1,125 research outputs found
Geikie's field researches and their geological controversies
All of us were introduced to the Moine Thrust Belt and its controversies by the late Mike Coward. We are indebted to him for instilling a passion for structural geology, challenging conventional wisdom and for tales of early protagonists. We also thank the late John Mendum, who kindly shared a copy of his notes on the Highlands Controversy, together with Robert Neller, Collections Officer at Haslemere Educational Museum, for facilitating access to Geikieâs field-notes and artwork.Peer reviewedPostprin
Ionic liquid-based strategy for predicting protein aggregation propensity and thermodynamic stability
Novel drug candidates are continuously being developed to combat the most life-threatening diseases; however, many promising protein therapeutics are dropped from the pipeline. During biological and industrial processes, protein therapeutics are exposed to various stresses such as fluctuations in temperature, solvent pH, and ionic strength. These can lead to enhanced protein aggregation propensity, one of the greatest challenges in drug development. Recently, ionic liquids (ILs), in particular, biocompatible choline chloride ([Cho]Cl)-based ILs, have been used to hinder stress-induced protein conformational changes. Herein, we develop an IL-based strategy to predict protein aggregation propensity and thermodynamic stability. We examine three key variables influencing protein misfolding: pH, ionic strength, and temperature. Using dynamic light scattering, zeta potential, and variable temperature circular dichroism measurements, we systematically evaluate the structural, thermal, and thermodynamic stability of fresh immunoglobin G4 (IgG4) antibody in water and 10, 30, and 50 wt % [Cho]Cl. Additionally, we conduct molecular dynamics simulations to examine IgG4 aggregation propensity in each system and the relative favorability of different [Cho]Cl-IgG4 packing interactions. We re-evaluate each system following 365 days of storage at 4 °C and demonstrate how to predict the thermodynamic properties and protein aggregation propensity over extended storage, even under stress conditions. We find that increasing [Cho]Cl concentration reduced IgG4 aggregation propensity both fresh and following 365 days of storage and demonstrate the potential of using our predictive IL-based strategy and formulations to radically increase protein stability and storage
California Extremely Large Telescope: Conceptual Design for a Thirty-Meter Telescope
Following great success in the creation of the Keck Observatory, scientists at the California Institute of
Technology and the University of California have begun to explore the scientific and technical prospects
for a much larger telescope. The Keck telescopes will remain the largest telescopes in the world for a
number of years, with many decades of forefront research ahead after that. Though these telescopes
have produced dramatic discoveries, it is already clear that even larger telescopes must be built if we
are to address some of the most profound questions about our universe. The time required to build a
larger telescope is approximately ten years, and the California community is presently well-positioned
to begin its design and construction. The same scientists who conceived, led the design, and guided
the construction of the Keck Observatory have been intensely engaged in a study of the prospects for
an extremely large telescope. Building on our experience with the Keck Observatory, we have concluded
that the large telescope is feasible and is within the bounds set by present-day technology. Our reference
telescope has a diameter of 30 meters, the largest size we believe can be built with acceptable risk. The
project is currently designated the California Extremely Large Telescope (CELT)
Quantised Vortices in an Exciton-Polariton Fluid
One of the most striking quantum effects in a low temperature interacting
Bose gas is superfluidity. First observed in liquid 4He, this phenomenon has
been intensively studied in a variety of systems for its amazing features such
as the persistence of superflows and the quantization of the angular momentum
of vortices. The achievement of Bose-Einstein condensation (BEC) in dilute
atomic gases provided an exceptional opportunity to observe and study
superfluidity in an extremely clean and controlled environment. In the solid
state, Bose-Einstein condensation of exciton polaritons has now been reported
several times. Polaritons are strongly interacting light-matter
quasi-particles, naturally occurring in semiconductor microcavities in the
strong coupling regime and constitute a very interesting example of composite
bosons. Even though pioneering experiments have recently addressed the
propagation of a fluid of coherent polaritons, still no conclusive evidence is
yet available of its superfluid nature. In the present Letter, we report the
observation of spontaneous formation of pinned quantised vortices in the
Bose-condensed phase of a polariton fluid by means of phase and amplitude
imaging. Theoretical insight into the possible origin of such vortices is
presented in terms of a generalised Gross-Pitaevskii equation. The implications
of our observations concerning the superfluid nature of the non-equilibrium
polariton fluid are finally discussed.Comment: 14 pages, 4 figure
Spatially Resolved Ultraviolet Spectroscopy of the Great Dimming of Betelgeuse
The bright supergiant, Betelgeuse (Alpha Orionis, HD 39801) experienced a
visual dimming during 2019 December and the first quarter of 2020 reaching an
historic minimum 2020 February 713. During 2019 September-November, prior to
the optical dimming event, the photosphere was expanding. At the same time,
spatially resolved ultraviolet spectra using the Hubble Space Telescope/Space
Telescope Imaging Spectrograph revealed a substantial increase in the
ultraviolet spectrum and Mg II line emission from the chromosphere over the
southern hemisphere of the star. Moreover, the temperature and electron density
inferred from the spectrum and C II diagnostics also increased in this
hemisphere. These changes happened prior to the Great Dimming Event. Variations
in the Mg II k-line profiles suggest material moved outwards in response to the
passage of a pulse or acoustic shock from 2019 September through 2019 November.
It appears that this extraordinary outflow of material from the star, likely
initiated by convective photospheric elements, was enhanced by the coincidence
with the outward motions in this phase of the 400 day pulsation cycle.
These ultraviolet observations appear to provide the connecting link between
the known large convective cells in the photosphere and the mass ejection event
that cooled to form the dust cloud in the southern hemisphere imaged in 2019
December, and led to the exceptional optical dimming of Betelgeuse in 2020
February.Comment: 11 pages, 8 figures, Astrophysical Journal, accepte
Measuring the mass of the central black hole in the bulgeless galaxy ngc 4395 from gas dynamical modeling
NGC 4395 is a bulgeless spiral galaxy, harboring one of the nearest known type 1 Seyfert nuclei. Although there is no consensus on the mass of its central engine, several estimates suggest it is one of the lightest massive black holes (MBHs) known. We present the first direct dynamical measurement of the mass of this MBH from a combination of two-dimensional gas kinematic data, obtained with the adaptive optics assisted near-infrared integral field spectrograph Gemini/NIFS and high-resolution multiband photometric data from Hubble Space Telescope's Wide Field Camera 3. We use the photometric data to model the shape and stellar mass-to-light ratio of the nuclear star cluster (NSC). From the Gemini/NIFS observations, we derive the kinematics of warm molecular hydrogen gas as traced by emission through the H2 1â0 S(1) transition. These kinematics show a clear rotational signal, with a position angle orthogonal to NGC 4395's radio jet. Our best-fitting tilted ring models of the kinematics of the molecular hydrogen gas contain a black hole with mass M={4}-3+8Ă {10}5 Mâ (3Ï uncertainties) embedded in an NSC of mass M=2Ă {10}6 Mâ. Our black hole mass measurement is in excellent agreement with the reverberation mapping mass estimate of Peterson et al. but shows some tension with other mass measurement methods based on accretion signals
The Cambridge Centre for Ageing and Neuroscience (Cam-CAN) study protocol: a cross-sectional, lifespan, multidisciplinary examination of healthy cognitive ageing.
BACKGROUND: As greater numbers of us are living longer, it is increasingly important to understand how we can age healthily. Although old age is often stereotyped as a time of declining mental abilities and inflexibility, cognitive neuroscience reveals that older adults use neural and cognitive resources flexibly, recruiting novel neural regions and cognitive processes when necessary. Our aim in this project is to understand how age-related changes to neural structure and function interact to support cognitive abilities across the lifespan. METHODS/DESIGN: We are recruiting a population-based cohort of 3000 adults aged 18 and over into Stage 1 of the project, where they complete an interview including health and lifestyle questions, a core cognitive assessment, and a self-completed questionnaire of lifetime experiences and physical activity. Of those interviewed, 700 participants aged 18-87 (100 per age decile) continue to Stage 2 where they undergo cognitive testing and provide measures of brain structure and function. Cognition is assessed across multiple domains including attention and executive control, language, memory, emotion, action control and learning. A subset of 280 adults return for in-depth neurocognitive assessment in Stage 3, using functional neuroimaging experiments across our key cognitive domains.Formal statistical models will be used to examine the changes that occur with healthy ageing, and to evaluate age-related reorganisation in terms of cognitive and neural functions invoked to compensate for overall age-related brain structural decline. Taken together the three stages provide deep phenotyping that will allow us to measure neural activity and flexibility during performance across a number of core cognitive functions. This approach offers hypothesis-driven insights into the relationship between brain and behaviour in healthy ageing that are relevant to the general population. DISCUSSION: Our study is a unique resource of neuroimaging and cognitive measures relevant to change across the adult lifespan. Because we focus on normal age-related changes, our results may contribute to changing views about the ageing process, lead to targeted interventions, and reveal how normal ageing relates to frail ageing in clinicopathological conditions such as Alzheimer's disease.The Cambridge Centre for Ageing and Neuroscience (Cam-CAN) research was supported by the Biotechnology and Biological Sciences Research Council (grant number BB/H008217/1).This is the final published version of the article. It first appeared from BioMed Central via http://dx.doi.org/10.1186/s12883-014-0204-
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