Spitzer/MIPS 24{\mu}m and Herschel/PACS catalogs. Results. We find a total of 25 LAE candidates, probing mainly the bright end of the LAE luminosity function with L_Ly {\alpha} ~ 1-15e42 erg/s. They display a range of masses of ~0.5-50e9 M_solar, and average ages from a few tens of Myr to 1 Gyr when assuming a constant star formation history. The majority of our candidates also show signs of recent elevated star formation. Three candidates have counterparts in the GOODS-Herschel far-IR catalogue, with luminosities consistent with ultra-luminous infrared galaxies (ULIRGs). Conclusions. The wide range of parameters derived from our SED fitting, as well as part of our sample being detected as ULIRGs, seems to indicate that at these Lyman alpha luminosities, LAEs do not necessarily have to be young dwarfs, and that a lack of dust is not required for Lyman alpha to escape.Comment: 16 pages, 12 figures. Accepted version for publication in A&

CARICOM Bilateral Trade: A Preliminary Analysis Using the Gravity Model

This paper investigates the determinants of intra-CARICOM bilateral trade and the CARICOM member's trade with the North American and European countries using the gravity model. Seventeen annual cross-sections are estimated for the period 1980 through 1996. Overall, the empirical results indicate that the gravity model has considerable potential to explain intra-CARICOM bilateral trade as well as trade between CARICOM members and non-members. The evidence suggests that both the importer's GDP per capita and the exporter's GDP per capita exert strong positive effects on CARICOM trade levels. Since these effects are found to be statistically the same, we conclude that the gravity model is symmetric with respect to GDP per capita. Further, sharing a common language, colonial ties, or membership in the CARICOM all significantly contribute to larger volumes of bilateral trade, while geographic distance has the opposite effect. Both the exporting and the importing countries' populations have a positive effect on trade levels, indicating that larger economies have a wider production base and thus export and import more than would smaller economies.Caribbean economies, CARICOM, FTAA, gravity model, regional integration, International Relations/Trade,

Multiple Loop Self-Triggered Model Predictive Control for Network Scheduling and Control

We present an algorithm for controlling and scheduling multiple linear time-invariant processes on a shared bandwidth limited communication network using adaptive sampling intervals. The controller is centralized and computes at every sampling instant not only the new control command for a process, but also decides the time interval to wait until taking the next sample. The approach relies on model predictive control ideas, where the cost function penalizes the state and control effort as well as the time interval until the next sample is taken. The latter is introduced in order to generate an adaptive sampling scheme for the overall system such that the sampling time increases as the norm of the system state goes to zero. The paper presents a method for synthesizing such a predictive controller and gives explicit sufficient conditions for when it is stabilizing. Further explicit conditions are given which guarantee conflict free transmissions on the network. It is shown that the optimization problem may be solved off-line and that the controller can be implemented as a lookup table of state feedback gains. Simulation studies which compare the proposed algorithm to periodic sampling illustrate potential performance gains.Comment: Accepted for publication in IEEE Transactions on Control Systems Technolog

Universal Probability Distribution Function for Bursty Transport in Plasma Turbulence

Bursty transport phenomena associated with convective motion present universal statistical characteristics among different physical systems. In this letter, a stochastic univariate model and the associated probability distribution function for the description of bursty transport in plasma turbulence is presented. The proposed stochastic process recovers the universal distribution of density fluctuations observed in plasma edge of several magnetic confinement devices and the remarkable scaling between their skewness $S$ and kurtosis $K$. Similar statistical characteristics of variabilities have been also observed in other physical systems that are characterized by convection such as the X-ray fluctuations emitted by the Cygnus X-1 accretion disc plasmas and the sea surface temperature fluctuations.Comment: 10 pages, 5 figure

The role of octreotide in preventing complications after pancreatoduodenectomy for cancer

Background Although the mortality rate of pancreatoduodenectomy has fallen sharply over the last two decades, there is still a risk of serious complications resulting from leakage at the site of anastomosis between the pancreatic remnant and the gastrointestinal tract. Numerous techniques have been described to minimise the risk of these anastomotic leaks, but they can be difficult to avoid if the distal pancreas is unobstructed with a soft parenchyma and a non-dilated duct. The risk of leakage is largely dependent upon the presence of activated pancreatic enzymes, and this fact provides a rationale for the perioperative use of the somatostatin analogue octreotide to inhibit exocrine pancreatic secretion. Discussion Six prospective randomised controlled trials have been published on the use of prophylactic octreotide in pancreatic surgery, five from Europe and one from the USA. The five (multicentre) European studies have consistently shown that octreotide reduces the postoperative complication rate, but the American study does not confirm this benefit. Methodological differences may explain the discrepancy, notably the fact that most of the US patients had received preoperative chemoradiation which is likely to have reduced enzyme secretion. A meta-analysis of four of these studies showed that octreotide lowered the rate of postoperative complications from 37 to 21%, chiefly by reducing the risk of pancreatic fistula. Prophylactic octreotide therapy is cost effective and should be used at least in patients with normal pancreatic parenchyma

Neutral gas in Lyman-alpha emitting galaxies Haro 11 and ESO 338-IG04 measured through sodium absorption

Context. The Lyman alpha emission line of galaxies is an important tool for finding galaxies at high redshift, and thus probe the structure of the early universe. However, the resonance nature of the line and its sensitivity to dust and neutral gas is still not fully understood. Aims. We present measurements of the velocity, covering fraction and optical depth of neutral gas in front of two well known local blue compact galaxies that show Lyman alpha in emission: ESO 338-IG 04 and Haro 11. We thus test observationally the hypothesis that Lyman alpha can escape through neutral gas by being Doppler shifted out of resonance. Methods. We present integral field spectroscopy from the GIRAFFE/Argus spectrograph at VLT/FLAMES in Paranal, Chile. The excellent wavelength resolution allows us to accurately measure the velocity of the ionized and neutral gas through the H-alpha emission and Na D absorption, which traces the ionized medium and cold interstellar gas, respectively. We also present independent measurements with the VLT/X-shooter spectrograph which confirm our results. Results. For ESO 338-IG04, we measure no significant shift of neutral gas. The best fit velocity is -15 (16) km/s. For Haro 11, we see an outflow from knot B at 44 (13) km/s and infalling gas towards knot C with 32 (12) km/s. Based on the relative strength of the Na D absorption lines, we estimate low covering fractions of neutral gas (down to 10%) in all three cases. Conclusions. The Na D absorption likely occurs in dense clumps with higher column densities than where the bulk of the Ly-alpha scattering takes place. Still, we find no strong correlation between outflowing neutral gas and a high Lyman alpha escape fraction. The Lyman alpha photons from these two galaxies are therefore likely escaping due to a low column density and/or covering fraction.Comment: 9 pages, 3 figure