The hydro-abrasive erosion wear behavior of duplex-treated surfaces of AISI H13 tool steel

The influence of duplex surface treatments consisting of a DC-pulsed plasma nitriding process and subsequent coatings of CrN and TiAlN deposited by physical vapor deposition(PVD)on AISI H13 tool steel was studied in this article.The treated samples were characterized using metallographic techniques,SEM,EDS,and microhardness methods.Hydro-abrasive erosion wear tests were performed in a specifically designed wear tester in which the samples were rotated in a wear tank containing a mixture of distilled water and ceramic abrasive chips with a fixed rotational speed.The wear rates caused by the abrasive particle impacts were assessed based on accumulated weight loss measurements.The worn surfaces were also characterized using optical microscopy,SEM,and EDS.Microhardness measurements indicated a significant increase in the surface hardness of the duplex-treated samples.The surfaces of the samples with the TiAlN coating were approximately 15 times harder than that of the untreated samples and 3 times that of the plasma nitrided samples.Hydro-abrasive erosion wear results showed that the duplex surface treatments,especially the CrN coating,displayed the highest erosion wear resistance.     

In vitro growth and drug sensitivity of tumor colony-forming units from human tumor xenografts

To investigate the feasibility of using tissue obtained from human tumor xenografts for in vitro screening of antineoplastic agents, we grew human tumor colony-forming units (CFU) in semisold agar from xenografts serially passaged in nude mice. Growth of human tumor CFU was accomplished from nine xenografts representing five different histological tumor types (ovarian carcinoma, adenocarcinoma of the colon, malignant melanoma, epidermoid carcinoma of the lung, and malignant astrocytoma). Cloning efficiency ranged from 0.04 to 0.1% and showed significant variability both between tumor types and between individual animals bearing the same type of xenograft. A high percentage of tumor CFU was in S phase [47 +/- 20% (S.D.)] as determined by the thymidine "suicide" technique. The number of tumor CFU observed increased linearly with increasing numbers of cells plated. In vitro drug sensitivity of the tumor CFU was assessed to Adriamycin, cis-platinum, and melphalan. The patterns of drug sensitivity were found to be reproducible and stable over a period of 9 months. Drug sensitivity curves to Adriamycin for five xenografts representing four tumor types showed complex patterns with plateau portions similar to those described for tumor CFU from primary tumors. The rank order of sensitivity of the tumors was compared to that of normal granulocyte-macrophage progenitors and, with the exception of the melanomas, was found to correlate well with clinical experience (order of sensitivity = colon less than ovary less than bone marrow). Growth of human tumor CFU from xenografts represents a reproducible and stable means for the study of the biology of tumor CFU and has potential applications as a means for screening new anticancer agents.     

Adaptive Q control for tapping-mode nanoscanning using a piezoactuated bimorph probe

A new approach, called adaptive Q control, for tapping-mode atomic force microscopy (AFM) is introduced and implemented on a homemade AFM setup utilizing a laser Doppler vibrometer and a piezoactuated bimorph probe. In standard Q control, the effective Q factor of the scanning probe is adjusted prior to the scanning depending on the application. However, there is a trade-off in setting the effective Q factor of an AFM probe. The Q factor is either increased to reduce the tapping forces or decreased to increase the maximum achievable scan speed. Realizing these two benefits simultaneously using standard Q control is not possible. In adaptive Q control, the Q factor of the probe is set to an initial value as in standard Q control, but then modified on the fly during scanning when necessary to achieve this goal. In this article, we present the basic theory behind adaptive Q control, the electronics enabling the online modification of the probe's effective Q factor, and the results of the experiments comparing three different methods: scanning (a) without Q control, (b) with standard Q control, and (c) with adaptive Q control. The results show that the performance of adaptive Q control is superior to the other two methods.     

A simulated annealing algorithm for multi-agent systems: a job-shop scheduling application

In this paper, a parallel implementation of the modular simulated annealing algorithm for classical job-shop scheduling is presented. The implementation is for a multi agent system running on the distributed resource machine, which is a novel, scalable, distributed virtual machine based on Java technology. The problems tackled are well known, difficult benchmarks, widely used to measure the efficiency of metaheuristics with respect to both the quality of the solutions and the central processing unit time. The empirical results obtained show that the method proposed is successful in comparison with a sequential version of modular simulated annealing algorithm and other methods described in the literature.     

Transformation calibration of a camera mounted on a robot

The paper describes the accurate calibration of the camera transformation for a vision system consisting of a camera mounted on a robot. The calibration includes an analysis of the linearity of the camera. A knowledge of the camera transformation allows the three-dimensional position of the object points to be determined using triangulation.     

A preclinical study of the effect of the animal polysaccharide chonsurid on reparative osteogenesis of the jaws

Experimental studies making use of morphological and x-ray methods demonstrated that in comparison with control (filling of mandibular bone defects with blood clots) chonsuride, an animal polysaccharide, promoted earlier filling of postoperative bone cavities with connective tissue replacement of this tissue with coarse-fiber bone tissue. Secondary restructuring and mineralization of bone regenerate were enhanced as well.     

Susceptibility to tropical theileriosis of calves born to dams immunized with Theileria annulata (Hisar) cell culture vaccine

Epidemiological evidence suggests that millet might play a role in the etiology of endemic goiter. Recently, we showed that a traditional fermentation procedure of two pearl millet (Pennisetum americanum L. Lecke) cultivars grown in Sudan modified their effects on the weight of the thyroid gland and thyroid hormone profile in rats. In the present study, we report that this fermentation procedure reduced the ash contents of millet by about 40% and removed considerable amounts of Mg (>50%), Zn (27-39%) and K (45%). Other minerals (Ca, Fe, Cu) were not affected. Feeding of one fermented cultivar resulted in significant reduction in bone Mg and Zn contents, whereas feeding of the other fermented cultivar resulted in reduction of bone Mg only. Dietary Mg intake and bone Mg contents correlated negatively with serum T3. Groups fed the millet diets had higher serum Se level compared to those fed wheat or casein diets and feeding of fermented millet resulted in a further increase in serum Se level. Thus our data indicate that in rats the enhanced effects of millet on the thyroid induced by fermentation is likely related to removal of minerals from millet and/or chemical transformation of the goitrogens contained in millet.     

Propagation dynamics of ultra-short high-power laser pulses in air: supercontinuum generation and transverse ring formation

Numerical and semi-analytical results of the propagation of high-power ultra-short near IR laser pulses propagating in ionizing air are presented.