证券组合的Markov链模型

本文将证券价格时间序列分解成趋势变动序列和 Markov链 ,建立了证券组合的 Markov链模型 ,应用 Markov链理论对此模型进行了分析 ,给出了充分大的一个时间内的收益率 ,风险和切点组合的计算公式     

Self-quenching smart probes as a platform for the detection of sequence-specific UV-induced DNA photodamage

Molecular beacons (MBs) are sensitive probes for many DNA sequence-specific applications, such as DNA damage detection, but suffer from technical and cost limitations. We have designed smart probes with self-quenching properties as an alternative to molecular beacons to monitor sequence-specific UV-induced photodamage of oligonucleotides. These probes have similar stem-loop structural characteristics as molecular beacons, but quenching is achieved instead via photoinduced intramolecular electron transfer by neighboring guanosine residues. Our results indicate that the probes are sensitive enough to detect nanomolar target concentrations and are specific enough to discriminate single-base damage. When the probes were used to monitor UV-induced photodamage in oligonucleotide sequences that differ by a single-base mismatch, the photodamage time constant was higher for the perfectly complementary target sequences than for the mismatch sequences, indicating that these probes are specific for each target sequence. In addition, time constants obtained for oligonucleotide target sequences with both stem and loop base mismatches are lower than those with only loop mismatches, suggesting that these sequences are also specifically distinguished by the smart probes. These probes thus constitute robust, sensitive, specific, and cheaper alternatives to MBs for sequence-specific DNA damage detection.     

Development and Application of Liquid Crystals as Stimuli-Responsive Sensors

This focused review presents various approaches or formats in which liquid crystals (LCs) have been used as stimuli-responsive sensors. In these sensors, the LC molecules adopt some well-defined arrangement based on the sensor composition and the chemistry of the system. The sensor usually consists of a molecule or functionality in the system that engages in some form of specific interaction with the analyte of interest. The presence of analyte brings about the specific interaction, which then triggers an orientational transition of the LC molecules, which is optically discernible via a polarized optical image that shows up as dark or bright, depending on the orientation of the LC molecules in the system (usually a homeotropic or planar arrangement). The various applications of LCs as biosensors for glucose, protein and peptide detection, biomarkers, drug molecules and metabolites are extensively reviewed. The review also presents applications of LC-based sensors in the detection of heavy metals, anionic species, gases, volatile organic compounds (VOCs), toxic substances and in pH monitoring. Additionally discussed are the various ways in which LCs have been used in the field of material science. Specific attention has been given to the sensing mechanism of each sensor and it is important to note that in all cases, LC-based sensing involves some form of orientational transition of the LC molecules in the presence of a given analyte. Finally, the review concludes by giving future perspectives on LC-based sensors.     

Ultraviolet resonance Raman spectroscopy as a robust spectroscopic tool for in situ sunscreen analysis

Current techniques being used for sunscreen analysis are incapable of direct determination of the active ingredients in sunscreen formulations. Therefore, the development of methodologies for rapid in situ analysis of sunscreens is desirable. This paper describes the application of ultraviolet resonance Raman spectroscopy (UVRRS) to the direct in situ analysis of sunscreen formulations. High-quality UV resonance Raman spectra were obtained for five sunscreen active ingredients (AIs), mixtures of the AIs and real sunscreen formulation samples. The spectra from the sunscreen formulations gave distinct spectral signatures indicative of the sunscreen AIs in each sample, with essentially no interference from the complex sunscreen matrix. Also, despite the fact that many of the AIs are fluorescent, no fluorescence interferences in the resonance Raman spectra were observed. Excitation wavelength-dependent studies throughout the 244-275 nm region demonstrate that the best discrimination of the AIs was achieved at an excitation wavelength of 244 nm. Thus, by tuning the excitation wavelength within the absorption bands of the AIs, complete identification of these analytes can be achieved in situ without any sample pretreatment or separation. The limit of detection found for a common AI in situ with this technique is 0.23% (w/w), the limit of quantitation is 0.78% (w/w), while the dynamic range is between 0.8% and 50% (w/w). The technique is fast, robust, lacks any major interference, and can be adapted for routine online quality control.     

Elucidating Peptide and Protein Structure and Dynamics: UV Resonance Raman Spectroscopy

UV resonance Raman spectroscopy (UVRR) is a powerful method that has the requisite selectivity and sensitivity to incisively monitor biomolecular structure and dynamics in solution. In this perspective, we highlight applications of UVRR for studying peptide and protein structure and the dynamics of protein and peptide folding. UVRR spectral monitors of protein secondary structure, such as the Amide III(3) band and the C(α)-H band frequencies and intensities can be used to determine Ramachandran Ψ angle distributions for peptide bonds. These incisive, quantitative glimpses into conformation can be combined with kinetic T-jump methodologies to monitor the dynamics of biomolecular conformational transitions. The resulting UVRR structural insight is impressive in that it allows differentiation of, for example, different α-helix-like states that enable differentiating π- and 3(10)- states from pure α-helices. These approaches can be used to determine the Gibbs free energy landscape of individual peptide bonds along the most important protein (un)folding coordinate. Future work will find spectral monitors that probe peptide bond activation barriers that control protein (un)folding mechanisms. In addition, UVRR studies of sidechain vibrations will probe the role of side chains in determining protein secondary, tertiary and quaternary structures.     

新疆苔藓植物资源的可持续开发潜能

苔藓植物是水生向陆生过渡的类群,为高等植物的一个重要门类．由于苔藓植物一般形体微校结构简单,为人类直接利用而产生经济效益的种类甚微,常被人们所忽视;然而它们在生态系统多样性中起着不可忽视的作用．新疆是全国苔藓植物资源最丰富的地区之一,资源分布广,可持续开发蕴藏量大,种类多和含有效成分量高,有较高的可持续开发利用的潜能．本文主要介绍新疆可供开发利用的药用苔藓植物资源、园林应用苔藓植物资源,环境监测苔藓植物资源、工农业应用苔藓植物资源、苔藓植物植被保护生态功能和苔藓植物作为科研试验材料．为利用好新疆植物资源,加快经济发展提供资料．     

新疆和田昆仑山区苔藓植物的初步研究

报道了新疆和田南部山区昆仑山中段的苔藓植物共计４０种１变种１变型,它们隶属于１５属６科,其中的缺齿藓属Ｍｉｅｌｉｃｈｈｏｆｅｒｉａ为新疆新记录属,狭叶墙藓Ｔｏｒｔｕｌａ ｃｅｒｎｕａ等２０种为新疆新记录种。该地区苔藓植被的主要特点是;１．从区系组成来持,全部由藓类组成,其中以真藓科,丛藓科和柳叶藓科的植物占优势;尚未有苔类及色苔类植物的发现。２．从群落分布来看,主要是水边土生,干旱土生及水中岩面生     

新疆藓类植物新纪录属——短月藓属(BRACHYMENIUM SCHWAEGR.)

本文报道了新疆真藓科(Bryaceae)新纪录属短月藓属(Brachymenium Schwaegr.)植物纤枝短月藓Brachymenium exile(Doz.et Molk.)Bosch et Lac.在新疆昆仑山西部叶城县的发现,并对其形态特征和生态环境及至新疆的分布进行了描述和讨论.     

Recent Progress in Polyaniline and its Composites for Supercapacitors

Polyaniline (PANI) has piqued the interest of nanotechnology researchers due to its potential as an electrode material for supercapacitors. Despite its ease of synthesis and ability to be doped with a wide range of materials, PANI′s poor mechanical properties have limited its use in practical applications. To address this issue, researchers investigated using PANI composites with materials with highly specific surface areas, active sites, porous architectures, and high conductivity. The resulting composite materials have improved energy storage performance, making them promising electrode materials for supercapacitors. Here, we provide an overview of recent developments in PANI-based supercapacitors, focusing on using electrochemically active carbon and redox-active materials as composites. We discuss challenges and opportunities of synthesizing PANI-based composites for supercapacitor applications. Furthermore, we provide theoretical insights into the electrical properties of PANI composites and their potential as active electrode materials. The need for this review stems from the growing interest in PANI-based composites to improve supercapacitor performance. By examining recent progress in this field, we provide a comprehensive overview of the current state-of-the-art and potential of PANI-based composites for supercapacitor applications. This review adds value by highlighting challenges and opportunities associated with synthesizing and utilizing PANI-based composites, thereby guiding future research directions.     

新疆藓属新纪录--拟白发藓属和砂藓属

在研究新疆布尔津县哈纳斯自然保护区的藓类植物时，发现新疆藓类2个新记录属和种．硬叶拟白发藓Paraleucobryum enerve(Thed．)Loesk和长枝砂藓Racomitrium ericoides(Hedw．)Brid，在本文中讨论了它们的形态特性．