Showing papers by "Tata Institute of Fundamental Research published in 1972"

An epidemiologic study of oral cancer and precancerous conditions among 101,761 villagers in Maharashtra, India.

Abstract: In an extensive epidemiologic house-to-house survey, undertaken to study oral cancer and precancerous conditions, 101,761 villagers were examined in the Poona district in the Maharashtra state in India. Besides detection of 12 oral cancers, prevalences were established for leukoplakia (0.67%), preleukoplakia (0.86%), and submucous fibrosis (0.03%). The sample was also studied for chewing and smoking habits, which were practised by 54.4% of the individuals. Among males the most common habit was chewing tobacco with lime, whereas the dominating habit among females was the use of mishri (burned tobacco). The strongest association found was between bidi smoking and mixed habits and leukoplakia. Only a few cases of leukoplakia were found among mishri users. Except for submucous fibrosis it was found that prevalence does not depend on sex if tobacco habits are taken into account. Une etude epidemiologique du cancer buccal et de l'etat precancŕeux chez 101 761 villageois du Maharashtra (Inde) Dans le cadre d'une vaste enquěte epidemiologique de porte en porte, entreprise dans le but d'etudier le cancer buccal et l'etat precancereux, 101 761 villageois on ete examines dans le district de Poona de l'Etat du Maharashtra (Inde). L'etude a permis de depister 12 cancers buccaux, mais aussi d'etablir des prevalences pour la leucoplasie (0.67%), la preleucoplasie (0.86%) et la fibrose sous-muqueuse (0.03%). On a egalement observe les habitudes de ces villageois en ce qui concerne l'usage du tabac et la mastication de certaines substances, qui sont pratiques par 54.4% d'entre eux. L'habitude la plus repandue chez les hommes consiste a mǎcher du tabac et de la chaux, alors que les femmes preferent le mishri (tabac brǔle). L'association que l'on a constatee le plus souvent est celle de l'usage du bidi ou d'habitudes combinees et de la leucoplasie. Quelques cas de leucoplasie ont ete observes chez les amateurs de mishri. La fibrose sous-muqueuse mise a part et compte tenu de l'usage du tabac, on constate que la prevalence ne depend pas du sexe.

Hard rock cosmic ray archaeology.

Abstract: Recent examinations of extraterrestrial materials exposed to cosmic rays for different intervals of time during the geological history of the solar system have generated a wealth of new information on the history of cosmic radiation. This information relates to the temporal variations in The above studies are entirely based on the natural detector method which utilises two principal cosmogenic effects observed in rocks, (i) isotopic changes and (ii) changes in the crystalline structure of rock constituents, due to cosmogenic interactions. The information available to date in the field of hard rock cosmic ray archaeology refers to meteorites and lunar rocks/soil. Additional information based on study of cosmogenic effects in man-made materials exposed to cosmic radiation in space is also discussed. It is shown that the natural detectors inspite of their extreme simplicity have begun to provide cosmic ray information in a very quantitative and precise manner comparable to the most sophisticated electronic particle detectors. The single handicap in using the hard rock detectors is however the uncertainty regarding their manner of exposure, geometry etc. At present, a variety of techniques are being used to study the evolutionary history of extraterrestrial materials and as this field grows, uncertainties in cosmic ray archaeology will correspondingly decrease.

A variational inequality with mixed boundary conditions

Abstract: In this paper we study a variational inequality for a second order uniformly elliptic operator on a bounded domain, the solution of which is required to lie above a given obstacle and to assume assigned values on a part of the boundary of the domain. We are mainly concerned with the regularity of the solution in relation to the regularity of the data.

The presence of Candida in 723 oral leukoplakias among Indian villagers.

Abstract: – Among 50,915 individuals from 4 different states of India, 723 oral leukoplakias were biopsied and examined for the presence of Candida. Histologic sections were stained by hernatoxylin-eosin and PAS; 6.8% of the biopsies showed Candida estimated on the basis of a single PAS stained section. All Candida-positive cases were seen in males. The most striking observation was that out of 325 palatal biopsies in reverse smokers only one Candida-positive case was seen on the palate and none was seen on the labial mucosa out of 33 biopsies. It was surprising that although the number of leukoplakias among tobacco chewers was high, all of the Candida-positive cases, except one, were observed among smokers. Seven (14%) of the 49 Candida-positive biopsies showed epithelial atypia. No significant association between Candida-positive cases and atypia was found.

Magnetic dilution effects on morin phase transition in hematite

Abstract: Mossbauer investigations, in the range 10 to 1000 °K, in (1−x) Fe2O3-x Al2O3 systems, have shown a nonlinear rapid decrease of the Morin temperature, TM, with the increasing magnetic dilution of the α-Fe2O3 lattice. The phase transition is not sharp and becomes more and more diffused as the magnetic dilution increases. An anomalous variation of the angle, θ, between the spin direction and the c-axis is seen for the 5.27 wt% diluted sample indicating the presence of three magnetic phases in this case. Unlike the case of undiluted α-Fe2O3, for the 0.56 wt% diluted sample at low temperatures, outside the phase transition region, the Fe3+ spins do not lie along the c-axis but are canted at an angle of about 30°. This angle, θ ≈ 30°, does not seem to change much with further increase in dilution. It is also seen that with dilution, the ratio TM/TN and the anisotropy energy, K, deduced from the temperature and concentration dependence of the hyperfine field, are decreased (TN Neel temperature). This supports the existing anisotropy theory. Mosbaueruntersuchungen im Bereich 10 bis 1000 °K in (1−x) Fe2O3-x Al2O3-Systemen zeigen einen nichtlinearen, schnellen Abfall der Morintemperatur TM mit steigender magnetischer Verdunnung des α-Fe2O3-Gitters. Der Phasenubergang ist nicht scharf und wird um so diffuser je groser die magnetische Verdunnung wird. Eine anomale Anderung des Winkels θ, zwischen der Spinrichtung und der c-Achse wird fur die 5,27 Gew.%-verdunnte Probe beobachtet, was die Existenz von drei magnetishen Phasen in diesem Fall zeigt. Im Gegensatz zu unverdunntem α-Fe2O3 liegen fur die 0,56 Gew.%-verdunnte Probe bei niedrigen Temperaturen, auserhalb des Bereichs des Phasenubergangs die Fe3+-Spins nicht in Richtung der c-Achse, sondern sind um einen Winkel von etwa 30° gekippt. Dieser Winkel, θ ≈ 30° scheint sich nicht viel mit weiterer Verdunnung zu andern. Es wird ebenfalls gezeigt, das mit Verdunnung das Verhaltnis TM/TN und die Anisotropieenergie K, die aus der Temperatur- und Konzentrationsabhangigkeit des Hyperfeinfeldes abgeleitet wurden, abnehmen (TN Neeltemperatur). Das unterstutzt die vorhandenen Anisotropietheorien.

Number of Deoxyribonucleic Acid Uptake Sites in Competent Cells of Bacillus subtilis

Abstract: Two direct methods are presented for estimating the average number of deoxyribonucleic acid (DNA) uptake sites in competent cells of Bacillus subtilis from measurement of (14)C- or (3)H-thymine-labeled DNA uptake by competent culture. Advantage is taken of two facts: (i) effective contact between competent cells and transforming DNA molecules is established within a short time after mixing them together, and (ii) DNA molecules enter the competent B. subtilis cells in a linear fashion at a finite speed. From the number of DNA molecules initially attached to competent cells by brief exposure to transforming DNA in the first method or from the rate of DNA uptake by competent culture in the second method, the average number of DNA uptake sites is calculated to be 20 to 53 per competent cell.

Diffuse cosmic gamma rays observed at an equatorial balloon altitude

Abstract: A 3″×3″ NaI(T1) crystal-photomultiplier assembly with a 4π charged particle anticoincidence shield is used to determine the gamma ray spectrum in the energy region of about 100 keV to 8.5 MeV at a balloon altitude of 4.7 g cm−2 over Hyderabad, India (geomagnetic latitude ∼8°N). The atmospheric growth curves are used to obtain the contribution of the diffuse cosmic gamma ray flux in the above energy range. The cosmic photon flux thus deduced up to about 8.5 MeV is consistent with a continuation of the power law spectrum observed at energies between 20 and 200 keV with an index of ∼−2.3, and hence contradicts the flattening trend observed in ERS-18 at an energy of a few MeV.

A study of the vestigial records of cosmic rays in lunar rocks using a thick section technique

Abstract: An experimental technique has been developed for systematic measurements of fossil tracks along selected planes cut from grains and rocks. With controlled etching, the technique allows successive revelation of tracks in different minerals in the same section, a typical sequence being olivine, anorthite, clinopyroxene. It thus becomes possible to study precisely the cosmic ray track density variations over dimensions much greater than those of individual crystals. The technique also provides accurate information on the relative recording characteristics of different minerals present in a rock and cosmic ray tracks can be studied with a minimum interference of tracks due to spontaneous fission of uranium and transuranic elements. Continuous chains of sections, each section measuring approximately 1 cm., have been cut along several different planes in fifteen rocks from Mare Tranquillitatis, Oceanus Procellarum and Fra Mauro region. The cosmic ray track measurements from these sections have provided dramatic evidence for a number of processes affecting lunar rocks. The statistical, and non-uniform nature of erosion by micrometeorite bombardment can be seen in sections intersecting exposed surface which show regions of very steep track density gradients interspersed with eroded regions having lower track densities. The thick section technique permits determination of the energy spectrum of VH nuclei from track density gradients that extend over distances limited only by the dimensions of the rock, and, more important, in samples of identical orientation. The latter is particularly important in higher energy regions (deeper within the rock) where variations in crystal orientation cause track density differences of the same order as real changes in the gradient. Also in the near surface regions of rocks where low energy particles produce steep track density gradient, the thick section method has proved indispensable since it permits accurate depth determinations not possible in the spot sampling procedure. In this paper the technique of studying track profiles in thick sections is described. Although developed primarily for studying lunar samples, the thick section technique is also useful for similar studies in meteorites, particularly for gas-rich meteorites containing irradiated grains. In contrast to single grain studies, thick sections preserve the grain boundaries and permit accurate depth—density measurements. In addition thick section studies have revealed occasional large uniformly irradiated lithic fragments which would not have been possible to discover by spot sampling methods.

Homology between RNA from Human Malignant Breast Tissue and DNA synthesized by Milk Particles

Abstract: THERE have been several recent investigations implicating a possible viral aetiology of human breast cancer1–8. We report here a malignant human breast tumour containing polysomal RNA that has sequences homologous with DNA products of reverse transcriptase from human milk particle isolates.

Energy spectrum and time variations of hard X-rays from Cyg X-1

Abstract: Experimental results on the intensity, energy spectrum and time variations in hard X-ray emission from Cyg X-1 based on a balloon observation made on 1971, April 6 from Hyderabad (India) are described. The average energy spectrum of Cyg X-1 in the 22–154 keV interval on 1971 April 6 is best represented by a power law dN/dE=(5.41±1.53)E −(1.92±0.10) photons cm−2s−1 keV−1 which is in very good agreement with the spectrum of Cyg X-1 derived from an earlier observation made by us on 1969 April 16 in the 25–151 keV band and given by dN/dE=(3.54±2.44)E −(1.89±0.22) photons cm−2s−1 keV−1. A thermal bremsstrahlung spectrum fails to give a good fit over the entire energy range for both the observations. Comparison with the observations of other investigators shows that almost all balloon experiments consistently give a spectrum of ∼E −2, while below 20 keV the spectrum varies fromE −1.7 toE −5. There is some indication of a break in the Cyg X-1 spectrum around 20 keV. Spectral analysis of data in different time intervals for the 1971 April 6 flight demonstrates that while the source intensity varies over time scales of a few minutes, there is no appreciable variation in the spectral slope. Analysis of various hard X-ray observations for long term variations shows that over a period of about a week the intensity of Cyg X-1 varies upto a factor of four. The binary model proposed by Dolan is examined and the difficulties in explaining the observed features of Cyg X-1 by this model are pointed out.

Solar flares, the lunar surface, and gas rich meteorites

Abstract: Investigations on the Fe-group nuclei track density vs depth in lunar rocks and Surveyor 3 TV camera filter glass were critically examined considering more factors than previously. The analysis gives a firmer basis to the observation of the preferential leakage of low energy Fe nuclei from the accelerating region of the sun. The track density gradients in lunar rock 12022 and filter glass are used to determine the lunar erosion rate of 3 angstroms/yr. Track gradients are less steep than predicted from energy spectrum observed in the Surveyor glass, perhaps due to sputtering. High densities of etchable tracks were found at all depths down to 60 cm in fines from Apollo cores and also in thin sections of the Pesjanoe, Pantar, and Fayetteville gas-rich meteorites. It is felt unlikely that suprathermal heavy ions were responsible for the high track densities.

NMR Spectra of Bicyclic Compounds Oriented in the Nematic Phase. Part 1. The Spectrum of Quinoxaline

Abstract: The possibility of the determination of the structure of molecules oriented in the nematic phase of liquid crystals for relatively large aromatic bicyclic compounds is studied. The spectrum of quinoxaline is investigated in the nematic phase of 4-methoxy benzylidene, 4-amino-α-methyl cinnamic acid-npropyl ester. The shape of the proton skeleton is iteratively determined. Values of some of the indirect spin spin coupling constants are determined. The molecule is shown to orient preferentially with its plane and the C2, axis along the direction of the magnetic field.

Spin-lattice relaxation studies on semiquinone ions

Abstract: Electron spin-lattice relaxation times ofp-benzosemiquinone, durosemiquinone and 2, 5 ditertiary butyl-p-benzosemiquinone ions have been measured by the pulsed saturation recovery technique The relaxation times of the different hyperfine components of a semiquinone ion are the same within the limits of experimental error in disagreement with the findings of Schreurs and Fraenkel The dependence of T1 on viscosity does not follow the BPP’s theory

Slowly rotating relativistic stars. VI - Stability of the quasi-radial modes.

Abstract: Dynamical analysis of the quasi-radial modes of slowly and rigidly rotating, relativistic stars. The quasi-radial modes are those modes which would be radial if the star were not rotating. They are the crucial modes for determining the stability of the rotating star and also the modes which store energy for the longest time against dissipation by gravitational radiation. An equation is derived that makes it possible to calculate the effects of the slow and rigid star rotation on the frequency of the quasi-radial modes of oscillation of relativistic stars. The rotation is treated to second order in the angular velocity, but no other approximations are made.

The spectrum of diffuse cosmic X-rays in the 20–125 keV range

Abstract: Diffuse cosmic X-rays in the energy range 20–125 keV were measured in four balloon flights from Hyderabad, India during 1968–70 using almost identical X-ray telescopes mounted on oriented platforms. The results from these flights show that the spectrum of the diffuse cosmic X-rays can be represented by the form dN/dE=29E−2.1±0.3 photons/(cm2 sr s keV) in 20–125 keV interval after corrections for photoelectric absorption and Compton scattering effects in the atmosphere. The best fit spectrum of all published results in the energy interval 20–200 keV can be represented by the form dN/dE=36E−2.1±0.1 photons/(cm2 sr s keV) after similar corrections are effected, and there is no need for a change of spectral index in this energy interval. The intensity at 20 keV obtained from the above spectrum agrees well with that given by the spectral form dN/dE=10E−1.7±0.1 photons/(cm2 sr s keV) in the energy interval 1–20 keV in several rocket experiments. Therefore it is concluded that if there is a break in the spectrum, it occurs between 10 and 20 keV with a change of spectral index by about 0.5, or the index is continuously changing from 1.7±0.1 to 2.1±0.1 in 10–20 keV interval. The implications of the results are briefly discussed.

NMR Spectra of Bicyclic Compunds Oriented in the Nematic Phase. Part II. The Spectrumof Phthalazine

Abstract: Abstract-The determination of the structure of molecules oriented in the nematic phase of liquid crystals for relatively large bicyclic aromatic compounds has been extended to phthalazine. The spectrum of the molecule is investigated in the nematic phase of a mixture of 80% 4-ethoxybenzylidene-4-n-butyl aniline and 20% o-carbo butoxy-4-oxybenzoic acid ethoxy phenyl ester. Values of the indirect spin-spin coupling constants are determined. The geometry of the proton skeleton of the molecule is iteratively computed. The phenyl part of the molecule has been found to be distorted compared to the benzene structure. The distance between the protons in the pyridazine part of the ring is found to be smaller than the para H-H distance in the phenyl part. The MolecuIe orients preferentially with its C,-axis paraIlel to the direction of the magnetic field (SC2 = 0.1864). The axis normal to the plane has the most negative 8-value (- 0.1703).

Nonlinear Response of Bound Electrons to X Rays

Abstract: In the high-frequency limit, general expressions for second- and third-order induced electronic current densities in a medium are derived. These are valid for any medium with arbitrary spatial electronic-density variations. It is shown that the second-order current density at x-ray frequencies depends directly on the gradient of the unperturbed electronic density, so that it is sensitive to density variations both near the surface and near the ionic cores in a solid.