S. Sen

Bio: S. Sen is an academic researcher from Saha Institute of Nuclear Physics. The author has contributed to research in topics: Medicine & DNA supercoil. The author has an hindex of 10, co-authored 35 publications receiving 269 citations.

In-vitro anticancer activity of standard extracts used in ayurveda

Abstract: The hydro-alcoholic extracts of five Ayurvedic medicinal plants, pericarp of Terminalia chebula, rhizome of Acorus calamus, stem bark of Bauhinia variegate, whole plant of Phyllanthus amarus, root of Glycyrrhiza glabra were evaluated for their antiproliferative activity on fourteen cancer cell lines These plant extracts were tested by sulforhodamine-B (SRB) assay for its anti proliferative activity and four extracts except Glycyrrhiza glabra were found active against prostrate cancer cell line (DU145 In addition to this Terminalia chebula exhibited activity against leukemia cancer cell line (K562)

Observation of magnetic rotation in odd-odd Ag-104

Abstract: The high spin level structure of $^{104}\text{Ag}$ has been extended to ${I}^{\ensuremath{\pi}}={20}^{+}$ and excitation energy of $7.159\phantom{\rule{0.3em}{0ex}}\text{MeV}$ through the discrete line $\ensuremath{\gamma}$-ray spectroscopy. The negative parity ground state band has been confirmed and extended to ${I}^{\ensuremath{\pi}}={18}^{\ensuremath{-}}$. Two new nonyrast dipole bands, one with positive and the other with negative parity, have been observed. The parities of the two bands have been established through polarization directional correlation measurement of the feed-out transitions from these bands. The level lifetimes have been measured in the ground state band and the positive parity dipole band. The measured total angular momenta and the $B(M1)$ rates have been compared with the predictions of hybrid version of the tilted axis cranking. The $B(M1)$ rates have also been compared with the values obtained from D\"onau's geometric formula. The tilted axis calculations give good overall agreement which suggests that all the three bands of $^{104}\text{Ag}$ exhibits magnetic rotation.

Characteristics of a Compton suppressed Clover detector up to 5 MeV

Abstract: The Clover detectors in their addback mode are excellent tools for detecting high-energy gamma rays (⩾2 MeV ) . The characteristics of these detectors, at energies above 2 MeV , are usually determined from simulation data or from extrapolation of the empirical data. This is the first time that the characteristics of a Compton suppressed Clover germanium detector have been studied up to 5 MeV using a radioactive 66 Ga (T 1/2 =9.41 h ) source.

Transition probability from the ground to the first-excited 2^+ state of even-even nuclides

Abstract: Adopted values for the reduced electric quadrupole transition probability, B(E2)↑, from the ground state to the first-excited 2+ state of even–even nuclides are given in Table I. Values of τ, the mean life of the 2+ state; E, the energy; and β, the quadrupole deformation parameter, are also listed there. The ratio of β to the value expected from the single-particle model is presented. The intrinsic quadrupole moment, Q0, is deduced from the B(E2)↑ value. The product E×B(E2)↑ is expressed as a percentage of the energy-weighted total and isoscalar E2 sum-rule strengths. Table II presents the data on which Table I is based, namely the experimental results for B(E2)↑ values with quoted uncertainties. Information is also given on the quantity measured and the method used. The literature has been covered to November 2000. The adopted B(E2)↑ values are compared in Table III with the values given by systematics and by various theoretical models. Predictions of unmeasured B(E2)↑ values are also given in Table III.

The path from the RNA world.

Abstract: We describe a sequential (step by step) Darwinian model for the evolution of life from the late stages of the RNA world through to the emergence of eukaryotes and prokaryotes. The starting point is our model, derived from current RNA activity, of the RNA world just prior to the advent of genetically-encoded protein synthesis. By focusing on the function of the protoribosome we develop a plausible model for the evolution of a protein-synthesizing ribosome from a high-fidelity RNA polymerase that incorporated triplets of oligonucleotides. With the standard assumption that during the evolution of enzymatic activity, catalysis is transferred from RNA → RNP → protein, the first proteins in the ``breakthrough organism'' (the first to have encoded protein synthesis) would be nonspecific chaperone-like proteins rather than catalytic. Moreover, because some RNA molecules that pre-date protein synthesis under this model now occur as introns in some of the very earliest proteins, the model predicts these particular introns are older than the exons surrounding them, the ``introns-first'' theory. Many features of the model for the genome organization in the final RNA world ribo-organism are more prevalent in the eukaryotic genome and we suggest that the prokaryotic genome organization (a single, circular genome with one center of replication) was derived from a ``eukaryotic-like'' genome organization (a fragmented linear genome with multiple centers of replication). The steps from the proposed ribo-organism RNA genome → eukaryotic-like DNA genome → prokaryotic-like DNA genome are all relatively straightforward, whereas the transition prokaryotic-like genome → eukaryotic-like genome appears impossible under a Darwinian mechanism of evolution, given the assumption of the transition RNA → RNP → protein. A likely molecular mechanism, ``plasmid transfer,'' is available for the origin of prokaryotic-type genomes from an eukaryotic-like architecture. Under this model prokaryotes are considered specialized and derived with reduced dependence on ssRNA biochemistry. A functional explanation is that prokaryote ancestors underwent selection for thermophily (high temperature) and/or for rapid reproduction (r selection) at least once in their history.