Methyl groups as probes for proteins and complexes in in-cell NMR experiments

Studying protein components of large intracellular complexes by in-cell NMR has so far been impossible because the backbone resonances are unobservable due to their slow tumbling rates. We describe a methodology that overcomes this difficulty through selective labeling of methyl groups, which possess more favorable relaxation behavior. Comparison of different in-cell labeling schemes with three different proteins, calmodulin, NmerA, and FKBP, shows that selective labeling with [(13)C]methyl groups on methionine and alanine provides excellent sensitivity with low background levels at very low costs.     

Optimizing the monomer structure of polyhedral oligomeric silsesquioxane for ion transport in hybrid organic–inorganic block copolymers

Poly(ethylene oxide)-b-polyhedral oligomeric silsesquioxane (PEO–POSS) mixed with lithium bis(trifluoromethanesulfonyl)imide salt is a nanostructured hybrid organic–inorganic block copolymer electrolyte that may enable lithium metal batteries. The synthesis and characteristics of three PEO–POSS block copolymer electrolytes which only differ by their POSS silica cage substituents (ethyl, isobutyl, and isooctyl) is reported. Changing the POSS monomer structure results in differences in both thermodynamics and ion transport. All three neat polymers exhibit lamellar morphologies. Adding salt results in the formation of a disordered window which closes and gives way to lamellae at higher salt concentrations. The width of disordered window decreases with increasing length of the POSS alkyl chain substituent from ethyl to isobutyl and is absent in the isooctyl sample. Rheological measurements demonstrate good mechanical rigidity when compared with similar all-organic block copolymers. While salt diffusion coefficient and current ratio are unaffected by substituent length, ionic conductivity increases as the length of the alkyl chain substituent decreases: the ethyl substituent is optimal for ion transport. This is surprising because conventional wisdom suggests that ion transport occurs primarily in the PEO-rich domains, that is, ion transport should be unaffected by substituent length after accounting for the minor change in conducting phase volume fraction. © 2020 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2020 © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 363–371     

智能传感器接口的优势

采用智能化更高的传感器接口能将16位的高性能CPU与16位ADC的处理功能相结合,从而大幅简化设计工作,尤其是在集成解决方案体积较小、价格较低的时候更是如此。本文将重点介绍上述数据采集系统架构的各种优势,其中包括更低功耗、更小体积、更少的主机CPU负载、功能齐备以及传输中可配置性等。     

The phase behavior of a polymer‐fullerene bulk heterojunction system that contains bimolecular crystals

Polymer:fullerene blends have been widely studied as an inexpensive alternative to traditional silicon solar cells. Some polymer:fullerene blends, such as blends of poly(2,5‐bis(3‐tetradecylthiophen‐2‐yl)thieno[3,2‐b]thiophene (pBTTT) with phenyl‐c71‐butyric acid methyl ester (PC₇₁BM), form bimolecular crystals due to fullerene intercalation between the polymer side chains. Here we present the determination of the eutectic pBTTT:PC₇₁BM phase diagram using differential scanning calorimetry (DSC) and two‐dimensional grazing incidence X‐ray scattering (2D GIXS) with in‐situ thermal annealing. The phase diagram explains why the most efficient pBTTT:PC₇₁BM solar cells have 75–80 wt % PC₇₁BM since these blends lie in the center of the only room‐temperature phase region containing both electron‐conducting (PC₇₁BM) and hole‐conducting (bimolecular crystal) phases. We show that intercalation can be suppressed in 50:50 pBTTT:PC₇₁BM blends by using rapid thermal annealing to heat the blends above the eutectic temperature, which forces PC₇₁BM out of the bimolecular crystal, followed by quick cooling to kinetically trap the pure PC₇₁BM phase. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Analysis of on- and off-line optimized predictive currentcontrollers for PWM converter systems

The problem of on-off current control for coupling of a DC voltage system with a three-phase (polyphase) AC voltage system via a pulsewidth modulated (PWM) converter is discussed. The AC voltage represents either the counter EMF (electromotive force) of an AC machine or the three-phase power supply system (mains). The following control concepts are investigated by digital computer simulation: a simple hysteresis controller; a predictive controller with online optimization (optimization with respect to minimum switching frequency); and a controller based on offline optimization (using a switching table). It is shown that the relatively involved predictive controller can be replaced by a switching table of very limited size. For rating of the treated controllers the switching frequency as a function of the RMS voltage of the AC system and the other system parameters is used     

A new McMurray-type inverter with asymmetric SCR's

The standard, simple McMurray inverter is improved in three steps. The first step, adding recharging and energy feedback pulses, keeps the inverter operating satisfactorily at low loads and also limits overcharging of the commutation capacitor. The second step involves replacing the standard LC ringing circuit (for commutation) by a long line which has to be approximated by concentrated elements. This changes the sinusoidal commutation current pulse to a rectangular shape and eliminates wasted time due to the rise of the sine wave in the standard circuit. The system therefore needs only 70% of the commutation time required for the standard system, so that about 1.4 times higher pulse frequencies can be realized. The third step, using newly developed asymmetric silicon-controlled rectifiers (ASCRs), is made possible by the structure of the improved inverter, where diodes are used in antiparallel to the main thyristors. The ASCRs require about 1/3 of the turn-off time of conventional thyristors. Altogether, inverter output frequencies of up to 1.4×3=4.2 times the frequencies achievable with conventional means were obtained     

Aberration correction and its automatic control in scanning electron microscopes

An automatic aberration correction method has been implemented in scanning electron microscopes (SEM). Necessity of the automatic aberration correction is discussed. The procedure of the automatic aberration correction is explained in detail, where deconvolution techniques are used in order to extract probe information from SEM images. Due to the precise digitization and the usage of proper combinations of correction fields, linearity has been found between the amplitude of each aberration and the corresponding field strength. Experimental results are shown which demonstrate that the aberrations are corrected automatically by a linear feedback control method. After the automatic aberration correction, the image quality has been improved drastically.     

Direct three-phase single-stage flyback-type power factor corrector

Based on the work of Hui and Chung (see ibid., vol. 33, no. 15, p.1274-76, 1997) a three-phase converter system consisting of three single-phase flyback-type AC/DC converter modules in star-connection is proposed and investigated     

A novel multicell DC-AC converter for applications in renewable energy systems

This paper presents a novel DC-AC converter for applications in the area of distributed energy generation systems, e.g., solar power systems, fuel-cell power systems in combination with supercapacitor or battery energy storage. The proposed converter is realized using an isolated multicell topology where the total AC output of the system is formed by series connection of several full-bridge converter stages. The DC links of the full bridges are supplied by individual DC-DC isolation stages which are arranged in parallel concerning the dc input of the. total system. Therefore, all switching cells of the proposed converter can be equipped with modern low-voltage high-current power MOSFETs, which results in an improved efficiency as compared to conventional isolated DC-AC converters. Furthermore, the cells are operated in an interleaved pulsewidth-modulation mode which, in connection with the low voltage level of each cell, significantly reduces the filtering effort on the AC output of the overall system. The paper describes the operating principle, analyzes the fundamental relationships which are relevant for component selection, and presents a specific circuit design. Finally, measurements taken from a 2-kW laboratory model are presented.