Effect of Wood Flour Content on the Thermal,Mechanical and Dielectric Properties of Poly(vinyl chloride)

Several composite formulations of poly(vinyl chloride)/olive wood flour (PVC/WF) were manufactured by dry‐blending PVC, wood flour, plasticizer and other processing additives in a high‐intensity mixer. The dry‐blended compounds were calendered into film samples (T = 180°C, calendered time = 8 min). The films obtained are cut into normalized samples for thermal, mechanical, and dielectric characterization. The results obtained show that stress as well as strain at break decrease sharply as the wood flour content increases. On the other hand, this filler content has little influence on the glass transition temperature. It decreases the temperature of decomposition setting and retards the PVC thermal decomposition. It increases permittivity as well as dielectric losses. The thermal stability, as measured by thermogravimetry (TGA) and differential scanning calorimetry (DSC) methods, is good enough to permit processing of these types of PVC compounds using conventional processing techniques and temperatures under 210°C.     

Enhanced electrocoagulation–electroflotation for turbidity removal by Opuntia ficus indica cladode mucilage

The optimisation of the electrocoagulation‐electroflotation (EC‐EF) process assisted by the mucilage of the Opuntia ficus indica (OFI), on the turbidity removal was performed through the response surface methodology (RSM). For a solution of 300 mg/L of silica gel, high turbidity removal (93.14% ± 1.31) was obtained under the optimal conditions of 2.5 mg/L, 21.2 V, 9.65 and 2.61 mS/cm for the mucilage concentration, voltage, pH and conductivity, respectively, this experimental value was close to the predicted value of 92.96% ± 0.3. OFI mucilage increases turbidity removal efficiency and reduces specific energy consumption at a fixed current density. The turbidity removal of the EC‐EF process was improved by 30.94% compared with the conventional EC–EF (EC–EF without OFI mucilage) which shows 62.02% ± 1.45 of turbidity removal.     

Effect of needle orientation during arteriovenous access puncture on needed compression time after hemodialysis: A randomized controlled trial

Background

There are two techniques for puncturing an arteriovenous fistula: one where the needle is inserted bevel up and then rotated to a bevel down position, and another where the needle is inserted bevel down. The aim of this study was to compare these two methods of needle insertion on minimum compression time required for hemostasis after needle removal.

Methods

This was a prospective, randomized, cross-over, blinded, single-center, routine care study. Each patient's average post-dialysis puncture site compression time was determined during a 2-week baseline period while using bevel-up access puncture. Subsequently, minimum post-dialysis puncture-site compression time was determined during each of two sequential follow-up periods, during which fistula puncture was done with needles inserted bevel up or down, respectively. The order of treatments (bevel up or bevel down insertion) was randomized. During each follow-up period, the minimum compression time necessary to avoid bleeding on needle removal was determined by progressively shortening the compression time. Puncture-associated pain was also assessed as prepump and venous pressures and ability to achieve desired blood flow rate during the dialysis session.

Results

Forty-two patients were recruited. The baseline compression time after needle removal averaged 9.99 ± 2.7 min During the intervention periods, the minimum compression time was on average 10.8 min (9.23–12.4) when the access needles had been inserted bevel down versus 11.1 min (9.61–12.5) when the access needles had been inserted bevel up (p = 0.72). There was no difference in puncture-associated pain between the two insertion techniques, and no difference in prepump or venous pressures or ability to achieve the desired blood flow rate during the dialysis session.

Conclusion

Bevel-up and bevel-down needle orientation during arteriovenous fistula puncture are equivalent techniques in terms of achieving hemostasis on needle removal, and puncture-associated pain.     

Commutation modelling and sparks reduction based on coupled circuit method

The commutating machines have a notable effect on the exchanges in brush–commutator contact area, which is particularly obvious when determining the intensity of sparks located on the brush. With time, higher current density at the descending edge promote sparks excitation, which itself increases intensity of the electrical erosion, brush temperature and thus also the wear. So in order to make an analytical study of commutation phenomenon, the coupled circuit method was developed. Therefore, a generalized mathematical model of the commutation, for brush–commutator, is established and can be extended for any other types of commutation on the basis of electromagnetic field (e.g. transformers and phase shift transformer. This model provides a greater efficiency to explain the impact of the electromagnetic fluxes surrounding brush area (or switch), specially for the current transition of the commutation process. Successful commutation is defined as operation in normal service, with no serious damages to the commutator, brushes or switches due to sparking that might require abnormal maintenance. It is recognized that some visible sparking are not evidence of unsuccessful commutation. The recommendation to improve the commutation (to achieve longer brush life) is the implementation of the proposal (slotted brush), which provides a linear and a sweet transition of currents in the coils of commutation. Copyright © 2012 John Wiley & Sons, Ltd.