Event--related desynchronization in diffusively coupled oscillator models

We seek explanation for the neurophysiological phenomenon of event related desynchronization (ERD) by using models of diffusively coupled nonlinear oscillators. We demonstrate that when the strength of the event is sufficient, ERD is found to emerge and the accomplishment of a behavioral/functional task is determined by the nature of the desynchronized state. We illustrate the phenomenon for the case of limit cycle and chaotic systems. We numerically demonstrate the occurrence of ERD and provide analytical explanation. We also discuss possible applications of the observed phenomenon in real physical systems other than the brain.Comment: Accepted in Physical Review Letter

A Study on Bacteriological Profile of Ventriculo Peritoneal Shunt Infections.

INTRODUCTION : hydrocephalus is the most frequent neurosurgical problem encountered in the paediatric age group with an incidence of 1 in 2000 births. It may also occur as a complication of any insult to the nervous system like infections, Intra-ventricular haemorrhage, brain tumours, and head injury. Cerebrospinal fluid (CSF) shunting is a process by which CSF is diverted from the lateral ventricles to another part of the body for absorption Cerebrospinal fluid diversion devices are essential in the management of this pathology. Ventriculoperitoneal shunt, a device inserted for the treatment of Hydrocephalus results in significant improvement in neurological function and survival of patients. Infection is one of the most serious complications after CSF shunt or external ventricular drain placement. It increases both morbidity and mortality and causes an increased incidence of seizures and neurological disturbances. A typical CSF shunt comprises of three parts, a proximal portion – Ventricular catheter, which is inserted into the CSF space, a valve and Reservoir and a distal portion – terminating in the peritoneal (ventriculoperitoneal shunt), pleural ventriculopleural shunt) or vascular Space (ventriculoatrial shunt). CSF shunts may become infected by retrograde infection from the distal end, through the skin, by haematogenous seeding or by colonization at the time of surgery. AIM OF THE STUDY : To isolate the causative organisms. To assess the risk factors associated with shunt infection. To find the incidence of infection associated with shunt related procedures. To determine the antimicrobial susceptibility pattern of the isolates to aid in management. To evaluate the outcome of management. MATERIALS AND METHODS : This is a cross sectional study involving 397 patients, among whom 275 patients had undergone primary ventriculoperitoneal shunt insertion and 122 patients had undergone shunt related procedures like shunt removal, revision, reinsertion, exteriorization and external ventricular drain placement. In this study population, 122 cases had developed symptoms of shunt infection and malfunction. Relevant data were collected from the patients as mentioned in the enclosed proforma. They include patients’ age and sex, aetiology of the hydrocephalus requiring ventriculoperitoneal shunt, date of shunt placement, number of prior revisions, history of prior shunt infections, results of culture of CSF, shunt tube or pus and follow-up. CONCLUSION : Ventriculoperitoneal shunt infection is one of the major complications associated with mortality and morbidity resulting in neurological disturbances. The infection rate in patients with ventriculoperitoneal shunt was 10.58%. A large number of infections occurred in children with congenital malformations and following meningitis. Most of the infections occurred within 6 months of surgery. CSF gram staining and biochemical parameters were very useful n identification of shunt infection enabling empirical antibiotic therapy. Staphylococcus epidermidis was the commonest pathogen isolated. Pseudomonas aeruginosa was isolated in many patients with external drainage procedures suggesting nosocomial infection. Promising results are obtained by early removal of the shunt hardware accompanied by appropriate antibiotic therapy until CSF culture turns negative, followed by shunt replacement. With the emergence of methicillin resistant strains, ESBL and MBL producers, diligent use of antibiotics will restrict the spread of drug resistant strains in the community and environment

Adaptive significance of circadian rhythms biological clocks and darwinian fitness in cyanobacteria

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Constrained RS coding for Low Peak to Average Power Ratio in FBMC -- OQAM Systems

Multi-carrier modulation techniques have now become a standard in many communication protocols. Filter bank based multi-carrier (FBMC) generation techniques have been discussed in the literature as a means for overcoming the shortcomings of IFFT/FFT based OFDM system. The Peak to Average Power Ratio (PAPR) is a problem faced by all multi-carrier techniques. This paper discusses the methods for reducing PAPR in a FBMC system while maintaining acceptable Bit Error Rate (BER). A new PAPR minimizing scheme called Constrained Reed Solomon (CRS) coding is proposed. The hybrid techniques using coding and companding are tested for different channel models and is found to yield promising results.Comment: 6 pages,6 Figures, Journal of Electrical and Electronics Engineerin

Correlation of hemoglobin with creatinine clearance, antioxidant status, lipid peroxidation and ceruloplasmin in patients with chronic kidney disease

Background: Anaemia in CRF is caused primarily by a combination of depressed erythropoiesis and shortened erythrocyte lifespan caused by oxidative stress. Therefore, the present study was designed to investigate the correlation between Hb concentration and antioxidant and lipid peroxidation levels.Methods: The study group consisted of 50 patients with chronic kidney disease who were on conservative treatment with the age group of 20 to 60 years. Based on the creatinine clearance values the patients were assigned in to 3 groups; Stage 3, Stage- 4 and Stage- 5 as per NKF DOQI guidelines. Control group consisted of 50 age and sex matched, non-diabetic, non-smoker healthy volunteers. About 5 ml of blood was collected and serum was used for the estimation of superoxide dismutase, ceruloplasmin and malondialdehyde and haemoglobin level using standard methods. The correlations between the different groups are performed by applying Pearson’s correlation test. The p value of ≤0.05 was taken as the level of significance.Results: A positive correlation of Hb with creatinine clearance (r=0.46, p=0.001), SOD level(r=0.4, p=0.009), serum ceruloplasmin (r=0.3, p=0.07) was observed. Significant positive correlation was found between creatinine clearance and SOD level (r=0.4, p=0.008), ceruloplasmin (r=0.3, p=0.04). A negative correlation was obtained between serum malondialdehyde levels and haemoglobin concentration (r=-0.4, p=0.007) and between creatinine clearance and MDA levels (r=-0.4, p=0.01).Conclusions: The study provides a better understanding of the biochemical parameters underlying anaemia in chronic kidney disease. The increased production of ROS and deficiency of antioxidant enzymes altered the oxidant and antioxidant equilibrium in the plasma of CKD patients

Developmental plasticity of the locomotor activity rhythm of Drosophila melanogaster

We used four replicate outbred populations of Drosophila melanogaster to investigate whether the light regimes experienced during the pre-adult (larval and pupal) and early adult stages influence the free-running period (tDD) of the circadian locomotor activity rhythm of adult flies. In a series of two experiments four different populations of flies were raised from egg to eclosion in constant light (LL), in light/dark (LD) 12:12 h cycle, and in constant darkness (DD). In the first experiment the adult male and female flies were directly transferred into DD and their locomotor activity was monitored, while in the second experiment the locomotor activity of the emerging adult flies was first assayed in LD 12:12 h for 15 days and then in DD for another 15 days. The tDD of the locomotor activity rhythm of flies that were raised in all the three light regimes, LL, LD 12:12 h and in DD was significantly different from each other. The tDD of the locomotor activity rhythm of the flies, which were raised in DD during their pre-adult stages, was significantly shorter than that of flies that were raised as pre-adults in LL regime, which in turn was significantly shorter than that of flies raised in LD 12:12 h regime. This pattern was consistent across both the experiments. The results of our experiments serve to emphasise the fact that in order to draw meaningful inferences about circadian rhythm parameters in insects, adequate attention should be paid to control and specify the environment in which pre-adult rearing takes place. The pattern of pre-adult and early adult light regime effects that we see differs from that previously observed in studies of mutant strains of D. melanogaster, and therefore, also points to the potential importance of inter-strain differences in the response of circadian organisation to external influences

Effect of different light regimes on pre-adult fitness in Drosophila melanogaster populations reared in constant light for over six hundred generations

Egg to eclosion development time and survivorship were assayed on four laboratory populations of Drosophila melanogaster that had been reared for over 600 generations in continuous light (LL) and constant temperature. The assays were performed in three environments: continuous light (LL), periodically varying light/dark cycles (LD 12:12 hr), and continuous darkness (DD). Development time in LL was significantly less than that in LD, which, in turn, was significantly less than that in DD, whereas survivorship did not differ significantly among the three treatments. The results indicate that individuals from Drosophila populations routinely maintained in LL do not suffer any deleterious effects of LL treatment on pre-adult fitness. Other studies on these populations have shown that free-running period (t) of the eclosion rhythm in DD is greater than that in LD. Our results are, thus, also consistent with the notion that development time may be a function of the free-running period