The problem of identification of statistically significant patterns in a sequence of data has been applied to many domains such as intrusion detection systems, financial models, web-click records, automated monitoring systems, computational biology, cryptology, and text analysis. An observed pattern of events is deemed to be statistically significant if it is unlikely to have occurred due to randomness or chance alone. We use the chi-square statistic as a quantitative measure of statistical significance. Given a string of characters generated from a memoryless Bernoulli model, the problem is to identify the substring for which the empirical distribution of single letters deviates the most from the distribution expected from the generative Bernoulli model. This deviation is captured using the chi-square measure. The most significant substring (MSS) of a string is thus defined as the substring having the highest chi-square value. Till date, to the best of our knowledge, there does not exist any algorithm to find the MSS in better than O(n 2 ) time, where n denotes the length of the string. In this paper, we propose an algorithm to find the most significant substring, whose running time is O(n 3/2 ) with high probability. We also study some variants of this problem such as finding the top-t set, finding all substrings having chi-square greater than a fixed threshold and finding the MSS among substrings greater than a given length. We experimentally demonstrate the asymptotic behavior of the MSS on varying the string size and alphabet size. We also describe some applications of our algorithm on cryptology and real world data from finance and sports. Finally, we compare our technique with the existing heuristics for finding the MSS.

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Background: The aim of the study is to compare intubating conditions and hemodynamic changes during awake fiber-optic intubation (AFOI) using midazolam and fentanyl versus dexmedetomidine in cases of difficult airway. Materials and Methods: A randomized prospective study was conducted in the department of oral and maxillofacial surgery, with a total of 60 patients, 18–55 years of age, ASA class I–II, of either sex with anticipated difficult airway planned for elective surgery. They were divided into two groups; group I patients received 1 μg/kg of dexmedetomidine and then an infusion of 0.5 to 0.7 μg/kg/hr of dexmedetomidine, whereas group II patients received 1 μg/kg of intra-venous (iv) fentanyl and 0.05 mg/kg of iv midazolam with additional doses of 0.02 mg/kg to achieve a Ramsay Sedation Scale score of ≥2. The ease of placement of the fiber-optic scope and the endotracheal tube and the patient's reaction to placement of the fiber-optic scope were assessed on a scale of 1–4 and were recorded as endoscopist satisfaction score and patient discomfort score, respectively. Results: The endoscopy time ranged from 2.66 ± 1.00 (group I) to 3.90 ± 0.96 (group II) minutes and was found to be statistically significant (p < 0.05). Also, the patient discomfort score was recorded during endoscopy (1–4) and ranged from 1.3 ± 0.53 (group I) and 2.33 ± 0.66 (group II) and was found to be statistically significant (p value < 0.05). Patients undergoing the procedure who received dexmedetomidine were thus more comfortable than those who received fentanyl and midazolam combination. Conclusion: Dexmedetomidine provided better intubating conditions, patient tolerance, higher endoscopist satisfaction, and reduced hemodynamic responses compared to fentanyl and midazolam combinations. Also, the major advantage of dexmeditomidine for preservation of airway with a lesser degree of respiratory depression allows for safer use of AFOI in cases of difficult airway.

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Extensive research is on-going to understand the flame holding criteria for the combustor near its lean blow out limit. Sudden blow out of combustor is not preferable, and thus blowout process in a laminar flame needs to be understood thoroughly. In this work, blow out process of the stagnation point stabilized flame is discussed in detail and effect of various velocity profiles on blowout process is analyzed. To understand the dynamics of the flame, high speed visualization was performed using direct chemiluminescence and third mirror schlieren techniques. The experiments were conducted for two nozzles having different length (L) to diameter (D) ratios; two velocity profiles associated with these two nozzles are top-hat velocity profile and fully developed velocity profile. The flame shape appears to be a flat circular disk and the flame edges were found to be flapping in case of top-hat velocity profile burner while the flapping motion was absent in the case of the burner having fully developed velocity profile. In both the cases, a 'hole' inside the flame was found prior to its blow out and it grows in size with time and eventually causes the flame to blow out. These precursor events (local extinction of the flame followed by its recovery) prior to blowout were not observed in the nozzle having fully developed velocity profile while this phenomenon was found to be existing in the nozzle having top-hat velocity profile.