Location and allocation of service units on a congested network

We consider the problem of locating facilities and allocating servers on a congested network (LASCN). Demands for service that originate from the nodes are assumed to be Poisson distributed and the servers provide a service time that is exponentially distributed. The objective is to minimize the total cost of the system which includes a fixed installation cost, a variable server cost, a cost associated with travel time and a cost associated with the waiting time in the facility for all the customers. The problem is formulated using non-linear programming and subsequently analyzed. Results for exact and approximate solution approaches are reported. We also show that we can modify the approaches to solve the LASCN with constraints limiting both the travel time to the servers and the waiting time of customers.     

The route expropriation problem

This paper considers the problem of selecting obnoxious routes (e.g., routes used to transport hazardous material) on a transportation network assuming that population centers on or outside the network within a certain distance from the selected routes can be expropriated at a given price. The objective is to select the routes so as to minimize the total weighted transportation and expropriation costs. For the single-flow problem, a polynomial algorithm is developed. For the multiple-flow problem, a branch-and-price algorithm using column generation is developed and its efficiency is tested with computational experiments.     

The associative memory deficit of older adults: The role of strategy utilization.

Past research has established an associative deficit hypothesis (e.g., M. Naveh-Benjamin, 2000) that attributes part of older adults' poor episodic memory performance to their difficulty in creating and retrieving cohesive episodes. Here, the authors evaluate the degree to which this deficit can be reduced by older adults' use of associative strategies. Young and older adults learned word pairs under either intentional-learning instructions or instructions eliciting associative strategies either at encoding or both at encoding and at retrieval, and they then took tests on their memory for both the components and the associations. Results replicated the associative deficit of older adults under intentional-learning instructions. In addition, they showed that instructions to use appropriate associative strategies during either encoding or, even more so, during encoding and retrieval resulted in a significant decrease in the associative deficit. The theoretical and applied implications of these results are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of two bowel preparations for colonoscopy: sodium picosulphate with magnesium citrate versus sulphate-free polyethylene glycol lavage solution

OBJECTIVES: Adequate preparation of the bowel is essential for accurate colonoscopic examination. We compared colonic preparation with sodium picosulphate plus magnesium citrate (SPS-Mg) with sulphate-free polyethylene glycol electrolyte lavage (PEG-EL) solution before colonoscopy, for quality of bowel cleansing, patient discomfort, and side effects. METHODS: Sixty-eight consecutive patients were randomly assigned to receive either 3 sachets of SPS-Mg (16.5 g each) (n = 39) or 3 L of PEG-EL (n = 29) on the day before colonoscopy. Shortly before the procedure each patient was interviewed to determine the degree of discomfort (1 = none or mild, 2 = moderate, 3 = severe) and side effects. The quality of bowel cleansing was graded by a gastroenterologist who was unaware of the method of preparation (from 1 = poor to 4 = excellent). RESULTS: Of the 29 PEG-EL patients, four (14%) did not complete the preparation because of side effects. The degree of discomfort was significantly greater with PEG-EL (mean score, 2.3 +/- 0.7) than with SPS-Mg (mean score, 1.4 +/- 0.5; p < 0.01). Nausea and vomiting were significantly more common in the PEG-EL group (38% vs 13%; p < 0.05). Using intention-to-treat analysis, bowel cleansing proved to be significantly better with SPS-Mg than with PEG-EL (mean score +/- SD, 3.05 +/- 0.9 and 2.57 +/- 1.0, respectively; p = 0.036). CONCLUSIONS: Colonic preparation with SPS-Mg is better tolerated, associated with significantly fewer side effects, and results in higher quality bowel cleansing than preparation with PEG-EL.     

Minimum fuel lunar trajectories for a low-thrust power-limited spacecraft

Minimum fuel trajectories from a low Earth parking orbit to a low Moon orbit are obtained for a low-thrust power-limited spacecraft with thrust acceleration levels of the order of 10^–3 G. The trajectories are found by matching an Earth spiral to a Moon spiral at some intermediate distance. Results are given for the planar case and for the three dimensional case where the Moon orbit is polar.Received his Ph.D. under Professor John V. Breakwell in 1990. Currently at Rafael, MOD, Israel.     

Digestion of delta-endotoxin by gut proteases may explain reduced sensitivity of advanced instar larvae of Spodoptera littoralis to CryIC

The present study describes the correlation between gut protease activity of lepidopteran larvae of different instars, the inactivation of Bacillus thuringiensis delta-endotoxins in crystalline and noncrystalline forms, and the reduced susceptibility of advanced larval instars of Spodoptera littoralis to the toxin. The original assembly of delta-endotoxins in a crystal structure is essential for causing efficient larval mortality. Denaturation and renaturation (D/R) of delta-endotoxin crystals increased the vulnerability of the toxin molecules to proteolysis, reduced their capability to kill neonate larvae of S. littoralis, but sustained most of their larval growth-inhibition activity. E. coli-produced CryIC delta-endotoxin applied as a fraction of inclusion bodies exerted a growth inhibition effect, similar to the molecules released from the crystals by denaturation and subsequent renaturation. Incubation of CryIC with gut juice of 1st or 2nd instar larvae, left part of the CryIC toxin intact, while the toxin was completely degraded when incubated with gut juice of 5th instar larvae. The degradation rate was consistent with the increase of protease specific activity of the gut juice during larval development. This increase in toxin degradation may account for the loss of sensitivity of 5th instar larvae to CryIC. Specific protease inhibitors such as PMSF and Leupeptin were shown to inhibit gut proteases activity in all instar larvae, while, 1,10 phenanthroline, TLCK and TPCK were effective only in young instar larvae. The differential effect of protease inhibitors on proteases obtained from different larval instars indicated that gut juice protease profiles change with larval age. The observed quantitative and qualitative differences in degradation of delta-endotoxin by larval gut proteases that occur during larval maturation may account for the difference in susceptibility to the delta-endotoxin. This finding should be taken into consideration when designing strategies for the development of transgenic crops expressing delta-endotoxins as potent insecticidal proteins.     

Locating service facilities to reduce lost demand

We analyze the problem of locating a set of service facilities on a network when the demand for service is stochastic and congestion may arise at the facilities. We consider two potential sources of lost demand: (i) demand lost due to insufficient coverage; and (ii) demand lost due to congestion. Demand loss due to insufficient coverage arises when a facility is located too far away from customer locations. The amount of demand lost is modeled as an increasing function of the travel distance. The second source of lost demand arises when the queue at a facility becomes too long. It is modeled as the proportion of balking customers in a Markovian queue with a fixed buffer length. The objective is to find the minimum number of facilities, and their locations, so that the amount of demand lost from either source does not exceed certain pre-set levels. After formulating the model, we derive and investigate several different integer programming formulations, focusing in particular on alternative representations of closest assignment constraints. We also investigate a wide variety of heuristic approaches, ranging from simple greedy-type heuristics, to heuristics based on time-limited branch and bound, tabu search, and random adaptive search heuristics. The results of an extensive set of computational experiments are presented and discussed.     

Thrombotic complications in essential thrombocythemia with relatively low platelet counts

The purpose of this prospective study was to determine the overall incidence and distribution of lumbo-sacral degenerative changes (i.e. disc protrusion or extrusion, facet degeneration, disc degeneration, nerve root canal stenosis and spinal stenosis) in patients with and without a lumbo-sacral transitional vertebra (LSTV). The study population consisted of 350 sequential patients with low back pain and/or sciatica, referred for medical imaging. In all cases CT scans of the lumbo-sacral region were obtained. In 53 subjects (15%) and LSTV was found. There was no difference in overall incidence of degenerative spine changes between the two groups. We did find, however, a different distribution pattern of degenerative changes between patients with and those without an LSTV. Disc protrusion and/or extrusion occurred more often at the level suprajacent to the LSTV than at the same level in patients without LSTV (45.3% vs 30.3%). This was also the case for disc degeneration (52.8% vs 28%), facet degeneration (60.4% vs 42.6%) and nerve root canal stenosis (52.8% vs 27.9%). For spinal canal stenosis there was no statistically significant difference between the two categories. In conclusion, our findings indicate that an LSTV does not in itself constitute a risk factor for degenerative spine changes, but when degeneration occurs, it is more likely to be found at the disc level above the LSTV.     

Auditory nerve representation as a front-end for speech recognition in a noisy environment

We describe here a computational model based upon the temporal characteristics of the information in the auditory nerve-fiber firing patterns. The model produces a frequency domain representation of the input signal in terms of the ensemble histogram of the inverse of the interspike intervals, measured from firing patterns generated by a simulated nerve-fiber array. The nerve-fiber mechanism is modeled by a multi-level-crossing detector at the output of each cochlear filter. We use 85 cochlear filters, equally spaced on a log-frequency scale from 200 Hz to 3200 Hz, and the level crossings are measured at positive threshold levels which are uniformly distributed in log scale. The resulting Ensemble Interval Histogram (EIH) pseudo spectrum shares two main properties: (1) fine spectral details are well preserved in the low-frequency region but become fuzzy at the high-frequency end; (2) the EIH spectrum is more robust in noise, compared with the traditional Fourier spectrum. This representation of the speech has been used as a front-end to a Dynamic Time Warping (DTW), speaker-dependent, isolated word recognizer. The database consisted of a 39-word alpha-digits vocabulary spoken by two male and two female speakers, in different levels of additive white noise. In the noise-free case, the performance of the EIH-based front-end is comparable to a conventional Fourier Transform (FFT)-based front-end. In the presence of noise, however, the EIH-based front-end is more robust. Compared with the FFT-based front-end, with increasing noise the recognition scores drop more slowly, the resulting gap increases as the SNR values decreases. Quantitatively, with the EIH-based front-end the recognizer achieves a given recognition score with global-SNR values which are between 5 dB and 15 dB lower.     

GYO reductions,canonical connections,tree and cyclic schemas,and tree projections

Database schemas may be partitioned into two subclasses: three schemas and cyclic schemas. The analysis of tree vs . cyclic schemas introduced the concepts of GYO reductions, canonical connections, and tree projections. This paper investigates the intricate relationships among these concepts in the context of universal relation databases.