2,534 research outputs found
Natural history contributions of the University of Glasgow Exploration Society to Scotland and the World
Expeditions with a natural history focus have been
organised by University of Glasgow staff and
students since the 1930s. The educational benefits of
such expeditions to students have been reported by
Harper
et
al.
(
Journal
of
Biological
Education
51, 3-
16; 2017). Here, we present a short history of these
expeditions, concentrating on their scientific
achievements. In addition to expedition reports, a
large number of PhD theses, masters and honours
project reports and scientific papers have been
based on expedition work. Many biological
specimens have been deposited in museums,
including some new species. We provide case
histories of four expedition locations, to demonstrate
the variety of work done, and the value of returning
many times to the same place: Scotland, Trinidad and
Tobago, North Cyprus and Ecuador. A major problem
for expeditions is funding. For many years, the
Carnegie Trust for the Universities of Scotland ran a
funding stream that was crucial to the viability of
Scottish university expeditions, but this has sadly
now closed. For Glasgow University expeditions, the
Blodwen Lloyd Binns Bequest has provided a reliable
source since 1994, and we hope that it will continue
to do so
Estrogen and Mitochondrial Function in Disease
Anecdotal and scientific evidence suggest that the sex hormone estrogen provides significant health benefits in women. Women have higher estrogen levels than men. Circulating estrogen reaches its highest level during the reproductive period and steadily declines with the onset of menopause. The role of estrogen and estrogen receptors in both cellular physiology and pathophysiology has been controversial. Estrogen has anti-inflammatory and anti-oxidant effects, which preserve cell viability during cardiovascular incidents, but it enhances disease progression in the context of breast cancer. Estrogen mediates these responses via activation of estrogen receptor subtypes located in the cell membrane, nucleus, and mitochondrion. Further, transcription of nuclear and mitochondrial genes by estrogen yields products that play an important role in regulating mitochondrial function. Mitochondria are part of a highly dynamic network and undergo fission and fusion, produce cellular energy, adenosine 5Ⲡtriphosphate (ATP), and regulate cell death. Herein, we review the cell and receptor specific effects of estrogen on mitochondrial structure, function, and cell death under normal physiological conditions and in the context of cardiovascular disease, inflammation, neurodegeneration, and cancer. Further research is needed to elucidate the specific role of estrogenic control of mitochondria in health and disease
Ferromagnetism of He Films in the Low Field Limit
We provide evidence for a finite temperature ferromagnetic transition in
2-dimensions as in thin films of He on graphite, a model system
for the study of two-dimensional magnetism. We perform pulsed and CW NMR
experiments at fields of 0.03 - 0.48 mT on He at areal densities of 20.5 -
24.2 atoms/nm. At these densities, the second layer of He has a
strongly ferromagnetic tendency. With decreasing temperature, we find a rapid
onset of magnetization that becomes independent of the applied field at
temperatures in the vicinity of 1 mK. Both the dipolar field and the NMR
linewidth grow rapidly as well, which is consistent with a large (order unity)
polarization of the He spins.Comment: 4 figure
Crawford, Davis & the Right of Confrontation: Where Do We Go from Here?
Afternoon Panel Discussio
Magnetic Phase Diagram of Spin-1/2 Two-Leg Ladder with Four-Spin Ring Exchange
We study the spin-1/2 two-leg Heisenberg ladder with four-spin ring exchanges
under a magnetic field. We introduce an exact duality transformation which is
an extension of the spin-chirality duality developed previously and yields a
new self-dual surface in the parameter space. We then determine the magnetic
phase diagram using the numerical approaches of the density-matrix
renormalization-group and exact diagonalization methods. We demonstrate the
appearance of a magnetization plateau and the Tomonaga-Luttinger liquid with
dominant vector-chirality quasi-long-range order for a wide parameter regime of
strong ring exchange. A "nematic" phase, in which magnons form bound pairs and
the magnon-pairing correlation functions dominate, is also identified.Comment: 18pages, 7 figure
Rater Reliability of the Hardy Classification for Pituitary Adenomas in the Magnetic Resonance Imaging Era
Objectives The Hardy classification is used to classify pituitary tumors for clinical and research purposes. The scale was developed using lateral skull radiographs and encephalograms, and its reliability has not been evaluated in the magnetic resonance imaging (MRI) era. Design Fifty preoperative MRI scans of biopsy-proven pituitary adenomas using the sellar invasion and suprasellar extension components of the Hardy scale were reviewed. Setting This study was a cohort study set at a single institution. Participants There were six independent raters. Main Outcome Measures The main outcome measures of this study were interrater reliability, intrarater reliability, and percent agreement. Results Overall interrater reliability of both Hardy subscales on MRI was strong. However, reliability of the intermediate scores was weak, and percent agreement among raters was poor (12-16%) using the full scales. Dichotomizing the scale into clinically useful groups maintained strong interrater reliability for the sellar invasion scale and increased the percent agreement for both scales. Conclusion This study raises important questions about the reliability of the original Hardy classification. Editing the measure to a clinically relevant dichotomous scale simplifies the rating process and may be useful for preoperative tumor characterization in the MRI era. Future research studies should use the dichotomized Hardy scale (sellar invasion Grades 0-III versus Grade IV, suprasellar extension Types 0-C versus Type D)
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On-resin N-methylation of cyclic peptides for discovery of orally bioavailable scaffolds.
Backbone N-methylation is common among peptide natural products and has a substantial impact on both the physical properties and the conformational states of cyclic peptides. However, the specific impact of N-methylation on passive membrane diffusion in cyclic peptides has not been investigated systematically. Here we report a method for the selective, on-resin N-methylation of cyclic peptides to generate compounds with drug-like membrane permeability and oral bioavailability. The selectivity and degree of N-methylation of the cyclic peptide was dependent on backbone stereochemistry, suggesting that conformation dictates the regiochemistry of the N-methylation reaction. The permeabilities of the N-methyl variants were corroborated by computational studies on a 1,024-member virtual library of N-methyl cyclic peptides. One of the most permeable compounds, a cyclic hexapeptide (molecular mass = 755 Da) with three N-methyl groups, showed an oral bioavailability of 28% in rat
Adjusting bone mass for differences in projected bone area and other confounding variables: an allometric perspective.
The traditional method of assessing bone mineral density (BMD; given by bone mineral content [BMC] divided by projected bone area [Ap], BMD = BMC/Ap) has come under strong criticism by various authors. Their criticism being that the projected bone "area" (Ap) will systematically underestimate the skeletal bone "volume" of taller subjects. To reduce the confounding effects of bone size, an alternative ratio has been proposed called bone mineral apparent density [BMAD = BMC/(Ap)3/2]. However, bone size is not the only confounding variable associated with BMC. Others include age, sex, body size, and maturation. To assess the dimensional relationship between BMC and projected bone area, independent of other confounding variables, we proposed and fitted a proportional allometric model to the BMC data of the L2-L4 vertebrae from a previously published study. The projected bone area exponents were greater than unity for both boys (1.43) and girls (1.02), but only the boy's fitted exponent was not different from that predicted by geometric similarity (1.5). Based on these exponents, it is not clear whether bone mass acquisition increases in proportion to the projected bone area (Ap) or an estimate of projected bone volume (Ap)3/2. However, by adopting the proposed methods, the analysis will automatically adjust BMC for differences in projected bone size and other confounding variables for the particular population being studied. Hence, the necessity to speculate as to the theoretical value of the exponent of Ap, although interesting, becomes redundant
Local modes, phonons, and mass transport in solid He
We propose a model to treat the local motion of atoms in solid He as a
local mode. In this model, the solid is assumed to be described by the Self
Consistent Harmonic approximation, combined with an array of local modes. We
show that in the bcc phase the atomic local motion is highly directional and
correlated, while in the hcp phase there is no such correlation. The correlated
motion in the bcc phase leads to a strong hybridization of the local modes with
the T phonon branch, which becomes much softer than that obtained
through a Self Consistent Harmonic calculation, in agreement with experiment.
In addition we predict a high energy excitation branch which is important for
self-diffusion. Both the hybridization and the presence of a high energy branch
are a consequence of the correlation, and appear only in the bcc phase. We
suggest that the local modes can play the role in mass transport usually
attributed to point defects (vacancies). Our approach offers a more overall
consistent picture than obtained using vacancies as the predominant point
defect. In particular, we show that our approach resolves the long standing
controversy regarding the contribution of point defects to the specific heat of
solid He.Comment: 10 pages, 10 figure
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