محمد امامی نسب

Microcrystalline cellulose is an important agent and additive in pharmaceutical, food, cosmetic and other industries. One of the important characteristics of microcrystalline cellulose powder is the degree of polymerization, which according to international standards, should be equal to or less than 350. In this research, using the Response Surface Methodology, the percentage of acid, reaction time, and input temperature are defined as the primary input variables affecting the degree of polymerization. The range of acid content to dry matter was set to be between 3 to 7%, temperature between 100 to 140 ° C and time between 120 to 150 minutes. Statistical analysis and mathematical modeling were performed to extract a nonlinear model (R2 =0.90) and then the optimum polymerization degree targeted to be 350. The acid percentage, temperature and time at the optimal degree of polymerization point were 3.34 %, 127 ° C, and 116 minutes, respectively. Using the optimal point data, the new experiment was carried out three times to validate the model. Then the average physical, mechanical and thermal properties of the produced microcrystalline cellulose were compared with the control sample. All physical and mechanical properties except for “ash” were in accordance with United States Pharmacopeia standards. The starting point of thermal degradation of the produced microcrystalline cellulose was 212 ° C compared to 226 ° C of the control sample, demonstrating improved thermal properties of the produced sample with the optimum values determined by the Design Expert software.

Despite the importance of Arasbaran forests, no dendrochronological research has been conducted in this region, yet. In this study, for the first time, the potential of two juniper species, Juniperus foetidissima and J. oblonga was evaluated to be used in dendroecology. The first and the second species are respectively in the form of trees and shrubs in Arasbaran forests. Twenty-five trees of each species were samples and the sample preparation, ring width measurements, cross-dating, and construction of tree-ring chronology were performed according to the standard procedures. Developed tree-ring chronologies for juniper tree and shrub covered around 60 and 40 years, respectively. The statistics for evaluating the qualities of chronologies i.e. mean sensitivity (MS), signal-to-noise ratio (SNR), and expressed population signal (EPS) proved the capability of both species to study climate-growth relationships and reconstruction of climate. The relations between radial growth and climatic factors showed that both species have similar responses to climate: high temperature before the growing season promoted the growth while a warm spring reduced growth rate. Rainfall before the growing season had no meaningful effect on growth while spring precipitation strongly stimulated the radial growth. Overall, given the good distribution of juniper species in Arasbaran forest, the success of the developing ring-width series for studied junipers and its strong relationship with climate factors, these species can be used for dendroecological studies. For extending the length of tree ring chronology, juniper logs of old local buildings can also be used.

Athel tamarisk (Tamarix aphylla) is a fast growing, evergreen tree succeeding in the most soils and can tolerate the saline conditions. Despite its ecological importance and wide distribution in central and southern parts of Iran, wood properties of this species has little been concerned. However, the potential of this species in cellulosic industries of Middle East dry countries has recently been focused. Hence, to study wood anatomy and physical and chemical properties of Athel tamarisk, 3 stands were selected and felled from the Zabol region (Sistan and Baluchestan province). Wood anatomical features of this species were studied and listed according to the list of microscopic features for hardwood identification by IAWA Committee. In addition, lignin distribution in xylem was studied using fluorescence microscopy. Calculating fiber biometry features assessed that although fiber quality is not perfect but meets the standards of paper production, comparing other commercially used hardwoods in this industry. According to chemical composition analysis, cellulose content of this wood is rather low (39%) which could be a result of large amount of thin-walled paranchyma cells in xylem. Lignin content is a bit higher than average hardwoods and this component is concentrated in vessels and fibers. Physical properties of studied wood samples (specific gravity and shrinkage values) were in the range of other light-weight and fast growing hardwoods and thus this wood is expected to have similar end-use quality.

In this research Tension Wood (TW) and Normal Wood (NW) of Poplar were analyzed for pulp production using Kraft pulping process. After preparing samples, Biometric characteristics of the NW and TW fibers were measured and samples were converted to pulp. Pulp hand sheets mechanical and physical properties were measured and results were showed that NW fibers compared to TW fibers had a higher Rankle coefficient and aspect ratio. However the flexibility of NW fibers was better than TW fibers. Based on Results, although TW pulp yield was 13 percent greater than NW pulp yield but kappa number in TW was 45 percent lower than NW. Mechanical and physical properties of hand sheets indicated that the tensile and burst strengths of tension wood were comparatively lower than that of normal wood. Also the papers produced by equally mixture of TW fibers and NW fibers were showed higher tensile and burst strengths. Optical and color analyses of samples were showed an improvement in brightness and whiteness for TW hand sheets compared to NW papers. General speaking results were showed that presence of TW fibers inside pulp had not a significant effect on quality of produced pulp and papers.

To understand the compatibility of xylem with dry climates, wood anatomy similarities and differences of four shrubs were investigated in dry and cold region of Sarab (Azarbaijan sharghi province). These shrubs were: Pteropyrum olivieri, Rosa canina, Tamarix gallica, and Rhamnus pallasii, while the wood anatomy of Pteropyrum sp. is reported for the first time, in this research. After preparing microscopic sections of mature xylem and staining them, wood anatomy of studied species were reported and compared. The results showed that Pteropyrum olivieri and Rosa canina are the most similar in terms of wood anatomy while Rhamnus pallasii and Tamarix gallica have the least similarities with each other. Those anatomical features which compensate the drought stress were different in these shrubs according to local distribution of studied species; among them was the occurrence and intensity of spiral thickenings in vessels, the presence of vascular / vasicentric tracheids, and the size and grouping of vessels. Tamarix gallica which were grown only near the lake had the least adaptation to drought in its stem while Rhamnus pallasii which could distribute in the harshest conditions were equipped with the best adaptive traits.