An investigation on the impact fatigue characteristics of valve leaves for small hermetic reciprocating compressors in a new automated test system

This paper presents an investigation on the impact fatigue characteristics of valve leaves that are prevalently used in hermetic reciprocating compressors especially for the household type refrigerators. A unique automated impact fatigue test system has been designed and produced, which enables to carry out impact fatigue tests of the compressor valve leaves under the desired impact velocities. The test system incorporates a noncontact actuation, a data acquisition system and an acoustic‐based damage detection technique, which continuously monitors the health of the structure. The damage detection system allows parametrical investigation on the impact fatigue life by detecting any possible damage and automatically terminating the test. The investigation relates the impact fatigue lifetime of the valve leaves with the impact velocity, asymmetrical impact, operation temperature, material type (carbon strip steel, stainless strip steel and new stainless strip steel grade) and tumbling operation duration. The observations show that the cracks have initiated from the edges of the valve leaf where is in contact with the valve plate. Subsequently, the cracks initially have propagated in the radial direction inwards the center of the impact area. Various failure cases have been resulted in by either a single crack or inter‐related multiple cracks. Microscopic and metallographic observations have been performed on the specimens to enhance the understanding of the damage mechanisms. The investigation and introduced test system guide the design optimization of the valve leaves in terms of compressor performance due to the energy consumption and lifetime of the valve leaf.     

A survey of the occurrence and properties of methicillin‐resistant Staphylococcus aureus and methicillin‐resistant Staphylococcus intermedius in water buffalo milk and dairy products in Turkey

Antimicrobial resistance, β‐lactamase activity and mecA gene of Staphylococcus aureus and Staphylococcus intermedius isolated from raw water buffalo milk and dairy products in Turkey were determined. All strains showed resistance to at least one antibiotic but none was resistant to vancomycin. Of the 97 S. aureus and 35 S. intermedius strains, 9 (9.2%) and 2 (5.7%) were resistant to oxacillin and harboured mecA gene. β‐lactamase activity of 13.4% and 5.7% of S. aureus and S. intermedius strains was positive, respectively. Overall, 2.5% and 0.55% of the samples were contaminated with methicillin‐resistant S. aureus and S. intermedius, respectively.     

LIQUID–SOLID EXTRACTION OF SOLUBLE SOLIDS AND TOTAL PHENOLIC COMPOUNDS OF CAROB BEAN (Ceratonia siliqua L.)

Total mass transfer coefficients of soluble solids (SS) and total phenolic compounds (TPC) were determined during carob extraction. The Arrhenius equation was applied to determine the efficiency of process temperature, as an alternative approach to Fick's second law. Carob pod, cut into small pieces (internal diameter: 5–7 mm), was contacted with water in batch system to extract SS by continuous circulation of water at different temperatures (20, 50 and 85C). The process was also performed at 85C using an industrial‐scale extractor. Activation energies for both SS and TPC diffusions were calculated as 5.84 and 0.072 × 10^?3 kJ/mol, respectively. As expected, higher extract concentrations were achieved with higher temperatures. In contrast, high extraction temperature, even at 85C, did not cause hydroxymethylfurfural (HMF) formation. As the increase in temperature does not affect formation of HMF during carob pod extraction, higher operational temperatures such as 80–90C may be applied to obtain higher solute concentrations.     

Oxygen permeability of macrocrystalline paraffin wax and relevance to wax coatings on natural corks used as wine bottle closures

The oxygen permeability of a commercial macrocrystalline paraffin wax was determined. This permeability figure and diffusion theory were used to calculate the theoretical ingress of oxygen through the paraffin coating of a cork used as a bottle closure. We wanted to ascertain whether macrocrystalline paraffin wax coatings used on corks could be permeable enough to allow oxidation of wine. We also employed electron microscopy to show the spread of coatings on waxed corks before and after insertion inside a bottle. Our calculations indicated that oxygen permeation along the length of paraffin coating on a cork closure would not allow ingress of sufficient oxygen to cause oxidation of wine during storage.     

KINETIC MODELING OF ANAEROBIC THERMAL DEGRADATION OF ASCORBIC ACID IN ROSE HIP (ROSA CANINA L) PULP

Ascorbic acid loss in thermally treated rose hip pulp was modeled mathematically. Isothermal experiments in the temperature range of 70–95C were utilized to determine the kinetics of ascorbic acid loss in the pulp during heating under anaerobic circumstances. Changes in ascorbic acid decomposition followed a first‐order reaction. Temperature dependence of the rate constant during thermal processing of rose hip pulp obeyed the Arrhenius relationship with an activation energy of 47.5 kJ/mole.     

THE EFFECTS OF ALTITUDE ON FRUIT QUALITY AND COMPRESSION LOAD FOR CRACKING OF WALNUTS (Juglans regia L.)

Nuts of walnut (Juglans regia L.), cultivated in the district of Denizli (altitude of 300 m) and Cameli (altitude, 1200 m) in the Aegean region of Turkey, were used to determine the effects of altitude on fruit quality and the force and energy required to crack the nuts. The varieties used were Bilecik, Sebin, Yalova‐1, Yalova‐3 and Yalova‐4. For all cultivars, walnut trees grown at the higher altitude produced small size nuts with thick shells. Based on the average for all cultivars, kernel removal quality decreased with high altitude. The nuts obtained from the high‐altitude location were lighter‐colored and required more force to fracture the nuts than those harvested at the low altitude. The amount of energy required to crack the nuts was higher for the nuts grown at the low‐altitude location except for the cultivar, Sebin.     

EFFECT OF ACID ADAPTATION AND DIFFERENT SALT CONCENTRATIONS ON SURVIVAL OF LISTERIA MONOCYTOGENES IN TURKISH WHITE CHEESE

ABSTRACT

Survival of acid‐adapted and nonacid adapted Listeria monocytogenes in Turkish white cheese with different salt concentrations (3.8 and 6.7% NaCl) was investigated. Cheese blocks were inoculated with L. monocytogenes and stored at 4C for 15 days. Samples were taken on different days and analyzed for the numbers of the pathogen, and the samples were challenged with simulated gastric fluid (SGF) for determining acid tolerance. There was no significant differences between the numbers of acid‐adapted and nonadapted L. monocytogenes cells regardless of the salt concentration on sampling days (P > 0.05). Challenge in SGF revealed that there was no significant difference between acid‐adapted and nonadapted bacteria in cheese with 3.8% NaCl throughout the storage period, while significant (P < 0.05) differences between those cells in cheese with 6.7% NaCl were found after day 5. These results suggest that acid‐adapted L. monocytogenes exposed to high salt concentration such as 6.7% may have an advantage in SGF.

PRACTICAL APPLICATIONS

Evaluation of potential stress responses of pathogens in food is important to understand the behavior of pathogens that can survive under stresses. As an environmental contaminant, Listeria monocytogenes may acquire adaptation to low acid conditions in cheese plants. Our results suggested that although there was no significant difference between acid‐adapted and nonadapted cells both in industrial (3.8% salt) and traditional (6.7% salt) white cheese, salt concentration significantly affected the survival of acid‐adapted cells in simulated gastric fluid (pH 2.3). These findings may indicate that L. monocytogenes, which is adapted to acid before contaminating high salt cheeses, may survive in stomach and cause infection. It can be said that increased salt concentration in cheese may not provide a barrier against acid‐adapted L. monocytogenes.

     

WATER ABSORPTION, LEACHING and COLOR CHANGES DURING the SOAKING FOR PRODUCTION of SOY-BULGUR

In this study, the soaking process, which is the first step of soy‐bulgur production to develop a new type food product, was investigated. the soaking operation was conducted at 30, 50 and 70C for 120 min and samples were taken from the soybean and soaking water at 10 min intervals. Moisture content and color (L, a, b and YI values) of soybean were measured, as well as soluble solids content and color (L, a, b and YI values) of soaking water during the soaking process. the results were analyzed by using ANOVA and Duncan test. Soaking time and temperature were significantly effective (P < 0.05) on all variables, except the time effect on the YI‐value. During the soaking, moisture content, lightness (L) and yellowness (b) increased and, redness (a) and yellowness index (YI) of soybean decreased. Soluble solids content, yellowness and yellowness index increased in contrast to a decrease in the lightness and greenness of the soaking water. As a result, soluble solids content in the soaking water increased, which illustrated the leaching of soluble solids from soybean to water. Color of soybean turned to lights, in contrast to darkening and opaqueness of water during soaking. Results showed that the moisture content, soluble solid content, L, a, b and YI values can be successfully modeled using polynomial equations, which can be used to estimate their changes during the soaking operation.     

Boldine provides protective effect against nephrotoxicity induced by cisplatin in Wistar rats: Role of oxidative stress,inflammation and caspase-3

Side effects of cisplatin, especially dose-dependent nephrotoxicity, are major factors limiting its use in cancer. Boldine ((S)-2, 9-dihydroxy-1, 10-dimethoxy-aporphine) is a natural alkaloid known for its strong antioxidant activity present in leaves/bark of boldo tree (Peumus boldus Molina), a native tree in Chile. Here, we aimed to investigate the nephroprotective effect of boldine and its underlying mechanisms on cisplatin-induced rat renal injury. Thirty Wistar albino rats divided into 5 groups (Control, Cis, Bold.40, Cis + Bold.20, Cis + Bold.40 groups) were used. Rats received boldine (20 or 40 mg/kg/day), or vehicle (saline) intraperitoneal for 14 days and a single dose cisplatin (7 mg/kg, ip) was applied on the 10th day to induce nephrotoxicity. Rats and kidney tissue were weighed to determine kidney index. Blood urea nitrojen (BUN) and creatinine levels, the amount of thiobarbituric acid reactive substances (TBARS, an index of lipid peroxidation), superoxide dismutase (SOD), glutathione peroxidase (GPx) enzyme activities and tumor necrosis factor alpha (TNF-α) levels were measured and histopathologic examination was performed. Inducible nitric oxide synthase (iNOS) and caspase-3 expressions were detected immunohistochemically. Nephrotoxicity induced by cisplatin was apparent by elevated levels of BUN, creatinine, kidney index, TBARS and TNF-α, and decreased body weight, SOD and GPx enzyme levels. Pretreatment with boldine protected the renal function at both boldine doses by fixing the renal damage markers, oxidative stress, caspase-3 and iNOS expression. Histopathological findings supported biochemical findings. Taken together these findings indicate that boldine has promising protective effect against cisplatin nephrotoxicity by improving oxidative stress, inflammation, histopathological alterations and by alleviating caspase 3 expression.     

FREE VIBRATION ANALYSIS OF KIRCHHOFF PLATES RESTING ON ELASTIC FOUNDATION BY MIXED FINITE ELEMENT FORMULATION BASED ON GÂTEAUX DIFFERENTIAL

The main objective of the present work is to give the systematic way for derivation of Kirchhoff plate-elastic foundation interaction by mixed-type formulation using the Gâteaux differential instead of well-known variational principles of Hellinger–Reissner and Hu–Washizu. Foundation is a Pasternak foundation, and as a special case if shear layer is neglected, it converges to Winkler foundation in the formulation. Uniform variation of the thickness of the plate is also included into the mixed finite element formulation of the plate element PLTVE4 which is an isoparametric C⁰ class conforming element discretization. In the dynamic analysis, the problem reduces to solution of the standard eigenvalue problem and the mixed element is based upon a consistent mass matrix formulation. The element has four nodes and at each node transverse displacement two bending and one torsional moment is the basic unknowns. Proper geometric and dynamic boundary conditions corresponding to the plate and the foundation is given by the functional. Performance of the element for bending and free vibration analysis is verified with a good accuracy on the numerical examples and analytical solutions present in the literature. © 1997 by John Wiley & Sons, Ltd.