8,706 research outputs found
Glass transition in Ultrathin Polymer Films : A Thermal Expansion Study
Glass transition process gets affected in ultrathin films having thickness
comparable to the size of the molecules. We observe systematic broadening of
glass transition temperature (Tg) as the thickness of the polymer film reduces
below the radius of gyration but the change in the average Tg was found to be
very small. Existence of reversible negative and positive thermal expansion
below and above Tg increased the sensitivity of our thickness measurements
performed using energy dispersive x-ray reflectivity. A simple model of Tg
variation as a function of depth expected from sliding motion could explain the
results. We observe clear glass transition even for 4 nm polystyrene film that
was predicted to be absent from ellipsometry measurements of thicker films.Comment: 11 pages, 5 figure
Basic Electric Furnace Practice for Low Alloy Steels
The low alloy steels generally find application in the construction of automobiles, locomotives, bridges, mach-inery and machine tools and many other equipment. These steels are used in "as forged" or "as rolled" condition
or is as castings after suitable heat-treatment, to develop the properties desired.
The chief alloying elements ill low alloy steels are Ni, Cr, Mn, Ito, V. Si, and Cu. These elements are used
either singly or very often in combination with others ill, various proportions : the total of the alloying elements generally does not exceed 8 per cent
Do Superstitious Traders Lose Money?
Do superstitious traders lose money? We answer this question in the context of trading in the Taiwan Futures Exchange, where we exploit the Chinese superstition that the number 8 is lucky and the number 4 is unlucky. We find that individual investors, but not institutional investors, submit disproportionately more limit orders at 8 than at 4. This imbalance, defined as the “superstition index” for each investor, is positively correlated with trading losses. Superstitious investors lose money mainly because of their bad market timing and stale orders. Nevertheless, the reliance on number superstition for limit order submissions does decrease with trading experience.postprin
Possible potentials responsible for stable circular relativistic orbits
Bertrand's theorem in classical mechanics of the central force fields
attracts us because of its predictive power. It categorically proves that there
can only be two types of forces which can produce stable, circular orbits. In
the present article an attempt has been made to generalize Bertrand's theorem
to the central force problem of relativistic systems. The stability criterion
for potentials which can produce stable, circular orbits in the relativistic
central force problem has been deduced and a general solution of it is
presented in the article. It is seen that the inverse square law passes the
relativistic test but the kind of force required for simple harmonic motion
does not. Special relativistic effects do not allow stable, circular orbits in
presence of a force which is proportional to the negative of the displacement
of the particle from the potential center.Comment: 11 pages, Latex fil
The effect of the neutron star crust on the evolution of a core magnetic field
We consider the expulsion of the magnetic field from the super-conducting
core of a neutron star and its subsequent decay in the crust. Particular
attention is paid to a strong feedback of the distortion of magnetic field
lines in the crust on the expulsion of the flux from the core. This causes a
considerable delay of the core flux expulsion if the initial field strength is
larger than 10^{11} G. It is shown that the hypothesis on the magnetic field
expulsion induced by the neutron star spin-down is adequate only for a
relatively weak initial magnetic field G. The expulsion
time-scale depends not only on the conductivity of the crust, but also on the
initial magnetic field strength itself. Our model of the field evolution
naturally explains the existence of the residual magnetic field of neutron
stars. Its strength is correlated with the impurity concentration in neutron
star crusts and anti-correlated with the initial field strengths.Comment: 15 pages, 6 figures, accepted to MNRA
Radiometric chronology of Changme-Khangpu glacier, Sikkim
The 32Si concentration in a sample of surface ice from the snout of Changme-Khangpu glacier is 0.36 disintegrations per minute/tonne compared to the fall-out value of 0.7 d.p.m./tonne. If this decrease is assumed to be solely due to decay of 32Si, an age of c. 100 years is estimated for the surface ice of the snout, leading to an average flow velocity of c. 40 m/year for the past century. A vertical profile of 210Pb in a core taken at an altitude of 5040 m shows two horizons where this isotope is enriched, one between 3 and 4 m and another between I I and 12 m, indicating that the primary concentration of 2l0Pb can change by physicochemical processes like adsorption on dust. None the less, a longitudinal profile along the glacier shows a systematic decrease of 2l0Pb activity with decreasing altitude, the surface ice of the snout giving a value of 0.2 d.p.m./I, corresponding to an age of 100 years which is concordant with the 32Si age. This surface flow-rate of the glacier is much larger than the average contemporary flow-rate (c. 13 m/year). The difference can be understood of the past history of advance and recession of the glacier as revealed by the geomorphic evidence
Oestrogen increases S-phase fraction and oestrogen and progesterone receptors in human cervical cancer in vivo.
Although cancer of the cervix is traditionally considered not to be responsive to steroid hormones, an in vitro study has reported that the addition of oestrogen increased cellular proliferation in a cervix cancer cell line that was inhibited by progesterone. We investigated whether the reported in vitro effects of oestrogen and progesterone on cellular proliferation can be replicated in locally advanced cervical cancer in vivo and whether these effects, if any, are related to oestrogen and progesterone receptor (ER and PgR) content of the tumour. One hundred post-menopausal patients with locally advanced cervical cancer were systematically allocated by rotation to the four treatment groups: (1) control group receiving no treatment; (2) ethinyl oestradiol 50 micrograms: (3) norethisterone 5 mg: (4) a combination of ethinyl oestradiol and norethisterone. Hormone treatment (five doses) was given orally every 12 h. Tissue biopsies were taken before and 12 h after the last hormone treatment. S-phase fraction (SpF) was measured by flow cytometry, and ER and PgR were measured by enzyme immunoassay. Results were analysed using two-factor analysis of variance, the factors being oestrogen-absent or present- and progesterone-absent or present. The main effects of oestrogen were increases in SpF, ER and PgR, which were statistically significant (P = 0.0056, 0.0009 and 0.01 respectively), indicating that there is much greater change in these three parameters in the presence of oestrogen (mean changes 7.808%, 6.258 fmol mg-1 and 12.716 fmol mg-1 for SpF, ER and PgR respectively) than in its absence (mean change -1.986%,-3.041 fmol mg-1 and 1.736 fmol mg-1 respectively). The progestogen main effect and the oestrogen-progestogen interaction were not significant. The rise in SpF, ER and PgR in the presence of oestrogen had a correlation coefficient with the initial ER values of -0.0565, -0.2863 and -0.1230 respectively, none being statistically significant, suggesting that the oestrogen actions were not strictly related to baseline ER concentrations. The combined median baseline ER and PgR values of the four groups were 1.48 fmol mg-1 and 0.80 fmol mg-1 respectively. Our results show that oestrogen is capable of increasing SpF in locally advanced cervical cancer in vivo and may help to revive interest in the use of oestrogen as a radiosensitizing agent in the treatment of this disease
Structure of cholest-5-en-3β-oxy-5-bromopentane by single-crystal X-ray diffraction at 130 K
Cholest-5-en-3β-oxy-5-bromopentane (1) and cholest-5-en-3β-oxy-11-bromoundecane (2), key precursors for the synthesis of novel cationic amphiphiles based on cholesterol, have been synthesized and characterized by 1H-NMR spectroscopy and X-ray crystallography. Thermal disorder and effect of length of the bromoalkyl segment on the crystal structure have been investigated. Possible molecular level explanation of the unusual alternating s-trans-gauche conformation of the bromopentyl side chain of (1) has been presented
Non-detection of a pulsar-powered nebula in Puppis A, and implications for the nature of the radio-quiet neutron star RX J0822-4300
We report on a deep radio search for a pulsar wind nebula associated with the
radio-quiet neutron star RX J0822-4300 in the supernova remnant Puppis A. The
well-determined properties of Puppis A allow us to constrain the size of any
nebula to less than 30 arcsec; however we find no evidence for such a source on
any spatial scale up to 30 arcmin. These non-detections result in an upper
limit on the radio luminosity of any pulsar-powered nebula which is three
orders of magnitude below what would be expected if RX J0822-4300 was an
energetic young radio pulsar beaming away from us, and cast doubt on a recent
claim of X-ray pulsations from this source. The lack of a radio nebula leads us
to conclude that RX J0822-4300 has properties very different from most young
radio pulsars, and that it represents a distinct population which may be as
numerous, or even more so, than radio pulsars.Comment: 5 pages, including 2 embedded EPS figures, uses emulateapj.sty.
Accepted to ApJ Letters (minor changes made following referee's report
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