Effect of Boronizing on Operating Stability of Steel AISI 304L under Erosion Impact of Hard Particles

Metal Science and Heat Treatment - The effect of solid boronizing at 950°C for 2 and 4 h on the phase composition, microstructure, hardness and abrasive wear of steel AISI 304L is studied...     

Second harmonic generation from a ferroelectric film

We derive an expression for transmittivity (T_SHG) of second harmonic generation (SHG) signals from a ferroelectric (FE) film. Intensities of up and down fields in the medium are investigated in relation to T_SHG. The derivations are made based on undepletion of input fields and nonlinear wave equation derived from the Maxwell equations. We present two cases: film without mirrors and with partial mirrors. Expressions for the newly derived nonlinear susceptibility coefficients of SHG for real crystal symmetry [J. Opt. Soc. Am. B 19 (2002) 2007] are used to get more realistic results. Variations in T_SHG with respect to film thickness are illustrated.     

Synthesis of heterocyclic metal complexes and their evaluation as marine antifoulants

4-Amino-3-thio-1,24-triazolidine (L₁) and 4-amino-5-thio-1,3,4-thiadiazole (L_II) as well as their metal complexes of the general formulae ML_I·2H₂O and ML_IICl (M; Pb(II), Cd(II) and Zn(II)) were prepared. With Sn(II), we obtained Sn(L_I)₂·2H₂O and SnL_IICl, respectively. The structures of the compounds were identified through elemental analysis, and IR and UV spectra measurements, in addition to thermal analysis in case of the metal complexes. The antifouling properties of the compounds were tested by their incorporation into paint formulations which were applied to PVC substrates and tested in water from Alexandria western harbour. When the compounds were added at 17·5% by volume, the coated panels were fouled after 3 months of immersion. The addition of 6·7% by volume of tributyltin oxide to 15·8% of the prepared compounds in one formulation elevated the paint efficiency and prevented fouling for 11 months. Paint containing solely tributyltin oxide at the same concentration was inactive against algae.     

The influence of socioeconomic and nutritional status on menarche in Nigerian school girls

Two once-daily electroconvulsive shocks (ECS) produced retrograde amnesia in rats trained on a Hebb-Williams maze; Verapamil (12.5 mg/kg, i.p.) or felodipine (10 mg/kg, p.o.) administered half an hour before each ECS attenuated this ECS-induced amnesia. Hence, these drugs may hold promise for the containment of amnesia induced by electroconvulsive therapy (ECT). Speculatively, one or more of several mechanisms may be involved: cerebral vasodilatation, enhancement of cholinergic tone, and inhibition of calcium-mediated impairment of neuronal function. These drugs may also act by attenuating the systolic surge in blood pressure during ECT, thereby decreasing edema due to cerebral hyperperfusion, as well as decreasing the possible transfer of potentially neurotoxic macromolecules through a putative breach in the blood-brain barrier.     

Capacitated Clustering Problems by Hybrid Simulated Annealing and Tabu Search

The capacitated clustering problem (CCP) is the problem in which a given set of weighted objects is to be partitioned into clusters so that the total weight of objects in each cluster is less than a given value (cluster ‘capacity’). The objective is to minimize the total scatter of objects from the ‘centre’ of the cluster to which they have been allocated. A simple constructive heuristic, a R-interchange generation mechanism, a hybrid simulated annealing (SA) and tabu search (TS) algorithm which has computationally desirable features using a new non-monotonic cooling schedule, are developed. A classification of the existing SA cooling schedules is presented. The effects on the final solution quality of the initial solutions, the cooling schedule parameters and the neighbourhood search strategies are investigated. Computational results on randomly generated problems with size ranging from 50 to 100 customers indicate that the hybrid SA/TS algorithm out-performs previous simulated annealing algorithms, a simple tabu search and local descent algorithms.     

The 9p21 region in bladder cancer cell lines: large homozygous deletion inactivate the CDKN2, CDKN2B and MTAP genes

Homozygous and hemizygous deletions of 9p21 are the earliest and most common genetic alteration in bladder cancer. The identification of two cell cycle regulators, CDKN2 and CDKN2B, that map to the common region of deletion has prompted the hypothesis that they are critical tumor suppressor genes in this malignancy. However, controversy as to whether these genes are the only or even the most important target in bladder cancer oncogenesis remains. To more clearly determine the effect of these 9p21 alterations, we mapped the homozygous deletions and performed a detailed mutational and expression analysis for CDKN2, CDKN2B and a closely linked gene, methylthioadenoside phosphorylase (MTAP), in 16 established bladder cancer cell lines. Nine of the 16 lines exhibit large (30 to > 2000 kb) homozygous deletions on 9p21. All deletions include at least one exon of CDKN2, eight of nine include CDKN2B, and six of nine include MTAP. MTAP function correlates with the genomic deletions. SSCP and sequence analysis does not reveal any inactivating point mutations of CDKN2 or of CDKN2B in any of the cell lines without homozygous deletions, and all express the CDKN2 and the CDKN2B mRNA as well as the encoded p16 protein. The p16 protein levels vary widely and are correlated with absent pRb expression. We conclude that the 9p21 deletions in bladder cancer usually inactivate the CDKN2. CDKN2B, and MTAP genes but that CDKN2 is the most common target. Other mechanisms for inactivating this gene in bladder cancer appear to be uncommon.     

Short-term preoperative radiotherapy results in down-staging of rectal cancer: a study of 1316 patients

OBJECTIVE: The incidence of back pain in children in our country is unknown. Several causes can produce this symptom, but it is necessary to rule out pathologies that require specific treatments. The goal of this work was to study the incidence and the etiology of back pain in children in our country. PATIENTS AND METHODS: We present a prospective study done in our Orthopedic Department during a period of 7 months. Twenty-two patients were referred with back pain of at least two months duration. The incidence was 2.9% compared to the total number of patients. The average age ranged from 7 to 17 years. RESULTS: A careful history and a radiological examination diagnosed 50% (11 cases) of the causes of backache in the present study. An idiopathic etiology was the most frequent cause and represented 9 patients (41%). In the remaining 12 cases (59%) pathological causes that required special treatment were identified including 2 cases of Scheuermann disease, 4 cases of painful scoliosis, 3 spondylolysis with spondylolisthesis, 2 cases of discitis, 1 benign neoplasm and 1 psychogenic cause. CONCLUSIONS: We recommend conservative management with the use of medication for relief of pain and physical therapy in the idiopathic cases. In the remaining cases, the specific treatment of the disease can improve the back pain.