New diketopyrrolopyrrole based D–A–D π-conjugated molecules: Synthesis,optical, electrochemical,morphological and photovoltaic properties

Two solution processable donor–acceptor, π-conjugated molecules that consist of diketopyrrolopyrrole (DPP) central acceptor unit with dibenzofuran (DPP-DBF) or acenaphtene (DPP-ACN) donor substituents, were prepared by Suzuki coupling reaction. The optical, electrochemical and film forming properties of these D–A–D molecules were investigated and used as active materials in bulk heterojunction solar cells.     

Hydrodynamics and heat transfer in bubbly flow in the turbulent boundary layer

In the work presented is a new approach to modelling the bubbly flow in the boundary layer. The approach is based on summation of dissipation energy coming from the shearing turbulent flow in the absence of bubbles and the dissipation contribution from the presence of bubbles. As a result we obtain the dissipation of equivalent single phase turbulent flow. The model has been solved using the method of asymptotic correction to provide an explicit differential equation describing the velocity profile. That can be solved with the assumption of constant void fraction distribution to yield the analytical velocity profile. Alternatively, author has developed his own model of lateral void migration, which is distinct from other models by virtue of presence of another rotational velocity. Velocity distributions calculated using the new model have been compared against the experimental data of turbulent bubble flows with small void fraction. A good consistency between calculations performed using a new model and available experimental data has been obtained. Additionally, a solution of the temperature field is also given. In the case of a constant void fraction distribution analytical distribution of the Nusselt number is given or the set of differential equations needs to be solved.     

Lipidation of Temporin-1CEb Derivatives as a Tool for Activity Improvement,Pros and Cons of the Approach

The alarming raise of multi-drug resistance among human microbial pathogens makes the development of novel therapeutics a priority task. In contrast to conventional antibiotics, antimicrobial peptides (AMPs), besides evoking a broad spectrum of activity against microorganisms, could offer additional benefits, such as the ability to neutralize toxins, modulate inflammatory response, eradicate bacterial and fungal biofilms or prevent their development. The latter properties are of special interest, as most antibiotics available on the market have limited ability to diffuse through rigid structures of biofilms. Lipidation of AMPs is considered as an effective approach for enhancement of their antimicrobial potential and in vivo stability; however, it could also have undesired impact on selectivity, solubility or the aggregation state of the modified peptides. In the present work, we describe the results of structural modifications of compounds designed based on cationic antimicrobial peptides DK5 and CAR-PEG-DK5, derivatized at their N-terminal part with fatty acids with different lengths of carbon chain. The proposed modifications substantially improved antimicrobial properties of the final compounds and their effectiveness in inhibition of biofilm development as well as eradication of pre-formed 24 h old biofilms of Candida albicans and Staphylococcus aureus. The most active compounds (C5-DK5, C12-DK5 and C12-CAR-PEG-DK5) were also potent against multi-drug resistant Staphylococcus aureus USA300 strain and clinical isolates of Pseudomonas aeruginosa. Both experimental and in silico methods revealed strong correlation between the length of fatty acid attached to the peptides and their final membranolytic properties, tendency to self-assemble and cytotoxicity.     

VUV spectroscopy and low temperature thermoluminescence of LSO:Ce and YSO:Ce

Radioluminescence and UV-excited photoluminescence spectra, photoluminescence time profiles, thermoluminescence glow curves and gamma-excited energy spectra (determining scintillation light yields) of several Lu₂SiO₅:Ce and Y₂SiO₅:Ce samples were recorded. The results are analyzed with attention focused on possible correlations between trap distributions, VUV responses, and light yields. The aspect of two distinct sites occupied by Ce³⁺ ions is also discussed.     

Bang-bang Controls and Piecewise Constant ones for Continuous Roesser Systems

In the paper, we prove the bang-bang principle for a continuous linear nonautonomous Roesser system and some approximation result (with respect to piecewise constant controls) for a continuous nonautonomous Roesser system which is linear in the state and nonlinear in the control. Published online: April 2006 The preparation of this paper was supported by the State Committee for Scientific Research, Poland, under Grant 7 T11A 004 21     

Structure and properties of polyolefin blends

Blends of ethylene–propylene–diene rubber (EPDM) and low density polyethylene (PE_id) or isotactic polypropylene (iPP) crosslinked by dicumyl peroxide (DCP) have been prepared. Their morphology, reactivity of the components and crystallinity have been studied. The blends are microheterogeneous. Both plastomers, but particularly iPP, decrease the crosslinking efficiency of EPDM by DCP. It was found that they also influence the mechanical properties of the blends. The effect of iPP is far more pronounced than that of PE_Id, because of an increase in crystalline phase content. iPP particles play a role as nuclei for propylene monomer units in EPDM, whereas PE_Id particles are solvated by the elastomer matrix.     

On a reliability problem by stochastic control methods

In the paper a problem of renewal of a nonhomogeneous Markov chain with incomplete information given by a point process is treated. A long run average cost is studied. The article applies the ‘crossing level’ method given by Davis. An example of exponentially distributed time-to-failure is given.     

Effects of a nonuniform vertical profile of chlorophyll concentration on remote-sensing reflectance of the ocean

Numerical simulations of radiative transfer were used to examine the effects of a nonuniform vertical profile of the inherent optical properties of the water column associated with the vertical profile of chlorophyll concentration, Chl(z), on the spectral remote-sensing reflectance, Rrs(gamma), of the ocean. Using the Gaussian function that describes the Chl(z) profile, we simulated a relatively broad range of open-ocean conditions characterized by the presence of a subsurface Chl maximum at depths greater than or equal to 20 m. The simulations for a vertically nonuniform Chl(z) were compared with reference simulations for a homogeneous ocean whose Chl was identical to the surface Chl of inhomogeneous cases. The range of values for the Gaussian parameters that produce significant differences in Rrs(gamma) (> 5%) was determined. For some vertical structures of Chl(z) considered, the magnitude of Rrs(gamma) and the blue-to-green band ratios of Rrs(gamma) differ significantly from the reference values of homogeneous ocean (> 70% in extreme cases of low surface chlorophyll of 0.02 mg m(-3) and shallow pigment maximum at 20 m). The differences are small or negligible when the nonuniform profiles are characterized by a surface Chl greater than 0.4 mg m(-3) or a depth of Chl maximum greater than 45 m (65 m in extremely clear waters with a surface Chl of 0.02 mg m(-3) or less). The comparison of modeling results with the current algorithm for retrieving the global distribution of chlorophyll from satellite imagery of ocean color suggests that strong effects of the subsurface chlorophyll maximum on reflectance at low surface chlorophyll concentrations can lead to a severalfold overestimation in the algorithm-derived surface chlorophyll. Examples of field data from the Sea of Japan and the north polar Atlantic Ocean are used to illustrate various nonuniform pigment profiles and their effect on the blue-to-green ratio of Rrs(gamma).     

Effect of preliminary grinding of the wheat grain on the pulverizing process

This article presents the results of investigations on the pulverizing grinding energy requirements for whole and preliminary ground wheat kernels regarding different moisture levels. Four common wheat cultivars (Triticum aestivum, ssp. vulgare) differing in kernel hardness were used for tests. When the moisture of kernels ranged from 14% to 20% w.b. the lower values of average particle size were obtained for preliminary ground wheat. The pulverizing energy requirements expressed by different grinding indices were considerably lower for preliminary ground kernels rather than for whole kernels. The values of specific pulverizing energy ranged from 32.6 to 79.0 kJ kg⁻¹ for whole kernels, whereas the values of total specific grinding energy (the sum of specific grinding energy and specific pulverizing energy) changed from 23.1 to 44.4 kJ kg⁻¹ for the two-stage ground wheat. In addition, the other values of pulverizing indices confirmed that preliminary size reduction significantly reduced the grinding energy requirements.     

New optical ceramics: High-entropy sesquioxide X2O3 multi-wavelength emission phosphor transparent ceramics

Highly transparent X₂O₃ sesquioxide ceramics were obtained from a solid solution of five different oxides (Lu₂O₃, Y₂O₃, Yb₂O₃, Gd₂O₃, and Dy₂O₃), mixed in an equal molar ratio according to the principle of high-entropy. The fabricated (Lu, Y, Yb, Gd, Dy)₂O₃ ceramics achieved 99.97 % of the relative density and exhibited a high degree of optical transparency with the in-line transmittance of almost 80 % in the visible wavelength range. Emissions of Gd³⁺ (⁶P_J → ⁸S_7/2 at 312 nm), Dy³⁺ (⁴F_9/2 → ⁶H_15/2 at 492 nm and ⁴F_9/2 → ⁶H_13/2 at 572 nm), and Yb³⁺ (²F_5/2 → ²F_7/2 at 1031 nm) suggested a potential application of the high-entropy ceramics as multi-wavelength emission phosphor transparent ceramics. High-entropy ceramics also exhibited lower specific heat and thermal conductivity compared to single-element sesquioxide ceramics. This work demonstrated that highly transparent oxide ceramics, with complex chemical compositions and good optical properties, could be obtained using the high-entropy principle.