Continuous Temperature Rise Research Articles

Motion of individual human spermatozoa, both normal and lacking the outer dynein arms, during a continuous temperature rise

The effect of increasing temperature from 22-25 degrees C to 37 degrees C on various motion characteristics of individual normal human spermatozoa and spermatozoa lacking the outer dynein arms (LODA) was studied by using a new automatic microscopic tracking method. It was found that: 1) The curvilinear velocity (Vc, measured between 1-3 sec) of both normal and LODA spermatozoa, fluctuated more or less intensely between spermatozoa; this fluctuation was not thermodependent. 2) The average Vc in the two groups of spermatozoa increased with the rise in temperature at a similar rate (1 micron/sec/degrees C), but LODA spermatozoa had an initial Vc lower than that of normal spermatozoa (12.5 +/- 5.3 microns/sec and 34.2 +/- 8.2 microns/sec, respectively). 3) The profile of the Vc increase associated with the temperature rise was different for the two groups of spermatozoa: for LODA spermatozoa it was linear between 25-37 degrees C, whereas for normal spermatozoa a plateau was reached at about 31 degrees C. 4) Various patterns of trajectory were found for both normal and LODA spermatozoa; these patterns were unrelated to temperature. However, LODA spermatozoa had more linear trajectories than normal spermatozoa. 5) Plots derived from reaction rate theory showed that the activation enthalpy, delta H was a function of the increase of Vc for both normal and LODA spermatozoa, but that delta H was higher for LODA spermatozoa.

A New Stability Test for Passivated NiCr Thin Film Resistors

A suitable short-time test for analysis of long term stability is presented for the case of passivated NiCr thin film resistors revealing an aging characteristic which is not of Arrhenius type. Based on the in-situ measurement of resistance change during a continuous temperature rise, so-called temperature ramp curve, a well-defined correlation is found between the film stability and a characteristic temperature Tpwhere the temperature ramp curve exhibits a maximum. In this way, a reliable prediction of the long term stability can be made within only a few hours. The influence of the heating rate on the characteristic temperature Tpis shown. Furthermore, it is experimentally proved that the values of Tpare not essentially determined by the reversible resistance changes due to differential temperature coefficient of resistance, but indeed by irreversible aging processes.

A resistivity study of 7012 Al-Zn-Mg alloy commercial tempers

Electrical resistance measurements, performed during continuous temperature rise, have been carried out on a series of commercial tempers of the AA 7012 Al-Zn-Mg alloy. Results confirmed previously obtained DSC data about the presence of a Guinier-Preston zone structure in T4 and T6 tempers, and η'(MgZn 2) semicoherent precipitates in T6 and T73 tempers. It is demonstrated that the electrical resistivity measurements can supply complementary information about the precipitation of coherent GP zones, discriminating between coherent and semicoherent or incoherent precipitates.

Ostwald Ripening in Two Phase Mixtures With Application to Rapid Solidification

ABSTRACTRapid solidification invariably results in fine-scale microstructures with concomitant fine-scale segregation. These microstructures, which are produced relatively far from equilibrium, have large. specific surface energies and tend to coarsen rapidly. Experiments were carried out on highly supercooled bulk specimens of elemental P4 in which the average temperature of rapidly solidified 2-phase mixtures was accurately monitored over time. A continuous rise in temperature toward the bulk melting point is always measured, independent of the volume fraction of solid produced at recalescence. New theoretical work outlined here shows that this temperature rise can be associated with the Ostwald ripening of the as-solidified solid-plusliquid mixture. The new theory permits calculation of coarsening rates after recalescence and the distribution of dendritic particle sizes as a function of time. Implications for establishing limiting dendritic particle sizes are discussed.

The solid state reaction between hexaamminechromium(III) complexes and L-α-alanine

The solid reaction between [Cr(NH 3) 6]X 3(X − = Cl, I, SCN and NO 3) and L-α-alanine was studied under continuous rise in temperature and isothermal heating. Under continuous rise in temperature, the main products were [Cr(NCS) 3-(NH 3) 3] (X − = NCS) and [Cr(L-ala) 3] (X − = NO 3), when [Cr(NH 3) 6]Cl 3 and [Cr(NH 3) 6]I 3 as starting complexes were used; in both cases only the decomposition proceeds. Under isothermal heating at 150°C the main products were [CrCl(NH 3) 5]-Cl 2 (X − = Cl), [Cr(NH 3) 6]I 2 (X − = I), [Cr(NCS) 3(NH 3) 3] (X − = SCN) and [Cr(L-ala) 3] (X − = NO 3). In those matrix reactions, the ease of anion coordination was: SCN − > Cl − > I − > alanine. For the synthesis of tris(alaninato)chromium(III) complex the most desirable starting complex was [Cr(NH 3) 6](NO 3) 3. The solid state reaction between [Cr(en) 3]X 3 type complexes and NH 4X (X − = F, Cl, Br, I and SCN), KX (X − = Cl, Br and I), and NaSCN have been reported by Wendlandt and Stembridge 1. They reported that the reaction product in most cases, was cis-[Cr(en) 2Y 2]X, where Y and X are the same or different anions, depending upon the matrix material employed and the thermal matrix method appears to be a useful new route for the synthesis of bis(ethylendiamine(chromium(III) complexes. In the previous paper 2, the solid state reaction between [Cr(NH 3) 6](NO 3) 3 and L-amino acids has been utilized in the preparation of tris(amino acidato)chromium(III) complexes. The preparation of [Cr(L-ala) 3] by the solid state reaction between [Cr(NH 3) 6](NO 3) 3 and L-alanine have been reported. No studies on the effect of the counter-ion have been reported. In this paper, various hexaamminechromium(III) complexes, [Cr(NH 3) 6]X 3 (X − = Cl, I, SCN and NO 3), were heated with L-α-alanine under continuous rise in temperature and under isothermal heating at 150°C for studies on the ease of anion coordination. It will seen that the anion which replaces the ammonia in the hexaamminechromium(III) complex comes from either the alanine or counter-ion.