Further analysis of the effects of baffles on combustion instability

A computerized analytical model, developed to predict the effects of baffles on combustion instability, was modified in an effort to improve the ability to properly predict stability effects. The model was modified: (1) to replace a single spatially-averaged response factor by separate values for each baffle compartment; (2) to calculate the axial component of the acoustic energy flux, and (3) to permit analysis of traveling waves in a thin annular chamber. Allowance for separate average response factors in each baffle compartment was found to significantly affect the predicted results. With this modification, an optimum baffle length was predicted which gave maximum stability

Analysis of the effects of baffles on combustion instability

An analytical model has been developed for predicting the effects of baffles on combustion instability. This model has been developed by coupling an acoustic analysis of the wave motion within baffled chambers with a model for the oscillatory combustion response of a propellant droplet developed by Heidmann. A computer program was developed for numerical solution of the resultant coupled equations. Diagnostic calculations were made to determine the reasons for the improper prediction. These calculations showed that the chosen method of representing the combustion response was a very poor approximation. At the end of the program, attempts were made to minimize this effect but the model still improperly predicts the stability trends. Therefore, it is recommended that additional analysis be done with an improved approximation

Analysis of combustion instability in liquid propellant engines with or without acoustic cavities

Analytical studies have been made of the relative combustion stability of various propellant combinations when used with hardware configurations representative of current design practices and with or without acoustic cavities. Two combustion instability models, a Priem-type model and a modification of the Northern Research and Engineering (NREC) instability model, were used to predict the variation in engine stability with changes in operating conditions, hardware characteristics or propellant combination, exclusive of acoustic cavity effects. The NREC model was developed for turbojet engines but is applicable to liquid propellant engines. A steady-state combustion model was used to predict the needed input for the instability models. In addition, preliminary development was completed on a new model to predict the influence of an acoustic cavity with specific allowance for the effects the nozzle, steady flow and combustion

Scanning Electron Microscopy of the Surface of Human Duodenum in Patients With and Without Duodenal Ulcer Disease

Endoscopic biopsy specimens of normal human duodenum from patients with duodenal ulcer disease were studied by light microscopy and by scanning electron microscopy. For scanning, the tissue was dried by the critical point-drying technique. SEM criteria for both normal and abnormal duodenal surfaces were determined. SEM evidence for the presence of tuft cells similar to those found on the surface of rat duodenum was found in both the normal and abnormal human material. Although other reports have described the favorable effects of carbenoxolone sodium treatment on duodenal ulcer disease, our SEM studies of four patients found that this treatment had no effect on the duodenal surface

Characterization of the Brain 26S Proteasome and its Interacting Proteins

Proteasome-mediated proteolysis is important for synaptic plasticity, neuronal development, protein quality control, and many other processes in neurons. To define proteasome composition in brain, we affinity purified 26S proteasomes from cytosolic and synaptic compartments of the rat cortex. Using tandem mass spectrometry, we identified the standard 26S subunits and a set of 28 proteasome-interacting proteins that associated substoichiometrically and may serve as regulators or cofactors. This set differed from those in other tissues and we also found several proteins that associated only with either the cytosolic or the synaptic proteasome. The latter included the ubiquitin-binding factor TAX1BP1 and synaptic vesicle protein SNAP-25. Native gel electrophoresis revealed a higher proportion of doubly-capped 26S proteasome (19S-20S-19S) in the cortex than in the liver or kidney. To investigate the interplay between proteasome regulation and synaptic plasticity, we exposed cultured neurons to glutamate receptor agonist NMDA. Within 4 h, this agent caused a prolonged decrease in the activity of the ubiquitin-proteasome system as shown by disassembly of 26S proteasomes, decrease in ubiquitin-protein conjugates, and dissociation of the ubiquitin ligases UBE3A (E6-AP) and HUWE1 from the proteasome. Surprisingly, the regulatory 19S particles were rapidly degraded by proteasomal, not lysosomal degradation, and the dissociated E3 enzymes also degraded. Thus the content of proteasomes and their set of associated proteins can be altered by neuronal activity, in a manner likely to influence synaptic plasticity and learning

Risk and Protective Factors of Dementia Among Adults With Post-Traumatic Stress Disorder: A Systematic Review Protocol

INTRODUCTION: Post-traumatic stress disorder (PTSD) is associated with an increased risk of dementia. Individual epidemiological studies have controlled for several confounders of the relationship between PTSD and increased dementia risk, yet particular risk factors underlying this relationship have not been determined. This systematic review protocol aims to identify risk and protective factors of dementia among adults with PTSD. METHODS AND ANALYSIS: We will conduct an electronic search of the databases: PubMed, CINAHL, PsychINFO, The Cochrane Library, Scopus and ProQuest Dissertation and Theses Global. After screening the studies, quantitative synthesis will be performed, if possible. Otherwise, a narrative synthesis will be performed. We will include randomised controlled trials and other types of research evidence including longitudinal cohort studies. Strength of evidence will be assessed using the Grading of Recommendations, Assessment, Development and Evaluations method. Examples of variables that will be extracted are: year of PTSD diagnosis, comorbid conditions, health behaviours, pharmacological treatments and year of mild cognitive impairment or dementia diagnosis. We developed this systematic review protocol according to the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols 2015 statement. ETHICS AND DISSEMINATION: The proposed study will not collect individual-level data and, therefore, does not require ethical approval. Results of this study will provide current evidence on risk and protective factors of dementia in adults with PTSD. Findings will be disseminated in peer-reviewed publications and conference presentations. PROSPERO REGISTRATION NUMBER: CRD42019128553

Cleavable Biotin Probes for Labeling of Biomolecules via Azide−Alkyne Cycloaddition

The azide−alkyne cycloaddition provides a powerful tool for bio-orthogonal labeling of proteins, nucleic acids, glycans, and lipids. In some labeling experiments, e.g., in proteomic studies involving affinity purification and mass spectrometry, it is convenient to use cleavable probes that allow release of labeled biomolecules under mild conditions. Five cleavable biotin probes are described for use in labeling of proteins and other biomolecules via azide−alkyne cycloaddition. Subsequent to conjugation with metabolically labeled protein, these probes are subject to cleavage with either 50 mM Na_2S_2O_4, 2% HOCH_2CH_2SH, 10% HCO_2H, 95% CF_3CO_2H, or irradiation at 365 nm. Most strikingly, a probe constructed around a dialkoxydiphenylsilane (DADPS) linker was found to be cleaved efficiently when treated with 10% HCO_2H for 0.5 h. A model green fluorescent protein was used to demonstrate that the DADPS probe undergoes highly selective conjugation and leaves a small (143 Da) mass tag on the labeled protein after cleavage. These features make the DADPS probe especially attractive for use in biomolecular labeling and proteomic studies

Differences in Suicidality in Non–Treatment-Seeking and Treatment-Seeking Law Enforcement Officers: A Cross-sectional Study

Objective: Law enforcement officers (LEOs) are exposed to high levels of occupational trauma and face added stress from heightened public scrutiny and COVID-19, which may result in suicide. It is crucial to understand differences between LEOs who seek treatment and those who do not. Method: We compared LEOs from the same greater metropolitan area who sought treatment with those who did not. Participants completed validated measures assessing posttraumatic stress disorder, generalized anxiety, depression, and suicidality. Results: The treatment-seeking sample scores were higher on all standardized assessments. Bivariate logistic regression results indicated that the non–treatment-seeking sample\u27s odds of experiencing suicidality were 1.76 times the odds for the treatment seeking sample. Conclusions: This suggests that many LEOs experiencing suicidality may not be seeking treatment and highlights the role that posttraumatic stress disorder may play in determining whether LEOs seek treatment or not

A laser-induced mouse model with long-term intraocular pressure elevation

Purpose: To develop and characterize a mouse model with intraocular pressure (IOP) elevation after laser photocoagulation on the trabecular meshwork (TM), which may serve as a model to investigate the potential of stem cell-based therapies for glaucoma. Methods: IOP was measured in 281 adult C57BL/6 mice to determine normal IOP range. IOP elevation was induced unilaterally in 50 adult mice, by targeting the TM through the limbus with a 532-nm diode laser. IOP was measured up to 24 weeks post-treatment. The optic nerve damage was detected by electroretinography and assessed by semiautomatic counting of optic nerve axons. Effects of laser treatment on the TM were evaluated by histology, immunofluorescence staining, optical coherence tomography (OCT) and transmission electron microscopy (TEM). Results: The average IOP of C57BL/6 mice was 14.5±2.6 mmHg (Mean ±SD). After laser treatment, IOP averaged above 20 mmHg throughout the follow-up period of 24 weeks. At 24 weeks, 57% of treated eyes had elevated IOP with the mean IOP of 22.5±2.5 mmHg (Mean ±SED). The difference of average axon count (59.0%) between laser treated and untreated eyes was statistically significant. Photopic negative response (PhNR) by electroretinography was significantly decreased. CD45+ inflammatory cells invaded the TM within 1 week. The expression of SPARC was increased in the TM from 1 to 12 weeks. Histology showed the anterior chamber angle open after laser treatment. OCT indicated that most of the eyes with laser treatment had no synechia in the anterior chamber angles. TEM demonstrated disorganized and compacted extracellular matrix in the TM. Conclusions: An experimental murine ocular hypertension model with an open angle and optic nerve axon loss was produced with laser photocoagulation, which could be used to investigate stem cell-based therapies for restoration of the outflow pathway integrity for ocular hypertension or glaucoma. Copyright