Luminescent thin films by the chemical aerosol deposition technology (CADT)

Zinc sulphide thin films have been deposited with CART using zinc chlorideand zinc acetylacetonate as Zn compounds and thiourea and 1,1,3,3-tetramethylthiourea as S compounds soluted in methanol, ethanol, isopropanol and cellosolve. After optimalization of the deposition process homogeneous layers with a c-axis oriented hexagonal columnar structure with a high density (up to 96%) were obtained. Luminescence was observed with films grown above 500°C. The influence of the hot plate temperature, flow of carrier gas, nozzle geometry, distance nozzle substrate, and volatility of the solvent and reactants on the growth rate, homogenity and density of the film has been shown. Some rules for the selection of the starting compound are given. TG analyses of the reactant compounds was used to compare their volatility and stability

The isolation of differentially expressed cDNA clones from the filarial nematode <i>Brugia pahangi</i>

A cDNA library constructed from 3 day post-infective L3 of the filarial nematode Brugia pahangi was screened by differential hybridization with cDNA probes prepared from different life-cycle stages. Five cDNA clones hybridizing selectively to the mosquito-derived L3 probe were isolated and characterized. Northern blot analysis of 4 of the clones confirmed that each was most highly expressed in the mosquito-derived L3. The expression of each mRNA during parasite development in the mosquito vector was investigated using RT-PCR, and all were shown to be abundant in the immature L3. Four of the 5 cDNAs cloned coded for structural proteins: 2 cuticular collagens, and the muscle proteins tropomyosin and troponin. Further studies on troponin using an antiserum raised to the recombinant protein demonstrated that the protein, unlike the mRNA, was present in all life-cycle stages examined, while immunogold labelling demonstrated that it was localized to the muscle blocks

Perceptions Of Internet Technology In Small Businesses: An Empirical Comparison Of The U.S., Mexico And Croatia

There is a dearth of literature comparing the perceptions of small business executives from developed, developing and emerging countries regarding the utilization of Internet technology. This empirical study analyzes and compares survey responses from U.S., Mexican and Croatian small business executives regarding the utilization of 13 different aspects of information/Internet technology.  The results indicate that U.S. small business executives have significantly higher perceptions than both Mexican and Croatian executives regarding the utilization of e-commerce, and that Croatian executives showed significantly higher perceptions than both U.S. and Mexican executives regarding the utilization of wireless phones

The Inflationary Process in Open Economies

While the concept of "imported inflation" and its relevance for open economies have received considerable attention in the policy-oriented literature, the theoretical underpinnings of this phenomenon have not been constructed as carefully as might be desirable in view of the controversial nature of the subject. The inflationary process can be transmitted to a country by developments in international capital and money markets or through the interaction of goods markets in one country with those of the rest of the world. The debate concerning the former transmission mechanism involves the difficulties in dichotomizing the balance of payments and the domestic money supply through the sterilization of foreign exchange gains or losses. In this paper, major emphasis will be given to the transmission of the inflationary process through the goods and services markets. Primarily,we are interested in investigating the determinants of the rate of inflation for a small country which, because of its size, is forced to accept certain conditions imposed by the external environment.

Direct Investment In The U.S. Balance Of Payments--A Portfolio Approach

The active control and operation of firms in other countries implied by direct foreign investment has dominated the international investment position of the U.S. vis-a-vis the rest of the world. At the end of 1967, 73% of U.S.long term foreign assets were held in the form of direct investment. On the other side of the coin, 35% of foreign long-term assets held in the U.S. were in this category. It is the purpose of this paper to explain the demand for these direct investment assets, both U.S. investment abroad and foreign investment in the U.S.

The Composition of Official International Reserves

The balance of this paper will take the following form: a hypothesis concerning the portfolio manangement of international reserves will be stated; then, this hypothesis will be tested statistically; finally, a discussion of these results and their meaning for the future will conclude the paper.

The Effectiveness of Stabilization Policy in a Small Open Economy

A small open economy is forced to operate in a constrained policy environment. Although for some products even a small country may have some monopoly power, in the aggregate these countries approximate more closely the behaviour of price takers than price makers. It is to economies such as these, and not larger or closed economies, that the analysis of this paper is devoted. The extremity of the assumptions is such as to make the analysis totally inapplicable to countries such as the United States. The purpose of the paper, then, is to investigate the characteristics peculiar to a small open economy and to incorporate them in a model which will allow us to discuss the effectiveness of stabilization policy in this constrained environment. In particular, it is proposed to re-examine Mundell's conclusions about monetary and fiscal policy under fixed and flexible exchange rates and to show that, under flexible exchange rates, an optimum policy combination exists that eliminates the trade-off between inflation and unemployment. As is common in these stabilization policy models, growth in factor supplies, and therefore output, is assumed not to exist.

Role of boronic acid moieties in poly(amido amine)s for gene delivery

The effects of the presence of two different types of phenylboronic acids as side groups in disulfide-containing poly(amido amine)s (SS-PAA) were investigated in the application of these polymers as gene delivery vectors. To this purpose, a para-carboxyphenylboronic acid was grafted on a SS-PAA with pending aminobutyl side chains, resulting in p(DAB–4CPBA) and an ortho-aminomethylphenylboronic acid was incorporated through copolymerization, resulting in p(DAB–2AMPBA). Both polymers have 30% of phenylboronic acid side chains and 70% of residual aminobutyl side chains and were compared with the non-boronated benzoylated analogue p(DAB–Bz) of similar Mw. It was found that the presence of phenylboronic acid moieties improved polyplex formation with plasmid DNA since smaller and more monodisperse polyplexes were formed as compared to their non-boronated counterparts. The transfection efficiency of polyplexes of p(DAB–4CPBA) was approximately similar to that of p(DAB–Bz) and commercial PEI (Exgen), both in the absence and the presence of serum, indicating that p(DAB–4CPBA) and p(DAB–Bz) are potent gene delivery vectors. However, the polymers with phenylboronic acid functionalities showed increased cytotoxicity, which is stronger for the ortho-aminophenylboronic acid containing polyplexes of p(DAB–2AMPBA) than for the p(DAB–4CPBA) analog. The cytotoxic effect may be caused by increased membrane disruptive interaction as was indicated by the increased hemolytic activity observed for these polymers

Poly(amido amine)s as Gene Delivery Vectors: Effects of Quaternary Nicotinamide Moieties in the Side Chains

To evaluate the effect of quaternary nicotinamide pendant groups on gene delivery properties, a series of poly(amido amine) (co)polymers were synthesized by Michael addition polymerization of N, N-cystaminebisacrylamide with variable ratios of 1-(4-aminobutyl)-3-carbamoylpyridinium (Nic-BuNH2), and tert-butyl-4-aminobutyl carbamate (BocNH-BuNH2), yielding poly(amido amine)s (NicX-NHBoc) with X=0, 10, 30, and 50 % of quaternary nicotinamide groups in the polymer side chains. Deprotection of the pendant Boc-NH groups afforded an analogous series of polymers (NicX-NH2) with higher charge density (due to the presence of protonated primary amino groups in the side chains) and subsequent acetylation yielded a series of polymers (NicX-NHAc) of lower hydrophobicity than the Boc-protected polymers. The polymers with the Boc-protected or the acetylated amino groups showed high buffer capacity in the range pH 5.1-7.4, which is a property that can contribute to endosomal escape of polyplexes. The presence of quaternary nicotinamide groups has distinct beneficial effects on the gene vector properties of these polymers. The polymers containing 30 % of quaternary nicotinamide groups in their side chains condense DNA into small, nanosized particles (200 nm) with positive surface charge (+15 mV). Fluorescence experiments using ethidium bromide as a competitor showed that the quaternary nicotinamide groups intercalate with DNA, contributing to a more intimate polymer-DNA binding and shielding. Polyplexes of nicotinamide-functionalized poly(amido amine)s NicX-NHBoc and NicX-NHAc, formed at 12/1 polymerDNA mass ratio, efficiently transfect COS-7 cells with efficacies up to four times higher than that of PEI (Exgen 500), and with essentially absence of cytotoxicity. NicX-NH2 polymers, possessing protonated primary amino groups in their side chains, have a higher cytotoxicity profile under these conditions, but at lower 3/1 polymer-DNA mass ratio also these polymers are capable of efficient transfection, while retaining full cell viability