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 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

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

Endoscopic Retrograde Pancreatic Duct Cannulation (ERPC): An Aid to Pancreatic Surgery

Retrograde endoscopic pancreatic duct cannulation for evaluation of patients with chronic pancreatitis is reviewed over the last two years. Of 40 patients that were endoscoped, 30 had a successful pancreatogram. The X-ray findings fell into three groups: 1) single and multiple stenosis, 2) diffuse narrowing, and 3) apparently normal duct. This procedure proved of value in ruling out or delaying surgical operation in 10 persons. Twenty-one patients underwent operations. Thirteen had a 95% pancreatectomy, one had drainage of a necrotic collection thought to be a pseudocyst and one had a pseudocyst resected. One had a gastrojejunostomy and vagotomy bypassing a stenosis of the second portion of the duodenum and three had exploratory laparotomies. In five of the operated patients, the papilla could not be entered because of retraction, scarring or edema. In eight the correlation of the ductogram and the pathology found in resected specimen was good, while in another seven patients the resected specimen showed much more pathology than was suspected from the ductogram. While the pancreatogram fortifies clinical judgment. It is not always reliable as an indicator of the need for surgical versus medical treatment

Super-resolution imaging and estimation of protein copy numbers at single synapses with DNA-PAINT

In the brain, the strength of each individual synapse is defined by the complement of proteins present or the "local proteome." Activity-dependent changes in synaptic strength are the result of changes in this local proteome and posttranslational protein modifications. Although most synaptic proteins have been identified, we still know little about protein copy numbers in individual synapses and variations between synapses. We use DNA-point accumulation for imaging in nanoscale topography as a single-molecule super-resolution imaging technique to visualize and quantify protein copy numbers in single synapses. The imaging technique provides near-molecular spatial resolution, is unaffected by photobleaching, enables imaging of large field of views, and provides quantitative molecular information. We demonstrate these benefits by accessing copy numbers of surface AMPA-type receptors at single synapses of rat hippocampal neurons along dendritic segments

Back to the ‘roots’ of research: a hypothesis‐driven approach provides predictive understanding of plant–herbivore–microbe interactions

This article is a Commentary on Böttner et al. (2023), 239: 1475–1489

Teaching old NCATs new tricks: using non-canonical amino acid tagging to study neuronal plasticity

The non-canonical amino acid labeling techniques BONCAT (bioorthogonal non-canonical amino acid tagging) and FUNCAT (fluorescent non-canonical amino acid tagging) enable the specific identification and visualization of newly synthesized proteins. Recently, these techniques have been applied to neuronal systems to elucidate protein synthesis dynamics during plasticity, identify stimulation-induced proteomes and subproteomes and to investigate local protein synthesis in specific subcellular compartments. The next generation of tools and applications, reviewed here, includes the development of new tags, the quantitative identification of newly synthesized proteins, the application of NCAT to whole animals, and the ability to genetically restrict NCAT labeling. These techniques will enable not only improved detection but also allow new scientific questions to be tackled

Cell-type-specific metabolic labeling, detection and identification of nascent proteomes in vivo

A big challenge in proteomics is the identification of cell-type-specific proteomes in vivo. This protocol describes how to label, purify and identify cell-type-specific proteomes in living mice. To make this possible, we created a Cre-recombinase-inducible mouse line expressing a mutant methionyl-tRNA synthetase (L274G), which enables the labeling of nascent proteins with the non-canonical amino acid azidonorleucine (ANL). This amino acid can be conjugated to different affinity tags by click chemistry. After affinity purification (AP), the labeled proteins can be identified by tandem mass spectrometry (MS/MS). With this method, it is possible to identify cell-type-specific proteomes derived from living animals, which was not possible with any previously published method. The reduction in sample complexity achieved by this protocol allows for the detection of subtle changes in cell-type-specific protein content in response to environmental changes. This protocol can be completed in ~10 d (plus the time needed to generate the mouse lines, the desired labeling period and MS analysis

A genetically encodable cell-type-specific protein synthesis inhibitor

Chemical inhibitors have revealed requirements for protein synthesis that drive cellular plasticity. We developed a genetically encodable protein synthesis inhibitor (gePSI) to achieve cell-type-specific temporal control of protein synthesis. Controlled expression of the gePSI in neurons or glia resulted in rapid, potent and reversible cell-autonomous inhibition of protein synthesis. Moreover, gePSI expression in a single neuron blocked the structural plasticity induced by single-synapse stimulation