基于数据库综合和SVG的网络制图综合系统研究

针对网络制图综合效率低和基于网络的不同详细程度的空间数据的自动生成问题,提出了一种应用z-value空间索引机制实现网络空间数据制图综合的方法。该方法可以有效地过滤无关的空间数据,为不同的应用生成恰当的细节层面,并且有效地提高空间数据网络传输的效率。在客户端采用可缩放矢量图形（SVG）技术显示,该方法读写速度快,易于进行编辑和修改,在显示速度和交互性方面表现不俗。测试表明该方法比传统方法更有效。     

空间信息检索及其数据库概化技术

在一个空间数据库中,空间数据总是以最细节的信息进行储存,以满足不同应用的需求.制图学中的制图综合就是为不同的应用生成恰当的细节层面.随着空间数据库应用的日益广泛,以及越来越多的基于Internet的空间应用的出现,对空间数据的有效自动综合成为一个紧要问题.深入探讨了当前这一领域存在的问题,提出一种面向数据库的概化处理技术,利用空间索引机制z-value进行扩展,并将其应用到空间数据的自动综合技术中,通过对空间数据库的设计和对空间操作的处理来实现一个有效的空间数据库自动综合系统.     

Use of Dacid-, Dbile-, zacid-, and zbile-Values in Evaluating Bifidobacteria with Regard to Stomach pH and Bile Salt Sensitivity

ABSTRACT: The survival of bifidobacteria in simulated conditions of the gastrointestinal (GI) tract was studied based on the D- and z-value concept. Some Bifidobacterium spp. are probiotics that improve microbial balance in the human GI tract. Because they are sensitive to low pH and bile salt concentrations, their viability in the GI tract is limited. The D- and z-value approach was therefore adopted as a result of observing constant log-cell reduction (90%) when Bifidobacterium spp. were exposed to these 2 different stressing factors. Survivals of one strain each or 4 species of Bifidobacterium was studied at pH between 3.0 and 4.5 and in ox-bile between 0.15% and 0.60% for times up to 41 h. From the D_acid- and D_bile-values, the order of resistance to acid and bile was B. bifidum > B. infantis > B. longum > B. adolescentis. While the former 3 strains retained high cell viability at pH 3.5 (>5.5 log CFU/mL after 5 h) and at elevated bile salt concentration of 0.6% (>4.5 log CFU/mL after 3 h), B. adolescentis was less resistant (<3.4 log CFU/mL). The z_acid- and z_bile-values calculated from the D_acid- and D_bile-values ranged from 1.11 to 1.55 pH units and 0.40% to 0.49%, respectively. The results suggest that the D_acid-, D_bile-, z_acid-, and z_bile-value approach could be more appropriate than the screening and selection method in evaluating survival of probiotic bacteria, and in measuring their tolerance or resistance to gastric acidity and the associated bile salt concentration in the small intestine. Practical Application: The evaluation of the tolerance of bifidobacteria to bile salts and low pH has been made possible by use of D- and z-value concept. The calculated z_acid- and z_bile-values were all fairly similar for the strains used and suggest the effect of increasing the bile salt concentration or decreasing the pH on the D_acid- and D_bile-values. This approach would be useful for predicting the suitability of bifidobacteria and other lactic acid bacteria (LAB) as probiotics for use in real-life situations.     

Effect of thermal processing on the texture of canned apricots

The effect of thermal processing on the texture of canned apricots was studied by using the main cultivar canned in Greece, Bebecou. The test temperature ranged from 82 to 95 °C. The loss of hardness was tested immediately after processing and after 3 months storage. The z -value was 16.7 °C and the energy of activation 116.5 kJ mol⁻¹. Some restoration in the hardness was found after 3 months storage, which might be attributable to the absorption of sucrose by the fruit.     

Effect of heat on microorganisms isolated from freshly caught chilled scad (Trachurus trachurus)

The effects of heat on bacteria making up part of the microFlora of the sea-Fish Trachurus trachurus were studied. From 80 bacterial isolates which were subject to primary identiFication four were selected. The bacteria were subjected to a heat stress of 55°C for 20 s both in pure and mixed suspensions, the D-values and post-stress recovery in nutrient broth were measured. Using differential plating on selective agents to identify sites of injury and recovery times, the growth parameters dissolved oxygen, redox potential and pH were measured during recovery. Bacteria presumptively identiFied as Shewanella putrefaciens and Pseudomonas putida were more sensitive to heat than other bacteria, suggesting that most heat treatments of Fish may reduce the number of these bacteria. After dissolved oxygen was used up during recovery in nutrient broth, Eh declined from positive to negative values typical of facultative bacteria showing that, after initial aerobic growth, the bacteria changed their metabolism to grow anaerobically. When dissolved oxygen reached zero, about 120 h after inoculation, the numbers of all bacteria were about 10⁷mL⁻¹, and corresponds to a minimum in the pH values, except for the most heat sensitive isolate (300 h after inoculation). Differential plating showed increased sensitivity to NaCl induced by heat treatments in some isolates.     

Predictive Models for Microbial Inactivation and Texture Degradation in Surimi Seafood During Thermal Processing

Models for Staphylococcus aureus inactivation and texture degradation during thermal processing of surimi seafood were developed based on the modified thermal‐death‐time (TDT) concept. Validation studies showed good fit between experimental and predicted values. The models allow input of processing parameters, resulting in a surface response that determines microbial inactivation and texture degradation. D‐values for microbial inactivation were determined between 55 and 95 °C. The z‐value, however, was not linear. Therefore, a polynomial equation was used to calculate D‐values at intermediate temperatures. Texture degradation between 55 and 95 °C followed a power function. Therefore, power “n” was used as the degradation rate for modeling purposes. Polynomial equation was used to calculate “n” at intermediate temperatures.     

Modeling the combined effects of pH, temperature and ascorbic acid concentration on the heat resistance of Alicyclobacillus acidoterrestis

In this study, thermal inactivation parameters (D- and z-values) of Alicyclobacillus acidoterrestris spores in McIlvaine buffers at different pH, apple juice and apple nectar produced with and without ascorbic acid addition were determined. The effects of pH, temperature and ascorbic acid concentration on D-values of A. acidoterrestris spores were also investigated using response surface methodology. A second order polynomial equation was used to describe the relationship between pH, temperature, ascorbic acid concentration and the D-values of A. acidoterrestris spores. Temperature was the most important factor on D-values, and its effect was three times higher than those of pH. Although the statistically significant, heat resistance of A. acidoterrestris spores was not so influenced from the ascorbic acid within the concentration studied. D-values in apple juice and apple nectars were higher than those in buffers as heating medium at similar pH. The D-values ranged from 11.1 (90 °C) to 0.7 min (100 °C) in apple juice, 14.1 (90 °C) to 1.0 min (100 °C) in apple nectar produced with ascorbic acid addition, and 14.4 (90 °C) to 1.2 min (100 °C) in apple nectar produced without ascorbic acid addition. However, no significant difference in z-values was observed among spores in the juices and buffers at different pH, and it was between 8.2 and 9.2 °C. The results indicated that the spores of A. acidoterrestris may survive in fruit juices and nectars after pasteurization treatment commonly applied in the food industry.     

Thermal kinetics of pungency loss in relation to the quality of pickled garlic

The kinetics of the loss of pungency (enzymatically formed pyruvate) from garlic slices during heating was investigated at selected temperatures (60, 65, 70 and 75 °C) with the aim of optimizing the water blanching treatment in the processing of pickled garlic. For each temperature, after a lag period, pungency appeared to decrease in two phases as heating progressed. The first and more important phase, which was used for the calculation of the kinetic parameters, followed first‐order kinetics. The calculated z‐value (9.4 °C) was significantly lower than z‐values generally reported for degradation of quality factors in foods. The effectiveness of thermal treatment to eliminate pungent flavour and inhibit green discolouration increased with increasing temperatures. Optimum blanch treatment was reached at 80 °C for 1.1 min. Pyruvate determination was shown to be a better indicator of pungency than allicin determination in blanched garlic slices.     

The influence of water activity on thermal stability of horseradish peroxidase

The thermal stability of horseradish peroxidase in the solid state was studied as a function of water activity, from 0.11 to 0.88. At all activities the enzyme was found to be much more stable in the solid state than in solution. Inactivation temperatures were in the range of 140–160°C. Inactivation curves show a biphasic behaviour which can be described by a model assuming two fractions (heat labile and heat stable) with independent first order inactivation kinetics. The labile fraction represents approximately 30% of the total activity. The z-value for both stable and labile fractions depends on water activity (moisture content) and has a maximum at a_w= 0.76 (44.4°C and 43.8°C, respectively).     

Thermal Stability of Bovine Milk Immunoglobulin G (IgG) and the Effect of Added Thermal Protectants on the Stability

D and z values and some thermodynamic parameters of immunoglobulin G (IgG) in phosphate buffer solution (PBS) (0.15 M NaCl/0.01 M phosphate buffer, pH 7.0) and colostral whey, with or without the presence of thermal protectants, were calculated in model systems. The D and z values for separated IgG in PBS were much lower than those for separated IgG in 20% glycerol, whey, and whey with 20% glycerol. IgG in colostral whey showed larger D and z values with the protectants. The heat denaturing rate constants at 70-82°C for separated IgG in PBS were larger than those of IgG in colostral whey; and the energies of activation for separated IgG in PBS, 0.2% glutamic acid, 10% whole milk, 20% maltose and 20% glycerol were also larger.