1,585 research outputs found
Fast chromatin immunoprecipitation assay
Chromatin immunoprecipitation (ChIP) is a widely used method to explore in vivo interactions between proteins and DNA. The ChIP assay takes several days to complete, involves several tube transfers and uses either phenol–chlorophorm or spin columns to purify DNA. The traditional ChIP method becomes a challenge when handling multiple samples. We have developed an efficient and rapid Chelex resin-based ChIP procedure that dramatically reduces time of the assay and uses only a single tube to isolate PCR-ready DNA. This method greatly facilitates the probing of chromatin changes over many time points with several antibodies in one experiment
Massive Neutrinos and (Heterotic) String Theory
String theories in principle address the origin and values of the quark and
lepton masses. Perhaps the small values of neutrino masses could be explained
generically in string theory even if it is more difficult to calculate
individual values, or perhaps some string constructions could be favored by
generating small neutrino masses. We examine this issue in the context of the
well-known three-family standard-like Z_3 heterotic orbifolds, where the theory
is well enough known to construct the corresponding operators allowed by string
selection rules, and analyze the D- and F-flatness conditions. Surprisingly, we
find that a simple see-saw mechanism does not arise. It is not clear whether
this is a property of this construction, or of orbifolds more generally, or of
string theory itself. Extended see-saw mechanisms may be allowed; more analysis
will be needed to settle that issue. We briefly speculate on their form if
allowed and on the possibility of alternatives, such as small Dirac masses and
triplet see-saws. The smallness of neutrino masses may be a powerful probe of
string constructions in general. We also find further evidence that there are
only 20 inequivalent models in this class, which affects the counting of string
vacua.Comment: 18 pages in RevTeX format. Single-column postscript version available
at http://sage.hep.upenn.edu/~bnelson/singpre.p
Instanton effects and linear-chiral duality
We discuss duality between the linear and chiral dilaton formulations, in the
presence of super-Yang-Mills instanton corrections to the effective action. In
contrast to previous work on the subject, our approach appeals directly to
explicit instanton calculations and does not rely on the introduction of an
auxiliary Veneziano-Yankielowicz superfield. We discuss duality in the case of
an axion that has a periodic scalar potential, and find that the bosonic fields
of the dual linear multiplet have a modified interpretation. We note that
symmetries of the axion potential manifest themselves as symmetries of the
equations of motion for the linear multiplet. We also make some brief remarks
regarding dilaton stabilization. We point out that corrections recently studied
by Dijkgraaf and Vafa can be used to stabilize the axion in the case of a
single super-Yang-Mills condensate.Comment: 1+18 pages, 1 figure, comments and references adde
Direct Recruitment of Insulin Receptor and ERK Signaling Cascade to Insulin-Inducible Gene Loci
Predicting climate-sensitive water-related disease trends based on health, seasonality and weather data in Fiji
Leptospirosis, typhoid and dengue are three water-related diseases influenced by environmental factors. We examined whether seasonality and rainfall predict reported syndromes associated with leptospirosis, typhoid and dengue in Fiji. Poisson generalised linear models were fitted with s6 early warning, alert and response system (EWARS) syndromic conditions from March 2016 until December 2020, incorporating seasonality, temperature and rainfall. Watery diarrhoea, prolonged fever and suspected dengue displayed seasonal trends with peaks corresponding with the rainy season, while bloody diarrhoea, acute fever with rash and acute jaundice syndrome did not. Seasonality was the most common predictor for watery and bloody diarrhoea, prolonged fever, suspected dengue, and acute fever plus rash in those aged 5 and over, explaining between 0.4 % – 37.8 % of the variation across all conditions. Higher rainfall was the most common predictor for acute fever plus rash and acute jaundice syndrome in children under 5, explaining between 1.0 % – 7.6 % variation across all conditions. Each EWARS syndromic condition case peak was associated with a different rainfall lag, varying between 0 and 11 weeks. The relationships between EWARS, rainfall and seasonality show that it is possible to predict when outbreaks will occur by following seasonality and rainfall. Pre-positioning of diagnostic and treatment resources could then be aligned with seasonality and rainfall peaks to plan and address water-related disease outbreaks
Altered skeletal muscle mitochondrial phenotype in COPD: disease vs. disuse
Patients with chronic obstructive pulmonary disease (COPD) exhibit an altered skeletal muscle mitochondrial phenotype, which often includes reduced mitochondrial density, altered respiratory function, and elevated oxidative stress. As this phenotype may be explained by the sedentary lifestyle that commonly accompanies this disease, the aim of this study was to determine whether such alterations are still evident when patients with COPD are compared to control subjects matched for objectively measured physical activity (PA; accelerometry). Indexes of mitochondrial density [citrate synthase (CS) activity], respiratory function (respirometry in permeabilized fibers), and muscle oxidative stress [4-hydroxynonenal (4-HNE) content] were assessed in muscle fibers biopsied from the vastus lateralis of nine patients with COPD and nine PA-matched control subjects (CON). Despite performing similar levels of PA (CON: 18 ± 3, COPD: 20 ± 7 daily minutes moderate-to-vigorous PA; CON: 4,596 ± 683, COPD: 4,219 ± 763 steps per day, P \u3e 0.70), patients with COPD still exhibited several alterations in their mitochondrial phenotype, including attenuated skeletal muscle mitochondrial density (CS activity; CON 70.6 ± 3.8, COPD 52.7 ± 6.5 U/mg, P \u3c 0.05), altered mitochondrial respiration [e.g., ratio of complex I-driven state 3 to complex II-driven state 3 (CI/CII); CON: 1.20 ± 0.11, COPD: 0.90 ± 0.05, P \u3c 0.05), and oxidative stress (4-HNE; CON: 1.35 ± 0.19, COPD: 2.26 ± 0.25 relative to β-actin, P \u3c 0.05). Furthermore, CS activity (r = 0.55), CI/CII (r = 0.60), and 4-HNE (r = 0.49) were all correlated with pulmonary function, assessed as forced expiratory volume in 1 s (P \u3c 0.05), but not PA (P \u3e 0.05). In conclusion, the altered mitochondrial phenotype in COPD is present even in the absence of differing levels of PA and appears to be related to the disease itself
Mitochondrial DNA suggests at least 11 origins of parasitism in angiosperms and reveals genomic chimerism in parasitic plants
Rapid Quenching of Galaxies at Cosmic Noon
The existence of massive quiescent galaxies at high redshift seems to require
rapid quenching, but it is unclear whether all quiescent galaxies have gone
through this phase and what physical mechanisms are involved. To study rapid
quenching, we use rest-frame colors to select 12 young quiescent galaxies at . From spectral energy distribution fitting, we find that they all
experienced intense starbursts prior to rapid quenching. We confirm this with
deep Magellan/FIRE spectroscopic observations for a subset of seven galaxies.
Broad emission lines are detected for two galaxies and are most likely caused
by AGN activity. The other five galaxies do not show any emission features,
suggesting that gas has already been removed or depleted. Most of the rapidly
quenched galaxies are more compact than normal quiescent galaxies, providing
evidence for a central starburst in the recent past. We estimate an average
transition time of for the rapid quenching phase. Approximately
of quiescent galaxies at have gone through rapid quenching; this
fraction increases to at . We identify analogs in the TNG100
simulation and find that rapid quenching for these galaxies is driven by AGN,
and for half of the cases, gas-rich major mergers seem to trigger the
starburst. We conclude that these massive quiescent galaxies are not just
rapidly quenched but also rapidly formed through a major starburst. We
speculate that mergers drive gas inflow towards the central regions and grow
supermassive black holes, leading to rapid quenching by AGN feedback.Comment: Submitted to ApJ. Comments are welcom
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