钢丝绳钢芯早期断裂失效分析

用户在使用搁置3 a的钢芯钢丝绳时,由于钢芯首先断裂,导致用后不久发生断股事故。经检验,钢芯的断裂为疲劳断裂,疲劳断裂的原因是由于钢丝绳生产工艺控制不严以及服役过程中受到弯曲振动载荷,使芯丝表面磨损和硬化,并在磨损面上出现纵横向裂纹和蚀坑,成为疲劳源,裂纹扩展导致芯丝过载断裂,直至钢芯断裂,从而导致绳股破断。钢丝绳因其钢芯过早断裂而报废,与钢丝绳芯丝抗拉强度波动、表面缺陷以及钢芯疲劳寿命与其钢丝绳疲劳寿命匹配较差有关。     

应用抗菌物质来提高新鲜农产品的安全性

农产品采收后,病原微生物,如腐败细菌、酵母、霉菌等会通过各种途径侵袭,这样不仅会使农产品加工业遭受重大损失,而且会导致人类食物性疾病的爆发。因此,农产品在加工或食用时必须进行杀菌,使用杀菌剂是一个较好的方法。通常使用的杀菌剂有氯、二氧化氯以及一些纯天然的生物化合物等。但在使用这些杀菌剂时,必须严格控制使用的剂量,使杀菌后的产品达到FDA制定的标准。     

Gelatinization of Rice Starch in Aqueous Urea Solutions

Addition of urea to starch slurry causes gelatinization of starch at room temperature. The time required for gelatinization, type of gel formed, rheological properties and apparent viscosity of starch suspension in urea solutions were determined. The latter did not decrease significantly after storing for up to 8 weeks whereas that of cooked starch decreased sharply after one week of storage. Suspensions of starch in urea solutions did not show any fermentation and retrogradation during 8 weeks storage. Its is suggested that urea interacts with starch to form adducts or urea starch complexes. The magnitude of the latter and its abundance is dependent on the concentrations of urea and starch. The urea starch complex acquires very high affinity to water thereby causing swelling and gelatinization of starch.     

Effect of storage and lipid extraction on the properties of leaf protein

At 4° and 28° extensive oxidation of leaf protein occurred, but there was little change in the digestibility of the protein, or in the N and P contents of the lipid. After heating at 60° the amount of extracted lipid decreased: a small decrease in digestibility was attributed to heat damage rather than oxidation of the lipid. Losses in digestibility after heatingat 100° wereattributable to two different reactions: (a)a lipid complexing reaction which depends on moisture content, but not on the presence of oxygen and (b) modification of the protein. The latter reaction occurred more slowly and depended mainly on the period of heating at 100°; it did not occur in completely dry protein, was not influenced by the presence of leaf lipid, and was not affected by lipid solvent extraction after heating. The possibility that lipid-protein complexing during preparation of leaf protein causes losses in digestibility is discussed. Similarities between the behaviour of leaf proteins and fishmeal on storage and heating are also discussed.     

Effect of processing on droplet cluster structure in emulsion gels

The fat droplet cluster structure in acidified and neutral emulsion gels is investigated after storage at fixed temperature or after temperature cycling. Amongst other techniques, the novel non-invasive Spin-echo Small-angle Neutron Scattering (SESANS) technique is applied to probe the structure of emulsion droplet aggregates up to a length scale of ∼10 μm.The SESANS data show that fat droplet clusters in non-cycled emulsions become smaller with increasing homogenisation pressure (next to the droplets themselves getting smaller as well), and that the emulsion gel becomes more homogeneous as a result. Upon temperature-cycling, it is found that the fat droplet clusters increase in size (next to the droplets themselves getting larger as well). The presence of these more lumpy aggregates is not the direct cause of the higher firmness of the emulsion gels, but the rearrangement process itself may promote the partial coalescence that causes an increase in firmness of these emulsion gels upon temperature-cycling.     

Reliability of the sensory analysis data of a panel of tasters

A method, the quantum measurement technique, is described which, by means of the conceptualisation of the information underlying a set of data which are considered as manifestations of a latent variable or theoretical construct, allows one to detect which are the data in sensorial analysis that, after obtaining a measure, do not fit the formulated conception. The theoretical foundation, based on Rasch probability and item response theory (IRT), detects and quantifies by means of the misfits the data that respond to unexpected scores. A detailed analysis of their residuals aids in finding the causes of these misfits. The technique is applied to the data of a tasting panel that form part of the sensory evaluation of virgin olive oil. © 2000 Society of Chemical Industry     

Lipoprotein lipase and lipolysis in milk

Bovine milk contains a lipoprotein lipase that accounts for most, if not all, of its lipolytic activity. The total lipase activity in raw milk is sufficient to cause rapid hydrolysis of a large proportion of the fat. However, in reality this does not happen, because the lipase is prevented from accessing the fat by the milkfat globule membrane. Physical damage to this membrane in raw milk initiates lipolysis. Furthermore, simply cooling certain individual milks soon after secretion can initiate the so-called spontaneous lipolysis. The biochemical basis of spontaneous lipolysis is still poorly understood, but it appears to be related to a balance between activating and inhibiting factors in the milk. Lipolysis in milk and milk products causes rancid off-flavours and other problems, and is a constant concern in the dairy industry. A thorough understanding of the mechanism of lipolysis and constant vigilance by operatives is required to minimize lipase-related problems.     

Necropsy as a means to gain additional information about causes of dairy cow deaths

High mortality among dairy cows constitutes a problem both financially and in relation to animal welfare. Knowledge about causes of death is a fundamental step toward reducing cow mortality. Several studies have evaluated causes of dairy cow deaths. However, the vast majority of studies describing causes of death are based on questionnaires with farmers or veterinarians. It is uncertain to what degree such information is sufficient and reflects the true cause of death or euthanasia. In this study, proximate causes of death were evaluated based on a thorough necropsy of a random sample of 79 Danish dairy cows at an incineration plant. The necropsy was combined with information about the farmer’s perception regarding the cause of death and information about disease treatments from the Danish Cattle Database. Pneumonia and locomotor disorders were found to be the most predominant proximate causes of death. Often the death occurred after a prolonged period during which the cow suffered several different disorders, even though this was often not noticed by the farmer. Causes of death stated by the farmers agreed with the necropsy results in 50 to 64% of cases. Information about disease treatments from the Danish Cattle Database agreed with the necropsy results in 34 to 39% of cases. All 3 sources of information about cause of death agreed in only 1 out of 4 cases, and even when the farmer and the disease recordings did agree with the necropsy results, the latter often gave additional information about the cause of death. In many situations, therefore, a necropsy may be a valuable tool when trying to control excessive cow mortality in a herd.     

汽车用Qst32-3冷镦钢丝表面粗糙原因分析

Qst32-3热轧盘条制作的汽车用冷镦钢丝冷成型后产品表面粗糙,严重影响产品质量。对冷镦钢丝进行化学成分和力学性能分析,均满足EN 10263-2标准要求;对Ф14 mm Qst32-3热轧盘条和Ф13.5 mm冷镦钢丝进行金相组织检验,盘条显微组织为铁素体和珠光体,铁素体晶粒度8.5级,经酸洗拉拔及球化退火后,冷镦钢丝显微组织为铁素体和球化体,中心部位铁素体晶粒度8级,表层局部区域铁素体晶粒度1级。试验及分析表明:热轧盘条球化后晶粒度级别不发生变化;压缩率小于7%时,球化后部分晶粒开始长大,压缩率在7%～26.5%时,球化后晶粒产生粗大现象。晶粒粗大导致表面粗糙,热轧盘条球化退火前的拉拔压缩率较小是造成表面粗晶的原因。     

Poultry manure phytotoxicity

Examination of samples of deep litter poultry manure which caused growth deformation in vegetable crops resulted in the isolation of a potent phytotoxic compound. The chemical properties and symptoms produced by tomato plants grown under hydroponic conditions, showed that it was not 2,4-D as suggested by other workers but a nitrogen heterocyclic compound with an attached carboxyl group. Poultry trials have shown that an impurity, 4-amino-3,5-dichloro-2,6-lutidine, in the coccidiostat clopidol (3,5-dichloro-2, 6-dimethyl-4-pyridinol) causes similar phytotoxicity. Increased potency after poultry ingestion indicates that this impurity is metabolised. The most likely metabolite is 4-amino-3,5-dichloro-6-methyl picolinic acid. Chemical and physical data of the metabolite are identical to that of the toxic compound isolated from original manure samples. Detailed symptomology produced by the toxic manure on tomato plants is described.     

Influence of Postmortem Changes in Bovine Muscle on the Water-Holding Capacity of Beef. Postmortem Storage of Muscle at 20°C

Rigor mortis occurs in bovine neck muscles as soon as pH 5.9 and an ATP level of about 1 μMol/g are reached. At 20°C muscle contraction does not occur before the onset of rigor. Postmortem changes in water-holding capacity (WHC) were followed by measuring the cooking loss of unsalted and salted (2% NaCl) muscle homogenates prepared after storage of the intact muscle tissue at 20°C for different periods postmortem. At tissue pH above 5.9 addition of salt causes a strong increase of WHC of muscle homogenates. There is a small decrease of WHC of both unsalted and salted homogenates during the prerigor phase which is apparently caused by the postmortem fall of pH. Rigor mortis does not influence the WHC of unsalted muscle homogenates but causes a strong decrease of WHC of salted homogenates. The reason for this difference is discussed. No more than one-third of the total postmortem decrease of WHC and protein solubility in salted muscle homogenates was attributed to the fall of pH, so at least two-thirds were due to the development of rigor.     

优选梳棉针布优化工艺减少棉结(下)

为了减少并条后的棉结以提高棉条质量,从牵伸工艺不符合纤维弯钩伸直理论、生条中纤维分离度和平行伸直度差、生条中短绒高等方面,分析了并条后棉结增加的主要原因.通过大量试验分析,提出有效降低并条后棉结增加的措施:普梳头并、精梳预并、普梳粗纱牵伸工艺应符合前弯钩纤维伸直理论;普梳二并、精梳卷或条并卷、普梳细纱牵伸工艺应符合后弯...     

Factors influencing the yield of free radicals in irradiated chicken bones

The exposure of foodstuffs containing bone or other calcified tissue to a dose of ionizing radiation results in the formation of long lived free radicals which give rise to characteristic ESR signals. The presence of this signal provides clear evidence that the sample has been irradiated. In order to determine the radiation dose by post-irradiation calibration, it is necessary to consider factors that might influence the radical yield and to allow for the stability of the radicals under likely conditions of storage. Using chicken bone we have shown that the yield is influenced by the nature of the bone, temperature of irradiation, and gaseous atmosphere, although not by dose rate, water content, or type of radiation. Cooking before irradiation greatly enhances the subsequent yield of radicals, while cooking after irradiation causes little or no destruction of the radiation-induced radicals, which also appear to be unaffected by length and conditions of storage.     

Studies on the supply of immunoglobulin G to newborn camel calves (Camelus dromedarius)

A major problem in camel productivity is the high mortality rate of camel calves in the first 3 months. The causes for mortality are mainly poor management practice and infectious diseases. The purpose of this research, carried out on a ranch in Kenya, was to determine the immunoglobulin G (IgG) concentration in camel colostrum as well as the extent of the calves' passive immunization by maternal antibodies. IgG concentration in colostrum and in the serum of the calf were measured during the first 3 d of life. Evaluation was carried out by comparing the respective values with those for horses and cattle. The average IgG concentration in the camel colostrum was higher than that found in literature for horses and cattle. IgG concentration in the serum of the camel calves reached its maximum 24 h after birth. In 39% of the examined calves, this maximum concentration was below 4 g/l, which is considered to be the critical value in horses and cattle. 61% of the calves achieved an IgG concentration of over 4 g/l. Since there is no correlation between IgG level in colostrum and early mortality, the results indicate that low colostrum intake during the first 24 h of life and not low IgG concentration in colostrum is presumably one of the main causes of early calf mortality. Therefore, it was recommended that the care of the newborn calves by herdsmen should be improved.     

Synthesis and distribution of cytokeratins in healthy and ulcerated bovine claw epidermis

Keratinization of the epidermal cells of the bovine claw generates the horn that gives the tissue its mechanical strength. Disruption of keratinization is likely to have a detrimental effect on the strength and integrity of the horn, and could lead to solar lesions and lameness. As part of a wider investigation of the cell biological causes of lameness in dairy animals, we have compared keratin synthesis and distribution in healthy bovine claw tissue with those in hooves with solar ulcers. Protein synthesis was measured by [35S]-labelled amino acid incorporation in claw tissue explant cultures. [35S]-labelled protein synthesis was higher in tissue from diseased claws than in healthy claws, and highest at the ulcer site. The identity of proteins synthesised in vitro did not differ between healthy and diseased tissue. DNA synthesis indicative of cell proliferation was also elevated in diseased tissue. Immunoblotting after one- or two-dimensional electrophoresis showed cytokeratins (CK) 4, 5/6, 10 and 14 to be amongst those expressed in healthy claw tissue. The relative abundance of these keratins was not altered in healthy regions of ulcerated hooves, nor at the ulcer site, but CK16, not usually found in healthy tissue, was detected in the sole of diseased claws. CK5/6 and CK14 were shown by immunohistochemistry to be present in the basal epidermis of healthy tissue, whereas CK10 was found in supra-basal layers. In healthy tissue from ulcerated claws, this distribution was unaltered, but at the site of solar ulcers, CK5/6 and CK14 were each found in both basal and supra-basal epidermis. The study suggests that solar ulceration of the bovine claw is not associated with gross alteration in the keratin composition of the tissue, but causes abnormal distribution of cytokeratins, perhaps as a result of loss of positional cues from the basement membrane. Ulceration did, however, stimulate cell repair involving epidermal protein synthesis (including keratins), and keratinocyte proliferation.     

The influence of the pre-oxidation of natural organic matter on the formation of N-nitrosodimethylamine (NDMA)

NDMA is a recently recognized disinfection byproduct that can be formed by a reaction of monochloramine with natural organic matter (NOM). This study was undertaken to examine the influence of various preoxidation strategies (including prechlorination) on the subsequent formation of NDMA and to determine how this is correlated to the subsequent loss in specific UV absorbance (SUVA) that preoxidation causes. Batch experiments were conducted using surface-water-derived NOM exposed to various oxidants that included free chlorine, permanganate, hydrogen peroxide, and ozone. Photochemical oxidation was also studied by exposing the water to simulated sunlight The amount of NDMA formed after monochloramine was added or formed in situ, in the case when free chlorine was the preoxidant, was significantly reduced by these treatments. The reduction was proportional to the reduction in SUVA that also occurred as a consequence of these treatments indicating that SUVA may be a good surrogate for NDMA precursor content. Furthermore, the change in NDMA formation per unit change in SUVA was a constant that did not depend on the nature of the oxidant     

南瓜粉对挤压米膳食血糖指数及品质的影响

针对稻米中可溶性碳水化合物含量高,食用后极易引起血糖升高,不适于糖尿病患者食用等问题。作者以燕麦粉、马铃薯全粉等为主要原料,研制一款适合糖尿病人的食疗挤压米。结果表明：南瓜粉添加量为质量分数15%时,体外消化实验血糖指数最低,GI值为68.36;扫描电镜观测到其截面平整,结构紧密;蒸煮后测其加热吸水率、膨胀率分别高至191.35%、266.67%,米汤可溶性固形物质量分数仅为26.042 mg/g;质构特性良好,米粒饱满,感官评分最高。     

Spray-dried whey protein/lactose/soybean oil emulsions. 1. Surface composition and particle structure

Emulsions made of whey protein, lactose and soybean oil were spray-dried and the chemical surface composition of the dried powders estimated by electron spectroscopy for chemical analysis. In particular, the ability of whey protein to encapsulate fat was highlighted. Additionally, the structure of the spray-dried powder particles was studied by scanning electron microscopy. The powders were examined after storage in both dry and humid atmospheres (relative humidity 75%, 4 days). It was found that the ability of whey protein to encapsulate soybean oil is rather low compared with sodium caseinate, with a large part of the powder surface covered by fat after spray-drying. After storage in humid atmosphere there is a release of encapsulated oil onto the powder surface in most cases, and an increase in fat coverage. The release offat onto the powder surfaces causes the particle structure to change dramatically for powders containing a critical amount of lactose. Such powders agglomerate and lose structure completely. In comparison, powders containing no lactose storage under humid conditions also cause a release of fat onto the powder; however, in this case particle structure remains intact. Powders containing only a small amount of lactose, up to ~25% of emulsion dry weight, do not exhibit the release of fat onto the powder surfaces after storage under humid conditions and the structure of these powder particles does not change. The presence of lactose in whey protein-stabilized emulsions, however, does not increase fat encapsulation by whey protein, as reported earlier for sodium caseinate-stabilized emulsions that were spray-dried. During spray-drying of whey protein/lactose solutions there is a strong overrepresentation of surface-active whey protein on the powder surface. Whey protein coverage increases even further when the powders are stored under humid conditions, also making them lose structure.     

Molecular cloning of CIF1, a yeast gene necessary for growth on glucose.

The cif1 mutation of Saccharomyces cerevisiae (Navon et al., Biochemistry 18, 4487-4499, 1979) causes inability to grow on glucose and absence of catabolite inactivation. We have cloned the CIF1 gene by complementation of function and located it in a 2.75 kb SphI-BstEII fragment situated at ca. 18 kb centromere distal of LYS2 and ca. 80 kb centromere proximal of TYR1 on chromosome II. Southern analysis demonstrated that CIF1 is present in a single copy in the yeast genome. Northern analysis revealed that the corresponding mRNA of 1.8 kb is more abundant in cells grown on galactose than in those grown on glucose. A protein of ca. 54 kDa was predicted from the open reading frame in the sequenced fragment. In strains carrying the cif1 mutation the intracellular concentration of ATP decreased immediately after addition of glucose while the intracellular concentration of cAMP did not increase. cAMP concentration increased in response to galactose or 2,4-dinitrophenol. Disruption of BCY1 or overexpression of CDC25 in a cif1 background did not restore growth on glucose, suggesting that the absence of cAMP signal is not the primary cause of lack of growth on glucose. Complementation tests showed that cif1 is not allelic to fdp1 although the two genes seem to be functionally related.     

Effects of early post-mortem pH and temperature on beef tenderness

The tenderness of loin steaks, prepared from beef sides after chilling, is strongly influenced by muscle temperature in the first 3 h after slaughter. Maintenance of about 37°C within the Longissimus muscle during this time, whether by heavy fat cover or by ambient-temperature manipulation, results in appreciable tenderness enhancement. Early post-mortem muscle pH (which varies over a wide range) also affects tenderness significantly; provided early and exceptionally fast chilling does not induce cold shortening, slow glycolysis promotes tenderness. Low-frequency (2 Hz) electrical stimulation, which accelerates glycolysis but causes negligible tissue disruption, significantly toughens the loin; in its normal mode (50–60 Hz), therefore, stimulation produces its desirable tenderising effect mainly—and perhaps solely—by fibre fracture.