Modifying the electronic properties of single-walled carbon nanotubes using designed surfactant peptides

The electronic properties of carbon nanotubes can be altered significantly by modifying the nanotube surface. In this study, single-walled carbon nanotubes (SWCNTs) were functionalized noncovalently using designed surfactant peptides, and the resultant SWCNT electronic properties were investigated. These peptides have a common amino acid sequence of X(Valine)(5)(Lysine)(2), where X indicates an aromatic amino acid containing either an electron-donating or electron-withdrawing functional group (i.e. p-amino-phenylalanine or p-cyano-phenylalanine). Circular dichroism spectra showed that the surfactant peptides primarily have random coil structures in an aqueous medium, both alone and in the presence of SWCNTs, simplifying analysis of the peptide/SWCNT interaction. The ability of the surfactant peptides to disperse individual SWCNTs in solution was verified using atomic force microscopy and ultraviolet-visible-near-infrared spectroscopy. The electronic properties of the surfactant peptide/SWCNT composites were examined using the observed nanotube Raman tangential band shifts and the observed additional features near the Fermi level in the scanning tunneling spectroscopy dI/dV spectra. The results revealed that SWCNTs functionalized with surfactant peptides containing electron-donor or electron-acceptor functional groups showed n-doped or p-doped altered electronic properties, respectively. This work unveils a facile and versatile approach to modify the intrinsic electronic properties of SWCNTs using a simple peptide structure, which is easily adaptable to obtain peptide/SWCNT composites for the design of tunable nanoscale electronic devices.     

Simultaneous SAXS/WAXS experiments on shear induced iPP crystallization near nominal melting temperature

Simultaneous small- and wide-angle synchrotron radiation X-ray scattering was performed to monitor the evolution of crystalline structure within the iPP melt during and after applying pulse shear. The iPP melt was subjected to a strong pulse shear of 240 s^?1 for 6 s at temperatures between 150 and 170 °C below and above the nominal melting temperature T_m. It was found that the imposed shear affected the melt only at lowest temperature. Structures generated during flow above 150 °C were too dilute to be detected. To extract the hidden structure, the melt was cooled to crystallization temperature of 150 °C either immediately after shearing or after annealing at shear temperature for up to 30 min. This treatment manifested with an anisotropic structure in a few minutes after quenching, undetectable when both shear and annealing temperatures presented the same value. The data obtained revealed also close correlations between annealing time, shear temperature and incubation time.     

一款数字化血压监护仪参考设计

数字化血压监护仪可以帮助内科医生诊断出高血压病并帮助患者控制高血压.便携式血压监护仪则能让病人在家里无需医生就可以经济地测量血压,从而有助于早期诊断和高血压控制.本文将介绍一款飞思卡尔公司的血压监护仪参考设计.     

Short-term and moderate UV-B radiation effects on secondary plant metabolism in different organs of nasturtium (Tropaeolum majus L.)

Glucotropaeolin and total phenolic concentrations were assessed in three different organs (inflorescences, leaves, unripe seeds) of nasturtium (Tropaeolum majus L.), which are consumed as herbal plant products, in order to determine the effect of short-term and moderate UV-B exposure as targeted postharvest stress treatment on the secondary plant metabolism. For this purpose, nasturtium plants were subjected to two UV-B radiation levels: 0.075 and 0.15 W h m^? 2. The results clearly demonstrate that the plant response to short-term and moderate UV-B exposure is organ-, plant tissue age-, and phytochemical-specific and that these factors influence a change of secondary metabolism as revealed by the different phytochemical concentration levels elicited.Industrial relevanceIn food processing UV treatment is mainly attributed to disinfection. This study examined the feasibility of short-term and moderate UV-B application as emerging technology for enhancing health-promoting phytochemicals in freshly consumed plant products (inflorescences, leaves, unripe seeds) demonstrated by the herbal plant nasturtium. Optimizing phytochemical concentration by targeted postharvest UV-B applications will add health value and subsequently generate new opportunities for growers and processors by achieving the health-oriented food market.     

GIS-supported mapping of shallow geothermal potential of representative areas in south-western Germany—Possibilities and limitations

The increasing interest in the utilization of shallow geothermal energy comes with the wish for better knowledge about the factors influencing its efficiency. For this purposes we focused on the subsurface condition's influence on the use of borehole heat exchangers (BHEs) coupled with a heat pump for heating purposes, since this is the most popular heat-extracting technique. We created maps showing the potential for this technique provided by the thermal underground properties. Therefore, we established an underground model for two study areas in south-western Germany with different geological settings using a geographic information system (GIS). The subsurface has been divided into layers with similar thermal properties based on geological, hydrogeological and lithological information. The layers have been attached with specific heat extraction values, according to the German VDI guideline 4640. For depths of 50 and 100 m, the weighted mean value of the specific heat extraction was calculated and presented within maps. These maps point out how the heat-extraction potential differs within and between the study areas and how it depends on depth.     

Bulk tank raw milk microbiota differs within and between farms: A moving goalpost challenging quality control

Microbial contamination of bovine raw milk often occurs at the farm. To acquire a deeper knowledge of the microbiota of farm tank milk, we studied milk from 45 farms situated in 2 geographical areas in Norway. Each farm was visited on 3 different occasions, with at least 2 wk between visits. We combined both bacterial cell counts and a sequence variant inference method of amplicon-based high-throughput sequencing to achieve a high-resolution overview of the microbiota in each sample. Compositional variation of the farm milk microbiota was shown in relation to the 2 areas, between the farms and between the sampling times. Despite the near constant level of bacteria enumerated in milk from each individual farm, the dominant microbiota differed significantly between the samplings. The predominant microbiota was dominated by spoilage genera, such as Pseudomonas and Bacillus, as well as the dairy fermentation genus Lactococcus and mastitis-causing organisms (Streptococcus). Analysis of the identified sequence variants within these genera showed that the populations of Pseudomonas and Lactococcus in milk had similar composition between the farms, but that Bacillus and, in particular, Streptococcus populations changed between collection days from the same farm and between farms and geographical areas. Furthermore, the levels and composition of Bacillus and Paenibacillus were different between the 2 geographical areas. The results presented here provide new insight into the farm milk microbiota and show that this microbiota is a dynamic community highly subject to variation.     

Experimental investigation of a liquid cooled high temperature proton exchange membrane (HT-PEM) fuel cell coupled to a sodium alanate tank

In high temperature proton exchange membrane (HT-PEM) fuel cells, waste heat at approximately 160 °C is produced, which can be used for thermal integration of solid state hydrogen storage systems. In the present study, an HT-PEM fuel cell stack (400 W) with direct liquid cooling is characterized and coupled to a separately characterized sodium alanate storage tank (300 g material). The coupled system is studied in steady state for 20 min operation and all relevant heat flows are determined. Even though heat losses at that specific power and temperature level cannot be completely avoided, it is demonstrated that the amount of heat transferred from the fuel cell stack to the cooling liquid circuit is sufficient to desorb the necessary amount of hydrogen from the storage tank. Furthermore, it is shown that the reaction rate of the sodium alanate at 160 °C and 1.7 bar is adequate to provide the hydrogen to the fuel cell stack. Based on these experimental investigations, a set of recommendations is given for the future design and layout of similar coupled systems.