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Sample records for repeated freeze-thaw stress

  1. Repeated freeze-thaw cycles do not alter the biomechanical properties of fibular allograft bone.

    Science.gov (United States)

    Shaw, Joshua M; Hunter, Shawn A; Gayton, J Christopher; Boivin, Gregory P; Prayson, Michael J

    2012-03-01

    Allograft tissues can undergo several freeze-thaw cycles between donor tissue recovery and final use by surgeons. However, there are currently no standards indicating the number of reasonable freeze-thaw cycles for allograft bone and it is unclear how much a graft may be degraded with multiple cycles. We therefore asked whether (1) the mechanical properties of fibular allograft bone would remain unchanged with increasing numbers of freeze-thaw cycles and (2) histologic alterations from increased numbers of freeze-thaw cycles would correspond to any mechanical changes. Fibular allograft segments were subjected to two, four, and eight freeze-thaw cycles and compared biomechanically and histologically with a control group (one freeze-thaw cycle). Two freeze-dried treatments, one after being subjected to one freeze-thaw cycle and the other after being subjected to three freeze-thaw cycles, also were compared with the control group. For all segments, the average ultimate stress was 174 MPa, average modulus was 289 MPa, average energy was 2.00 J, and the average stiffness was 1320 N/mm. The material properties of the freeze-thaw treatment groups were similar to those of the control group: ultimate stress and modulus were a maximum of 16% and 70% different, respectively. Both freeze-dried treatments showed increased stiffness (maximum 53% ± 71%) and energy to failure (maximum 117% ± 137%) but did not exhibit morphologic differences. There were no alterations in the histologic appearance of the bone sections in any group. Fibular allograft segments can be refrozen safely up to eight times without affecting the biomechanical or morphologic properties. Freeze-dried treatments require further study to determine whether the detected differences are caused by the processing. Cryopreserved cortical allografts are thawed by surgeons in preparation for procedures and then occasionally discarded when not used. Refreezing allograft tissues can result in a cost savings because of a

  2. Improvement of tolerance to freeze-thaw stress of baker's yeast by cultivation with soy peptides.

    Science.gov (United States)

    Izawa, Shingo; Ikeda, Kayo; Takahashi, Nobuyuki; Inoue, Yoshiharu

    2007-06-01

    The tolerance to freeze-thaw stress of yeast cells is critical for frozen-dough technology in the baking industry. In this study, we examined the effects of soy peptides on the freeze-thaw stress tolerance of yeast cells. We found that the cells cultured with soy peptides acquired improved tolerance to freeze-thaw stress and retained high leavening ability in dough after frozen storage for 7 days. The final quality of bread regarding its volume and texture was also improved by using yeast cells cultured with soy peptides. These findings promote the utilization of soy peptides as ingredients of culture media to improve the quality of baker's yeast.

  3. Aroma improvement by repeated freeze-thaw treatment during Tuber melanosporum fermentation

    Science.gov (United States)

    Xiao, Deng-Rong; Liu, Rui-Sang; He, Long; Li, Hong-Mei; Tang, Ya-Ling; Liang, Xin-Hua; Chen, Tao; Tang, Ya-Jie

    2015-01-01

    The aroma attributes of sulfurous, mushroom and earthy are the most important characteristics of the aroma of Tuber melanosporum. However, these three aroma attributes are absent in the T. melanosporum fermentation system. To improve the quality of the aroma, repeated freeze-thaw treatment (RFTT) was adopted to affect the interplay of volatile organic compounds (VOCs). Using RFTT, not only was the score on the hedonic scale of the aroma increased from the “liked slightly” to the “liked moderately” grade, but the aroma attributes of sulfurous, mushroom and earthy could also be smelled in the T. melanosporum fermentation system for the first time. A total of 29 VOCs were identified, and 9 compounds were identified as the key discriminative volatiles affected by RFTT. Amino acid analysis revealed that methionine, valine, serine, phenylalanine, isoleucine and threonine were the key substrates associated with the biosynthesis of the 9 key discriminative VOCs. This study noted that amino acid metabolism played an important role in the regulation of the aroma of the T. melanosporum fermentation system. PMID:26607288

  4. Aroma improvement by repeated freeze-thaw treatment during Tuber melanosporum fermentation.

    Science.gov (United States)

    Xiao, Deng-Rong; Liu, Rui-Sang; He, Long; Li, Hong-Mei; Tang, Ya-Ling; Liang, Xin-Hua; Chen, Tao; Tang, Ya-Jie

    2015-11-26

    The aroma attributes of sulfurous, mushroom and earthy are the most important characteristics of the aroma of Tuber melanosporum. However, these three aroma attributes are absent in the T. melanosporum fermentation system. To improve the quality of the aroma, repeated freeze-thaw treatment (RFTT) was adopted to affect the interplay of volatile organic compounds (VOCs). Using RFTT, not only was the score on the hedonic scale of the aroma increased from the "liked slightly" to the "liked moderately" grade, but the aroma attributes of sulfurous, mushroom and earthy could also be smelled in the T. melanosporum fermentation system for the first time. A total of 29 VOCs were identified, and 9 compounds were identified as the key discriminative volatiles affected by RFTT. Amino acid analysis revealed that methionine, valine, serine, phenylalanine, isoleucine and threonine were the key substrates associated with the biosynthesis of the 9 key discriminative VOCs. This study noted that amino acid metabolism played an important role in the regulation of the aroma of the T. melanosporum fermentation system.

  5. Durability of Concrete Subjected to the Combined Actions of Flexural Stress,Freeze-thaw Cycles and Bittern Solutions

    Institute of Scientific and Technical Information of China (English)

    YU Hongfa; SUN Wei; ZHANG Yunsheng; GUO Liping; LI Meidan

    2008-01-01

    Freeze-thaw durabilities of three types of concretes-normal portland cement concrete (OPC),high strength concrete (HSC) and steel fiber reinforced high strength concrete (SFRHSC)were systemically investigated under the attacks of chemical solution,and combination of external flexural stress and chemical solution.Four kinds of bitterns from salt lakes in Sinkiang,Qinghai,Inner Mongolia and Tibet provinces of China were used as chemical attack solutions.The relative dynamic modulus (RDM) was used as an index for evaluating the damage degree during the course of chemical attack and stress corrosion.The experimental results show that the freeze-thaw durability of concrete is visibly reduced in the present of the flexural stress,i e,stress accelerates the damage process.In order to quantify the stress accelerated effect,a stress accelerating coefficient was proposed.The stress accelerating coefficient is closely related with the types of bitterns and the numbers of freeze-thaw cycles is.The more numbers of freeze-thaw cycles is,the greater the stress accelerating coefficient for various concretes will be.In addition,there also exists a critical ratio of external stress to the maximum flexural stress.If the stress ratio exceeds the critical one,the freeze-thaw durability of various concretes will be greatly decreased compared to the responding concretes without applied stress.The critical stress ratio of OPC,HSC and SFRHSC is 0.30,0.40 and 0.40,respectively,indicating that HSC and SFRHSC have advantages over OPC and are suitable to use in the bittern erosion regions.

  6. NMR Pore Structure and Dynamic Characteristics of Sandstone Caused by Ambient Freeze-Thaw Action

    Directory of Open Access Journals (Sweden)

    Bo Ke

    2017-01-01

    Full Text Available For a deeper understanding of the freeze-thaw weathering effects on the microstructure evolution and deterioration of dynamic mechanical properties of rock, the present paper conducted the nuclear magnetic resonance (NMR tests and impact loading experiments on sandstone under different freeze-thaw cycles. The results of NMR test show that, with the increase of freeze-thaw cycles, the pores expand and pores size tends to be uniform. The experimental results show that the stress-strain curves all go through four stages, namely, densification, elasticity, yielding, and failure. The densification curve is shorter, and the slope of elasticity curve decreases as the freeze-thaw cycles increase. With increasing freeze-thaw cycles, the dynamic peak stress decreases and energy absorption of sandstone increases. The dynamic failure form is an axial splitting failure, and the fragments increase and the size diminishes with increasing freeze-thaw cycles. The higher the porosity is, the more severe the degradation of dynamic characteristics is. An increase model for the relationships between the porosity or energy absorption and freeze-thaw cycles number was built to reveal the increasing trend with the freeze-thaw cycles increase; meanwhile, a decay model was built to predict the dynamic compressive strength degradation of rock after repeated freeze-thaw cycles.

  7. Phenome data - Freeze-thaw stress - DGBY | LSDB Archive [Life Science Database Archive metadata

    Lifescience Database Archive (English)

    Full Text Available ces Genome Database; http://www.yeastgenome.org/ ) GENE Standard Gene Name in SGD Growth rate BM/BW Rate of growth in non-strees...AW represents rate of growth after exposure to freeze-thaw strees (Mutant/Wild-type), (AM/AW)/(BM/BW) repres

  8. In Vitro Study on Lethal Effect of Human Choroidal Melanoma OCM-1 Cell Line by Repeating-70℃Freeze Thawing%In Vitro Study on Lethal Effect of Human Choroidal Melanoma OCM-1 Cell Line by Repeating-70℃ Freeze Thawing

    Institute of Scientific and Technical Information of China (English)

    Bin Liu; Yongping Li; Bo Zhang; Wenxin Zhang

    2007-01-01

    Objective: To investigate the effects of repeating -70℃ freeze thawing on human choroidal melanoma cell line OCM-1.Methods: OCM-1 cells were frozen by repeating -70℃ freeze thawing with various durations and frequencies. Then the inhibit rate of cells was examined by MTT essay.The cell viability was measured by monoclonal formation assay. We also used the HE staining, immunohistochemistry staining and the laser-scanning confocal microscopy (LSCM) to investigate the morphological changes of the cells.Results: The growth of OCM-1 cells was inhibited by repeating -70℃ freeze thawing in time-dependent and frequency-dependent manners (P < 0.01). Different morphous including necrosis and apoptosis of the cells could be observed after -70℃ freeze thawing by the LSCM.Conclusion: Repeating -70℃ freeze thawing can not only kill cells directly and induce considerable cells to apoptosis, but also inhibit the growth of the survivals. The kill and wound ratio of the cells disposal with different times and frequencies present variance. And the distinction when treated with different frequencies during the same time is much more significant than different times with the same frequency, which guide clinical workers to choose repeating cryotherapy with short term method instead of single cryotherapy with long term in choroidal melanoma treatment.

  9. The effect of repeated freeze-thaw cycles on human muscle tissue visualized by postmortem computed tomography (PMCT).

    Science.gov (United States)

    Klop, Anthony C; Vester, Marloes E M; Colman, Kerri L; Ruijter, Jan M; Van Rijn, Rick R; Oostra, Roelof-Jan

    2017-09-01

    The aim of this study was to determine whether effects of repetitive freeze-thaw cycles, with various thawing temperatures, on human muscle tissue can be quantified using postmortem computed tomography (PMCT) technology. An additional objective was to determine the preferred thawing temperature for muscle tissue in this study. Human cadaver upper extremities were divided into two different thawing temperature groups and underwent a series of four freeze-thaw cycles in total. Axial CT scans were performed after each cycle. CT attenuation (in Hounsfield units, HU) was measured in four muscles of the upper extremities. HU values changed significantly with the introduction of each subsequent freeze-thaw cycle. Moreover, the changes in HU values were different for each thawing group. There was a significant increase of HU values in both groups between t0 and t1 . Unfrozen tissue showed large variation of HU values in all samples. It was possible to distinguish between samples thawed at different thawing temperatures based on their respective HU values. It is advisable to keep the number of freeze-thaw cycles to just one, if the human cadaveric tissue is to be used for educational purposes. The preferred thawing temperature in this study is 2°C. Clin. Anat. 30:799-804, 2017. © 2017Wiley Periodicals, Inc. © 2017 The Authors Clinical Anatomy published by Wiley Periodicals, Inc. on behalf of American Association of Clinical Anatomists.

  10. The cytoplasmic Cu,Zn superoxide dismutase of saccharomyces cerevisiae is required for resistance to freeze-thaw stress. Generation of free radicals during freezing and thawing

    DEFF Research Database (Denmark)

    Park, J I; Grant, C M; Davies, Michael Jonathan

    1998-01-01

    The involvement of oxidative stress in freeze-thaw injury to yeast cells was analyzed using mutants defective in a range of antioxidant functions, including Cu,Zn superoxide dismutase (encoded by SOD1), Mn superoxide dismutase (SOD2), catalase A, catalase T, glutathione reductase, gamma-glutamylc...

  11. TonEBP/NFAT5 regulates downstream osmoregulatory proteins during freeze-thaw stress in the wood frog.

    Science.gov (United States)

    Zhang, Yichi; Al-Attar, Rasha; Storey, Kenneth B

    2017-09-22

    Rana sylvatica, known as the wood frog, can survive extremely cold temperatures during winter by undergoing full-body freezing, where it tolerates freezing of 65-70% of its total body water. During freezing, cellular dehydration decreases damage to the cell by preventing ice crystallization. Challenged with many stresses, these animals are forced to develop physiological adaptations to osmoregulation and osmoprotection that are necessary to ensure their survival. The purpose of this study was to elucidate a potential mechanism by which the transcription factor, NFAT5, regulates the expression of three osmoregulatory proteins (aldose reductase, SMIT, and BGT-1). These three proteins control cellular concentrations of the organic osmolytes: betaine (BGT-1), myo-inositol (SMIT), and sorbitol (aldose reductase). We studied this mechanism during the freeze-thaw stress in R. sylvatica liver, kidney, and skeletal muscle. Protein expression of BGT-1, SMIT, aldose reductase, and NFAT5 were examined using immunoblotting. We identified that the NFAT5 pathway facilitated osmoregulation in a tissue-specific manner during freezing. In skeletal muscle, we demonstrated that NFAT5 upregulation in thawing led to increases in the protein levels of BGT-1. In liver, NFAT5 was upregulated during freezing, along with aldose reductase. Furthermore, neither of these patterns of expression were observed in kidney as none of these four proteins showed differential expression during freezing or thawing. Therefore, the NFAT5 osmoregulatory pathway appears to be tissue-specific. Our novel findings on a mechanism of osmoregulation in R. sylvatica highlight the importance of studying naturally stress-tolerant animals to identify novel pro-survival pathways. Copyright © 2017. Published by Elsevier Inc.

  12. EPINEPHRINE CONCENTRATION IN WILD BOAR (SUS SCROFA L. SERUM AFTER REPEATED ELISA TESTED FREEZE-THAWING CYCLES

    Directory of Open Access Journals (Sweden)

    Neška Vukšić

    2013-06-01

    Full Text Available Blood samples for determining of epinephrine concentration and biochemical parameters in the blood serum of wild boars were taken from 42 healthy wild boars, both sexes, during the hunting season. All animals in good condition, body weight 20 to 95 kg, were divided into two groups up to 50 kg (group A and up to 95 kg (Group B. Epinephrine concentration was determined by ELISA twice: one week after taking samples and a month after repeated freezing at -80°C. It was higher in relation to the reference value of domestic pigs and human (109.45 pg/ml in A and 119.54 pg/ml in B group. Repeated freezing and re-analysis after a month were resulted in lower concentrations of epinephrine (12% in young and 11.17% in adult animal, but without statistical significance (P>0.05. Biochemical analysis results’ show increased glucose and triglycerides concentrations compared to the reference values, while other indicators were observed within or slightly increased referring to the normal range. The correlation between glucose and epinephrine was not determined.

  13. The repeated drying-wetting and freezing-thawing cycles affect only the active pool of soil organic matter

    Science.gov (United States)

    Semenov, Vyacheslav; Zinyakova, Natalya; Tulina, Anastasiya

    2016-04-01

    The decrease in the content of soil organic carbon, particularly in active form, is one of the major problems of the 21st century, which is closely related to the disturbance of the biogeochemical carbon cycle and to the increase in the emission of carbon dioxide into the atmosphere. The main reasons for the SOM losses are the surplus of the SOM active pool losses due to mineralization, erosion, and infiltration over the input of fresh organic matter to the soil, as well as the changes in the soil conditions and processes due to natural and anthropogenic disturbing impacts. Experiments were carried out with mixed samples from the upper layers of soddy-podzolic soil, gray forest soil, and typical chernozems. Soil samples as controls were incubated after wetting for 150 days. The dynamics and cumulative production of C-CO2 under stable temperature (22°C) and moisture conditions were determined; the initial content of potentially mineralizable organic matter (C0) in the soil at the beginning of the incubation was then calculated to use these data as the control. Other soil samples were exposed in flasks to the following successive treatments: wetting →incubation → freezing → thawing → incubation →drying. Six repeated cycles of disturbing impacts were performed for 140 days of the experiment. After six cycles, the soil samples were incubated under stable temperature and moisture conditions for 150 days. The wetting of dried soils and the thawing of frozen soils are accompanied by the pulsed dynamics of the C-CO2 production with an abrupt increase in the rate of the C-CO2 emission within several days by 2.7-12.4 and 1.6-2.7 times, respectively, compared to the stable incubation conditions. The rate of the C-CO2 production pulses under each subsequent impact decreased compared to the preceding one similarly for all studied soils, which could be due to the depletion in potentially mineralizable soil organic matter (C0). The cumulative extra C-CO2 production by

  14. Behavior of High Water-cement Ratio Concrete under Biaxial Compression after Freeze-thaw Cycles

    Institute of Scientific and Technical Information of China (English)

    SHANG Huaishuai; SONG Yupu; OU Jinping

    2008-01-01

    The high water-cement ratio concrete specimens under biaxial compression that completed in a triaxial testing machine were experimentally studied.Strength and deformations of plain concrete specimens after 0,25,50 cycles of freeze-thaw.Influences of freeze-thaw cycles and stress ratio on the peak stress and deformation of this point were analyzed aecording to the experimental results.Based on the test data,the failure criterion expressed in terms of principal stress after difierent cycles of freeze-thaw,and the failure criterion with consideration of the influence of freeze-thaw cycle and sffess ratio were proposed respectively.

  15. Damage Evaluation on Freeze-Thawing Process of Food by Using NMR

    Science.gov (United States)

    Andou, Hiroko; Fukuoka, Mika; Miyawaki, Osato; Suzuki, Toru

    Freeze-thawing process gives significant damages for food structure. Several new techniques have been attempted for quantitative evaluation of the damages. In this study, using NMR (nuclear magnetic resonance) with a stimulated echo method, restricted diffusion phenomena of water molecules was measured for damaged food (onion and tuna) tissues that were subjected to the repeat of freeze-thawing, Through experiments, water permeability of tissue membrane was calculated. The water permeability of fresh tissues for onion showed clearly restricted diffusion, but after freeze-thawing, it disappeared. On the other hand, the water permeability of fresh tuna tissue was small significantly, even though it was a little higher after freeze-thawing. After all, the damage level after freeze-thawing showed a significant difference between onion and tuna. These results support the view that plant tissue is very sensitive to freeze-thawing and that the water permeability of plant is much lower than that of animal.

  16. Freeze-thaw stress of Alhydrogel ® alone is sufficient to reduce the immunogenicity of a recombinant hepatitis B vaccine containing native antigen.

    Science.gov (United States)

    Clapp, Tanya; Munks, Michael W; Trivedi, Ruchit; Kompella, Uday B; Braun, LaToya Jones

    2014-06-24

    Preventing losses in vaccine potency due to accidental freezing has recently become a topic of interest for improving vaccines. All vaccines with aluminum-containing adjuvants are susceptible to such potency losses. Recent studies have described excipients that protect the antigen from freeze-induced inactivation, prevent adjuvant agglomeration and retain potency. Although these strategies have demonstrated success, they do not provide a mechanistic understanding of freeze-thaw (FT) induced potency losses. In the current study, we investigated how adjuvant frozen in the absence of antigen affects vaccine immunogenicity and whether preventing damage to the freeze-sensitive recombinant hepatitis B surface antigen (rHBsAg) was sufficient for maintaining vaccine potency. The final vaccine formulation or Alhydrogel(®) alone was subjected to three FT-cycles. The vaccines were characterized for antigen adsorption, rHBsAg tertiary structure, particle size and charge, adjuvant elemental content and in-vivo potency. Particle agglomeration of either vaccine particles or adjuvant was observed following FT-stress. In vivo studies demonstrated no statistical differences in IgG responses between vaccines with FT-stressed adjuvant and no adjuvant. Adsorption of rHBsAg was achieved; regardless of adjuvant treatment, suggesting that the similar responses were not due to soluble antigen in the frozen adjuvant-containing formulations. All vaccines with adjuvant, including the non-frozen controls, yielded similar, blue-shifted fluorescence emission spectra. Immune response differences could not be traced to differences in the tertiary structure of the antigen in the formulations. Zeta potential measurements and elemental content analyses suggest that FT-stress resulted in a significant chemical alteration of the adjuvant surface. This data provides evidence that protecting a freeze-labile antigen from subzero exposure is insufficient to maintain vaccine potency. Future studies should

  17. BEHAVIOR OF AIR-ENTRAINED CONCRETE AFTER FREEZE-THAW CYCLES

    Institute of Scientific and Technical Information of China (English)

    Huaishuai Shang; Yupu Song; Jinping Ou

    2009-01-01

    The experimental study of air-entrained concrete specimens subjected to different cycles of freeze-thaw was completed. The dynamic modulus of elasticity, weight loss, the cubic compressive strength, compressive strength, tensile strength and cleavage strength of air-entrained concrete were measured after 0, 100, 200, 300, 400 cycles of freeze-thaw. The experimental results showed that the dynamic modulus of elasticity and strength decreased as the freeze-thaw was repeated. The influences of freeze-thaw cycles on the mechanical properties, the dynamic modulus of elasticity and weight loss were analyzed according to the experimental results. It can serve as a reference for the maintenance, design and the life prediction of dams, hydraulic structures, offshore structures, concrete roads and bridges in northern cold regions.

  18. Automated freeze-thaw cycles for decellularization of tendon tissue - a pilot study.

    Science.gov (United States)

    Roth, Susanne Pauline; Glauche, Sina Marie; Plenge, Amelie; Erbe, Ina; Heller, Sandra; Burk, Janina

    2017-02-14

    Decellularization of tendon tissue plays a pivotal role in current tissue engineering approaches for in vitro research as well as for translation of graft-based tendon restoration into clinics. Automation of essential decellularization steps like freeze-thawing is crucial for the development of more standardized decellularization protocols and commercial graft production under good manufacturing practice (GMP) conditions in the future. In this study, a liquid nitrogen-based controlled rate freezer was utilized for automation of repeated freeze-thawing for decellularization of equine superficial digital flexor tendons. Additional tendon specimens underwent manually performed freeze-thaw cycles based on an established procedure. Tendon decellularization was completed by using non-ionic detergent treatment (Triton X-100). Effectiveness of decellularization was assessed by residual nuclei count and calculation of DNA content. Cytocompatibility was evaluated by culturing allogeneic adipose tissue-derived mesenchymal stromal cells on the tendon scaffolds. There were no significant differences in decellularization effectiveness between samples decellularized by the automated freeze-thaw procedure and samples that underwent manual freeze-thaw cycles. Further, we inferred no significant differences in the effectiveness of decellularization between two different cooling and heating rates applied in the automated freeze-thaw process. Both the automated protocols and the manually performed protocol resulted in roughly 2% residual nuclei and 13% residual DNA content. Successful cell culture was achieved with samples decellularized by automated freeze-thawing as well as with tendon samples decellularized by manually performed freeze-thaw cycles. Automated freeze-thaw cycles performed by using a liquid nitrogen-based controlled rate freezer were as effective as previously described manual freeze-thaw procedures for decellularization of equine superficial digital flexor tendons

  19. 反复冻融对草鱼和鲤鱼冷冻鱼糜品质变化的影响%Effect of Repeated Freeze-Thaw Cycles on Quality Properties of Frozen Surimis of Grass Carp and Common Carp

    Institute of Scientific and Technical Information of China (English)

    吴晓; 孙卫青; 杨华; 马俪珍

    2012-01-01

    In order to explore the effect of repeated freeze-thaw cycles on their quality,color parameters,cooking loss,water-holding capacity,shearing force and TBARS of frozen surimis of grass carp and common carp were determined during 4 repeated freeze-thaw cycles.More freeze-thaw cycles could result in a significant increase(P0.05) in cooking loss of grass carp and common carp surimi and a significant reduction(P0.05) in water-holding capacity but no significant difference between both fish species was observed.The shearing force of grass carp surimi was inversely proportional to the number of freeze-thaw cycles.The first freeze-thaw cycle caused denaturation and contraction of protein in common carp surimi and resulted in an increase in its shearing force,whereas the parameter declined with increasing number of freeze-thaw cycles.Repeated freeze-thaw cycles aggravated lipid oxidation in surimi from both fish species.As a result,significantly increased TBARS(P0.05) was observed and a significant difference(P0.05) was also between both fish species.After the fourth freeze-thaw cycle,surimi from both carp species lost their original color.%为了解反复冻融对淡水冷冻鱼糜品质变化的影响,本实验以草鱼和鲤鱼冷冻鱼糜为研究对象,通过测定二者在反复冷冻-解冻后的色泽、蒸煮损失、持水性、剪切力和硫代巴比妥酸值等指标,分析冷冻鱼糜冷冻贮存4个月过程中,期间反复冻融4次后其品质的变化。结果表明:随着冻融次数的增加,两种鱼糜的蒸煮损失均显著增加(P〈0.05),持水性显著降低(P〈0.05),而两种鱼之间差异不显著。草鱼冷冻鱼糜的剪切力随着冻融次数的增加直线式下降;第1次冻融,鲤鱼鱼糜蛋白变性收缩,剪切力提高,之后随着冻融次数的增加剪切力下降。反复冻融促进了两种冷冻鱼糜的脂肪氧化,TBARS值显著增加(P〈0.05),且组间差异也显著(P〈0.05)。

  20. Freeze-thaw induced gelation of alginates.

    Science.gov (United States)

    Zhao, Ying; Shen, Wei; Chen, Zhigang; Wu, Tao

    2016-09-01

    Adding divalent ions or lowering pH below the pKa values of alginate monomers are common ways in preparing alginate gels. Herein a new way of preparing alginate gels using freeze-thaw technique is described. Solvent crystallization during freezing drove the polymers to associate into certain structures that became the junction zones of hydrogels after thawing. It enabled the preparation of alginate gels at pH 4.0 and 3.5, two pH at which the gel could not be formed previously. At pH 3.0 where alginate gel could be formed initially, applying freeze-thaw treatment increased the gel storage modulus almost 100 times. The formation of hydrogels and the resulting gel properties, such as dynamic moduli and gel syneresis were influenced by the pH values, number of freeze-thaw cycles, alginate concentrations, and ionic strengths. The obtained hydrogels were soft and demonstrated a melting behavior upon storage, which may find novel applications in the biomedical industry.

  1. Freezing-thawing behaviour of fine-grained soils subjected to surcharge loads

    Directory of Open Access Journals (Sweden)

    Ahmet Şahin Zaimoğlu

    2013-03-01

    Full Text Available In cold climate zones, the shallow foundation soils belonging to civil engineering constructions such as highways, railways, irrigation channels are subject to freezing-thawing under these loads. In this study, with the purpose of representing such soils the freeze-thaw experiment has been carried out for the situation where load is applied on the samples in addition to the traditional method where there is no load on the sample. The experiments have been conducted on samples prepared with the compaction under standard proctor energy of fine grained soils. In the experiments conducted in the traditional method the unconfined compressive strength values of samples after 1, 3, 5 and 10 cycles have been determined. Then the freeze-thaw experiments were repeated while a load representing 25 %, 35 % and 50 % of these values was on the samples. As a result of the experiments conducted with both methods, the freeze-thaw resistances of the samples have been determined. It was observed that the freeze-thaw resistance values of soils under load are less than those found by the traditional method.

  2. The Potential for Achieving Freeze/Thaw Protection in Concrete through the addition of Rubber Crumb

    OpenAIRE

    Richardson, Alan; Coventry, Kathryn; Pienaar, Jaques

    2011-01-01

    This paper evaluates the use of recycled rubber tyres in the form of rubber crumb as a freeze/thaw protection agent when used in concrete. Reusing scrap tyres in the form of rubber crumb, in concrete could benefi t the environment by reducing landfi ll and reducing the chemical usage of air entraining agents. The test procedure involved subjecting concrete to freeze/thaw cycles at 5 days of age. Thawing was conducted in water to ensure full saturation of pores and maximum stress on the concre...

  3. Freeze-Thaw Cycles Effects on Soil Compaction in a Clay Loam

    Science.gov (United States)

    Jabro, J.; Evans, R.; Iversen, W.

    2012-04-01

    Inappropriate soil management practices and heavier farm machinery and equipment have led to an increase in soil compaction in the last two decades prompting increased global concern regarding the impact of soil compaction on crop production and soil quality in modern mechanized agriculture. A 3-yr comprehensive study was established to evaluate the dynamic of freeze-thaw cycles on soil compaction in a clay loam soil. Plots of frozen soils were compared with plots where soils were prevented from freezing with electrically heated blankets commonly used on concrete. Results showed that frequent freeze-thaw cycles over the winter alleviated a majority of soil compaction at the 0 - 20 cm depth. Soil penetration resistance in compacted soils was reduced by 73 and 68% over the winter at the 0 - 10 and 10 - 20 cm depths, respectively, due to dynamic effects of freeze-thaw cycles on soil structure and particles configuration. In unfrozen compacted soils, the penetration resistance was also reduced by 50 and 60% over winter at the 0 - 10 and 10 - 20 cm depths, respectively, due to the biology of soil, microbial activity, and disruptive effects of shrink-swell cycles. These results have demonstrated of how repeated freeze-thaw cycles can alleviate soil compaction, alter soil physical quality and create optimal soil conditions required for profitable growth of agricultural crops. The results from this study will save growers considerable time, money and energy currently required to alleviate soil compaction using other methods such as sub-soiling and deep tillage. We believe that Mother Nature provides ways to reverse soil compaction and improve soil structure and aggregation through the dynamic of freeze-thaw cycles that soils in Montana and other parts of the country go through each year. We concluded that the Mother Nature is the most effective and cheapest way to alleviate soil compaction.

  4. Disaggregating meteorites by automated freeze thaw.

    Science.gov (United States)

    Charles, Christopher R J

    2011-06-01

    An automated freeze-thaw (AFT) instrument for disaggregating meteorites is described. Meteorite samples are immersed in 18.2 MΩ water and hermetically sealed in a clean 30 ml Teflon vial. This vial and its contents are dipped between baths of liquid nitrogen and hot water over a number of cycles by a dual-stepper motor system controlled by LabView. Uniform and periodic intervals of freezing and thawing induce multiple expansions and contractions, such that cracks propagate along natural flaws in the meteorite for a sufficient number of AFT cycles. For the CR2 chondrite NWA801, the boundaries between different phases (i.e., silicates, metal, matrix) became progressively weaker and allowed for an efficient recovery of 500 individual chondrules and chondrule fragments spanning 0.2-4.7 mm diameters after 243 AFT cycles over 103.3 h. Further FT experiments on a basalt analog showed that the time required for freezing and thawing the same number of cycles can be reduced by a factor of ∼4. © 2011 American Institute of Physics

  5. Evaluating Freeze-Thaw Deterioration with Tensile Strength

    Science.gov (United States)

    Komar, A. J. K.; Boyd, A. J.

    2017-06-01

    Freeze-thaw damage is one of the leading contributors to infrastructure deterioration in temperate northern climates. Deterioration caused by freeze-thaw cycling is primarily induced by hydraulic pressures within the hydrated cement paste matrix that cause tensile cracking. Such damage should, therefore, be more effectively detected with tensile testing. This work presents the detection and evaluation of ongoing freeze-thaw (F/T) damage in plain concrete cylinders using the pressure tensile strength test, as it compares to compressive strength evaluation. Pressure tension test results exhibited significantly higher levels of deterioration compared to compression testing, with the samples losing up to 90% of their undamaged tensile capacity. Moreover, it was shown that tensile strength testing is far more sensitive to freeze-thaw deterioration, evidenced by a significant drop in the tensile to compressive strength ratio to below 5%.

  6. 岩体冻融疲劳损伤模型与评价指标研究%FATIGUE DAMAGE MODELAND EVALUATION INDEX FOR ROCK MASS UNDER FREEZING-THAWING CYCLES

    Institute of Scientific and Technical Information of China (English)

    刘泉声; 黄诗冰; 康永水; 黄兴

    2015-01-01

    Frost heaving pressure in rock mass undergoes a process of initiation,development and dissipation under the freezing-thawing condition,which results in the fatigue degradation of the physical and mechanical properties of rock. The freezing-thawing damage model and the damage evaluation method are the key problems for the rock mass in cold regions. There are many evaluation indexes of freezing-thawing damage including the porosity,the longitudinal wave velocity and the elastic modulus. The frost heaving pressure was considered to be equivalent to the triaxial tensile stress for frozen rock mass. A freezing-thawing fatigue damage model was established based on the equivalent triaxial tensile stress. The equation describing the freezing-thawing damage variation has the same expression but the different physical meaning with that obtained under repeated uniaxial tensile stress. A new unified damage variable depending on the p-wave velocity and the porosity was deduced based on the definition of the dynamic modulus of elasticity. The damage variable includes the effect of dual physical parameters,and is a better prediction index for the uniaxial compressive strength under different freeze-thaw cycles. The loss of 40% of dynamic elastic modulus was defined as the damage threshold. With the damage threshold,the maximum failure freeze-thaw cycle was determined. The freezing-thawing damage model was solved in combination with the unified damage variable. Finally,the validity and applicability of the freezing-thawing fatigue damage model were illustrated through two examples.%岩体冻融损伤模型与评价是研究岩体经历冻胀力萌生、发展与消散反复作用后物理力学性质劣化的主要内容,现有对岩体冻融循环后的损伤评价指标主要有孔隙率、纵波波速、静动弹性模量等物理参数。冻胀力对于岩体可等效为三轴拉伸应力,首先基于三向等效拉应力建立岩体冻融疲劳损伤模型,该冻融

  7. The combined effect of freeze thaw events and heavy metal pollution leads to distinct lethal synergy in Enchytraeus albidus

    DEFF Research Database (Denmark)

    Boas, Sara Wincentz; Slotsbo, Stine; Holmstrup, Martin

    Many anthropogenic activities negatively affect the environment and stress the organisms living here in various ways. Due to global warming it is likely that freeze-thaw events will replace permanent freezing of soils in arctic regions. Metals are some of the most common contaminants in soil....... Bioaccumulation of copper was also quantified to expose any increase in body burden in freeze-thaw treated worms. Regardless of the physiological responses, it is evident that arctic organisms are negatively affected by the environmental impact of global warming and exploitation of mineral deposits through mining....

  8. Determination of long-term strength of frozen loess after numerous freeze-thaw cycles

    Institute of Scientific and Technical Information of China (English)

    Hong Zhou; Ze Zhang; WenJie Feng; Jiao Ming; ZhongQiong Zhang

    2014-01-01

    In order to determine the changing rule of long-term frozen soil strength and elucidate the connection between long-term strength and soil physical properties, frozen loess was subjected to 4, 6, 8, 10, and 50 freeze-thaw cycles, under closed-state conditions in a constant-temperature box. The frozen samples were tested on a spherical template indenter, and the results show that under the effect of repeated freeze-thaw cycles, the long-term strength of frozen loess decreased;changes in the mechanical property indices were highly unstable during the first 10 cycles;the soil strength and density were the greatest at the eighth cycle while the void ratio was the smallest;and after eight cycles all of the indices had less fluctuation and certain rising or falling tendencies. By converting the number of freeze-thaw cycles into elapsed time in the tests, three different forecasting methods of long-term soil strength could be assessed and the soil equivalent cohesive force after 10 years, 20 years, or 30 years could be estimated.

  9. Evaluation Effects of the Short- and Long-Term Freeze-Thaw Exposure on the Axial Behavior of Concrete-Filled Glass Fiber-Reinforced-Polymer Tubes

    Directory of Open Access Journals (Sweden)

    Hend El-Zefzafy

    2013-01-01

    Full Text Available Previous studies have demonstrated the high performance of the concrete-filled fiber-reinforced polymer (FRP tubes (CFFTs as a stay-in-place formwork and confining material for concrete structures. However, there are several concerns related to the behavior of CFFT as a protective jacket against harsh environmental effects. The environmental effects such as freeze-thaw cycles and deicing salt solutions may affect materials properties, which may affect the structural response of CFFT members as well. This paper presents the test results of experimental investigation on the durability of short- and long-term behaviors of CFFT members. Test variables included the effect of confining using GFRP tubes, freeze-thaw cycles exposure in salt water, and the number of freeze-thaw cycles. CFFT cylinders (150 × 300 mm were prepared and exposed to 100 and 300 freeze-thaw cycles in salt water condition. Then, pure axial compression tests were conducted in order to evaluate the performance of specimens due to freeze-thaw exposure, by comparing the stress-strain behavior and their ultimate load capacities. Test results indicated that the confinement using CFFT technique significantly protected the concrete when subjected to freeze-thaw exposure.

  10. Evaluation and Comparison of Freeze-Thaw Tests and Air Void Analysis of Pervious Concrete

    DEFF Research Database (Denmark)

    Lund, Mia Schou Møller; Hansen, Kurt Kielsgaard; Kevern, John T.;

    2016-01-01

    to eval-uate the freeze-thaw resistance of fresh or hardened pervious concrete and correspondingly what constitutes acceptable freeze-thaw durability. A greater understanding of the correlation between the freeze-thaw performance and the air void structure of pervious concrete is needed. In the present...... effectively relieve the pressure when water freezes....

  11. Classification and Assessment of Freeze-Thaw Erosion in Tibet, China

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jian-guo; YANG Yong-hong; LIU Shu-zhen

    2005-01-01

    Based on the analysis of existing relevant research result, a theoretical basis for the defining freeze-thaw erosion zones of Qinghai-Tibet Plateau was been put forward, and a equation for calculating the altitude of the lower bound of the freeze-thaw erosion zones of Qinghai-Tibet Plateau was been established in this paper. Moreover, the freeze-thaw erosion zones in Tibet was been identified by using Geographical Information System (GIS) software. Next, based on the comprehensive analysis of impact factors of freeze-thaw erosion, this paper chooses annul temperature range, slop and vegetation as three indexes, works out the criteria for relative classification of freeze-thaw erosion, and realizes the relative classification of the freeze-thaw erosion in Tibet under the support of GIS software. Then, a synthetic assessment of freeze-thaw erosion in Tibet was been done according to the relative classification result.

  12. Freeze/thaw phenomena in concrete at low temperatures

    DEFF Research Database (Denmark)

    Johannesson, Björn

    2007-01-01

    Freeze/thaw damage in concrete is by general practice concluded to be a problem that can be avoided by using air-entraining agents to develop an air bubble structure in the hardened concrete together with the use of a relatively low water to cement ratio in mix. This fact is true for inner damages......, however, the so-called salt-frost damage, occurring mainly at the surfaces of concrete constructions, can not totally be avoided by the above mentioned method. The performance and the mechanisms occurring in concrete, with a substantial amount of water in its micro-structure, at very low temperature are......, however, in most part unknown. In this work samples of concrete at different water to cement ratios and air bubble contents subjected to freeze/thaw cycles with the lowest temperature at about -80 oC are investigated. By adopting a novel technique a scanning calorimeter is used to obtain data from which...

  13. Effect of waxy rice flour and cassava starch on freeze-thaw stability of rice starch gels.

    Science.gov (United States)

    Charoenrein, Sanguansri; Preechathammawong, Nutsuda

    2012-10-01

    Repeatedly frozen and thawed rice starch gel affects quality. This study investigated how incorporating waxy rice flour (WF) and cassava starch (CS) in rice starch gel affects factors used to measure quality. When rice starch gels containing 0-2% WF and CS were subjected to 5 freeze-thaw cycles, both WF and CS reduced the syneresis in first few cycles. However CS was more effective in reducing syneresis than WF. The different composite arrangement of rice starch with WF or CS caused different mechanisms associated with the rice starch gel retardation of retrogradation, reduced the spongy structure and lowered syneresis. Both swollen granules of rice starch and CS caused an increase in the hardness of the unfrozen and freeze-thawed starch gel while highly swollen WF granules caused softer gels. These results suggested that WF and CS were effective in preserving quality in frozen rice starch based products.

  14. Freezing-Thawing Characteristics of Botanical Tissues and Influence of Water Morphology

    Institute of Scientific and Technical Information of China (English)

    WU Hai-Ling; MA Yuan; PENG Xiao-Feng

    2004-01-01

    @@ A series of visualization experiments were conducted to investigate the transport phenomena and interface behaviour during the freezing-thawing process of typical botanical tissues. Attention was paid to the growth of ice crystals and the advance of the phase-change interface. A comparison was made to identify the freezing/thawing behaviour for different tissues under various freezing conditions. Based on the experimental observation, analyses were conducted to explore the influence of water morphology on the freezing/thawing characteristics.

  15. STUDY ON THE DAMAGE MECHANISM OF PORE STRUCTURE IN CONCRETE SUBJECTED TO FREEZE-THAW CYCLES

    OpenAIRE

    Ben Li; Kaiyuan Wang; Jize Mao; Qingyong Guo

    2015-01-01

    It is well know that freeze-thaw cycles play the most significant role in the durability evolution in concrete structures, freeze-thaw cycles have been accounted as one of the major factors on the damage and demolition of concrete. Microscopic parameters have been used for describing the characterizations of damage in concrete under freeze-thaw actions by researchers. However, their models could not provide specific damage factors or parameters. In this paper, a new damage model and equation ...

  16. Freeze-thaw bond properties of new-old concrete

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Using composite cubic specimens of new-old concrete, the bond splitting tensile strength and failure mechanism for the interface of new-old concrete in saturating state were explored when exposed to freeze-thaw cycling. Specimens were experienced for 0,25,50,75,100 and 125 freezing cycles. The roughness and ad hesion agent including cement paste, cement mortar and cement paste with 10 percent of UEA expanding agent were also investigated. The test results indicate that the bond splitting tensile strength decreases with increased numbers of freezing-and-thawing cycles. The roughness and adhesion agent have different effects on the bond strength.

  17. Advances in studies on concrete durability and countermeasures against freezing-thawing effects

    Institute of Scientific and Technical Information of China (English)

    WuJian Yan; FuJun Niu; XianJun Zhang; Jing Luo; GuoAn Yin

    2014-01-01

    This-paper-is-a-meta-analysis-of-recent-domestic-and-foreign-research-on-freezing-thawing-effects-on-concrete-durability.-The-main-theories-on-the-mechanisms-of-freeze-thaw-damage-to-concrete-are-introduced:-the-hydrostatic-pressure-theory,-the-osmotic-pressure-theory,-the-critical-water-saturation-degree-theory,-the-dual-mechanism-theory,-and-the-mi-cro-ice-crystal-lens-model-theory.-The-influence-laws-of-freezing-thawing-on-the-mechanical-properties-of-concrete-are-summarized,-and-countermeasures-to-improve-concrete-durability-in-freezing-thawing-circumstances-are-presented.-This-work-provides-valuable-references-for-future-engineering-constructions-in-cold-regions.

  18. Alpha-ketoglutarate enhances freeze-thaw tolerance and prevents carbohydrate-induced cell death of the yeast Saccharomyces cerevisiae.

    Science.gov (United States)

    Bayliak, Maria M; Hrynkiv, Olha V; Knyhynytska, Roksolana V; Lushchak, Volodymyr I

    2017-08-05

    Stress resistance and fermentative capability are important quality characteristics of baker's yeast. In the present study, we examined protective effects of exogenous alpha-ketoglutarate (AKG), an intermediate of the tricarboxylic acid cycle and amino acid metabolism, against freeze-thaw and carbohydrate-induced stresses in the yeast Saccharomyces cerevisiae. Growth on AKG-supplemented medium prevented a loss of viability and improved fermentative capacity of yeast cells after freeze-thaw treatment. The cells grown in the presence of AKG had higher levels of amino acids (e.g., proline), higher metabolic activity and total antioxidant capacity, and higher activities of catalase, NADP-dependent glutamate dehydrogenase and glutamine synthase compared to control ones. Both synthesis of amino acids and enhancement of antioxidant system capacity could be involved in AKG-improved freeze-thaw tolerance in S. cerevisiae. Cell viability dramatically decreased under incubation of stationary-phase yeast cells in 2% glucose or fructose solutions (in the absence of the other nutrients) as compared with incubation in distilled water or in 10 mM AKG solution. The decrease in cell viability was accompanied by acidification of the medium, and decrease in cellular respiration, aconitase activity, and levels of total protein and free amino acids. The supplementation with 10 mM AKG effectively prevented carbohydrate-induced yeast death. Protective mechanisms of AKG could be associated with the intensification of respiration and prevention of decreasing protein level as well as with direct antioxidant AKG action.

  19. Effect of freeze-thaw cycles on load transfer between the biomineral and collagen phases in bovine dentin

    Energy Technology Data Exchange (ETDEWEB)

    Deymier-Black, A.C., E-mail: AlixDeymier2010@u.northwestern.edu [Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208 (United States); Almer, J.D., E-mail: almer@aps.anl.gov [Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439 (United States); Haeffner, D.R., E-mail: haeffner@aps.anl.gov [Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439 (United States); Dunand, D.C., E-mail: dunand@northwestern.edu [Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208 (United States)

    2011-10-10

    Stabilization of biological materials by freezing is widespread in the fields of medicine and biomaterials research and yet, in the case of hard biomaterials such as dentin, there is not a good understanding of how such treatments might affect the mechanical properties. The freezing and thawing may have a number of different effects on dentin including formation of cracks in the microstructure and denaturation of the collagen. Using high-energy synchrotron X-ray diffraction, the apparent moduli of bovine dentin samples were measured before and after various numbers of freeze-thaw cycles. It was determined that repeated freezing and thawing has no measurable effect on the hydroxyapatite or fibrillar apparent moduli up to 10 cycles. This confirms that the use of low temperature storage for stabilization of dentin is reasonable in cases where stiffness is a property of importance. Highlights: {yields} Studied the effect of freezing on the load transfer of HAP and fibrils in dentin. {yields} X-ray scattering measured HAP and fibril apparent moduli vs. freezing cycles. {yields} Apparent moduli did not vary significantly between 0 and 10 freeze thaw cycles. {yields} Residual strains imply no widespread cracking due to volumetric expansion of water. {yields} Dentin can be freeze-thawed with no significant effects on elastic properties.

  20. Supplementation freeze-thawed media with selenium protect adipose-derived mesenchymal stem cells from freeze-thawed induced injury.

    Science.gov (United States)

    Valadbeygi, Arash; Naji, Tahere; Pirnia, Afshin; Gholami, Mohammadreza

    2016-10-01

    Successful freezed-thaw of adipose-derived mesenchymal stem cells (ADMSCs) could be a major step in regenerative medicine as well as in the cloning of animal breeds. The aim of this study was to evaluate the efficacy of selenium on the optimizing of freezed-thaw media in the ADMSCs. ADMSCs were extracted from NMRI mice and purified with positive selection Monoclonal CD105 Antibody (PE) and negative selection Monoclonal CD31 and CD45 Antibody using MACS method as well as differentiation to adipose and bone tissue. ADMSCs were divided into four groups. ADMSCs were freezed-thaw under standard condition with or without the addition of 5 ng/ml selenium to both the cryopreservation and thawing solutions. Frozen cells were thawed after four months and viability and cytotoxicity of the cells were analyzed by the Trypan blue test and MTT assay respectively. RNA was extracted and cDNA was synthesized and the expression of apoptotic genes (P53, Fas, Bax, Caspase3, and Bcl2) was examined using Real time-PCR Rotor gene 2009. This study compares slow and rapid methods of cryopreservation. After thawing, viability of the cells treated with selenium was higher than the control group in rapid and slow cryopreserved ADMSCs. Also, the percentage of living cells in the slow cooling method was considerably more than with the rapid cooling method. After analysis of the results using Real time-PCR, the Bcl2 gene was shown to be expressed in both the rapid and slow cooling methods. In the rapid cooling group in addition to the BCL-2 gene, p53 was also expressed. It appears that selenium prevented the apoptotic genes from expression due to its anti-apoptotic effects. The slow cooling method is better and more optimized for ADMSCs protecting them from oxidative damage to a greater extent compared to the rapid cooling method. Copyright © 2016 Elsevier Inc. All rights reserved.

  1. Diurnal freeze/thaw cycles of the ground surface on the Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    YANG MeiXue; YAO TanDong; GOU XiaoHua; HIROSE Nozomu; FUJII Hide Yuki; HAO LiSheng; D.F.LEVIA

    2007-01-01

    The exchange of energy and water between the lithosphere and atmosphere mainly takes place at the ground surface. Therefore, freeze/thaw condition at the ground surface is an important factor in examining the interactions between the land surface and atmosphere. Based on the observation data obtained by CEOP/CAMP-Tibet, the diurnal freeze/thaw cycles of the ground surface near Naqu, central Tibetan Plateau was preliminarily analyzed. The results show that the surface layer was completely frozen for approximately one month. However, the time that the ground surface experienced diurnal freeze/thaw cycles was about 6 months. The high frequency of freeze/thaw cycles at the ground surface significantly influences water and energy exchanges between ground and atmosphere over half a year. The interaction processes between the ground and atmosphere under different soil conditions (such as complete thaw, complete freeze and diurnal freeze/thaw cycles) are issues worthy of further examination.

  2. 冻融试验对土中含水量分布的影响%Freeze-Thaw Experiment Influence on Moisture Content Distrution of Soil

    Institute of Scientific and Technical Information of China (English)

    杨成松; 何平; 程国栋; 顾同欣

    2004-01-01

    The silty clay and silty loam are two typical soil types obtained from two test sites along the Qinghai-Tibet railway. The two types of soil have been designed various initial dry densities, water eontents, temperature conditions in repeated freezing and thawing tests with free access to water at the bottom. Afterfreeze-thaw cycles, the moisture content in the freeze-thaw zone increases more than that in the unfrozen zone to the peak approximately at the top of the samples. With comparison of the water contents in the frozen and thawed states, the moisture content in the upper freeze-thaw zone in the frozen state is greater than that in the thawed state, while that in unfrozen zone in the frozen state is smaller than that in the thawed state. Within the region of the frost front, the water content in frozen state is smaller than that in thawed state. These findings help to study the freeze-thaw mechanisms deeply and perfect the forecasting module of moisture transferring in freeze-thaw cycles.

  3. Polyvinyl alcohol/chitosan/montmorillonite nanocomposites preparation by freeze/thaw cycles and characterization

    Directory of Open Access Journals (Sweden)

    Părpăriţă Elena

    2014-12-01

    Full Text Available Polyvinyl alcohol (PVA and chitosan (CS based hydrogels are often chosen to obtain hydrogels as being considered non-toxic for human body. The present study aims the preparation and physical chemical characterisation of hydrogels based PVA and CS by using an environmental friendly method i.e. freeze/thaw. In this method the only parameters affecting the hydrogels’ properties is the PVA concentration in solution, time and number of cycles of freezing / thawing. Repeated freezing and thawing cycles resulted in production of a highly elastic polyvinyl alcohol hydrogel with higher degree of crystallization. Adding chitosan in polyvinyl alcohol hydrogel is giving to the newly formed material, biocompatibility and antibacterial properties due to the free amino groups of chitosan. Higher mechanical and thermal characteristics of PVA/CS based hydrogels were obtained by addition of a small amount of inorganic nanoparticles (montmorillonite clay, C30B into the matrix (i.e. 1%. Scanning electron microscopy (SEM, Fourier transform infrared spectroscopy (FT-IR, near-infrared chemical imaging spectroscopy (NI-CI, X-ray diffraction (XRD, thermogravimetric analysis (TG, swelling and rheological measurements were used to characterize the polyvinyl alcohol/chitosan/montmorillonite properties. The swelling degree increased with decreasing chitosan content in hydrogels and the variation is opposite in nanocomposites, decreasing after introducing the nanoclay. The swelling behaviour was influenced by the presence of the nanoparticles. The plasticizer effect of the nanoparticles was reflected by obtaining a more compact hydrogel network with higher mechanical and thermal properties. The proposed materials can be a promising alternative in biomedical applications

  4. Influence of Freeze-Thaw Cycles on RNA Integrity of Gastrointestinal Cancer and Matched Adjacent Tissues.

    Science.gov (United States)

    Hu, Ying; Han, Haibo; Wang, Yixue; Song, Lijie; Cheng, Xiaojing; Xing, Xiaofang; Dong, Bin; Wang, Xiaohong; Chen, Meng; Zhang, Lianhai; Ji, Jiafu

    2017-06-01

    Comparative analysis of RNA expression profiles between cancer and adjacent noncancerous tissues is an important part of cancer research. High-quality RNA is essential for consistent, reliable results, especially for identification of cancer biomarkers. However, the impact of freeze-thaw cycles on the quality of RNA both in gastrointestinal cancer and paired adjacent tissues is still unclear. To investigate the influence of freeze-thaw cycles on RNA integrity and overall histomorphology of gastrointestinal cancer and paired adjacent noncancerous tissues. Gastrointestinal cancer and matched adjacent noncancerous tissues were frozen and thawed twice before extracting RNA. Total RNA in each sample was extracted with TRIzol reagents and the RNA integrity was assessed by RNA integrity number (RIN) on an Agilent Bioanalyzer. Light microscopy was then used to assess tissue composition and morphology. RIN values for all samples tended to decrease in correlation with the frequency of freeze-thawing. With an RIN cutoff value of 6, RNA extracted from pancreatic cancer tissues was not qualified after the first freeze-thaw cycle. Moreover, all RNA extracted from adjacent noncancerous tissues had nonqualifying RIN scores after the first freeze-thaw cycle, except for liver tissues. Microscopically, all samples displayed qualified tissue morphology regardless of freeze-thaw cycle frequency. Freeze-thawing affects the RNA integrity, but not the tissue morphology of gastrointestinal cancer and paired adjacent noncancerous tissues. Furthermore, the RNA extracted from adjacent noncancerous tissues is more easily degraded than that in cancer tissues.

  5. Resillient modulus of freez-thaw affected granular soils for pavement design and evaluation. Part 1: Laboratory tests on soils from Winchendon, Massachusetts, test sections

    Science.gov (United States)

    Cole, D.; Bentley, D.; Durell, G.; Johnson, T.

    1986-07-01

    This is the first of a series of four reports about laboratory and field testing of various granular road and airfield subgrades. This report details the acquisition, testing and analysis of six soils from a test site in Winchendon, Massachusetts. Repeated load triaxial tests were done on frozen and thawed soils to characterize the variations in the their resilient properties throughout the seasons. Linear regression yielded empirical equations relating the resilient modulus to applied stress, unfrozen water content (for frozen soils), moisture tension (for thawed soils) and density. Equipment and test procedures (given in detail) were developed that allowed simulation in the laboratory of the gradual recovery of stiffness that occurs in the field after thawing. The resilient moduli were strongly dependent on soil state, dropping at least two orders of magnitude upon thawing. For all soils the moduli increased with increasing confining stress, generally decreased with increasing principal stress ratio, and increased with increasing moisture tension levels. The resilient moduli increased by a factor of approximately two as the materials recovered from the effects of a freeze-thaw cycle. The recovery process is well modeled as a function of soil moisture tension level. The stress sensitivity did not appear to be a function of the soil moisture tension level. The report also includes tabulations of all the repeated load triaxial test data.

  6. Substantiation of Reference Method For Determining Concrete’s Freeze-Thaw Resistance

    Science.gov (United States)

    Nikolskiy, S.; Pertseva, O.

    2017-01-01

    It has been analytically proved that using concrete’s rate of set ε as a measure of damage, instead of decreasing of tensile strength R, increases freeze-thaw resistance’s accuracy of estimation a lot under otherwise equal conditions by the time of freeze-thaw cycling. Also it has been experimentally shown that ratio of relative decreasing R to ε in direction, perpendicular to compression, is assumed to be independent on values R and ε for a given concrete and on the ways of achieving them during mechanical or freeze-thaw cycling. Taking this into account patented methods for estimation of concrete’s freeze-thaw resistance as per values R and ε received after freezing and thawing cycles of some specimens and their postliminary failure by linear compression was substantiated.

  7. Effect of high doses of chemical admixtures on the strength development and freeze-thaw durability of portland cement mortar

    Science.gov (United States)

    Korhonen, Charles J.

    This thesis examines the low-temperature strength development of portland cement concrete made with high doses of chemical admixtures dissolved in the mixing water and the possible beneficial effect of these admixtures on that concrete's long-term freeze-thaw durability. The literature shows that high doses of chemical admixtures can protect fresh concrete against freezing and that, under certain conditions, these admixtures can enhance the freeze-thaw durability of concrete. The challenge is that there are no acceptance standards in the U.S. that allow chemicals to be used to protect concrete against freezing. Also, the perception is that chemicals might somehow harm the concrete. This perception seems to be based on the fact that deicing salts, when applied to concrete pavement, cause roadways to scale away. This study investigated the effect of high doses of commercially available admixtures on fresh concrete while it gained strength at low temperature and on hardened concrete exposed to repeated cycles of freezing and thawing in a moist environment. The reason for studying off-the-shelf admixtures was that these materials are approved for use in concrete; they were already governed by their own set of standards. Four mortars were examined, each with a different cement and water content, when dosed with five commercial admixtures. This allowed the fresh mortar to gain appreciable strength when it was kept at nearly -10C. The admixtures also enhanced the freeze-thaw durability of the mortar, even when it was not air-entrained. Clearly, as the dosage of admixture increased beyond approximately 22% by weight of water, the mortar appeared to be unaffected by up to 700 cycles of freezing and thawing.

  8. Remote sensing of freeze-thaw transitions in Arctic soils using the complex resistivity method

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Yuxin [Lawrence Berkeley National Laboratory (LBNL); Hubbard, Susan S [Lawrence Berkeley National Laboratory (LBNL); Ulrich, Craig [Lawrence Berkeley National Laboratory (LBNL); Wullschleger, Stan D [ORNL

    2013-01-01

    Our ability to monitor freeze - thaw transitions is critical to developing a predictive understanding of biogeochemical transitions and carbon dynamics in high latitude environments. In this study, we conducted laboratory column experiments to explore the potential of the complex resistivity method for monitoring the freeze - thaw transitions of the arctic permafrost soils. Samples for the experiment were collected from the upper active layer of Gelisol soils at the Barrow Environmental Observatory, Barrow Alaska. Freeze - thaw transitions were induced through exposing the soil column to controlled temperature environments at 4 C and -20 C. Complex resistivity and temperature measurements were collected regularly during the freeze - thaw transitions using electrodes and temperature sensors installed along the column. During the experiments, over two orders of magnitude of resistivity variations were observed when the temperature was increased or decreased between -20 C and 0 C. Smaller resistivity variations were also observed during the isothermal thawing or freezing processes that occurred near 0 C. Single frequency electrical phase response and imaginary conductivity at 1 Hz were found to be exclusively related to the unfrozen water in the soil matrix, suggesting that these geophysical 24 attributes can be used as a proxy for the monitoring of the onset and progression of the freeze - thaw transitions. Spectral electrical responses and fitted Cole Cole parameters contained additional information about the freeze - thaw transition affected by the soil grain size distribution. Specifically, a shift of the observed spectral response to lower frequency was observed during isothermal thawing process, which we interpret to be due to sequential thawing, first from fine then to coarse particles within the soil matrix. Our study demonstrates the potential of the complex resistivity method for remote monitoring of freeze - thaw transitions in arctic soils. Although

  9. Effects of the soil freeze-thaw process on the regional climate of the Tibet Plateau

    Science.gov (United States)

    Luo, S., Sr.; Chen, B.; Lu, S.; Zhang, Y.; Ma, D.

    2015-12-01

    Single-point and regional simulation experiments on the Tibet Plateau, both with and without consideration of the soil freeze-thaw process, were set up with CLM3.5 and RegCM4 models. Comparison of the simulated soil temperature and moisture, surface energy flux, and upper-lower atmospheric circulation showed that the regional climate can be influenced by the freeze-thaw process of soil. The results indicate that the freeze-thaw process is a buffer to the seasonal changes in soil and near-surface temperatures and strengthens the energy exchange between the soil and the atmosphere. During the freeze (thaw) process, releasing (absorbing) of phase change energy retards the cooling (heating) effect of air temperature on soil. The soil freeze-thaw process increases (decreases) the surface heat source of the plateau in winter (summer), which increases (decreases) the near-surface temperature in winter (summer). Promoted by atmospheric circulation, the soil freeze-thaw process influences climate at the high and low altitudes of the plateau; this may also contribute to the maintenance of the South Asia High. In the early stages of permafrost degradation, the regional climate effects of freezing and thawing may accelerate the degradation of permafrost.

  10. Freeze-thaw performance of chemically stabilized natural and recycled highway materials

    Institute of Scientific and Technical Information of China (English)

    Tuncer B Edil; Bora Cetin

    2015-01-01

    This article provides an overview of several previous studies that investigated the stiffness and strength performance of chemically stabilized roadway materials under winter conditions (freeze-thaw cycling). The objective of this research was to understand the behavior of different materials stabilized with different type of binders when they were subjected to freeze-thaw cycling. Nine different materials including natural soils (organic soil, clay, silt, sand, and road surface gravel), reclaimed pavement material, and recycled asphalt pavement stabilized with nine different binders (five different fly ashes, lime, cement, lime kiln dust, cement kiln dust) were discussed. This article investigated how the volume, resilient modulus and unconfined compressive strength of soils/materials stabilized with different binders change in response to freeze-thaw cycling. Overall, the review results indicate that the stiffness and strength of all stabilized materials decrease somewhat with freeze-thaw cycling. However, the reduced strength and stiffness of stabilized materials after freeze-thaw cycling was still higher than that of unstabilized-unfrozen original soils and materials. In addition, materials stabilized with cement kiln dust provided the best performance against freeze-thaw cycling.

  11. The Adsorption and Desorption of Pb(2+) and Cd(2+) in Freeze-Thaw Treated Soils.

    Science.gov (United States)

    Li, Linhui; Ma, Jincai; Xu, Meng; Li, Xu; Tao, Jiahui; Wang, Guanzhu; Yu, Jitong; Guo, Ping

    2016-01-01

    Adsorption and desorption are important processes that influence the potential toxicity and bioavailability of heavy metals in soils. However, information regarding adsorption and desorption behavior of heavy metals in soils subjected to freeze-thaw cycles is poorly understood. In the current study, the effect of freeze-thaw cycles with different freezing temperature (-15, -25, -35°C) on soil properties was investigated. Then the adsorption and desorption behavior of Pb(2+) and Cd(2+) in freeze-thaw treated soils was studied. The adsorption amounts of Pb(2+) and Cd(2+) in freeze-thaw treated soils were smaller than those in unfrozen soils (p adsorption amounts of Pb(2+) and Cd(2+) in soils treated with lower freezing temperatures were higher than those in soils treated with higher freezing temperatures. Desorption percentages of Pb(2+) and Cd(2+) in unfrozen soils were smaller than those in freeze-thaw treated soils (p adsorption and desorption behavior of typical heavy metals in freeze-thaw treated soils located in seasonal frozen soils zone in northeast China.

  12. Influence of Freeze-Thaw Damage on the Steel Corrosion and Bond-Slip Behavior in the Reinforced Concrete

    Directory of Open Access Journals (Sweden)

    Fangzhi Zhu

    2016-01-01

    Full Text Available This paper mainly studies the behavior of steel corrosion in various reinforced concrete under freeze-thaw environment. The influence of thickness of concrete cover is also discussed. Additionally, the bond-slip behavior of the reinforced concrete after suffering the freeze-thaw damage and steel corrosion has also be presented. The results show that the freeze-thaw damage aggravates the steel corrosion in concrete, and the results become more obvious in the concrete after suffering serious freeze-thaw damage. Compared with the ordinary concrete, both air entrained concrete and waterproofing concrete possess better resistance to steel corrosion under the same freeze-thaw environment. Moreover, increasing the thicknesses of concrete cover is also an effective method of improving the resistance to steel corrosion. The bond-slip behavior of reinforced concrete with corroded steel decreases with the increase of freeze-thaw damage, especially for the concrete that suffered high freeze-thaw cycles. Moreover, there exists a good correlation between the parameters of bond-slip and freeze-thaw cycles. The steel corrosion and bond-slip behavior of reinforced concrete should be considered serious under freeze-thaw cycles environment, which significantly impact the durability and safety of concrete structure.

  13. Damage Characteristics of Altered and Unaltered Diabases Subjected to Extremely Cold Freeze-Thaw Cycles

    Science.gov (United States)

    Luo, Xuedong; Jiang, Nan; Zuo, Changqun; Dai, Zhenwei; Yan, Suntao

    2014-11-01

    Altered and unaltered diabases are commonly deposited on hydrothermally mineralized slopes. To study their damage characteristics during freeze-thaw cycles, they were sampled from Cihai iron ore mine located in an extremely cold region, Xinjiang, China and examined using acoustic and X-ray diffraction experiments to analyze the differences in their main mineral components and explore their damage characteristics under freeze-thaw conditions. Based on the results of these experiments, their damage and degradation patterns were obtained and the evolution of their physical characteristics including the rock mass loss rate ( L F), rock strength loss rate ( R σ ), P-wave velocity loss rate ( V l), and freeze-thaw coefficient ( K f) was analyzed. In addition, two groups of equations were established to characterize the relationships of these physical and mechanical properties of the rock specimens with the number and temperature of freeze-thaw cycles. The results show that the mineral composition of diabase changes during its alteration, showing increased clay and calcite, and the degradation and evolution patterns of the physical and mechanical parameters ( L F, R σ , V l, and K f) of the altered rocks during freeze-thaw cycles are different from those of diabase, with the altered diabase exhibiting greater damage than the diabase.

  14. Characteristics of sugar surfactants in stabilizing proteins during freeze-thawing and freeze-drying.

    Science.gov (United States)

    Imamura, Koreyoshi; Murai, Katsuyuki; Korehisa, Tamayo; Shimizu, Noriyuki; Yamahira, Ryo; Matsuura, Tsutashi; Tada, Hiroko; Imanaka, Hiroyuki; Ishida, Naoyuki; Nakanishi, Kazuhiro

    2014-06-01

    Sugar surfactants with different alkyl chain lengths and sugar head groups were compared for their protein-stabilizing effect during freeze-thawing and freeze-drying. Six enzymes, different in terms of tolerance against inactivation because of freeze-thawing and freeze-drying, were used as model proteins. The enzyme activities that remained after freeze-thawing and freeze-drying in the presence of a sugar surfactant were measured for different types and concentrations of sugar surfactants. Sugar surfactants stabilized all of the tested enzymes both during freeze-thawing and freeze-drying, and a one or two order higher amount of added sugar surfactant was required for achieving protein stabilization during freeze-drying than for the cryoprotection. The comprehensive comparison showed that the C10-C12 esters of sucrose or trehalose were the most effective through the freeze-drying process: the remaining enzyme activities after freeze-thawing and freeze-drying increased at the sugar ester concentrations of 1-10 and 10-100 μM, respectively, and increased to a greater extent than for the other surfactants at higher concentrations. Results also indicate that, when a decent amount of sugar was also added, the protein-stabilizing effect of a small amount of sugar ester through the freeze-drying process could be enhanced. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

  15. Importance of freeze-thaw events in low temperature ecotoxicology of cold tolerant enchytraeids.

    Science.gov (United States)

    Silva, Ana L Patrício; Enggrob, Kirsten; Slotsbo, Stine; Amorim, Mónica J B; Holmstrup, Martin

    2014-08-19

    Due to global warming it is predicted that freeze-thaw cycles will increase in Arctic and cold temperate regions. The effects of this variation becomes of particular ecological importance to freeze-tolerant species when it is combined with chemical pollutants. We compared the effect of control temperature (2 °C), daily freeze-thaw cycles (2 to -4 °C) and constant freezing (-2 °C) temperatures on the cold-tolerance of oligochaete worms (Enchytraeus albidus) and tested how survival was influenced by pre-exposure to 4-nonylphenol (4-NP), a common nonionic detergent found in sewage sludge amended soils. Results showed that combined effect of 4-NP and daily freeze-thaw cycles can cause higher mortality to worms as compared with sustained freezing or control temperature. Exposure to 4-NP caused a substantial depletion of glycogen reserves which is catabolized during freezing to produce cryoprotective concentrations of free glucose. Further, exposure to freeze-thaw cycles resulted in higher concentrations of 4-NP in worm tissues as compared to constant freezing or control temperature (2 °C). Thus, worms exposed to combined effect of freeze-thaw cycles and 4-NP suffer higher consequences, with the toxic effect of the chemical potentiating the deleterious effects of freezing and thawing.

  16. Experimental Investigation of the Variation of Concrete Pores under the Action of Freeze-Thaw Cycles by Using X-Ray CT

    Directory of Open Access Journals (Sweden)

    Jie Yuan

    2014-01-01

    Full Text Available The variation of concrete pores under the action of freeze-thaw cycles was investigated experimentally by using the X-ray CT. Firstly, the statistical characteristics of pores of concrete specimens were obtained by using the X-ray image analysis. Secondly, the variation of porosity and pore volume of concrete pores were analyzed and discussed by comparing with above characteristics. Thirdly, the failure process of the concrete specimens acted by the freeze-thaw cycles was investigated by scanning the interior of concrete specimens. The results showed that the pore volumes of concrete pores whose volumes were located at the interval [0.5 mm3, 20 mm3] have no big variation in both the amounts and volume of concrete pores, while others were found to have huge change during the process of experiment. The extent of damage acted by the repeated freezing and thawing gradually ranged from surface to complete disintegration of the interior of concrete specimens after 30 cycles of freeze-thaw acting.

  17. Comparison Study of Three Common Technologies for Freezing-Thawing Measurement

    Directory of Open Access Journals (Sweden)

    Xinbao Yu

    2010-01-01

    Full Text Available This paper describes a comparison study on three different technologies (i.e., thermocouple, electrical resistivity probe and Time Domain Reflectometry (TDR that are commonly used for frost measurement. Specially, the paper developed an analyses procedure to estimate the freezing-thawing status based on the dielectric properties of freezing soil. Experiments were conducted where the data of temperature, electrical resistivity, and dielectric constant were simultaneously monitored during the freezing/thawing process. The comparison uncovered the advantages and limitations of these technologies for frost measurement. The experimental results indicated that TDR measured soil dielectric constant clearly indicates the different stages of the freezing/thawing process. Analyses method was developed to determine not only the onset of freezing or thawing, but also the extent of their development. This is a major advantage of TDR over other technologies.

  18. Effect of multiple freeze-thaw cycles on detection of measles, mumps, and rubella virus antibodies.

    Science.gov (United States)

    Pinsky, Norman A; Huddleston, Jeanne M; Jacobson, Robert M; Wollan, Peter C; Poland, Gregory A

    2003-01-01

    We investigated the effect of multiple freeze-thaw cycles on mumps, measles, and rubella virus serum antibody levels with whole-virus immunoglobulin G enzyme-linked immunoassays. Fresh serum samples from nine healthy adult volunteers were divided into six sets of five aliquots each. Samples were taken through a total of 10 freeze-thaw cycles and stored at 4 degrees C until assayed. Each assay measurement was done in replicates of five, and the mean value was reported. After completing 10 freeze-thaw cycles, we found no clinically or statistically significant effect on measured antibody levels and found no discernible detrimental effect on the ability to measure these antibodies by enzyme-linked immunoassays.

  19. Compressive Strength, Chloride Permeability, and Freeze-Thaw Resistance of MWNT Concretes under Different Chemical Treatments

    Directory of Open Access Journals (Sweden)

    Xingang Wang

    2014-01-01

    Full Text Available This study investigated compressive strength, chloride penetration, and freeze-thaw resistance of multiwalled carbon nanotube (MWNT concrete. More than 100 cylindrical specimens were used to assess test variables during sensitivity observations, including water-cement ratios (0.75, 0.5, and 0.4 and exposure to chemical agents (including gum arabic, propanol, ethanol, sodium polyacrylate, methylcellulose, sodium dodecyl sulfate, and silane. To determine the adequate sonication time for MWNT dispersal in water, the compressive strengths of MWNT concrete cylinders were measured after sonication times ranging from 2 to 24 minutes. The results demonstrated that the addition of MWNT can increase the compressive strength of concrete by up to 108%. However, without chemical treatment, MWNT concretes tend to have poor freeze-thaw resistance. Among the different chemical treatments, MWNT concrete treated with sodium polyacrylate has the best compressive strength, chloride resistance, and freeze-thaw durability.

  20. Freeze-thaw regime effects on carbon and nitrogen dynamics in sub-arctic heath tundra mesocosms

    DEFF Research Database (Denmark)

    Grogan, P.; Michelsen, A.; Ambus, P.;

    2004-01-01

    Freeze-thaw fluctuations in soil temperature may be critical events in the annual pattern of nutrient mobilisation that supplies plant growth requirements in some temperate, and most high latitude and high altitude ecosystems. We investigated the effects of two differing freeze-thaw regimes, each...

  1. Durability of Lining Concrete of Subsea Tunnel under Combined Action of Freeze-thaw Cycle and Carbonation

    Institute of Scientific and Technical Information of China (English)

    TIAN Li; CHEN Jingru; ZHAO Tiejun

    2012-01-01

    Through the fast freeze-thaw cycle test,accelerated carbonation test,and natural carbonation test,the durability performance of lining concrete under combined action of freeze-thaw cycle and carbonation were studied.The experimental results indicate that freeze-thaw cycle apparently accelerates the process of concrete carbonation and carbonation deteriorates the freeze resistance of concrete.Under the combined action of freeze-thaw cycle and carbonation,the durability of lining concrete decreases.The carbonation depth of lining concrete at tunnel openings under freeze-thaw cycles and tunnel condition was predicted.For the high performance concrete with proposed mix ratio,the lining concrete tends to be unsafe because predicted carbonation depth exceeds the thickness of reinforced concrete protective coating.Adopting other measurements simultaneously to improve the durability of lining concrete at the tunnel openings is essential.

  2. Behaviour of polycyclic aromatic hydrocarbons (PAH) in soils under freeze-thaw cycles

    Science.gov (United States)

    Zschocke, Anne; Schönborn, Maike; Eschenbach, Annette

    2010-05-01

    The arctic region will be one of the most affected regions by climate change due to the predicted temperature rise. As a result of anthropogenic actions as mining, exploration and refining as well as atmospheric transport pollutions can be found in arctic soils. Therefore questions on the behaviour of organic contaminants in permafrost influenced soils are of high relevance. First investigations showed that permafrost can act as a semi-permeable layer for PAH (Curtosi et al., 2007). Therefore it can be assumed that global warming could result in a mobilization of PAH in these permafrost influenced soils. On the other hand a low but detectable mineralization of organic hydrocarbons by microorganisms under repeated freeze-thaw cycles was analysed (Börresen et al. 2007, Eschenbach et al. 2000). In this study the behaviour and distribution of PAH under freezing and periodically freezing and thawing were investigated in laboratory column experiments with spiked soil materials. Two soil materials which are typical for artic regions, a organic matter containing melt water sand and a well decomposed peat, were homogeneously spiked with a composite of a crude oil and the PAH anthracene and benzo(a)pyrene. After 14days preincubation time the soil material was filled in the laboratory columns (40cm high and 10 cm in diameter). Based on studies by Chuvilin et al. (2001) the impact of freezing of the upper third of the column from the surface downwards was examined. The impact of freezing was tested in two different approaches the first one with a single freezing step and the second one with a fourfold repeated cycle of freezing and thawing which takes about 6 or 7 days each. The experimental design and very first results will be shown and discussed. In some experiments with the peat a higher concentration of anthracene and benzo(a)pyrene could be detected below the freezing front in the unfrozen part of the column. Whereas the concentration of PAH had slightly decreased in

  3. Stimulation of nitrogen turnover due to nutrients release from aggregates affected by freeze-thaw in wetland soils

    Science.gov (United States)

    Song, Yang; Zou, Yuanchun; Wang, Guoping; Yu, Xiaofei

    2017-02-01

    The freeze-thaw phenomenon will occur more frequently in mid-high latitude ecosystems under climate change which has a remarkable effect on biogeochemical processes in wetland soils. Here, we used a wet sieving procedure and a barometric process separation (BaPS) technique to examine the responses of wetland soil aggregates and related carbon and nitrogen turnover affected by the freeze-thaw treatment. Wetland soil samples were divided into a treatment group and a control group. The treatment group was incubated at temperatures fluctuating from 10 °C to -10 °C, whereas the control group was incubated at the constant temperature of 10 °C. A 24 h process was set as the total freeze-thaw cycle, and the experiment had 20 continuous freeze-thaw cycles. In our results, the freeze-thaw process caused great destruction to the >2 mm water-stable aggregates (WSA) fraction and increased the carbon (DOC) content was stimulated during the initial freeze-thaw cycles followed by a rapid decline, and then still increased during subsequent freeze-thaw cycles, which was mainly determined by the soil organic carbon (SOC). The NH4+ and NO3- content, respiration rate and gross nitrification rate were all significantly improved by the freeze-thaw effect. Because the amount of NH4+ and NO3- expressed prominent negative responses to the content of >2 mm WSA fraction and the gross nitrification rate can be stimulated at the initial freeze-thaw cycles, nutrients and substrates may play a leading role in the freeze-thaw treatment regardless of the minimal influences on microbial biomass pools.

  4. Snow cover, freeze-thaw, and the retention of nutrients in an oceanic mountain ecosystem

    NARCIS (Netherlands)

    Wipf, Sonja; Sommerkorn, Martin; Stutter, Marc I.; Wubs, E. R. Jasper; van der Wal, René

    2015-01-01

    As the climate warms, winters with less snow and therefore more soil freeze-thaw cycles are likely to become more frequent in oceanic mountain areas. It is a concern that this might impair the soil's ability to store carbon and nutrients, and lead to increased leaching losses of dissolved C and nutr

  5. Freeze-thaw Effects on Sorption/Desorption of Dissolved Organic Carbon in Wetland Soils

    Institute of Scientific and Technical Information of China (English)

    YU Xiaofei; ZHANG Yuxia; ZHAO Hongmei; LU Xianguo; WANG Guoping

    2010-01-01

    The effects of freeze-thaw cycles on sorption/desorption of dissolved organic carbon (DOC) in two wetland soils and one reclaimed wetland soil were investigated. DOC concentrations added were 0-600 mg/L. Laboratory in-cubations of sorption/desorption of DOC had been carried out at -15℃ for 10 h, and then at +5℃ for 13 h. Soil sam-ples were refrozen and thawed subsequently for 5 cycles. Initial Mass model was used to describe sorption behavior of DOC. The results indicate that freeze-thaw cycles can significantly increase the sorption capacity of DOC and reduce the desorption capacity of DOC in the three soils. The freeze-thaw effects on desorption of DOC in soils increase with the increasing freeze-thaw cycles. The conversion of natural wetlands to soybean farmland can decrease the sorption capacity and increase the desorption capacity of DOC in soils. Global wanning and reclamation may increase DOC re-lease, and subsequently increase the loss of carbon and the emission of greenhouse gas.

  6. Transformation of Rhizobia with Broad-Host-Range Plasmids by Using a Freeze-Thaw Method

    OpenAIRE

    Vincze, Eva; Bowra, Steve

    2006-01-01

    Several species of rhizobia were successfully transformed with broad-host-range plasmids of different replicons by using a modified freeze-thaw method. A generic binary vector (pPZP211) was maintained in Mesorhizobium loti without selection and stably inherited during nodulation. The method could extend the potential of rhizobia as a vehicle for plant transformation.

  7. Analysis of Different Freezing/Thawing Parameterizations using the UTOPIA Model

    Directory of Open Access Journals (Sweden)

    Claudio Cassardo

    2010-08-01

    Full Text Available Soil moisture changes are generally due to external factors (precipitation, evaporation, etc. and internal forces (gravitational force, capillarity, transpiration, etc.. When soil temperatures remain below 0 °C for a long time (hours or even entire consecutive days, part of the liquid water content of the soil can freeze, thus freezing/thawing effects must be taken into account in those conditions. The present work is devoted to the numerical modeling of the water phase change in the soil. The model used in this study for the land surface processes is UTOPIA (University of TOrino land Process Interaction in Atmosphere model, which is the updated version of LSPM (Land Surface Process Model. Scientific literature proposes some formulations to account for freezing/thawing processes. Three different parameterizations have been compared using a synthetic dataset in order to assess which one performs best from a physical point of view. Parameterizing freezing/thawing processes creates numerical instability and water overproduction in the UTOPIA model. These problems have been solved and described in the paper by means of synthetic data created to test the new parameterizations. The results show that UTOPIA is able to capture the freezing/thawing physical processes.

  8. Influence of carbonation and freeze-thaw on macro-properties of concrete

    Science.gov (United States)

    Rao, M. J.; Dong, Y.; Yang, H. Q.; Li, M. X.; Yu, Z.

    2017-01-01

    Concrete can be damaged under the effects of carbonation and the freeze-thaw cycle, which is a common cause of premature failure for concrete structures. In this study, range analysis was performed for compressive strength results after carbonation and freeze-thaw cycles for 90 days. A carbonation test, freeze-thaw test, and the alternating cycle of carbonation and freeze-thaws were performed to measure the relative dynamic elastic modulus and flexural strength of concrete samples. The results showed that specimens subjected to thawing first, then carbonation suffered the greatest impairment to strength due to expansion and osmotic pressures caused by water motion after thawing; this caused some of the original closed pores to link together, which loosened the internal organization and increased total porosity. The dynamic elastic modulus loss and weight loss of carbonized specimens were smaller than those of uncarbonized specimens within a reasonable range of carbonation. The flexural strength carbonation declined as the water-binder ratio or fly ash content increased.

  9. Efficient encapsulation of plasmid DNA in anionic liposomes by a freeze/thaw extrusion procedure

    NARCIS (Netherlands)

    Schoen, P; Bijl, L; Wilschut, J

    1998-01-01

    In this study we investigated whether intact plasmid DNA can be efficiently encapsulated in anionic liposomes prepared by freeze/thaw and extrusion techniques. There is controversy about this method of DNA encapsulation, especially as to whether DNA remains intact and retains its biological activity

  10. Rubber crumb used in concrete to provide freeze-thaw protection

    OpenAIRE

    Richardson, Alan; Coventry, Kathryn; Diaz, Eli

    2015-01-01

    This research has examined the use of rubber crumb, used as an additive to concrete that would provide maximum freeze-thaw protection to concrete. The rubber crumb as used in the paper was divided into five batches, with increasing particle size, graded in increments of 0.5mm, from

  11. Crumb rubber used in concrete to provide freeze-thaw protection (OPTIMAL particle size)

    OpenAIRE

    Richardson, Alan; Coventry, Kathryn; Edmondson, Vikki; Dias, Eli

    2016-01-01

    This research has examined the optimum particle size of crumb rubber, used as an additive to concrete that would provide maximum freeze-thaw protection whilst minimising the compressive strength loss. The crumb rubber as used in the paper was divided into five batches, with increasing particle size, graded in increments of 0.5mm, from

  12. Differential proteome association study of freeze-thaw damage in ram sperm.

    Science.gov (United States)

    He, Yuxuan; Wang, Ke; Zhao, Xingxu; Zhang, Yong; Ma, Youji; Hu, Junjie

    2016-02-01

    In this study proteomics analysis was performed to investigate damage caused to ram sperm by the freeze-thaw process. Sperm motility, viability, reactive oxygen species (ROS) and adenosine triphosphate (ATP) content were measured to evaluate sperm quality. Compared with fresh groups, motility, viability and ATP content were all lower in freeze-thawed sperm (P < 0.001), and ROS content was higher (P < 0.001). Moreover, 25 differential protein spots were detected in two-dimensional gels using PDQuest 8.0 software and the corresponding proteins were identified using matrix-assisted laser desorption/ionization tandem time-of-flight mass spectrometry (MALDI-TOF-TOF MS) coupled with searching of the NCBI protein sequence database. Among these proteins, hexokinase1 (HXK1), the enzyme that catalyzes the first step of glycolysis in the sperm glycolytic pathway, is known to be associated with sperm motility. Casein kinase II subunit alpha (CSNK2A2), a serine/threonine-selective protein kinase, is associated with sperm apoptosis. We used immunoblotting and immunofluorescence to analyze the expression and localization of these two proteins. HXK1 and CSNK2A2 expression levels in fresh sperm were significantly higher than that in freeze-thawed sperm (P < 0.001). HXK1 and CSNK2A2 were detected in the main part of the sperm flagellum, and the immunofluorescence signal from these proteins was weakened in the freeze-thawed group. Decreased expression of HXK1 and CSNK2A2 may be associated with decreased sperm motility and viability following freeze-thawing.

  13. SLAPex-Initial Results from a Soil Freeze-Thaw Airborne Campaign

    Science.gov (United States)

    Kim, E. J.

    2016-12-01

    The SLAPex Freeze/Thaw airborne campaign took place in early November, 2015, near Carman, Manitoba, Canada (near Winnipeg). NASA Goddard's Scanning L-band Active Passive (SLAP) sensor—an airborne simulator of the Soil Moisture Active Passive (SMAP) satellite mission—made 11 flights on the NASA Langley B200 aircraft to observe frozen and thawed soil conditions. Detailed ground truth was collected by a joint US-Canadian team. Future soil moisture satellite missions are expected to include soil freeze/thaw products, just as SMAP does. The loss of the radar on SMAP means that airborne radar-radiometer observations like those from SLAPex freeze/thaw are very unique assets for freeze/thaw algorithm development. SLAP freeze/thaw airborne observations are also directly applicable to the science interests of NASA's Arctic-Boreal Vulnerability Experiment (ABoVE) project. SLAP has both passive (radiometer) and active (radar) microwave L-band imaging capabilities. The radiometer observes at 1.4 GHz using duplicate front end hardware from the SMAP satellite radiometer. It also includes a duplicate of the digital backend development unit for SMAP, thus the novel Radio Frequency Interference (RFI) detection and mitigation features and algorithms for SMAP are duplicated with very high fidelity in SLAP. The digital backend provides 4-Stokes polarization capability. The real-aperture radar operates in the 1215-1300 MHz band with quad-pol capability. Radar and radiometer share one antenna. This paper will present flight data, imagery, and comparisons with ground truth with respect to frozen or thawed state, soil moisture, and brightness temperature (comparison with ground-based radiometers). The high sensitivity of the The passive and active signatures seen in the SLAP observations indicates that microwave signatures of frozen vs. thawed soil can yield information on the controlling processes and ramifications for the water, energy, and carbon cycles

  14. Dietary flax seed oil and/or Vitamin E improve sperm parameters of cloned goats following freezing-thawing.

    Science.gov (United States)

    Kargar, Rohollah; Forouzanfar, Mohsen; Ghalamkari, Gholamreza; Nasr Esfahani, Mohammad Hossein

    2017-02-01

    Semen cryopreservation is affected by individual differences and use of clones animal from the same source is the main tool to eliminate genetic variation. Among many nutrients that are necessary for fertility, essential fatty acids and antioxidants are vital for production of healthy sperm by improving sperm membrane integrity and protecting sperm from oxidative stress. The goal of the current study was to investigate whether a flax seed oil or/and Vitamin E dietary supplementation could improve semen quality of cloned bucks following semen cryopreservation. Accordingly, eight adult cloned Bakhtiari bucks were divided randomly into four groups. Bucks were offered a base diet of hay and concentrate. The concentrate was enriched with flax seed oil, 30 gr/kg body weight/day (OIL), Vitamin E (VIT), 3 gr/kg body weight/day, or combined flax seed oil and the vitamin E (OIL-VIT). The concentrate with no supplements was considered as control group (CONT). Both flax seed oil and Vitamin E supplements were added to the total diet. The bucks were fed with their corresponding diets for a total of 9 weeks while sperm collection was carried out within 10-14 weeks. Ejaculates were diluted with Andromed(®) and were frozen in liquid nitrogen. Sperm parameters and reactive oxygen species (ROS) contents were evaluated following freezing/thawing. According to the results of our study, dietary supplementation with flax seed oil, or/and Vitamin E can improve sperm motility, vitality and number of sperm with intact plasma membrane following freezing-thawing. But the degree of improvement in these parameters was significantly higher when Flax seed oil and vitamin E were co-supplemented.

  15. Effects of freezing/thawing on motile sperm subpopulations of boar and donkey ejaculates.

    Science.gov (United States)

    Flores, E; Taberner, E; Rivera, M M; Peña, A; Rigau, T; Miró, J; Rodríguez-Gil, J E

    2008-10-01

    The main aim of this study is to assess the influence of freeze/thawing on motile sperm subpopulations in ejaculates from two phylogenetically different mammalian species, boar and donkey. Our results indicate that, whereas boar and donkey sperm respond very differently in their mean motion characteristics to freezing/thawing, this process did not change the existence of a 4-subpopulations structure in the ejaculates in either species when these subpopulations were defined by taking values of curvilinear velocity (VCL) as reference. Moreover, the freezing/thawing-linked changes in mean sperm-motion characteristics in both boar and donkey semen were especially due to changes in the proportion among each concrete subpopulation. In this way, the freezing/thawing-induced mean increase in motion characteristics observed in boar sperm was a result of the decrease in the percentage of sperm in Subpopulation 1 (from 53.9%+/-4.7% to 31.2%+/-3.9% after thawing) and a concomitant increase of sperm from Subpopulations 3 (from 13.3%+/-2.5% to 32.6%+/-3.9% after thawing) and 4 (from 3.4%+/-0.9% to 8.0%+/-1.1% after thawing). On the contrary, changes in mean motility of frozen/thawed donkey sperm were linked to an increase in the percentage of sperm in Subpopulation 1 (from 31.5%+/-4.3% to 58.8%+/-4.9% after thawing) and a concomitant decrease of sperm from Subpopulations 3 (from 32.4%+/-3.2% to 6.6%+/-1.8% after thawing) and 4 (from 12.2%+/-2.5% to 7.3%+/-1.9% after thawing). In conclusion, our results seem to indicate that motility changes induced by the freezing/thawing protocol are linked to concomitant changes in both the specific parameters and, more importantly, to the specific percentage of each of the motile sperm subpopulations. These changes did not affect the overall proportion of motile sperm present in both boar and donkey, which is conserved despite the detrimental effect caused by freezing/thawing in both species. Finally, the presence of some kind of motile sperm

  16. Stabilization of tetanus toxoid formulation containing aluminium hydroxide adjuvant against freeze-thawing.

    Science.gov (United States)

    Solanki, Vipul A; Jain, Nishant K; Roy, Ipsita

    2011-07-29

    Exposure to subzero temperature leads to loss of vaccine potency. This can happen due to degradation of adjuvant surface and/or inactivation of the antigen. When adsorbed on aluminium hydroxide and subjected to freeze-thawing, tetanus toxoid was desorbed from the gel matrix and the preparation was found to lose its antigenicity. Analyses showed that the gel particles were denatured after freezing. When freeze-thawing was carried out in the presence of glucose, sorbitol and arginine, the degradation of gel particles was inhibited. A higher fraction of the protein could be retained on the gel. However, the antigenicity of these preparations was quite low. In the presence of trehalose, the protein could be partially retained on aluminium hydroxide. Being a cryoprotectant, trehalose was also able to inhibit the freezing-induced denaturation of tetanus toxoid, which resulted in retention of antigenicity of the adjuvanted toxoid.

  17. Freeze/thaw protection of concrete with optimum rubber crumb content

    OpenAIRE

    Richardson, Alan; Coventry, Kathryn; Ward, Gavin

    2012-01-01

    This research looks at utilising an optimum quantity of rubber crumb as an air entraining ad-mixture in concrete, thus providing maximum freeze-thaw protection and maximum strength. Microscopic and chemical analysis was carried out on the rubber sample to investigate how rubber crumb entrains air and reacts with the surrounding concrete. The work contained two pilot studies that informed the main test methodology. The pilot studies examined the air content/compressive strength relationship (1...

  18. Freeze-Thaw Resistance of Normal and High Strength Concretes Produced with Fly Ash and Silica Fume

    Directory of Open Access Journals (Sweden)

    Cenk Karakurt

    2015-01-01

    Full Text Available This study is based on determination of the freeze-thaw resistance of air-entrained and non-air-entrained normal strength concrete (NC and high strength concrete (HSC produced with fly ash and silica fume according to surface scaling. The procedure allows us to measure the amount of scaling per unit surface area due to a number of well defined freezing and thawing cycles in the presence of deicing salt. The weight loss, surface scaling, moisture uptake, and internal damage were measured after 0 and after every 4th freeze-thaw cycle. The test results showed that the freeze-thaw resistance is influenced directly by the compressive strength property of the concrete. Silica fume significantly reduced the resistance of normal strength concrete against freeze-thaw effect without plasticizing agent. The surface scaling of silica fume concrete without admixture was 22% higher than reference normal concrete.

  19. Biofilm, ice recrystallization inhibition and freeze-thaw protection in an epiphyte community.

    Science.gov (United States)

    Wu, Z; Kan, F W K; She, Y-M; Walker, V K

    2012-01-01

    Microbial communities found on the surface of overwintering plants may be exposed to low temperatures as well as multiple freeze-thaw events. To explore the adaptive mechanisms of these epiphytes, with the objective of identifying products for freeze-protection, enrichment libraries were made from frost-exposed leaves. Of 15 identified bacteria from 60 individual clones, approximately half had ice-association activities, with the great majority showing high freeze-thaw resistance. Isolates with ice nucleation activity and ice recrystallization inhibition activity were recovered. Of the latter, two (Erwinia billingiae J10, and Sphingobacterium kitahiroshimense Y2) showed culture and electron microscopic evidence of motility and/or biofilm production. Mass spectrometric characterization of the E. billingiae extracellular polymeric substance (EPS) identified the major proteins as 35 kDa outer membrane protein A and F, supporting its biofilm character. The addition of the EPS preparation increased the freeze-thaw survival of the more susceptible bacteria 1000-10000 times, and protection was at least partially dependent on the protein component.

  20. Adsorption and Desorption of Ammonium in Wetland Soils Subject to Freeze-Thaw Cycles

    Institute of Scientific and Technical Information of China (English)

    YU Xiao-Fei; ZHANG Yu-Xia; ZOU Yuan-Chun; ZHAO Hong-Mei; LU Xian-Guo; WANG Guo-Ping

    2011-01-01

    Nitrogen (N) cycling in boreal peatland ecosystems may be influenced in important ways by freeze-thaw cycles (FTCs). Adsorption and desorption of ammonium ions (NH4+) were examined in a controlled laboratory experiment for soils sampled from palustrine wetland, riverine wetland, and farmland reclaimed from natural wetland in response to the number of FTCs. The results indicate that freeze-thaw significantly increased the adsorption capacity of NH4+ and reduced the desorption potential of NH4+ in the wetland soils. There were significant differences in the NH4+ adsorption amount between the soils with and without freeze-thaw treatment.The adsorption amount of NH4+ increased with increasing FTCs. The palustrine wetland soil had a greater adsorption capacity and a weaker desorption potential of NH4+ than the riverine wetland soil because of the significantly higher clay content and cation exchange capacity (CEC) of the riverine wetland soil. Because of the altered soil physical and chemical properties and hydroperiods, the adsorption capacity of NH4+ was smaller in the farmland soil than in the wetland soils, while the desorption potential of the farmland soil was higher than that of the wetland soils. Thus, wetland reclamation would decrease adsorption capacity and increase desorption potential of NH4+, which could result in N loss from the farmland soil. FTCs might mitigate N loss from soils and reduce the risk of water pollution in downstream ecosystems.

  1. Oil recovery from refinery oily sludge via ultrasound and freeze/thaw.

    Science.gov (United States)

    Zhang, Ju; Li, Jianbing; Thring, Ronald W; Hu, Xuan; Song, Xinyuan

    2012-02-15

    The effective disposal of oily sludge generated from the petroleum industry has received increasing concerns, and oil recovery from such waste was considered as one feasible option. In this study, three different approaches for oil recovery were investigated, including ultrasonic treatment alone, freeze/thaw alone and combined ultrasonic and freeze/thaw treatment. The results revealed that the combined process could achieve satisfactory performance by considering the oil recovery rate and the total petroleum hydrocarbon (TPH) concentrations in the recovered oil and wastewater. The individual impacts of five different factors on the combined process were further examined, including ultrasonic power, ultrasonic treatment duration, sludge/water ratio in the slurry, as well as bio-surfactant (rhamnolipids) and salt (NaCl) concentrations. An oil recovery rate of up to 80.0% was observed with an ultrasonic power of 66 W and an ultrasonic treatment duration of 10 min when the sludge/water ratio was 1:2 without the addition of bio-surfactant and salt. The examination of individual factors revealed that the addition of low concentration of rhamnolipids (recovery from the combined treatment process. The experimental results also indicated that ultrasound and freeze/thaw could promote the efficiency of each other, and the main mechanism of oil recovery enhancement using ultrasound was through enhanced desorption of petroleum hydrocarbons (PHCs) from solid particles. Copyright © 2011 Elsevier B.V. All rights reserved.

  2. Effects of freeze-thaw on soil nitrogen and phosphorus availability at the Keerqin Sandy Lands, China

    Institute of Scientific and Technical Information of China (English)

    ZHAO Qiong; ZENG De-hui; FAN Zhi-ping

    2008-01-01

    A laboratory simulated freeze-thaw was conducted to determine the effects of freeze-thaw on soil nutrient availability in temperate semi-arid regions. Soil samples were collected from sandy soils (0-20 cm) of three typical ecosystems (grassland, Mongolian pine plantation and poplar plantation) in southeastern Keerqin Sandy Lands of China and subjected to freeze-thaw treatment (-12℃ for 10 days, then 20℃ for 10 days) or incubated at constant temperature (20℃ for 20 days). Concentrations of the soil NO3--N, NH4+-N, NaHCO3 extractable inorganic P (LPi) and microbial biomass P (MBP) were determined on three occasions: at the start of the incubation, immediate post-thawing and at the 10th day post-thawing. The results showed that soil net nitrification and N mineralization rates at three sites were negatively affected by freeze-thaw treatment, and decreased by 50%-85% as compared to the control, of which the greatest decline occurred in the soil collected from poplar plantation. In contrast, the concentration of soil NH4+-N, NaHCO3 extractable inorganic P (LPi) and microbial biomass P were insignificantly influenced by freeze-thaw except that LPi and NH4+-N showed a slight increase immediate post-thawing. The effects of freeze-thaw on soil N transformation were related to soil biological processes and the relatively constant available P was ascribed to severe soil aridity.

  3. Effects of aging and freezing/thawing sequence on quality attributes of bovine and

    Directory of Open Access Journals (Sweden)

    Hyun-Wook Kim

    2017-02-01

    Full Text Available Objective The effects of aging and freezing/thawing sequence on color, physicochemical, and enzymatic characteristics of two beef muscles (Mm. gluteus medius, GM and biceps femoris, BF were evaluated. Methods Beef muscles at 3 d postmortem were assigned to four different combinations of aging and freezing/thawing sequence as follows; aging at 2°C for 3 wk (A3, never-frozen control, freezing at −28°C for 2 wk then thawing (F2, frozen/thawed-only, aging at 2°C for 3 wk, freezing at −28°C for 2 wk then thawing (A3F2, and freezing at −28°C for 2 wk, thawing then further aging at 2°C for 3 wk (F2A3. Results No significant interactions between different aging/freezing/thawing treatments and muscle type on all measurements were found. Postmortem aging, regardless of aging/freezing/thawing sequence, had no impact on color stability of frozen/thawed beef muscles (p<0.05. F2A3 resulted in higher purge loss than F2 and A3F2 treatments (p<0.05. A3F2 and F2A3 treatments resulted in lower shear force of beef muscles compared to F2 (p<0.05. Although there was no significant difference in glutathione peroxidase (GSH-Px activity, F2A3 had the highest β-N-acetyl glucominidase (BNAG activity in purge, but the lowest BNAG activity in muscle (p<0.05. GM muscle exhibited higher total color changes and purge loss, and lower GSH-Px activity than BF muscle. Conclusion The results from this present study indicate that different combinations of aging/freezing/thawing sequence would result in considerable impacts on meat quality attributes, particularly thaw/purge loss and tenderness. Developing a novel freezing strategy combined with postmortem aging will be beneficial for the food/meat industry to maximize its positive impacts on tenderness, while minimizing thaw/purge loss of frozen/thawed meat.

  4. Freeze-thaw and high-voltage discharge allow macromolecule uptake into ileal brush-border vesicles.

    Science.gov (United States)

    Donowitz, M; Emmer, E; McCullen, J; Reinlib, L; Cohen, M E; Rood, R P; Madara, J; Sharp, G W; Murer, H; Malmstrom, K

    1987-06-01

    High-voltage discharge or one cycle of freeze-thawing are shown to transiently permeabilize rabbit ileal brush-border membrane vesicles to macromolecules. Uptake of the radiolabeled macromolecule dextran, mol wt 70,000, used as a marker for vesicle permeability, was determined by a rapid filtration technique, with uptake defined as substrate associated with the vesicle and releasable after incubation of vesicles with 0.1% saponin. Dextran added immediately after electric shock (2,000 V) or at the beginning of one cycle of freeze-thawing was taken up approximately eightfold compared with control; with both techniques, the concentration of dextran after being taken up into the vesicles was similar to that in the incubation medium, suggesting attainment of equilibrium. ATP also was taken up into freeze-thawed vesicles, whereas there was no significant uptake into control vesicles. The increase in vesicle permeability was reversible, based on Na-dependent D-glucose uptake being decreased when studied 5 but not 15 min after electric shock, and was not significantly decreased after completion of one cycle of freeze-thawing. In addition, adenosine 3',5'-cyclic monophosphate and Ca2+-calmodulin-dependent protein kinase activity were similar in control vesicles and vesicles exposed to high-voltage discharge or freeze-thawing. Also, vesicles freeze-thawed with [32P]ATP demonstrated increased phosphorylation compared with nonfrozen vesicles, while freeze-thawing did not alter vesicle protein as judged by Coomassie blue staining. These techniques should allow intestinal membrane vesicles to be used for studies of intracellular control of transport processes, for instance, studies of protein kinase regulation of transport.

  5. Nuclear magnetic resonance analysis of freeze-thaw damage in natural pumice concrete

    Directory of Open Access Journals (Sweden)

    Wang, Xiaoxiao

    2016-06-01

    Full Text Available This paper presents an analysis of the damage propagation features of the pore structure of natural pumice lightweight aggregate concrete (LWC under freeze-thaw cyclic action. After freeze-thaw cycling, we conducted nuclear magnetic resonance (NMR tests on the concrete and acquired the porosity, distribution of transverse relaxation time T2, and magnetic resonance imaging (MRI results. The results showed the following. The T2 distribution of the LWC prior to freeze-thaw cycling presented four peaks representative of a preponderance of small pores. After 50, 100, 150, and 200 freeze-thaw cycles, the total area of the T2 spectrum and the porosity increased significantly. The MRI presented the changing spatial distribution of pores within the LWC during freeze-thaw cycling. Ultrasonic testing technology was applied simultaneously to analyze the NMR results, which verified that the new NMR technology demonstrated high accuracy and practicability for research regarding freeze-thaw concrete damage.En este trabajo se analiza la propagación de los daños que se producen en la estructura porosa de hormigón aligerado a base de piedra pómez natural sometido a la acción cíclica de hielo-deshielo. Después de realizarse los ensayos de hielo-deshielo, el hormigón se analizó mediante resonancia magnética nuclear (RMN, determinándose la porosidad y la distribución del tiempo de relajación transversal, T2, y registrándose las imágenes captadas por resonancia magnética. De acuerdo con los resultados obtenidos, antes de los ciclos de hielo-deshielo la distribución de T2 del hormigón aligerado presentaba cuatro picos, indicativos de un predominio de poros pequeños. Después de que se sometiera a 50, 100, 150, y 200 ciclos, se observó un aumento importante tanto de la porosidad como de la superficie total del espectro de T2. Las imágenes captadas por resonancia magnética evidenciaron la modificación de la distribución espacial de los poros del

  6. Freeze-thaw stability and long-term stability of 84 synthetic cannabinoids in serum.

    Science.gov (United States)

    Hess, Cornelius; Krueger, Lynn; Unger, Michael; Madea, Burkhard

    2016-11-08

    Information about stability of synthetic cannabinoids is important to give recommendations for storage conditions in cases in which use of synthetic cannabinoids is suspected. In this study, freeze-thaw stability (3 cycles at -20 °C at 1.5 ng/mL) and long-term stability at room temperature, 4°C and -20°C (for 150 days) were tested by a validated liquid chromatographic-mass spectrometric method for 80 synthetic cannabinoids. Results demonstrated good freeze-thaw stability for most of the substances. For 5 F-ABICA (72.6% of peak area of time point zero), 5 F- 2 ADB PINACA 2 Isomer (68.7 %), 5Cl-AB-PINACA (84.2 %), AB FUBINACA 2-Isomer (33.5 %), 5 F-PCN (89.7 %), ADB-FUBINACA (78.0 %), EG 018 (88.9 %), and PX-1 (89.4 %) three freeze-thaw cycles led to absolute peak areas < 90% compared to 6 control samples. For 51 of the 84 substances, stability in serum could be demonstrated after 315 days of storage at -20°C. For 82 of the 84 substances, stability in serum could be shown for at least 1 month at -20°C. Long- term stability at 4°C or 20°C showed worse results. Therefore, it is our recommendation to store real serum samples at -20°C until analysis. Copyright © 2016 John Wiley & Sons, Ltd.

  7. 反复冷冻-解冻对鲢品质的影响%Effect of freeze-thaw cycles on the quality of silver carp (Hypophthalmichthys molitrix

    Institute of Scientific and Technical Information of China (English)

    史策; 崔建云; 王航; 沈慧星; 罗永康

    2012-01-01

    consumption. Repeated freezing and thawing processes are common in storage and at retail outlets, in homes, and restaurants. Despite this, the effects of freezing/thawing on changes of color, muscle texture and protein physicochemistry have not been fully investigated. We stored fresh silver carp at -18°C for 10 days. After being thawed by flowing water, the thawed carp were re frozen at the same temperature for another 5 days. This freeze-thaw cycle was repeated five times. After the first, third, and fifth cycles, we randomly selected three silver carp and measured changes in thawing loss, cooking loss, hardness, chewiness, resilience, thiobarbituric acid (TBA), L* value, b* value, salt soluble protein (SSP) content, Ca2+-ATPase activity, total sulfhydryl groups (SH) content, surface hydrophobicity, and sensory scores. During the first freeze-thaw cycle, hardness, chewiness, resilience, salt soluble protein (SSP) content, and Ca2+-ATPase activity decreased significantly (/>0.05) in cooking loss following five freeze-thaw cycles. After the fifth freeze-thaw cycle, the sensory scores were 47, which were unacceptable. Our results confirm that the freeze-thaw process causes thawing loss, discoloration, softening of muscle tissue, lipid oxidation, decrease in SSP content, and protein conformational changes. These changes have a detrimental effect on the quality of silver carp tissue. So it is important to prevent fluctuation of temperature during storage, transportation, and retail to avoid the negative effects of freeze-thaw cycles on silver carp tissue quality.

  8. Influence of waxy rice flour substitution for wheat flour on characteristics of batter and freeze-thawed cake.

    Science.gov (United States)

    Jongsutjarittam, Nisachon; Charoenrein, Sanguansri

    2013-09-12

    This study aimed to improve the freeze-thawed cake properties by10-20% waxy rice flour (WRF) substitution for wheat flour (WF). Viscosity of WRF-substituted batters was lower; consequently, trapped air was less uniformly distributed than WF batter. After five freeze-thaw cycles, firmness and enthalpy of melting retrograded amylopectin of WF- and WRF-substituted cakes increased and the matrix surrounding the air pores from SEM images was denser than in fresh-baked cakes. Sensory evaluation showed an increase in firmness and a decrease in firmness acceptability of freeze-thawed cakes. However, freeze-thawed cake with WRF substitution had significantly less firmness, less dense matrix and more acceptability than WF cake. This could have been due to a low amylose content of WRF and the spread of ruptured waxy rice starch granules around swollen wheat starch granules as observed by CLSM. Thus, WRF could be used for WF substitution to improve the firmness in freeze-thawed cake. Copyright © 2013 Elsevier Ltd. All rights reserved.

  9. Finite element analysis on deformation of high embankment in heavy-haul railway subjected to freeze-thaw cycles

    Institute of Scientific and Technical Information of China (English)

    ChengYi Yu; Shuang Tian; Liang Tang; XianZhang Ling; GuoQing Zhou

    2015-01-01

    Finite element simulations are increasingly providing a versatile environment for this topic. In this study, a two-dimensional finite element analysis is conducted to predict the deformation of high embankment in Bazhun heavy-haul railway, China. A recently developed nonlinear softening-type constitutive model is utilized to model the be-havior of subgrade filling materials subjected to freeze-thaw cycles. For the convenience of practical application, the dynamic loading induced by a vehicle is treated as a quasi-static axle load. The deformation of this embankment with different moisture content under freeze-thaw cycles is compared. The results show that when subjected to the first freeze-thaw cycle, the embankment experienced significant deformation variations. Maximum deformation was usually achieved after the embankment with optimum moisture content experienced six freeze-thaw cycles, however, the em-bankment with moisture content of 8.0% and 9.5% deforms continuously even after experiencing almost ten freeze-thaw cycles. Overall, this study provides a simple nonlinear finite element approach for calculating the deformation of the embankment in changing climate conditions.

  10. 冷冻-解冻循环对鲤鱼肉物理化学特性的影响%Effect of Number of Freeze-thaw Cycles on Physico-chemical Characteristics of Carp Muscle

    Institute of Scientific and Technical Information of China (English)

    郭园园; 孔保华; 夏秀芳; 杨振

    2011-01-01

    研究不同冷冻-解冻循环次数(0、1、3、5次)对鲤鱼脊背肉pH值、失水率、蒸煮损失、剪切力、肌肉颜色、硫代巴比妥酸值(TBARS)、羰基含量和电泳图谱的影响,从而确定冻融次数对鱼肉物理化学特性的影响。结果表明:随着冷冻-解冻循环次数的增加,鱼肉pH值呈现出先上升后下降的趋势;失水率和蒸煮损失不断增加,到第5次循环时分别增加了8.77%和20.28%,且差异显著(P〈0.05);剪切力经1次冷冻-解冻循环后降低56.3%,随后缓慢下降;TBARS值、羰基含量L*和b*值不断增加,而a*值逐渐降低;鱼肉肌原纤%The pH,water loss rate,cook loss,shear force,color parameters,thiobarbituric acid reactive substances(TBARS),carnonyl content and sodium dodecyl sulphate polyacrylamide gel electrophoresis(SDS-PAGE) pattern of carp back muscles were measured after different freeze-thaw cycles(0,1,3 and 5) with the aim of determining the effect of number of freeze-thaw cycles on the physicochemical characteristics of carp muscle.Results indicated that pH value showed a trend to first increase and then decrease as the number of freeze-thaw cycle increased.Water loss rate and cooking loss exhibited an upward trend and were increased by 8.77% and 20.28%,respectively,after the fifth freeze-thaw cycle(P0.05).Shearing force was decreased by 56.3% after one freeze-thaw cycle(P0.05),followed by a slow decline.Five freeze-thaw cycles could significantly increase TBARS,carnonyl content,L*value and b*value,and decrease a* values(P0.05).All myofibrillar protein bands in the SDS-PAGE pattern got lighter in color and even disappeared with increasing number of freeze-thaw cycles,indicating protein degradation and denaturation.Good correlations were found between lipid oxidation and either protein oxidation or color change.In summary,repeated freeze-thaw could cause protein denaturation and has a detrimental effect on the quality

  11. Determination of the Gelation Mechanism of Freeze-Thawed Hen Egg Yolk.

    Science.gov (United States)

    Au, Carmen; Acevedo, Nuria C; Horner, Harry T; Wang, Tong

    2015-11-25

    A study of yolks stored up to 168 d at -20 °C was conducted to determine the gelation behavior and mechanism of freeze-thawed yolk. Methods used were rheology, native and sodium dodecyl sulfate polyacrylamide gel electrophoresis (native- and SDS-PAGE), differential scanning calorimetry (DSC), transmission electron microscopy (TEM), particle size analysis, and proton nuclear magnetic resonance ((1)H NMR) spectroscopy for matrix mobility. Results indicate that both constituents of plasma and granules contributed to gelation of yolk under freezing. PAGE analyses suggest that granular proteins participated in aggregation during freeze-thaw. Increasing gel strength and particle size and decreasing water and lipid-water mobility indicate that lipoproteins or apolipoproteins aggregated. At storage times ≥84 d, increased protein and lipid mobility, the detection of smaller particles, and secondarily increased gel strength suggest the liberation of protein or lipoprotein components from previously formed aggregates and further aggregation of these constituents. Disruption of the gelled yolk matrix observed with TEM supported that ice crystal formation was required for gelation to occur. A two-stage dynamic gelation model is thus proposed.

  12. Superplasticizer effect on cement paste structure and concrete freeze-thaw resistance

    Science.gov (United States)

    Shuldyakov, Kirill; Kramar, Lyudmila; Trofimov, Boris; Ivanov, Ilya

    2016-01-01

    Article presents the results of studies of various types of superplasticizer additives and their influence on concrete structure and resistance under cyclic freezing-thawing. Glenium ACE 430 was taken as a polycarboxylate superplasticizer, and SP-1 - as a naphthalene-formaldehyde superplasticizer. It is revealed that at identical structure, W/C and fluidity of concrete mix, application of the polycarboxylate superplasticizer, Glenium AC 430, in comparison to the naphthalene-formaldehyde one SP-1, facilitates the increase of the concrete grade in freeze and thaw resistance from F2300 to F2400, concrete freeze and thaw resistance can be possible even higher if the gravel with higher freeze and thaw resistance is applied. To assess the superplasticizers influence on cement paste structure tests of the phase composition of the cement paste of the studied concrete were conducted. It is established that the use of polycarboxylate superplasticizer together with silica fume facilitates formation of cement plaster structure from tobermorite gel. This gel has increased basicity and is resistant to crystallization due to cyclic freezing. It is shown that in the presence of SP-1+SF in the cement paste of concrete during hydration the structure of hydrosilicate phases preferably comprises of C-S-H(I) and C-S-H(II) phases which actively crystallize while cyclic freezing and thawing and reduce freeze-thaw resistance of concrete.

  13. Investigation of freeze/thaw durability in polymer electrolyte fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Soo-Jin; Park, Gu-Gon; Sohn, Young-Jun; Yim, Sung-Dae; Yang, Tae-Hyun; Kim, Chang-Soo [Fuel Cell Research Center, Korea Institute of Energy Research, 102, Gajeong-ro, Yuseong-gu, Daejeon 305-343 (Korea, Republic of); Park, Jin-Soo [Department of Environmental Engineering, College of Engineering, Sanmyung University, 300 Anseo-dong, Dongnam-gu, Cheonam, Chungnam Province 330-720 (Korea, Republic of); Hong, Bo Ki [Fuel Cell Vehicle Team 1, Ecotechnology Center, Hyundai-Kia Motors Company, 104, Mabuk-dong, Giheung-gu, Yongin-si, Gyeonggi-do 446-912 (Korea, Republic of)

    2010-12-15

    This study aims to investigate the effect of different gas diffusion layers (GDLs) on freeze/thaw condition durability in polymer electrolyte fuel cells (PEFCs). Three kinds of GDLs-cloth, felt and paper type - with similar basic properties except thickness and bending stiffness were used. The changes in the properties and cell performance were investigated from the -30 to 70 C range of freeze/thaw cycles. The I-V performance degradation was observed to be negligible for the felt GDL whereas the cloth and paper GDLs showed a marked I-V performance loss. No distinctive correlation between the changes in electrochemical properties, such as active metal surface area, hydrogen crossover rates and decreased I-V performance, was observed except an increase in ohmic resistance revealed by ac-impedance spectroscopy. The physical destruction of electrodes was also shown by scanning electron microscope (SEM) analysis. The present study found that sufficient mechanical supporting force between the interfaces of materials enhances PEFC durability in sub-zero temperature conditions. (author)

  14. Inlfuence of Freeze-thaw Cycles on Properties of Integral Water Repellent Concrete

    Institute of Scientific and Technical Information of China (English)

    MA Zhiming; WITTMANN Folker H; XIAO Jianzhuang; ZHAO Tiejun

    2016-01-01

    Service life of reinforced concrete structures usually was designed on the basis of one selected deteriorating mechanism as for instance carbonation, chloride penetration, and frost action. It could be shown in the meantime by numerous authors, however, that combined actions such as chloride penetration under mechanical load or chloride penetration in combination with freeze-thaw cycles may shorten the service life of reinforced concrete structures more than individual processes acting alone. We have found that chloride penetration is accelerated significantly by freeze-thaw cycles. Frost damage not only reduces mechanical strength and elastic modulus but migration of chloride is facilitated in the damaged pore structure. Chloride penetration can be retarded by the addition of silane emulsion to the fresh concrete. In this way Integral Water Repellent Concrete (IWRC) can be produced. Migration of water and ions dissolved in water can not be prevented by integral water repellent treatment but it is slowed down. The combination of damage mechanisms and the protective measures by integral water repellent treatment have to be taken into consideration in realistic service life prediction and design.

  15. Compressive strength and frost heave resistance of different types of semi-rigid base materials after freeze-thaw cycles

    Institute of Scientific and Technical Information of China (English)

    ZhenYa Liu; JingYu Liu; QingZhi Wang; JianKun Liu

    2015-01-01

    Freeze-thaw damage is the most common disease of semi-rigid bases in cold regions, which may greatly affect the dura-bility of roadways. In this study, the compressive strength and frost resistance of four different types of semi-rigid bases (lime-fly ash-stabilized sand, cement-stabilized sand, lime-fly ash-stabilized gravel, and cement-stabilized gravel) are assessed by varying the materials content. Based on freeze-thaw and compressive strength tests, this paper presents the performance of the different materials, each having different physical properties, and the optimal amounts of materials contents are proposed.

  16. The classification and assessment of freeze-thaw erosion in Tibet%西藏冻融侵蚀的分级和评价

    Institute of Scientific and Technical Information of China (English)

    张建国; 刘淑珍; 杨思全

    2007-01-01

    Freeze-thaw erosion is the third largest soil erosion type after water erosion and wind erosion. Restricted by many factors, few researches on freeze-thaw erosion have so far been done at home and abroad, especially those on the assessment method of freeze-thaw erosion. Based on the comprehensive analysis of impact factors of free-thaw erosion, this paper chooses six indexes, including the annual temperature range, annual precipitation,slope, aspect, vegetation and soil, to build the model for relative classification of freeze-thaw erosion using weighted and additive methods, and realizes the relative classification of the freeze-thaw erosion in Tibet with the support of GIS software. Then a synthetic assessment of freeze-thaw erosion in Tibet has been carried out according to the relative classification result. The result shows that the distribution of freeze-thaw eroded area is very extensive in Tibet, accounting for 55.3% of the total local land area; the spatial differentiation of freeze-thaw erosion with different intensities is obvious; and the difference in distribution among different regions is also obvious.

  17. Simulation and field monitoring of moisture in alpine rock walls during freeze-thaw events

    Science.gov (United States)

    Rode, Matthias; Sass, Oliver

    2013-04-01

    Detachment of rock fragments from alpine rockwalls is mainly assigned to frost weathering. However, the actual process of frost weathering as well as the contribution of further weathering processes (e.g. hydration, thermal fatigue) is poorly understood. Rock moisture distribution during freeze-thaw events is key to understanding weathering. For this purpose, different measuring systems were set up in two study areas (Dachstein - permafrost area (2700m a.s.l.) and Gesäuse - non permafrost area (900m a.s.l.), Styria, Austria) within the framework of the research project ROCKING ALPS (FWF-P24244). We installed small-scale 2D-geoelectric survey lines in north and in south facing rockwalls, supplemented by high resolution temperature and moisture sensors. Moisture is determined by means of resistivity measurements which are difficult to calibrate, but provide good time series. Additional novel moisture sensors were developed which use the heat capacity of the surrounding rock as a proxy of water content. These sensors give point readings from a defined depth and are independent from soluble salt contents. Pore water pressure occurring during freeze-thaw events is recorded by means of pressure transducers (piezometers). First results from the Dachstein show that short term latent heat effects during the phase change have crucial influence on the moisture content. These results are cross-checked by simulation calculations. Based on meteorologic and lithologic input values, the simulation routine calculates, in an iterative procedure, the hourly energy and water transport at different depths, the latter in the liquid and in the vapor phase. The calculated profile lines and chronological sequences of rock moisture allow - in combination with temperature data - to detect possible periods of active weathering. First simulations from the Gesäuse show that maximum values of pore saturation occur from May to September. The thresholds of the "classical" frost shattering theory

  18. Direct N2O Fluxes from Agroecosystems in Cold Climates: Importance of Soil Freeze-Thaw

    Science.gov (United States)

    Congreves, K. A.; Wagner-Riddle, C.; Abalos, D.; Ambadan, J. T.; Brown, S. E.; Tenuta, M.; Gao, X.; Amiro, B. D.; Berg, A. A.

    2016-12-01

    To develop effective climate change mitigation strategies and reduce N2O emissions, the global contribution of freeze-thaw cycles from croplands must be characterized; we present the first study to do so. Long-term N2O flux datasets from micrometeorological approaches were compiled from two Canadian sites (Elora ON & Glenlea MB). Measurements encompassed a total of 21-yr on 16-ha of land producing annual field crops, yielding an unprecedented record of N2O fluxes (42118 half-hourly values) at sites subjected to freeze-thaw cycles from Nov-Apr. At Elora (the warmer site) N2O flux events were associated with thaw cycles throughout Nov-Apr and the main thaw event took place between mid/end of April when air temperatures rose above 0°C and snow melted. The continental site (Glenlea) did not have significant N2O flux events during the prolonged freeze period, but had considerably higher emissions over the thaw period when soil temperature and liquid water content increased more slowly than Elora. Based on cumulative N2O emissions from both sites (Nov-Apr), emissions were closely related to freezing degree days (FDD). An exponential-to-plateau model significantly fit (p<0.0001, r= 0.72) the relationship between N2O emissions and FDD, characterizing larger N2O emissions as FDD increased (y=1.95 (1-exp-0.00852x), y=cumulative N2O-N kg ha-1 and x=FDD). To estimate the global contribution of N2O emissions from seasonally frozen croplands in the northern hemisphere, we applied the algorithm to a global map of FDD derived from three reanalysis products (ERA-Interim, MERRA-Land, GLDAS-NOAH) combined with MODIS land fraction data for croplands. Average global freeze-thaw induced N2O emissions for croplands was estimated at 1.07 Tg N, though it may range from 0.79 - 1.35 Tg N due to model error and variation. This global contribution of N2O from seasonally frozen cropland soils may be responsible for previously observed discrepancies between top-down and bottom-up approaches.

  19. The influence of the curing conditions of concrete on durability after freeze-thaw accelerated testing

    Directory of Open Access Journals (Sweden)

    Al-Assadi, G.

    2015-12-01

    Full Text Available This work relates the curing conditions of concrete with the damage caused by rapid freeze-thaw cycles (ASTM C 666. The “potential” durability of concrete after testing is also studied. In countries with a continental climate, the curing of concrete in summer is performed under high-temperature and low-humidity conditions, and during the winter the concrete undergoes freezing and thawing. This paper shows the experimental results of the behaviour of concrete specimens cured under climatic summer conditions and then subjected to freeze-thaw cycles. Curing of the specimens includes conditions of good and bad practice in relation to wetting and protection of the concrete. Mechanical properties, cement hydration, volume and pore sizes, oxygen permeability, chloride diffusion and water penetration under pressure tests of the concrete are assessed. These tests were performed before and after the application of the freeze-thaw cycles. Statistical analysis of the correlation among variables is also included.Este trabajo relaciona las condiciones de curado del hormigón con los daños causados por ciclos hielo-deshielo (ASTM C 666. Estudia la durabilidad “potencial” del hormigón dañado por este ensayo. En países con clima continental, el curado del hormigón en verano se realiza con alta temperatura y baja humedad, y durante el invierno sufre condiciones de hielo-deshielo. Se presentan los resultados experimentales de probetas de hormigón curadas bajo condiciones climáticas del verano y luego sometidas a ciclos hielo-deshielo. El curado de las probetas incluye condiciones de buenas y malas prácticas en relación con el curado del hormigón. Se miden las propiedades mecánicas, grado de hidratación, volumen de poros y distribución de tamaños, permeabilidad al oxígeno, penetración de agua bajo presión y coeficiente de difusión de cloruros antes y después de la aplicación de los ciclos de hielo-deshielo. Se incluye un estudio estad

  20. Observations of the freeze/thaw performance of lithium fluoride by motion picture photography

    Science.gov (United States)

    Jaworske, D. A.; Perry, W. D.

    1991-01-01

    To gain direct observation of the molten salt phase change, a novel containerless technique was developed where the high surface tension of lithium fluoride was used to suspend a bead of the molten salt inside a specially designed wire cage. By varying the current passing through the wire, the cage also served as a variable heat source. In this way, the freeze/thaw performance of the lithium fluoride could be photographed by motion picture photography without the influence of container walls. The motion picture photography of the lithium fluoride sample revealed several zones during the phase change, a solid zone and a liquid zone, as expected, and a slush zone that was predicted by thermal analysis modeling.

  1. Multiscale model of a freeze-thaw process for tree sap exudation

    CERN Document Server

    Graf, Isabell; Stockie, John M

    2015-01-01

    Sap transport in trees has long fascinated scientists, and a vast literature exists on experimental and modelling studies of trees during the growing season when large negative stem pressures are generated by transpiration from leaves. Much less attention has been paid to winter months when trees are largely dormant but nonetheless continue to exhibit interesting flow behaviour. A prime example is sap exudation, which refers to the peculiar ability of sugar maple (Acer saccharum) and related species to generate positive stem pressure while in a leafless state. Experiments demonstrate that ambient temperatures must oscillate about the freezing point before significantly heightened stem pressures are observed, but the precise causes of exudation remain unresolved. The prevailing hypothesis attributes exudation to a physical process combining freeze-thaw and osmosis, which has some support from experimental studies but remains a subject of active debate. We address this knowledge gap by developing the first math...

  2. Effects of freeze-thaw on characteristics of new KMP binder stabilized Zn- and Pb-contaminated soils.

    Science.gov (United States)

    Wei, Ming-Li; Du, Yan-Jun; Reddy, Krishna R; Wu, Hao-Liang

    2015-12-01

    For viable and sustainable reuse of solidified/stabilized heavy metal-contaminated soils as roadway subgrade materials, long-term durability of these soils should be ensured. A new binder, KMP, has been developed for solidifying/stabilizing soils contaminated with high concentrations of heavy metals. However, the effects of long-term extreme weather conditions including freeze and thaw on the leachability and strength of the KMP stabilized contaminated soils have not been investigated. This study presents a systematic investigation on the impacts of freeze-thaw cycle on leachability, strength, and microstructural characteristics of the KMP stabilized soils spiked with Zn and Pb individually and together. For comparison purpose, Portland cement is also tested as a conventional binder. Several series of tests are conducted including the toxicity characteristic leaching procedure (TCLP), modified European Community Bureau of Reference (BCR) sequential extraction procedure, unconfined compression test (UCT), and mercury intrusion porosimetry (MIP). The results demonstrate that the freeze-thaw cycles have much less impact on the leachability and strength of the KMP stabilized soils as compared to the PC stabilized soils. After the freeze-thaw cycle tests, the KMP stabilized soils display much lower leachability, mass loss, and strength loss. These results are assessed based on the chemical speciation of Zn and Pb, and pore size distribution of the soils. Overall, this study demonstrates that the KMP stabilized heavy metal-contaminated soils perform well under the freeze-thaw conditions.

  3. Role of freeze-thaw cycles and chlorpyrifos insecticide use on diffuse Cd loss and sediment accumulation.

    Science.gov (United States)

    Wang, Fangli; Ouyang, Wei; Hao, Fanghua; Jiao, Wei; Shan, Yushu; Lin, Chunye

    2016-06-02

    Freeze-thaw cycles are predicted to increase in cold temperate regions. The potential influence of the interactions of freeze-thaw cycles and agrochemicals on the release of Cd into river water is unknown. In this study, the interactions of freeze-thaw cycles and chlorpyrifos (FC) on Cd mobility in soils were analysed. The spatial variability of soil Cd under long-term intensive tillage in a freeze-thaw agro-system was also identified. The temporal variation of sediment Cd was detected based on analysis of the sediment geochemistry. The results showed that FC increased soil Cd mobility, with an increase of approximately 10% in CaCl2-extractable Cd. The increased mobile fractions of water-soluble and exchangeable Cd originated from the decreased fraction of Fe-Mn-oxide-associated Cd and organic matter-bound Cd. The total Cd content in the surface soil followed the zonally decreasing trend of dry land > paddy land > natural land. The Cd concentrations and sedimentation rates of the sediment core generally increased from 1943 to 2013 due to agricultural exploration and farmland irrigation system construction, indicating an increase of the Cd input flux into water. The results provide valuable information about the soil Cd transport response to the influence of climatic and anthropogenic factors in cold intensive agro-systems.

  4. Role of freeze-thaw cycles and chlorpyrifos insecticide use on diffuse Cd loss and sediment accumulation

    Science.gov (United States)

    Wang, Fangli; Ouyang, Wei; Hao, Fanghua; Jiao, Wei; Shan, Yushu; Lin, Chunye

    2016-06-01

    Freeze-thaw cycles are predicted to increase in cold temperate regions. The potential influence of the interactions of freeze-thaw cycles and agrochemicals on the release of Cd into river water is unknown. In this study, the interactions of freeze-thaw cycles and chlorpyrifos (FC) on Cd mobility in soils were analysed. The spatial variability of soil Cd under long-term intensive tillage in a freeze-thaw agro-system was also identified. The temporal variation of sediment Cd was detected based on analysis of the sediment geochemistry. The results showed that FC increased soil Cd mobility, with an increase of approximately 10% in CaCl2-extractable Cd. The increased mobile fractions of water-soluble and exchangeable Cd originated from the decreased fraction of Fe-Mn-oxide-associated Cd and organic matter-bound Cd. The total Cd content in the surface soil followed the zonally decreasing trend of dry land > paddy land > natural land. The Cd concentrations and sedimentation rates of the sediment core generally increased from 1943 to 2013 due to agricultural exploration and farmland irrigation system construction, indicating an increase of the Cd input flux into water. The results provide valuable information about the soil Cd transport response to the influence of climatic and anthropogenic factors in cold intensive agro-systems.

  5. Freezing tolerance of winter wheat as influenced by extended growth at low temperature and exposure to freeze-thaw cycles

    Science.gov (United States)

    As the seasons progress, autumn-planted winter wheat plants (Triticum aestivum L.) first gain, then progressively lose freezing tolerance. Exposing the plants to freeze-thaw cycles of -3/3°C results in increased ability to tolerate subsequent freezing to potentially damaging temperatures. This stu...

  6. The interplay between inner and outer frost damage and its implication for accelerated freeze-thaw testing

    DEFF Research Database (Denmark)

    Hasholt, Marianne Tange

    2014-01-01

    In the present project salt frost scaling was registered during an accelerated freeze-thaw test (CEN/TS 12390-9). After the test, inner damage was evaluated by observing the crack patterns on fluorescence impregnated plane sections. The results indicate that the developments of inner and outer...

  7. Freeze-thaw cycles and their influence on marble deterioration: a long-term experiment

    Science.gov (United States)

    Ondrasina, J.; Kirchner, D.; Siegesmund, S.

    2003-04-01

    The deterioration of three marbles (Palissandro, Sterzing and Carrara) differing in composition and rock fabric has been studied using measurements of the thermal dilatation in the temperature range from -40°C up to 60°C. A long-term freeze-thaw experiment was performed to characterize the frost weathering via Youngs's modulus.The results shown that the combined effect of heating and cooling under dry and water-saturated conditions significantly influences the material properties. The thermal dilatation and its anisotropy can be explained by the crystallographic preferred orientation of calcite and dolomite as well as with the thermal expansion behaviour of these minerals. The residual strain, i.e. the permanent length change, after thermal treatment is different for the investigated samples and less pronounced for the dolomitic Palissandro marble. A hygric expansion is of only minor importance for marble. However, a weak hygric expansion was observed in the phlogopite-bearing Palissandro sample at a direction parallel to the foliation. Fresh and artificially weathered marbles were exposed to 204 freeze-thaw cycles. The Young's modulus for the Carrara marble decreases from 55GPa to 28GPa while the porosity increases from 0.25% to 0.62%. The effect on the Palissandro and the calcitic Sterzing marbles is less pronounced. However, artificially weathered marbles clearly exhibit a drastic reduction in Young's modulus. The progressive loss in strength is caused by progressive microfracturing or the loss of cohesion along grain boundaries due to the crystallization pressure of ice growth. The experimental data along with existing theoretical models lead to the conclusion that the physical weathering of marble is influenced by cooling and heating under mid-European climatic conditions.

  8. A land surface model incorporated with soil freeze/thaw and its application in GAME/Tibet

    Institute of Scientific and Technical Information of China (English)

    HU Heping; YE Baisheng; ZHOU Yuhua; TIAN Fuqiang

    2006-01-01

    Land surface process is of great importance in global climate change,moisture and heat exchange in the interface of the earth and atmosphere,human impacts on the environment and ecosystem,etc.Soil freeze/thaw plays an important role in cold land surface processes.In this work the diurnal freeze/thaw effects on energy partition in the context of GAME/Tibet are studied.A sophisticated land surface model is developed,the particular aspect of which is its physical consideration of soil freeze/thaw and vapor flux.The simultaneous water and heat transfer soil sub-model not only reflects the water flow from unfrozen zone to frozen fringe in freezing/thawing soil,but also demonstrates the change of moisture and temperature field induced by vapor flux from high temperature zone to low temperature zone,which makes the model applicable for various circumstances.The modified Picard numerical method is employed to help with the water balance and convergence of the numerical scheme.Finally,the model is applied to analyze the diurnal energy and water cycle characteristics over the Tibetan Plateau using the Game/Tibet datasets observed in May and July of 1998.Heat and energy transfer simulation shows that: (i) There exists a negative feedback mechanism between soil freeze/thaw and soil temperature/ground heat flux; (ii) during freezing period all three heat fluxes do not vary apparently,in spite of the fact that the negative soil temperature is higher than that not considering soil freeze; (iii) during thawing period,ground heat flux increases,and sensible heat flux decreases,but latent heat flux does not change much; and (iv) during freezing period,soil temperature decreases,though ground heat flux increases.

  9. Results of molten salt panel and component experiments for solar central receivers: Cold fill, freeze/thaw, thermal cycling and shock, and instrumentation tests

    Energy Technology Data Exchange (ETDEWEB)

    Pacheco, J.E.; Ralph, M.E.; Chavez, J.M.; Dunkin, S.R.; Rush, E.E.; Ghanbari, C.M.; Matthews, M.W.

    1995-01-01

    Experiments have been conducted with a molten salt loop at Sandia National Laboratories in Albuquerque, NM to resolve issues associated with the operation of the 10MW{sub e} Solar Two Central Receiver Power Plant located near Barstow, CA. The salt loop contained two receiver panels, components such as flanges and a check valve, vortex shedding and ultrasonic flow meters, and an impedance pressure transducer. Tests were conducted on procedures for filling and thawing a panel, and assessing components and instrumentation in a molten salt environment. Four categories of experiments were conducted: (1) cold filling procedures, (2) freeze/thaw procedures, (3) component tests, and (4) instrumentation tests. Cold-panel and -piping fill experiments are described, in which the panels and piping were preheated to temperatures below the salt freezing point prior to initiating flow, to determine the feasibility of cold filling the receiver and piping. The transient thermal response was measured, and heat transfer coefficients and transient stresses were calculated from the data. Freeze/thaw experiments were conducted with the panels, in which the salt was intentionally allowed to freeze in the receiver tubes, then thawed with heliostat beams. Slow thermal cycling tests were conducted to measure both how well various designs of flanges (e.g., tapered flanges or clamp type flanges) hold a seal under thermal conditions typical of nightly shut down, and the practicality of using these flanges on high maintenance components. In addition, the flanges were thermally shocked to simulate cold starting the system. Instrumentation such as vortex shedding and ultrasonic flow meters were tested alongside each other, and compared with flow measurements from calibration tanks in the flow loop.

  10. Modified control strategies for critical source area of nitrogen (CSAN) in a typical freeze-thaw watershed

    Science.gov (United States)

    Wei, Peng; Ouyang, Wei; Gao, Xiang; Hao, Fanghua; Hao, Zengchao; Liu, Hongbin

    2017-08-01

    The management of critical source areas of diffuse nitrogen (CSANs) remains challenging in freeze-thaw areas due to the different N loss characteristics in different hydrological conditions and seasons. To address these challenges, a modified strategy was proposed in this study using the Soil and Water Assessment Tool (SWAT) to simulate diffuse N loads in the study catchments. Specifically, the spatial and temporal variations of CSANs caused by differences in precipitation and seasons were considered. In addition, the selection of best management practices (BMPs) was selected according to BMP performance and their seasonal characteristics in diffuse N control. The diffuse N load formed during freeze-thaw seasons accounts for approximately 50% of the annual diffuse N load. The diffuse N load discharged to rivers was higher in wet conditions than dry conditions by 127.4% and 181.5% during freeze-thaw seasons and growing seasons, respectively. The spatial distribution of CSANs was more sensitive to differences between freeze-thaw and growing seasons. Among BMPs, buffer strips (BS), no tillage (NT) and reducing N fertilizer applications (RNFA) all showed differences in their diffuse N removal efficiency under different hydrological conditions and seasons, while reforestation operations were not affected by these factors. The benefit of reforestation operations was lower in flatter areas. When areas with slopes greater than 2 degrees were reforested, the average N removal efficiency of the 1st CSAN could be as high as 82.4%. In the 2nd CSAN, the average N removal efficiency of BS was relatively constant across freeze-thaw seasons. Across growing seasons, the N removal efficiency of BS in wet years was 8%-10% higher than in dry conditions due to the lower percentage of lateral flow. The average N removal efficiency of NT was higher during freeze-thaw seasons and lower during growing seasons with average values of 9.3% and 6.1%, respectively. The N control efficiency of

  11. Giant panda (Ailuropoda melanoleuca) sperm morphometry and function after repeated freezing and thawing.

    Science.gov (United States)

    Santiago-Moreno, J; Esteso, M C; Pradiee, J; Castaño, C; Toledano-Díaz, A; O'Brien, E; Lopez-Sebastián, A; Martínez-Nevado, E; Delclaux, M; Fernández-Morán, J; Zhihe, Z

    2016-05-01

    This work examines the effects of subsequent cycles of freezing-thawing on giant panda (Ailuropoda melanoleuca) sperm morphometry and function, and assesses whether density-gradient centrifugation (DGC) can increase the number of freezing-thawing cycles this sperm can withstand. A sperm sample was collected by electroejaculation from a mature giant panda and subjected to five freezing-thawing cycles. Although repeated freezing-thawing negatively affected (P 60% of the sperm cells in both treatments showed acrosome integrity even after the fifth freezing cycle. In fresh semen, the sperm head length was 4.7 μm, the head width 3.6 μm, area 14.3 μm(2) and perimeter length 14.1 μm. The present results suggest that giant panda sperm trends to be resistant to repeated freezing-thawing, even without DGC selection. © 2015 Blackwell Verlag GmbH.

  12. Relationships of soil physical and microbial properties with nitrous oxide emission affected by freeze-thaw event

    Institute of Scientific and Technical Information of China (English)

    Lianfeng WANG; Xin SUN; Yanjiang CAI; Hongtu XIE; Xudong ZHANG

    2008-01-01

    Freeze-thaw event often occurs in regions at mid-high latitude and high altitude.This event can affect soil physical and biological properties,such as soil water status,aggregate stability,and microbial biomass and community structure.Under its effects,the bio-indicators of soil microbes including the kinds and quantities of some specific amino sugars may vary,and the process and intensity of soil nitrogen transformation may change,which can result in an increase in nitrous oxide (N2O)production and emission,making the soil as the major source of N2O emission.This paper summarizes the research progress on the aspects mentioned above,and suggests further research directions on the theoretical problems of soil N2O production and emission under the effects of freeze-thaw event.

  13. Rapid yeast DNA extraction by boiling and freeze-thawing without using chemical reagents and DNA purification

    Directory of Open Access Journals (Sweden)

    Gildo Almeida da Silva

    2012-04-01

    Full Text Available The purpose of this work was to study a rapid yeast DNA extraction by boiling and freeze-thawing processes without using chemical reagents or any purification procedures, to obtain a high grade PCR-product. A specific DNA fragment of the 18S region of Dekkera bruxellensis and Saccharomyces cerevisiae was chosen. The described boiling and freeze-thawing protocols generated the PCR-grade product preparations and could be used to process many samples. The amplification of the fragments could be observed after 30 and 35 cycles. These processes of extraction without using any kind of chemical reagents, especial water, and purification procedures proved to be efficient, reproducible, simple, fast, and inexpensive.

  14. Estimation model of soil freeze-thaw erosion in Silingco watershed wetland of Northern Tibet.

    Science.gov (United States)

    Kong, Bo; Yu, Huan

    2013-01-01

    The freeze-thaw (FT) erosion is a type of soil erosion like water erosion and wind erosion. Limited by many factors, the grading evaluation of soil FT erosion quantities is not well studied. Based on the comprehensive analysis of the evaluation indices of soil FT erosion, we for the first time utilized the sensitivity of microwave remote sensing technology to soil moisture for identification of FT state. We established an estimation model suitable to evaluate the soil FT erosion quantity in Silingco watershed wetland of Northern Tibet using weighted summation method of six impact factors including the annual FT cycle days, average diurnal FT phase-changed water content, average annual precipitation, slope, aspect, and vegetation coverage. Finally, with the support of GIS, we classified soil FT erosion quantity in Silingco watershed wetland. The results showed that soil FT erosion are distributed in broad areas of Silingco watershed wetland. Different soil FT erosions with different intensities have evidently different spatial and geographical distributions.

  15. Impact of Freeze-Thaw Cycles on Compressive Characteristics of Asphalt Mixture in Cold Regions

    Institute of Scientific and Technical Information of China (English)

    SI Wei; LI Ning; MA Biao; REN Junping; WANG Hainian; HU Jian

    2015-01-01

    Low average temperature, large temperature difference and continual freeze-thaw (F-T) cycles have signiifcant impacts on mechanical property of asphalt pavement. F-T cycles test was applied to illustrate the mixtures’ compressive characteristics. Exponential model was applied to analyze the variation of compressive characteristics with F-T cycles; Loss ratio model and Logistic model were used to present the deterioration trend with the increase of F-T cycles. ANOVA was applied to show the signiifcant impact of F-T cycles and asphalt-aggregate ratio. The experiment results show that the compressive strength and resilient modulus decline with increasing F-T cycles; the degradation is sharp during the initial F-T cycles, after 8 F-T cycles it turns to gentle. ANOVA results show that F-T cycles, and asphalt-aggregate ratio have signiifcant inlfuence on the compressive characteristics. Exponential model, Loss ratio model and Logistic model are signiifcantly iftting the test data from statistics view. These models well relfect the compressive characteristics of asphalt mixture degradation trend with increasing F-T cycles.

  16. Durability of cracked fibre reinforced concrete exposed to freeze-thaw and deicing salt

    DEFF Research Database (Denmark)

    Hansen, Ernst Jan De Place

    1998-01-01

    -thaw and deicing salt. The concrete has a water-powder ratio of 0.38 including both fly ash and silica fume. Both steel fibres (ZP, 0.4 vol%) and polypropylene fibres (PP, 1 vol%) are used as well as main reinforcement. The freeze-thaw test emphasizes the need for a critical evaluation of the mix design and mixing......Durability studies are carried out by subjecting FRC-beams to combined mechanical and environmental load. Mechanical load is obtained by subjecting beams to 4-point bending until a predefined crack width is reached. Specimens sawn from the beams after unloading are exposed to freeze...... methods when designing FRC-structures. The scaling is increased by a factor 5 to 10 when adding fibres to the concrete while the air content is below 4% by volume. The variation of the scaling increases when adding fibres. Capillary water uptake in uncracked specimens of FRC was 20-30% higher at 1°C than...

  17. Effect of Salvia miltiorrhiza polysaccharides on boar spermatozoa during freezing-thawing.

    Science.gov (United States)

    Shen, Tao; Jiang, Zhong-Liang; Liu, Hong; Li, Qing-Wang

    2015-08-01

    Salvia miltiorrhiza polysaccharides (SMPs) were extracted from S. miltiorrhiza in this study. The aim of the present study was to evaluate the effect of SMP on the motility of boar sperm, including the antioxidant effect of SMP on boar sperm and the effect of SMP on the in vivo fertilizing ability of frozen-thawed boar sperm. Fifty ejaculates from 5 Swagger boars were collected and diluted with an extender, which contained 3% glycerol (v/v) with five concentrations of SMP (0.2, 0.4, 0.6, 0.8, and 1.0mg/mL). The semen was frozen in 0.25mL straws at 1.0×10(9) cells/mL. Sixty gilts were inseminated using fresh semen, frozen semen with 0.4mg/mL of SMP and frozen semen without SMP. The results indicate that the addition of SMP to the extender results in a higher percentage of motile sperm post-thaw (Pboar sperm from peroxidative damage and increase sperm motility and litter size during the process of freezing-thawing. The optimal concentration of SMP for the frozen extenders in this study was determined to be 0.4mg/mL.

  18. ASCAT vs. borehole data for extracting seasonal freeze/thaw cycling in soil

    Science.gov (United States)

    Schwamborn, G.; Bartsch, A.; Heim, B.; Günther, F.; Overduin, P.

    2012-04-01

    Freeze-thaw (F/T) cycling in soil is a main driver of physical weathering in polar latitudes. The higher the amount of F/T is during a season the greater is the production of debris that will result from rock breakdown. The ASCAT sensor (Advanced SCATterometer aperture radar on board of Metop) provides an estimate of seasonal F/T due to a daily coverage of northern latitudes at >50°. It operates at 5.255 GHz (C-band) and is sensitive to detect frozen and unfrozen conditions in soil. Whereas the spring signatures suffer from a snow melt response that dominates much of the backscatter, the autumn signals with little to no snow cover can be validated using borehole temperature data. We use temperature time series of two sites in the Russian Arctic (El'gygytgyn Impact Crater, mountainous Chukotka; Mamontovy Klyk, northern Yakutian lowland) for comparing satellite derived F/T with ground truth derived F/T. On the basis of error bars we examine the potential to create a pan-arctic map that aids interpreting the physical weathering dynamics in the north.

  19. Effects of Diatomite and SBS on Freeze-Thaw Resistance of Crumb Rubber Modified Asphalt Mixture

    Directory of Open Access Journals (Sweden)

    Haibin Wei

    2017-01-01

    Full Text Available Asphalt mixture is susceptible to moisture damage under the effect of freeze-thaw (F-T cycles. In this paper, crumb rubber (CR was used to modify stone mastic asphalt (SMA and the effects of diatomite and styrene butadiene styrene (SBS on antifreezing performances of crumb rubber modified SMA (CRSMA were investigated. Regression analysis and modified grey model (MGM were used to construct the prediction models for properties of modified mixtures. CRSMA, CR and diatomite modified SMA (CRDSMA, and CR and SBS modified SMA (CRSSMA were prepared in laboratory, respectively. Process of F-T cycles was designed. Air void, indirect tensile strength (ITS, and indirect tensile stiffness modulus (ITSM were measured to evaluate the antifreezing performances of CRSMA, CRDSMA, and CRSSMA. Results indicate that air voids increase with the increasing of F-T cycles. ITS and ITSM all decrease with the increasing of F-T cycles. The addition of diatomite and SBS can reduce the air void and improve the ITS and ITSM of CRSMA. CRSSMA presents the lowest air void, highest tensile strength, and largest stiffness modulus, which reveals that CRSSMA has the best F-T resistance among three different kinds of mixtures. Moreover, MGM (1, 2 models present more favorable accuracy in prediction of air void and ITS compared with regression ones.

  20. Thermal Destabilization of Collagen Matrix Hierarchical Structure by Freeze/Thaw.

    Directory of Open Access Journals (Sweden)

    Altug Ozcelikkale

    Full Text Available This study aims to characterize and understand the effects of freezing on collagen structures and functionality. Specifically, thermodynamic destabilization of collagen at molecular- and fibril-levels by combination of low temperatures and freezing were experimentally characterized using modulated differential scanning calorimetry. In order to delineate the effects of sub-zero temperature and water-ice phase change, we hypothesized that the extent of destabilization can be determined based on post-thaw heat induced thermal denaturation of collagen. It is found that thermal denaturation temperature of collagen in hydrogel decreases by 1.4-1.6°C after freeze/thaw while no such decrease is observed in the case of molecular solution. The destabilization is predominantly due to ice formation. Exposure to low temperatures in the absence of ice has only minimal effect. Calorimetry measurements combined with morphological examination of collagen matrices by scanning electron microscopy suggest that freezing results in destabilization of collagen fibrils due to expansion of intrafibrillar space by ice formation. This fibril-level damage can be alleviated by use of cryoprotectant DMSO at concentrations as low as 0.5 M. A theoretical model explaining the change in collagen post-thaw thermal stability by freezing-induced fibril expansion is also proposed.

  1. Development and freeze-thaw durability of high flyash-content concrete

    Energy Technology Data Exchange (ETDEWEB)

    Sajadi, J.

    1987-01-01

    Objectives were to investigate the effects on concrete strength, drying shrinkage, freeze-thaw durability, and air-void system parameters of replacing various amounts of portland cement with different types of fly ash and to compare selected characteristics of such fly-ash concretes and fly-ash concretes containing a high-range water-reducing admixture to those of a control mixture. It was concluded that concrete mixtures with 90-day compressive strengths equal to the control could be produced when large amounts of cement were replaced by fly ash. In addition, when the high-range water-reducing admixtures was employed, very large amounts of cement could be replaced by fly ash to yield mixtures whose compressive strengths were equal to or greater than the strengths of the control mix at all ages. The maximum amount of cement that could be replaced for equal-strength mixtures depended upon the nature of the fly ash. Drying shrinkage of plain fly-ash concretes and fly-ash concretes containing the high-range water-reducing admixture were similar to those of the control mix. The optimum fly-ash content in a concrete is comparable in strength and durability to a conventional (control) concrete was influenced by the chemical and physical characteristics of the fly ash.

  2. A Simulation and Validation of CLM during Freeze-Thaw on the Tibetan Plateau

    Directory of Open Access Journals (Sweden)

    Xuewei Fang

    2016-01-01

    Full Text Available The applicability of a new soil hydraulic property of frozen soil scheme applied in Community Land Model 4.5 (CLM4.5, in conjunction with an impedance factor for the presence of soil ice, was validated through two offline numerical simulations conducted at Madoi (GS and Zoige (ZS on the Tibetan Plateau (TP. Sensitivity analysis was conducted via replacing the new soil hydraulic property scheme in CLM4.5 by the old one, using default CLM4.5 runs as reference. Results indicated that the new parameterization scheme ameliorated the surface dry biases at ZS but enlarged the wet biases which existed at GS site due to ignoring the gravel effect. The wetter surface condition in CLM4.5 also leads to a warmer surface soil temperature because of the greater heat capacity of liquid water. In addition, the combined impact of new soil hydraulic property schemes and the ice impedance function on the simulated soil moisture lead to the more reasonable simulation of the starting dates of freeze-thaw cycle, especially at the thawing stage. The improvements also lead to the more reasonable turbulent fluxes simulations. Meanwhile, the decreased snow cover fraction in CLM4.5 resulted in a lower albedo, which tended to increase net surface radiation compared to previous versions. Further optimizing is needed to take the gravel into account in the numerical description of thermal-hydrological interactions.

  3. Sensory properties determined by starch type in white sauces: effects of freeze/thaw and hydrocolloid addition.

    Science.gov (United States)

    Arocas, A; Sanz, T; Salvador, A; Varela, P; Fiszman, S M

    2010-03-01

    The effect of 5 types of starch (rice, potato, waxy corn, corn, and modified waxy corn) on the sensory properties of white sauces was studied. A comparative study was also made of variations resulting from freezing/thawing and effect of replacing 0.15% starch with 2 nonstarchy hydrocolloids, xanthan gum (XG), or locust bean gum (LBG) in samples to be frozen. The sensory properties were studied through descriptive analysis by a panel of 10 trained judges. Principal components analysis and cluster analysis were used to group each of the samples according to the scores for consistency, resilience, graininess, thickness, heterogeneity, creaminess, and mouth coating, the sensory attributes which were chosen to define the sauces under study. Significant differences were found between the different starches employed: the rice and modified starches presented similar behavior to each other, as did the potato starch and corn starch, while the waxy starch sauce stood apart from the rest because of its resilience. The freeze/thaw cycle had the greatest effect on the corn-starch sauce, increasing its graininess and heterogeneity values owing to retrogradation. Adding XG or LBG to the sauces subjected to a period of freezing/thawing did not have a significant effect on the sensory attributes of the reheated sauces made with rice, potato, or waxy or modified starch, but lower graininess and heterogeneity values were observed in the sauce made with corn starch.

  4. Encapsulation of Nucleic Acids into Giant Unilamellar Vesicles by Freeze-Thaw: a Way Protocells May Form

    Science.gov (United States)

    Qiao, Hai; Hu, Na; Bai, Jin; Ren, Lili; Liu, Qing; Fang, Liaoqiong; Wang, Zhibiao

    2016-11-01

    Protocells are believed to consist of a lipid membrane and encapsulated nucleic acid. As the lipid membrane is impermeable to macromolecules like nucleic acids, the processes by which nucleic acids become encapsulated inside lipid membrane compartments are still unknown. In this paper, a freeze-thaw method was modified and applied to giant unilamellar vesicles (GUVs) and deoxyribonucleic acid (DNA) in mixed solution resulting in the efficient encapsulation of 6.4 kb plasmid DNA and similar length linear DNA into GUVs. The mechanism of encapsulation was followed by observing the effect of freeze-thaw temperatures on GUV morphological change, DNA encapsulation and ice crystal formation, and analyzing their correlation. Following ice crystal formation, the shape of spherical GUVs was altered and membrane integrity was damaged and this was found to be a necessary condition for encapsulation. Heating alone had no effects on DNA encapsulation, but was helpful for restoring the spherical shape and membrane integrity of GUVs damaged during freezing. These results suggested that freeze-thaw could promote the encapsulation of DNA into GUVs by a mechanism: the vesicle membrane was breached by ice crystal formation during freezing, DNA entered into damaged GUVs through these membrane gaps and was encapsulated after the membrane was resealed during the thawing process. The process described herein therefore describes a simple way for the encapsulation of nucleic acids and potentially other macromolecules into lipid vesicles, a process by which early protocells might have formed.

  5. A Study on Accelerated Corrosion Test by Combined Deteriorating Action of Salt Damage and Freeze-Thaw

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sang-Soon; So, Byung-Tak [Sangmyung University, Cheonan (Korea, Republic of)

    2016-01-15

    In this study, the accelerated corrosion test by combined deteriorating action of salt damage and freeze-thaw was investigated. freeze-thaw cycle is one method for corrosion testing; corrosion initiation time was measured in four types of concrete samples, i.e., two samples mixed with fly ash (FA) and blast furnace slag (BS), and the other two samples having two water/cement ratio (W/C = 0.6, 0.35) without admixture (OPC60 and OPC35). The corrosion of rebar embedded in concrete occurred most quickly at the 30th freeze-thaw cycle. Moreover, a corrosion monitoring method with a half-cell potential measurement and relative dynamic elastic modulus derived from resonant frequency measures was conducted simultaneously. The results indicated that the corrosion of rebar occurred when the relative dynamic elastic modulus was less than 60%. Therefore, dynamic elastic modulus can be used to detect corrosion of steel bar. The results of the accelerated corrosion test exhibited significant difference according to corrosion periods combined with each test condition. Consequently, the OPC60 showed the lowest corrosion resistance among the samples.

  6. A combination of solvent extraction and freeze thaw for oil recovery from petroleum refinery wastewater treatment pond sludge.

    Science.gov (United States)

    Hu, Guangji; Li, Jianbing; Hou, Haobo

    2015-01-01

    A combination of solvent extraction and freeze thaw was examined for recovering oil from the high-moisture petroleum refinery wastewater treatment pond sludge. Five solvents including cyclohexane (CHX), dichloromethane (DCM), methyl ethyl ketone (MEK), ethyl acetate (EA), and 2-propanol (2-Pro) were examined. It was found that these solvents except 2-Pro showed a promising oil recovery rate of about 40%, but the recycling of DCM solvent after oil extraction was quite low. Three solvents (CHX, MEK and EA) were then selected for examining the effect of freeze/thaw treatment on improving the quality of recovered oil. This treatment increased the total petroleum hydrocarbon (TPH) content in recovered oil from about 40% to 60% for both MEK and EA extractions, but little effect was observed for CHX extraction. Although the solid residue after oil recovery had a significantly decreased TPH content, a high concentration of heavy metals was observed, indicating that this residue may require proper management. In general, the combination of solvent extraction with freeze/thaw is effective for high-moisture oily hazardous waste treatment.

  7. Cavitation and water fluxes driven by ice water potential in Juglans regia during freeze-thaw cycles.

    Science.gov (United States)

    Charra-Vaskou, Katline; Badel, Eric; Charrier, Guillaume; Ponomarenko, Alexandre; Bonhomme, Marc; Foucat, Loïc; Mayr, Stefan; Améglio, Thierry

    2016-02-01

    Freeze-thaw cycles induce major hydraulic changes due to liquid-to-ice transition within tree stems. The very low water potential at the ice-liquid interface is crucial as it may cause lysis of living cells as well as water fluxes and embolism in sap conduits, which impacts whole tree-water relations. We investigated water fluxes induced by ice formation during freeze-thaw cycles in Juglans regia L. stems using four non-invasive and complementary approaches: a microdendrometer, magnetic resonance imaging, X-ray microtomography, and ultrasonic acoustic emissions analysis. When the temperature dropped, ice nucleation occurred, probably in the cambium or pith areas, inducing high water potential gradients within the stem. The water was therefore redistributed within the stem toward the ice front. We could thus observe dehydration of the bark's living cells leading to drastic shrinkage of this tissue, as well as high tension within wood conduits reaching the cavitation threshold in sap vessels. Ultrasonic emissions, which were strictly emitted only during freezing, indicated cavitation events (i.e. bubble formation) following ice formation in the xylem sap. However, embolism formation (i.e. bubble expansion) in stems was observed only on thawing via X-ray microtomography for the first time on the same sample. Ultrasonic emissions were detected during freezing and were not directly related to embolism formation. These results provide new insights into the complex process and dynamics of water movements and ice formation during freeze-thaw cycles in tree stems.

  8. Does Platelet-Rich Plasma Freeze-Thawing Influence Growth Factor Release and Their Effects on Chondrocytes and Synoviocytes?

    Directory of Open Access Journals (Sweden)

    Alice Roffi

    2014-01-01

    Full Text Available PRP cryopreservation remains a controversial point. Our purpose was to investigate the effect of freezing/thawing on PRP molecule release, and its effects on the metabolism of chondrocytes and synoviocytes. PRP was prepared from 10 volunteers, and a half volume underwent one freezing/thawing cycle. IL-1β, HGF, PDGF AB/BB, TGF-β1, and VEGF were assayed 1 hour and 7 days after activation. Culture media of chondrocytes and synoviocytes were supplemented with fresh or frozen PRP, and, at 7 days, proliferation, gene expression, and secreted proteins levels were evaluated. Results showed that in the freeze-thawed PRP the immediate and delayed molecule releases were similar or slightly lower than those in fresh PRP. TGF-β1 and PDGF AB/BB concentrations were significantly reduced after freezing both at 1 hour and at 7 days, whereas HGF concentration was significantly lower in frozen PRP at 7 days. In fresh PRP IL-1β and HGF concentrations underwent a significant further increase after 7 days. Similar gene expression was found in chondrocytes cultured with both PRPs, whereas in synoviocytes HGF gene expression was higher in frozen PRP. PRP cryopreservation is a safe procedure, which sufficiently preserves PRP quality and its ability to induce proliferation and the production of ECM components in chondrocytes and synoviocytes.

  9. 混凝土的抗冻融破坏试验研究%Experimental study of concrete resisting to freeze-thaw damage

    Institute of Scientific and Technical Information of China (English)

    张海燕

    2001-01-01

    简述混凝土抗冻融破坏现状及机理。通过配合比设计试验,分析影响混凝土抗冻融的因素。%This thesis simply described status and mechanism of freeze-thaw damage in concrete. Based on the designing and experiment of mix-proportion, the elements influenced on concrete resisting to freeze-thaw damage were analysed.

  10. Estimation of high-resolution near-surface freeze/thaw state by the integration of microwave and thermal infrared remote sensing data on the Tibetan Plateau

    Science.gov (United States)

    Zhao, Tianjie; Shi, Jiancheng; Hu, Tongxi; Zhao, Lin; Zou, Defu; Wang, Tianxing; Ji, Dabin; Li, Rui; Wang, Pingkai

    2017-08-01

    The objective of this study is to investigate how the complementarity between microwave and thermal infrared remote sensing can be exploited for a high-resolution near-surface freeze/thaw state estimation. The basic idea is to establish a feasible relationship between the microwave-derived freeze/thaw state and thermal infrared observations. A quantitative freeze/thaw index from microwave observations at 18.7 and 36.5 GHz is innovatively defined and is assumed to be linearly correlated with land surface temperature from thermal infrared observations. Thus, a linear regression method is proposed and verified to be effective over a multiscale network of Naqu of the Tibetan Plateau. In order to demonstrate the potentiality of the proposed method, it is implemented in the entire Tibetan Plateau. It is found that the linear relationship is quite reliable for most areas and can obtain a high-resolution near-surface soil freeze/thaw state with integrated information from microwave and thermal infrared remote sensing. The validation of the high-resolution freeze/thaw state against soil temperature measured at active layer monitoring sites along the Qinghai-Tibet Highway illustrates a moderate accuracy over a decade scale. This study provides new insights for high-resolution freeze/thaw mapping beyond the Soil Moisture Active Passive mission.

  11. Freeze-thaw treatment effects on the dynamic mechanical properties of articular cartilage

    Directory of Open Access Journals (Sweden)

    Muldrew Ken

    2010-10-01

    Full Text Available Abstract Background As a relatively non-regenerative tissue, articular cartilage has been targeted for cryopreservation as a method of mitigating a lack of donor tissue availability for transplant surgeries. In addition, subzero storage of articular cartilage has long been used in biomedical studies using various storage temperatures. The current investigation studies the potential for freeze-thaw to affect the mechanical properties of articular cartilage through direct comparison of various subzero storage temperatures. Methods Both subzero storage temperature as well as freezing rate were compared using control samples (4°C and samples stored at either -20°C or -80°C as well as samples first snap frozen in liquid nitrogen (-196°C prior to storage at -80°C. All samples were thawed at 37.5°C to testing temperature (22°C. Complex stiffness and hysteresis characterized load resistance and damping properties using a non-destructive, low force magnitude, dynamic indentation protocol spanning a broad loading rate range to identify the dynamic viscoelastic properties of cartilage. Results Stiffness levels remained unchanged with exposure to the various subzero temperatures. Hysteresis increased in samples snap frozen at -196°C and stored at -80°C, though remained unchanged with exposure to the other storage temperatures. Conclusions Mechanical changes shown are likely due to ice lens creation, where frost heave effects may have caused collagen damage. That storage to -20°C and -80°C did not alter the mechanical properties of articular cartilage shows that when combined with a rapid thawing protocol to 37.5°C, the tissue may successfully be stored at subzero temperatures.

  12. Assimilation of Freeze - Thaw Observations into the NASA Catchment Land Surface Model

    Science.gov (United States)

    Farhadi, Leila; Reichle, Rolf H.; DeLannoy, Gabrielle J. M.; Kimball, John S.

    2014-01-01

    The land surface freeze-thaw (F-T) state plays a key role in the hydrological and carbon cycles and thus affects water and energy exchanges and vegetation productivity at the land surface. In this study, we developed an F-T assimilation algorithm for the NASA Goddard Earth Observing System, version 5 (GEOS-5) modeling and assimilation framework. The algorithm includes a newly developed observation operator that diagnoses the landscape F-T state in the GEOS-5 Catchment land surface model. The F-T analysis is a rule-based approach that adjusts Catchment model state variables in response to binary F-T observations, while also considering forecast and observation errors. A regional observing system simulation experiment was conducted using synthetically generated F-T observations. The assimilation of perfect (error-free) F-T observations reduced the root-mean-square errors (RMSE) of surface temperature and soil temperature by 0.206 C and 0.061 C, respectively, when compared to model estimates (equivalent to a relative RMSE reduction of 6.7 percent and 3.1 percent, respectively). For a maximum classification error (CEmax) of 10 percent in the synthetic F-T observations, the F-T assimilation reduced the RMSE of surface temperature and soil temperature by 0.178 C and 0.036 C, respectively. For CEmax=20 percent, the F-T assimilation still reduces the RMSE of model surface temperature estimates by 0.149 C but yields no improvement over the model soil temperature estimates. The F-T assimilation scheme is being developed to exploit planned operational F-T products from the NASA Soil Moisture Active Passive (SMAP) mission.

  13. Assimilation of freeze-thaw observations into the NASA Catchment land surface model

    Science.gov (United States)

    Farhadi, L.; Reichle, R. H.; Delannoy, G.

    2012-12-01

    The land surface freeze-thaw (F/T) state controls hydrological and carbon cycling and thus affects water and energy exchanges at land surface. In this research an Observing System Simulation Experiment experiment is conducted using synthetically generated measurements of the F/T state for a region in North America (90-110oW longitude, 45-55oN latitude). The synthetic "truth" is generated using the NASA Catchment land surface model forced with surface meteorological fields from the Modern-Era Retrospective Reanalysis for Research and Applications (MERRA). To generate synthetic measurements, the true categorical F/T state is corrupted with a prescribed amount of F/T classification error. The assimilation experiment employs the same Catchment model except that forcing errors (relative to truth) are introduced via the application of meteorological forcing fields from the Global Land Data Assimilation System (GLDAS). A rule-based approach that incorporates model and observational errors is developed and used for assimilating the categorical F/T measurements into the land surface model (F/T analysis). The effect of the F/T analysis on land surface temperature, soil temperature and soil moisture is examined. In a real-world experiment, the synthetic F/T observations are replaced with F/T observations from the Advanced Microwave Scanning Radiometer Enhanced (AMSR-E). The ultimate goal of this project is to provide a framework for the assimilation of SMAP (Soil Moisture Active Passive) F/T observations into the NASA Catchment land surface model.

  14. Freeze/thaw-induced embolism: probability of critical bubble formation depends on speed of ice formation

    Directory of Open Access Journals (Sweden)

    Sanna eSevanto

    2012-06-01

    Full Text Available Bubble formation in the conduits of woody plants sets a challenge for uninterrupted water transportation from the soil up to the canopy. Freezing and thawing of stems has been shown to increase the number of air-filled (embolized conduits, especially in trees with large conduit diameters. Despite numerous experimental studies, the mechanisms leading to bubble formation during freezing have not been addressed theoretically. We used classical nucleation theory and fluid mechanics to show which mechanisms are most likely to be responsible for bubble formation during freezing and what parameters determine the likelihood of the process. Our results confirm the common assumption that bubble formation during freezing is most likely due to gas segregation by ice. If xylem conduit walls are not permeable to the salts expelled by ice during the freezing process, osmotic pressures high enough for air seeding could be created. The build-up rate of segregated solutes in front of the ice-water interface depends equally on conduit diameter and freezing velocity. Therefore, bubble formation probability depends on these variables. The dependence of bubble formation probability on freezing velocity means that the experimental results obtained for cavitation threshold conduit diameters during freeze/thaw cycles depend on the experimental setup; namely sample size and cooling rate. The velocity dependence also suggests that to avoid bubble formation during freezing trees should have narrow conduits where freezing is likely to be fast (e.g. branches or outermost layer of the xylem. Avoidance of bubble formation during freezing could thus be one piece of the explanation why xylem conduit size of temperate and boreal zone trees varies quite systematically.

  15. The role of snow cover affecting boreal-arctic soil freeze-thaw and carbon dynamics

    Science.gov (United States)

    Yi, Y.; Kimball, J. S.; Rawlins, M. A.; Moghaddam, M.; Euskirchen, E. S.

    2015-10-01

    Northern Hemisphere permafrost affected land areas contain about twice as much carbon as the global atmosphere. This vast carbon pool is vulnerable to accelerated losses through mobilization and decomposition under projected global warming. Satellite data records spanning the past 3 decades indicate widespread reductions (~ 0.8-1.3 days decade-1) in the mean annual snow cover extent and frozen-season duration across the pan-Arctic domain, coincident with regional climate warming trends. How the soil carbon pool responds to these changes will have a large impact on regional and global climate. Here, we developed a coupled terrestrial carbon and hydrology model framework with a detailed 1-D soil heat transfer representation to investigate the sensitivity of soil organic carbon stocks and soil decomposition to climate warming and changes in snow cover conditions in the pan-Arctic region over the past 3 decades (1982-2010). Our results indicate widespread soil active layer deepening across the pan-Arctic, with a mean decadal trend of 6.6 ± 12.0 (SD) cm, corresponding to widespread warming. Warming promotes vegetation growth and soil heterotrophic respiration particularly within surface soil layers (≤ 0.2 m). The model simulations also show that seasonal snow cover has a large impact on soil temperatures, whereby increases in snow cover promote deeper (≥ 0.5 m) soil layer warming and soil respiration, while inhibiting soil decomposition from surface (≤ 0.2 m) soil layers, especially in colder climate zones (mean annual T ≤ -10 °C). Our results demonstrate the important control of snow cover on northern soil freeze-thaw and soil carbon decomposition processes and the necessity of considering both warming and a change in precipitation and snow cover regimes in characterizing permafrost soil carbon dynamics.

  16. Fracturing and Damage to Sandstone Under Coupling Effects of Chemical Corrosion and Freeze-Thaw Cycles

    Science.gov (United States)

    Han, Tielin; Shi, Junping; Cao, Xiaoshan

    2016-11-01

    Rapid freeze-thaw (FT) cycles were adopted to explore the damage deterioration mechanism and mechanical properties of sandstone specimens under the coupling effects of different chemical solutions and FT cycles. The variation regularities of the FT cycles and physical and mechanical properties of sandstone specimens immersed in different chemical solutions were analyzed by using sandstone sampled from a Chinese riverbank slope. The damage variable based on porosity variation was used in the quantitative analysis of the damage to the sandstone under the coupling effects of chemical corrosion and FT cycles. Experimental results showed that the sandstone specimens weakened substantially under those effects. Their fracture toughness K IC, splitting tensile strength, and compressive strength showed a similar deteriorating trend with various numbers of FT cycles. However, a difference exists in the deterioration degree of their mechanical parameters, i.e., the deterioration degree of their fracture toughness K IC is the greatest followed by that of splitting tensile strength, and that of compressive strength is relatively small. Strong acid solutions may aggravate the deterioration of FT damage in sandstones, but at the early stage of the experiment, strong alkaline solutions inhibited sandstone damage deterioration. However, the inhibiting effect disappeared when the number of FT cycles exceeded 25. The different chemical solutions had a different effect on the FT damage degree of the sandstone specimens; for example, SO4 2- ions had a greater effect on FT damage than did HCO3 - ions. Water-chemical solutions and FT cycles promote each other in deteriorating rocks and simultaneously affect the damage deterioration degree of sandstones.

  17. 提高大豆蛋白冻融后乳化性改性工艺优化%Processing optimization for improving soybean protein’s emulsifying properties after freeze-thaw

    Institute of Scientific and Technical Information of China (English)

    孙洪蕊; 张英华; 王喜波; 姜国川; 江连洲

    2014-01-01

    为了制备出经冷冻-融化后仍能保持较高乳化性的大豆蛋白,试验以葡聚糖为糖基化供体,采用湿法糖基化技术改性大豆蛋白。根据单因素试验的结果,建立了Box-Behnken模型对加工工艺进行优化,所得的模型拟合度高,切实可行,可用于实际分析和预测。利用响应面分析法探讨了蛋白浓度、蛋白与糖质量比、反应时间3因素对改性产物冻融前后乳化活性和乳化稳定性的影响,优化的工艺条件为:大豆分离蛋白(soybean protein isolate, SPI)质量浓度40 mg/mL,SPI与葡聚糖的质量比为1∶3,反应时间4 h。在此条件下得到的改性产物冻融稳定性显著(P<0.05)高于未改性蛋白,冻融前后的乳化活性(emulsifying activity index,EAI)分别是空白对照样的1.687和1.780倍,乳化稳定性(emulsion stability index,ESI)分别是空白对照样的1.367和1.274倍。傅里叶红外光谱证明葡聚糖通过共价键接到大豆蛋白分子中,研究结果为制备冷冻食品加工专用大豆蛋白的产业化生产提供参考。%Soybean protein has become an important raw material in food processing industries due to its high nutritional value and good functional properties. One of the most important properties of (soybean protein isolate) SPI is emulsifying in food. However, native soy globulins function poorly because of their compact globular structures, which makes it difficult to be utilized directly in food processing. Protein stabilized emulsions are highly sensitive to environmental stresses such as low temperature, and therefore coalescence and creaming occur, which limit their utilization in frozen food. There are no soy protein products specialized for freeze-thaw foods in China. The quality of freeze-thaw foods will be destroyed by the low temperature because the functionalities of soy protein are difficult to maintain. Maillard reaction, a condensation reaction between the

  18. A Brightness-Temperature-Variance-Based Passive Microwave Algorithm for Monitoring Soil Freeze/Thaw State on the Tibetan Plateau

    Science.gov (United States)

    Han, M.; Yang, K.; Qin, J.; Jin, R.; Ma, Y.; Wen, J.; Chen, Y.; Zhao, L.; La, Z.; Tang, W.

    2014-12-01

    The land surface on the Tibetan Plateau experiences typical diurnal and seasonal freeze/thaw processes that play important roles in the regional water and energy exchanges, and recent passive microwave satellites provide opportunities to detect the soil state for the unique region. With the support of three soil moisture and temperature networks in the Tibetan Plateau, a dual-index microwave algorithm with AMSR-E (Advanced Microwave Scanning Radiometer-Earth Observing System) data is developed for the detection of soil surface freeze/thaw state. One index is the standard deviation index (SDI) of brightness temperature (TB), which is defined as the standard deviation of horizontally polarized brightness temperatures at all AMSR-E frequencies. It is the major index and is used to reflect the reduction of liquid water content after soils get frozen. The other index is the 36.5 GHz vertically-polarized brightness temperature, which is linearly correlated with ground temperature and thus is utilized to detect it. The threshold values of the two indices (SDI and the brightness temperature at 36.5 GHz vertically-polarized) are determined based on a part of in situ data from the network located in a semi-arid climate, and the algorithm was validated against other in situ data from this network. Further validations were conducted based on the other two networks located in different climates (semi-humid and arid, respectively). Results show that this algorithm has accuracy of more than 90% for the semi-humid and semi-arid regions, and misclassifications mainly occur at the transition period between unfrozen and frozen seasons. Nevertheless, the microwave signals have limited capability in identifying the soil surface freeze/thaw state in the arid region, because they can penetrate deep dry soils and thus embody the bulk information beneath the surface.

  19. Snowmelt and Surface Freeze/Thaw Timings over Alaska derived from Passive Microwave Observations using a Wavelet Classifier

    Science.gov (United States)

    Steiner, N.; McDonald, K. C.; Dinardo, S. J.; Miller, C. E.

    2015-12-01

    Arctic permafrost soils contain a vast amount of organic carbon that will be released into the atmosphere as carbon dioxide or methane when thawed. Surface to air greenhouse gas fluxes are largely dependent on such surface controls as the frozen/thawed state of the snow and soil. Satellite remote sensing is an important means to create continuous mapping of surface properties. Advances in the ability to determine soil and snow freeze/thaw timings from microwave frequency observations improves upon our ability to predict the response of carbon gas emission to warming through synthesis with in-situ observation, such as the 2012-2015 Carbon in Arctic Reservoir Vulnerability Experiment (CARVE). Surface freeze/thaw or snowmelt timings are often derived using a constant or spatially/temporally variable threshold applied to time-series observations. Alternately, time-series singularity classifiers aim to detect discontinuous changes, or "edges", in time-series data similar to those that occur from the large contrast in dielectric constant during the freezing or thaw of soil or snow. We use multi-scale analysis of continuous wavelet transform spectral gradient brightness temperatures from various channel combinations of passive microwave radiometers, Advanced Microwave Scanning Radiometer (AMSR-E, AMSR2) and Special Sensor Microwave Imager (SSM/I F17) gridded at a 10 km posting with resolution proportional to the observational footprint. Channel combinations presented here aim to illustrate and differentiate timings of "edges" from transitions in surface water related to various landscape components (e.g. snow-melt, soil-thaw). To support an understanding of the physical basis of observed "edges" we compare satellite measurements with simple radiative transfer microwave-emission modeling of the snow, soil and vegetation using in-situ observations from the SNOw TELemetry (SNOTEL) automated weather stations. Results of freeze/thaw and snow-melt timings and trends are

  20. Satellite-based estimation of watershed groundwater storage dynamics in a freeze-thaw area under intensive agricultural development

    Science.gov (United States)

    Ouyang, Wei; Liu, Bing; Wu, Yuyang

    2016-06-01

    Understanding the temporal-spatial characteristics of groundwater storage is critical for agricultural planning and management in the future, thereby causing more challenges in water resource management. However, the special hydrological features of the snow water equivalent, soil moisture, and total canopy water storage in the freeze-thawing agricultural area requires the innovative methods for the water resource analysis. The watershed land cover variation and the expanding pattern of the farmlands over a decade were identified using the TM-Landsat series data. Combined with the traditional measurements of the water resource, the monthly gravity field data from the Gravity Recovery And Climate Experiment (GRACE) was validated and applied. The water resources distribution based on the remotely sensed data demonstrated that the forest in the watershed center had a larger amount of water storage. The inter-annual and seasonal variability of total water storage (TWS) over the agricultural area was analyzed and the higher value appeared in the thawing period of April. The correlations of the TWS streamflow, soil moisture and snow water equivalent with precipitation were all identified. The precipitation was the dominant factor for the watershed TWS and the groundwater dynamics. Under the similar precipitation condition, the lower groundwater storage in recent years was the consequence of the expanding of farmland. The watershed averaged decrease rate of groundwater level from 2003 to 2012 was 1.06 mm/year, which was much lower than the rates in other agricultural areas. The freeze-thawing process with smelt snow and rainfall in summer had more time and chance to recharge the groundwater resource and provided the sustainable water resource. This study proved that the application of GRACE was an effective method for the temporal-spatial estimation of the TWS anomalies in the freeze-thawing agricultural area.

  1. Validating a Satellite Microwave Remote Sensing Based Global Record of Daily Landscape Freeze-Thaw Dynamics

    Science.gov (United States)

    Kimball, J. S.; Kim, Y.; McDonald, K. C.

    2012-12-01

    The freeze-thaw (FT) parameter from satellite microwave remote sensing quantifies the predominant landscape frozen or thawed state and is closely linked to surface energy budget and hydrologic activity, vegetation growth, terrestrial carbon budgets and land-atmosphere trace gas exchange. A global Earth System Data Record of daily landscape FT status (FT-ESDR) was developed using a temporal change classification of overlapping 37 GHz brightness temperature (Tb) series from the Scanning Multichannel Microwave Radiometer (SMMR) and Special Sensor Microwave Imager (SSM/I), and encompassing land areas where seasonal frozen temperatures influence ecosystem processes. A temporally consistent, long-term (>30 yr) FT record was created by ensuring cross-sensor consistency through pixel-wise adjustment of the SMMR Tb record based on empirical analyses of overlapping SMMR and SSM/I measurements. The FT-ESDR is designed to determine the FT status of the composite landscape vegetation-snow-soil medium with sufficient accuracy to characterize frozen temperature constraints to surface water mobility, vegetation productivity and land-atmosphere CO2 fluxes. A multi-tier validation scheme was applied using in situ temperature measurements, other satellite FT retrievals and synergistic biophysical data. These results are incorporated into the product metadata structure, including mean daily spatial classification accuracies and annual quality assessment (QA) maps accounting for landscape heterogeneity, algorithm limitations and sensor retrieval gaps. The resulting FT-ESDR shows mean annual spatial classification accuracies of 91 (+/-8.6) and 84 (+/-9.3) percent for PM and AM overpass retrievals. Accuracy is reduced during seasonal transition periods when FT heterogeneity is maximized within the relatively coarse (~25-km) satellite footprint. The QA rankings range from low (estimated accuracy 90%) categories; mean annual QA results for the 1979-2011 period show relative proportions of

  2. Development and commisioning of a test procedure for the investigation of the impact of freeze-thaw cycles on the sealing material of geothermal probes; Entwicklung und Inbetriebnahme eines Pruefverfahrens zur Bestimmung des Frost-Tau-Wechseleinflusses auf das Verpressmaterial von Erdwaermesonden

    Energy Technology Data Exchange (ETDEWEB)

    Anbergen, Hauke [Knabe Enders Duehrkop Ingenieure GmbH, Hamburg (Germany); Technische Univ. Darmstadt (Germany); Frank, Jens [Knabe Enders Duehrkop Ingenieure GmbH, Hamburg (Germany); Sass, Ingo [Technische Univ. Darmstadt (Germany)

    2011-10-24

    In order to exploit the full potential of near-surface geothermal probes, an operation at brine temperatures below the freezing point of water is necessary. This can result in a cyclic freezing and thawing of the surrounding sealing materials. Thus, such a material must have permanently a water permeability below defined limits even after the freeze-thaw stress. For this, test conditions had to be defined, and a measurement method has to be developed. For this purpose, a measuring cell was modified according to DIN 18130 so that freezing processes can be simulated under in-situ conditions using an axially integrated cooling pipe, and the water permeability can be measured as a function of the number of freeze-thaw cycles. The authors of the contribution under consideration report on the test procedure as well as on the results of a complete series of tests.

  3. Freeze-Thaw Performance and Moisture-Induced Damage Resistance of Base Course Stabilized with Slow Setting Bitumen Emulsion-Portland Cement Additives

    Directory of Open Access Journals (Sweden)

    Mojtaba Shojaei Baghini

    2015-01-01

    Full Text Available Freeze-thaw (FT cycles and moisture susceptibility are important factors influencing the geotechnical characteristics of soil-aggregates. Given the lack of published information on the behavior of cement-bitumen emulsion-treated base (CBETB under environmental conditions, especially freezing and thawing, this study investigated the effects of these additives on the CBETB performance. The primary goal was to evaluate the resistance of CBETB to moisture damage by performing FT, Marshall conditioning, and AASHTO T-283 tests and to evaluate the long-term stripping susceptibility of CBETB while also predicting the liquid antistripping additives to assess the mixture’s durability and workability. Specimens were stabilized with Portland cement (0%–6%, bitumen emulsion (0%–5%, and Portland cement-bitumen emulsion mixtures and cured for 7 days, and their short- and long-term performances were studied. Evaluation results of both the Marshall stability ratio and the tensile strength ratio show that the additions of additives increase the resistance of the mixtures to moisture damage. Results of durability tests performed for determining the resistance of compacted specimens to repeated FT cycles indicate that the specimen with the 4% cement-3% bitumen emulsion mixture significantly improves water absorption, volume changes, and weight losses. This indicates the effectiveness of this additive as a road base stabilizer with excellent engineering properties for cold regions.

  4. Development of a low resolution (1)H NMR spectroscopic technique for the study of matrix mobility in fresh and freeze-thawed hen egg yolk.

    Science.gov (United States)

    Au, Carmen; Wang, Tong; Acevedo, Nuria C

    2016-08-01

    Three experiments were conducted in developing a low resolution proton nuclear magnetic resonance ((1)H NMR) spectroscopic technique to study matrix mobility in fresh and freeze-thawed gelled yolk. The Carr-Purcell-Meiboom-Gill (CPMG) sequence was used to measure spin-spin relaxation times of proton pools representing major yolk constituents. A component identification test distinguished 3-4 pools. The least mobile pool was assigned to proteins, protein-lipid and protein-water interactions, and the most mobile to unbound water. The remaining pools were assigned to lipids, lipid-protein and lipid-water interactions. A stability test indicated that yolk had varied matrix mobility within the same sample across five days of refrigeration storage. A reproducibility test demonstrated high repeatability of fresh yolk measurements, but significant differences (p<0.05) were found within gelled yolk samples. This research determined that (1)H NMR spectroscopy, a non-destructive technique, can identify yolk components and detect changes in the matrix.

  5. Effects of low-density lipoproteins extracted from different avian yolks on boar spermatozoa quality following freezing-thawing.

    Science.gov (United States)

    Wang, Peng; Wang, Yan-Feng; Wang, Chun-Wei; Bu, Shu-Hai; Hu, Jian-Hong; Li, Qing-Wang; Pang, Wei-Jun; Yang, Gong-She

    2014-05-01

    Low-density lipoproteins (LDL) is known to protect boar sperm during freezing-thawing, but little information is known about the effects of LDL extracted from different avian egg yolks on post-thaw boar semen quality. The purpose of this study was to compare and analyze the effects of LDL at various concentrations and different species on boar sperm quality after freezing-thawing. LDL extracted from the yolk of hen egg, duck egg, quail egg, pigeon egg or ostrich egg was added to the extender at the concentrations of 0.06, 0.07, 0.08, 0.09 and 0.1 g/ml, respectively, and their effects on frozen-thawed boar sperm quality were assessed. According to all measured parameters, the results showed that sperm motility, acrosome integrity and plasma membrane integrity were 43.20%, 52.57% and 48.13%, respectively, after being frozen-thawed with 0.09 g/ml LDL extracted from pigeon egg yolk. All these quality parameters were higher than that of other groups (P boar sperm among all of the groups supplemented with LDL from five kinds of avian egg in extender. The optimum concentration of LDL extracted from pigeon egg in boar semen freezing extender was 0.09 g/ml.

  6. Effect of rapid freezing-thawing techniques on the sperm parameters and ultrastructure of Chinese Taihang black goat spermatozoa.

    Science.gov (United States)

    Shi, Liguang; Ren, Youshe; Zhou, Hanlin; Hou, Guanyu; Xun, Wenjuan; Yue, Wenbin; Zhang, Chunxiang; Yang, Rujie

    2014-02-01

    Supercooling sperm in liquid nitrogen vapour is a feasible and economic technique for the practical production. The study aimed to reveal the negative effects of this rapid freezing and thawing processes on Taihang black goat spermatozoa and to find out the changing of spermatozoa motility and ultrastructure by using CASA and TEM. Qualified semen samples, which collected from twenty Chinese Taihang black goats using artificial vagina were pooled and investigated the kinematics parameters and ultrastructural morphology. The results showed that freezing-thawing caused a significant reduction in the spermatozoon total motility (Psperm nucleus characterized by ruptures, bend and deformity was observed. The plasma membranes were broken, and nucleoplasm erupted. The mitochondria in the middle piece were disturbed by partial absence or additional accumulations. Swelling, coiling, vacuolization and structural disorganization of mitochondria were also observed. In conclusion, Freezing-thawing procedure has a detrimental effect on motility, membrane integrity and mitochondria of goat spermatozoa. Transmission electron microscopy provides an intuitive observation to investigate deformity spermatozoa.

  7. Effect of multiple freezing/thawing cycles on the structural and functional properties of waxy rice starch.

    Directory of Open Access Journals (Sweden)

    Han Tao

    Full Text Available The structural and functional properties of non-gelatinized waxy rice starch were investigated after 1, 3, 7, and 10 freezing/thawing cycles. Freezing caused an increasing damaged starch from 1.36% in native waxy rice starch to 5.77% in 10 freezing/thawing-treated starch (FTS, as evidenced by the cracking surface on starch granules. More dry matter concentration was leached, which was characterized by high amylopectin concentration (4.34 mg/mL. The leaching was accompanied by a decrease in relative crystallinity from 35.19% in native starch to 31.34% in 10 FTS. Freezing treatment also led to significant deviations in the functional characteristics, for instance decreased gelatinization temperature range, enthalpy, and pasting viscosities. The resistant starch content of 10FTS significantly decreased from 58.9% to 19%, whereas the slowly digested starch content greatly increased from 23.8% in native starch to 50.3%. The increase in susceptibility to enzyme hydrolysis may be attributed to porous granular surface, amylopectin leaching, and the decrease in the relative crystallinity caused by freezing water.

  8. Effect of Multiple Freezing/Thawing Cycles on the Structural and Functional Properties of Waxy Rice Starch

    Science.gov (United States)

    Tao, Han; Yan, Juan; Zhao, Jianwei; Tian, Yaoqi; Jin, Zhengyu; Xu, Xueming

    2015-01-01

    The structural and functional properties of non-gelatinized waxy rice starch were investigated after 1, 3, 7, and 10 freezing/thawing cycles. Freezing caused an increasing damaged starch from 1.36% in native waxy rice starch to 5.77% in 10 freezing/thawing-treated starch (FTS), as evidenced by the cracking surface on starch granules. More dry matter concentration was leached, which was characterized by high amylopectin concentration (4.34 mg/mL). The leaching was accompanied by a decrease in relative crystallinity from 35.19% in native starch to 31.34% in 10 FTS. Freezing treatment also led to significant deviations in the functional characteristics, for instance decreased gelatinization temperature range, enthalpy, and pasting viscosities. The resistant starch content of 10FTS significantly decreased from 58.9% to 19%, whereas the slowly digested starch content greatly increased from 23.8% in native starch to 50.3%. The increase in susceptibility to enzyme hydrolysis may be attributed to porous granular surface, amylopectin leaching, and the decrease in the relative crystallinity caused by freezing water. PMID:26018506

  9. Investigation of the stabilizing effects of hydroxyethyl cellulose on LDH during freeze drying and freeze thawing cycles.

    Science.gov (United States)

    Al-Hussein, Anas; Gieseler, Henning

    2015-01-01

    The objective of this study was to investigate both the cryoprotective and lyoprotective effects of the polymer hydroxyethyl cellulose (HEC) on the model protein lactate dehydrogenase (LDH) during freeze thawing and freeze drying cycles. The effect of annealing on both protein stability and the physical state of HEC was evaluated. HEC was used as a sole excipient in the protein formulations, and its stabilizing was compared to that of other excipients which are commonly used in freeze dried protein formulations. Furthermore, other quality aspects of the freeze dried samples containing solely HEC were investigated, such as, reconstitution time and product elegance. Protein stability was evaluated functionally by measuring the activity recovery of the model protein LDH. The physical state of HEC after freeze drying was investigated and compared to this of other studied solutes using differential scanning calorimetry and X-ray powder diffractometry. HEC showed superior cryoprotective effects on LDH during freeze thawing, and considerable lyoprotective effects during the freeze drying process. Annealing had limited influence on the stabilizing effect of HEC. The extensive reconstitution times of the HEC lyophilisates could be greatly improved by incorporation of the surfactant Tween 80 into the formulations prior to freeze drying.

  10. A Global Record of Daily Landscape Freeze-Thaw Status from Satellite Microwave Remote Sensing

    Science.gov (United States)

    Kimball, J. S.; Kim, Y.; Colliander, A.; McDonald, K. C.

    2011-12-01

    The freeze-thaw (FT) parameter from satellite microwave remote sensing quantifies the predominant landscape frozen or thawed state and is closely linked to surface energy budget and hydrologic activity, seasonal vegetation growth dynamics and terrestrial carbon budgets. A global Earth System Data Record (ESDR) of daily landscape FT status (FT-ESDR) was developed using a temporal change classification of 37 GHz brightness temperature (Tb) series from the Scanning Multichannel Microwave Radiometer (SMMR) and Special Sensor Microwave Imager (SSM/I), and encompassing land areas where seasonal frozen temperatures influence ecosystem processes. A consistent, long-term (>30 yr) FT record was created by ensuring cross-sensor consistency through pixel-wise adjustment of the SMMR Tb record based on empirical analyses of overlapping SMMR and SSM/I measurements. The product is designed to determine the FT status of the composite landscape vegetation-snow-soil medium with sufficient accuracy to characterize frozen temperature constraints to surface water mobility, vegetation productivity and land-atmosphere CO2 fluxes. A multi-tier product validation is applied using in situ temperature and tower carbon flux measurements, and other satellite FT retrievals. The FT-ESDR record shows mean annual spatial classification accuracies of 91 (+/-8.6) and 84 (+/-9.3) percent for PM and AM overpass retrievals relative to surface air temperature measurements from global weather stations. Other comparisons against spatially dense temperature observations from an Alaska ecological transect reveal satellite sensor frequency dependence and variable FT sensitivity to surface air, vegetation, soil and snow properties. Other satellite sensor retrievals, including AMSR-E and SMOS show similar FT classification accuracies, but variable sensitivity to different landscape elements. Sensor FT classification differences reflect differences in microwave frequency, footprint resolution and satellite

  11. Survival of microbial isolates from clouds toward simulated atmospheric stress factors

    Science.gov (United States)

    Joly, Muriel; Amato, Pierre; Sancelme, Martine; Vinatier, Virginie; Abrantes, Magali; Deguillaume, Laurent; Delort, Anne-Marie

    2015-09-01

    In the atmosphere, airborne microbial cells are exposed to conditions that are thought to affect their survival. Here, we investigated the survival of 5 microorganisms among the most represented in the cultivable community of clouds (4 bacteria affiliated to Pseudomonas, Sphingomonas and Arthrobacter and 1 yeast of Dioszegia) after exposition to different atmospheric factors generally considered stressful for cells: artificial solar light (10 h), oxidant (hydrogen peroxide: 0-1 mM for 90 min), osmotic shocks (0.1-2.5 M NaCl) and freeze-thaw cycles (6 cycles of 5 °C/-40 °C). Each condition was applied separately to cell suspensions, and survival rates were examined by culture. Survival was highly strain and stress dependent, with no relationship with pigmentation or ice nucleation activity. In all strains, solar light had no or mitigated influence, and exposition to H2O2 at the concentration measured in cloud water only slightly impacted viability (>70% of the cells survived). The strain Sphingomonas sp. was particularly impacted by osmotic shocks while repeated freeze-thaw was particularly damaging for Arthrobacter and Pseudomonas species. Overall, our results tend to indicate that in the atmosphere, the most stringent selection factors on living organisms are probably freeze-thaw and condensation/evaporation (osmotic shocks) cycles, whereas the impacts of oxidants and of solar light are limited.

  12. Repeated vitrification/warming of human sperm gives better results than repeated slow programmable freezing

    Institute of Scientific and Technical Information of China (English)

    Teraporn Vutyavanich; Worashorn Lattiwongsakorn; Waraporn Piromlertamorn; Sudarat Samchimchom

    2012-01-01

    In this study,we compared the effects of repeated freezing/thawing of human sperm by our in-house method of rapid freezing with slow programmable freezing.Sperm samples from 11 normozoospermic subjects were processed through density gradients and divided into three aliquots:non-frozen,rapid freezing and slow programmable freezing.Sperm in the rapid freezing group had better motility and viability than those in the slow freezing group (P<O.01) after the first,second and third cycles of freezing/thawing,but there was no difference in morphology.In the second experiment,rapid freezing was repeated three times in 20 subjects.The samples from each thawing cycle were evaluated for DNA fragmentation using the alkaline comet assay.DNA fragmentation began to increase considerably after the second cycle of freezing/thawing,but to a level that was not clinically important.In the third experiment,rapid freezing was done repeatedly in 10 subjects,until no motile sperm were observed after thawing.The median number of repeated freezing/thawing that yielded no motile sperm was seven (range:5-8,mean:6.8).In conclusion,we demonstrated that repeated freezing/thawing of processed semen using our rapid freezing method gave better results than standard slow programmable freezing.This method can help maximize the usage of precious cryopreserved sperm samples in assisted reproduction technology.

  13. Stability Evaluation of Volcanic Slope Subjected to Rainfall and Freeze-Thaw Action Based on Field Monitoring

    Directory of Open Access Journals (Sweden)

    Shima Kawamura

    2011-01-01

    Full Text Available Rainfall-induced failures of natural and artificial slopes such as cut slopes, which are subjected to freezing and thawing, have been frequently reported in Hokkaido, Japan. In particular, many failures occur intensively from spring to summer seasons. Despite numerous field studies, explanation of their mechanical behavior based on in situ data has not yet been completely achieved due to the difficulty in grasping failure conditions. This study aims at clarifying the aspects of in-situ volcanic slopes subjected to rainfall and freeze-thaw action. The changes in soil moisture, pore pressure, deformations, and temperatures in the slope were investigated using soil moisture meters, tensiometers, thermocouple sensors, clinometers, settlement gauges, an anemovane, a snow gauge, and a rainfall gauge. The data generated from these measures indicated deformation in the slope examined mainly proceeded during the drainage process according to changes in soil moisture. Based on this data, a prediction method for failures is discussed in detail.

  14. Comparison of cook loss, shear force, and sensory descriptive profiles of broiler breast fillets cooked from a frozen state and cooked after freeze/thaw

    Science.gov (United States)

    Four replications were conducted to compare quality measurements, cook loss, shear force, and sensory quality profiles of cooked broiler breast meat (pectoralis major) prepared directly from a frozen state and prepared after freeze/thaw. In each replication, fresh broiler fillets (removed from carca...

  15. Petroleum hydrocarbon biodegradation under seasonal freeze-thaw soil temperature regimes in contaminated soils from a sub-Arctic site.

    Science.gov (United States)

    Chang, Wonjae; Klemm, Sara; Beaulieu, Chantale; Hawari, Jalal; Whyte, Lyle; Ghoshal, Subhasis

    2011-02-01

    Several studies have shown that biostimulation in ex situ systems such as landfarms and biopiles can facilitate remediation of petroleum hydrocarbon contaminated soils at sub-Arctic sites during summers when temperatures are above freezing. In this study, we examine the biodegradation of semivolatile (F2: C10-C16) and nonvolatile (F3: C16-C34) petroleum hydrocarbons and microbial respiration and population dynamics at post- and presummer temperatures ranging from -5 to 14 °C. The studies were conducted in pilot-scale tanks with soils obtained from a historically contaminated sub-Arctic site in Resolution Island (RI), Canada. In aerobic, nutrient-amended, unsaturated soils, the F2 hydrocarbons decreased by 32% during the seasonal freeze-thaw phase where soils were cooled from 2 to -5 °C at a freezing rate of -0.12 °C d(-1) and then thawed from -5 to 4 °C at a thawing rate of +0.16 °C d(-1). In the unamended (control) tank, the F2 fraction only decreased by 14% during the same period. Biodegradation of individual hydrocarbon compounds in the nutrient-amended soils was also confirmed by comparing their abundance over time to that of the conserved diesel biomarker, bicyclic sesquiterpanes (BS). During this period, microbial respiration was observed, even at subzero temperatures when unfrozen liquid water was detected during the freeze-thaw period. An increase in culturable heterotrophs and 16S rDNA copy numbers was noted during the freezing phase, and the (14)C-hexadecane mineralization in soil samples obtained from the nutrient-amended tank steadily increased. Hydrocarbon degrading bacterial populations identified as Corynebacterineae- and Alkanindiges-related strains emerged during the freezing and thawing phases, respectively, indicating there were temperature-based microbial community shifts.

  16. The role of snow cover and soil freeze/thaw cycles affecting boreal-arctic soil carbon dynamics

    Directory of Open Access Journals (Sweden)

    Y. Yi

    2015-07-01

    Full Text Available Northern Hemisphere permafrost affected land areas contain about twice as much carbon as the global atmosphere. This vast carbon pool is vulnerable to accelerated losses through mobilization and decomposition under projected global warming. Satellite data records spanning the past 3 decades indicate widespread reductions (∼ 0.8–1.3 days decade−1 in the mean annual snow cover extent and frozen season duration across the pan-Arctic domain, coincident with regional climate warming trends. How the soil carbon pool responds to these changes will have a large impact on regional and global climate. Here, we developed a coupled terrestrial carbon and hydrology model framework with detailed 1-D soil heat transfer representation to investigate the sensitivity of soil organic carbon stocks and soil decomposition to changes in snow cover and soil freeze/thaw processes in the Pan-Arctic region over the past three decades (1982–2010. Our results indicate widespread soil active layer deepening across the pan-Arctic, with a mean decadal trend of 6.6 ± 12.0 (SD cm, corresponding with widespread warming and lengthening non-frozen season. Warming promotes vegetation growth and soil heterotrophic respiration, particularly within surface soil layers (≤ 0.2 m. The model simulations also show that seasonal snow cover has a large impact on soil temperatures, whereby increases in snow cover promote deeper (≥ 0.5 m soil layer warming and soil respiration, while inhibiting soil decomposition from surface (≤ 0.2 m soil layers, especially in colder climate zones (mean annual T ≤ −10 °C. Our results demonstrate the important control of snow cover in affecting northern soil freeze/thaw and soil carbon decomposition processes, and the necessity of considering both warming, and changing precipitation and snow cover regimes in characterizing permafrost soil carbon dynamics.

  17. The role of snow cover and soil freeze/thaw cycles affecting boreal-arctic soil carbon dynamics

    Science.gov (United States)

    Yi, Y.; Kimball, J. S.; Rawlins, M. A.; Moghaddam, M.; Euskirchen, E. S.

    2015-07-01

    Northern Hemisphere permafrost affected land areas contain about twice as much carbon as the global atmosphere. This vast carbon pool is vulnerable to accelerated losses through mobilization and decomposition under projected global warming. Satellite data records spanning the past 3 decades indicate widespread reductions (∼ 0.8-1.3 days decade-1) in the mean annual snow cover extent and frozen season duration across the pan-Arctic domain, coincident with regional climate warming trends. How the soil carbon pool responds to these changes will have a large impact on regional and global climate. Here, we developed a coupled terrestrial carbon and hydrology model framework with detailed 1-D soil heat transfer representation to investigate the sensitivity of soil organic carbon stocks and soil decomposition to changes in snow cover and soil freeze/thaw processes in the Pan-Arctic region over the past three decades (1982-2010). Our results indicate widespread soil active layer deepening across the pan-Arctic, with a mean decadal trend of 6.6 ± 12.0 (SD) cm, corresponding with widespread warming and lengthening non-frozen season. Warming promotes vegetation growth and soil heterotrophic respiration, particularly within surface soil layers (≤ 0.2 m). The model simulations also show that seasonal snow cover has a large impact on soil temperatures, whereby increases in snow cover promote deeper (≥ 0.5 m) soil layer warming and soil respiration, while inhibiting soil decomposition from surface (≤ 0.2 m) soil layers, especially in colder climate zones (mean annual T ≤ -10 °C). Our results demonstrate the important control of snow cover in affecting northern soil freeze/thaw and soil carbon decomposition processes, and the necessity of considering both warming, and changing precipitation and snow cover regimes in characterizing permafrost soil carbon dynamics.

  18. Temporal monitoring of the soil freeze-thaw cycles over snow-cover land by using off-ground GPR

    KAUST Repository

    Jadoon, Khan

    2013-07-01

    We performed off-ground ground-penetrating radar (GPR) measurements over a bare agricultural field to monitor the freeze-thaw cycles over snow-cover. The GPR system consisted of a vector network analyzer combined with an off-ground monostatic horn antenna, thereby setting up an ultra-wideband stepped-frequency continuous-wave radar. Measurements were performed during nine days and the surface of the bare soil was exposed to snow fall, evaporation and precipitation as the GPR antenna was mounted 110 cm above the ground. Soil surface dielectric permittivity was retrieved using an inversion of time-domain GPR data focused on the surface reflection. The GPR forward model used combines a full-waveform solution of Maxwell\\'s equations for three-dimensional wave propagation in planar layered media together with global reflection and transmission functions to account for the antenna and its interactions with the medium. Temperature and permittivity sensors were installed at six depths to monitor the soil dynamics in the top 8 cm depth. Significant effects of soil dynamics were observed in the time-lapse GPR, temperature and permittivity data and in particular freeze and thaw events were clearly visible. A good agreement of the trend was observed between the temperature, permittivity and GPR time-lapse data with respect to five freeze-thaw cycles. The GPR-derived permittivity was in good agreement with sensor observations. The proposed method appears to be promising for the real-time mapping and monitoring of the frozen layer at the field scale. © 2013 IEEE.

  19. The Experimental Study on the Physical and Mechanical Properties of Red Sandstone under the Action of Freeze_thaw Cycles%冻融循环条件下红砂岩物理力学特性试验研究

    Institute of Scientific and Technical Information of China (English)

    张慧梅; 张蒙军; 谢祥妙; 曹海波

    2015-01-01

    对采自陕西的红砂岩进行冻融循环压缩试验,以模拟红砂岩的冻融风化过程。试验共进行40次冻融循环,在冻融0,5,10,20,40次时分别测量岩样的质量、体积及其纵波波速,并对岩样进行单轴抗压试验;分析了岩石强度与应力_应变曲线及损伤扩展力学特性随冻融循环次数的变化规律。研究结果表明,随着冻融循环次数的增加,岩样的质量、密度、波速及冻融系数减小;岩样的弹性模量及强度逐渐减小,应力_应变曲线压缩性增大,弹性增长段减小,塑性增强;冻融与荷载的共同作用使岩石总损伤加剧,并最终导致岩石破坏。最后,利用陕西红砂岩物理力学特性随冻融循环的变化规律,为寒区岩土工程的建设提供相应的参考数据。%The red sandstones collected from Shaanxi were taken as the samples in the com_pression test under the action of freeze_thaw cycle to simulate the freeze_thaw weathering process of red sandstone .The mass ,volume and longitudinal wave velocity of rock samples were measured when the freeze_thaw cycle number were 0 ,5 ,10 ,20 ,40 times ,and uniaxial compressive test were conducted on them .The laws of the change in rock strength and stress_strain curves as well as the mechanical properties of damage propagation with the freeze_thaw cycles were analyzed .The re_sults show that :the mass ,density ,velocity of rock samples decreased as the freeze_thaw cycles number increased ;Rock samples freeze_thaw coefficient ,elastic modulus and strength decreased gradually ,the compression of stress_strain curve increased ,the elastic grow th segment decreased , and plasticity was reinforced ;The total damage aggravated under the joint action of freeze_thaw and loads ,and eventually led to rock failure .Finally ,the change law about the mechanical proper_ties of Shaanxi red sandstone with the freezethaw cycles is used to provide a reference data for the

  20. Towards an Improved Algorithm for Estimating Freeze-Thaw Dates of a High Latitude Lake Using Texture Analysis of SAR Images

    Science.gov (United States)

    Uppuluri, A. V.; Jost, R. J.; Luecke, C.; White, M. A.

    2008-12-01

    Analyzing the freeze-thaw dates of high latitude lakes is an important part of climate change studies. Due to the various advantages provided by the use of SAR images, with respect to remote monitoring of small lakes, SAR image analysis is an obvious choice to estimate lake freeze-thaw dates. An important property of SAR images is its texture. The problem of estimating freeze-thaw dates can be restated as a problem of classifying an annual time series of SAR images based on the presence or absence of ice. We analyzed a few algorithms based on texture to improve the estimation of freeze-thaw dates for small lakes using SAR images. We computed the Gray Level Co-occurrence Matrix (GLCM) for each image and extracted ten different texture features from the GLCM. We used these texture features (namely, Energy, Contrast, Correlation, Homogeneity, Entropy, Autocorrelation, Dissimilarity, Cluster Shade, Cluster Prominence and Maximum Probability as previously used in studies related to the texture analysis of SAR sea ice imagery) as input to a group of classification algorithms to find the most accurate classifier and set of texture features that can help to decide the presence or absence of ice on the lake. The accuracy of the estimated freeze-thaw dates is dependent on the accuracy of the classifier. It is considered highly difficult to differentiate between open water (without wind) and the first day of ice formed on the lake (due to the similar mean backscatter values) causing inaccuracy in calculating the freeze date. Similar inaccuracy in calculating the thaw date arise due to the close backscatter values of water (with wind) and later stages of ice on the lake. Our method is promising but requires further research in improving the accuracy of the classifiers and selecting the input features.

  1. Investigation on the Mechanical Properties of a Cement-Based Material Containing Carbon Nanotube under Drying and Freeze-Thaw Conditions

    Directory of Open Access Journals (Sweden)

    Wei-Wen Li

    2015-12-01

    Full Text Available This paper aimed to explore the mechanical properties of a cement-based material with carbon nanotube (CNT under drying and freeze-thaw environments. Mercury Intrusion Porosimetry and Scanning Electron Microscopy were used to analyze the pore structure and microstructure of CNT/cement composite, respectively. The experimental results showed that multi-walled CNT (MWCNT could improve to different degrees the mechanical properties (compressive and flexural strengths and physical performances (shrinkage and water loss of cement-based materials under drying and freeze-thaw conditions. This paper also demonstrated that MWCNT could interconnect hydration products to enhance the performance of anti-microcracks for cement-based materials, as well as the density of materials due to CNT’s filling action.

  2. Satellite remote sensing of landscape freeze/thaw state dynamics for complex Topography and Fire Disturbance Areas Using multi-sensor radar and SRTM digital elevation models

    Science.gov (United States)

    Podest, Erika; McDonald, Kyle; Kimball, John; Randerson, James

    2003-01-01

    We characterize differences in radar-derived freeze/thaw state, examining transitions over complex terrain and landscape disturbance regimes. In areas of complex terrain, we explore freezekhaw dynamics related to elevation, slope aspect and varying landcover. In the burned regions, we explore the timing of seasonal freeze/thaw transition as related to the recovering landscape, relative to that of a nearby control site. We apply in situ biophysical measurements, including flux tower measurements to validate and interpret the remotely sensed parameters. A multi-scale analysis is performed relating high-resolution SAR backscatter and moderate resolution scatterometer measurements to assess trade-offs in spatial and temporal resolution in the remotely sensed fields.

  3. Satellite remote sensing of landscape freeze/thaw state dynamics for complex Topography and Fire Disturbance Areas Using multi-sensor radar and SRTM digital elevation models

    Science.gov (United States)

    Podest, Erika; McDonald, Kyle; Kimball, John; Randerson, James

    2003-01-01

    We characterize differences in radar-derived freeze/thaw state, examining transitions over complex terrain and landscape disturbance regimes. In areas of complex terrain, we explore freezekhaw dynamics related to elevation, slope aspect and varying landcover. In the burned regions, we explore the timing of seasonal freeze/thaw transition as related to the recovering landscape, relative to that of a nearby control site. We apply in situ biophysical measurements, including flux tower measurements to validate and interpret the remotely sensed parameters. A multi-scale analysis is performed relating high-resolution SAR backscatter and moderate resolution scatterometer measurements to assess trade-offs in spatial and temporal resolution in the remotely sensed fields.

  4. Improvement on the freeze-thaw stability of corn starch gel by the polysaccharide from leaves of Corchorus olitorius L.

    Science.gov (United States)

    Yamazaki, Eiji; Sago, Toru; Kasubuchi, Yoshiaki; Imamura, Kazuhito; Matsuoka, Toshio; Kurita, Osamu; Nambu, Hironobu; Matsumura, Yasuki

    2013-04-15

    Effect of the polysaccharide from leaves of Corchorus olitorius L. (PLC) on the freeze-thaw (FT) stability of corn starch gel was studied. PLC was incorporated into the starch gel at 0.7% and total solid was adjusted to 6.0%. The syneresis was measured by the centrifugal-filtration method and, as a result, addition of PLC reduced effectively the syneresis of the starch gel even after 5 FT cycles, which was less than one third that of the normal starch gel. The rheological changes of the starch/PLC gel during the FT treatments were evaluated while the gel remained on the rheometer plate. The starch/PLC gel had less significant changes in the rheological parameters during the FT cycles than starch/guar gum or xanthan gum gel systems. SEM images showed that PLC stabilized the gel matrix surrounding pores, which would contribute to both a lower syneresis production and a higher stability in the rheological behavior at FT.

  5. Reduced glutathione and procaine hydrochloride protect the nucleoprotein structure of boar spermatozoa during freeze-thawing by stabilising disulfide bonds.

    Science.gov (United States)

    Yeste, Marc; Flores, Eva; Estrada, Efrén; Bonet, Sergi; Rigau, Teresa; Rodríguez-Gil, Joan E

    2013-01-01

    One important change the head of boar spermatozoa during freeze-thawing is the destabilisation of its nucleoprotein structure due to a disruption of disulfide bonds. With the aim of better understanding these changes in frozen-thawed spermatozoa, two agents, namely reduced glutathione (GSH) and procaine hydrochloride (ProHCl), were added at different concentrations to the freezing media at different concentrations and combinations over the range 1-2mM. Then, 30 and 240 min after thawing, cysteine-free residue levels of boar sperm nucleoproteins, DNA fragmentation and other sperm functional parameters were evaluated. Both GSH and ProHCl, at final concentrations of 2mM, induced a significant (Psperm head disulfide bonds 30 and 240 min after thawing compared with the frozen-thawed control. This effect was accompanied by a significant (Psperm peroxide levels, motility patterns and plasma membrane integrity. In conclusion, the results show that both GSH and ProHCl have a stabilising effect on the nucleoprotein structure of frozen-thawed spermatozoa, although only GSH exerts an appreciable effect on sperm viability.

  6. A prediction model for uniaxial compressive strength of deteriorated pyroclastic rocks due to freeze-thaw cycle

    Science.gov (United States)

    İnce, İsmail; Fener, Mustafa

    2016-08-01

    Either directly or indirectly, building stone is exposed to diverse atmospheric interactions depending on the seasonal conditions. Due to those interactions, objects of historic and cultural heritage, as well as modern buildings, partially or completely deteriorate. Among processes involved in rock deterioration, the freeze-thaw (F-T) cycle is one of the most important. Even though pyroclastic rocks have been used as building stone worldwide due to their easy workability, they are the building stone most affected by the F-T cycle. A historical region in Central Anatolia, Turkey, Cappadoia encompasses exceptional natural wonders characterized by fairy chimneys and unique historical and cultural heritage. Human-created caves, places of worship and houses have been dug into the pyroclastic rocks, which have in turn been used in architectural construction as building stone. Using 10 pyroclastic rock samples collected from Cappadocia, we determined the rock's index-mechanical properties to develop a statistical model for estimating percentage loss of uniaxial compressive strength a critical parameter of F-T cycle's important value. We used dry density (ρd), ultrasonic velocity (Vp), point load strengths (IS(50)), and slake-durability test indexes (Id4) values of unweathered rocks in our model, which is highly reliable (R2 = 0.84) for predetermination of percentage loss of uniaxial compressive strengths of pyroclastic rocks without requiring any F-T tests.

  7. Comparative study of deterioration procedure in chemical-leavened steamed bread dough under frozen storage and freeze/thaw condition.

    Science.gov (United States)

    Wang, Pei; Yang, Runqiang; Gu, Zhenxin; Xu, Xueming; Jin, Zhengyu

    2017-08-15

    Successive freeze/thaw (FT) cycle was a widely used empirical approach to shorten the experimental period since it could accelerate frozen dough deterioration compared with frozen storage (FS). In order to compare the effect of FS and FT cycle on deterioration procedure of chemical-leavened steamed bread dough, kinetic studies of bread quality indices were performed and the relationships between bread quality and dough components were further established. Results showed that degradation of steamed bread loaf volume and firmness followed first-order kinetics during FS and zero-order kinetics during FT, respectively. Glutenin macropolymers (GMP) depolymerization and dough weight loss occurred steadily throughout FS and FT. Significant enhancement of damaged starch and crystallinity were observed at the later FS period and FT cycle. Multiple regression study led to the conclusion that dough weight loss contributed the most to the reduced bread loaf volume under FS whereas GMP depolymerization dominated under FT condition. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Role of cold climate and freeze-thaw on the survival, transport, and virulence of Yersinia enterocolitica.

    Science.gov (United States)

    Asadishad, Bahareh; Ghoshal, Subhasis; Tufenkji, Nathalie

    2013-12-17

    Surface and near-surface soils in cold climate regions experience low temperature and freeze-thaw (FT) conditions in the winter. Microorganisms that are of concern to groundwater quality may have the potential to survive low temperature and FT in the soil and aqueous environments. Although there is a body of literature on the survival of pathogenic bacteria at different environmental conditions, little is known about their transport behavior in aquatic environments at low temperatures and after FT. Herein, we studied the survival, transport, and virulence of a Gram-negative bacterial pathogen, Yersinia enterocolitica, when subjected to low temperature and several FT cycles at two solution ionic strengths (10 and 100 mM) in the absence of nutrients. Our findings demonstrate that this bacterium exhibited higher retention on sand after exposure to FT. Increasing the number of FT cycles resulted in higher bacterial cell surface hydrophobicity and impaired the swimming motility and viability of the bacterium. Moreover, the transcription of flhD and fliA, the flagellin-encoding genes, and lpxR, the lipid A 3'-O-deacylase gene, was reduced in low temperature and after FT treatment while the transcription of virulence factors such as ystA, responsible for enterotoxin production, ail, attachment invasion locus gene, and rfbC, O-antigen gene, was increased. Y. enterocolitica tends to persist in soil for long periods and may become more virulent at low temperature in higher ionic strength waters in cold regions.

  9. Manuscript Title: Influence of Glucose, Sucrose and Trehalose on the Freeze-Thaw Stability of Tapioca Starch Gels

    Directory of Open Access Journals (Sweden)

    Xiaoyu Zhang

    2012-08-01

    Full Text Available The aim of this study is to study influence of glucose, sucrose and trehalose on the Freeze-Thaw (FT stability of tapioca starch gels. The effects of glucose, sucrose and trehalose (3%, 6% and 12%, w: w on the freezethaw stability of Tapioca Starch (TS gels were investigated at the concentration of starch 6% (w: w. Syneresis experiment showed the FT stability of TS gels could be improved by sugar addition, according to the sugar type and concentration. And the improvement of syneresis% was in the order: trehalose>sucrose>glucose. SEM and DSC experiments were also applied to determine the effects of sugars (6%, w: w on the FT stability of TS gels after FT 5 cycles. SEM tests showed that the pore sizes and surrounding matrixes corresponded with the sugars order mentioned above and the pores of gels containing trehalose were smallest and the matrixes surrounding were thickest. DSC experiments showed that retrogradation of starch was retarded in the presence of sugars and trehalose was more effective than sucrose or glucose. Therefore, trehalose is a good candidate for improving the FT stability of TS gels.

  10. Mechanical Performance and Chloride Diffusivity of Cracked RC Specimens Exposed to Freeze-Thaw Cycles and Intermittent Immersion in Seawater

    Directory of Open Access Journals (Sweden)

    Bei Shen

    2016-01-01

    Full Text Available The effects of crack width on chloride ingress and mechanical behavior of reinforced concrete (RC specimens were experimentally studied after exposure to 300 cycles of freeze-thaw and seawater immersion (75 times. Cracks were induced prior to exposure by an eccentric compression load which was sustained until the end of the exposure period. The maximum cracks widths induced in the four column specimens were 0, 0.06, 0.11, and 0.15 mm, respectively. Results show that when the crack width was less than 0.06 mm, the effect of cracks on chloride ingress could be neglected. However, when the crack width was more than 0.11 mm, chloride ingress was accelerated. Results of static loading tests show that both yield load and ultimate load of RC columns decreased as crack width increased. When the crack width was 0.15 mm, yield load and ultimate load of RC column specimen decreased by 17.0% and 18.9%, respectively, compared to a specimen without cracks. It was concluded that crack width significantly promoted local chloride ingress and mechanical performance degradation of RC structures in cold coastal regions or exposed to deicing salts.

  11. PVA/CM-chitosan/honey hydrogels prepared by using the combined technique of irradiation followed by freeze-thawing

    Science.gov (United States)

    Afshari, M. J.; Sheikh, N.; Afarideh, H.

    2015-08-01

    Hydrogels with three components, poly(vinyl alcohol) (PVA), carboxymethylate chitosan (CM-chitosan) and honey have been prepared by using radiation method and radiation followed by freeze-thawing cycles technique (combinational method). The solid concentration of the polymer solution is 15 wt% and the ratios of PVA/CM-chitosan/honey are 10/1.5/3.5, 10/2/3, 10/3/2, and 10/3.5/1.5. The applied irradiation doses are 25, 30 and 40 kGy. Various tests have been done to evaluate the hydrogel properties to produce materials to be used as wound dressing. The results show that combinational method improves the mechanical strength of hydrogels while it has no significant effect on the water evaporation rate of gels. The combinational method decreases the swelling of hydrogels significantly, albeit this parameter is still acceptable for wound dressing. Microbiological analyses show that the hydrogel prepared by both methods can protect the wound from Escherichia coli bacterial infection. The wound healing test shows the good performance of the gels in mice.

  12. Nitrogen deposition may enhance soil carbon storage via change of soil respiration dynamic during a spring freeze-thaw cycle period

    OpenAIRE

    Guoyong Yan; Yajuan Xing; Lijian Xu; Jianyu Wang; Wei Meng; Qinggui Wang; Jinghua Yu; Zhi Zhang; Zhidong Wang; Siling Jiang; Boqi Liu; Shijie Han

    2016-01-01

    As crucial terrestrial ecosystems, temperate forests play an important role in global soil carbon dioxide flux, and this process can be sensitive to atmospheric nitrogen deposition. It is often reported that the nitrogen addition induces a change in soil carbon dioxide emission in growing season. However, the important effects of interactions between nitrogen deposition and the freeze-thaw-cycle have never been investigated. Here we show nitrogen deposition delays spikes of soil respiration a...

  13. Studies on the protective efficacy of freeze thawed promastigote antigen of Leishmania donovani along with various adjuvants against visceral leishmaniasis infection in mice.

    Science.gov (United States)

    Thakur, Ankita; Kaur, Harpreet; Kaur, Sukhbir

    2015-09-01

    Visceral leishmaniasis (VL) caused by Leishmania donovani persists as a major public health issue in tropical and subtropical areas of the world. Current treatment of this disease relies on use of drugs. It is doubtful that chemotherapy can alone eradicate the disease, so there is a need for an effective vaccine. Killed antigen candidates remain a good prospect considering their ease of formulation, stability, low cost and safety. To enhance the efficacy of killed vaccines suitable adjuvant and delivery system are needed. Therefore, the current study was conducted to determine the protective efficacy of freeze-thawed L. donovani antigen in combination with different adjuvants against experimental infection of VL. For this, BALB/c mice were immunized thrice at an interval of two weeks. Challenge infection was given two weeks after last immunization. Mice were sacrificed after last immunization and on different post challenge/infection days. Immunized mice showed significant reduction in parasite burden, enhanced DTH responses with increased levels of Th1 cytokines and lower levels of Th2 cytokines, thus indicating the development of a protective Th1 response. Maximum protection was achieved with liposome encapsulated freeze thawed promastigote (FTP) antigen of L. donovani and it was followed by group immunized with FTP+MPL-A, FTP+saponin, FTP+alum and FTP antigen (alone). The present study highlights greater efficacy of freeze thawed promastigote antigen as a potential vaccine candidate along with effective adjuvant formulations against experimental VL infection.

  14. Measurements of the salt-removal of NaCl, KCl and MgCl using a carbon electrode prepared with freezing thawing method in capacitive deionization

    Science.gov (United States)

    Endarko, Sari, Intan Permata; Fatimah, Iim

    2016-04-01

    Carbon electrodes prepared with freezing thawing method for desalination purpose has been synthesized and characterized. The carbon electrodes were prepared with an activated carbon (700 - 1400 m2/g) and polyvinyl alcohol (PVA) as a binder using freezing thawing method with 3 and 4 cycles (1 cycle is 12 hours for freezing and 12 hours for thawing). Electrical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were used to analyze their electrochemical properties. The main study was to measure the salt-removal of 180 µS/cm NaCl, MgCl and KCl using a capacitive deionization (CDI) unit cell with five pairs of carbon electrodes. The applied potential of 2.0 V and a flow rate of 25 mL/min were used to desalination tests, the result showed that the salt-removal percentage of KCl solution has greater than NaCl and MgCl. The highest value for the salt-removal of NaCl, KCl and MgCl can be achieved for the freezing thawing method with 4 cycles. The salt-removal percentage of KCl was achieved at 64.10% whilst resulted in 54.30 and 54.47 % for NaCl and MgCl, respectively.

  15. Nitrogen deposition may enhance soil carbon storage via change of soil respiration dynamic during a spring freeze-thaw cycle period

    Science.gov (United States)

    Yan, Guoyong; Xing, Yajuan; Xu, Lijian; Wang, Jianyu; Meng, Wei; Wang, Qinggui; Yu, Jinghua; Zhang, Zhi; Wang, Zhidong; Jiang, Siling; Liu, Boqi; Han, Shijie

    2016-06-01

    As crucial terrestrial ecosystems, temperate forests play an important role in global soil carbon dioxide flux, and this process can be sensitive to atmospheric nitrogen deposition. It is often reported that the nitrogen addition induces a change in soil carbon dioxide emission in growing season. However, the important effects of interactions between nitrogen deposition and the freeze-thaw-cycle have never been investigated. Here we show nitrogen deposition delays spikes of soil respiration and weaken soil respiration. We found the nitrogen addition, time and nitrogen addition×time exerted the negative impact on the soil respiration of spring freeze-thaw periods due to delay of spikes and inhibition of soil respiration (p annual C emissions. Therefore, we show interactions between nitrogen deposition and freeze-thaw-cycle in temperate forest ecosystems are important to predict global carbon emissions and sequestrations. We anticipate our finding to be a starting point for more sophisticated prediction of soil respirations in temperate forests ecosystems.

  16. An investigation and characterization on alginate hydogel dressing loaded with metronidazole prepared by combined inotropic gelation and freeze-thawing cycles for controlled release.

    Science.gov (United States)

    Sarheed, Omar; Rasool, Bazigha K Abdul; Abu-Gharbieh, Eman; Aziz, Uday Sajad

    2015-06-01

    The purpose of this study was to investigate the effect of combined Ca(2+) cross-linking and freeze-thawing cycle method on metronidazole (model drug) drug release and prepare a wound film dressing with improved swelling property. The hydrogel films were prepared with sodium alginate (SA) using the freeze-thawing method alone or in combination with ionotropic gelation with CaCl2. The gel properties such as morphology, swelling, film thickness, and content uniformity and in vitro dissolution profiles using Franz diffusion cell were investigated. The cross-linking process was confirmed by differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy. In vitro protein adsorption test, in vivo wound-healing test, and histopathology were also performed. The hydrogel (F2) composed of 6% sodium alginate and 1% metronidazole prepared by combined Ca(2+) cross-linking and freeze-thawing cycles showed good swelling. This will help to provide moist environment at the wound site. With the in vivo wound-healing and histological studies, F2 was found to improve the wound-healing effect compared with the hydrogel without the drug, and the conventional product.

  17. Development of Fracture Energy of FRC Materials. Freeze-Thaw Resistance of FRC Materials

    DEFF Research Database (Denmark)

    Stoklund Larsen, E.

    During the past four years research has been carried out at the Danish Building Research Institute on different aspects of the long term performance of fibre reinforced cementitious composites (FRC) exposed to climate stresses. Some of the most important results have been brought together in this...

  18. Development of Fracture Energy of FRC Materials. Freeze-Thaw Resistance of FRC Materials

    DEFF Research Database (Denmark)

    Stoklund Larsen, E.

    During the past four years research has been carried out at the Danish Building Research Institute on different aspects of the long term performance of fibre reinforced cementitious composites (FRC) exposed to climate stresses. Some of the most important results have been brought together in this...

  19. 冻融和氯盐侵蚀耦合作用下的大掺量粉煤灰混凝土耐久性探讨%Durability of High Fly Ash Content Concrete under the Coupling Effect of Freeze-Thaw and Chlorine Salt Erosion

    Institute of Scientific and Technical Information of China (English)

    艾红梅; 郭建华; 杨晨光; 戴碧琳

    2015-01-01

    The north sea environment is very bad,which damages the concrete seriously,so the current research of concrete durability mainly focuses on the chloride ion penetration,sulphate erosion,freeze - thaw action and so on. Among them,the damage to concrete from chlorine salt erosion and freeze -thaw is particularly serious,so frost resistance and salt stress resistance design of marine engineering is particularly important. Considering the dominant factor of concrete degradation and cost,high fly ash content concrete( HFCC ) is becoming more and more attractive because of its economic and environmental profits. The author mainly discusses the durability of HFCC under the coupling effect of freeze-thaw and chlorine salt.%鉴于北方海洋环境十分恶劣,对混凝土的破坏严重,目前对于海工混凝土耐久性问题的研究主要集中在氯离子渗透、硫酸盐侵蚀、冻融作用等方面。其中,氯盐侵蚀和冻融作用对混凝土造成的破坏尤为严重,所以对海工混凝土进行抗冻、抗盐害的设计尤为重要。出于混凝土劣化的主导因素和经济性的考虑,在海工结构中,大掺量粉煤灰混凝土( High Fly Ash Content Concrete,简称HFCC)以其经济效益和环境效益被人们愈来愈重视。主要对氯盐和冻融耦合作用下的大掺量粉煤灰混凝土的耐久性进行了探讨。

  20. Effect of Freeze-thaw Cycles on Bond Strength between Steel Bars and Concrete

    Institute of Scientific and Technical Information of China (English)

    JI Xiaodong; SONG Yupu; LIU Yuan

    2008-01-01

    The effect of freezing and thawing cycles on mechanical properties of concrete(compressive,splitting tensile strength)was experimentally investigated.According to the pullout test data of three kinds of deformed steel bars,the bond stress-slip curves after freezing and thawing were obtained.The empirical equations of peak bond strength were proposed that the damage accounted for effects of freezing and thawing cycle.Meanwhile,the mechanism of bond deterioration between steel bars and concrete after freezing and thawing cycles was discussed.All these conclusions will be useful to the durability design and reliability calculation of RC structures in cold region.

  1. Ultrasonic Measurements of Unconsolidated Saline Sediments During Freeze/Thaw Cycles: The Seismic Properties of Cryopeg Environments

    Science.gov (United States)

    Dou, S.; Ajo Franklin, J. B.

    2013-12-01

    Saline permafrost and cryopegs (hypersaline unfrozen layers/zones within permafrost) are widespread in the Arctic coastal area as a result of marine transgression and regression in recent geological history. Owing to the freezing-point depression effect of soluble salts, they contain more unfrozen water than non-saline frozen sediments when subjected to the same permafrost temperatures (e.g., from 0 to -15 °C). Mapping subsurface cryopeg structure remains a challenging geophysical task due to the poor penetration of GPR in highly conductive fluids and related limitations for lower frequency EM techniques. Seismic profiling, particularly surface wave characterization, provides one possible approach to delineate the extent of cryopeg bodies. However, interpretation of such surveys is currently limited by the sparse database of measurements examining the seismic properties of unconsolidated materials saturated with saline fluids at sub-zero temperatures. We present the results of experiments examining seismic velocity in the ultrasonic range for both synthetic and natural permafrost sediments during freeze/thaw cycles; in these experiments, use of a range of brine salinities allows us to evaluate the properties of cryopeg sediments at in-situ conditions, a prerequisite for quantitative interpretation of seismic imaging results. Because of the abundant unfrozen water and less developed inter-granular ice structure, the seismic properties of saline permafrost typically falls between frozen and unfrozen soils. We conducted ultrasonic measurements of a freeze-thaw cycle on 20-30 Ottawa sand (grain size 590-840 μm) as well as natural mineral soils from the Barrow Environmental Observatory (BEO) saturated with brines of different salinities (0-2.5 M NaCl). For each salinity, seismic properties were measured using the ultrasonic (~1 MHz) pulse-transmission method in the temperature range from 20 to -30 °C. Similar to sediments saturated with low salinity fluids, seismic

  2. Evaluation of the freeze-thaw/evaporation process for the treatment of produced waters. Final report, August 1992--August 1996

    Energy Technology Data Exchange (ETDEWEB)

    Boysen, J.E.; Walker, K.L.; Mefford, J.L.; Kirsch, J.R. [Resource Technology Corp., Laramie, WY (United States); Harju, J.A. [North Dakota Univ., Grand Forks, ND (United States). Energy and Environmental Research Center

    1996-06-01

    The use of freeze-crystallization is becoming increasingly acknowledged as a low-cost, energy-efficient method for purifying contaminated water. The natural freezing process can be coupled with natural evaporative processes to treat oil and gas produced waters year round in regions where subfreezing temperatures seasonally occur. The climates typical of Colorado`s San Juan Basin and eastern slope, as well as the oil and gas producing regions of Wyoming, are well suited for application of these processes in combination. Specifically, the objectives of this research are related to the development of a commercially-economic FTE (freeze-thaw/evaporation) process for the treatment and purification of water produced in conjunction with oil and natural gas. The research required for development of this process consists of three tasks: (1) a literature survey and process modeling and economic analysis; (2) laboratory-scale process evaluation; and (3) field demonstration of the process. Results of research conducted for the completion of these three tasks indicate that produced water treatment and disposal costs for commercial application of the process, would be in the range of $0.20 to $0.30/bbl in the Rocky Mountain region. FTE field demonstration results from northwestern New Mexico during the winter of 1995--96 indicate significant and simultaneous removal of salts, metals, and organics from produced water. Despite the unusually warm winter, process yields demonstrate disposal volume reductions on the order of 80% and confirm the potential for economic production of water suitable for various beneficial uses. The total dissolved solids concentrations of the FTE demonstration streams were 11,600 mg/L (feed), 56,900 mg/L (brine), and 940 mg/L (ice melt).

  3. The Role of Snow Cover in Affecting Pan-Arctic Soil Freeze/Thaw and Carbon Dynamics

    Science.gov (United States)

    Yi, Y.; Kimball, J. S.; Rawlins, M. A.; Moghaddam, M.; Euskirchen, E. S.

    2015-12-01

    Satellite data records spanning the past 3 decades indicate widespread reductions (~0.8-1.3 days decade-1) in mean annual snow cover and frozen season duration across the pan-Arctic domain, coincident with regional climate warming. How the northern soil carbon pool responds to these changes will have a large impact on projected regional and global climate trends. The objective of this study was to assess how northern soil thermal and carbon dynamics respond to changes in surface snow cover and freeze/thaw (F/T) cycles indicated from satellite observations. We developed a coupled permafrost, hydrology and carbon model framework to investigate the sensitivity of soil organic carbon stocks and soil decomposition to recent climate variations across the pan-Arctic region from 1982 to 2010. The model simulations were also evaluated against satellite observation records on snow cover and F/T processes. Our results indicate that surface warming promotes wide-spread soil thawing and active layer deepening due to strong control of surface air temperature on upper (-5°C) and promote permafrost degradation in these areas. Our results also show that seasonal snow cover has a large impact on soil temperatures, whereby increases in snow cover promote deeper (≥0.5 m) soil layer warming and soil respiration, while inhibiting soil decomposition from surface (≤0.2 m) soil layers, especially in colder climate zones (mean annual Tair≤-10 °C). This non-linear relationship between snow cover and soil decomposition is particularly important in permafrost areas, where a large amount of soil carbon is stored in deep perennial frozen soils that are potentially vulnerable to thawing, with resulting mobilization and accelerated carbon losses from near-term climate change.

  4. Spatial Variability of L-Band Brightness Temperature during Freeze/Thaw Events over a Prairie Environment

    Directory of Open Access Journals (Sweden)

    Alexandre Roy

    2017-08-01

    Full Text Available Passive microwave measurements from space are known to be sensitive to the freeze/thaw (F/T state of the land surface. These measurements are at a coarse spatial resolution (~15–50 km and the spatial variability of the microwave emissions within a pixel can have important effects on the interpretation of the signal. An L-band ground-based microwave radiometer campaign was conducted in the Canadian Prairies during winter 2014–2015 to examine the spatial variability of surface emissions during frozen and thawed periods. Seven different sites within the Kenaston soil monitoring network were sampled five times between October 2014 and April 2015 with a mobile ground-based L-band radiometer system at approximately monthly intervals. The radiometer measurements showed that in a seemingly homogenous prairie landscape, the spatial variability of brightness temperature (TB is non-negligible during both frozen and unfrozen soil conditions. Under frozen soil conditions, TB was negatively correlated with soil permittivity (εG. This correlation was related to soil moisture conditions before the main freezing event, showing that the soil ice volumetric content at least partly affects TB. However, because of the effect of snow on L-Band emission, the correlation between TB and εG decreased with snow accumulation. When compared to satellite measurements, the average TB of the seven plots were well correlated with the Soil Moisture Ocean Salinity (SMOS TB with a root mean square difference of 8.1 K and consistent representation of the strong F/T signal (i.e., TB increases and decreases when soil freezing and thawing, respectively. This study allows better quantitative understanding of the spatial variability in L-Band emissions related to landscape F/T, and will help the calibration and validation of satellite-based F/T retrieval algorithms.

  5. Modeling different freeze/thaw processes in heterogeneous landscapes of the Arctic polygonal tundra using an ecosystem model

    Directory of Open Access Journals (Sweden)

    S. Yi

    2013-09-01

    Full Text Available Freeze/thaw (F/T processes can be quite different under the various land surface types found in the heterogeneous polygonal tundra of the Arctic. Proper simulation of these different processes is essential for accurate prediction of the release of greenhouse gases under a warming climate scenario. In this study we have modified the dynamic organic soil version of the Terrestrial Ecosystem Model (DOS-TEM to simulate F/T processes beneath the polygon rims, polygon centers (with and without water, and lakes that are common features in Arctic lowland regions. We first verified the F/T algorithm in the DOS-TEM against analytical solutions, and then compared the results with in situ measurements from Samoylov Island, Siberia. In the final stage, we examined the different responses of the F/T processes for different water levels at the various land surface types. The simulations revealed that (1 the DOS-TEM was very efficient and its results compared very well with analytical solutions for idealized cases, (2 the simulations compared reasonably well with in situ measurements although there were a number of model limitations and uncertainties, (3 the DOS-TEM was able to successfully simulate the differences in F/T dynamics under different land surface types, and (4 permafrost beneath water bodies was found to respond highly sensitive to changes in water depths between 1 and 2 m. Our results indicate that water is very important in the thermal processes simulated by the DOS-TEM; the heterogeneous nature of the landscape and different water depths therefore need to be taken into account when simulating methane emission responses to a warming climate.

  6. Damage development, phase changes, transport properties, and freeze-thaw performance of cementitious materials exposed to chloride based salts

    Science.gov (United States)

    Farnam, Yaghoob

    Recently, there has been a dramatic increase in premature deterioration in concrete pavements and flat works that are exposed to chloride based salts. Chloride based salts can cause damage and deterioration in concrete due to the combination of factors which include: increased saturation, ice formation, salt crystallization, osmotic pressure, corrosion in steel reinforcement, and/or deleterious chemical reactions. This thesis discusses how chloride based salts interact with cementitious materials to (1) develop damage in concrete, (2) create new chemical phases in concrete, (3) alter transport properties of concrete, and (4) change the concrete freeze-thaw performance. A longitudinal guarded comparative calorimeter (LGCC) was developed to simultaneously measure heat flow, damage development, and phase changes in mortar samples exposed to sodium chloride (NaCl), calcium chloride (CaCl 2), and magnesium chloride (MgCl2) under thermal cycling. Acoustic emission and electrical resistivity measurements were used in conjunction with the LGCC to assess damage development and electrical response of mortar samples during cooling and heating. A low-temperature differential scanning calorimetry (LT-DSC) was used to evaluate the chemical interaction that occurs between the constituents of cementitious materials (i.e., pore solution, calcium hydroxide, and hydrated cement paste) and salts. Salts were observed to alter the classical phase diagram for a salt-water system which has been conventionally used to interpret the freeze-thaw behavior in concrete. An additional chemical phase change was observed for a concrete-salt-water system resulting in severe damage in cementitious materials. In a cementitious system exposed to NaCl, the chemical phase change occurs at a temperature range between -6 °C and 8 °C due to the presence of calcium sulfoaluminate phases in concrete. As a result, concrete exposed to NaCl can experience additional freeze-thaw cycles due to the chemical

  7. Mechanism of freeze-thaw treatment influencing quality of puffing product for sweet potato using low-field nuclear magnetic resonance%利用LF-NMR探讨冻融处理影响甘薯膨化产品品质的机理

    Institute of Scientific and Technical Information of China (English)

    郭婷; 何新益; 邓放明; 陈益能

    2013-01-01

    investigation of the whole process of samples proton transition after an attack by radio-frequency pulse to interpret the variation of water in samples from the microscopic point. The LF-NMR technology has been successfully applied to study the water content and distribution of the process of repeated freeze-thaw of meat, carrot drying process, banana ripening process, and potato heating and refrigeration process. Freeze-thaw treatment has two processes, including freezing and thawing. Freeze-thaw treatment can change the water content and its distribution, physical properties, and solute distribution of raw materials of fruit and vegetables, thus affecting drying characteristics, physicochemical characteristics, and sensory quality of dry fruits and vegetables. Freeze-thaw can be used to improve quality of fruit & vegetable products dried by explosion puffing drying at variable temperature and pressure difference. Freeze-thaw process will help to improve the crispness and lower the hardness of explosion puffing drying carrot and sweet potato. In order to investigate the effect and mechanism of freeze-thaw on the quality of sweet potato by explosion puffing drying at variable temperature and pressure difference, the water distribution and water status of each group in the sweet potato after freeze-thaw were studied using low-field nuclear magnetic resonance (LF-NMR). The effects of the times of freeze-thaw on the hardness, color, and porosity of the sweet potato by explosion puffing were compared. The results showed that there were four distinct water populations in the data of multi-exponential fitting of sweet potato LF-NMR T2 transverse relaxation time, which were T21(0.25-0.55 ms), T22(1-2.5 ms), T23(5-12 ms) and T24 (40-200 ms), respectively. With the increasing of freeze-thaw cycles, the free water content (mT24) and the closely combined water content (mT21) increased first and then decreased, the porosity and rehydration of the dried product gradually increased, and

  8. Influence of morphology and polymorphic transformation of fat crystals on the freeze-thaw stability of mayonnaise-type oil-in-water emulsions.

    Science.gov (United States)

    Ishibashi, C; Hondoh, H; Ueno, S

    2016-11-01

    This study examined the destabilization of an oil-in-water (O/W) emulsion by freeze-thawing with a focus on the influence of the morphology and polymorph of fat crystals. For a model of food emulsion, this study used a mayonnaise-type O/W emulsion containing 70wt% canola oil (canola emulsion) or soybean oil (soybean emulsion) stored at -15, -20, and -30°C. The freeze-thaw stabilities of the emulsions were evaluated by measuring the upper oil layer after freeze-thawing. The soybean emulsion kept at -20°C had the highest stability; the other emulsions were destabilized during 6h of storage. Crystallization in the emulsions was determined using differential scanning calorimetry (DSC), time variation of temperature, X-ray diffraction measurement, and polarized light microscopy. DSC thermograms indicated that crystallization in emulsions occurred first in the high-melting fraction of oil, followed by water and, last, in the low-melting fraction of oil during cooling to -40°C. In the canola emulsion, the amount of fat crystals derived from the low-melting fraction of oil increased during storage at all temperatures, resulting in partial coalescence. The soybean emulsion was expected to be destabilized by polymorphic transformation (sub-α to β' and β) of fat crystals derived from the high-melting fraction during storage at -15 and -20°C. However, the soybean emulsion did not exhibit polymorphic transformation stored at -30°C, and the amount of fat crystals did not increase during freezing; thus, it was destabilized via a different mechanism. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. The synthesis of novel pH-sensitive poly(vinyl alcohol) composite hydrogels using a freeze/thaw process for biomedical applications.

    Science.gov (United States)

    Mc Gann, Michael J; Higginbotham, Clement L; Geever, Luke M; Nugent, Michael J D

    2009-05-08

    Physically cross-linked hydrogels composed of 75% poly(vinyl alcohol) PVA and 25% poly(acrylic acid) were prepared by a freeze/thaw treatment of aqueous solutions. Between 0.5 and 1wt% of aspirin was incorporated into the systems. The purpose of the research was the development of a novel pH-sensitive hydrogel composite for the delivery of aspirin to wounds. Extensive research has being conducted on freeze/thaw poly(vinyl alcohol) hydrogels for use in active pharmaceutical ingredient (API) delivery. However very little research has been reported on the effects of an API on the overall properties of a freeze/thaw hydrogel. From the rheological analysis undertaken it was apparent that aspirin has a limiting effect on the formation of hydrogen bonding leading to hydrogels with reduced mechanical strength. To counteract this, a novel hydrogel system was developed encompassing a reinforcing film in the centre of the hydrogels. Freezing profiles were obtained to gain a better knowledge of the freezing behaviour of the hydrogels during the formation stage. Thermograms obtained from modulated differential scanning calorimetry (MDSC) indicated that the aspirin lowered the glass transition temperatures (T(g)) of the constituent polymers. The pH-sensitive nature of the hydrogels was apparent from solvent uptake studies carried out. Increasing alkaline media led to a greater degree of swelling due to increased ionisation of PAA. The hydrogels exhibited non-Fickian release kinetics. The release rates were relatively slow with total release achieved at between 30 and 40 h. The quantity of drug incorporated was found to influence the release rates considerably.

  10. Greenhouse gas emissions from penguin guanos and ornithogenic soils in coastal Antarctica: Effects of freezing-thawing cycles

    Science.gov (United States)

    Zhu, Renbin; Liu, Yashu; Ma, Erdeng; Sun, Jianjun; Xu, Hua; Sun, Liguang

    In coastal Antarctica, freezing and thawing influence many physical, chemical and biological processes for ice-free tundra ecosystems, including the production of greenhouse gases (GHGs). In this study, penguin guanos and ornithogenic soil cores were collected from four penguin colonies and one seal colony in coastal Antarctica, and experimentally subjected to three freezing-thawing cycles (FTCs) under ambient air and under N 2. We investigated the effects of FTCs on the emissions of three GHGs including nitrous oxide (N 2O), carbon dioxide (CO 2) and methane (CH 4). The GHG emission rates were extremely low in frozen penguin guanos or ornithogenic soils. However, there was a fast increase in the emission rates of three GHGs following thawing. During FTCs, cumulative N 2O emissions from ornithogenic soils were greatly higher than those from penguin guanos under ambient air or under N 2. The highest N 2O cumulative emission of 138.24 μg N 2O-N kg -1 was observed from seal colony soils. Cumulative CO 2 and CH 4 emissions from penguin guanos were one to three orders of magnitude higher than those from ornithogenic soils. The highest cumulative CO 2 (433.0 mgCO 2-C kg -1) and CH 4 (2.9 mgCH 4-C kg -1) emissions occurred in emperor penguin guanos. Penguin guano was a stronger emitter for CH 4 and CO 2 while ornithogenic soil was a stronger emitter for N 2O during FTCs. CO 2 and CH 4 fluxes had a correlation with total organic carbon (TOC) and soil/guano moisture (M c) in penguin guanos and ornithogenic soils. The specific CO 2-C production rate (CO 2-C/TOC) indicated that the bioavailability of TOC was markedly larger in penguin guanos than in ornithogenic soils during FTCs. This study showed that FTC-released organic C and N from sea animal excreta may play a significant role in FTC-related GHG emissions, which may account for a large proportion of annual fluxes from tundra ecosystems in coastal Antarctica.

  11. The effect of firing temperature on the irreversible expansion, water absorption and pore structure of a brick body during freeze-thaw cycles

    Directory of Open Access Journals (Sweden)

    Mikuláš ŠVEDA

    2013-12-01

    Full Text Available The paper deals with the monitoring of brick body in the process of volumetric freezing and thawing. The samples were fired at temperatures of 900, 1000 and 1060 °C. Attention is focused on monitoring of the irreversible expansion, water absorption and pore structure of a brick body. We found that in all cases the endpoints take place continuously, where the amount firing temperature plays a crucial role. The greatest influence of freeze/thaw cycles on the change of the pore structure was also observed at the lowest temperature. The change of the pore system during the freeze-thaw cycles occurs in such a way, that the pore volume of small pores further decreases and conversely, the pore volume of large pores increases. The knowledge gained can be used not only in the production of new but also in predicting the remaining durability of older clay roofing tiles. DOI: http://dx.doi.org/10.5755/j01.ms.19.4.2741

  12. The effect of firing temperature on the irreversible expansion, water absorption and pore structure of a brick body during freeze-thaw cycles

    Directory of Open Access Journals (Sweden)

    Mikuláš ŠVEDA

    2013-12-01

    Full Text Available The paper deals with the monitoring of brick body in the process of volumetric freezing and thawing. The samples were fired at temperatures of 900, 1000 and 1060 °C. Attention is focused on monitoring of the irreversible expansion, water absorption and pore structure of a brick body. We found that in all cases the endpoints take place continuously, where the amount firing temperature plays a crucial role. The greatest influence of freeze/thaw cycles on the change of the pore structure was also observed at the lowest temperature. The change of the pore system during the freeze-thaw cycles occurs in such a way, that the pore volume of small pores further decreases and conversely, the pore volume of large pores increases. The knowledge gained can be used not only in the production of new but also in predicting the remaining durability of older clay roofing tiles. DOI: http://dx.doi.org/10.5755/j01.ms.19.4.2741

  13. Temporal Monitoring of the Soil Freeze-Thaw Cycles over a Snow-Covered Surface by Using Air-Launched Ground-Penetrating Radar

    KAUST Repository

    Jadoon, Khan

    2015-09-18

    We tested an off-ground ground-penetrating radar (GPR) system at a fixed location over a bare agricultural field to monitor the soil freeze-thaw cycles over a snow-covered surface. The GPR system consisted of a monostatic horn antenna combined with a vector network analyzer, providing an ultra-wideband stepped-frequency continuous-wave radar. An antenna calibration experiment was performed to filter antenna and back scattered effects from the raw GPR data. Near the GPR setup, sensors were installed in the soil to monitor the dynamics of soil temperature and dielectric permittivity at different depths. The soil permittivity was retrieved via inversion of time domain GPR data focused on the surface reflection. Significant effects of soil dynamics were observed in the time-lapse GPR, temperature and dielectric permittivity measurements. In particular, five freeze and thaw events were clearly detectable, indicating that the GPR signals respond to the contrast between the dielectric permittivity of frozen and thawed soil. The GPR-derived permittivity was in good agreement with sensor observations. Overall, the off-ground nature of the GPR system permits non-invasive time-lapse observation of the soil freeze-thaw dynamics without disturbing the structure of the snow cover. The proposed method shows promise for the real-time mapping and monitoring of the shallow frozen layer at the field scale.

  14. Effects of PVA, agar contents, and irradiation doses on properties of PVA/ws-chitosan/glycerol hydrogels made by γ-irradiation followed by freeze-thawing

    Science.gov (United States)

    Yang, Xiaomin; Zhu, Zhiyong; Liu, Qi; Chen, Xiliang; Ma, Mingwang

    2008-08-01

    Poly(vinyl alcohol) (PVA)/water soluble chitosan (ws-chitosan)/glycerol hydrogels were prepared by γ-irradiation and γ-irradiation followed by freeze-thawing, respectively. The effects of irradiation dose and the contents of PVA and agar on the swelling, rheological, and thermal properties of these hydrogels were investigated. The swelling capacity decreases while the mechanical strength increases with increasing PVA or agar content. Increasing the irradiation dose leads to an increase in chemical crosslinking density but a decrease in physical crosslinking density. Hydrogels made by irradiation followed by freeze-thawing own smaller swelling capacity but larger mechanical strength than those made by pure irradiation. The storage modulus of the former hydrogels decreases above 50 °C and above 70 °C it comes to the same value as that prepared by irradiation. The ordered association of PVA is influenced by both chemical and physical crosslinkings and by the presence of ws-chitosan and glycerol. These hydrogels are high sensitive to pH and ionic strength, indicating that they may be useful in stimuli-responsive drug release system.

  15. Temporal Monitoring of the Soil Freeze-Thaw Cycles over a Snow-Covered Surface by Using Air-Launched Ground-Penetrating Radar

    Directory of Open Access Journals (Sweden)

    Khan Zaib Jadoon

    2015-09-01

    Full Text Available We tested an off-ground ground-penetrating radar (GPR system at a fixed location over a bare agricultural field to monitor the soil freeze-thaw cycles over a snow-covered surface. The GPR system consisted of a monostatic horn antenna combined with a vector network analyzer, providing an ultra-wideband stepped-frequency continuous-wave radar. An antenna calibration experiment was performed to filter antenna and back scattered effects from the raw GPR data. Near the GPR setup, sensors were installed in the soil to monitor the dynamics of soil temperature and dielectric permittivity at different depths. The soil permittivity was retrieved via inversion of time domain GPR data focused on the surface reflection. Significant effects of soil dynamics were observed in the time-lapse GPR, temperature and dielectric permittivity measurements. In particular, five freeze and thaw events were clearly detectable, indicating that the GPR signals respond to the contrast between the dielectric permittivity of frozen and thawed soil. The GPR-derived permittivity was in good agreement with sensor observations. Overall, the off-ground nature of the GPR system permits non-invasive time-lapse observation of the soil freeze-thaw dynamics without disturbing the structure of the snow cover. The proposed method shows promise for the real-time mapping and monitoring of the shallow frozen layer at the field scale.

  16. Rapid N2O fluxes at high level of nitrate nitrogen addition during freeze-thaw events in boreal peatlands of Northeast China

    Science.gov (United States)

    Cui, Qian; Song, Changchun; Wang, Xianwei; Shi, Fuxi; Wang, Lili; Guo, Yuedong

    2016-06-01

    Freeze-thaw (FT) events and increasing nitrogen (N) availability may alter N turnover and nitrous oxide (N2O) emissions in permafrost peatlands. However, the responses of N2O emissions to different N levels and additions during FT events are far from clear. We conducted an incubation study to investigate the impacts of different N addition levels (LN: 0.07 mg N g-1, HN: 0.14 mg N g-1) and N addition forms (AC: ammonium chloride, NS: sodium nitrate) on the emissions of N2O under FT and non-freeze-thaw (NFT) conditions in boreal peatlands of Northeast China. Results indicated that the FT condition significantly increased N2O emissions compared with the NFT condition and peaks occurred during thawing. Compared with AC treatments, NS treatments significantly elevated the accumulation of N2O emissions under the FT condition, exhibiting significant differences in different NS levels. N2O emissions were also positively dependent on soil NO3- concentrations to supply nitrate for denitrification. Nitrate-N addition was mainly responsible for the burst of N2O with denitrification as the main process during FT events. Therefore, these results suggest that N2O emissions potentially increase during FT events with increasing nitrate-N deposition in permafrost peatlands, which would contribute to global climate warming.

  17. A convection-conduction model for analysis of the freeze-thaw conditions in the surrounding rock wall of a tunnel in permafrost regions

    Institute of Scientific and Technical Information of China (English)

    何春雄; 吴紫汪; 朱林楠

    1999-01-01

    Based on the analyses of fundamental meteorological and hydrogeological conditions at the site of a tunnel in the cold regions, a combined convection-conduction model for air flow in the tunnel and temperature field in the surrounding has been constructed. Using the model, the air temperature distribution in the Xiluoqi No. 2 Tunnel has been simulated numerically. The simulated results are in agreement with the data observed. Then, based on the in situ conditions of air temperature, atmospheric pressure, wind force, hydrogeology and engineering geology, the air-temperature relationship between the temperature on the surface of the tunnel wall and the air temperature at the entry and exit of the tunnel has been obtained, and the freeze-thaw conditions at the Dabanshan Tunnel which is now under construction is predicted.

  18. 冻融法转化苜蓿中华根瘤菌%Freeze thaw transform plasmid into Sinorhizobium meliloti 1021

    Institute of Scientific and Technical Information of China (English)

    薛海英; 汪滢; 尹若春

    2012-01-01

    The transformation for Sinorhizobium meliloti 1021 was limited to triparental-conjugational and electric-shock methods. Plasmid containing GUS and spectinomycin-resistance gene was used in our experiment. After transformation, resistant clones on the plate were identified by PCR with GUS primers. This report firstly described a freeze-thaw mediated transformation of 5. meliloti 1021. The result showed that the transformation efficiency was 2. 2 10 / g. Compared with the traditional methods, the freeze-thaw mediated transformation is a simple, faster, shorter time and lower cost method to transform Sinorhizobium meliloti.%对于苜蓿中华根瘤菌转化方法的研究仅限于三亲杂交法和电激转化,本实验首次将冻融法用于转化苜蓿中华根瘤菌.将携带GUS片段并且含有壮观霉素抗性的质粒用冻融法转移至野生型苜蓿中华根瘤菌菌株,得到的抗性克隆用GUS引物进行PCR扩增鉴定.经过计算,冻融法的转化率为2.2×105/μg.与传统方法比较,冻融法操作简单,转化过程快速,转化率较高,所需时间较短,转化成本低,是适合用于苜蓿中华根瘤菌的转化方法.

  19. Biogenic C5 VOCs: release from leaves after freeze-thaw wounding and occurrence in air at a high mountain observatory

    Science.gov (United States)

    Fall, Ray; Karl, Thomas; Jordan, Alfons; Lindinger, Werner

    During investigations of the formation of volatile organic compounds (VOCs) in leaves, we observed C5 VOCs during leaf drying, senescence, and following freeze-thaw damage. VOCs were quantified by proton-transfer-reaction mass spectrometry (PTR-MS). In freeze-damaged leaves, VOC products were verified with a gas chromatography PTR-MS system, showing that a variety of plants produced 1-penten-3-ol and 1-penten-3-one with smaller amounts of 2(Z)-penten-1-ol and pentenals; similar VOCs have been detected in soybean seed homogenates (Gardner et al., J. Agric. Food Chem. 44 (1996) 882). Most plants wounded in this way also released hexenals and hexanal, and clover also released methylbutanals. The formation of the C5 products was oxygen-dependent, consistent with the involvement of the enzyme lipoxygenase, and pentenone appeared to form independent of an alcohol dehydrogenase reaction; the latter is apparently disrupted by the freeze-thaw treatment. In parallel with these laboratory experiments, on-line PTR-MS measurements of ambient air were conducted at the Sonnblick Observatory in the Austrian Alps (3106 m a.s.l.). Following a hard freeze in central Austria, substantial amounts of C5 VOCs, ranging from 300 pptv to 6 ppbv and including 1-penten-3-ol, methylbutanals and probably pentenone, were detected at this site for several days peaking after midnight. Factor analysis supported their biogenic origin. We speculate that these VOCs were derived from freeze-damaged local vegetation by processes similar to those seen in laboratory freezing studies. If confirmed, these results suggest that leaf-freezing events in forests will give rise to the release of substantial levels of reactive C5 and C6 VOCs that can contribute to regional tropospheric chemistry.

  20. Relationship of aquaporins 3 (AQP3), 7 (AQP7), and 11 (AQP11) with boar sperm resilience to withstand freeze-thawing procedures.

    Science.gov (United States)

    Prieto-Martínez, N; Vilagran, I; Morató, R; Rivera Del Álamo, M M; Rodríguez-Gil, J E; Bonet, S; Yeste, M

    2017-09-21

    Cryopreservation is the most suitable method to preserve boar spermatozoa over long-term storage. However, freeze-thawing protocols inflict extensive damage to sperm cells, reducing their viability and compromising their fertilizing ability. In addition, high individual variability is known to exist between boar ejaculates, which may be classified as of good (GFE) or poor (PFE) freezability. While conventional spermiogram parameters fail to predict sperm cryotolerance in fresh spermatozoa, high levels of certain proteins, also known as freezability markers, have been found to be related to the sperm resilience to withstand freeze-thawing procedures. In this context, the hypothesis of this study was that aquaporins AQP3, AQP7, and AQP11 could be linked to boar sperm cryotolerance. Twenty-nine ejaculates were evaluated and subsequently classified as GFE or PFE based upon their sperm viability and motility at post-thawing. Fourteen ejaculates resulted to be GFE, whereas the other fifteen were found to be PFE. Relative abundances of AQP3, AQP7, and AQP11 and their localization patterns were evaluated in all fresh and frozen-thawed ejaculates through immunoblotting and immunocytochemistry. Prior to cryopreservation, relative amounts of AQP3 and AQP7 were found to be significantly (p PFE. In contrast, no significant differences (p > 0.05) between freezability groups were found for AQP11, despite GFE tending to present higher levels of this protein. The localization of AQP7, but not that of AQP3 or AQP11, was observed to be affected by cryopreservation procedures. In conclusion, these results suggest that AQP3 and AQP7 are related to boar sperm cryotolerance and may be used as freezability markers. © 2017 American Society of Andrology and European Academy of Andrology.

  1. Freeze/thaw conditions at periglacial landforms in Kapp Linné, Svalbard, investigated using field observations, in situ, and radar satellite monitoring

    Science.gov (United States)

    Eckerstorfer, M.; Malnes, E.; Christiansen, H. H.

    2017-09-01

    In periglacial landscapes, snow dynamics and microtopography have profound implications of freeze-thaw conditions and thermal regime of the ground. We mapped periglacial landforms at Kapp Linné, central Svalbard, where we chose six widespread landforms (solifluction sheet, nivation hollow, palsa and peat in beach ridge depressions, raised marine beach ridge, and exposed bedrock ridge) as study sites. At these six landforms, we studied ground thermal conditions, freeze-thaw cycles, and snow dynamics using a combination of in situ monitoring and C-band radar satellite data in the period 2005-2012. Based on these physical parameters, the six studied landforms can be classified into raised, dry landforms with minor ground ice content and a thin, discontinuous snow cover and into wet landforms with high ice content located in the topographical depressions in-between with medium to thick snow cover. This results in a differential snow-melting period inferred from the C-band radar satellite data, causing the interseasonal and interlandform variability in the onset of ground surface thawing once the ground becomes snow free. Therefore, variability also exists in the period of thawed ground surface conditions. However, the length of the season with thawed ground surface conditions does not determine the mean annual ground surface temperature, it only correlates well with the active layer depths. From the C-band radar satellite data series, measured relative backscatter trends hint toward a decrease in snow cover through time and a more frequent presence of ice layers from mid-winter rain on snow events at Kapp Linné, Svalbard.

  2. Ultrasonic emissions from conifer xylem exposed to repeated freezing.

    Science.gov (United States)

    Mayr, Stefan; Zublasing, Verena

    2010-01-01

    Ultrasonic emission measurements enable the analysis of xylem cavitation induced by drought and freeze-thaw events. Several studies have indicated that ultrasonic acoustic emissions (UAE) in conifers occur upon freezing and not upon thawing, although classical theory has postulated gas bubble formation during freezing and cavitation during thawing. We analyzed the pattern and quality of freeze-thaw-induced UAE in seven conifers (Abies alba, Larix decidua, Juniperus communis, Picea abies, Pinus cembra, Pinus mugo, Pinus sylvestris). Axes samples dehydrated to different water potentials were exposed to repeated frost cycles. The number, amplitude and energy of UAE signals were registered and related to water potential, temperature course and wood characteristics (wood density, tracheid diameter). For P. abies, ultrasonic emission analysis was also performed on bark samples, xylem samples without bark, as well as on stems of young potted trees. In all conifers, UAE were registered in water-stressed samples but not in saturated or dehydrated samples. No signals were emitted by the bark of P. abies. Ultrasonic activity occurred only upon freezing, and identical patterns were observed in axes samples and stems of potted P. abies trees. A weak positive relationship between tracheid diameter and UAE energy was observed, indicating wide tracheids to emit signals with higher energy. The classical bubble formation hypothesis cannot sufficiently explain the occurrence of UAE during freezing and upon repeated temperature cycles, as demonstrated in this study. We suggest that the low water potential of ice induces air-seeding near the ice-water interface, and consequently, causes UAE.

  3. Effect of Airfield Pavement Deicer on Freeze-thaw Durability of High Performance Concrete%机场道面除冰液对高性能 混凝土抗冻性的影响

    Institute of Scientific and Technical Information of China (English)

    麻海燕; 余红发; 白康; 曹文涛; 周鹏; 韩丽娟

    2011-01-01

    Influence of calcium magnesium acetate (CMA) , which is the main composition of the most frequently used as airfield pavement dicer, on the freezing-thaw durability of high performance concrete (HPC ) were investigated. Freeze-thaw durability of HPC was tested by accelerated freezing-thawing test. Five kinds of solutions, namely tap water, 3.5%NaCl solution, 3.5%-25% calcium magnesium acetate (CMA), 25% glycol solution and commercial aircraft deicer were employed to be the freeze-thaw mediums. Results show that freeze-thaw durability of HPC exposed to CMA solutions is related to the solution concentrations. CMA solution with a concentration of 3. 5% is beneficial to durability of HPC. Freeze-thaw failure of concrete exposed to 3. 5% CMA solution is 1. 09 of that of HPC exposed to tap water; both are resulted from propagation of inner cracks. While freeze-thaw failure of HPC exposed toNaCl solution is different and characterized by surface deterioration. 25% CM A solution shows no damage to HPC'freeze-thaw durability, while both 25% glycol solution and commercial aircraft deicer demonstrate obviously damage to HPC'freeze-thaw durability. The results showed that CMA can effectively improve the freeze-thaw durability of HPC.%采用快冻法测定了高性能混凝土(High Performance Concrete,HPC)在水、浓度为3.5%的NaCl除冰盐、3.5%~25%的醋酸钙镁(Calcium magnesium acetate,CMA,机场道面除冰液)、25%的乙二醇(飞机除冰液)和商品飞机除冰液中的抗冻性.结果表明,在3.5% CMA溶液中,HPC抗冻性比水中冻融提高了1.09倍,其冻融破坏特征与水中冻融一样,均属于内部微裂纹扩展,完全不同于HPC在3.5% NaCl溶液中的盐冻表面剥蚀.在浓度为25%的条件下,CMA机场道面除冰液对HPC无冻融破坏作用,而乙二醇飞机除冰液、尤其是商品飞机除冰液对HPC有明显的冻融破坏作用.因此,CMA机场道面除冰液能够有效地延缓HPC的冻融破坏.

  4. Influence of Thermalstable Ice-Structuring Proteins Extracted from Oat Flour and Chinese Privet Leaves on Freeze-Thaw Stability of Wheat Starch Gels%热稳定冰结构蛋白对小麦淀粉凝胶冻融稳定性的影响

    Institute of Scientific and Technical Information of China (English)

    贾春利; 黄卫宁; 邹奇波; 甘小红; Patricia RAYAS-DUARTE

    2012-01-01

    The effect of thermostable ice-structuring proteins extracted from oat flour and Chinese Privet (Ligustrum vulgare) leaves separately added at 0.5% on the freeze-thaw stability of wheat starch gels was investigated. The syneresis, freezable water content, microstructure and texture of starch gels after going through different freeze-thaw cycles were analyzed using centrifugation, differential scanning calorimetry, scanning electron microscopy and texture analyzer, respectively. The results showed that as freeze-thaw process happened repeatedly, the syneresis and freezable water content of starch gels increased obviously, the microstructure was damaged seriously, ice cell cavities became larger and uneven, the hardness increased markedly, and the springness decreased significantly. The introduction of TSISP extracted from oat flour and Chinese Privet (Ligustrum vulgare) leaves into wheat starch gels improved the freeze-thaw stability, which was indicated by a significant decrease in syneresis, freezable water content, the size of ice cell cavities and springiness and an increase in hardness.%研究燕麦粉和女贞叶中热稳定冰结构蛋白(TSISP)对淀粉凝胶冻融稳定性的影响。应用差示扫描量热仪(DSC)、扫描电子显微镜(SEM)和质构仪分别研究燕麦粉、女贞叶TSISP对淀粉凝胶冻融后析水率、可冻结水含量、超微结构、硬度及弹性的影响。结果表明:冻融过程显著地增加淀粉凝胶析水率、可冻结水含量,严重地破坏淀粉凝胶超微结构、增力孔洞尺寸、减小孔洞均匀性,最后导致淀粉凝胶硬度明显增大,弹性明显减小;而燕麦粉和女贞叶中TSISP的添加显著地减小淀粉凝胶冻融后析水率和可冻结水含量,同时显著地改善淀粉凝胶超微结构,使得淀粉凝胶孔洞增大幅度明显得到抑制,孔洞均匀性更好,结果也对淀粉凝胶质构产生明显的改善效果,延缓硬度的增

  5. 冻融对早胜牛肉品质及微细结构的影响%Effects of Freezing-thawing on Muscle Quality and Microstructure of Zaosheng Cattle Meat

    Institute of Scientific and Technical Information of China (English)

    阿依木古丽; 蔡勇; 陈士恩; 申晓荣

    2011-01-01

    In order to study the effects of repetitive freezing-thawing on beef quality, 2. 0-2. 5 years old bullock Zaosheng cattle were selected, longissimus dorsi (LD) were collected and cut into 6 samples randomly, weighted and vacuum packed and repetitively freezing-thawing different times, then thawing loss (TL) , cooking loss (CL) , water loss(WL) , shear force(SF) , pH and microstructure were studied. The results showed that compared with fresh beef, repetitive freezing-thawing significantly increased the TL and CL; WL were increased significantly after freezing-thawing once; SF were significantly increased when freezing-thawing twice and then decreased; Freezing-thawing increased the spaee between muscle fiber, confused fiber bundles, and shortened sarcomere, vacuolated structure formation in the mitochondria, blurred even disappeared Z disc. The results demonstrated that repetitive freezingthawing seriously damaged the structure of beef and declined the muscle quality of Zaosheng cattle.%为探讨反复冻融对早胜牛肉品质的影响,选取2.0~2.5岁阉割牛背最长肌,随机分成6组,称重,真空包装,进行不同次数的反复冷冻-解冻试验,分别榆测原料肉解冻损失、煮制损失、失水率、熟肉剪切力及pH,并观察原料肉显微超微结构的变化.结果显示,随着反复冻融次数的增加,原料肉解冻损失和煮制损失极显著增加,失水率只在第1次冻融后显著增加,剪切力先显著增加后再降低,pH随着冻融次数增加而显著降低,肌纤维结构混乱,肌束及肌原纤维间隙增加,肌节略微缩短,线粒体肿胀、空泡样变,Z线错位排列,甚至溶解、消失.结果表明,反复冻融严重破坏了早胜牛肉的组织结构,显著降低了肉品质.

  6. Dryland soil hydrological processes and their impacts on the nitrogen balance in a soil-maize system of a freeze-thawing agricultural area.

    Directory of Open Access Journals (Sweden)

    Wei Ouyang

    Full Text Available Understanding the fates of soil hydrological processes and nitrogen (N is essential for optimizing the water and N in a dryland crop system with the goal of obtaining a maximum yield. Few investigations have addressed the dynamics of dryland N and its association with the soil hydrological process in a freeze-thawing agricultural area. With the daily monitoring of soil water content and acquisition rates at 15, 30, 60 and 90 cm depths, the soil hydrological process with the influence of rainfall was identified. The temporal-vertical soil water storage analysis indicated the local albic soil texture provided a stable soil water condition for maize growth with the rainfall as the only water source. Soil storage water averages at 0-20, 20-40 and 40-60 cm were observed to be 490.2, 593.8, and 358 m3 ha-1, respectively, during the growing season. The evapo-transpiration (ET, rainfall, and water loss analysis demonstrated that these factors increased in same temporal pattern and provided necessary water conditions for maize growth in a short period. The dry weight and N concentration of maize organs (root, leaf, stem, tassel, and grain demonstrated the N accumulation increased to a peak in the maturity period and that grain had the most N. The maximum N accumulative rate reached about 500 mg m-2d-1 in leaves and grain. Over the entire growing season, the soil nitrate N decreased by amounts ranging from 48.9 kg N ha-1 to 65.3 kg N ha-1 over the 90 cm profile and the loss of ammonia-N ranged from 9.79 to 12.69 kg N ha-1. With soil water loss and N balance calculation, the N usage efficiency (NUE over the 0-90 cm soil profile was 43%. The soil hydrological process due to special soil texture and the temporal features of rainfall determined the maize growth in the freeze-thawing agricultural area.

  7. Influence of time, storage temperature and freeze/thaw cycles on the activity of digestive enzymes from gilthead sea bream (Sparus aurata).

    Science.gov (United States)

    Solovyev, Mikhail; Gisbert, Enric

    2016-10-01

    In this study, we tested the effects of long-term storage (2 years) at -20 °C and short-term storage (several hours) in ice and freeze/thaw cycles on the activities of pancreatic, gastric and intestinal (brush border and cytosolic) digestive enzymes in a teleost fish species. The results revealed a significant lose in activity of pancreatic (trypsin, chymotrypsin, total alkaline proteases and α-amylase) and intestinal cytosolic (leucine-alanine peptidase) enzymes between 140 and 270 days of storage at -20 °C, whereas in contrast, the activity of all the assayed brush border enzymes remained constant during the first 2 years of storage at -20 °C. During short-term storage conditions, the most stable enzymes assayed were those of the enterocytes of the brush border, which did not show any change in activity after being held for 5 h in ice. Five freezing and thawing cycles did not affect the activity of the intestinal brush border enzymes and the cytosolic ones, whereas the activity of trypsin, α-amylase and bile-salt-activated lipase was significantly affected by the number of freezing and thawing cycles. No changes in pepsin activity were found in samples exposed to 1 and 2 freezing and thawing cycles.

  8. Effects of different concentrations of BHT on microscopic and oxidative parameters of Mahabadi goat semen following the freeze-thaw process.

    Science.gov (United States)

    Naijian, Hamid Reza; Kohram, Hamid; Shahneh, Ahmad Zare; Sharafi, Mohsen; Bucak, Mustafa Numan

    2013-04-01

    Oxidative damage to sperm is one of the main causes for decline in motility and fertility of frozen-thawed sperm. Thus, it is crucial to use cryoprotectant agents in extender in order to prevent lethal intracellular ice crystal formation. The present study aims to evaluate the effects of different concentrations of the antioxidant butylated hyroxytoluene (BHT) on sperm parameters post-thaw. Semen was diluted into five equal aliquots of extender containing different concentrations of BHT (0, 0.5, 1, 2 and 4mM), aspirated into 0.25 mL straws, and equilibrated at 5°C for 2h. After equilibration, straws were frozen in liquid nitrogen vapor and plunged into liquid nitrogen for storage. Sperm parameters, including motility and progressive motility, viability, membrane integrity, acrosome integrity and capacitation status, were assessed. Malondialdehiyde (MDA) and glutathione peroxidase (GSH-PX) activity were also evaluated after freezing-thawing. Results of this experiment show that addition of 1mM of BHT to the extender for freezing of goat semen can improve motility, progressive motility and viability (PBHT (P>0.05). Therefore, we conclude that the optimum concentration of BHT for cryopreservation of goat semen is 1mM. Copyright © 2013 Elsevier Inc. All rights reserved.

  9. Stabilization of heavy metals in municipal sewage sludge by freeze-thaw treatment with a blend of diatomite, FeSO4, and Ca(OH)2.

    Science.gov (United States)

    Wang, Jing; Fu, Rongbing; Xu, Zhen

    2017-08-01

    In this work, the effects of diatomite with 15% FeSO4•7H2O and 7.5% Ca(OH)2 on sludge stabilization were investigated using batch leaching tests. The influence of cell rupture caused by freezing and thawing on stabilization was also evaluated. The results indicated that the optimal diatomite percentage was 2%. Cell rupture by freezing and thawing reduced heavy metal leachability, followed by cell death and decrease of organic groups. The concentration of heavy metals in sludge leachate increased after cell rupture, indicating that the heavy metal leachability was reduced after freezing and thawings. Moreover, the stabilization effects were generally improved after freezing and thawing. As compared with the stabilization of the original sludge, the unstable fractions decreased and the residual fractions of the heavy metals increased in the stabilized sludge after cell rupture. This study developed a method to stabilize heavy metals in municipal sewage sludge. Diatomite combined with FeSO4·7H2O and Ca(OH)2 improved the treatment of sewage sludge contaminated by heavy metals. Cell lysis by freeze-thaw treatment reduced the risk of leaching heavy metals caused by cell death and decreased major organic groups in the sludge.

  10. Enhanced salt-removal percentage in capacitive deionization with addition of ion-exchange membrane using carbon electrode synthesized with freezing thawing method

    Science.gov (United States)

    Sari, Intan Permata; Endarko

    2016-04-01

    Ion-exchange membrane technology has shown a great potential to enhance the desalting efficiency. Ion-exchange membranes are placed in front of the electrodes so that the charged ions can be selectively passed through the membrane layer and captured by the oppositely charged electrode more quickly, so as to increase the efficiency of desalination. In this research, carbon electrodes have been synthesized from an activated carbon (700 - 1400 m2/g) and polyvinyl alcohol (PVA) as a binder using freezing thawing method. A solution with 180 µS/cm NaCl was pumped to the capacitive deionization (CDI) cell using a Boyu Submersible pump (model SP-601) at a flow rate of 25 mL/min and the voltage was set at 2 V. The result showed that the CDI cell with ion-exchange membrane (MCDI) has the salt removal efficiency greater than the CDI cell without ion-exchange membrane. The salt-removal percentage of MCDI was achieved at 66.36%, meanwhile the CDI cell without ion-exchange membrane resulted in 54.4%.

  11. Experimental Studies on the Effects of Cyclic Freezing-Thawing, Salt Crystallization, and Thermal Shock on the Physical and Mechanical Characteristics of Selected Sandstones

    Science.gov (United States)

    Ghobadi, M. H.; Babazadeh, R.

    2015-05-01

    Rocks are used in engineering works as monuments, building stones, and architectural covering stones. Their weathering behaviors and physical and mechanical properties are the most important factors controlling their suitability as building stones. The aim of this study is to evaluate the weathering behaviors of sandstones from the Qazvin area (western Iran). In total, nine sandstones (A, B, C, CG, S, S1, Min, Tr, and Sh) were analyzed. Accelerated weathering processes, namely freezing-thawing (F-T), salt crystallization (SC), heating-cooling (H-C), and heating-cooling-wetting (H-C-W), were used. Sandstones were subjected to 60 cycles of F-T, H-C, and H-C-W and 20 cycles of SC, and changes in characteristics including weight loss (%), P-wave velocity loss (%), and changes in uniaxial compressive strength (UCS) and point load strength were recorded after different numbers of cycles. The results from our laboratory studies indicate that rocks from the same stratigraphic layer can show major differences in weathering properties, and their sensitivity to these processes are different. Also, it was found that the thermal behavior of sandstones under wet and dry conditions were different. In the next stage of this study, a decay function model was used to statistically evaluate the disintegration rate. This model showed that the disintegration rate was higher for salt recrystallization compared with F-T, H-C, and H-C-W processes.

  12. 冻融循环作用下宽级配砾质土的渗透特性%HYDRAULIC CONDUCTIVITY OF COMPACTED WIDE GRADING GRAVEL SOILS UNDER FREEZE-THAW CYCLING

    Institute of Scientific and Technical Information of China (English)

    王红雨; 唐少容; 邢毓航; 张学科

    2015-01-01

    针对西北地区特殊的气候条件和砾质土料源丰富的实际情况,提出采用宽级配砾质土代替黏土作为土工合成材料膨润土垫(GCls)的保护层共同构成垃圾填埋场复合防渗系统的构想。文中选取宁夏银川地区冲-洪积作用形成的天然砾质土料,经人工掺和制配成满足规范对 GCls 防渗垫保护层渗透系数要求的宽级配砾质土样,在实验室对该土样进行了冻融循环作用下的渗透性能试验研究。结果显示,随着冻融次数的逐渐增加,土样的冻胀率逐渐变大,渗透系数也相应增大,经过12次冻融循环后,渗透系数约增大1~2个数量级;冻融循环初期,冻融作用对土样的影响最为剧烈,随着冻融循环次数的增加以及时间的延续,土样性状逐渐趋于稳定。由于宽级配砾质土对冻融循环作用的敏感性小于粉质黏性土,故采用宽级配砾质土作为 Cls/GM的保护层共同组成填埋场复合防渗系统是值得期待的。%The design conception of composite liners is consisted of a geomembrane(GM),geosynthetic clay liners (GCls) and compacted gravel soils in landfills.This conception is presented on the basis of the climate characteristics,gravel soils material rich in nature,and GCls that have been exported all over the world for various applications.The artificially graded gravel soils are taken from natural sediment zone for flood alluvial at Yinchuan suburb in Ningxia.The gravel soil is figured out to meet the requirement of permeability coefficient through the compaction and penetration experiment.The frost-heaving ratio and hydraulic conductivity of gravel soil samples are tested under freeze-thaw cycling in this paper.The test results indicate that the frost-heaving ratio increases as the number of freeze-thaw increases.As the number of freeze-thaw increases,the permeability coefficient also increases. The permeability coefficient is increased by one to

  13. Pathogen reduction in unpasteurized apple cider: adding cranberry juice to enhance the lethality of warm hold and freeze-thaw steps.

    Science.gov (United States)

    Ingham, Steven C; Schoeller, Erica L; Engel, Rebecca A

    2006-02-01

    U.S. Food and Drug Administration (FDA) regulations require processors of apple cider sold wholesale to use processing steps that ensure a 5-log reduction in numbers of the pertinent pathogen, generally considered to be Escherichia coli O157:H7. Current widely used validated pathogen-reduction steps are thermal pasteurization and UV light treatment. These techniques may be unaffordable or undesirable for some processors. This study investigated the cran-cider process, which is the addition of cranberry juice at a 15% (vol/vol) level, followed by warm hold (45 degrees C for 2 h) and freeze-thaw steps (-20 degrees C for 24 h, 5 degrees C for 24 h). When enumeration procedures did not include injury repair, the cran-cider process achieved a > or = 5-log reduction in numbers of E. coli O157:H7, Salmonella serovars, and Listeria monocytogenes. However, an injury-repair step was included in the pathogen enumeration procedure in confirmatory trials, and the resulting E. coli O157:H7 reductions of 3.5 to 4.2 log did not meet the FDA requirement. Consumer evaluation of apple cider subjected to the cran-cider process was favorable with a mean (n = 197) score of 5.8 on a seven-point hedonic scale (where 6 equals "like moderately") and 89% of panelists giving the product a positive score of 5, 6, or 7. The cran-cider process provides a novel way to improve microbial safety of unpasteurized apple cider, but it does not meet FDA-mandated pathogen reductions for wholesalers. However, cider makers selling apple cider only at retail could use the process to improve the safety of their product, provided containers were labeled with the FDA-mandated consumer warning.

  14. Repeated swim stress alters brain benzodiazepine receptors measured in vivo

    Energy Technology Data Exchange (ETDEWEB)

    Weizman, R.; Weizman, A.; Kook, K.A.; Vocci, F.; Deutsch, S.I.; Paul, S.M.

    1989-06-01

    The effects of repeated swim stress on brain benzodiazepine receptors were examined in the mouse using both an in vivo and in vitro binding method. Specific in vivo binding of (/sup 3/H)Ro15-1788 to benzodiazepine receptors was decreased in the hippocampus, cerebral cortex, hypothalamus, midbrain and striatum after repeated swim stress (7 consecutive days of daily swim stress) when compared to nonstressed mice. In vivo benzodiazepine receptor binding was unaltered after repeated swim stress in the cerebellum and pons medulla. The stress-induced reduction in in vivo benzodiazepine receptor binding did not appear to be due to altered cerebral blood flow or to an alteration in benzodiazepine metabolism or biodistribution because there was no difference in (14C)iodoantipyrine distribution or whole brain concentrations of clonazepam after repeated swim stress. Saturation binding experiments revealed a change in both apparent maximal binding capacity and affinity after repeated swim stress. Moreover, a reduction in clonazepam's anticonvulsant potency was also observed after repeated swim stress (an increase in the ED50 dose for protection against pentylenetetrazol-induced seizures), although there was no difference in pentylenetetrazol-induced seizure threshold between the two groups. In contrast to the results obtained in vivo, no change in benzodiazepine receptor binding kinetics was observed using the in vitro binding method. These data suggest that environmental stress can alter the binding parameters of the benzodiazepine receptor and that the in vivo and in vitro binding methods can yield substantially different results.

  15. 机场道面除冰液作用下大掺量粉煤灰混凝土的抗冻性%Freeze-thaw Durability of High Volume Fly Ash Content Concrete Exposed to Airfield Pavement Deicer

    Institute of Scientific and Technical Information of China (English)

    麻海燕; 吴雅玲; 余红发; 白康; 袁银峰

    2014-01-01

    The freeze-thaw durability of high volume fly ash content concrete (HFCC)specimens were tested by fast freezing-thawing experiments.In the experiments,HFCC specimens exposed to different solutions which were composed of airfield pavement deicer,NaCl solution,aircraft deicer (AD),commercial deicer and water.The airfield pavement deicer mainly contained calcium magnesium acetate (CMA)and was changed at mass fractions of 3.5%,12.5% and 25%.The mass fractions of NaCl solution,aircraft deicer and commercial deicer were 3 .5%,3 .5% and 25%,respectively.Through the experiments,the change rules of the mass loss rate per unit area and the relative dynamic elastic modulus of HFCC were obtained.The results show that freeze-thaw damage of HFCC exposed to 3 .5% NaCl solution is closely attributed to surface deterioration.When HFCC specimens exposed to 3 .5% AD or 3 .5% CMA solution,it will be damaged by internal freeze-thaw damage.Compared with water,freeze-thaw damage effect of HFCC is delayed by 3 .5% CMA solution.Freeze-thaw durability of concrete exposed to CMA solutions is closely related to the solution mass fractions,the higher the CMA mass fraction is,the smaller the freeze-thaw damage effects are.When the CMA mass fraction is greater than 12.5%, the mass loss rate and the relative dynamic elastic modulus losses are small after 600 times fast freeze-thaw cycle.HFCC has a poor freeze-thaw durability when exposed to 25% commercial deicer and has a good freeze-thaw durability when exposed to 25% airfield pavement deicer. Therefore,HFCC can be completely applied to the cement concrete airfield runway which is deiced by high mass fractions of CMA.%通过大掺量粉煤灰混凝土(HFCC)试件在质量分数为3.5%,12.5%,25%机场道面除冰液(CMA溶液)、质量分数为3.5%的NaCl溶液、质量分数为3.5%的飞机除冰液(AD溶液)、质量分数为25%的商品飞机除冰液与水中快速冻融试验

  16. An extended global Earth system data record on daily landscape freeze-thaw status determined from satellite passive microwave remote sensing

    Science.gov (United States)

    Kim, Youngwook; Kimball, John S.; Glassy, Joseph; Du, Jinyang

    2017-02-01

    The landscape freeze-thaw (FT) signal determined from satellite microwave brightness temperature (Tb) observations has been widely used to define frozen temperature controls on land surface water mobility and ecological processes. Calibrated 37 GHz Tb retrievals from the Scanning Multichannel Microwave Radiometer (SMMR), Special Sensor Microwave Imager (SSM/I), and SSM/I Sounder (SSMIS) were used to produce a consistent and continuous global daily data record of landscape FT status at 25 km grid cell resolution. The resulting FT Earth system data record (FT-ESDR) is derived from a refined classification algorithm and extends over a larger domain and longer period (1979-2014) than prior FT-ESDR releases. The global domain encompasses all land areas affected by seasonal frozen temperatures, including urban, snow- and ice-dominant and barren land, which were not represented by prior FT-ESDR versions. The FT retrieval is obtained using a modified seasonal threshold algorithm (MSTA) that classifies daily Tb variations in relation to grid-cell-wise FT thresholds calibrated using surface air temperature data from model reanalysis. The resulting FT record shows respective mean annual spatial classification accuracies of 90.3 and 84.3 % for evening (PM) and morning (AM) overpass retrievals relative to global weather station measurements. Detailed data quality metrics are derived characterizing the effects of sub-grid-scale open water and terrain heterogeneity, as well as algorithm uncertainties on FT classification accuracy. The FT-ESDR results are also verified against other independent cryospheric data, including in situ lake and river ice phenology, and satellite observations of Greenland surface melt. The expanded FT-ESDR enables new investigations encompassing snow- and ice-dominant land areas, while the longer record and favorable accuracy allow for refined global change assessments that can better distinguish transient weather extremes, landscape phenological shifts

  17. Effect of freezing-thawing process on epldidymal spermatozoa%冻融对附睾精子ICSI结局及其形态的影响

    Institute of Scientific and Technical Information of China (English)

    石宇; 龙晓林; 高兴成; 杜红姿; 张文; 黄玉玲; 李莉; 张文红

    2009-01-01

    目的 探讨冻融对PESA-ICSI结局以及附睾精子形态的影响.方法 回顾性分析2006年1月~2008年12月广州医学院第三附属医院生殖中心因梗阻性无精症或严重少弱精症首次接受PESA-ICSI或ICSI不孕夫妇的治疗结果.共行226周期助孕治疗,包括22个冻融成功的PESA-ICSI周期(研究组),164个新鲜PESA-ICSI周期(对照组)和40个射出精液ICSI周期(研究对照组).比较三组的受精率、临床妊娠率、种植卒和流产率.对33例患者冻存的PESA精子冻融前后均进行形态学观察,自身对照比较正常精子百分率、头部异常百分率、颈及中段异常百分率、尾部异常百分率及TZI、SDI的变化.结果 研究组、对照组及空白对照组三组患者的一般情况无统计学差别(P>0.05),三组受精卒、临床率、种植率及流产卒相比亦无统计学差别(P>0.05).PESA精子冻融后TZI较冻融前明显降低,1.43±0.11vs1.36±0.08(P0.05). TZI of epididymal spermatozoa after thawed was significant decreased, 1.43±0.11 vs 1.36±0.08(P<0.01)respectively. Conclusions Freezing-thawing process does not affect the outcome of epididymal spermatozoa-ICSI and this process can also get rid of some deformity sperm.

  18. Grey relational analysis on strength loss rate in freeze-thaw cycles of polypropylene fiber concrete%聚丙烯纤维混凝土强度冻融损失率灰色关联分析

    Institute of Scientific and Technical Information of China (English)

    王金圳

    2013-01-01

    利用灰色系统理论的灰色关联分析,在文献数据基础上,对影响聚丙烯纤维混凝土强度冻融损失率的4个主要参数(水灰比、纤维含量、粉煤灰含量、减水剂含量)的关联度大小进行分析,并利用灰色预测模型建立关于聚丙烯纤维混凝土强度冻融损失率 GM(1,N)方程。结果表明:对聚丙烯纤维混凝土强度冻融损失率影响因素关系为水灰比>减水剂含量>粉煤灰含量>纤维含量,可利用灰色关联分析的方法有效预测聚丙烯纤维混凝土强度冻融损失率。灰色预测模型 GM(1,5)的冻融损失率的预测结果有较好精度。%Using the grey relational analysis of grey system theory,the correlation of four main parameters of the effect strength loss rate of polypropylene fiber concrete on freeze-thaw cycles:water-cement ratio,vol-ume fraction of fiber,fly ash content,and superplasticizer content was analyzed based on literature,and u-sing the grey prediction model,the GM(1,N)equation of the strength loss rate of polypropylene fiber con-crete in freeze-thaw cycles was established.The results showed that influencing factors of the strength loss rate of polypropylene fiber concrete in freeze-thaw cycles were as follows:water-cement ratio >superplasti-cizer content >fly ash content >volume fraction of fiber.The results of grey forecasting model GM(1,5) showed good agreement with the experimental results.It was shown that could effectively predict the strength loss rate of polypropylene fiber concrete in freeze-thaw cycles by using the method of grey relation-al analysis.

  19. Progress of the effect factors of freeze-thawing behavior and modification mechanisms of corn starch%玉米淀粉颗粒冻融特性影响因素及机制研究进展

    Institute of Scientific and Technical Information of China (English)

    余世锋; 郑喜群

    2012-01-01

    玉米淀粉是一种供应稳定、价格低廉,广泛应用于焙烤食品、医药及食品工业等领域的重要原材料。综述了玉米淀粉变性方法现状,详细分析了玉米淀粉颗粒冻融特性的影响因素,探讨了玉米淀粉颗粒冻融变性机制,玉米淀粉颗粒冻融变性机制可能是冰晶微机械破坏力和水分迁移渗透压力共同作用的结果。%Corn starch was one of the most important industry materials, which is widely used in baking foods, pharmacology and food manufacturing. In the paper, the modification methods of corn starch were reviewed, and the effect factors of freeze-thawing behavior of corn starch granule were analyzed. The corn starch modification mechanism of freeze-thawing was discussed, and the corn starch granule modification mechanisms maybe were the destruction of ice-matrix expansion pressure and water penetration pressure together.

  20. Freeze-thaw cycle test and microstructural analysis on lightweight polymer mortar%轻质聚合物抹面砂浆冻融循环及微观机理研究

    Institute of Scientific and Technical Information of China (English)

    苏志杰; 路永华; 宋跃军

    2014-01-01

    It was studied on the mechanical properties and strain of polymer plaster mortars for external thermal insulation composite systems(ETICS) under freeze-thaw cycle test.The results demonstrated that after freeze-thaw cycle test,the total micro-strain and incre-ment of the flexural and compressive strength ratio of lightweight polymer mortar were less than commonly used polymer mortar.As a re-sult,the lightweight polymer mortar have better flexibility and durability.At the same time,it was studied on the microstructure using SEM about these three mortars.%针对外墙外保温体系用聚合物抹面砂浆在经受冻融循环试验条件下的应变和力学性能进行研究,结果表明:聚合物抹面砂浆经历一定次数的冻融循环后,轻质系列聚合物抹面砂浆总微应变量和压折比增加量均小于常用聚合物抹面砂浆,具有更好的柔韧性,提高了砂浆的耐久性。同时,利用 SEM 对三种砂浆进行了微观机理研究。

  1. Effect of Different Food Ingredients on Retrogradation Degree and Freeze-thaw Stabilization of Yam Starch%食品成分对山药淀粉老化度和冻融稳定性的影响

    Institute of Scientific and Technical Information of China (English)

    李昌文; 彭雪萍

    2012-01-01

    研究了氯化钠、蔗糖、单甘酯对山药淀粉老化度和冻融稳定性的影响,结果表明山药淀粉的老化度随氯化钠浓度的增大而有所增大,随蔗糖浓度、单甘酯浓度的增大而有所减小;山药淀粉的冻融稳定性随氯化钠浓度、蔗糖浓度、单甘酯浓度的增大而改善,氯化钠、蔗糖、单甘酯对山药淀粉的冻融稳定性有促进作用。%Study the effect of sodium chloride,sucrose and monoglyceride on retrogradation degree and freeze-thaw stabilization of yam starch.The results showed that the retrogradation degree increased with the increase of concentration of sodium chloride and decreased with the increase of sucrose concentration and monoglyceride concentration.Sodium chloride,sucrose and monoglyceride could improve the freeze-thaw stabilization of yam starch.

  2. 超声辅助制备抗冻融大豆分离蛋白工艺优化%Processing optimization for improving freeze-thaw stability of soybean protein isolate by ultrasonic assisted glycosylation

    Institute of Scientific and Technical Information of China (English)

    王喜波; 张泽宇; 葛洪如; 徐晔晔; 夏如鑫; 江连洲

    2016-01-01

    Soybean protein isolate (SPI) has been widely used in food industry because of its ability to improve texture which is contributing to the nutritional and health benefits of protein-based foods. It can be used as emulsifiers in food emulsions due to the surface-active properties of their constitutive proteins, the storage globulins 7S and 11S. Oil-in-water (o/w) emulsions are thermodynamically unstable systems and sensitive to environmental changes, for example cooling and freezing. Freezing and frozen-food storage can maintain microbiological and chemical stability, while extending the shelf life of food products. There are many potential applications for o/w emulsions that can be frozen and then thawed prior to use, such as refrigerated and frozen food. Nevertheless, most of o/w emulsions are highly unstable when they are frozen and will have rapid breakdown after thawing. When an o/w emulsion is stored at low temperature, a variety of physicochemical processes can occur including ice formation, fat crystallization, freeze-concentration, interfacial phase transitions and biopolymer conformational changes. These phase transitions may lead to creaming, oiling off, coalescence and flocculation of the emulsions, which limit its utilization in frozen food. In order to improve the freeze-thaw stability of SPI, the SPI-D (dextran) grafts were prepared by ultrasonic-assisted glycosylation. Based on the early study of single-factor experiment, we found that the emulsion stability index (ESI) before freeze-thaw and the creaming index (CI) after freeze-thaw had high correlation. So the ESI and CI were set as the response values, the concentration of SPI, ultrasonic temperature and ultrasonic power were as factors, the Box-Behnken model of optimizaiton process was established to improve the emulsifying properties and freeze-thaw stability of SPI. The results showed that under the condition of the concentration of 40 mg/mL SPI, 80 ℃ ultrasonic temperature, 5 W/mL power

  3. Freeze-thaw cycles weathering degrading properties of bamboo flour-polypropylene foamed composites%冻融循环老化降低竹粉/聚丙烯发泡复合材料性能

    Institute of Scientific and Technical Information of China (English)

    周吓星; 黄舒晟; 苏国基; 余雁; 陈礼辉

    2014-01-01

    The wood-plastic foamed composites have lower density and higher specific strengths than wood-plastic composites (WPC) and thus have wide applications in fields such as building, decoration, packing, and the automobile industry. Previous studies showed that the weathering causes color fading, strength weakening, chemical changes of WPC, thereby restricting the specific outdoor applications of WPC. In order to explore their weathering mechanism and broaden their outdoor applications, it is of great importance to evaluate the durability of BF/PP foamed composites. The objective of this research was to study the impact of weathering of freeze-thaw cycle on the physical and thermal properties of bamboo flour-polypropylene foamed composite. The foamed composites of bamboo flour (BF), high melted strength polypropylene (HMSPP), polypropylene (PP), 1% modified azodicarbonamide (AC) foaming agent, and maleic anhydride grafted polypropylene (MAPP) coupling agent blends were prepared by injection molding. The composites with different BF contents of 0, 20%, 33% and 42% were exposed to accelerated cycling of water immersion followed by freeze thaw at the temperature of -40-60℃ for 0, 3, 6, and 9 cycles. The effects of freeze-thaw cycles accelerated weathering on the color change and the physico-mechanical properties and thermal behavior of the foamed composites were investigated. The surfaces morphology of composites non-weathered and freeze-thaw cycles weathered were investigated by (Environmental Scanning Electronic Microscopy, ESEM) and the chemical structures were also analyzed by FTIR. The results showed that the composites at higher BF content exhibited greater color change and larger decreases in physico-mechanical properties especially the tensile and impact strengths as compared to the one without weathering. The negative effects of the weathering increased with the growing number of freeze-thaw cycles. The color changeΔE* of 0, 20%, 33%, and 42% BF/PP composites

  4. 冻融魔芋凝胶特性及结构表征%Characteristics and structure characterization of freeze-thawing konjac gel

    Institute of Scientific and Technical Information of China (English)

    施念; 文声扬; 李斌

    2015-01-01

    Objective To explore the characteristics and the structure changes of konjac gel after freezing and thawing treatment. Methods The water binding capacity of konjac gel after freeze-thawing treatment was measured and Fourier transform infrared spectrometry (FT-IR), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the structure and properties of the konjac vermicelli after treatment under different freezing temperature. Results Taking water binding capacity and moisture content after soaking as the evaluation index, the optimal treatment conditions were: frozen temperature of -12 ℃, frozen time of 2 h, drying time of 4 h, drying temperature of 90 ℃. In the process of freezing and thawing, freezing and drying treatment had little effect on the molecular chain of konjac glucomannan (KGM) in konjac gel, but freezing temperature would exert influence on the micro structure of konjac gel. Conclusion This research can provide theoretical guidance for the development of a kind of konjac gel vermicelli with low calories through a concise and effective way, which will further provide a new type of product for the food industry.%目的:探讨魔芋凝胶经冻融处理后其特性及结构的变化。方法测定魔芋凝胶在冻融前后的持水性能;并结合傅里叶红外光谱法(Fourier transform infrared spectrometry, FT-IR)、差示扫描量热分析法(differential scanning calorimetry,DSC)、X 射线衍射法(X-ray diffraction,XRD)和扫描电镜分析法(scanning electron microscopy, SEM)分析不同冷冻温度处理后魔芋粉丝的结构。结果以持水性能中的持水倍数和复水后含水量为评价指标,魔芋凝胶冷冻处理的最佳条件为:冷冻温度-12℃,冷冻时间2 h,烘干时间4 h,烘干温度90℃。冻融过程中冷冻和干燥处理对魔芋凝胶中魔芋葡甘聚糖分子链中基团的影响微弱,但冷冻温度会对微观结构产生

  5. Validating a refractometer to evaluate immunoglobulin G concentration in Jersey colostrum and the effect of multiple freeze-thaw cycles on evaluating colostrum quality.

    Science.gov (United States)

    Morrill, K M; Robertson, K E; Spring, M M; Robinson, A L; Tyler, H D

    2015-01-01

    The objectives of this study were to (1) validate a method using refractometry to rapidly and accurately determine immunoglobulin (IgG) concentration in Jersey colostrum, (2) determine whether there should be different refractive index (nD) and %Brix cut points for Jersey colostrum, and (3) evaluate the effect of multiple freeze-thaw (FT) cycles on radial immunodiffusion (RID) and a digital refractometer to determine IgG concentration in Jersey colostrum. Samples (n=58; 3L) of colostrum were collected from a dairy in northwestern Iowa. Samples were analyzed within 2h of collection for IgG concentration by RID, %Brix, and nD by refractometer and an estimate of IgG by colostrometer. Samples were frozen, placed on dry ice, and transported to the laboratory at Iowa State University (Ames). Samples arrived frozen and were placed in a -20°C manual-defrost freezer until further analysis. On d 7 (1FT), d 14 (2FT), and 1yr (3FT) all samples were thawed, analyzed for IgG by RID, %Brix, nD by refractometer, and IgG estimate by colostrometer, and frozen until reanalysis at the next time point. Fresh colostrum had a mean (±SD) IgG concentration of 72.91 (±33.53) mg/mL, 21.24% (±4.43) Brix, and nD 1.3669 (±0.0074). Multiple FT cycles did affect IgG as determined by RID and colostrometer reading. The IgG concentrations were greater in fresh and 1FT samples as compared with 2FT and 3FT samples (72.91, 75.38, 67.20, and 67.31mg of IgG/mL, respectively). The colostrometer reading was lower in 1FT samples compared with fresh and 2FT samples. Multiple FT cycles had no effect on nD or %Brix reading. In fresh samples, IgG concentration was moderately correlated with nD (r=0.79), %Brix (r=0.79), and colostrometer reading (r=0.79). Diagnostic test characteristics using the recommended cut point of 1.35966 nD resulted in similar sensitivities for 1FT and 2 FT samples (94.87 and 94.74%, respectively). Cut points of 18 and 19% Brix resulted in the greatest sensitivities (92.31 and 84

  6. Re-analysis of martian gully orientation and slope for comparison with climate model predictions of freeze-thaw and dry-ice sublimation.

    Science.gov (United States)

    Conway, Susan; Harrison, Tanya; Lewis, Stephen; Balme, Matthew; Soare, Richard; Britton, Andrew

    2016-04-01

    during which the surface temperature was below the CO2 condensation point of 149K. We use these data as a proxy for where CO2sublimation processes can be active. (ii) The number of sols for which the daily minimum is below 273K and the daily maximum is above 273K. We use these data as a proxy for where ice could be stable and then melt during freeze-thaw cycles. Our results reveal that neither of these simple modelling cases exactly fits the observational data, therefore we conclude that it is likely that a mixture of CO2 and water related processes are responsible for forming martian gullies. We aim to perform a number of tests to assess both the applicability of these simple proxies and to test a wider range of substrate properties (buried ice) and orbital parameters (perihelion and increased atmospheric pressure at high obliquity) to see if they give better fits to our observations.

  7. Repeatedly stressed rats have enhanced vulnerability to amygdala kindling epileptogenesis.

    Science.gov (United States)

    Jones, Nigel C; Lee, Han Ee; Yang, Meng; Rees, Sandra M; Morris, Margaret J; O'Brien, Terence J; Salzberg, Michael R

    2013-02-01

    Psychiatric disorders associated with elevated stress levels, such as depression, are present in many epilepsy patients, including those with mesial Temporal Lobe Epilepsy (mTLE). Evidence suggests that these psychiatric disorders can predate the onset of epilepsy, suggesting a causal/contributory role. Prolonged exposure to elevated corticosterone, used as a model of chronic stress/depression, accelerates limbic epileptogenesis in the amygdala kindling model. The current study examined whether exposure to repeated stress could similarly accelerate experimental epileptogenesis. Female adult non-epileptic Wistar rats were implanted with a bipolar electrode into the left amygdala, and were randomly assigned into stressed (n=18) or non-stressed (n=19) groups. Rats underwent conventional amygdala kindling (two electrical stimulations per day) until 5 Class V seizures had been experienced ('the fully kindled state'). Stressed rats were exposed to 30min restraint immediately prior to each kindling stimulation, whereas non-stressed rats received control handling. Restraint stress increased circulating corticosterone levels (pre-stress: 122±17ng/ml; post-stress: 632±33ng/ml), with no habituation observed over the experiment. Stressed rats reached the 'fully kindled state' in significantly fewer stimulations than non-stressed rats (21±1 vs 33±3 stimulations; p=0.022; ANOVA), indicative of a vulnerability to epileptogenesis. Further, seizure durations were significantly longer in stressed rats (p<0.001; ANOVA). These data demonstrate that exposure to repeated experimental stress accelerates the development of limbic epileptogenesis, an effect which may be related to elevated corticosterone levels. This may have implications for understanding the effects of chronic stress and depression in disease onset and progression of mTLE in humans.

  8. 季节性冻融期亚高山/高山森林细根分解动态%Fine Root Decomposition Dynamics during Freeze-Thaw Season in the Subalpine/Alpine Forests

    Institute of Scientific and Technical Information of China (English)

    魏圆云; 武志超; 杨万勤; 吴福忠

    2013-01-01

    The ongoing winter warming inevitably alters the process of fine root decomposition in high-altitude area by changing the pattern of seasonal soil freezing and thawing.As yet,the dynamics of fine root decomposition at different stages in the freeze-thaw season remain uncertainty.In order to characterize the dynamics of fine root decomposition at different stages of a freeze-thaw season in cold biomes under climate change scenarios,litterbags with 10 g fine roots of Picea asperata,Betula albo-sinensis and Abies faxoniana were buried in the forest soil at the 3 582,3 298 and 3 023 m altitudes in western Sichuan,China.These litterbags were recovered at onset of freezing (OF),deep frozen stage (DF),early thawing stage (ETS),middle thawing stage (MTS),and later thawing stage (LTS) from December 10,2009 to April 28,2010.The residual rate of fine roots was 88%-92% after a freeze-thaw season,and varied significantly with altitudes and tree species.The fine root decomposition occurred at all stages of the freeze-thaw season,among which OF had the highest rate of fine root decomposition.However,the rate of the fine root decomposition declined as decomposing,especially in the lower altitude.The decay rate constant of fine roots varied from 0.177 6 to 0.242 4,and the relative mass loss was correlated closely with soil temperature at the different stages,but the rate of the fine root decomposition was not significantly correlated with the indices of the measured initial qualities of fine roots.The regression model based on average soil temperature,fluctuated soil temperature,calcium concentration of fine roots and the ratio of lignin to nitrogen in fine roots during the freeze-thaw season,interpreted 95% of the reason of differences in the fine root decay rate.It is concluded that the soil freeze-thaw process caused by temperature fluctuations was an important factor in influencing the rate of the fine root decomposition during the freeze-thaw season in the high

  9. Mechanical properties and fast freezing-thawing characteristics of double admixture high performance concrete%双掺高性能混凝土力学性能及快速冻融特性

    Institute of Scientific and Technical Information of China (English)

    姚志雄; 吴波

    2015-01-01

    研究了矿物质对水泥砂浆及混凝土基本力学性能的影响规律,并通过快速冻融试验探讨快速冻融、腐蚀介质双重因素共同作用下混凝土力学性能劣化情况。结果表明,掺矿物质混凝土前期强度低于素混凝土,但龄期达到28 d时其活性得到发挥,到60 d时甚至超过素混凝土,弥补前期强度不足的缺陷。在快速冻融及盐水腐蚀双重因素共同作用下,掺矿物质混凝土的强度及相对动弹性模量出现不同程度降低,质量出现轻微波动,但降低或波动幅度均明显小于素混凝土,表明掺矿物质对改善混凝土结构,提升耐久性有益,而双掺的效果更佳,并给出矿物质较优掺量。%Experiments were carried out to study the effect of mineral on the basic mechanical performance of cement mortar and con-crete.Then the fast freezing-thawing tests were carried out to investigate the mechanics performance degradation of concrete under the double actions of quick freezing-thawing and corrosion medium. The results show the early strength of mixed minerals concrete is low-er than the plain concrete,but the age to 28 d when the active works,to 60d even more than the plain concrete,and it makes up the de-fects of the insufficient early strength. Under the action of fast freezing-thawing and salt water corrosion,the concrete strength,relative dynamic elastic modulus reduced in a certain degree,and concrete mass fluctuates slightly,but the reduction and fluctuation amplitude is significantly less than the plain concrete. The results show that adding minerals is beneficial to improve the microstructure and promote the durability of concrete,and the double mixing effect is better,and the optimal dosage of mineral is given.

  10. Studying on the permeability of waterproofing concrete processed with silane emuslion under freezing-thawing environment%冻融环境下硅烷防水混凝土渗透性试验研究

    Institute of Scientific and Technical Information of China (English)

    赵炜; 黄巍林; 宋强; 徐建光

    2016-01-01

    For studying the influence of freezing-thawing damage on the anti-permeability of integral waterproofing concrete,the con-crete specimens with different W/C and the amount of silane emulsion were prepared.The water absorption and chloride penetration testes were respectively carried out after different freezing-thawing cycles.Eventually,the curves of water absorption and chloride tent are drawn, which aims to evaluate the anti-permeability of integral water proofing concrete.The results show that the anti-frost property of integral wa-terproof concrete is decreased with the addition of silane emulsion.After the same freezing-thawing cycles,the integral water proofing con-crete possesses a better anti-permeability than ordinary concrete that without silane emulsion adding.%为研究冻融损伤对整体混凝土抗渗透性能影响,制备不同水灰比、不同硅烷乳液掺量的整体防水混凝土试件。在不同冻融循环次数下,测定不同试件相对动弹性模量以评价整体防水混凝土抗冻性能。同时,对经过不同冻融循环次数下的试件进行毛细吸水试验和氯离子侵蚀试验,并绘制毛细吸水曲线和氯离子含量曲线,以评价不同冻融损伤下整体防水混凝土的抗渗透性能。试验结果表明,随着硅烷乳液掺量的增加,整体防水混凝土的抗冻性能降低。但是在相同冻融循环次数下,整体防水混凝土仍较普通混凝土具有较好的抗渗透性能。

  11. 冻融环境下引气混凝土的抗钢筋锈蚀能力研究%Study on Ability of Resistance to Steel Corrosion of Air Entraining Concrete Under Freeze-thaw Environment

    Institute of Scientific and Technical Information of China (English)

    马志鸣; 赵铁军; 巴光忠; 管庭

    2014-01-01

    对带钢筋的普通混凝土及引气混凝土试件进行抗冻融循环试验,在不同冻融损伤程度下对试件进行氯离子侵蚀试验。利用半电池电位法和线性极化法分别测定经过不同冻融循环次数下混凝土试件内部钢筋的电位和腐蚀电流密度,从而定量地确定混凝土内部钢筋的锈蚀情况。研究结果表明:向混凝土内部掺入一定比例引气剂,可以提高混凝土的抗冻性能,从而增强其在腐蚀环境下抗钢筋锈蚀能力,提高了混凝土的耐久性能;对试件进行劈裂试验后,钢筋的实际锈蚀情况与利用由化学方法测定结果一致。%The freeze-thaw cycle tests of the ordinary concrete specimen and the air entraining concrete specimen with steel were carried out ,and the chloride corrosion tests under different freeze-thaw damage degrees were done . The potential values and corrosion current density of steel in concrete specimens were determined under different freeze-thaw cycle times by using half-cell potential method and linear polarization method ,then the steel corrosion condition in concrete was qualitatively determined . The study results show that adding air entraining agent can improve the anti-freeze property of concrete ,promote the ability of resistance to steel corrosion , and prolong the durability of concrete structure .After specimen splitting test ,the actual steel corrosion condition has the same result with the result by chemical approach .

  12. Hippocampal ER stress and learning deficits following repeated pyrethroid exposure.

    Science.gov (United States)

    Hossain, Muhammad M; DiCicco-Bloom, Emanuel; Richardson, Jason R

    2015-01-01

    Endoplasmic reticulum (ER) stress is implicated as a significant contributor to neurodegeneration and cognitive dysfunction. Previously, we reported that the widely used pyrethroid pesticide deltamethrin causes ER stress-mediated apoptosis in SK-N-AS neuroblastoma cells. Whether or not this occurs in vivo remains unknown. Here, we demonstrate that repeated deltamethrin exposure (3 mg/kg every 3 days for 60 days) causes hippocampal ER stress and learning deficits in adult mice. Repeated exposure to deltamethrin caused ER stress in the hippocampus as indicated by increased levels of C/EBP-homologous protein (131%) and glucose-regulated protein 78 (96%). This was accompanied by increased levels of caspase-12 (110%) and activated caspase-3 (50%). To determine whether these effects resulted in learning deficits, hippocampal-dependent learning was evaluated using the Morris water maze. Deltamethrin-treated animals exhibited profound deficits in the acquisition of learning. We also found that deltamethrin exposure resulted in decreased BrdU-positive cells (37%) in the dentate gyrus of the hippocampus, suggesting potential impairment of hippocampal neurogenesis. Collectively, these results demonstrate that repeated deltamethrin exposure leads to ER stress, apoptotic cell death in the hippocampus, and deficits in hippocampal precursor proliferation, which is associated with learning deficits.

  13. 大掺量粉煤灰混凝土在海水中冻融循环后的试验研究%Experimental research on the freezing-thawing circle of high volume fly ash concrete in seawater

    Institute of Scientific and Technical Information of China (English)

    覃丽坤; 宋宏伟; 王秀伟

    2014-01-01

    为研究粉煤灰混凝土的抗冻性能,研究了水胶比为0.35,粉煤灰掺量为52%的大掺量粉煤灰混凝土在海水中的抗冻性能,利用混凝土快速冻融试验机,对海水中粉煤灰混凝土分别进行了0、100、200、300、400次快速冻融循环试验,并对冻融循环后的混凝土进行了单轴压力学性能试验。测得了冻融循环后混凝土的质量损失,动弹性模量以及单轴抗压强度。根据试验结果,系统地分析了冻融循环次数对大掺量粉煤灰混凝土单轴抗压强度的影响。结论表明:随冻融循环次数的增加,海水中大掺量粉煤灰混凝土的单轴强度逐渐降低,并具有一定规律性。这些结论可以为粉煤灰混凝土在寒冷地区海工混凝土构筑物的应用提供理论依据。%In order to study on frost resistance of fly ash concrete.The authors using the rapid freezing and thawing of concrete test ma-chine,tested the frost resistance performance of high volume fly ash concrete in seawater,whose water-binder ratio was 0.35,the amount of fly ash was 52%.The fast freezing-thawing test was carried on 0、100、200、300 and 400 cycles,then uniaxial compression test,the mass loss after freezing-thawing cycles,the dynamic elastic modulus and uniaxial compressive strength were tested.According to the test results, the systematic analysis of the influence of freezing-thawing cycles on the uniaxial compressive strength of high volume fly ash concrete. Conclusion:with the increase in the number of freezing-thawing cycles,the uniaxial strength mixed with high volume fly ash concrete in seawater decreased gradually,and which has certain regularity.These conclusions can provide a theoretical basis for the application of fly ash concrete in cold area of marine concrete qstructures.

  14. 不同体外受精方式对胚胎玻璃化冷冻复苏的影响%Effects of different in vitro fertilization procedures on embryo vitrification freezing - thawing

    Institute of Scientific and Technical Information of China (English)

    孙丽君; 钱秋然; 王兴玲; 王雪梅; 郝大勇; 刘景; 张彩霞

    2011-01-01

    目的:观察常规体外受精和卵胞浆内单精子注射两种不同体外受精方式对胚胎玻璃化冷冻复苏的影响.方法:将移植冷冻复苏胚胎的患者(均为玻璃化法)分为两组.IVF组:新鲜周期采取常规体外受精方式而获得的胚胎;ICSI组:新鲜周期采取卵胞浆内单精子注射方式受精而得到的胚胎;比较两组的不孕类型、不孕原因以及冷冻复苏周期的复苏率、着床率、临床妊娠率和流产率等.结果:IVF组和ICSI组的复苏率、着床率、临床妊娠率差异无统计学意义(P>0.05),ICSI组的流产率明显高于IVF组但差异无统计学意义(P>0.05),IVF组和ICSI组原发不孕所占比例、继发不孕所占比例差异有统计学意义(P<0.05),IVF组和ICSI组男方因素不孕所占比例、输卵管因素不孕所占比例差异有统计学意义(P<0.05).结论:ICSI不影响胚胎玻璃化冷冻周期的复苏率、着床率及临床妊娠率,ICSI后胚胎玻璃化冷冻复苏流产率有升高的趋势,ICSI体外受精方式主要用于原发不孕患者以及男方因素导致的不孕患者.%Objective: To observe the effects of conventional in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) on embryo vitrification freezing - thawing. Methods: The patients receiving freezing - thawing embryo transfer ( vitrification - recovery cycles) were divided into two groups; the embryos in IVF group were obtained by conventional IVF based on fresh cycles, while the embryos in ICSI group were obtained by ICSI based on fresh cycles; the infertile types, infertile causes and recurrence rates of freezing - thawing cycles, implantation rates, clinical pregnancy rates and abortion rates in the two groups were compared. Results; There was no significant difference in recovery rate, implantation rate and clinical pregnancy rate between IVF group and ICSI group (P >0.05) ; the abortion rate in ICSI group was higher than that in IVF group, but

  15. 冻融后小鼠休眠胚胎超微结构的变化%Ultrastructural observation of dormant mouse embryos cultured in vitro after freezing-thawing

    Institute of Scientific and Technical Information of China (English)

    顾美超; 卢天罡; 刘云海; 倪和民; 张劭俣; 翟椿东; 邢书涵; 郭勇

    2014-01-01

    Objective The aim of this study was to investigate the differences of the cell ultrastucture of normal mouse hatched blastocysts and their dormant ones cultured in vitro after freezing-thawing, and to explore whether the dor-mant embryos have a better anti-freezing shock property than the normal hatched mouse embryos .Methods By transmis-sion electron microscopy , the ultrastructure of these two types of mouse embryos was observed and analyzed .Results By comparative analysis of their ultrastructure , the results showed that the dormant embryos before freezing are being austerity and with lower energy metabolism at a ‘ground state ’ .After freezing-thawing and culture , their cellular structure seemed to be similar to that of the normal embryos cultured in vitro before freezing.However, after freezing-thawing and culture, the number of mitochondria decreased , the nuclei were loose , and their heterochromatin also increased .Conclusions From the ultrastructural observation , compared with the normal mouse hatched embryos , the cellular state of dormant mouse em-bryos after freezing-thawing is more favorable for material storage and energy metabolism , thus, indicating that they have a better anti-freezing property than normal hatched embryos .%目的:从亚细胞超微结构的角度揭示其抗冻能力优于正常孵化胚胎的原因。方法利用透射电子显微镜观察小鼠休眠胚胎与正常孵化期胚胎在细胞连接和各细胞器形态与分布上的差异,以及冻融培养后的变化,并进行相关比较分析。结果通过亚细胞结构对比分析发现:冷冻前小鼠休眠胚胎为紧缩状,处于能量代谢较低的“基态”,通过冻融后培养,细胞器结构恢复与正常孵化胚胎冷冻前相似;而正常孵化胚胎经过冻融后,线粒体数量减少,细胞核松散,异染色质增多。结论小鼠休眠胚胎与正常孵化胚胎冻融后相比,其细胞状态更有利于物质储存及能

  16. Influence of fly ash on concrete permeability under freezing-thawing cycle condition%冻融循环条件下粉煤灰对混凝土渗透性的影响

    Institute of Scientific and Technical Information of China (English)

    汪振双; 王立久

    2011-01-01

    In order to analyze the influnce of fly ash on the concret permeability under freezing-thawing cycle condition, the fly ash was used to replace the cement equivalently with mixing contents of 10%, 20% and 30%, and the water-binder ratios of 0. 42 and 0. 35 were adopted in the experiment. The freezeing-thawing cycle and alternating current permeability tests were carded out for the concrete with different mixing contents of fly ash, and the results were compared with those of ordinary concrete. The experimental results show that when the water-binder ratio is 0. 42, the permeation resistance of the concrete gets enhanced while the freezing resistance of the concrete decreases with increasing the content of fly ash. When the water-binder ratio is 0. 35, the permeation resistance of the concrete is improved while the freezing resistance of the concrete firstly increases and then reduces with increasing the content of fly ash. After freezing-thawing cycle, the concrete permeability increases obviously. And the freezing damage resistance of the concrete can be characterized by the permeation resistance loss of the concrete after freezing-thawing cycle.%为了分析冻融循环条件下粉煤灰对混凝土渗透性的影响,试验采用粉煤灰等量替代水泥掺量的10%、20%和30%,水胶比为0.42和0.35,对不同掺量粉煤灰混凝土进行了冻融循环试验和交流电渗透性试验,并与普通混凝土进行了对比.试验结果表明,当水胶比为0.42时,随着粉煤灰含量的增加,混凝土的抗渗透性能提高,而抗冻性能降低;当水胶比为0.35时,随着粉煤灰含量的增加,混凝土的抗渗透性能提高,而抗冻性能先提高后降低,存在一个最佳值.冻融循环后,混凝土的渗透性明显增大,可以用冻融循环后混凝土渗阻损失率来表征混凝土的抗冻破坏程度.

  17. 拉萨地区不同空隙率的半柔性路面材料冻融试验研究%Freezing-Thawing Test Research of Semi-Flexible Pavement Materials with Different Void Fraction in Lhasa

    Institute of Scientific and Technical Information of China (English)

    李成洋; 张鹏; 王文奇; 田荣燕

    2016-01-01

    为解决现有水泥混凝土和沥青混凝土路面材料在拉萨地区推广应用中受冻融作用破坏的问题,对不同空隙率的半柔性路面材料在拉萨的应用进行研究。采用灌注式的方式将水泥胶浆灌入不同空隙率的开级配沥青混合料母体中制成试件,并根据拉萨独特的气候特征设定冻融试验的时间和温度;再进行高温稳定试验和低温抗裂试验,得出趋近于真实冻融环境的试验数据。分析试验数据可得,半柔性路面材料在受到冻融作用破坏时,低温抗裂强度随着空隙率的增大呈逐渐上升趋势,劈裂位移量随着空隙率的增大呈逐渐减小趋势;而表征高温稳定性能的动稳定度随着空隙率的增大呈先上升后下降的趋势,变形速率随着空隙率的增大呈先下降后上升的趋势。研究结果表明,半柔性路面材料采用27%的空隙率并添加塑弹性材料有利于抵抗冻融破坏,从而能够在高原地区推广和应用。%In order to solve the problem that the cement concrete and asphalt concrete pavement materi⁃al were damaged by freezing-thawing action during their popularization and application in Lhasa, a re⁃search about the application of semi-flexible pavement materials with different void fraction in Lhasa was carried out. Test specimens were made by the way of pouring cement mortar into open-graded as⁃phalt mixture matrix with different void fraction. The time and temperature of freezing-thawing test were set based on the special environment of Lhasa. Then the high-temperature stability test and low-temper⁃ature crack resistance test were carried out to obtain the test data closing to the real environment. By ana⁃lyzing the test data, it was educed that:when semi-flexible pavement material was destroyed by freezing-thawing action, with the increasing of void fraction, the low-temperature crack resistance increased grad⁃ually, and the split displacement

  18. Effect of freeze-thaw cycles on the immunogenicity of Litopenaeus vannamei allergens%冻融循环过程中虾过敏原的免疫原性变化

    Institute of Scientific and Technical Information of China (English)

    吴丽莎; 李振兴; 刘一璇; 陈瑜; 林洪

    2011-01-01

    In order to study the activity of shrimp allergens in freeze-thaw cycles, Penaeus vannamei were used to extract allergen,respectively stored at -3 ℃, -20 ℃ and -80 ℃ for one to five cycles.For the purpose of exploring the best activated condition of the allergen extract, protein concentration was determined by BCA;SDS-PAGE electrophoresis was used to evaluate protein composition;indirect ELISA and Westernblotting were used to survey allergens activity.The results showed that when shrimp allergen extract was in the cycle of freezing and thawing for five cycless at -80 ℃, -20 ℃ and -3 ℃, the protein concentration decreased by 33.1% ,30.0% and 24.2% respectively.The major allergen bands were degraded ,when the shrimp protein extract was freezed and thawed for four cycles at -80 ℃ and -20 ℃, on the other hand the major allergen bands didn' t change at -3 ℃ for five cycles of freezing and thawing.The allergenic activity of shrimp protein extract had reduced when freezed and thawed for five cycles at -80 ℃ and -20 ℃ and three cycles at -3 ℃.The major allergen Western-blotting bands disappeared when five cycles of freezing and thawing were advanced at -80 ℃ and -20 ℃ ,while the major Western-blotting bands didn't change at - 3 ℃.Therefore, when the allergens protein was storaged, the cycles of freeze-thawing should be reduced to ensure the allergenic activity of shrimp didn' t change, then at -80 ℃ and -20 ℃ within four freezethaw cycles and at -3 ℃ less than two freeze-thaw cycles were allowed.%采用凡纳滨对虾为研究对象,分别将过敏原提取物在-3,-20和-80℃的贮存条件下反复冻融1~5次,通过测定每次冻融后的蛋白浓度,过敏原免疫原性等探讨过敏原在不同温度循环下的变化,分析冻融循环对过敏原提取物活性的影响.结果表明,虾过敏原提取物在-80、-20、-3℃冻融循环5次时,蛋白浓度分别下降33.1%、30.0%和24.2%;在-80和-20℃冻融循环4

  19. Experimental study on soil moisture content of geogrid-reinforced clay under freezing-thawing cycle%冻融循环下格栅加筋粘土土体含水率试验研究

    Institute of Scientific and Technical Information of China (English)

    赵荣飞; 宓永宁; 姜广田; 金丹; 高微

    2012-01-01

    通过一系列室内含水率测试试验,研究了格栅加筋粘土在多次冻融循环条件下土体含水率的变动情况,探讨了填料压实度,加筋层数和初始含水率对冻融后土体含水率变动的影响规律.结果表明,压实度对土体ωi影响最大,低压实度时,△ω1为正值,高压实度时,△ω1为负值;加筋层数次之,ω1值随加筋层数增加而减小,在压实度高的土体中尤为显著;初始含水率影响最弱,仅在土体压实度较低时,较大的初始含水率会引起较大的△ω1值.%Through a series of lab-tests on moisture content of soil, the change of the moisture content of the grid-reinforced clay under freezing-thawing cycle is studied herein, and then the law of the impact from the compaction degree, the reinforcement layers and the initial moisture content of the soil on the moisture content of the soil under freezing-thawing cycles are discussed. The result shows that the compaction degree has the greatest impact on the soil body ωi, i. e. △ω1 is positive when the compaction degree is low and △ω1, is negative when the compaction degree is high; meanwhile, the number of the reinforcement layers only has a secondary impact on the soli body, i. e. the value of ω1, is decreased along with the increase of the number of the reinforcement layers, while it is significant in the highly compacted soil; moreover, the impact from the initial moisture content is much less and the greater value of △ω1 is to be only arisen from a greater initial moisture content when the compaction degree of soil is low.

  20. Combination Effects of Ultrasonication and Freeze-thawing on Physicochemical Properties of Sewage Sludge%超声-冻融联合技术对污泥理化性质的影响

    Institute of Scientific and Technical Information of China (English)

    丁园; 余小芬; 刘运坤; 史蓉蓉

    2014-01-01

    To enhance the cracking efficiency of sewage sludge,ultrasonic and freeze-thawing technologies were applied in sewage sludge sampled from secondary sedimentation tank of typical municipal sewage treatment plants in Nanchang.After taking ultrasonic density,ultrasonic time,freezing time and freezing temperature as factors,a three-factor two-level and one-factor two-level combined orthogonal experiment was designed to analyze the change of physicochemical properties of test sludge.Results:All control factors could not only promote the release of SCOD (soluble chemical oxygen demand),TN (total nitrogen)and TP (total phosphorus), but also reduce the content of heavy metals in the sludge. Moreover,the effect of ultrasonication was better than freeze-thawing. SCOD, TN and TP in the supernate were 5.70,5.34 and 1.94 times as much as the control respectively,and ωI (weight ion impulse)of heavy metal in the sludge reduced to 88% of control.%为提高污泥的破解效率,采用超声-冻融联合技术破解南昌市某污水处理厂二沉层污泥,选择声能密度、超声时间、冷冻时间、冷冻温度等4个因素为试验参数,设计3因素4水平和1因素2水平(34×12)的混合正交试验,分析在不同处理条件下污泥的理化性质。结果表明:超声和冻融不仅可促进污泥中可溶性化学需氧量、总氮和总磷的释放,还能有效降低污泥重金属含量,且超声的作用效果优于冻融。在最佳试验条件下污泥向上清液释放的 SCOD、TN 和 TP 分别是原来的5.70、5.34和1.94倍,污泥重金属权重离子冲量ωI 降至原来的88%。

  1. Antarctic Ice-Sheet Freeze-Thaw Detection Based on Improved Wavelet Transform%基于改进的小波变换的南极冰盖冻融探测

    Institute of Scientific and Technical Information of China (English)

    王星东; 熊章强; 李新武; 梁雷

    2013-01-01

    小波变换模型算法中的双高斯模型拟合干湿雪分类的最优阈值时,受初始值影响且典型样本区的选取比较费时,针对这些缺点提出了自动阈值分割的改进的小波变换算法,即用广义高斯模型自动拟合干湿雪分类的最优阈值.该算法继承和发展了冰盖冻融探测无需依赖于实测数据的优点,更好地实现了南极地区冰盖冻融监测系统建设的业务化运行目标.通过对改进前后的结果对比分析表明:改进后的方法与原方法相比,不仅提高了冰盖冻融探测方法的计算效率、实用性和可操作性,而且还在一定程度上提高了冰盖冻融探测的精度.%When the double-Gaussian model of the current wavelet-transform algorithm fits the optimal threshold value of the dry and wet snow classification,it is easily affected by the initial value and has the shortcomings of consuming more time in selecting the typical sample zones. According to the fact,this paper proposed the improved wavelet-transform algorithm for the automatic threshold segmentation,that is,generalized Gaussian model automatically fits the optimal wet and dry snow classification threshold. The algorithm inherits and develops the advantage of ice-sheet freeze-thaw detection, which does not rely on the measured data and achieves the goal of Antarctic ice-sheet monitoring system business more effectively. By comparing and analyzing of the two algorithms, we can see that the improved algorithm improves the computational efficiency, usability and operability in the ice-sheet freeze-thaw detection as well as the accuracy of detection to some extent.

  2. Post-stress rumination predicts HPA axis responses to repeated acute stress.

    Science.gov (United States)

    Gianferante, Danielle; Thoma, Myriam V; Hanlin, Luke; Chen, Xuejie; Breines, Juliana G; Zoccola, Peggy M; Rohleder, Nicolas

    2014-11-01

    Failure of the hypothalamus-pituitary-adrenal (HPA) axis to habituate to repeated stress exposure is related with adverse health outcomes, but our knowledge of predictors of non-habituation is limited. Rumination, defined as repetitive and unwanted past-centered negative thinking, is related with exaggerated HPA axis stress responses and poor health outcomes. The aim of this study was to test whether post-stress rumination was related with non-habituation of cortisol to repeated stress exposure. Twenty-seven participants (n=13 females) were exposed to the Trier Social Stress Test (TSST) twice on consecutive afternoons. Post-stress rumination was measured after the first TSST, and HPA axis responses were assessed by measuring salivary cortisol 1 min before, and 1, 10, 20, 60, and 120 min after both TSSTs. Stress exposure induced HPA axis activation on both days, and this activation showed habituation indicated by lower responses to the second TSST (F=3.7, p=0.015). Post-stress rumination after the first TSST was associated with greater cortisol reactivity after the initial stress test (r=0.45, pHPA axis responses. This finding implicates rumination as one possible mechanism mediating maladaptive stress response patterns, and it might also offer a pathway through which rumination might lead to negative health outcomes.

  3. An experimental study on freeze-thaw resistance of runway pavement concrete mixed with fly ash%掺粉煤灰机场道面混凝土抗冻融试验研究

    Institute of Scientific and Technical Information of China (English)

    徐洪坤; 蔡汉

    2012-01-01

    In view of the bad durability phenomenon of airport pavement concrete in cold region of our country, based on an airport project, experimental studies on the feezing and thawing durability of runway pavement concrete mixed with fly ash. The effects of water-cement ratio,fly ash amount ratio and fly air-entraining agent of concrete were investigated. With the fly ash and content increased,the freeze-thaw resistance has been improved .which is essential to design,maintenance and predict the remaining life of cement concrete of airport pavement.%针对我国高寒地区机场道面混凝土抗冻融性能不良的现象,结合某机场工程,对掺粉煤灰机场道面混凝土进行冻融试验,探讨了水胶比、粉煤灰掺量、引气减水剂掺量对粉煤灰混凝土抗冻融耐久性的影响.结果表明,随着粉煤灰及引气减水剂掺量的增加,机场混凝土道面的抗冻融性能会相应地提高.可对高寒地区机场水泥混凝土道面设计、维护及剩余寿命预测等问题提供参考.

  4. Experimental study of reinforced expansive soil slope in freeze-thaw environment%冻融环境下加筋膨胀土边坡力学模型试验与研究

    Institute of Scientific and Technical Information of China (English)

    徐丽丽; 张滨; 李兆宇; 吴志琴

    2014-01-01

    针对寒区膨胀土边坡冻胀问题,提出采用土工织物加筋处理技术。通过加筋处理及未处理两组室内冻土力学模型试验对比分析,研究在冻融循环作用下土工织物加筋膨胀土边坡的运行机制和效果。试验结果表明:①在土体冻结过程中,未处理的膨胀土边坡不均匀冻胀明显,土工织物加筋能有效抑制结构不均匀冻胀;②土工织物对水分的迁移有阻隔作用,加筋土处理模型的冻深略大于未处理模型;③碎石聚氨酯固脚具有一定的保温防冻胀作用。%For freeze injury of expansive soil slope , a technology using geotextile reinforced was handled .In accordance with the comparation and analysis of the treated and untreated frozen mechanical model test , the operation mechanism and effects of geotextile-reinforced expansive soil slope under freezing thaw cycle conditions are analyzed.Conclusion: ① In the process of soil freezing , untreated expansive soil slope uneven heaving obvious, geotextile-reinforced structure can effectively suppress uneven frost heave; ②Geotextile can block water migration in the soil , frozen deep of geotextile-reinforced model is slightly larger than the untreated models; ③Elastocoast can increase heat resistance;the Elastocoast protection-foundation has heat preservation effect .

  5. 冻融循环制备天然水溶性甲壳素及其特性%Preparation and characterization of natural water-soluble-chitin using freezing-thawing-cylic treatment

    Institute of Scientific and Technical Information of China (English)

    刘廷国; 查萍萍; 杨凌霄; 李斌

    2011-01-01

    Partially deacetylated chitin with different degree of deacetylation (DDA) were prepared by alkaline treatment under homogeneous conditions using freezing-thawing-cyclic treatment. The water solubility (WS) and DDA was determined and the influence of DDA, crystalline index (Xc) and the hydrogen bonding interaction were investigated by Fourier transform infared spectroscory (FT-IR),differential scanning calorimenty (DSC) and X-ray diffraction (XRD). There was a close relationship between solubility and crystal structure and crystallinity. The analysis shows that there was no essential difference between the water-soluble-chitin (WSC) and commercial chitosan, being a surely native water soluble chitin.%利用冻融循环处理制备甲壳素均相溶液,在温和的均相条件下脱乙酰化制备了不同脱乙酰度的天然水溶性甲壳素,并测定了样品的水溶性和脱乙酰度.利用X-射线衍射(XRD)、傅里叶红外光谱(FT-IR)和差示扫描量热法(DSC)研究了样品的结晶指数和氢键相互作用与样品水溶性和脱乙酰度之间的关系.结果表明:样品的水溶性与结晶结构和结晶度关系密切;样品与商品壳聚糖没有本质差异,是一种真正的天然水溶性甲壳素.

  6. Influence of repeated daily diving on decompression stress.

    Science.gov (United States)

    Zanchi, J; Ljubkovic, M; Denoble, P J; Dujic, Z; Ranapurwala, S; Pollock, N W

    2014-06-01

    Acclimatization (an adaptive change in response to repeated environmental exposure) to diving could reduce decompression stress. A decrease in post-dive circulating venous gas emboli (VGE or bubbles) would represent positive acclimatization. The purpose of this study was to determine whether four days of daily diving alter post-dive bubble grades. 16 male divers performed identical no-decompression air dives on 4 consecutive days to 18 meters of sea water for 47 min bottom times. VGE monitoring was performed with transthoracic echocardiography every 20 min for 120 min post-dive. Completion of identical daily dives resulted in progressively decreasing odds (or logit risk) of having relatively higher grade bubbles on consecutive days. The odds on Day 4 were half that of Day 1 (OR 0.50, 95% CI: 0.34, 0.73). The odds ratio for a >III bubble grade on Day 4 was 0.37 (95% CI: 0.20, 0.70) when compared to Day 1. The current study indicates that repetitive daily diving may reduce bubble formation, representing a positive (protective) acclimatization to diving. Further work is required to evaluate the impact of additional days of diving and multiple dive days and to determine if the effect is sufficient to alter the absolute risk of decompression sickness.

  7. Estrogen protects against the detrimental effects of repeated stress on glutamatergic transmission and cognition.

    Science.gov (United States)

    Wei, J; Yuen, E Y; Liu, W; Li, X; Zhong, P; Karatsoreos, I N; McEwen, B S; Yan, Z

    2014-05-01

    Converging evidence suggests that females and males show different responses to stress; however, little is known about the mechanism underlying the sexually dimorphic effects of stress. In this study, we found that young female rats exposed to 1 week of repeated restraint stress show no negative effects on temporal order recognition memory (TORM), a cognitive process controlled by the prefrontal cortex (PFC), which was contrary to the impairment in TORM observed in stressed males. Concomitantly, normal glutamatergic transmission and glutamate receptor surface expression in PFC pyramidal neurons were found in repeatedly stressed females, in contrast to the significant reduction seen in stressed males. The detrimental effects of repeated stress on TORM and glutamate receptors were unmasked in stressed females when estrogen receptors were inhibited or knocked down in PFC, and were prevented in stressed males with the administration of estradiol. Blocking aromatase, the enzyme for the biosynthesis of estrogen, revealed the stress-induced glutamatergic deficits and memory impairment in females, and the level of aromatase was significantly higher in the PFC of females than in males. These results suggest that estrogen protects against the detrimental effects of repeated stress on glutamatergic transmission and PFC-dependent cognition, which may underlie the stress resilience of females.

  8. REPEATED ACUTE STRESS INDUCED ALTERATIONS IN CARBOHYDRATE METABOLISM IN RAT

    Directory of Open Access Journals (Sweden)

    Nirupama R.

    2010-09-01

    Full Text Available Acute stress induced alterations in the activity levels of rate limiting enzymes and concentration of intermediates of different pathways of carbohydrate metabolism have been studied. Adult male Wistar rats were restrained (RS for 1 h and after an interval of 4 h they were subjected to forced swimming (FS exercise and appropriate controls were maintained. Five rats were killed before the commencement of the experiment (initial controls, 5 control and equal number of stressed rats were killed 2 h after RS and remaining 5 rats in each group were killed 4 h after FS. There was a significant increase in the adrenal 3β- hydroxy steroid dehydrogenase activity following RS, which showed further increase after FS compared to controls and thereby indicated stress response of rats. There was a significant increase in the blood glucose levels following RS which showed further increase and reached hyperglycemic condition after FS. The hyperglycemic condition due to stress was accompanied by significant increases in the activities of glutamate- pyruvate transaminase, glutamate- oxaloacetate transaminase, glucose -6- phosphatase and lactate dehydrogenase and significant decrease in the glucose -6- phosphate dehydrogenase and pyruvate dehydrogenase activities, whereas pyruvate kinase activity did not show any alteration compared to controls. Further, the glycogen and total protein contents of the liver were decreased whereas those of pyruvate and lactate showed significant increase compared to controls after RS as well as FS.The results put together indicate that acute stress induced hyperglycemia results due to increased gluconeogenesis and glycogenolysis without alteration in glycolysis. The study first time reveals that after first acute stress exposure, the subsequent stressful experience augments metabolic stress response leading to hyperglycemia. The results have relevance to human health as human beings are exposed to several stressors in a day and

  9. Habituation to repeated stress: get used to it.

    OpenAIRE

    Grissom, Nicola; Bhatnagar, Seema

    2008-01-01

    Habituation, as described in the landmark paper by Thompson and Spencer (1966), is a form of simple, nonassociative learning in which the magnitude of the response to a specific stimulus decreases with repeated exposure to that stimulus. A variety of neuronal and behavioral responses have been shown to be subject to habituation based on the criteria presented in that paper. It has been known for several decades that the magnitude of hypothalamic-pituitary-adrenal (HPA) activation occurring in...

  10. 冷冻-解冻循环及气体吹扫对质子交换膜燃料电池的影响%Effects of Freeze/Thaw Cycles and Gas Purging Method on Polymer Electrolyte Membrane Fuel Cells

    Institute of Scientific and Technical Information of China (English)

    张生生; 俞红梅; 朱红; 侯俊波; 衣宝廉; 明平文

    2006-01-01

    At subzero temperature, the startup capability and performance of polymer electrolyte membrane fuel cell (PEMFC) deteriorates markedly. The object of this work is to study the degradation mechanism of key components of PEMFC-membrane-electrode assembly (MEA) and seek feasible measures to avoid degradation. The effect of freeze/thaw cycles on the structure of MEA is investigated based on porosity and SEM measurement. The performance of a single cell was also tested before and after repetitious freeze/thaw cycles. The experimental results indicated that the performance of a PEMFC decreased along with the total operating time as well as the pore size distribution shifting and micro configuration changing. However, when the redundant water had been removed by gas purging, the performance of the PEMFC stack was almost resumed when it experienced again the same subzero temperature test. These results show that it is necessary to remove the water in PEMFCs to maintain stable performance under subzero temperature and gas purging is proved to be the effective operation.

  11. Mechanical Alterations Associated with Repeated Treadmill Sprinting under Heat Stress

    Science.gov (United States)

    Brocherie, Franck; Morin, Jean-Benoit; Racinais, Sébastien; Millet, Grégoire P.; Périard, Julien D.

    2017-01-01

    Purpose Examine the mechanical alterations associated with repeated treadmill sprinting performed in HOT (38°C) and CON (25°C) conditions. Methods Eleven recreationally active males performed a 30-min warm-up followed by three sets of five 5-s sprints with 25-s recovery and 3-min between sets in each environment. Constant-velocity running for 1-min at 10 and 20 km.h-1 was also performed prior to and following sprinting. Results Mean skin (37.2±0.7 vs. 32.7±0.8°C; P<0.001) and core (38.9±0.2 vs. 38.8±0.3°C; P<0.05) temperatures, together with thermal comfort (P<0.001) were higher following repeated sprinting in HOT vs. CON. Step frequency and vertical stiffness were lower (-2.6±1.6% and -5.5±5.5%; both P<0.001) and contact time (+3.2±2.4%; P<0.01) higher in HOT for the mean of sets 1–3 compared to CON. Running distance per sprint decreased from set 1 to 3 (-7.0±6.4%; P<0.001), with a tendency for shorter distance covered in HOT vs. CON (-2.7±3.4%; P = 0.06). Mean vertical (-2.6±5.5%; P<0.01), horizontal (-9.1±4.4%; P<0.001) and resultant ground reaction forces (-3.0±2.8%; P<0.01) along with vertical stiffness (-12.9±2.3%; P<0.001) and leg stiffness (-8.4±2.7%; P<0.01) decreased from set 1 to 3, independently of conditions. Propulsive power decreased from set 1 to 3 (-16.9±2.4%; P<0.001), with lower propulsive power values in set 2 (-6.6%; P<0.05) in HOT vs. CON. No changes in constant-velocity running patterns occurred between conditions, or from pre-to-post repeated-sprint exercise. Conclusions Thermal strain alters step frequency and vertical stiffness during repeated sprinting; however without exacerbating mechanical alterations. The absence of changes in constant-velocity running patterns suggests a strong link between fatigue-induced velocity decrements during sprinting and mechanical alterations. PMID:28146582

  12. Effect of Ostrich Egg Yolk on Boar Spermatozoa Quality after Freezing-thawing%鸵鸟卵黄对猪精子冷冻后质量的影响

    Institute of Scientific and Technical Information of China (English)

    马玲琴; 贾永宏; 马国际; 袁建民

    2012-01-01

    为了提高猪冷冻精液品质和精子抵抗低温打击的能力,本研究以5%、10%、15%、20%和25%等不同浓度的鸵鸟卵黄作为冷冻保护剂,以20%的鸡蛋卵黄和20%的鸽蛋卵黄为对照,将冷冻-解冻后的精子活率、质膜完整率和顶体完整率作为评价指标,分析鸵鸟卵黄对猪精子的抗冷冻保护作用。结果表明:稀释液中添加20%鸽蛋卵黄时,精子活率、顶体完整率和质膜完整性分别为52.11%、55.62%和54.94%,显著高于其他组(P〈0.05)。虽然稀释液中添加15%鸵鸟卵黄时,冷冻-解冻后精子活率、顶体完整率和质膜完整率显著高于5%、10%、20%和25%鸵鸟卵黄组,但仍然显著低于稀释液中添加20%鸽蛋卵黄处理组。本研究表明,鸵鸟卵黄在冷冻过程中对猪精子具有一定的保护作用,但相对于鸽子蛋和鸡蛋卵黄效果并不理想。%In order to improve the frozen semen quality and sperm resistance to cold shock,the different concentrations of 5%,10%,15%,20% and 25% ostrich egg yolk were added in extender as cryoprotectants,and 20% egg yolk and 20% pigeon egg yolk were control.The cryoprotective effects of ostrich egg yolk on the boar spermatozoa were analyzed and spermatozoa motility,acrosome integrity and membrane integrity after freezing-thawing were evaluated.The results indicated that the sperm motility,acrosome integrity,membrane integrity were 52.11%,55.62% and 54.94% respectively while the extender was supplied with 20% pigeon egg yolk,which was higher than that of other groups(P0.05).Although sperm motility,acrosome integrity and membrane integrity in the extender supplemented with 15% ostrich egg yolk were significantly higher than that of 5%,10%,20% and 25% ostrich egg yolk groups,they were significantly lower than that of 20% pigeon egg yolk group.According to our study,the ostrich egg yolk could protect the boar spermatozoa during the frozen-thawed,but is not as effective as pigeon egg yolk and egg

  13. 鸵鸟卵黄低密度脂蛋白对猪精子冻后品质的影响%Effects of Ostrich Egg Yolk LDL on Boar Spermatozoa Quality Following Freezing-Thawing

    Institute of Scientific and Technical Information of China (English)

    侯丽鹏; 石芳萍; 卜书海; 李青旺; 胡建宏

    2012-01-01

    在家畜精液冷冻中,卵黄被广泛应用,且其中的低密度脂蛋白(LDL)对精子起主要保护作用.本研究利用含6%、7%、8%和9%鸵鸟卵黄LDL配制的稀释液制作猪细管冷冻精液,分析鸵鸟卵黄LDL对冷冻-解冻后猪精子质量参数的影响.结果表明:在含不同浓度鸵鸟卵黄LDL的稀释液中,8%LDL的稀释液冷冻效果最好,冻后精子活率平均可达52.13%,显著高于其他组(P<0.05);精子顶体完整率平均为58.33%,质膜完整率为72.38%,与其他处理组相比差异显著(P<0.05).但与鸡蛋卵黄LDL和鸽子蛋卵黄LDL处理组相比,鸵鸟卵黄LDL处理组冷冻-解冻后猪精子质量参数相对较低.本研究表明,虽然鸵鸟卵黄LDL在冷冻过程中对猪精子具有一定的保护作用,但相对于鸽子蛋和鸡蛋卵黄LDL效果并不理想.%Egg yolk has been widely used in boar frozen semen dilution and the protective action of yolk is largely attributed to the low-density lipoprotein (LDL). In this study, LDL of ostrich egg yolk was added at concentrations of 6-9% to the extenders used to freeze boar semen and its effects on the quality of frozen-thawed sperm were assessed. The results indicated that supplementation of LDL at 8% LDL resulted in significantly higher spermatozoa motility (52.13%) than that of other groups(P< 0.05), and there was higher acrosome integrity (58.33%) and membrane integrity(72.38%) (P < 0.05) compared with other treatment groups. But the quality parameters of boar sperm after freezing-thawing following the LDL of ostrich egg yolk is lower compared with the extender containing LDL of egg yolk and pigeon yo!k. According to all measured parameters, the extender containing 8% LDL of ostrich egg yolk showed beneficial cryoprotective effects on frozen-thawed boar spermatozoa. But its effect is not best compared with 9% egg yolk LDL and 8% pigeon egg yolk LDL.

  14. 基于COUPMODEL模型的冻融土壤水热耦合模拟研究%The Water-thermal Characteristics of Frozen Soil Under Freeze-thaw Based on CoupModel

    Institute of Scientific and Technical Information of China (English)

    胡国杰; 赵林; 李韧; 吴通华; 肖瑶; 焦克勤; 乔永平; 焦永亮

    2013-01-01

    利用COUPMODEL模型,对唐古拉研究区活动层土壤的水热特征进行模拟,与观测结果进行对比发现,在活动层土壤温度方面,COUPMODEL模型的模拟结果R2>0.94,其平均值为0.98,均方根误差较小,模拟效果较理想;在活动层水分特征方面,模拟结果存在一定偏差,R2介于0.88~0.93之间,平均值0.90,均方根误差平均值4.24,基本反映了高海拔多年冻土区活动层水热变化;在土壤热通量方面,0~20 cm土壤热通量的模拟结果与观测值基本一致;模型模拟的冻结深度在3m左右,接近观测值,COUPMODEL模型可用于多年冻土区活动层土壤水热变化规律研究.%To study the water-heat characteristics of soil in the active layer in high altitude permafrost regions and to examine the interaction between soil and moisture under freeze-thaw cycles, a physical process by the CoupModel was used to simulate the soil temperature and moisture in the active layer, using the meteorological, the soil thermal and the moisture data on different depths in the active layer at the Tanggula test site. Comparisons between simulated and monitored data in situ showed that: 1) for soil temperature in the active layer, the simulated results fit well with the monitored, and the determination coefficient (R2) is more than 0.94 with the mean value of 0.98 while mean square deviation is relatively small, implying the CoupModel could successfully simulate the soil temperatures. 2) For soil moisture, results generally reflect water content variation in the active layer with R2 ranging from 0.88 to 0.93, the mean is 0.90 and the mean square deviation is 4.24, indicating a bit poor accuracy compared to soil temperature. 3) As to the heat flux of soil within the depth of 0-20 cm, results simulated is consistent with the monitored. The simulation accuracy is improved with depths, which may be related to the depth from the natural ground surface. The frozen depth is about 3.0 m, which is

  15. Repeated stressful experiences differently affect brain dopamine receptor subtypes

    Energy Technology Data Exchange (ETDEWEB)

    Puglisi-Allegra, S.; Cabib, S. (Istituto di Psicobiologia e Psicofarmacologia (CNR), Roma (Italy)); Kempf, E.; Schleef, C. (Centre de Neurochimi, Strasbourg (Italy))

    1991-01-01

    The binding of tritiated spiperone (D2 antagonist) and tritiated SCH 23390 (D1 antagonist), in vivo, was investigated in the caudatus putamen (CP) and nucleus accumbens septi (NAS) of mice submitted to ten daily restraint stress sessions. Mice sacrificed 24 hr after the last stressful experience presented a 64% decrease of D2 receptor density (Bmax) but no changes in D1 receptor density in the NAS. In the CP a much smaller (11%) reduction of D2 receptor density was accompanied by a 10% increase of D1 receptors. These results show that the two types of dopamine (DA) receptors adapt in different or even opposite ways to environmental pressure, leading to imbalance between them.

  16. Preparation of Freeze-thaw Stability and Physical-themical Properties of One-step Combined Modifications of Crosslink-phosphorylated Maize Starch%一步法制备冻融稳定型复合变性淀粉及其性质研究

    Institute of Scientific and Technical Information of China (English)

    荆晶; 程建军

    2011-01-01

    One-step combined modifications of crosslink-phosphorylated starch was prepared with maize starch,sodium trimetaphosphate and sodium tripolyphosphat.Using Box-Behnken design and response surface analysis method to study on the major factors,the best technologcial conditions could be obtained: the reaction temperature 130.62 ℃,the reaction time 126.71 min,the pH 9.78,the starch mixture with opproximately 23.85% moisture content.The corresponding value of syneresis rate was 11.76%.The freeze-thaw stability of native,crosslinked and combined modified starch pastes for four cycles were studied.The combined modified starch was provided the highest freeze-thaw stability,which was 15.86%.And this type of combined modified starch could be used to prepare food products with good freeze-thaw stability.The pasting temperature and the transparency of which were 35.3 ℃ and 79.5%,with 0.18% phosphor content.%以玉米淀粉为原料,三偏磷酸钠、三聚磷酸钠为交联酯化剂,通过一步法制备交联酯化复合变性淀粉。采用Box-Behnken优化设计对制备工艺进行优化,最佳工艺条件为:反应温度130.62℃,反应时间126.71 min,pH 9.78,含水量23.85%,制得复合变性淀粉析水率为11.76%。经4次冻融循环后复合变性淀粉析水率仅为15.86%,具有良好的冻融稳定性。冻融稳定型复合变性淀粉的糊化开始温度降低至35.3℃、透光度增加至79.5%、磷含量为0.18%、抗凝沉性良好。这些特性使其可以改善冷冻食品的品质,在速冻食品中得以广泛应用。

  17. The effects of a freeze-thaw cycle and pre-analytical storage temperature on the stability of insulin-like growth factor-I and pro-collagen type III N-terminal propeptide concentrations: Implications for the detection of growth hormone misuse in athletes.

    Science.gov (United States)

    Guha, Nishan; Erotokritou-Mulligan, Ioulietta; Bartlett, Christiaan; Cowan, David A; Bassett, E Eryl; Stow, Michael; Sönksen, Peter H; Holt, Richard I G

    2012-06-01

    A method based on two serum biomarkers - insulin-like growth factor-I (IGF-I) and pro-collagen type III N-terminal propeptide (P-III-NP) - has been devised to detect growth hormone (GH) misuse. The aims of this study were to determine the stability of IGF-I and P-III-NP concentrations in serum stored at -20°C and to establish the effects of one freeze-thaw cycle. Blood was collected from 20 healthy volunteers. Serum aliquots were analyzed after storage for one day at 4°C and one day, one week, five weeks, and three months at -20°C. IGF-I and P-III-NP results were combined to calculate a GH-2000 discriminant function score for each volunteer. Inter-assay precision was determined by analysing one quality control sample at each time-point. A single freeze-thaw cycle, storage of serum at 4°C for one day and at -20°C for up to three months had no significant effect on IGF-I or P-III-NP concentration. Intra-sample variability for IGF-I was 6.8% (Immunotech assay) and 12.9% (DSL assay). Intra-sample variability for P-III-NP was 10.9% (Cisbio assay) and 13.7% (Orion assay). When IGF-I and P-III-NP results were combined, intra-sample variability of the GH-2000 score expressed as a standard deviation varied between 0.31 and 0.50 depending on the assay combination used. Variability in IGF-I and P--III-NP results of stored samples is largely determined by the characteristics of the assays. A single freeze-thaw cycle, storage of serum at 4°C for one day or at -20°C for up to 3 months does not result in a significant change in GH-2000 score.

  18. Over-representation of repeats in stress response genes: a strategy to increase versatility under stressful conditions?

    Science.gov (United States)

    Rocha, Eduardo P C; Matic, Ivan; Taddei, François

    2002-05-01

    The survival of individual organisms facing stress is enhanced by the induction of a set of changes. As the intensity, duration and nature of stress is highly variable, the optimal response to stress may be unpredictable. To face such an uncertain future, it may be advantageous for a clonal population to increase its phenotypic heterogeneity (bet-hedging), ensuring that at least a subset of cells would survive the current stress. With current techniques, assessing the extent of this variability experimentally remains a challenge. Here, we use a bioinformatic approach to compare stress response genes with the rest of the genome for the presence of various kinds of repeated sequences, elements known to increase variability during the transfer of genetic information (i.e. during replication, but also during gene expression). We investigated the potential for illegitimate and homologous recombination of 296 Escherichia coli genes related to repair, recombination and physiological adaptations to different stresses. Although long repeats capable of engaging in homologous recombination are almost absent in stress response genes, we observed a significant high number of short close repeats capable of inducing phenotypic variability by slipped-mispair during DNA, RNA or protein synthesis.

  19. Exaggerated phosphorylation of brain tau protein in CRH KO mice exposed to repeated immobilization stress.

    Science.gov (United States)

    Kvetnansky, Richard; Novak, Petr; Vargovic, Peter; Lejavova, Katarina; Horvathova, Lubica; Ondicova, Katarina; Manz, George; Filipcik, Peter; Novak, Michal; Mravec, Boris

    2016-07-01

    Neuroendocrine and behavioral stress responses are orchestrated by corticotropin-releasing hormone (CRH) and norepinephrine (NE) synthesizing neurons. Recent findings indicate that stress may promote development of neurofibrillary pathology in Alzheimer's disease. Therefore, we investigated relationships among stress, tau protein phosphorylation, and brain NE using wild-type (WT) and CRH-knockout (CRH KO) mice. We assessed expression of phosphorylated tau (p-tau) at the PHF-1 epitope and NE concentrations in the locus coeruleus (LC), A1/C1 and A2/C2 catecholaminergic cell groups, hippocampus, amygdala, nucleus basalis magnocellularis, and frontal cortex of unstressed, singly stressed or repeatedly stressed mice. Moreover, gene expression and protein levels of tyrosine hydroxylase (TH) and CRH receptor mRNA were determined in the LC. Plasma corticosterone levels were also measured. Exposure to a single stress increases tau phosphorylation throughout the brain in WT mice when compared to singly stressed CRH KO animals. In contrast, repeatedly stressed CRH KO mice showed exaggerated tau phosphorylation relative to WT controls. We also observed differences in extent of tau phosphorylation between investigated structures, e.g. the LC and hippocampus. Moreover, CRH deficiency leads to different responses to stress in gene expression of TH, NE concentrations, CRH receptor mRNA, and plasma corticosterone levels. Our data indicate that CRH effects on tau phosphorylation are dependent on whether stress is single or repeated, and differs between brain regions. Our findings indicate that CRH attenuates mechanisms responsible for development of stress-induced tau neuropathology, particularly in conditions of chronic stress. However, the involvement of central catecholaminergic neurons in these mechanisms remains unclear and is in need of further investigation.

  20. Myricetin Attenuates Depressant-Like Behavior in Mice Subjected to Repeated Restraint Stress

    Directory of Open Access Journals (Sweden)

    Zegang Ma

    2015-11-01

    Full Text Available Increasing evidence has shown that oxidative stress may be implicated in chronic stress-induced depression. Several flavonoids with anti-oxidative effects have been proved to be anti-depressive. Myricetin is a well-defined flavonoid with the anti-oxidative, anti-inflammatory, anti-apoptotic, and neuroprotective properties. The aim of the present study is to investigate the possible effects of chronic administration of myricetin on depressant-like behaviors in mice subjected to repeated restraint (4 h/day for 21 days. Our results showed that myricetin administration specifically reduced the immobility time in mice exposed to chronic stress, as tested in both forced swimming test and tail suspension test. Myricetin treatment improved activities of glutathione peroxidase (GSH-PX in the hippocampus of stressed mice. In addition, myricetin treatment decreased plasma corticosterone levels of those mice subjected to repeated restraint stress. The effects of myricetin on the brain-derived neurotrophic factor (BDNF levels in hippocampus were also investigated. The results revealed that myricetin normalized the decreased BDNF levels in mice subjected to repeated restraint stress. These findings provided more evidence that chronic administration of myricetin improves helpless behaviors. The protective effects of myricetin might be partially mediated by an influence on BDNF levels and might be attributed to myricetin-mediated anti-oxidative stress in the hippocampus.

  1. Repeated predictable stress causes resilience against colitis-induced behavioral changes in mice

    Science.gov (United States)

    Hassan, Ahmed M.; Jain, Piyush; Reichmann, Florian; Mayerhofer, Raphaela; Farzi, Aitak; Schuligoi, Rufina; Holzer, Peter

    2014-01-01

    Inflammatory bowel disease is associated with an increased risk of mental disorders and can be exacerbated by stress. In this study which was performed with male 10-week old C57Bl/6N mice, we used dextran sulfate sodium (DSS)-induced colitis to evaluate behavioral changes caused by intestinal inflammation, to assess the interaction between repeated psychological stress (water avoidance stress, WAS) and colitis in modifying behavior, and to analyze neurochemical correlates of this interaction. A 7-day treatment with DSS (2% in drinking water) decreased locomotion and enhanced anxiety-like behavior in the open field test and reduced social interaction. Repeated exposure to WAS for 7 days had little influence on behavior but prevented the DSS-induced behavioral disturbances in the open field and SI tests. In contrast, repeated WAS did not modify colon length, colonic myeloperoxidase content and circulating proinflammatory cytokines, parameters used to assess colitis severity. DSS-induced colitis was associated with an increase in circulating neuropeptide Y (NPY), a rise in the hypothalamic expression of cyclooxygenase-2 mRNA and a decrease in the hippocampal expression of NPY mRNA, brain-derived neurotrophic factor mRNA and mineralocorticoid receptor mRNA. Repeated WAS significantly decreased the relative expression of corticotropin-releasing factor mRNA in the hippocampus. The effect of repeated WAS to blunt the DSS-evoked behavioral disturbances was associated with a rise of circulating corticosterone and an increase in the expression of hypothalamic NPY mRNA. These results show that experimental colitis leads to a particular range of behavioral alterations which can be prevented by repeated WAS, a model of predictable chronic stress, while the severity of colitis remains unabated. We conclude that the mechanisms underlying the resilience effect of repeated WAS involves hypothalamic NPY and the hypothalamic-pituitary-adrenal axis. PMID:25414650

  2. Repeated Predictable Stress Causes Resilience against Colitis-Induced Behavioral Changes in Mice

    Directory of Open Access Journals (Sweden)

    Ahmed M Hassan

    2014-11-01

    Full Text Available Inflammatory bowel disease is associated with an increased risk of mental disorders and can be exacerbated by stress. In this study which was performed with male 10-week old C57Bl/6N mice, we used dextran sulfate sodium (DSS-induced colitis to evaluate behavioral changes caused by intestinal inflammation, to assess the interaction between repeated psychological stress (water avoidance stress, WAS and colitis in modifying behavior, and to analyze neurochemical correlates of this interaction. A 7-day treatment with DSS (2 % in drinking water decreased locomotion and enhanced anxiety-like behavior in the open field test and reduced social interaction. Repeated exposure to WAS for 7 days had little influence on behavior but prevented the DSS-induced behavioral disturbances in the open field and social interaction tests. In contrast, repeated WAS did not modify colon length, colonic myeloperoxidase content and circulating proinflammatory cytokines, parameters used to assess colitis severity. DSS-induced colitis was associated with an increase in circulating neuropeptide Y (NPY, a rise in the hypothalamic expression of cyclooxygenase-2 mRNA and a decrease in the hippocampal expression of NPY mRNA, brain-derived neurotrophic factor mRNA and mineralocorticoid receptor mRNA. Repeated WAS significantly decreased the relative expression of corticotropin-releasing factor mRNA in the hippocampus. The effect of repeated WAS to blunt the DSS-evoked behavioral disturbances was associated with a rise of circulating corticosterone and an increase in the expression of hypothalamic NPY mRNA. These results show that experimental colitis leads to a particular range of behavioral alterations which can be prevented by repeated WAS, a model of predictable chronic stress, while the severity of colitis remains unabated. We conclude that the mechanisms underlying the resilience effect of repeated WAS involves hypothalamic NPY and the hypothalamic-pituitary-adrenal axis.

  3. Repeated stress increases catalytic TrkB mRNA in rat hippocampus.

    Science.gov (United States)

    Nibuya, M; Takahashi, M; Russell, D S; Duman, R S

    1999-05-28

    Northern blot analysis was utilized to distinguish between catalytic and truncated TrkB mRNA on the basis of transcript size. Repeated (10 days), but not acute, immobilization stress significantly increased levels of catalytic TrkB mRNA, but did not influence expression of truncated TrkB transcripts in rat hippocampus. Exposure to another paradigm, a combination of different, unpredictable stressors, also increased levels of catalytic, but not truncated, TrkB mRNA. In situ hybridization analysis demonstrated that chronic stress up-regulated TrkB mRNA in CA1 and CA3 pyramidal and dentate gyrus granule cells layers of hippocampus. As previously reported, both acute and chronic immobilization stress decreased expression of BDNF mRNA, suggesting that up-regulation of catalytic TrkB mRNA may be a compensatory adaptation to repeated stress.

  4. Changes in Liver Proteome Expression of Senegalese Sole (Solea senegalensis) in Response to Repeated Handling Stress

    DEFF Research Database (Denmark)

    Cordeiro, O. D.; Silva, Tomé Santos; Alves, R. N.

    2012-01-01

    the detection of 287 spots significantly affected by repeated handling stress (Wilcoxon–Mann–Whitney U test, p stress seems to have affected protein synthesis, folding and turnover (40S ribosomal protein S12...... hormone metabolism (3-oxo-5-β-steroid 4-dehydrogenase), and purine salvage (hypoxanthine phosphoribosyltransferase). Further characterization is required to fully assess the potential of these markers for the monitoring of fish stress response to chronic stressors of aquaculture environment.......The Senegalese sole, a high-value flatfish, is a good candidate for aquaculture production. Nevertheless, there are still issues regarding this species’ sensitivity to stress in captivity. We aimed to characterize the hepatic proteome expression for this species in response to repeated handling...

  5. 聚丙烯纤维和高效减水剂双掺对铁尾矿粉泡沫混凝土抗冻性能的影响∗%The Study of Effects on the Resistance to Freezing-thawing of Foam Concrete with Iron Tailings Mixed with Polypropylene Fiber and Polycarboxylate Superplasticizer

    Institute of Scientific and Technical Information of China (English)

    肖力光; 李杨; 张士停

    2015-01-01

    Foam concrete with iron tailings is prepared by iron tailings, cement, fly ash, mineral admixtures with high performance, foaming agent, polypropylene fiber, polycarboxylate superplasticizer, et al. In this study, the influences on the resistance to freezing-thawing of foam concrete with iron tailings mixed with polypropylene fiber and poly-carboxylate superplasticizer were investigated, and its microstructure was observed. The results show that the resist-ance to freezing-thawing of foam concrete with iron tailings is greatly increased by adding polypropylene fiber and polycarboxylate superplasticizer, and the microstructure of pore in foam concrete is improved obviously.%铁尾矿粉泡沫混凝土由铁尾矿粉、水泥、粉煤灰、高性能矿物掺合料、泡沫剂、聚丙烯纤维、聚羧酸系高效减水剂等制成。本实验研究了聚丙烯纤维和聚羧酸系高效减水剂双掺对铁尾矿粉泡沫混凝土抗冻性能的影响及其微观结构,实验结果表明,聚丙烯纤维和聚羧酸系高效减水剂双掺大大提高了铁尾矿粉泡沫的抗冻性能,使铁尾矿粉泡沫混凝土的孔微观结构有了明显的改善。

  6. Exogenous daytime melatonin modulates response of adolescent mice in a repeated unpredictable stress paradigm.

    Science.gov (United States)

    Onaolapo, Adejoke Yetunde; Adebayo, Ajibola Nurudeen; Onaolapo, Olakunle James

    2017-02-01

    The immediate and short-term behavioural and physiological implications of exposure to stressful scenarios in the adolescent period are largely unknown; however, increases in occurrence of stress-related physiological and psychological disorders during puberty highlight the need to study substances that may modulate stress reactivity during a crucial stage of maturation. Seven groups of mice (12-15 g each) were administered distilled water (DW) (non-stressed and stressed controls), sertraline (10 mg/kg), diazepam (2 mg/kg) or one of three doses of melatonin (5, 10 and 15 mg/kg). Mice were exposed to 30 min of chronic mild stress (25 min of cage shaking, cage tilting, handling and 5 min of forced swimming in tepid warm water at 25 °C, in a random order) after administration of DW or drugs, daily for 21 days. Behavioural assessments were conducted on day 1 and day 21 (after which mice were sacrificed, blood taken for estimation of corticosterone levels and brain homogenates used for estimation of antioxidant activities). Administration of melatonin resulted in an increase in horizontal locomotion and self-grooming, while rearing showed a time-dependent increase, compared to non-stress and stress controls. Working memory improved with increasing doses of melatonin (compared to controls and diazepam); in comparison to setraline however, working memory decreased. A dose-related anxiolytic effect is seen when melatonin is compared to non-stressed and stressed controls. Melatonin administration reduced the systemic/oxidant response to repeated stress. Administration of melatonin in repeatedly stressed adolescent mice was associated with improved central excitation, enhancement of working memory, anxiolysis and reduced systemic response to stress.

  7. Physiological responses to repeated stress in individuals with high and low trait resilience.

    Science.gov (United States)

    Lü, Wei; Wang, Zhenhong; You, Xuqun

    2016-10-01

    This study examined individual differences in trait resilience in physiological recovery from, and physiological habituation to, repeated stress (i.e. public speaking). Eighty-two college students were categorized as either high (n=40) or low (n=42) on trait resilience, based on the scores of the Connor-Davidson Resilience Scale (CD-RISC). Subjective and physiological data were collected from participants across seven laboratory stages: baseline, stress anticipation 1, stress 1, post-stress 1, stress anticipation 2, stress 2, and post-stress 2. Results indicated that high-trait-resilient participants exhibited more complete heart rate (HR), systolic and diastolic blood pressure (SBP, DBP) recovery from the first and second stress anticipation exposures as compared to low-trait-resilient participants. High-trait-resilient participants demonstrated higher resting respiratory sinus arrhythmia (RSA) coupled with more complete RSA recovery from the first and second stress anticipation exposures as compared to their low-trait-resilient counterparts. Moreover, high-trait-resilient participants exhibited pronounced SBP and DBP habituation across two successive stress anticipation exposures, with greater decreases in SBP and DBP reactivity to recurrent stress anticipation as compared to the low-trait-resilient participants. These findings suggest an adaptive physiological response pattern to recurrent stress in high-trait-resilient individuals. Copyright © 2016 Elsevier B.V. All rights reserved.

  8. Classification of chicken breasts with different freezing-thawing cycles by impedance properties and artificial neural networks%基于阻抗特性和神经网络的鸡胸肉冻融次数鉴别方法

    Institute of Scientific and Technical Information of China (English)

    李伟明; 王鹏; 陈天浩; 徐幸莲; 周光宏

    2014-01-01

    为了探究利用肉的介电特性检测冷冻肉品质的可能性,研究了新鲜鸡胸肉和不同冻融次数的鸡胸肉的品质以及阻抗的幅值和相位角变化状况。在0.05~200 kHz频率范围内,选择了16个不同的频率点进行阻抗特性分析。试验结果表明:鸡胸肉阻抗的幅值会随着频率上升而下降,相位角则相反。冷鲜肉与冷冻肉高频段相位角相差一个数量级,低频段阻抗的幅值差异也极显著(P<0.01)。多次冻融处理后,解冻损失、丙二醛含量上升显著(P<0.05),pH值变化不明显(P>0.05)。反复冻融后低频段阻抗幅值降低(P<0.05),大于50 kHz时,相位角有增大的趋势(P<0.05),这与正常1次冻结-解冻肉的相位角变化趋势相反。利用径向基函数(radial basis function, RBF)神经网络提取阻抗和幅值信息建立判别模型可以对不同冻融次数的肉进行较为准确的分类。研究结果表明,阻抗测量作为一种冷冻肉快速无损检测方法具有很大的发展潜力。%Electric impedance properties of biological tissue closely relate with their tissue structure. A few published investigations have shown that electric impedance has a rapid detection capability to meat quality. To explore the impedance detection ability for frozen-thawed meat, electric impedance magnitude and phase properties of unfrozen and frozen-thawed chicken breasts subjected to different thawing times were studied. The maximum freezing-thawing circle was three times. Sixteen different frequencies from 50 Hz to 200 kHz and quality parameters like thawing loss, cooking loss, pH value, and TBARS (Thiobarbituric acid reactive substances) of 20 samples of each group were investigated. The impedance of the samples was measured by an LCR electronic bridge at the voltage of 3 V. Copper needle electrodes with a length up to 15 mm and a distance of 15 mm between two electrodes were used. The

  9. The estrous cycle of the ewe is resistant to disruption by repeated, acute psychosocial stress.

    Science.gov (United States)

    Wagenmaker, Elizabeth R; Breen, Kellie M; Oakley, Amy E; Tilbrook, Alan J; Karsch, Fred J

    2010-06-01

    Five experiments were conducted to test the hypothesis that psychosocial stress interferes with the estrous cycle of sheep. In experiment 1, ewes were repeatedly isolated during the follicular phase. Timing, amplitude, and duration of the preovulatory luteinizing hormone (LH) surge were not affected. In experiment 2, follicular-phase ewes were subjected twice to a "layered stress" paradigm consisting of sequential, hourly application of isolation, restraint, blindfold, and predator cues. This reduced the LH pulse amplitude but did not affect the LH surge. In experiment 3, different acute stressors were given sequentially within the follicular phase: food denial plus unfamiliar noises and forced exercise, layered stress, exercise around midnight, and transportation. This, too, did not affect the LH surge. In experiment 4, variable acute psychosocial stress was given every 1-2 days for two entire estrous cycles; this did not disrupt any parameter of the cycle monitored. Lastly, experiment 5 examined whether the psychosocial stress paradigms of experiment 4 would disrupt the cycle and estrous behavior if sheep were metabolically stressed by chronic food restriction. Thirty percent of the food-restricted ewes exhibited deterioration of estrous cycle parameters followed by cessation of cycles and failure to express estrous behavior. However, disruption was not more evident in ewes that also encountered psychosocial stress. Collectively, these findings indicate the estrous cycle of sheep is remarkably resistant to disruption by acute bouts of psychosocial stress applied intermittently during either a single follicular phase or repeatedly over two estrous cycles.

  10. Heat stress impairs repeated jump ability after competitive elite soccer games

    DEFF Research Database (Denmark)

    Mohr, Magni; Krustrup, Peter

    2013-01-01

    ABSTRACT:: The present study examined the effect of environmental heat stress on repeated jump performance after elite competitive soccer games. Male elite soccer players (n=19) from two Scandinavian teams participated (age; 26.7±1.0 yrs, height; 181.7±1.1 cm, body mass; 75.8±1.0 kg). The players...

  11. Repeating seismicity in the shallow crust modulated by transient stress perturbations

    Science.gov (United States)

    Frank, William B.; Shapiro, Nikolaï M.; Husker, Allen L.; Kostoglodov, Vladimir; Campillo, Michel

    2016-09-01

    Recent studies have reported seismic phenomena that are modulated by small stress perturbations (∼10 kPa), revealing their critically stressed nature. Such observations have been principally limited to plate interfaces with their occurrence linked to high fluid pore-pressure. In this study, we report observations of nine repeating seismic sources in the shallow crust in Guerrero, Mexico that emit events at rates comparable to other seismic phenomena in low stress environments. Testing their susceptibility to small stress perturbations, we find that all nine sources appear to be modulated by mining activity, tides, and a large slow slip event (Mw 7.5). Our results suggest that the fault conditions necessary for low effective stress seismicity can occur away from plate interfaces.

  12. Facilitation of hypothalamic-pituitary-adrenal responses to novel stress following repeated social stress using the resident/intruder paradigm.

    Science.gov (United States)

    Bhatnagar, Seema; Vining, Courtenay

    2003-01-01

    Our goal in these studies was to characterize some specific aspects of hypothalamic-pituitary-adrenal (HPA) activity in rats exposed to repeated social stress. We used a modification of the resident/intruder paradigm in which male intruder rats were subjected to defeat and then separated from the resident by an enclosure for a total of 30 min on Day 1. On Days 2-7, intruder rats were exposed to different resident rats every day through a wire mesh enclosure for 30 min in order to minimize injurious physical contact between the two rats. The intruder rats gained significantly less weight than controls over the 7-day period of stress though basal corticosterone levels and adrenal and thymus weights were not significantly different between the two groups. On Day 8, repeatedly stressed rats exhibited facilitation of HPA responses to novel restraint compared to controls but no differences in negative feedback sensitivity to dexamethasone (0.05 or 0.2 mg/kg) were observed. Thus, the HPA axis of socially stressed rats remains responsive to a stimulus that has never been encountered. Using this type of repeated presentation to an aggressive resident allows us to examine the neuroendocrine and behavioral consequences, and their underlying neural mechanisms, of exposure to a stressor that is social in nature and naturalistic for rodents.

  13. Within-session effect of repeated stress exposure on extinction circuitry function in social anxiety disorder.

    Science.gov (United States)

    Åhs, Fredrik; Gingnell, Malin; Furmark, Tomas; Fredrikson, Mats

    2017-03-30

    Anxiety reduction following repeated exposure to stressful experiences is generally held to depend on neural processes involved in extinction of conditioned fear. We predicted that repeated exposure to stressful experiences would change activity throughout the circuitry serving extinction, including ventromedial prefrontal cortex (vmPFC), the hippocampus and the amygdala. To test this prediction, 36 participants diagnosed with SAD performed two successive speeches in front of an observing audience while regional cerebral blood flow (rCBF) was recorded using positron emission tomography. To control for non-anxiolytic effects of repeated exposure, rCBF was also measured during repeated presentations of neutral and angry facial expressions. Results showed that anxiety ratings and heart rate decreased from the first to the second speech, indicating an anxiolytic effect of repeated exposure. Exposure attenuated rCBF in the amygdala whereas no change in rCBF was observed in the vmPFC or hippocampus. The rCBF-reductions in the amygdala were greater following repetition of the speech task than repetition of face exposure indicating that they were specific to anxiety attenuation and not due to a reduced novelty. Our findings suggest that amygdala-related attenuation processes are key to understanding the working mechanisms of exposure therapy.

  14. Behavioural, endocrine and immune responses to repeated social stress in pregnant gilts.

    Science.gov (United States)

    Couret, D; Otten, W; Puppe, B; Prunier, A; Merlot, E

    2009-01-01

    Pregnant sows are exposed to various stressors in intensive pig husbandry that may have negative consequences on their health, reproductive performances and welfare. Social stress is one of these challenges, because gestating sows have to be housed in groups according to EU guidelines (2001/88/CE). The purpose of this study was to determine the consequences of repeated social stress in pregnant female pigs on their behavioural, endocrine and immunological responses and on pregnancy outcome. Pregnant gilts were submitted to a repeated social stress procedure induced by housing unfamiliar gilts in pairs changed twice a week between days 77 and 105 of gestation (S group, n = 18). Control gilts were housed in stable pairs during the same period (C group, n = 18). Agonistic behaviour was observed during the first 3 h after each grouping. Skin lesions were numbered 2 h after each grouping. Salivary cortisol was measured before and repeatedly during the 4 weeks of grouping. Gilts were immunized against keyhole limpet haemocyanin (KLH) on days 81 and 95 of gestation. Immunoglobulins G against KLH, proliferative responses to concanavalin A, lipopolysaccharide, pokeweed mitogen and KLH and peripheral blood leukocyte numbers were evaluated 1 week before the first grouping and 3 days after the last one. Agonistic interactions and skin lesions were observed in S gilts at each grouping, although there was a decline between the first and the last grouping (P Gestation length tended to be shorter in S gilts (P = 0.09), but litter size, piglet weight or mortality at birth were not affected. Variability of the response of S gilts to groupings was partly explained by their average success value determined according to the outcome (defeat or win) of all the groupings. In conclusion, our study demonstrates that the application of repeated social stress to pregnant gilts during the last third of their gestation repeatedly activates their hypothalamo-pituitary-adrenal axis but does not

  15. Contrasting effects of diazepam and repeated restraint stress on latent inhibition in mice.

    Science.gov (United States)

    Mongeau, Raymond; Marcello, Stefania; Andersen, Jacob Sparre; Pani, Luca

    2007-11-02

    The effects on latent inhibition (LI; a delay in conditioning when a CS has been pre-exposed without consequences) of repeated restraint stress and the anxiolytic drug diazepam were examined in C57BL/6 mice to know whether previous aversive events or anxiolysis are factors determining the expression of LI. The LI model was optimized for this strain particularly sensitive to stress (using both the CER and the conditioned freezing procedures) and characterized with typical (haloperidol) and atypical (clozapine and olanzapine) antipsychotic drugs administered either during the conditioning or the pre-exposure phases. An acute challenge with amphetamine, a dopamine releaser, was done to verify the enhancement of hyperactivity in C57BL/6 mice after the restraint stress sensitization. At all doses tested, diazepam decreased latent inhibition when administered during the pre-exposure phase (similarly to atypical antipsychotic drugs). Repeated restraint stress enhanced LI by blocking the CS-induced freezing in pre-exposed mice. In contrast, pre-treatment with diazepam before pre-exposure allowed the expression of CS-induced freezing in stressed mice pre-exposed to the tone. It is suggested that stress and anxiolytic drugs can have opposite effects on attention or perseveration processes during learning of conflicting contingency responses.

  16. Repeated forced swim stress differentially affects formalin-evoked nociceptive behaviour and the endocannabinoid system in stress normo-responsive and stress hyper-responsive rat strains.

    Science.gov (United States)

    Jennings, Elaine M; Okine, Bright N; Olango, Weredeselam M; Roche, Michelle; Finn, David P

    2016-01-01

    Repeated exposure to a homotypic stressor such as forced swimming enhances nociceptive responding in rats. However, the influence of genetic background on this stress-induced hyperalgesia is poorly understood. The aim of the present study was to compare the effects of repeated forced swim stress on nociceptive responding in Sprague-Dawley (SD) rats versus the Wistar Kyoto (WKY) rat strain, a genetic background that is susceptible to stress, negative affect and hyperalgesia. Given the well-documented role of the endocannabinoid system in stress and pain, we investigated associated alterations in endocannabinoid signalling in the dorsal horn of the spinal cord and amygdala. In SD rats, repeated forced swim stress for 10 days was associated with enhanced late phase formalin-evoked nociceptive behaviour, compared with naive, non-stressed SD controls. In contrast, WKY rats exposed to 10 days of swim stress displayed reduced late phase formalin-evoked nociceptive behaviour. Swim stress increased levels of monoacylglycerol lipase (MAGL) mRNA in the ipsilateral side of the dorsal spinal cord of SD rats, an effect not observed in WKY rats. In the amygdala, swim stress reduced anandamide (AEA) levels in the contralateral amygdala of SD rats, but not WKY rats. Additional within-strain differences in levels of CB1 receptor and fatty acid amide hydrolase (FAAH) mRNA and levels of 2-arachidonylglycerol (2-AG) were observed between the ipsilateral and contralateral sides of the dorsal horn and/or amygdala. These data indicate that the effects of repeated stress on inflammatory pain-related behaviour are different in two rat strains that differ with respect to stress responsivity and affective state and implicate the endocannabinoid system in the spinal cord and amygdala in these differences.

  17. STRESS-STRAIN STATE IN EMBEDMENT OF REINFORCEMENT IN CASE OF REPEATED LOADINGS

    Directory of Open Access Journals (Sweden)

    Mirsayapov Ilshat Talgatovich

    2016-05-01

    Full Text Available The author offer transforming the diagram of ideal elastic-plastic deformations for the description of the stress-strain state of embedment of reinforcement behind a critical inclined crack at repeatedly repeating loadings. The endurance limit of the adhesion between concrete and reinforcement and its corresponding displacements in case of repeated loadings are accepted as the main indicators. This adhesion law is the most appropriate for the description of physical and mechanical phenomena in the contact zone in case of cyclic loading, because it simply and reliably describes the adhesion mechanism and the nature of the deformation, and greatly simplifies the endurance calculations compared to the standard adhesion law. On the basis of this diagram the author obtained the equations for the description of the distribution of pressures and displacements after cyclic loading with account for the development of deformations of cyclic creep of the concrete under the studs of reinforcement.

  18. Contribution of soil fauna to mass loss of Abies faxoniana leaf litter during the freeze-thaw season%季节性冻融期间土壤动物对岷江冷杉凋落叶质量损失的贡献

    Institute of Scientific and Technical Information of China (English)

    夏磊; 吴福忠; 杨万勤

    2011-01-01

    冬季凋落物的质量损失是中高纬度和高海拔地区凋落物分解的关键,但冬季凋落物分解是否与土壤动物的贡献有关,不同冻融时期(冻融初期、深冻期和融化期)的土壤动物对凋落物分解的贡献是否存在差异?对这两个问题仍缺乏必要的关注.为了解季节性冻融期间土壤动物对岷江冷杉(Abies faxoniana)凋落物分解的贡献,采用凋落物分解袋法,调查了季节性冻融期间(2010年10月底至2011年4月中旬)’不同网孔(0.020 mm、0.125 mm、1.000mm和3.000 mm)凋落物分解袋内的岷江冷杉凋落叶质量损失,分析了微型、中型和大型土壤动物对岷汀冷杉凋落叶分解的贡献.在季节性冻融期间,0.020mm、0.125mm、1.000mm和3.000mm分解袋内的岷江冷杉凋落叶质量损失率分别为12.13%、13.07%、14.95%和18.74%.不同体径的土壤动物对季节性冻融期间岷江冷杉凋落叶质量损失的贡献率总共为35.28%;不同孔径凋落物袋内土壤动物的类 ,群和个体相对密度与凋落叶的质量损失率呈现相对·致的变化趋势.在季节性冻融的3个阶段中,十壤动物对岷江冷杉凋落叶质量损失的贡献率均为:微型土壤动物<中型土壤动物<大型土壤动物.其中,微型、中型和大型土壤动物分别在深冻期、冻融初期和融化期表现出最高的贡献率,分别为6.56%、11.77%和21.94%.然而相对于其他冻融时期,深冻期中型和大型土壤动物对岷汀冷杉凋落叶质量损失的贡献率最低.这些结果清晰地表明了川西高山季节性冻融期间土壤动物调控着凋落物分解的生态过程,是高山冬季凋落物分解的重要因素之一.%Aims Mass loss in wintertime is one of the key processes in litter decomposition in cold biomes. The contribution of soil fauna to litter decomposition has been unclear, and the contribution might be different in different winter periods (OF: the onset of the freeze-thaw

  19. Systemic and Local Responses to Repeated HL Stress-Induced Retrograde Signaling in Arabidopsis.

    Science.gov (United States)

    Gordon, Matthew J; Carmody, Melanie; Albrecht, Verónica; Pogson, Barry

    2012-01-01

    CHLOROPLASTS OF LEAVES UNDER HIGH LIGHT STRESS INITIATE SIGNALS TO THE NUCLEI OF BOTH EXPOSED AND DISTAL LEAVES IN ORDER TO ACCLIMATE AGAINST THE POTENTIAL THREAT OF OXIDATIVE DAMAGE: a process known as high light systemic acquired acclimation (HL SAA). This study explores the nature of HL SAA, synergistic interactions with other environmental stresses, and the impact of repeated HL stress on the acclimation response of exposed and distal leaves. This necessitated the development of novel experimental systems to investigate the initiation, perception, and response to HL SAA. These systems were used to investigate the HL SAA response by monitoring the induction of mRNA in distal leaves not exposed to the HL stress. Acclimation to HL is induced within minutes and the response is proportionally dependent on the quality and quantity of light. HL SAA treatments in conjunction with variations in temperature and humidity reveal HL SAA is influenced by fluctuations in humidity. These treatments also result in changes in auxin accumulation and auxin-responsive genes. A key question in retrograde signaling is the extent to which transient changes in light intensity result in a "memory" of the event leading to acclimation responses. Repeated exposure to short term HL resulted in acclimation of the exposed tissue and that of emerging and young leaves (but not older leaves) to HL and oxidative stress.

  20. Repeated exposure to conditioned fear stress increases anxiety and delays sleep recovery following exposure to an acute traumatic stressor

    Directory of Open Access Journals (Sweden)

    Benjamin N Greenwood

    2014-10-01

    Full Text Available Repeated stressor exposure can sensitize physiological responses to novel stressors and facilitate the development of stress-related psychiatric disorders including anxiety. Disruptions in diurnal rhythms of sleep-wake behavior accompany stress-related psychiatric disorders and could contribute to their development. Complex stressors that include fear-eliciting stimuli can be a component of repeated stress experienced by humans, but whether exposure to repeated fear can prime the development of anxiety and sleep disturbances is unknown. In the current study, adult male F344 rats were exposed to either control conditions or repeated contextual fear conditioning for 22 days followed by exposure to either no, mild (10, or severe (100 acute uncontrollable tail shock stress. Exposure to acute stress produced anxiety-like behavior as measured by a reduction in juvenile social exploration and exaggerated shock-elicited freezing in a novel context. Prior exposure to repeated fear enhanced anxiety-like behavior as measured by shock-elicited freezing, but did not alter social exploratory behavior. The potentiation of anxiety produced by prior repeated fear was temporary; exaggerated fear was present 1 day but not 4 days following acute stress. Interestingly, exposure to acute stress reduced REM and NREM sleep during the hours immediately following acute stress. This initial reduction in sleep was followed by robust REM rebound and diurnal rhythm flattening of sleep / wake behavior. Prior repeated fear extended the acute stress-induced REM and NREM sleep loss, impaired REM rebound, and prolonged the flattening of the diurnal rhythm of NREM sleep following acute stressor exposure. These data suggest that impaired recovery of sleep / wake behavior following acute stress could contribute to the mechanisms by which a history of prior repeated stress increases vulnerability to subsequent novel stressors and stress-related disorders.

  1. Distinct effects of repeated restraint stress on basolateral amygdala neuronal membrane properties in resilient adolescent and adult rats.

    Science.gov (United States)

    Hetzel, Andrea; Rosenkranz, J Amiel

    2014-08-01

    Severe and repeated stress has damaging effects on health, including initiation of depression and anxiety. Stress that occurs during development has long-lasting and particularly damaging effects on emotion. The basolateral amygdala (BLA) plays a key role in many affective behaviors, and repeated stress causes different forms of BLA hyperactivity in adolescent and adult rats. However, the mechanism is not known. Furthermore, not every individual is susceptible to the negative consequences of stress. Differences in the effects of stress on the BLA might contribute to determine whether an individual will be vulnerable or resilient to the effects of stress on emotion. The purpose of this study is to test the cellular underpinnings for age dependency of BLA hyperactivity after stress, and whether protective changes occur in resilient individuals. To test this, the effects of repeated stress on membrane excitability and other membrane properties of BLA principal neurons were compared between adult and adolescent rats, and between vulnerable and resilient rats, using in vitro whole-cell recordings. Vulnerability was defined by adrenal gland weight, and verified by body weight gain after repeated restraint stress, and fecal pellet production during repeated restraint sessions. We found that repeated stress increased the excitability of BLA neurons, but in a manner that depended on age and BLA subnucleus. Furthermore, stress resilience was associated with an opposite pattern of change, with increased slow afterhyperpolarization (AHP) potential, whereas vulnerability was associated with decreased medium AHP. The opposite outcomes in these two populations were further distinguished by differences of anxiety-like behavior in the elevated plus maze that were correlated with BLA neuronal excitability and AHP. These results demonstrate a substrate for BLA hyperactivity after repeated stress, with distinct membrane properties to target, as well as age-dependent factors that

  2. Impacts of freeze-thaw processes on antioxidant activities and osmolyte contents of Syntrichia caninervis under different desert microhabitats%冻融过程对荒漠区不同微生境下齿肋赤藓渗透调节物含量和抗氧化酶活力的影响

    Institute of Scientific and Technical Information of China (English)

    尹本丰; 张元明

    2015-01-01

    ünggüt Desert, which is a temperate northern desert of Central Asia. It appears able to endure frequent and intensive freeze-thaw cycles in the surface soil and maintain physiological functions active even under extreme low temperatures in winter. However, there have been few studies exploring the adaptive strategies of the species during freeze-thaw processes and interpret-ing well the phenomena. One of the major goals of this study was to investigate physiological regulatory mecha-nisms of the species when undergoing freezing-thawing periods and relevant antioxidant enzyme activities. Methods A series of microclimate and soil conditions were continuously monitored in the sampling sites starting from November 2013. The samples of the moss were collected during the early spring of 2014 from February to April and from three microhabitats including the sites under live shrub, under dead shrub and on an open ground. The moss samples were quickly treated in the field for keeping freshness and then brought to laboratory for meas-urement and analysis. The traits/characteristics that reflect physiological and biochemical activities were measured for analyzing responses of the species to freeze-thaw processes and for comparing the impacts of different habi-tats, which included water content, concentrations of proline, soluble sugar, soluble protein and malondialdehyde (MDA), as well as catalase (CAT), peroxidase (POD), superoxide dismutase (SOD) activities Important findings The results showed that, during different freeze-thaw periods, microhabitats and their inter-actions with alternative freeze-thaw processes significantly affect the contents of proline, soluble sugar, soluble protein and MDA in shoots of the species, as well as the enzyme activities of CAT, POD, and SOD. Extreme low temperature and drought caused significantly higher soluble sugar and MDA contents, higher CAT, POD and SOD activities, but lower soluble protein content, in snow covered period (February) and dry

  3. Effects of different temperatures and time of freeze-thawing on storage quality of sugar beet roots%不同冻化温度和冻化时间对甜菜块根贮藏品质的影响

    Institute of Scientific and Technical Information of China (English)

    黄剑萍; 朱璇; 贾盼盼; 周永昌; 逄焕明

    2011-01-01

    探讨不同冻化温度和冻化时间对甜菜块根采后品质的影响。以甜菜品种BETA218为试验材料,研究冻固甜菜在0、4℃和10℃下化冻贮藏时蔗糖含量、还原糖含量、有机酸含量、蛋白质含量、氨基酸含量、总酚含量及失重率的变化情况。结果表明:在不同冻化温度和冻化时间下,甜菜块根蔗糖含量呈下降趋势;还原糖、氨基酸、蛋白质、总酚和失重率均呈上升趋势。其中,10℃冻化的甜菜块根这些品质指标变化最为明显,品质下降最快,而0℃冻化的甜菜块根能有效地减慢贮藏品质的下降速度。%The effect of different temperatures and time of freeze-thawing on storage quality of sugar beet roots were discussed. The root of sugar beet BETA 218 was used as the trial material in this experiment. The change of sucrose content, reduce sugar content, protein content, amino acid content, total phenol content, organic acidity content and weight loss of the freeze sugar beet thawed at 0℃, 4 ℃ and 10 ℃ were studied. The results showed that the content of sucrose exhibited decline trend while the content of reduce sugar, organic acidity, soluble protein, free amino acid, total phenol and weight loss showed a increasing tendency at the tested freeze-thawing temperatures and time. The change of these physiological index of sugar beet root thawed at 10 ℃ was obviously, while that thawed at 0℃ could effectively reduce the decline rate of storage quality.

  4. Ventral tegmental area dopamine revisited: effects of acute and repeated stress.

    Science.gov (United States)

    Holly, Elizabeth N; Miczek, Klaus A

    2016-01-01

    Aversive events rapidly and potently excite certain dopamine neurons in the ventral tegmental area (VTA), promoting phasic increases in the medial prefrontal cortex and nucleus accumbens. This is in apparent contradiction to a wealth of literature demonstrating that most VTA dopamine neurons are strongly activated by reward and reward-predictive cues while inhibited by aversive stimuli. How can these divergent processes both be mediated by VTA dopamine neurons? The answer may lie within the functional and anatomical heterogeneity of the VTA. We focus on VTA heterogeneity in anatomy, neurochemistry, electrophysiology, and afferent/efferent connectivity. Second, recent evidence for a critical role of VTA dopamine neurons in response to both acute and repeated stress will be discussed. Understanding which dopamine neurons are activated by stress, the neural mechanisms driving the activation, and where these neurons project will provide valuable insight into how stress can promote psychiatric disorders associated with the dopamine system, such as addiction and depression.

  5. Gene deficiency and pharmacological inhibition of soluble epoxide hydrolase confers resilience to repeated social defeat stress.

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    Ren, Qian; Ma, Min; Ishima, Tamaki; Morisseau, Christophe; Yang, Jun; Wagner, Karen M; Zhang, Ji-Chun; Yang, Chun; Yao, Wei; Dong, Chao; Han, Mei; Hammock, Bruce D; Hashimoto, Kenji

    2016-03-29

    Depression is a severe and chronic psychiatric disease, affecting 350 million subjects worldwide. Although multiple antidepressants have been used in the treatment of depressive symptoms, their beneficial effects are limited. The soluble epoxide hydrolase (sEH) plays a key role in the inflammation that is involved in depression. Thus, we examined here the role of sEH in depression. In both inflammation and social defeat stress models of depression, a potent sEH inhibitor, TPPU, displayed rapid antidepressant effects. Expression of sEH protein in the brain from chronically stressed (susceptible) mice was higher than of control mice. Furthermore, expression of sEH protein in postmortem brain samples of patients with psychiatric diseases, including depression, bipolar disorder, and schizophrenia, was higher than controls. This finding suggests that increased sEH levels might be involved in the pathogenesis of certain psychiatric diseases. In support of this hypothesis, pretreatment with TPPU prevented the onset of depression-like behaviors after inflammation or repeated social defeat stress. Moreover, sEH KO mice did not show depression-like behavior after repeated social defeat stress, suggesting stress resilience. The sEH KO mice showed increased brain-derived neurotrophic factor (BDNF) and phosphorylation of its receptor TrkB in the prefrontal cortex, hippocampus, but not nucleus accumbens, suggesting that increased BDNF-TrkB signaling in the prefrontal cortex and hippocampus confer stress resilience. All of these findings suggest that sEH plays a key role in the pathophysiology of depression, and that epoxy fatty acids, their mimics, as well as sEH inhibitors could be potential therapeutic or prophylactic drugs for depression.

  6. Exposure to repeated immobilization stress inhibits cocaine-induced increase in dopamine extracellular levels in the rat ventral tegmental area.

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    Sotomayor-Zárate, Ramón; Abarca, Jorge; Araya, Katherine A; Renard, Georgina M; Andrés, María E; Gysling, Katia

    2015-11-01

    A higher vulnerability to drug abuse has been observed in human studies of individuals exposed to chronic or persistent stress, as well as in animal models of drug abuse. Here, we explored the effect of repeated immobilization stress on cocaine-induced increase in dopamine extracellular levels in VTA and its regulation by corticotropin-releasing factor (CRF) and GABA systems. Cocaine (10mg/Kg i.p.) induced an increase of VTA DA extracellular levels in control rats. However, this effect was not observed in repeated stress rats. Considering the evidence relating stress with CRF, we decided to perfuse CRF and CP-154526 (selective antagonist of CRF1 receptor) in the VTA of control and repeated stress rats, respectively. We observed that perfusion of 20μM CRF inhibited the increase of VTA DA extracellular levels induced by cocaine in control rats. Interestingly, we observed that in the presence of 10μM CP-154526, cocaine induced a significant increase of VTA DA extracellular levels in repeated stress rats. Regarding the role of VTA GABA neurotransmission, cocaine administration induced a significant increase in VTA GABA extracellular levels only in repeated stress rats. Consistently, cocaine was able to increase VTA DA extracellular levels in repeated stress rats when 100μM bicuculline, an antagonist of GABAA receptor, was perfused intra VTA. Thus, both CRF and GABA systems are involved in the lack of response to cocaine in the VTA of repeated stress rats. It is tempting to suggest that the loss of response in VTA dopaminergic neurons to cocaine, after repeated stress, is due to an interaction between CRF and GABA systems. Copyright © 2015 Elsevier Ltd. All rights reserved.

  7. Repeated trauma exposure does not impair distress reduction during imaginal exposure for posttraumatic stress disorder.

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    Jerud, Alissa B; Farach, Frank J; Bedard-Gilligan, Michele; Smith, Hillary; Zoellner, Lori A; Feeny, Norah C

    2017-08-01

    Based on experimental research on threat extinction, individuals exposed to repeated traumatic events may have impaired outcome in exposure therapy compared to those who have experienced a single trauma (Lang & McTeague, ). This study examined whether repeated trauma exposure predicts smaller changes in self-reported distress during imaginal exposure and worse outcomes for patients with posttraumatic stress disorder (PTSD). Adults (N = 116) with chronic PTSD received up to 10 sessions of prolonged exposure (PE) therapy. Trauma exposure was assessed via interview and number of traumatic events were summed for each participant. To examine reductions in distress during treatment, mean and peak values of distress during imaginal exposure were calculated for the first imaginal session (initial distress activation) and subsequent sessions (between-session change in distress). Change in PTSD symptoms from pre- to posttreatment and follow-up provided an additional index of outcome. In-session distress during imaginal exposure decreased over the course of treatment. PTSD symptoms also decreased over treatment, with gains being maintained through follow-up. Repeated trauma exposure was not significantly correlated with initial distress activation. Additionally, linear mixed-model analyses showed no significant association between repeated trauma exposure and between-session change in distress or PTSD symptoms. Contrary to recent speculation, repeated trauma exposure did not predict less change in self-reported distress during imaginal exposure or worse PTSD outcomes. The bench-to-bedside linkage of threat extinction to exposure therapy is discussed, noting strengths and weaknesses. Patients with repeated trauma exposure show reductions in distress with exposure treatment and benefit from PE as much as patients with single-exposure trauma histories. © 2016 Wiley Periodicals, Inc.

  8. B-type natriuretic peptide (BNP serum levels in rats after forced repeated swimming stress

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    Almira Hadžovic-Džuvo

    2011-02-01

    Full Text Available Aim To estimate the effects of forced repeated swimming stress on BNP serum levels in rats. Methods Adult male Wistar rats weighting between 280-330 g were divided into two groups: control group (n =8 and stress group (n =8. Rats in the stress group were exposed to forced swimming stress daily, for 7 days. The rats were forced to swim in plastic tanks (90 cm wide, 120 cm deep containing tap water (temperature ca. 25°C. The depth of water was 40 cm. Duration of each swimming session progressively increased from 10 minutes on the irst day to 40 minutes on days 6 and 7. Rats were sacriiced and blood was drawn from abdominal aorta for BNP analysis immediately after the last swimming session. B-type natriuretic serum level was determined by ELISA method using RAT BNP-32 kit (Phoenix Pharmaceutical Inc.. Results There was no statistically signiicant difference between mean BNP serum level in the stress group after the swimming period (0.81±0.14 ng/ml as compared to the unstressed group of rats (0.8 ±0.08ng/ml. After the swimming period mean body weight slightly decreased in the stress group in comparison with values before stress period (296.3 g vs.272.8 g, but this difference was not statistically signiicant. The stress period had no inluence on food intake in the stress rat group. Conclusion The workload consisting of 40-minutes long swimming session is not suficient to provoke BNP release from myocardium in rats.

  9. Activation of physiological stress responses by a natural reward: Novel vs. repeated sucrose intake.

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    Egan, Ann E; Ulrich-Lai, Yvonne M

    2015-10-15

    Pharmacological rewards, such as drugs of abuse, evoke physiological stress responses, including increased heart rate and blood pressure, and activation of the hypothalamic-pituitary-adrenal (HPA) axis. It is not clear to what extent the natural reward of palatable foods elicits similar physiological responses. In order to address this question, HPA axis hormones, heart rate, blood pressure and brain pCREB immunolabeling were assessed following novel and repeated sucrose exposure. Briefly, adult, male rats with ad libitum food and water were given either a single (day 1) or repeated (twice-daily for 14 days) brief (up to 30 min) exposure to a second drink bottle containing 4 ml of 30% sucrose drink vs. water (as a control for bottle presentation). Sucrose-fed rats drank more than water-fed on all days of exposure, as expected. On day 1 of exposure, heart rate, blood pressure, plasma corticosterone, and locomotion were markedly increased by presentation of the second drink bottle regardless of drink type. After repeated exposure (day 14), these responses habituated to similar extents regardless of drink type and pCREB immunolabeling in the hypothalamic paraventricular nucleus (PVN) also did not vary with drink type, whereas basolateral amygdala pCREB was increased by sucrose intake. Taken together, these data suggest that while sucrose is highly palatable, physiological stress responses were evoked principally by the drink presentation itself (e.g., an unfamiliar intervention by the investigators), as opposed to the palatability of the offered drink.

  10. Individual differences and repeatability in vocal production: stress-induced calling exposes a songbird's personality

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    Guillette, Lauren M.; Sturdy, Christopher B.

    2011-11-01

    Recent research in songbirds has demonstrated that male singing behavior varies systematically with personality traits such as exploration and risk taking. Here we examine whether the production of bird calls, in addition to bird songs, is repeatable and related to exploratory behavior, using the black-capped chickadee ( Poecile atricapillus) as a model. We assessed the exploratory behavior of individual birds in a novel environment task. We then recorded the vocalizations and accompanying motor behavior of both male and female chickadees, over the course of several days, in two different contexts: a control condition with no playback and a stressful condition where chick-a-dee mobbing calls were played to individual birds. We found that several vocalizations and behaviors were repeatable within both a control and a stressful context, and across contexts. While there was no relationship between vocal output and exploratory behavior in the control context, production of alarm and chick-a-dee calls in the stressful condition was positively associated with exploratory behavior. These findings are important because they show that bird calls, in addition to bird song, are an aspect of personality, in that calls are consistent both within and across contexts, and covary with other personality measures (exploration).

  11. Repeated psychosocial stress at night, but not day, affects the central molecular clock.

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    Bartlang, Manuela S; Savelyev, Sergey A; Johansson, Anne-Sofie; Reber, Stefan O; Helfrich-Förster, Charlotte; Lundkvist, Gabriella B S

    2014-11-01

    We have recently demonstrated that the outcome of repeated social defeat (SD) on behavior, physiology and immunology is more negative when applied during the dark/active phase as compared with the light/inactive phase of male C57BL/6 mice. Here, we investigated the effects of the same stress paradigm, which combines a psychosocial and novelty stressor, on the circadian clock in transgenic PERIOD2::LUCIFERASE (PER2::LUC) and wildtype (WT) mice by subjecting them to repeated SD, either in the early light phase (social defeat light = SDL) or in the early dark phase (social defeat dark = SDD) across 19 days. The PER2::LUC rhythms and clock gene mRNA expression were analyzed in the suprachiasmatic nucleus (SCN) and the adrenal gland, and PER2 protein expression in the SCN was assessed. SDD mice showed increased PER2::LUC rhythm amplitude in the SCN, reduced Per2 and Cryptochrome1 mRNA expression in the adrenal gland, and increased PER2 protein expression in the posterior part of the SCN compared with single-housed control (SHC) and SDL mice. In contrast, PER2::LUC rhythms in the SCN of SDL mice were not affected. However, SDL mice exhibited a 2-hour phase advance of the PER2::LUC rhythm in the adrenal gland compared to SHC mice. Furthermore, plasma levels of brain-derived neurotrophic factor (BDNF) and BDNF mRNA in the SCN were elevated in SDL mice. Taken together, these results show that the SCN molecular rhythmicity is affected by repeated SDD, but not SDL, while the adrenal peripheral clock is influenced mainly by SDL. The observed increase in BDNF in the SDL group may act to protect against the negative consequences of repeated psychosocial stress.

  12. Cold stress improves the ability of Lactobacillus plantarum L67 to survive freezing.

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    Song, Sooyeon; Bae, Dong-Won; Lim, Kwangsei; Griffiths, Mansel W; Oh, Sejong

    2014-11-17

    The stress resistance of bacteria is affected by the physiological status of the bacterial cell and environmental factors such as pH, salts and temperature. In this study, we report on the stress response of Lactobacillus plantarum L67 after four consecutive freeze-thaw cycles. The cold stress response of the cold-shock protein genes (cspC, cspL and cspP) and ATPase activities were then evaluated. The cold stress was adjusted to 5 °C when the bacteria were growing at the mid-exponential phase. A comparative proteomic analysis was performed with two-dimensional gel electrophoresis (2D SDS-PAGE) and a matrix assisted laser desorption/ionization-mass spectrometer. Only 56% of the L. plantarum L67 cells without prior exposure to cold stress survived after four consecutive freeze-thaw cycles. However, 78% of the L. plantarum L67 cells that were treated with cold stress at 5 °C for 6 h survived after freeze-thaw conditions. After applying cold stress to the culture for 6h, the cells were then stored for 60 days at 5 °C, 25 °C and 35 °C separately. The cold-stressed culture of L. plantarum L67 showed an 8% higher viability than the control culture. After applying cold stress for 6h, the transcript levels of two genes (cspP and cspL) were up-regulated 1.4 (cspP) and 1.2 (cspL) times compared to the control. However, cspC was not up-regulated. A proteomic analysis showed that the proteins increased after a reduction of the incubation temperature to 5 °C. The importance of the expression of 13 other relevant proteins was also determined through the study. The exposure of L. plantarum cells to low temperatures aids their ability to survive through subsequent freeze-thaw processes and lyophilization.

  13. Enhancement of the proline and nitric oxide synthetic pathway improves fermentation ability under multiple baking-associated stress conditions in industrial baker's yeast

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    Sasano Yu

    2012-04-01

    Full Text Available Abstract Background During the bread-making process, industrial baker's yeast, mostly Saccharomyces cerevisiae, is exposed to baking-associated stresses, such as air-drying and freeze-thaw stress. These baking-associated stresses exert severe injury to yeast cells, mainly due to the generation of reactive oxygen species (ROS, leading to cell death and reduced fermentation ability. Thus, there is a great need for a baker's yeast strain with higher tolerance to baking-associated stresses. Recently, we revealed a novel antioxidative mechanism in a laboratory yeast strain that is involved in stress-induced nitric oxide (NO synthesis from proline via proline oxidase Put1 and N-acetyltransferase Mpr1. We also found that expression of the proline-feedback inhibition-less sensitive mutant γ-glutamyl kinase (Pro1-I150T and the thermostable mutant Mpr1-F65L resulted in an enhanced fermentation ability of baker's yeast in bread dough after freeze-thaw stress and air-drying stress, respectively. However, baker's yeast strains with high fermentation ability under multiple baking-associated stresses have not yet been developed. Results We constructed a self-cloned diploid baker's yeast strain with enhanced proline and NO synthesis by expressing Pro1-I150T and Mpr1-F65L in the presence of functional Put1. The engineered strain increased the intracellular NO level in response to air-drying stress, and the strain was tolerant not only to oxidative stress but also to both air-drying and freeze-thaw stresses probably due to the reduced intracellular ROS level. We also showed that the resultant strain retained higher leavening activity in bread dough after air-drying and freeze-thaw stress than that of the wild-type strain. On the other hand, enhanced stress tolerance and fermentation ability did not occur in the put1-deficient strain. This result suggests that NO is synthesized in baker's yeast from proline in response to oxidative stresses that induce ROS

  14. Effects of repeated psychological stress training on the spectrum of serum protein expression in special troops

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    Li ZHANG

    2011-10-01

    Full Text Available Objective To investigate the effects of repeated psychological stress training on the serum protein expression in soldiers under mental stress.Methods Ninety-six male commando soldiers were randomly assigned into the common psychological training group,the circulation psychological training group and the control group(32 each.After a 4-week training,all the soldiers were instructed to attend an one-day high-intensity simulated anti-riot exercise,and 3 days later attended another unannounced high-intensity simulated anti-riot exercise.Blood samples were collected from all the soldiers within 4 hours after each exercise,and the changes in serum protein expression were determined and statistically analyzed by using surface-enhanced laser desorption/ionization time of flight mass spectrometry(SELDI-TOF-MS combined with ProteinChip technology.Results The variance analysis showed that significant differences existed among the three groups(P < 0.05 in the relative contents of proteins with M/Z values of 6417.8,9134.2,15171.9 and 14972.7D after the first anti-riot exercise,and the relative contents of all the above mentioned proteins increased in the circulatory psychological training group;meanwhile,markedly increasing trends of the relative contents of all the proteins were observed in the three groups after the second anti-riot exercise(P < 0.05,and in control group the relative contents of the 4 above mentioned proteins were significantly higher than those after the first anti-riot exercise.Conclusion Psychological training may up-regulate the expression of serum proteins that are down-regulated after stress,and the repeated high-intensity mental training can rapidly improve the soldiers’ ability to counteract stress.

  15. Synaptic Impairment in Layer 1 of the Prefrontal Cortex Induced by Repeated Stress During Adolescence is Reversed in Adulthood

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    Negrón-Oyarzo, Ignacio; Dagnino-Subiabre, Alexies; Muñoz Carvajal, Pablo

    2015-01-01

    Chronic stress is a risk factor for the development of psychiatric disorders, some of which involve dysfunction of the prefrontal cortex (PFC). There is a higher prevalence of these chronic stress-related psychiatric disorders during adolescence, when the PFC has not yet fully matured. In the present work we studied the effect of repeated stress during adolescence on synaptic function in the PFC in adolescence and adulthood. To this end, adolescent Sprague-Dawley rats were subjected to seven consecutive days of restraint stress. Afterward, both synaptic transmission and short- and long-term synaptic plasticity were evaluated in layer 1 of medial-PFC (mPFC) slices from adolescent and adult rats. We found that repeated stress significantly reduced the amplitude of evoked field excitatory post-synaptic potential (fEPSP) in the mPFC. Isolation of excitatory transmission reveled that lower-amplitude fEPSPs were associated with a reduction in α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor-mediated transmission. We also found that repeated stress significantly decreased long-term depression (LTD). Interestingly, AMPA/kainate receptor-mediated transmission and LTD were recovered in adult animals that experienced a three-week stress-free recovery period. The data indicates that the changes in synaptic transmission and plasticity in the mPFC induced by repeated stress during adolescence are reversed in adulthood after a stress-free period. PMID:26617490

  16. Perfectionism Affects Blood Pressure in Response to Repeated Exposure to Stress.

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    Albert, Phebe; Rice, Kenneth G; Caffee, Lauren

    2016-04-01

    This pilot study examined the effects of perfectionism on blood pressure (BP) in response to repeated exposure to mental arithmetic stressors. College students (N = 30) in a laboratory setting were administered a series of challenging mathematical tasks. BP was measured at baseline and after each task. Multilevel modelling analyses revealed that BP tended to decline over the course of the mathematical tasks. However, higher levels of performance standards predicted relatively stable levels of systolic BP, whereas moderate and lower levels of standards predicted declines in systolic BP. Higher levels of self-critical perfectionism predicted generally sustained levels of diastolic BP, with moderate and low self-criticism predicting declines in diastolic BP during the repeated stressors. These preliminary results suggest that students with higher levels of perfectionism may be at risk for physiological problems associated with stress reactivity, perhaps especially so in situations in which they experience persistent stress. Although results were qualified by a relatively small sample size, effects were statistically significant and supported the importance of examining the short-term and long-term implications of the effects of perfectionism on cardiovascular function and the different implications of elevations in systolic and diastolic BP.

  17. How integrated are behavioral and endocrine stress response traits? A repeated measures approach to testing the stress-coping style model.

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    Boulton, Kay; Couto, Elsa; Grimmer, Andrew J; Earley, Ryan L; Canario, Adelino V M; Wilson, Alastair J; Walling, Craig A

    2015-02-01

    It is widely expected that physiological and behavioral stress responses will be integrated within divergent stress-coping styles (SCS) and that these may represent opposite ends of a continuously varying reactive-proactive axis. If such a model is valid, then stress response traits should be repeatable and physiological and behavioral responses should also change in an integrated manner along a major axis of among-individual variation. While there is some evidence of association between endocrine and behavioral stress response traits, few studies incorporate repeated observations of both. To test this model, we use a multivariate, repeated measures approach in a captive-bred population of Xiphophorus birchmanni. We quantify among-individual variation in behavioral stress response to an open field trial (OFT) with simulated predator attack (SPA) and measure waterborne steroid hormone levels (cortisol, 11-ketotestosterone) before and after exposure. Under the mild stress stimulus (OFT), (multivariate) behavioral variation among individuals was consistent with a strong axis of personality (shy-bold) or coping style (reactive-proactive) variation. However, behavioral responses to a moderate stressor (SPA) were less repeatable, and robust statistical support for repeatable endocrine state over the full sampling period was limited to 11-ketotestosterone. Although post hoc analysis suggested cortisol expression was repeatable over short time periods, qualitative relationships between behavior and glucocorticoid levels were counter to our a priori expectations. Thus, while our results clearly show among-individual differences in behavioral and endocrine traits associated with stress response, the correlation structure between these is not consistent with a simple proactive-reactive axis of integrated stress-coping style. Additionally, the low repeatability of cortisol suggests caution is warranted if single observations (or indeed repeat measures over short sampling

  18. Repeated exposure to heat stress results in a diaphragm phenotype that resists ventilator-induced diaphragm dysfunction.

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    Yoshihara, Toshinori; Ichinoseki-Sekine, Noriko; Kakigi, Ryo; Tsuzuki, Takamasa; Sugiura, Takao; Powers, Scott K; Naito, Hisashi

    2015-11-01

    Controlled mechanical ventilation (CMV) is a life-saving intervention for patients in respiratory failure. Unfortunately, prolonged mechanical ventilation (MV) results in diaphragmatic atrophy and contractile dysfunction, both of which are predicted to contribute to problems in weaning patients from the ventilator. Therefore, developing a strategy to protect the diaphragm against ventilator-induced weakness is important. We tested the hypothesis that repeated bouts of heat stress result in diaphragm resistance against CMV-induced atrophy and contractile dysfunction. Male Wistar rats were randomly divided into six experimental groups: 1) control; 2) single bout of whole body heat stress; 3) repeated bouts of whole body heat stress; 4) 12 h CMV; 5) single bout of whole body heat stress 24 h before CMV; and 6) repeated bouts of whole body heat stress 1, 3, and 5 days before 12 h of CMV. Our results revealed that repeated bouts of heat stress resulted in increased levels of heat shock protein 72 in the diaphragm and protection against both CMV-induced diaphragmatic atrophy and contractile dysfunction at submaximal stimulation frequencies. The specific mechanisms responsible for this protection remain unclear: this heat stress-induced protection against CMV-induced diaphragmatic atrophy and weakness may be partially due to reduced diaphragmatic oxidative stress, diminished activation of signal transducer/transcriptional activator-3, lower caspase-3 activation, and decreased autophagy in the diaphragm.

  19. Repeated stress-induced stimulation of catecholamine response is not followed by altered immune cell redistribution.

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    Imrich, Richard; Tibenska, Elena; Koska, Juraj; Ksinantova, Lucia; Kvetnansky, Richard; Bergendiova-Sedlackova, Katarina; Blazicek, Pavol; Vigas, Milan

    2004-06-01

    Stress response is considered an important factor in the modulation of immune function. Neuroendocrine hormones, including catecholamines, affect the process of immune cell redistribution, important for cell-mediated immunity. This longitudinal investigation was aimed at evaluating the effect of repeated stress-induced elevation of catecholamines on immune cell redistribution and expression of adhesive molecules. We assessed the responses of epinephrine (EPI), norepinephrine (NE), cortisol, changes in lymphocytes subpopulations, and percentages of CD11a+, CD11b+, and CD62L+ lymphocytes to a 20-min treadmill exercise of an intensity equal to 80% of the individual's Vo(2)max. The exercise was performed before and after 6 weeks of endurance training consisting of a 1-h run 4 times a week (ET) and after 5 days of bed rest (HDBR) in 10 healthy males. We did not observe any significant changes in the basal levels of EPI, NE, and cortisol in the plasma, nor in the immune parameters after ET and HDBR. The exercise test led to a significant (P <.001) elevation of EPI and NE levels after both ET and HDBR, a significant elevation (P <.01) of cortisol after HDBR, an increase in the absolute numbers of leukocytes, granulocytes, monocytes, CD3+, CD4+, CD8+, CD16+, CD19+ lymphocytes, percentage of CD11a+ and CD11b+ lymphocytes, and to a decrease of CD62L1 before, after ET, and after HDBR. We found comparable changes in all measured immune parameters after ET and HDBR. In conclusion, repeated stress-induced elevation of EPI and NE was not associated with an alteration in immune cell redistribution found in response to the single bout of exercise.

  20. Impact of repeated stress on traumatic brain injury-induced mitochondrial electron transport chain expression and behavioral responses in rats

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    Guoqiang eXing

    2013-12-01

    Full Text Available A significant proportion of the military personnel returning from Iraq and Afghanistan conflicts have suffered from both mild traumatic brain injury (mTBI and post-traumatic stress disorder (PTSD. The mechanisms are unknown. We used a rat model of repeated stress and mTBI to examine brain activity and behavioral function. Adult male Sprague-Dawley rats were divided into 4 groups: Naïve; 3 days repeated tail-shock stress; lateral fluid percussion mTBI; and repeated stress followed by mTBI (S-mTBI. Open field activity, sensorimotor responses, and acoustic startle responses were measured after mTBI. The protein expression of mitochondrial electron transport chain (ETC complex subunits (CI-V and pyruvate dehydrogenase (PDHE1α1 were determined in 4 brain regions at day 7 post mTBI. Compared to Naïves, repeated stress decreased horizontal activity; repeated stress and mTBI both decreased vertical activity; and the mTBI and S-mTBI groups were impaired in sensorimotor and acoustic startle responses. Repeated stress significantly increased CI, CII, and CIII protein levels in the prefrontal cortex (PFC, but decreased PDHE1α1 protein in the PFC and cerebellum, and decreased CIV protein in the hippocampus. The mTBI treatment decreased CV protein levels in the ipsilateral hippocampus. The S-mTBI treatment resulted in increased CII, CIII, CIV, and CV protein levels in the PFC, increased CI level in the cerebellum, and increased CIII and CV levels in the cerebral cortex, but decreased CI, CII, CIV, and PDHE1α1 protein levels in the hippocampus. Thus, repeated stress or mTBI alone differentially altered ETC expression in heterogeneous brain regions. Repeated stress followed by mTBI had synergistic effects on brain ETC expression, and resulted in more severe behavioral deficits. These results suggest that repeated stress could have contributed to the high incidence of long-term neurologic and neuropsychiatric morbidity in military personnel with or without

  1. Possible stimulation of anti-tumor immunity using repeated cold stress: a hypothesis

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    Radoja Sasa

    2007-11-01

    Full Text Available Abstract Background The phenomenon of hormesis, whereby small amounts of seemingly harmful or stressful agents can be beneficial for the health and lifespan of laboratory animals has been reported in literature. In particular, there is accumulating evidence that daily brief cold stress can increase both numbers and activity of peripheral cytotoxic T lymphocytes and natural killer cells, the major effectors of adaptive and innate tumor immunity, respectively. This type of regimen (for 8 days has been shown to improve survival of mice infected with intracellular parasite Toxoplasma gondii, which would also be consistent with enhanced cell-mediated immunity. Presentation of the hypothesis This paper hypothesizes that brief cold-water stress repeated daily over many months could enhance anti-tumor immunity and improve survival rate of a non-lymphoid cancer. The possible mechanism of the non-specific stimulation of cellular immunity by repeated cold stress appears to involve transient activation of the sympathetic nervous system, hypothalamic-pituitary-adrenal and hypothalamic-pituitary-thyroid axes, as described in more detail in the text. Daily moderate cold hydrotherapy is known to reduce pain and does not appear to have noticeable adverse effects on normal test subjects, although some studies have shown that it can cause transient arrhythmias in patients with heart problems and can also inhibit humoral immunity. Sudden immersion in ice-cold water can cause transient pulmonary edema and increase permeability of the blood-brain barrier, thereby increasing mortality of neurovirulent infections. Testing the hypothesis The proposed procedure is an adapted cold swim (5–7 minutes at 20 degrees Celsius, includes gradual adaptation to be tested on a mouse tumor model. Mortality, tumor size, and measurements of cellular immunity (numbers and activity of peripheral CD8+ T lymphocytes and natural killer cells of the cold-exposed group would be compared to

  2. Specific anti-tumor immune responses of dendritic cells pulsed with recombinant human rhHSP70 and freeze-thaw cellular lysates derived from breast cancer%rhHSP70联合冻融抗原修饰树突状细胞诱导的抗乳腺癌作用*

    Institute of Scientific and Technical Information of China (English)

    李斌; 陈鹏; 郑建云

    2013-01-01

      目的:利用rhHSP70联合树突状细胞递呈肿瘤抗原的特性提高细胞毒T淋巴细胞(CTLs)对乳腺癌细胞的杀伤活性。方法:外周血单个核细胞体外经GM-CSF和IL-4诱导产生树突状细胞,负载冻融抗原肽的同时加入新型热休克蛋白(rhHSP70),不同分组分别诱导自体CTLs产生。ELISA测定CTLs杀伤活性和细胞因子的分泌。结果:冻融抗原肽致敏的DCs促进CTLs增殖,上调CTLs中CD3+和CD8+T细胞群及Th1型细胞因子的分泌;体外实验中具有对人乳腺癌细胞MCF-7的杀伤活性,在加入rhHSP70后效果更加明显,并能显著增强CTLs对肿瘤细胞的杀伤率。结论:rhHSP70联合肝癌冻融抗原修饰DCs,能够促进DCs的成熟,增强DCs刺激淋巴细胞增殖的能力,诱导的CTLs在体外对乳腺癌细胞能产生高效杀伤力。rhHSP70增强DCs抗肿瘤能力的机制可能与其促进DCs成熟有关。%Objective:This work aims to use the characteristics of dendritic cells (DCs) pulsed with recombinant human HSP70, which can present and process tumor antigens, to enhance the killing activity of cytotoxic t lymphocytes (CTLs) against breast neoplasms. Methods:Autologous DCs were isolated from peripheral blood mononuclear cells and then stimulated in vitro with granulocyte macrophage-colony stimulating factor and interleukin-4. The DCs were loaded with A549 tumor cell freeze-thaw lysate, and rhHSP70 was added as an immune adjuvant. The specific groups were subjected to tumor-specific cytotoxic assay, enzyme-linked immunosorbent assay, and fluores-cence-activated cell sorting. Results:DCs pulsed with A549 tumor cell lysate enhanced the growth expansion of CTLs, upregulated CD40 and CD80 populations in CTLs, and augmented Th1 cytokines. In addition, the cytotoxicity of specific CTLs against A549 was highly enhanced. The above indications became more obvious after the addition of rhHSP70. Conclusion:DCs pulsed with freeze-thaw cell

  3. Dynamic damage and stress-strain relations of ultra-high performance cementitious composites subjected to repeated impact

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Ultra-high performance cementitious composites (UHPCC) were prepared by replacing 60% of cement with ultra-fine industrial waste powders.The dynamic damage and compressive stress-strain relations of UHPCC were studied using split Hopkinson pressure bar (SHPB).The damage of UHPCC subjected to repeated impact was measured by the ultrasonic pulse velocity method.Results show that the dynamic damage of UHPCC increases linearly with impact times and the abilities of repeated impact resistance of UHPCC are improved with increasing fiber volume fraction.The stress waves on impact were recorded and the average stress,strain and strain rate of UHPCC were calculated based on the wave propagation theory.The effects of strain rate,fibers volume fraction and impact times on the stress-strain relations of UHPCC were studied.Results show that the peak stress and elastic modulus decrease while the strain rate and peak strain increase gradually with increasing impact times.

  4. Effect of acute and repeated restraint stress on glucose oxidation to CO2 in hippocampal and cerebral cortex slices

    Directory of Open Access Journals (Sweden)

    Torres I.L.S.

    2001-01-01

    Full Text Available It has been suggested that glucocorticoids released during stress might impair neuronal function by decreasing glucose uptake by hippocampal neurons. Previous work has demonstrated that glucose uptake is reduced in hippocampal and cerebral cortex slices 24 h after exposure to acute stress, while no effect was observed after repeated stress. Here, we report the effect of acute and repeated restraint stress on glucose oxidation to CO2 in hippocampal and cerebral cortex slices and on plasma glucose and corticosterone levels. Male adult Wistar rats were exposed to restraint 1 h/day for 50 days in the chronic model. In the acute model there was a single exposure. Immediately or 24 h after stress, the animals were sacrificed and the hippocampus and cerebral cortex were dissected, sliced, and incubated with Krebs buffer, pH 7.4, containing 5 mM glucose and 0.2 µCi D-[U-14C] glucose. CO2 production from glucose was estimated. Trunk blood was also collected, and both corticosterone and glucose were measured. The results showed that corticosterone levels after exposure to acute restraint were increased, but the increase was smaller when the animals were submitted to repeated stress. Blood glucose levels increased after both acute and repeated stress. However, glucose utilization, measured as CO2 production in hippocampal and cerebral cortex slices, was the same in stressed and control groups under conditions of both acute and chronic stress. We conclude that, although stress may induce a decrease in glucose uptake, this effect is not sufficient to affect the energy metabolism of these cells.

  5. 不同储存条件和反复冻融对血清和血浆乙酰胆碱受体抗体水平的影响%Effect of storage conditions and freeze/thaw cycles on serum and plasma levels of anti-acetylcholine receptor antibody

    Institute of Scientific and Technical Information of China (English)

    郝洪军; 洪宇; 谢琰臣; 李海峰

    2014-01-01

    Objective To evaluate the intra‐assay reproducibility of anti‐acetylcholine receptor antibody (AChRAb) level in serum and plasma samples among various pre‐treatment conditions consisting of different storage schemes and subsequent freeze/thaw cycles .Methods The serum and plasma samples were collected from a patient with myasthenia gravis and allocated in aliquots pre‐treated in various conditions (stored at room temperature [RT ] ,4℃ or -80℃ with subsequent freeze/thaw cycles) .Each aliquot was examined in duplicate with commercial AChRAb ELISA kit .The coefficient of variability (CV) was calculated for inhibition rate of AChRAb in each pre‐treatment condition .Inhibition rates of AChRAb in serum or plasma samples were compared among each condition ,and compared between serum and plasma samples in each condition .Results Except for plasma sample at RT ,the CVs of all the other samples in various conditions were 0.05) .Conclusions There was good intra‐test reproducibility of the ELISA kit in determining the AChRAb levels in serum and plasma samples stored at -80℃ directly with various subsequent freeze/thaw cycles .There was good intra‐test reproducibility in serum samples stored at RT ,4℃ and frozen conditions and in plasma samples stored in frozen conditions ,which were examined in several days after blood collection .%目的:探讨不同储存条件和反复冻融对血清和血浆乙酰胆碱受体抗体(AChRAb)水平的影响。方法将1例重症肌无力患者的血清和血浆标本分成数等份,置于不同储存条件下(常温、4℃或-80℃)并经过不同次数的冻融,不同等分的样本使用同一批次商品化ELISA试剂盒双平行孔检测AChRAb水平。计算各种条件下血清和血浆标本AChRAb抑制率的变异系数(CV ),比较不同处理条件下的抑制率以及同一条件下血清和血浆标本的抑制率。结果除常温条件下血浆标本 CV>10%外,其余条件下 CV

  6. Repeated otilonium bromide administration prevents neurotransmitter changes in colon of rats underwent to wrap restraint stress.

    Science.gov (United States)

    Traini, Chiara; Evangelista, Stefano; Girod, Vincent; Faussone-Pellegrini, Maria Simonetta; Vannucchi, Maria Giuliana

    2017-04-01

    Otilonium bromide (OB) is a spasmolytic drug successfully used for the treatment of irritable bowel syndrome (IBS). Its efficacy has been attributed to the block of L- and T-type Ca(2+) channels and muscarinic and tachykinin receptors in the smooth muscle. Furthermore, in healthy rats, repeated OB administration modified neurotransmitter expression and function suggesting other mechanisms of action. On this basis, we investigated whether repeated OB treatment prevented the functional and neurochemical changes observed in the colon of rats underwent to wrap restrain stress (WRS) a psychosocial stressor considered suitable to reproduce the main IBS signs and symptoms. In control, WRS and OB/WRS rats functional parameters were measured in vivo and morphological investigations were done ex vivo in the colon. The results showed that OB counteracts most of the neurotransmitters changes caused by WRS. In particular, the drug prevents the decrease in SP-, NK1r-, nNOS-, VIP-, and S100β-immunoreactivity (IR) and the increase in CGRP-, and CRF1r-IR. On the contrary, OB does not affect the increase in CRF2r-IR neurons observed in WRS rats and does not interfere with the mild mucosal inflammation due to WRS. Finally, OB per se increases the Mr2 expression in the muscle wall and decreases the number of the myenteric ChAT-IR neurons. Functional findings show a significantly reduction in the number of spontaneous abdominal contraction in OB treated rats. The ability of OB to block L-type Ca(2+) channels, also expressed by enteric neurons, might represent a possible mechanism through which OB exerts its actions. © 2016 The Authors. Journal of Cellular and Molecular Medicine published by John Wiley & Sons Ltd and Foundation for Cellular and Molecular Medicine.

  7. GSTM1 and APE1 genotypes affect arsenic-induced oxidative stress: a repeated measures study

    Directory of Open Access Journals (Sweden)

    Quamruzzaman Quazi

    2007-12-01

    Full Text Available Abstract Background Chronic arsenic exposure is associated with an increased risk of skin, bladder and lung cancers. Generation of oxidative stress may contribute to arsenic carcinogenesis. Methods To investigate the association between arsenic exposure and oxidative stress, urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG was evaluated in a cohort of 97 women recruited from an arsenic-endemic region of Bangladesh in 2003. Arsenic exposure was measured in urine, toenails, and drinking water. Drinking water and urine samples were collected on three consecutive days. Susceptibility to oxidative stress was evaluated by genotyping relevant polymorphisms in glutathione-s transferase mu (GSTM1, human 8-oxoguanine glycosylase (hOGG1 and apurinic/apyrimidinic endonuclease (APE1 genes using the Taqman method. Data were analyzed using random effects Tobit regression to account for repeated measures and 8-OHdG values below the detection limit. Results A consistent negative effect for APE1 was observed across water, toenail and urinary arsenic models. APE1 148 glu/glu + asp/glu genotype was associated with a decrease in logged 8-OHdG of 0.40 (95%CI -0.73, -0.07 compared to APE1 148 asp/asp. An association between total urinary arsenic and 8-OHdG was observed among women with the GSTM1 null genotype but not in women with GSTM1 positive. Among women with GSTM1 null, a comparison of the second, third, and fourth quartiles of total urinary arsenic to the first quartile resulted in a 0.84 increase (95% CI 0.27, 1.42, a 0.98 increase (95% CI 033, 1.66 and a 0.85 increase (95% CI 0.27, 1.44 in logged 8-OHdG, respectively. No effects between 8-OHdG and toenail arsenic or drinking water arsenic were observed. Conclusion These results suggest the APE1 variant genotype decreases repair of 8-OHdG and that arsenic exposure is associated with oxidative stress in women who lack a functional GSTM1 detoxification enzyme.

  8. Protective Effect of Repeatedly Preadministered Brazilian Propolis Ethanol Extract against Stress-Induced Gastric Mucosal Lesions in Rats

    Directory of Open Access Journals (Sweden)

    Tadashi Nakamura

    2014-01-01

    Full Text Available The present study was conducted to clarify the protective effect of Brazilian propolis ethanol extract (BPEE against stress-induced gastric mucosal lesions in rats. The protective effect of BPEE against gastric mucosal lesions in male Wistar rats exposed to water-immersion restraint stress (WIRS for 6 h was compared between its repeated preadministration (50 mg/kg/day, 7 days and its single preadministration (50 mg/kg. The repeated BPEE preadministration attenuated WIRS-induced gastric mucosal lesions and gastric mucosal oxidative stress more largely than the single BPEE preadministration. In addition, the repeated BPEE preadministration attenuated neutrophil infiltration in the gastric mucosa of rats exposed to WIRS. The protective effect of the repeated preadministration of BPEE against WIRS-induced gastric mucosal lesions was similar to that of a single preadministration of vitamin E (250 mg/kg in terms of the extent and manner of protection. From these findings, it is concluded that BPEE preadministered in a repeated manner protects against gastric mucosal lesions in rats exposed to WIRS more effectively than BPEE preadministered in a single manner possibly through its antioxidant and anti-inflammatory actions.

  9. Effect of Repeated Stress Treatments During the Follicular Phase and Early Pregnancy on Reproductive Performance of Gilts

    NARCIS (Netherlands)

    Soede, N.M.; Roelofs, J.B.; Verheijen, R.J.E.; Schouten, W.G.P.; Hazeleger, W.; Kemp, B.

    2007-01-01

    In pig husbandry, stress is being considered an important cause of impaired reproductive performance. Therefore, an experiment was performed to quantify effects of repeated stressors during the follicular phase and/or during early pregnancy on reproductive performance of gilts. Eighty-one cyclic

  10. Hydraulic conductivity of GCLs in MSW landfills

    Institute of Scientific and Technical Information of China (English)

    LI Guo-cheng; YANG Wu-chao; DAN Tang-hui

    2008-01-01

    The state of the art of the study on the hydraulic conductivity of GCLs is presented in terms of the in-fluence of the effective stress, chemical interactions, freeze - thaw cycles and temperature gradients. The chan-ges of void ratio caused by changes of effective stress have a direct linear effect on the hydraulic conductivity, regardless of the cation concentration or the thickness of the adsorbed layer. The hydraulic conductivity is relat-ed to the relative abundance of monovalent and divalent cation(RMD), and RMD has a great effect on the hy-draulic conductivity in weak solution. The long-term susceptibility of GCLs to increased hydraulic conductivity as a response to repeated freeze-thaw cycling is minimal, which has been proved after 150 freeze-thaw cycles. The potential of desiccation cracking increases with the increasing temperature gradient and is related to the ini-tial subsoil water content, the applied overburden stress, etc.

  11. Repeated exposure of adult rats to transient oxidative stress induces various long-lasting alterations in cognitive and behavioral functions.

    Directory of Open Access Journals (Sweden)

    Yoshio Iguchi

    Full Text Available Exposure of neonates to oxidative stress may increase the risk of psychiatric disorders such as schizophrenia in adulthood. However, the effects of moderate oxidative stress on the adult brain are not completely understood. To address this issue, we systemically administrated 2-cyclohexen-1-one (CHX to adult rats to transiently reduce glutathione levels. Repeated administration of CHX did not affect the acquisition or motivation of an appetitive instrumental behavior (lever pressing rewarded by a food outcome under a progressive ratio schedule. In addition, response discrimination and reversal learning were not affected. However, acute CHX administration blunted the sensitivity of the instrumental performance to outcome devaluation, and this effect was prolonged in rats with a history of repeated CHX exposure, representing pro-depression-like phenotypes. On the other hand, repeated CHX administration reduced immobility in forced swimming tests and blunted acute cocaine-induced behaviors, implicating antidepressant-like effects. Multivariate analyses segregated a characteristic group of behavioral variables influenced by repeated CHX administration. Taken together, these findings suggest that repeated administration of CHX to adult rats did not cause a specific mental disorder, but it induced long-term alterations in behavioral and cognitive functions, possibly related to specific neural correlates.

  12. GSTM1 and APE1 genotypes affect arsenic-induced oxidative stress: a repeated measures study

    National Research Council Canada - National Science Library

    Breton, Carrie V; Kile, Molly L; Catalano, Paul J; Hoffman, Elaine; Quamruzzaman, Quazi; Rahman, Mahmuder; Mahiuddin, Golam; Christiani, David C

    2007-01-01

    .... Generation of oxidative stress may contribute to arsenic carcinogenesis. To investigate the association between arsenic exposure and oxidative stress, urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG...

  13. 反复冻融法辅助提取油菜花粉多糖的研究%Technics of Extracting Polysaccharides from Rapeseed Pollen with Repeated Freezing and Thawing Method

    Institute of Scientific and Technical Information of China (English)

    郭卫芸; 刘海英; 白玉敏; 杨公明

    2013-01-01

    Rapeseed pollen was taken as the main raw material and repeated freezing and thawing method was adopted to break the wall of the pollen. The effects on the wall-broken of the rapeseed pollen made by the water content, freeze time, defrosting degree, freezing-thawing times was studied. Through the orthogonal test, the water content was 40 mL/100 g, the freeze time was 4 hours, the defrosting was 80℃, the freezing-thawing was twice. Under the optimal conditions, the dissolving rate of soluble polysaccharide of the rapeseed pollen was 21.79%.%  通过对加水量、冻结时间、解冻温度、冻融次数等进行单因素试验及正交试验,验证反复冻融法对油菜花粉中多糖的辅助提取效果,确定最佳处理条件为:加水量40 mL/100 g,冻结时间4 h,解冻温度80℃,冻融次数2次,在此条件下,油菜花粉可溶性多糖溶出率可达到21.79%。

  14. The development of behavioral and endocrine abnormalities in rats after repeated exposure to direct and indirect stress.

    Science.gov (United States)

    Daniels, Willie Mark Uren; de Klerk Uys, Joachim; van Vuuren, Petra; Stein, Daniel Joseph

    2008-04-01

    The present study compared the effects of direct and indirect stress on the behavior and hypothalamic-pituitary-adrenal axis of rats. Animals were placed in a two compartment box. In one compartment the direct stressed rat was subjected to electric foot shocks randomly applied for 10 minutes (0.5 mA of 1 s duration). In the adjacent compartment, the indirect stressed rats witnessed the application of these electric foot shocks. Our data showed substantial behavioral changes in the open field test, but limited effects in the elevated plus maze. The findings suggested that single and repeated stress exposure may have different consequences, that the effects of stress exposure may develop over time and persist for an extended period, and that both direct and indirect stressed rats displayed a hyposensitive HPA axis following acute restraint stress. Overall our observations moderately indicate direct exposure to elicit behavioral changes, and both direct and indirect exposure to stress to result in aberrations within the neuroendocrine system. With additional development our stress models may be considered for studying the complex interrelationship between an external stressor, and the experience of the organism.

  15. Anxiolytic profile of fluoxetine as monitored following repeated administration in animal rat model of chronic mild stress

    Directory of Open Access Journals (Sweden)

    Muhammad Farhan

    2016-09-01

    Full Text Available Background: Fluoxetine, a selective serotonin re-uptake inhibitor (SSRI, has been proposed to be more effective as an antidepressive drug as compared to other SSRIs. After chronic SSRI administration, the increase in synaptic levels of 5-HT leads to desensitization of somatodentritic 5-HT autoreceptors in the raphe nuclei. Chronic stress may alter behavioral, neurochemical and physiological responses to drug challenges and novel stressors. Methods: Twenty four male rats were used in this study. Animals of CMS group were exposed to CMS. Animals of stressed and unstressed group were administrated with fluoxetine at dose of 1.0 mg/kg s well as 5.0 mg/kg repeatedly for 07 days 1 h before exposed to CMS. The objective of the present study was to evaluate that repeated treatment with fluoxetine could attenuate CMS-induced behavioral deficits. Results: Treatment with fluoxetine attenuated CMS-induced behavioral deficits. Fluoxetine administration induced hypophagia in unstressed as well as CMS rats. Acute and repeated administration of fluoxetine increased motor activity in familiar environment but only repeated administration increased exploratory activity in open field. Anxiolytic effects of fluoxetine were greater in unstressed rats. These anxiolytic effects were produced as result of repeated administration not on acute administration of fluoxetine at 1.0 mg/kg as well as 5.0 mg/kg. Conclusion: The present study demonstrated that CMS exposure resulted into behavioral deficits and produced depressive-like symptoms. Fluoxetine, an SSRI, administration attenuated behavioral deficits induced by CMS. Anxiolytic effects of repeated fluoxetine administration were greater in unstressed than CMS animals.

  16. Over-representation of repeats in stress response genes: a strategy to increase versatility under stressful conditions?

    OpenAIRE

    Rocha, Eduardo P. C.; Matic, Ivan; Taddei, François

    2002-01-01

    The survival of individual organisms facing stress is enhanced by the induction of a set of changes. As the intensity, duration and nature of stress is highly variable, the optimal response to stress may be unpredictable. To face such an uncertain future, it may be advantageous for a clonal population to increase its phenotypic heterogeneity (bet-hedging), ensuring that at least a subset of cells would survive the current stress. With current techniques, assessing the extent of this variabili...

  17. Repeated stressors do not provoke habituation or accumulation of the stress response in the catfish Rhamdia quelen

    Directory of Open Access Journals (Sweden)

    Gessi Koakoski

    2013-06-01

    Full Text Available Fish repeatedly experience stressful situations under experimental and aquaculture conditions, even in their natural habitat. Fish submitted to sequential stressors can exhibit accumulation or habituation on its cortisol response. We posed a central question about the cortisol response profiles after exposure to successive acute stressors of a similar and different nature in Rhamdia quelen. We have shown that successive acute stressors delivered with 12-h, 48-h, and 1-week intervals provoked similar cortisol responses in juvenile R. quelen, without any habituation or accumulation. The cumulative stress response is more associated to short acute stressors with very short intervals of minutes to hours. In our work, we used an interval as short as 12h, and no cumulative response was found. However, if the length of time between stressors is of a day or week as used in our work the most common and an expected phenomenon is the attenuation of the response. Thus, also, the absence of both accumulation of the stress response and the expected habituation is an intriguing result. Our results show that R. quelen does not show habituation or accumulation in its stress responses to repeated stressors, as reported for other fish species

  18. Lactation-induced reduction in hippocampal neurogenesis is reversed by repeated stress exposure

    OpenAIRE

    Hillerer, K.M.; Neumann, I. D.; Couillard-Despres, S.; Aigner, L.; Slattery, D.A.

    2014-01-01

    The peripartum period is a time of high susceptibility for mood and anxiety disorders, some of which have recently been associated with alterations in hippocampal neurogenesis. Several factors including stress, aging, and, perhaps unexpectedly, lactation have been shown to decrease hippocampal neurogenesis. Intriguingly, lactation is also a time of reduced stress responsivity suggesting that the effect of stress on neurogenic processes may differ during this period. Therefore, the aim of the ...

  19. Chronic exercise prevents repeated restraint stress-provoked enhancement of immobility in forced swimming test in ovariectomized mice.

    Science.gov (United States)

    Han, Tae-Kyung; Lee, Jang-Kyu; Leem, Yea-Hyun

    2015-06-01

    We assessed whether chronic treadmill exercise attenuated the depressive phenotype induced by restraint stress in ovariectomized mice (OVX). Immobility of OVX in the forced swimming test was comparable to that of sham mice (CON) regardless of the postoperative time. Immobility was also no difference between restrained mice (exposure to periodic restraint for 21 days; RST) and control mice (CON) on post-exposure 2nd and 9th day, but not 15th day. In contrast, the immobility of ovariectomized mice with repeated stress (OVX + RST) was profoundly enhanced compared to ovariectomized mice-alone (OVX), and this effect was reversed by chronic exercise (19 m/min, 60 min/day, 5 days/week for 8 weeks; OVX + RST + Ex) or fluoxetine administration (20 mg/kg, OVX + RST + Flu). In parallel with behavioral data, the immunoreactivity of Ki-67 and doublecortin (DCX) in OVX was significantly decreased by repeated stress. However, the reduced numbers of Ki-67- and DCX-positive cells in OVX + RST were restored in response to chronic exercise (OVX + RST + Ex) and fluoxetine (OVX + RST + Flu). In addition, the expression pattern of cAMP response element-binding protein (CREB) and calcium-calmodulin-dependent kinase IV (CaMKIV) was similar to that of the hippocampal proliferation and neurogenesis markers (Ki-67 and DCX, respectively). These results suggest that menopausal depression may be induced by an interaction between repeated stress and low hormone levels, rather than a deficit in ovarian secretion alone, which can be improved by chronic exercise.

  20. Estabilidade de géis de amido de milho normal, ceroso e com alto teor de amilose adicionados de gomas guar e xantana durante os processos de congelamento e descongelamento Freeze-thaw stability of normal, waxy and high amylose corn starch gels with added guar and xanthan gums

    Directory of Open Access Journals (Sweden)

    Fernanda Hart Weber

    2008-06-01

    Full Text Available O objetivo do presente trabalho foi estudar os efeitos das gomas guar e xantana sobre a estabilidade dos géis de amido de milho normal, ceroso e com alto teor de amilose submetidos aos processos de congelamento e descongelamento. Os géis desses amidos, com concentração total de sólidos de 10% e adicionados das gomas (0,15; 0,50; 0,85 e 1%, foram submetidos a 5 ciclos de congelamento (20 horas a -18 °C e descongelamento (4 horas a 25 °C, com exceção dos géis com alto teor de amilose, que foram submetidos a apenas 1 ciclo, devido à perda da estrutura de gel. A determinação da sinérese (porcentagem de água liberada foi realizada pela diferença entre a massa inicial e a massa final das amostras. O gel de amido de milho normal liberou 74,45% de água, sendo que a adição de 1% da goma xantana reduziu significativamente a sinérese para 66,43%. A adição de 0,85 e 1% da goma xantana também reduziu a sinérese dos géis de amido ceroso. O menor teor de sinérese foi obtido com a utilização de 1% de goma xantana ao gel de amido de milho com alto teor de amilose, evidenciando a ação crioprotetora desta goma.The objective of the present work was to study the effects of guar and xanthan gums on the stability of normal, waxy and high amylose corn starch gels, submitted to freeze-thaw processes. The gels of these starches with a total solids content of 10% and added gums (0.15;0.50;0.85and1%, were submitted to 5 freezing (20 hours, -18 °C and thawing (4 hours, 25 °C cycles, with exception of the high amylose gels that were submitted to only 1 cycle. Syneresis (% water released was determined by the difference between the initial and final masses of the samples. The normal corn starch gel released 74.45% water and the addition of 1% xanthan gum significantly reduced syneresis to 66.43%. The incorporation of 0.85 and 1% xanthan gum also reduced syneresis of waxy starch gels. The lowest level of syneresis was reached with the use of 1

  1. Study on hormone replacement therapy for patients with poor endometrial growth to freezing-thawing embryo transfer%激素替代方案应用于子宫内膜生长不良患者冻胚移植内膜准备

    Institute of Scientific and Technical Information of China (English)

    朱鹏云; 林妍; 刘芸

    2012-01-01

    Objective To investigate the effects of hormone replacement therapy on endometrial thickness of different dosages and different duration of the patients with poor endometrial growth receiving oral estrogen in frozen-thawed embryo transfer cycles. Methods Retrospective analysis was performed on 97 frozen-thawed embryo transfer cycles of patients with poor endometrial growth treated with estrogen. Patients were divided into implantation group and non-implantation group based on clinical outcome to analyze the relation between embryo implantation outcome and endometrial thickness. Furthermore, the duration and dosage of estrogen were analyzed to detect the effects of different durations and dosages of estrogen on endometrial thickness. Results ( 1 )lt was observed that there was no statistical difference of the endometrial thickness in the estrogen application time and the day of deciding embryo transfer between the embryo implantation group and non-implantation group. However, the endometrial thickening value( thickness value of the day of deciding embryo transfer minus the value of the 12th day of estrogen treatment )of implantation group was significantly higher than that of non-implantation group( P 0. 05 ). ( 3 )There was no significant different on the endometrial thickness and endometrial thickening value between the groups of taking 6 mg estrogen and 9 mg estrogen on the day of deciding embryo transfer( P > 0. 05 ). Conclusions For patients with poor endometrial growth treated with estrogen for preparing endometria in freezing-thawing embryo transfer, the endometrial thickening value was one of the important factors for outcome of frozen-thawed embryo transfer. Taking the estrogen within 19-21 days was favorable for endometrial growth and embryo implantation, but increasing the dosage had no effect on endometrial growth.%目的 探讨子宫内膜生长不良患者行激素替代方案冻融胚胎移植周期中口服雌激素的不同时间及剂量

  2. Baseline and stress-induced glucocorticoid concentrations are not repeatable but covary within individual great tits (Parus major).

    Science.gov (United States)

    Baugh, Alexander T; van Oers, Kees; Dingemanse, Niels J; Hau, Michaela

    2014-11-01

    In evolutionary endocrinology, there is a growing interest in the extent and basis of individual variation in endocrine traits, especially circulating concentrations of hormones. This is important because if targeted by selection, such individual differences present the opportunity for an evolutionary response to selection. It is therefore necessary to examine whether hormone traits are repeatable in natural populations. However, research in this area is complicated by the fact that different hormone traits can be correlated. The nature of these trait correlations (i.e., phenotypic, within-, or among-individual) is critically relevant in terms of the evolutionary implications, and these in turn, depend on the repeatability of each hormone trait. By decomposing phenotypic correlations between hormone traits into their within- and among-individual components it is possible to describe the multivariate nature of endocrine traits and generate inferences about their evolution. In the present study, we repeatedly captured individual great tits (Parus major) from a wild population and measured plasma concentrations of corticosterone. Using a mixed-modeling approach, we estimated repeatabilities in both initial (cf. baseline; CORT0) and stress-induced concentrations (CORT30) and the correlations between those traits among- and within-individuals. We found a lack of repeatability in both CORT0 and CORT30. Moreover, we found a strong phenotypic correlation between CORT0 and CORT30, and due to the lack of repeatability for both traits, there was no among-individual correlation between these two traits-i.e., an individual's average concentration of CORT0 was not correlated with its average concentration of CORT30. Instead, the phenotypic correlation was the result of a strong within-individual correlation, which implies that an underlying environmental factor co-modulates changes in initial and stress-induced concentrations within the same individual over time. These results

  3. Effects of winter irrigation and soil surface mulching during freezing-thawing period on soil water-heat-salt for cotton fields in south Xinjiang%冻融期灌水和覆盖对南疆棉田水热盐的影响

    Institute of Scientific and Technical Information of China (English)

    姚宝林; 李光永; 王峰

    2016-01-01

    Scarce water resources and soil salinity are important limiting factors for agricultural production and environmental melioration in extremely drought area and fragile ecological environment of Tarim Basin in southern Xinjiang. The under-film drip irrigation has gained universal applications as an efficient and economically viable irrigation method for increasing water use efficiency and reducing the adverse effects of cotton growth. But for winter and spring irrigation quotas are relatively high and cause groundwater level to rise, after freezing-thawing in winter, salinization occurs on soil surface and it is harmful to the growth and development of cotton seedlings. Soil surface mulching can effectively reduce soil water loss and soil salt accumulation in winter fallow periods, reduce winter and spring irrigation quota, and achieve the purpose of water saving and salinity controlling. To explore the freezing-thawing characteristics in drip irrigation cotton fields under different soil surface mulching and winter irrigation quotas, field experiments were carried out, which included 3 soil surface mulching methods: bare fields (cotton stubble and plastic film were removed before winter irrigation), high stubble fields (cotton stubble and plastic film remained in fields before winter irrigation), corn straw mulching fields (cotton stubble, plastic film remained in fields and mulched corn residue had the length of about 5-10 cm length and the thickness of 5 cm, 400 kg/hm2), and 2 winter irrigation quotas: winter irrigation 200 mm quota and no winter irrigation.Theexperiment was composed of 6 treatments: winter irrigation with bare land (WIB), winter irrigation with high cotton stubble (WICS), winter irrigation with corn straw mulching (WICM), no winter irrigation with bare land (NWIB), no winter irrigation with high cotton stubble (NWICS), and no winter irrigation with corn straw mulching (NWICM). The soil temperatures in 5, 10, 15, 20, 30, 40, 60, 80 and 100 cm

  4. Repeated static contractions increase mitochondrial vulnerability toward oxidative stress in human skeletal muscle

    DEFF Research Database (Denmark)

    Sahlin, Kent; Nielsen, Jens Steen; Mogensen, Martin

    2006-01-01

    Repeated static contractions (RSC) induce large fluctuations in tissue oxygen tension and increase the generation of reactive oxygen species (ROS). This study investigated the effect of RSC on muscle contractility, mitochondrial respiratory function, and in vitro sarcoplasmic reticulum (SR) Ca(2+...

  5. Recovery from hybrid breakdown in a marine invertebrate is faster, stronger and more repeatable under environmental stress.

    Science.gov (United States)

    Hwang, A S; Pritchard, V L; Edmands, S

    2016-09-01

    Understanding how environmental stress alters the consequences of hybridization is important, because the rate of hybridization and the likelihood of hybrid speciation both appear elevated in harsh, disturbed or marginal habitats. We assessed fitness, morphometrics and molecular genetic composition over 14 generations of hybridization between two highly divergent populations of the marine copepod Tigriopus californicus. Replicated, experimental hybrid populations in both control and high-salinity conditions showed a decline in fitness, followed by a recovery. Recovery was faster in the salinity stress treatment, returning to parental levels up to two generations earlier than in the control. This recovery was stable in the high-salinity treatment, whereas in the control treatment, fitness dropped back below parental levels at the final time point. Recovery in the high-salinity treatment was also stronger in terms of competitive fitness and heat-shock tolerance. Finally, consequences of hybridization were more repeatable under salinity stress, where among-replicate variance for survivorship and molecular genetic composition was lower than in the control treatment. In a system with low effective population sizes (estimates ranged from 17 to 63), where genetic drift might be expected to be the predominate force, strong selection under harsh environmental conditions apparently promoted faster, stronger and more repeatable recovery from depressed hybrid fitness.

  6. Cognitive and neuroinflammatory consequences of mild repeated stress are exacerbated in aged mice

    Science.gov (United States)

    Buchanan, J.B.; Sparkman, N.L.; Chen, J.; Johnson, R.W.

    2008-01-01

    Summary Peripheral immune stimulation as well as certain types of psychological stress increases brain levels of inflammatory cytokines such as interleukin-1β (IL-1β), IL-6 and tumor necrosis factor α (TNFα). We have demonstrated that aged mice show greater increases in central inflammatory cytokines, as well as greater cognitive deficits, compared to adults in response to peripheral lipopolysaccharide (LPS) administration. Because aged mice are typically more sensitive to systemic stressors such as LPS, and certain psychological stressors induce physiological responses similar to those that follow LPS, we hypothesized that aged mice would be more sensitive to the physiological and cognitive effects of mild stress than adult mice. Here, adult (3–5 mo) and aged (22–23 mo) male BALB/c mice were trained in the Morris water maze for 5 days. Mice were then exposed to a mild restraint stress of 30 minutes before being tested in a working memory version of the water maze over a 3 day period. On day 4 mice were stressed and then killed for collection of blood and brain. In a separate group of animals, mice were killed immediately after one, two or three 30 min restraint sessions and blood for peripheral corticosterone and cytokine protein measurement, and brains were dissected for central cytokine mRNA measurement. Stress disrupted spatial working memory in both adult and aged mice but to a much greater extent in the aged mice. In addition, aged mice showed an increase in stress-induced expression of hippocampal IL-1β mRNA and MHC class II protein compared to non-stressed controls while expression in adult mice was unaffected by stress. These data show that aged mice are more sensitive to both the cognitive and inflammatory effects of mild stress than are adult mice and suggest a possible a role for IL-1β. PMID:18407425

  7. Effect of repeated stress in early childhood on the onset of diabetes mellitus in male Spontaneously Diabetic Torii rats.

    Science.gov (United States)

    Ookawa, Katumasa; Mochizuki, Kazuo; Yokogoshi, Hidehiko

    2008-02-01

    Spontaneously Diabetic Torii (SDT) rats were discovered from SD rats and represent a confirmed spontaneous type 2 diabetes mellitus model. We investigated the effect of repeated stress in early childhood on SDT rats fed a high-fat diet, on locomotor activity and on the onset of diabetes mellitus. Regarding stress, a water immersion-restraint stress (WIRS) burden was applied 10 times every other day from 4 weeks of age. The results of the study showed, that the locomotor activity of the young SDT rats was clearly lower than that of the SD rats, and their locomotor activity was inferred to be congenitally low. In addition, the stress-burdened SDT rats showed delayed onset of diabetes mellitus and impaired glucose tolerance compared with the rats not receiving stress burden. The locomotor activity of SDT rats is less than that of SD rats, and they SDT rats are thought to have poor at spontaneous energy expenditure. On the other hand, the feeding efficiency of the WIRS-burdened SDT rats was reduced, and in comparison with the SDT rats with no WIRS burden, energy expenditure was increased; this is suggested to influence the onset of diabetes mellitus.

  8. Modification of hippocampal markers of synaptic plasticity by memantine in animal models of acute and repeated restraint stress: implications for memory and behavior.

    Science.gov (United States)

    Amin, Shaimaa Nasr; El-Aidi, Ahmed Amro; Ali, Mohamed Mostafa; Attia, Yasser Mahmoud; Rashed, Laila Ahmed

    2015-06-01

    Stress is any condition that impairs the balance of the organism physiologically or psychologically. The response to stress involves several neurohormonal consequences. Glutamate is the primary excitatory neurotransmitter in the central nervous system, and its release is increased by stress that predisposes to excitotoxicity in the brain. Memantine is an uncompetitive N-methyl D-aspartate glutamatergic receptors antagonist and has shown beneficial effect on cognitive function especially in Alzheimer's disease. The aim of the work was to investigate memantine effect on memory and behavior in animal models of acute and repeated restraint stress with the evaluation of serum markers of stress and the expression of hippocampal markers of synaptic plasticity. Forty-two male rats were divided into seven groups (six rats/group): control, acute restraint stress, acute restraint stress with Memantine, repeated restraint stress, repeated restraint stress with Memantine and Memantine groups (two subgroups as positive control). Spatial working memory and behavior were assessed by performance in Y-maze. We evaluated serum cortisol, tumor necrotic factor, interleukin-6 and hippocampal expression of brain-derived neurotrophic factor, synaptophysin and calcium-/calmodulin-dependent protein kinase II. Our results revealed that Memantine improved spatial working memory in repeated stress, decreased serum level of stress markers and modified the hippocampal synaptic plasticity markers in both patterns of stress exposure; in ARS, Memantine upregulated the expression of synaptophysin and brain-derived neurotrophic factor and downregulated the expression of calcium-/calmodulin-dependent protein kinase II, and in repeated restraint stress, it upregulated the expression of synaptophysin and downregulated calcium-/calmodulin-dependent protein kinase II expression.

  9. Repeated oral administration of capsaicin increases anxiety-like behaviours with prolonged stress-response in rats

    Indian Academy of Sciences (India)

    Y-J Choi; J Y Kim; S B Yoo; J-H Lee; J W Jahng

    2013-09-01

    This study was conducted to examine the psycho-emotional effects of repeated oral exposure to capsaicin, the principal active component of chili peppers. Each rat received 1 mL of 0.02% capsaicin into its oral cavity daily, and was subjected to behavioural tests following 10 daily administrations of capsaicin. Stereotypy counts and rostral grooming were significantly increased, and caudal grooming decreased, in capsaicin-treated rats during the ambulatory activity test. In elevated plus maze test, not only the time spent in open arms but also the percent arm entry into open arms was reduced in capsaicin-treated rats compared with control rats. In forced swim test, although swimming duration was decreased, struggling increased in the capsaicin group, immobility duration did not differ between the groups. Repeated oral capsaicin did not affect the basal levels of plasma corticosterone; however, the stress-induced elevation of plasma corticosterone was prolonged in capsaicin treated rats. Oral capsaicin exposure significantly increased c-Fos expression not only in the nucleus tractus of solitarius but also in the paraventricular nucleus. Results suggest that repeated oral exposure to capsaicin increases anxiety-like behaviours in rats, and dysfunction of the hypothalamic-pituitary-adrenal axis may play a role in its pathophysiology.

  10. Lipid Profile and Oxidative Stress Markers in Wistar Rats following Oral and Repeated Exposure to Fijk Herbal Mixture

    Directory of Open Access Journals (Sweden)

    Oluyomi Stephen Adeyemi

    2014-01-01

    Full Text Available This study determined the effect of the oral and repeated administration of Fijk herbal mixture on rat biochemical and morphological parameters. Twenty-four Wistar rats were distributed into four groups of 6. Group A served as control and received oral administration of distilled water daily. The experimental groups B, C, and D were daily and orally exposed to Fijk herbal mixture at 15, 30, and 45 mg/kg, respectively. Treatments lasted for 21 days. The rats were sacrificed under mild diethyl ether anesthesia 24 hr after cessation of treatment. The blood and liver samples were collected and used for the biochemical and morphological analyses. Oral exposure to Fijk caused elevated levels of rat plasma ALT, AST, triglycerides, LDL, and MDA. In contrast, rat plasma HDL, GSH, and ALP levels were lowered by Fijk oral exposure. Also, the herbal remedy caused a dose-dependent elevation in the plasma atherogenic index. The histopathology examinations of rat liver sections revealed inimical cellular alterations caused by repeated exposure to Fijk. Study provides evidence that oral and repeated exposure to Fijk in rats raised the atherogenic index and potentiated oxidative stress as well as hepatic injury.

  11. Response of the Hypothalamic-Pituitary-Adrenal System to Repeated Moderate Psychoemotional Stress Exposure Is Associated with Behavioral Parameters.

    Science.gov (United States)

    Goncharova, N D; Chigarova, O A; Oganyan, T E

    2017-05-01

    Individual features of the response of the hypothalamic-pituitary-adrenal axis (HPAA) to repeated moderate stress exposure (daily 2-h restraint stress for 10 days) was studied in young female rhesus monkeys with healthy normal behavior and combined group of female rhesus monkeys with abnormal depression-like and anxious behavior. No between-group differences in the response of ACTH and cortisol were found on day 1. On day 10, a rapid and less pronounced increase in ACTH secretion was observed in all animals in comparison with day 1. Analysis of between-group differences in HPAA response showed higher increase in ACTH level and lower increase in cortisol concentration in animals with depression-like and anxious behavior. These changes were similar to the previously described differences in the response of the adenohypophysis and adrenal cortex to acute restraint stress in old monkeys with similar behavior. Thus, individuals with depression-like and anxious behavior demonstrate impaired stress-induced reactivity of HPAA as early as in young age.

  12. Stress Levels of Agricultural Science Cooperating Teachers and Student Teachers: A Repeated Measures Comparative Assessment

    Science.gov (United States)

    McKim, Billy R.; Rayfield, John; Harlin, Julie; Adams, Andy

    2013-01-01

    This study compared job stress levels of Texas agricultural science cooperating teachers and Texas agricultural science student teachers across a semester. The research objectives included describing secondary agricultural science cooperating teachers and student teachers perceptions of stressors, by time of semester (beginning, middle, and end),…

  13. Plasma catecholamine, corticosterone and glucose responses to repeated stress in rats : Effect of interstressor interval length

    NARCIS (Netherlands)

    de Boer, S.F.; Koopmans, S.J.; Slangen, J L; Van der Gugten, J

    1990-01-01

    Plasma noradrenaline (NA), adrenaline (A), corticosterone (CS) and glucose concentrations were determined in blood frequently sampled via a cardiac catheter from freely behaving rats exposed to five successive trials of water-immersion stress (WIS) with an interval between successive trials (interst

  14. Environmental heat stress modulates thyroid status and its response to repeated endotoxin (LPS) challenge in steers

    Science.gov (United States)

    Thyroid hormones are important in the adaptation to heat stress, allowing the adjustment of metabolic rates in favor of decreased energy utilization and heat production. Thyroid status is compromised in a variety of acute and chronic infections and toxin-mediated disease states. Our objective was to...

  15. Repeated measures of inflammation and oxidative stress biomarkers in preeclamptic and normotensive pregnancies.

    Science.gov (United States)

    Ferguson, Kelly K; Meeker, John D; McElrath, Thomas F; Mukherjee, Bhramar; Cantonwine, David E

    2017-05-01

    Preeclampsia is a prevalent and enigmatic disease, in part characterized by poor remodeling of the spiral arteries. However, preeclampsia does not always clinically present when remodeling has failed to occur. Hypotheses surrounding the "second hit" that is necessary for the clinical presentation of the disease focus on maternal inflammation and oxidative stress. Yet, the studies to date that have investigated these factors have used cross-sectional study designs or small study populations. In the present study, we sought to explore longitudinal trajectories, beginning early in gestation, of a panel of inflammation and oxidative stress markers in women who went on to have preeclamptic or normotensive pregnancies. We examined 441 subjects from the ongoing LIFECODES prospective birth cohort, which included 50 mothers who experienced preeclampsia and 391 mothers with normotensive pregnancies. Participants provided urine and plasma samples at 4 time points during gestation (median, 10, 18, 26, and 35 weeks) that were analyzed for a panel of oxidative stress and inflammation markers. Oxidative stress biomarkers included 8-isoprostane and 8-hydroxydeoxyguanosine. Inflammation biomarkers included C-reactive protein, the cytokines interleukin-1β, -6, and -10, and tumor necrosis factor-α. We created Cox proportional hazard models to calculate hazard ratios based on time of preeclampsia diagnosis in association with biomarker concentrations at each of the 4 study visits. In adjusted models, hazard ratios of preeclampsia were significantly (Pinflammation biomarkers that were measured at visit 2 (median, 18 weeks; hazard ratios, 1.31-1.83, in association with an interquartile range increase in biomarker). Hazard ratios at this time point were the most elevated for C-reactive protein, for interleukin-1β, -6, and -10, and for the oxidative stress biomarker 8-isoprostane (hazard ratio, 1.68; 95% confidence interval, 1.14-2.48) compared to other time points. Hazard ratios for

  16. Mediation of the Relationship between Maternal Phthalate Exposure and Preterm Birth by Oxidative Stress with Repeated Measurements across Pregnancy.

    Science.gov (United States)

    Ferguson, Kelly K; Chen, Yin-Hsiu; VanderWeele, Tyler J; McElrath, Thomas F; Meeker, John D; Mukherjee, Bhramar

    2017-03-01

    Mediation analysis is useful for understanding mechanisms and has been used minimally in the study of the environment and disease. We examined mediation of the association between phthalate exposure during pregnancy and preterm birth by oxidative stress. This nested case-control study of preterm birth (n = 130 cases, 352 controls) included women who delivered in Boston, Massachusestts, from 2006 through 2008. Phthalate metabolites and 8-isoprostane, an oxidative stress biomarker, were measured in urine from three visits in pregnancy. We applied four counterfactual mediation methods: method 1, utilizing exposure and mediator averages; method 2, using averages but allowing for an exposure-mediator interaction; method 3, incorporating longitudinal measurements of the exposure and mediator; and method 4, using longitudinal measurements and allowing for an exposure-mediator interaction. We observed mediation of the associations between phthalate metabolites and all preterm birth by 8-isoprostane, with the greatest estimated proportion mediated observed for spontaneous preterm births specifically. Fully utilizing repeated measures of the exposure and mediator improved precision of indirect (i.e., mediated) effect estimates, and including an exposure-mediator interaction increased the estimated proportion mediated. For example, for mono(2-ethyl-carboxy-propyl) phthalate (MECPP), a metabolite of di(2-ethylhexyl) phthalate (DEHP), the percent of the total effect mediated by 8-isoprostane increased from 47% to 60% with inclusion of an exposure-mediator interaction term, in reference to a total adjusted odds ratio of 1.67 or 1.48, respectively. This demonstrates mediation of the phthalate-preterm birth relationship by oxidative stress, and the utility of complex regression models in capturing mediated associations when repeated measures of exposure and mediator are available and an exposure-mediator interaction may exist. Citation: Ferguson KK, Chen YH, VanderWeele TJ, Mc

  17. Modulatory influence of rarely repeated of immobilization episodes on the interleukin-1β-dependent reaction of blood leukocytes and hepatoprotective effect of restraint stress.

    Science.gov (United States)

    Tseilikman, O B; Tseilikman, V E; Linin, A V; Gubkin, D A; Rudina, E A; Trubetskoy, S A; Ivanov, P V; Pozdnyakov, E A

    2011-02-01

    Repeated episodes of 1-h restraint stress were accompanied by a decrease in the sensitivity of blood leukocytes and cytochrome P450-dependent monooxygenases of the liver to recombinant IL-1β. These changes are associated with the anti-inflammatory hepatoprotective effect of chronic stress.

  18. Electric signal emissions during repeated abrupt uniaxial compressional stress steps in amphibolite from KTB drilling

    Directory of Open Access Journals (Sweden)

    D. Triantis

    2007-01-01

    Full Text Available Laboratory experiments have confirmed that the application of uniaxial stress on rock samples is accompanied by the production of weak electric currents, to which the term Pressure Stimulated Currents – PSC has been attributed. In this work the PSC emissions in amphibolite samples from KTB drilling are presented and commented upon. After having applied sequential loading and unloading cycles on the amphibolite samples, it was ascertained that in every new loading cycle after unloading, the emitted PSC exhibits lower peaks. This attitude of the current peaks is consistent with the acoustic emissions phenomena, and in this work is verified for PSC emissions during loading – unloading procedures. Consequently, the evaluation of such signals can help to correlate the state and the remaining strength of the sample with respect to the history of its mechanical stress.

  19. Effects of Repeated Acute Stress in Obese and Non-Obese Rats

    Science.gov (United States)

    2008-04-02

    levels in the body. The effects of a dysregulated stress responses and, in particular, elevated cortisol levels are evident in the brain and...has a mutated leptin receptor gene (Duclos et aI., 2005). This gene produces the hormone leptin which is expressed in adipose tissue (Kandel...and to greater adipose tissue in diet-induced obese rats (Levin & Dunn-Meynell, 2000). Other methods to induce obesity in animals include I IU t

  20. The effect of freezing-thawing cycle on the combined forms and availability of the adsorbed Cd2+ in soil%冻融对土壤吸附态镉赋存形态及生物活性的影响

    Institute of Scientific and Technical Information of China (English)

    王展; 张玉龙; 张砚铭; 王丽娟; 郑明明

    2013-01-01

    The effect of the freezing and thawing frequency and soil water content on the combined forms and availability of absorbed Cd of brown soil collected from the Northeast China was investigated. 20 mg·L-1 Cd was added to the soil and the soil was incubated at - 30 ℃ and 20 ℃ for 24 h, respectively. Soil samples of different water content (10% , 40% , 70% , 100% and 120% of the field capacity) were subsequently refrozen and thawed for 0,1,3,6,9 cycles. The different combined forms of Cd2 + were determined with sequential extraction method. The result showed that the order of the ratio of different combined forms of Cd to the adsorbed Cd + was exchangeable form > residual form > bound to carbonates form > bound to Fe-Mn oxides form > bound to organic matter form. The ratios of different combined forms of Cd to the adsorbed Cd2 + varied along with the change of freezing-thawing cycle frequency and soil water content. The effect of the freezing and thawing times on exchangeable Cd, bound to carbonates Cd, bound to Fe-Mn oxides Cd and residual Cd was significant, while the effect on bound to organic matter Cd was insignificant. The effect of soil water content on exchangeable Cd, bound to carbonates Cd, bound to Fe-Mn oxides Cd was significant, while the effect on bound to organic matter Cd and residual Cd was insignificant. The absorbed Cd in the sampled soil possessed very strong availability, and the availability index ( K) and mobility index (M) were 65. 9638% and 62.9851% , respectively. The K and M increased firstly, then decreased and finally reached a plateau with the increasing freezing and thawing frequency, which indicated that the soil had buffer capacity in some extent.%以东北地区棕壤为供试土壤,通过人工控温、室内培养的方法,测定了不同冻融次数(冻融温度-30~20℃,冻融时间24 h,冻融次数0、1、3、6、9次)和不同土壤含水量处理下(田间持水量的10%、40%、70%、100%、120

  1. Central serotonin depletion modulates the behavioural, endocrine and physiological responses to repeated social stress and subsequent c-fos expression in the brains of male rats.

    Science.gov (United States)

    Chung, K K; Martinez, M; Herbert, J

    1999-01-01

    Intraspecific confrontation has been used to study effect of depleting central serotonin on the adaptation of male rats to repeated social stress (social defeat). Four groups of adult male rats were used (serotonin depletion/sham: stressed; serotonin depletion/sham: non-stressed). Central serotonin was reduced (by 59-97%) by a single infusion of the neurotoxin 5,7-dihydroxtryptamine (150 microg) into the cerebral ventricles; levels of dopamine and noradrenaline were unaltered (rats received appropriate uptake blockers prior to neurotoxic infusions). Sham-operated animals received solute only. Rats were then either exposed daily for 10 days to a second larger aggressive male in the latter's home cage, or simply transferred to an empty cage (control procedure). Rats with reduced serotonin failed to show the increased freezing behaviour during the pre-defeat phase of the social interaction test characteristic of sham animals. There was no change in the residents' behaviour. Core temperature increased during aggressive interaction in sham rats, and this did not adapt with repeated stress. By contrast, stress-induced hyperthermia was accentuated in serotonin-reduced rats as the number of defeat sessions increased. Basal core temperature was unaffected by serotonin depletion. Heart rate increased during social defeat, but this did not adapt with repeated stress; serotonin depletion had no effect on this cardiovascular response. Basal corticosterone was increased in serotonin-depleted rats, but the progressive reduction in stress response over days was not altered. C-fos expression in the brain was not altered in control (non-stressed) rats by serotonin reduction in the areas examined, but there was increased expression after repeated social stress in the medial amygdala of 5-HT depleted rats. These experiments show that reduction of serotonin alters responses to repeated social stress in male rats, and suggests a role for serotonin in the adaptive process.

  2. Permanent relief from intermittent cold stress-induced fibromyalgia-like abnormal pain by repeated intrathecal administration of antidepressants

    Directory of Open Access Journals (Sweden)

    Mukae Takehiro

    2011-09-01

    Full Text Available Abstract Background Fibromyalgia (FM is characterized by chronic widespread pain, which is often refractory to conventional painkillers. Numerous clinical studies have demonstrated that antidepressants are effective in treating FM pain. We previously established a mouse model of FM-like pain, induced by intermittent cold stress (ICS. Results In this study, we find that ICS exposure causes a transient increase in plasma corticosterone concentration, but not in anxiety or depression-like behaviors. A single intrathecal injection of an antidepressant, such as milnacipran, amitriptyline, mianserin or paroxetine, had an acute analgesic effect on ICS-induced thermal hyperalgesia at post-stress day 1 in a dose-dependent manner. In addition, repeated daily antidepressant treatments during post-stress days 1-5 gradually reversed the reduction in thermal pain threshold, and this recovery was maintained for at least 7 days after the final treatment. In addition, relief from mechanical allodynia, induced by ICS exposure, was also observed at day 9 after the cessation of antidepressant treatment. In contrast, the intravenous administration of these antidepressants at conventional doses failed to provide relief. Conclusions These results suggest that the repetitive intrathecal administration of antidepressants permanently cures ICS-induced FM pain in mice.

  3. Loss of Sustained Activity in the Ventromedial Prefrontal Cortex in Response to Repeated Stress in Individuals with Early-Life Emotional Abuse: Implications for Depression Vulnerability

    Directory of Open Access Journals (Sweden)

    Lihong eWang

    2013-06-01

    Full Text Available Repeated psychosocial stress in early life has significant impact on both behavior and neural function which, together, increase vulnerability to depression. However, neural mechanisms related to repeated stress remain unclear. We hypothesize that early-life stress may result in a reduced capacity for cognitive control in response to a repeated stressor, particularly in individuals who developed maladaptive emotional processing strategies, namely trait rumination. Individuals who encountered early-life stress but have adaptive emotional processing, namely trait mindfulness, may demonstrate an opposite pattern. Using a mental arithmetic task to induce mild stress and a mindful breathing task to induce a mindful state, we tested this hypothesis by examining blood perfusion changes over time in healthy young men. We found that subjects with early-life stress, particularly emotional abuse, failed to sustain neural activation in the orbitofrontal and ventromedial prefrontal cortex (vmPFC over time. Given that the vmPFC is known to regulate amygdala activity during emotional processing, we subsequently compared the perfusion in the vmPFC and the amygdala in depression-vulnerable (having early life stress and high in rumination and resilient (having early life stress and high in mindfulness subjects. We found that depression-vulnerable subjects had increased amygdala perfusion and reduced vmPFC perfusion during the later runs than that during the earlier stressful task runs. In contrast, depression resilient individuals showed the reverse pattern. Our results indicate that the vmPFC of depression-vulnerable subjects may have a limited capacity to inhibit amygdala activation to repeated stress over time, whereas the vmPFC in resilient individuals may adapt to stress quickly. This pilot study warrants future investigation to clarify the stress-related neural activity pattern dynamically to identify depression vulnerability at an individual level.

  4. Repeated measures of urinary oxidative stress biomarkers during pregnancy and preterm birth.

    Science.gov (United States)

    Ferguson, Kelly K; McElrath, Thomas F; Chen, Yin-Hsiu; Loch-Caruso, Rita; Mukherjee, Bhramar; Meeker, John D

    2015-02-01

    The purpose of this study was to investigate oxidative stress as a mechanism of preterm birth in human subjects; we examined associations between urinary biomarkers of oxidative stress that were measured at multiple time points during pregnancy and preterm birth. This nested case-control study included 130 mothers who delivered preterm and 352 mothers who delivered term who were originally recruited as part of an ongoing prospective birth cohort at Brigham and Women's Hospital. Two biomarkers that included 8-hydroxydeoxyguanosine (8-OHdG) and 8-isoprostane were measured in urine samples that were collected at up to 4 time points (median 10, 18, 26, and 35 weeks) during gestation. Urinary concentrations of 8-isoprostane and 8-OHdG decreased and increased, respectively, as pregnancy progressed. Average levels of 8-isoprostane across pregnancy were associated with increased odds of spontaneous preterm birth (adjusted odds ratio, 6.25; 95% confidence interval, 2.86-13.7), and associations were strongest with levels measured later in pregnancy. Average levels of 8-OHdG were protective against overall preterm birth (adjusted odds ratio, 0.19; 95% confidence interval, 0.10-0.34), and there were no apparent differences in the protective effect in cases of spontaneous preterm birth compared with cases of placental origin. Odds ratios for overall preterm birth were more protective in association with urinary 8-OHdG concentrations that were measured early in pregnancy. Maternal oxidative stress may be an important contributor to preterm birth, regardless of subtype and timing of exposure during pregnancy. The 2 biomarkers that were measured in the present study had opposite associations with preterm birth; an improved understanding of what each represents may help to identify more precisely important mechanisms in the pathway to preterm birth. Copyright © 2015 Elsevier Inc. All rights reserved.

  5. Repeated Thermal Stress, Shading, and Directional Selection in the Florida Reef Tract

    Directory of Open Access Journals (Sweden)

    Robert van Woesik

    2017-06-01

    Full Text Available Over the last three decades reef corals have been subjected to an unprecedented frequency and intensity of thermal-stress events, which have led to extensive coral bleaching, disease, and mortality. Over the next century, the climate is predicted to drive sea-surface temperatures to even higher levels, consequently increasing the risk of mass bleaching and disease outbreaks. Yet, there is considerable temporal and spatial variation in coral bleaching and in disease prevalence. Using data collected from 2,398 sites along the Florida reef tract from 2005 to 2015, this study examined the temporal and spatial patterns of coral bleaching and disease in relation to coral-colony size, depth, temperature, and chlorophyll-a concentrations. The results show that coral bleaching was most prevalent during the warmest years in 2014 and 2015, and disease was also most prevalent in 2010, 2014, and 2015. Although the majority of the corals surveyed were found in habitats with low chlorophyll-a concentrations, and high irradiance, these same habitats showed the highest prevalence of coral bleaching and disease outbreaks during thermal-stress events. These results suggest that directional selection in a warming ocean may favor corals able to tolerate inshore, shaded environments with high turbidity and productivity.

  6. Physical exercise affects the epigenetic programming of rat brain and modulates the adaptive response evoked by repeated restraint stress.

    Science.gov (United States)

    Kashimoto, R K; Toffoli, L V; Manfredo, M H F; Volpini, V L; Martins-Pinge, M C; Pelosi, G G; Gomes, M V

    2016-01-01

    Epigenetics has recently been linked to molecular adaptive responses evoked by physical exercise and stress. Herein we evaluated the effects of physical exercise on global DNA methylation and expression of the Dnmt1 gene in the rat brain and also verified its potential to modulate responses evoked by repeated restraint stress (RRS). Wistar rats were classified into the following experimental groups: (1) physically active (EX): animals submitted to swimming during postnatal days 53-78 (PND); (2) stress (ST): animals submitted to RRS during 75-79PND; (3) exercise-stress (EX-ST): animals submitted to swimming during 53-78PND and to RRS during 75-79PND, and (4) control (CTL): animals that were not submitted to intervention. Samples from the hippocampus, cortex and hypothalamus were obtained at 79PND. The global DNA methylation profile was assessed using an ELISA-based method and the expression of Dnmt1 was evaluated by real-time PCR. Significantly increased methylation was observed in the hypothalamus of animals from the EX group in comparison to CTL. Comparative analysis involving the EX-ST and ST groups revealed increased global DNA methylation in the hippocampus, cortex, and hypothalamus of EX-ST, indicating the potential of physical exercise in modulating the responses evoked by RRS. Furthermore, decreased expression of the Dnmt1 gene was observed in the hippocampus and hypothalamus of animals from the EX-ST group. In summary, our data indicate that physical exercise affects DNA methylation of the hypothalamus and might modulate epigenetic responses evoked by RRS in the hippocampus, cortex, and hypothalamus. Copyright © 2015 Elsevier B.V. All rights reserved.

  7. Corticosterone stress response shows long-term repeatability and links to personality in free-living Nazca boobies.

    Science.gov (United States)

    Grace, Jacquelyn K; Anderson, David J

    2014-11-01

    The concept of "coping styles", or consistently different responses to stressors, is of broad interest in behavioral ecology and biomedicine. Two critical predictions of this concept are individual consistency of neurophysiological and behavioral responses (relative to population variability) and a negative relationship between aggression/proactivity and hypothalamic-pituitary-adrenal axis reactivity. Recent studies failed to provide strong support for these predictions, especially outside of strictly controlled conditions, and long-term measures to test the first prediction are rare. Here, we demonstrate individual repeatability across 2-3years of maximum circulating corticosterone concentration [CORT] and area under the [CORT] response curve (AUCI) during a standard capture-restraint test in wild, free-living adult Nazca boobies (Sula granti). We also show that the stress response predicts the personality traits aggression and anxiety in these birds (measured in the wild); however, the strength of these results was weak. Maximum [CORT] and AUCI showed higher repeatability between years than baseline [CORT]. After controlling breeding status, sex, mass, date sampled, and their interactions, baseline [CORT] was most closely related to personality traits, followed by AUCI, and then maximum [CORT]. The direction of these relationships depended on whether the testing context was social or non-social. [CORT] parameters had little to no relationship with cross-context plasticity in personality traits. Our results generally affirm two critical predictions of coping styles, but match the emerging trend that these relationships are weak in the wild, and may depend on testing context.

  8. Neuronal changes and oxidative stress in adolescent rats after repeated exposure to mephedrone

    Energy Technology Data Exchange (ETDEWEB)

    López-Arnau, Raúl; Martínez-Clemente, José [Department of Pharmacology and Therapeutic Chemistry (Pharmacology Section), Faculty of Pharmacy, University of Barcelona (Spain); Institute of Biomedicine (IBUB), Faculty of Pharmacy, University of Barcelona (Spain); Rodrigo, Teresa [Animal Experimentation Unit of Psychology and Pharmacy, University of Barcelona (Spain); Pubill, David [Department of Pharmacology and Therapeutic Chemistry (Pharmacology Section), Faculty of Pharmacy, University of Barcelona (Spain); Institute of Biomedicine (IBUB), Faculty of Pharmacy, University of Barcelona (Spain); Camarasa, Jorge, E-mail: jcamarasa@ub.edu [Department of Pharmacology and Therapeutic Chemistry (Pharmacology Section), Faculty of Pharmacy, University of Barcelona (Spain); Institute of Biomedicine (IBUB), Faculty of Pharmacy, University of Barcelona (Spain); Escubedo, Elena [Department of Pharmacology and Therapeutic Chemistry (Pharmacology Section), Faculty of Pharmacy, University of Barcelona (Spain); Institute of Biomedicine (IBUB), Faculty of Pharmacy, University of Barcelona (Spain)

    2015-07-01

    Mephedrone is a new designer drug of abuse. We have investigated the neurochemical/enzymatic changes after mephedrone administration to adolescent rats (3 × 25 mg/kg, s.c. in a day, with a 2 h interval between doses, for two days) at high ambient temperature (26 ± 2 °C), a schedule that intends to model human recreational abuse. In addition, we have studied the effect of mephedrone in spatial learning and memory. The drug caused a transient decrease in weight gain. After the first dose, animals showed hypothermia but, after the subsequent doses, temperature raised over the values of saline-treated group. We observed the development of tolerance to these thermoregulatory effects of mephedrone. Mephedrone induced a reduction of the densities of dopamine (30% in the frontal cortex) and serotonin (40% in the frontal cortex and the hippocampus and 48% in the striatum) transporters without microgliosis. These deficits were also accompanied by a parallel decrease in the expression of tyrosine hydroxylase and tryptophan hydroxylase 2. These changes matched with a down-regulation of D{sub 2} dopamine receptors in the striatum. Mephedrone also induced an oxidative stress evidenced by an increase of lipid peroxidation in the frontal cortex, and accompanied by a rise in glutathione peroxidase levels in all studied brain areas. Drug-treated animals displayed an impairment of the reference memory in the Morris water maze one week beyond the cessation of drug exposure, while the spatial learning process seems to be preserved. These findings raise concerns about the neuronal long-term effects of mephedrone. - Highlights: • We studied the dopaminergic and serotonergic neurotoxicity of mephedrone in rats. • Mephedrone induced a transient hypothermia following sustained hyperthermia. • In a weekend consumption pattern, mephedrone induced selective neurotoxicity. • Mephedrone generated oxidative stress. • Mephedrone induced an impairment in memory function.

  9. Montmorency cherries reduce the oxidative stress and inflammatory responses to repeated days high-intensity stochastic cycling.

    Science.gov (United States)

    Bell, Phillip G; Walshe, Ian H; Davison, Gareth W; Stevenson, Emma; Howatson, Glyn

    2014-02-21

    This investigation examined the impact of Montmorency tart cherry concentrate (MC) on physiological indices of oxidative stress, inflammation and muscle damage across 3 days simulated road cycle racing. Trained cyclists (n = 16) were divided into equal groups and consumed 30 mL of MC or placebo (PLA), twice per day for seven consecutive days. A simulated, high-intensity, stochastic road cycling trial, lasting 109 min, was completed on days 5, 6 and 7. Oxidative stress and inflammation were measured from blood samples collected at baseline and immediately pre- and post-trial on days 5, 6 and 7. Analyses for lipid hydroperoxides (LOOH), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), interleukin-8 (IL-8), interleukin-1-beta (IL-1-β), high-sensitivity C-reactive protein (hsCRP) and creatine kinase (CK) were conducted. LOOH (p < 0.01), IL-6 (p < 0.05) and hsCRP (p < 0.05) responses to trials were lower in the MC group versus PLA. No group or interaction effects were found for the other markers. The attenuated oxidative and inflammatory responses suggest MC may be efficacious in combating post-exercise oxidative and inflammatory cascades that can contribute to cellular disruption. Additionally, we demonstrate direct application for MC in repeated days cycling and conceivably other sporting scenario's where back-to-back performances are required.

  10. Montmorency Cherries Reduce the Oxidative Stress and Inflammatory Responses to Repeated Days High-Intensity Stochastic Cycling

    Directory of Open Access Journals (Sweden)

    Phillip G. Bell

    2014-02-01

    Full Text Available This investigation examined the impact of Montmorency tart cherry concentrate (MC on physiological indices of oxidative stress, inflammation and muscle damage across 3 days simulated road cycle racing. Trained cyclists (n = 16 were divided into equal groups and consumed 30 mL of MC or placebo (PLA, twice per day for seven consecutive days. A simulated, high-intensity, stochastic road cycling trial, lasting 109 min, was completed on days 5, 6 and 7. Oxidative stress and inflammation were measured from blood samples collected at baseline and immediately pre- and post-trial on days 5, 6 and 7. Analyses for lipid hydroperoxides (LOOH, interleukin-6 (IL-6, tumor necrosis factor-alpha (TNF-α, interleukin-8 (IL-8, interleukin-1-beta (IL-1-β, high-sensitivity C-reactive protein (hsCRP and creatine kinase (CK were conducted. LOOH (p < 0.01, IL-6 (p < 0.05 and hsCRP (p < 0.05 responses to trials were lower in the MC group versus PLA. No group or interaction effects were found for the other markers. The attenuated oxidative and inflammatory responses suggest MC may be efficacious in combating post-exercise oxidative and inflammatory cascades that can contribute to cellular disruption. Additionally, we demonstrate direct application for MC in repeated days cycling and conceivably other sporting scenario’s where back-to-back performances are required.

  11. De novo characterization of the Dialeurodes citri transcriptome: mining genes involved in stress resistance and simple sequence repeats (SSRs) discovery.

    Science.gov (United States)

    Chen, E-H; Wei, D-D; Shen, G-M; Yuan, G-R; Bai, P-P; Wang, J-J

    2014-02-01

    The citrus whitefly, Dialeurodes citri (Ashmead), is one of the three economically important whitefly species that infest citrus plants around the world; however, limited genetic research has been focused on D. citri, partly because of lack of genomic resources. In this study, we performed de novo assembly of a transcriptome using Illumina paired-end sequencing technology (Illumina Inc., San Diego, CA, USA). In total, 36,766 unigenes with a mean length of 497 bp were identified. Of these unigenes, we identified 17,788 matched known proteins in the National Center for Biotechnology Information database, as determined by Blast search, with 5731, 4850 and 14,441 unigenes assigned to clusters of orthologous groups (COG), gene ontology (GO), and SwissProt, respectively. In total, 7507 unigenes were assigned to 308 known pathways. In-depth analysis of the data showed that 117 unigenes were identified as potentially involved in the detoxification of xenobiotics and 67 heat shock protein (Hsp) genes were associated with environmental stress. In addition, these enzymes were searched against the GO and COG database, and the results showed that the three major detoxification enzymes and Hsps were classified into 18 and 3, 6, and 8 annotations, respectively. In addition, 149 simple sequence repeats were detected. The results facilitate the investigation of molecular resistance mechanisms to insecticides and environmental stress, and contribute to molecular marker development. The findings greatly improve our genetic understanding of D. citri, and lay the foundation for future functional genomics studies on this species.

  12. Neuronal changes and oxidative stress in adolescent rats after repeated exposure to mephedrone.

    Science.gov (United States)

    López-Arnau, Raúl; Martínez-Clemente, José; Rodrigo, Teresa; Pubill, David; Camarasa, Jorge; Escubedo, Elena

    2015-07-01

    Mephedrone is a new designer drug of abuse. We have investigated the neurochemical/enzymatic changes after mephedrone administration to adolescent rats (3×25 mg/kg, s.c. in a day, with a 2 h interval between doses, for two days) at high ambient temperature (26±2 °C), a schedule that intends to model human recreational abuse. In addition, we have studied the effect of mephedrone in spatial learning and memory. The drug caused a transient decrease in weight gain. After the first dose, animals showed hypothermia but, after the subsequent doses, temperature raised over the values of saline-treated group. We observed the development of tolerance to these thermoregulatory effects of mephedrone. Mephedrone induced a reduction of the densities of dopamine (30% in the frontal cortex) and serotonin (40% in the frontal cortex and the hippocampus and 48% in the striatum) transporters without microgliosis. These deficits were also accompanied by a parallel decrease in the expression of tyrosine hydroxylase and tryptophan hydroxylase 2. These changes matched with a down-regulation of D2 dopamine receptors in the striatum. Mephedrone also induced an oxidative stress evidenced by an increase of lipid peroxidation in the frontal cortex, and accompanied by a rise in glutathione peroxidase levels in all studied brain areas. Drug-treated animals displayed an impairment of the reference memory in the Morris water maze one week beyond the cessation of drug exposure, while the spatial learning process seems to be preserved. These findings raise concerns about the neuronal long-term effects of mephedrone.

  13. Environmental heat stress modulates thyroid status and its response to repeated endotoxin challenge in steers.

    Science.gov (United States)

    Kahl, S; Elsasser, T H; Rhoads, R P; Collier, R J; Baumgard, L H

    2015-07-01

    The objective of this study was to evaluate in cattle, the effects of acute exposure to a heat stress (HS) environment on the status of the pituitary (thyrotropin, TSH)-thyroid (thyroxine, T4)-peripheral tissue T4 deiodination (type 1 5'-deiodinase [D1]; triiodothyronine [T3]; reverse-triiodothyronine [rT3]) axis, and the further response of this pituitary-thyroid-peripheral tissue axis (PTTA) to perturbation caused by the induction of the proinflammatory innate immune state provoked by the administration of gram-negative bacteria endotoxin (lipopolysaccharide [LPS]). Ten steers (318 ± 49 kg body weight) housed in controlled environment chambers were subjected to either a thermoneutral (TN: constant 19°C) or HS temperature conditions (cyclical daily temperatures: 32.2°C-40.0°C) for a total period of 9 d. To minimize the effects of altered plane of nutrition due to HS, steers in TN were pair-fed to animals in HS conditions. Steers received 2 LPS challenges 3 d apart (LPS1 and LPS2; 0.2 μg/kg body weight, intravenously, Escherichia coli 055:B5) with the first challenge administered on day 4 relative to the start of the environmental conditioning. Jugular blood samples were collected at 0, 1, 2, 4, 7, and 24 h relative to the start of each LPS challenge. Plasma TSH, T4, T3, and rT3 were measured by radioimmunoassay. Liver D1 activity was measured in biopsy samples collected before the LPS1 (0 h) and 24 h after LPS2. Before the start of LPS1, HS decreased (P thyroid components of the PTTA, whereas a normal capacity to generate T3 from T4 in the liver is preserved. The data also suggest that LPS challenge further suppresses all components of the PTTA including liver T3 generation, and these PTTA perturbations are more pronounced in steers that encounter a HS exposure. Published by Elsevier Inc.

  14. Influence of single and repeated cannabidiol administration on emotional behavior and markers of cell proliferation and neurogenesis in non-stressed mice.

    Science.gov (United States)

    Schiavon, Angélica Pupin; Bonato, Jéssica Mendes; Milani, Humberto; Guimarães, Francisco Silveira; Weffort de Oliveira, Rúbia Maria

    2016-01-04

    Therapeutic effects of antidepressants and atypical antipsychotics may arise partially from their ability to stimulate neurogenesis. Cannabidiol (CBD), a phytocannabinoid present in Cannabis sativa, presents anxiolytic- and antipsychotic-like effects in preclinical and clinical settings. Anxiolytic-like effects of repeated CBD were shown in chronically stressed animals and these effects were parallel with increased hippocampal neurogenesis. However, antidepressant-like effects of repeated CBD administration in non-stressed animals have been scarcely reported. Here we investigated the behavioral consequences of single or repeated CBD administration in non-stressed animals. We also determined the effects of CBD on cell proliferation and neurogenesis in the dentate gyrus (DG) and subventricular zone (SVZ). Single CBD 3mg/kg administration resulted in anxiolytic-like effect in mice submitted to the elevated plus maze (EPM). In the tail suspension test (TST), single or repeated CBD administration reduced immobility time, an effect that was comparable to those of imipramine (20 mg/kg). Moreover, repeated CBD administration at a lower dose (3 mg/kg) increased cell proliferation and neurogenesis, as seen by an increased number of Ki-67-, BrdU- and doublecortin (DCX)-positive cells in both in DG and SVZ. Despite its antidepressant-like effects in the TST, repeated CBD administration at a higher dose (30 mg/kg) decreased cell proliferation and neurogenesis in the hippocampal DG and SVZ. Our findings show a dissociation between behavioral and proliferative effects of repeated CBD and suggest that the antidepressant-like effects of CBD may occur independently of adult neurogenesis in non-stressed Swiss mice.

  15. Increasing the repeating units of ethylene glycol-based dimethacrylates directed toward reduced oxidative stress and co-stimulatory factors expression in human monocytic cells.

    Science.gov (United States)

    Tamura, Atsushi; Fukumoto, Izumi; Yui, Nobuhiko; Matsumura, Mitsuaki; Miura, Hiroyuki

    2015-03-01

    The ethylene glycol-based dimethacrylates are commonly used in biomaterials and dental restorative materials as a cross-linking agent. In this study, toxic effect of triethylene glycol dimethacrylate (TEGDMA) and poly(ethylene glycol) dimethacrylates (PEG-DMAs) with various ethylene glycol repeating units was investigated in terms of cytotoxicity, oxidative stress, and the expression of co-stimulatory factors in human leukemia cell line (THP-1 cells) to verify the effect of ethylene glycol repeating units. Note that the 1-octanol/water partition coefficient of PEG-based dimethacrylates decreased with increasing the ethylene glycol repeating units, indicating that the hydrophilicity of PEG-DMAs increased with ethylene glycol repeating units. The toxic effect of PEG-DMAs such as cytotoxicity, oxidative stress, and the expression of CD86 in treated THP-1 cells are reduced with increasing the ethylene glycol repeating units in PEG-DMAs. However, the expression of CD54 in treated THP-1 cells was not influenced with the ethylene glycol repeating units and the maximal expression level of CD54 was observed at the concentration range of 2-4 mM for all samples. Accordingly, hydrophilic character of PEG-DMAs with long ethylene glycol chains definitely alleviates the some toxic aspect of PEG-based DMAs. This finding would provide important insight into the design of new biomaterials and dental materials with superior biocompatibility. © 2014 Wiley Periodicals, Inc.

  16. 降温速率和反复冻融对白蛾周氏啮小蜂过冷却点测定的影响%Effects of Cooling Rate and Repeated Freezing and Thawing on Determination of Supercooling Point in Chouioia cunea

    Institute of Scientific and Technical Information of China (English)

    孙守慧; 许哲; 王亚斌; 杨宏光; 祁金玉; 郑雅楠; 刘振凯

    2011-01-01

    Hyphantria cunea were effectively controlled by using Chouioia cunea as a natural enemy. In order to determine coldresistance indices of the mature larvae of Chouioia cunea,,the supercooling point and freezing point were tested with reference to substitute host Tenebrio molitor and Antheraea pernyi by using the different cooling rate and repeated freeze-thaw methods.The results showed that the supercooling point and freezing point measurements on the mature larvae of Chouioia cunea and Tenebrio molitor in the cooling rate range from 0.1℃·min-1 to 15.0℃·min-1, the supercooling point were (-18.44±0.93)℃ and (-8.16± 3.15)℃, the freezing point were (-14.27±1.25)℃ and (-2.19±2.03)℃, respectively. It was found that the supercooling point and freezing point of the nature larvae of Chouioia cunea, Tenebrio molitor and the pupae of Antheraea pernyi was determinated in repeated freeze-thaw, no obvious difference was found in the first three cycles of repeated freeze-thaw. They still maintained a stable cold resistance of physiological characteristics after being repeated freeze-thaw, this provides a basis for study on cold resistance mechanism.%白蛾周氏啮小蜂(Chouioia cunea Yang)是防治美国白蛾的重要天敌,为研究其耐寒性,采用不同的降温速率和反复冻融的方法对其老熟幼虫的耐寒性生理指标过冷却点(SCP)和冰点(FP)进行了测定,并以其替代寄主柞蚕(Antheraea pernyi GuérinMéneville)和黄粉甲(Tenebrio molitor Linnaeus)做为参照.结果表明:白蛾周氏啮小蜂及黄粉甲虫老熟幼虫在0.1~15.0℃·min-1降温范围内均可有效地测定出SCP与FP,其SCP分别为(-18.44±0.93)℃和(-8.16±3.15)℃,FP分别为(-14.27±1.25)℃和(-2.19±2.03)℃;试验还发现白蛾周氏啮小蜂老熟幼虫、黄粉甲老熟幼虫和柞蚕蛹的过冷却点与冰点均能进行反复冻融测定,且冻融的前3个循环的数值差异不显著(α=0.05),3种昆虫在反复冻融后

  17. Physiological heterogeneities in microbial populations and implications for physical stress tolerance

    DEFF Research Database (Denmark)

    Carlquist, Magnus; Fernandes, Rita Lencastre; Helmark, Søren

    2012-01-01

    may be unfavourable on the one hand (reduces yields and productivities), but also beneficial on the other hand (facilitates quick adaptation to new conditions - i.e. increases the robustness of the fermentation process). Understanding and control of microbial population heterogeneity is thus of major...... importance for improving microbial cell factory processes. Results: In this work, a dual reporter system was developed and applied to map growth and cell fitness heterogeneities within budding yeast populations during aerobic cultivation in well-mixed bioreactors. The reporter strain, which was based...... it was possible to distinguish subpopulations with high and low cell membrane robustness and hence ability to withstand freeze-thaw stress. A strong inverse correlation between growth and cell membrane robustness was observed, which further supports the hypothesis that cellular resources are limited and need...

  18. Evidence against a critical role of CB1 receptors in adaptation of the hypothalamic-pituitary-adrenal axis and other consequences of daily repeated stress.

    Science.gov (United States)

    Rabasa, Cristina; Pastor-Ciurana, Jordi; Delgado-Morales, Raúl; Gómez-Román, Almudena; Carrasco, Javier; Gagliano, Humberto; García-Gutiérrez, María S; Manzanares, Jorge; Armario, Antonio

    2015-08-01

    There is evidence that endogenous cannabinoids (eCBs) play a role in the control of the hypothalamic-pituitary-adrenal (HPA) axis, although they appear to have dual, stimulatory and inhibitory, effects. Recent data in rats suggest that eCBs, acting through CB1 receptors (CB1R), may be involved in adaptation of the HPA axis to daily repeated stress. In the present study we analyze this issue in male mice and rats. Using a knock-out mice for the CB1 receptor (CB1-/-) we showed that mutant mice presented similar adrenocorticotropic hormone (ACTH) response to the first IMO as wild-type mice. Daily repeated exposure to 1h of immobilization reduced the ACTH response to the stressor, regardless of the genotype, demonstrating that adaptation occurred to the same extent in absence of CB1R. Prototypical changes observed after repeated stress such as enhanced corticotropin releasing factor (CRH) gene expression in the paraventricular nucleus of the hypothalamus, impaired body weight gain and reduced thymus weight were similarly observed in both genotypes. The lack of effect of CB1R in the expression of HPA adaptation to another similar stressor (restraint) was confirmed in wild-type CD1 mice by the lack of effect of the CB1R antagonist AM251 just before the last exposure to stress. Finally, the latter drug did not blunt the HPA, glucose and behavioral adaptation to daily repeated forced swim in rats. Thus, the present results indicate that CB1R is not critical for overall effects of daily repeated stress or proper adaptation of the HPA axis in mice and rats.

  19. Reversible inactivation of rostral nucleus raphe pallidus attenuates acute autonomic responses but not their habituation to repeated audiogenic stress in rats.

    Science.gov (United States)

    Nyhuis, Tara J; Masini, Cher V; Taufer, Kirsten L; Day, Heidi E W; Campeau, Serge

    2016-01-01

    The medullary nucleus raphe pallidus (RPa) mediates several autonomic responses evoked by acute stress exposure, including tachycardia and hyperthermia. The present study assessed whether the RPa contributes to the decline/habituation of these responses observed during repeated audiogenic stress. Adult male rats were implanted with cannulae aimed at the RPa, and abdominal E-mitters that wirelessly acquire heart rate and core body temperature. After surgical recovery, animals were injected with muscimol or vehicle (aCSF) in the RPa region, followed by 30 min of 95-dBA loud noise or no noise control exposures on 3 consecutive days at 24-h intervals. Forty-eight hours after the third exposure, animals were exposed to an additional, but injection-free, loud noise or no noise test to assess habituation of hyperthermia and tachycardia. Three days later, rats were restrained for 30-min to evaluate their ability to display normal acute autonomic responses following the repeated muscimol injection regimen. The results indicated that the inhibition of cellular activity induced by the GABAA-receptor agonist muscimol centered in the RPa region reliably attenuated acute audiogenic stress-evoked tachycardia and hyperthermia, compared with vehicle-injected rats. Animals in the stress groups exhibited similar attenuated tachycardia and hyperthermia during the injection-free fourth audiogenic stress exposure, and displayed similar and robust increases in these responses to the subsequent restraint test. These results suggest that cellular activity in neurons of the RPa region is necessary for the expression of acute audiogenic stress-induced tachycardia and hyperthermia, but may not be necessary for the acquisition of habituated tachycardic responses to repeated stress.

  20. Resistance of human spermatozoa to cryoinjury in repeated cycles of thaw-refreezing

    Directory of Open Access Journals (Sweden)

    Sidney Verza Jr.

    2009-10-01

    Full Text Available Objective: To study the resistance of human spermatozoa to cryoinjury in repeated cycles of thaw-refreezing by using the fast liquid nitrogen vapor method. Material and Methods: Semen specimens were obtained from sixteen normal and oligozoospermic individuals who required disposal at the sperm bank. Five of them had testicular cancer. Specimens were thawed and an aliquot was removed for analysis. The remaining specimens were refrozen without removing the cryomedia. Repeated freeze-thaw cycles were performed until no motile sperm were observed. Sperm motility, number of motile spermatozoa and viability were determined after thawing. Resistance to cryoinjury was compared between groups and also after each refreezing cycle within groups. Results: Motile spermatozoa were recovered after five and two refreeze-thawing cycles in normozoospermic and oligozoospermic specimens, respectively. There were no significant differences in the recovery of motile spermatozoa between thaws within each group of normal and oligozoospermic specimens, but percentage motility and total number of motile spermatozoa were significantly lower in the oligozoospermic one. Specimens from men with cancer were exposed to six refreeze-thawing cycles. Although recovery of motile spermatozoa was significantly impaired after each thawing, there were no significant differences in the recovery of motile sperm between thaws in cancer and non-cancer groups. Conclusions: Human spermatozoa resist repeated cryopreservation using the fast liquid nitrogen vapor method. Normozoospermic specimens withstand refreezing for an average two cycles longer than oligozoospermic ones. Specimens from cancer patients seem to resist repeated cryoinjury similarly to non-cancer counterparts. Resistance to repeated cryoinjury was related to the initial semen quality.

  1. Research on the friction and wear mechanism of Poly(vinyl alcohol)/hydroxylapatite composite hydrogel

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Poly(vinyl alcohol)/Hydroxylapatite(PVA/HA) composite hydrogel was prepared with poly(vinyl alcohol) and hydroxylapatite as raw materials, using the method of repeated freezing and thawing.The morphologies of PVA/HA composite hydrogel were observed by means of high-accuracy 3D profiler and scanning electron microscope(SEM).The compressive elastic modulus and the stress relaxation characteristics of PVA/HA composite hydrogel were measured using the flat-head cylinder indenter.The friction and wear tests between PVA/HA composite hydrogel and bovine knee articular cartilage were performed on the micro-tribometer.The worn morphologies of PVA/HA composite hydrogel were observed with environmental scanning electron microscope(ESEM).The results showed that PVA/HA composite hydrogel has the cross-link network microstructure which is similar to that of the natural bovine knee articular cartilages.With the increase of freezing-thawing cycles and the HA content, the degree of cross-link and the crystallization of PVA/HA composite hydrogel both increase, the elastic modulus increases evidently, the rate of stress relaxation is improved and the value of balance stress decreases.The friction coefficient decreases with the increase of the freezing-thawing cycles and the HA content.The more the freezing-thawing cycles are, the earlier the friction coefficient reaches the stable balance value.The friction deformation depth between PVA/HA composite hydrogel and bovine knee articular cartilage is inversely proportional to freezing-thawing cycles and the HA content.The main wear mechanisms of PVA/HA composite hydrogel are plastic flowing and adhesive flaking.The wear severity degree decreases with the increase of freezing-thawing cycles and the HA content.

  2. Research on the friction and wear mechanism of Poly(vinyl alcohol)/hydroxylapatite composite hydrogel

    Institute of Scientific and Technical Information of China (English)

    ZHANG DeKun; SHEN YanQiu; GE ShiRong

    2009-01-01

    Poly(vinyl alcohol)/Hydroxylapatite(PVA/HA)composite hydrogel was prepared with poly(vinyl alcohol)and hydroxylapatite as raw materials,using the method of repeated freezing and thawing.The morphologies of PVA/HA composite hydrogel were observed by means of high-accuracy 3D profiler and scanning electron microscope(SEM).The compressive elastic modulus and the stress relaxation characteristics of PVA/HA composite hydrogel were measured using the flat-head cylinder indenter.The friction and wear tests between PVA/HA composite hydrogel and bovine knee articular cartilage were performed on the micro-tribometer.The worn morphologies of PVA/HA composite hydrogel were observed with environmental scanning electron microscope(ESEM).The results showed that PVA/HA composite hydrogel has the cross-link network microstructure which is similar to that of the natural bovine knee articular cartilages.With the increase of freezing-thawing cycles and the HA content,the degree of cross-link and the crystallization of PVA/HA composite hydrogel both increase,the elastic modulus increases evidently,the rate of stress relaxation is improved and the value of balance stress decreases.The friction coefficient decreases with the increase of the freezing-thawing cycles and the HA content.The more the freezing-thawing cycles are,the earlier the friction coefficient reaches the stable balance value.The friction deformation depth between PVA/HA composite hydrogel and bovine knee articular cartilage is inversely proportional to freezing-thawing cycles and the HA content.The main wear mechanisms of PVA/HA composite hydrogel are plastic flowing and adhesive flaking.The wear severity degree decreases with the increase of freezing-thawing cycles and the HA content.

  3. The E-subgroup Pentatricopeptide Repeat Protein family in Arabidopsis thaliana and confirmation of the responsiveness PPR96 to abiotic stresses

    Directory of Open Access Journals (Sweden)

    Jia-Ming Liu

    2016-12-01

    Full Text Available Pentatricopeptide repeat (PPR proteins are extensive in all eukaryotes. Their functions remain as yet largely unknown. Mining potential stress responsive PPRs, and checking whether known PPR editing factors are affected in the stress treatments. It is beneficial to elucidate the regulation mechanism of PPRs involved in biotic and abiotic stress. Here, we explored the characteristics and origin of the 105 E subgroup PPRs in Arabidopsis thaliana. Phylogenetic analysis categorized the E subgroup PPRs into five discrete groups (Cluster I to V, and they may have a common origin in both A. thaliana and rice. An in silico expression analysis of the 105 E subgroup PPRs in A. thaliana was performed using available microarray data. 34 PPRs were differentially expressed during A. thaliana seed imbibition, seed development stage(s, and flowers development processes. To explore potential stress responsive PPRs, differential expression of 92 PPRs was observed in A. thaliana seedlings subjected to different abiotic stresses. qPCR data of E subgroup PPRs under stress conditions revealed that the expression of 5 PPRs was responsive to abiotic stresses. In addition, PPR96 is involved in plant responses to salt, abscisic acid (ABA, and oxidative stress. The T-DNA insertion mutation inactivating PPR96 expression results in plant insensitivity to salt, ABA, and oxidative stress. The PPR96 protein is localized in the mitochondria, and altered transcription levels of several stress-responsive genes under abiotic stress treatments. Our results suggest that PPR96 may important function in a role connecting the regulation of oxidative respiration and environmental responses in A. thaliana.

  4. Density and permeability of a loess soil: long-term organic matter effect and the response to compressive stress

    DEFF Research Database (Denmark)

    Arthur, Emmanuel; Schjønning, Per; Møldrup, Per

    2013-01-01

    Pa). Investigated indicators for compression resistance included compression index, precompression stress, and resistance and resilience indices based on measured soil physical properties (bulk density, air-filled porosity, air permeability, and void ratio). Soil resilience was assessed following exposure...... of compacted cores to freeze-thaw (FT) and wet-dry (WD) cycles. The OC content increased with increased fertilisation and resulted in decreased initial bulk density, higher air-filled and total porosities, and increased organisation of the pore space. Soil resistance decreased with increasing OC content...... but the correlation was not significant. However, initial bulk density (ρbi) and initial gravimetric water content (wi) were significantly positively correlated to the indices of soil compression resistance, with the effect of ρbi being significantly stronger. Significant recovery of airfilled porosity and air...

  5. Repeatability of baseline corticosterone and short-term corticosterone stress responses, and their correlation with testosterone and body condition in a terrestrial breeding anuran (Platymantis vitiana).

    Science.gov (United States)

    Narayan, Edward J; Cockrem, John F; Hero, Jean-Marc

    2013-06-01

    Repeatability of physiological response variables, such as the stress hormone corticosterone, across numerous sampling occasions is an important assumption for their use as predictors of behaviour, reproduction and fitness in animals. Very few studies have actually tested this assumption in free-living animals under uncontrolled natural conditions. Non-invasive urine sampling and standard capture handling protocol have enabled the rapid quantification of baseline corticosterone and short-term corticosterone stress responses in anuran amphibians. In this study, established non-invasive methods were used to monitor physiological stress and urinary testosterone levels in male individuals of the terrestrial breeding Fijian ground frog (Platymantis vitiana). Adult male frogs (n = 20) were sampled at nighttime on three repeated occasions at intervals of 14 days during their annual breeding season on Viwa Island, Fiji. All frogs expressed urinary corticosterone metabolite responses to the capture and handling stressor, with some frogs showing consistently higher urinary corticosterone responses than others. Ranks of corticosterone values at 0, 4 and 8 h, and the corrected rank were highly significant (r = 0.75-0.99) between the three repeated sampling occasions. Statistical repeatabilities were high for baseline corticosterone (r = 0.973) and for corticosterone values at 2 h (r = 0.862), 4 h (r = 0.861), 6 h (r = 0.820) and 8 h (r = 0.926), and also for the total (inclusive of baseline corticosterone values) and the corrected integrated responses (index of the acute response) [r = 0.867 and r = 0.870]. Urinary testosterone levels also showed high statistical repeatability (r = 0.78). Furthermore, variation in baseline and short-term corticosterone stress responses was greater between individuals than within individuals. Baseline urinary corticosterone was significantly negatively correlated with the corrected integrated corticosterone response (r = -0.3, p breeding period

  6. Allopurinol Reduces Oxidative Stress in the Ovine Fetal Cardiovascular System After Repeated Episodes of Ischemia-Reperfusion

    NARCIS (Netherlands)

    Derks, Jan B.; Oudijk, Martijn A.; Torrance, Helen L.; Rademaker, Carin M. A.; Benders, Manon J.; Rosen, Karl G.; Cindrova-Davies, Tereza; Thakor, Avnesh S.; Visser, Gerard H. A.; Burton, Graham J.; van Bel, Frank; Giussani, Dino A.

    2010-01-01

    In complicated labor, neonatal outcome may depend not only on the extent of fetal asphyxia and acidosis but also on the effects on the fetal cardiovascular system of reactive oxygen species (ROS) generated during the ischemia-reperfusion (I/R) associated with repeated compressions of the umbilical c

  7. Icariin attenuates glucocorticoid insensitivity mediated by repeated psychosocial stress on an ovalbumin-induced murine model of asthma.

    Science.gov (United States)

    Li, Bei; Duan, Xiaohong; Xu, Changqing; Wu, Jinfeng; Liu, Baojun; Du, Yiji; Luo, Qingli; Jin, Hualiang; Gong, Weiyi; Dong, Jingcheng

    2014-04-01

    Evidence shows that psychosocial stress exacerbates asthma, but there is little intervention to alleviate negative effects of psychosocial stress on asthma. We investigated the role of icariin in anti-inflammation and anti-anxiety potential in a murine model combined psychosocial stress with allergic exposure. The results indicated that icariin administered remarkable increased activity in the center of the open field, reversed airway hyperresponsivenesss, reduced inflammatory cytokine infiltration to the lung and whole body and also in part recovered glucocorticoid responsiveness. Furthermore, our data also showed that icariin significantly inhibited increases of corticosterone and markedly increased glucocorticoid receptor mRNA and protein expression in the lungs of mice exposed to both stress and allergen. Collectively, we speculate that inducing glucocorticoid receptor modulation might be the potential mechanisms of icariin to facilitate corticosteroid responsiveness of cytokine production.

  8. Murine Model of Repeated Exposures to Conspecific Trained Aggressors Simulates Features of Post-Traumatic Stress Disorder

    Science.gov (United States)

    2012-07-20

    Rasmusson and Charney [95], Stam et al. [96], and Siegmund and Wotjak [6]. In our studies, the persis- tence of some acutely altered behaviors after...served in Iraq and Afghanistan: possible explanations. Journal of Traumatic Stress 2010;23:59–68. [6] Siegmund A, Wotjak CT. Toward an animal model...Posttraumatic Stress Disorder (PTSD). Behavioural Brain Research 2009;205:544–9. ral BrR. Hammamieh et al. / Behaviou [11] Siegmund A, Dahlhoff M, Habersetzer

  9. The phenome analysis of mutant alleles in Leucine-Rich Repeat Receptor-Like Kinase genes in rice reveals new potential targets for stress tolerant cereals.

    Science.gov (United States)

    Dievart, Anne; Perin, Christophe; Hirsch, Judith; Bettembourg, Mathilde; Lanau, Nadège; Artus, Florence; Bureau, Charlotte; Noel, Nicolas; Droc, Gaétan; Peyramard, Matthieu; Pereira, Serge; Courtois, Brigitte; Morel, Jean-Benoit; Guiderdoni, Emmanuel

    2016-01-01

    Plants are constantly exposed to a variety of biotic and abiotic stresses that reduce their fitness and performance. At the molecular level, the perception of extracellular stimuli and the subsequent activation of defense responses require a complex interplay of signaling cascades, in which protein phosphorylation plays a central role. Several studies have shown that some members of the Leucine-Rich Repeat Receptor-Like Kinase (LRR-RLK) family are involved in stress and developmental pathways. We report here a systematic analysis of the role of the members of this gene family by mutant phenotyping in the monocotyledon model plant rice, Oryza sativa. We have then targeted 176 of the ∼320 LRR-RLK genes (55.7%) and genotyped 288 mutant lines. Position of the insertion was confirmed in 128 lines corresponding to 100 LRR-RLK genes (31.6% of the entire family). All mutant lines harboring homozygous insertions have been screened for phenotypes under normal conditions and under various abiotic stresses. Mutant plants have been observed at several stages of growth, from seedlings in Petri dishes to flowering and grain filling under greenhouse conditions. Our results show that 37 of the LRR-RLK rice genes are potential targets for improvement especially in the generation of abiotic stress tolerant cereals.

  10. Narrative exposure therapy for posttraumatic stress disorder associated with repeated interpersonal trauma in patients with severe mental illness: a mixed methods design

    Directory of Open Access Journals (Sweden)

    Maria W. Mauritz

    2016-09-01

    Full Text Available Background: In the Netherlands, most patients with severe mental illness (SMI receive flexible assertive community treatment (FACT provided by multidisciplinary community mental health teams. SMI patients with comorbid posttraumatic stress disorder (PTSD are sometimes offered evidence-based trauma-focused treatment like eye movement desensitization reprocessing or prolonged exposure. There is a large amount of evidence for the effectiveness of narrative exposure therapy (NET within various vulnerable patient groups with repeated interpersonal trauma. Some FACT-teams provide NET for patients with comorbid PTSD, which is promising, but has not been specifically studied in SMI patients. Objectives: The primary aim is to evaluate NET in SMI patients with comorbid PTSD associated with repeated interpersonal trauma to get insight into whether (1 PTSD and dissociative symptoms changes and (2 changes occur in the present SMI symptoms, care needs, quality of life, global functioning, and care consumption. The second aim is to gain insight into patients’ experiences with NET and to identify influencing factors on treatment results. Methods: This study will have a mixed methods convergent design consisting of quantitative repeated measures and qualitative semi-structured in-depth interviews based on Grounded Theory. The study population will include adult SMI outpatients (n=25 with comorbid PTSD and receiving NET. The quantitative study parameters will be existence and severity of PTSD, dissociative, and SMI symptoms; care needs; quality of life; global functioning; and care consumption. In a longitudinal analysis, outcomes will be analyzed using mixed models to estimate the difference in means between baseline and repeated measurements. The qualitative study parameters will be experiences with NET and perceived factors for success or failure. Integration of quantitative and qualitative results will be focused on interpreting how qualitative results

  11. Narrative exposure therapy for posttraumatic stress disorder associated with repeated interpersonal trauma in patients with severe mental illness: a mixed methods design

    Science.gov (United States)

    Mauritz, Maria W.; Van Gaal, Betsie G. I.; Jongedijk, Ruud A.; Schoonhoven, Lisette; Nijhuis-van der Sanden, Maria W. G.; Goossens, Peter J. J.

    2016-01-01

    Background In the Netherlands, most patients with severe mental illness (SMI) receive flexible assertive community treatment (FACT) provided by multidisciplinary community mental health teams. SMI patients with comorbid posttraumatic stress disorder (PTSD) are sometimes offered evidence-based trauma-focused treatment like eye movement desensitization reprocessing or prolonged exposure. There is a large amount of evidence for the effectiveness of narrative exposure therapy (NET) within various vulnerable patient groups with repeated interpersonal trauma. Some FACT-teams provide NET for patients with comorbid PTSD, which is promising, but has not been specifically studied in SMI patients. Objectives The primary aim is to evaluate NET in SMI patients with comorbid PTSD associated with repeated interpersonal trauma to get insight into whether (1) PTSD and dissociative symptoms changes and (2) changes occur in the present SMI symptoms, care needs, quality of life, global functioning, and care consumption. The second aim is to gain insight into patients’ experiences with NET and to identify influencing factors on treatment results. Methods This study will have a mixed methods convergent design consisting of quantitative repeated measures and qualitative semi-structured in-depth interviews based on Grounded Theory. The study population will include adult SMI outpatients (n=25) with comorbid PTSD and receiving NET. The quantitative study parameters will be existence and severity of PTSD, dissociative, and SMI symptoms; care needs; quality of life; global functioning; and care consumption. In a longitudinal analysis, outcomes will be analyzed using mixed models to estimate the difference in means between baseline and repeated measurements. The qualitative study parameters will be experiences with NET and perceived factors for success or failure. Integration of quantitative and qualitative results will be focused on interpreting how qualitative results enhance the

  12. Tolerance to repeated stress in rats with lesions of the serotoninergic neurons of the Median Raphe Nucleus and chronically treated with imipramine.

    Science.gov (United States)

    Silva, K; Carvalho, M C; Padovan, C M

    2016-04-01

    Repeated exposure to aversive events leads to the development of tolerance to stress, which involves the serotonergic pathway originated in the Median Raphe Nucleus (MnRN) to the Dorsal Hippocampus (DH). However, it is not clear whether these lesion-induced deficits can be attenuated by treatment with antidepressants. Therefore, the aim of this work was to investigate the effects of chronic treatment with Imipramine (IMI) in rats with lesions in the MnRN and exposed to restraint stress. Male Wistar rats with or without neurochemical lesions of the MnRN serotonergic neurons with the neurotoxin 5,7-DHT were submitted to acute (2h) or chronic restraint (2h/day/seven consecutive days) and treated with saline (1 ml/kg) or imipramine (15 mg/kg) via intraperitoneal twice a day during the same period. In acutely restrained rats, stress occurred on the last day of treatment. Test in the elevated plus maze (EPM) was performed 24h later. After EPM test, animals were sacrificed and had their brains removed. Dorsal hippocampus and striatum were dissected and the levels of 5-HT and 5-hydroxy-indoleacetic acid (5-HIAA) measured by HPLC analysis. Our results showed that in control rats exposure to acute restraint stress decreased exploration of the open and enclose arms of the EPM, an effect that was attenuated by imipramine. In rats with 5,7-DHT lesions, acute restraint did not change the exploration of the EPM, independently of the treatment. On the other hand, when chronically restrained, saline treated rat with 5,7-DHT lesion showed a reduced exploration of the open arms of the EPM. This effect was attenuated by simultaneous treatment with imipramine. HPLC analysis showed significantly decreases on 5-HT and 5-HIAA levels in the hippocampus, but not in the striatum. These later results confirm that 5,7-DHT lesions of the MnRN had significant impact on the serotonergic projections to the dorsal hippocampus which seems to be essential for the development of tolerance to repeated

  13. Enhanced Giant Piezoresistance Performance of Sandwiched ZnS/Si/SiO2 Radial Heterostructure Nanotubes for Nonvolatile Stress Memory with Repeatable Writing and Erasing.

    Science.gov (United States)

    Cheng, Baochang; Xiong, Li; Cai, Qiangsheng; Shi, Haiping; Zhao, Jie; Su, Xiaohui; Xiao, Yanhe; Lei, Shuijin

    2016-12-21

    It is a challenge to realize nonvolatile stress-writing memory. Herein, we propose a strategy to construct rewritable stress information storage devices, consisting of deliberately designing individual sandwiched ZnS/Si/SiO2 radial heterostructure nanotubes synthesized by one-step thermal evaporation method. A bulk trap-related Poole-Frenkel hopping mechanism is proposed. Carriers are localized in a narrow bandgap Si intermediate layer; moreover, incorporated impurities and heterointerface defects can serve as charge trap centers or storage mediators. Compressive strain can induce trap barrier height to decrease at relatively low operation bias voltage, whereas tensile strain can induce it to increase, resulting in a giant piezoresistance effect. After both loading compressive and tensile strains at low bias voltage, additionally, the emptying of trap states results in a high resistance state. However, the emptied trap states can be filled by applying a relatively high bias voltage without strains and, correspondingly, the memories return to low resistance state. The emptying and filling of trap states, respectively applied by strains and high electric field, result in a repeatable writing/erasing nonvolatile memory effect. The results indicate that the creation and modification of trap states in multiscale nanostructures can give an avenue to the development of novel nanodevices for rewritable nonvolatile stress sensor and memory.

  14. Neutron Computed Tomography of Freeze/thaw Phenomena in Polymer Electrolyte Fuel Cells

    Energy Technology Data Exchange (ETDEWEB)

    Matthew M. Mech; Jack Brenizer; Kenan Unlu; A.K. Heller

    2008-12-12

    This report summarizes the final year's progress of the three-year NEER program. The overall objectives of this program were to 1) design and construct a sophisticated hight-resolution neutron computed tomography (NCT) facility, 2) develop novel and sophisticated liquid water and ice quantification analysis software for computed tomography, and 3) apply the advanced software and NCT capability to study liquid and ice distribution in polymer electrolyte fuel cells (PEFCs) under cold-start conditions. These objectives have been accomplished by the research team, enabling a new capability for advanced 3D image quantification with neutron imaging for fuel cell and other applications. The NCT water quantification methodology and software will greatly add to the capabilities of the neutron imaging community, and the quantified liquid water and ice distribution provided by its application to PEFCs will enhance understanding and guide design in the fuel cell community.

  15. Analysis of the building constructions from the point of view of possible freeze-thaw deterioration

    Science.gov (United States)

    Maděra, Jiří; Černý, Robert

    2016-07-01

    A mathematical model for the calculation of the amount of frozen water in the porous building materials is presented in this paper. The model is based on the analysis of temperature and moisture content fields in the investigated material together with its pore size distribution function and is primarily designed for the relative assessment of building constructions. The newly formulated model is applied on several wall assemblies made of traditional structural materials and their hygrothermal performance is analyzed in terms of possible frost induced damage. Based on the model outputs some future objectives are drawn.

  16. Ageing of rice husk biochar along a freeze-thaw cycles

    OpenAIRE

    Miao Wei; Cheng Xiao Ying; Meng Jun; Tang Liang

    2016-01-01

    In order to elucidate the aging possess of biochar, the experiment with treatment biochar with soil were performed. For accelerating aging process, freeing-thawing cycle were conducted to simulate the changing process of the physical and chemical properties of biochar and explore the roles of biochar in the changes of the soil nutrition. Aging treatment has a significant impact on the physical and chemical properties of biochar. The pH values, element composition, oxidation of the surface, ab...

  17. Ultrasonic monitoring of fish thawing process optimal time of thawing and effect of freezing/thawing

    Directory of Open Access Journals (Sweden)

    Youssef Ait El Kadi

    2013-09-01

    Full Text Available Introduction. Fish quality is traditionally controlled by chemical and microbiological analysis. The non-de- structive control presents an enormous professional interest thanks to the technical contribution and precision of the analysis to which it leads. This paper presents the results obtained from a characterisation of fish thaw­ing process by the ultrasonic technique, with monitoring thermal processing from frozen to defrosted states. Material and methods. The study was carried out on fish type red drum and salmon cut into fillets of 15 mm thickness. After being frozen at -20°C, the sample is enclosed in a plexiglas vessel with parallel walls at the ambient temperature 30°C and excited in perpendicular incidence at 0.5 MHz by an ultrasonic pulser-receiver Sofranel 5052PR. the technique of measurement consists to study the signals reflected by fish during its thaw­ing, the specific techniques of signal processing are implemented to deduce informations characterizing the state of fish and its thawing process by examining the evolution of the position echoes reflected by the sample and the viscoelastic parameters offish during its thawing. Results. The obtained results show a relationship between the thermal state offish and its acoustic proper­ties, which allowed to deduce the optimal time of the first thawing in order to restrict the growth of microbial flora. For salmon, the results show a decrease of 36% of the time of the second thawing and an increase of 10.88% of the phase velocity, with a decrease of 65.5% of the peak-to-peak voltage of the signal reflected, thus a decrease of the acoustic impedance. Conclusions. This study shows an optimal time and an evolution rate of thawing specific to each type offish and a correlation between the acoustic behavior of fish and its thermal state which approves that this tech­nique of ultrasonic monitoring can substitute the control using the destructive chemical analysis in order to monitor the thawing process and to know whether a fish has suffered an accidental thawing.

  18. Seasonal ERT monitoring of subsurface processes connected to freezing, thawing, snow accumulation and melt cycles

    Science.gov (United States)

    Krzeminska, Dominika; Starkloff, Torsten; Bloem, Esther; Stolte, Jannes

    2016-04-01

    For a better understanding of processes that influence snowmelt infiltration and runoff, and their consequences on soil erosion during spring periods, we established a long-term winter-spring ERT transect in the Gryteland catchment (Norway). The ERT transect is 71 m long, with 1 m spacing between the electrodes. It covers a depression with a north and south facing slope. The readings are collected once a week and, if needed, after a sudden change in weather conditions. Additionally, the soil transect is equipped with six TDR profiles, which register soil moisture and soil temperature every thirty minutes, at five depths (5, 10, 20, 30, 40 cm), for quantifying the ERT readings. The measurements performed during winter 2014/2015 gave promising results and showed the potential of ERT monitoring for understanding the soil thermal and hydraulic processes occurring during a winter and early spring. Moreover, there are visible differences in temporal trends and spatial variations in observed ERT patterns on the opposite facing slopes, which are of special interest. With the on-going experiment, we are aiming to understand the reoccurrence of the observed processes as well as to quantify soil moisture patterns. Herein, we would like to present the preliminary result of two ERT experiments (2014/2015 and 2015/2016) and discuss the advantages and limitations of our experiments. Moreover, we would like to stimulate the discussion about the potential of ERT for spatial and temporal monitoring of soil hydraulic and thermal processes and indirect measurements of soil water content.

  19. Effects of freezing-thawing on sensory descriptive profiles of cooked poultry breast meat

    Science.gov (United States)

    Freezing is a common method used by consumers to extend meat shelf life and by researchers to allow for subsequent meat quality assessments and processing. However, the effects of freezing on the sensory quality of cooked poultry breast meat are not well documented. The objective of this study was t...

  20. Freezing and thawing or freezing, thawing, and aging effects on beef tenderness

    National Research Council Canada - National Science Library

    Grayson, A L; King, D A; Shackelford, S D; Koohmaraie, M; Wheeler, T L

    2014-01-01

    The objective of this study was to determine the effect of freezing and thawing or freezing and thawing with an additional aging period after frozen storage on the tenderness of longissimus lumborum (LL...

  1. Freezing and thawing or freezing, thawing, and aging effects on beef tenderness1,2,3

    National Research Council Canada - National Science Library

    A L Grayson; D A King; S D Shackelford; M Koohmaraie; T L Wheeler

    2014-01-01

      The objective of this study was to determine the effect of freezing and thawing or freezing and thawing with an additional aging period after frozen storage on the tenderness of longissimus lumborum (LL...

  2. Biomimetic synthesis of hybrid nanocomposite scaffolds by freeze-thawing and freeze-drying

    Indian Academy of Sciences (India)

    S Nayar; A K Pramanick; A Guha; B K Mahato; M Gunjan; A Sinha

    2008-06-01

    The aim of this study is to biomimetically synthesize hydroxyapatite–hydrophilic polymer scaffolds for biomedical applications. This organic–inorganic hybrid has been structurally characterized and reveals a good microstructural control as seen by the SEM analysis and the nanosize of the particulates is confirmed by AFM microscopy. The characterization of such nano-structured composites would allow researchers to design new systems, tailoring properties for different applications.

  3. A controlled rate freeze/thaw system for cryopreservation of biological materials

    Science.gov (United States)

    Anselmo, V. J.; Harrison, R. G.

    1979-01-01

    A system which allows programmable temperature-time control for a 5 cc sample volume of an arbitrary biological material was constructed. Steady state and dynamic temperature control was obtained by supplying heat to the sample volume through resistive elements constructed as an integral part of the sample container. For cooling purposes, this container was totally immersed into a cold heat sink. Sample volume thermodynamic property data were obtained by measurements of heater power and heat flux through the container walls. Using a mixture of dry ice and alcohol at -79 C, sample volume was controlled from +40 C to -60 C at rates from steady state to + or - 65 C/min. Steady state temperature precision was better than 0.2 C while the dynamic capability depends on the temperature rate of change as well as the thermal mass of the sample and the container.

  4. Multi-Scale Process of Soil Freezing, Thawing, and Thaw-Settlement

    Science.gov (United States)

    2013-02-18

    utilities, cracked pavements , jacked up bridge foundations, tilted structures, are all examples of damage suffered from frost action. Long-term...a thermal process was simulated. The soil column is 0.07 m in height. The vertical walls of the column are adiabatic and rigid . The initial

  5. Can repeating glacial seismic events be used to monitor stress changes within the underlying volcano? -Case study from the glacier overlain Katla volcano, Iceland

    Science.gov (United States)

    Jonsdottir, K.; Vogfjord, K. S.; Bean, C. J.; Martini, F.

    2013-12-01

    individual families are usually clustered in time over several months, and sometimes families may reappear even up to several years later. Using families including many events and covering long periods (10-20 months) we compare the coda (the tail) of individual events within a family. This is repeated for all the surrounding stations. The analysis, coda wave interferometry (cwi) is a correlation method that builds on the fact that changes in stress in the edifice lead to changes in seismic velocities. The coda waves are highly sensitive to small stress changes. By using a repeating source, implying we have the same source mechanism and the same path, we can track temporal stress changes in the medium between the source and the receiver. Preliminary results from Katla suggest that by using the repeating glacial events and the coda wave interferometry technique we observe annual seismic velocity changes around the volcano of ca. 0.7%. We find that seismic velocities increase from January through July and decrease in August to December. These changes can be explained by pore-water pressure changes and/or loading and de-loading of the overlain glacier. We do not find immediate precursors for an impending eruption at Katla; however we now have a better understanding of its background seismicity.

  6. Molecular mechanism of dehydrin in response to environmental stress in plant

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yuxiu; WANG Zi; XU Jin

    2007-01-01

    Dehydrins, known as the D-11 subgroup of late embryogenesis abundant (LEA) protein, are an immunologically distinct family of proteins, which typically accumulate in desiccation-tolerant seed embryo or in vegetative tissues in response to various environmental stresses such as drought, salinity and freezing. The existence of conservative sequences designated as K, S, and Y segments is a structural feature of dehydrins, and the K segment found in all dehydrins represents a highly conserved 15 amino acid motif (EKKGIMDKIKEKLPG) and forms an amphiphilic a-helix. According to the arrangement of these domains and clustering analysis, dehydrins are subdivided into 5 subtypes: YnSK, Kn, KnS, SKn and YnK. Different types of dehydrins are induced by different environmental stress in plants. Study results showed that dehydrins might play important protective roles under abiotic stress via a number of different mechanisms, including improving or protecting enzyme activities by the cryoprotective activity in responding to freeze/thaw or dehydration; stabilizing vesicles or other endomembrane structures by function as the membrane stabilizer during freeze induced dehydration,and preventing the membrane system from the oxidative damage induced by reactive oxygen radicals as the radical scavenger. Here, the gene expression and molecular mechanisms of dehydrin in response to stress in plants are discussed.

  7. Repeated administration of AC-5216, a ligand for the 18 kDa translocator protein, improves behavioral deficits in a mouse model of post-traumatic stress disorder.

    Science.gov (United States)

    Qiu, Zhi-Kun; Zhang, Li-Ming; Zhao, Nan; Chen, Hong-Xia; Zhang, You-Zhi; Liu, Yan-Qin; Mi, Tian-Yue; Zhou, Wen-Wen; Li, Yang; Yang, Ri-Fang; Xu, Jiang-Ping; Li, Yun-Feng

    2013-08-01

    Post-traumatic stress disorder (PTSD) is a severely disabling anxiety disorder that may occur following exposure to a serious traumatic event. It is a psychiatric condition that can afflict anyone who has experienced a life-threatening or violent event. Previous studies have shown that changes in 18 kDa translocator protein (TSPO) expression (or function), a promising target for treating neurological disorders without benzodiazepine-like side effects, may correlate with PTSD. However, few studies have investigated the anti-PTSD effects of TSPO ligands. AC-5216, a ligand for TSPO, induces anxiolytic- and anti-depressant-like effects in animal models. The present study aimed to determine whether AC-5216 ameliorates PTSD behavior in mice. Following the training session consisting of exposure to inescapable electric foot shocks, animals were administered AC-5216 daily during the behavioral assessments, i.e., situational reminders (SRs), the open field (OF) test, the elevated plus-maze (EPM) test, and the staircase test (ST). The results indicated that exposure to foot shocks induced long-term behavioral deficiencies in the mice, including freezing and anxiety-like behavior, which were significantly ameliorated by repeated treatment with AC-5216 but without any effect on spontaneous locomotor activity or body weight. In summary, this study demonstrated the anti-PTSD effects of AC-5216 treatment, suggesting that TSPO may represent a therapeutic target for anti-PTSD drug discovery and that TSPO ligands may be a promising new class of drugs for the future treatment of PTSD.

  8. Improvement of fermentation ability under baking-associated stress conditions by altering the POG1 gene expression in baker's yeast.

    Science.gov (United States)

    Sasano, Yu; Haitani, Yutaka; Hashida, Keisuke; Oshiro, Satoshi; Shima, Jun; Takagi, Hiroshi

    2013-08-01

    During the bread-making process, yeast cells are exposed to many types of baking-associated stress. There is thus a demand within the baking industry for yeast strains with high fermentation abilities under these stress conditions. The POG1 gene, encoding a putative transcription factor involved in cell cycle regulation, is a multicopy suppressor of the yeast Saccharomyces cerevisiae E3 ubiquitin ligase Rsp5 mutant. The pog1 mutant is sensitive to various stresses. Our results suggested that the POG1 gene is involved in stress tolerance in yeast cells. In this study, we showed that overexpression of the POG1 gene in baker's yeast conferred increased fermentation ability in high-sucrose-containing dough, which is used for sweet dough baking. Furthermore, deletion of the POG1 gene drastically increased the fermentation ability in bread dough after freeze-thaw stress, which would be a useful characteristic for frozen dough baking. Thus, the engineering of yeast strains to control the POG1 gene expression level would be a novel method for molecular breeding of baker's yeast.

  9. Construction of chitin/PVA composite hydrogels with jellyfish gel-like structure and their biocompatibility.

    Science.gov (United States)

    He, Meng; Wang, Zhenggang; Cao, Yan; Zhao, Yanteng; Duan, Bo; Chen, Yun; Xu, Min; Zhang, Lina

    2014-09-08

    High strength chitin/poly(vinyl alcohol) (PVA) composite hydrogels (RCP) were constructed by adding PVA into chitin dissolved in a NaOH/urea aqueous solution, and then by cross-linking with epichlorohydrin (ECH) and freezing-thawing process. The RCP hydrogels were characterized by field emission scanning electron microscopy, FTIR, differential scanning calorimetry, solid-state (13)C NMR, wide-angle X-ray diffraction, and compressive test. The results revealed that the repeated freezing/thawing cycles induced the bicrosslinked networks consisted of chitin and PVA crystals in the composite gels. Interestingly, a jellyfish gel-like structure occurred in the RCP75 gel with 25 wt % PVA content in which the amorphous and crystalline PVA were immobilized tightly in the chitin matrix through hydrogen bonding interaction. The freezing/thawing cycles played an important role in the formation of the layered porous PVA networks and the tight combining of PVA with the pore wall of chitin. The mechanical properties of RCP75 were much higher than the other RCP gels, and the compressive strength was 20× higher than that of pure chitin gels, as a result of broadly dispersing stress caused by the orderly multilayered networks. Furthermore, the cell culture tests indicated that the chitin/PVA composite hydrogels exhibited excellent biocompatibility and safety, showing potential applications in the field of tissue engineering.

  10. Deployment Repeatability

    Science.gov (United States)

    2016-04-01

    controlled to great precision, but in a Cubesat , there may be no attitude determination at all. Such a Cubesat might treat sun angle and tumbling rates as...could be sensitive to small differences in motor controller timing. In these cases, the analyst might choose to model the entire deployment path, with...knowledge of the material damage model or motor controller timing precision. On the other hand, if many repeated and environmentally representative

  11. Association between repeated unpredictable chronic mild stress (UCMS procedures with a high fat diet: a model of fluoxetine resistance in mice.

    Directory of Open Access Journals (Sweden)

    Elsa Isingrini

    Full Text Available Major depressive disorder is a debilitating disease. Unfortunately, treatment with antidepressants (ADs has limited therapeutic efficacy since resistance to AD is common. Research in this field is hampered by the lack of a reliable natural animal model of AD resistance. Depression resistance is related to various factors, including the attendance of cardiovascular risk factors and past depressive episodes. We aimed to design a rodent model of depression resistance to ADs, associating cardiovascular risk factors with repeated unpredicted chronic mild stress (UCMS. Male BALB/c mice were given either a regular (4% fat or a high fat diet (45% fat and subjected to two 7-week periods of UCMS separated by 6 weeks. From the second week of each UCMS procedure, vehicle or fluoxetine (10 mg/kg, i.p. was administrated daily. The effects of the UCMS and fluoxetine in both diet conditions were assessed using physical (coat state and body weight and behavioural tests (the reward maze test and the splash test. The results demonstrate that during the second procedure, UCMS induced behavioural changes, including coat state degradation, disturbances in self-care behaviour (splash test and anhedonia (reward maze test and these were reversed by fluoxetine in the regular diet condition. In contrast, the high-fat diet regimen prevented the AD fluoxetine from abolishing the UCMS-induced changes. In conclusion, by associating UCMS-an already validated animal model of depression-with high-fat diet regimen, we designed a naturalistic animal model of AD resistance related to a sub-nosographic clinical entity of depression.

  12. Association between Repeated Unpredictable Chronic Mild Stress (UCMS) Procedures with a High Fat Diet: A Model of Fluoxetine Resistance in Mice

    Science.gov (United States)

    Isingrini, Elsa; Camus, Vincent; Le Guisquet, Anne-Marie; Pingaud, Maryse; Devers, Séverine; Belzung, Catherine

    2010-01-01

    Major depressive disorder is a debilitating disease. Unfortunately, treatment with antidepressants (ADs) has limited therapeutic efficacy since resistance to AD is common. Research in this field is hampered by the lack of a reliable natural animal model of AD resistance. Depression resistance is related to various factors, including the attendance of cardiovascular risk factors and past depressive episodes. We aimed to design a rodent model of depression resistance to ADs, associating cardiovascular risk factors with repeated unpredicted chronic mild stress (UCMS). Male BALB/c mice were given either a regular (4% fat) or a high fat diet (45% fat) and subjected to two 7-week periods of UCMS separated by 6 weeks. From the second week of each UCMS procedure, vehicle or fluoxetine (10 mg/kg, i.p.) was administrated daily. The effects of the UCMS and fluoxetine in both diet conditions were assessed using physical (coat state and body weight) and behavioural tests (the reward maze test and the splash test). The results demonstrate that during the second procedure, UCMS induced behavioural changes, including coat state degradation, disturbances in self-care behaviour (splash test) and anhedonia (reward maze test) and these were reversed by fluoxetine in the regular diet condition. In contrast, the high-fat diet regimen prevented the AD fluoxetine from abolishing the UCMS-induced changes. In conclusion, by associating UCMS—an already validated animal model of depression—with high-fat diet regimen, we designed a naturalistic animal model of AD resistance related to a sub-nosographic clinical entity of depression. PMID:20436931

  13. PnLRR-RLK27, a novel leucine-rich repeats receptor-like protein kinase from the Antarctic moss Pohlia nutans, positively regulates salinity and oxidation-stress tolerance

    Science.gov (United States)

    Wang, Jing; Liu, Shenghao; Li, Chengcheng; Wang, Tailin; Chen, Kaoshan

    2017-01-01

    Leucine-rich repeats receptor-like kinases (LRR-RLKs) play important roles in plant growth and development as well as stress responses. Here, 56 LRR-RLK genes were identified in the Antarctic moss Pohlia nutans transcriptome, which were further classified into 11 subgroups based on their extracellular domain. Of them, PnLRR-RLK27 belongs to the LRR II subgroup and its expression was significantly induced by abiotic stresses. Subcellular localization analysis showed that PnLRR-RLK27 was a plasma membrane protein. The overexpression of PnLRR-RLK27 in Physcomitrella significantly enhanced the salinity and ABA tolerance in their gametophyte growth. Similarly, PnLRR-RLK27 heterologous expression in Arabidopsis increased the salinity and ABA tolerance in their seed germination and early root growth as well as the tolerance to oxidative stress. PnLRR-RLK27 overproduction in these transgenic plants increased the expression of salt stress/ABA-related genes. Furthermore, PnLRR-RLK27 increased the activities of reactive oxygen species (ROS) scavengers and reduced the levels of malondialdehyde (MDA) and ROS. Taken together, these results suggested that PnLRR-RLK27 as a signaling regulator confer abiotic stress response associated with the regulation of the stress- and ABA-mediated signaling network. PMID:28241081

  14. Blocking glucocorticoid receptors at adolescent age prevents enhanced freezing between repeated cue-exposures after conditioned fear in adult mice raised under chronic early life stress

    NARCIS (Netherlands)

    Arp, J.M.; ter Horst, J.P.; Loi, M.; den Blaauwen, J.; Bangert, E.L.; Fernández, G.; Joëls, M.; Oitzl, M.S.; Krugers, H.J.

    2016-01-01

    Early life adversity can have long-lasting impact on learning and memory processes and increase the risk to develop stress-related psychopathologies later in life. In this study we investigated i) how chronic early life stress (ELS) - elicited by limited nesting and bedding material from postnatal

  15. Blocking glucocorticoid receptors at adolescent age prevents enhanced freezing between repeated cue-exposures after conditioned fear in adult mice raised under chronic early life stress

    NARCIS (Netherlands)

    Marit Arp, J; Ter Horst, Judith P; Loi, Manila; den Blaauwen, Jan; Bangert, Eline; Fernández, Guillén; Joëls, Marian; Oitzl, Melly S; Krugers, Harm

    2016-01-01

    Early life adversity can have long-lasting impact on learning and memory processes and increase the risk to develop stress-related psychopathologies later in life. In this study we investigated i) how chronic early life stress (ELS) - elicited by limited nesting and bedding material from postnatal d

  16. Blocking glucocorticoid receptors at adolescent age prevents enhanced freezing between repeated cue-exposures after conditioned fear in adult mice raised under chronic early life stress

    NARCIS (Netherlands)

    Arp, J.M.; Horst, J.P. ter; Loi, M.; Blaauwen, J. den; Bangert, E.; Fernandez, G.S.E.; Joels, M.; Oitzl, M.S.; Krugers, H.J.

    2016-01-01

    Early life adversity can have long-lasting impact on learning and memory processes and increase the risk to develop stress-related psychopathologies later in life. In this study we investigated (i) how chronic early life stress (ELS) - elicited by limited nesting and bedding material from postnatal

  17. Blocking glucocorticoid receptors at adolescent age prevents enhanced freezing between repeated cue-exposures after conditioned fear in adult mice raised under chronic early life stress

    NARCIS (Netherlands)

    Arp, J.M.; ter Horst, J.P.; Loi, M.; den Blaauwen, J.; Bangert, E.L.; Fernández, G.; Joëls, M.; Oitzl, M.S.; Krugers, H.J.

    2016-01-01

    Early life adversity can have long-lasting impact on learning and memory processes and increase the risk to develop stress-related psychopathologies later in life. In this study we investigated i) how chronic early life stress (ELS) - elicited by limited nesting and bedding material from postnatal d

  18. Blocking glucocorticoid receptors at adolescent age prevents enhanced freezing between repeated cue-exposures after conditioned fear in adult mice raised under chronic early life stress

    NARCIS (Netherlands)

    Arp, J.M.; Horst, J.P. ter; Loi, M.; Blaauwen, J. den; Bangert, E.; Fernandez, G.S.E.; Joels, M.; Oitzl, M.S.; Krugers, H.J.

    2016-01-01

    Early life adversity can have long-lasting impact on learning and memory processes and increase the risk to develop stress-related psychopathologies later in life. In this study we investigated (i) how chronic early life stress (ELS) - elicited by limited nesting and bedding material from postnatal

  19. Stress

    Science.gov (United States)

    ... diabetes. Shopdiabetes.org: Your Stress-Free System for Family Dinners! - 2017-03-book-oclock-scramble.html Shopdiabetes.org Your Stress-Free System for Family Dinners! A year of delicious meals to help prevent ...

  20. Stress

    Science.gov (United States)

    ... sudden negative change, such as losing a job, divorce, or illness Traumatic stress, which happens when you ... stress, so you can avoid more serious health effects. NIH: National Institute of Mental Health

  1. Effects of repeated ether stress on the hypothalamic-pituitary-testes axis in adult rats with special reference to inhibin secretion.

    Science.gov (United States)

    Tohei, A; Tomabechi, T; Mamada, M; Akai, M; Watanabe, G; Taya, K

    1997-05-01

    Effects of ether stress on the hypothalamo-hypophysial-gonadal axis in adult male rats were examined. To clarify the role of adrenal glucocorticoids in gonadal function, the effects of adrenalectomy and Dexamethasone treatment were also investigated. Ether stress increased the plasma concentrations of ACTH and corticosterone, but decreased the plasma concentrations of LH, FSH, inhibin and testosterone. The pituitary responsiveness to LH-RH for LH release and testicular responsiveness to the endogenous LH for testosterone release were maintained in stressed rats. Adrenalectomy caused an increase in the plasma concentrations of ACTH, but decreased the plasma concentrations of LH, FSH and testosterone. Dexamethasone treatment in adrenalectomized rats recovered the levels of plasma gonadotropins to control levels. The concentration of plasma inhibin did not change in adrenalectomized rats, but it was decreased compared to control rats by Dexamethasone treatment. Treatments of Dexamethasone in intact male rats resulted in a decline in plasma levels of testosterone and inhibin without a decrease in the levels of LH and FSH, indicating the direct effect of Dexamethasone on the testes. These results indicate that increased ACTH secretion in stressed rats is probably due to hypersecretion of CRH from the hypothalamus, which suppresses gonadotropin secretion via the inhibition of LH-RH. The decreased levels of testosterone may be caused by a stress-induced decrease in plasma LH concentrations and increased secretion of corticosterone in the ether stressed rats. The low levels of plasma inhibin in stressed rats was also probably due to the direct effect of corticosterone on the Sertoli cells.

  2. GsLRPK, a novel cold-activated leucine-rich repeat receptor-like protein kinase from Glycine soja, is a positive regulator to cold stress tolerance.

    Science.gov (United States)

    Yang, Liang; Wu, Kangcheng; Gao, Peng; Liu, Xiaojuan; Li, Guangpu; Wu, Zujian

    2014-02-01

    Plant LRR-RLKs serve as protein interaction platforms, and as regulatory modules of protein activation. Here, we report the isolation of a novel plant-specific LRR-RLK from Glycine soja (termed GsLRPK) by differential screening. GsLRPK expression was cold-inducible and shows Ser/Thr protein kinase activity. Subcellular localization studies using GFP fusion protein indicated that GsLRPK is localized in the plasma membrane. Real-time PCR analysis indicated that temperature, salt, drought, and ABA treatment can alter GsLRPK gene transcription in G. soja. However, just protein induced by cold stress not by salinity and ABA treatment in tobacco was found to possess kinase activity. Furthermore, we found that overexpression of GsLRPK in yeast and Arabidopsis can enhance resistance to cold stress and increase the expression of a number of cold responsive gene markers.

  3. Repeated forced swim stress enhances CFA-evoked thermal hyperalgesia and affects the expressions of pCREB and c-Fos in the insular cortex.

    Science.gov (United States)

    Imbe, H; Kimura, A; Donishi, T; Kaneoke, Y

    2014-02-14

    Stress affects brain activity and promotes long-term changes in multiple neural systems. Exposure to stressors causes substantial effects on the perception and response to pain. In several animal models, chronic stress produces lasting hyperalgesia. The insular (IC) and anterior cingulate cortices (ACC) are the regions exhibiting most reliable pain-related activity. And the IC and ACC play an important role in pain modulation via the descending pain modulatory system. In the present study we examined the expression of phospho-cAMP response element-binding protein (pCREB) and c-Fos in the IC and ACC after forced swim stress (FS) and complete Freund's adjuvant (CFA) injection to clarify changes in the cerebral cortices that affect the activity of the descending pain modulatory system in the rats with stress-induced hyperalgesia. FS (day 1, 10min; days 2-3, 20min) induced an increase in the expression of pCREB and c-Fos in the anterior IC (AIC). CFA injection into the hindpaw after the FS shows significantly enhanced thermal hyperalgesia and induced a decrease in the expression of c-Fos in the AIC and the posterior IC (PIC). Quantitative image analysis showed that the numbers of c-Fos-immunoreactive neurons in the left AIC and PIC were significantly lower in the FS+CFA group (L AIC, 95.9±6.8; L PIC, 181.9±23.1) than those in the naive group (L AIC, 151.1±19.3, pthermal hyperalgesia through dysfunction of the descending pain modulatory system.

  4. Post-traumatic Stress Disorder Symptoms in a Female Patient Following Repeated Teasing: Treatment with Gabapentin and Lamotrigine and the Possible Role of Sensitization

    OpenAIRE

    Kishimoto, Akira; Goto, Yurie; Hashimoto, Kenji

    2014-01-01

    Post-traumatic stress disorder (PTSD) is a pathological response to trauma characterized by frequent recollections, recurrent nightmares, and flashbacks of the traumatic event(s). To date, the precise mechanisms underlying the development of PTSD remain unknown. Several studies have suggested that antiepileptic drugs, such as gabapentin and lamotrigine, may be effective in the treatment of PTSD symptoms. We report on a 15-year-old Japanese female junior high school student who developed PTSD ...

  5. Oxidative stress and inflammatory reaction modulation by white wine.

    Science.gov (United States)

    Bertelli, Alberto A E; Migliori, Massamiliano; Panichi, Vincenzo; Longoni, Bianamaria; Origlia, Nicola; Ferretti, Agnese; Cuttano, Maria Giuseppa; Giovannini, Luca

    2002-05-01

    Wine and olive oil, essential components of the Mediterranean diet, are considered important factors for a healthy life style. Tyrosol (T) and caffeic acid (CA) are found in both extra virgin olive oil and in white wine. Three white wines from the northeast Italy and four white wines from Germany were analyzed for their content of T and CA. These compounds were tested for their antioxidant activity and their capacity to modulate three different cytokines: IL-1 beta, IL-6, and TNF-alpha, which are currently considered to be the major cytokines influencing the acute phase of the inflammatory response. Furthermore, the antioxidant activity of T and CA was analyzed by monitoring the oxidation of a redox-sensitive probe by using laser scanning confocal microscopy. T and CA, applied at nanomolar range, were found to significantly reduce the generation of oxidants induced by azobis-amidinopropanedihydrochloride. Peripheral blood mononuclear cells (PBMC) from healthy volunteers were incubated at 37 degrees C for 12 hours with 100 ng LPS (E. coli and P. maltofilia). Increasing doses of T and CA (150 nM to 300 microM) were added and cell-associated IL-1 beta and TNF-alpha were determined by immunoreactive tests after three freeze-thaw cycles. IL-6 release was also determined in cell surnatants. LPS-stimulated PBMC showed a significant increase in cytokine release, while T and CA, used at nanomolar concentrations, were able to modulate their expression. Taken together, these results suggest a remarkable effect of white wine non-alcoholic compounds on oxidative stress and inflammatory reaction.

  6. Stress

    DEFF Research Database (Denmark)

    Keller, Hanne Dauer

    2015-01-01

    Kapitlet handler om stress som følelse, og det trækker primært på de få kvalitative undersøgelser, der er lavet af stressforløb.......Kapitlet handler om stress som følelse, og det trækker primært på de få kvalitative undersøgelser, der er lavet af stressforløb....

  7. Stress

    DEFF Research Database (Denmark)

    Keller, Hanne Dauer

    2015-01-01

    Kapitlet handler om stress som følelse, og det trækker primært på de få kvalitative undersøgelser, der er lavet af stressforløb.......Kapitlet handler om stress som følelse, og det trækker primært på de få kvalitative undersøgelser, der er lavet af stressforløb....

  8. Relative contributions of interface pressure, shear stress, and temperature on ischemic-induced, skin-reactive hyperemia in healthy volunteers: a repeated measures laboratory study.

    Science.gov (United States)

    Lachenbruch, Charlie; Tzen, Yi-Ting; Brienza, David; Karg, Patricia E; Lachenbruch, Peter A

    2015-02-01

    Although the primary risk factors for pressure ulcer development - pressure, shear, skin temperature, moisture, and friction - have been identified for decades, the relative contribution of each to this risk remains unclear. To confirm the results of and expand upon earlier research into the relative contributions of interface pressures, shear stress, and skin temperature among 4 healthy volunteers, a study involving 6 additional healthy 40- to 75-year-old volunteers was conducted and results of the 2 studies were pooled. All 3 variables (interface pressures, shear stress, and skin temperature) were systematically and randomly varied. In the prone position, volunteers each underwent 18 test conditions representing different combinations of temperature (28˚ C, 32˚ C, 36˚ C), pressure (8.0 and 13.3 kPa), and shear (0, 6.7, and 14.0 kPa) using a computer-controlled indenter applied to the sacrum for 20 minutes exerting weights of 100 g and 200 g to induce 0.98 N and 1.96 N of shear force, respectively. Each condition was tested twice, resulting in a total of 360 trials. Magnitude of postload reactive hyperemia as an index of ischemia was measured by laser Doppler flowmetry. Fixed effects regression models were used to predict 3 different indices of reactive hyperemic magnitude. Friedman tests were performed to compare the reactive hyperemia among 3 different skin temperatures or shear stresses under the same amount of localized pressure. In all regression models, pressure and temperature were highly significant predictors of the extent of reactive hyperemia (P pressure and shear stress, and the difference was more profound between 32˚ C and 36˚ C than between 28˚ C and 32˚ C. These results confirm that, in laboratory settings, temperature is an important factor in tissue ischemia. Additional studies examining the relative importance of pressure, shear, and temperature and potential effects of lowering temperature on tissue ischemia in healthy volunteers and

  9. Repeat-until-success quantum repeaters

    Science.gov (United States)

    Bruschi, David Edward; Barlow, Thomas M.; Razavi, Mohsen; Beige, Almut

    2014-09-01

    We propose a repeat-until-success protocol to improve the performance of probabilistic quantum repeaters. Conventionally, these rely on passive static linear-optics elements and photodetectors to perform Bell-state measurements (BSMs) with a maximum success rate of 50%. This is a strong impediment for entanglement swapping between distant quantum memories. Every time a BSM fails, entanglement needs to be redistributed between the corresponding memories in the repeater link. The key ingredients of our scheme are repeatable BSMs. Under ideal conditions, these turn probabilistic quantum repeaters into deterministic ones. Under realistic conditions, our protocol too might fail. However, using additional threshold detectors now allows us to improve the entanglement generation rate by almost orders of magnitude, at a nominal distance of 1000 km, compared to schemes that rely on conventional BSMs. This improvement is sufficient to make the performance of our scheme comparable to the expected performance of some deterministic quantum repeaters.

  10. Stress Fractures

    Science.gov (United States)

    Stress fractures Overview Stress fractures are tiny cracks in a bone. They're caused by repetitive force, often from overuse — such as repeatedly jumping up and down or running long distances. Stress fractures can also arise from normal use of ...

  11. The child accident repeater: a review.

    Science.gov (United States)

    Jones, J G

    1980-04-01

    The child accident repeater is defined as one who has at least three accidents that come to medical attention within a year. The accident situation has features in common with those of the child who has a single accident through simple "bad luck", but other factors predispose him to repeated injury. In the child who has a susceptible personality, a tendency for accident repetition may be due to a breakdown in adjustment to a stressful environment. Prevention of repeat accidents should involve the usual measures considered appropriate for all children as well as an attempt to provide treatment of significant maladjustment and modification of a stressful environment.

  12. Storage of stock cultures of filamentous fungi at -80 degrees C: effects of different freezing-thawing methods.

    Science.gov (United States)

    Juarros, E; Tortajada, C; García, M D; Uruburu, F

    1993-04-01

    Freezing and storage at -80 degrees C has been applied to the preservation of nonsporulated filamentous fungi Phytophthora, Pythium, Sclerotinia and Rhizoctonia, and the results are presented. We had tested different methods of freezing and thawing, finding that the best results were obtained pre-cooling at 4 degrees C during 1 hour followed by freezing at -80 degrees C. The best thawing method was achieved at 37 degrees C. The technique was found to be simple and reliable for the culture collections labours of fungi maintenance.

  13. Effects of drying-wetting and freezing-thawing cycle on leachability of metallic elements in mine soils

    Science.gov (United States)

    Bang, H.; Kim, J.; Hyun, S.

    2016-12-01

    Mine leachate derived from contaminated mine sites with metallic elements can pose serious risks on human society and environment. Only labile fraction of metallic elements in mine soils is subject to leaching and movement by rainfall. Lability of metallic element in soil is a function of bond strengths between metal and soil surfaces, which is influenced by environmental condition (e.g., rainfall intensity, duration, temperature, etc.) The purpose of this study was to elucidate the effects of various climate conditions on the leaching patterns and lability of metallic elements in mine soils. To do this, two mine soils were sampled from two abandoned mine sites located in Korea. Leaching test were conducted using batch decant-refill method. Various climatic conditions were employed in leaching test such as (1) oven drying (40oC) - wetting cycles, (2) air drying (20oC) - wetting cycle, and (3) freezing (-40oC) - thawing cycles. Duration of drying and freezing were varied from 4 days to 2 weeks. Concentration of metallic elements, pH, Eh and concentration of dissolved iron and sulfate in leachate from each leaching process was measured. To identify the changes of labile fraction in mine soils after each of drying or freezing period, sequential extraction procedure (five fraction) was used to compare labile fraction (i.e., F1 + F2) of metallic elements. The concentration of metallic elements in mine leachate was increased after drying and freezing procedure. The amounts of released metallic element from mine soils was changed depending on their drying or freezing period. In addition, labile fraction of metallic elements in soil was also changed after drying and freezing. The changes in labile fraction after drying and freezing might be due to the increased soil surface area by pore water volume expansion. Further study is therefore needed to evaluate the impact of altered physical properties of soils such as hydration of soil surface area and shrinking by drying and freezing cycles.

  14. Large-scale InSAR monitoring of permafrost freeze-thaw cycles on the Tibetan Plateau

    Science.gov (United States)

    Daout, Simon; Doin, Marie-Pierre; Peltzer, Gilles; Socquet, Anne; Lasserre, Cécile

    2017-01-01

    Multitemporal interferometric synthetic aperture radar (InSAR) observations are used to characterize spatial variations of the permafrost active layer and its temporal evolution in Northwestern Tibet. We develop a method to enhance InSAR performances for such difficult terrain conditions and construct an 8 year timeline of the surface deformation over a 60,000 km2 area. The ground movement induced by the active layer's response to climate forcing is limited to Cenozoic sedimentary basins and is spatially variable in both its seasonal amplitude (2.5-12 mm) and multiannual trend (-2 to 3 mm/yr). A degree-day integrated model adjusted to the data indicates that subsidence occurs when the surface temperature exceeds zero (May to October) over areas where seasonal movements are large (>8 mm). The period of subsidence is delayed by 1-2 months over areas where smaller seasonal movements are observed, suggesting an unsaturated soil where water occurs in the deeper part of the active layer.

  15. Investigations into the fouling mechanism of parvovirus filters during filtration of freeze-thawed mAb drug substance solutions.

    Science.gov (United States)

    Barnard, James G; Kahn, David; Cetlin, David; Randolph, Theodore W; Carpenter, John F

    2014-03-01

    Filtration to remove viruses is one of the single most expensive steps in the production of mAb drug products. Therefore, virus filtration steps should be fully optimized, and any decline in flow rates warrants investigation into the causes of such membrane fouling. In the current study, it was found that freezing and thawing of a mAb bulk drug solution caused a substantial decrease in viral filter membrane flow rate. Freezing and thawing also caused formation of aggregates and particles across a broad size range, including particles that could be detected by microflow imaging (≥1 μm in size). However, removal of these particles offered little protection against flow rate decline during viral filtration. Further investigation revealed that trace amounts of aggregates (ca. 10⁻⁶ of the total mass of protein in solution) approximately 20-40 nm in size were primarily responsible for the observed membrane fouling.

  16. Shallow subsurface temperature and moisture monitoring at rock walls during freeze thaw cycles in the Northern Calcareous Alps, Austria

    Science.gov (United States)

    Rode, Matthias; Sass, Oliver

    2014-05-01

    The process of frost weathering as well as the contribution of further weathering processes (e.g. hydration, thermal fatigue) is poorly understood. For this purpose, different measuring systems were set up in two study areas (Dachstein massif - permafrost area (2700m asl, 47° 28' 32″ N, 13° 36' 23″ E) and Gesäuse mountains - non permafrost area (900m asl, 47° 35' 19″ N, 14° 39' 32″ E) located in Styria, Austria within the framework of the research project ROCKING ALPS (FWF-P2444). A key to understand frost weathering is to observe the rock temperature with several high resolution temperature sensors from the rock surface down to -20cm depth. The temperatures are measured hourly at north and south exposed rock walls since 2012 in the headwalls of the Dachstein glacier at the Koppenkarstein (built up of limestone) in about 2600m asl. Since 2013 the same measurement setup is installed in the lower Johnsbachtal (Gesäuse mountains, prevailing rock type is dolomite) in about 800m asl. To know the temperature is crucial to understand internal heat flow and transport and latent heat effects during freezing and thawing caused by night frost (lasting some hours), cold fronts (lasting some days) or winter frost of several weeks or months. At these study points we also have installed small-scale 2D-geoelectric survey lines, supplemented by moisture sensors. Moisture is determined by means of resistivity measurements which are difficult to calibrate, but provide good time series. Additional novel moisture sensors were developed which use the heat capacity of the surrounding rock as a proxy of water content. These sensors give point readings from a defined depth and are independent from soluble salt contents. First results from the Dachstein show that short term latent heat effects during the phase change have crucial influence on the moisture content. The moisture distribution and movements during temperature changes inside the rock are discussed upon the two main frost weathering theories - (A) volume expansion of moisture during the phase change and (B) the ice segregation.

  17. Effect of High Doses of Chemical Admixtures on the Freeze-Thaw Durability of Portland Cement Concrete

    Science.gov (United States)

    2002-02-01

    volume (Neville 1988). The hydrated cement is often referred to as cement gel, which has a characteristic porosity of about 28% ( Mindess and Young...Structure, Properties, and Materials. New York: Prentice-Hall. Mindess , S., and J.F. Young (1981) Concrete. New York: Prentice-Hall. Neville, A.M

  18. Effect of Storage Temperature on the Outgrowth and Toxin Production of Staphylococcus aureus in Freeze-Thawed Precooked Tuna Meat.

    Science.gov (United States)

    Kataoka, Ai; Enache, Elena; Napier, Carla; Hayman, Melinda; Weddig, Lisa

    2016-04-01

    The aim of this study was to determine the time for a 3-log CFU/g outgrowth of Staphylococcus aureus and its toxin production in previously frozen precooked tuna meat (albacore [Thunnus alalunga] prepared as loin, chunk, and flake or skipjack [Katsuwonus pelamis] prepared as chunk and flake) held either at 21 or 27°C. A five-strain cocktail of enterotoxin-producing S. aureus was surface inoculated with ∼10(3) CFU/g onto tuna samples. The experimental time-temperature conditions were designed to mimic common industry holding conditions. After a 3-h incubation at 37°C, inoculated samples were individually vacuum sealed and stored at 20°C for 4 weeks. Following frozen storage, samples were thawed to the target temperature (21 or 27°C) and then incubated aerobically. Growth of S. aureus in tuna was then monitored using Baird Parker agar; simultaneously, aerobic plate counts, enterotoxin production, and sensory profile (color and odor) were determined. The results showed that the time for a 3-log CFU/g increase was >20 h at 21°C and 8 to 12 h at 27°C for albacore, with toxin production observed at 14 to 16 h at 21°C and at 8 h at 27°C. A 3-log CFU/g increase for skipjack occurred at 22 to 24 h at 21°C and at 10 to 14 h at 27°C. The toxin production in skipjack started at 20 to 22 h at 21°C and at 8 to 10 h at 27°C. Toxin production was observed before a 3-log increase was achieved in albacore samples at 21°C. Under all conditions, toxins were detected when the cell density of S. aureus was 6 log CFU/g. Overall, significantly faster S. aureus growth was observed in albacore compared with skipjack (P aureus and to design manufacturing controls that ensure food safety.

  19. Mix design for improved strength and freeze-thaw durability of pervious concrete fill in Pearl-Chain Bridges

    DEFF Research Database (Denmark)

    Lund, Mia Schou Møller; Kevern, John T.; Schaefer, Vernon R.

    2017-01-01

    different mixture proportions using two different sizes of granite coarse aggregate and at two different water-to-cement ratios. The specimens had an average void content of 24-28 %. Specimens containing air entraining and high-range water reducing admixtures were most workable, as determined by fresh......Pearl-Chain Bridges are an innovative precast arch bridge technology which can utilize pervious concrete as fill material. The present study investigates how the mix design of the pervious concrete fill can be influenced by use of an air-entraining admixture, a high-range water reducing admixture...... density, and thus the easiest to place. The addition of a high-range water reducing admixture and lightweight sand (expanded shale) for internal curing improved the 28-day compressive strength and splitting tensile strength. The coarse aggregate gradation had a large influence on permeability; however...

  20. Methanosarcina soligelidi sp. nov., a desiccation- and freeze-thaw-resistant methanogenic archaeon from a Siberian permafrost-affected soil.

    Science.gov (United States)

    Wagner, Dirk; Schirmack, Janosch; Ganzert, Lars; Morozova, Daria; Mangelsdorf, Kai

    2013-08-01

    A methanogenic archaeon, strain SMA-21(T), was isolated from a permafrost-affected soil by serial dilution in liquid medium. The cells were non-motile, stained Gram-negative and grew as irregular cocci with a diameter of 1.3-2.5 µm. Optimal growth was observed at 28 °C, pH 7.8 and 0.02 M NaCl. The strain grew on H2/CO2, methanol and acetate, but not on formate, ethanol, 2-butanol, 2-propanol, monomethylamine, dimethylamine, trimethylamine or dimethyl sulfide. Major membrane lipids of strain SMA-21(T) were archaeol phosphatidylglycerol, archaeol phosphatidylethanolamine and the corresponding hydroxyarchaeol compounds. The G+C content of the genomic DNA was 40.9 mol%. The 16S rRNA gene sequence was closely related to those of Methanosarcina mazei DSM 2053(T) (similarity 99.9 %) and Methanosarcina horonobensis HB-1(T) (similarity 98.7 %). On basis of the level of DNA-DNA hybridization (22.1 %) between strain SMA-21(T) and Methanosarcina mazei DSM 2053(T) as well as of phenotypic and genotypic differences, strain SMA-21(T) was assigned to a novel species of the genus Methanosarcina, for which the name Methanosarcina soligelidi sp. nov. is proposed. The type strain is SMA-21(T) (=DSM 26065(T) [corrected] = JCM 18468).

  1. Methanosarcina soligelidi sp. nov., a desiccation- and freeze-thaw-resistant methanogenic archaeon from a Siberian permafrost-affected soil

    National Research Council Canada - National Science Library

    Wagner, Dirk; Schirmack, Janosch; Ganzert, Lars; Morozova, Daria; Mangelsdorf, Kai

    2013-01-01

    .... Optimal growth was observed at 28 °C, pH 7.8 and 0.02 M NaCl. The strain grew on H2/CO2, methanol and acetate, but not on formate, ethanol, 2-butanol, 2-propanol, monomethylamine, dimethylamine, trimethylamine or dimethyl sulfide...

  2. A comparative study of sodium dodecyl sulfate and freezing/thawing treatment on wheat starch: The role of water absorption.

    Science.gov (United States)

    Tao, Han; Wang, Pei; Zhang, Bao; Wu, Fengfeng; Jin, Zhengyu; Xu, Xueming

    2016-06-05

    The effect of freezing on functionality of native and sodium dodecyl sulfate (SDS)-treated wheat starches was investigated, with the aim of understanding the role of water absorption during freezing process. SDS is one of most efficient detergents to remove non-starch components (such as proteins and lipids) for starches but does not cause any apparent damage on granular structure. Slow swelling could be converted to rapid swelling by SDS washing, indicating higher water absorption. Freezing process induced slight roughness on starch granules but the non-starch components content was little affected. Combined SDS+freezing treatment significantly decreased both amylose and proteins non-starch components contents, which was accompanied with high gelatinization temperatures, melting enthalpy, and pasting viscosities. A smaller bread specific volume was obtained from SDS+freezing-treated starches while the crumb firmness significantly increased (pstarch granules, leading to high water absorption and making granules sensitive to the freezing treatment.

  3. Effect of glycine on pH changes and protein stability during freeze-thawing in phosphate buffer systems.

    Science.gov (United States)

    Pikal-Cleland, Katherine A; Cleland, Jeffrey L; Anchordoquy, Thomas J; Carpenter, John F

    2002-09-01

    Previous studies have established that the selective precipitation of a less soluble buffer component during freezing can induce a significant pH shift in the freeze concentrate. During freezing of sodium phosphate solutions, crystallization of the disodium salt can produce a pH decrease as great as 3 pH units which can dramatically affect protein stability. The objective of our study was to determine how the presence of glycine (0-500 mM), a commonly used bulking agent in pharmaceutical protein formulations, affects the pH changes normally observed during freezing in sodium phosphate buffer solutions and to determine whether these pH changes contribute to instability of model proteins in glycine/phosphate formulations. During freezing in sodium phosphate buffers, the presence of glycine significantly influenced the pH. Glycine at the lower concentrations (phosphate buffer, possibly by reducing the nucleation rate of salt and thereby decreasing the extent of buffer salt crystallization. The presence of glycine at higher concentration (> 100 mM) in the sodium phosphate buffer resulted in a more complete crystallization of the disodium salt as indicated by the frozen pH values closer to the equilibrium value (pH 3.6). Although high concentrations of glycine can facilitate more buffer salt crystallization and these pH shifts may prove to be potentially damaging to the protein, glycine, in its amorphous state, can also act to stabilize a protein via the preferential exclusion mechanism.

  4. Stress

    OpenAIRE

    Jensen, Line Skov; Lova, Lotte; Hansen, Zandra Kulikovsky; Schønemann, Emilie; Larsen, Line Lyngby; Colberg Olsen, Maria Sophia; Juhl, Nadja; Magnussen, Bogi Roin

    2012-01-01

    Stress er en tilstand som er meget omdiskuteret i samfundet, og dette besværliggør i en vis grad konkretiseringen af mulige løsningsforslag i bestræbelsen på at forebygge den såkaldte folkesygdom. Hovedkonklusionen er, at selv om der bliver gjort meget for at forebygge, er der ikke meget der aktivt kan sættes i værk for at reducere antallet af stressramte, før en fælles forståelse af stressårsager og effektiv stresshåndtering er fremlagt. Problemformuleringen er besvaret gennem en undersø...

  5. RNA-seq analysis of oil palm under cold stress reveals a different C-repeat binding factor (CBF mediated gene expression pattern in Elaeis guineensis compared to other species.

    Directory of Open Access Journals (Sweden)

    Xintao Lei

    Full Text Available Elaeis guineensis as a tropical oil-crop is particularly sensitive to low temperature. Improvement of cold-tolerance may significantly increase the total cultivation area of this tropical oil-crop worldwide. We sequenced cold-treated and control (untreated samples of Elaeis guineensis. De novo assembly generated 51,452 unigenes with an average length of 703 bp. Subsequently, these expressed sequences were functionally annotated. In the K category (transcription factors of COG (Cluster of Orthologous Group annotation, the largest proportion of genes induced and repressed at least two-fold under cold stress were from the AP2/ERE family, indicating that C-repeat binding factor, (CBFs, members of the AP2/ERE family may play a central role in cold tolerance in Elaeis guineensis. Subsequently, the CBF-mediated signal transduction pathway was reconstructed based on transcriptome data and the gene expression profile involving the pathway was examined using real-time quantitative RT-PCR (qRT-PCR. CBFs reached maximum transcript level both at medium (4 h and long period time points (7 days, contrary to the expression pattern of CBFs in Arabidopsis and rice. Moreover, the promoters of downstream Cold Responsive gene (CORs regulated by CBFs were analyzed. Conservation, mutation and absence of the DRE core motif were detected in the promoters of six CORs. These mutations in DRE motifs suggest that CORs may not be induced via cold stress in Elaeis guineensis.

  6. RNA-seq analysis of oil palm under cold stress reveals a different C-repeat binding factor (CBF) mediated gene expression pattern in Elaeis guineensis compared to other species.

    Science.gov (United States)

    Lei, Xintao; Xiao, Yong; Xia, Wei; Mason, Annaliese S; Yang, Yaodong; Ma, Zilong; Peng, Ming

    2014-01-01

    Elaeis guineensis as a tropical oil-crop is particularly sensitive to low temperature. Improvement of cold-tolerance may significantly increase the total cultivation area of this tropical oil-crop worldwide. We sequenced cold-treated and control (untreated) samples of Elaeis guineensis. De novo assembly generated 51,452 unigenes with an average length of 703 bp. Subsequently, these expressed sequences were functionally annotated. In the K category (transcription factors) of COG (Cluster of Orthologous Group) annotation, the largest proportion of genes induced and repressed at least two-fold under cold stress were from the AP2/ERE family, indicating that C-repeat binding factor, (CBFs, members of the AP2/ERE family) may play a central role in cold tolerance in Elaeis guineensis. Subsequently, the CBF-mediated signal transduction pathway was reconstructed based on transcriptome data and the gene expression profile involving the pathway was examined using real-time quantitative RT-PCR (qRT-PCR). CBFs reached maximum transcript level both at medium (4 h) and long period time points (7 days), contrary to the expression pattern of CBFs in Arabidopsis and rice. Moreover, the promoters of downstream Cold Responsive gene (CORs) regulated by CBFs were analyzed. Conservation, mutation and absence of the DRE core motif were detected in the promoters of six CORs. These mutations in DRE motifs suggest that CORs may not be induced via cold stress in Elaeis guineensis.

  7. Preliminary observations on the impact of complex stress histories on sandstone response to salt weathering: laboratory simulations of process combinations

    Science.gov (United States)

    McCabe, S.; Smith, B. J.; Warke, P. A.

    2007-03-01

    Historic sandstone structures carry an inheritance, or a ‘memory’, of past stresses that the stone has undergone since its placement in a façade. This inheritance, which conditions present day performance, may be made up of long-term exposure to a combination of low magnitude background environmental factors (for example, salt weathering, temperature and moisture cycling) and, superimposed upon these, less frequent but potentially high magnitude events or ‘exceptional’ factors (for example, lime rendering, severe frost events, fire). The impact of complex histories on the decay pathways of historic sandstone is not clearly understood, but this paper seeks to improve that understanding through the use of a laboratory ‘process combination’ study. Blocks of quartz sandstone (Peakmoor, from NW England) were divided into subsets that experienced different histories (lime rendering and removal, fire and freeze-thaw cycles in isolation and combination) that reflected the event timeline of a real medieval sandstone monument in NE Ireland, Bonamargy Friary (McCabe et al. 2006b). These subsets were then subject to salt weathering cycles using a 10% salt solution of NaCl and MgSO4 that represents the ‘every-day’ stress environment of, for example, sandstone structures in coastal, or polluted urban, location. Block response to salt weathering was monitored by collecting, drying and weighing the debris that was released as blocks were immersed in the salt solution at the beginning of each cycle. The results illustrate the complexity of the stone decay system, showing that seemingly small variations in stress history can produce divergent response to salt weathering cycles. Applied to real-world historic sandstone structures, this concept may help to explain the spatial and temporal variability of sandstone response to background environmental factors on a single façade, and encourage conservators to include the role of stress inheritance when selecting and

  8. Quantum repeated games revisited

    CERN Document Server

    Frackiewicz, Piotr

    2011-01-01

    We present a scheme for playing quantum repeated 2x2 games based on the Marinatto and Weber's approach to quantum games. As a potential application, we study twice repeated Prisoner's Dilemma game. We show that results not available in classical game can be obtained when the game is played in the quantum way. Before we present our idea, we comment on the previous scheme of playing quantum repeated games.

  9. Mouse repeated electroconvulsive seizure (ECS) does not reverse social stress effects but does induce behavioral and hippocampal changes relevant to electroconvulsive therapy (ECT) side-effects in the treatment of depression

    Science.gov (United States)

    Sigrist, Hannes; Seifritz, Erich; Fikse, Lianne; Bosker, Fokko J.; Schoevers, Robert A.; Klein, Hans C.

    2017-01-01

    Electroconvulsive therapy (ECT) is an effective treatment for depression, but can have negative side effects including amnesia. The mechanisms of action underlying both the antidepressant and side effects of ECT are not well understood. An equivalent manipulation that is conducted in experimental animals is electroconvulsive seizure (ECS). Rodent studies have provided valuable insights into potential mechanisms underlying the antidepressant and side effects of ECT. However, relatively few studies have investigated the effects of ECS in animal models with a depression-relevant manipulation such as chronic stress. In the present study, mice were first exposed to chronic social stress (CSS) or a control procedure for 15 days followed by ECS or a sham procedure for 10 days. Behavioral effects were investigated using an auditory fear conditioning (learning) and expression (memory) test and a treadmill-running fatigue test. Thereafter, immunohistochemistry was conducted on brain material using the microglial marker Iba-1 and the cholinergic fibre marker ChAT. CSS did not increase fear learning and memory in the present experimental design; in both the control and CSS mice ECS reduced fear learning and fear memory expression. CSS induced the expected fatigue-like effect in the treadmill-running test; ECS induced increased fatigue in CSS and control mice. In CSS and control mice ECS induced inflammation in hippocampus in terms of increased expression of Iba-1 in radiatum of CA1 and CA3. CSS and ECS both reduced acetylcholine function in hippocampus as indicated by decreased expression of ChAT in several hippocampal sub-regions. Therefore, CSS increased fatigue and reduced hippocampal ChAT activity and, rather than reversing these effects, a repeated ECS regimen resulted in impaired fear learning-memory, increased fatigue, increased hippocampal Iba-1 expression, and decreased hippocampal ChAT expression. As such, the current model does not provide insights into the

  10. Saccharomyces cerevisiae glycerol/H+ symporter Stl1p is essential for cold/near-freeze and freeze stress adaptation. A simple recipe with high biotechnological potential is given

    Directory of Open Access Journals (Sweden)

    Ferreira Célia

    2010-11-01

    Full Text Available Abstract Background Freezing is an increasingly important means of preservation and storage of microbial strains used for many types of industrial applications including food processing. However, the yeast mechanisms of tolerance and sensitivity to freeze or near-freeze stress are still poorly understood. More knowledge on this regard would improve their biotechnological potential. Glycerol, in particular intracellular glycerol, has been assigned as a cryoprotectant, also important for cold/near-freeze stress adaptation. The S. cerevisiae glycerol active transporter Stl1p plays an important role on the fast accumulation of glycerol. This gene is expressed under gluconeogenic conditions, under osmotic shock and stress, as well as under high temperatures. Results We found that cells grown on STL1 induction medium (YPGE and subjected to cold/near-freeze stress, displayed an extremely high expression of this gene, also visible at glycerol/H+ symporter activity level. Under the same conditions, the strains harbouring this transporter accumulated more than 400 mM glycerol, whereas the glycerol/H+ symporter mutant presented less than 1 mM. Consistently, the strains able to accumulate glycerol survive 25-50% more than the stl1Δ mutant. Conclusions In this work, we report the contribution of the glycerol/H+ symporter Stl1p for the accumulation and maintenance of glycerol intracellular levels, and consequently cell survival at cold/near-freeze and freeze temperatures. These findings have a high biotechnological impact, as they show that any S. cerevisiae strain already in use can become more resistant to cold/freeze-thaw stress just by simply adding glycerol to the broth. The combination of low temperatures with extracellular glycerol will induce the transporter Stl1p. This solution avoids the use of transgenic strains, in particular in food industry.

  11. Reconfigurable multiport EPON repeater

    Science.gov (United States)

    Oishi, Masayuki; Inohara, Ryo; Agata, Akira; Horiuchi, Yukio

    2009-11-01

    An extended reach EPON repeater is one of the solutions to effectively expand FTTH service areas. In this paper, we propose a reconfigurable multi-port EPON repeater for effective accommodation of multiple ODNs with a single OLT line card. The proposed repeater, which has multi-ports in both OLT and ODN sides, consists of TRs, BTRs with the CDR function and a reconfigurable electrical matrix switch, can accommodate multiple ODNs to a single OLT line card by controlling the connection of the matrix switch. Although conventional EPON repeaters require full OLT line cards to accommodate subscribers from the initial installation stage, the proposed repeater can dramatically reduce the number of required line cards especially when the number of subscribers is less than a half of the maximum registerable users per OLT. Numerical calculation results show that the extended reach EPON system with the proposed EPON repeater can save 17.5% of the initial installation cost compared with a conventional repeater, and can be less expensive than conventional systems up to the maximum subscribers especially when the percentage of ODNs in lightly-populated areas is higher.

  12. Revisiting the TALE repeat.

    Science.gov (United States)

    Deng, Dong; Yan, Chuangye; Wu, Jianping; Pan, Xiaojing; Yan, Nieng

    2014-04-01

    Transcription activator-like (TAL) effectors specifically bind to double stranded (ds) DNA through a central domain of tandem repeats. Each TAL effector (TALE) repeat comprises 33-35 amino acids and recognizes one specific DNA base through a highly variable residue at a fixed position in the repeat. Structural studies have revealed the molecular basis of DNA recognition by TALE repeats. Examination of the overall structure reveals that the basic building block of TALE protein, namely a helical hairpin, is one-helix shifted from the previously defined TALE motif. Here we wish to suggest a structure-based re-demarcation of the TALE repeat which starts with the residues that bind to the DNA backbone phosphate and concludes with the base-recognition hyper-variable residue. This new numbering system is consistent with the α-solenoid superfamily to which TALE belongs, and reflects the structural integrity of TAL effectors. In addition, it confers integral number of TALE repeats that matches the number of bound DNA bases. We then present fifteen crystal structures of engineered dHax3 variants in complex with target DNA molecules, which elucidate the structural basis for the recognition of bases adenine (A) and guanine (G) by reported or uncharacterized TALE codes. Finally, we analyzed the sequence-structure correlation of the amino acid residues within a TALE repeat. The structural analyses reported here may advance the mechanistic understanding of TALE proteins and facilitate the design of TALEN with improved affinity and specificity.

  13. Recursive quantum repeater networks

    CERN Document Server

    Van Meter, Rodney; Horsman, Clare

    2011-01-01

    Internet-scale quantum repeater networks will be heterogeneous in physical technology, repeater functionality, and management. The classical control necessary to use the network will therefore face similar issues as Internet data transmission. Many scalability and management problems that arose during the development of the Internet might have been solved in a more uniform fashion, improving flexibility and reducing redundant engineering effort. Quantum repeater network development is currently at the stage where we risk similar duplication when separate systems are combined. We propose a unifying framework that can be used with all existing repeater designs. We introduce the notion of a Quantum Recursive Network Architecture, developed from the emerging classical concept of 'recursive networks', extending recursive mechanisms from a focus on data forwarding to a more general distributed computing request framework. Recursion abstracts independent transit networks as single relay nodes, unifies software layer...

  14. The Pentapeptide Repeat Proteins

    Energy Technology Data Exchange (ETDEWEB)

    Vetting,M.; Hegde, S.; Fajardo, J.; Fiser, A.; Roderick, S.; Takiff, H.; Blanchard, J.

    2006-01-01

    The Pentapeptide Repeat Protein (PRP) family has over 500 members in the prokaryotic and eukaryotic kingdoms. These proteins are composed of, or contain domains composed of, tandemly repeated amino acid sequences with a consensus sequence of [S, T,A, V][D, N][L, F]-[S, T,R][G]. The biochemical function of the vast majority of PRP family members is unknown. The three-dimensional structure of the first member of the PRP family was determined for the fluoroquinolone resistance protein (MfpA) from Mycobacterium tuberculosis. The structure revealed that the pentapeptide repeats encode the folding of a novel right-handed quadrilateral {beta}-helix. MfpA binds to DNA gyrase and inhibits its activity. The rod-shaped, dimeric protein exhibits remarkable size, shape and electrostatic similarity to DNA.

  15. Repeating the Past

    Science.gov (United States)

    Moore, John W.

    1998-05-01

    As part of the celebration of the Journal 's 75th year, we are scanning each Journal issue from 25, 50, and 74 years ago. Many of the ideas and practices described are so similar to present-day "innovations" that George Santayana's adage (1) "Those who cannot remember the past are condemned to repeat it" comes to mind. But perhaps "condemned" is too strong - sometimes it may be valuable to repeat something that was done long ago. One example comes from the earliest days of the Division of Chemical Education and of the Journal.

  16. All-optical repeater.

    Science.gov (United States)

    Silberberg, Y

    1986-06-01

    An all-optical device containing saturable gain, saturable loss, and unsaturable loss is shown to transform weak, distorted optical pulses into uniform standard-shape pulses. The proposed device performs thresholding, amplification, and pulse shaping as required from an optical repeater. It is shown that such a device could be realized by existing semiconductor technology.

  17. Bidirectional Manchester repeater

    Science.gov (United States)

    Ferguson, J.

    1980-01-01

    Bidirectional Manchester repeater is inserted at periodic intervals along single bidirectional twisted pair transmission line to detect, amplify, and transmit bidirectional Manchester 11 code signals. Requiring only 18 TTL 7400 series IC's, some line receivers and drivers, and handful of passive components, circuit is simple and relatively inexpensive to build.

  18. Beneficial Effects of Nitric Oxide Induced Mild Oxidative Stress on Post-Thawed Bull Semen Quality

    Directory of Open Access Journals (Sweden)

    Mohsen Sharafi

    2015-07-01

    Full Text Available Background: Cryopreservation of semen requires optimized conditions to minimize the harmful effects of various stresses. The main approach for protection of sperm against stress is based on the use of antioxidants and cryoprotectants, which are described as defensive methods. Recently, the application of controlled mild stressors has been described for activation of a temporary response in oocyte, embryo and somatic cells. In this study a sub-lethal oxidative stress induced by precise concentrations of nitric oxide (NO has been evaluated for sperm during cryopreservation. Materials and Methods: In this experimental study, we used different concentrations of NO [0 μM (NO-0, 0.01 μM (NO-0.01, 0.1 μM (NO-0.1, 1 μM (NO-1, 10 μM (NO-10 and 100 μM (NO-100] during cryopreservation of bull semen. Their effects on post-thawed sperm quality that included motility and velocity parameters, plasma membrane functionality, acrosome integrity, apoptosis status, mitochondrial activity and lipid peroxidation after freezing-thawing were investigated. Results: Exposure of sperm before freezing to NO-1 significantly increased total motility (88.4 ± 2.8%, progressive motility (50.4 ± 3.2% and average path velocity (VAP, 53.8 ± 3.1 μm/s compared to other extenders. In addition, NO-1 significantly increased plasma membrane functionality (89.3 ± 2.9% compared to NO-0 (75.3 ± 2.9%, NO-0.01 (78.3 ± 2.9%, NO-0.1 (76.4 ± 2.9%, NO-10 (64 ± 2.9% and NO-100 (42 ± 2.9%. Sperm exposed to NO-1 produced the highest percentage of viable (85.6 ± 2.3% and the lowest percentage of apoptotic (10.8 ± 2.4% spermatozoa compared to the other extenders. Also, NO-100 resulted in a higher percentage of dead spermatozoa (27.1 ± 2.7% compared to the other extenders. In terms of mitochondrial activity, there was no significant difference among NO-0 (53.4 ± 3.2, NO-0.01 (52.1 ± 3.2, NO-0.1 (50.8 ± 3.2 and NO-1 (53.1 ± 3.2. For acrosome integrity, no significant different

  19. Cataractogenesis after Repeat Laser in situ Keratomileusis

    Directory of Open Access Journals (Sweden)

    Ahmad M. Mansour

    2012-08-01

    Full Text Available There has been the unsubstantiated clinical impression that laser refractive surgery accelerates cataract development along with solid experimental data about the cataractogenic effects of excimer laser treatment. We present the first documented case of significant cataract formation in a young myope after repeat excimer laser ablation necessitating phacoemulsification with a posterior chamber implant. Proposed explanations include focusing of the ablation wave on the posterior capsule (acoustic wave lens epithelial damage, photooxidative stress of the lens (ultraviolet and inflammatory oxidative stress, and corticosteroid-induced cataract (lens toxicity.

  20. Triggering of repeating earthquakes in central California

    Science.gov (United States)

    Wu, Chunquan; Gomberg, Joan; Ben-Naim, Eli; Johnson, Paul

    2014-01-01

    Dynamic stresses carried by transient seismic waves have been found capable of triggering earthquakes instantly in various tectonic settings. Delayed triggering may be even more common, but the mechanisms are not well understood. Catalogs of repeating earthquakes, earthquakes that recur repeatedly at the same location, provide ideal data sets to test the effects of transient dynamic perturbations on the timing of earthquake occurrence. Here we employ a catalog of 165 families containing ~2500 total repeating earthquakes to test whether dynamic perturbations from local, regional, and teleseismic earthquakes change recurrence intervals. The distance to the earthquake generating the perturbing waves is a proxy for the relative potential contributions of static and dynamic deformations, because static deformations decay more rapidly with distance. Clear changes followed the nearby 2004 Mw6 Parkfield earthquake, so we study only repeaters prior to its origin time. We apply a Monte Carlo approach to compare the observed number of shortened recurrence intervals following dynamic perturbations with the distribution of this number estimated for randomized perturbation times. We examine the comparison for a series of dynamic stress peak amplitude and distance thresholds. The results suggest a weak correlation between dynamic perturbations in excess of ~20 kPa and shortened recurrence intervals, for both nearby and remote perturbations.

  1. Duct Leakage Repeatability Testing

    Energy Technology Data Exchange (ETDEWEB)

    Walker, Iain [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Sherman, Max [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2014-01-01

    Duct leakage often needs to be measured to demonstrate compliance with requirements or to determine energy or Indoor Air Quality (IAQ) impacts. Testing is often done using standards such as ASTM E1554 (ASTM 2013) or California Title 24 (California Energy Commission 2013 & 2013b), but there are several choices of methods available within the accepted standards. Determining which method to use or not use requires an evaluation of those methods in the context of the particular needs. Three factors that are important considerations are the cost of the measurement, the accuracy of the measurement and the repeatability of the measurement. The purpose of this report is to evaluate the repeatability of the three most significant measurement techniques using data from the literature and recently obtained field data. We will also briefly discuss the first two factors. The main question to be answered by this study is to determine if differences in the repeatability of these tests methods is sufficient to indicate that any of these methods is so poor that it should be excluded from consideration as an allowed procedure in codes and standards.

  2. Repeatability of Cryogenic Multilayer Insulation

    Science.gov (United States)

    Johnson, W. L.; Vanderlaan, M.; Wood, J. J.; Rhys, N. O.; Guo, W.; Van Sciver, S.; Chato, D. J.

    2017-01-01

    Due to the variety of requirements across aerospace platforms, and one off projects, the repeatability of cryogenic multilayer insulation has never been fully established. The objective of this test program is to provide a more basic understanding of the thermal performance repeatability of MLI systems that are applicable to large scale tanks. There are several different types of repeatability that can be accounted for: these include repeatability between multiple identical blankets, repeatability of installation of the same blanket, and repeatability of a test apparatus. The focus of the work in this report is on the first two types of repeatability. Statistically, repeatability can mean many different things. In simplest form, it refers to the range of performance that a population exhibits and the average of the population. However, as more and more identical components are made (i.e. the population of concern grows), the simple range morphs into a standard deviation from an average performance. Initial repeatability testing on MLI blankets has been completed at Florida State University. Repeatability of five GRC provided coupons with 25 layers was shown to be +/- 8.4 whereas repeatability of repeatedly installing a single coupon was shown to be +/- 8.0. A second group of 10 coupons have been fabricated by Yetispace and tested by Florida State University, through the first 4 tests, the repeatability has been shown to be +/- 16. Based on detailed statistical analysis, the data has been shown to be statistically significant.

  3. Use of butane-isobutane refrigerant spray in the management of a mucocoele in a visually impaired child.

    Science.gov (United States)

    Birapu, Uday Chowdary; Puppala, Ravindar; Kethineni, Balaji; Banavath, Sunitha

    2016-01-01

    Mucocoeles are commonly observed lesions in children and young adults. Conventional management using a scalpel aims at enucleation, requiring psychological preparation of the parent as well as the child because of inherent fear and apprehension towards surgery. This is still more complex in children with visual impairment. The other management techniques are laser, cryotherapy and micromarsupialisation, management strategies that, being painless and tolerable, reduce the anxiety of the child and are therefore more acceptable. The basic technique of cryotherapy stresses on rapid cooling, gradual thawing and repeated freezing to ensure tissue destruction. We report a case of a 13-year-old boy with visual impairment, presenting with a mucocoele on the lower lip, which was managed using butane-isobutane refrigerant spray, which is otherwise routinely employed for pulp vitality testing. A single, 2 min freeze/thaw cycle was used. The healing was uneventful.

  4. Intragenic tandem repeat variation between Legionella pneumophila strains

    Directory of Open Access Journals (Sweden)

    Jarraud Sophie

    2008-12-01

    Full Text Available Abstract Background Bacterial genomes harbour a large number of tandem repeats, yet the possible phenotypic effects of those found within the coding region of genes are only beginning to be examined. Evidence exists from other organisms that these repeats can be involved in the evolution of new genes, gene regulation, adaptation, resistance to environmental stresses, and avoidance of the immune system. Results In this study, we have investigated the presence and variability in copy number of intragenic tandemly repeated sequences in the genome of Legionella pneumophila, the etiological agent of a severe pneumonia known as Legionnaires' disease. Within the genome of the Philadelphia strain, we have identified 26 intragenic tandem repeat sequences using conservative selection criteria. Of these, seven were "polymorphic" in terms of repeat copy number between a large number of L. pneumophila serogroup 1 strains. These strains were collected from a wide variety of environments and patients in several geographical regions. Within this panel of strains, all but one of these seven genes exhibited statistically different patterns in repeat copy number between samples from different origins (environmental, clinical, and hot springs. Conclusion These results support the hypothesis that intragenic tandem repeats could play a role in virulence and adaptation to different environments. While tandem repeats are an increasingly popular focus of molecular typing studies in prokaryotes, including in L. pneumophila, this study is the first examining the difference in tandem repeat distribution as a function of clinical or environmental origin.

  5. Antioxidant effect of rosemary (Rosmarinus officinalis L.) extract in soybean lecithin-based semen extender following freeze-thawing process of ram sperm.

    Science.gov (United States)

    Motlagh, Mahdi Khodaei; Sharafi, Mohsen; Zhandi, Mahdi; Mohammadi-Sangcheshmeh, Abdollah; Shakeri, Malak; Soleimani, Masoud; Zeinoaldini, Saeed

    2014-10-01

    The aim of current study was to evaluate effect of rosemary aqueous extract on post-thawed ram sperm quality in a soybean lecithin-based (SL) extender. Ram semen samples were obtained, extended with SL extender and supplemented with 0% (SL-R0), 2% (SL-R2), 4% (SL-R4), 6% (SL-R6), and 8% (SL-R8) rosemary aqueous extract. Following equilibration, the straws were frozen, and then plunged into the liquid nitrogen. After thawing, sperm motility and velocity parameters, plasma membrane functionality, viability, acrosomal and capacitation status were evaluated. Membrane lipid peroxidation was also analyzed through the malondialdehyde (MDA) concentration. Our results showed that SL-R4 and SL-R6 groups resulted in higher (p 0.05) by different levels of rosemary aqueous extract. Lower (p ram sperm quality in a dose dependent manner.

  6. Influencia de los ciclos hielo-deshielo en la resistencia del concreto (caso Tunja Influence of freeze-thaw cycles in the resistance concrete (Tunja case

    Directory of Open Access Journals (Sweden)

    Diego Fernando Páez Moreno

    2009-07-01

    Full Text Available El presente artículo contiene el análisis de afectación de un agente de deterioro del concreto, conocido como ciclo hielo-deshielo, que se presenta en Tunja en época de heladas. En él se explica cómo el fenómeno afecta al concreto tanto cualitativa como cuantitativamente en propiedades físicas y mecánicas como porosidad, absorción y resistencia, y en su apariencia física. En la etapa de experimentación se empleó un grupo de 24 probetas cilíndricas de concreto, y se manejaron como variables de experimentación la relación agua/cemento y el tipo de curado, con las que se planteó una matriz de distribución. Para obtener resultados inmediatos se hizo la simulación de este proceso de forma acelerada, llevando los especímenes de concreto a períodos de hielo en la noche y de deshielo en el día, durante un tiempo continuo, en los que se manejaron dos ambientes: uno artificial (refrigerador - temperatura baja y uno natural (ambiente.This article refers to the analysis of a concrete deterioration agent affectation, known as cycle ice - defrosting, which appears in Tunja at time of frosts. It is explained how the phenomenon qualitative and quantitatively affects the concrete in physical and mechanical properties like porosity, absorption, and resistance, as well as in its physical appearance. In the experimentation stage, a group of 24 cylindrical test tubes of concrete was used. Water/cement relation and type fop curing were used as experimentation variables, with them a distribution matrix was proposed. In order to obtain immediate results, a simulation of this process in an accelerated way was made: concrete parts were taken to frosting periods at night and to defrosting periods during the day, at a continuous time in which two environments were used, an artificial one (refrigerator - low temperature and a natural one (the environment.

  7. Effect of various levels of catalase antioxidant in semen extenders on lipid peroxidation and semen quality after the freeze-thawing bull semen

    Directory of Open Access Journals (Sweden)

    Reza Asadpour

    2011-11-01

    Full Text Available The objective of this study was to evaluate effect of different concentrations of catalase in two extenders on motility, viability and lipid peroxidation bull spermatozoa during semen freezing process. Thirty ejaculates collected from ten Holstein bulls were pooled and evaluated at 37 °C. Pool ejaculated was split into two main experimental groups, 1 and 2. In experiment 1, specimen was diluted to a final concentration of 30 × 106 spermatozoa with citrate-egg yolk and in experiment 2; specimen was diluted with tris-egg yolk extender to the same concentration. In both experiments diluted semen was divided into three aliquots, including a control and two test groups. Each aliquot was rediluted with an equal volume of extender either without (control or with one of the antioxidants contained one of the following antioxidants: catalase (CAT; 100 IU mL-1 catalase (CAT; 200 IU mL-1 and control group. No significant differences were observed in sperm viability and motility following addition of catalase enzyme at concentration of 100 IU mL-1 and 200 IU mL-1 to citrate-egg yolk extender. But the highest sperm viability was achieved by addition of 100 IU mL-1 and 200 IU mL-1 catalase to tris-egg yolk semen extender compared with the control group (P < 0.05. Malondialdehyde levels did not change with addition of catalase in both extenders compared with the control group. The obtained results provide a new approach to the cryopreservation of bull semen, and could positively contribute to intensive cattle production.

  8. Resilient Modulus of Freeze-Thaw Affected Granular Soils for Pavement Design and Evaluation. Part 2. Field Validation Tests at Winchendon, Massachusetts, Test Sections,

    Science.gov (United States)

    1986-10-01

    techniques to express the resil- on the riding qualities, integrity , and durability of ient modulus Mr as a function of density, soil pavements are...in the second series of tests in ciated instrumentation integrates the velocity sig- February 1979, when the test soils were frozen. As nal and reads...analysis of the six test sections are sum- Radius (m) •0 0 2 04 0 6 08 1 0 o E 400 Actual Basin - -- j/ / Calculoated Baosin 00 .. ~~~~~ ~~1200 1 1

  9. Monitoring Surface Soil Moisture and Freeze-Thaw State with the High-Resolution Radar of the Soil Moisture Active/Passive (SMAP) Mission

    Science.gov (United States)

    2010-05-01

    km resolution and 6-hourly. Vegetation water content (VWC) was derived from MODIS NDVI data using a simple empirical relationship. Static fields...air temperature and precipitation ) derived from the NCEP/NCAR reanalysis project. The PWBM simulations are daily and are provided on a Northern

  10. Taqman MGB探针冻融稳定性研究%Study on Freeze-thaw Cycles on Taqman MGB Stability

    Institute of Scientific and Technical Information of China (English)

    臧超; 王晶; 李亮; 隋志伟; 余笑波; 黎朋

    2011-01-01

    Taqman MGB探针的稳定性是实时荧光定量PCR准确定量的关键因素之一.然而在实验过程中,常常因为运输、实验室保存或使用条件的变化,造成探针的反复冻融,影响实验结果.采用高效液相色谱技术定量研究了反复冻融的MGB探针的稳定性;并比较分析了冻融探针对qPCR的影响程度.结果表明:MGB探针可以耐受30次以内的反复冻融,随着探针浓度的降低,探针反复冻融后qPCR量值波动区间增大,因此,为保证结果稳定性,qPCR实验使用的MGB探针应尽量减少反复冻融次数.

  11. Structural and magnetic behavior of ferrogels obtained by freezing thawing of polyvinyl alcohol/poly (acrylic acid) (PAA)-coated iron oxide nanoparticles

    OpenAIRE

    Moscoso Londoño, Oscar; Gonzalez, Jimena Soledad; Muraca, D.; Hoppe, Cristina Elena; Alvarez, Vera Alejandra; López Quintela, A.; Socolovsky, Leandro Martin; Pirota, K. R.

    2015-01-01

    Superparamagnetic ferrogels with high swelling ability and potential applications as solvent absorbers and stimuli-responsive drug delivery devices were obtained by a non-toxic and environmentally friendly route based on dispersion of poly(acrylic acid)-coated iron oxide nanoparticles (PAA-coated NPs) in poly(vinyl alcohol) (PVA) solutions followed by freezing–thawing. Presence of carboxylate groups arising from the PAA coating allowed hydrogen bonding formation between NPs and PVA and enable...

  12. Classification of broiler breast fillets according to storage and to freeze-thaw treatment using near infrared spectroscopy and multivariate analysis

    Science.gov (United States)

    Visible/near-infrared (NIR) spectroscopy has shown potential for successfully classifying broiler breast fillets according to their texture properties. Freshness and shelf life are also important quality characteristics of boneless skinless chicken breast products in the marketplace. This study deal...

  13. Expansion of protein domain repeats.

    Directory of Open Access Journals (Sweden)

    Asa K Björklund

    2006-08-01

    Full Text Available Many proteins, especially in eukaryotes, contain tandem repeats of several domains from the same family. These repeats have a variety of binding properties and are involved in protein-protein interactions as well as binding to other ligands such as DNA and RNA. The rapid expansion of protein domain repeats is assumed to have evolved through internal tandem duplications. However, the exact mechanisms behind these tandem duplications are not well-understood. Here, we have studied the evolution, function, protein structure, gene structure, and phylogenetic distribution of domain repeats. For this purpose we have assigned Pfam-A domain families to 24 proteomes with more sensitive domain assignments in the repeat regions. These assignments confirmed previous findings that eukaryotes, and in particular vertebrates, contain a much higher fraction of proteins with repeats compared with prokaryotes. The internal sequence similarity in each protein revealed that the domain repeats are often expanded through duplications of several domains at a time, while the duplication of one domain is less common. Many of the repeats appear to have been duplicated in the middle of the repeat region. This is in strong contrast to the evolution of other proteins that mainly works through additions of single domains at either terminus. Further, we found that some domain families show distinct duplication patterns, e.g., nebulin domains have mainly been expanded with a unit of seven domains at a time, while duplications of other domain families involve varying numbers of domains. Finally, no common mechanism for the expansion of all repeats could be detected. We found that the duplication patterns show no dependence on the size of the domains. Further, repeat expansion in some families can possibly be explained by shuffling of exons. However, exon shuffling could not have created all repeats.

  14. DWI Repeaters and Non-Repeaters: A Comparison.

    Science.gov (United States)

    Weeber, Stan

    1981-01-01

    Discussed how driving-while-intoxicated (DWI) repeaters differed signigicantly from nonrepeaters on 4 of 23 variables tested. Repeaters were more likely to have zero or two dependent children, attend church frequently, drink occasionally and have one or more arrests for public intoxication. (Author)

  15. To Repeat or Not to Repeat a Course

    Science.gov (United States)

    Armstrong, Michael J.; Biktimirov, Ernest N.

    2013-01-01

    The difficult transition from high school to university means that many students need to repeat (retake) 1 or more of their university courses. The authors examine the performance of students repeating first-year core courses in an undergraduate business program. They used data from university records for 116 students who took a total of 232…

  16. Attenuation of pCREB and Egr1 expression in the insular and anterior cingulate cortices associated with enhancement of CFA-evoked mechanical hypersensitivity after repeated forced swim stress.

    Science.gov (United States)

    Imbe, Hiroki; Kimura, Akihisa

    2017-09-01

    The perception and response to pain are severely impacted by exposure to stressors. In some animal models, stress increases pain sensitivity, which is termed stress-induced hyperalgesia (SIH). The insular cortex (IC) and anterior cingulate cortex (ACC), which are typically activated by noxious stimuli, affect pain perception through the descending pain modulatory system. In the present study, we examined the expression of phospho-cAMP response element-binding protein (pCREB) and early growth response 1 (Egr1) in the IC and ACC at 3h (the acute phase of peripheral tissue inflammation) after complete Freund's adjuvant (CFA) injection in naïve rats and rats preconditioned with forced swim stress (FS) to clarify the effect of FS, a stressor, on cortical cell activities in the rats showing SIH induced by FS. The CFA injection into the hindpaw induced mechanical hypersensitivity and increased the expression of the pCREB and Egr1 in the IC and ACC at 3h after the injection. FS (day 1, 10min; days 2-3, 20min) prior to the CFA injection enhanced the CFA-induced mechanical hypersensitivity and attenuated the increase in the expression of pCREB and Egr1 in the IC and ACC. These findings suggested that FS modulates the CFA injection-induced neuroplasticity in the IC and ACC to enhance the mechanical hypersensitivity. These findings are thought to signify stressor-induced dysfunction of the descending pain modulatory system. Copyright © 2017 Elsevier Inc. All rights reserved.

  17. Nifty Nines and Repeating Decimals

    Science.gov (United States)

    Brown, Scott A.

    2016-01-01

    The traditional technique for converting repeating decimals to common fractions can be found in nearly every algebra textbook that has been published, as well as in many precalculus texts. However, students generally encounter repeating decimal numerals earlier than high school when they study rational numbers in prealgebra classes. Therefore, how…

  18. Nifty Nines and Repeating Decimals

    Science.gov (United States)

    Brown, Scott A.

    2016-01-01

    The traditional technique for converting repeating decimals to common fractions can be found in nearly every algebra textbook that has been published, as well as in many precalculus texts. However, students generally encounter repeating decimal numerals earlier than high school when they study rational numbers in prealgebra classes. Therefore, how…

  19. Focused Weathering Control of Convex Waterfalls Along the Niobrara River in Cherry and Brown Counties, Nebraska

    Science.gov (United States)

    Mason, L. J.; Pederson, D. T.; Goble, R. J.

    2004-12-01

    More than 200 waterfalls exist along the southern spring branch tributaries that feed an approximately twenty-five mile section of the Niobrara River, east of Valentine, Nebraska. Many of these waterfalls posses a convex shape in the horizontal plane and are buttressed. This morphology is controlled by focused, season-specific weathering along the escarpments adjacent to the waterfall face and a lack of stream erosion on the actual waterfall face. The waterfalls are composed of the Rosebud Formation, a poorly indurated siltstone that should be easily eroded by stream flow. The spring creeks are ineffective at significantly eroding the waterfall face mainly due to their relatively low discharge, three to five cubic feet per second, and low sediment load. The erosive power of the streams is further reduced at the site of the waterfall by the buttressed shape spreading the flow into a thin sheet. The buttressed shape of the waterfall develops in response to stress relief. The only areas of the waterfall face showing stream erosion and lack of diatom cover is where free falling water is impacting the waterfall face. Large, loose talus slopes at the base of the waterfall escarpments further support that the weathering processes operate at a faster rate than stream erosion. Observable groundwater seepage from the escarpments on either side of the waterfalls exposes the faces to season-specific weathering processes. The moisture content of the escarpments varies with exposure to sunlight and changes in air temperature. Cyclic differential expansion and contraction of clays and minerals as well as precipitation and hydration of salts operate on a daily and seasonal basis. These repeated stresses give the escarpments a flaky, shingle like appearance and can cause rapid deterioration of the escarpment. During the winter, the seeping groundwater and waterfall spray form large ice flows on either side of the waterfall face. Freeze-thaw processes operate on a seasonal and

  20. All-photonic quantum repeaters

    Science.gov (United States)

    Azuma, Koji; Tamaki, Kiyoshi; Lo, Hoi-Kwong

    2015-01-01

    Quantum communication holds promise for unconditionally secure transmission of secret messages and faithful transfer of unknown quantum states. Photons appear to be the medium of choice for quantum communication. Owing to photon losses, robust quantum communication over long lossy channels requires quantum repeaters. It is widely believed that a necessary and highly demanding requirement for quantum repeaters is the existence of matter quantum memories. Here we show that such a requirement is, in fact, unnecessary by introducing the concept of all-photonic quantum repeaters based on flying qubits. In particular, we present a protocol based on photonic cluster-state machine guns and a loss-tolerant measurement equipped with local high-speed active feedforwards. We show that, with such all-photonic quantum repeaters, the communication efficiency scales polynomially with the channel distance. Our result paves a new route towards quantum repeaters with efficient single-photon sources rather than matter quantum memories. PMID:25873153

  1. Antioxidant Effects of Selenium on Seminiferous Tubules of Immature Mice Testis

    Directory of Open Access Journals (Sweden)

    Davoud Kushki

    2015-12-01

    Full Text Available Background: The freezing of immature testis tissue and then the transplant of it can be considered as a major step in fertility preservation for young boys with cancer, the survival of animal generation exposed to extinction and cloning animalistic desirable species. One of the most prevalent of damages in during the freezing-thawing process is oxidative stress. Objectives: The objective of this study was to investigate the antioxidant effects of selenium compound (Na2SeO3 on rate of seminiferous tubules injury in during of cryopreservation. Materials and Methods: In this experimental study, 8 BALB/c immature male mice (6 - 8 days old were randomly selected, and the testes removed surgically (n = 16. The testes divided into 2 groups: experimental group, control group (opposite testes. For each of the two experimental and control groups, two types of soluble (freezing solution and thawing solution were prepared. These solutions, which contain 2 mg/mL solution of Na2SeO3 and control solution, were prepared in the DMEM (Dulbecco’s modified eagle medium base medium. Of each group were 4 testes into fast freezing-thawing procedure and 4 testes were into slow freezing-thawing procedure. Then this testis for analyzing injury, after preparatory process, was stained with hematoxylin-eosin. Results: At the slow freezing-thawing procedure, seminiferous tubules injury significantly reduced in experimental group compared to control group. At the fast freezing-thawing procedure, seminiferous tubules injury significantly reduced in experimental group compared with of control group. Conclusions: It seems that Se due to its antioxidant properties, the harmful effects of freezing-thawing process reduces and protects seminiferous tubules from oxidative injury.

  2. Greater physiological and behavioral effects of interrupted stress pattern compared to daily restraint stress in rats.

    Directory of Open Access Journals (Sweden)

    Wei Zhang

    Full Text Available Repeated stress can trigger a range of psychiatric disorders, including anxiety. The propensity to develop abnormal behaviors after repeated stress is related to the severity, frequency and number of stressors. However, the pattern of stress exposure may contribute to the impact of stress. In addition, the anxiogenic nature of repeated stress exposure can be moderated by the degree of coping that occurs, and can be reflected in homotypic habituation to the repeated stress. However, expectations are not clear when a pattern of stress presentation is utilized that diminishes habituation. The purpose of these experiments is to test whether interrupted stress exposure decreases homotypic habituation and leads to greater effects on anxiety-like behavior in adult male rats. We found that repeated interrupted restraint stress resulted in less overall homotypic habituation compared to repeated daily restraint stress. This was demonstrated by greater production of fecal boli and greater corticosterone response to restraint. Furthermore, interrupted restraint stress resulted in a lower body weight and greater adrenal gland weight than daily restraint stress, and greater anxiety-like behavior in the elevated plus maze. Control experiments demonstrated that these effects of the interrupted pattern could not be explained by differences in the total number of stress exposures, differences in the total number of days that the stress periods encompased, nor could it be explained as a result of only the stress exposures after an interruption from stress. These experiments demonstrate that the pattern of stress exposure is a significant determinant of the effects of repeated stress, and that interrupted stress exposure that decreases habituation can have larger effects than a greater number of daily stress exposures. Differences in the pattern of stress exposure are therefore an important factor to consider when predicting the severity of the effects of repeated

  3. Physiological consequences of repeated exposures to conditioned fear.

    Science.gov (United States)

    Thompson, Robert S; Strong, Paul V; Fleshner, Monika

    2012-06-01

    Activation of the stress response evokes a cascade of physiological reactions that may be detrimental when repeated or chronic, and when triggered after exposure to psychological/emotional stressors. Investigation of the physiological mechanisms responsible for the health damaging effects requires animal paradigms that repeatedly evoke a response to psychological/emotional stressors. To this end, adult male Sprague Dawley rats were repeatedly exposed (2X per day for 20 days) to a context that they were conditioned to fear (conditioned fear test, CFT). Repeated exposure to CFT produced body weight loss, adrenal hypertrophy, thymic involution, and basal corticosterone elevation. In vivo biotelemetry measures revealed that CFT evokes sympathetic nervous system driven increases in heart rate (HR), mean arterial pressure (MAP), and core body temperature. Extinction of behavioral (freezing) and physiological responses to CFT was prevented using minimal reinstatement footshock. MAP responses to the CFT did not diminish across 20 days of exposure. In contrast, HR and cardiac contractility responses declined by day 15, suggesting a shift toward vascular-dominated MAP (a pre-clinical marker of CV dysfunction). Flattened diurnal rhythms, common to stress-related mood/anxiety disorders, were found for most physiological measures. Thus, repeated CFT produces adaptations indicative of the health damaging effects of psychological/emotional stress.

  4. Physiological Consequences of Repeated Exposures to Conditioned Fear

    Directory of Open Access Journals (Sweden)

    Robert S. Thompson

    2012-05-01

    Full Text Available Activation of the stress response evokes a cascade of physiological reactions that may be detrimental when repeated or chronic, and when triggered after exposure to psychological/emotional stressors. Investigation of the physiological mechanisms responsible for the health damaging effects requires animal paradigms that repeatedly evoke a response to psychological/emotional stressors. To this end, adult male Sprague Dawley rats were repeatedly exposed (2X per day for 20 days to a context that they were conditioned to fear (conditioned fear test, CFT. Repeated exposure to CFT produced body weight loss, adrenal hypertrophy, thymic involution, and basal corticosterone elevation. In vivo biotelemetry measures revealed that CFT evokes sympathetic nervous system driven increases in heart rate (HR, mean arterial pressure (MAP, and core body temperature. Extinction of behavioral (freezing and physiological responses to CFT was prevented using minimal reinstatement footshock. MAP responses to the CFT did not diminish across 20 days of exposure. In contrast, HR and cardiac contractility responses declined by day 15, suggesting a shift toward vascular-dominate