An elementary proof of Sylvester’s double sums for subresultants

In 1853 Sylvester stated and proved an elegant formula that expresses the polynomial subresultants in terms of the roots of the input polynomials. Sylvester’s formula was also recently proved by Lascoux and Pragacz using multi-Schur functions and divided differences. In this paper, we provide an elementary proof that uses only basic properties of matrix multiplication and Vandermonde determinants.     

Variable cross-resistance to Cry11B from Bacillus thuringiensis subsp. jegathesan in Culex quinquefasciatus (Diptera: Culicidae) resistant to single or multiple toxins of Bacillus thuringiensis subsp. israelensis

A novel mosquitocidal bacterium, Bacillus thuringiensis subsp. jegathesan, and one of its toxins, Cry11B, in a recombinant B. thuringiensis strain were evaluated for cross-resistance with strains of the mosquito Culex quinquefasciatus that are resistant to single and multiple toxins of Bacillus thuringiensis subsp. israelensis. The levels of cross-resistance (resistance ratios [RR]) at concentrations which caused 95% mortality (LC95) between B. thuringiensis subsp. jegathesan and the different B. thuringiensis subsp. israelensis-resistant mosquito strains were low, ranging from 2.3 to 5.1. However, the levels of cross-resistance to Cry11B were much higher and were directly related to the complexity of the B. thuringiensis subsp. israelensis Cry toxin mixtures used to select the resistant mosquito strains. The LC95 RR obtained with the mosquito strains were as follows: 53.1 against Cq4D, which was resistant to Cry11A; 80.7 against Cq4AB, which was resistant to Cry4A plus Cry4B; and 347 against Cq4ABD, which was resistant to Cry4A plus Cry4B plus Cry11A. Combining Cyt1A with Cry11B at a 1:3 ratio had little effect on suppressing Cry11A resistance in Cq4D but resulted in synergism factors of 4.8 and 11.2 against strains Cq4AB and Cq4ABD, respectively; this procedure eliminated cross-resistance in the former mosquito strain and reduced it markedly in the latter strain. The high levels of activity of B. thuringiensis subsp. jegathesan and B. thuringiensis subsp. israelensis, both of which contain a complex mixture of Cry and Cyt proteins, against Cry4- and Cry11-resistant mosquitoes suggest that novel bacterial strains with multiple Cry and Cyt proteins may be useful in managing resistance to bacterial insecticides in mosquito populations.     

MDMA ('Ecstasy') enhances 5-HT1A receptor density and 8-OH-DPAT-induced hypothermia: blockade by drugs preventing 5-hydroxytryptamine depletion

One week after a single administration of 3,4-methylenedioxymethamphetamine (MDMA HCI, 30 mg/kg i.p.), 5-HT1A receptor density was significantly increased by approximately 25-30% in the frontal cortex and hypothalamus of rats. The increased density correlated with the potentiation of the hypothermic response to the 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT, 1 mg/kg s.c.). Hypothalamic 5-HT7 receptors, which also bind 8-OH-DPAT, were not changed, however, by MDMA. Fluoxetine (5 mg/kg s.c.), ketanserin (5 mg/kg s.c.) or haloperidol (2 mg/kg i.p.), given 15 min prior to MDMA, prevented the depletion of 5-hydroxytryptamine (5-HT) induced by MDMA and also blocked the effects of this neurotoxin on 5-HT1A receptor density and on 8-OH-DPAT-induced hypothermia. The protection afforded by drugs against 5-HT loss did not correlate, however, with the antagonism of the acute hyperthermic effect of MDMA. The present results indicate that drugs able to prevent or to attenuate MDMA-induced 5-HT loss also prevent the changes in 5-HT1A receptor density as well as the enhanced hypothermic response to the 5-HT1A receptor agonist 8-OH-DPAT in MDMA-treated rats.     

Effect of cisplatin and c-myb antisense phosphorothioate oligodeoxynucleotides combination on a human colon carcinoma cell line in vitro and in vivo

We investigated the effect of c-myb antisense phosphorothioate oligodeoxynucleotides [(S)ODNs] and cisplatin (CDDP) combination on the human colon carcinoma cell line LoVo Dx both in vitro and in nude mice bearing LoVo Dx solid tumour. We show that antisense (S)ODN treatment decreases c-myb mRNA and protein expression, induces growth arrest in the G1 phase of the cell cycle, and inhibits cell proliferation. In vivo treatment with c-myb antisense (S)ODNs results in a reduction in tumour growth. A greater inhibition of cell proliferation in vitro and a higher increase of tumour growth inhibition and growth delay in vivo were obtained with the combination of (S)ODNs and CDDP than when the two agents were administered separately. This comparative study, using the same tumour cell line in vitro and in vivo, suggests that c-myb antisense (S)ODNs might be useful in the therapy of colon cancer in combination with antineoplastic drugs.     

Preoperative evaluation of 54 gliomas by PET with fluorine-18-fluorodeoxyglucose and/or carbon-11-methionine

This study evaluates the usefulness of PET for the preoperative evaluation of brain gliomas and methods of quantification of PET results. METHODS: Fifty-four patients with brain gliomas were studied by PET with 18F-fluorodeoxyglucose (FDG) (n = 45) and/or 11C-methionine (MET) (n = 41) before any treatment. Results of visual analysis, calculation of glucose consumption and five tumor-to-normal brain ratios for both tracers were correlated with two histologic grading systems and with follow-up. RESULTS: Visual analysis (for FDG) and tumor-to-mean cortical uptake (T/MCU) ratio proved to be the best tools for the evaluation of PET results. Methionine was proven to be better than FDG at delineating low-grade gliomas. Tumor-to-mean cortical uptake ratios for FDG and MET were clearly correlated (r = 0.78), leading to the equation T/MCU(FDG) = 0.4 x T/MCU(MET). We showed a good correlation between FDG PET and histologic grading. MET uptake could not differentiate between low-grade and anaplastic astrocytomas but was significantly increased in glioblastomas. Low-grade oligodendrogliomas exhibited high uptake of FDG and MET, probably depending more on oligodendroglial cellular differentiation than on proliferative potential. Uptake was decreased in anaplastic oligodendrogliomas, probably due to dedifferentiation. Care must be taken with peculiar histologic subgroups, i.e., juvenile pilocytic astrocytomas and oligodendrogliomas, because of a discrepancy between high PET metabolism and low proliferative potential (good prognosis). Both tracers proved useful for the prediction of survival prognosis. Methionine proved slightly superior to FDG for predicting the histologic grade and prognosis of gliomas, despite the impossibility of differentiation between Grades II and III astrocytomas with MET. This superiority of MET could be explained by patient sampling (low number of Grade III gliomas submitted to examination with both tracers). The combination of both tracers improved the overall results compared to each tracer alone. CONCLUSION: Both tracers are useful for the prediction of the histologic grade and prognosis. The apparent superiority of MET over FDG could be due to the small number of Grade III gliomas studied with both tracers.     

A Web‐based Open‐source Geoinformation Tool for Regional Water Resources Assessment

Water Resources Management - To reduce the impact of droughts and increase the resilience of regional water systems, various competing demands, such as hydropower, supply, irrigation and river...     

Characterization of modified PbTiO3 ceramic particles by statistical treatment of their size distribution

Microstructural characteristics of (Pb, Ca)TiO₃ piezoelectric ceramic particles have been deduced from computer analysis of their images and the corresponding statistical treatment of the data obtained. It is intended that this study should be used as a nexus, or link, between the geometrical parameters of these particles and some of their physical properties.     

Hull-form stochastic optimization via computational-cost reduction methods

In this paper, analytical functions for the estimation of the temperature-dependent behaviors of poorly and highly dispersed graphene oxide reinforced nanocomposite (GORNC) materials are studied in the framework of a machine learning-based approach. The validity of the presented models is shown comparing the results achieved from this modeling with those reported in the open literature. Also, the application of the obtained functions in solving the thermal buckling problem of beams constructed from such nanocomposites is demonstrated based on an energy-based method incorporated with a shear deformable beam hypothesis. The verification of the results indicates that the presented mechanical model can approximate the buckling behaviors of nanocomposite beams with remarkable precision. It can be realized from the results that the temperature plays an indispensable role in the determination of the buckling load which can be endured by the nanocomposite structure.

     

Valuation of online social networks taking into account users’ interconnectedness

Online social networks have been gaining increasing economic importance in light of the rising number of their users. Numerous recent acquisitions priced at enormous amounts have illustrated this development and revealed the need for adequate business valuation models. The value of an online social network is largely determined by the value of its users, the relationships between these users, and the resulting network effects. Therefore, the interconnectedness of a user within the network has to be considered explicitly to get a reasonable estimate for its economic value. Established standard business valuation models, however, do not account for these aspects sufficiently. Thus, we propose an economic model for the valuation of online social networks, which takes into account the users’ interconnectedness within the network. Furthermore, we analyze different centrality measures, which can be used to quantify users’ interconnectedness in online social networks and propose a measure which is based on the PageRank-algorithm. Finally, the practical application of the model is illustrated by an example of the European online social network XING.com.