Effect of exfoliated graphite nanoplatelets on the mechanical and viscoelastic properties of poly(lactic acid) biocomposites reinforced with kenaf fibers

The focus of this study is to explore synergy between nanomaterials such as exfoliated graphite nanoplatelets (xGnP) and micro-size reinforcements such as kenaf natural fibers, in poly(lactic acid) based composites. The nano-biocomposites are made by melt-mixing followed by injection molding. Prior to melt-mixing the kenaf fibers were coated with the xGnP using sonication. The reinforcement content used in the study was up to 5 wt% and up to 40 wt% for xGnP and kenaf fibers, respectively. The flexural strength and modulus and the viscoelastic properties such as storage modulus were determined. It was found that addition of 5 wt% xGnP did not increase the viscosity of the polymer melt, enhanced the flexural modulus by 25–30% at any fiber loading used but did not increase the strength, indicating insufficient load transfer at the polymer-xGnP or xGnP-kenaf interface. Finally, addition of xGnP had a positive effect on the heat distortion temperature but only at higher fiber loadings.     

Vapor‐induced swelling of supported methacrylic and siloxane polymer films: Determination of interaction parameters

White light reflectance spectroscopy is applied to monitor vapor‐induced thickness changes of polymer films, supported on suitable silicon substrates. Assuming unidirectional swelling due to the constraining support, the equilibrium volume swelling of four methacrylic polymers and two siloxane‐based copolymers upon exposure to various activities of water, methanol, ethanol, and ethyl acetate vapor, at 30°C is evaluated. The deduced sorption isotherms were fitted to the Flory‐Huggins equation and interaction parameters, as well as solubility coefficients at infinite solute dilution, were deduced for each binary system. The relative sorption capacity of the different classes of polymers toward the four vapors are in line with the expected solubility interactions between solvent and solute. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Low cholesterol along with inflammation predicts morbidity and mortality in hemodialysis patients

Low and not high cholesterol seems to predict high mortality in hemodialysis (HD) patients. The confirmation of this reverse epidemiology as well as its possible interconnection with the increased inflammatory activity observed in this population is being explored in the present study. A group of 136 HD patients was prospectively studied for 2 years, and cardiovascular disease (CVD) as well as all-cause mortality and morbidity were recorded. Baseline lipid profile, inflammatory status, and patients' characteristics were studied as potential survival and hospitalization predictors. During the 24-month follow-up, 21 deaths (52.4% due to CVD) and 38 hospitalizations (55.3% due to CVD) were recorded. In multivariate Cox regression analysis, decreased interleukin-10 (IL-10) and decreased total serum cholesterol (TChol) were the only independent predictors of CVD mortality while C-reactive protein and decreased TChol predicted all-cause mortality. Interleukin-10 at baseline was 11.29 ± 21.49 vs. 5.51 ± 4.57 pg/mL (P<0.018) and TChol 167.37 ± 47.84 vs.122.04 ± 26.48 mg/dL (P<0.000) in survivors vs. nonsurvivors from CVD, while C-reactive protein at baseline was 9.37 ± 11.54 vs. 23.15 ± 18.76 mg/L (P<0.000) and TChol 169.26 ± 46.42 vs. 133.26 ± 46.33 mg/dL (P<0.003) in survivors vs. nonsurvivors from any cause of death. Using the same method of statistical analysis, IL-6 and decreased soluble gp130 (sgp130)—an antagonist of IL-6 action—were found to be the only independent prognostic factors for hospitalization due to CVD while decreased soluble gp130 remained the sole predictor of hospitalization due to any cause. In conclusion, reverse epidemiology regarding cholesterol is confirmed in the present study. Furthermore, inflammatory activity also predicts, independently of or in conjunction with low-cholesterol, CVD and all-cause morbidity and mortality in HD patients.     

Comparison of the efficacy and safety of tropisetron, metoclopramide, and chlorpromazine in the treatment of emesis associated with far advanced cancer

BACKGROUND: A single institution, prospective, randomized trial was performed in terminal cancer patients to compare tropisetron (TRO), metoclopramide (MET), and chlorpromazine (CHL) in the management of nausea and emesis. Patients had far advanced cancer, were far removed from chemotherapy or radiotherapy, and their nausea and emesis was not due to bowel obstruction, drug intake, or cranial, electrolytic, or metabolic causes. The effects of antiemetic treatments were evaluated from Days 1-15. METHODS: Two hundred and eighty patients were randomized to receive 1) MET+ dexamethasone (DEX) (10 mg*4 and 2 mg*1, respectively, orally), 2) TRO (5 mg*1, orally), 3) TRO + MET (5 mg*1 and 10 mg*2, respectively, orally), 4) TRO + MET + DEX (5 mg*1, 10 mg*2, and 2 mg*1, respectively, orally), 5) CHL + DEX (25 mg*2 and 2 mg*1, respectively, orally), 6) TRO + CHL (5 mg*1 and 12.5 mg*2, respectively, orally), or 7) TRO + CHL + DEX (5 mg*1, 12.5 mg*2, and 2 mg*1, respectively, orally). Total control was defined as no nausea or emesis. RESULTS: By the end of the 15th day, total control of emesis was obtained in 23.6% (9 of 38) of MET + DEX patients, 78.9% (30 of 38) of TRO patients, 84.2% (32 of 38) of TRO + MET patients, 92.3% (36 of 39) of TRO + MET + DEX patients, 33.3 (13 of 39) of CHL + DEX patients, 84.6% (33 of 39) of TRO + CHL patients, and 92.5% (37 of 40) of TRO + CHL + DEX patients. Total control of nausea was achieved in 18.4% (7 of 38) of MET + DEX patients, 65.7% (25 of 38) of TRO patients, 73.6% (28 of 38) of TRO + MET patients, 87.1% (34 of 39) of TRO + MET + DEX patients, 17.9% (7 of 39) of CHL + DEX patients, 74.3% (29 of 39) of TRO + CHL patients, and 85% (34 of 40) of TRO + CHL + DEX patients. When comparing MET + DEX versus TRO; MET + DEX versus TRO + MET; MET + DEX versus TRO + MET + DEX; MET + DEX versus TRO + CHL; MET + DEX versus TRO + CHL + DEX; CHL + DEX versus TRO; CHL + DEX versus TRO + MET; CHL + DEX versus TRO + MET + DEX; CHL + DEX versus TRO + CHL; and CHL + DEX versus TRO + CHL + DEX, significant differences were noted. All antiemetic drugs were well tolerated with no severe side effects observed in any treatment arm. CONCLUSIONS: These data suggest that 5-HT3 receptor antagonists such as tropisetron clinically are more effective in the control of emesis of patients with far advanced cancer than previously used agents. This study raises important issues when attempting to decide which antiemetic therapy to choose for an individual patient with far advanced disease.     

Physico-chemical properties of whey protein isolate films containing oregano oil and their antimicrobial action against spoilage flora of fresh beef

Antimicrobial films were prepared by incorporating different levels of oregano oil (0.5%, 1.0%, and 1.5% w/w in the film forming solution) into sorbitol-plasticized whey protein isolate (WPI) films. The moisture uptake behavior and the water vapor permeability (WVP) were not affected by the addition of oregano oil at any of the concentrations used. A reduction of the glass transition temperature (∼10–20 °C), as determined by dynamic mechanical thermal analysis (DMTA), was caused by addition of oil into the protein matrix. A decrease of Young modulus (E) and maximum tensile strength (σ_max) accompanied with an increase in elongation at break (%EB) was observed with increasing oil concentration up to a level of 1.0% (w/w). Wrapping of beef cuts with the antimicrobial films resulted in smaller changes in total color difference (ΔΕ) and saturation difference (Δ_chroma) during refrigeration (5 °C, 12 days). The maximum specific growth rate (μ_max) of total flora (total viable count, TVC) and pseudomonads were significantly reduced (P < 0.05) by a factor of two with the use of antimicrobial films (1.5% w/w oil in the film forming solution), while the growth of lactic acid bacteria was completely inhibited. These results pointed to the effectiveness of oregano oil containing whey protein films to increase the shelf life of fresh beef.     

New assembly techniques and fast reservation protocols for optical burst switched networks based on traffic prediction

We propose new burst assembly schemes and fast reservation (FR) protocols for Optical Burst Switched (OBS) networks that are based on traffic prediction. The burst assembly schemes aim at minimizing (for a given burst size) the average delay of the packets incurred during the burst assembly process, while the fast reservation protocols aim at further reducing the end-to-end delay of the data bursts. The burst assembly techniques use a linear prediction filter to estimate the number of packet arrivals at the ingress node in the following interval, and launch a new burst into the network when a certain criterion, different for each proposed scheme, is met. The fast reservation protocols use prediction filters to estimate the expected length of the burst and the time needed for the burst assembly process to complete. A Burst Header Packet (BHP) packet carrying these estimates is sent before the burst is completed, in order to reserve bandwidth at intermediate nodes for the time interval the burst is expected to pass from these nodes. Reducing the packet aggregation delay and the time required to perform the reservations, reduces the total time needed for a packet to be transported over an OBS network and is especially important for real-time applications. We evaluate the performance of the proposed burst assembly schemes and show that a number of them outperform the previously proposed timer-based, length-based and average delay-based burst assembly schemes. We also look at the performance of the fast reservation (FR) protocols in terms of the probability of successfully establishing the reservations required to transport the burst.     

Flexible Organic Photovoltaic Cells with In Situ Nonthermal Photoreduction of Spin‐Coated Graphene Oxide Electrodes

The first reduction methodology, compatible with flexible, temperature‐sensitive substrates, for the production of reduced spin‐coated graphene oxide (GO) electrodes is reported. It is based on the use of a laser beam for the in situ, non‐thermal, reduction of spin‐coated GO films on flexible substrates over a large area. The photoreduction process is one‐step, facile, and is rapidly carried out at room temperature in air without affecting the integrity of the graphene lattice or the flexibility of the underlying substrate. Conductive graphene films with a sheet resistance of as low as 700 Ω sq^?1 and transmittance of 44% can be obtained, much higher than can be achieved for flexible layers reduced by chemical means. As a proof of concept of our technique, laser‐reduced GO (LrGO) films are utilized as transparent electrodes in flexible, bulk heterojunction, organic photovoltaic (OPV) devices, replacing the traditional ITO. The devices displayed a power‐conversion efficiency of 1.1%, which is the highest reported so far for OPV device incorporating reduced GO as the transparent electrode. The in situ non‐thermal photoreduction of spin‐coated GO films creates a new way to produce flexible functional graphene electrodes for a variety of electronic applications in a process that carries substantial promise for industrial implementation.     

Tribological Study Comparing PAG and POE Lubricants Used in Air-Conditioning Compressors under the Presence of CO2

Polyalkylene glycol (PAG) and polyolester (POE) synthetic lubricants are good candidates for air-conditioning systems that work with alternative refrigerants such as carbon dioxide (CO₂). Both synthetic lubricants are widely used in air-conditioning compressors and have been optimized for use with hydrofluorocarbon (HFC) refrigerants. However, it is still not clear which lubricant is more suitable for use in compressors operating with CO₂ as a refrigerant. This study compares the performance of PAG and POE lubricants of the same viscosity (ISO VG 68) used in air-conditioning compressors. The materials used were Al390-T6 disks and hardened steel SAE 52100 pins. The tests were performed using a high pressure tribometer (pin-on-disk configuration) in the presence of CO₂. The results showed that scuffing and wear resistance of Al390-T6 tested with PAG were superior compared to the samples tested with the POE lubricant. Chemical analysis using X-ray photoelectron spectroscopy showed that PAG tends to promote the formation of carbonate layers on the surface, leading to improvement in the tribological performance of the interface.     

A New Vision of Classical Multi-regional Input–Output Models

We present classical multi-regional multi-sectoral input–output trade structures from the perspective of networks. Unlike existing approaches by which dynamic changes in structures are studied, here, emphasis is given on recovering the stable structure architecture of interrelations in the input–output model. By self-explanatory visual outputs we display the connectivity patterns, interactions of the trading partners, the number of trade linkages per trader and the density of interrelations of the network. Our network analysis traces causal relationships, feedback loops and examines certain global structural properties. The whole computational approach is implemented in Mathematica. Our programming style allows for the creation of iterative schemes explaining the the linkage development among sectors, the influence of regions and sectors system-wise, aspects of the nature of trade and, the evolution of spatial trading/production cycles in growing trading networks.     

Programming Correlation Criteria with free CAS Software

Our contribution in this work is to set the directions for specialized econometric computations in a free computer algebra system, Xcas. We focus on the programming of a routine dedicated to correlation criteria for multiple regression models. We program several operations for detecting and evaluating collinearity by applying the diagnostic techniques of linear regression analysis. In order to illustrate the computational performance of our Xcas codes, we repeat most of the analysis carried out in widely used commercial software, along with some extra statistics. Xcas could constitute a supplemental tool in a collinear data study. Its use is proposed complementary to established econometric software or as substitute software.