Experiments on Quantum and Thermal Desorption from ^4He Films

Desorption of He atoms from thin films may be resolved experimentally into quantum and thermal components. We show that quantum desorption becomes the dominant part of the signal in submonolayer films. We also show that, when all effects of collisions between desorbed atoms are eliminated, quantum desorption is not focused normal to the surface of optically polished sapphire crystals

Physical Therapy for Hospitalized COVID-19 Patients in Isolation: Feasibility and pilot implementation of telehealth for delivering individualized therapy.

Objective To optimize the ability of hospitalized patients isolated due to COVID-19 to participate in physical therapy. Design This was a prospective, quality improvement trial of the feasibility and acceptability of a hybrid in-person and telerehabilitation platform to deliver physical therapy to hospitalized adults. Setting Inpatient wards of a tertiary care, multi-specialty academic medical center in the greater New York City metropolitan area. Participants A convenience sample of 39 COVID-19+ adults, mean age 57.3 years, 69% male, all previously community dwelling agreed to participate in a combination of in-person and telerehabilitation sessions (TR). Intervention Initial in-person evaluation by physical therapist followed by twice daily PT sessions, one in-person and one via a telehealth platform meeting Health Insurance Portability and Accountability Act (HIPAA) confidentiality requirements. The communication platform was downloaded to each participant\u27s personal smart device to establish audiovisual contact with the Physical Therapist. Measures The 6-clicks Activity Measure for Post-Acute Care (AM-PAC) was used to score self-reported functional status pre-morbidly by, and by the therapist at baseline and discharge. Results Functional status measured by AM-PAC 6-clicks demonstrated improvement from admission to discharge. Barriers to participation were identified and strategies are planned to facilitate use of the platform in future. Conclusions A consistent and structured protocol for engaging patient participation in PT delivered via a telehealth platform was successfully developed. A process was put in place to allow for further development, recruitment and testing in a randomized trial

Sticking probability of ^4He on solid surfaces at low temperature

The first low-temperature (<4 K) determination of the sticking probability S of a 4He atom on a solid surface is presented. It is found that 2/3~<VS<1 for a thermal distribution of incident atoms with beam temperature 10 to 20 K. This result is not affected by the presence of a preadsorbed, ~< 1-monolayer He film

Desorption of helium atoms from thin films

Investigation is made of the desorption of He atoms from thin films. Three different experimental geometries are used to study the dependence on substrate material, film temperature, and duration of the heat pulse. The major conclusions are that (a) the speed distribution is similar to a Maxwellian, (b) the angular distribution is strongly focused about the normal direction, (c) desorption time constants differ systematically from estimates, and (d) a phonoatomic effect analogous to the photoelectric effect is observed. The measurements are analyzed in terms of several theoretical models. Conclusions are drawn about the time evolution of the film thickness and temperature

All-optical silicon simplified passive modulation

In this paper we present an all-optical silicon based modulator suggested also for high power operation and for pulse picker application being used as part of fiber lasers system. The paper theoretically and experimentally investigates several new and important insights involving the dependence of the relative transmission on the pump pulse energy for different finesse values of the constructed cavity as well as the dependence of the response rate of the device to the pump wavelength due to coexistence of two physical recombination processes: fast surface effect and slow bulk recombination. To adapt the constructed silicon based cavity to be used in lasers applications, we aligned the pump and the signal beams to co-propagate through the device while the usage of a cavity allowed a low power pump to yield a significant extinction ratio at the output of the device

Dynamic changes in eIF4F-mRNA interactions revealed by global analyses of environmental stress responses

BACKGROUND: Translation factors eIF4E and eIF4G form eIF4F, which interacts with the messenger RNA (mRNA) 5' cap to promote ribosome recruitment and translation initiation. Variations in the association of eIF4F with individual mRNAs likely contribute to differences in translation initiation frequencies between mRNAs. As translation initiation is globally reprogrammed by environmental stresses, we were interested in determining whether eIF4F interactions with individual mRNAs are reprogrammed and how this may contribute to global environmental stress responses. RESULTS: Using a tagged-factor protein capture and RNA-sequencing (RNA-seq) approach, we have assessed how mRNA associations with eIF4E, eIF4G1 and eIF4G2 change globally in response to three defined stresses that each cause a rapid attenuation of protein synthesis: oxidative stress induced by hydrogen peroxide and nutrient stresses caused by amino acid or glucose withdrawal. We find that acute stress leads to dynamic and unexpected changes in eIF4F-mRNA interactions that are shared among each factor and across the stresses imposed. eIF4F-mRNA interactions stabilised by stress are predominantly associated with translational repression, while more actively initiating mRNAs become relatively depleted for eIF4F. Simultaneously, other mRNAs are insulated from these stress-induced changes in eIF4F association. CONCLUSION: Dynamic eIF4F-mRNA interaction changes are part of a coordinated early translational control response shared across environmental stresses. Our data are compatible with a model where multiple mRNA closed-loop complexes form with differing stability. Hence, unexpectedly, in the absence of other stabilising factors, rapid translation initiation on mRNAs correlates with less stable eIF4F interactions

Relaxation time of an adsorbing ^4He film

The readsorption of ^4He atoms on a constantan heater surface was studied after flash desorption by the heat pulse technique. The replenishment of the desorbed film after the heat pulse was found to be essentially linear with the time between the pulses, reaching saturation at some critical value, t_(rc), which strongly depended on the pressure in the vapor, P_g. With the help of kinetic theory for the flux of atoms striking a surface, the measured value of t_(rc) could be calibrated to give P_g. We have verified this formula directly and used it to measure pressures down to 10^(−9) Torr