Low charge polyvinylamine nanogels offer sustained,low‐level gene expression

Cationic polymer charge and polymer degradability each play a crucial role for packaging and delivering plasmid DNA. High density cationic charge has been shown to enhance transfection efficiency but may give rise to undesirable toxicity. Polyvinylamine (PVAm) nanogels bearing discrete amounts of surface charge were used to systematically examine the balance between transfection efficiency and cytotoxicity. Poly(N‐vinylformamide) (PNVF) nanogels were prepared via an inverse emulsion polymerization reaction and crosslinked with a nondegradable or acid‐labile crosslinker. The nanogels were then hydrolyzed to yield varying degrees of primary amines. The degree of conversion from PNVF to PVAm was controlled using different concentrations of NaOH and hydrolysis times. PVAm nanogel size and charge ranged from 150 to 310 nm, and +3.5 to +18 mV, respectively. These cationic particles were then complexed with pDNA encoding for luciferase. The cytotoxicity of PVAm nanogels and the transfection efficiency of PVAm/DNA complexes were evaluated in carcinomic human alveolar basal epithelial cells (A549). The cytotoxicity of PVAm nanogels increased with increasing accessible charge as expected. Transfection efficiency increased with increasing amounts of amine groups for nondegradable nanogels. Interestingly, acid‐labile nanogels bearing low charge demonstrated more sustained gene transfection when compared with the more highly charged nanogels. These observations suggested that the use of degradable particles with less charge may reduce cytotoxicity without compromising overall transfection efficiency. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

A boundary‐perturbation finite element approach for shape optimization

A numerical method is proposed for the efficient solution of shape optimization problems, which combines the boundary perturbation technique and finite element analysis. The method is computationally efficient in that it requires a number of finite element analyses with a fixed geometry, as opposed to standard shape optimization which requires re‐analysis with varying geometry. The application of the method to general shape optimization is considered. In addition, a special optimization scheme is devised for a class of problems governed by linear partial differential equations. The performance of the method is illustrated via an example which involves acoustic wave scattering from an obstacle. Copyright © 2000 John Wiley & Sons, Ltd.     

Breathable polymeric materials based on high-density polyethylene prepared by environmental crazing

This work addresses the preparation of breathable materials based on high-density polyethylene (HDPE) and characterization of their performance. The sustainable HDPE mesoporous materials were prepared by the tensile drawing of the HDPE films in the presence of physically active liquids (PALEs) via the mechanism of environmental intercrystallite crazing (EIC). The prepared mesoporous materials were characterized by the different physicochemical methods such as differential scanning calorimetry (DSC), atomic force microscopy (AFM), low-temperature nitrogen adsorption (LTNA), and so forth. Water vapor transmission rate (WVTR) of the breathable materials can be tailored by varying the tensile strain upon the EIC and is found to be equal to 597–1345 g m⁻² day⁻¹. The breathable HDPE-based materials are characterized by good mechanical and insulating properties as well as by high water entry pressure (~43–47 bar). Hence, the deformation of HDPE films via the EIC mechanism provides an efficient route for the preparation of mesoporous breathable materials based on the low-cost commercial polymers, which can be used as waterproof, protective, subroof, gas storage, and packaging materials. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48567.     

Estimation and prediction of the heats of formation for non-aromatic polynitro compounds on the basis of the QSPR approach

The analysis of “Quantitative Structure-Property Relationship”(QSPR), concerning the heat of formation in the condensed state, is performed for non-aromatic polynitrocompounds. The QSPR approach and our original computer program “EMMA”(Efficient Modelling of Molecular Activity) are used. This approach is based on the construction of optimal linear regression models involving physical-chemical, topological, informational, and substructural indices; it can be used as an alternative to traditional additive schemes for evaluating physical-chemical characteristics of energetic materials. On the basis of the QSPR method, the “structure-heat of formation (ΔH°_f)” relationship is revealed for a data base of non-aromatic polynitrocompounds, and ΔH°_f is predicted for some hypothetic substances.     

Comparative Characteristic of Energy Content Calculating Methods for the furazan series as an example of energetic materials

The significant expenditures for organic synthesis of high-energy materials necessitate an a priori evaluation of prospects for physical-chemical parameters. The most important of these parameters is the heat of formation characterizing this or the other compound suggested for synthesis. This study describes and analyzes the most well-known and widely used schemes and methods for evaluating and predicting the energy capacity of high-energetic materials. The accuracy of calculations is evaluated for different schemes; the limits of their applicability are determined.     

Reversible Hydriding of LaNi5 − xAlx ― Pd Composites in the Presence of Carbon Monoxide

Carbon monoxide is one of the most dangerous impurities in gas mixtures involved in the hydriding of intermetallic compounds, and up to the present time the concentration limit 0.03 vol.% CO has not been surmounted. The objective of the present work was to investigate the possibility of reversibly hydriding LaNi_{5 ? x} Al _x ― Pd composites in gas mixtures containing up to 5 vol.% CO. The experimental specimens were mixtures of palladium black and LaNi₅, LaNi_4.7Al_0.3, LaNi_4.5Al_0.5, LaNi_4.2Al_0.8, and LaNi₄Al powders cold pressed at 300 MPa. The intermetallics were preliminarily dispersed by hydriding and mechanical grinding. The concentration of palladium black in the powder mixtures was varied from 0 to 1.5 mass%. It was shown that it is possible to reversibly hydride LaNi_{5 ? x} Al _x ― Pd composites in mixtures of hydrogen and carbon monoxide containing up to 5 vol.% CO at the temperatures 423 and 473 K. It was established that alloying LaNi₅ with aluminum in amounts which raised the stoichiometric concentration above 0.5 stabilized the absorption properties of LaNi_{5 ? x} Al _x ― Pd in the presence of CO. The composition LaNi₄Al was optimal. Palladium additions to LaNi_{5 ? x} Al _x ― Pd composites also increased the stability of hydrogen absorption by the intermetallic. It is noted that the effect of palladium was more positive than that of aluminum.