Multi-robot task allocation problem with multiple nonlinear criteria using branch and bound and genetic algorithms

The paper proposes the formulation of a single-task robot (ST), single-robot task (SR), time-extended assignment (TA), multi-robot task allocation (MRTA) problem with multiple, nonlinear criteria using discrete variables that drastically reduce the computation burden. Obtaining an allocation is addressed by a Branch and Bound (B&B) algorithm in low scale problems and by a genetic algorithm (GA) specifically developed for the proposed formulation in larger scale problems. The GA crossover and mutation strategies design ensure that the descendant allocations of each generation will maintain a certain level of feasibility, reducing greatly the range of possible descendants, and accelerating their convergence to a sub-optimal allocation. The proposed MRTA algorithms are simulated and analyzed in the context of a thermosolar power plant, for which the spatially distributed Direct Normal Irradiance (DNI) is estimated using a heterogeneous fleet composed of both aerial and ground unmanned vehicles. Three optimization criteria are simultaneously considered: distance traveled, time required to complete the task and energetic feasibility. Even though this paper uses a thermosolar power plant as a case study, the proposed algorithms can be applied to any MRTA problem that uses a multi-criteria and nonlinear cost function in an equivalent way. The performance and response of the proposed algorithms are compared for four different scenarios. The results show that the B&B algorithm can find the global optimal solution in a reasonable time for a case with four robots and six tasks. For larger problems, the genetic algorithm approaches the global optimal solution in much less computation time. Moreover, the trade-off between computation time and accuracy can be easily carried out by tuning the parameters of the genetic algorithm according to the available computational power.

Dairy cows fed on tropical legume forages: effects on milk yield, nutrients use efficiency and profitability

Two trials with multiparous dairy cows were conducted. Experiment 1 tested the effects of increasing forage proportion in the diet (500, 600, and 700 g/kg DM) when a mixed sorghum (Sorghum bicolor) and jackbean (Cannavalia ensiformis) silage was used as forage. Experiment 2 studied the substitution of sorghum silage and soybean meal by jackbean silage or fresh cowpea (Vigna unguiculata) forage in the diet. All diets were iso-energetic and iso-proteic. In each experiment, 30 cows were used and separated into three groups. In experiment 1, there were no differences in dry matter intake (DMI), milk yield (MY), or apparent total tract digestibility (aTTd) among the three diets, but milk fat content increased with increasing forage proportion, even though the similar neutral detergent fiber of all diets. Nitrogen use efficiency was highest in the diet containing 600 g forage/kg DM, and some evidence was observed for a better profitability with this forage proportion. In experiment 2, feeding legumes increased DMI despite no effects on aTTd. Milk yield increased in line with DMI, with a larger increase for the fresh cowpea. Nitrogen use efficiency and milk composition were not affected by the diets. The increased MY and lower feed costs increased the economic benefits when feeding legumes, particularly when feeding fresh cowpea. Feeding fresh cowpea or jackbean silage to dairy cows appears to be an alternative to soybean as protein source, ideally at a forage proportions of 600 g/kg DM, without altering milk yield and quality and increasing the farm profitability.

[Intravitreal triamcinolone combined with grid laser photocoagulation for patients with cystoid macular edema and advanced diabetic retinopathy: pilot study]

BACKGROUND

To determine if primary intravitreal injection of triamcinolone acetonide (TA) plus grid laser photocoagulation (GLP) is effective in treating cystoid diabetic macular edema (DME).

METHODS

Prospective comparative non-randomized clinical trial. Fourteen eyes (14 patients) diagnosed with cystoid DME were treated with GLP according to the Early Treatment Diabetic Retinopathy Study (ETDRS) guidelines, plus an intravitreal injection of 4 mg of TA. A matched control group (16 eyes [16 patients]) treated with GLP was selected retrospectively from our medical records. Best-corrected visual acuity (BCVA), and quantitative change in optical coherence tomography (OCT) macular thickness were assessed.

RESULTS

Mean follow up was 14.9 months (12 to 19 months). In 3 (21.4%) eyes BCVA increased > 2 ETDRS lines, in 5 (35.7%) eyes BCVA remained the same, and BCVA decreased >2 ETDRS lines in 6 (42.8%) eyes. Central macular thickness, as measured by OCT, decreased a mean of 106.2 μm (30.2%). The difference with the control group was not statistically significant (P = .2). Four (28.5%) eyes developed an increased in intraocular pressure in our study group.

CONCLUSIONS

Although all of our patients showed an improvement of cystoid DME by means of OCT and fluorescein angiography, 42.8% (6 eyes) lost 2 or more lines in BCVA with primary intravitreal injection of TA plus GLP. Primary intravitreal injection of TA plus GLP may not be effective for cystoid DME at 12-months.

Prognostic value of flow cytometry in surgically treated primary gastric lymphoma

AIM

To investigate whether flow cytometry could help to define the optimal therapeutic strategy of primary gastric lymphomas.

MATERIAL AND METHOD

Retrospective study of 46 patients having primary gastric lymphoma--according to Dawson criteria--in Ann Arbor stage IE and IIE, who were surgically treated. From selected paraffin-embedded tissue blocks of the tumor, DNA content was studied by flow cytometry (FC). Other pathological tumor features were analysed by hematoxiline-eosine and Giemsa stains as well as immunohistochemical study; any possible influence on postoperative survival was investigated through statistical analysis.

RESULTS

The DNA ploidy pattern was diploid in 40 cases (87%) and aneuploid (hyperdiploid) in 6 (13%). Postoperative survival probability (PSP) was 62.7% at 5 years. Statistical analysis showed significant prognostic value for Ann Arbor classification--with higher PSP for stage IE (p = 0.009)--and FC parameters: diploid tumors had higher PSP than aneuploid tumors. Also tumors having S-phase (p = 0.044) or G2-M phase values (p = 0.023) under the respective mean values had higher PSP. No influence on PSP was found for wall invasion, Helicobacter pylori infection, Isaacson's histologic type or resection margin involvement. No significant relationship was appreciated between Isaacson's histologic type and DNA ploidy patterns.

CONCLUSION

FC could be useful in assessing gastric lymphoma prognosis.

Absence of port-site metastases following staging laparoscopy for gastric carcinoma

BACKGROUND

port-site metastases (PSM) have been reported following oncological laparoscopic surgery. However, their frequency after laparoscopic examination in gastric cancer has not been well established.

MATERIAL AND METHODS

prospective follow-up of 41 patients having had a staging laparoscopy and a follow-up longer than 12 months. Mean age was 65 years (29-89). After staging, an open gastrectomy was performed in 33 cases. Mean follow-up was 21.4 (12-66) months. PSM was defined as a node in the former port-site wound with adenocarcinoma histology at biopsy.

RESULTS

no patient showed clinical signs of PSM or port-site recurrence, even in advanced stages. We had no morbidity or postoperative mortality attributable to laparoscopic manoeuvres, and no need for laparotomy in cases without a gastrectomy indication.

CONCLUSIONS

our results suggest that staging laparoscopy is a safe procedure in gastric carcinoma, as it is not associated with PSM after even considerable follow-up, and has a very low complication rate.

Do current indications for surgery of primary gastric lymphoma exist?

OBJECTIVE

To analyze the results of our series in order to assess whether surgical excision is still a valid therapeutic option in case the patient needs surgery. Secondarily, to analyze Helicobacter pylori infection rate.

PATIENTS AND METHOD

A retrospective study of 69 consecutive patients having stage IE-IIE primary gastric lymphoma; of these, 65 were treated by gastrectomy between 1974 and 1999. Mean age: 62.6 years (28-85). New staining of paraffin-embedded samples from the surgical specimen were carried out (hematoxiline-eosine, Giemsa, immunohistochemistry) and reviewed. The histological classification was performed according to Isaacson's criteria. The statistical analysis was done by Chi-squared and Fisher's exact tests, as well as Kaplan-Meier and Log-Rank tests.

RESULTS

Mortality was 9.2%. There were non-fatal complications in 10.8%. Helicobacter pylori was identified in 62.7%. Seven patients (11.9%) suffered a relapse. The 5-year survival probability was 87%. The statistical analysis did not show any influences of Ann Arbor stage, gastric wall invasion, Helicobacter pylori infection, histological type, or margin resection involvement on survival.

CONCLUSIONS

Surgical excision provides a high rate of complete remissions and excellent long-term survival with acceptable mortality. Therefore it appears to be a valid treatment in case of emergency surgery, incidental finding, or lack of histological diagnosis.

Surprising sun: a new step towards a complete picture?

Important revisions of the solar model ingredients have appeared recently. We first show that the updated CNO composition suppresses the anomalous position of the Sun in the known galactic enrichment. The following law, He/H = 0.075 + 44.6 O/H in number fraction, is now compatible with all the indicators. We then suggest some directions of investigation to solve the discrepancies between the standard model and solar seismic observations. We finally update our predicted neutrino fluxes using a seismic model and all the recent progress. We get 5.31 +/- 0.6 x 10(6)/cm2/s for the total 8B neutrinos, 66.5 +/- 4.4 SNU and 2.76 +/- 0.4 SNU for the gallium and chlorine detectors, all in remarkable agreement with the detected values including neutrino oscillations for the last two. So, the acoustic modes and detected neutrinos see the same Sun, but the standard model fails to reproduce them.

Cholesterol stabilizes hemifused phospholipid bilayer vesicles

Cholesterol was found to inhibit full fusion of oppositely charged phospholipid bilayer vesicles by stabilizing the contacting membranes at the stage of the hemifused intermediate. Vesicles of opposite charge containing different amounts of cholesterol were prepared using cationic (1,2-dioleoyl-sn-glycero-3-ethylphosphocholine) and anionic (dioleoylphosphatidylglycerol) phospholipids. Pairwise interactions between such vesicles were observed by fluorescence video microscopy in real time after electrophoretically maneuvering the vesicles into contact. Hemifusion accounted for more than 80% of the observed events when the vesicles contained 33-50 mole% cholesterol. In contrast, vesicles containing only a small proportion of cholesterol (</=10 mole%), underwent full fusion in approx. 70% of the interactions monitored. The role of cholesterol is explained both as favoring the formation of the hemifused intermediate according to the adhesion-condensation mechanism of bilayer fusion and as disfavoring the transition from hemifusion to full fusion on the basis of reduced tension in the vesicle bilayers.

Calcium triggers an intramolecular association of the C2 domains in synaptotagmin

Synaptotagmin I is a critical component of the synaptic machinery that senses calcium influx and triggers synaptic vesicle fusion and neurotransmitter release. Fluorescence resonance energy transfer studies conducted on synaptotagmin demonstrate that calcium concentrations required for fusion induce a conformational change (EC(50) approximately 3 mM) that brings the two calcium-binding C2 domains in synaptotagmin closer together. Analytical ultracentrifugation studies reveal that synaptotagmin is monomeric under these conditions, indicating that this calcium-triggered association between the C2 domains is intramolecular, rather than intermolecular. These results suggest a mechanism for synaptotagmin function at the presynaptic plasma membrane that involves the self-association of C2 domains.

Glutamate metabolism by squid nerve fiber sheaths

The extrasynaptic region of the squid giant nerve fiber exhibits neuron-Schwann cell interactions that appear to involve glutamate as a mediator. In an earlier work, it was demonstrated that the periaxonal sheaths of such nerves (where the Schwann cells are located) possess the capacity to transport glutamate. However there was no information available about the possible fate of the glutamate incorporated into the sheaths. In this study, it is demonstrated that the periaxonal sheaths of the extrasynaptic region of squid giant nerves are capable of metabolizing glutamate. Sheaths incubated with 10 microM [1-14C] glutamate produced [14C] O2 in a manner proportional to time and estimated cell water volume. At least 45% of this CO2 production was determined to be independent of transaminase catalyzed isotopic exchange, thus reflecting real degradation (decarboxylation) of glutamate. It was also demonstrated that the sheaths were capable of glutamine synthesis. Taken together, the findings of our laboratory indicate not only that the Schwann cells of the sheaths fulfil the requirements for a site for the uptake and metabolism of transmitter glutamate in the squid giant nerve but also that certain metabolic characteristics associated with the neuro-glial unit around synapses are also found in non-synaptic areas of nerve fibers.

Substructure and responses of cholinergic synaptic vesicles in the atomic force microscope

The substructure and responses of individual 100-nm synaptic vesicles to osmotic stress have been probed with an atomic force microscope (AFM) operating in tapping mode. Cholinergic synaptic vesicles from the electric organ of Torpedo californica were imaged continuously as the osmolarity of the buffer was decreased. Vesicles in hyposmotic buffer lysed to form flat circular structures on the mica surface with a diameter about two times that of intact vesicles and a thickness of 7.2 +/- 1.7 nm, which can accommodate the lipid bilayer plus the internal proteoglycan. Images of intact vesicles in air reveal creases in the membrane surface. Phase mode AFM images of lysed vesicles in air show the presence of a material not seen on intact vesicles that might be intravesicular proteoglycan released from the membrane at very low osmotic and ionic strength.

Glutamate uptake by squid nerve fiber sheaths

The squid giant nerve exhibits neuron-Schwann cell interactions that appear to involve glutamate as a mediator; however, there is no information available about the possible fate of the released glutamate. In this study, it is demonstrated that the periaxonal sheaths of the extrasynaptic regions of squid giant nerves (where the glial cells are located) possess the capacity to transport glutamate. In whole intact nerves incubated with low-glutamate concentrations for long periods of time, the majority of the glutamate incorporated into the tissue was found in the sheaths. Axoplasm-free sheaths incubated for long periods of time with low concentrations of glutamate were able to accumulate this amino acid against a large apparent concentration gradient. Sheath glutamate uptake occurred in a sodium-dependent fashion over a wide concentration range and displayed both high- and low-affinity components. Glutamate uptake at concentrations below the Km of the high affinity component was independent of homoexchange and displayed a specificity that is similar to that described for high-affinity glutamate transport in mammalian brain. It is proposed that the sheath transport systems may be involved in the regulation of glutamate levels in the intercellular clefts of the nerve fiber, as part of the glutamatergic neuron-glial signaling mechanisms in the squid giant nerve fiber.

Aspartate aminotransferase and glutamate dehydrogenase activities in the squid giant nerve

The present study sought to investigate the presence and distribution of some enzymatic activities involved in the metabolism of glutamate in the giant nerve fiber of the tropical squid Sepioteuthis sepioidea. Specific activities of aspartate aminotransferase and glutamate dehydrogenase were evaluated in homogenates of the isolated giant fiber, extruded axoplasm, and axoplasm-free giant nerve fiber sheaths. The activities of both enzymes were present in the tissue. The specific activity of aspartate aminotransferase was similar in axoplasm and sheaths. However, the specific activity of glutamate dehydrogenase was an order of magnitude higher in the sheaths. This finding is discussed in the framework of the hypothesis that proposes that a differential distribution of the enzymes of the glutamatergic system between the axonal and neuroglial compartments forms part of a system of communication between these cells whose neuronal signal may be glutamate.

Potentiation by levamisole, methisoprinol, and adenine or adenosine of the inhibitory activity of human interferon against encephalomyocarditis virus

The antiviral action of different human interferons against encephalomyocarditis virus in HeLa cell cultures was analyzed. Cell treatment with levamisole (200 micrograms/ml), methisoprinol (1 mg/ml), or adenine or adenosine (33 or 100 micrograms/ml, respectively) potentiated the anti-encephalomyocarditis virus activity of human interferon by 8- to 32-fold. A higher level of potentiation (256-fold) was achieved either by combined treatments with levamisole plus methisoprinol or by treatment with one of these compounds plus adenine or adenosine.