The modern generation of electronic detectors, such as the CCD, have made improved photometry possible, especially at magnitudes near photographic plate limits and at wavelengths extending to the near infrared. Vigorous efforts should now be made to extend measurements to longer wavelengths since VandenBerg and Bell (1985) have recently calculated BVRI synthetic isochrones. Consequently, we have embarked on a program of CCD BVRI photometry for determining the ages of globular clusters.
From BVRI CCD frames obtained with the 1.54 Danish telescope at ESO-La Silla we have at this moment completed the reductions of the following 5 globular clusters: NGC 104 (47 Tuc), NGC 2298, NGC 5139 ( 0) Cen), NGC 6121 (M4), and NGC 6362. For these clusters, we have derived ages all close to 17x10^0y. Providing strong evidence that the globular cluster system is coeval, and that the epoch of the galactic contraction was short.
Changes in leaf growth, photosynthetic efficiency, and incorporation pattern of photosynthetically fixed 14CO2 in leaves 1 and 2 from plant apex, in roots, and rhizome induced in Curcuma by growing in a solution culture at Fe concentration of 0 and 5.6 g m-3 were studied. 14C was incorporated into primary metabolites (sugars, amino acids, and organic acids) and secondary metabolites (essential oil and curcumin). Fe deficiency resulted in a decrease in leaf area, its fresh and dry mass, chlorophyll (Chl) content, and CO2 exchange rate at all leaf positions. The rate of 14CO2 fixation declined with leaf position, maximum being in the youngest leaf. Fe deficiency resulted in higher accumulation of sugars, amino acids, and organic acids in leaves at both positions. This is due to poor translocation of metabolites. Roots and rhizomes of Fe-deficient plants had lower concentrations of total photosynthate, sugars, and amino acids whereas organic acid concentration was higher in rhizomes. 14CO2 incorporation in essential oil was lower in the youngest leaf, as well as incorporation in curcumin content in rhizome. Fe deficiency influenced leaf area, its fresh and dry masses, CO2 exchange rate, and oil and curcumin accumulation by affecting translocation of assimilated photosynthates. and Deeksha Dixit, N. K. Srivastava.
Možno dnes to znie ako prekvapujúce konštatovanie, ale fyzika na Slovensku nemá bohatú tradíciu, pretože jej rozvoj sa v podstate datuje od roku 1940, keď na Slovenskú vysokú školu technickú v Bratislave prichádza z Prahy Dionýz Ilkovič a keď sa následne zakladá aj Prírodovedecká fakulta Univerzity Komenského v Bratislave. Pod vedením prof. Ilkoviča sa na Ústave fyziky grupujú mladí slovenskí fyzici, medzi ktorými bol aj Vladimír Hajko. Tu, najprv ako vysokoškolák a potom ako asistent, sa zapája do pedagogickej a vedeckej činnosti., Alexander Feher., and Obsahuje seznam literatury
When compared to satellite detector measurements of dust particles of mass < 10^-6 g and optical meteor observations for mass > 10^-2 g, the flux of the interstitial radar meteors is discrepant: the radars render fluxes which seem too small by a factor of about 20-30. This has usually been explained as being due to the majority of the flux being held in low-velocity meteors which produce little ionization and hence have limited radar detectabilities. We propose an alternative hypothesis: that the discrepancy is due to wavelength-dependent effects, implying that conventional meteor radars {f > 20 MHz) only detect the lower-altitude underdense meteors. To test this we have determined the height distribution of radar meteors at 2 and 6 MHz, at which frequencies the echo ceilings are much higher than the 100-105 km limits of VHP radars. We find that the distributions peak at “105 km, fully 10 km above the peaks of VHP radars, with many meteors occurring to at least 140 km altitude. Additional observations using the powerful Jindalee radar in central Australia confirm these results, and show that the cumulative flux of particles of mass > 10"-6 g is about 9 x 10^-8 m^-2 sec^-1; this is consistent with satellite data and is over an order of magnitude larger than derived in previous radar meteor experiments.