Ultrasound propagation in the sodium borosilicate glass system

Measurements of ultrasound wave velocity and attenuation are used to investigate the structure of Na(_2)O-B(_2)O(_3)-SiO(_2) glasses. The propagation characteristics of longitudinal and shear waves between 1.3 K and 400 K at frequencies between 12 MHz and 60 MHz are dominated by a broad and intense acoustic loss peak whose height and position are frequency sensitive. Of the previously proposed models for the mechanism of the acoustic loss, which also occurs in other inorganic glasses, the ultrasound absorption is most consistent with a thermally activated structural relaxation involving the transverse vibration of an oxygen atom between two potential wells of equal or nearly equal depth in the plane of a non linear cation-oxygen-cation bond. An Akhieser type acoustic phonon-thermal phonon interaction is shown no to be responsible for the observed loss. An attempt frequency of l0(^13)Hz and a distribution of activation energies out to 12 K cal/mole but with a mean value of about 3 K cal/mole are found for the relaxation mechanism in the Na(_2)O-B(_2)O(_3)-SiO(_2) glasses. The absolute value and the temperature coefficient of ultrasound velocity, and the maximum acoustic loss are strongly dependent on the total Na(_2)O content of the glasses. Ultrasound propagation characteristics are also affected by phase-separation inducing heat treatment: the steady rise in the height of the loss peak and the complex behaviour of the ultrasound velocity with time of treatment suggest that structural rearrangement is still taking place in the individual glassy phases even after long periods of heat treatment. Also reported is the existence of a small acoustic loss peak at liquid helium temperatures in the Na(_2)O-B(_2)O(_2)-SiO(_2) glasses. This feature of the ultrasound absorption spectrum is characteristic of many tetrahedrally coordinated inorganic glasses. On the assumption of an Arrhenius activation process for this loss peak, an activation energy of 60 ± 15 cal/mole and an attempt frequency of 10(^10) to 10(^12) Hz is indicated

Probiotic Use and Their Effect on IBS Symptoms: A Review of Literature

Aim: Probiotics are an attractive therapy for patients dealing with irritable bowel syndrome (IBS) in light of decreased financial costs, fewer medications, and a more natural approach. In this review of literature our purpose was to answer the following PICO question: “In adults with IBS, how does supplemental probiotic use compared to no probiotic use affect IBS symptoms?” Methods: In our review of the literature, the databases searched were CINAHL, MEDLINE, Cochrane, PubMed, Google Scholar, and Onesearch from the years 2008-2018; from which we found ten articles published within the last six years. Results: Seventy percent of the articles reviewed for our research identified that both the experimental (probiotic) and control (placebo) groups showed equal significant improvement in the management of IBS symptoms. Sixty percent of our articles studying multispecies versus monospecies probiotic therapy observed a greater therapeutic response when using probiotics in combination rather than individually. Lastly, 60% observed a therapeutic response in the reduction of IBS symptoms. Conclusion: The results of our review indicated that there was significant evidence for the use of probiotics in alleviating symptoms of IBS. However, the benefit of probiotics was equal to that of the placebo or not significantly greater. Therefore, we concluded that a pilot of change in practice should be considered, but there is still a need for further investigation on this topic. Keywords: Probiotics, Efficacy, Irritable Bowel Syndrome, Treatment, Management, Therapeutic, Effective

APAP titration in patients with mild to moderate OSAS and periodic limb movement syndrome

(APAP) titration in a partially attended setting; 2) to verify whether APAP performance depends on the apneahypopnea and periodic limb movement indexes (PLMI). Methods. 65 CPAP naïve subjects with a sleep disorder of breathing and daytime sleepiness underwent a standard polysomnography (first night), APAP titration (second night, partially attended), and a standard polysomnography using continuous positive airway pressure (CPAP) at the effective pressure (Peff) established from the APAP titration (third night) in a sleep disorder laboratory in a 400-bed community hospital. We examined the apnea-hypopnea index (AHI), sleep stages, arousals induced by respiratory events (RESPa) and PLM (PLMa), and oxygen saturation during the first and third nights on CPAP at the Peff. Patients were divided into three groups according to their AHI and PLMI. Results. At the Peff defined using APAP on the third night, the mean AHI dropped from 29.6 ± 21.8 to 3.1 ± 3.4, and the RESPa index from 16.5 ± 16.2 to 1.7 ± 2.6. No differences emerged in sleep stages or spontaneous arousals (first vs third night). Overall, 92% of the patients met the standard for an acceptable outcome of positive pressure titration. Baseline AHI and PLMI did not affect the outcome of titration. Conclusions. In patients with mild to moderate OSAS and PLMS, APAP titration enables the optimal fixed pressure for CPAP home therapy to be determined in at least 90% of patients

TRANSPORT AND INSTALLATION OF CRYO-MAGNETS IN CERN'S LARGE HADRON COLLIDER TUNNEL

The arcs of the Large Hadron Collider (LHC) will contain around 1700 main superconducting dipoles and quadrupoles. The long and heavy magnets are supported on fragile composite support posts inside a cryostat to reduce the heat in-leak to the magnets' super fluid helium bath. The presence of fragile components and the need to avoid geometry changes make the cryo-magnets very difficult to handle and transport. The transport and installation of the LHC cryo-magnets in the LEP tunnels originally designed for smaller, lighter LEP magnets has required development of completely new handling solutions. The paper explains the constraints imposed by the cryo-magnet characteristics, the existing tunnel infrastructure and schedule considerations. The development and realisation of transport and handling solutions are described, starting from conceptual design, through manufacture and testing to the installation of the first cryo-magnet. Integration studies to verify and reserve space needed for manoeuvre and the preparation of the infrastructure for transport and installation operations are also presented. The paper includes conclusions and some of the lessons learned

Remote Inspection, Measurement and Handling for LHC

Personnel access to the LHC tunnel will be restricted to varying extents during the life of the machine due to radiation, cryogenic and pressure hazards. The ability to carry out visual inspection, measurement and handling activities remotely during periods when the LHC tunnel is potentially hazardous offers advantages in terms of safety, accelerator down time, and costs. The first applications identified were remote measurement of radiation levels at the start of shut-down, remote geometrical survey measurements in the collimation regions, and remote visual inspection during pressure testing and initial machine cool-down. In addition, for remote handling operations, it will be necessary to be able to transmit several real-time video images from the tunnel to the control room. The paper describes the design, development and use of a remotely controlled vehicle to demonstrate the feasibility of meeting the above requirements in the LHC tunnel. Design choices are explained along with operating experience to-date and future development plans

Otras voces: cartilla de citación

Esta cartilla pretende incentivar en los eafitenses una cultura del respeto por los derechos de autor y la honestidad académica . Esta contiene los estilos de citación más utilizados para la realización de trabajos académicos, además de dar las indicaciones sobre la localización de estos en línea y en la Biblioteca

The Impact of the COVID-19 Pandemic on the Psychological Well-Being of Caregivers of People with Dementia or Mild Cognitive Impairment: A Systematic Review and Meta-Analysis

The aim of this systematic review was to investigate the effects of the COVID-19 lockdown on the psychological well-being of caregivers of people with dementia or mild cognitive impairment (PwD/MCI). Electronic databases were searched from inception to August 2022 for observational studies investigating the COVID-19 lockdown and psychological well-being of caregivers of PwD/MCI. Summary estimates of standardized mean differences (SMD) in psychological well-being scores pre- versus during COVID-19 were calculated using a random-effects model. Fifteen studies including 1702 caregivers (65.7% female, mean age 60.40 ± 12.9 years) with PwD/MCI were evaluated. Five studies found no change in psychological well-being parameters, including depression, anxiety, distress, caregiver burden, and quality of life. Ten studies found a worsening in at least one parameter: depression (six studies, n = 1368; SMD = 0.40; 95%CI: 0.09–0.71; p = 0.01, I2 = 86.8%), anxiety (seven studies, n = 1569; SMD = 1.35; 95%CI: 0.05–2.65; I2 = 99.2%), caregiver distress (six studies, n = 1320, SMD = 3.190; 95%CI: 1.42–4.95; p < 0.0001; I2 = 99.4%), and caregiver burden (four studies, n = 852, SMD = 0.34; 95%CI: 0.13–0.56; p = 0.001; I2 = 54.1%) (p < 0.05). There was an increase in depression, anxiety, caregiver burden, and distress in caregivers of PwD/MCI during the lockdown in the COVID pandemic. This could have longer term consequences, and it is essential that caregivers’ psychological well-being is assessed and supported, to benefit both themselves and those for whom they care