From Network Structure to Dynamics and Back Again: Relating dynamical stability and connection topology in biological complex systems

The recent discovery of universal principles underlying many complex networks occurring across a wide range of length scales in the biological world has spurred physicists in trying to understand such features using techniques from statistical physics and non-linear dynamics. In this paper, we look at a few examples of biological networks to see how similar questions can come up in very different contexts. We review some of our recent work that looks at how network structure (e.g., its connection topology) can dictate the nature of its dynamics, and conversely, how dynamical considerations constrain the network structure. We also see how networks occurring in nature can evolve to modular configurations as a result of simultaneously trying to satisfy multiple structural and dynamical constraints. The resulting optimal networks possess hubs and have heterogeneous degree distribution similar to those seen in biological systems.Comment: 15 pages, 6 figures, to appear in Proceedings of "Dynamics On and Of Complex Networks", ECSS'07 Satellite Workshop, Dresden, Oct 1-5, 200

Static and dynamic characteristics of protein contact networks

The principles underlying protein folding remains one of Nature's puzzles with important practical consequences for Life. An approach that has gathered momentum since the late 1990's, looks at protein hetero-polymers and their folding process through the lens of complex network analysis. Consequently, there is now a body of empirical studies describing topological characteristics of protein macro-molecules through their contact networks and linking these topological characteristics to protein folding. The present paper is primarily a review of this rich area. But it delves deeper into certain aspects by emphasizing short-range and long-range links, and suggests unconventional places where "power-laws" may be lurking within protein contact networks. Further, it considers the dynamical view of protein contact networks. This closer scrutiny of protein contact networks raises new questions for further research, and identifies new regularities which may be useful to parameterize a network approach to protein folding. Preliminary experiments with such a model confirm that the regularities we identified cannot be easily reproduced through random effects. Indeed, the grand challenge of protein folding is to elucidate the process(es) which not only generates the specific and diverse linkage patterns of protein contact networks, but also reproduces the dynamic behavior of proteins as they fold. Keywords: network analysis, protein contact networks, protein foldingComment: Added Appendix

Outcome and Quality of Life of Patients following Valve Replacement Surgery: Predictors of Healthy Survival

Background: In search of factors influencing the postoperative health-related quality of life after heart valve replacement, the present study was designed to see the effects of valve replacement on the long-term healthy survival. The aim of the study was to explore whether the Preoperative variables, such as clinical characteristics and test data could he used to predict the effects of valve replacement on functional status and quality of life in patients with heart valve malfunctions after alter surgical intervention.Method: We retrospectively identified 200 patients who underwent heart valve replacement for stenosis between 2005 and 20l2 in the department of Cardiac Surgery. BSMMU. Dhaka. Bangladesh and survived the surgery and initial 30 day postoperative period. Late follow-up between January 2013 and July 2015 was done and completed in 50% cases.Results: Among 100 study population, 47 were male and the rest 53 were female, aged 22 to 65 years (mean 37.0±7.4 years). The quality of life was assessed with the Medical Outcomes Study Short Form -36 (MOS SF-36) and the functional outcome was evaluated using New York Heart Association (NYHA) functional class scores, in addition to analysis of laboratory tests, like ECG, X-ray chest, echocardiography, prothrombin time. Evaluation of preoperative medical history revealed that there were hypertension in 7l%, diabetes mellitus in l3%, and history of stroke in 09% patients. Prolonged length of stay in intensive care unit and in hospital (mean: 14.7 and 37.l days respectively) was observed in 17% patients. Late postoperative survival rate was 86% at l year and 63% at the end of 5 years. Predictors of late morbidity and mortality were Preoperative or Perioperative complications, preoperative history of stroke, chronic obstructive pulmonary disease. postoperative renal dysfunction. The mean NYHA functional class for all late survivors improved from 3.6 ± 0.9 to 1.9 ± 0.7. Late survival was worse for those who were in an advanced NYHA functional class before surgery. Patient in NYHA Functional class Ill and IV had a worse late survival late than those in Class I or ll. There was Significant improvement in all 8 health domains of the SF-36 Questionnaire in the overall sample.Conclusion: The present study indicated that the late survival rate and functional outcome after heart valve replacement in Bangladeshi population with major valvular dysfunction was satisfactory. It was also observed that the preoperative physical as well as mental health status were identified as the only risk factors for potential non-improving quality of healthy survival following heart valve replacement after correction for age, gender and type after surgery.Cardiovasc. j. 2017; 10(1): 21-30</jats:p

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Free Revascularized Fibula Graft for Reconstruction of Mandibular Continuity Defects

Mandibular reconstruction represents a challenge to the oral and maxillofacial surgeon and has been revolutionized by the modern microvascular techniques Objective: To evaluate the usefulness of the free vascularized fibula graft for reconstruction of discontinuity defects of Mandible after resections of benign aggressive odontogenic tumours. The results of 7 vascularized free fibula graft without a skin paddle that were used for mandibular reconstruction is presented. The "double barrel" technique was used in 1 case. The donor site was closed directly in all cases. All procedures were performed by the same surgical team in oral and Maxillofacial Surgery department of BSMMU and Health &amp; Hope Hospital from January, 2006 to December 2011. A total of patients (3 males, 4 females) were treated. All flaps except 1 were viable. Success rate was 85.71% .The average length of the fibula graft was 10.96 cm, and the number of osteotomies ranged from 0 to 3. There were no long-term functional complications in the lower leg. The fibula flap provides a successful bone graft for mandibular restoration with an acceptably low complication rate. DOI: http://dx.doi.org/10.3329/bmj.v41i1.18782 Bangladesh Medical Journal 2012 Vol. 41 No. 1; 45-49</jats:p

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Environmental radioactivity of the St. Martin's island of Bangladesh

The activity concentration of natural and anthropogenic radionuclides in soil and rock, and in benthic algae, corals and oysters across the St. Martin's island of Bangladesh were investigated together with physicochemical parameters and texture of soil with an aim of evaluating the radioecology of the island. Soil and rock samples from the twenty-two locations of the island, eleven species of benthic algae, six species of corals and two species of oysters were analyzed. The activity of 226Ra in soil was found in the range of 7.22–103.8, in benthic algae 2.5–9.7, in coral 5.5–10 and in oyster 4.2–11.5 Bq kg-1. The activity of 232Th in soil was found in the range of 14.56–216, in benthic algae 1.3–12.6, in coral 4.4–15.6 and in oyster 3.2–8.4 Bq kg-1; and the activity of 40K in soil was in the range of 322–732, in benthic algae 17.1–45.5, in coral 21–146 and in oyster 24–32 Bq kg-1. The external radiation dose rate due to activity concentration of natural radionuclides in soil was assessed. The activity of anthropogenic 137Cs was found below detection limit.