Precracking and interfacial delamination in a bi-material structure: Static and dynamic loadings

The behavior of a precracked bi-material structure interface under given static and dynamic axial loading is an interest object in the present paper.Firstly,it is shown that the shear-lag model is a proper tool to analyze a delamination process in a precracked bi-material structure undergoing static loading.Secondly,the"shear-lag model"is applied to the structure under dynamic loading.To solve the problem for an interface delamination of the structure and to determine the debond length along the interface,our own 2D boundary element method(BEM)code is proposed in the case of static loading,and the shear-lag model together with the Laplace transforms and half-analytical calculations are used in the case of dynamic loading.The interface layer is assumed as a very thin plate compared with the other two.The parametric(geometric and elastic)analysis of the debond length and interface shear stress is done. The results from the 2D BEM code proved the validity of analytical solutions to the shear-lag model.In the dynamic case,the influence of loading characteristics,i.e.,frequencies and amplitude fluctuations on the shear stress and the value of debond length for an interval of time,is discussed. The analysis of the obtained results is illustrated by an example of the modern ceramic-metal composite,namely cermet, and depicted in figures.     

Penalized likelihood regression for generalized linear models with non-quadratic penalties

One of the popular method for fitting a regression function is regularization: minimizing an objective function which enforces a roughness penalty in addition to coherence with the data. This is the case when formulating penalized likelihood regression for exponential families. Most of the smoothing methods employ quadratic penalties, leading to linear estimates, and are in general incapable of recovering discontinuities or other important attributes in the regression function. In contrast, non-linear estimates are generally more accurate. In this paper, we focus on non-parametric penalized likelihood regression methods using splines and a variety of non-quadratic penalties, pointing out common basic principles. We present an asymptotic analysis of convergence rates that justifies the approach. We report on a simulation study including comparisons between our method and some existing ones. We illustrate our approach with an application to Poisson non-parametric regression modeling of frequency counts of reported acquired immune deficiency syndrome (AIDS) cases in the UK.     

SHORT-RANGE MOLECULAR INTERACTIONS AND STABILITY OF AMPHIPHILE BILAYER

A new approach is proposed for the study of short-range molecular interactions between first neighboring molecules in amphiphile bilayers by means of experimentally determined dependencies of the bilayer mean lifetime on the surfactant concentration and of the critical concentration for bilayer formation on the temperature. Short-range molecular interactions are demonstrated by the parameters binding energy Q of an amphiphile molecule in the bilayer and specific line energy γ of the nucleus hole. These parameters are calculated from the experimental dependencies by using the hole-nucleation theory [D. Kashchiev and D. Exerowa, J. Colloid Interface Sci., 77, 501 (1980)] describing the stability of amphiphile bilayers. It is shown the decisive role of the short-range molecular interactions for the bilayer stability and the occurrence of first-order phase transition in phospholipid foam bilayers. The values of Q and γ are calculated for various amphiphile bilayers: anionic and nonionic surfactants, phospholipids and their natural mixtures.     

Substituted Esters of Coumarin-3-phosphonic Acid—Linear-Polarized IR-Spectroscopic Elucidation

Correlation between the structure and IR-spectroscopic properties of two halogen and one amino substituted esters of coumarin-3-phosphonic acid has been studied by means of linear-polarized IR-spectroscopy of oriented colloid suspensions in nematic host. The influence of the ester group on the peak positions of the IR-characteristic bands of these derivatives and in particular, on phosphorus group is investigated by a comparison with the data for corresponding coumarin-3-phosphonic acids. Theoretical quantum chemical DFT calculations (B3LYP/6-311++G??) are carried out, thus supporting the experimental assignment of the IR-bands and predicting the electronic structure of all of the compounds studied.     

Crystal Structure and Spectroscopic Properties of (2-oxo-2H-chromen-3-yl)phosphonic Acid Monoethyl Ester Trihydrate

Abstract

(2-Oxo-2H-chromen-3-yl)phosphonic acid monoethyl ester trihydrate (1) was synthesized, isolated, and spectroscopically as well as structurally characterized by means of single crystal X-ray diffraction; conventional and linear-polarized IR spectroscopy; electronic (UV-VIS-NIR) spectroscopy; ¹H, ¹³C, and ³¹P NMR. Quantum chemical DFT calculations have been performed in order to obtain information on the electronic structure and vibrational properties of 1, thus supporting the experimental data. The correlation between the structure and spectroscopic characteristics is discussed.

GRAPHICAL ABSTRACT      

A new and efficient method for the synthesis of 3,4-disubstituted pyrrolidine-2,5-diones

A newly found reaction for the synthesis of 3,4-disubstituted 1-hydroxy-pyrrolidine-2,5-diones from 3-substituted coumarins and nitromethane has been elaborated. The reaction involved a simple and convenient experimental procedure. The applicability of the rearrangement reaction is determined.     

Influence of nutrient medium composition on in vitro growth, polyphenolic content and antioxidant activity of Alchemilla mollis

Alchemilla mollis (Buser) Rothm. (Rosaceae) is a high-mountain medicinal plant growing in the Balkan Peninsula, with only one population in Bulgaria. Alchemilla plants (Lady's mantle) are commonly used in traditional medicine for treatment of many gynecological diseases. The commercial drugs "Herba Alchemillae" induce a rapid regeneration of skin epithelium and have styptic and anti-inflammatory actions. Because of the high content of phenolic compounds (tannins and flavonoids) and the ecological plasticity of the species, field cultivation or in vitro biomass production of A. mollis are possible alternatives to its collection from nature. Four MS based nutrient media differing in the concentration of the minerals and supplemented with alpha-naphthaleneacetic acid (NAA) and benzylaminopurine (BAP) were tested in order to examine their influence on the shoot multiplication effectiveness and the antioxidant activity of A. mollis, and also the possible relation between these parameters under the conditions of in vitro culture. The cultures grown for two months on these media differed significantly in their multiplication rates (p < 0.001), as well as in their morphological features--height, leaf color and root development. Methanol extracts of in vitro cultivated and ex vitro adapted and acclimated on Vitosha Mt. (1500 m a. s. l.) plants were analyzed for tannin and flavonoid content and for free radical scavenging activity. The contents of flavonoids and tannins in the in vitro cultures of A. mollis cultivated on the four tested media differed significantly (p < 0.05). The highest flavonoid content was found in the shoots cultivated on the control MS medium, as well as in the ex vitro adapted plants. The antioxidant activity of the in vitro cultures correlated positively with the concentrations of the PGRs in the respective media, and the ex vitro adapted plants had the highest antioxidant activity (IC50 13.1 +/- 1.9 microg/mL) commensurable with that of the commercial antioxidant butylated hydroxytoluene (BHT) used as a positive control, with an IC50 of 12.65 microg/mL.     

Surface flavonoid aglycones in newly studied plant species

Several newly studied species of the Scrophulariaceae, Lamiaceae, and Ranunculaceae spread in Bulgaria have been analyzed for their surface flavonoid profiles. Except Pulsatilla montana (Hope) Rchb. (Ranunculaceae) all taxa now studied accumulated mainly apigenin, luteolin, and it's derivatives. This is the first report for the presence on external flavonoid aglycones in genus Pulsatilla. Quercetin-3'-methyl ether is a new citation for P. montana. The presence on surface flavonoid aglycones in species Veronica bellidioides L., V. persica Poir., Odontites verna (Bell.) Dum., Laminiastrum galeobdolon Heist ex Fabr., Glechoma herbaceae L., Ajuga genevensis L., and A. reptans L. are reported for the first time too.