Low stress no distortion welding for aerospace shell structures

To fit in with the strict geometrical integrity and ensure dimensionally consistent fabrication of the welded aerospace structures. the low stress no distortion(LSND)welding, a technique for thin materials, was poineered and developed to provide an ininprocess active control of welding distortion. Satisfactory distortion free results were achieved in both welding of jet engine cases of heat-resistance alloys and rocket fuel tanks of aluminuim alloys, and there need no. reworking operations for post-weld distortion correction. Based on the 'static' method a newly developed method for dvnamic in-process control is also discussed in this paper. Both methods provide quanutiative in-process control of incompatible strains in weld zone and low stress no distortion welding results.

Comparison of Low Stress Mechanical Properties of Light Weight Wool and Wool Blend Fabrics using the KES-F and FAST Instruments

This study compares the test results of the FAST (Fabric Assurance by Simple Testing) with those of the KES - F (Kawabata Evaluation Systems for Fabrics) for a range of nineteen light weight wool and wool blend fabrics in terms of the low - stress mechanical properties of bending, shear, and tensile deformation. It is found that there are very significant correlations between the corresponding parameters for extensibility and shear rigidity obtained from the test results of the two systems. The correlation between the values of bending rigidity obtained from the two systems is only moderate. Furthermore, for the fabrics tested in this study, the values of bending rigidity, shear rigidity, and extensibility measured using the KES - F instruments are higher than those of the corresponding parameters measured using the FAST instruments. The linear regression equation is given for each pair of corresponding parameter.

Genome-Wide Exploration of the Grape GLR Gene Family and Differential Responses of VvGLR3.1 and VvGLR3.2 to Low Temperature and Salt Stress

Grapes,one of the oldest tree species globally,are rich in vitamins.However,environmental conditions such as low temperature and soil salinization significantly affect grape yield and quality.The glutamate receptor(GLR)family,comprising highly conserved ligand-gated ion channels,regulates plant growth and development in response to stress.In this study,11 members of the VvGLR gene family in grapes were identified using whole-genome sequence analysis.Bioinformatic methods were employed to analyze the basic physical and chemical properties,phylogenetic trees,conserved domains,motifs,expression patterns,and evolutionary relationships.Phylogenetic and collinear analyses revealed that the VvGLRs were divided into three subgroups,showing the high conservation of the grape GLR family.These members exhibited 2 glutamate receptor binding regions(GABAb and GluR)and 3-4 transmembrane regions(M1,M2,M3,and M4).Real-time quantitative PCR analysis demonstrated the sensitivity of all VvGLRs to low temperature and salt stress.Subsequent localization studies in Nicotiana tabacum verified that VvGLR3.1 and VvGLR3.2 proteins were located on the cell membrane and cell nucleus.Additionally,yeast transformation experiments confirmed the functionality of VvGLR3.1 and VvGLR3.2 in response to low temperature and salt stress.Thesefindings highlight the significant role of the GLR family,a highly conserved group of ion channels,in enhancing grape stress resistance.This study offers new insights into the grape GLR gene family,providing fundamental knowledge for further functional analysis and breeding of stress-resistant grapevines.

Effects of Low Temperature Stress on Germination and Physiological Characteristics of Different Sweet Maize Varieties

[Objectives]The paper was to explore the effects of low temperature stress on germination and physiological characteristics of different sweet maize varieties.[Methods]Taking Taitian 264,Zhexuetian 1 and Chaotian 4 as the research objects,the changes in germination potential,germination index,plant height,biomass,and antioxidant enzyme activity of maize seeds were studied under optimal temperature conditions(25℃)and low temperature stress conditions(10℃).[Results]Under 10℃stress,the germination rate and germination index of Taitian 264 were higher than that of Zhexuetian 1 and Chaotian 4.Under low temperature stress,Taitian 264 exhibited the least reduction in height and biomass,while Zhexuetian 1 had the most reduction.Additionally,the SOD and POD activities of Taitian 264 were higher than that of Zhexuetian 1 and Chaotian 4 under both temperature conditions,while the MDA content of Taitian 264 was lower.Taitian 264 showed strong germination ability against low temperature stress.[Conclusions]This study provides a basis for timely sowing practices of sweet maize in agricultural production.

Advances in Molecular Regulatory Mechanisms of Fruit Trees under Low Temperature Stress

The most recent research findings on the tolerance of fruit trees to cold stress are reviewed from a molecular perspective,including the perception and transduction of low temperature calcium signaling,CBF-dependent molecular regulatory mechanisms,non-CBF-dependent molecular regulatory mechanisms,and so forth.The objective is to provide a reference basis for further improving the cold resistance of fruit trees and cultivating new varieties of hardy plants.

De Novo Transcriptome Analysis in Hevea brasiliensis to Unveil Genes Involved in Low Temperature Stress Response

Low temperature is one of the adversities threatening the growth and development and reduces the yield of rubber trees.However,molecular mechanisms toward rubber trees in response to low temperature are largely unclear.In this study,7,159 and 7,600 differentially expressed genes(DEGs)were identified in‘Reyan 73397’rubber trees.Through GO analysis,the catalytic activity was the representative of the GO term in the only DEGs at the two studied temperatures(room temperature and 4°C,respectively),while KEGG analysis showed that carbon metabolism was the most important grouping under the comparison of these two temperatures.In addition,expression of 9 members of transcription factor MYB family genes were further verified by qRT-PCR,and MYB family genes may play important roles in the regulation of rubber trees under low temperature stress.This study provided a theoretical foundation for(1)revealing the molecular mechanisms of rubber trees in response to low temperature and(2)breeding of tolerant varieties of rubber trees.

Analysis of microRNA Expression Characteristics Related to Low Temperature Stress in Chewing Cane

[Objectives]To explore microRNA expression characteristics related to low temperature stress in chewing cane.[Methods]The research on miRNA under abiotic stress of sugarcane at home and abroad mainly focused on the types and regulation of miRNA under cold,heat,drought,high salt,and mechanical stress.However,there are few studies on miRNA under low temperature stress in chewing cane.The target genes of miR394 and miR825 in chewing cane were predicted and functionally analyzed by bioinformatics technology.[Results]The results showed that the target genes of miR394 and miR825 were mainly members of the WRKY transcription factor family,involved in plant growth,development and stress resistance.Real-time fluorescence quantitative PCR analyzed the expression characteristics of target miRNA in different tissues of chewing cane at different periods of low temperature stress.[Conclusions]The results showed that the expression of chewing cane miR394 and miR408 had temporal and spatial specificity and tissue specificity,both of which could respond to low temperature stress with significant differential expression.

DEGENERATIVE MECHANISM OF ARTICULAR CARTILAGE INDUCED BY LOW STRESS A MORPHOLOGICAL STUDY

Immobilization leads not only to diminished joint movement but also low stress of articular cartilage. The present investigation was undertaken to observe the morphological changes which arose in articular cartilage with low stress. The joint motion remained intact. Articular cartilage from the left knees of 66 rats whose left calcaneal tendons had been transected was examined under transmission electron microscope and light microscope. The degenerative changes were observed: decreased functional activity of chondrocytes progressively degenerated cartilage and lack of compensatory proliferation of chondrocytes at the early stage. We propose that the degeneration of articular cartilage induced by immobilization is the result of combination of low stress and lack of joint motion. The following degenerative mechanism begins with chondrocytes. Chondrocyte and matrix influence each other in a vicious cycle. Low stress may restrain the repair activities.

A Flow Stress Model for High Strength Steels with Low Carbon Bainite Structure

Two kinds of steels （YP960 and YP690） with low carbon bainite structure were designed, and their flow stress and strain hardening exponents were studied. The results showed that, when Hollomon relation was applied to descrihe the flow stress, there were significanl errors between the experimental and calculated points in specimens tempered below 400 ℃, while a high precision was ohserved in samples tempered above 400℃. Whereas, the modijied Voce relation could effectively predici the flow stress as well as the strain hardening exponent at different tempe ring temperatures, which was verified by unbiased estimators such as maximum relative error （MRXE） and average ahsolute relative error （AARE）. Besides, the modified Voee relation was also applied to estimate the maximum uniform strain, and the correlation coefficients （R） between the experimental data and calculated maximum uniform strain were more than 0.91. The high correlation coefficients indicated that the modified Vote relation could effec lively predict the uniform deformation ability of high strength steels with low carbon bainite structure at different tempering temperatures.

Gene Expression and Activities of SOD in Cucumber Seedlings Were Related with Concentrations of Mn^(2+),Cu^(2+),or Zn^(2+) Under Low Temperature Stress

Effects of increasing Mn^2＋, Cu^2＋, or Zn^2＋ on SOD expressions were studied in cucumber seedlings under low temperature stress. Both gene expressions and activities of Cu/Zn-SOD and Mn-SOD in cucumber seedling leaves were induced by increasing Mn^2＋, Cu^2＋, or Zn^2＋ under low temperature stress, especially 48 h afterwards. The activities of Cu/Zn-SOD and Mn-SOD at 0 and 48 h after treatment were in accordance with their gene expression levels, which implied that the transcriptional regulation plays key roles in regulating their activities at the early stage of low temperature stress. Gene expressions of Cu/Zn-SOD and Mn-SOD declined at 96 h, but Cu/Zn-SOD and Mn-SOD activities still remain high, which suggested that Cu/Zn-SOD and Mn-SOD activities might be regulated by other factors after transcription at the later stage of low temperature stress. Therefore, we concluded that the increasing Mn^2＋, Cu^2＋, or Zn^2＋ could increase the capacity of scavenging ROS in cucumber seedlings under low temperature stress by inducing gene expressions of Cu/ Zn-SOD and Mn-SOD, elevating activities of Cu/Zn-SOD, Mn-SOD, or regulating other factors after transcription.

Regulation of Calcium on Peanut Photosynthesis Under Low Night Temperature Stress

The effects of different levels of CaCl 2 on photosynthesis under low night temperature（8°C） stress in peanuts were studied in order to find out the appropriate concentration of Ca2＋through the artificial climate chamber potted culture test.The results indicated that Ca2＋,by means of improving the stomatal conductivity of peanut leaves under low night temperature stress,may mitigate the decline of photosynthetic rate in the peanut leaves.The regulation with 15 mmol L-1CaCl 2（Ca15） was the most effective,compared with other treatments.Subsequently,the improvement of Ca2＋on peanut photosynthesis under low night temperature stress was validated further through spraying with Ca15,Ca2＋chelator（ethylene glycol bis（2-aminoethyl） tetraacetic acid; EGTA） and calmodulin antagonists（trifluonerazine; TFP）.And CaM（Ca2＋-modulin） played an important role in the nutritional signal transduction for Ca2＋mitigating photosynthesis limitations in peanuts under low night temperature stress.

Response of Nitrate Metabolism in Seedlings of Oilseed Rape(Brassica napus L.) to Low Oxygen Stress

In order to understand the response of nitrate metabolism in seedlings of oilseed rape （Brassica napus L.） to low oxygen stress （LOS）, two cultivars were studied at different light, LOS time and exogenous nitrate concentrations under hydroponic stress. Results show that N-uptake and dry matter of rape seedlings were decreased after LOS stress while nitrate accumulation （NA） under LOS was induced by darkness. Nitrate accumulation peaked at 3 d while root activity （RA, deifned as dehydrogenase activity） decreased with prolonged waterlogging exposure. Exogenous nitrate signiifcantly elevated NA and RA. Tungstate （TS） and LOS inhibited nitrate reductase （NR） activity while NR transcription and activity were enhanced by exogenous nitrate. Low oxygen stress stimulated the activity of superoxide dismutase （SOD） and peroxidase （POD） slightly, but inhibited that of catalase （CAT）. B. napus L. Zhongshuang 10 （ZS10）, a LOS tolerant cultivar, displayed smaller decrease upon dry matter under LOS, higher NA in darkness and lower NA in light than B. napus L. Ganlan CC （GAC）, a LOS sensitive variety. ZS10 had lower NA and higher RA after waterlogging and exogenous nitrate treatment, and higher NR activity under TS inhibition than GAC, but the activity of antioxidant enzymes did not change under LOS. The results indicate that nitrate metabolism involved tolerance of rape seedlings to LOS, with lower accumulation and higher reduction of nitrate being related to higher LOS tolerance of rape seedlings exposed to waterlogging.

Altered Expression of Transcription Factor Genes in Rice Flag Leaf under Low Nitrogen Stress

The response of transcription factor genes to low nitrogen stress was studied to provide molecular basis for improving the absorption and utilization efficiency of nitrogen fertilizer in rice. The agilent rice genome arrays were used to study the varied expression of transcription factor genes in two rice varieties （SN 196 and Toyonishhiki） with different chlorophyll contents under low nitrogen stress. The results showed that a total of 53 transcription factor genes （35 down-regulated and 18 up-regulated genes at the transcription level） in flag leaves of super-green rice SN196 and 27 transcription factor genes （21 down-regulated and 6 up-regulated genes at the transcription level） in flag leaves of Toyonishiki were affected by low nitrogen stress. Among those nitrogen-responsive genes, 48 transcription factor genes in SN196 and 22 in Toyonishiki were variety-specific. There were overlapped transcription factor genes responded to low nitrogen stress between SN196 and Toyonishiki, with 1 up-regulated and 4 down-regulated at the transcription level. Distributions of low nitrogen responsive genes on chromosomes were different in two rice varieties.

Effects of Phosphate Fertilizer on Cold Tolerance and Its Related Physiological Parameters in Rice Under Low Temperature Stress

The study was designated to explore the physiological mechanism of cold tolerance enhanced by phosphate in rice. An experiment was conducted to investigate the effects of different levels of phosphate fertilizer on cold tolerance and its related physiological parameters in rice seedings （chilling-sensitive cv. Changbai 9 and chilling-tolerant cv. Jijing 81） under low temperature stress. At the same time, the identification of cold tolerance was conducted. Compared with the normal temperature treatment, the relative chlorophyll content, photosynthesis rate, Fv/Fm and qP decreased and index of unsaturated fatty acid increased in rice under low temperature stress. The effect of chilling-sensitive cultivars was more than that of chilling-tolerant cultivars, more phosphorus fertilizer properly improved seedling quality of rice, slowed relative chlorophyll content dropping degree of rice seeding, increased photosynthesis rate, Fv/Fm, qP and index of unsaturated fatty acids, and enhanced the ability to chilling-tolerant cultivars under low temperature. The effect on chilling-tolerant cultivars was significantly higher than that on chilling sensitive cultivars by applying more phosphorus fertilizer. Phosphate regulated photosynthetic physiology and membrane fluidity to reduce injury by low temperature, and increasd the cold tolerance capacity of rice.

Effects of PQQ on Protective System in Cucumber Cotyledons under Low Temperature Stress

The authors have studied the effects of Pyrroioguinloine quinone (PQQ) on superoxide dismutase (SOD), Ascorbid acid(AsA) peroxidase (AsAPOD), glutathion (GSH) and electrolytic leakage of cotyledon in cucumber seedling under low temperature stress, meanwhile, 8-hydroquinone (8-HQ) and AsA (activeoxiygen scavengers) have been made use of in comparison with PQQ. The results indicate that the activities of SOD, AsAPOD and content of GSH can be increased by PQQ. The relative conductivity of cotyledon in cucumber seedling is decreased for PQQ possesses the ability of cleaning up free redical of oxygen. We came to the conclusion that PQQ can act as a kind of active oxygen scavenger and adjust the metabolism on free radical of oxygen to balance in plants and enhance resistance finally in plants.

The Effects of Low Phosphorus Stress on Morphological and Physiological Characteristics of Maize (Zea mays L.) Landraces

A field trial was conducted to investigate main morphological and physiological changes of different maize landraces to low-P stress at the stage of seedling. P-deficiency significantly decreased root volume, total leaf area, and plant dry weight, but greatly increased density of root hairs and root top ratio. In addition, P-deficiency induced the significant enhancement of phosphorus utilization efficiency and the amount of proline, malondialdehye （MDA）, acid phosphatase （APase）, peroxidase （POD） and superoxide dismutase （SOD）, but the significant reduction of P uptake and soluable protein content. Since P-deficiency had smaller effects on the P-tolerant maize landraces DP-44, DP-32 and DP-33 as compared with P-sensitive landraces DP-29 and DP-24, it was demonstrated that differences of tolerance to P-deficiency existed among different maize landraces. The results based on the correlation analysis showed that the economic yield of maize landraces had relationships with their morphological and physiological characteristics under P-deficiency.

Evaluation of Rice Seedling Tolerance to Constant and Intermittent Low Temperature Stress

M202, IR50 and advanced backcross （BC4F6） lines carrying the cold tolerance QTLs qCTS4 and qCTS12 were evaluated using three low temperature stress assays （constant, intermittent and constant with recovery period）. Under constant stress, two BC4F6 lines （MIb 4853-9 and MIb 6885-2） exhibited differences in seedling growth and accumulation of stress-related compounds although both carry the two QTLs in the IRS0 background. Differences between these lines were also observed in the constant with recovery period assay, although both of them performed comparably under intermittent stress, MIb 6885-2 performed more similarly to M202 in the constant and constant with recovery period assays, suggesting that this line contains an introgressed region（s） not present in MIb 4853-9. The three assays were also applied to assess variations in cold tolerance in a set of diverse germplasms. Performance metrics and visual ratings were comparable for evaluating tolerance to constant stress. However, differences in response to intermittent stress were more evident from growth and total chlorophyll measurements than from visual ratings. With regard to the constant with recovery period assay, about 15% of the germplasm accessions did not recover. However, some lines which exhibited chilling injuries of comparable severity were able to overcome them. This recovery phenotype may improve rice performance in the field and warrant further investigation.

Low temperature stress on the hematological parameters and HSP gene expression in the turbot Scophthalmus maximus

To study the effect of low temperature stress on hematological parameters and HSP gene expression in the turbot( Scophthalmus maximus),water temperature was lowered rapidly from 18 to 1°C.During the cooling process,three individuals were removed from culture tanks at 18,13,8,5,3,and 1°C.Blood samples and tissues were taken from each individual,hematological indices and HSP gene expression in tissues were measured.The red blood cell count,white blood cell count,and hemoglobin concentration decreased significantly( P < 0.05) as temperature decreased.Enzyme activities of plasma alanine transaminase and creatine kinase increased as temperature decreased,whereas aspartic transaminase and γ-glutamyl transpeptidase activities displayed no obvious changes above 1°C and lactate dehydrogenase activity increased first and then decreased.Blood urea nitrogen and uric acid levels were highest at 8°C,and creatinine concentration was highest at 3°C.The concentrations of plasma cortisol,cholesterol,and triglyceride all increased significantly( P < 0.05) as temperature decreased.The serum glucose concentration increased first and then decreased to the initial level.The HSP70 m RNA expression showed various patterns in different tissues,whereas HSP90 m RNA expression showed the same tendency in all tissues.Overall,these results indicate that temperature decreases in the range of 8 to 5°C may induce a stress response in S.maximus and that temperature should be kept above 8°C in the aquaculture setting to avoid damage to the fish.

Phosphorus Nutrient Characteristics of Different Maize (Zea mays L.) Inbreds for Tolerance to Low-P Stress

Phosphorus nutrient characteristics of different maize inbred lines to low-P stress were studied at stages of seedling, steming, earing, silking under pot culture. In the periods of seedling and steming, P uptake efficiency was the main contributor to P tolerance, and the relative P content in P-tolerant genotypes, 99180 and 99239 were higher than that in sensitive genotype, 99152. At earing stage, P-tolerant genotypes, compared to P-sensitive ones, had higher accumulation of P in upper leaves. When came to the silking stage, P uptake and redistribution efficiency of P-tolerant genotypes were higher than those in 99152. The results also suggested that there are different mechanisms of P nutrient uptake and distribution in different P-tolerant genotypes. Inbred line 99239, according to the investigation, was considered as an efficient stock in the P-uptake while 99180 fallen to the efficient stock of P redistribution.

Effects of Low Temperature Stress on Seedling Growth of Plateau Japonica Rice

[ Objective ] The study aimed to screen rational seedling raising date and seedling raising mode for plateau japonica rice, in order to reduce the effect of low temperature on seedlings. [ Method ] The seedlings of conventional japonica rice Hexi 22-2 and giant embryo No. 1 japonica rice were treated at day tempera- ture 12℃/night temperature 8℃ and day temperature 14 ℃/night temperature 10 ℃, and the indicators including chlorophyll content, soluble sugar content, sol- uble protein content, survival rate, plant height, number of ≥ 1 cm roots, leaf wilting degree and aboveground dry matter weight were determined after treated for 0, 3 and 6 d, respectively. [ Result] Chlorophyll content of seedlings decreased when treated by low temperature for a certain period; with the prolongation of treat- ment time, contents of soluble sugar and soluble protein in some low temperature treatments increased, while plant height, number of ≥ 1 cm roots and aboveground dry matter weight increased slowly, but the growth rate was significantly lower than that at room temperature; with the decrease of temperature and the prolongation of treatment time, leaf wilting degree increased. The comprehensive experimental results showed that with the increasing duration of low temperature, when two japonica rice varieties grew under the same low temperature, seedlings grew more and more slowly, probably because the lower the treatment temperature, the greater the damage on plants. Giant Embryo No. 1 had weaker cold tolerance than Hexi 22-2. [ Conclusion] The study provides a theoretical basis for formula- tion of seedling raising technique of plateau japonica rice.