Latex influence on the mechanical behavior and durability of cementitious materials

The results of an experimental program conducted on latex-modified mortars are presented in this article. These mortars have become of growing interest in the field of construction. They were used as superplasticizers, or water reducers, for finishing work applications and for repairs, coatings, and waterproofing. This study is about using two polymers (latex), i.e. styrene–butadiene rubber and styrene–acrylic, in order to assess their performance in replacing cement in mortars. A series of mortar mixtures, containing 0, 2.5, 5, 10, 15, and 20% of solid polymer latex (by weight), were prepared and tested in the fresh and hardened states. The test parameters include the fluidity, compressive and flexural strengths, porosity accessible to water, adhesion to clay bricks, and cementitious substrates. The experimental results showed that substituting cement into modified mortars improves their fluidity and adhesion. In the case of clay substrates, a cohesive failure occurs within the substrate layer beyond 10% of substitution, while the rupture takes place at the interface for all formulations tested on cementitious substrates. It was also noted that the flexural tensile strength improved beyond 60 days. However, the compressive strength of polymer mortars decreased with the substitution rate of cement, for all maturities considered. However, for porosity accessible to water, the results follow a linear function, with an inflection at 5% of latex substitution.     

Rheological and sensory properties of fish gelatin gels as influenced by agar from Gracilaria tenuistipitata

Agar extracted from Gracilaria tenuistipitata and commercial agars were incorporated into fish gelatin at various levels (0, 5, 10, 15 and 20% gelatin substitution). G. tenuistipitata agar (GA) had lower failure stress (~16 kPa) than commercial agar (CA) (~20 kPa). However, the former showed higher failure strain (~30%) with lower melting temperature (65.9 °C). The critical linear stress and failure stress of agar/gelatin mixed gels increased with increasing agar levels (P < 0.05). At 15 and 20% of agar used, the mixed gels containing CA exhibited higher failure stress than those with added GA (P < 0.05). Two melting points of agar/gelatin mixed gels were observed, corresponding to the melting temperatures of gelatin and agar gels. Nevertheless, the incorporation of agar lowered the likeness score of gelatin gel. Thus, both GA and CA had the impact on rheological property and the selected sensory characteristics of fish gelatin, depending on the level of substitution.     

Intensive regimen of cytokines with interleukin-2 and interferon alfa-2b in selected patients with metastatic renal carcinoma

We conducted a Phase II trial using an intensive regimen combining interleukin-2 (IL2), interferon-alfa-2b (IFN), and lymphokine-activated killer (LAK) cells. The aim of this study was to evaluate the toxicity and the efficacy of this combination in selected patients with metastatic renal cell carcinoma. Thirty-one assessable patients were treated with at least one cycle of a regimen consisting of 20 x 10(6) IU/day s.c. IFN for 5 days, followed 2 days later by i.v. injections of 24 x 10(6) IU/m2/day IL2 every 8 h together with i.v. bolus of 5 x 10(6) IU/m2/day IFN every 8 h during 5 days. After a 6-day break, during which four leukophereses were performed, this i.v. combination was administered along with the LAK cell reinjections for a maximum of 5 days. Twenty-seven patients underwent the two parts of the first course of treatment; respectively, 42% and 46% of the planned dose of IL2 and IFN were administered. Several severe toxicities were observed including two treatment-related deaths. Significant tumor responses were observed in seven patients, including two complete remissions. Two of these patients remain alive without evidence of disease 36 and 40 months after treatment, respectively. This intensive regimen of IL2 together with IFN and LAK cells cannot be recommended even in selected patients with metastatic renal cell carcinoma. In addition, our results argue against the concept of a dose-response relationship in this setting.     

Side effects of identity management in SIP VoIP environment

In this article, we summarize the security threats targeting SIP proxy servers or other infrastructures in NGN by misusing a specific signaling authentication mechanism, which has been proposed in RFC 4474 (Peterson and Jennings, 2006). This mechanism is designed to authenticate inter-domain SIP requests based on domain certificates to prevent identity theft. Nevertheless, despite its contribution, this protection raises some “side effects”, that actually lead to new vulnerabilities in both the availability and confidentiality of SIP services. We provide an overview of different attack possibilities and explain them in more detail, including attacks utilizing algorithm complexity, certificates storage, and certificates distribution. We also suggest some alternative design to prevent or reduce the attacks. SIP, VoIP, NGN, Authentication, Denial of Service, Timing attack.     

Learning and backtracking in non-preemptive scheduling of tasks under timing constraints

We propose two novel heuristic search techniques to address the problem of scheduling tasks under hard timing constraints on a single processor architecture. The underlying problem is NP-hard in the strong sense and it is a fundamental challenge in feedback-control theory and automated cybernetics. The proposed techniques are a learning-based approaches and they take much less memory space. A partial feasible schedule is maintained and extended over a repeated problem solving trials, previously assigned priorities are refined according to the gained information about the problem to lead the convergence to a complete feasible schedule if one exists. First, we present the learning in hard-real-time with single learning (LHRTS-SL) algorithm where a single learning function is utilized, then we discuss its drawback and we propose the LHRTS with double learning algorithm in which a second learning function is integrated to cope up with LHRTS-SL drawback. Experimental results show the efficiency of the proposed techniques in terms of success ratio when used to schedule randomly generated problem instances.     

Isomérisation du n‐hexane sur des catalyseurs Ni‐WOx/Al2O3‐SiO2

Isomerization of n‐hexane into bi‐ and tri‐branched products was studied at atmospheric pressure on Ni‐WO_x/Al₂O₃‐SiO₂ catalysts. Two groups of catalysts (A and B) were prepared by using the sol‐gel method. The objective of the present study is the selection of the catalyst having the best isomer (bi‐ and tri‐branched) yield under optimum operating conditions (reaction temperature, reduction temperature, flow duration, etc.). The results show that the introduction of tungsten (group B) modifies siginificantly the catalyst activity and that the optimum nickel amount in these catalysts is 15 wt. %. When a steady flow is achieved (100 min), the catalyst containing 15 % nickel and 10 % tungsten exhibits the highest and largest selectivity at a reaction temperature of 250°C and a reduction temperature of 430°C.