ATRP grafting from silica surface to create first and second generation of grafts

Summary (11'-Chlorodimethylsilylundecyl)-2-chloro-2-phenylacetate 2 as an atom transfer radical polymerisation (ATRP) initiator was bound covalently to the surface of silica. ATRP grafting of styrene monomer from the silica surface was achieved and the grafts were detached from the solid particles for analysis. It is shown that after polymerisation of a first generation of grafts and work-up of the thus grafted silica the chain ends of the grafts are still active to initiate a second monomer feed to further chain growth. Received: 17 July 1999/Revised version: 12 December 1999/Accepted: 10 January 2000     

针对EDGE网络设计的B5PL极性环射频发射器架构

EDGE技术采用高效的8PSK(8进制相移键控)调制码方案,然而这也令为GSM手机设计出合适的射频芯片架构的工作变得愈加复杂。与GMSK(高斯滤波最小频移键控)发射器不同的是,EDGE收发器必须在全部功率电平范围内满足线性要求。本文讲述了一个像极性环(Polar Loop)这样的反馈系统是如何达到所需要的线性化效果的。B5PL是一种基于极性环的射频芯片,它能够使功率放大器工作在一个高效的模式下。极性环具有预失真相位和幅度信号能力,能够有效补偿由功率放大器导入的AM-AM和AM-PM失真。射频芯片和功放模块组成一个紧凑的系统解决方案,能够解决其他射频架构不能解决的所有问题。B5PL具有低接收频带噪声、功率控制线性化、精确幅度跟踪、低寄生内容、极低的负载偏移灵敏度,发射VCO(压控振荡器)锁相等很多特性。现在,B5PL是符合所有3GPP技术规范的一种相当流行的射频产品并且已经经过了FTA认证。     

Pipelined architecture for fast CMOS buffer RAMs

A novel pipeline architecture for CMOS static RAMs (SRAMs) that allows operation at very high clock rates is described. Basic requirements for achieving high speed are the implementation of a hierarchical architecture and a memory cell with separate READ and WRITE data lines. The access speed of hierarchically organized memory blocks was between 2.5 and 3.5 ns. The maximum operating frequency of a 16 K pipelined hierarchical SRAM (PHSRAM) is in the range of 300 MHz. The hierarchical architecture and a seven-transistor memory cell provide a circuit using digital swings all over. Key advantages of the full-swing static logic circuitry are robustness with respect to fabrication tolerances and a high-noise immunity. Moreover, the circuit can be reduced to finer structure sizes without any redesign, since there are no critical analog circuit parts     

Results of pathological-anatomical studies of limbs and spinal column

The pathomorphological study was carried out on a total of 360 broiler chicken which had been random-sampled on days 22 and 35 of the mast period, respectively, from those flocks that were to be compared. Furthermore, 161 animals with evidence of movement disturbance that were slaughtered in the last two mast weeks, were also evaluated. With regard to incidence, severity of movement disturbance and the spectrum of pathomorphological changes of the skeleton there were no differences between the different groups. When histological and morphometrical methods were applied, no differences in the skeleton structure were noted between flocks with conventional housing and flocks with reduced population density. Equally, no differences were ascertained with regard to dry substance and ash content of the bones including the minerals calcium and phosphorus. Furthermore, there were no group differences in serum calcium, phosphorus and alkaline phosphatase. In numerous chicken from all groups a plantar pododermatitis with differing incidence and strongly varying intensity was observed. The lesions were characterized by a papillomatous proliferation of the basal epithelial layers. There was widespread inflammation with loss of the epithelial layer and deep necroses of the sole. A latent infection with papilloma viruses is discussed. About 90% of the random-sampled chicken of all groups showed bending of the vertebral column by 20 degrees at the height of the 6th thoracic vertebra. In numerous chicken the 6th thoracic vertebra was dislocated and slightly rotated which caused encroachment of the vertebral canal. Whether this alteration may be responsible for the frequently observed movement disturbance of broilers in the last third of the mast period can not be decided on the basis of the pathomorphological study. In any case it must be assumed that both the pododermatitis and the bending and encroachment of the vertebral column cause pain. Thus, both lesions should be evaluated from the viewpoint of animal protection.     

Time-resolved fluorescence imaging of slab gels for lifetime base-calling in DNA sequencing applications

A compact time-resolved near-IR fluorescence imager was constructed to obtain lifetime and intensity images of DNA sequencing slab gels. The scanner consisted of a microscope body with f/1.2 relay optics onto which was mounted a pulsed diode laser (repetition rate 80 MHz, lasing wavelength 680 nm, average power 5 mW), filtering optics, and a large photoactive area (diameter 500 microns) single-photon avalanche diode that was actively quenched to provide a large dynamic operating range. The time-resolved data were processed using electronics configured in a conventional time-correlated single-photon-counting format with all of the counting hardware situated on a PC card resident on the computer bus. The microscope head produced a timing response of 450 ps (fwhm) in a scanning mode, allowing the measurement of subnano-second lifetimes. The time-resolved microscope head was placed in an automated DNA sequencer and translated across a 21-cm-wide gel plate in approximately 6 s (scan rate 3.5 cm/s) with an accumulation time per pixel of 10 ms. The sampling frequency was 0.17 Hz (duty cycle 0.0017), sufficient to prevent signal aliasing during the electrophoresis separation. Software (written in Visual Basic) allowed acquisition of both the intensity image and lifetime analysis of DNA bands migrating through the gel in real time. Using a dual-labeling (IRD700 and Cy5.5 labeling dyes)/two-lane sequencing strategy, we successfully read 670 bases of a control M13mp18 ssDNA template using lifetime identification. Comparison of the reconstructed sequence with the known sequence of the phage indicated the number of miscalls was only 2, producing an error rate of approximately 0.3% (identification accuracy 99.7%). The lifetimes were calculated using maximum likelihood estimators and allowed on-line determinations with high precision, even when short integration times were used to construct the decay profiles. Comparison of the lifetime base calling to a single-dye/four-lane sequencing strategy indicated similar results in terms of miscalls, but reduced insertion and deletion errors using lifetime identification methods, improving the overall read accuracy.