Long term hygroscopic characteristics of polypropylene based hybrid composites with and without organo-modified clay

Recycled PP contains various impurities and has poor and variable mechanical properties compared to virgin PP. This, in general, rules out the use of recycled PP in the original applications and in other high-value applications. Hence, this study investigated the effects of polymer matrix type, weight fraction of wood flour and organoclay on the thickness swelling and water absorption behavior of PP based hybrid composites. WPCs based on polypropylene (virgin and recycled), wood flour, organoclay and maleated polypropylene (MAPP) were made using melt compounding and subsequent injection molding. Composites made from recycled polypropylene (rPP) exhibited better dimensional stability compared to the virgin (vPP) based ones. Besides, wood flour did not completely encapsulate in the polymer matrix at 50 % weight fraction. Incorporation of nanoclay exhibited a beneficial effect on both the water absorption and thickness swelling by creating a tortuous path as a result of its characteristic barrier property. The improvements in hygroscopic characteristics of hybrid composites using rPP and nanoclay were further supported by scanning electron microscopy and X-ray diffraction methods. Conclusively, PP recycled from post-consumer applications can be used in value-added composites without accepting the expense of separating out impurities from the polymer.     

Preparation of Some Br-ended MMA Three Arm Star Block Copolymers via ATRP and Other Amphiphilic Hydroxyl Ended Ones

MMA-St, MMA-VA, MMA-St-MA, and MMA-VA-n-BuMA three arm star block copolymers were prepared via ATRP by using trifunctional initiator. TMED CuBr catalytic system was involved in such polymerization processes at 90°C. Subsequent transformation of the bromine ends to hydroxyl ones were carried out on MMA-St and MMA-VA copolymers as two different examples, and two variable routes were involved in the transformation processes using ethanolamine and silver, respectively.     

Evaluation of fiber optic sensors for remote health monitoring of bridge structures

Health monitoring of civil infrastructure systems has recently emerged as a powerful tool for condition assessment of structural performance. With the widespread use of modern telecommunication technologies, structures could be monitored periodically from a central station located several miles away from the field. Sensors are placed at several critical locations along the structure, and send structural information to the central station. This remote capability allows immediate damage detection, so that necessary actions that ensure public safety are taken. The goal of this research work is to evaluate the use of Fiber Optic sensing technology as a tool for structural health monitoring. To perform this task, a case study involving installation of Fiber Optic Sensors on a selected bridge structure during its construction phase was conducted. The bridge is located in the state of Florida, USA and is considered the first smart structure in this state. Static and Dynamic testing of the bridge were performed using loaded SU4 trucks. A 3-dimensional analytical finite element model of the bridge was developed and its results were compared to the test data. The study confirmed the accuracy of the sensors in estimating the bridge behavior under heavy truck loads. In addition, the sensors were connected to a data acquisition system permanently installed on-site. The acquisition system could be accessed through remote communication, which permits the evaluation of the bridge behavior under live traffic loads. Currently, live structural data under traffic loading is being transmitted continuously to the central maintenance office. The study revealed that the proposed health monitoring technology will enable practical, cost-effective, and reliable maintenance of bridge structures.     

Cooperative Association/Re-association Approaches to Optimize Energy Consumption for Real-Time IEEE 802.15.4/ZigBee Wireless Sensor Networks

The major challenge of real-time Wireless Sensor Networks stills the optimization of both constraints: energy consumption, to get long network lifetime and the communication delay, to meet real-time requirements. In the context of IEEE 802.15.4/ZigBee networks, the association procedure has a direct effect on building paths optimizing those constraints. In this paper, we are interested on the definition of an ideal approach of load balancing to fairly distribute energy consumption among nodes in IEEE 802.15.4/ZigBee WSNs. This approach leads to conserve energy of each node in order to extend the network lifetime. To be closer to this ideal, we propose new dynamic association/re-association approaches allowing path alternation relative to association criteria and their threshold parameters. The implementation of those approaches in NS2 simulator highlights the efficiency of cooperative and dynamic association criteria particularly the one based on the sum of the inverses of remaining energy. Indeed, this approach gives better results with regard to energy distribution according to ideal approach which leads to a longer lifetime. It also performs lower latency for real time communication.     

Use of polymeric materials as a solid phase for radioimmunoassay and immunoradiometric assay techniques

Poly(acrylamide-acrylic acid-acrylonitrile)-ferrous sulfate, p(AM-AA-AN)-FeSO₄·7H₂O, resin was used as a solid phase for estimation of thyroid stimulating hormone (TSH) by radioimmunoassay (RIA) and immunoradiometric assay (IRMA) techniques. Comparison with cellulose particles as a known polymer solid phase was made. The tracers for RIA and IRMA were prepared by radioiodination of TSH antigen and TSH monoclonal antibody, respectively, using Iodogen as oxidizing agent. The tracers were purified by gel chromatography on Sephadex G-25 column. The polyclonal anti-TSH antibody was prepared via immunization of three white New Zealand rabbits with highly purified TSH antigen. The polymer was prepared by addition of aqueous solution of comonomer (AA-AN) and FeSO₄ as cross-linker to polyacrylamide p(AM) and irradiation of the mixture at ambient temperature in a ⁶⁰Co γ-cell. The polymer prepared and cellulose particles were activated using 1,1-carbonyldiimidazole, and these activated particles were coupled with the polyclonal TSH antibody. Optimization and validation of the RIA and IRMA techniques were made.     

Immunoradiometric assay for estimation of thyroid stimulating hormone using solid phase anti-TSH Sepharose particles

A procedure for immunoradiometric assay (IRMA) using solid phase Sepharose particles for the measurement of thyroid stimulating hormone (TSH) in human serum or plasma was developed, optimized, and validated. The ¹²⁵I-anti-TSH monoclonal antibody (MoAb) was prepared using N-bromosuccinimide as oxidizing agent and was purified by HPLC. The coupling of activated sepharose particles with polyclonal antiobody of TSH produced using rabbit as a host animal was undertaken. Optimization and validation of the assay were carried out. The reproducibility as measured by the intra- and interassay variations is acceptable. The recovery and dilution tests confirmed that the calibration was accurate and the matrix was appropriate. The results agree well with those obtained with the currently used commercial kit. The technique developed proved to be sensitive, specific, precise, and accurate for routine laboratory use.     

Mechanical testing of recombinant human bone morphogenetic protein-7 regenerated bone in sheep mandibles

A new method was developed in this study for testing excised sheep mandibles as a cantilever. The method was used to determine the strength and stiffness of sheep hemi-mandibles including a 35 mm defect bridged by regenerated bone. Recombinant human bone morphogenetic protein-7 (rhBMP-7) in a bovine collagen type-I carrier was used for the bone regeneration. Initial tests on ten intact sheep mandibles confirmed that the strength, stiffness and area beneath the load-deformation curves of the right and left hemi-mandibles were not significantly different, confirming the validity of using the contra-lateral hemi-mandible as a control side. Complete bone regeneration occurred in six hemi-mandibles treated with rhBMP, but the quality and mechanical properties of the bone were very variable. The new bone in three samples contained fibrous tissue and was weaker and less stiff than the contra-lateral side (strength, 10-20 per cent; stiffness, 6-15 per cent). The other half had better-quality bone and was significantly stiffer and stronger (p < 0.05), with strength 45-63 per cent and stiffness 35-46 per cent of the contra-lateral side. Hemi-mandibles treated with collagen alone had no regenerated bone bridge suggesting that 35 mm is a critical-size bone defect.     

Progressive collapse of cold-formed steel framed structures

This study investigated the possibility of progressive collapse of a cold-formed steel framed structure. Five different analysis cases were considered, exterior wall column removal specified in General Services Administration (GSA) guidelines and Department of Defense (DoD) guidelines, corner wall column removal specified in GSA and DoD guidelines, and analysis by Successive Removal. The results showed that the removal of corner wall columns appeared to cause progressive collapse of a portion of the second and third floor of the end bay directly associated with the column removal, and not the entire building.     

Reservoir Management Using a Network Flow Optimization Model Considering Quadratic Convex Cost Functions on Arcs

The allocation of water resources between different users is a hard task for water managers because they must deal with conflicting objectives. The main objective is to obtain the most accurate distribution of the resource and the associated circulating flows through the system. This induces the need for a river basin optimization model that provides optimized results. This article presents a network flow optimization model to solve the water allocation problem in water resource systems. Managing a water system consists in providing water in the right proportion, at the right place and at the right time. Time expanded network allows to take into consideration the temporal dimension in the decision making. Since linear cost functions on arcs present many limitations and are not realistic, quadratic convex cost functions on arcs are considered here. The optimization algorithm developed herein extend the cycle canceling algorithm developed for linear cost functions. The methodology is applied to manage the three reservoirs of La Haute-Vilaine’s watershed located in the north west of France to protect a three vulnerable areas from flooding. The results obtained with the algorithm are compared to a reference scenario which consists in considering reservoirs transparent. The results show that the algorithm succeeds in managing the reservoir releases efficiently and keeps the flow rates below the vigilance flow in the vulnerable areas.     

Insulin receptor substrate-2 amino acid polymorphisms are not associated with random type 2 diabetes among Caucasians

OBJECTIVE: We sought to reevaluate the prevalence of thyroid dysfunction and thyroid autoimmunity in 47 patients with celiac disease; 91 healthy subjects were studied as controls. Both patients and controls were from Sardinia, Italy. METHODS: Diagnosis of celiac disease was made on the basis of clinical history, presence of positive antigliadin IgA (AGA-A) and IgG (AGA-G) antibodies, antireticulin antibodies (ARA), antiendomysium antibodies (EMA), and was confirmed by jejunal biopsy. HLA class II typing for DQB1 and DQA1 alleles was performed in 36/47 celiac patients. Thyroid was evaluated by palpation and echography; serum free thyroid hormones (FT4, FT3), thyrotropic hormone (TSH), and antithyroid peroxidase autoantibodies (anti-TPO) were assayed by radioimmunoassays. RESULTS: The prevalence of anti-TPO was higher in celiac patients (29.7%) than in healthy controls (9.6%) (p < 0.001) and thyroid echography frequently displayed (42.5%) a hypoechogenic pattern. Five anti-TPO-positive celiac patients were hypothyroid (two overt, three subclinical). A higher but not significantly different prevalence of anti-TPO (3/7 = 42.8%) was found in celiac patients displaying the DQB1*0502 genotype, when compared with the remaining patients (8/29 = 27.6%). CONCLUSIONS: An elevated prevalence of clinical and subclinical autoimmune thyroid autoimmunity was found in Sardinian celiac patients, especially in those displaying the DQB1*0502 genotype; this finding could be related to a particular genetic background of the Sardinian population.