Dual exposure interferometry

The application of dual exposure differential interferometry to gas dynamics and flow visualization is discussed. A differential interferometer with Wallaston prisms can produce two complementary interference fringe systems, depending on the polarization of the incident light. If these two systems are superimposed on a film, with one exposure during a phenomenon, the other before or after, the phenomenon will appear on a uniform background. By regulating the interferometer to infinite fringe distance, a resolution limit of approximately lambda/500 can be obtained in the quantitative analysis of weak phase objects. This method was successfully applied to gas dynamic investigations

Analysis of focused laser differential interferometry

A computational method for predicting the output of a focused laser differential interferometer (FLDI) given an arbitrary density field is presented. The method is verified against analytical predictions and experimental data. The FLDI simulation software is applied to the problem of measuring Mack-mode wave packets in a hypervelocity boundary layer on a 5° half-angle cone. The software is shown to complement experiments by providing the necessary information to allow quantitative density fluctuation magnitudes to be extracted from experimental measurements

QMRA in the Drinking Water Distribution System

AbstractA Quantitative Microbial Risk Assessment (QMRA) model was developed for contamination events after mains repairs. The sensitivity analysis showed that the contamination concentration is the most important parameter, next to the pathogen dose response relation. The time of opening valves and of consumption are also important parameters. The event location within the network and the amount of consumption are of smaller importance. Issuing a boil water advice and opening only one valve before “releasing” the entire isolation section are effective measures to reduce the number of infected people per event by a factor of 2 to 4

Reflected Shock Tunnel Noise Measurement by Focused Differential Interferometry

A series of experiments is conducted where a quantitative non-intrusive optical technique is used to investigate disturbances in the free-stream of T5, the free-piston driven reflected shock tunnel at Caltech. The optical technique, focused laser differential interferometry (FLDI), measures fluctuations in density. In the test matrix, reservoir enthalpy is varied while the reservoir pressure is held fixed. The results show the perturbations in density are not a strong function of the reservoir enthalpy. During one experiment, exceptional levels of noise were detected; this unique result is attributed to non-ideal operation of the shock tunnel. The data indicate that rms density fluctuations of less than 0.75% are achievable with attention to tunnel cleanliness. In addition, the spectral content of density fluctuation does not change throughout the test time

Atom lithography without laser cooling

Using direct-write atom lithography, Fe nanolines are deposited with a pitch of 186 nm, a full width at half maximum (FWHM) of 50 nm, and a height of up to 6 nm. These values are achieved by relying on geometrical collimation of the atomic beam, thus without using laser collimation techniques. This opens the way for applying direct-write atom lithography to a wide variety of elements.Comment: 7 pages, 11 figure

Pandemic panic?:Results of a 14 month longitudinal study on fear of COVID-19

BACKGROUND: Fear is an evolutionary adaptive emotion that serves to protect the organism from harm. Once a threat diminishes, fear should also dissipate as otherwise fear may become chronic and pathological. While actual threat of the COVID-19 pandemic (i.e., number of infections, hospitalizations, and deaths) has substantially varied over the course of the pandemic, it remains unclear whether (subjective) fear has followed a similar pattern. METHOD: To examine the development of fear of COVID-19 during the pandemic and investigate potential predictors of chronic fear, we conducted a large online longitudinal study (N = 2000) using the Prolific platform between April 2020 and June 2021. Participants were voluntary response samples and consisted of residents of 34 different countries. The Fear of the Coronavirus Questionnaire (FCQ) and several other demographic and psychological measures were completed monthly. RESULTS: Overall, we find that fear steadily decreased since April 2020. Additional analyses showed that elevated fear was predicted by region (i.e., North America > Europe), anxious traits, gender, risks for loved ones, general health, and media use. LIMITATIONS: The interpretation of the results of this study is limited by the non-representativeness of the sample and the lack of data points between August 2020 and June 2021. CONCLUSIONS: This study helps to characterize the trajectory of fear levels throughout the COVID-19 pandemic and establish several relevant predictors of increased fear

The latent and item structure of COVID-19 fear:A comparison of four COVID-19 fear questionnaires using SEM and network analyses

Since the outbreak of the coronavirus disease (COVID-19), several reports have shown that fear relating to COVID-19 has sharply increased. To measure fear of COVID-19, various questionnaires have been developed in parallel. However, fear concerning COVID-19 is not necessarily a uniform construct and the different questionnaires may cover diverse aspects. To examine the underlying structure of fear of COVID-19, we conducted structural equation modelling and network analyses on four scales in an online convenience sample (N = 829). Particularly, the Fear of COVID-19 Scale (Ahorsu et al., 2020), the Fear of the Coronavirus Questionnaire (Mertens et al., 2020), and the COVID Stress Scales (Taylor, Landry, Paluszek, Fergus et al., 2020, Taylor, Landry, Paluszek, Rachor et al., 2020) were included in our study, along with a new scale that also assessed socio-economic worries relating to COVID-19. We found that fear of COVID-19 was best classified into four clusters: Fear of health-related consequences, fear of supplies shortages and xenophobia, fear about socio-economic consequences, and symptoms of fear (e.g., compulsions, nightmares). We also find that a central cluster of items centered on fear of health, which likely represents the core of fear of COVID-19. These results help to characterize fear due to COVID-19 and inform future research

Evaluation of work-related psychosocial factors and regional musculoskeletal pain: results from a EULAR Task Force

Objectives: to establish whether review articles provide consistent conclusions on associations between workplace psychosocial factors and musculoskeletal pain and, if differences exist, to explore whether this is related to the methods used.Methods: reviews, reported up to February 2007, that included consideration of workplace psychosocial factors and upper limb, back or knee pain were identified through searches of multiple databases. The specific work-related psychosocial factors considered were job demands, support, job autonomy and job satisfaction. The conclusions of each review on one or more of the psychosocial/musculoskeletal pain associations were extracted.Results: 15 review articles were identified that considered one or more of the regional pain syndromes included in the study. For back pain, the most consistent conclusions (four reviews positive out of six) were with high job demands and low job satisfaction. The studies of upper limb pain were exclusively related to shoulder and/or neck pain, and the most consistent positive conclusions were with high and low job demands (four reviews positive out of six and two reviews positive out of three, respectively). For knee pain, only a single review was identified. For individual reviews of back and upper limb pain, there were marked differences in the number of associations concluded to be positive between reviews.Conclusions: the reasons for reviews coming to different conclusions included that they were often evaluating different bodies of evidence (according to their search criteria, the year when the review was conducted, the role that quality assessment played in whether studies contributed to evidence, and the combination of risk factors addressed in individual studies), but more important was whether the review specified explicit criteria for making conclusions on strength of evidence. These conclusions emphasise the importance of developing standardised methods for conducting such evaluations of existing evidence and the importance of new longitudinal studies for clarifying the temporal relationship between psychosocial factors and musculoskeletal pain in the workplac