211 research outputs found
Using the Hadamard and related transforms for simplifying the spectrum of the quantum baker's map
We rationalize the somewhat surprising efficacy of the Hadamard transform in
simplifying the eigenstates of the quantum baker's map, a paradigmatic model of
quantum chaos. This allows us to construct closely related, but new, transforms
that do significantly better, thus nearly solving for many states of the
quantum baker's map. These new transforms, which combine the standard Fourier
and Hadamard transforms in an interesting manner, are constructed from
eigenvectors of the shift permutation operator that are also simultaneous
eigenvectors of bit-flip (parity) and possess bit-reversal (time-reversal)
symmetry.Comment: Version to appear in J. Phys. A. Added discussions; modified title;
corrected minor error
Factors Influencing Vocal Pitch in Articulatory Speech Synthesis: A Study Using PRAAT
(Abstract to follow
In vivo kinetics of transcription initiation of the lar promoter in Escherichia coli. Evidence for a sequential mechanism with two rate-limiting steps
<p>Abstract</p> <p>Background</p> <p>In <it>Escherichia coli </it>the mean and cell-to-cell diversity in RNA numbers of different genes vary widely. This is likely due to different kinetics of transcription initiation, a complex process with multiple rate-limiting steps that affect RNA production.</p> <p>Results</p> <p>We measured the <it>in vivo </it>kinetics of production of individual RNA molecules under the control of the lar promoter in <it>E. coli</it>. From the analysis of the distributions of intervals between transcription events in the regimes of weak and medium induction, we find that the process of transcription initiation of this promoter involves a sequential mechanism with two main rate-limiting steps, each lasting hundreds of seconds. Both steps become faster with increasing induction by IPTG and Arabinose.</p> <p>Conclusions</p> <p>The two rate-limiting steps in initiation are found to be important regulators of the dynamics of RNA production under the control of the lar promoter in the regimes of weak and medium induction. Variability in the intervals between consecutive RNA productions is much lower than if there was only one rate-limiting step with a duration following an exponential distribution. The methodology proposed here to analyze the <it>in vivo </it>dynamics of transcription may be applicable at a genome-wide scale and provide valuable insight into the dynamics of prokaryotic genetic networks.</p
Coastal Aquaculture - Mussel farming; Progress and prospects
During the seventies, the Central Marine Fisheri^ lleseardi Institute gave a lead in researches on
mariculture and has carved for itself a pioneering role in the R& D programmes of mariculture in the countiy
which has been well recognised. Impressed by the outstanding contributions made during the decade, the
infrastructure facilities built up and, above all, the scientific and techni<ial competence it has acquittdi jm
UNDP/ICAR Centre of Advanced Studies in Mariculture has been instituted at the Central Marine Fisheries
Research Institute since June 1979. The Centre aims at providing postgraduate education in the new
discipline of Mariculture and improvmg the quality of research through doct(»ral and post-doctoral research
programmes in identified areas.
One of the priority areas of mariculture in India is mussel culture. Although considered a poor relation
of the oyster in Europe, mussel has one of the highest potentials in India for increaang production of protein-
rich sea food. Mussel gives the highest conversion of primary producera ^hytojrfankton) to human food and
culture production in column waters enhances the yield several fold. India has a traditional sustenance
fishery for the mmsels at a few centres but the scope for increasing natural production from the existing beds
is rather limited
Spawning periodicity of the ribbon fish, Trichiurus lepturus (F.), with a note on its rate of growth
The spawning periodicity of Trichiurus lepturus is briefly re-examined here in tlie
light of certain recent observations. It is seen that this species spawns more than once
in a year along the Madras coast and the two seasons are roughly around May-June and
later in November-December. This fact also leads to a revision in the interpretation
of the rate of growth of the fish. It is now estimated that the fish at the end of
one year attains an average of 300 mm in length and that those above about 900 mm
are just over four years
Cell-to-cell diversity in protein levels of a gene driven by a tetracycline inducible promoter
<p>Abstract</p> <p>Background</p> <p>Gene expression in <it>Escherichia coli </it>is regulated by several mechanisms. We measured in single cells the expression level of a single copy gene coding for green fluorescent protein (GFP), integrated into the genome and driven by a tetracycline inducible promoter, for varying induction strengths. Also, we measured the transcriptional activity of a tetracycline inducible promoter controlling the transcription of a RNA with 96 binding sites for MS2-GFP.</p> <p>Results</p> <p>The distribution of GFP levels in single cells is found to change significantly as induction reaches high levels, causing the Fano factor of the cells' protein levels to increase with mean level, beyond what would be expected from a Poisson-like process of RNA transcription. In agreement, the Fano factor of the cells' number of RNA molecules target for MS2-GFP follows a similar trend. The results provide evidence that the dynamics of the promoter complex formation, namely, the variability in its duration from one transcription event to the next, explains the change in the distribution of expression levels in the cell population with induction strength.</p> <p>Conclusions</p> <p>The results suggest that the open complex formation of the tetracycline inducible promoter, in the regime of strong induction, affects significantly the dynamics of RNA production due to the variability of its duration from one event to the next.</p
The present status of ribbonfish fishery in India
The ribbonfishes, of the family TrichiurkJae, an Important
group of food fishes in India, registered an average annual
catch of 53.475 tonnes during 1970-81. In this period, forming
4.25% of the total marine fish catch, thsy formed the 7th
exploited fish group in the order of predominance.
There are 8 known ribbonfish species in India (an identification
key to the species is given in the beginning of thearticle)
The information available on the various aspects of biology of
each of these species is summarised, which clearly indicates
that while our knowledge on the biology of Trichiurus lepturua,
Lepturecanthus savale, Eupleurogrammus nwticus and Eupleurogrammus
glossodon is considereble, we know little about
the other species.
Traditionally, the ribbonfishes are caught by boatseines,
shoreseines, bag nets and gill nets, operating from nonpowered
country crafts. But, during the last two decades, the small mechanized vessels (10-15 m long, with 15-100 hp engines)
that are operating otter trawls, too, are increasingly landing
ribbonfish. The fishery is confined to the depth-zone usually
shallower than 50 m. T. lepturus, the most widely distributed,
forms the mainstay of the ribbonfish fishery, contributing to
the bulk of the landings along almost all our coastline. Data
on spatial and seasonal variations in abundance, size and age
composition in the commercial catches and diurnal movements
and depthwise distributions of shoals of this species are
therefore reviewed.
Stock assessment studies show that, in the shelf region
from Ratnagiri on the west coast round to Gulf of Mannar on
the east, there had been an average standing stock of 67,200
tonnes of ribbonfish (mostly L Lepturus) in 1972-75, which is
about 4 times what was actually landed from the region during
the period.
It therefore follows that a doubling of the catch will not
adversely affect the stock in the region. Studies on the population
dynamics of T. lepturus from the Kakinada area during
1967-71 has shown that the fishing mortality and the exploitation
rates are low, at 0.3 and 0.17 respectively. The average
annual stock and average standing stock along the Andhra and
Tamil Nadu coasts are estimated at 85,000 and 48,000 tonnes,
respectively, for T. lepturus, against an estimated annual
average catch of 14,400 tonnes during 1967-71. It thus appears
that the stock of T. lepturus along the east coast also is likewise
underfishad,
The need for extension of fishing operations into the
Exclusive Economic Zone with larger vessels, equipped with
suitable gears like bottom and pelagic trawls, is emphasized-
Suggestions on future lines of research are given
Modeling Basal Ganglia for understanding Parkinsonian Reaching Movements
We present a computational model that highlights the role of basal ganglia
(BG) in generating simple reaching movements. The model is cast within the
reinforcement learning (RL) framework with the correspondence between RL
components and neuroanatomy as follows: dopamine signal of substantia nigra
pars compacta as the Temporal Difference error, striatum as the substrate for
the Critic, and the motor cortex as the Actor. A key feature of this
neurobiological interpretation is our hypothesis that the indirect pathway is
the Explorer. Chaotic activity, originating from the indirect pathway part of
the model, drives the wandering, exploratory movements of the arm. Thus the
direct pathway subserves exploitation while the indirect pathway subserves
exploration. The motor cortex becomes more and more independent of the
corrective influence of BG, as training progresses. Reaching trajectories show
diminishing variability with training. Reaching movements associated with
Parkinson's disease (PD) are simulated by (a) reducing dopamine and (b)
degrading the complexity of indirect pathway dynamics by switching it from
chaotic to periodic behavior. Under the simulated PD conditions, the arm
exhibits PD motor symptoms like tremor, bradykinesia and undershoot. The model
echoes the notion that PD is a dynamical disease.Comment: Neural Computation, In Pres
Industrial fisheries off Madras coast based on exploratory surveys during 1973-1980
At the Madras Research Centre of CMFRI, there existed data for areas (Fig. 1) south of 15°40'N
Upto the latitude zone of I0°40'N off Velanganni in depths ranging from 10 to 130 m for a eight year period
From 1973 to 1980. The results of analysis of these data are presented here with a view to providing information on and extending our knowledge about the spatial and seasonal distribution of various indusirially important fisheries as also their resource potential along the north Tamil Nadu-South Andhra Coast
Nanostructured AgBr loaded TiO2: An efficient sunlight active photocatalyst for degradation of Reactive Red 120
The AgBr loaded TiO2 catalyst was prepared by a feasible approach with AgBr and tetraisopropyl orthotitanate and characterized by BET surface area measurement, diffuse reflectance spectra (DRS), scanning electron microscope (SEM), energy dispersive spectra (EDS), X-ray diffraction (XRD), transmission electron microscope (TEM) and atomic force microscope (AFM) analysis. The results of characterization reveal that AgBr loaded TiO2 has a nanostructure. Formation of the nanostructure in AgBr loaded TiO2 results in substantial shifting of the absorption edge of TiO2 to red and enhancement of visible light absorption. Electrochemical impedance spectroscopy measurements reveal that AgBr loaded TiO2 has a higher photoconductivity than prepared TiO2 due to higher separation efficiency of electron-hole pairs. Cyclic voltammetric studies reveal enhanced conductivity in AgBr loaded TiO2, which causes an increase in its photocatalytic activity. AgBr loaded TiO2 exhibited a higher photocatalytic activity than TiO2-P25 and prepared TiO2 in the photodegradation of Reactive Red 120 (RR 120)
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