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Las Cruces, NM, United States

Giraud A.,CNRS Georesources lab | Sevostianov I.,NMSU
International Journal of Rock Mechanics and Mining Sciences | Year: 2013

A new micromechanical approach to analytical modeling of oolitic limestone is proposed. Limestone is modeled as a multiphase composite consisting of sparry calcite matrix, spherical oolitic inhomogeneities, oblate spheroidal pores of aspect ratio 0.2, and concave pores in the shape of superspheres (the concavity factor is the key parameter affecting overall properties). Maxwell's homogenization scheme is used to calculate effective bulk and shear moduli of this multiphase composite as functions of total porosities. The results are in good agreement with experimental data available in the literature. © 2013 Elsevier Ltd. Source

Flores I.C.,UTEP | Walker W.S.,UTEP | Walton J.C.,UTEP | Santiago I.,UTEP | Palacios R.,NMSU
AMTA/AWWA Membrane Technology Conference and Exposition 2013 | Year: 2013

The need for clean potable water is often overlooked in first world countries, like the United States, where people tend to assume that access to clean water is universal. However, such is not the case. Families outside the water utilities' coverage are often provided with temporary solutions that may be found wanting in terms of quality. This is the situation that some people in the "Paso Del Norte" (Far West Texas and Southern New Mexico) region live as their houses are beyond the reach of the pipe distribution of the local water utility. One solution proposed to address this problem comes in the form of Point of Use (POU) filters. POU filters would provide the households in question with access to reliable drinking-quality water, which may be used for tasks such as drinking and washing dishes, until they are finally connected to the main water line. The goal of this project is to improve the water quality of the people in the Paso Del Norte Region with an economically feasible and sustainable filtration system. Two main areas from the Paso Del Norte Region have been selected for this study: southeastern Doña Ana County, NM and northeastern El Paso County, TX. The objectives of this research are to (1) assess the region's current water source and its quality, and (2) review commercially available POU filters and identify economically and environmentally sustainable filtration systems. A principal water source for colonias in southeastern Doña Ana County is shallow-groundwater, which is commonly contaminated with arsenic. On the other hand, the main source of water for eastern El Paso County is hauled, certified drinking-water that may become re-contaminated with pathogenic microbes by long-term storage in large tanks without disinfection. Several filter configurations have been identified to adequately address the types of contamination in each region, such as: pitcher-filter, differential-height bucket system, faucet adapter, and in-line, under-the-sink system. These configurations may use sorption or membrane filtration for contaminant removal. For example, sorption media may be used to remove arsenic, and some hollow-fiber ultrafiltration systems are capable of excluding all bacteria and most viruses. Water quality sampling will be performed in the fall of 2012, and filter testing methodology will be completed by December 2012. This paper highlights the challenges and potential advantages of POU filtration systems in colonias. © 2013 American Water Works Association. Source

Estell R.E.,U.S. Department of Agriculture | Utsumi S.A.,W.K. Kellogg Biological Station | Cibils A.F.,NMSU | Anderson D.M.,U.S. Department of Agriculture
Journal of Chemical Ecology | Year: 2014

Differential plant use by herbivores has been observed for several woody plant species and has frequently been attributed to plant secondary metabolites. We examined the relationship between terpenoid concentration and Juniperus monosperma herbivory by small ruminants. Two groups of animals (10 goats or 5 goats plus 4 sheep) browsed 16 paddocks (20 × 30 m) containing one-seed juniper for six days during two seasons. Juniper leaves were sampled from 311 saplings immediately after browsing. Saplings were categorized by size (short [<0.5 m], medium [0.5-1.0 m], or tall [>1.0 m]), and by browsing intensity (light [<33 %], moderate [33-66 %], or heavy [>66 %]). Juniper bark was collected from 12 saplings during spring. Total estimated terpenoid concentrations in leaves and bark were 18.3 ± 0.3 and 8.9 ± 0.8 mg/g, respectively, and the dominant terpene in both tissues was α-pinene (11.1 ± 0.2 and 7.6 ± 0.7 mg/g, respectively). Total terpenoid concentration of juniper leaves was greater in spring than summer (20.6 ± 0.5 vs. 16.7 ± 0.3 mg/g, respectively) and was lower in short saplings than medium or tall saplings (16.5 ± 0.6 vs. 19.8 ± 0.4 and 19.5 ± 0.4 mg/g, respectively). Total terpenoid concentration of leaves also differed among the three defoliation categories (21.2 ± 0.6, 18.7 ± 0.5, and 16.1 ± 0.4 mg/g for light, moderate, and heavy, respectively). The smallest subset of terpenoids able to discriminate between light and heavy browsing intensity categories included eight compounds ([E]-β-farnesene, bornyl acetate, γ-eudesmol, endo-fenchyl acetate, γ-cadinene, α-pinene, cis-piperitol, and cis-p-menth-2-en-1-ol). Our results suggest terpenoid concentrations in one-seed juniper are related to season, sapling size, and browsing by small ruminants. © 2014 Springer Science+Business Media New York (outside the USA). Source

Viswanathan S.P.,NMSU
2016 Indian Control Conference, ICC 2016 - Proceedings | Year: 2016

Design considerations for agile, precise and reliable attitude control of micro-spacecraft using Adaptive Singularity-free Control Moment Gyroscope (ASCMG) actuators are presented here. A complete dynamics model of a spacecraft with an ASCMG is derived using the principles of variational mechanics, relaxing some assumptions made in prior literature on Control Moment Gyroscopes (CMG). The dynamics so obtained shows the complex nonlinear coupling between the internal degrees of freedom associated with an ASCMG and the spacecraft base body's attitude motion. By default, the general ASCMG model is equivalent to that of a Variable Speed Control Moment Gyroscope without symmetrical rotor and gimbal, and can operate as a CMG by spinning the rotor at constant speed. This dynamics model is then extended to include the effects of multiple ASCMGs placed in the spacecraft bus, and sufficient conditions for non-singular ASCMG cluster configurations are obtained to operate the cluster in CMG mode. The adverse effects of the simplifying assumptions that lead to the standard CMG design, and how they lead to CMG singularities, are described. A bare minimum hardware prototype of an ASCMG using low cost COTS components, is shown. A control scheme for agile and precise attitude pointing control of a cubesat using a finite number of ASCMGs in the absence of external torques, is presented. A Geometric Variational Integration scheme is obtained for this multibody spacecraft for numerical and micro-controller implementation. © 2016 IEEE. Source

Walker M.,NMSU
Bioethics | Year: 2014

The primary question to be addressed here is whether pre-implantation genetic diagnosis (PGD), used for both negative and positive trait selection, benefits potential supernumerary embryos. The phrase 'potential supernumerary embryos' is used to indicate that PGD is typically performed on a set of embryos, only some of which will be implanted. Prior to any testing, each embryo in the set is potentially supernumerary in the sense that it may not be selected for implantation. Those embryos that are not selected, and hence destroyed or frozen, are 'actually supernumerary'. The argument to be advanced is hypothetical: If embryos may be said to benefit or be harmed by our actions, then PGD used to select for an embryo or embryos with the highest expected Wellbeing benefits potential supernumerary embryos. © 2012 John Wiley & Sons Ltd. Source

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