322 research outputs found
Design of crystal-like aperiodic solids with selective disorder--phonon coupling
Functional materials design normally focuses on structurally-ordered systems
because disorder is considered detrimental to many important physical
properties. Here we challenge this paradigm by showing that particular types of
strongly-correlated disorder can give rise to useful characteristics that are
inaccessible to ordered states. A judicious combination of low-symmetry
building unit and high-symmetry topological template leads to aperiodic
"procrystalline" solids that harbour this type of topological disorder. We
identify key classes of procrystalline states together with their
characteristic diffraction behaviour, and establish a variety of mappings onto
known and target materials. Crucially, the strongly-correlated disorder we
consider is associated with specific sets of modulation periodicities
distributed throughout the Brillouin zone. Lattice dynamical calculations
reveal selective disorder-phonon coupling to lattice vibrations characterised
by these same periodicities. The principal effect on the phonon spectrum is to
bring about dispersion in energy rather than wave-vector, as in the
poorly-understood "waterfall" effect observed in relaxor ferroelectrics. This
property of procrystalline solids suggests a mechanism by which
strongly-correlated topological disorder might allow new and useful
functionalities, including independently-optimised thermal and electronic
transport behaviour as required for high-performance thermoelectrics.Comment: 4 figure
The effect of the COVID-19 health disruptions on breast cancer mortality for older women: A semi-Markov modelling approach
We propose a methodology to quantify the impact on breast cancer mortality of
diagnostic delays caused by public health measures introduced as a response to
the COVID-19 pandemic. These measures affected cancer pathways by halting
cancer screening, delaying diagnostic tests, and reducing the numbers of
patients starting treatment. We introduce a semi-Markov model, to quantify the
impact of the pandemic based on publicly available population data for women
age 65{89 years in England and relevant medical literature. We quantify
age-specific excess deaths, for a period up to 5 years, along with years of
life expectancy lost and change in cancer mortality by cancer stage. Our
analysis suggests a 3-6% increase in breast cancer deaths, corresponding to
more than 40 extra deaths, per 100,000 women, after age 65 years old over 5
years, and a 4-6% increase in registrations of advanced (Stage 4) breast
cancer. Our modelling approach exhibits consistent results in sensitivity
analyses, providing a model that can account for changes in breast cancer
diagnostic and treatment services
Insurance pricing for breast cancer under different multiple state models
In this paper we consider pricing of insurance contracts for breast cancer
risk based on three multiple state models. Using population data in England and
data from the medical literature, we calibrate a collection of semi-Markov and
Markov models. Considering an industry-based Markov model as a baseline model,
we demonstrate the strengths of a more detailed model while showing the
importance of accounting for duration dependence in transition rates. We
quantify age-specific cancer incidence and cancer survival by stage along with
type-specific mortality rates based on the semi-Markov model which accounts for
unobserved breast cancer cases and progression through breast cancer stages.
Using the developed models, we obtain actuarial net premiums for a specialised
critical illness and life insurance product. Our analysis shows that the
semi-Markov model leads to results aligned with empirical evidence. Our
findings point out the importance of accounting for the time spent with
diagnosed or undiagnosed pre-metastatic breast cancer in actuarial
applications
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Translation of Diverse Aramid- And 1,3-Dicarbonyl-peptides by Wild Type Ribosomes in Vitro
Here, we report that wild type Escherichia coli ribosomes accept and elongate precharged initiator tRNAs acylated with multiple benzoic acids, including aramid precursors, as well as malonyl (1,3-dicarbonyl) substrates to generate a diverse set of aramid-peptide and polyketide-peptide hybrid molecules. This work expands the scope of ribozyme- and ribosome-catalyzed chemical transformations, provides a starting point for in vivo translation engineering efforts, and offers an alternative strategy for the biosynthesis of polyketide-peptide natural products
Individuals with higher metabolic rates have lower levels of reactive oxygen species in vivo
There is increasing interest in the effect of energy metabolism on oxidative stress, but much ambiguity over the relationship between the rate of oxygen consumption and the generation of reactive oxygen species (ROS). Production of ROS (such as hydrogen peroxide, H2O2) in the mitochondria is primarily inferred indirectly from measurements in vitro, which may not reflect actual ROS production in living animals. Here, we measured in vivo H2O2 content using the recently developed MitoB probe that becomes concentrated in the mitochondria of living organisms, where it is converted by H2O2 into an alternative form termed MitoP; the ratio of MitoP/MitoB indicates the level of mitochondrial H2O2 in vivo. Using the brown trout Salmo trutta, we tested whether this measurement of in vivo H2O2 content over a 24 h-period was related to interindividual variation in standard metabolic rate (SMR). We showed that the H2O2 content varied up to 26-fold among fish of the same age and under identical environmental conditions and nutritional states. Interindividual variation in H2O2 content was unrelated to mitochondrial density but was significantly associated with SMR: fish with a higher mass-independent SMR had a lower level of H2O2. The mechanism underlying this observed relationship between SMR and in vivo H2O2 content requires further investigation, but may implicate mitochondrial uncoupling which can simultaneously increase SMR but reduce ROS production. To our knowledge, this is the first study in living organisms to show that individuals with higher oxygen consumption rates can actually have lower levels of H2O2
Closed forms and multi-moment maps
We extend the notion of multi-moment map to geometries defined by closed
forms of arbitrary degree. We give fundamental existence and uniqueness results
and discuss a number of essential examples, including geometries related to
special holonomy. For forms of degree four, multi-moment maps are guaranteed to
exist and are unique when the symmetry group is (3,4)-trivial, meaning that the
group is connected and the third and fourth Lie algebra Betti numbers vanish.
We give a structural description of some classes of (3,4)-trivial algebras and
provide a number of examples.Comment: 36 page
Negative area compressibility in silver(i) tricyanomethanide
The metal–organic framework copper(I) tricyanomethanide, Cu(tcm), undergoes a ferroelastic transition on cooling below Tf = 240 K. Thermal expansion measurements reveal an order-of-magnitude variation in framework flexibility across Tf. The low-temperature phase α-Cu(tcm) exhibits colossal positive and negative thermal expansion that is the strongest ever reported for a framework material. On exposure to acetonitrile, Cu(tcm) undergoes a reconstructive solid-phase transition to acetonitrilocopper(I) tricyanomethanide. This transition can be reversed by heating under vacuum. Infrared spectroscopy measurements are sensitive to the phase change, suggesting that Cu(tcm) may find application in solid-phase acetonitrile sensing
Estimating the global cost of vision impairment and its major causes: protocol for a systematic review
Introduction: Vision impairment (VI) places a burden on individuals, health systems and society in general. In order to support the case for investing in eye health services, an updated cost of illness study that measures the global impact of VI is necessary. To perform such a study, a systematic review of the literature is needed. Here we outline the protocol for a systematic review to describe and summarise the costs associated with VI and its major causes.
Methods and analysis: We will systematically search in Medline (Ovid) and the Centre for Reviews and Dissemination database which includes the National Health Service Economics Evaluation Database. No language or geographical restriction will be applied. Additional literature will be identified by reviewing the references in the included studies and by contacting field experts. Grey literature will be considered. The review will include any study published from 1 January 2000 to November 2019 that provides information about costs of illness, burden of disease and/or loss of well-being in participants with VI due to an unspecified cause or due to one of the seven leading causes globally.
Two reviewers will independently screen studies and extract relevant data from included studies. Methodological quality of economic studies will be assessed based on the British Medical Journal checklist for economic submissions adapted to costs of illness studies. This protocol has been prepared following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis protocols and has been published prospectively in Open Science Framework.
Ethics and dissemination Formal ethical approval is not required, as primary data will not be collected in this review. The findings of this study will be disseminated through peer-reviewed publications, stakeholder meetings and inclusion in the ongoing Lancet Global Health Commission on Global Eye Health.
Registration details https://osf.io/9au3w (DOI 10.17605/OSF.IO/6F8VM)
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