Odd Perfect Numbers: Some New Issues

Periodica Mathematica Hungarica -     

Anomalous magnetic hysteresis loops and smallH c1 values in highT c superconductors

We have studied the hysteresis loops of RBa₂Cu₃O₇ (R=Gd, Ho and Y) and detected anomalies in some of them. The observed anomalies support a recent prediction by Ravi Kumar and Chaddah based on an extension of Bean’s model. The anomalies indicate lowH _c1 values and we have confirmed this by studying the onset of low-field hysteresis in less than 10 Oe at 77 K for these highT _c superconductors.     

Ligand effect in epoxidatidns by hydroperoxides using molybdenum catalyst: epox idation of 3-carene

Epoxidation of (+)-3-carene with pinane hydroperoxide in presence of various transition metal catalysts, has been evaluated as a preparative method for (+)-3α,4α-epoxycarane. Catalysts based on Mo(VI) were found to be most suitable. A distinct ligand effect was noted for this oxidation and a plausible rationale is put forward.     

Benzohydroxamic acid as a reductometric titrant: Determination of manganese, chromium and vanadium in steels

A method has been developed for the rapid determination of manganese and chromium by direct stepwise reductometric titration with benzohydroxamic acid, and of vanadium by titration with ascorbic acid (with benzohydroxamic acid as indicator) in the same aliquot. The method is free from the interference of common alloying elements present in steels. Some BCS steel samples have been analysed with good precision and accuracy.     

Organic reactions in a solid matrix-vi: Silica-gel supported reagents for the isolation of aldehydes and ketones

Semicarbazide-on silica gel and Girard-T-on-silica gel are described and evaluated as convenient reagents for efficient isolation of aldehydes and ketones from mixtures with other usual neutral organic components Semicarbazide-on-silica gel, which can be readily prepared, can effectively replace the classical Girard reagents, for the isolation of aldehydes and ketones in most cases.     

Self-assembly of C(3)(h) and C(s) symmetric keto-enamine forms of tris(N-salicyl-ideneanilines) into columnar phases: a new family of discotic liquid crystals

A new class of discotic liquid crystals derived from tris(N-salicylideneanilines) existing exclusively in their C3h and Cs keto-enamine tautomeric forms is reported. These compounds self-assemble to form columnar liquid crystalline phases with a small core-core separation as evidenced by X-ray diffraction studies.     

Analysis of the effect of the temperature variation on transistor parameters and gain

The variations of the hybridh-parameters and the gain of the transistor with temperature have been studied by obtaining an analytical expression. The values of theh-parameters are calculated in the entire temperature range 213–473 K with the help of the expression obtained and the calculated values are in good agreement with the experimental data. The gain of the transistor extracted from the obtained values of the parameters is seen to be in excellent agreement with the experimental values.

---

Zusammenfassung Die Änderung des Hybrid-Parameters und die Verstärkung des Transistors mit der Temperatur wurden untersucht, indem ein analytischer Ausdruck hierfür erhalten worden ist. Die Werte derh-Parameter wurden im ganzen Temperaturbereich von 213 bis 473 K mit Hilfe des erhaltenen Ausdrucks berechnet und die berechneten Angaben sind in guter Übereinstimmung mit den Versuchsergebnissen. Die aus den erhaltenen Parameterwerten errechnete Transistorverstärkung stimmt mit den Versuchswerten sehr gut überein.

---

Résumé On a étudié, à l'aide d'une expression analytique obtenue pour le but poursuivi, la variation des paramètresh hybrides et l'amplification du transistor avec la température. On a calculé, à l'aide de cette expression, les paramètresh dans tout l'intervalle des températures comprises entre 213 et 473 K. Les valeurs calculées sont en bon accord avec les données d'expériences. L'amplification du transistor, calculée à partir des valeurs obtenues, est en excellent accord avec les valeurs d'expériences.

---

h- . h 213–473 . , , , .

---

---

Ex-student (M.Sc.) of Department of Physica, R.E.C. Waranga-506004, India.

---

The work was done in the Department of Physica, R.E.C. Warangal-506004, India.

---

The authors wish to express their thanks to Dr. V. V. Rao and Dr. G. S. Verma for their interest in the present project. One of us (K.S.D.) is also grateful to Dr. R. A. Rashid and Dr. R. H. Misho.