基于场景坏点检测的面阵CCD暗电流估计方法

利用CCD中的部分坏点作为温度敏感器,提取CCD温度估计值,建立温度估计值与暗电流的函数模型,并结合均值滤波的方法,在真实场景图像中提取CCD温度估计值,实现了面阵CCD的暗电流估计。在方法分析的基础上,以真实的暗电流数据为基准参考,对暗电流的估计结果进行了比对实验。实验结果表明,在不同的积分时间及大动态范围的成像条件下暗电流的估计结果十分准确,偏差小于0.4%,并且具有一定的抗噪性。该方法利用场景本身的特征信息对拍摄时刻的暗电流进行估计,不需要额外采集暗电流数据,节省了图像采集时间,十分适合于积分时间较长的高光谱成像或天文观测领域,采用无温度控制的低成本CCD成像探测系统进行实时图像采集。     

Controllable synthesis of hierarchical strontium molybdate by sonochemical method

Large‐scale chrysanthemum‐like strontium molybdate (SrMoO₄) with hierarchical structure has been successfully synthesized via a facile and fast ultrasound irradiation approach at room temperature. By varying the experimental conditions, SrMoO₄ with different morphologies, such as spindles, peanuts, spheres, and rods, can be obtained. The products are characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected‐area electron diffraction (SAED). The influent parameters including concentration, pH value, and surfactants have been investigated. A possible growth mechanism is proposed and the shape evolution of the products is characterized. The as‐prepared chrysanthemum‐like SrMoO₄ particles are used as the precursor for electrorheological fluid and their electrorheological property is investigated.     

Large roomtemperature magnetocaloric effect with negligible magnetic hysteresis losses in Mn1−xVxCoGe alloys

The magnetic and magnetocaloric properties have been investigated in a series of Mn_1−xV_xCoGe (x=0.01, 0.02, 0.03, and 0.05) alloys. The substitution of V for Mn reduces the structural transformation temperature of MnCoGe alloy effectively and results in a second-order magnetic transition in Mn_0.95V_0.05CoGe alloys. Large room temperature magnetocaloric effect and almost zero magnetic hysteresis losses are simultaneously achieved in the alloys with x=0.01, 0.02, and 0.03. The reasons for the negligible magnetic hysteresis losses and the potential application for the roomtemperature magnetic refrigeration are discussed.     

Target-oriented multifunctional organocatalysis for enantioselective synthesis of bicyclo[3.3.1]nona-2,6-dien-9-ones. A formal asymmetric synthesis of huperzine A

A target-oriented highly enantioselective multifunctional organocatalytic approach has been developed to construct the bicycle-[3.3.1]nona-2,6-dien-9-one core of (?)-huperzine A for the first time, with up to 95% ee in the gram-scale procedure. The newly established methodology is also eligible to synthesize a variety of bicyclo[3.3.1]nona-2,6-dien-9-ones in high enantiopurities, and thus is useful for the future development of novel huperzine A analogs with medicinal interests.     

An efficient synthesis of 2H-indazoles via reductive cyclization of 2-nitrobenzylamines induced by low-valent titanium reagent

An efficient and improved synthesis of 2H-indazoles via reductive cyclization of 2-nitrobenzylamines induced by low-valent titanium reagent (TiCl₄/Zn) is described. In this reaction triethylamine (TEA) was used to control the pH value. This method has the advantages of easily accessible starting materials, convenient manipulation, higher yield, shorter reaction time, and wider substrate scope.     

An LPCC approach to nonconvex quadratic programs

Filling a gap in nonconvex quadratic programming, this paper shows that the global resolution of a feasible quadratic program (QP), which is not known a priori to be bounded or unbounded below, can be accomplished in finite time by solving two linear programs with linear complementarity constraints, i.e., LPCCs. Specifically, this task can be divided into two LPCCs: the first confirms whether the QP is bounded below on the feasible set and, if not, computes a feasible ray on which the QP is unbounded; the second LPCC computes a globally optimal solution if it exists, by identifying a stationary point that yields the best quadratic objective value. In turn, the global resolution of these LPCCs can be accomplished by a parameter-free, mixed integer-programming based, finitely terminating algorithm developed recently by the authors, which can be enhanced in this context by a new kind of valid cut derived from the second-order conditions of the QP and by exploiting the special structure of the LPCCs. Throughout, our treatment makes no boundedness assumption of the QP; this is a significant departure from much of the existing literature which consistently employs the boundedness of the feasible set as a blanket assumption. The general theory is illustrated by 3 classes of indefinite problems: QPs with simple upper and lower bounds (existence of optimal solutions is guaranteed); same QPs with an additional inequality constraint (extending the case of simple bound constraints); and nonnegatively constrained copositive QPs (no guarantee of the existence of an optimal solution). We also present numerical results to support the special cuts obtained due to the QP connection.     

Time-dependent partitioning theory of the control of radiationless transitions in 24-mode pyrazine

We consider the control of internal conversion between the S(2)((1)B(2u)) excited electronic state of pyrazine and the S(1)((1)B(3u)) state. The study is performed both during and after the femtosecond excitation of the ground electronic state S(0)((1)A(g)) to form the S(2) state. The dynamics is examined using the newly developed "effective modes" technique which enables the full computation of quantum dynamics in multi-dimensional spaces. Using this technique, we also investigate the coherent control of population transfer from S(0) to the S(2) and S(1) electronic states. We find that the use of shaped laser pulses enables a significant delay of the internal conversion. For example, after 60 fs, the S(2) population amounts to ～60% of the initial S(0) population, and remains at ～20% after 100 fs, in contrast to the S(0) electronic state which is completely depopulated within 75 fs.     

Proteomic analysis reveals platelet factor 4 and beta-thromboglobulin as prognostic markers in severe acute respiratory syndrome

Previously, we reported that proteomic fingerprints were present in sera of patients with severe acute respiratory syndrome (SARS), and could separate patients into subgroups with different prognoses. In the present study, we examined the prognostic values of the SARS-associated proteomic features by biostatistical analysis, and deciphered the identities of those with prognostic values. Data of 20 SARS-associated serum proteomic features and ten serological variables from 38 SARS adult patients before treatment were subjected to multivariate logistic regression. Proteomic features of m/z 6634, m/z 7769, m/z 8635, and m/z 8865 were identified as independent prognostic markers. After purification by cation-exchange chromatography and gel electrophoresis, proteomic features of m/z 7769 and m/z 8865 were found to be platelet factor 4 (PF4) and beta-thromboglobulin (beta-TG) by tandem mass spectrometry, respectively. The associations of decreased serum PF4 and increased serum beta-TG levels with poor prognosis were confirmed by Western blot. Previous studies suggest that PF4 and beta-TG are involved in the pathogenesis of acute respiratory distress syndrome (ARDS) in a negative and positive way, respectively. Our results suggest that PF4 and beta-TG may also play similar roles in the development of ARDS in SARS patients.     

A new hederagenin glycoside from <Emphasis Type="Italic">Nephelium lappaceum</Emphasis>

A new oleane-type triterpene oligoglycoside, hederagenin 3-O-(3-O-acetyl-β-D-xylopyranosyl)-(1→3)-α-L-arabinopyranoside (2), together with four known compounds, hederagenin (1), hederagenin 3-O-(4-O-acetyl-α-L-arabinopyranosyl)-(1→3)-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranoside (3), hederagenin 3-O-α-L-arabinopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranoside (4), hederagenin 3-O-β-D-glucopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→4)-β-D-xylopyranoside (5), was isolated from the hull of Nephelium lappaceum. All the isolates were obtained from the hull of rambutan for the first time.