The prediction of precipitation strengthening in microalloyed steels

The effectiveness of interphase precipitation strengthening in microalloyed steels depends on the temperature dependence of the solubility of the precipitation phase in austenite and on the temperature utilized in soaking. Using an approximate method of calculating the solubility of microalloying elements in the presence of both carbon and nitrogen, a precipitation strengthening potential parameter was developed. On relating this parameter to the chemical compositions and thermal histories of microalloyed steels, it was determined that the interphase precipitation strengthening determined in this and other studies increases linearly with the strengthening potential parameter. On the basis of the linear dependence of precipitation strengthening on the precipitation potential and other observations, it appears that interphase precipitation strengthening is not due to the Orowan looping mechanism but rather to interactions of gliding dislocations with the strain fields of coherent precipitates.     

The origin of efferent pathways from the primary visual cortex, area 17, of the macaque monkey as shown by retrograde transport of horseradish peroxidase

The retrograde transport of horseradish peroxidase has been used to identify efferent cells in area 17 of the macaque. Cells projecting to the lateral geniculate nucleus are small to medium sized pyramidal neurons with somata in lamina 6 and the adjacent white matter. The projection to the parvocellular division arises preferentially from the upper half of lamina 6, while that to the magnocellular division arises preferentially from the lower part of the lamina. The projection to both superior colliculus and inferior pulvinar arises from all sizes of pyramidal neurons lying in lamina 58 (Lund and Boothe, '75); at least pyramidal neurons of lamina 5B send collateral axon branches to both destinations. Injections with extensive spread of horseradish peroxidase show that many cells of lamina 4B and the large pyramidal neurons of upper lamina 6 also project extrinsically but their terminal sites have not been identified. Other studies have indicated that cells of laminae 2 and 3 project to areas 18 and 19. Therefore every lamina of the visual cortex, with the exception of those receiving a direct thalamic input, contains cells projecting extrinsically. Further, each lamina projects to a different destination and from Golgi studies can be shown to contain cells with specific patterns of dendritic branching which relate to the distribution of thalamic afferents and to the patterns of intracortical connections. These findings emphasise the significance of the horizontal organisation of the cortex with relation to the flow of information through it and contrast with the current concept of columnar organisation shown in physiological studies.     

Primary synovial chondromatosis of the ankle. A case report

A case of primary diffuse synovial chondromatosis of the ankle with long-term follow-up is reported. Trauma is implicated as a precipitating factor. This unusual, distinctive synovial neoplasm presents readily recognizable pathological features (Fig. 2). Specific diagnostic criteria are presented. The differential diagnosis of primary synovial chondromatosis includes secondary reactive synovial chondromatosis and synovial chondrosarcoma. The usual sources of osteochondritic loose bodies, on the other hand, are traumatic joint disruption, osteoarthritis, and infectious disorders. Acute primary synovial chondromatosis is adequately treated by removal of the loose bodies and synovectomy. Postoperative prognosis is dependent on the stage of the disease at the time of surgery. In this acute case, the patient had minimum impairment, and ankle roentgenograms twenty years after the arthrotomy were normal (Fig. 3).     

The Uba2 and Ufd1 proteins of Saccharomyces cerevisiae interact with poly(A) polymerase and affect the polyadenylation activity of cell extracts

We investigated calcium influx in the long lasting potentiation induced in area CA1 of rat hippocampus by brief bath application of the G-protein activator A1F4-(NaF/AlCl3). Brief (10 min) bath application of A1F4 in standard saline (with 2 mM Ca2+) consistently induced a long lasting potentiation which was not observed if A1F4 was bath-applied in nominally calcium free saline. Increasing the potential calcium influx, either by raising extracellular calcium concentration to 3.5 mM or by addition of the voltage operated calcium channel (VOCC) agonist BayK8644, failed to increase the number of slices exhibiting potentiation or the mean level of potentiation. Bath application of AlF4 in the presence of the VOCC antagonist failed to block the potentiation and A1F4- readily induced a long lasting potentiation under voltage clamp conditions, strongly suggesting that the calcium influx required for A1F4-induced potentiation is not through NMDA receptors or VOCC channels. It is suggested that the calcium required may be provided by an ongoing recharging and emptying of IP3 sensitive intracellular Ca2+ stores.