Preparation and characteristics of bombyx mori sericin / tussah silk fibroin / gelatin-based blended antibacterial films北大核心CSCD

A large number of wound dressings are currently used in the treatment of burns chronic ulcers etc. An ideal wound dressing should prevent dehydration of the wound and retain a favorable moist environment at the wound interface. It should have good antibacterial properties and be easily removed without trauma too. Wound dressings are generally made of readily available bio-materials that require minimal processing possess nontoxic non-allergenic and antimicrobial properties as well as promote wound healing. Clinically collagen chitin chitosan etc. are usually used as materials for producing wound dressings as these materials are capable of accelerating the healing processes at molecular cellular and individual levels. Tussah silk fibroin bombyx mori sericin and gelatin non-toxic and extensive have good bio-compatibility degradability and film-forming properties which are conducive to cell adhesion. In order to prepare safe biofilms with excellent antibacterial properties we prepared a kind of bombyx mori sericin / tussah silk fibroin / gelatin BS-TSF-GEL blended film by using tussah silk fibroin bombyx mori sericin and gelatin as bio-based materials and polyethylene glycol 200 as the cross-linking agent. Firstly we designed the single factor experiment and orthogonal experiment to optimize the preparation process of the BS-TF-GEL blended film. On this basis the blended film was modified with ethanol of different concentrations to improve its strength and crystallinity. The structure and properties of the blended film were characterized by measuring the dissolution loss rate tensile properties microscopic morphology and crystal structure. Finally antimicrobial peptides were loaded by adsorption to obtain the BS-TSF-GEL antimicrobial film. The results showed that the ratio of the optimum formula for the (BS-TSF-GEL) blended film required a mixture of bombyx mori sericin (4. 50 μg / mL) and tussah silk fibroin (27. 5 mg / mL) with a volume ratio of 2:1 polyethylene glycol 200 and gelatin solution (360 mg / mL) which accounted for 35% 40% and 25% respectively of the total system. The dissolution loss rate of the BS-TSF-GEL blended film was 34. 62% the elongation at break was 34. 15% and the breaking strength was 578. 8 kPa after being treated with anhydrous ethanol. FTIR and X-ray diffraction results showed that Silk Ⅱ dominated the BS-TSF-GEL blended film while Silk Ⅰ was in a small amount. The BS-TSF-GEL blended film was pale yellow and porous on the surface which was the ideal material for loading antimicrobial peptides. The BS-TSF-GEL blended film loaded with antimicrobial peptides had a good inhibitory effect on both Escherichia coli and Staphylococcus aureus. It is expected to be used in the field of disposable biomedical materials such as wound dressings. In this study three natural materials with unique advantages were selected as substrates for biofilms and polyethylene glycol with high bio-safety was used as the cross-linking agent to enhance the application value of the blended film by loading antimicrobial peptides. The results broaden the application field of silkworm silk and provide a new way for the development and exploitation of silk fibroin in biological dressings and other medical bio-materials. Bombyx mori sericin tussah silk fibroin and gelatin have been widely used in biological tissue engineering as natural biological materials. In this study three natural materials were used as the biofilm substrate to successfully prepare excellent-performance BS-TSF-GEL blend film using polyethylene glycol cross-linking and ethanol post-treatment techniques. Moreover specific properties can be conferred by replacing different loading substances such as antimicrobial biofilm carrying antimicrobial peptides and biofilm sustained release carrier loading drugs. In addition 3D printing electrostatic spinning and other technologies can also be used to shape the BS-TSF-GEL into different shapes to meet the application requirements under different conditions. In conclusion the research results explore a new way for the application of silk protein. © 2022 Authors. All rights reserved.     

Research progress on chemical modification of silk fibroin and its applications北大核心CSCD

Mulberry silk is composed of the two major parts of two triangle-like silk fibroin fibers and sericin covering the fibers and a few lipids. After removing the sericin on the raw silk what is left is the silk fibroin fiber. Silk fibroin is the main part of silk accounting for about 75% of the total weight. Silk fibroin contains 18 natural amino acids such as glycine Gly alanine Ala serine Ser serine aspartic acid Asp and tyrosine Tyr . The secondary structure of silk fibroin has three main conformations α-helix β-fold and random coil. Under certain conditions the three conformations can transform into each other and change the mechanical properties of the silk fibroin material. Silk fibroin extracted from silk fiber is a natural polymer with biocompatibility and biodegradability. It can be further processed into different forms of materials nanoparticles films hydrogels sponges etc. It has been applied in many fields such as biomedicine and cosmetics. In order to meet the needs of different fields researchers have conducted further chemical modification treatment based on the original excellent properties of silk fibroin. Meanwhile the active groups on various amino acid residues in silk fibroin also provide chemical reaction sites for the chemical modification of silk fibroin. The chemical modification methods of silk fibroin mainly include amino acid residue modification macromolecular grafting modification and crosslinking reaction modification. Among them amino acid residue modification can modify protein amino acid residues by chemical reagents and some groups can be introduced into the side chains of silk fibroin macromolecules. Grafting modification of silk fibroin macromolecules is one of the main means to bind functional compounds to silk fibroin macromolecular chains. The properties of grafted silk fibroin are affected by the type and grafting rate of the grafts. The chemical crosslinking reaction modification of silk fibroin macromolecules is to make the macromolecular chains connected by covalent bonds and form a network structure by means of crosslinking agents enzymes or ultraviolet irradiation. The cross-linking reaction can not only form covalent bonds within and between the molecular chains of silk fibroin thus changing its structural properties and improving its stability but be used to form covalent bonds with other polymers. At present the chemical modification of silk fibroin is mainly applied in the fields of silk textiles biomedicine and environmental science. In the field of silk textiles graft copolymerization modification of vinyl and other monomers crosslinking agent modification and other methods are used to overcome the shortcomings of silk like being easy to wrinkle. The graft modified monomers mainly include ethylene methacrylate and methylacrylamide. The active groups on crosslinking agents such as polycarboxylic acid / anhydride and epoxide are covalently combined with carboxyl hydroxyl and amino groups on macromolecules of silk fibroin to improve the wrinkle resistance of silk fabrics. In the field of biomedicine silk fibroin materials with appropriate chemical modification have better biological activity drug delivery ability antimicrobial properties and mechanical properties. The optimization of these properties enables silk fibroin materials to show great potential in drug control delivery tissue regeneration and wound repair. The applied research in the field of environmental science mainly focuses on the adsorption separation and catalysis of impurities in water. Therefore the modification of amino acid residues grafting and cross-linking of protein macromolecules can change some important properties of silk fibroin and meet the requirements of various applications and functionalization of silk fibroin. In many fields of chemical modification and application of silk fibroin protein fruitful results have been achieved which has laid a good foundation for the further development of related fields and also shows that the chemical modification of silk fibroin material has great potential and application prospects. However there are still some problems that need to be overcome and further improved in the current chemical modification methods such as mild modification conditions and accurate adjustment of the degree of modification which will be the research direction of related fields in the future. © 2022 Authors. All rights reserved.     

丝素降解生成的低分子多肽对细胞生长性能的影响

分析丝素降解生成的低分子多肽(low-molecular-weight silk fibroin peptides,LMW-SF)对细胞生长的影响。LMW-SF通过中性蛋白酶酶解丝素蛋白(silk fibroin,SF)获得,分别采用过滤除菌和高压蒸汽灭菌处理后,在0.1~5.0 mg/m L体积浓度条件下,检测LMW-SF对人正常肝细胞(L02)、人肝癌细胞(HepG2)的生长影响,计算相对增殖率(relative growth rate,RGR)。结果显示:当LMW-SF体积浓度较低(0.1 mg/m L和0.5 mg/m L)时,LMW-SF对细胞生长影响较小;当其体积浓度较高(2.5 mg/m L和5.0 mg/m L)时,RGR值最低至8.3%,呈强抑制细胞生长作用;高压蒸汽灭菌处理后,RGR最高达227.4%,呈强促细胞生长作用。研究结果表明:高压蒸汽处理可以使LMW-SF变性失活,并实现强促细胞生长作用,可成为蛋白类物质应用于组织工程支架时的必需工艺环节。     

Heat Transfer Analysis of Sterilization of Canned Milk Using Computational Fluid Dynamics Simulations

A uniform and effective heat distribution inside the canned milk is very crucial for achieving effective sterilization. It is extremely difficult to establish the temperature profile inside the canned milk during continuous industrial scale operation. Computational fluid dynamics （CFD） simulation can be a useful tool to determine the temperature distribution of the fluid inside the can during the sterilization process. A CFD model was developed for the sterilization of canned milk at 121 ~C. The simulation results were validated with the experimental measurements of temperatures. The formation and movement of slowest heating zone （SHZ） during the sterilization process was tracked. Moreover, effect of can position （vertical and horizontal） during processing on milk temperature distribution inside the can was also investigated. Higher Grashof and Rayleigh numbers were obtained for vertical positioning of can compared to horizontal can processing. Further, effectiveness of the process was calculated based on F-value and these results reinforced the positive effect of horizontal position of can during the sterilization process.     

Study on the structure and properties of modified silk with ultraviolet absorbent北大核心CSCD

The silk fiber has an irreplaceable position in textile fibers and related silk fabrics have the advantages of light and airy texture good moisture absorption and breathability comfort in wear etc. It is also widely used in other fields such as the biomedical sector. However silk also has its own limitations poor light resistance and susceptibility to ultraviolet light especially the ultraviolet light of 290-400 nm wavelength in daylight such as under which condition it is prone to yellowing and photodegradation. The yellowing of silk is due to the photo-oxidation of tyrosine and tryptophan in silk protein under the action of ultraviolet light from sunlight and due to the production of yellow substances which affects the whiteness of silk. In addition from the molecular structure of silk most of the amino acids susceptible to UV light are distributed in the amorphous region. As the amorphous region is affected the structure of the crystalline region is also gradually relaxed the local degradation begins and the silk protein macromolecule chain is cleaved which leads to the decrease of the mechanical properties of silk fibers and accelerates the aging of silk fibers and fabrics. Therefore it is necessary to modify the silk products outside the anti-purple line. The current methods used to modify silk are mostly for post finishing modification including coating impregnation and chemical grafting methods but these methods often affect the original color or feel of the fabric and the durability of the modified effect is also poor. The feeding method is a green method to obtain modified silk by spraying mulberry leaves or artificial feed mixed with modifier which is ingested by silkworm and transferred to silk gland. In this study five aminobenzene UV absorbers were used as exogenous additive food for silkworms. The effect of molecular polarity on the transport of modifiers to silk glands was investigated and their effects on silkworm development and silk structural properties were studied. It was found that the aminobenzene UV absorbers were more easily transferred to the central silk gland silk glue and less to the posterior silk gland (fibroin). 4-dimethylaminobenzoic acid was found to be the highest in the posterior silk gland with a content of 3. 27 μg / strip. The cocoon width and cocoon quality of this group were significantly lower than those of the control group and the silk gum content was increased when this group was used as the study object. Compared with the control group the relative content of β-folded structure and crystallinity of the silk in the addition feeding group decreased slightly. The silkworm silk in the feeding group showed a certain UV absorption ability. After 330 h UV irradiation the breaking strength and elongation of the control group decreased by 48. 95% and 43. 52% respectively while those of the feeding group decreased by 42. 03% and 34. 18% respectively. In this paper UV absorbers were added to silkworms to obtain modified silk mainly focusing on the transfer of the modifier to the silk gland and the structural properties of the modified silk only for the most UV absorbers to enter the silk gland of the posterior group of silk. Other properties of the modified silk such as washing resistance have not been studied and some more in-depth studies are required. For instance it needs to be studied in depth for the limited absorption of exogenous additives by silkworms additive food's being not always absorbed by silkworms and transferred to the silk gland and the mechanism of action between the additive food and silk protein after the former's entering the silk gland. © 2022 Authors. All rights reserved.     

Preliminary Findings on Anticancer and Lymphocyte Stimulated Activities of Bioactive Compounds Extracted from Vietnam Carica papaya Leaves

In this study, the target bioactive compounds （e.g., alkaloids, flavonoids, saponins and other polar compounds） in Vietnamese Caricapapaya leaves were extracted. The cytotoxic activities of the papaya leaves extracts on the selected tumor cell lines, such as lung cancer cell line LU-1, carcinoma cell line KB, breast cancer cells MCF7 and leukemia cell line HL-60, were examined. Preliminary findings showed a high inhibitive activity of papaya leave extracts against the four tested tumor cell lines at the concentration of 100 μg/mL. Out of the bioactive compounds in papaya leaves extract, alkaloids showed the highest inhibitive activity （105.95% on MCF7 and 91.86% on LU-1）, followed by polar compounds （62.88% on LU-1 and 21.80% on KB）, and saponins （59.74% on MCF7 and 25.25% on LU-1）. Flavonoids has the lowest inhibitive activity on cell lines （e.g., 45.51% on MCF7 and 20.32% on LU-1）. Taken together, the results suggest that alkaloids have a relatively high inhibitive activity on the selected tumor cell lines and their stimulated concentration at 50% （IC50） values for on MCF7 and KB were 24.67 μg/mL and 33.56 μg/mL, respectively. However, the result pointed out the immunostimulatory ability of only polar compounds and saponins which could stimulate the growth of in vitro lymphocytes but not flavonoids and alkaloids. The SC50 （stimulated concentration at 50%） values of polar compounds and saponins were 287.87μg/mL and 192.99 μg/mL, respectively.     

臭氧冰在水产品保鲜中的研究(英文)

The effects of ozone ice on the shelf life of Pseudosciaena crocea and cuttlefish,stored under refrigeration(4 ± 0.5℃) were studied by monitoring the microbiological,chemical and sensory changes for a period of 17 days.Results showed that the shelf life could be lengthened 4～5 days preserved by 4mg/kg ozone ice.The total volatility basis nitrogen(TVB-N) was reduced and the bacteria colony was decreased by 92%.The bactericidal effectiveness of ozone ice is strong enough to attain better preservation effect.As a convenient,simple and environmental friendly method,it could be used in the preservation and transportation of fishery products.     

Research on biochemical degumming process of meyer sedge北大核心

In this paper, biochemical degumming process was conducted to meyer sedge stems. Based on the residual gum rate as the study index, orthogonal experiment was proposed to optimize the biochemical enzymes degumming process and the influence of enzyme concentration, reaction time, pH value, reaction temperature on biochemical degumming process was investigated and the effects of alkali concentration, degumming time, temperature on the enzymatic degumming process were also analyzed. The results of experiments indicated that, effect of enzyme concentration and alkali concentration on the degumming effect was remarkable on biochemical degumming process of meyer sedge, when the concentration of enzyme preparation was 10% (owf), pH value was 5.0, the reaction temperature was 60 °C, lye concentration was 10% (owf), alkali boiling time was 4 h and the temperature was 130 °C, the degumming effect was the best.     

Preparation of Lignin Based Anion Exchanger for Nitrate and Phosphate Removal

Tertiary amino alkali lignin (TA-AL) was successfully synthesized by a two-step approach;its application as an adsorbent for nitrate and phosphate ions in effluents was investigated.TA-AL was characterized by FT-IR,zeta potential,SEM,and elemental analysis.Kinetic and equilibrium adsorption isotherms were determined to investigate the adsorption capacity of TAAL.The results revealed that TA-AL had a very strong adsorption capacity towards anions;the value of pHPZC (PZC,point of zero charge) was about 9.2.The adsorption of nitrate and phosphate ions was related to effluent pH and initial anion concentration.The maximum absorption of nitrate and phosphate ions was about 26.9 and 18.4 mg/g when the initial concentration of the ions was 50 mg/L.The adsorption kinetics conformed to the pseudo-second-order kinetic equation,and the equilibrium data were suitably expressed by the Freundlich model.The regeneration studies confirmed that the lignin-based material was a promising adsorbent for nitrate and phosphate ions in water.     

吡虫啉拌种对烟蚜防效及烟草生长的影响

The objective of this study was to explore the effects of tobacco seed dressing with imidacloprid against Myzus persicae and towards growth of tobacco at 4 different doses which was conducted through floating seedlings and the field plot experiment. The results showed that, the treatments of seed dressing with 48.27 μL per one thousand tobacco seeds imidacloprod could inhibit seed germination and delay germination time. The treatments didn`t effect significantly on the economical characters of tobacco in the seedling stage. Moreover, on the control of Myzus persicae, the treatments had the supreme control effect of 69.63%. They also showed a significantly positive effect on the economical characters of tobacco in the stage of growth after transplant. Overall, the present results indicate that the treatments of seed dressing with 48.27 μL per one thousand tobacco seeds imidacloprod are recommended.      

One-step Fabrication of Cellulose/Graphene Conductive Paper

In this study,a straightforward,one-step wet-end formation process was employed to prepare cellulose/graphene conductive paper for antistatic packing materials.Cationic polyacrylamide was introduced into the cellulose/graphene slurry to improve the graphene loading on the surfaces of the cellulose fibers.The effect of the super calender process on the properties of the cellulose/graphene conductive paper was investigated.When 55 wt% graphene was added,the volume resistivity of the cellulose/graphene conductive paper was 94.70 W·cm,decreasing to 35.46 W·cm after the super calender process.The cellulose/graphene conductive paper possessed excellent anti-static ability and could be used as an anti-static material.     

PSO-based Parameter Tuning for a Two-Degree-of-Freedom IMC Scheme and Its Application to Paper Basis Weight Control

Basis weight is an important indicator for evaluating paper quality and a major factor directly affecting the economic benefits of enterprises. Focusing on the large time-delay, time-varying, and nonlinear characteristics of a basis weight control system, a two-degree-of-freedom(TDF) internal model control(IMC) method based on a particle swarm optimization(PSO) algorithm was proposed. The method took the integral of time multiplied by the absolute error(ITAE) as the objective function, and the PSO algorithm was used to optimize the time constant of the tuning IMC filter. The simulation results for the control system under the proposed TDF-IMC method based on the PSO algorithm demonstrate good set-point tracking performance, strong anti-interference capabilities, and good robustness properties. The application results revealed that the basis weight fluctuation range of the paper was ±2 g/m~2, which significantly improved both the control quality and the product quality.     

Effects of Probiotic Lactobacillus gasseri Strains of Breast-Fed Infant in a Murine Model

The ingestion of probiotic lactic acid bacteria has been evaluated and noted that it has an effect on the balance of desirable microbiota in the gastrointestinal tract. Lactobacillus gasseri demonstrates good survival in the gastrointestinal tract, and it has been associated with a variety of probiotic activities and roles, including the reduction of fecal mutagenic enzymes, the production of bacteriocins and the stimulation of macrophages immunomodulation. The aim of the study was to evaluate the effects of a pool of L. gasseri strains isolated from the feces of breastfed infants added in the human milk of healthy women. The milk was both pasteurized and unpasteurized, to verify the cell cytotoxicity of macrophages and to quantify the production of immunologic mediators such as IL-4, IL-6, IFN-γ, TNF-α, NO and oxygen intermediary compounds （H2O2）. The administration of raw human milk and pasteurized human milk to infants is a regular, encouraged practice in units of intensive therapy （UITs） and our present investigation verified the beneficial effect of addition of a pool of L. gasseri to pasteurized human milk （PHML）. Our results show that probiotic supplementation helped to maintain cell viability, reduced IL-6 and IFN-γ production and stimulated TNF-α, NO, H2O2, IL-4 production. Nevertheless, the results indicate that the addition of lactobacillus to human milk was not a determinant in the production of TNF-α. L. gasseri added to breast milk did not present a cytotoxic risk, and the addition ofL. gasseri to pasteurized milk of human milk bank would benefit newborns that depend on milk banks for the colonization of more desirable microbiota.     

Adsorption of Cu2+ by Crosslinked Graft Copolymers of Starch

With the use of acrylic acid(AA)as a monomer,humic acid(HA)and starch as raw materials,potassium persulfate(KPS)as initiator,and N,Ndimethylacrylamide(MBA)as a cross-linking agent,AA/HA/Starch graft copolymer was prepared and characterized by SEM and FT-IR.The effects of temperature,adsorption time,adsorbent dosage,pH value and Cu²⁺initial concentration of the solution on the adsorption performance of the crosslinked graft copolymer were also investigated.The results showed that the Cu²⁺adsorption capacity of the AA/HA/Starch graft copolymer increased firstly and then decreased with increasing adsorbent dosage and the initial pH value of Cu²⁺solution.With the increase of Cu²⁺initial concentration and the extension of adsorption time,the adsorption amount of Cu²⁺increased rapidly and then stabilized.And it decreased slightly with the increase of temperature.At pH value of 5.5,temperature of 298 K,adsorbent dosage of 50 mg,adsorption time of 125 min,and 100 mL Cu²⁺solution with Cu²⁺initial concentration of 100 mg/L,the Cu²⁺adsorption capacity of the crosslinked graft copolymer was 238 mg/g.The adsorption of Cu²⁺by the adsorbent followed the pseudo-second-order kinetic equation and Langmuir isothermal adsorption model,and the adsorption was attached to monolayer chemical adsorption.This study proved that AA/HA/Starch graft copolymer could be used as an efficient adsorbent for the removal of harmful and toxic metal cations such as Cu²⁺from industrial wastewater.     

Determination of Antioxidant and Cytotoxic Activities of Red Seaweed, （Gracilaria manilaensis） against Different Cancer Cell Lines

Antioxidants play an important role in inhibiting and scavenging free radicals in human, providing protection against cellular damage in relation to cancer initiation. Seaweeds have been proved to have high antioxidant activity. Thus, this research was carried out to determine the antioxidant and anticancer properties of edible red seaweed, Gracilaria manilaensis （Gracilariales, Rhodophyta）. The extracts were prepared by Soxhlet extraction using organic solvents with different polarities. The antioxidant activities of extracts were determined in terms of their flee radical scavenging activity （RSA IC50） and total phenolic content （TPC）. The cytotoxic activity of extracts were tested against human ovarian cancer cell line （Caov-3）, human breast cancer cell line （MDA-MB-231 and MCF-7）, human cervical cell line （HeLa）, mouse fibroblast cell line （L929） and Madin-Darby canine kidney （MDCK） and the cell viability after 72 h incubation was determined by methylene blue assay. The findings showed that acetone extract has the lowest DPPH IC50 value followed by ethyl acetate extract. Both extracts also showed high values of TPC. Dichloromethane extract had the strongest cytotoxic on MDA-MB-231 （53.90 μg/mL ± 5.59 μg/mL） and HeLa （95.50 μg/mL）. While, acetone and ethyl acetate extracts were cytotoxic on MCF-7 （66.07 μg/mL） and Caov-3 （69.67 μg/mL ± 13.94 μg/mL）. It could be concluded that the antioxidant and cytotoxic activities of G. manilaensis were influenced by the types of solvents used and thus had a potential to develop as a cancer chemoprevention or anticancer agent against selected cancer.     

Primary Studies on the Microbial Fermentation of 10 - Hydroxy - 2 - Decenoic Acid By Candida BH002

1 Introduction10-hydroxy-2-decenoic acid（10-HDA）, an unsaturated fattyacid, is the most effectual composition in the royal jelly. Studies [1～6]showed that the 10-HAD had remarkable curative effect on restrict-ing the growth of the cancer cell, AIDS virus and others.Now the obtained 10-HDA, wildly used in functional healthyfood and therapeutic medicine, is purified from the royal jelly. Theroyal jelly is limited in nature and the content of 10-HDA in royaljelly is finite, which lead…     

特征峰斜率还原模型快速测定水产品中硝酸盐含量的研究(英文)

Nitrate is closely related to the content of nitrosamine,which is known to be toxic and is determined in aquatic products.In this paper,a new sensitive UV spectrophotometry method based on K-model for rapid determination of nitrate in different kinds of samples was developed.The UV characteristic absorbance points of nitrate were selected and optimized.Under the optimized experimental conditions the calibration equation and K-model were obtained.The calibration curve is linear in the concentration range of 1 to 100μg/ml(R2=0.9973).This method was found to exhibit good accuracy,precision and repeatability.The developed method could be applied to the determination of nitrate in aquatic products and other food products.     

Antimicrobial treatment for wool using quaternary ammonium salt as the biocide北大核心

Antimicrobial treatments of textiles, especially cotton and synthetic fibres, have attracted considerable attention in research and manufacturing. The treatments prevent odour formation and fabric deterioration that arise from the growth of microbes on the textiles during their use or storage. However, wool is more difficult to treat due to its unique surface properties. In this report,we demonstrate that the pretreated wool was also able to exhaust up to 10% ( owf ) (on weight of fabric) of benzalkonium chloride,a cationic quaternary ammonium salt with biocidal activity. The exhaustion on the pretreated wool did not vary between 20 °C and 60 °C and was slightly affected by acidic pH value. Wool fabrics finished with 6% (owf) or more benzalkonium chloride exhibited strong antimicrobial abilities, deactivating 95. 5% ∼99. 9% of E. coli in quantitative antimicrobial assays.     

浆纱压出回潮率与上浆率间的关系

Due to the fact that the relationship between the extrudation moisture regain of sized yarns and size pick-up is expressed only by an approximate equation,and which is not suitable for prewetting sizing process,accurate equations to express the relationships between the extrudation moisture regain of sized yarns and size pick-up for traditional sizing process(including high-pressure sizing) and prewetting sizing are derived.When the prewetting sizing has the same extrudation moisture regain of sized yarns and the same size concentration as the traditional sizing process,prewetting sizing leads to lower size pick-up.The deviation of the extrudation moisture regain obtained by the approximate equation increases with increasing of size concentration.     

Optimization of the Design and Drying Process Adapted to Pineapple Slices

The present work is a study on the influence of temperature and the velocity of air on the drying kinetics of pineapple slices. The main objective is to define from this drying kinetics rules to help a designer choose an adequate principle or drying configuration and optimize the design of dryers adapted to the use of it. The experiments were made in an electric dryer using a parallel flow system. The air was used at three different temperatures （40, 50 and 60 ~C） and at four different velocities （0.27, 0.5, 1 and 1.8 m/s） during the experiment. The results show that an increase of 10 ℃ of the drying temperature reduced the drying time by 45% and increased the drying velocity by 30%. On the set of air velocities tested, it was noticed that the influence of air velocity on drying was more striking at the beginning than at the end of the drying process （variation of less than 20%）. Whatever the variation of parameters during the drying process, the best performance was observed when the products water content during the drying process was between 50% and 80%.