Design of a Purlin System

This paper is concerned with the design of cold-formed steel structural members which span between the frames of a building and carry cladding which is usually either single- or double-skin profiled metal sheeting or a sandwich panel. The cladding is fIxed to these purlins or sheeting rails at regular intervals and the performance in service, and therefore the design, is strongly influenced by interaction with the sheeting. The connection between the purlins and the supporting structure also has a significant influence on performance so that, historically, the emphasis has tended to be on empirical methods of design rather than detailed calculations of the structural behaviour. In a previous paper[1], the fIrst author described the design of a purlin system, known as Multibeam Mark 2, based on a cold-formed steel Sigma profile. The alternative approaches to design were reviewed and a semi-empirical design procedure was described which resulted in safe but competitive load-span tables. This paper describes the design of Multibeam Mark 3. This involves a further evolution of the cross-section together with further improvement of the design procedure. The tendency is to continue to move away from reliance on testing and towards an approach which is much more orientated towards design by calculation, a trend which is becoming increasingly necessary in view of the proliferation of different cladding types, all offering different degrees of restraint to the purlin. It is shown that, in the present state-of-the-art, a design procedure based entirely on calculation, while taking into account such practical factors as restraint from alternative cladding systems and distortion and partial plasticity at internal supports, is now feasible. However, as the profession may not yet be ready for such a radical approach, the design procedure used for Multibeam Mark 3 is backed up by a comprehensive test programme

De novo assembly of potential linear artificial chromosome constructs capped with expansive telomeric repeats

<p>Abstract</p> <p>Background</p> <p>Artificial chromosomes (ACs) are a promising next-generation vector for genetic engineering. The most common methods for developing AC constructs are to clone and combine centromeric DNA and telomeric DNA fragments into a single large DNA construct. The AC constructs developed from such methods will contain very short telomeric DNA fragments because telomeric repeats can not be stably maintained in <it>Escherichia coli</it>.</p> <p>Results</p> <p>We report a novel approach to assemble AC constructs that are capped with long telomeric DNA. We designed a plasmid vector that can be combined with a bacterial artificial chromosome (BAC) clone containing centromeric DNA sequences from a target plant species. The recombined clone can be used as the centromeric DNA backbone of the AC constructs. We also developed two plasmid vectors containing short arrays of plant telomeric DNA. These vectors can be used to generate expanded arrays of telomeric DNA up to several kilobases. The centromeric DNA backbone can be ligated with the telomeric DNA fragments to generate AC constructs consisting of a large centromeric DNA fragment capped with expansive telomeric DNA at both ends.</p> <p>Conclusions</p> <p>We successfully developed a procedure that circumvents the problem of cloning and maintaining long arrays of telomeric DNA sequences that are not stable in <it>E. coli</it>. Our procedure allows development of AC constructs in different eukaryotic species that are capped with long and designed sizes of telomeric DNA fragments.</p

Liver transplantation in mainland China: the overview of CLTR 2011 annual scientific report

China Liver Transplant Registry (CLTR) is the official national liver transplant registry in Mainland China that has been authorized by the National Health and Family Planning Commission of the People's Republic of China (NHFPC) and serves for both regulatory and scientific purposes. The CLTR 2011 annual scientific reports released national statistics describing current status of liver transplant (LT) in China. This article, as an accompanying document of CLTR 2011 annual scientific report, provides an overview of scientific results for LT in China. Up to December 2011, a total number of 20,877 LT performed during 1980-2011 in 81 certified transplant centers had been reported to CLTR. Of these donated livers, 92.63% were procured from deceased donors (N=19,338) and 7.37% were from living donors (N=1,539). In March 2010, the pilot project of the new deceased organ donation was initiated. From the initiation of the pilot program to the end of 2011, there were 115 LT (0.55% of all LT) using the liver grafts from Chinese categories donors. The recipient post-transplant survival had been significantly improved over years. The median post-transplant follow-up was 14.74 months, of which the longest follow-up time was 192.47 months. The 1-year, 3-year and 5-year cumulative survival rate for all recipients was 77.97%, 65.38% and 60.53%, respectively.published_or_final_versio

Neurochemical characterization of pERK-expressing spinal neurons in histamine-induced itch

Date of Acceptance: 08/07/2015 Acknowledgements This work was supported by grants from the Ministry of Science and Technology of China (2012CB966904, 2011CB51005), National Natural Science Foundation of China (31271182, 81200692, 91232724, 81200933, 81101026), Shanghai Natural Science Foundation (12ZR1434300), Key Specialty Construction Project of Pudong Health Bureau of Shanghai (PWZz2013-17), Shenzhen Key Laboratory for Molecular Biology of Neural Development (ZDSY20120617112838879), Fundamental Research Funds for the Central Universities (1500219072) and Sino-UK Higher Education Research Partnership for PhD Studies.Peer reviewedPublisher PD

Mechanisms of grain refinement by intensive shearing of AZ91 alloy melt

The official published version of the article can be accessed at the link below.It has been demonstrated recently that intensive melt shearing can be an effective approach to the grain refinement of both shape casting and continuous casting of Mg alloys. In the present study, the mechanisms of grain refinement by intensive melt shearing were investigated through a combination of both modelling and experimental approaches. The measurement of the cooling curves during solidification, quantification of grain size of the solidified samples, and image analysis of the MgO particle size and size distribution in the pressurized filtration samples were performed for the AZ91 alloy with and without intensive melt shearing. The experimental results were then used as input parameters for the free growth model to investigate the mechanisms of grain refinement by intensive melt shearing. The experimental results showed that, although intensive melt shearing does not change the nucleation starting temperature, it increases the nucleation finishing temperature, giving rise to a reduced nucleation undercooling. The theoretical modelling using the free growth model revealed quantitatively that intensive melt shearing can effectively disperse MgO particles densely populated in the oxide films into more individual particles in the alloy melt, resulting in an increase in the MgO particle density by three orders of magnitude and the density of active nucleating MgO particles by a factor of 20 compared with those of the non-sheared melt. Therefore, the grain refining effect of intensive melt shearing can be confidently attributed to the significantly increased refining efficiency of the naturally occurring MgO particles in the alloy melt as potent nucleation sites.Financial support under Grant EP/H026177/1 from the EPSRC

Generation of Ultrastable Microwaves via Optical Frequency Division

There has been increased interest in the use and manipulation of optical fields to address challenging problems that have traditionally been approached with microwave electronics. Some examples that benefit from the low transmission loss, agile modulation and large bandwidths accessible with coherent optical systems include signal distribution, arbitrary waveform generation, and novel imaging. We extend these advantages to demonstrate a microwave generator based on a high-Q optical resonator and a frequency comb functioning as an optical-to-microwave divider. This provides a 10 GHz electrical signal with fractional frequency instability <8e-16 at 1 s, a value comparable to that produced by the best microwave oscillators, but without the need for cryogenic temperatures. Such a low-noise source can benefit radar systems, improve the bandwidth and resolution of communications and digital sampling systems, and be valuable for large baseline interferometry, precision spectroscopy and the realization of atomic time

Spectral Line-by-Line Pulse Shaping of an On-Chip Microresonator Frequency Comb

We report, for the first time to the best of our knowledge, spectral phase characterization and line-by-line pulse shaping of an optical frequency comb generated by nonlinear wave mixing in a microring resonator. Through programmable pulse shaping the comb is compressed into a train of near-transform-limited pulses of \approx 300 fs duration (intensity full width half maximum) at 595 GHz repetition rate. An additional, simple example of optical arbitrary waveform generation is presented. The ability to characterize and then stably compress the frequency comb provides new data on the stability of the spectral phase and suggests that random relative frequency shifts due to uncorrelated variations of frequency dependent phase are at or below the 100 microHertz level.Comment: 18 pages, 4 figure