Effect of calcium chloride addition on ice cream structure and quality

The influence of calcium fortification by the addition of calcium chloride on quality parameters of ice cream based on physical properties was investigated, as was the effect of κ-carrageenan at modifying the effects of this calcium fortification. Four ice cream mixes of conventional composition, with added κ-carrageenan (0 or 0.025%) and added calcium chloride (0 or 4.4 g L⁻¹ = 40 mM of added Ca²⁺), were prepared. Modulated temperature-differential scanning calorimetry was used to investigate the effect of calcium chloride on the nucleation temperature, enthalpy of melting, and freezing point depression. The protein composition of 15.4% (wt/wt) reconstituted skim milk powder solutions with or without 4.4 g L⁻¹ added CaCl₂ and in the supernatant after ultracentrifugation was determined. Fat particle size distributions in ice cream were characterized by light scattering. Ice crystal sizes before and after temperature cycling were determined by cold-stage light microscopy. The results demonstrated that the addition of calcium chloride led to a substantial increase in ice crystal sizes and in fat partial coalescence, which were exacerbated by the addition of κ-carrageenan. These results can be explained by the interaction between Ca²⁺ ions and casein micelles, rather than any effects on freezing point depression. The calcium ions led to a more compact micelle, less serum β-casein, and high fat destabilization, all of which would be expected to reduce macromolecular structure and volume occupancy in the unfrozen phase, which led to increased rates of ice recrystallization.     

Degradation of lead-contaminated lignocellulosic waste by Phanerochaete chrysosporium and the reduction of lead toxicity

Lead, as one of the most hazardous heavy metals to the environment interferes with lignocellulosic biomass bioconversion and carbon cycles in nature. The degradation of lead-polluted lignocellulosic waste and the restrain of lead hazards by solid-state fermentation with Phanerochaete chrysosporium were studied. Phanerochaete chrysosporium effectively degraded lignocellulose, formed humus and reduced active lead ions, even at the concentration of 400 mg/kg dry mass of lead. The highest lignocellulose degradation (56.8%) and organic matter loss (64.0%) were found at the concentration of 30 mg/kg of lead, and at low concentration of lead the capability of selective lignin biodegradation was enhanced. Microbial growth was delayed in polluted substrate at the initial stage of fermentation, and organic matter loss is correlated positively with microbial biomass after 12 day fermentation. It might be because Phanerochaete chrysosporium developed active defense mechanism to alleviate the lead toxicity. Scanning electron micrographs with energy spectra showed that lead was immobilized via two possible routes: adsorption and cation exchange on hypha, and the chelation by fungal metabolite. The present findings will improve the understandings about the degradation process and the lead immobilization pathway, which could be used as references for developing a fungi-based treatment technology for metal-contaminated lignocellulosic waste.     

国内外换热器技术进展

本文主要介绍改善管壳式换热器壳侧和管侧换热的几种方法，以及可拆式板式换热器、焊接式板式换热器，鼓泡式换热器，螺旋板式换热器国内外大型化发展的趋势。     

模拟风洞的冷态调试试验

一、概述模拟风洞试验台是我所新建的一套试验装置,用于对空冷式换热器的各种传热元部件进行传热和流动阻力特性的研究,这就为设计新型高效紧凑式空冷器、强化现有空冷器传热性能以及节约能源、广泛开展各种低温热能的利用和回收提供了必需的试验手段。模拟风洞试验台的试件用迎风截面积为0.0625m~2的各类换热器元件芯子,迎风截面尺寸为250×250mm,迎风速度可在1～34m/s的范围内任意调     

Background corrections for laser-induced-fluorescence measurements of nitric oxide in lean, high-pressure, premixed methane flames

An experimental technique is presented that both minimizes and accounts for the interference background when laser-induced-fluorescence (LIF) measurements are made of NO in lean, high-pressure, premixed, CH(4)/O(2)/N(2) flames. Measurement interferences such as fluorescence and Raman scattering from secondary species become increasingly important for high-pressure LIF studies. O(2) fluorescence interferences are particularly troublesome in lean premixed flames. An excitation-detection scheme that minimizes the effects of these interferences is identified. A procedure that corrects the resulting LIF signal so as to account for any remaining interference signal is then developed. This correction is found to vary from less than 10% of the overall NO signal at atmospheric pressure to over 40% of the overall signal at 14.6 atm for LIF measurements of NO in a series of worst-case flames (phi = 0.6, dilution ratio 2.2). The correction technique is further demonstrated to be portable over a useful range of flame conditions at each pressure.     

On the mechanical properties of bovine serum albumin (BSA) adhesives

Biological adhesives, natural and synthetic, are of current active interest. These adhesives offer significant advantages over traditional sealant techniques, in particular, they are easier to use, and can play an integral part in the healing mechanism of tissue. Thus, biological adhesives can play a major role in medical applications if they possess adequate mechanical behavior and stability over time. In this work, we report on the method of preparation of bovine serum albumin (BSA) into a biological adhesive. We present quantitative measurements that show the effect of BSA concentration and cross-linker content on the bonding strength of BSA adhesive to wood. A comparison is then made with synthetic poly(glycidyl methacrylate) (PGMA) adhesive, and a commercial cyanoacrylate glue, which was used as a control adhesive. In addition, BSA samples were prepared and characterized for their water content, tensile strength, and elasticity. We show that on dry surface, BSA adhesive exhibits a high bonding strength that is comparable with non-biological commercial cyanoacrylate glues, and synthetic PGMA adhesive. Tensile testing on wet wood showed a slight increase in the bonding strength of BSA adhesive, a considerable decrease in the bonding strength of cyanoacrylate glue, and negligible adhesion of PGMA. Tests performed on BSA samples demonstrate that initial BSA concentration and final water content have a significant effect on the stress–strain behavior of the samples.     

Peptide-nanoparticle hybrid SERS probes for optical detection of protease activity

Real-time in situ detection of active proteases is crucial for early-stage cancer screening and cell signaling pathway study; however, it is difficult to achieve using fluorescence or radioactive probes at volumes below 1 nL. Here we demonstrated a hybrid optical probe by incorporating nanocrescent particle and peptides with artificial tag molecules. We performed a proof-of-concept study using prostate specific antigen (PSA), one of the most prominent prostate cancer markers, and a serine protease present in patients' seminal fluid and serum. The Raman spectral signal from the tag molecules is enhanced by the nanocrescent and the signal is monitored as the indicator for peptide cleavage in a femtoliter reaction volume, at levels close to a single proteolytically active PSA molecule. The high reaction specificity of the peptides on individual nanoparticles minimizes the false detection of other serine proteases and background Raman signal, which results in a high-fidelity and high-signal-to-noise-ratio cancer nanoprobe that can be easily incorporated into nano/microfluidic devices.     

采用软启动方式的VSC-HVDC黑启动能力研究

合理的黑启动方案对于快速可靠地恢复供电至关重要。分析了VSC-HVDC作为黑启动电源的优势。通过PSCAD/EMTDC软件验证了VSC-HVDC软启动主要电力设备的能力。仿真过程中记录的波形显示了VSC-HVDC良好的电压、频率特性。对VSC-HVDC黑启动控制到正常潮流控制的转换过程也做了仿真研究。仿真结果表明,当采用软启动方式时,VSC-HVDC是一种理想的黑启动电源。     

T-S模糊控制器设计新方法及应用仿真

以具有非线性和非最小相位特性的水轮发电机调速系统为例,提出了T-S模糊控制器设计的新方法———基于PID控制器知识样本的T-S模糊控制器设计方法。将模糊控制器运用于水轮机控制,并对其进行仿真,把得到的模糊控制响应曲线与PID控制器进行比较,从调节时间、超调量、鲁棒性等方面可以看出,模糊控制器控制效果要优于PID控制。