2,432 research outputs found
Cloning and expression of hmgr1 gene from Hevea brasiliensis
Biosynthesis of natural rubber (cis-1,4-polyisoprene) takes place through mevalonate pathway in Hevea. The enzyme 3-hydroxy- 3-methyl glutaryl-CoA reductase (HMGR), which catalyses the synthesis of mevalonate from HMG-CoA is a key regulatory enzyme in this pathway. This study aimed to clone and express hmgr1 gene, in order to obtain the HMGR protein in vitro and to further use this protein as a marker for yield potential in Hevea. For this purpose, mRNA was isolated from the latex of Hevea (clone RRII 105). cDNA was synthesized and PCR amplification of coding region of hmgr1 was performed using hmgr1 specific primers. The PCR amplified product (~1.8 kb) was cloned into an expression vector (pRSET-A) and transformed into E. coli (BL21DE3) cells. Protein expression in transformed cells when monitored by SDS-PAGE analysis indicated the presence of HMGR protein (61.6 kDa). The protein would be used for developing specific antibody that could be further utilized for the quantification of HMGR in different Hevea clones for screening the yield potential. The details of cloning and expression of hmgr1 are presented and discussed
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Scale-invariant moving finite elements for nonlinear partial differential equations in two dimensions
A scale-invariant moving finite element method is proposed for the adaptive solution of nonlinear partial differential equations. The mesh movement is based on a finite element discretisation of a scale-invariant conservation principle incorporating a monitor function, while the time discretisation of the resulting system of ordinary differential equations is carried out using a scale-invariant time-stepping which yields uniform local accuracy in time.
The accuracy and reliability of the algorithm are successfully tested against exact self-similar solutions where available, and otherwise against a state-of-the-art h-refinement scheme for solutions of a two-dimensional porous medium equation problem with a moving boundary. The monitor functions used are the dependent variable and a monitor related to the surface area of the solution manifold
Expression analysis of rubber biosynthetic pathway genes in Hevea brasiliensis
Hevea brasiliensisis, the primary commercial source of natural rubber (cis-1, 4-polyisoprene), is a fundamental raw material used for manufacturing a wide range of industrial and domestic rubber products in automobile, medical and defense industries. In Hevea, biosynthesis of rubber takes place through mevalonate pathway. Clonal variations in the productivity of rubber may be the result of variations in the activities of the enzymes involved in rubber biosynthesis in different Hevea clones. In this study, expression of 14 genes corresponding to enzymes/regulatory proteins involved in rubber biosynthesis was analyzed in high and low latex yielding clones of Hevea brasiliensis. The level of expression of HbSUT3, a sucrose transporter and enzymes related to the synthesis of rubber such as hydroxymethyl glutaryl-CoA synthase (hmgs), HMG-CoA reductase (hmgr) and mevalonate diphosphate decarboxylase (MVD) were found to be significantly higher in high rubber yielding clones compared to the low rubber yielding clones. The higher expression of these genes might result in an increased supply of IPP, the isoprenoid monomer, required for rubber biosynthesis. Expression of genes in the downstream rubber biosynthetic pathway such as FPPS, RuT and REF2 were also found to be significantly higher in high rubber yielding clones than low yielders. The results suggest that high rubber yield is associated with high expression of these genes and these genes can be used as markers for high yield potential in Hevea
Role of microenvironment in the mixed Langmuir-Blodgett films
This paper reports the pi-A isotherms and spectroscopic characteristics of
mixed Langmuir and Langmuir-Blodgett (LB) films of non-amphiphilic carbazole
(CA) molecules mixed with polymethyl methacrylate (PMMA) and stearic acid (SA).
pi-A isotherm studies of mixed monolayer and as well as also the collapse
pressure study of isotherms definitely conclude that CA is incorporated into
PMMA and SA matrices. However CA is stacked in the PMMA/SA chains and forms
microcrystalline aggregates as is evidenced from the scanning electron
micrograph picture. Nature of these aggregated species in the mixed LB films
has been revealed by UV-Vis absorption and fluorescence spectroscopic studies.
The presence of two different kinds of band systems in the fluorescence spectra
of the mixed LB films have been observed. This may be due to the formation of
low dimensional aggregates in the mixed LB films. Intensity distribution of
different band system is highly sensitive to the microenvironment of two
different matrices as well as also on the film thicknessComment: 11 pages, 5 figure
Mersenne Primes, Polygonal Anomalies and String Theory Classification
It is pointed out that the Mersenne primes and associated
perfect numbers play a significant role in string
theory; this observation may suggest a classification of consistent string
theories.Comment: 10 pages LaTe
Gyrations: The Missing Link Between Classical Mechanics with its Underlying Euclidean Geometry and Relativistic Mechanics with its Underlying Hyperbolic Geometry
Being neither commutative nor associative, Einstein velocity addition of
relativistically admissible velocities gives rise to gyrations. Gyrations, in
turn, measure the extent to which Einstein addition deviates from commutativity
and from associativity. Gyrations are geometric automorphisms abstracted from
the relativistic mechanical effect known as Thomas precession
Magmatic Origins of Extensional Structures in Tempe Terra, Mars
Abstract
Numerous graben features transect the Tempe Terra plateau in the northeastern Tharsis Rise, Mars, making it one of the most heavily structured regions of Tharsis. The origin of the complex fault geometries, generated over three distinct stages of tectonic activity, is poorly understood. This work distinguishes between Tempe Terra structures of local and regional origin, to isolate regional deformation patterns related to the general development of the Tharsis Rise from the patterns due to effects of local stress mechanisms. Comparison of structural observations to predicted deformation patterns from different drivers of graben formation in the Martian crust demonstrates the important role of magmatic activity at a variety of scales in driving tectonism in Tempe Terra. Noachian (Stage 1) faulting resulted from local magmatic underplating and associated heating and uplift, which formed part of an incipient stage of widespread Tharsis volcanism that predated development of the main Tharsis Rise. Early Hesperian (Stage 2) faults reflect the interaction of regional stresses from growth of Tharsis with magmatic activity highly localized along the Tharsis Montes Axial Trend—a linear volcanotectonic trendline including the alignment of the Tharsis Montes volcanoes. Early–Late Hesperian (Stage 3) faulting resulted from a series of dyke swarms from a Tharsis-centered plume, which propagated in a regional stress field generated by growth of the Tharsis Rise. As only Stage 2 NNE faults and Stage 3 ENE faults are linked to regional, Tharsis-related stresses, other observed Tempe Terra fault trends can be excluded when evaluating models of Tharsis's tectonic evolution.
Key Points
The 3 stages of Tempe Terra's tectonic activity have different origins, with local and regional scale magmatic sources driving deformation
Magmatectonic activity began in Tempe Terra prior to development of the Tharsis Rise topographic bulge and associated major volcanoes
Only 2 Tempe Terra fault trends (NNE and ENE), both Hesperian age, represent stresses related to the growth of the Tharsis Rise
Plain Language Summary
Tharsis is the largest volcanic province on Mars and its formation was a major driver of the deformation we see at the surface. Tectonic structures that record this deformation are therefore used to understand how and when Tharsis formed. However, local structural patterns may obscure regional trends associated with Tharsis-forming stresses, complicating our ability to assess models for how Tharsis developed. As such, distinguishing between faults with local and regional origins is essential. We study the Tempe Terra region in northeastern Tharsis to determine the origin of the region's extensive faulting, generated over three stages of tectonic activity. By comparing surface observations to expected evidence of different sources of stress, such as uplift from local volcanoes or dyke intrusion, we found that each stage of tectonic activity had a different origin. A combination of local (from within Tempe Terra) and regional (from Tharsis) magmatic sources drove deformation, and tectonic activity began before the main structures and volcanoes of Tharsis had developed. Only two fault trends in Tempe Terra can be linked to regional stresses related to the growth of Tharsis: NNE-trending and ENE-trending faults. Isolating these regional trends provides clearer criteria for assessing models of Tharsis development in the future
Non-Perturbative Corrections and Modularity in N=1 Type IIB Compactifications
Non-perturbative corrections and modular properties of four-dimensional type
IIB Calabi-Yau orientifolds are discussed. It is shown that certain
non-perturbative alpha' corrections survive in the large volume limit of the
orientifold and periodically correct the Kahler potential. These corrections
depend on the NS-NS two form and have to be completed by D-instanton
contributions to transform covariantely under symmetries of the type IIB
orientifold background. It is shown that generically also the D-instanton
superpotential depends on the two-form moduli as well as on the complex
dilaton. These contributions can arise through theta-functions with the dilaton
as modular parameter. An orientifold of the Enriques Calabi-Yau allows to
illustrate these general considerations. It is shown that this compactification
leads to a controlled four-dimensional N=1 effective theory due to the absence
of various quantum corrections. Making contact to the underlying topological
string theory the D-instanton superpotential is proposed to be related to a
specific modular form counting D3, D1, D(-1) degeneracies on the Enriques
Calabi-Yau.Comment: 35 page
Micro-Hall Magnetometry Studies of Thermally Assisted and Pure Quantum Tunneling in Single Molecule Magnet Mn12-Acetate
We have studied the crossover between thermally assisted and pure quantum
tunneling in single crystals of high spin (S=10) uniaxial single molecule
magnet Mn12-acetate using micro-Hall effect magnetometry. Magnetic hysteresis
experiments have been used toinvestigate the energy levels that determine the
magnetization reversal as a function of magnetic field and temperature. These
experiments demonstrate that the crossover occurs in a narrow (~0.1 K) or broad
(~1 K) temperature interval depending on the magnitude and direction of the
applied field. For low external fields applied parallel to the easy axis, the
energy levels that dominate the tunneling shift abruptly with temperature. In
the presence of a transverse field and/or large longitudinal field these energy
levels change with temperature more gradually. A comparison of our experimental
results with model calculations of this crossover suggest that there are
additional mechanisms that enhance the tunneling rate of low lying energy
levels and broaden the crossover for small transverse fields.Comment: 5 pages, 5 figure
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