Thermal degradation of Cross-Linked Polyisoprene and Polychloroprene

Polyisoprene and polychloroprene have been cross-linked either in solution or in solid state using free radical initiators. In the comparable experimental conditions higher cross-linking density was observed in the solid state process. Independent of the cross-linking method, polychloroprene tended to give a higher gel content and cross-link density than does polyisoprene. Infrared characterization of the cross-linked materials showed cis-trans isomerization occurred in the polyisoprene initiated by benzoyl peroxide, whereas no isomerization was found in the samples initiated by dicumyl peroxide. Polyisoprene does not cross-link by heating in a thermal analyzer, whereas polychloroprene easily undergoes cross-linking in such conditions. Infrared spectroscopy showed that in the case of polyisoprene, rearrangements occur upon heating which lead to the formation of terminal double bonds, while polychloroprene loses hydrogen chlorine which leads to a conjugated structure. There is apparently some enhancement of the thermal and thermal oxidative stability of polyisoprene because of the cross-linking. Cross-linked polychloroprene is less thermally stable than the virgin polymer. Cross-linking promotes polymers charring in the main step of weight loss in air, which leads to enhanced transitory char

Introduction: pen, print and communication in the eighteenth century

The eighteenth century, perhaps more than any other, was a pivotal time in the development of the mechanics and methods of communication. Commercial, political, legal, social and religious interactions were all facilitated by a variety of material processes such as handwriting, painting, drawing, printing and engraving which coexisted alongside more ephemeral and immaterial means of communication including voice, gesture, costume and performance. New sites for consuming the products of communication emerged such as coffee houses, oratories, libraries, institutes, theatres, shops and galleries. Developments in road and water transport and postal systems facilitated means of communication and enabled the products of pen and print to travel further and faster than ever before. This introduction and subsequent chapter, considers pen, print and other forms of communication in the eighteenth century

Early Contrast Enhancement: a novel Magnetic Resonance Imaging biomarker of pleural malignancy

Introduction: Pleural Malignancy (PM) is often occult on subjective radiological assessment. We sought to define a novel, semi-objective Magnetic Resonance Imaging (MRI) biomarker of PM, targeted to increased tumour microvessel density (MVD) and applicable to minimal pleural thickening. Materials and methods: 60 consecutive patients with suspected PM underwent contrast-enhanced 3-T MRI then pleural biopsy. In 58/60, parietal pleura signal intensity (SI) was measured in multiple regions of interest (ROI) at multiple time-points, generating ROI SI/time curves and Mean SI gradient (MSIG: SI increment/time). The diagnostic performance of Early Contrast Enhancement (ECE; which was defined as a SI peak in at least one ROI at or before 4.5 min) was compared with subjective MRI and Computed Tomography (CT) morphology results. MSIG was correlated against tumour MVD (based on Factor VIII immunostain) in 31 patients with Mesothelioma. Results: 71% (41/58) patients had PM. Pleural thickening was <10 mm in 49/58 (84%). ECE sensitivity was 83% (95% CI 61–94%), specificity 83% (95% CI 68–91%), positive predictive value 68% (95% CI 47–84%), negative predictive value 92% (78–97%). ECE performance was similar or superior to subjective CT and MRI. MSIG correlated with MVD (r = 0.4258, p = .02). Discussion: ECE is a semi-objective, perfusion-based biomarker of PM, measurable in minimal pleural thickening. Further studies are warranted

Silver as Seed-Particle Material for GaAs Nanowires-Dictating Crystal Phase and Growth Direction by Substrate Orientation

Here we investigate the feasibility of silver as seed-particle material to synthesize GaAs nanowires and show that both crystal phase and growth direction can be controlled by choice of substrate orientation. A (111)B substrate orientation can be used to form vertically aligned wurtzite GaAs nanowires and a (100) substrate orientation to form vertically aligned zinc blende GaAs nanowires. A 45-50% yield of vertical nanowire growth is achieved on the (100) substrate orientation without employing any type of surface modification or nucleation strategy to promote a vertical growth direction. In addition, photoluminescence measurements reveal that the photon emission from the silver seeded wurtzite GaAs nanowires is characterized by a single and narrow emission peak at 1.52 eV

Integrative analyses of genetic variation in enzyme activities of primary carbohydrate metabolism reveal distinct modes of regulation in Arabidopsis thaliana

Multiparallel QTL analysis of 15 Arabidopsis primary carbohydrate metabolism enzymes reveals that traits affecting primary metabolism are often correlated

Sulfur cycling connects microbiomes and biogeochemistry in deep-sea hydrothermal plumes

In globally distributed deep-sea hydrothermal vent plumes, microbiomes are shaped by the redox energy landscapes created by reduced hydrothermal vent fluids mixing with oxidized seawater. Plumes can disperse over thousands of kilometers and their characteristics are determined by geochemical sources from vents, e.g., hydrothermal inputs, nutrients, and trace metals. However, the impacts of plume biogeochemistry on the oceans are poorly constrained due to a lack of integrated understanding of microbiomes, population genetics, and geochemistry. Here, we use microbial genomes to understand links between biogeography, evolution, and metabolic connectivity, and elucidate their impacts on biogeochemical cycling in the deep sea. Using data from 36 diverse plume samples from seven ocean basins, we show that sulfur metabolism defines the core microbiome of plumes and drives metabolic connectivity in the microbial community. Sulfur-dominated geochemistry influences energy landscapes and promotes microbial growth, while other energy sources influence local energy landscapes. We further demonstrated the consistency of links among geochemistry, function, and taxonomy. Amongst all microbial metabolisms, sulfur transformations had the highest MW-score, a measure of metabolic connectivity in microbial communities. Additionally, plume microbial populations have low diversity, short migration history, and gene-specific sweep patterns after migrating from background seawater. Selected functions include nutrient uptake, aerobic oxidation, sulfur oxidation for higher energy yields, and stress responses for adaptation. Our findings provide the ecological and evolutionary bases of change in sulfur-driven microbial communities and their population genetics in adaptation to changing geochemical gradients in the oceans

Dual Loop Line-Focusing Solar Power Plants with Supercritical Brayton Power cycles

Most of the deployed commercial line-focusing solar power plants with Parabolic Troughs (PTC) or Linear Fresnel (LF) solar collectors and Rankine power cycles use a Single Loop Solar Field (SF), Configuration 1 illustrated in Fig. 2, with synthetic oil as Heat Transfer Fluid (HTF) [1, 2]. However, thermal oils maximum operating temperature should be below ~400ºC for assuring no oil degradation, hence limiting the power cycle gross efficiency up to ~38%. For overcoming this limitation Molten Salts (MS) as HTF in linear solar collectors (PTC and LF) were recently experimented in pilot facilities [3, 4]. Direct MS main drawbacks are the equipments and components material corrosion and the salts freezing temperature, requiring heat tracing to avoid any sald solidification, hence increasing the Solar Field (SF) capital investment cost and parasitic energy looses. Concentrated Solar Power plants (CSP) with Dual Loop SF are being studied since 2012 [5] for gaining the synergies between thermal oils and MS properties. In the Dual Loop SF the HTF in the primary loop is thermal oil (Dowtherm A) [6] for heating the Balance Of Plant (BOP) working fluid from ~300ºC up to ~400ºC, and a secondary loop with Solar Salt (60% NaNO3, 40% KNO3) as HTF, for boosting the working fluid temperature from ~400ºC up to 550ºC [7, 8, 9]. The CSP Dual Loop state of the art technology includes Rankine power cycles, the main innovation of this paper is the integration between Dual Loop SF and the supercritical Carbon Dioxide (s-CO2) Brayton power cycles [10], see Configurations 2 and 3 illustrated in Fig. 3a, Fig 3b. A secondary innovation studied in this paper is the integration between thermal oil HTF (Dowtherm A) in linear solar collectors, a widely validated and mature technology, with the s-CO2 Brayton power cycles. This technical solution is very cost competitive with carbon steel receiver pipes, low SF operating pressure, and no requiring any heat tracing. Two main conclusions are deducted from this researching study. Firstly we demonstrated the higher gross plant efficiency ~44.4%, with 550ºC Turbine Inlet Temperature (TIT), provided by the Dual Loop with the Simple recuperated s-CO2 Brayton cycle with reheating, in comparison with 41.8% obtained from the Dual Loop SF and subcritical water Rankine power cycle. And finally the second conclusion obtained is the selection of the most cost competitive plant configuration with a Single loop SF with Dowtherma A and a s-CO2 Brayton power cycle due to the receiver material low cost and no heat tracing for the thermal oil