Pressurant requirements for discharge of liquid methane from a 1.52-meter-(5-ft-) diameter spherical tank under both static and slosh conditions

Pressurized expulsion tests were conducted to determine the effect of various physical parameters on the pressurant gas (methane, helium, hydrogen, and nitrogen) requirements during the expulsion of liquid methane from a 1.52-meter-(5-ft-) diameter spherical tank and to compare results with those predicted by an analytical program. Also studied were the effects on methane, helium, and hydrogen pressurant requirements of various slosh excitation frequencies and amplitudes, both with and without slosh suppressing baffles in the tank. The experimental results when using gaseous methane, helium, and hydrogen show that the predictions of the analytical program agreed well with the actual pressurant requirements for static tank expulsions. The analytical program could not be used for gaseous nitrogen expulsions because of the large quantities of nitrogen which can dissolve in liquid methane. Under slosh conditions, a pronounced increase in gaseous methane requirements was observed relative to results obtained for the static tank expulsions. Slight decreases in the helium and hydrogen requirements were noted under similar test conditions

Intensity-Dependent Changes in Quantified Resting Cerebral Perfusion with Multiple Sessions of Transcranial DC Stimulation

Transcranial direct current stimulation (tDCS) to the left prefrontal cortex has been shown to produce broad behavioral effects including enhanced learning and vigilance. Still, the neural mechanisms underlying such effects are not fully understood. Furthermore, the neural underpinnings of repeated stimulation remain understudied. In this work, we evaluated the effects of the repetition and intensity of tDCS on cerebral perfusion [cerebral blood flow (CBF)]. A cohort of 47 subjects was randomly assigned to one of the three groups. tDCS of 1- or 2-mA was applied to the left prefrontal cortex on three consecutive days, and resting CBF was quantified before and after stimulation using the arterial spin labeling MRI and then compared with a group that received sham stimulation. A widespread decreased CBF was found in a group receiving sham stimulation across the three post-stimulation measures when compared with baseline. In contrast, only slight decreases were observed in the group receiving 2-mA stimulation in the second and third post-stimulation measurements, but more prominent increased CBF was observed across several brain regions including the locus coeruleus (LC). The LC is an integral region in the production of norepinephrine and the noradrenergic system, and an increased norepinephrine/noradrenergic activity could explain the various behavioral findings from the anodal prefrontal tDCS. A decreased CBF was observed in the 1-mA group across the first two post-stimulation measurements, similar to the sham group. This decreased CBF was apparent in only a few small clusters in the third post-stimulation scan but was accompanied by an increased CBF, indicating that the neural effects of stimulation may persist for at least 24 h and that the repeated stimulation may produce cumulative effects

Optometric Measurements Predict Performance but Not Comfort on a Virtual Object Placement Task With a Stereoscopic 3D Display

Twelve participants were tested on a simple virtual object precision placement task while viewing a stereoscopic 3D (S3D) display. Inclusion criteria included uncorrected or best corrected vision of 20/20 or better in each eye and stereopsis of at least 40 arc sec using the Titmus stereo test. Additionally, binocular function was assessed, including measurements of distant and near phoria (horizontal and vertical) and distant and near horizontal fusion ranges using standard optometric clinical techniques. Before each of six 30 minute experimental sessions, measurements of phoria and fusion ranges were repeated using a Keystone View Telebinocular and an S3D display, respectively. All participants completed experimental sessions in which the task required the precision placement of a virtual object in depth at the same location as a target object. Subjective discomfort was assessed using the Simulator Sickness Questionnaire (SSQ). Individual placement accuracy in S3D trials was significantly correlated with several of the binocular screening outcomes: viewers with larger convergent fusion ranges (measured at near distance), larger total fusion ranges (convergent plus divergent ranges, measured at near distance), and/or lower (better) stereoscopic acuity thresholds were more accurate on the placement task. No screening measures were predictive of subjective discomfort, perhaps due to the low levels of discomfort induced

On the Surface Structure of Strange Superheavy Nuclei

Bound, strange, neutral superheavy nuclei, stable against strong decay, may exist. A model effective field theory calculation of the surface energy and density of such systems is carried out assuming vector meson couplings to conserved currents and scalar couplings fit to data where it exists. The non-linear relativistic mean field equations are solved assuming local baryon sources. The approach is calibrated through a successful calculation of the known nuclear surface tension.Comment: 12 pages, 9 figure

Native and foreign born as predictors of pediatric asthma in an Asian immigrant population: a cross sectional survey

<p>Abstract</p> <p>Background</p> <p>Asthma prevalence is lower in less developed countries and among some recent immigrant populations in the US, but the reasons for this are not clear. One possibility is that early childhood infections are protective against asthma.</p> <p>Methods</p> <p>We surveyed Asian immigrant children (n = 204; age 4–18) to assess the relationship between asthma and native or foreign place of birth. We included questions about environmental exposures, demographic variables and family history of asthma to test whether they might explain effects of place of birth on asthma.</p> <p>Results</p> <p>The native and foreign born groups were similar in most respects. Analysis of association with diagnosed asthma for all ages together resulted in two logistic regression models. Both retained born in the US (ORs were 3.2 and 4.3; p < 0.01) and family history of asthma (ORs were 6.4 and 7.2; p < 0.001). One model retained living near heavy motor traffic (OR = 2.6; p = 0.012). The other retained language (OR = 3.2; p = 0.003). However, for older children (11–18 years of age) being born in the US lost some of its predictive power.</p> <p>Conclusion</p> <p>Our findings are consistent with early childhood infections that are prevalent outside the US protecting against asthma.</p

The acquisition of Sign Language: The impact of phonetic complexity on phonology

Research into the effect of phonetic complexity on phonological acquisition has a long history in spoken languages. This paper considers the effect of phonetics on phonological development in a signed language. We report on an experiment in which nonword-repetition methodology was adapted so as to examine in a systematic way how phonetic complexity in two phonological parameters of signed languages — handshape and movement — affects the perception and articulation of signs. Ninety-one Deaf children aged 3–11 acquiring British Sign Language (BSL) and 46 hearing nonsigners aged 6–11 repeated a set of 40 nonsense signs. For Deaf children, repetition accuracy improved with age, correlated with wider BSL abilities, and was lowest for signs that were phonetically complex. Repetition accuracy was correlated with fine motor skills for the youngest children. Despite their lower repetition accuracy, the hearing group were similarly affected by phonetic complexity, suggesting that common visual and motoric factors are at play when processing linguistic information in the visuo-gestural modality

The Impact of Biomechanics in Tissue Engineering and Regenerative Medicine

Biomechanical factors profoundly influence the processes of tissue growth, development, maintenance, degeneration, and repair. Regenerative strategies to restore damaged or diseased tissues in vivo and create living tissue replacements in vitro have recently begun to harness advances in understanding of how cells and tissues sense and adapt to their mechanical environment. It is clear that biomechanical considerations will be fundamental to the successful development of clinical therapies based on principles of tissue engineering and regenerative medicine for a broad range of musculoskeletal, cardiovascular, craniofacial, skin, urinary, and neural tissues. Biomechanical stimuli may in fact hold the key to producing regenerated tissues with high strength and endurance. However, many challenges remain, particularly for tissues that function within complex and demanding mechanical environments in vivo. This paper reviews the present role and potential impact of experimental and computational biomechanics in engineering functional tissues using several illustrative examples of past successes and future grand challenges.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/78125/1/ten.teb.2009.0340.pd

Calcineurin and Protein kinase G regulate C. elegans behavioral quiescence during locomotion in liquid

<p>Abstract</p> <p>Background</p> <p>Most rhythmic motor behaviors in nature are episodic i.e. they alternate between different behavioral states, including quiescence. Electrophysiological studies in invertebrate behavioral switching, maintenance and quiescence have elucidated several neuronal mechanisms that generate a temporal pattern in behavior. However, the genetic bases of these processes are less well studied. We have previously uncovered a novel episodic behavior exhibited by <it>C. elegans </it>in liquid media where they alternate between distinct phases of rhythmic swimming and quiescence. Here, we have investigated the effect of several genes and their site of action on the behavioral quiescence exhibited in liquid by the nematode <it>C. elegans</it>.</p> <p>Results</p> <p>We have previously reported that high cholinergic signaling promotes quiescence and command interneurons are critical for timing the quiescence bout durations. We have found that in addition to command interneurons, sensory neurons are also critical for quiescence. We show that the protein phosphatase calcineurin homolog <it>tax-6 </it>promotes swimming whereas the protein kinase G homolog <it>egl-4 </it>promotes quiescence. <it>tax-6 </it>expression in the sensory neurons is sufficient to account for its effect. <it>egl-4 </it>also acts in multiple sensory neurons to mediate its effect on quiescence. In addition our data is consistent with regulation of quiescence by <it>egl-4 </it>acting functionally downstream of release of acetylcholine (ACh) by motor neurons.</p> <p>Conclusions</p> <p>Our study provides genetic evidence for mechanisms underlying the maintenance of a behavioral state operating at multiple neuronal levels through the activities of a kinase and a phosphatase. These results in a genetically tractable organism establish a framework for further dissection of the mechanism of quiescence during episodic behaviors.</p

Defining Smallness for Gestational Age in the Early Years of the Danish Medical Birth Registry

Background: Being born small for gestational age (SGA) is associated with decreased insulin sensitivity and increased blood pressure in childhood, but the association with clinical disease in early adulthood is less certain. The Danish Medical Birth Registry has registered all births in Denmark since 1973, but due to variable data quality, data is most often used only from 1981 onwards, and birth registers in other countries may have similar problems for the early years. We wanted to examine whether the data can be used for identification of children born SGA and used in future research. Methodology/Principal Findings: All persons born between 1974 and 1996 were identified in the Danish Medical Birth Registry (n = 1.704.890). Immigrants and children without data on gestational age and birth weight were excluded, and a total of 1.348.106 children were included in the analysis. The difference between the different variables used in the history of the registry were examined, and the quality of data in the birth registry from 1974-1981 was examined and compared to subsequent years. Data on birth weight and gestational age in the early years of the registry is inconsistent, and the identification of children born SGA is inaccurate, with 49 % false-positives. The biggest source of error is due to the rough and inaccurate intervals used for gestational age. By using –3 standard deviations as a cut-off for the identification of children born SGA, the number of false-positives was reduced to 9%, while the amount of false-negatives were increased. Conclusion: Choosing –3 standard deviations for identifying children born SGA is a viable, though not optimal solution fo

Dopamine Signaling Is Essential for Precise Rates of Locomotion by C. elegans

Dopamine is an important neuromodulator in both vertebrates and invertebrates. We have found that reduced dopamine signaling can cause a distinct abnormality in the behavior of the nematode C. elegans, which has only eight dopaminergic neurons. Using an automated particle-tracking system for the analysis of C. elegans locomotion, we observed that individual wild-type animals made small adjustments to their speed to maintain constant rates of locomotion. By contrast, individual mutant animals defective in the synthesis of dopamine made larger adjustments to their speeds, resulting in large fluctuations in their rates of locomotion. Mutants defective in dopamine signaling also frequently exhibited both abnormally high and abnormally low average speeds. The ability to make small adjustments to speed was restored to these mutants by treatment with dopamine. These behaviors depended on the D2-like dopamine receptor DOP-3 and the G-protein subunit GOA-1. We suggest that C. elegans and other animals, including humans, might share mechanisms by which dopamine restricts motor activity levels and coordinates movement