141 research outputs found
Enhanced rigid-bond restraints
An extension is proposed to the rigid-bond description of atomic thermal motion in crystals
RNA oligomers at atomic resolution containing 1âmethylpseudouridine, an essential building block of mRNA vaccines
All widely used mRNA vaccines against COVIDâ19 contain in their sequence 1âmethylpseudouridine (m1Κ) instead of uridine. In this publication, we report two high resolution crystal structures (at up to 1.01 and 1.32â
Ă
, respectively) of one such doubleâstranded 12âmer RNA sequence crystallized in two crystal forms. The structures are compared with similar structures which do not contain this modification. Additionally, the Xâray structure of 1âmethylâpseudouridine itself was determined
ANODE: anomalous and heavy-atom density calculation
The program ANODE determines anomalous (or heavy-atom) densities by reversing the usual procedure for experimental phase determination. Instead of adding a phase shift to the heavy-atom phases to obtain a starting value for the native protein phase, this phase shift is subtracted from the native phase to obtain the heavy-atom substructure phase
A multi-wavelength polarimetric study of the blazar CTA 102 during a Gamma-ray flare in 2012
We perform a multi-wavelength polarimetric study of the quasar CTA 102 during
an extraordinarily bright -ray outburst detected by the {\it Fermi}
Large Area Telescope in September-October 2012 when the source reached a flux
of F photons cm s.
At the same time the source displayed an unprecedented optical and NIR
outburst. We study the evolution of the parsec scale jet with ultra-high
angular resolution through a sequence of 80 total and polarized intensity Very
Long Baseline Array images at 43 GHz, covering the observing period from June
2007 to June 2014. We find that the -ray outburst is coincident with
flares at all the other frequencies and is related to the passage of a new
superluminal knot through the radio core. The powerful -ray emission is
associated with a change in direction of the jet, which became oriented more
closely to our line of sight (1.2) during the ejection of
the knot and the -ray outburst. During the flare, the optical polarized
emission displays intra-day variability and a clear clockwise rotation of
EVPAs, which we associate with the path followed by the knot as it moves along
helical magnetic field lines, although a random walk of the EVPA caused by a
turbulent magnetic field cannot be ruled out. We locate the -ray
outburst a short distance downstream of the radio core, parsecs from the black
hole. This suggests that synchrotron self-Compton scattering of near-infrared
to ultraviolet photons is the probable mechanism for the -ray
production.Comment: Accepted for publication in The Astrophysical Journa
DESIGN FOR CONTAINMENT TECHNIQUES TO REDUCE SPACECRAFT RE-ENTRY FOOTPRINT
Clean Space is an ESA initiative to address the technological challenges in reaching sustainability of space activities on Earth and in orbit. Its purpose is to guarantee the safety of the human population and future space activities. Under this initiative, different solutions, such as Design for Demise (D4D) and debris removal, are studied.
Design for Containment (D4C) is the design of spacecraft systems using methods that keep harmful objects under control or within limits, so as to reduce the number of impacting fragments on ground during re-entry events. While potentially increasing the impact mass, the lower number of fragments may significantly reduce the overall casualty risk. These methods could render future un-controlled re-entry missions compliant to the space debris mitigation guidelines without major design changes, that could put them at cost or schedule risk. In this paper, the system level investigations, simulation results and first findings of the on-going ESA funded study "Containment Techniques to Reduce Spacecraft Re-Entry Footprintâ (also called the D4C study) are presented. The study aims to identify and validate promising containment techniques and to provide an update to the current material database for re-entry models (ESTIMATE). Feedback to the ESA guidelines for demise verification (DIVE) will also be a valuable outcom
Haplotype differences for copy number variants in the 22q11.23 region among human populations: a pigmentation-based model for selective pressure.
Two gene clusters are tightly linked in a narrow region of chromosome 22q11.23: the macrophage migration inhibitory factor (MIF) gene family and the glutathione S-transferase theta class. Within 120âkb in this region, two 30-kb deletions reach high frequencies in human populations. This gives rise to four haplotypic arrangements, which modulate the number of genes in both families. The variable patterns of linkage disequilibrium (LD) between these copy number variants (CNVs) in diverse human populations remain poorly understood. We analyzed 2469 individuals belonging to 27 human populations with different ethnic origins. Then we correlated the genetic variability of 22q11.23 CNVs with environmental variables. We confirmed an increasing strength of LD from Africa to Asia and to Europe. Further, we highlighted strongly significant correlations between the frequency of one of the haplotypes and pigmentation-related variables: skin color (R2=0.675, P<0.001), distance from the equator (R2=0.454, P<0.001), UVA radiation (R2=0.439, P<0.001), and UVB radiation (R2=0.313, P=0.002). The fact that all MIF-related genes are retained on this haplotype and the evidences gleaned from experimental systems seem to agree with the role of MIF-related genes in melanogenesis. As such, we propose a model that explains the geographic and ethnic distribution of 22q11.23 CNVs among human populations, assuming that MIF-related gene dosage could be associated with adaptation to low UV radiatio
The Repeating Flaring Activity of Blazar AO 0235+164
Context. Blazar AO 0235+164, located at redshift z = 0.94, has undergone
several sharp multi-spectral-range flaring episodes during the last decades. In
particular, the episodes peaking in 2008 and 2015, that received extensive
multi-wavelength coverage, exhibited interesting behavior.
Aims. We study the actual origin of these two observed flares by constraining
the properties of the observed photo-polarimetric variability, those of the
broad-band spectral energy-distribution and the observed time-evolution
behavior of the source as seen by ultra-high resolution total-flux and
polarimetric Very-long-baseline interferometry (VLBI) imaging.
Methods. The analysis of VLBI images allows us to constrain kinematic and
geometrical parameters of the 7 mm jet. We use the Discrete Correlation
Function to compute the statistical correlation and the delays between emission
at different spectral ranges. Multi-epoch modeling of the spectral energy
distributions allows us to propose specific models of emission; in particular
for the unusual spectral features observed in this source in the X-ray region
of the spectrum during strong multi spectral-range flares.
Results. We find that these X-ray spectral features can be explained by an
emission component originating in a separate particle distribution than the one
responsible for the two standard blazar bumps. This is in agreement with the
results of our correlation analysis that do not find a strong correlation
between the X-rays and the remaining spectral ranges. We find that both
external Compton dominated and synchrotron self-Compton dominated models can
explain the observed spectral energy distributions. However, synchrotron
self-Compton models are strongly favored by the delays and geometrical
parameters inferred from the observations
Search for CP Violation in the Decay Z -> b (b bar) g
About three million hadronic decays of the Z collected by ALEPH in the years
1991-1994 are used to search for anomalous CP violation beyond the Standard
Model in the decay Z -> b \bar{b} g. The study is performed by analyzing
angular correlations between the two quarks and the gluon in three-jet events
and by measuring the differential two-jet rate. No signal of CP violation is
found. For the combinations of anomalous CP violating couplings, and , limits of \hat{h}_b < 0.59h^{\ast}_{b} < 3.02$ are given at 95\% CL.Comment: 8 pages, 1 postscript figure, uses here.sty, epsfig.st
Stable isotope and minor element proxies for Eocene climate of Seymour Island, Antarctica
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94846/1/palo900.pd
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