Parametric Evaluation of Governing Heat and Mass Transfer Resistances in Membrane Based Heat and Moisture Exchangers

To provide a healthy environment inside buildings, there must be some exchange of indoor conditioned air with fresh outdoor air. The outdoor air is then mechanically conditioned to a comfortable temperature and humidity. Research suggests human health and productivity increase with the amount of fresh air available in buildings. This conflicts with the desire to reduce building energy use since the conditioning process is energy intensive, especially in warm and humid climates. While sensible heat recovery using a standard heat exchanger is of some value, much of the energy consumption is due to dehumidification of air. More substantial reductions in energy consumption can be obtained by preconditioning the supply air with the previously conditioned exhaust air using a porous polymer membrane heat and moisture exchanger. As membrane technology improves, the convective heat and mass transfer resistances in the airstream can become the dominant resistance in these devices. This requires potentially new flow passage architecture to optimize heat and mass transfer, while maintaining acceptable pressure loss. Thus, the objective of this study is to develop an analytical model of a counterflow membrane based heat and mass exchanger with different internal flow geometries using the Engineering Equations Solver (EES) platform. The exchanger consists of multiple supply and exhaust air streams flowing in counterflow, separated by a thin membrane layer. The air flow passages are either a bare high aspect rectangular channel, or a high aspect channel with a pin-fin spacer inserted. The model is discretized along the length of the exchanger to more accurately calculate the air and vapor properties along the exchanger. In each segment the model considers the coupled convective heat and mass transfer resistances in each air stream. Heat and mass transfer coefficients are related through the Chilton and Colburn analogy, while representative values for membrane thermal conductivity and effective diffusivity are obtained from the literature. Conservation of energy and mass in each segment provides closure to the model. The model is then used to parametrically evaluate the effect of various exchanger dimensions and operating conditions on the dominant heat and mass transfer resistances, sensible and latent effectiveness, and pressure loss of the exchanger. The primary dimensions considered are hydraulic diameter and geometry (i.e., high aspect versus pin filled channels) of the channels, number of channels, membrane thickness and overall length, width and depth of the exchanger. The effect of operating parameters including air flow rate, water diffusivity of the membrane and allowable pressure drop on system performance and dominant transport mechanisms are also explored.

Inhibition of growth of OV-1063 human epithelial ovarian cancers and c- jun and c- fos oncogene expression by bombesin antagonists

Receptors for bombesin are present on human ovarian cancers and bombesin-like peptides could function as growth factors in this carcinoma. Therefore, we investigated the effects of bombesin/gastrin-releasing peptide (GRP) antagonists RC-3940-II and RC-3095 on the growth of human ovarian carcinoma cell line OV-1063, xenografted into nude mice. Treatment with RC-3940-II at doses of 10 μg and 20 μg per day s.c. decreased tumour volume by 60.9% (P< 0.05) and 73.5% (P< 0.05) respectively, after 25 days, compared to controls. RC-3095 at a dose of 20 μg per day reduced the volume of OV-1063 tumours by 47.7% (P = 0.15). In comparison, luteinizing hormone-releasing hormone (LH-RH) antagonist Cetrorelix at a dose of 100 μg per day caused a 64.2% inhibition (P< 0.05). RT-PCR analysis showed that OV-1063 tumours expressed mRNA for bombesin receptor subtypes BRS-1, BRS-2, and BRS-3. In OV-1063 cells cultured in vitro, GRP(14–27) induced the expression of mRNA for c- jun and c- fos oncogenes in a time-dependent manner. Antagonist RC-3940-II inhibited the stimulatory effect of GRP(14–27) on c- jun and c- fos in vitro. In vivo, the levels of c- jun and c- fos mRNA in OV-1063 tumours were decreased by 43% (P< 0.05) and 45% (P = 0.05) respectively, after treatment with RC-3940-II at 20 μg per day. Exposure of OV-1063, UCI-107 and ES-2 ovarian carcinoma cells to RC-3940-II at 1 μM concentration for 24 h in vitro, extended the latency period for the development of palpable tumours in nude mice. Our results indicate that antagonists of bombesin/GRP inhibit the growth of OV-1063 ovarian cancers by mechanisms that probably involve the downregulation of c- jun and c- fos proto-oncogenes. © 2000 Cancer Research Campaig

Targeted cytotoxic analogue of bombesin/ gastrin-releasing peptide inhibits the growth of H-69 human small-cell lung carcinoma in nude mice

Recently, we developed a powerful cytotoxic analogue of bombesin AN-215, in which the bombesin-like carrier peptide Gln–Trp–Ala–Val–Gly–His–Leu–Ψ(CH2-NH)–Leu–NH2 (RC-3094) is conjugated to a potent derivative of doxorubicin, 2-pyrrolinodoxorubicin (AN-201). Small-cell lung carcinomas (SCLCs) are known to express high levels of bombesin receptors. We evaluated whether these receptors could be used for targeting cytotoxic bombesin analogue to H-69 SCLC cells. H-69 cells were xenografted into male nude mice, which then received an intravenous injection of AN-215, cytotoxic radical AN-201, the carrier peptide RC-3094 alone or unconjugated mixture of RC-3094 and AN-201. The levels of mRNA for bombesin receptor subtypes were evaluated by reverse transcription-polymerase chain reaction. In vitro, both the analogue AN-215 and the radical AN-201 showed strong antiproliferative effects on H-69 cells, AN-215 requiring more time to exert its action at 10–8M concentration than AN-201. In vivo, the growth of H-69 SCLC tumours was significantly inhibited by the treatment with 200 nmol kg–1 of AN-215, while equimolar doses of the cytotoxic radical AN-201 or the mixture of AN-201 and the carrier peptide were toxic and produced only a minor tumour inhibition as compared with control groups. mRNA for bombesin receptor subtypes 2 (BRS-2) and 3 (BRS-3) was detected in H-69 tumours. The mRNA levels for BRS-3, but not for BRS-2, were lower in the AN-215-treated tumours as compared with controls. Our results demonstrate that the cytotoxic bombesin analogue AN-215 could be considered for targeted therapy of tumours, such as SCLC, that express bombesin receptors. © 1999 Cancer Research Campaig

Evaluation of Governing Heat and Mass Transfer Resistances in Membrane Based Energy Recovery Ventilators with Internal Support Structures

Energy recovery ventilators (ERVs) are an effective way to reduce energy consumption in buildings while satisfying ventilation standards. As membrane technology and manufacturing methods improve, membrane based ERVs are seeing increased market penetration. In the present study, the feasibility of membrane ERV designed to fit in a commercial building wall cavity is investigated. A heat and mass transfer resistance and pressure drop model is developed for a low aspect ratio (width/height) exchanger and is used to evaluate the sensible and latent effectiveness of a counter-flow ERV with internal support structures. The performance of strip-fin and pin-fin structures are compared and dominant heat and mass transfer resistances are investigated. It is shown that for all cases the sensible heat transfer is dominated by the convective resistance while the dominant mass transfer resistance shifted to the membrane at smaller hydraulic diameters. The results suggest that as membrane technology improves, enhancements to the air-side heat and mass transfer coefficients will be required to continue to realize performance gains

Antagonists of growth hormone-releasing hormone (GH-RH) inhibit IGF-II production and growth of HT-29 human colon cancers

Insulin-like growth factors (IGFs) I and II are implicated in progression of various tumours including colorectal carcinomas. To interfere with the production of IGFs, we treated male nude mice bearing xenografts of HT-29 human colon cancer with various potent growth hormone-releasing hormone (GH-RH) antagonists. Twice daily injections of antagonist MZ-4-71, 10 μg intraperitoneally or 5 μg subcutaneously (s.c.) resulted in a significant 43–45% inhibition of tumour growth. Longer acting GH-RH antagonists, MZ-5-156 and JV-1-36 given once daily at doses of 20 μg s.c. produced a 43–58% decrease in volume and weight of cancers. Histological analyses of HT-29 cancers demonstrated that both a decreased cell proliferation and an increased apoptosis contributed to tumour inhibition. GH-RH antagonists did not change serum IGF-I or IGF-II levels, but significantly decreased IGF-II concentration and reduced mRNA expression for IGF-II in tumours. In vitro studies showed that HT-29 cells produced and secreted IGF-II into the medium, and addition of MZ-5-156 dose-dependently decreased IGF-II production by about 40% as well as proliferation of HT-29 cells. Our studies demonstrate that GH-RH antagonists inhibit growth of HT-29 human colon cancers in vivo and in vitro. The effect of GH-RH antagonists may be mediated through a reduced production and secretion of IGF-II by cancer cells. © 2000 Cancer Research Campaig

RAMAN DIFFERENCE SPECTROPHOTOMETRIC STUDY OF COMPETITIVE REACTIONS OF NUCLEOTIDES WITH CIS-DIMETHYLGOLD(III); AND THE INVESTIGATION OF PROBLEMS ASSOCIATED WITH THE SYNTHESIS OF THERMALLY STABLE SALTS OF LITHIUM PERMETHYLMETALLATES

Competitive reactions of the heavy metal electrophile cis-dimethylgold(III) with a mixture of 20 mM 5\u27-GMP, 20 mM 5\u27-CMP, 30 mM 5\u27-AMP, 30 mM 5\u27-UMP have been studied at pH 7, 25(DEGREES)C. Raman difference spectroscopy was used to establish whether there is selectivity in the metal binding to the nucleic acids. The labile, bifunctional cis-dimethylgold(III) reacts with all four nucleotides with no selectivity in the coordination to pyrimidine over purine nucleotides. Attack is mainly at imino nitrogens with substitution of the metal for a proton. Cis-dimethylgold(III) exhibits little selectivity in its reaction with nucleotides. A study of the C211 cryptand was conducted to investigate the effect of this ligand upon the stability of salts of lithium cation. The reactions of the C211 cryptand with cyano complexes of lithium cyanide with cyanides of copper, silver and gold were studied. The following complexes were isolated and characterized by elemental analysis and infrared spectroscopy: Li(C211)Cu(,2)(CN)(,3), Li(C211)Cu(CN)(,4)(.)nH(,2)O(.)nEt(,2)O, Li(C211)Ag(CN)(,2), Li(C211)Au(CN)(,2) and Li(C211)Au(CN)(,4). Complexes containing more than one lithium cation (e.g. Li(,3)(C211)Cu(CN)(,4)(.)nH(,2)O(.)nEt(,2)O) may precipitate from solution with only a portion of the lithium complexed by C211. The infrared spectra of the complexes isolated revealed that the C211 cryptand complexes lithium such that little perturbation of the anionic species occurs. The reactions of the C211 cryptand with solutions of lithium permethylmetallates of chromium, tungsten, tin and copper were studied. The reactions of C211 with trimethylstannyllithium in THF and of C211 with dilithium octamethyltungstate in diethyl ether resulted in the syntheses of thermally stable solids containing Sn(CH(,3))(,3)(\u27-) and W(CH(,3))(,8)(\u272-). Satisfactory elemental analyses for the tin and tungsten complexes could not be obtained, however, these permethylmetallates were identified by (\u271)H nmr and infrared spectroscopies. The reaction of C211 with a solution of lithium dimethylcuprate in diethyl ether resulted in the synthesis of a thermally stable solid. The elemental analysis of this air sensitive solid suggests that the solid contains a permethyl complex of copper. The C211 cryptand reacts with Li(,3)Cr(CH(,3))(,6) in diethyl ether to give an unidentified side product. The low temperature (-40(DEGREES)C) Raman difference spectra of solutions containing mixtures of MeLi and LiBr in diethyl ether were obtained. Solutions of halide-free MeLi in diethyl ether exhibit bands in the low frequency region of the Raman spectra which are due to the Li(,4)C(,4) cluster vibrations of the MeLi tetramer. These low frequency bands are not observed in 1/1 solutions of MeLi/LiBr. These results obtained at -40(DEGREES)C are in agreement with previous Raman data obtained room temperature which suggests that the MeLi tetramers are altered or broken down in the presence of lithium halides

Passive Adaptive Flow Control Simulator

<p>Evaluates heat transfer and pressure drop in channels with orifice outlets that have a temperature dependent pressure drop.</p

High yield conversion of doxorubicin to 2-pyrrolinodoxorubicin, an analog 500-1000 times more potent: structure-activity relationship of daunosamine-modified derivatives of doxorubicin.

A convenient, high yield conversion of doxorubicin to 3'-deamino-3'-(2''-pyrroline-1''-yl)doxorubicin is described. This daunosamine-modified analog of doxorubicin is 500-1000 times more active in vitro than doxorubicin. The conversion is effected by using a 30-fold excess of 4-iodobutyraldehyde in anhydrous dimethylformamide. The yield is higher than 85%. A homolog of this compound, 3'-deamino-3'-(1'',3''-tetrahydropyridine-1''-yl)doxorubicin, was also synthesized by using 5-iodovaleraldehyde. In this homolog, the daunosamine nitrogen is incorporated into a six- instead of a five-membered ring. This analog was 30-50 times less active than its counterpart with a five-membered ring. A similar structure-activity relationship was found when 3'-deamino-3'-(3''-pyrrolidone-1''-yl)doxorubicin (containing a five-membered ring) and 3'-deamino-3'-(3''-piperidone-1''-yl)doxorubicin (with a six-membered ring) were tested in vitro, the former being 5 times more potent than the latter. To further elucidate structure-activity relationships, 3'-deamino-3'-(pyrrolidine-1''-yl)doxorubicin, 3'-deamino-3'-(isoindoline-2''-yl)doxorubicin, 3'-deamino-3'-(2''-methyl-2''-pyrroline-1''-yl)doxorubicin, and 3'-deamino-3'-(3''-pyrroline-1''-yl)doxorubicin were also synthesized and tested. All the analogs were prepared by using reactive halogen compounds for incorporating the daunosamine nitrogen of doxorubicin into a five- or six-membered ring. These highly active antineoplastic agents can be used for incorporation into targeted cytotoxic analogs of luteinizing hormone-releasing hormone intended for cancer therapy