Silicon carbide resonant tuning fork for microsensing applications in high temperature and high G shock environments

We present the fabrication and testing of a silicon carbide(SiC)balanced mass double-ended tuning fork that survives harsh environments without compromising the device strain sensitivity and resolution bandwidth.The device features a material stack that survives corrosive environments and enables high-temperature operation.To perform high-temperature testing,a specialized setup was constructed that allows the tuning fork to be characterized using traditional silicon electronics.The tuning fork has been operated at 600 ℃ in the presence of dry steam for short durations.This tuning fork has also been tested to 64 000 G using a hard-launch,soft-catch shock implemented with a light gas gun.However,the device still has a strain sensitivity of 66 Hz/με and strain resolution of 0.045 με in a 10 kHz bandwidth.As such,this balanced-mass double-ended tuning fork can be used to create a variety of different sensors including strain gauges,accelerometers,gyroscopes,and pressure transducers.Given the adaptable fabrication process flow,this device could be useful to micro-electro-mechanical systems(MEMS) designers creating sensors for a variety of different applications.     

手性锌卟啉的合成及其与咪唑类配体配位反应热力学研究

以Ｌ－（＋）－酒石酸为手性源,合成了一类新型手性锌（Ⅱ）卟啉配合物,用元素分析,比旋光、紫外可见光谱等手段对产物及其中间体进行了表征,研究了这类卟啉与三种咪唑类配体轴位反应热力学性质,发现取代基的电子效应强烈地影响锌卟啉和配体的热力学性质,并用分子力学、半经验量化计算的方法对卟啉和配体的结构进行了优化和计算,得到和实验现象相一致的结果。     

私营资本参与基础设施PPP项目的政府激励措施

政府往往需要提供激励措施才能吸引私营资本在基础设施公私合营(PPP)项目的投资。该文选取北京国家体育场等案例,归纳实际项目中的各种政府激励措施;并通过实证问卷调查私营部门的综合评价。结果表明:政府激励措施包括政府投资赞助、政府对融资的协助、政府担保、税收减免优惠和开发新市场;私营部门充分肯定各种激励措施的有效性,其中税收减免措施得分最高,政府投资赞助得分最低;而私营部门需客观评估政府激励措施,切勿索要不合理激励,以避免项目实施过程中出现因政府无法履行承诺而导致的项目中止或者失败。     

A novel <Emphasis Type="Italic">in vitro</Emphasis> angiogenesis model based on a microfluidic device

Angiogenesis is very important for many physiological and pathological processes. However, the molecular mechanisms of angiogenesis are unclear. To elucidate the molecular mechanisms of angiogenesis and to develop treatments for "angiogenesis-dependent" diseases, it is essential to establish a suitable in vitro angiogenesis model. In this study, we created a novel in vitro angiogenesis model based on a microfluidic device. Our model provides an in vivo-like microenvironment for endothelial cells (ECs) cultures and monitors the response of ECs to changes in their microenvironment in real time. To evaluate the potential of this microfluidic device for researching angiogenesis, the effects of pro-angiogenic factors on ECs proliferation, migration and tube-like structure formation were investigated. Our results showed the proliferation rate of ECs in 3D matrix was significantly promoted by the pro-angiogenic factors (with an increase of 59.12%). With the stimulation of pro-angiogenic factors gradients, ECs directionally migrated into the Matrigel from low concentrations to high concentrations and consequently formed multi-cell chords and tube-like structures. These results suggest that the device can provide a suitable platform for elucidating the mechanisms of angiogenesis and for screening pro-angiogenic or anti-angiogenic drugs for "angiogenesis-dependent" diseases.     

Stimulus-dependent myristoylation of a major substrate for protein kinase C

Bacterial lipopolysaccharide (LPS), the major surface component of gram-negative bacteria, exerts a profound effect on the immune system by enhancing the release of proteins and arachidonic acid metabolites from macrophages (for review see ref. 1). The molecular mechanism(s) by which LPS induces these various secretory responses is unknown. We previously reported that LPS promotes the myristoylation of several macrophage proteins including one with a relative molecular mass (Mr) of 68K2. We have now found that by several criteria the 68K myristoylated protein is similar or identical to the 80/87K protein, a major specific substrate for protein kinase C (PKC) found in brain and fibroblasts (for review see refs 7,8). We have also found that the myristoylated PKC substrate is quantitatively associated with the membrane fraction. Myristoylation of the PKC substrate may target it to the membrane and constitute a transduction pathway for stimulus-response coupling.     

新颖手性胺基膦配体在烯胺不对称催化氢化反应中的应用

将新颖的手性胺基磷配体，6，6'－二甲氧基－2，2'－双（二苯胺基膦）－1，1'－连苯的铑铬合物应用于烯胺类化合物的不对称催化氢化反应中，发现这个铑络合物是一个有效的手性催化剂，各种手性胺产物的转化率为100％，光学选择性（ee）也达到了51％－43％。     

Macroeconomic forecasting with mixed data sampling frequencies: Evidence from a small open economy

The aim of this study was to forecast the Singapore gross domestic product (GDP) growth rate by employing the mixed‐data sampling (MIDAS) approach using mixed and high‐frequency financial market data from Singapore, and to examine whether the high‐frequency financial variables could better predict the macroeconomic variables. We adopt different time‐aggregating methods to handle the high‐frequency data in order to match the sampling rate of lower‐frequency data in our regression models. Our results showed that MIDAS regression using high‐frequency stock return data produced a better forecast of GDP growth rate than the other models, and the best forecasting performance was achieved by using weekly stock returns. The forecasting result was further improved by performing intra‐period forecasting.