Development of a radio frequency heating system for sterilization of vacuum-packed fish in water

We developed equipment that quickly and uniformly heats packed whole fish in circulating tap water using radio frequency (RF) heating. Four vacuumed plastic-packed Pacific sauries in tap water were set in a radial arrangement between coaxial cylindrical electrodes in a closed vessel. For sterilization testing, Bacillus subtilis spores added in the center of the sauries were counted after treatment. For quality assurance, meat color and backbone hardness were measured after treatment. The temperature at the center of the sauries was increased up to 130 °C for 19 min using 9 kW RF heating, and up to 119 °C for 45 min using conventional heating (CH) at 120 °C. B. subtilis spores were decreased by five logarithmic orders using RF heating and by four logarithmic orders using CH. The RF-treated meat was brighter than the CH-treated meat, and the RF-treated backbone was softer than CH-treated one.     

Regional and interannual variations in spawning activity of Pacific saury Cololabis saira during northward migration in spring in the north-western Pacific

Regional and interannual variations in spawning activity of Pacific saury Cololabis saira during the northward migration in spring were investigated for 1995–1997 in the north-western Pacific. Only females with a large body size (≥270–290 mm knob length) appeared to spawn. Almost all females in this cohort were actively spawning in a region of sea surface temperature ( T _SS) >18° C, the proportion of active spawners appeared positively related to T _SS in a region of 13° C < T _SS≤ 18° C, and no females were spawning in the region of T _SS≤13° C. Although this relationship between spawning activity and T _SS was common in all years, the distribution of females in the large-size cohort among the regions varied interannually. Consequently, the proportion of active spawners among adult females showed considerable interannual variations.     

Minimizing the effects of radio-frequency heating in multidimensional NMR experiments

Summary Application of radio-frequency power in multidimensional NMR experiments can significantly increase the sample temperature compared to that of the surrounding gas flow. Radio-frequency heating effects become more severe at higher magnetic field strengths and ionic strengths. The effects are particularly noticeable for experiments that utilize ¹H and/or ¹³C isotropic mixing and broadband decoupling. If radio-frequency power is applied during the systematically increasing evolution period t₁, the sample temperature can change with t₁ and thereby cause line-shape distortions. Such distortions are easily avoided by ensuring that the average radio-frequency power remains constant during the entire experiment.     

Characteristic features of ecology of the Pacific saury Cololabis saira (Scomberesocidae, Beloniformes) in open waters and in the northeast Pacific ocean

The results of long-term studies of the spatial distribution, size composition, and spawning intensity of the Pacific saury Cololabis saira in open waters of the North Pacific Ocean and the northeastern part of the Pacific Ocean off the west coast of North America are presented. In the open waters of the Pacific Ocean, saury forms aggregations early in summer; intraseasonal changes in their distribution pattern have been identified. Migrations of Pacific saury stocks in the northeastern part of the Pacific Ocean were considered, and assumptions about their causes were made. The differences in the size composition of Pacific saury in different parts of the range are associated with the peculiarities of occurrence of favorable conditions for the formation of aggregations. Intensive spawning of Pacific saury in the northeastern part of the Pacific Ocean is observed in winter and spring, and that in open waters is observed in summer. The distribution of the early progeny of Pacific saury is associated with the systems of currents; its findings in the extreme northern regions in the 1980s are explained.     

Long-term changes in the population size and geographical distribution of Pennella sp. (Copepoda) on the saury,Cololabis saira,in the western North Pacific Ocean and adjacent seas

Changes in the population size and geographical distribution of the mesoparasitic copepod Pennella sp. (Siphonostomatoida: Pennellidae) on the saury, Cololabis saira, were studied for a period of six years (1981–86) in the western North Pacific Ocean and adjacent seas. The parasite was first recorded in the western North Pacific in 1981. Its population size increased rapidly in 1982–83 and declined slightly in 1984. During these years, infected fish were widely distributed in the western and central North Pacific and also found in the Sea of Okhotsk and the Sea of Japan. However, the population declined dramatically in 1985 and its distributional range was reduced. The parasite disappeared in 1986. The observed frequency distributions of parasites on the host population were the Poisson in 1981 and 1985, but those during 1982–1984 were over-dispersed and fitted the negative binomial.Parasites of the saury, Cololabis saira (Brevoort)-IV.     

The feminizing effect of metabolic heating in Green Turtle (Chelonia mydas) clutches in the eastern Mediterranean

Metabolic heating has been poorly investigated in eastern Mediterranean coastline of Turkey, which host some of the most important Green Turtle (Chelonia mydas) nesting sites in the Mediterranean. We studied the effects of clutch size and embryo numbers on nest temperature and discuss the feminizing effect of metabolic heating. Two test sites were conducted in Sugözü Beaches (Turkey). Data loggers were placed in eight nests with different clutch sizes. Nest temperature was strongly correlated with embryo numbers and metabolic heating produced by embryos was calculated to be 0.019°C per late stage embryo and 0.020°C per hatchling. Metabolic heating was calculated to be 0.6°C in the middle third of the incubation period during which sex is determined. It was estimated that metabolic heating increased 10.4% of female hatchlings. The heat produced by embryos should be taken into consideration while estimating sex ratios indirectly by nest and sand temperatures. Additionally, the metabolic heating value should be known for conservation measures, such as nest relocation, dividing the nest for controlling nest temperature, especially related to climate change.     

Little population structuring and recent evolution of the Pacific saury (Cololabis saira) as indicated by mitochondrial and nuclear DNA sequence data

Genetic population structure of the Pacific saury (Cololabis saira) was investigated using nucleotide sequence analysis on the mitochondrial DNA control region (355-361 bp). Although the left domain of the control region is known to be highly variable in many species, extremely low nucleotide and haplotype diversities (π = 0.17% and h = 0.418, respectively) were observed in a total of 141 individuals collected from five distant locales (East China Sea, Sea of Okhotsk, northwest Pacific, central North Pacific and northeast Pacific). No significant haplotype frequency differences were detected among widely separated samples, therefore we were unable to reject the null hypothesis of no genetic structuring in the Pacific saury population. Moderate levels of nucleotide substitution (p-distance) were observed between the Pacific saury and its Atlantic counterpart (Scomberesox saurus) in the control region (7.44%), cytochrome b gene (4.64%), and internal transcribed spacer (ITS1) (11.49%), indicating that the low sequence diversity of the control region in the Pacific saury is not due to the slow mutation rate. The molecular data suggest the Pacific saury may be a relatively recent offshoot among the extant members in the family Scomberesocidae.     

The effect of sub-floor heating on house-dust-mite populations on floors and in furniture

It is well known that dehydrating conditions for house dust mites can be created by simply raising the temperature, causing loss of body water and eventually death. Thus, it can be expected that conditions for dust mites are less favourable on floors supplied with sub-floor heating. This was examined in a study of 16 houses with sub-floor heating and 21 without. The pattern of changes in air humidity and temperature on the floors was investigated and compared to known data of the tolerance of dust mites. Also the resident mite populations were compared. Floors with sub-floor heating had, on average, fewer mites, but the difference with unheated floors was small. It was remarkable that mite numbers were also lower in upholstered furniture. Another important observation was that some houses with sub-floor heating had high mite numbers, indicating that this type of heating is compatible with a thriving mite population. Temperature and humidity conditions of heated floors may allow mites not only to survive, but also to remain active in winter. A moderate increase in temperature, a moderate decrease inf (absolute) air humidity, or a combination of both, will suffice to keep the humidity all winter below the Critical Equilibrium Humidity, the level of air humidity that is critical for mite growth and reproduction, hence for allergen production. However, it is argued that measures to suppress allergen production by house dust mites are likely to be far more effective if taken in summer rather than in winter. This revised version was published online in July 2006 with corrections to the Cover Date.     

The effect of direct and indirect hand heating on finger blood flow and dexterity during cold exposure

1. The aim of this study was to investigate if finger temperature or finger blood flow is the critical factor for maintenance of finger dexterity during cold exposure.

2. Subjects were exposed twice to −25°C air for 3 h by using a Torso Heating Test (THT) where the torso was maintained to 42°C with a heating vest while the hands were bare, and a Hand Heating Test (HHT) where the hands were heated with heated gloves.

3. Despite similar finger temperatures, finger blood flow was eight times lower and finger dexterity was decreased in HHT as compared to THT.

4. It is concluded that finger blood flow is the critical factor to maintain finger dexterity in the cold.

Energy analysis of solar water heating systems in india

This analysis can be called energy accounting of solar water heating systems. Five types of solar water heating systems have been considered. With the help of material balance, energy content has been found in these systems. Yearly output of systems has been found by conducting transient simulations using hourly data of radiation and ambient temperature. Such analysis has been done separately for one representative city of each of six climatic zones of India. The energy payback for India ranges from 0.73 to 4.16 years for the thirty cases considered here.     

Combined effect of water activity and pH on inhibition of toxin production by Clostridium botulinum in cooked, vacuum-packed potatoes

The effects of water activity (aw, 0.955 to 0.970), pH (4.75 to 5.75), and storage time (up to 60 days) on toxin production by Clostridium botulinum in cooked, vacuum-packed potatoes were studied by using factorial design experiments and most-probable-number methodology. Samples were inoculated with 10(3), 10(4), or 10(5) spores of a mixture of five type A and five proteolytic type B strains, incubated at 25 degrees C, and analyzed for toxin production. Toxin was produced at pH levels of greater than or equal to 4.75 when the aw was greater than or equal to 0.970, pH greater than 5.25 when the aw was 0.965, and pH greater than or equal to 5.75 at an aw of 0.960. No toxin was detected when the aw was 0.955. The probability of toxigenesis was significantly affected (P less than 0.0001) by storage time, aw, pH, and the interactions aw.pH and aw.storage time. The response to a decrease in pH was linear, while the response to a decrease in aw was curvilinear. Using multiple linear regression, equations were derived which could predict the length of time until toxin production and the probability of toxigenesis by a single spore under defined conditions.     

Effects of reduction in beef surface water activity on the survival of Salmonella Typhimurium DT104 during heating

Aim: To investigate the influence of reducing beef surface water activity (a_w) on the survival of Salmonella Typhimurium DT104 during heating. Methods and Results: Beef discs were surface inoculated with S. Typhimurium DT104 and either untreated or dried to achieve surface a_w values of 0·95, 0·85 and 0·70. The samples were vacuum packed, heat‐treated at 60°C and removed at predetermined times. The inactivation curves were influenced by a_w and treatment time. Biphasic inactivation curves were observed for S. Typhimurium DT104 heat‐treated on beef samples with altered a_w values, which were characterized by an initial decline in cell numbers at commencement of heating followed by a much slower rate of inactivation during the remaining treatment period. Point estimates of the heating time required to achieve a 1 log reduction on beef surfaces with a_w of 0·99, 0·95, 0·85 and 0·70 were 0·5, 1·55, 11·25 and 17·79 min, respectively. Conclusions: A decrease in beef surface a_w can substantially enhance the survival of S. Typhimurium DT104 after heating. Significance and Impact of the Study: Caution needs to be taken using dry air as a decontamination method as this may rapidly decrease product surface and pathogen a_w values resulting in enhanced survival.     

化学杀菌剂对太原集中供热水体中有害菌群杀灭作用研究

研究了戊二醛、十二烷基二甲基苄基氯化铵对太原热网循环水中脱硫弧菌、鞘铁细菌、棒状杆菌、微球菌、葡萄球菌、芽孢杆菌和不动细菌等7类细胞的杀菌效果,结果表明：（1）不同浓度的戊二醛与十二烷基二甲基苄基氯化铵对7类细胞的杀菌效果差异极显著,而且随着杀菌剂浓度的增加这些细菌的死亡率呈线性上升;（2）戊二醛的杀菌浓度在100mg/L较为适宜,而二十烷基二甲基苄基氯化铵对脱硫弧菌和鞘铁细菌的杀菌浓度以100mg/L为宜,而对其余5类细菌的浓度以120mg/L较好;（3）戊二醛的杀菌效果明显优于十二烷基二甲基苄基氯化铵。     

The effect of nitrogen on plant water relations in tea (Camellia sinensis)

An experiment was carried out to study the effect of nitrogen deficiency on the water relations of tea (Camellia sinensis). The plants were grown in sand and nitrogen deficiency induced by witholding the supply of nitrogen. Nitrogen deficiency increased stomatal resistance and reduced transpiration. The capacity of the stomata to open fully in the morning was not impaired by nitrogen deficiency. Leaf water potential and probably root resistance were not affected by nitrogen deficiency. The sensitivity of transpiration and stomatal resistance to sand water stress was increased by nitrogen deficiency.     

Combined effect of water activity and pH on inhibition of toxin production by Clostridium botulinum in cooked, vacuum-packed potatoes.

The effects of water activity (aw, 0.955 to 0.970), pH (4.75 to 5.75), and storage time (up to 60 days) on toxin production by Clostridium botulinum in cooked, vacuum-packed potatoes were studied by using factorial design experiments and most-probable-number methodology. Samples were inoculated with 10(3), 10(4), or 10(5) spores of a mixture of five type A and five proteolytic type B strains, incubated at 25 degrees C, and analyzed for toxin production. Toxin was produced at pH levels of greater than or equal to 4.75 when the aw was greater than or equal to 0.970, pH greater than 5.25 when the aw was 0.965, and pH greater than or equal to 5.75 at an aw of 0.960. No toxin was detected when the aw was 0.955. The probability of toxigenesis was significantly affected (P less than 0.0001) by storage time, aw, pH, and the interactions aw.pH and aw.storage time. The response to a decrease in pH was linear, while the response to a decrease in aw was curvilinear. Using multiple linear regression, equations were derived which could predict the length of time until toxin production and the probability of toxigenesis by a single spore under defined conditions.     

Impact of microwave heating on the physico-chemical properties of a starch–water model system

The objective of this work was to understand the physico-chemical changes induced in a wheat starch model system as a result of microwave heating. Wheat starch dispersions in water, with final solids content of 33%, 40% or 50%, were heated in a microwave oven. Following heating the samples were stored at 25 °C for up to 120 h and analyzed periodically. Microwave heated gels were significantly different from conduction heated gels in all parameters measured. The differences in properties are a reflection of the differences in the heat and mass transfer of the different modes of heating. The lack of granule swelling and the resulting soft gel are two key observations. The results of this study suggest a different mechanism of starch gelatinization compared to conduction heating. The vibrational motion and the rapid increase in temperature also result in granule rupture and formation of film polymers coating the granule surface.     

Glucose reactions within the heating period and the effect of heating rate on the reactions in hot compressed water

Glucose reactions were conducted in hot compressed water (473-773 K, 4-40 MPa) by means of a batch-type reactor. The reactions in the heating period (about for 60s) were observed. More than 80% of the glucose was consumed in the heating period above 573 K. Gasification of glucose was promoted with increasing temperature. The effect of heating rate (from 4.2 to 15.8K/s) on glucose conversion was also examined, and gasification of glucose was enhanced with increasing the heating rate.     

仪器的加热效应校正对生态系统碳水通量估算的影响

涡度相关技术的广泛应用为获取生态系统碳、水通量提供了可能,但在开路式涡度相关系统中,仪器的加热效应增大了观测数据的不确定性。为了衡量仪器的加热效应,以ChinaFLUX3个典型生态系统(长白山温带针阔混交林(CBS)、海北灌丛草甸(HBGC)、鼎湖山亚热带常绿阔叶林(DHS))为研究对象,就仪器的加热效应校正对碳、水通量估算的影响进行分析。结果表明:加热校正没有改变生态系统的能量闭合特征,也没有对水汽通量的估算产生影响,但显著减小了CBS和HBGC非生长季的净生态系统生产力(NEP),进而减少了NEP的年总量,对DHS没有显著影响。NEP减小幅度受到温度的强烈影响,CBS为7.7%～10.4%,远小于HBGC的76.6%～85.2%,HBGC的NEP大幅降低主要是由夜间NEP的改变导致生态系统呼吸(RE)的增大而引起。因而,在温带生态系统中,充分考虑加热校正对于准确估算生态系统的碳收支具有重要作用。     

微等离子束对豚鼠皮肤超微结构分析和羟脯氨酸测定

目的观察微等离子束对豚鼠皮肤胶原组织作用效应的组织学和超微结构变化及羟脯氨酸含量测定,探讨微等离子束的作用机理。方法选择15只豚鼠,每只豚鼠背部划分为实验侧和空白对照侧2个等分区域,给予60W/10 kJ微等离子束照射,于作用后即刻、1周后和1月后分别切取实验侧及空白对照部位皮肤行组织病理维多利亚-立春红染色,透射电镜分析和羟脯氨酸检测试剂盒进行含量测定。结果 60 W/10 kJ即刻表现为表皮局灶性出现点阵状改变,部分表皮出现汽化缺失或者坏死变性,真皮浅层胶原组织出现点阵化表现和明显均质化;特殊染色显示微等离子束主要影响真皮胶原纤维,形成局灶性胶原纤维凝集和变性。1周后皮肤浅层胶原组织结构逐渐致密,排列有序,有少量组织细胞。1月后皮肤浅层胶原组织明显增厚,胶原纤维增粗并排列致密,弹力纤维呈局灶性增粗。透射电镜显示微等离子束作用后表皮细胞较完整,细胞间结构正常,但真皮胶原丧失正常结构,细胞结构消失,大量细胞凋亡明显,1月后仍可见少量细胞凋亡的表现但胶原结构逐渐恢复,浅层胶原纤维排列明显致密。羟脯氨酸测定显示微等离子束作用1周后羟脯氨酸含量要高于作用之前,但是差异性不具有统计学意义（P〉0.05）;1月后羟脯氨酸含量要明显高于作用前,差异性具有统计学意义（P〈0.05）。结论微等离子束对豚鼠皮肤胶原组织作用有明显的刺激效应,其主要靶组织为真皮胶原组织,可以明显促进皮肤新生胶原的增生。