656 research outputs found
Vibrational Excitations in Weakly Coupled Single-Molecule Junctions: A Computational Analysis
In bulk systems, molecules are routinely identified by their vibrational
spectrum using Raman or infrared spectroscopy. In recent years, vibrational
excitation lines have been observed in low-temperature conductance measurements
on single molecule junctions and they can provide a similar means of
identification. We present a method to efficiently calculate these excitation
lines in weakly coupled, gateable single-molecule junctions, using a
combination of ab initio density functional theory and rate equations. Our
method takes transitions from excited to excited vibrational state into account
by evaluating the Franck-Condon factors for an arbitrary number of vibrational
quanta, and is therefore able to predict qualitatively different behaviour from
calculations limited to transitions from ground state to excited vibrational
state. We find that the vibrational spectrum is sensitive to the molecular
contact geometry and the charge state, and that it is generally necessary to
take more than one vibrational quantum into account. Quantitative comparison to
previously reported measurements on pi-conjugated molecules reveals that our
method is able to characterize the vibrational excitations and can be used to
identify single molecules in a junction. The method is computationally feasible
on commodity hardware.Comment: 9 pages, 7 figure
Theoretical study of the absorption spectra of the sodium dimer
Absorption of radiation from the sodium dimer molecular states correlating to
Na(3s)-Na(3s) is investigated theoretically. Vibrational bound and continuum
transitions from the singlet X Sigma-g+ state to the first excited singlet A
Sigma-u+ and singlet B Pi-u states and from the triplet a Sigma-u+ state to the
first excited triplet b Sigma-g+ and triplet c Pi-g states are studied
quantum-mechanically. Theoretical and experimental data are used to
characterize the molecular properties taking advantage of knowledge recently
obtained from ab initio calculations, spectroscopy, and ultra-cold atom
collision studies. The quantum-mechanical calculations are carried out for
temperatures in the range from 500 to 3000 K and are compared with previous
calculations and measurements where available.Comment: 19 pages, 8 figures, revtex, eps
Corrigendum to “Counting adolescents in: the development of an adolescent health indicator framework for population-based settings”
The authors were recently made aware of an oversight such that parts of the text in the Introduction and Methods sections, which describe shortcomings in the existing literature and the methods in this work to identify frameworks and indicators, were missing attribution to published work cited elsewhere in the manuscript. To clarify, we adjust the relevant sections to fully attribute the prior work in three areas, as described below. Underlined text is additional to the original: While both school- and community-based modalities can provide nationally representative data among eligible adolescents, several shortcomings in adolescent health measurement in LMICs were noted by the GAMA Advisory Group (Reference 13 as in the original paper). First, these measurements do not equally cover all adolescent subgroups, with evidence gaps being largest for males, younger adolescents aged 10–14 years, adolescents of diverse genders, ethnicities, and religions, as well as those out of school and migrants. Second, age-disaggregated data are often lacking—due in part to incomplete age coverage—limiting their use for program planning. Third, several aspects of adolescent health are inadequately covered including mental health, substance use, injury, sexual and reproductive health among unmarried adolescents, and positive aspects of adolescent health and well-being. Fourth, the definitions and assessment methods used across adolescent health indicator frameworks are inconsistent. For example, adolescent overweight and obesity—a major cause of non-communicable diseases and a public health risk for future and intergeneration health—is inconsistently captured across indicator frameworks and strikingly absent from the SDGs (Reference 13 as in the original paper). Additional shortcomings include, current adolescent health data systems often lack intersectoral coordination beyond health (e.g., with education, water and sanitation, and social protection systems) and suffer from irregularities in coverage and timing (Reference 6 as in the original paper). Broadly, these indicator frameworks and strategy documents captured disease burden, health risks, and prominent social determinants of health during adolescence. To be congruent with the existing global recommendations and guidelines (References 3–7 as in the original paper) and global measurement efforts (References 10 and 16 as in the original paper), the indicator framework documents had to meet three inclusion criteria, as laid out by the GAMA Advisory Group (Reference 14 as in the original paper): (1) provide recommendations about the measurement of adolescents' health and well-being; (2) include indicators for “adolescents” covering the adolescent age range (10–19 years) in the whole or part; and (3) be global or regional in scope. Using the GAMA's approach (Reference 13 as in the original paper), the recommendations of Lancet Adolescent Health Commission (Reference 6 as in the original paper), and several other guidelines (References 7, 9, 12, 17–19 as in the original paper), we selected adolescent health and well-being domains based on four key aspects of adolescents in LMICs: a) population trends; b) disease burden; c) drivers of health inequality; and d) opportunity for interventions
Counting adolescents in: the development of an adolescent health indicator framework for population-based settings
Changing realities in low- and middle-income countries (LMICs) in terms of inequalities, urbanization, globalization, migration, and economic adversity shape adolescent development and health, as well as successful transitions between adolescence and young adulthood. It is estimated that 90% of adolescents live in LMICs in 2019, but inadequate data exist to inform evidence-based and concerted policies and programs tailored to address the distinctive developmental and health needs of adolescents. Population-based data surveillance such as Health and Demographic Surveillance Systems (HDSS) and school-based surveys provide access to a well-defined population and provide cost-effective opportunities to fill in data gaps about adolescent health and well-being by collecting population-representative longitudinal data. The Africa Research Implementation Science and Education (ARISE) Network, therefore, systematically developed adolescent health and well-being indicators and a questionnaire for measuring these indicators that can be used in population-based LMIC settings. We conducted a multistage collaborative and iterative process led by network members alongside consultation with health-domain and adolescent health experts globally. Seven key domains emerged from this process: socio-demographics, health awareness and behaviors; nutrition; mental health; sexual and reproductive health; substance use; and healthcare utilization. For each domain, we generated a clear definition; rationale for inclusion; sub-domain descriptions, and a set of questions for measurement. The ARISE Network will implement the questionnaire longitudinally (i.e., at two time-points one year apart) at ten sites in seven countries in sub-Saharan Africa and two countries in Asia. Integrating the questionnaire within established population-based data collection platforms such as HDSS and school settings can provide measured experiences of young people to inform policy and program planning and evaluation in LMICs and improve adolescent health and well-being
Alanine Scanning mutagenesis of the prototypic cyclotide reveals a cluster of residues essential for bioactivity
The cyclotides are stable plant-derived mini-proteins with a topologically circular peptide backbone and a knotted arrangement of three disulfide bonds that form a cyclic cystine knot structural framework. they display a wide range of pharmaceutically important bioactivities, but their natural function is in plant defense as insecticidal agents
Antiferromagnetic spintronics
Antiferromagnetic materials are magnetic inside, however, the direction of
their ordered microscopic moments alternates between individual atomic sites.
The resulting zero net magnetic moment makes magnetism in antiferromagnets
invisible on the outside. It also implies that if information was stored in
antiferromagnetic moments it would be insensitive to disturbing external
magnetic fields, and the antiferromagnetic element would not affect
magnetically its neighbors no matter how densely the elements were arranged in
a device. The intrinsic high frequencies of antiferromagnetic dynamics
represent another property that makes antiferromagnets distinct from
ferromagnets. The outstanding question is how to efficiently manipulate and
detect the magnetic state of an antiferromagnet. In this article we give an
overview of recent works addressing this question. We also review studies
looking at merits of antiferromagnetic spintronics from a more general
perspective of spin-ransport, magnetization dynamics, and materials research,
and give a brief outlook of future research and applications of
antiferromagnetic spintronics.Comment: 13 pages, 7 figure
Dermal Sensory Regenerative Peripheral Nerve Interface for Reestablishing Sensory Nerve Feedback in Peripheral Afferents in the Rat
Background: Without meaningful, intuitive sensory feedback, even the most advanced myoelectric devices require significant cognitive demand to control. The dermal sensory regenerative peripheral nerve interface (DS-RPNI) is a biological interface designed to establish high-fidelity sensory feedback from prosthetic limbs. Methods: DS-RPNIs were constructed in rats by securing fascicles of residual sensory peripheral nerves into autologous dermal grafts, with the objectives of confirming regeneration of sensory afferents within DS-RPNIs and establishing the reliability of afferent neural response generation with either mechanical or electrical stimulation. Results: Two months after implantation, DS-RPNIs were healthy and displayed well-vascularized dermis with organized axonal collaterals throughout and no evidence of neuroma. Electrophysiologic signals were recorded proximal from DS-RPNI's sural nerve in response to both mechanical and electrical stimuli and compared with (1) full-thickness skin, (2) deepithelialized skin, and (3) transected sural nerves without DS-RPNI. Mechanical indentation of DS-RPNIs evoked compound sensory nerve action potentials (CSNAPs) that were like those evoked during indentation of full-thickness skin. CSNAP firing rates and waveform amplitudes increased in a graded fashion with increased mechanical indentation. Electrical stimuli delivered to DS-RPNIs reliably elicited CSNAPs at low current thresholds, and CSNAPs gradually increased in amplitude with increasing stimulation current. Conclusions: These findings suggest that afferent nerve fibers successfully reinnervate DS-RPNIs, and that graded stimuli applied to DS-RPNIs produce proximal sensory afferent responses similar to those evoked from normal skin. This confirmation of graded afferent signal transduction through DS-RPNI neural interfaces validate DS-RPNI's potential role of facilitating sensation in human-machine interfacing. Clinical Relevance Statement: The DS-RPNI is a novel biotic-abiotic neural interface that allows for transduction of sensory stimuli into neural signals. It is expected to advance the restoration of natural sensation and development of sensorimotor control in prosthetics.</p
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