The development of a data acquisition system for a vacuum-ultraviolet spectroradiometer

An improved vacuum-ultraviolet spectroradiometer has been developed for use in the characterization of rocket plume radiant emission and the study of combustion processes in liquid rocket engines. The system acquires and processes the data so as to display the spectrum in units of volts per pixel. With proper calibration, it will display the spectrum in spectral radiance units of power per unit solid angle per unit source area per unit wavelength. The spectrometer displays the plume\u27s radiant emission in terms of its electromagnetic spectrum. Two light image intensifier (LII) tubes and two charge- coupled device (CCD) arrays convert the spectrum to an electrical signal and pass the signal on to the electronic hardware. The hardware digitizes the signal and stores the data in a buffer until a computer can transfer it to disk. The computer\u27s software controls the entire operation. Off-line, code reduces the acquired data to engineering units and displays the spectrum on the computer\u27s monitor. This thesis describes the development of the data acquisition system (CCDs, electronic hardware, computer, and software) of the improved spectroradiometer. The device can monitor a continuous spectral range of 44 nm or two ranges of 22 nm each anywhere in the ultraviolet (UV) spectrum extending from 120 nm to 320 nm. The device can also provide simultaneous spatial-spectral measurements. That is, the charges in each CCD pixel column can be summed as one vertical group with a minimum integration period of 50 ms or the pixel column can be divided and summed in 2, 10, or 20 vertical groups with minimum integration periods of 120 ms, 600 ms, or 1200 ms, respectively

Design considerations to ensure accuracy when using the resazurin reduction assay to noninvasively quantify cell expansion within perfused extracellular matrix scaffolds

Analysis of perfusion-based bioreactors for organ engineering and a detailed evaluation of dynamic changes within maturing cell-laden scaffolds are critical components of ex vivo tissue development that remain understudied topics in the tissue and organ engineering literature. Precise measurement of cell numbers within bioartificial tissues and extracellular matrix scaffolds is necessary to provide measurement assurance and rigorous characterization of cell behavior within three-dimensional (3D) scaffolds. Accurate benchmarking of tissue function and biosynthetic activity to cell number facilitates comparison of data across experiments and between laboratories to increase rigor and reproducibility in tissue engineering and biofabrication. Soluble, fluorescent indicators of metabolic activity are valuable, noninvasive tools for estimating viable cell number. We investigated experimental conditions in which resazurin is a reliable indicator of cell content within 3D extracellular matrix kidney and liver scaffolds, and we present recommendations on experimental methodology for its optimal use. Resazurin is reduced to resorufin in proportion to metabolic activity of viable cells. Using three renal cell lines and one hepatic cell line, we show that correlation of viable cell number with the rate of resorufin generation may deviate from linearity at higher cell density, low resazurin working volumes, and/or longer incubation times – all of which contribute to depleting the working pool of resazurin. Importantly, we also show that the resazurin reduction rate in cell-conditioned medium is about double that in fresh culture medium. This finding has the potential to increase assay sensitivity, while saving expensive media. In conclusion, while the resazurin reduction assay provides a powerful, noninvasive readout for cell growth within extracellular matrix scaffolds, assay conditions may strongly influence its applicability for accurate quantification of cell number. The approach and recommendations developed in this study to maintain the pool of reducible resazurin may be used as a guide for application-specific optimization of the resazurin reduction assay to obtain accurate measurements of cell content in bioengineered tissues

What Type of Engagement Predicts Success in a Facebook Weight Loss Group?

Studies of social media-delivered behavioral interventions generally reveal that engagement, as defined as total number of posts, is associated with better outcomes. Little is known about whether the type of engagement, volume of content posted, or timing of engagement matters. In the present study, we analyzed the content, volume, and timing of participant posts in a Facebook weight loss intervention. Content was analyzed via thematic analyses. Volume was defined as total characters posted. We explored types of posts and for each, how frequency and volume overall, and in first half and second half of intervention were related to weight loss at end of treatment. Findings revealed that reporting a healthy choice was the most common type of post. The frequency and volume of most types of posts except negative posts predicted weight loss, but those occurring in second half of intervention were more strongly related to weight loss

An Uncommon Cause of Acute Abdominal Pain: Primary Epiploic Appendagitis in the Emergency Setting

In the emergency setting, the diagnosis of benign causes of acute abdominal pain can prevent unnecessary medical interventions. To illustrate this point, we report the case of a 28-year-old man who presented to the emer- gency department with symptoms suggestive of acute diverticulitis. Abdominal computed tomography (CT) established, instead, a diagnosis of primary epiploic appendagitis (PEA), which was managed expectantly. The patient’s symptoms resolved within one week of hospital discharge and he remained free of pain at a five-month phone follow-up. Increased awareness of PEA and its self-limited course can help the emergency physician avoid unnecessary imaging studies and expectantly manage this cause of acute abdominal pain.

Predicting participant engagement in a social-media delivered lifestyle intervention using micro-level conversational data: A pilot feasibility randomized trial (Preprint)

BACKGROUND Social media-delivered lifestyle interventions have shown promising outcomes, often generating modest but significant weight loss. Participant engagement appears to be an important predictor of weight loss outcomes in these interventions, but engagement generally declines over time and is highly variable both within and across studies. Research on factors that influence participant engagement remains scant in the context of social media-delivered lifestyle interventions. OBJECTIVE The objective of this study was to identify predictors of participant engagement in a social media delivered lifestyle intervention including characteristics of the participants, the posts and the conversation that followed the post. METHODS We performed secondary analyses using data from a pilot randomized trial that delivered two lifestyle interventions via Facebook. We analyzed 80 participants’ engagement data (defined as reply/comment) with each of the 761 posts generated over the 16-week intervention period, and linked them to predictors including characteristics of the posts they engaged on, conversation sentiment, and participant characteristics using mixed-effects model. We also performed machine-learning based classification to explore how well the aforementioned measures can predict whether participants will engage with a specific post. RESULTS We found that the probability of participants’ engagement with each post decreased by 0.28% each week (P&lt;.001, 95% CI: 0.16-0.4%) and the probability of participants engaging with posts generated by interventionists was 6.3% (P &lt;.001, 95% CI: 5.1-7.5%) higher than posts generated by other participants. Participants also had 6.5% (P &lt;.001, 95% CI: 4.9-8.1%) and 6.1% (P &lt;.001, 95% CI: 4.1-8.1%) higher probability of engaging with posts that directly mentioned weight and goals, respectively, than other types of posts. Participants were 44.8% (P &lt;.001, 95% CI: 42.8-46.9%) and 46% (P &lt;.001, 95% CI: 44.1-48.0%) more likely to engage with a post when they were replied by other participants and by interventionists, respectively. A 1 standard-deviation decrease in the sentiment of the conversation on a specific post was associated with 5.4% (P &lt;.001, 95% CI: 4.9-5.9%) increase in the probability of participant’s subsequent engagement with the post. Participants’ engagement on previous posts was also a predictor of engagement in subsequent posts (P &lt;.001, 95% CI: 0.74-0.79%). In addition, an ensemble of gradient boosting machine and deep-learning based classification algorithms confirmed the importance of the predictors previously identified, and achieved an accuracy of 90.9% in terms of predicting participants’ engagement using a balanced testing sample with 1,600 observations. CONCLUSIONS Findings revealed several predictors of engagement derived from the content generated by interventionists and other participants. Results have implications for increasing engagement in asynchronous, remotely delivered lifestyle interventions, which could improve outcomes. Our results also point to the potential of data science and natural language processing to analyze micro-level conversational data and identify factors influencing participant engagement. Future studies should validate these results in larger trials. </sec

Case Report Enterococcus hirae Bacteremia Associated with Acute Pancreatitis and Septic Shock

Infection with Enterococcus hirae has rarely been reported in humans but is not uncommon in mammals and birds. We describe a case of Enterococcus hirae bacteremia associated with acute pancreatitis, acute cholecystitis, and septic shock responsive to antibiotic therapy and supportive critical care management. Unique aspects of this case of Enterococcus hirae bacteremia are its association with acute pancreatitis and its geographical origin. To our knowledge, this is the first report of Enterococcus hirae bacteremia occurring in a patient in the United States. Although human infection with this organism appears to be rare, all cases reported to date describe bacteremia associated with severe and life-threatening illness. Thus, physicians need to be cognizant of the clinical significance of this heretofore little recognized pathogen