Compressor pulsation noise attenuation using reactive silencer with various configurations: A theoretical and experimental study

Compressors are a significant source of noise in various industries. Silencers can be utilized to mitigate this noise. This study aims to design and construct an expansion silencer that can effectively reduce the pulsating noise produced by a reciprocating compressor. This study employed a model-experimental approach to investigate the performance of four different sizes of expansion silencers in controlling the pulsating noise in the suction part of the compressor. Initially, the silencers' sound transmission loss and pressure loss were simulated using the finite element method with COMSOL software. Subsequently, the sound transmission loss of the silencers was measured according to the E261109 standard using an impedance tube. Finally, the pressure loss of the silencers was measured using a Pitot tube upstream and downstream of the silencer at various flow rates. The results of the modeling showed that increasing the diameter of the silencer leads to an increase in transmission loss at all frequencies. Additionally, raising the length of the silencer only increased the number of sound transmission loss peaks in the frequency bandwidth without significant change in sound transmission loss. Furthermore, the results of the experimental measurements with an impedance tube revealed that increasing the diameter results in increased transmission loss, while increasing the silencer length leads to an increase in the number of transmission loss peaks without altering the transmission loss. Moreover, the modeling and experimental pressure loss results indicated that increasing the diameter of the expansion chamber causes an increase in pressure loss, while increasing the length of the expansion chamber results in a minor change in pressure loss. Finally, the research results showed relatively good agreement between modeling and experimental outcomes.

An enhancer sequence in the intrinsically disordered region of FtsZ promotes polymer‐guided substrate processing by ClpXP protease

The essential bacterial division protein in Escherichia coli, FtsZ, assembles into the FtsZ-ring at midcell and recruits other proteins to the division site to promote septation. A region of the FtsZ amino acid sequence that links the conserved polymerization domain to a C-terminal protein interaction site was predicted to be intrinsically disordered and has been implicated in modulating spacing and architectural arrangements of FtsZ filaments. While the majority of cell division proteins that directly bind to FtsZ engage either the polymerization domain or the C-terminal interaction site, ClpX, the recognition and unfolding component of the bacterial ClpXP proteasome, has a secondary interaction with the predicted intrinsically disordered region (IDR) of FtsZ when FtsZ is polymerized. Here, we use NMR spectroscopy and reconstituted degradation reactions in vitro to demonstrate that this linker region is indeed disordered in solution and, further, that amino acids in the IDR of FtsZ enhance the degradation in polymer-guided interactions.

Degradation of the E. coli antitoxin MqsA by the proteolytic complex ClpXP is regulated by zinc occupancy and oxidation

It is well established that the antitoxins of toxin-antitoxin (TA) systems are selectively degraded by bacterial proteases in response to stress. However, how distinct stressors result in the selective degradation of specific antitoxins remains unanswered. MqsRA is a TA system activated by various stresses, including oxidation. Here, we reconstituted the Escherichia coli ClpXP proteolytic machinery in vitro to monitor degradation of MqsRA TA components. We show that the MqsA antitoxin is a ClpXP proteolysis substrate, and that its degradation is regulated by both zinc occupancy in MqsA and MqsR toxin binding. Using NMR chemical shift perturbation mapping, we show that MqsA is targeted directly to ClpXP via the ClpX substrate targeting N-domain, and ClpX mutations that disrupt N-domain binding inhibit ClpXP mediated degradation in vitro. Finally, we discovered that MqsA contains a cryptic N-domain recognition sequence that is accessible only in the absence of zinc and MqsR toxin, both of which stabilize the MqsA fold. This recognition sequence is transplantable and sufficient to target a fusion protein for degradation in vitro and in vivo. Based on these results, we propose a model in which stress selectively targets nascent, zinc-free MqsA, resulting in exposure of the ClpX recognition motif for ClpXP mediated degradation.

Effects of Aloe vera cream on chronic anal fissure pain, wound healing and hemorrhaging upon defection: a prospective double blind clinical trial

Aloe vera is a medicinal plant that promotes wound healing in burn injuries. A prospective clinical trial was conducted to evaluate the effects of a topical cream containing 0.5% Aloe vera juice powder in the treatment of chronic anal fissures. The aloe cream was applied by the patients to the wound site 3 times per day for 6 weeks following the instructions of a physician. Pain was assessed with a visual analog scale before treatment and at the end of each week of treatment. Wound healing and the amount and severity of bleeding were examined and evaluated before and at the end of each week of treatment. There were statistically significant differences in chronic anal fissure pain, hemorrhaging upon defection and wound healing before and at the end of the first week of treatment also in comparison with control group (p < 0.0001). In this study, a topical cream containing aloe vera juice was an effective treatment for chronic anal fissures. This is a promising result indicating that further comparative studies are justified.

Development and validation of a rapid HPLC method for simultaneous analysis of budesonide and its novel synthesized hemiesters in colon specific formulations

A simple and reliable reversed-phase high performance liquid chromatographic (HPLC) method was developed, validated and applied for determination of budesonide and its novel synthesized hemiesters in colon specific formulations and dissolution media. The method was employed on a μ-Bondapak C(18) column (250 mm × 4.6 mm, 5 μm) at ambient temperature. The mobile phase consisted of acetonitrile: monobasic potassium phosphate containing orthophosphoric acid (55:45, pH 3.2) at a flow rate of 1 ml/min. The UV detection wavelength was set at 244 nm and 50 μL of sample was injected into the HPLC system. Dexamethasone was used as the internal standard. The retention times for internal standard and budesonide were 4.5 and 7.2 min, respectively. The method was linear in the concentration range of 1-20 μg/ml of budesonide (R(2)>0.999). Limit of detection and limit of quantitation were 0.05 and 0.5 μg/ml, respectively. The method presented the requisite accuracy, selectivity, sensitivity and precision and showed good resolution for separation of the drug and related derivatives in the presence of excipients. The proposed method was successfully used for analysis of the drug and its derivatives in dissolution media and oral colon specific formulations prepared in our laboratory with enough reproducibility.

Development of novel budesonide pellets based on CODES(TM) technology: In vitro/in vivo evaluation in induced colitis in rats

BACKGROUND AND THE PURPOSE OF THE STUDY

Budesonide is the drug of choice for treatment of active inflammatory bowel disease (IBD). The aim of this study was to develop budesonide pellets based on a novel colon drug delivery system (CODES).

METHODS

Pellet cores containing lactulose or mannitol were prepared by extrusion/spheronization and coated with an acid soluble polymer (Eudragit E100), hydroxypropylmethyl cellulose (HPMC) and an enteric coat (Eudragit FS 30D) sequentially. In vitro drug release of coated pellets was studied using USP dissolution apparatus type II in buffers of pH 1.2 (2 hrs), pH of 7.4 (4 hrs) and pH of 6.8 containing 8% rat cecal contents (RCC) (18 hrs). The efficacy of the optimized formulation (containing 50% lactulose coated with Eudragit E (30% w/w) and Eudragit FS 30D (12% w/w)) was evaluated against 2, 4, 6-trinitrobenzenesulfonic acid (TNBS)-induced colitis in rats.

RESULTS

The results of the kind of bacteria in vitro dissolution tests indicated absence of drug release in pHs of 1.2 and 7.4 and controlled release in buffer of pH 6.8 containing RCC. It was found that release rate was controlled by the type and amount of polysaccharide and the thickness of the acid soluble layer. The prepared formulation showed promising results in alleviating the conditions of experimental model of colitis.

CONCLUSION

The results of this study suggest that pellets based on CODES technology could be useful for colonic delivery of budesonide.