727 research outputs found
Solution of the symmetric eigenproblem AX=lambda BX by delayed division
Delayed division is an iterative method for solving the linear eigenvalue problem AX = lambda BX for a limited number of small eigenvalues and their corresponding eigenvectors. The distinctive feature of the method is the reduction of the problem to an approximate triangular form by systematically dropping quadratic terms in the eigenvalue lambda. The report describes the pivoting strategy in the reduction and the method for preserving symmetry in submatrices at each reduction step. Along with the approximate triangular reduction, the report extends some techniques used in the method of inverse subspace iteration. Examples are included for problems of varying complexity
Effects of cutouts on the behavior of symmetric composite laminates subjected to bending and twisting loads
Composite structures are used for a wide variety of aerospace applications. Practical structures contain cutouts and these structures are subjected to in-plane and out-of-plane loading conditions. Structurally efficient designs for composite structures require a thorough understanding of the effects of cutouts on the response of composite plates subjected to inplane or out-of-plane loadings. Most investigations of the behavior of composite plates with cutouts have considered in-plane loadings only. Out-of-plane loadings suchas bending or twisting have received very limited attention. The response of homogeneous plates (e.g., isotropic or orthotropic plates) subjected to bending or twisting moments has been studied analytically. These analyses are for infinite plates and neglect finite-plate effects. Recently, analytical and experimental studies were conducted to determine the effects of cutouts on the response of laminated composite plates subjected to bending moments. No analytical or experimental results are currently available for the effects of cutouts on the response of composite laminates subjected to twisting moments
Possibilities for an Aerial Biosphere in Temperate Sub Neptune-Sized Exoplanet Atmospheres
The search for signs of life through the detection of exoplanet atmosphere
biosignature gases is gaining momentum. Yet, only a handful of rocky exoplanet
atmospheres are suitable for observation with planned next-generation
telescopes. To broaden prospects, we describe the possibilities for an aerial,
liquid water cloud-based biosphere in the atmospheres of sub Neptune-sized
temperate exoplanets, those receiving Earth-like irradiation from their host
stars. One such planet is known (K2-18b) and other candidates are being
followed up. Sub Neptunes are common and easier to study observationally than
rocky exoplanets because of their larger sizes, lower densities, and extended
atmospheres or envelopes. Yet, sub Neptunes lack any solid surface as we know
it, so it is worthwhile considering whether their atmospheres can support an
aerial biosphere. We review, synthesize, and build upon existing research.
Passive microbial-like life particles must persist aloft in a region with
liquid water clouds for long enough to metabolize, reproduce, and spread before
downward transport to lower altitudes that may be too hot for life of any kind
to survive. Dynamical studies are needed to flesh out quantitative details of
life particle residence times. A sub Neptune would need to be a part of a
planetary system with an unstable asteroid belt in order for meteoritic
material to provide nutrients, though life would also need to efficiently reuse
and recycle metals. The origin of life may be the most severe limiting
challenge. Regardless of the uncertainties, we can keep an open mind to the
search for biosignature gases as a part of general observational studies of sub
Neptune exoplanets.Comment: Published in Universe: https://www.mdpi.com/2218-1997/7/6/17
Analysis of MAGSAT data of the Indian region
Progress in the development of software for reading MAGSAT data tapes and for the reduction of anomaly data, and in the preparation of data for magnetic anomaly maps is reported
Molecular line mapping of the giant molecular cloud associated with RCW 106 - II. Column density and dynamical state of the clumps
We present a fully sampled C^{18}O (1-0) map towards the southern giant
molecular cloud (GMC) associated with the HII region RCW 106, and use it in
combination with previous ^{13}CO (1-0) mapping to estimate the gas column
density as a function of position and velocity. We find localized regions of
significant ^{13}CO optical depth in the northern part of the cloud, with
several of the high-opacity clouds in this region likely associated with a
limb-brightened shell around the HII region G333.6-0.2. Optical depth
corrections broaden the distribution of column densities in the cloud, yielding
a log-normal distribution as predicted by simulations of turbulence.
Decomposing the ^{13}CO and C^{18}O data cubes into clumps, we find relatively
weak correlations between size and linewidth, and a more sensitive dependence
of luminosity on size than would be predicted by a constant average column
density. The clump mass spectrum has a slope near -1.7, consistent with
previous studies. The most massive clumps appear to have gravitational binding
energies well in excess of virial equilibrium; we discuss possible
explanations, which include magnetic support and neglect of time-varying
surface terms in the virial theorem. Unlike molecular clouds as a whole, the
clumps within the RCW 106 GMC, while elongated, appear to show random
orientations with respect to the Galactic plane.Comment: 17 pages, to appear in MNRA
A Search for Propylene Oxide and Glycine in Sagittarius B2 (LMH) and Orion
We have used the Mopra Telescope to search for glycine and the simple chiral
molecule propylene oxide in the Sgr B2 (LMH) and Orion KL, in the 3-mm band. We
have not detected either species, but have been able to put sensitive upper
limits on the abundances of both molecules. The 3-sigma upper limits derived
for glycine conformer I are 3.7 x 10^{14} cm^{-2} in both Orion-KL and Sgr B2
(LMH), comparable to the reported detections of conformer I by Kuan et al.
However, as our values are 3-sigma upper limits rather than detections we
conclude that this weighs against confirming the detection of Kuan et al. We
find upper limits for the glycine II column density of 7.7 x 10^{12} cm^{-2} in
both Orion-KL and Sgr B2 (LMH), in agreement with the results of Combes et al.
The results presented here show that glycine conformer II is not present in the
extended gas at the levels detected by Kuan et al. for conformer I. Our ATCA
results (Jones et al.) have ruled out the detection of glycine (both conformers
I and II) in the compact hot core of the LMH at the levels reported, so we
conclude that it is unlikely that Kuan et al. have detected glycine in either
Sgr B2 or Orion-KL. We find upper limits for propylene oxide abundance of 3.0 x
10^{14} cm^{-2} in Orion-KL and 6.7 x 10^{14} cm^{-2} in Sgr B2 (LMH). We have
detected fourteen features in Sgr B2 and four features in Orion-KL which have
not previously been reported in the ISM, but have not be able to plausibly
assign these transitions to any carrier.Comment: 12 pages, 3 figures. Accepted by MNRAS 12th January 200
Cell–cell and cell–matrix interactions at the presumptive stem cell niche of the chick corneal limbus
(1) Background: Owing to its ready availability and ease of acquisition, developing chick corneal tissue has long been used for research purposes. Here, we seek to ascertain the three-dimensional microanatomy and spatiotemporal interrelationships of the cells (epithelial and stromal), extracellular matrix, and vasculature at the corneo-scleral limbus as the site of the corneal stem cell niche of the chicken eye. (2) Methods: The limbus of developing (i.e., embryonic days (E) 16 and 18, just prior to hatch) and mature chicken eyes was imaged using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and the volume electron microscopy technique, serial-block face SEM (SBF-SEM), the latter technique allowing us to generate three-dimensional reconstructions from data sets of up to 1000 serial images; (3) Results: Data revealed that miniature limbal undulations of the embryonic basement membrane, akin to Palisades of Vogt (PoV), matured into distinct invaginations of epithelial cells that extended proximally into a vascularized limbal stroma. Basal limbal epithelial cells, moreover, occasionally exhibited a high nuclear:cytoplasmic ratio, which is a characteristic feature of stem cells. SBF-SEM identified direct cell–cell associations between corneal epithelial and stromal cells at the base of structures akin to limbal crypts (LCs), with cord-like projections of extracellular matrix extending from the basal epithelial lamina into the subjacent stroma, where they made direct contact with stomal cells in the immature limbus. (4) Conclusion: Similarities with human tissue suggest that the corneal limbus of the mature chicken eye is likely the site of a corneal stem cell niche. The ability to study embryonic corneas pre-hatch, where we see characteristic niche-like features emerge, thus provides an opportunity to chart the development of the limbal stem cell niche of the cornea
Gasless laparoscopy in rural India-registry outcomes and evaluation of the learning curve
Background
A program of gasless laparoscopy (GL) has been implemented in rural North-East India. To facilitate safe adoption, participating rural surgeons underwent rigorous training prior to independent clinical practice. An online registry was established to capture clinical data on safety and efficacy and to evaluate initial learning curves for gasless laparoscopy.
Methods
Surgeons who had completed the GL training program participated in the online RedCap Registry. Patients included in the registry provided informed consent for the use of their data. Data on operative times, conversion rates, perioperative complications, length of stay, and hospital costs were collected. Fixed reference cumulative sum (CUSUM) model was used to evaluate the learning curve based on operative times and conversion rates published in the literature.
Results
Four surgeons from three rural hospitals in North-East India participated in the registry. The data were collected over 12 months, from September 2019 to August 2020. One hundred and twenty-three participants underwent GL procedures, including 109 females (88.6%) and 14 males. GL procedures included cholecystectomy, appendicectomy, tubal ligation, ovarian cystectomy, diagnostic laparoscopy, and adhesiolysis. The mean operative time was 75.3 (42.05) minutes for all the surgeries. Conversion from GL to open surgery occurred in 11.4% of participants, with 8.9% converted to conventional laparoscopy. The main reasons for conversion were the inability to secure an operative view, lack of operating space, and adhesions. The mean length of stay was 3 (2.1) days. The complication rate was 5.7%, with one postoperative death. The CUSUM analysis for GL cholecystectomy showed a longer learning curve for operative time and few conversions. The learning curve for GL tubal ligation was relatively shorter.
Conclusion
Gasless laparoscopy can be safely implemented in the rural settings of Northeast India with appropriate training programs. Careful case selection is essential during the early stages of the surgical learning curve
Interleukin 7 from Maternal Milk Crosses the Intestinal Barrier and Modulates T- Cell Development in Offspring
Background
Breastfeeding protects against illnesses and death in hazardous environments, an
effect partly mediated by improved immune function. One hypothesis suggests that
factors within milk supplement the inadequate immune response of the offspring,
but this has not been able to account for a series of observations showing that
factors within maternally derived milk may supplement the development of the
immune system through a direct effect on the primary lymphoid organs. In a
previous human study we reported evidence suggesting a link between IL-7 in
breast milk and the thymic output of infants. Here we report evidence in mice of
direct action of maternally-derived IL-7 on T cell development in the offspring.
Methods and Findings
 We have used recombinant IL-7 labelled with a fluorescent dye to trace the
movement in live mice of IL-7 from the stomach across the gut and into the
lymphoid tissues. To validate the functional ability of maternally derived IL-
7 we cross fostered IL-7 knock-out mice onto normal wild type mothers. Subsets
of thymocytes and populations of peripheral T cells were significantly higher
than those found in knock-out mice receiving milk from IL-7 knock-out mothers.
Conclusions/Significance Our study provides direct evidence that interleukin 7,
a factor which is critical in the development of T lymphocytes, when maternally
derived can transfer across the intestine of the offspring, increase T cell
production in the thymus and support the survival of T cells in the peripheral
secondary lymphoid tissue
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