University of Tabriz

About: University of Tabriz is a education organization based out in Tabriz, Iran. It is known for research contribution in the topics: Population & Nanocomposite. The organization has 12141 authors who have published 20976 publications receiving 313982 citations.

Applications of carboxymethyl cellulose- and pectin-based active edible coatings in preservation of fruits and vegetables: A review

Abstract: Background The perishable nature of fruits and vegetables makes their shelf-life limited. Environmental factors, transportation and preservation conditions through postharvest could decrease the storage time and quality. Therefore, prolonging supply time of fruits and vegetables by safer postharvest treatments direct the preservation methods to edible coatings. Active edible coatings incorporating different types of functional substances can be used as a preservation method to boost strategies in improving quality, safety and shelf-life of fruits and vegetables upon storage. Scope and approach This review attempts to present a complete overview of carboxymethyl cellulose (CMC) and pectin as a basis for edible coatings and recent developments related to their application as active coatings for preservation of fruits and vegetables quality. Key findings and conclusion CMC and pectin are two main polysaccharides with great potential in making edible coatings. The CMC- and pectin-based edible coatings are commonly odorless, tasteless, non-toxic, non-allergic, water-soluble, transparent and resistant to oil and fats. CMC and pectin, additionally, could be good carriers for active additives. In this sense, CMC and pectin-based active coatings could provide a great potential both for their protective effect and carrying functional compounds such as antimicrobials, antioxidants, anti-browning agents, texture enhancers and nutraceuticals into their coating matrix to prevent unwanted reactions (e.g., microbial growth, oxidation, enzymatic browning and softening) in horticultural products. Such strategy could inhibit microbial decays and enzymatic or biochemical damages and prevent physical or textural deteriorations in fruits and vegetables during storage.

Dispersive dark optical soliton with Tzitzéica type nonlinear evolution equations arising in nonlinear optics

Abstract: A improvement of the expansion methods namely the improved $$\tan \left( \varPhi (\xi )/2\right)$$ -expansion method for solving the Tzitzeica type nonlinear evolution equations is proposed. In this work, the dispersive optical solitons that are governed by the Tzitzeica type nonlinear evolution equations. As a result, many new and more general exact travelling wave solutions are obtained including periodic function solutions, soliton-like solutions and trigonometric function solutions. The exact particular solutions containing four types hyperbolic function solution, trigonometric function solution, exponential solution and rational solution. We obtained the further solutions comparing with other methods. Recently this method is developed for searching exact travelling wave solutions of nonlinear partial differential equations. Abundant exact travelling wave solutions including solitons, kink, periodic and rational solutions have been found. These solutions might play important role in engineering fields. It is shown that this method, with the help of symbolic computation, provides a straightforward and powerful mathematical tool for solving the nonlinear problems.

Extreme weather events in Iran under a changing climate

Abstract: Observations unequivocally show that Iran has been rapidly warming over recent decades, which in sequence has triggered a wide range of climatic impacts. Meteorological records of several ground stations across Iran with daily temporal resolution for the period 1951–2013 were analyzed to investigate the climate change and its impact on some weather extremes. Iran has warmed by nearly 1.3 $$^{\circ }$$ C during the period 1951–2013 (+0.2 $$^{\circ }$$ C per decade), with an increase of the minimum temperature at a rate two times that of the maximum. Consequently, an increase in the frequency of heat extremes and a decrease in the frequency of cold extremes have been observed. The annual precipitation has decreased by 8 mm per decade, causing an expansion of Iran’s dry zones. Previous studies have pointed out that warming is generally associated with more frequent heavy precipitation because a warmer air can hold more moisture. Nevertheless, warming in Iran has been associated with more frequent light precipitation, but less frequent moderate, heavy and extremely heavy precipitation. This is because in the subtropical dry zones, a longer time is required to recharge the atmosphere with water vapour in a warmer climate, causing more water vapour to be transported from the subtropics to high latitudes before precipitations forms. In addition, the altitude of the condensation level increases in a warmer climate in subtropical regions, causing an overall decrease of precipitation. We argue that changing in the frequency of heavy precipitation in response to warming varies depending on the geographical location. Warming over the dry subtropical regions is associated with a decrease in the frequency of heavy precipitation, while an increase is expected over both subpolar and tropical regions. The warmer climate has also led to the increase in the frequency of both thunderstorms (driven by convective heating) and dust events over Iran.

Temperature dependence of microstructure evolution during hot pressing of ZrB2–30 vol.% SiC composites

Abstract: Microstructure evolutions of ZrB 2 –30 vol.% SiC composites, prepared by hot pressing at different processing temperatures (1700, 1850 and 2000 °C) for 30 min under 10 MPa, were investigated by optical microscopy, scanning electron microscopy and transmission electron microscopy (TEM). The microstructures of the fabricated composites were compared with and the effects of the processing temperature on the sintering process and densification behavior during the hot pressing were found. The amount and the orientation of dislocations which were indicated by TEM analysis in the sample hot pressed at 1700 °C showed that no plastic deformation and atomic diffusion occurred. But the presence of amorphous phases and rearrangement of particles are signs of the fact that liquid phase sintering and particle fragmentation/rearrangement is the main densification mechanism. On the other hand, in the sample hot pressed at 1850 °C, aggregation of dislocations behind the grain boundaries and the presence of twinnings addressed wide plastic deformations which were introduced as the main densification mechanism at 1850 °C. Finally in the sample hot pressed at 2000 °C, lower amounts of un-oriented dislocations and also some annealing twinnings were observed in TEM micrographs together with fractographical SEM analysis and showed that the atomic diffusion is the dominant densification mechanism of hot pressed ZrB 2 –30 vol.% SiC composite.