Evidence for Widespread 26Al in the Solar Nebula and Constraints for Nebula Time Scales     

SS Russell  G Srinivasan  GR Huss  GJ Wasserburg  GJ MacPherson 《Science (New York, N.Y.)》1996,273(5276):757-762

A search was made for 26Mg (26Mg*) from the decay of 26Al (half-life = 0.73 million years) in Al-rich objects from unequilibrated ordinary chondrites. Two Ca-Al-rich inclusions (CAIs) and two Al-rich chondrules (not CAIs) were found that contained 26Al when they formed. Internal isochrons for the CAIs yielded an initial 26Al/27Al ratio [(26Al/27Al)0] of 5 x 10(-5), indistinguishable from most CAIs in carbonaceous chondrites. This result shows that CAIs with this level of 26Al are present throughout the classes of chondrites and strengthens the notion that 26Al was widespread in the early solar system. The two Al-rich chondrules have lower 26Mg*, corresponding to a (26Al/27Al)0 ratio of approximately 9 x 10(-6). Five other Al-rich chondrules contain no resolvable 26Mg*. If chondrules and CAIs formed from an isotopically homogeneous reservoir, then the chondrules with 26Al must have formed or been last altered approximately2 million years after CAIs formed; the 26Mg*-free chondrules formed >1 to 3 million years later still. Because 26Mg*-containing and 26Mg*-free chondrules are both found in Chainpur, which was not heated to more than approximately400°C, it follows that parent body metamorphism cannot explain the absence of 26Mg* in some of these chondrules. Rather, its absence indicates that the lifetime of the solar nebula over which CAIs and chondrules formed extended over approximately5 million years.  相似文献   

Association between line per se and hybrid performance under excessive soil moisture stress in tropical maize (Zea mays L.)     

P.H. Zaidi  P. Mani Selvan  Rafat Sultana  Ashish Srivastava  Anup K. Singh  G. Srinivasan  R.P. Singh  P.P. Singh 《Field Crops Research》2007

Excessive moisture (EM) stress during the summer–rainy season is one of the major production constraints for maize (Zea mays L.) in large areas of South and South-East Asia. A key question in breeding for tolerance to excessive moisture is the extent to which the performance of maize hybrids can be predicted on the basis of per se performance of inbred lines under excessive moisture. We attempted to identify the relationship between morpho-physiological traits and grain yield measured on inbred parents and their single cross progenies under EM stress. Responses of various morpho-physiological traits, except days to 50% anthesis, differ significantly under normal versus EM stress. Superiority of hybrid progenies over parental inbred lines increased under EM stress, suggesting that hybrids were comparatively more tolerant to EM stress than inbred progenies. Across moisture regimes, all morpho-physiological traits of hybrids, except lodging and root porosity under normal moisture, were found to be positively and significantly correlated with mid-parent traits. Our data suggest that per se performance of lines was a relatively more important factor in determining hybrid performance under EM stress, while under optimum soil moisture conditions mid-parent heterosis was relatively more important than per se performance of mid-parent. Phenotypic correlation between hybrid and mid-parent yields showed a strong relationship under EM stress (r = 0.66^**). The relationship was statistically significant under normal moisture as well, though it was comparatively weak (r = 0.41^*). Our findings suggest that performance of hybrid progenies under excessive moisture can be predicted and improved to some extent on the basis of their inbred parents that have been systematically selected and improved for EM stress.  相似文献   

Pyrrolysine encoded by UAG in Archaea: charging of a UAG-decoding specialized tRNA     

Srinivasan G  James CM  Krzycki JA 《Science (New York, N.Y.)》2002,296(5572):1459-1462

Pyrrolysine is a lysine derivative encoded by the UAG codon in methylamine methyltransferase genes of Methanosarcina barkeri. Near a methyltransferase gene cluster is the pylT gene, which encodes an unusual transfer RNA (tRNA) with a CUA anticodon. The adjacent pylS gene encodes a class II aminoacyl-tRNA synthetase that charges the pylT-derived tRNA with lysine but is not closely related to known lysyl-tRNA synthetases. Homologs of pylS and pylT are found in a Gram-positive bacterium. Charging a tRNA(CUA) with lysine is a likely first step in translating UAG amber codons as pyrrolysine in certain methanogens. Our results indicate that pyrrolysine is the 22nd genetically encoded natural amino acid.  相似文献   

Quantum cascade surface-emitting photonic crystal laser     

Colombelli R  Srinivasan K  Troccoli M  Painter O  Gmachl CF  Tennant DM  Sergent AM  Sivco DL  Cho AY  Capasso F 《Science (New York, N.Y.)》2003,302(5649):1374-1377

We combine photonic and electronic band structure engineering to create a surface-emitting quantum cascade microcavity laser. A high-index contrast two-dimensional photonic crystal is used to form a micro-resonator that simultaneously provides feedback for laser action and diffracts light vertically from the surface of the semiconductor surface. A top metallic contact allows electrical current injection and provides vertical optical confinement through a bound surface plasmon wave. The miniaturization and tailorable emission properties of this design are potentially important for sensing applications, while electrical pumping can allow new studies of photonic crystal and surface plasmon structures in nonlinear and near-field optics.  相似文献   

Clitoria ternatea root extract enhances acetylcholine content in rat hippocampus   总被引：1，自引：0，他引：1  

Rai KS  Murthy KD  Karanth KS  Nalini K  Rao MS  Srinivasan KK 《Fitoterapia》2002,73(7-8):685-689

Treatment with 100 mg/kg of Clitoria ternatea aqueous root extract (CTR), for 30 days in neonatal and young adult age groups of rat, significantly increased acetylcholine (ACh) content in their hippocampi as compared to age matched controls. Increase in ACh content in their hippocampus may be the neurochemical basis for their improved learning and memory.  相似文献   

Anti-inflammatory activity of Syzygium cumini bark     

Muruganandan S  Srinivasan K  Chandra S  Tandan SK  Lal J  Raviprakash V 《Fitoterapia》2001,72(4):369-375

The ethanolic extract of the bark of Syzygium cumini was investigated for its anti-inflammatory activity in animal models. The extract did not show any sign of toxicity up to a dose of 10.125 g/kg, p.o. in mice. Significant anti-inflammatory activity was observed in carrageenin (acute), kaolin-carrageenin (subacute), formaldehyde (subacute)-induced paw oedema and cotton pellet granuloma (chronic) tests in rats. The extract did not induce any gastric lesion in both acute and chronic ulcerogenic tests in rats. Thus, the present study demonstrated that S. cumini bark extract has a potent anti-inflammatory action against different phases of inflammation without any side effect on gastric mucosa.  相似文献   

RAPD and virulence analyses of Colletotrichum capski isolates from chilli (Capsicum annuum)     

Madhavan  Srinivasan  Paranidharan  Vaikuntavasan  Velazhahan  Rethinasamy 《植物病害和植物保护杂志》2010,117(6):253-257

Journal of Plant Diseases and Protection - Chilli (Capsicum annuum) fruits showing symptoms of an-thracnose disease were collected from farmer’s fields in different chilli-growing areas of...  相似文献   

A note on the coagulase production and other properties of Staphylococci of canine origin     

V A Srinivasan  C V Rao  A T Venugopalan  R A Balaprakasam 《The Indian veterinary journal》1979,56(12):1063-1064

  相似文献   

Ablation of polymers and biological tissue by ultraviolet lasers   总被引：9，自引：0，他引：9  

R Srinivasan 《Science (New York, N.Y.)》1986,234(4776):559-565

When pulsed, ultraviolet laser radiation falls on the surface of an organic polymer or biological tissue, the material at the surface is spontaneously etched away to a depth of 0.1 to several micrometers. In the process, the depth of etching is controlled by the width of the pulse and the fluence of the laser, and there is no detectable thermal damage to the substrate. The material that is removed by etching consists of products ranging from atoms to small fragments of the polymer. They are ejected at supersonic velocities. This dry photoetching technique is useful in patterning polymer films. It is also under serious investigation in several areas in surgery.  相似文献   

Fiber Separation from Ground Corn Flour Using an Electrostatic Method     

Tejas S. Pandya  Radhakrishnan Srinivasan  Courtney Paige Thompson 《Cereal Chemistry》2013,90(6):535-539

Corn kernels contain 9% fiber by weight, which is not digested well by nonruminants such as chicken and swine. Also, fiber is nonreactive in the dry‐grind process for ethanol production and is considered as feedstock for the production of second‐generation bioethanol. Fiber separation can enhance starch concentration in animal feed and increase starch loading in ethanol plants. Electrostatic separation is used to separate particles from granular mixtures under the influence of electrical forces. The Elusieve process, a combination of sieving and air classification, separates fiber by taking advantage of differences in size, shape, and density. Differences in dielectric properties could also be exploited for fiber separation. The aim of this study was to evaluate the effectiveness of electrostatic separation of fiber particles from corn. When the electrostatic method was used in conjunction with Elusieve processing, the fiber product had higher neutral detergent fiber (NDF, 52.9%) compared with Elusieve processing alone (NDF of 40.5%). Also, a higher quantity of enhanced flour (95.0% yield) was produced when the electrostatic method was used in conjunction with Elusieve processing compared with Elusieve processing alone (93.0% yield), without any change in quality of the enhanced flour (NDF of 6.6% in both cases). The electrostatic method improved fiber separation when used in conjunction with Elusieve processing.  相似文献