Co‐Extrusion of Multilayer Glass Fiber‐Optic Preforms: Prediction of Layer Dimensions in the Extrudate

A three‐dimensional, incompressible and noncavitating model of a glass‐stack coextrusion process, under isothermal and non‐isothermal conditions is numerically simulated by means of computational fluid dynamics. A dynamic mesh approach is taken in a domain‐subdomain type setup to simulate the transient steps in the steady‐velocity phase of the experimental co‐extrusion. The multiphase setup consists of a glass‐stack which is composed of different glass compositions. Experimentally measured glass properties, such as the temperature coefficient of the viscosity of the supercooled glass melts are used to define the flow behavior of the glasses in the starting stack when extruded. The modeled extrudate is numerically verified for transient and spatial errors, leading to the choice of a suitable mesh. Excellent agreement is found between modeling and experiment when plotting the core/cladding dimensions of a step‐index extruded fiber‐optic preform along the length of the preform. This approach can identify the stable part of the preform, in terms of constant core/cladding layer geometry, obviating costly and time‐consuming experimental iteration. Also, the modeling allows prediction of the starting glass‐stack dimensions for a specified fiber design.     

Reconstitution of Membrane Proteins into Model Membranes: Seeking Better Ways to Retain Protein Activities

The function of any given biological membrane is determined largely by the specific set of integral membrane proteins embedded in it, and the peripheral membrane proteins attached to the membrane surface. The activity of these proteins, in turn, can be modulated by the phospholipid composition of the membrane. The reconstitution of membrane proteins into a model membrane allows investigation of individual features and activities of a given cell membrane component. However, the activity of membrane proteins is often difficult to sustain following reconstitution, since the composition of the model phospholipid bilayer differs from that of the native cell membrane. This review will discuss the reconstitution of membrane protein activities in four different types of model membrane—monolayers, supported lipid bilayers, liposomes and nanodiscs, comparing their advantages in membrane protein reconstitution. Variation in the surrounding model environments for these four different types of membrane layer can affect the three-dimensional structure of reconstituted proteins and may possibly lead to loss of the proteins activity. We also discuss examples where the same membrane proteins have been successfully reconstituted into two or more model membrane systems with comparison of the observed activity in each system. Understanding of the behavioral changes for proteins in model membrane systems after membrane reconstitution is often a prerequisite to protein research. It is essential to find better solutions for retaining membrane protein activities for measurement and characterization in vitro.     

Electro-Kinetic Technology as a Low-Cost Method for Dewatering Food By-Product

Increasing volumes of food waste, intense environmental awareness, and stringent legislation have imposed increased demands upon conventional food waste management. Food by-products that were once considered to be without value are now being utilized as reusable materials, fuels, and energy in order to reduce waste. One major barrier to the valorization of food by-products is their high moisture content. This has brought about the necessity of dewatering food waste for any potential re-use for certain disposal options. A laboratory system for experimentally characterizing electro-kinetic dewatering of food by-products was evaluated. The bench scale system, which is an augmented filter press, was used to investigate the dewatering at constant voltage. Five food by-products (brewer's spent grain, cauliflower trimmings, mango peel, orange peel, and melon peel) were studied. The results indicated that electro-kinetic dewatering combined with mechanical dewatering can reduce the percentage of moisture from 78% to 71% for brewer's spent grain, from 77% to 68% for orange peel, from 80% to 73% for mango peel, from 91% to 74% for melon peel, and from 92% to 80% for cauliflower trimmings. The total moisture reduction showed a correlation with electrical conductivity (R² = 0.89). The energy consumption of every sample was evaluated and was found to be up to 60 times more economical compared to thermal processing.     

HANDBOOK OF INDUSTRIAL DRYING

Papermaking is a massive dehydration operation. Thermal removal of moisture which can not be removed mechanically is a key process stage in papermaking. It is well known that it is a highly energy intensive step. However, it is less readily recognized that it also influences some of the most important physical, optical or functional properties of the product. With the advent of new drying technologies- some already commercialized while some still at pilot or laboratory stage - it is increasingly important to devote attention to the interaction between the drying conditions and the final product quality as measured by generally accepted standard test results. Aside from the drying parameters one must also examine paper/pulp parameters in the hope of achieving in the long term some predictive capability as well as drying-quality effects. This bibliography is selective in coverage and is compiled to ease the task of the interested reader in locating appropriate references covering his/her areas of interest.. Some general observations are made on the basis of the literature cited.

important problem.This is influenced by the composition and characteristics of the coating colour and raw stock and also by the type and rate of drying.

The following selected bibliography covers the effect of drying on pulp, paper and paperboard properties. Some available literature on coated paper drying is also included. It is encouraging to note a trend towards considering the effect of drying on the product quality as an integral part of drying R&;D projects. Earlier, the drying work was confined to optimising only the heat and mass transfer parameters. It should be noted also that this bibliography includes a substantial number of publications which are not in english. The availability of their translations into english is not known to the authors.

It is noteworthy that an international symposium - The Helsinki Symposium on Alternate Drying Technologies will be held in Helsinki in June 1991 to discuss the competing new drying technologies from the papermakers viewpoint.     

Human AKR1C Isoforms Oxidize the Potent Proximate Carcinogen 7,12-DMBA-3,4-diol in the Human Lung A549 Carcinoma Cell Line

Aldo-keto reductases (AKRs) oxidize structurally diverse PAH trans -dihydrodiols to yield reactive and redox active o -quinones. This study examined the ability of AKR1C2 and AKR1C4 to oxidize PAH trans -dihydrodiols of the benz[ a ]anthracene series. The enzymes oxidized 100% of the racemic trans -dihydrodiols and the highest utilization ratios were observed for the more potent proximate carcinogens 7,12-dimethylbenz[ a ]anthracene-3,4-diol (DMBA-3,4-diol) and 7-methylbenz[ a ]anthracene-3,4-diol (7-MBA-3,4-diol). Human multiple tissue expression array analysis revealed high expression of AKR1C isoforms in the human lung carcinoma cell line A549. Both Western blot analysis using AKR1C9 antisera and enzymatic assays using 1-acenapthanol as substrate confirmed the presence of active AKR1C enzymes in A549 cells. To determine the importance of AKR1C-mediated trans -dihydrodiol oxidation in A549 cells, DMBA-3,4-diol was incubated with cell lysates in the presence of 2-mercaptoethanol. Liquid chromatography/mass spectrometric analysis identified peaks that corresponded to the synthetically prepared mono- and bis -thioether conjugates of DMBA-3,4-dione confirming the ability of these cells to oxidize DMBA-3,4-diol to the corresponding o -quinone. Together, these studies demonstrate the importance of human AKR1Cs in PAH activation and their possible role in lung cancer.     

POLYCYCLIC AROMATIC HYDROCARBON O-QUINONES MUTATE p53 IN HUMAN LUNG ADENOCARCINOMA (A549) CELLS

Human lung adenocarcinoma (A549) cells form reactive and redox active PAH-o-quinones via constitutively expressed aldo-keto reductases. To determine whether these metabolites mutate p53, A549 cells were treated with N-methyl-N-nitroso-N-nitroguanidine (MNNG an alkylating mutagen), anti-BPDE (diol-epoxide) and benzo[a]pyrene-7,8-dione (o-quinone). p53 cDNA was amplified from the treated cells and cotransfected with a gap-repair plasmid designed to express p53 in yeast. When mutant p53 is expressed, it fails to drive the expression of an ADE2 reporter, and the yeast strain yIG397 turns red. The following mutational frequencies were observed versus the solvent controls: 1 mM MNNG (24.2% red colonies p = .02), 1 μ M anti-BPDE (9.9% red colonies p = .02), and 10 μ M BP-7,8-dione (9.3% red colonies p = .03). MNNG gave a high frequency (49%) of the expected C > T (G > A) mutations (p = .25). While anti-BPDE and BP-7,8-dione gave A > G (T > C) transitions (p = .034 – p = .054). These mutations would result from stable N⁶-deoxyadenosine adducts, but not from oxidatively damaged bases.     

SYNTHESES OF ADDUCTS OF ACTIVE METABOLITES OF CARCINOGENIC POLYCYCLIC AROMATIC HYDROCARBONS WITH 2′-DEOXYRIBONUCLEOSIDES

Syntheses are reported for: (1 Harvey, R. G. 1991. Polycyclic Aromatic Hydrocarbons: Chemistry and Carcinogenicity, Cambridge, , U.K.: Cambridge University Press.  [Google Scholar]) adducts of the quinone metabolites of benzo[a]pyrene (BPQ) and benz[a]anthracene (BAQ) with 2′-deoxyadenosine and 2′-deoxyguanosine; (2 Conney, A. H. 1982. Induction of Microsomal Enzymes by Foreign Chemicals and Carcinogenesis by Polycyclic Aromatic Hydrocarbons. Cancer Res., 42: 4875–4917. [PUBMED][INFOTRIEVE][CSA][PubMed], [Web of Science ®] , [Google Scholar]) ¹⁵ N-labelled analogs of these adducts (four or five nitrogen atoms ¹⁵ N-labelled); (3 Dipple, A. 1994. “Reactions of Polycyclic Aromatic Hydrocarbons with DNA”. In DNA Adducts: Identification and Biological Significance, Edited by: Hemminki, K., Dipple, A., Segerbäck, D., Kadulbar, F. F., Shuker, D. and Bartsch, H. pp. 107–129. IARC Scientific Publication No. 125.  [Google Scholar]) depurinated adducts of BPQ and BAQ with adenine or guanine covalently linked to the N7 or N9 positions of the purine bases; (4 Jeffrey, A. M., Weinstein, I. B., Jennette, K., Grzeskowiak, K., Nakanishi, K., Harvey, R. G., Autrup, H. and Harris, C. 1977. Structures of Benzo[a]pyrene-Nucleic Acid Adducts Formed in Human and Bovine Bronchial Explants. Nature (London)., 269: 348–350. [CSA][CROSSREF][Crossref], [PubMed], [Web of Science ®] , [Google Scholar]) ¹³ C-labelled derivatives of benzo[a]pyrene, BPQ, benzo[a]pyrene trans-7,8-dihydrodiol, and the benzo[a]pyrene anti-diol epoxide (with ¹³ C-atoms at the 5- and 11-positions); and (5 Jennette, K., Jeffrey, A. M., Blobstein, S. H., Beland, F. A., Harvey, R. G. and Weinstein, I. B. 1977. Characterization of Nucleoside Adducts from the in Vitro Reaction of Benzo[a]pyrene-7,8-dihydrodiol-9,10-oxide or Benzo[a]pyrene-4,5-oxide with Nucleic Acids. Biochemistry, 16: 932–938. [PUBMED][INFOTRIEVE][CSA][CROSSREF][Crossref], [PubMed], [Web of Science ®] , [Google Scholar]) depurinated adducts formed by reactions of the benzo[a]pyrene radical-cation at the C ⁸ -, N ⁷ -, and N ⁹ -positions of adenine and guanine.     

Reference Gene Selection for Quantitative PCR Studies in Sheep Neutrophils

Reference genes are essential for studying mRNA expression with quantitative PCR (qPCR). We investigated 11 potential neutrophil reference genes (RPL19, GAPDH, ACTB, B2M, HPRT, G6PD, TFRC, PGK1, YWHAZ, SDHA and GYPC) for sheep under disease conditions of foot rot (FR) and with or without Se supplementation. Initial screening was based on gene expression level (<28 Cq cycles) and variability (SD < 1.5 Cq cycles) and excluded TFRC, GYPC and HPRT from further analysis. Expression stability of the remaining genes was evaluated using four software programs: geNorm, NormFinder, BestKeeper and the comparative delta Cq method. The neutrophil reference genes, G6PD, YWHAZ, GAPDH, RPL19 and SDHA, consistently ranked among the top five most stable genes under these experimental conditions. The SDHA gene expression was not stable in FR-diseased sheep receiving Se treatment and, thus, cannot be recommended as a reference gene. The commonly used genes, PGK1, ACTB and B2M, were not reliable reference genes, underscoring the need to validate neutrophil reference genes under different experimental conditions. Multiple references genes rather than a single gene may provide more robust and reliable results. The best pair of reference genes was SDHA/G6PD in healthy sheep and GADPH/YWHAZ in FR-diseased sheep.     

Energetic,Low‐Melting Salts of Simple Heterocycles

The synthesis of three new families of heterocyclic‐based salts was undertaken and accomplished. Three triazole systems, 1H‐1,2,4‐triazole, 4‐amino‐1,2,4‐triazole, and 1H‐1,2,3‐triazole, were used as proton bases with nitric (HNO₃), perchloric (HClO₄), and dinitramidic (HN(NO₂)₂) acid systems. In all cases, stable salts were recovered and fully characterized by vibrational spectra (IR, Raman), multinuclear NMR spectroscopy, material balance, density measurements, and elemental analyses, as well as DSC, TGA and initial safety testing (impact). Many of these salts have melting points well below 100 °C, yet high decomposition onsets, defining them as new, highly energetic members of the well known class of materials identified as ionic liquids. Additionally, the single crystal X‐ray diffraction study of 1,2,4‐triazolium perchlorate was investigated, revealing the expected structure.