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Fluctuations in slab plasma produced by electron cyclotron waves in an open magnetic configuration with vertical (B z ) and toroidal (B t) fields are investigated as a function of B z /B t (field pitch) using a high speed visible camera in the spherical tokamak QUEST. Higher order moments (skewness s and kurtosis k) of spatio-temporal fluctuations are investigated. Background fluctuations, generation of coherent convective structures (blobs) and their propagation are analysed at the intensity gradient (R im) and the source-free (essentially vacuum on the low-field side) regions, respectively. Parabolic relation (k = As 2 + C) is observed between s and k on the entire R–Z plane for a wide range of B z /B t. Progressive shift from the Gaussian statistics beyond R im is observed with increasing B z /B t. From the moments of the probability density functions, possible location for blob generation is inferred to be R im. Direct correspondence is observed with the prominence of the blobs and increase in stochastic forces with the increase in field pitch. Distribution of waiting time suggests that the blob generation may be a Poisson process. Accelerated cross field transport is observed for reasonably large-sized blobs.

Trunk neural crest cells delaminate from the dorsal neural tube as an uninterrupted sheet; however, they convert into segmentally organized streams before migrating through the somitic territory. These neural crest cell streams join the segmental trajectories of pathfinding spinal motor axons, suggesting that interactions between these two cell types might be important for neural crest cell migration. Here, we show that in the zebrafish embryo migration of both neural crest cells and motor axons is temporally synchronized and spatially restricted to the center of the somite, but that motor axons are dispensable for segmental neural crest cell migration. Instead, we find that muscle-specific receptor kinase (MuSK) and its putative ligand Wnt11r are crucial for restricting neural crest cell migration to the center of each somite. Moreover, we find that blocking planar cell polarity (PCP) signaling in somitic muscle cells also results in non-segmental neural crest cell migration. Using an F-actin biosensor we show that in the absence of MuSK neural crest cells fail to retract non-productive leading edges, resulting in non-segmental migration. Finally, we show that MuSK knockout mice display similar neural crest cell migration defects, suggesting a novel, evolutionarily conserved role for MuSK in neural crest migration. We propose that a Wnt11r-MuSK dependent, PCP-like pathway restricts neural crest cells to their segmental path.

In Aditya tokamak [S. B. Bhatt et al. Indian J. Pure Appl. Phys. 27, 710 (1989)], an increase in the Hα and C2+ intensity fluctuations from the edge region is observed with an increase in the magnetohydrodynamic (MHD) activity. Very small fluctuation amplitudes of Hα and C2+ intensity are observed in discharges where there is no MHD activity compared to the discharges with MHD activity. These fluctuations in the Hα and C2+, measured by optical filter—photomultiplier tube combination—are modulated by Mirnov oscillations having a dominant peak with a common frequency ∼7–10 kHz. Further investigation reveals the presence of strong coherent fluctuations in density and floating potential at same frequency as well. These observations indicate the existence of a nonelectrostatic instability, which may be based on the coupled mode of the drift mode and the Alfven mode. The coherent density fluctuations give rise to the experimentally observed coherent Hα and C2+ intensity fluctuations.

A tomographic reconstruction code had been reported by us for inferring the poloidal emissivity of tokamak plasma from tangentially acquired images. Here we present modifications to the code that account for any diffuse reflections from the surfaces of walls enclosing the plasma. It is generally recognized that such reconstruction codes are highly susceptible to noise in the data. In this work we have analysed the sensitivity to noise for varying degrees of over-determinism in the set of equations; over-determinism is defined as the ratio of the number of detector signals available to the grid resolution of reconstruction. A tractable scheme for dividing the poloidal cross section into a finite number of unknown sub-tori and voids, while still keeping the over-determinism high, is incorporated. Finally it is shown that noise level >20% can be handled with over-determinism achievable from present day detector array/cameras. The singular value decomposition of the matrix, as used here, can be expected to converge even if any ill-conditioned matrix is encountered due to computational round-off errors in the estimation of chord lengths through sub-tori and voids.

A diagnostic system based on a multi-fiber input high resolution spectrograph has been set up on the Aditya tokamak (Bhatt et al 1989 Ind. J. Pure Appl. Phys. 27 710) for utilizing the passive light emission to measure different kinds of plasma flow and to identify the location of emissions of hydrogen and impurities along with their temperatures. Eight simultaneous vertically collimated lines-of-sight from a top port view a poloidal cross-section of the plasma. This arrangement simplifies the analysis of spectra in terms of making the Zeeman splitting easier to account for, since each chord passes through a region of nearly constant toroidal magnetic field (BT). This paper describes the complete set-up, the wavelength and intensity calibrations performed and the initial results including the impurity emissivity profiles and simultaneous flow measurements in the inboard and outboard regions of the Aditya tokamak.

Fast camera systems for imaging tokamak plasmas are becoming increasingly popular. Edge fluctuations and plasma instabilities can be imaged in the visible and X-ray wavelengths using presently available cameras. While viewing the plasma tangentially, the lines of sight (LOS) pass through the plasma integrating the light through a number of flux surfaces. Here we report a reconstruction code for tomographic unfolding of the emissivity profile of the poloidal cross section from the tangential image, using pixel method. The poloidal cross section of the tokamak has been divided into pixels, each of which is a footprint of a subtorus. The emissivity of each of this subtorus (pixels) is assumed to be constant and uniform around the torus.

The infrared fluorescence and optical gain characteristics of optically transparent nanocomposites consisting of (THF)14Er10S6Se12I6 (“Er10”) or (DME)2Er(SC6F5)3 (“Er1”) clusters dissolved in a transparent hexafluoroisopropyl (6F) variant of a perfluorocyclobutyl (PFCB)-based fluoropolymer are reported. Under excitation at 980 nm, fluorescence was observed at 1540 nm from both Er10 and Er1 with a 3dB bandwidth of 96 and 60 nm, respectively. The maximum gain computed for Er10 and Er1 was 2.8 and 0.021dB∕cm, respectively. The corresponding threshold pump powers for Er10 and Er1 were calculated to be 1.7 and 0.2 mW, respectively. These computations are consistent with gain characteristics measured by the amplified spontaneous emission technique and suggest that these nanocomposites are promising materials for active optical devices.

A 37-year-old female presented with a fungating cauliflower-like growth over the right inguinal region with fracture of the right distal femur. Clinical examination revealed an asthenic individual and showed a large fungating protuberant mass over right inguinal region and right knee. Investigations revealed pancytopenia, massive splenomegaly with right iliac lymphadenopathy on ultrasonography of abdomen and a soft tissue mass over upper end of femur and fracture of distal femur on radiological examination. CT scan showed multiple deposits in the lungs with splenomegaly and lymphadenopathy. Fine needle aspiration cytology showed poorly cohesive cellular aspirate with spindle and round cell population with no pigment. Biopsy showed replacement of the dermis by coalescent nests of malignant melanocytes. S-100 antigen was found to be positive. The patient was diagnosed as a case of amelanotic malignant melanoma in Stage III disease and treated with general measures, stabilization of the fracture site followed by oncological management.

Mirror examination being still the quickest way to assess the nasopharynx, a further modification of the conventional method has been attempted by devising a new Two-in-one type of P.N.S. Mirror, with advantages.

Bedding-plane markings in the Chorhat Sandstone (lower Vindhyan), central India, were recently interpreted as burrows produced by triploblastic animals. Because the rocks were thought to be older than 1000 Ma, these structures were regarded as the oldest fossil evidence for metazoan life. However, the biological origin of the markings has been questioned, as has their age. Current age estimates are based on K-Ar, Rb-Sr, and fission- track dates, though some contentious evidence suggests that the rocks may be only 540 Ma. Here we provide the first robust age data for the lower Vindhyan by using SHRIMP (sensitive, high-resolution ion microprobe) U-Pb zircon geochronology to date silicified tuffs bounding the Chorhat Sandstone. Our results show that the sediments were deposited between 1628 ± 8 Ma and 1599 ± 8 Ma. If the Chorhat markings are burrows left by worm-like animals, then our data suggest that complex metazoans had evolved before 1600 Ma, 1 b.y. before the “Cambrian explosion” when animals rapidly diversified and became ecologically dominant. However, given the doubts expressed about the origin of the bedding-plane structures, as well as the surprisingly “old” age of the host rocks, further studies are urgently required to provide supportive evidence.

This study presents a review on palaeogeographic implications and temporal variations of glaucony covering both modern and ancient records. Phanerozoic glaucony preferably forms in a shelf depositional setting. Deep marine conditions and low seawater temperature discourage formation of glaucony. Around 75% of glaucony is recorded from the Cretaceous to the Holocene sediments, which are related to the abundance of the most common substrates, faecal pellets and bioclasts. TFe 2 O 3 (total), Al 2 O 3 , K 2 O and MgO contents of glaucony vary appreciably through geological time. While TFe 2 O 3 content of most Mesozoic and Cenozoic glaucony exceeds 20%, it is always less than 20% in Precambrian varieties. High K 2 O, Al 2 O 3 , MgO and low TFe 2 O 3 distinguish the Precambrian glaucony from its Phanerozoic counterpart. Precambrian glaucony, preferably formed within a K-feldspar substrate, is always rich in potassium irrespective of its degree of evolution, while high K-content in Phanerozoic evolved glaucony indicates significant stratigraphic condensation. K 2 O vs. TFe 2 O 3 relationship of glaucony exhibits three different evolutionary trends corresponding to three common modes of origin. Depositional conditions may influence the composition of glaucony as slightly reducing conditions favour Fe enrichment, whereas oxidising conditions cause Fe depletion in glaucony.

Chemistry Department, Jadavpur University,Calcutta-700 032 Manuscript received 5 February 1986, revised 25 September 1987,accepted 30 October 1987 Use of Molybdate. Oxidative Decarboxylation of α-Hydroxvcarboxylic Acids.

Chemistry Department, Jadavpur University, Calcutta-700 032 Manuscript received 17 July 1986, revised 26 September 1987, accepted 30 October 1987 Use of Vanadate. Oxidative Decarboxylation of ��-Hydroxy Acids.

Chemistry Department, Jadavpur University,Calcutta-700 032 Manuscript received 17 July 1986, revised 26 September 1987,accepted 30 October 1987 Use of Vanadate. Oxidative Decarboxylation of α-Hydroxy Acids.

Several excursions of the geomagnetic field during the Brunhes epoch have been postulated on the basis of paleomagnetic data from sediments. It has further been suggested that these excursions may represent sudden fluctuations of the geomagnetic field, manifested especially in fluctuations of the local geomagnetic inclination. In this study we present high-resolution data of inclination variations recorded in the sediments of two Minnesota postglacial lakes. To the best of our knowledge, our data cover two overlapping time windows, 0 to 9600 B.P. and about 9000 to 16,000 B.P. The results strongly suggest that no excursions have occurred in Minnesota over the past 16,000 yr. Thus, it appears that the Gothenburg (Sweden) excursion at about 12,500 B.P. is not worldwide and that the regional Erieau (Lake Erie) excursion does not extend to Minnesota. We suggest that these two previously claimed excursions might not reflect geomagnetic field behavior but merely poor paleomagnetic “recording” within the sediments used for these studies.

We have known since at least the 16th century that the Earth's magnetic field varies with time as well as geographic position. This secular variation (SV), which has been monitored instrumentally at various locations since that time, is fundamentally important to a complete understanding of the geomagnetic field and its origin. Unfortunately, the instrument record for SV is very short in duration and if we wish to extend this record backward through time we must use a very different recording process. Paleomagnetists have considered this problem for well over 100 years, and have discovered two processes by which the SV may be commonly recorded. The first, thermoremanent magnetization (TRM), essentially causes a rock, which has been heated above a characteristic temperature, to acquire a remanent magnetization parallel to the field present when the rock cools. In this manner, lava flows and fired pottery or bricks record an instantaneous picture of the field during their cooling process.

A rare case of mixed tumour of the pinna is presented and characteristics of its rarity are discussed.

Ammonium (or sodium) vanadate in dilute perchloric acid was found to be an excellent reagent for the determination of glucose. The method involves refluxing a mixture containing glucose and an excess of vanadate solution in dilute perchloric acid over a small flame for 40 min. To this reaction mixture potassium iodide was added to determine the residual vanadate iodimetrically. The amount of glucose can then be determined by standardising the vanadate solution with either sodium thiosulphate or glucose solutions of known strengths; the latter gave consistently better results.