326 research outputs found
Phase transition kinetics revealed in laser-heated dynamic diamond anvil cells
We report on a novel approach to dynamic compression of materials that
bridges the gap between previous static- and dynamic- compression techniques,
allowing to explore a wide range of pathways in the pressure-temperature space.
By combining a dynamic-diamond anvil cell setup with double-sided laser-heating
and in situ X-ray diffraction, we are able to perform dynamic compression at
high temperature and characterize structural transitions with unprecedented
time resolution. Using this method, we investigate the phase
transition of iron under dynamic compression for the first time, reaching
compression rates of hundreds of GPa/s and temperatures of 2000 K. Our results
demonstrate a distinct response of the and
transitions to the high compression rates achieved. These findings open up new
avenues to study tailored dynamic compression pathways in the
pressure-temperature space and highlight the potential of this platform to
capture kinetic effects in a diamond anvil cell.Comment: Reworked the text and figures to be more in line with the format of
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Phase transition kinetics revealed by <i>in situ</i> x-ray diffraction in laser-heated dynamic diamond anvil cells
We report successful coupling of dynamic loading in a diamond anvil cell and stable laser heating, which enables compression rates up to 500 GPa/s along high-temperature isotherms. Dynamic loading in a diamond-anvil cell allows exploration of a wider range of pathways in the pressure-temperature space compared to conventional dynamic compression techniques. By in situ x-ray diffraction, we are able to characterize and monitor the structural transitions with the appropriate time resolution i.e., millisecond timescales. Using this method, we investigate the γ−ε phase transition of iron under dynamic compression, reaching compression rates of hundreds of GPa/s and temperatures of 2000 K. Our results demonstrate a distinct response of the γ−ε and α− ε transitions to the high compression rates achieved, possibly due to the different transition mechanisms. These findings open up new avenues to study tailored dynamic compression pathways in the pressure-temperature space and highlight the potential of this platform to capture kinetic effects (over ms time scales) in a diamond anvil cell
Three-dimensional structure determination from a single view
The ability to determine the structure of matter in three dimensions has
profoundly advanced our understanding of nature. Traditionally, the most widely
used schemes for 3D structure determination of an object are implemented by
acquiring multiple measurements over various sample orientations, as in the
case of crystallography and tomography (1,2), or by scanning a series of thin
sections through the sample, as in confocal microscopy (3). Here we present a
3D imaging modality, termed ankylography (derived from the Greek words ankylos
meaning 'curved' and graphein meaning 'writing'), which enables complete 3D
structure determination from a single exposure using a monochromatic incident
beam. We demonstrate that when the diffraction pattern of a finite object is
sampled at a sufficiently fine scale on the Ewald sphere, the 3D structure of
the object is determined by the 2D spherical pattern. We confirm the
theoretical analysis by performing 3D numerical reconstructions of a sodium
silicate glass structure at 2 Angstrom resolution and a single poliovirus at 2
- 3 nm resolution from 2D spherical diffraction patterns alone. Using
diffraction data from a soft X-ray laser, we demonstrate that ankylography is
experimentally feasible by obtaining a 3D image of a test object from a single
2D diffraction pattern. This approach of obtaining complete 3D structure
information from a single view is anticipated to find broad applications in the
physical and life sciences. As X-ray free electron lasers (X-FEL) and other
coherent X-ray sources are under rapid development worldwide, ankylography
potentially opens a door to determining the 3D structure of a biological
specimen in a single pulse and allowing for time-resolved 3D structure
determination of disordered materials.Comment: 30 page
Guidelines for the Development of Comprehensive Care Centers for Congenital Adrenal Hyperplasia: Guidance from the CARES Foundation Initiative
Patients with rare and complex diseases such as congenital adrenal hyperplasia (CAH) often receive fragmented and inadequate care unless efforts are coordinated among providers. Translating the concepts of the medical home and comprehensive health care for individuals with CAH offers many benefits for the affected individuals and their families. This manuscript represents the recommendations of a 1.5 day meeting held in September 2009 to discuss the ideal goals for comprehensive care centers for newborns, infants, children, adolescents, and adults with CAH. Participants included pediatric endocrinologists, internal medicine and reproductive endocrinologists, pediatric urologists, pediatric surgeons, psychologists, and pediatric endocrine nurse educators. One unique aspect of this meeting was the active participation of individuals personally affected by CAH as patients or parents of patients. Representatives of Health Research and Services Administration (HRSA), New York-Mid-Atlantic Consortium for Genetics and Newborn Screening Services (NYMAC), and National Newborn Screening and Genetics Resource Center (NNSGRC) also participated. Thus, this document should serve as a “roadmap” for the development phases of comprehensive care centers (CCC) for individuals and families affected by CAH
Guidelines for the Development of Comprehensive Care Centers for Congenital Adrenal Hyperplasia: Guidance from the CARES Foundation Initiative
Patients with rare and complex diseases such as congenital adrenal hyperplasia (CAH) often receive fragmented and inadequate care unless efforts are coordinated among providers. Translating the concepts of the medical home and comprehensive health care for individuals with CAH offers many benefits for the affected individuals and their families. This manuscript represents the recommendations of a 1.5 day meeting held in September 2009 to discuss the ideal goals for comprehensive care centers for newborns, infants, children, adolescents, and adults with CAH. Participants included pediatric endocrinologists, internal medicine and reproductive endocrinologists, pediatric urologists, pediatric surgeons, psychologists, and pediatric endocrine nurse educators. One unique aspect of this meeting was the active participation of individuals personally affected by CAH as patients or parents of patients. Representatives of Health Research and Services Administration (HRSA), New York-Mid-Atlantic Consortium for Genetics and Newborn Screening Services (NYMAC), and National Newborn Screening and Genetics Resource Center (NNSGRC) also participated. Thus, this document should serve as a “roadmap” for the development phases of comprehensive care centers (CCC) for individuals and families affected by CAH
Rational Design of Temperature-Sensitive Alleles Using Computational Structure Prediction
Temperature-sensitive (ts) mutations are mutations that exhibit a mutant phenotype at high or low temperatures and a wild-type phenotype at normal temperature. Temperature-sensitive mutants are valuable tools for geneticists, particularly in the study of essential genes. However, finding ts mutations typically relies on generating and screening many thousands of mutations, which is an expensive and labor-intensive process. Here we describe an in silico method that uses Rosetta and machine learning techniques to predict a highly accurate “top 5” list of ts mutations given the structure of a protein of interest. Rosetta is a protein structure prediction and design code, used here to model and score how proteins accommodate point mutations with side-chain and backbone movements. We show that integrating Rosetta relax-derived features with sequence-based features results in accurate temperature-sensitive mutation predictions
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