3,476 research outputs found
Coal pump development phase 3
Techniques for achieving continuous coal sprays were studied. Coazial injection with gas and pressure atomization were studied. Coal particles, upon cooling, were found to be porous and fragile. Reactivity tests on the extruded coal showed overall conversion to gases and liquids unchanged from that of the raw coal. The potentials for applications of the coal pump to eight coal conversion processes were examined
Laser microprobe for the study of noble gases and nitrogen in single grains: a case study of individual chondrules from the Dhajala meteorite
A laser microprobe capable of analysing nitrogen and noble gases in individual grains with masses less than a milligram is described. It can be used in both continuous wave (CW) mode, useful for stepwise heating of an individual grain, as well as in pulsed mode, useful for ablating material from a small selected area of a sample, for gas extraction. We could achieve low blanks (in ccSTP units) for 4He(4.8 × 10{-12}),22Ne(1.0 × 10{-12}),36Ar(1.0 × 10 -13),84Kr(2.9 × 10{-14}),132 Xe(2.6 × 10{-14}), and N (87 pg), using this system. Preliminary data for individual chondrules from the Dhajala meteorite show that noble gases and nitrogen from grains as small as 170 microgram can be analysed using the present laser microprobe setup. The amount of trapped neon in Dhajala chondrules is very small, and nitrogen in the chondrules is isotopically heavier as compared to the bulk meteorite
Electronic structure of spin 1/2 Heisenberg antiferromagnetic systems: Ba_2Cu(PO_4)_2 and Sr_2Cu(PO_4)_2
We have employed first principles calculations to study the electronic
structure and magnetic properties of the low-dimensional phosphates,
Ba2Cu(PO4)2 and Sr2Cu(PO4)2. Using the self-consistent tight-binding lin-
earized muffin-tin orbital method and the Nth order muffin-tin orbital method,
we have calculated the various intrachain as well as the interchain hopping
parameters between the magnetic ions Cu2+ for both the com- pounds. We find
that the nearest-neighbor intrachain hopping t is the dominant interaction
suggesting the compounds to be indeed one dimensional. Our analysis of the band
dispersion, orbital projected band struc- tures, and the hopping parameters
confirms that the Cu2+-Cu2+ super-super exchange interaction takes place along
the crystallographic b direction mediated by O-P-O. We have also analyzed in
detail the origin of short-range exchange interaction for these systems. Our ab
initio estimate of the ratio of the exchange inter- action of Sr2Cu(PO4)2 to
that of Ba2Cu(PO4)2 compares excellently with available experimental results.Comment: 6 pages, 4 figure
Balancing Bounded Treewidth Circuits
Algorithmic tools for graphs of small treewidth are used to address questions
in complexity theory. For both arithmetic and Boolean circuits, it is shown
that any circuit of size and treewidth can be
simulated by a circuit of width and size , where , if , and otherwise. For our main construction,
we prove that multiplicatively disjoint arithmetic circuits of size
and treewidth can be simulated by bounded fan-in arithmetic formulas of
depth . From this we derive the analogous statement for
syntactically multilinear arithmetic circuits, which strengthens a theorem of
Mahajan and Rao. As another application, we derive that constant width
arithmetic circuits of size can be balanced to depth ,
provided certain restrictions are made on the use of iterated multiplication.
Also from our main construction, we derive that Boolean bounded fan-in circuits
of size and treewidth can be simulated by bounded fan-in
formulas of depth . This strengthens in the non-uniform setting
the known inclusion that . Finally, we apply our
construction to show that {\sc reachability} for directed graphs of bounded
treewidth is in
Possible spin-orbit driven spin-liquid ground state in the double perovskite phase of Ba3YIr2O9
We report the structural transformation of hexagonal Ba3YIr2O9 to a cubic
double perovskite form (stable in ambient conditions) under an applied pressure
of 8GPa at 1273K. While the ambient pressure (AP) synthesized sample undergoes
long-range magnetic ordering at 4K, the high pressure(HP) synthesized sample
does not order down to 2K as evidenced from our susceptibility, heat capacity
and nuclear magnetic resonance (NMR) measurements. Further, for the HP sample,
our heat capacity data have the form gamma*T+beta*T3 in the temperature (T)
range of 2-10K with the Sommerfeld coefficient gamma=10mJ/mol-Ir K2. The 89Y
NMR shift has no T-dependence in the range of 4-120K and its spin-lattice
relaxation rate varies linearly with T in the range of 8-45K (above which it is
T-independent). Resistance measurements of both the samples confirm that they
are semiconducting. Our data provide evidence for the formation of a 5d based,
gapless, quantum spin-liquid (QSL) in the cubic (HP) phase of Ba3YIr2O9. In
this picture, the T term in the heat capacity and the linear variation of 89Y
1/T1 arises from excitations out of a spinon Fermi surface. Our findings lend
credence to the theoretical suggestion [G. Chen, R. Pereira, and L. Balents,
Phys. Rev. B 82, 174440 (2010)] that strong spin-orbit coupling can enhance
quantum fluctuations and lead to a QSL state in the double perovskite lattice.Comment: 6 pages 5 figure
Bose-Einstein condensation of triplons in the S=1 tetramer antiferromagnet K2Ni2(MoO4)3: A compound close to quantum critical point
The structure of K2Ni2(MoO4)3 consists of S=1 tetramers formed by Ni^{2+}
ions. The magnetic susceptibility chi(T) and specific heat Cp(T) data on a
single crystal show a broad maximum due to the low-dimensionality of the system
with short-range spin correlations. A sharp peak is seen in chi(T) and Cp(T) at
about 1.13 K, well below the broad maximum. This is an indication of magnetic
long-range order i.e., the absence of spin-gap in the ground state.
Interestingly, the application of a small magnetic field (H>0.1 T) induces
magnetic behavior akin to Bose-Einstein condensation (BEC) of triplon
excitations observed in some spin-gap materials. Our results demonstrate that
the temperature-field (T-H) phase boundary follows a power-law
(T-T_{N})propotional to H^(1/alpha) with the exponent 1/alpha close to 2/3, as
predicted for BEC scenario. The observation of BEC of triplon excitations in
small H infers that K2Ni2(MoO4)3 is located in the proximity of a quantum
critical point, which separates the magnetically ordered and spin-gap regions
of the phase diagram.Comment: 5 pages, 5 figures, Accepted in Phys. Rev. B Rapid Communication
Evidence that simvastatin prevents induction of nitric oxide synthase by LPS in the porcine isolated coronary artery
Spin Dynamics near the Superconductor-to-Insulator Transition in Impurity-Doped YBa2Cu4O8
We studied low-frequency spin dynamics near the impurity-induced
superconductor-to-insulator transition for underdoped high-Tc superconductor
YBa2(Cu1-xMx)4O8 (M=Ni, Zn) using the Cu nuclear quadrupole resonance (NQR)
spin-echo technique. We observed remarkable suppression of the normal-state
pseudo spin-gap and a loss of Cu NQR spectrum intensity at low temperatures
around the critical impurity concentration.Comment: 6 pages, 4 figures. To be published in J. Phys. Soc. Jpn. Vol.70,
No.7 (2001
Ayurveda and Modern perspective on Food Poisoning and its Medical Management
Food poisoning, also known as food borne illness, arises from consuming tainted food, with infectious agents or their toxins contaminating the food at any stage of processing. Mishandling or improper cooking at home can also lead to contamination. Symptoms include vomiting, nausea, diarrhea, stomach discomfort and fever. In Ayurveda, the body's equilibrium is governed by three Doshas; Vata, Pitta and Kapha. Disproportion in any of these Doshas can result in ailments. Aalsak and Visuchika are Ayurvedic conditions akin to food poisoning, preventable through a balanced diet and lifestyle. Ayurveda also suggested some drugs such as; Hinguvachaadi Choornam, Dashamoolarishtam, Hinguvachadi Gulika and Dhaanwantharam Kashaayam, etc. to address condition of food poisoning. Present article discussed Ayurveda and modern perspective on food poisoning and its medical management
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