Three-D CFD Analysis of Hydrostatic Bearings

The hydrostatic bearing promises life and speed characteristics currently unachievable with rolling element bearings alone. In order to achieve the speed and life requirements of the next generation of rocket engines, turbopump manufacturers are proposing hydrostatic bearings to be used in place of, or in series with, rolling element bearings. The design of a hydrostatic bearing is dependent on accurate pressure in the bearing. The stiffness and damping of the hydrostatic bearing is very sensitive to the bearing recess pressure ratio. In the conventional approach, usually ad hoc assumptions were made in determining the bearing pressure of this approach is inherently incorrect. In the present paper, a more elaborate approach to obtain bearing pressure is used. The bearing pressure and complete flow features of the bearing are directly computed by solving the complete 3-D Navier Stokes equation. The code used in the present calculation is a modified version of REACT3D code. Several calculations have been performed for the hydrostatic bearing designed and tested at Texas A&M. Good agreement has been obtained between computed and test results. Detailed flow features in the bearing will also be described and discussed

The structure of the UDP-Glc/GlcNAc 4-epimerase from the human pathogen Campylobacter jejuni

Worldwide, the food-born pathogen Campylobacter jejuni is the leading bacterial source of human gastroenteritis. C. jejuni produces a variety of diverse cell-surface carbohydrates that are essential for pathogenicity. A critical component of these oligo- and polysaccharides is the sugar N-acetylgalactosamine (GalNAc). The sole source of this sugar is the epimerization of UDP-N-acetylglucosamine (GlcNAc), a reaction catalyzed by the enzyme UDP-GlcNAc 4-epimerase (Gne). This enzyme is unique among known bacterial epimerases in that it also catalyzes the equivalent reaction with the non-N-acetylated sugars. Understanding how CjGne catalyzes these various interconversions is critical to designing novel inhibitors of this enzyme. Here, to further the mechanistic understanding we present a 2.0Å structure of CjGne with its NAD⁺ co-factor bound. Based on novel features found in the structure we perform a variety of biochemical studies to probe the mechanism and compare these results to another bifunctional epimerase, human GalE. We further show that ebselen, previously identified for inhibition of HsGalE, is active against CjGne, suggesting a route for antibiotic development

Structural Health Monitoring for Bridge Structures using Smart Sensors

Structural health monitoring (SHM) has drawn significant attention in recent decades because of its potential to reduce maintenance costs and increase the reliability of structures. An important class of structures that can potentially benefit from SHM are bridges, many of which are structurally deficient due to lack of adequate maintenance. Through condition assessment of these bridges, an effective plan of maintenance can be determined, offering the possibility to prolong service life, as well as to prevent catastrophic disasters due to sudden collapse. To date, numerous damage detection algorithms have been proposed. Still, challenges remain in applying such algorithms to monitor bridges in the field. In reality, the extent of an SHM system is limited by available budgets, which define the number of sensors that can be deployed. A solution to include many sensors within a limited budget with increased efficiency is to use a Wireless Smart Sensor Network (WSSN) because of the merits of low cost, easy installation, and effective data management. An acceleration-based SHM algorithm for WSSN has been developed with a decentralized network topology. This approach has been implemented into a modularized damage detection service. The SHM application is designed to leverage the on-board computation capability of the WSSN, reducing the transmitted data size by distributing the computation burden. The SHM application for WSSN has been validated in lab-scale experiments on a truss bridge model. Nonetheless, the real challenge of SHM is in the deployment on full-scale bridges for continuous monitoring. The usability and stability of WSSN has been validated on an architectural staircase in the Siebel Center. Based on the usability investigation, the deployment of the world’s largest WSSN on the Jindo Bridge, a cable-stayed bridge has been achieved in South Korea. The main purpose of the deployment was to validate the bridge monitoring system using WSSN and energy harvesting devices in a long-term manner. The ultimate goal of this report is to deploy the developed on-board decentralized damage identification application using WSSN on a historic truss bridge. As a first step, a series of dynamic tests were conducted for modal analysis using both wired and wireless sensor systems. During the tests, the functionality of the wireless sensor system with ISHMP Services Toolsuite was confirmed. For model-based damage identification approach developed herein, a finite element (FE) model was created. The initial FE model was updated based on a visual estimate of the corrosion. The updated model was used to generate baseline information for damage detection. Finally, the WSSN-based autonomous SHM system using the decentralized damage detection application was deployed on the historic bridge. The permanent SHM system was installed on the bridge, and the damage detection application was successfully run on the bridge. The damage detection results using the decentralized comprehensive application will be compared with those from the centralized approach using WSSN. The performance of WSSN and energy harvesting devices will be evaluated. In summary, this report provides a robust SHM system for bridge structures in use of WSSN.Financial support for this research was provided in part by a Samsung Scholarship, the National Science Foundation (NSF) under NSF grant CMS 06-00433 (Dr. S. C. Liu, Program Manager), and the Global Research Network program from the Natural Research Foundation in Korea (NRF-2008-220-D00117).Ope

Extended Lifetime in Computational Evolution of Isolated Black Holes

Solving the 4-d Einstein equations as evolution in time requires solving equations of two types: the four elliptic initial data (constraint) equations, followed by the six second order evolution equations. Analytically the constraint equations remain solved under the action of the evolution, and one approach is to simply monitor them ({\it unconstrained} evolution). The problem of the 3-d computational simulation of even a single isolated vacuum black hole has proven to be remarkably difficult. Recently, we have become aware of two publications that describe very long term evolution, at least for single isolated black holes. An essential feature in each of these results is {\it constraint subtraction}. Additionally, each of these approaches is based on what we call "modern," hyperbolic formulations of the Einstein equations. It is generally assumed, based on computational experience, that the use of such modern formulations is essential for long-term black hole stability. We report here on comparable lifetime results based on the much simpler ("traditional") $\dot g$ - $\dot K$ formulation. We have also carried out a series of {\it constrained} 3-d evolutions of single isolated black holes. We find that constraint solution can produce substantially stabilized long-term single hole evolutions. However, we have found that for large domains, neither constraint-subtracted nor constrained $\dot g$ - $\dot K$ evolutions carried out in Cartesian coordinates admit arbitrarily long-lived simulations. The failure appears to arise from features at the inner excision boundary; the behavior does generally improve with resolution.Comment: 20 pages, 6 figure

Comprehensive proteomic profiling of outer membrane vesicles from Campylobacter jejuni

Gram-negative bacteria constitutively release outer membrane vesicles (OMVs) during cell growth that play significant roles in bacterial survival, virulence and pathogenesis. In this study, comprehensive proteomic analysis of OMVs from a human gastrointestinal pathogen Campylobacter jejuni NCTC11168 was performed using high-resolution mass spectrometry. The OMVs of C. jejuni NCTC11168 were isolated from culture supernatants then characterized using electron microscopy and dynamic light scattering revealing spherical OMVs of an average diameter of 50 nm. We then identified 134 vesicular proteins using high-resolution LTQ-Orbitrap mass spectrometry. Subsequent functional analysis of the genes revealed the relationships of the vesicular proteins. Furthermore, known N-glycoproteins were identified from the list of the vesicular proteome, implying the potential role of the OMVs as a delivery means for biologically relevant bacterial glycoproteins. These results enabled us to elucidate the overall proteome profile of pathogenic bacterium C. jejuni and to speculate on the function of OMVs in bacterial infections and communication

Morphological Properties of Superclusters of Galaxies

We studied superclusters of galaxies in a volume-limited sample extracted from the Sloan Digital Sky Survey Data Release 7 (SDSS/DR7) and from mock catalogues based on a semi-analytical model of galaxy evolution in the Millenium Simulation. A density field method was applied to a sample of galaxies brighter than $M_r= -21+5 \log h_{100}$ to identify superclusters, taking into account selection and boundary effects. In order to evaluate the influence of threshold density, we have chosen two thresholds: the first maximizes the number of objects (D1), and the second constrains the maximum supercluster size to $\sim$120~h$^{-1}$Mpc (D2). We have performed a morphological analysis, using Minkowski Functionals, based on a parameter which increases monotonically from filaments to pancakes. An anti-correlation was found between supercluster richness (and total luminosity or size) and the morphological parameter, indicating that filamentary structures tend to be richer, larger and more luminous than pancakes in both observed and mock catalogues. We have also used the mock samples to compare supercluster morphologies identified in position and velocity spaces, concluding that our morphological classification is not biased by the peculiar velocities. Monte Carlo simulations designed to investigate the reliability of our results with respect to random fluctuations show that these results are robust. Our analysis indicates that filaments and pancakes present different luminosity and size distributions.Comment: 12 pages, 17 figures Accepted to MNRA

The UV Upturn in Elliptical Galaxies as an Age Indicator

We show that the UV flux of old stellar systems can tell us about their ages. Two independent populations synthesis groups that have had wildly different views have here worked together and generated two solutions that can be easily tested using space telescopes. Proposed tests will constrain the ages of giant Es, that are often considered the oldest populations in the universe, and thus cosmology.Comment: LaTeX and 11 eps figures Accepted for publication in Ap

Just how long can you live in a black hole and what can be done about it?

We study the problem of how long a journey within a black hole can last. Based on our observations, we make two conjectures. First, for observers that have entered a black hole from an asymptotic region, we conjecture that the length of their journey within is bounded by a multiple of the future asymptotic ``size'' of the black hole, provided the spacetime is globally hyperbolic and satisfies the dominant-energy and non-negative-pressures conditions. Second, for spacetimes with ${\Bbb R}^3$ Cauchy surfaces (or an appropriate generalization thereof) and satisfying the dominant energy and non-negative-pressures conditions, we conjecture that the length of a journey anywhere within a black hole is again bounded, although here the bound requires a knowledge of the initial data for the gravitational field on a Cauchy surface. We prove these conjectures in the spherically symmetric case. We also prove that there is an upper bound on the lifetimes of observers lying ``deep within'' a black hole, provided the spacetime satisfies the timelike-convergence condition and possesses a maximal Cauchy surface. Further, we investigate whether one can increase the lifetime of an observer that has entered a black hole, e.g., by throwing additional matter into the hole. Lastly, in an appendix, we prove that the surface area $A$ of the event horizon of a black hole in a spherically symmetric spacetime with ADM mass $M_{\text{ADM}}$ is always bounded by $A \le 16\pi M_{\text{ADM}}^2$, provided that future null infinity is complete and the spacetime is globally hyperbolic and satisfies the dominant-energy condition.Comment: 20 pages, REVTeX 3.0, 6 figures included, self-unpackin

Changes in the expression of NO synthase isoforms after ozone: the effects of allergen exposure

BACKGROUND: The functional role of nitric oxide (NO) and various nitric oxide synthase (NOS) isoforms in asthma remains unclear. OBJECTIVE: This study investigated the effects of ozone and ovalbumin (OVA) exposure on NOS isoforms. METHODS: The expression of inducible NOS (iNOS), neuronal NOS (nNOS), and endothelial NOS (eNOS) in lung tissue was measured. Enhanced pause (P(enh)) was measured as a marker of airway obstruction. Nitrate and nitrite in bronchoalveolar lavage (BAL) fluid were measured using a modified Griess reaction. RESULTS: The nitrate concentration in BAL fluid from the OVA-sensitized/ozone-exposed/OVA-challenged group was greater than that of the OVA-sensitized/saline-challenged group. Methacholine-induced P(enh )was increased in the OVA-sensitized/ozone-exposed/OVA-challenged group, with a shift in the dose-response curve to the left, compared with the OVA-sensitized/saline-challenged group. The levels of nNOS and eNOS were increased significantly in the OVA-sensitized/ozone-exposed/OVA-challenged group and the iNOS levels were reduced compared with the OVA-sensitized/saline-challenged group. CONCLUSION: In mice, ozone is associated with increases in lung eNOS and nNOS, and decreases in iNOS. None of these enzymes are further affected by allergens, suggesting that the NOS isoforms play different roles in airway inflammation after ozone exposure

Design and Automation of a Solar Powered Soil Moisture Monitoring System (SPSMMS)

A solar powered soil moisture monitoring system (SPSMMS) was developed and evaluated at Cavite State University (CvSU) Main Campus, Cavite. The study evaluated the operating performance of the fabricated SPSMMS in terms of sensitivity of sensors, accuracy of reading, and transmission system efficiency. The device was fabricated using locally available materials. Its overall dimension in terms of length, width and height is 0.36m x 0.31m x 2m, respectively. The device is composed of the main frames, automation system, power system. The automation system is composed of main parts such as Arduino Mega2560, resistor type sensors, GSM module, data logger, and RTC. The system reads the moisture level every one (1) hour and thirty (30) minutes and send SMS every three (3) hours of operation. The study has two (2) installations placed in the crop production area of CvSU. The soil moisture was at the highest in the first installation compared from the second installation due to different environmental conditions. Installation 1 was placed in a fully irrigated area, slightly shaded, and vegetated. While, installation 2 was placed in a fully open, not vegetated, and not well irrigated. The total fabrication cost of two (2) devices is PhP 31,866.00. The total operating cost per year of the SPSMMS was compared to the standard soil moisture meter (Extech Meter Model) which is PhP 11,520 .00 and PhP 87,600.00, respectively