Polymer degradation initiated via infectious behavior

Understanding polymer degradation phenomena is of critical importance for material reliability. A novel dual stage chemiluminescence detection system has been developed and applied to probe for material interaction effects during polymer degradation. Evidence is presented for the first time that in an oxidizing environment a degrading polymer A (in this case polypropylene, PP) is capable of infecting a different polymer B (in this case polybutadiene, HTPB) over a relatively large distance. In the presence of the degrading material A, the thermal degradation of polymer B is observed over a significantly shorter time period. Infectious intermediate volatiles from material A are able to initiate and shorten the degradation processes in material B. This observation documents infectious behavior that will have significant consequences for materials interactions, understanding material degradation processes and long-term aging effects in combined material exposures.     

Ruthenium-containing MCM-22 and ITQ-2 as potential redox catalysts for benzhydrol oxidation

Journal of Porous Materials - About 5 wt% of ruthenium (Ru) was incorporated on layered zeolite frameworks, such as MCM-22 and ITQ-2, using the incipient wetness method. The well-dispersed...     

Optimization of preparation conditions on the dielectric properties of polyaniline

The dielectric response in the microwave field of polyaniline prepared at different temperatures and using different inorganic and organic dopants was studied. Chemical oxidative polymerization of aniline was done at low temperature (0–5°C), at room temperature, and at high (60°C) temperature using different inorganic dopants like HCl, HNO₃, H₂SO₄, HClO₄, etc. Polyaniline was also prepared with different organic dopants like camphor sulfonic acid, Toluene sulfonic acid, and Naphthalene sulfonic acid. All polymers formed were characterized using IR, TGA, DSC, and SEM, etc. The dielectric responses of all polymers are studied using cavity perturbation technique in the microwave field. The studies indicates that the polyaniline prepared with perchloric acid at room temperature shows higher conductivity and absorption coefficient compared with all other samples. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Analysis and prediction of laser cutting parameters of fibre reinforced plastics (FRP) composite materials

A theoretical model is presented considering the spatial distribution of the laser beam, interaction time between the laser and the work material, absorption coefficient of the laser beam at the laser wavelength and the thermal properties of the material. It is assumed that the laser energy is absorbed through the entire thickness of the material. The developed model predicts the various parameters in laser cutting of composite materials such as kerf width at the entry and at the exit, material removal rate and energy transmitted through the cut kerf. The theoretical analysis also determines the position of the beam with respect to the cutting front. Experiments for different laser and material combinations to evaluate the effects of cutting parameters on the cut quality were carried out to compare with the predicted results. The results obtained show very good agreement.     

Impression Creep Behavior of 316LN Stainless Steel

Impression creep tests have been carried out at 923 K on 316LN SS containing 0.07, 0.14, and 0.22 wt.% nitrogen, under different applied stress levels. It was observed that the impression creep depth versus time curves were similar to the creep curves obtained from conventional uniaxial creep tests. The impression creep curves were characterized by a loading strain and primary and secondary creep stages similar to uniaxial creep curves. The tertiary stage observed in uniaxial creep curves was absent. The steady-state impression velocity was found to increase with increasing applied stress. The equivalent steady-state creep rates calculated from impression velocities were found to be in good agreement with the steady-state creep rates obtained from conventional uniaxial creep tests. Equivalence between applied stress and steady-state impression velocity with uniaxial creep stress and steady-state creep rate, respectively, has been established based on the laws of mechanics for time-dependent plasticity. It was found that impression velocity was sensitive to the variation in nitrogen content in the steel; impression velocity decreased with increasing nitrogen content, and the results obtained in this study were in agreement with those obtained from uniaxial creep tests.     

XRD study of the grain growth in CdTe films annealed at different temperatures

The CdTe thin films electrodeposited on stainless steel substrates were annealed in air at various temperatures and time durations in order to investigate the influence of post-deposition heat treatments on the grain growth of the films. The recrystallization process at lower annealing temperature is different from that of the high-temperature annealing. The annealing at lower temperature promotes better grain growth by maintaining the preference for the (1 1 1) plane. In general the grain size increases due to annealing and the recrystallization happens in three phases. The grain growth exponent is a function of temperature and time. In the beginning of the annealing, irrespective of the annealing temperatures the grain growth obeys the ideal parabolic law and for longer annealing times it deviates from the ideal case.     

Summer water circulation in Frenchman's Bay,a shallow coastal embayment connected to Lake Ontario

Water movements due to temperature gradients and short-term water level fluctuations control the flushing timescale of the many shallow embayments in the Great Lakes. In this article the water circulation within Frenchman's Bay is reported and estimates made of the hydraulic flushing timescale. This shallow freshwater embayment is permanently connected to Lake Ontario through a channel of width 30 m and depth of 2 m. The water flushing timescale is estimated by using a salt mass budget, leading to a flushing timescale of 7–10 days. During the summer, the exchange of water between the bay and the lake can be driven by a combination of horizontal thermal gradients, and by small but ubiquitous 1–5 cm oscillations in the water level of Lake Ontario. The water movements that are predicted due to water level fluctuations (caused by seiches, storm surges and tides) and due to horizontal thermal gradients leads to estimates of the flushing time of water within Frenchman's Bay in the range of 12–13.5 days, i.e. the same order of magnitude as the salt budget. One consequence of the temperature driven exchange flows is to cause strong and persistent temperature stratification within the bay, which in combination with high nutrient loading and low winds in summer leads to frequent anoxic events.     

Effects of antibiotic regimens on the fecal shedding patterns of pigs infected with salmonella typhimurium

An experiment was conducted to determine (i) the effects of antibiotic regimens on the shedding patterns of pigs infected with Salmonella Typhimurium and (ii) whether antibiotic resistance increases the incidence of pathogen shedding. The experiment involved 48 50-day-old pigs challenged with Salmonella Typhimurium and receiving one of four antibiotic regimens including (i) intramuscular injection of ceftiofur sodium followed by inclusion of oxytetracycline in the feed; (ii) apramycin in the feed for 14 days followed by oxytetracycline; (iii) carbadox in the feed until pigs reached 35 kg followed by oxytetracycline; (iv) no antibiotics (control). Fecal samples were collected preinoculation, 2 and 4 days postinoculation (DPI) and at weekly and biweekly intervals thereafter to determine shedding patterns. Salmonella Typhimurium isolates from 2, 4, 7, 21, 42, and 70 DPI were analyzed for antibiotic resistance. A time effect (P < 0.05) was observed, indicating that the proportion of isolates resistant to at least one antibiotic varied over time. Overall resistance was determined to be 46% at 2 DPI and increased significantly (P < .05) thereafter. Treatment x time and antibiotic x time interactions were also observed (P < 0.05) as the percentage of isolates resistant to each test antibiotic increased over time. In no case did the development of antibiotic resistance result in an increased incidence of shedding of the original inoculate. The incidence of shedding was reduced in pigs receiving the apramycin-oxytetracycline treatment, when compared to control pigs; however, no differences were observed between antibiotic treatments.     

Experimental investigation of a cook-off temperature in a hot barrel

The experimental investigations of the effect of contact time/temperature on initiating the cook-off using 7.62 mm calibre cartridge cases （CC） were conducted previously. These cartridges were filled with commercial off-the-shelf （COTS） double based （DB） propellant （Bulls Eye） and were loaded in a hot chamber. The thermal explosion temperature is of great significance to both weapon designers and safety inspectors as it provides the operational limit and safe operating temperature. For CC under test, it was found that the cook-off temperatures of this propellant were encountered with the heat transfer profile of the simulated gun barrel between 151.4 ℃ and 153.4 ℃, with a reaction occurring in less than 300 s after the round was chambered. Usefully, each experiment was found to be consistent and repeatable.