Infrared temperature control system for a completely noncontact polymerase chain reaction in microfluidic chips

A completely noncontact temperature system is described for amplification of DNA via the polymerase chain reaction (PCR) in glass microfluidic chips. An infrared (IR)-sensitive pyrometer was calibrated against a thermocouple inserted into a 550-nL PCR chamber and used to monitor the temperature of the glass surface above the PCR chamber during heating and cooling induced by a tungsten lamp and convective air source, respectively. A time lag of less than 1 s was observed between maximum heating rates of the solution and surface, indicating that thermal equilibrium was attained rapidly. Moreover, the time lag was corroborated using a one-dimensional heat-transfer model, which provided insight into the characteristics of the device and environment that caused the time lag. This knowledge will, in turn, allow for future tailoring of the devices to specific applications. To alleviate the need for calibrating the pyrometer with a thermocouple, the on-chip calibration of pyrometer was accomplished by sensing the boiling of two solutions, water and an azeotrope, and comparing the pyrometer output voltage against the known boiling points of these solutions. The "boiling point calibration" was successful as indicated by the subsequent chip-based IR-PCR amplification of a 211-bp fragment of the B. anthracis genome in a chamber reduced beyond the dimensions of a thermocouple. To improve the heating rates, a parabolic gold mirror was positioned above the microfluidic chip, which expedited PCR amplification to 18.8 min for a 30-cycle, three-temperature protocol.     

Optical determination of thallium(I) and cesium(I) with a fluorogenic calix[4]arenebis(crown-6 ether) containing one pendent dansyl group

A fluorogenic derivative of 1,3-alternate calix[4]arenebis(crown-6) (1) containing a dansyl group in the proton-ionizable side arm has been employed in selective sensing of Tl+ and Cs+ at low concentration levels in MeCN-H2O (1:1) mixed solvent. Optical recognition of these two metal cations by 1 occurs in contrasting modes. On the basis of the results of fluorescence, matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), and 1H NMR studies, Tl+ and Cs+ react with 1 via formation of 1:1 complexes that differ in coordination arrangement around the metal ion.     

Study of mechanical degradation of UHMWPE acetabular components due to clinical X-ray procedures

The use of multi-component femoral implants to replace the femur head and re-establish bone motion has been widespread since the 70s. Frequently these implants have spherical metallic heads made of, for example, 316-L stainless steel or Cr–Co alloys, which allow rotational motion towards a polymeric component (UHMWPE). One of the major causes of implant rejection is the generation of UHMWPE debris on the surface between the implant head and the polymeric component. The gamma ray sterilization of implants and the periodical X-ray medical control could contribute to premature degradation of the polymeric surface, resulting in increased wear and shortened lifetime of the implant. In this work we study the degradation degree of the polymeric UHMWPE component as function of the X-ray dose. The elasto-plastic deformation and recovery were carried out by means of a nanohardness tester equipment and the polymer degradation was measured using a fast Fourier transform infra-red (FT-IR) equipment. The results show the compromise among the irradiation doses, the surface oxidation and the mechanical properties of the samples.     

Design and facile production of recombinant resilin-like polypeptides: gene construction and a rapid protein purification method

Resilin is an elastic protein found in specialized regions of the cuticle of insects, which displays unique resilience and fatigue lifetime properties. As is the case with many elastomeric proteins, including elastin, gliadin and spider silks, resilin contains distinct repetitive domains that appear to confer elastic properties to the protein. Recent work within our laboratory has demonstrated that cloning and expression of exon 1 of the Drosophila melanogaster CG15920 gene, encoding a putative resilin-like protein, results in a recombinant protein that can be photochemically crosslinked to form a highly resilient, elastic biomaterial (Rec1 resilin). The current study describes a recursive cloning strategy for generating synthetic genes encoding multiple copies of consensus polypeptides, based on the repetitive domains within resilin-like genes from D. melanogaster and Anopheles gambiae. A simple non-chromatographic purification method that can be applied to these synthetic proteins and Rec1 is also reported. These methods for the design and purification of resilin-like periodic polypeptides will facilitate the future investigation of structural and functional properties of resilin, and the development of novel highly resilient biomaterials.     

The vocational hygienic training of the food industry at present

In article the problem of vocational hygienic training of the food industry workers is presented. Offers on perfection of this work are given.     

Global leaf companies control the tobacco market in Malawi

Objective

To examine the influence of US‐based tobacco leaf‐buying companies, Universal Corporation and Alliance One International, on Malawi''s economy and trade policy in 2000–6.

Design

Analyses of ethnographic data and tobacco industry documents.

Results

Universal Corporation and Alliance One International, through their subsidiary companies Limbe Leaf and Alliance One, respectively, in Malawi, control policy‐making advisory groups and operate a tobacco cartel to influence Malawi''s economic and trade sectors. Limbe Leaf''s corporate secretary and lawyer is a member of several policy‐making committees that advise the Malawi government on tobacco‐related trade policy. The corporate representative''s presence prevents other committee members from taking positions against the tobacco industry and ensures government policy that advances industry interests to obtain low‐cost tobacco. The World Bank and Malawi''s Anti‐corruption Bureau report allegations of collusion between Limbe Leaf and Alliance One over prices at tobacco markets. Allegations of collusion between Limbe Leaf and Alliance One prompted Malawi President Bingu Mutharika in 2006 to warn the companies to end non‐competitive practices or leave the country, but there was no meaningful follow‐up action. Findings from interviews with small‐scale tobacco traders in Malawi suggest that Universal and Alliance One International purchase smuggled raw tobacco from the neighbouring countries, Zambia and Mozambique, undermining growers'' efforts to benefit from tobacco farming in Malawi.

Conclusion

These actions restrict competition, depress tobacco prices for Malawi''s farmers and contribute to poverty in Malawi, while keeping the country dependent on tobacco growing.Malawi (fig 1​1)) is the 13th poorest country in the world.¹ In all, 76% of Malawians, survive on less than US$2 (£1.02, €150) per day.¹ Malawi derives 65% of its foreign earnings from tobacco, making Malawi the most tobacco‐reliant country in the world.² Tobacco accounts for 43% of the agricultural gross domestic product,³ 13% of the overall gross domestic product⁴ and 23% of Malawi''s total tax base.⁴ Out of a total workforce of 5 million people, between 600 000 and 2 million people are employed in Malawi''s tobacco sector.⁵ Land devoted to tobacco growing in Malawi occupies 122 000 hectares out of 4.6 million hectares under cultivation.^6,7 Over 98% of Malawi''s leaf (mostly burley tobacco^8,9) is exported to 68 countries,^3,5,10 with the European Union (EU; 44% of exports) and US (13% of exports) being the top destinations.¹¹ US‐based leaf‐buying companies Universal Corporation and Alliance One International purchase Malawi''s tobacco and sell it to Philip Morris and British American Tobacco (BAT).Open in a separate windowFigure 1 Malawi is a landlocked country that transports its tobacco overland to ports in Mozambique and South Africa. Smuggling raw tobacco occurs in both directions along Malawi''s borders with Zambia and Mozambique (shaded area).Tobacco Journal International, a tobacco industry trade publication, reported in September 2006 that low and uncertain tobacco prices in Malawi created friction between tobacco farmers and leaf‐ buying companies.^12,13 This trade publication, however, did not analyse the role of leaf companies, through their buying practices, in influencing tobacco prices or identify the cigarette manufacturers as the beneficiaries of Malawi''s low and uncertain tobacco prices. Our study goes beyond the Tobacco Journal International report to reveal how leaf companies and manufacturers hide behind explanations of supply and demand to deflect discussion on tobacco sectors and public dialogue on tobacco prices in Malawi from the economic practices of leaf companies and manufacturers to market forces. The purpose of this paper is to show the ways Universal and Alliance One, the main buyers of Malawi''s tobacco, control the local tobacco sector, influence Malawi''s trade policy to ensure access to low‐cost raw tobacco and depress raw tobacco prices, preventing Malawi from benefiting from tobacco growing.     

Size and surface effects on the MRI relaxivity of manganese ferrite nanoparticle contrast agents

Superparamagnetic MnFe2O4 nanocrystals of different sizes were synthesized in high-boiling ether solvent and transferred into water using three different approaches. First, we applied a ligand exchange in order to form a water soluble polymer shell. Second, the particles were embedded into an amphiphilic polymer shell. Third, the nanoparticles were embedded into large micelles formed by lipids. Although all approaches lead to effective negative contrast enhancement, we observed significant differences concerning the magnitude of this effect. The transverse relaxivity, in particular r2*, is greatly higher for the micellar system compared to the polymer-coated particles using same-sized nanoparticles. We also observed an increase in transverse relaxivities with increasing particle size for the polymer-coated nanocrystals. The results are qualitatively compared with theoretical models describing the dependence of relaxivity on the size of magnetic spheres.     

利用光束偏移技术使显微镜分辨率超出瑞利分辨极限

新近问世的两个荧光显微系统声称其所达到的分辨率已突破瑞利分辨极限。这两个系统工作时运用两束聚焦于样品上的偏移光束,并成像于光重叠区域。本文介绍一个与之相类似的系统,其工作方式也相近,但不用荧光,对这些系统的成像性能进行分析后,作者发现尽管它们的分辨率都有所改进,但关键的是光波带宽并未得到增加。尽管这些系统应用效果良好,并且其工作方式与光瞳面滤光器相似,但这些系统仅只衰减了空间频率,值得鉴赏的是,与以前的论文内容相反,这两系统都未提及真正的超限分辨率这一点重要。     

Sorption of phthalate esters and PCBs in a marine ecosystem

Dialkyl phthalate esters (DPEs) are widely used industrial chemicals with octanol-seawater partition coefficients ranging between 10(1.80) for dimethyl phthalate to 10(10.0) for diiso-decyl phthalate, indicating a propensity to sorb strongly to particulate matter in aquatic environments. Sorption plays a key role in controlling the long-term fate of DPEs in aquatic systems and exposure to organisms in aquatic food-webs. However, field observations of the sorption of many commercial DPEs do not exist. To characterize the sorptive nature of DPEs in a real-world aquatic ecosystem, we measured concentrations of DPEs congeners, commercial DPE mixtures, and 10 polychlorinated biphenyls (PCBs) in water, suspended sediments, and bottom sediments of a marine inlet. Sorption coefficients of spiked and native DPEs and PCBs between suspended sediments and water indicate that the apparent sorptive nature of DPEs and PCBs is substantially greater than expected from K(ow)-based sorption models. Particulate and dissolved organic matter showed similar (i.e., not statistically different) sorption affinities for native analytes. The apparent fraction of the total aqueous concentration of DPEs that is freely dissolved and absorbable via the respiratory tract of aquatic organisms varied from virtually 100% for DMP to 0.0003% for C10. The observed decline in concentration of most DPEs between suspended and bottom sediments, compared to an increase in the concentration of high Kow PCBs, suggests that the rate of desorption and degradation of DPEs exceeds that of organic carbon mineralization and contributes to the previously observed lack of biomagnification of DPEs in the aquatic food-web of this system.     

In vivo prediction of carcass composition and muscularity in purebred Texel lambs

A subjective assessment of the shape of the hind limb of purebred Texel lambs was evaluated as an in vivo predictor of carcass composition and muscularity. Lambs were taken from two flocks that were managed in a common environment, but which had either been selected for lean tissue growth rate or for improved conformation. Lambs were slaughtered at a mean age of 139 days at the end of an 11 week performance test in which they were reared indoors on a concentrate diet. Pre-slaughter measurements of live weight and ultrasonic muscle (UMD) and fat (UFD) depths at the position of the third lumbar vertebra, body length (L) and a subjective leg shape score were recorded. After slaughter, measurements were recorded for carcass side length (SL), leg length (T) and the maximum width (A) and depth (B) of the longissimus thoracis and lumborum (LTL) muscle. The side was fully dissected and various muscle weights and skeletal dimensions were used to calculate indices of muscularity as √(muscle weight/length) per unit length or as UMD/L, A/SL or B/SL. The leg shape score was positively correlated with lean weight (0.23) and proportion (0.24), lean:bone ratio (0.25), measures of LTL dimensions (0.27-0.38) and muscularity traits (0.27-0.57) but was not significantly (P>0.05) correlated with fat weights or proportions in the carcass. Live weight was the best single predictor of lean weight (RSD=0.403) and the addition of leg shape score (RSD=0.381) to prediction equations was less effective than the inclusion of UMD and UFD in combination (RSD=0.357). The addition of leg shape score to equations that included ultrasonic traits gave a significant (P<0.05) but marginal improvement in prediction (RSD=0.347). The leg shape score was the most useful in vivo predictor of carcass muscularity traits and, with R(2) in the range 0.30-0.50, had comparable predictive power to a leg muscularity score derived from muscle weight and femur length. It is concluded that the leg shape score showed potential as a predictor of carcass muscularity that was largely independent of live weight and fatness at a fixed age and was marginally associated with superior lean yield and lean:bone ratio.