Hollow cathode sustained plasma microjets: Characterization and application to diamond deposition

Extending the principle of operation of hollow cathode microdischarges to a tube geometry has allowed the formation of stable, high-pressure plasma microjets in a variety of gases including Ar, He, and H2. Direct current discharges are ignited between stainless steel capillary tubes (d = 178 µm) which are operated as the cathode and a metal grid or plate that serves as the anode. Argon plasma microjets can be sustained in ambient air with plasma voltages as low as 260 V for cathode-anode gaps of 0.5 mm. At larger operating voltage, this gap can be extended up to several millimeters. Using a heated molybdenum substrate as the anode, plasma microjets in CH4/H2 mixtures have been used to deposit diamond crystals and polycrystalline films. Micro-Raman spectroscopy of these films shows mainly sp3 carbon content with slight shifting of the diamond peak due to internal stresses. Optical emission spectroscopy of the discharges used in the diamond growth experiments confirms the presence of atomic hydrogen and CH radicals

High-pressure micro-discharges in etching and deposition applications

High-pressure micro-discharges are promising sources of light, ions, and radicals and offer some advantages in materials processing applications as compared to other more conventional discharges. We review here results from etching experiments using stencil masks where the discharge is formed only in the pattern cutout. The mask consists of a thin metal-dielectric structure and is pressed against a Si wafer, which becomes part of the electric circuit. Pattern transfer takes place, albeit the profile shape appears to be limited by the expansion of the plasma into the etched hole at long etch times. We also review experiments on using micro-discharges as sources of radicals for materials deposition applications. In the latter case, the micro-discharges form in metal capillary tubes permitting incorporation of gas flow and a short reaction zone that can be controlled to favour production of specific radicals. We demonstrate these concepts by using CH4/H2 chemistry for diamond deposition on a heated Mo substrate. Good quality micro- and nano-diamond crystals could be produced

SDSS J092712.64+294344.0: recoiling black hole or merging galaxies?

We report long-slit spectroscopic observations of SDSS J092712+294344 carried-out at the recently commissioned 2m telescope in IUCAA Girawali Observatory, India. This AGN-like source is known to feature three sets of emission lines at zem = 0.6972, 0.7020 and 0.7128. Different scenarios such as a recoiling black hole after asymmetric emission of gravitational waves, binary black holes and possible merging systems are proposed for this object. We test these scenarios by comparing our spectra with that from the Sloan Digital Sky Survey (SDSS), obtained 4 years prior to our observations. Comparing the redshifts of [OIII]4960,5008 we put a 3 sigma limit on the relative acceleration to be less than 32 km s^-1 yr^-1 between different emitting regions. Using the 2D spectra obtained at different position angles we show that the [OIII]5008 line from the zem = 0.7128 component is extended beyond the spectral point spread function. We infer the linear extent of this line emitting region is ~8 kpc. We also find a tentative evidence for an offset between the centroid of the [OIII]5008 line at zem = 0.7128 and the QSO trace when the slit is aligned at a position angle of 299 degrees. This corresponds to the zem = 0.7128 system being at an impact parameter of ~1 kpc with respect to the zem = 0.6972 in the north west direction. Based on our observations we conclude that the binary black hole model is most unlikely. The spatial extent and the sizes are consistent with both black hole recoil and merging scenarios.Comment: accepted for publication in MNRAS Letter

Argon excimer emission from high-pressure microdischarges in metal capillaries

We report on argon excimer emission from high-pressure microdischarges formed inside metal capillaries with or without gas flow. Excimer emission intensity from a single tube increases linearly with gas pressure between 400 and 1000 Torr. Higher discharge current also results in initial intensity gains until gas heating causes saturation or intensity drop. Argon flow through the discharge intensifies emission perhaps by gas cooling. Emission intensity was found to be additive in prealigned dual microdischarges, suggesting that an array of microdischarges could produce a high-intensity excimer source

Probing the time variability of five Fe low broad absorption line quasars

We study the time variability of five Fe Low ionization Broad Absorption Line (FeLoBAL) QSOs using repeated spectroscopic observations with the 2m telescope at IUCAA Girawali observatory (IGO) spanning an interval of upto 10 years. We report a dramatic variation in Al III and Fe III fine-structure lines in the spectra of SDSS J221511.93-004549.9 (z_em ~ 1.478). However, there is no such strong variability shown by the C IV absorption. This source is known to be unusual with (i) the continuum emission dominated by Fe emission lines, (ii) Fe III absorption being stronger than Fe II and (iii) the apparent ratio of Fe III UV 48 to Fe III UV 34 absorption suggesting an inverted population ratio. This is the first reported detection of time variability in the Fe III fine-structure lines in QSO spectra. There is a strong reduction in the absorption strength of these lines between year 2000 and 2008. Using the template fitting techniques, we show that the apparent inversion of strength of UV lines could be related to the complex spectral energy distribution of this QSO. The observed variability can be related to change in the ionization state of the gas or due to transverse motion of this absorbing gas. The shortest variability timescale of Al III line gives a lower limit on the electron density of the absorbing gas as n_e >= 1.1 x 10^4 cm^-3. The remaining 4 FeLoBALs do not show any changes beyond the measurement uncertainties either in optical depth or in the velocity structure. We present the long-term photometric light curve for all of our sources. Among them only SDSS J221511.93-004549.9 shows significant (>= 0.2 mag) variability.Comment: 15 pages, 9 figures, 3 tables, Accepted for publication in MNRA

India's twelfth finance commission : a view from Kerala

The focus of the paper is to review the Terms of Reference (TOR) of the Twelfth Finance Commission with special reference to Kerala. It also critically examines the emphasis on fiscal deficit reduction without paying attention to its quality and finds that this has led to the Centre and the States resorting to a softer option of cutting productive capital and necessary maintenance and social sector expenditure. This is likely to have adverse consequences on equitable growth and to impede the process of relieving the economy of structural constraints on growth. There is an urgent need for analysing the quality of fiscal consolidation instead of focusing merely on quantity of reduction of deficits as a proportion of Gross Domestic Product (GDP). The study hence suggests incorporating the concept of Quality of Fiscal Discipline. It is found that there has been an enlargement of the scope of Finance Commissions [since the Eleventh Finance Commission (11th FC)] into mandates for recommending mechanisms for achieving macroeconomic balance, equitable growth, and suggestions for disinvestments and privatisation, while its role in the traditional area of grant devolution has been restricted to non-Plan grants only. In fact, the enlargement of the role in the traditional area of grant devolution would be more desirable. There is sufficient scope for augmenting resource mobilisation from direct and indirect taxes at the Central level. Emphasis is to be placed on integrating services and manufacturing into a single CENVAT (Central Value Added Tax) and on direct taxes reform. The second generation tax reform should concentrate on States’ tax administration and inter-State coordination prior to moving on to a State level VAT. There is need for a constitutional amendment to place service tataxation in the Concurrent List and enable States to tax more services. On the expenditure side, steep increases in items like wages and salaries and interest expenditure are unlikely in the near future. Hence maintenance and social sector expenditure should not be sacrificed. At the same time, efficiency in spending and cutting unproductive expenditure and leakages should be strictly monitored. A decentralised district level monitoring system for maintenance expenditure of capital assets is also suggested. The paper argues that bringing privatisation in the Terms of Reference of the Finance Commission seems avoidable. It is also felt that more effective time bound implementation of State Finance Commission Reports is needed. Along with devolution of funds, transfer of administrative functions is necessary for avoiding duplication of expenditure. As for Kerala-specific issues, it is found that achievements on the human development front are not rewarded. Certain changes in the existing criteria (of the Eleventh Finance Commission) are hence suggested. Kerala’s tax effort, though better than richer States like Punjab, is facing structural constraints. The fast expanding services sector is outside the tax net of the State. The tax-GDP ratio of Kerala showed a mild decline at 9.84 percent in the 1990s as compared to 10.29 percent in the 1980s despite a much higher growth rate of State Domestic Product, mainly because the State was not able to tax the dominant sector of the State Domestic Product, that is, the services sector. Key words : finance commission, fiscal deficit, revenue mobilisation, devolution JEL Classification : H77, H60, H2

Electrostatic Steering Accelerates C3d:CR2 Association.

Electrostatic effects are ubiquitous in protein interactions and are found to be pervasive in the complement system as well. The interaction between complement fragment C3d and complement receptor 2 (CR2) has evolved to become a link between innate and adaptive immunity. Electrostatic interactions have been suggested to be the driving factor for the association of the C3d:CR2 complex. In this study, we investigate the effects of ionic strength and mutagenesis on the association of C3d:CR2 through Brownian dynamics simulations. We demonstrate that the formation of the C3d:CR2 complex is ionic strength-dependent, suggesting the presence of long-range electrostatic steering that accelerates the complex formation. Electrostatic steering occurs through the interaction of an acidic surface patch in C3d and the positively charged CR2 and is supported by the effects of mutations within the acidic patch of C3d that slow or diminish association. Our data are in agreement with previous experimental mutagenesis and binding studies and computational studies. Although the C3d acidic patch may be locally destabilizing because of unfavorable Coulombic interactions of like charges, it contributes to the acceleration of association. Therefore, acceleration of function through electrostatic steering takes precedence to stability. The site of interaction between C3d and CR2 has been the target for delivery of CR2-bound nanoparticle, antibody, and small molecule biomarkers, as well as potential therapeutics. A detailed knowledge of the physicochemical basis of C3d:CR2 association may be necessary to accelerate biomarker and drug discovery efforts

A Study of Fracture in a Rotating Disc

This investigation deals with the fracture produced in a disc by simple rotation cycles as well as rotation cycles under an imposed hydrostatic pressure. In both the cases, relations are obtained between the critical angular speed omega and the number of cycles N, required to cause fracture