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51.
52.
The present study is a comparison of the energy efficiency of three types of shifting agriculture, known locally as ‘jhum’, in north-eastern India. Longer cycles of 30 and 10 years, which are rather rare now, are compared with the more common 5-year cycle of the present time. Of the three land use practices, jhum and valley agricultural systems are more efficient from the energy viewpoint, with higher output/input ratios compared with terrace cultivation, which is least efficient due to heavy fertiliser input requirements. For jhum, a 10-year cycle, however, is more efficient from the energy and land use points of view, with an effective energy output of 5660·1 MJ compared with 1892·2 MJ under a 30-year cycle or 4771·6 MJ under a 5-year cycle. Cereal cultivation, if its is to be sustained, must be on the basis of valley cultivation, which is sustainable year after year, or on basis of a 10-year jhum cycle. The implications of these findings are discussed in the light of the relative significance of land and energy constraints. 相似文献
53.
54.
Protein synthesis requires several guanosine triphosphatase (GTPase) factors, including elongation factor Tu (EF-Tu), which delivers aminoacyl-transfer RNAs (tRNAs) to the ribosome. To understand how the ribosome triggers GTP hydrolysis in translational GTPases, we have determined the crystal structure of EF-Tu and aminoacyl-tRNA bound to the ribosome with a GTP analog, to 3.2 angstrom resolution. EF-Tu is in its active conformation, the switch I loop is ordered, and the catalytic histidine is coordinating the nucleophilic water in position for inline attack on the γ-phosphate of GTP. This activated conformation is due to a critical and conserved interaction of the histidine with A2662 of the sarcin-ricin loop of the 23S ribosomal RNA. The structure suggests a universal mechanism for GTPase activation and hydrolysis in translational GTPases on the ribosome. 相似文献
55.
Shivachandra SB Kumar AA Biswas A Ramakrishnan MA Singh VP Srivastava SK 《Tropical animal health and production》2004,36(8):743-750
An investigation was carried out to study the antibiotic sensitivity of avian strains of Pasteurella multocida and to select an effective antimicrobial agent for control of avian pasteurellosis in India. A total of 123 strains of P. multocida recently isolated from different avian species (chicken, duck, turkey, quail, and goose), from different regions of India were subjected to antibiotic sensitivity tests using 20 different antibiotics. Absolute resistance was observed against sulfadiazine. The studies indicated that the strains were most sensitive to chloramphenicol (73.98%), followed by enrofloxacin (71.54%), lincomycin (64.23%), norfloxacin (61.79%) and doxycycline-HCl (56.91%). The majority of the strains were found to exhibit intermediate sensitivity. Chloramphenicol was selected and suggested for treatment. Antibiogram studies also revealed the emergence of multidrug-resistant strains of P. multocida among Indian poultry. 相似文献
56.
Rice‐straw amendment increased methane production by 3‐fold over that of unamended control. Application of P as single superphosphate at 100 μg (g soil)–1 inhibited methane (CH4) production distinctly in flooded alluvial rice soil, in the absence more than in the presence of rice straw. CH4 emission from rice plants (cv. IR72) from alluvial soil treated with single superphosphate as basal application, in the presence and absence of rice straw, and held under non‐flooded and flooded conditions showed distinct variations. CH4 emission from non‐flooded soil amended with rice straw was high and almost similar to that of flooded soil without rice‐straw amendment. The cumulative CH4 efflux was highest (1041 mg pot–1) in rice‐straw‐amended flooded soil. Appreciable methanogenic reactions in rice‐straw‐amended soils were evident under both flooded and non‐flooded conditions. Rice‐straw application substantially altered the balance between total aerobic and anaerobic microorganisms even in non‐flooded soil. The mitigating effects of single‐superphosphate application or low‐moisture regime on CH4 production and emission were almost nullified due to enhanced activities of methanogenic archaea in the presence of rice straw. 相似文献
57.
58.
P. K. Kanungo B. Ramakrishnan V. Rajaramamohan Rao 《Biology and Fertility of Soils》1997,25(2):103-108
The placement effects of organic sources (cellulose and rice straw) at different depths on nitrogenase activity (acetylene
reduction assay, ARA) associated with four tropical rice soils were investigated. Results showed that placement of organic
sources in the top profile (1–2 cm) produced a higher nitrogenase activity; while placement in the 2–4 cm and 4–6cm profiles
significantly decreased the activity irrespective of soil type. The effect of organic sources on nitrogenase varied depending
on the soil type. Cellulose and rice straw caused differential stimulation in response to the placement. Evidence was provided
for the creation of favourable redox potential supporting higher nitrogenase activity in series receiving organic amendments
in the top profile. Higher nitrogenase activity in the top profile was associated with greater populations of nitrogen-fixing
Azospirillum sp., anaerobic nitrogen fixers and Azotobacter sp. Moreover, the lower amounts of reducing sugars and higher carbon dioxide evolution gave evidence of higher microbial
activity in the top profile. These results clearly indicate the positive relationship between nitrogenase activity, nitrogen-fixing
populations and redox status in the top layers of flooded tropical rice soils.
Received: 5 June 1996 相似文献
59.
Carter AP Clemons WM Brodersen DE Morgan-Warren RJ Hartsch T Wimberly BT Ramakrishnan V 《Science (New York, N.Y.)》2001,291(5503):498-501
Initiation of translation at the correct position on messenger RNA is essential for accurate protein synthesis. In prokaryotes, this process requires three initiation factors: IF1, IF2, and IF3. Here we report the crystal structure of a complex of IF1 and the 30S ribosomal subunit. Binding of IF1 occludes the ribosomal A site and flips out the functionally important bases A1492 and A1493 from helix 44 of 16S RNA, burying them in pockets in IF1. The binding of IF1 causes long-range changes in the conformation of H44 and leads to movement of the domains of 30S with respect to each other. The structure explains how localized changes at the ribosomal A site lead to global alterations in the conformation of the 30S subunit. 相似文献
60.
Raj Kumar Singh Muthannan Andavar Ramakrishnan Kumaragurubaran Karthik Rekha Khandia 《The Veterinary quarterly》2017,37(1):98-135
Ebola virus (EBOV) is an extremely contagious pathogen and causes lethal hemorrhagic fever disease in man and animals. The recently occurred Ebola virus disease (EVD) outbreaks in the West African countries have categorized it as an international health concern. For the virus maintenance and transmission, the non-human primates and reservoir hosts like fruit bats have played a vital role. For curbing the disease timely, we need effective therapeutics/prophylactics, however, in the absence of any approved vaccine, timely diagnosis and monitoring of EBOV remains of utmost importance. The technologically advanced vaccines like a viral-vectored vaccine, DNA vaccine and virus-like particles are underway for testing against EBOV. In the absence of any effective control measure, the adaptation of high standards of biosecurity measures, strict sanitary and hygienic practices, strengthening of surveillance and monitoring systems, imposing appropriate quarantine checks and vigilance on trade, transport, and movement of visitors from EVD endemic countries remains the answer of choice for tackling the EBOV spread. Herein, we converse with the current scenario of EBOV giving due emphasis on animal and veterinary perspectives along with advances in diagnosis and control strategies to be adopted, lessons learned from the recent outbreaks and the global preparedness plans. To retrieve the evolutionary information, we have analyzed a total of 56 genome sequences of various EBOV species submitted between 1976 and 2016 in public databases. 相似文献