Nanowire encapsulation with polymer for electrical isolation and enhanced optical properties

Light management and electrical isolation are essential for the majority of optoelectronic nanowire (NW) devices.Here,we present a cost-effective technique,based on vapor-phase deposition of parylene-C and subsequent annealing,that provides conformal encapsulation,anti-reflective coating,improved optical properties,and electrical insulation for GaAs nanowires.The process presented allows facile encapsulation and insulation that is suitable for any nanowire structure.In particular,the parylene-C encapsulation functions as an efficient antireflection coating for the nanowires,with reflectivity down to ＜1％ in the visible spectrum.Furthermore,the parylene-C coating increases photoluminescence intensity,suggesting improved light guiding to the NWs.Finally,based on this process,a NW LED was fabricated,which showed good diode performance and a clear electroluminescence signal.We believe the process can expand the fabrication possibilities and improve the performance of optoelectronic nanowire devices.     

Genetic changes in intraductal breast cancer detected by comparative genomic hybridization

Ductal carcinoma in situ (DCIS) is considered a direct precursor of invasive ductal breast cancer (IDC). We combined tissue microdissection and comparative genomic hybridization to identify genetic changes in five DCIS lesions with no invasion and in two that were adjacent to IDC. Extensive genetic changes characterized pure DCIS cases with gains of 1q, 6q, 8q, and Xq as well as losses of 17p and chromosome 22 being most often involved. Except for the Xq gain, these changes are also common to IDC. Separate analysis of DCIS and IDC components in the same tumor revealed an almost identical pattern of genetic changes in one case, whereas substantial differences were found in another. We conclude that many of the common genetic changes in IDC may take place before development of invasive growth. However, a simple linear progression model may not always account for the DCIS-IDC transition.     

Heat and Mass Transfer Analogy Studies of Binary Liquid Mixture in Comparison with Eteanol-n-Heptane Evaporating to Air

ABSTRACT

An expenmental and theoretical study of heat and mass transfer analogy and a comparison of that to a binary liquid mixture evaporation is presented. Common organic solvents, ethanol and n-heptane, were used to form an alcohol - hydrocarbon mixture. Studies were carried out in a horizontal rectangular channel having air flow velocities of 0.2 – 0.9 m/s. Heat transfer coefficients were measured with a copper plate resistor and mass transfer coefficients with a square pool. The heat and mass transfer analogy is presented for a system having two evaporating compounds with a fixed value of air flow and verified by measuring and comparing mass transfer coefficients for distilled water with air flow velocities of 0.2 - 0.9 mls. An illustrative example of the use of the theory for industrial ventilation is presented.     

Synthesis,characterization and crosslinking of functional star‐shaped poly(ε‐caprolactone)

Star‐shaped low molecular weight poly(ε‐caprolactone)s (PCLs) were synthesized and functionalized with crosslinkable terminal groups for subsequent crosslinking. The ε‐caprolactone (CL) prepolymers were polymerized by ring‐opening in the presence of polyglycerine (PGL) as an initiator (1, 3 and 5 mol%) and Sn(II)2‐ethylhexanoate as a catalyst. Characterization of the prepolymer by ¹³C/¹H nuclear magnetic resonance (NMR) spectroscopy, size exclusion chromatography (SEC), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) revealed a six‐armed star‐shaped structure for the prepolymer with the molecular weight controlled by the ratio of PGL and CL. Functionalization of the hydroxyl‐terminated prepolymer was carried out with maleic or itaconic anhydride. In both cases, the characterization of the functionalized prepolymer showed that the hydroxyl groups were completely substituted. The functionalized PCLs were successfully crosslinked through the reaction of double bonds. The crosslinking was induced either thermally with organic peroxide or photochemically with a photosensitive initiator. Characterization of the crosslinked PCLs by Soxhlet extraction, DSC and FTIR showed that the itaconic double bond was much more reactive in thermal crosslinking than the maleic double bond. Thus, the crosslinked prepolymers that were functionalized with itaconic double bonds achieved a gel content of about 90%. A gel content of 100% was achieved with several compositions where crosslinking agents were employed. © 2002 Society of Chemical Industry     

Authentication of Particulate Air Samples by Aerosol

A method was developed for the protection of aerosol filters against tampering that can be applied to any particulate sampler. In this method, tagged particles are dispersed into the sampled aerosol volume by liquid atomization to guarantee homogeneous distribution of the tag and deposition into the filter matrix. The tagged aerosols are collected insitu, together with the sampled dust particles. The tag can be measured in different ways. This feature can be used for self protection of the method. The authentication of the individual filters is preserved through the lifetime of the filter sample. Long-term field tests of the equipment indicate reliable performance.     

Leaf and root litter of a legume tree as nitrogen sources for cacaos with different root colonisation by arbuscular mycorrhizae

Traditionally cacao (Theobroma cacao L.) is cultivated under legume shade trees, which produce N-rich litter that improves soil organic matter content, microbial activity, and recycles N to the crop. Arbuscular mycorrhiza forming fungi (AMF) are known to play an important role in plant nutrient uptake, yet their role in plant N uptake from organic residues in tropical agroforestry systems is not clear. We studied root and leaf litter of the legume shade tree Inga edulis Mart. as a source of N for cacao and the importance of AMF colonisation in the uptake of litter N under controlled conditions. Leaf and root litter of I. edulis enriched with ¹⁵N was added to cacao pots filled with field soil. Half of the cacao saplings were AMF-inoculated and the soil of non-inoculated saplings was treated with fungicide to suppress AMF. During the 10-week experiment, young cacao leaves were sampled for ¹⁵N analyses and at the end of the experiment whole plants were harvested. Microbial populations in the soil were determined using phospholipid fatty acid (PLFA) analysis, and AMF structures in the roots were quantified. Fungicide treatment decreased AMF structures in roots and increased bacterial populations, but did not affect the decomposition rate of either litter type. Inoculated and non-inoculated cacao saplings used 2.6 and 2.1%, respectively, of N added to the pots in leaf litter and 12.1 and 7.1% of N available in root litter indicating that root litter of I. edulis may be a more efficient N source than leaf litter for cacao. Although the fungicide treatment did not completely suppress AMF in non-inoculated pots, it created sufficient contrast in root AMF colonisation for concluding that AMF significantly enhanced cacao N use from both litter types. The role of root litter of shade trees as a N source in agroforestry should not be neglected.     

Effects of Silage Fermentation and Post-ruminal Casein Supplementation in Lactating Dairy Cows: 2—Energy Metabolites and Plasma Amino Acids

Four cows were used in a 4×4 Latin square design with a 2×2 factorial arrangement of treatments to examine the effects of the extent of silage fermentation and post-ruminal casein infusion on the arterial concentrations and mammary arterial–venous (A–V) difference of energy-yielding nutrients and plasma amino acids. Of the two silages one was preserved with formic acid (FA-silage) and the other with an inoculant of lactic acid bacteria (LAB-silage). Both silages were given ad libitum with 8 kg day^-1 of barley, without or with duodenal casein infusing (400 g day^-1). Blood was sampled from the coccygeal vessel and milk vein. FA-silage less fermented than LAB-silage as indicated by higher concentration (g kg^-1 dry matter) of water soluble carbohydrates (178 vs 68) and lower concentration of lactic acid (32 vs 147). Plasma concentration of glucose was lower (P<0·05) and concentrations of essential amino acids (P<0·001) and blood β-hydroxybutyrate (BHB) (P<0·01) were higher with FA-silage than with LAB-silage. There was a strong linear relationship between arterial concentration and mammary A–V difference of blood metabolites, except BHB, and amino acids. The relationship between arterial concentration and mammary A–V difference of glucose was different between the silages. Mammary extraction rates of glucose, BHB, histidine, leucine and lysine were affected by their arterial concentrations. The interaction between silage fermentation and casein infusion was significant (P<0·05) in arterial concentration of branched-chain amino acids, the increase being greater with FA-silage than with LAB-silage. The results suggest that the supply of glucose may limit milk synthesis in cows given restrictively fermented grass silage and barley, whereas the supply of amino acids may be more limiting with extensively fermented silages. It is further suggested that the mammary gland has a capacity to adapt it's efficiency of nutrient uptake according to the supply and mammary demand of nutrients. © 1997 SCI.