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

Chimera and globally clustered chimera: Impact of time delay

Following a short report of our preliminary results [Phys. Rev. E 79, 055203(R) (2009)], we present a more detailed study of the effects of coupling delay in diffusively coupled phase oscillator populations. We find that coupling delay induces chimera and globally clustered chimera (GCC) states in delay coupled populations. We show the existence of multi-clustered states that act as link between the chimera and the GCC states. A stable GCC state goes through a variety of GCC states, namely periodic, aperiodic, long-- and short--period breathers and becomes unstable GCC leading to global synchronization in the system, on increasing time delay. We provide numerical evidence and theoretical explanations for the above results and discuss possible applications of the observed phenomena.Comment: 10 pages, 10 figures, Accepted in Phys. Rev.

Biochemical changes in cotton plants due to infestation by cotton mealybug Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae)

The study on biochemical changes in cotton plants (Gossypium hirsutum L.) due to infestation by cotton mealybug Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) was conducted at CICR Nagpur during 2014-15. Total protein contents estimated from the shoots of the healthy plants (4.29 mg/g) indicated 50.5% increase over the healthy plants (2.85 mg/g). Total phenol content increased by 185.7% in the mealybug infested plants (0.20?g/g) over the healthy plants (0.07?g/g). Insignificant difference in the level of total soluble sugar was observed in mealybug infested plants (1.00?g/g) as compared to healthy plants (0.90?g/g). Total reducing sugar was found to be unaffected with the mealybug infestation. Although there was depletion in all the photosynthetic pigments viz., chlorophyll a (19.1%), chlorophyll b (23.7%), total chlorophyll (21.2%) and carotenoids (20.8%) due to the mealybug infestation, these values were not statistically different in the healthy plants. This is the first report on biochemical changes in cotton plant due to infestation of P. solenopsis

Globally clustered chimera states in delay--coupled populations

We have identified the existence of globally clustered chimera states in delay coupled oscillator populations and find that these states can breathe periodically, aperiodically and become unstable depending upon the value of coupling delay. We also find that the coupling delay induces frequency suppression in the desynchronized group. We provide numerical evidence and theoretical explanations for the above results and discuss possible applications of the observed phenomena.Comment: Accepted in Phys. Rev. E as a Rapid Communicatio

Poly(D,L-lactic-co-glycolic acid) nanoencapsulation reduces erlotinib-Induced subacute toxicity in rat

Erlotinib-HCl is a quinazoline derivative used as a drug in the therapy of non-small-cell lung cancer. The present study was conducted to compare the subacute toxicity induced by Erlotinib-HCl delivered to rats as nanoparticles and as free drug. Wistar rats were orally administered with a daily dosage of 200 mg kg−1 Erlotinib-HCl either as free drug or as Poly(D,L-lactic-co-glycolic acid) (PLGA) encapsulated nanoparticles. After four weeks of treatment, the animals were analyzed for toxicological changes. Although nanoparticulate form of the drug did not induce any toxicity, free drug significantly reduced the levels of white blood cells (WBC), red blood cells (RBC) and haemoglobin, while increasing the levels of neutrophils and corpuscular haemoglobin. Moreover, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels were significantly increased in the animals administered with free drug. Histopathological studies confirmed significant damage to the internal organs of animals treated with free drug. Whereas, the internal organs of animals treated with the drug encapsulated in PLGA nanoparticles were more or less similar to the healthy organs. Our results show that Erlotinib-HCl delivered in the form of nanoparticles has less toxic effect than the free drug in experimental rats

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

Free energy barrier for melittin reorientation from a membrane-bound state to a transmembrane state

An important step in a phospholipid membrane pore formation by melittin antimicrobial peptide is a reorientation of the peptide from a surface into a transmembrane conformation. In this work we perform umbrella sampling simulations to calculate the potential of mean force (PMF) for the reorientation of melittin from a surface-bound state to a transmembrane state and provide a molecular level insight into understanding peptide and lipid properties that influence the existence of the free energy barrier. The PMFs were calculated for a peptide to lipid (P/L) ratio of 1/128 and 4/128. We observe that the free energy barrier is reduced when the P/L ratio increased. In addition, we study the cooperative effect; specifically we investigate if the barrier is smaller for a second melittin reorientation, given that another neighboring melittin was already in the transmembrane state. We observe that indeed the barrier of the PMF curve is reduced in this case, thus confirming the presence of a cooperative effect

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

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