A semi-implicit time-splitting scheme for a regional nonhydrostatic atmospheric model

In this study a semi-implicit finite difference scheme is proposed for the nonhydrostatic atmospheric model based on the Euler equations for compressible ideal gas. Fast acoustic and gravity waves are approximated implicitly, while slow inertial processes are treated explicitly. Such time approximation requires the solution of 3D elliptic equations at each time step. An efficient elliptic solver is based on decoupling in the vertical direction and splitting in the horizontal directions. Stability analysis of the scheme shows that the time step is restricted only by the maximum wind speed and does not depend on the propagation velocity of the fast waves. A specific approximation of the advection terms keeping the second order of accuracy and possessing extended stability is employed to achieve larger time steps. The performed numerical experiments show the computational efficiency of the designed scheme and accuracy of the predicted atmospheric fields.     

Living cationic polymerization of styrene with 1-phenylethyl chloride/TiCl4/Bu2O

Summary Living polymerization of styrene was obtained in the system 1-phenylethyl chloride/TiC1₄/Bu₂O in mixture of 1,2-dichloroethane and n-hexane (55:45 v/v) at -15^°C. The number-average molecular weights (M_n) of the polymers obtained increased in direct proportion to the monomer conversion and agreed well with the calculated values. The first-order kinetic plots were linear. The molecular weight distributions were narrow (M_n/M_n=1.46-1.56). Received: 3 1 January 2002/Revised version: 7 October 2002/Accepted: 7 October 2002 Correspondence to Sergei V. Kostjuk     

Heterogeneity of active sites of Ziegler‐Natta catalysts: The effect of catalyst composition on the MWD of polyethylene

Experimental data on the molecular weight distribution (MWD) of polyethylene (PE) produced over a broad number of Ziegler‐Natta catalysts differing in composition and preparation procedure are presented. These catalysts include nonsupported TiCl₃ catalyst, four types of supported titanium‐magnesium catalysts (TMC) differing in the content of titanium and the presence of various modifiers in the composition of the support, and a supported catalyst containing VCl₄ as an active component instead of TiCl₄. The studied catalysts produce PE with different molecular weights within a broad range of polydispersity (M_w/M_n = 2.8–16) under the same polymerization conditions. The heterogeneity of active sites of these catalysts was studied by deconvolution of experimental MWD curves into Flory components assuming a correlation between the number of Flory components and the number of active site types. Five Flory components were found for PE produced over nonsupported TiCl₃ catalysts (M_w/M_n = 6.8), and three–four Flory components were found for PE produced over TMC of different composition. A minimal number of Flory components (three) was found for PE samples (M_w/M_n values from 2.8 to 3.3) produced over TMC with a very low titanium content (0.07 wt %) and TMC modified with dibutylphtalate. It was shown that five Flory components are sufficient to fit the experimental MWD curve for bimodal PE (M_w/M_n = 16) produced over VMC. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Dry powder inhaler of colistimethate sodium for lung infections in cystic fibrosis: optimization of powder construction

Abstract

Colistimethate sodium (CMS) for treatment of lung infections in cystic fibrosis patient was transformed into a dry powder for inhalation by spray drying. Design of Experiment was applied for understanding the role of the spray-drying process parameters on the critical quality attributes of the CMS spray-dried (SD) powders and agglomerates thereof. Eleven experimental SD microparticle powders were constructed under different process conditions according to a central composite design. The SD microparticles were then agglomerated in soft pellets. Eleven physico-chemical characteristics of SD CMS microparticle powders or agglomerates thereof were selected as critical quality attributes. The yield of SD process was higher than 75%. The emitted fraction of agglomerates from RS01 inhaler was 75–84%, and the fine particle fraction (particles <5?µm) was between 58% and 62%. The quality attributes of CMS SD powders and respective agglomerates that were significantly influenced by spray-drying process parameters were residual solvent and drug content of the SD microparticles as well as bulk density and respirable dose of the agglomerates. These attributes were also affected by the combination of the process variables. The air aspiration rate was found as the most positively influential on drug and solvent content and respirable dose. The residual solvent content significantly influenced the powder bulk properties and aerodynamic behavior of the agglomerates, i.e. quality attributes that govern drug metering in the device and the particles lungs deposition. Agglomerates of CMS SD microparticles, in combination with RS01?DPI, showed satisfactory results in terms of dose emitted and fine particle fraction.     

Movement as a Positive Modulator of Aging

The aging of human populations, including those in Europe, is an indisputable fact. The challenge for the future is not simply prolonging human life at any cost or by any means but rather extending self-sufficiency and quality of life. Even in the most advanced societies, the eternal questions remain. Who will take care of the older generations? Will adult children’s own circumstances be sufficient to support family members as they age? For a range of complex reasons, including socioeconomic conditions, adult children are often unable or unwilling to assume responsibility for the care of older family members. For this reason, it is imperative that aging adults maintain their independence and self-care for as long as possible. Movement is an important part of self-sufficiency. Moreover, movement has been shown to improve patients’ clinical status. At a time when the coronavirus pandemic is disrupting the world, older people are among the most vulnerable. Our paper explores current knowledge and offers insights into the significant benefits of movement for the elderly, including improved immunity. We discuss the biochemical processes of aging and the counteractive effects of exercise and endogenous substances, such as vitamin D.     

VTOA/VolP/N-ISDN Telephony Gateway

This article presents the architecture and implementation of a telephony gateway for interworking between N- ISDN, ATM and IP telephony. In this way, interworking is achieved both within private networks and with the PSTN, address translation being performed according to both the vtoa (atm interface) and H .323 (ip interface) specifications. The gateway implementation is based on a PC, presenting a cost- effective alternative to the equipment currently available on the market. Moreover, its highly modular software architecture allows new telephony interfaces to be easily added.     

Regulation of Ribosomal Protein Synthesis in Mycobacteria: The Autogenous Control of rpsO

The autogenous regulation of ribosomal protein (r-protein) synthesis plays a key role in maintaining the stoichiometry of ribosomal components in bacteria. In this work, taking the rpsO gene as a classic example, we addressed for the first time the in vivo regulation of r-protein synthesis in the mycobacteria M. smegmatis (Msm) and M. tuberculosis (Mtb). We used a strategy based on chromosomally integrated reporters under the control of the rpsO regulatory regions and the ectopic expression of Msm S15 to measure its impact on the reporter expression. Because the use of E. coli as a host appeared inefficient, a fluorescent reporter system was developed by inserting Msm or Mtb rpsO-egfp fusions into the Msm chromosome and expressing Msm S15 or E. coli S15 in trans from a novel replicative shuttle vector, pAMYC. The results of the eGFP expression measurements in Msm cells provided evidence that the rpsO gene in Msm and Mtb was feedback-regulated at the translation level. The mutagenic analysis showed that the folding of Msm rpsO 5′UTR in a pseudoknot appeared crucial for repression by both Msm S15 and E. coli S15, thus indicating a striking resemblance of the rpsO feedback control in mycobacteria and in E. coli.     

Analysis of the gas phase of cigarette smoke by gas chromatography coupled with UV-diode array detection

A gas chromatography method, coupled with diode array photometric spectral detection in the ultraviolet region (167-330 nm), was developed for the analysis of the gas phase of cigarette smoke. The method enabled us to identify more than 20 volatiles present in the vapor phase of cigarette smoke. In that way, all major volatile organic compounds (including aldehydes, conjugated dienes, ketones, sulfides, furans, and single-ring aromatics), as well as nitric oxide (NO) and hydrogen sulfide (H(2)S), can be analyzed in a straightforward manner through a single chromatographic run of <50-min duration. The method can easily be applied by the introduction of a small volume of the gas-phase stream into the GC injection loop directly through the smoking apparatus exhaust circuit, thus providing an excellent alternative to available methods, which usually require extraction or concentration steps prior to any chromatographic analysis. Furthermore, all problems concerning aging of the gas phase are eliminated. Twelve compounds (including NO) were chosen for quantification through the use of appropriate calibration standards. Comparison of the vapor phase yields of these compounds for the reference cigarette Kentucky 1R4F with already reported data indicates that this method is very reliable as far as accuracy and reproducibility of the results are concerned. Finally, the proposed methodology was used to compare the concentration of these cigarette smoke gas-phase constituents among individual puffs.     

RESPIRATORY DEFICIENT MUTANTS OF BOTTOM BREWER'S YEAST II. TECHNOLOGICAL PROPERTIES OF SOME RD MUTANTS

Five spontaneous respiratory deficient mutants of one strain of bottom brewer's yeast were studied, being chosen for differences in their cytochrome system, and in rates of growth and fermentation. Pilot plant experiments showed that these 5 mutants differed from the original type also in the utilization of nitrogen compounds, in the sequence of utilization of sugars, and in the pattern of sedimentation. The beers prepared using these mutants were more aromatic, had higher contents of nitrogen compounds and of anthocyanogens, lower contents of most free amino acids and substantially lower contents of higher aliphatic alcohols. Their pH values were higher as well as their buffering capacities. One of the 5 mutants studied produced beer of better flavour than the original type.