2Vrms:音视频产品中的一种有趣的旧标准

投放市场的一些新型产品正迅速地改变音视频产品的市场格局,因为它们都具有许多单电源器件和一个可生成负电源轨的内置电荷泵.如果一些设计人员正在做的工作是如何驱动输出线路驱动器,那么他们最终会问自己系统中为什么需要较高的电压轨.因此,一些新型产品具有单电源器件和一个生成负电源轨的内置电荷泵(例如使用直接路径技术),这些产品正迅速改变着音视频产品市场的格局.     

The study of complex mineral silicates by trimethylsilylation

The Lentz trimethylsilylation technique has been applied to study four micas: biotite, phlogopite, muscovite and suzorite. The Lentz derivitisation technique is shown to be independent of the exact amount of phase transfer agent (propan-2-ol or ethanol) present in the trimethylsilylation of the micas as long as the ratio of mineral to hexamethyldisiloxane is held constant. The polyorganosiloxane product distribution is shown to be largely dependent on the amount and distribution of Al³⁺ present in the tetrahedral layers of the micas.     

The reaction of tetrakis(trimethylsiloxy)silane,QM4, and hexakis(trimethylsiloxy)disiloxane,Q2M6, with sodium hydroxide in ethanol

The reaction of the two model polyorganosiloxanes. QM₄ and Q₂M₆, with ethanolic sodium hydroxide is reported (Q=SiO_{4 2} andM=Me₃SiO_{1 2}). Removal of theM groups from QM₄ was rapid and led to the formation of a sodium silicate species which was insoluble in organic solvents. The reaction with Q₂M₆, however, was incomplete and gave hybrid structures of the type Q₂M₆ (O_{1 2}Na). A possible pathway for the formation of the sodium silicate species from QM₄ is proposed.     

Design and characterisation of an artificial DNA-binding cytochrome

We aim to design novel proteins that link specific biochemical binding events, such as DNA recognition, with electron transfer functionality. We want these proteins to form the basis of new molecules that can be used for templated assembly of conducting cofactors or for thermodynamically linking DNA binding with cofactor chemistry for nanodevice applications. The first examples of our new proteins recruit the DNA-binding basic helix region of the leucine zipper protein GCN4. This basic helix region was attached to the N and C termini of cytochrome b(562) (cyt b(562)) to produce new, monomeric, multifunctional polypeptides. We have fully characterised the DNA and haem-binding properties of these proteins, which is a prerequisite for future application of the new molecules. Attachment of a single basic helix of GCN4 to either the N or C terminus of the cytochrome does not result in specific DNA binding but the presence of DNA-binding domains at both termini converts the cytochrome into a specific DNA-binding protein. Upon binding haem, this chimeric protein attains the spectral characteristics of wild-type cyt b(562). The three forms of the protein, apo, oxidised holo and reduced holo, all bind the designed (ATGAcgATGA) target DNA sequence with a dissociation constant, K(D), of approximately 90 nM. The protein has a lower affinity (K(D) ca. 370 nM) for the wild-type GCN4 recognition sequence (ATGAcTCAT). The presence of only half the consensus DNA sequence (ATGAcgGGCC) shifts the K(D) value to more than 2500 nM and the chimera does not bind specifically to DNA sequences with no target recognition sites. Ultracentrifugation revealed that the holoprotein-DNA complex is formed with a 1:1 stoichiometry, which indicates that a higher-order protein aggregate is not responsible for DNA binding. Mutagenesis of a loop linking helices 2 and 3 of the cytochrome results in a chimera with a haem-dependent DNA binding affinity. This is the first demonstration that binding of a haem group to a designed monomeric protein can allosterically modulate the DNA binding affinity.     

Direct binding of a redox protein for single-molecule electron transfer measurements

An electron transfer protein is engineered with two thiol groups introduced at different positions in the molecular structure to allow robust binding to two gold electrodes. Atomic force microscopy and scanning tunneling microscopy single-molecule studies show that the engineered proteins: (1) bind to a gold electrode in defined orientation dictated by the thiol-pair utilised, and (2) have a higher conductance than the wild-type proteins indicating a more efficient electron transmission due to the strong gold-thiol contacts.     

强保留固定相的色谱特性

在新方法的发展过程当中,色谱方法最重要的目标之一是得到具有一致性且可重现的分离。选取具有高重现性和良好性能的高效液相色谱（HPLC）柱是实现这一目标最基本的要素。对装入HPLC柱的色谱介质进行物理测试毋庸置疑也是非常重要的,该测试可以揭示HPLC柱的部分色谱特性。柱的本身特性以及如何与一个宽范围的分析物相互作用只能通过严格的色谱评估来获得。     

Comparative proteomic analysis of low stage and high stage endometrioid ovarian adenocarcinomas

Ovarian cancer, the second most common gynecological malignancy, accounts for 3% of all cancers among women in the United States, and has a high mortality rate, largely because existing therapies for widespread disease are rarely curative. Ovarian endometrioid adenocarcinoma (OEA) accounts for about 20% of the overall incidence of all ovarian cancer. We have used proteomics profiling to characterize low stage (FIGO stage 1 or 2) versus high stage (FIGO stage 3 or 4) human OEAs. In general, the low stage tumors lacked p53 mutations and had frequent CTNNB1, PTEN, and/or PIK3CA mutations. The high stage tumors had mutant p53, were usually high grade, and lacked mutations predicted to deregulate Wnt/β‐catenin and PI3K/Pten/Akt signaling. We utilized 2‐D liquid‐based separation/mass mapping techniques to elucidate molecular weight and pI measurements of the differentially expressed intact proteins. We generated 2‐D protein mass maps to facilitate the analysis of protein expression between both the low stage and high stage tumors. These mass maps (over a pI range of 5.6–4.6) revealed that the low stage OEAs demonstrated protein over‐expression at the lower pI ranges (pI 4.8–4.6) in comparison to the high stage tumors, which demonstrated protein over‐expression in the higher pI ranges (pI 5.4–5.2). These data suggest that both low and high stage OEAs have characteristic pI signatures of abundant protein expression probably reflecting, at least in part, the different signaling pathway defects that characterize each group. In this study, the low stage OEAs were distinguishable from high stage tumors based upon the proteomic profiles. Interestingly, when only high‐grade (grade 2 or 3) OEAs were included in the analysis, the tumors still tended to cluster according to stage, suggesting that the altered protein expression was not solely dependent upon tumor cell differentiation. Further, these protein profiles clearly distinguish OEA from other types of ovarian cancer at the protein level.     

An investigation into the preparation of polyorganosiloxane materials from olivine

Modification of the Lentz trimethylsilylation technique was used to synthesize Q_xM_y and Q_xM_y(OH)₂ polyorganosiloxanes from olivine (Q = SiO_4/2, M = (Me₃SiO_1/2). The products ranged from viscous mobile liquids to hydrophobic insoluble solids with a molecular weight distribution between 3 × 10³ and 400 × 10³ depending on the time of addition of silylating agent, hexamethyldisiloxane (MM), to the preformed silicic acids. The stabilisation of the silicic acids leached from olivine was controlled by varying the period of silicic acid condensation-polymerisation reactions and their solution concentration. The absence of the phase transfer agent propan-2-ol from the modified trimethylsilylation reaction resulted in the formation of silica gel. Propan-2-ol, by associating with silicic acids leached from olivine, produced a stable pre-polymer suspension consisting of partially capped silicic acids.     

Towards an unrestricted domain TTS system for African tone languages

In this paper we discuss the procedural problems, issues and challenges involved in developing a generic speech synthesizer for African tone languages. We base our development methodology on the “MultiSyn” unit-selection approach, supported by Festival Text-To-Speech (TTS) Toolkit for Ibibio, a Lower Cross subgroup of the (New) Benue-Congo language family widely spoken in the southeastern region of Nigeria. We present in a chronological order, the several levels of infrastructural and linguistic problems as well as challenges identified in the Local Language Speech Technology Initiative (LLSTI) during the development process (from the corpus preparation and refinement stage to the integration and synthesis stage). We provide solutions to most of these challenges and point to possible outlook for further refinement. The evaluation of the initial prototype shows that the synthesis system will be useful to non-literate communities and a wide spectrum of applications.     

Structure-Guided Engineering of a Family IV Cold-Adapted Esterase Expands Its Substrate Range

Cold active esterases have gained great interest in several industries. The recently determined structure of a family IV cold active esterase (EstN7) from Bacillus cohnii strain N1 was used to expand its substrate range and to probe its commercially valuable substrates. Database mining suggested that triacetin was a potential commercially valuable substrate for EstN7, which was subsequently proved experimentally with the final product being a single isomeric product, 1,2-glyceryl diacetate. Enzyme kinetics revealed that EstN7’s activity is restricted to C2 and C4 substrates due to a plug at the end of the acyl binding pocket that blocks access to a buried water-filled cavity. Residues M187, N211 and W206 were identified as key plug forming residues. N211A stabilised EstN7 allowing incorporation of the destabilising M187A mutation. The M187A-N211A double mutant had the broadest substrate range, capable of hydrolysing a C8 substrate. W206A did not appear to have any significant effect on substrate range either alone or when combined with the double mutant. Thus, the enzyme kinetics and engineering together with a recently determined structure of EstN7 provide new insights into substrate specificity and the role of acyl binding pocket plug residues in determining family IV esterase stability and substrate range.