Strength and fracture of Si micropillars: A new scanning electron microscopy-based micro-compression test

A novel method for in situ scanning electron microscope (SEM) micro-compression tests is presented. The direct SEM observation during the instrumented compression testing allows for very efficient positioning and assessment of the failure mechanism. Compression tests on micromachined Si pillars with volumes down to 2 μm3 are performed inside the SEM, and the results demonstrate the potential of the method. In situ observation shows that small diameter pillars tend to buckle while larger ones tend to crack before failure. Compressive strength increases with decreasing pillar diameter and reaches almost 9 GPa for submicrometer diameter pillars. This result is in agreement with earlier bending experiments on Si. Difficulties associated with precise strain measurements are discusse

Laboratory simulations of astrophysical jets and solar coronal loops: new results

An experimental program underway at Caltech has produced plasmas where the shape is neither fixed by the vacuum chamber nor fixed by an external coil set, but instead is determined by self-organization. The plasma dynamics is highly reproducible and so can be studied in considerable detail even though the morphology of the plasma is both complex and time-dependent. A surprising result has been the observation that self-collimating MHD-driven plasma jets are ubiquitous and play a fundamental role in the self-organization. The jets can be considered lab-scale simulations of astrophysical jets and in addition are intimately related to solar coronal loops. The jets are driven by the combination of the axial component of the J×B force and the axial pressure gradient resulting from the non-uniform pinch force associated with the flared axial current density. Behavior is consistent with a model showing that collimation results from axial non-uniformity of the jet velocity. In particular, flow stagnation in the jet frame compresses frozen-in azimuthal magnetic flux, squeezes together toroidal magnetic field lines, thereby amplifying the embedded toroidal magnetic field, enhancing the pinch force, and hence causing collimation of the jet

Statistical Precision of a Replicated Farm Grazing Trial Versus Replicated Paddock Trials

The experimental unit for animal average daily gain (ADG) and gain/ha in grazing trials is the paddock. Grazing trials on research stations often are conducted using small paddocks because animal and land costs restrict the number of treatments, replicates, and animals per paddock. Land and animal restrictions can be reduced by conducting trials on farms using animals provided by cooperating farmers. Farmers typically want only a single replicate on their farms and as result, virtually all on-farm trials in the USA and elsewhere have been un-replicated demonstration trials from which estimates of experimental error cannot be obtained. Farms can be used as replicates but concerns about statistical precision and the ability to detect treatment differences to date has limited the use of this design in the USA to a single study which we conducted in the Central Great Plains in the 1990\u27s. Our objective is to compare the statistical precision of this on-farm grazing trial with replicated paddock trials on research stations in the same geographical region

Relationship of Visual and Quantitative Methods of Grass Sward Development

The objective of this study was to determine the relationship between visual and quantitative estimates of the morphological development of perennial grass swards. Pure stands of intermediate wheatgrass [Thinopyrum intermedium (Host) Barkw. & D.R. Dewey] and switchgrass (Panicum virgatum L.) were hand-clipped to ground level at 2-wk intervals in 1991 at Mead, NE, morphologically classified as mean stage count (MSC), and visually estimated for sward development. Visual estimations of sward development for both species were representative of quantitative measurements during vegetative growth. However, as sward development advanced to the elongation and heading stages, visual methods over-estimated the population maturity. The morphological development of perennial forage grasses can be visually estimated during vegetative growth. However, more quantitative and less subjective measurements are necessary to compensate for the visual dominance of elongating and reproductive tillers

Star Formation in the vicinity of Nuclear Black Holes: Young Stellar Objects close to Sgr A*

It is often assumed that the strong gravitational field of a super-massive black hole disrupts an adjacent molecular cloud preventing classical star formation in the deep potential well of the black hole. Yet, young stars have been observed across the entire nuclear star cluster of the Milky Way including the region close ($<$0.5~pc) to the central black hole, Sgr A*. Here, we focus particularly on small groups of young stars, such as IRS 13N located 0.1 pc away from Sgr A*, which is suggested to contain about five embedded massive young stellar objects ($<$1 Myr). We perform three dimensional hydrodynamical simulations to follow the evolution of molecular clumps orbiting about a $4\times10^6~M_{\odot}$ black hole, to constrain the formation and the physical conditions of such groups. The molecular clumps in our models assumed to be isothermal containing 100 $M_{\odot}$ in $<$0.2 pc radius. Such molecular clumps exist in the circumnuclear disk of the Galaxy. In our highly eccentrically orbiting clump, the strong orbital compression of the clump along the orbital radius vector and perpendicular to the orbital plane causes the gas densities to increase to values higher than the tidal density of Sgr A*, which are required for star formation. Additionally, we speculate that the infrared excess source G2/DSO approaching Sgr A* on a highly eccentric orbit could be associated with a dust enshrouded star that may have been formed recently through the mechanism supported by our models.Comment: 18 pages, 11 figures, accepted for publication in MNRA

The integration of YidC into the cytoplasmic membrane of Escherichia coli requires the signal recognition particle, SecA and SecYEG

The integration of the polytopic membrane protein YidC into the inner membrane of Escherichia coli was analyzed employing an in vitro system. Upon integration of in vitro synthesized YidC, a 42-kDa membrane protected fragment was detected, which could be immunoprecipitated with polyclonal anti-YidC antibodies. The occurrence of this fragment is in agreement with the predicted topology of YidC and probably encompasses the first two transmembrane domains and the connecting 320-amino acid-long periplasmic loop. The integration of YidC was strictly dependent on the signal recognition particle and SecA. YidC could not be integrated in the absence of SecY, SecE, or SecG, suggesting that YidC, in contrast to its mitochondrial orthologue Oxa1p, cannot engage a SecYEG-independent protein-conducting channel

A remark on the Hankel determinant formula for solutions of the Toda equation

We consider the Hankel determinant formula of the $\tau$ functions of the Toda equation. We present a relationship between the determinant formula and the auxiliary linear problem, which is characterized by a compact formula for the $\tau$ functions in the framework of the KP theory. Similar phenomena that have been observed for the Painlev\'e II and IV equations are recovered. The case of finite lattice is also discussed.Comment: 14 pages, IOP styl

Development and initial testing of the self‐care of chronic illness inventory

Aim The aim was to develop and psychometrically test the self‐care of chronic illness Inventory, a generic measure of self‐care. Background Existing measures of self‐care are disease‐specific or behaviour‐specific; no generic measure of self‐care exists. Design Cross‐sectional survey. Methods We developed a 20‐item self‐report instrument based on the Middle Range Theory of Self‐Care of Chronic Illness, with three separate scales measuring Self‐Care Maintenance, Self‐Care Monitoring, and Self‐Care Management. Each of the three scales is scored separately and standardized 0–100 with higher scores indicating better self‐care. After demonstrating content validity, psychometric testing was conducted in a convenience sample of 407 adults (enrolled from inpatient and outpatient settings at five sites in the United States and ResearchMatch.org). Dimensionality testing with confirmatory factor analysis preceded reliability testing. Results The Self‐Care Maintenance scale (eight items, two dimensions: illness‐related and health‐promoting behaviour) fit well when tested with a two‐factor confirmatory model. The Self‐Care Monitoring scale (five items, single factor) fitted well. The Self‐Care Management scale (seven items, two factors: autonomous and consulting behaviour), when tested with a two‐factor confirmatory model, fitted adequately. A simultaneous confirmatory factor analysis on the combined set of items supported the more general model. Conclusion The self‐care of chronic illness inventory is adequate in reliability and validity. We suggest further testing in diverse populations of patients with chronic illnesses