Economic production order quantity and quality

The purpose of this study is to integrate a conventional production-inventory management approach and a process-quality design approach so as to promote quality and reduce costs. Because the integration of these two approaches into a single system is conducted under the influence of a deterioration process, estimated costs of production must be modified. Only then can these various costs be presented as a total cost for the present integrated system. This total cost includes: a setup cost for production reordering and process resetting, quality-related costs stemming from the loss of product quality along with a tolerance-related production process cost and a failure cost for product defects, backorder costs for production shortage, carrying costs generated by the storing and handling of inventory, and material costs for determining the process mean. The Taguchi quality loss function is introduced to assess quality loss in the system. The decision variables include the initial setting (process mean), process tolerance, and production order quantity. These variables need to be determined simultaneously to minimise the average total cost for a cycle time. An example is presented to demonstrate the proposed approach.     

Dietary niacin deficiency lowers tissue poly(ADP-ribose) and NAD+ concentrations in Fischer-344 rats

Poly(ADP-ribose) is synthesized in response to DNA strand breaks, using NAD+ as substrate, and has been implicated in the process of DNA repair. Because NAD+ can be synthesized from niacin or tryptophan, both of these components must be manipulated to alter niacin status. Six dietary treatments were used, including niacin-deficient (ND) diets and niacin-replete (NR) diets consumed ad libitum and the NR diets pair-fed (PF) to the ND intake. The ND, NR and PF diets contained either 80 g casein + 50 g gelatin/kg diet (8-5 diets) or 70 g casein + 60 g gelatin/kg diet (7-6 diets) to control tryptophan content. The 8-5ND and 7-6ND diets induced mild and severe symptoms of niacin deficiency, respectively, over a 3-wk period in male weanling Fischer-344 rats. Food intake and weight gain were suppressed in both of the ND groups compared with their respective NR controls. Weight gain was not different between ND animals and their PF counterparts. At 3 wk, blood, liver, kidney, heart and lung NAD+ concentrations for both 8-5ND and 7-6ND animals were all significantly lower than those for their respective PF groups. In the groups fed the 8-5 diets, liver poly(ADP-ribose) was lower in the ND group (64% of PF), with no difference between the NR and PF groups. In rats fed the 7-6 diets, poly(ADP-ribose) levels were further decreased in the ND group (43% of PF), but food restriction also exerted an independent effect (PF levels were 46% of NR levels).(ABSTRACT TRUNCATED AT 250 WORDS)     

Inhibition of human colon cancer cell growth by selective inhibition of cyclooxygenase-2

A considerable amount of evidence collected from several different experimental systems indicates that cyclooxygenase-2 (COX-2) may play a role in colorectal tumorigenesis. Large epidemiologic studies have shown a 40-50% reduction in mortality from colorectal cancer in persons taking aspirin or other nonsteroidal antiinflammatory drugs on a regular basis. One property shared by all of these drugs is their ability to inhibit COX, a key enzyme in the conversion of arachidonic acid to prostaglandins. Two isoforms of COX have been characterized, COX-1 and COX-2. COX-2 is expressed at high levels in intestinal tumors in humans and rodents. In this study, we selected two transformed human colon cancer cell lines for studies on the role of COX-2 in intestinal tumorigenesis. We evaluated HCA-7 cells which express high levels of COX-2 protein constitutively and HCT-116 cells which lack COX-2 protein. Treatment of nude mice implanted with HCA-7 cells with a selective COX-2 inhibitor (SC-58125), reduced tumor formation by 85-90%. SC-58125 also inhibited colony formation of cultured HCA-7 cells. Conversely, SC-58125 had no effect on HCT-116 implants in nude mice or colony formation in culture. Here we provide evidence that there may be a direct link between inhibition of intestinal cancer growth and selective inhibition of the COX-2 pathway.     

Polymorphic Mixes of Zirconia from a Borate Glass Melt

Yttria-stabilized zirconia crystals were produced by devitrification within a sodium borate glass containing zirconia and yttria. Yttria (3, 6, or 10 mol%) in zirconia was added as part of the starting material of the glass batch. Phase separation and crystallization occurred during the cooling and subsequent heat treatment of the glasses. The zirconia powders obtained after leaching away the sodium borate had surface areas between 16 and 48 m²/g. X-ray diffraction traces revealed a mixture of monoclinic, tetragonal, and cubic phases, the phase ratios of which depended on the composition of the glass.     

A model of cortically induced synchronization in the lateral geniculate nucleus of the cat: a role for low-threshold calcium channels

Recently Sillito et al. (Nature 1994;369:479-82) discovered correlations in the spike trains of a relatively distant pair of cat lateral geniculate nucleus cells when simultaneously stimulated by a drifting grating; no such correlation occurs when the visual cortex is removed. In a further analysis of the data, we have found that short, high-frequency bursts contribute substantially to the synchronization and we hypothesize that the origin of the bursts is the low-threshold calcium spike. Guided by this hypothesis, our model of the corticogeniculate pathway and early visual system reproduces the experimental data in nearly every detail, as well as making predictions about cortical activity during the synchronizing process. We also discuss the possible behavioral relevance of correlations in the geniculo-cortical loop as well as other neural systems.     

Improved high resolution image processing of bright field electron micrographs: II. Experiment

The new methods of nonlinear image processing are applied to high resolution experimental micrographs of chlorinated copper phthalocyanine taken on the Kyoto 500 kV electron microscope. With these new methods of image processing the phase and amplitude of the specimen transmission function are reconstructed from a defocus series of conventional transmission electron micrographs (bright field). Strong scattering, partial coherence and statistical noise have been included. Both of these new methods are based on the MAP (maximum a posteriori) criterion generalized to include reconstruction from multiple input images. In a companion paper (the first part of this two-part report) the theory behind these methods was presented and in this paper it is tested on actual experimental micrographs. A significant increase in resolution has been obtained with computer image processing. The point-to-point resolution obtained here with computer image processing of 500 kV electron micrographs is of the order of 1.2–1.4 Å which represents a 30–50% increase in resolution.     

Economic tolerance design for quality

This paper provides a few general mathematical models for determining product tolerances which minimize the combined manufacturing costs and quality loss. The models contain quality cost with a quadratic loss function and represent manufacturing costs with geometrical decay functions. The models are also formulated with multiple variables which represent the set of characteristics in a part. Applications of these models include minimizing the total cost with effective tolerance allocation in product design.