197 research outputs found
On the photoionization of the outer electrons in noble gas endohedral atoms
We demonstrate the prominent modification of the outer shell photoionization
cross-section in noble gas (NG) endohedral atoms NG@F under the action of the
fullerene F electron shell. This shell leads to two important effects, namely
to strong enhancement of the cross-section due to fullerenes shell polarization
under the action of the incoming electromagnetic wave and to prominent
oscillation of this cross-section due to the reflection of the photoelectron
from NG by the F shell.
All but He noble gas atoms are considered. The polarization of the fullerene
shell is expressed via the total photoabsorption cross-section of F. The
reflection of the photoelectron is taken into account in the frame of the
so-called bubble potential that is a spherical zero --thickness potential.
It is assumed in the derivations that NG is centrally located in the
fullerene. It is assumed also, in accord with the existing experimental data,
that the fullerenes radius R is much bigger than the atomic radius and the
thickness of the fullerenes shell . These assumptions permit, as it was
demonstrated recently, to present the NG@F photoionization cross-section as a
product of the NG cross-section and two well defined calculated factors.Comment: 19 pages, 9 figure
Imaging Molecular Structure through Femtosecond Photoelectron Diffraction on Aligned and Oriented Gas-Phase Molecules
This paper gives an account of our progress towards performing femtosecond
time-resolved photoelectron diffraction on gas-phase molecules in a pump-probe
setup combining optical lasers and an X-ray Free-Electron Laser. We present
results of two experiments aimed at measuring photoelectron angular
distributions of laser-aligned 1-ethynyl-4-fluorobenzene (C8H5F) and
dissociating, laseraligned 1,4-dibromobenzene (C6H4Br2) molecules and discuss
them in the larger context of photoelectron diffraction on gas-phase molecules.
We also show how the strong nanosecond laser pulse used for adiabatically
laser-aligning the molecules influences the measured electron and ion spectra
and angular distributions, and discuss how this may affect the outcome of
future time-resolved photoelectron diffraction experiments.Comment: 24 pages, 10 figures, Faraday Discussions 17
Giant resonances of endohedral atoms
We demonstrate for the first time that the effect of fullerene shell upon
photoionization of the "caged" atom in an endohedral can result in formation of
Giant Endohedral Resonances or GER. This is illustrated by the concrete case of
Xe@C60 photoionization cross-section that exhibits at 17 eV a powerful
resonance with total oscillator strengths of about 25. The prominent
modification of the 5p6 electron photoionization cross-section of Xe@C60 takes
place due to strong fullerene shell polarization under the action of the
incoming electromagnetic wave and oscillation of this cross-section due to the
reflection of the photoelectron from Xe by the C60. These two factors transform
the smoothly decreasing 5p6 cross-section of Xe into a rather complex curve
with a powerful maximum for Xe@C60, with the oscillator strength being equal to
25! We present also the results for the dipole angular anisotropy parameter
that is strongly affected by the reflection of the photoelectron waves but not
modified by C60 polarization. The polarization of C60 is expressed via its
total photoabsorption cross-section. The reflection of the photoelectron is
taken into account in the frame of the so-called bubble potential that is a
spherical delta-type potential.Comment: 7pages, 3 figures, 14 references,some previous references are remove
Application of time-dependent density functional theory to optical activity
As part of a general study of the time-dependent local density approximation
(TDLDA), we here report calculations of optical activity of chiral molecules.
The theory automatically satisfies sum rules and the Kramers-Kronig relation
between circular dichroism and optical rotatory power. We find that the theory
describes the measured circular dichroism of the lowest states in methyloxirane
with an accuracy of about a factor of two. In the chiral fullerene C_76 the
TDLDA provides a consistent description of the optical absorption spectrum, the
circular dichroism spectrum, and the optical rotatory power, except for an
overall shift of the theoretical spectrum.Comment: 17 pages and 13 PostScript figure
towards time-resolved imaging of molecular structure
We demonstrate an experimental method to record snapshot diffraction images of
polyatomic gas-phase molecules, which can, in a next step, be used to probe
time-dependent changes in the molecular geometry during photochemical
reactions with femtosecond temporal and angstrom spatial resolution.
Adiabatically laser-aligned 1-ethynyl-4-fluorobenzene (C8H5F) molecules were
imaged by diffraction of photoelectrons with kinetic energies between 31 and
62 eV, created from core ionization of the fluorine (1s) level by ≈80 fs x-ray
free-electron-laser pulses. Comparison of the experimental photoelectron
angular distributions with density functional theory calculations allows
relating the diffraction images to the molecular structure
Jumping into the deep-end: results from a pilot impact evaluation of a community-based aquatic exercise program
This multi-center quasi-experimental pilot study aimed to evaluate changes in pain, joint stiffness, physical function, and quality of life over 12 weeks in adults with musculoskeletal conditions attending ‘Waves’ aquatic exercise classes. A total of 109 adults (mean age, 65.2 years; range, 24–93 years) with musculoskeletal conditions were recruited across 18 Australian community aquatic centers. The intervention is a peer-led, 45 min, weekly aquatic exercise class including aerobic, strength, flexibility, and balance exercises (n = 67). The study also included a control group of people not participating in Waves or other formal exercise (n = 42). Outcomes were measured using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and EuroQoL five dimensions survey (EQ-5D) at baseline and 12 weeks. Satisfaction with Waves classes was also measured at 12 weeks. Eighty two participants (43 Waves and 39 control) completed the study protocol and were included in the analysis. High levels of satisfaction with classes were reported by Waves participants. Over 90 % of participants reported Waves classes were enjoyable and would recommend classes to others. Waves participants demonstrated improvements in WOMAC and EQ-5D scores however between-group differences did not reach statistical significance. Peer-led aquatic exercise classes appear to improve pain, joint stiffness, physical function and quality of life for people with musculoskeletal conditions. The diverse study sample is likely to have limited the power to detect significant changes in outcomes. Larger studies with an adequate follow-up period are needed to confirm effects
Acupuncture treatment for insulin sensitivity of women with polycystic ovary syndrome and insulin resistance: a study protocol for a randomized controlled trial
Recommendations from the international evidence-based guideline for the assessment and management of polycystic ovary syndrome
Study QuestionWhat is the recommended assessment and management of women with polycystic ovary syndrome (PCOS), based on the best available evidence, clinical expertise, and consumer preference? Summary AnswerInternational evidence-based guidelines including 166 recommendations and practice points, addressed prioritized questions to promote consistent, evidence-based care and improve the experience and health outcomes of women with PCOS. What is Known AlreadyPrevious guidelines either lacked rigorous evidence-based processes, did not engage consumer and international multidisciplinary perspectives, or were outdated. Diagnosis of PCOS remains controversial and assessment and management are inconsistent. The needs of women with PCOS are not being adequately met and evidence practice gaps persist. Study Design, Size, DurationInternational evidence-based guideline development engaged professional societies and consumer organizations with multidisciplinary experts and women with PCOS directly involved at all stages. Appraisal of Guidelines for Research and Evaluation (AGREE) II-compliant processes were followed, with extensive evidence synthesis. The Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) framework was applied across evidence quality, feasibility, acceptability, cost, implementation and ultimately recommendation strength. Participants/Materials, Setting, MethodsGovernance included a six continent international advisory and a project board, five guideline development groups (GDGs), and consumer and translation committees. Extensive health professional and consumer engagement informed guideline scope and priorities. Engaged international society-nominated panels included pediatrics, endocrinology, gynecology, primary care, reproductive endocrinology, obstetrics, psychiatry, psychology, dietetics, exercise physiology, public health and other experts, alongside consumers, project management, evidence synthesis, and translation experts. Thirty-seven societies and organizations covering 71 countries engaged in the process. Twenty face-to-face meetings over 15months addressed 60 prioritized clinical questions involving 40 systematic and 20 narrative reviews. Evidence-based recommendations were developed and approved via consensus voting within the five guideline panels, modified based on international feedback and peer review, with final recommendations approved across all panels. Main Results and the Role of ChanceThe evidence in the assessment and management of PCOS is generally of low to moderate quality. The guideline provides 31 evidence based recommendations, 59 clinical consensus recommendations and 76 clinical practice points all related to assessment and management of PCOS. Key changes in this guideline include: (a) considerable refinement of individual diagnostic criteria with a focus on improving accuracy of diagnosis; (b) reducing unnecessary testing; (c) increasing focus on education, lifestyle modification, emotional wellbeing and quality of life; and (d) emphasizing evidence based medical therapy and cheaper and safer fertility management. Limitations, Reasons for CautionOverall evidence is generally low to moderate quality, requiring significantly greater research in this neglected, yet common condition, especially around refining specific diagnostic features in PCOS. Regional health system variation is acknowledged and a process for guideline and translation resource adaptation is provided. Wider Implications of the FindingsThe international guideline for the assessment and management of PCOS provides clinicians with clear advice on best practice based on the best available evidence, expert multidisciplinary input and consumer preferences. Research recommendations have been generated and a comprehensive multifaceted dissemination and translation program supports the guideline with an integrated evaluation program.Peer reviewe
Effectiveness of electroacupuncture for polycystic ovary syndrome: study protocol for a randomized controlled trial
Data Descriptor: Ash leaf metabolomes reveal differences between trees tolerant and susceptible to ash dieback disease
CMS was funded by the ‘Nornex’ project jointly by UK BBSRC (BBS/E/J/000CA5323) and DEFRA and a BBSRC Tools and Resources grant (BB/N021452/1) awarded to M.G. and D.J.S
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