Relative equilibria for the generalized rigid body

This paper gives necessary and sufficient conditions for the (n-dimensional) generalized free rigid body to be in a state of relative equilibrium. The conditions generalize those for the case of the three-dimensional free rigid body, namely that the body is in relative equilibrium if and only if its angular velocity and angular momentum align, that is, if the body rotates about one of its principal axes. For the n-dimensional rigid body in the Manakov formulation, these conditions have a similar interpretation. We use this result to state and prove a generalized Saari’s Conjecture (usually stated for the N-body problem) for the special case of the generalized rigid body

TUTORIAL: TRANSIENT MODELING AND ANALYSIS OF CENTRIFUGAL COMPRESSORS

TutorialCentrifugal compressors are subject to transient events, such as emergency shutdowns, which can cause energetic surge events during rapid shutdown transients. Many modeling tools are used to predict the behavior of compressor systems during fast transient events. Even more, centrifugal compressor dynamic modeling is a valuable assessment tool that can help improve the design of the compressor anti-surge system to prevent harsh conditions while the unit is coasting down. Modeling of centrifugal compressor transient events requires a detailed evaluation of many system variables to obtain accurate results. Additionally, many parameters should be included and analyzed to adjust the model and obtain acceptable predictions. Those parameters can include recycle valve characteristics, the controller and actuator, suction and discharge piping volumes, aftercoolers, and operating conditions. Other parameters, such as machine coast down speed and inertia and different control response times will determine if the compressor will reach its surge limit at a detrimental high head condition, avoid it or go through it at low acceptable energy conditions. Many designs use general guidelines to select and plan the compressor anti-surge system and its main components. For example, the recycle valve type, size and actuation time are key parameters during the shutdown of the compressor unit since they directly affect the amount of flow through the compressor and its reaction time. Other factors are also relevant and should be assessed in detail to assure a proper design to avoid such transient events as a sudden shutdown of a compressor from a full load or high head operating conditions resulting in damaging surge events. In order to refine the simulation approach of the transients in centrifugal compressors, an extensive assessment has been conducted of the main parameters that will affect the modeling predictions. Parameters such as recycle valve size, type, actuation time, after-cooler volume, friction factors, unit speed coast down predictions, compressor map, isolation valve control, acting time, as well as placement of the discharge check valve influence the modeling predictions considerably. Therefore, parametric studies of some of those variables have helped to refine and adjust the modeling technique while improving the accuracy of the results. Moreover, computational predictions have been compared against high fidelity – high accuracy data collected in a full scale compressor system. Initial comparisons indicated reasonable results while adjustments in the technique and main assumptions improved the modeling predictions considerably. A generic methodology to improve modeling predictions and main considerations are part of the analysis. In addition, a comparison of the modeling results and experimental data are presented and complemented with parametric studies of different variables. In general, this work should provide guidelines for advancing the modeling of centrifugal compressor transients as well as showing the application of a valuable tool for designing surge control systems for centrifugal compressors

Youth Development Approaches in Adolescent Family Life Demonstration Projects

Youth development (YD) strategies in conjunction with appropriate age-graded sexuality and family life education programs/curricula may have an important role to play in formulating convincing answers to these questions. Youth development approaches help youth enhance their assets rather than concentrating on their difficulties. They focus on where youth are going, helping them develop a belief in a viable future and in their ability to take actions that will bring that future about. The commitment to a future that would be disrupted by a pregnancy during adolescence is about the only thing that Zabin and her colleagues (1986) found to differentiate among Baltimore adolescents using teen clinics who did and did not get pregnant. Teens without a strong reason to avoid pregnancy got pregnant at the same rate as those who wanted to get pregnant; the only teens who were successful at avoiding pregnancy were those who had a future goal that a pregnancy would disrupt. Thus, incorporating youth development principles along with some specific techniques into the work of the Office of Adolescent Pregnancy Programs' (OAPP) abstinence-oriented programs would seem to be an important program enhancement with potentially valuable impacts

Microbial Activity Response to Solar Radiation across Contrasting Environmental Conditions in Salar de Huasco, Northern Chilean Altiplano

Indexación: Web of Science; Scopus.In high altitude environments, extreme levels of solar radiation and important differences of ionic concentrations over narrow spatial scales may modulate microbial activity. In Salar de Huasco, a high-altitude wetland in the Andean mountains, the high diversity of microbial communities has been characterized and associated with strong environmental variability. Communities that differed in light history and environmental conditions, such as nutrient concentrations and salinity from different spatial locations, were assessed for bacterial secondary production (BSP, H-3-leucine incorporation) response from short-term exposures to solar radiation. We sampled during austral spring seven stations categorized as: (a) source stations, with recently emerged groundwater (no-previous solar exposure); (b) stream running water stations; (c) stations connected to source waters but far downstream from source points; and (d) isolated ponds disconnected from ground sources or streams with a longer isolation and solar exposure history. Very high values of 0.25 mu E m(-2) s(-1), 72 W m(-2) and 12 W m(-2) were measured for PAR, UVA, and UVB incident solar radiation, respectively. The environmental factors measured formed two groups of stations reflected by principal component analyses (near to groundwater sources and isolated systems) where isolated ponds had the highest BSP and microbial abundance (35 microalgae taxa, picoeukaryotes, nanoflagellates, and bacteria) plus higher salinities and PO43- concentrations. BSP short-term response (4 h) to solar radiation was measured by H-3-leucine incorporation under four different solar conditions: full sun, no UVB, PAR, and dark. Microbial communities established in waters with the longest surface exposure (e.g., isolated ponds) had the lowest BSP response to solar radiation treatments, and thus were likely best adapted to solar radiation exposure contrary to ground source waters. These results support our light history (solar exposure) hypothesis where the more isolated the community is from ground water sources, the better adapted it is to solar radiation. We suggest that factors other than solar radiation (e.g., salinity, PO43-, NO3-) are also important in determining microbial productivity in heterogeneous environments such as the Salar de Huasco.http://journal.frontiersin.org/article/10.3389/fmicb.2016.01857/ful

Optimizing MRFâ ASL scan design for precise quantification of brain hemodynamics using neural network regression

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154517/1/mrm28051.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154517/2/mrm28051_am.pd

Utilizing Lipopolysaccharide in Exhaled Breath Condensate to Diagnose Gram Negative Pneumonia

A device for collecting exhaled breath condensate from a subject. The device comprises a plunger assembly and a stopper. The stopper is connected to the plunger disk of the plunger assembly by a plurality of support pins and is configured for sealing engagement. The device is utilized to collect exhaled breath condensate from both spontaneously breathing and mechanically ventilated subjects and the devices utilized to determine whether lipopolysaccharide is present in the collected exhaled breath condensate

Utilizing lipopolysaccharide in exhaled breath condensate to diagnose gram negative pneumonia

A device for collecting exhaled breath condensate from a subject. The device comprises a plunger assembly and a stopper. The stopper is connected to the plunger disk of the plunger assembly by a plurality of support pins and is configured for sealing engagement. The device is utilized to collect exhaled breath condensate from both spontaneously breathing and mechanically ventilated subjects and the devices utilized to determine whether lipopolysaccharide is present in the collected exhaled breath condensate