Synchronization framework for modeling transition to thermoacoustic instability in laminar combustors

We, herein, present a new model based on the framework of synchronization to describe a thermoacoustic system and capture the multiple bifurcations that such a system undergoes. Instead of applying flame describing function to depict the unsteady heat release rate as the flame's response to acoustic perturbation, the new model considers the acoustic field and the unsteady heat release rate as a pair of nonlinearly coupled damped oscillators. By varying the coupling strength, multiple dynamical behaviors, including limit cycle oscillation, quasi-periodic oscillation, strange nonchaos, and chaos can be captured. Furthermore, the model was able to qualitatively replicate the different behaviors of a laminar thermoacoustic system observed in experiments by Kabiraj et al.~[Chaos 22, 023129 (2012)]. By analyzing the temporal variation of the phase difference between heat release rate oscillations and pressure oscillations under different dynamical states, we show that the characteristics of the dynamical states depend on the nature of synchronization between the two signals, which is consistent with previous experimental findings.Comment: 18 pages, 7 figure

A quantitative analysis of germ cells and the histone variants in the testes of vitamin A-deficient rats and during subsequent repletion with vitamin A

A quantitative analysis of the different types of germ cells present in the seminiferous tubules of vitamin A-deficient-retinoate maintained rats revealed that the number of pachytene spermatocytes and spermatogonia was greatly reduced in the deficient rats. Spermatids were virtually absent in the deficient tubules which contained mostly spermatogonia and preleptotene spermatocytes along with the Sertoli cells. There was no change in the number of Sertoli cells present in the tubules of deficient rats as compared to that of normal rats. Following supplementation of retinyl acetate to vitamin A-deficient-retinoate maintained rats, there was an immediate thinning of the germinal epithelium resulting from the sloughing off of the damaged spermatocytes which were beyond repair. However, after 12 days of vitamin A supplementation fresh batch of pachytene spermatocytes started appearing while by day 16 round spermatids could be seen. Analysis of the acid soluble proteins from nuclei on different types of Polyacrylamide gel electrophoretic systems has revealed that the levels of the testis specific histone variants Hlt, TH2A and TH2B, synthesized predominantly in the pachytene spermatocytes were greatly reduced in the testes of retinoate maintained rats. Following supplementation of retinyl acetate for either 4 days or 8 days the levels of these histone variants further decreased which correlated with the decrease in the number of pachytene spermatocytes. However, by day 12 of supplementation onwards, their levels started increasing and reached near normal levels by day 24 of vitamin A-supplementation

A Comparative study to Assess the Outcome and Complications of Grahams Omental Patch Closure Versus Modified Grahams Omental Patch Closure in Perforated Duodenal Ulcer among Patients admitted in General Surgery Department, Government Rajaji Hospital, Madurai

INTRODUCTION: Duodenal ulcer perforation is one of the manifestation of Peptic ulcer disease. Duodenal ulcer represent almost 2/3rd of all peptic ulcer diseases. Perforated duodenal ulcer remains a major health problem world wide. Peptic ulcer disease is primarily associated with H-pylori infection and excessive use of NSAIDs. Since the burden of peptic ulcer disease and its complications are significant worldwide, it is important to conduct a study based on peptic ulcer disease. Life prevalence of duodenal ulcer has found to be 11-14% for males and 8-10% for women. Male to female ratio of duodenal ulcer have reduced from 10:1 to 1.5:1. Duodenal ulcer have been characterized by the presence of a well demarcated break in the mucosa that may extend into muscularis propriya of the duodenum. Duodenal perforation is the second most common complication of PUD and occurs in as many as 10% of patients with PUD. My study compares the outcome and complications of two surgical procedures done for perforated duodenal ulcer namely Grahams Omental Patch Repair and Modified Grahams Omental Patch Closure. AIM OF THE STUDY: The aim of this study is to compare outcome and complications of Graham’s Omental Patch Closure Versus Modified Graham’s Omental Patch Closure for treating perforated duodenal ulcers. OBJECTIVES: To compare outcome and complications of Graham’s Omental Patch Closure Versus Modified Graham’s Omental Patch closure for treating perforated duodenal ulcers. MATERIALS AND METHODS: Study Design: Period of Study: 6 months (April 2018 – September 2018). Place of Study: Government Rajaji Hospital, Madurai. Selection of Study Subjects: All patients diagnosed with peritonitis secondary to hollow viscus perforation who are willing for definitive surgery. Sample Size: 60 patients. Data Collection: Data regarding history, clinical examination,laboratory values & postoperative analysis. METHODS: Prospective comparitative study. ELIGIBILITY CRITERIA: Inclusion Criteria: All patients with perforated duodenal ulcer size < 20 mm who are admitted in general surgery department GRH, Madurai. Exclusion Criteria: Duodenal perforation of other origin such as traumatic and neoplasia. Large duodenal perforation > 20 mm, Posterior duodenal perforation, Sealed duodenal perforation, Patient who expired before definitive surgery, Patient not willing for definitive surgery, Patient not willing for the study. MATERIALS USED: Proforma containing patient history, clinical examination, Informed consent forms. METHODOLOGY: After obtaining clearance and approval from the institutional ethical committee and patients fulfilling the inclusion / exclusion criteria were included in the study after obtaining informed consent. • Patients admitted in surgery department who are diagnosed with perforated duodenal ulcer are grouped into group 1 and group 2. • Non probability purposive sampling technique was used to allocate the subjects into group 1(Grahams omental patch closure) and group 2 (Modified Graham’s omental patch closure). • Initial preoperative work up and resuscitation with intravenous fluids, antibiotics, analgesics, nasogastric decompression was done in all the cases. DISCUSSION In our study we included 60 patients. 30 patients were under Group 1 (GRAHAMS OMENTAL PATCH REPAIR) and 30 patients under Group 2 (MODIFIED GRAHAMS OMENTAL PATCH REPAIR). Age distribution of the patients affected ranged from 13-70 years in the present study. The maximum number of cases studied were in the age group of 31 to 40 (25%). In group 1 mean age was 40.7 (SD – 15.020). In group 2 the mean age was 40.83 (SD-23.181). The two tailed P value equals 0.9795. This difference is considered to be statistically not significant. Most of the patients were males (males 51%). Male female ratio was 51:9. Comparing the two groups chi square statistics is 3.268. The p value is 0.70645. This result is not significant at p < 0.05. Majority of patients presented with symptoms of abdominal pain for 1 to 2 days. (mean days of presentation- 1.68 days). 9 out of 60 patients were diabetic, 3 out of 60 patients were hypertensive. 41 patients out of 60 patients studied had history of smoking (68.3%). 9 out of 60 patients had history of NSAID abuse (15%). The mean duration of ventilator support was 0.3667 days in group 1 and 0.43333 days in group 2. Comparing the two groups the two tailed p value is 0.9409. This result is not statistically significant at p < 0.05. Patients in group 1 have return of bowel activity in an average of 3.43 days. Patients in group 1 have return of bowel activitiy in an average of 3.966 days. Comparing the two groups the two tailed p value is 0.3788. This result is not statistically significant at p < 0.05. 8 out of 30 patients in group 1 developed surgical site infection, while 6 out of 30 patients in group 2 developed surgical site infection. Comparing the two groups chi square statistics is 0.3727 the p value is 0.541552. This result is not statistically significant at p < 0.05. 2 out of 30 patients in group 1 developed metabolic abnormalities post operatively. 2 out of 30 patients in group 2 developed metabolic abnormalities post operatively Comparing the two groups chi square statistics is 0 .the p value is 1. This result is not statistically significant at p < 0.05. Average days of hospital stay in group 1 is 9.9 days. Average days of hospital stay in group 2 is 8.46 days. Comparing the two groups. The two tailed p value is 0.7840. This result is not statistically significant at p < 0.05. 4 out of 30 patients in group 1 died during hospital stay. 4 out of 30 patients in group 2 died during hospital stay. Comparing the two groups chi square statistics is 0 .the p value is 1. This result is not statistically significant at p < 0.05. CONCLUSION: The outcome and complication of both surgeries for perforated duodenal ulcer, that is GRAHAMS OMENTAL PATCH REPAIR and MODIFIED GRAHAMS OMENTAL PATCH REPAIR are independent of the method of surgery done. Thus it is the surgeons choice to select one of the two methods. The major contributing factor for outcome and complication of surgery are the age, day of presentation, peritonitis index and comorbidities of patient rather than the type of surgery done

Inhibiting the onset of thermoacoustic instability through targeted control of critical regions

This experimental study investigates the dynamical transition from stable operation to thermoacoustic instability in a turbulent bluff-body stabilised dump combustor. We conduct experiments to acquire acoustic pressure and local heat release rate fluctuations and use them to characterise this transition as we decrease the equivalence ratio towards a fuel-lean setting. More importantly, we observe a significant increase in local heat release rate fluctuations at critical locations well before thermoacoustic instability occurs. One of these critical locations is the stagnation zone in front of the bluff-body. By strategically positioning slots (perforations) on the bluff-body, we ensure the reduction of the growth of local heat release rate fluctuations at the stagnation zone near the bluff-body well before the onset of thermoacoustic instability. We show that this reduction in local heat release rate fluctuations inhibits the transition to thermoacoustic instability. We find that modified configurations of the bluff-body that do not quench the local heat release rate fluctuations at the stagnation zone result in the transition to thermoacoustic instability. We also reveal that an effective suppression strategy based on the growth of local heat release rate fluctuations requires an optimisation of the slots' area-ratio for a given bluff-body position. Further, the suppression strategy also depends on the spatial distribution of perforations on the bluff-body. Notably, an inappropriate distribution of the slots, which does not quench the local heat release rate fluctuations at the stagnation zone but creates new critical regions, may even result in a dramatic increase in the amplitudes of pressure oscillations

Detection of dynamical regime transitions with lacunarity as a multiscale recurrence quantification measure

We propose lacunarity as a novel recurrence quantification measure and illustrate its efficacy to detect dynamical regime transitions which are exhibited by many complex real-world systems. We carry out a recurrence plot-based analysis for different paradigmatic systems and nonlinear empirical data in order to demonstrate the ability of our method to detect dynamical transitions ranging across different temporal scales. It succeeds to distinguish states of varying dynamical complexity in the presence of noise and non-stationarity, even when the time series is of short length. In contrast to traditional recurrence quantifiers, no specification of minimal line lengths is required and geometric features beyond linear structures in the recurrence plot can be accounted for. This makes lacunarity more broadly applicable as a recurrence quantification measure. Lacunarity is usually interpreted as a measure of heterogeneity or translational invariance of an arbitrary spatial pattern. In application to recurrence plots, it quantifies the degree of heterogeneity in the temporal recurrence patterns at all relevant time scales. We demonstrate the potential of the proposed method when applied to empirical data, namely time series of acoustic pressure fluctuations from a turbulent combustor. Recurrence lacunarity captures both the rich variability in dynamical complexity of acoustic pressure fluctuations and shifting time scales encoded in the recurrence plots. Furthermore, it contributes to a better distinction between stable operation and near blowout states of combustors

COVID-19 an atypical presentation

Coronavirus disease 2019 (COVID-19) pneumonia usually presents as an unilateral or bilateral lower zone opacities. We wish to highlight a case of COVID 19 presenting as upper lobe consolidation with pre-existing co morbidities and unknown primary source of infection

Bacteroides muris sp. nov. isolated from the cecum of wild-derived house mice

Two bacterial strains, KH365_2T and KH569_7, were isolated from the cecum contents of wild-derived house mice. The strains were characterized as Gram-negative, rod-shaped, strictly anaerobic, and non-motile. Phylogenetic analysis based on 16S rRNA gene sequences revealed that both strains were most closely related to Bacteroides uniformis ATCC 8492T. Whole genome sequences of KH365_2T and KH569_7 strains have a DNA G + C content of 46.02% and 46.03% mol, respectively. Most morphological and biochemical characteristics did not differ between the newly isolated strains and classified Bacteroides strains. However, the average nucleotide identity (ANI) and dDNA–DNA hybridization (dDDH) values clearly distinguished the two strains from described members of the genus Bacteroides. Here, we present the phylogeny, morphology, and physiology of a novel species of the genus Bacteroides and propose the name Bacteroides muris sp. nov., with KH365_2T (DSM 114231T = CCUG 76277T) as type strain