宏小区高天线环境下波达角度和时间的预测

为提高对空时到达分布预测的准确度,介绍了一种适用于小区高天线环境下波达角度和时间预测、的改进的圆散射模型。分别给出了波达角度和时间分布概率密度函数的表达式。仿真结果与实测数据的比较表明,较传统的基于散射体的单反宏小区模型而言,改进的圆模型能更合理地对传播建模,且在波达角度和时间的预测方面具有更高的准确度。     

垂直水声通信中的伪随机序列精确定时算法*

针对垂直水声通信中时变多普勒引起的定时偏差问题,研究一种基于伪随机序列的迭代定时估计及补偿算法。该方法利用伪随机序列作为同步信号,分三步估计时变多普勒：采用低复杂度的模糊函数法粗补偿接收信号内的平均多普勒;通过迭代插值法实现残留时变多普勒的精确估计及补偿;利用基于信道相关函数的相位信息,纠正均衡后信号的偏转相位。为实现高阶海试数据的有效解调,采用基于伪随机序列均方误差的多通道加权合并方式,获得空间分集增益。仿真及海试数据处理结果证明所提方法具有良好的时变多普勒估计及补偿性能,同时对30个通道内的1024QAM数据进行合并处理,在500 m的通信距离下,误码率为0.04,信道容量达到7.6 bits/symbol。与传统数据帧结构相比,无需使用线性调频信号,可以提高有效数据传输率。     

国有大旅行社市场渠道策略变革探讨

通过对近年来国有大旅行社渠道建设的现状分析,总结出国有大旅行社渠道变革的三大趋势,并分析这些变革趋势的动因。     

热应激对果蝇早老素突变体钙电流的影响

为研究与淀粉样前体蛋白(am y lo id precursorprote in,APP)无关的早老素引发阿尔茨海默氏病(A lzhe im er’s d isease,AD)的致病机理,用双电极电压钳方法记录果蝇体壁肌肉细胞的钙通道。结果显示:在几种早老素突变体果蝇中,无论是正常条件下培养还是将幼虫暴露在持续稳定的高温下,电压激活的C a2 电流都没有受到影响。而撤去高温条件后,C a2 尾电流失活速度明显变慢,但其他过程不受影响。说明在正常或应激条件下并不需要早老素来维持C a2 通道的功能,但是在撤去应激条件后的一段时期内,早老素对于C a2 通道的正常功能是必要的。提示早老素对于细胞在波动环境中维持正常功能起重要作用。     

Screening an In-House Isoquinoline Alkaloids Library for New Blockers of Voltage-Gated Na+ Channels Using Voltage Sensor Fluorescent Probes: Hits and Biases

Voltage-gated Na⁺ (Na_V) channels are significant therapeutic targets for the treatment of cardiac and neurological disorders, thus promoting the search for novel Na_V channel ligands. With the objective of discovering new blockers of Na_V channel ligands, we screened an In-House vegetal alkaloid library using fluorescence cell-based assays. We screened 62 isoquinoline alkaloids (IA) for their ability to decrease the FRET signal of voltage sensor probes (VSP), which were induced by the activation of Na_V channels with batrachotoxin (BTX) in GH3b6 cells. This led to the selection of five IA: liriodenine, oxostephanine, thalmiculine, protopine, and bebeerine, inhibiting the BTX-induced VSP signal with micromolar IC₅₀. These five alkaloids were then assayed using the Na⁺ fluorescent probe ANG-2 and the patch-clamp technique. Only oxostephanine and liriodenine were able to inhibit the BTX-induced ANG-2 signal in HEK293-hNa_V1.3 cells. Indeed, liriodenine and oxostephanine decreased the effects of BTX on Na⁺ currents elicited by the hNa_V1.3 channel, suggesting that conformation change induced by BTX binding could induce a bias in fluorescent assays. However, among the five IA selected in the VSP assay, only bebeerine exhibited strong inhibitory effects against Na⁺ currents elicited by the hNav1.2 and hNav1.6 channels, with IC₅₀ values below 10 µM. So far, bebeerine is the first BBIQ to have been reported to block Na_V channels, with promising therapeutical applications.     

Neutrophil Immunomodulatory Activity of (−)-Borneol,a Major Component of Essential Oils Extracted from Grindelia squarrosa

Grindelia squarrosa (Pursh) Dunal is used in traditional medicine for treating various diseases; however, little is known about the immunomodulatory activity of essential oils from this plant. Thus, we isolated essential oils from the flowers (GEO_Fl) and leaves (GEO_Lv) of G. squarrosa and evaluated the chemical composition and innate immunomodulatory activity of these essential oils. Compositional analysis of these essential oils revealed that the main components were α-pinene (24.7 and 23.2% in GEO_Fl and GEO_Lv, respectively), limonene (10.0 and 14.7%), borneol (23.4 and 16.6%), p-cymen-8-ol (6.1 and 5.8%), β-pinene (4.0 and 3.8%), bornyl acetate (3.0 and 5.1%), trans-pinocarveol (4.2 and 3.7%), spathulenol (3.0 and 2.0%), myrtenol (2.5 and 1.7%), and terpinolene (1.7 and 2.0%). Enantiomer analysis showed that α-pinene, β-pinene, and borneol were present primarily as (−)-enantiomers (100% enantiomeric excess (ee) for (−)-α-pinene and (−)-borneol in both GEO_Fl and GEO_Lv; 82 and 78% ee for (−)-β-pinene in GEO_Fl and GEO_Lv), while limonene was present primarily as the (+)-enantiomer (94 and 96 ee in GEO_Fl and GEO_Lv). Grindelia essential oils activated human neutrophils, resulting in increased [Ca²⁺]_i (EC₅₀ = 22.3 µg/mL for GEO_Fl and 19.4 µg/mL for GEO_Lv). In addition, one of the major enantiomeric components, (−)-borneol, activated human neutrophil [Ca²⁺]_i (EC₅₀ = 28.7 ± 2.6), whereas (+)-borneol was inactive. Since these treatments activated neutrophils, we also evaluated if they were able to down-regulate neutrophil responses to subsequent agonist activation and found that treatment with Grindelia essential oils inhibited activation of these cells by the N-formyl peptide receptor 1 (FPR1) agonist fMLF and the FPR2 agonist WKYMVM. Likewise, (−)-borneol inhibited FPR-agonist-induced Ca²⁺ influx in neutrophils. Grindelia leaf and flower essential oils, as well as (−)-borneol, also inhibited fMLF-induced chemotaxis of human neutrophils (IC₅₀ = 4.1 ± 0.8 µg/mL, 5.0 ± 1.6 µg/mL, and 5.8 ± 1.4 µM, respectively). Thus, we identified (−)-borneol as a novel modulator of human neutrophil function.     

多输入多输出系统发射天线选择对系统信道容量的影响

针对多输入多输出(MIMO)系统信道矩阵秩亏引起信道容量下降的问题,基于信道容量上限提出了一种发射天线选择方法.该方法利用信道矩阵与发射空间相关矩阵秩相同的特点,重新构建了蕴含模型物理参数的信道模型.在对空间相关矩阵QR分解的基础上,采用随机矩阵理论推导了迫零接收机信噪比的概率密度函数,从而得到了MIMO系统信道容量的上限.该方法不需要已知信道的瞬时状态信息,只取决于衰落的空间相关,计算的复杂度较低,易于实现.仿真结果表明:在低散射环境中,适当地选择发射天线可以使系统的信道容量增加约1 b/s;当接收信噪比大于6.5 dB时,发射端采用均匀圆阵系统的性能要优于采用均匀线阵系统的性能.     

基于TCB子集的访问控制信息安全传递模型

综合考虑应用层向内核层传递访问控制信息的安全需求,提出了一种基于TCB子集的访问控制信息安全传递模型。应用层安全管理器与内核层安全管理器通过安全通路相联,安全通路为已加密状态,密钥存放在可信平台模块TPM(trusted platform model)中,访问控制信息进入安全通路前必须通过TPM的控制处理;安全通路解密后应用层安全通路接口把访问控制信息和校验标签传到内核层安全通路接口,随后应用层接口进行随机抽查,内核层接口返回验证证据并由应用层接口判断数据真实性和有效性。安全传递模型不仅可以有效地保证访问控制信息的安全性,还可以抵抗恶意欺骗和恶意攻击从而提高了访问控制的可靠性与有效性。     

利用脱硫石膏水热合成硫酸钙晶须

以脱硫石膏为原料,采用水热法工艺制备硫酸钙晶须.借助电导率、化学电位、XRD和SEM等分析方法,在不同反应条件下研究了硫酸钙晶须生长的变化规律,随着反应温度、反应时间、固液比和初始pH值的增加,硫酸晶须的长径比呈先增加后减小的趋势.在本实验条件下最佳工艺参数为:反应温度140℃,反应时间120min,固液比为1∶10,初始pH值为5,原料粒度1.36μm.此时所制备的硫酸钙晶须长径比可以达到82.57.     

循环法制备高纯碳酸钙工艺研究

目的制备电子陶瓷工业用高纯碳酸钙。方法以工业碳酸钙为原料,采用改进的氢氧化物沉淀法,经过煅烧、浸出、沉淀、碳化等步骤制备高纯碳酸钙,并用原子吸收分光光度法和电位滴定法对杂质进行了分析,用粒度分析仪对产品粒度分布进行了测定。结果得到一条循环法生产高纯碳酸钙的优化工艺路线,该工艺过程如下:原料经煅烧后与氯化铵反应,加入沉淀剂过滤,除去杂质;将前工序煅烧时产生的CO2气体通入过滤后的滤液中,进行碳化反应;生成物经过滤干燥后即得到高纯碳酸钙;滤液循环使用。结论浸出温度,浸出时间,pH,pH调节试剂,碳化温度,洗涤水温等对产品均有影响。