1,073 research outputs found
Self-Energy Correction to the Bound-Electron g Factor of P States
The radiative self-energy correction to the bound-electron g factor of 2P_1/2
and 2P_3/2 states in one-electron ions is evaluated to order alpha (Z alpha)^2.
The contribution of high-energy virtual photons is treated by means of an
effective Dirac equation, and the result is verified by an approach based on
long-wavelength quantum electrodynamics. The contribution of low-energy virtual
photons is calculated both in the velocity and in the length gauge and gauge
invariance is verified explicitly. The results compare favorably to recently
available numerical data for hydrogenlike systems with low nuclear charge
numbers.Comment: 8 pages, RevTe
Shape selection of surface-bound helical filaments: biopolymers on curved membranes
Motivated to understand the behavior of biological filaments interacting with
membranes of various types, we study a theoretical model for the shape and
thermodynamics of intrinsically-helical filaments bound to curved membranes. We
show filament-surface interactions lead to a host of non-uniform shape
equilibria, in which filaments progressively unwind from their native twist
with increasing surface interaction and surface curvature, ultimately adopting
uniform-contact curved shapes. The latter effect is due to non-linear coupling
between elastic twist and bending of filaments on anisotropically-curved
surfaces, such as the cylindrical surfaces considered here. Via a combination
of numerical solutions and asymptotic analysis of shape equilibria we show that
filament conformations are critically sensitive to the surface curvature in
both the strong- and weak-binding limits. These results suggest that local
structure of membrane-bound chiral filaments is generically sensitive to the
curvature-radius of the surface to which it is bound, even when that radius is
much larger than the filament intrinsic pitch. Typical values of elastic
parameters and interaction energies for several prokaryotic and eukaryotic
filaments indicate that biopolymers are inherently very sensitive to the
coupling between twist, interactions and geometry and that this could be
exploited for regulation of a variety of processes such as the targeted
exertion of forces, signaling and self-assembly in response to geometric cues
including the local mean and Gaussian curvatures
SAMplus: adaptive optics at optical wavelengths for SOAR
Adaptive Optics (AO) is an innovative technique that substantially improves
the optical performance of ground-based telescopes. The SOAR Adaptive Module
(SAM) is a laser-assisted AO instrument, designed to compensate ground-layer
atmospheric turbulence in near-IR and visible wavelengths over a large Field of
View. Here we detail our proposal to upgrade SAM, dubbed SAMplus, that is
focused on enhancing its performance in visible wavelengths and increasing the
instrument reliability. As an illustration, for a seeing of 0.62 arcsec at 500
nm and a typical turbulence profile, current SAM improves the PSF FWHM to 0.40
arcsec, and with the upgrade we expect to deliver images with a FWHM of
arcsec -- up to 0.23 arcsec FWHM PSF under good seeing
conditions. Such capabilities will be fully integrated with the latest SAM
instruments, putting SOAR in an unique position as observatory facility.Comment: To appear in Proc. SPIE 10703 (Ground-based and Airborne
Instrumentation for Astronomy VII; SPIEastro18
Mortality in non-exacerbating COPD: a longitudinal analysis of UK primary care data
Introduction: Non-exacerbating patients with chronic obstructive pulmonary disease (COPD) are a less studied phenotype. We investigated clinical characteristics, mortality rates and causes of death among non-exacerbating compared with exacerbating patients with COPD. Methods: We used data from the Clinical Practice Research Datalink, Hospital Episode Statistics and Office for National Statistics between 1 January 2004 and 31 December 2018. Ever smokers with a COPD diagnosis with minimum 3 years of baseline information were included. We compared overall using Cox regression and cause-specific mortality rates using competing risk analysis, adjusted for age, sex, deprivation, smoking status, body mass index, GOLD stage and comorbidities. Causes of death were identified using International Classification of Diseases-10 codes. Results: Among 67 516 patients, 17.3% did not exacerbate during the 3-year baseline period. Mean follow-up was 4 years. Non-exacerbators were more likely to be male (63.3% vs 52.4%, p<0.001) and less often had a history of asthma (33.9% vs 43.6%, p<0.001) or FEV1<50% predicted (23.7 vs 31.8%) compared with exacerbators. Adjusted HR for overall mortality in non-exacerbators compared with exacerbators was 0.62 (95% CI 0.56 to 0.70) in the first year of follow-up and 0.87 (95% CI 0.83 to 0.91) thereafter. Non-exacerbating patients with COPD died less of respiratory causes than exacerbators (29.2% vs 40.3%) and more of malignancies (29.4% vs 23.4%) and cardiovascular diseases (26.2% vs 22.9%). HRs for malignant and circulatory causes of death were increased after the first year of follow-up. Discussion: In this primary care cohort, non-exacerbators showed distinct clinical characteristics and lower mortality rates. Non-exacerbators were equally likely to die of respiratory, malignant or cardiovascular diseases
Heat dissipation after nonanatomical lung resection using a laser is mainly due to emission to the environment: an experimental ex vivo study
Laser-directed resection of lung metastases is performed more frequently in recent years. The energy-loaded laser rays heat up the lung tissue, considerably. It is still unclear which mechanism is more important for tissue heat dissipation: the lung perfusion or the tissue emission. Therefore, we created a special experimental model to investigate the spontaneous heat dissipation after nonanatomical lung resection using a diode-pumped laser with a high output power. Experiments were conducted on paracardiac pig lung lobes (n = 12) freshly dissected at the slaughterhouse. Nonanatomical resection of lung parenchyma was performed without lobe perfusion in group 1 (n = 6), while group 2 (n = 6) was perfused at a physiological pressure of 25 cm H(2)O at 37 °C with saline via the pulmonary artery. For this, we used a diode-pumped neodymium-doped yttrium aluminum garnet (Nd:YAG) LIMAX® 120 laser (Gebrüder Martin GmbH & Co. KG, Tuttlingen, Germany) with a wavelength of 1,318 nm and a power output of 100 W. Immediately after completing laser resection, the lungs were monitored with an infrared camera (Type IC 120LV; Trotec, Heinsberg, Germany) while allowed to cool down. The resection surface temperature was taken at 10-s intervals and documented in a freeze-frame until a temperature of 37 °C had been reached. The temperature drop per time unit was analyzed in both groups. Immediately after laser resection, the temperature at the lung surface was 84.33 ± 8.08 °C in group 1 and 76.75 ± 5.33 °C in group 2 (p = 0.29). Group 1 attained the final temperature of 37 °C after 182.95 ± 53.76 s, and group 2 after 121.70 ± 16.02 s (p = 0.01). The temperature drop occurred exponentially in both groups. We calculated both groups’ decays using nonlinear regression, which revealed nearly identical courses. The mean time of tissue temperature of >42 °C, as a surrogate marker for tissue damage, was 97.14 ± 26.90 s in group 1 and 65.00 ± 13.78 s in group 2 (p = 0.02). Heat emission to the environment surpasses heat reduction via perfusion in nonanatomically laser-resected lung lobes. In developing a cooling strategy, a topical cooling method would be promising
Experimental access to higher-order Zeeman effects by precision spectroscopy of highly charged ions in a Penning trap
We present an experimental concept and setup for laser-microwave
double-resonance spectroscopy of highly charged ions in a Penning trap. Such
spectroscopy allows a highly precise measurement of the Zeeman splittings of
fine- and hyperfine-structure levels due the magnetic field of the trap. We
have performed detailed calculations of the Zeeman effect in the framework of
quantum electrodynamics of bound states as present in such highly charged ions.
We find that apart from the linear Zeeman effect, second- and third-order
Zeeman effects also contribute to the splittings on a level of 10^-4 and 10^-8,
respectively, and hence are accessible to a determination within the achievable
spectroscopic resolution of the ARTEMIS experiment currently in preparation
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