Flow-induced currents in nanotubes: a Brownian dynamics approach

Motivated by recent experiments [Science {\bf 299}, 1042 (2003)] reporting that carbon nanotubes immersed in a flowing fluid displayed an electric current and voltage, we numerically study the behaviour of a collection of Brownian particles in a channel, in the presence of a flow field applied on similar but slower particles in a wide chamber in contact with the channel. For a suitable range of shear rates, we find that the flow field induces a unidirectional drift in the confined particles, and is stronger for narrower channels. The average drift velocity initially rises with increasing shear rate, then shows saturation for a while, thereafter starts decreasing, in qualitative agreement with recent theoretical studies [Phys. Rev. B {\bf 70}, 205423 (2004)] based on Brownian drag and ``loss of grip''. Interestingly, if the sign of the interspecies interaction is reversed, the direction of the induced drift remains the same, but the flow-rate at which loss of grip occurs is lower, and the level of fluctuations is higher.Comment: 7 pages, 9 figure

Early diagnosis of Carpal Tunnel Syndrome (CTS) in Indian patients by nerve conduction studies

The present study was carried out for early confirmation of clinicallydiagnosed patients of Carpal Tunnel Syndrome (CTS) by electro-diagnostic tests which included motor conduction, sensory conduction studies and F-wave studies. The aim of the study was early confirmation of clinically suspected patients of CTS by motor and sensory conduction studies of median and ulnar nerves. Eighty subjects of age group 30-50 years (40 clinically suspected patients of CTS, 40 as control group) were studied. Motor and Sensory conduction velocities, distal motor and sensory latencies and F wave latencies of median and ulnar nerves were performed using RMS EMG EP Mark –II. Statistically significant (P < 0.001) slowing of motor conduction velocities for both nerves was seen in the CTS group as compared to control group. Decrease in sensory conduction velocity wasmore pronounced in CTS group as compared to Control group. Statistically significant (P < 0.001) increase in distal motor and sensory latencies was also observed for both median and ulnar nerves in the CTS group as compared to Control group, with more increase in distal motor latency than sensory latency. Increase in F wave latencies of both nerves was seen in the CTS group. Electrophysiological studies confirmed the early diagnosis of CTS with a high degree of sensitivity. Present results confirm selective slowing of sensory & motor conduction within wrist to palm segment in patients of CTS which is attributable to compression by the transverse carpal ligament or to a disease process of the terminal segment.KEY WORDS: Nerve entrapments; Median neuropathy; Electro-physiological diagnosis; Distal and motor sensory latencies; Palm wrist conductio

Epidemiology of ovarian malignancies

Background: The location of the ovaries makes it difficult to diagnose ovarian cancer at an earlier more curable stage. This study was done with intend of developing insight into risk factors, clinical presentation and prognostic factors for the same.Methods: An observational prospective study was undertaken over a period of 2 years of 77 cases in a tertiary care hospital with cancer unit. Case records of cases during study period were evaluted and epidemiology studied.Results: Most of the malignant tumors i.e. 35.1% were in the age group of 40- 50 yrs and 42 % of tumors seen in the age group of 41-60 years. 9.1% were post hysterectomy, 46.8% were premenopausal and 44.2% were postmenstrual. Majority cases were parous women and none had used oral contraceptive pills. In the present study, blood group A was found more commonly more commonly associated with ovarian tumors in comparison to the general population. the most common complaint of the patient was pain in abdomen (70.1%) followed by distension of abdomen (45.5%) and menstrual irregularities (16.9 %).Conclusions: The epidemiology and presentation of ovarian tumours has remained unchanged since last 3 decades. Nulliparity is not as significant a factor in the aetiology of ovarian malignancy however contraception leading to anovulatory cycles (OC pills) may have a protective role. Infertility can be suggested as a risk factor but the treatment for infertility & its role in oncogenesis remains controversial

Rapidity distribution as a probe for elliptical flow at intermediate energies

Interplay between the spectator and participant matter in heavy-ion collisions is investigated within isospin dependent quantum molecular dynamics (IQMD) model in term of rapidity distribution of light charged particles. The effect of different types and size rapidity distributions is studied in elliptical flow. The elliptical flow patterns show important role of the nearby spectator matter on the participant zone. This role is further explained on the basis of passing time of the spectator and expansion time of the participant zone. The transition from the in-plane to out-of-plane is observed only when the mid-rapidity region is included in the rapidity bin, otherwise no transition occurs. The transition energy is found to be highly sensitive towards the size of the rapidity bin, while weakly on the type of the rapidity distribution. The theoretical results are also compared with the experimental findings and are found in good agreement.Comment: 8 figure

Event-by-event study of DCC-like fluctuation in ultra-relativistic nuclear collisions

A method based on sliding window scheme is developed to search for patches in the pseudorapidity-azimuth plane, on an event-by-event basis, having unusual fluctuation in the neutral pion fraction which may arise due to the formation of Disoriented Chrial Condensates (DCC) in high energy nuclear collisions. The efficiency of the method to extract the patches and the purity of the extracted sample are studied for possible experimental situations.Comment: 10 pages, 5 figure

Anemia in experimental protein deficiency in the rhesus monkey with special reference to iron metabolism

1. This investigation deals with a study of the anemia of protein deficiency in Rhesus monkeys. 2. Protein deficiency was induced in 17 rhesus monkeys. Seven animals, given a protein-rich diet, served as controls. The diets of both the groups were identical in all respects, except protein. All animals were tube-fed to ensure adequate caloric intake. Hematocrit, hemoglobin, erythroctye count, serum iron, serum iron binding capacity, plasma iron tolerance curves, and iron absorption using the Fe59 fecal recovery method were studied before and at intervals of the experiment in both deficient and control groups. Protein-deficient monkeys consistently developed normocytic normochromic anemia of moderate severity. A striking fall in serum iron binding capacity, total proteins and albumin with a rise in gamma globulin was observed in all deficient animals. A significant and comparable fall in serum iron was also observed. The Fe59 absorption was depressed and there was flattening of plasma iron tolerance curves. Two deficient animals, refed a high protein diet, showed reversal of all these changes. The control animals did not show any of these changes. The mechanism of anemia and decreased iron absorption observed in the protein-deficient animals and the relevance of these findings to those in Kwashiorkor are discussed

Structure of poly(propyl ether imine) (PETIM) dendrimer from fully atomistic molecular Dynamics Simulation and by Small Angle X-ray scattering

We study the structure of carboxylic acid terminated neutral poly (propyl ether imine) (PETIM) dendrimer from generation 1 through 6 (G1-G6) in a good solvent (water) by fully atomistic molecular dynamics (MD) simulations. We determine as a function of generation such structural properties as: radius of gyration, shape tensor, asphericity, fractal dimension, monomer density distribution, and end-group distribution functions. The sizes obtained from the MD simulations have been validated by Small Angle X-Ray Scattering (SAXS) experiment on dendrimer of generation 2 to 4 (G2-G4). A good agreement between the experimental and theoretical value of radius of gyration has been observed. We find a linear increase in radius of gyration with the generation. In contrast, Rg scales as ~ N^x with the number of monomers. We find two distinct exponents depending on the generations: x = 0.47 for G1-G3 and x = 0.28 for G3-G6 which reveals their non-space filling nature. In comparison with the amine terminated PAMAM dendrimer, we find Rg of G-th generation PETIM dendrimer is nearly equal to that of (G+1)-th generation of PAMAM dendrimer as observed by Maiti et. al. [Macromolecules,38, 979 2005]. We find substantial back folding of the outer sub generations into the interior of the dendrimer. Due to their highly flexible nature of the repeating branch units, the shape of the PETIM dendrimer deviates significantly from the spherical shape and the molecules become more and more spherical as the generation increases. The interior of the dendrimer is quite open with internal cavities available for accommodating guest molecules suggesting using PETIM dendrimer for guest-host applications. We also give a quantitative measure of the number of water molecules present inside the dendrimer.Comment: 33 page

"Universal" resistance jump of vortices at the melting transition

We consider the jump in resistance at the melting transition, which is experimentally observed to be constant, independent of magnetic field (vortex density). We present an explanation of this effect based on vortex cuttings, and universalities of the structure factor at the freezing transition (the Hansen-Verlet criterion)