Analyzing the quasi-static puncture resistance performance of shear thickening fluid enhanced p-aramid composite

The quasi-static (QS) puncture resistance of p-aramid Twaron fabric impregnated with shear thickening fluid (STF) based on the molecular weight variation of the base liquid has been investigated. To synthesis the STF, the 12 nm silica particles have been dispersed in polyethylene glycol (PEG) with two different molecular weights, 200 and 400 g/mol by means of mechanical mixing. The weight percentages of silica particles in the continuous phase were selected as 15, 25 and 35 wt%. The results of rheological tests indicate that with the increase of the polymer’s molecular weight, the viscosity and instability of the suspension increase, while its critical shear rate diminishes. The STF impregnated Twaron fabrics were subjected to QS puncture resistance tests according to the ASTM standard D6264. The quasi-static puncture resistance increased about 4.5 fold for Twaron fabric impregnated with 35 wt% concentration STF relative to the neat Twaron. Also, with the increase of the PEG’s molecular weight in Twaron fabrics impregnated with 15 and 25 wt% concentration STFs, the QS puncture resistance of Twaron fabrics improved considerably, but it didn’t change too much in the Twaron fabric impregnated with 35 wt% concentration STF.     

Temperature influences postdispersal predation of weed seeds

Temperature is a key factor for the living organisms on earth. It influences weed management practices, either directly or indirectly. Field experiments were conducted to determine the effect of temperature on the postdispersal seed predation of four important weed species (Cuscuta compestris, Stellaria media, Taraxacum officinale and Veronica persica) in two lucerne fields in Mashhad and Chenaran, north‐eastern Iran. These two cities have the same climate: temperate and cold alpine but the temperature varies between them. Wire mesh cages were used to determine the relative importance of birds in predation and pitfall traps were used to detect the species and the activity density of invertebrate predators. The results showed that the predation preference of different weed species was significantly different between and within fields. Seed predation fluctuated widely throughout the sampling periods, matching the periodic forage harvest and regrowth cycle of lucerne. Despite the level of seed predation fluctuating, it declined toward the last sampling periods. Using wire mesh exclusion cages showed no significant effect of birds on weed seed predation in both fields. Ants, crickets and carabid beetles were the invertebrate seed predators that were caught in the pitfall traps. There were significant correlations between the mean temperature and predator activity densities and also between the predated seeds and the mean air temperature in both locations. The results of this study indicate the significant effect of temperature on postdispersal weed seed predation. Therefore, with respect to climate change and increasing global warming, it would be possible to focus on postdispersal seed predation in weed management in the future.     

Electrospun nanostructures based on polyurethane/MWCNTs for strain sensing applications

Electrically conductive nanofibers were fabricated from elastic polyurethane (PU) and PU/multiwalled carbon nanotubes (MWCNTs) nanocomposite by electrospinning method. The nanocomposites were electrospun at various MWCNTs loading. Electron microscopy was used to investigate nanofibers morphology and dispersion of MWCNTs in the electrospun nanofibers. The results showed that the presence of the MWCNTs promoted the creation of fibrous structures in comparison with the PU without MWCNTs. On the other hand, increasing the MWCNTs content resulted in a slight increase in the average fiber diameter. TEM micrographs and mechanical properties of the electrospun mats indicated that the homogeneous dispersion of MWCNTs throughout PU matrix is responsible for the considerable enhancement of mechanical properties of the nanofiber mats. Electrical behavior of the conductive mats was also studied, in view of possible sensor applications. Cyclic experiments were conducted to establish whether the electrical properties were reversible, which is an important requirement for sensor materials.     

Association between climate indices,aridity index,and rainfed crop yield in northeast of Iran

Agricultural drought occurs when there is a deficit in soil water supply to crops. Severe drought limits crop water availability and reduces yield. Rainfed crop production is very vulnerable to drought conditions and farmers in northeast of Iran who heavily depend on their rainfed cereals production usually suffer from drought occurrence. Based on history, any severe drought resulted in severe financial problems and forced the affected farmers to move to cities in search of alternative jobs. Any possibility to enable the farmers to mitigate or adapt to drought is highly required. In this study, the relationship between aridity index (AI) and detrended crop yield (1985–2005) of selected crops (wheat and barley) and the influence of three climate indices (AO, NAO and NINO-3.4) were assessed for Khorasan province in northeast of Iran. All associations were assessed at annual, seasonal (wet and dry seasons) and monthly scale considering both concurrent and lag correlations (1-year and 2-year lag). Our results indicated a significant correlation (P < 0.05) between the AI and crops yield mostly in central Khorasan province. Our study also showed that correlation coefficient between AI and barley yield was stronger than AI and wheat yield across all study locations. Seasonal (wet) AI showed significant correlation with crops yield. These results demonstrated that, in some areas of Khorasan, drought is one of the key causes of interannual yield variability. We also observed a significant association between NAO and NINO-3.4 with AI. Precipitation is one of the components of AI, so AI response to NAO and NINO-3.4 can be related to the observed association between this index and precipitation. It seems that these indices could be useful tools to monitor drought patterns and subsequent yield variability in some regions of Khorasan province.     

Improvement in In Vitro Fertilization Rate,Decrease in Reactive Oxygen Species and Spermatozoa Death Incidence in Rams by Dietary Fish Oil

Our aim was to evaluate the effects of fish oil feeding on sperm classical parameters, level of reactive oxygen spices (ROS), spermatozoa death incidence and in vitro fertilization (IVF) rate in rams. We randomly assigned nine rams, into two experimental groups (isoenergetic and isonitrogenous rations with constant level of vitamin E supplement): control (CTR; n = 5) and fish oil (FO; n = 4, 35 g/day/ram). Diets were fed for 70 days during the physiological breeding season. After a 21‐day dietary adaptation period, semen was collected weekly from each ram by an artificial vagina. Sperm classical parameters were determined by the computer‐assisted sperm analyzer system (CASA), and it was prepared for IVF process by swim‐up technique. These evaluations were performed during the first and last weeks of sampling. Intracellular ROS level and spermatozoa death incidence were detected by flow cytometry on a weekly basis after adaptation. Data were analysed with SPSS 15. The volume, concentration (3.6 and 2.7 × 10⁹/ml) and sperm progressive motility (60 and 48%) were significantly improved in the FO group compared with the CTR (p < 0.05). A comparison of two‐cell stage embryos following IVF in the two groups showed a significantly higher fertilization rate in the FO group (56%) compared with the CTR (49%). Superoxide anion (O₂^?) rate was significantly lower (p < 0.05) at the third week of sampling in the FO. Although the H₂O₂ rate was numerically lower in the FO group compared with the CTR, this difference was not significant. In addition, apoptosis showed a significant difference in the third week of sampling (15 and 30% for FO and CTR, respectively; p < 0.05). Overall, adding fish oil to the ram diet not only improved sperm quality and IVF results, it also could reduce oxygen‐free radicals and the incidence of spermatozoa death.     

A serologic study on Toxoplasma gondii infection in slaughtered sheep and goats in Qazvin Province,Iran

Background

Toxoplasma gondii is a common protozoan parasite among all mammals, in particular small ruminants, worldwide. Traditional husbandry can be a major risk factor for infection of sheep and goats with this parasite.

Objectives

The present study aimed to determine the current status of the prevalence for T. gondii in livestock of Qazvin Province.

Methods

In this cross-sectional study, the sera of 455 sheep and 375 goats were examined to detect anti-Toxoplasma IgG antibodies by using in-house indirect ELISA.

Results

Overall, 33.62% (153/455) of sheep and 36.41% (130/375) of goats were positive for anti-Toxoplasma IgG antibodies with no statistically significant difference. The prevalence rate of T. gondii among the sheep of Qazvin County was significantly higher than in Abyek and Abhar counties (p < 0.001).

Conclusions

The results of the present study indicate that the prevalence of T. gondii in sheep and goats of the study area is high. Therefore, the meat of the animals reared in this area can be a potential source of human infections by this parasite.

     

Evaluation of Genetic Diversity in Wild Diploid Wheat Triticum boeoticum from Iran Using AFLP Markers

Although Iran is a main center of distribution of wild wheats, but little information is available regarding genetic variation in wild wheat relatives from this country （Tabatabaei and Massoumi, 2001）. The habitats of wild wheats in the west of Iran （east of Fertile Crescent） are potentially the ideal areas to explore the suitable genes for further transferring into the cultivated wheat. In the Near East, primary habitats of Z boeoticum occur in the northern and eastern parts of the Fertile Crescent （Harlan and Zohary, 1996）.Various sites of excavations such as Ali KOSH （Iran）, Catal HUYUK and HACILAR （Turkey）, from where specimens of Z monococcum have been recovered are within the general area of distribution of Z boeoticum （Harlan and Zohary, 1996）. Iran is a main center of distribution of wild wheats and the associated compositions of Z boeoticum with Aegilops spp. as the ＂richest wheat gene pool＂ has been found in this region （Tabatabaei and Massoumi, 2001）.Therefore, it is supposed that the populations of Z boeoticum in this region contain high levels of genetic diversity and may provide significant information regarding their potential for breeding purposes. In this study,     

Investigating impact of converging training walls of the ogee spillways on hydraulic performance

Paddy and Water Environment - Due to their economical and structural aspects, ogee-crested spillways can be constructed and operated in a wide variety of situations. In this study, a...     

Investigating monthly precipitation variability using a multiscale approach based on ensemble empirical mode decomposition

Paddy and Water Environment - In environmental and hydrological studies, the issue of variability in precipitation is of great importance, particularly for regions situated in arid and semiarid...