Influence of Aluminium Alkyl Compounds on the High‐Pressure Polymerization of Ethylene with Ternary Metallocene‐Based Catalysts. Investigation of Chain Transfer to the Aluminium

The influence of aluminium alkyl compounds on metallocene‐catalyzed high pressure polymerizations of ethylene has been investigated at 150 MPa and 180°C in a continuously operated autoclave. The catalysts were based on the metallocenes bis(cyclopentadienyl)zirconium dichloride (Cp₂ZrCl₂) and diphenylmethylene (cyclopentadienylfluorenyl)zirconium dichloride (Ph₂C‐(CpFlu)ZrCl₂), which were preactivated outside the reactor with triisobutylaluminium (TiBA) and N,N‐dimethylanilinium tetrakis(pentafluorophenyl)borate (DMAP, [PhNHMe₂][B(C₆F₅)₄]). The concentrations of triisobutylaluminium (TiBA) and triethylaluminium (TEA) in the reactor were varied over a wide range, using a separate dosing for these two aluminium alkyl compounds. Productivity and polymer properties strongly depended on the type and the concentration of the aluminium alkyl compound used. Highest productivities and molecular weights were obtained with low concentrations of TiBA in the reactor. Up to a concentration of 30 molppm Al in the reactor, unimodal polymers were formed with M̄_w/M̄_n between 2 and 3. With higher aluminium concentrations the products formed contained small amounts of waxes, due to oligomerization catalyzed by the aluminium alkyl compounds. The molecular weight distributions (MWDs) of these products could be described as a superimposition of two Schulz‐Zimm distributions. All MWDs were analyzed with regard to the amount of waxes produced by ethylene oligomerization and with regard to the influence of chain transfer reactions to the aluminium. The rate constants of chain transfer to aluminium, in relation to the rate constants of insertion of ethylene, were estimated.     

New Dry Process for Separating HCl from Flue Gases by Adsorption on MgO

Fossil fuels are still the most important source for supplying the world's energy and heating needs. The growing demands of more stringent pollution control regulations make it necessary to develop new flue gas cleaning processes. Up to now there is no known process that allows the dry separation of hydrogen chloride from flue gases with ready adsorbent regeneration. The well known BF-Uhde process cannot be applied to flue gases containing hydrogen chloride. Our aim was to develop a process for dry separation of hydrogen chloride from flue gases that can be used in combination with the BF-Uhde process. The new process is based on a gas-solid reaction between active magnesia and hydrogen chloride at temperatures of about 120 °C. The new process performed well in experiments conducted under industrial conditions. The adsorbent can be regenerated at temperatures of about 450 °C. Hydrogen fluoride is the only known flue gas component that interferes with the regeneration capability of the adsorbent.     

Defect studies on as-synthesized and purified carbon nanostructures produced by arc-discharge in solution process

Carbon nanostructures are synthesized using a novel arc-discharge in solution process. A multitude of defects on nanotubes and nanostructures is found. Evidence of these defects in as-synthesized carbon nanostructures is explored using high-resolution transmission electron microscopy (HRTEM). Tri-, tetra-, penta-, hexa-, heptagonal, toroidal, oval, and spherical nanoshells are found in HRTEM investigation along with carbon nanotubes, carbon nanohorns, carbon rods, nanoporous carbon, dislodged graphene sheets, and amorphous carbon. Purifications are carried out through two oxidation methods to eliminate the amorphous carbon. Several different defects caused by oxidations are also found in purified samples.     

Neutral loss fragmentation pattern based screening for arginine-rich natural products in xenorhabdus and photorhabdus

Although sharing a certain degree of structural uniformity, natural product classes exhibit variable functionalities such as different amino acid or acyl residues. During collision induced dissociation, some natural products exhibit a conserved fragmentation pattern close to the precursor ion. The observed fragments result from a shared set of neutral losses, creating a unique fragmentation pattern, which can be used as a fingerprint for members of these natural product classes. The culture supernatants of 69 strains of the entomopathogenic bacteria Photorhabdus and Xenorhabdus were analyzed by MALDI-MS(2), and a database comprising MS(2) data from each strain was established. This database was scanned for concordant fragmentation patterns of different compounds using a customized software, focusing on relative mass differences of the fragment ions to their precursor ion. A novel group of related natural products comprising 25 different arginine-rich peptides from 16 different strains was identified due to its characteristic neutral loss fragmentation pattern, and the structures of eight compounds were elucidated. Two biosynthesis gene clusters encoding nonribosomal peptide synthetases were identified, emphasizing the possibility to identify a group of structurally and biosynthetically related natural products based on their neutral loss fragmentation pattern.     

Energy consumption, costs and environmental impacts for urban water cycle services: Case study of Oslo (Norway)

Energy consumption in the operation and maintenance phase of the urban water and wastewater network is directly related to both the quantity and the desired quality of the supplied water/treated wastewater - in other words, to the level of service provided to consumers. The level of service is dependent on not just the quantity and quality of the water but also the state of the infrastructure. Maintaining the infrastructure so as to be able to provide the required high level of service also demands energy. Apart from being a significant operational cost component, energy use also contributes to life-cycle environmental impacts. This paper studies the direct energy consumption in the operation and maintenance phase of the water and wastewater system in Oslo; and presents a break-up among the different components of the network, of quantities, costs and environmental impacts. Owing to the diversity in the periods of time for which comprehensive data for the whole system are available, the study period is restricted to years 2000-2006. The per-capita annual consumption of energy in the operational phase of the system varied between 220 and 260 kWh; and per-capita annual expenses on energy in inflation-adjusted year-2006-Euros ranged between 6.5 and 11 Euros. The energy consumed on the upstream, per unit volume water supplied was around 0.4 kWh on average, while the corresponding value for the downstream was 0.8 kWh per cubic metre wastewater treated. The upstream Greenhouse gas (GHG) emissions ranged between 70 and 80 g per cubic metre of water supplied, about 22% greater on average than the corresponding specific GHG emissions on the downstream.     

Porous silicon bulk acoustic wave resonator with integrated transducer

ABSTRACT: : We report that porous silicon acoustic Bragg reflectors and AlN-based transducers can be successfully combined and processed in a commercial solidly mounted resonator production line. The resulting device takes advantage of the unique acoustic properties of porous silicon in order to form a monolithically integrated bulk acoustic wave resonator.     

Rugulactone and its analogues exert antibacterial effects through multiple mechanisms including inhibition of thiamine biosynthesis

Rugulactone is a dihydro-α-pyrone isolated from the plant Cryptocarya rugulosa in 2009. It has been reported to display IkB kinase (IKK) inhibitory activity, as well as antibiotic activity in several strains of pathogenic bacteria. However, its biological targets and mode of action in bacteria have not yet been explored. Here we present enantioselective syntheses of rugulactone and of some corresponding activity-based protein profiling (ABPP) probes. We found that the ABPP probes in this study are more potent than rugulactone against Staphyloccocus aureus NCTC 8325, S. aureus Mu50, Listeria welshimeri SLCC 5334 and Listeria monocytogenes EGD-e, and that molecules of this class probably exert their antibacterial effect through a combination of targets. These targets include covalent inhibition of 4-amino-5-hydroxymethyl-2-methylpyrimidine phosphate (HMPP) kinase (ThiD), which is an essential component of the thiamine biosynthesis pathway in bacteria. This represents the first example of a small-molecule inhibitor of ThiD.     

Photodegradation of Selected Aromatic Constituents of Creosote in Organic Solvents

Polycyclic aromatic hydrocarbons (PAHs), naphthalene, phenanthrene, anthracene, and pyrene were irradiated in acetonitrile (CH₃CN) and in dichloromethane (CH₂Cl₂) on individual PAH compounds and in the presence of other compounds. The observed photodegradation of PAHs was dependent on the structure of the compound. Anthracene and pyrene were the most photoreactive in dichloromethane: with total degradation after 0.5 h irradiation for anthracene and 1.5 h for pyrene. The decomposition of PAHs was faster in dichloromethane than in acetonitrile.