A critical assessment of two types of personal UV dosimeters

Doses of erythemally weighted irradiances derived from polysulphone (PS) and electronic ultraviolet (EUV) dosimeters have been compared with measurements obtained using a reference spectroradiometer. PS dosimeters showed mean absolute deviations of 26% with a maximum deviation of 44%, the calibrated EUV dosimeters showed mean absolute deviations of 15% (maximum 33%) around noon during several test days in the northern hemisphere autumn. In the case of EUV dosimeters, measurements with various cut-off filters showed that part of the deviation from the CIE erythema action spectrum was due to a small, but significant sensitivity to visible radiation that varies between devices and which may be avoided by careful preselection. Usually the method of calibrating UV sensors by direct comparison to a reference instrument leads to reliable results. However, in some circumstances the quality of measurements made with simple sensors may be over-estimated. In the extreme case, a simple pyranometer can be used as a UV instrument, providing acceptable results for cloudless skies, but very poor results under cloudy conditions. It is concluded that while UV dosimeters are useful for their design purpose, namely to estimate personal UV exposures, they should not be regarded as an inexpensive replacement for meteorological grade instruments.     

Crystallization of dyes by directed aggregation of colloidal intermediates: a model case

The crystallization of two oil-soluble dyes, oil red and oil blue, from the 125-nm-sized nanodroplets of miniemulsions, results in larger well-crystallized species of high quality, which must have been grown by aggregation of colloidal intermediates. This model case not only allows the existence of this nonclassical crystallization process to be proven but also gives evidence for the presence of "super-van der Waals" forces operating between the single nanocrystalline moieties.     

Biological Investigation of Amaryllidaceae Alkaloid Extracts from the Bulbs of Pancratium trianthum Collected in the Senegalese Flora

Amaryllidaceae plants are rich in alkaloids with biological properties. Pancratium trianthum is an Amaryllidaceae species widely used in African folk medicine to treat several diseases such as central nervous system disorders, tumors, and microbial infections, and it is used to heal wounds. The current investigation explored the biological properties of alkaloid extracts from bulbs of P. trianthum collected in the Senegalese flora. Alkaloid extracts were analyzed and identified by chromatography and mass spectrometry. Alkaloid extracts from P. trianthum displayed pleiotropic biological properties. Cytotoxic activity of the extracts was determined on hepatocarcinoma Huh7 cells and on acute monocytic leukemia THP-1 cells, while agar diffusion and microdilution assays were used to evaluate antibacterial activity. Antiviral activity was measured by infection of extract-treated cells with dengue virus (DENV_GFP) and human immunodeficiency virus-1 (HIV-1_GFP) reporter vectors. Cytotoxicity and viral inhibition were the most striking of P. trianthum’s extract activities. Importantly, non-cytotoxic concentrations were highly effective in completely preventing DENV_GFP replication and in reducing pseudotyped HIV-1_GFP infection levels. Our results show that P. trianthum is a rich source of molecules for the potential discovery of new treatments against various diseases. Herein, we provide scientific evidence to rationalize the traditional uses of P. trianthum for wound treatment as an anti-dermatosis and antiseptic agent.     

Enzymatic Polymerization towards Biodegradable Polyester Nanoparticles

The direct enzymatic polymerization of miniemulsions consisting of lactone nanodroplets represents a new and convenient pathway for the synthesis of biodegradable polymer nanoparticles, where the chemical composition and molecular weight can be varied in a certain range. Oligoesters completely end‐capped with an alkene or diene group can also be prepared by this technique. These building blocks extend polyester application as they allow to impart improved biodegradability to both siloxane and resin chemistry.

TEM image of the polyester particles obtained by enzymatic polymerization in miniemulsion.     

Simulation of Solute Transport Through Fractured Rock: A Higher-Order Accurate Finite-Element Finite-Volume Method Permitting Large Time Steps

Discrete-fracture and rock matrix (DFM) modelling necessitates a physically realistic discretisation of the large aspect ratio fractures and the dissected material domains. Using unstructured spatially adaptively refined finite-element meshes, we find that the fastest flow often occurs in the smallest elements. Flow velocity and element size vary over many orders of magnitude, disqualifying global Courant number (CFL)-dependent transport schemes because too many time steps would be necessary to investigate displacements of interest. Here, we present a higher-order accurate implicit pressure–(semi)-implicit transport scheme for the advection–diffusion equation that overcomes this CFL limitation for DFM models. Using operator splitting, we solve the pressure and the transport equations on finite-element, node-centred finite-volume meshes, respectively, using algebraic multigrid methods. We apply this approach to field data-based DFM models where the fracture flow velocity and mesh refinement is 2–4 orders of magnitude greater than that of the matrix. For a global CFL of ≤10,000, this implies sub-CFL, second-order accurate behaviour in the matrix, and super-CFL, at least first-order accurate, transports in fast-flowing fractures. Their greater refinement, however, largely offsets this numerical dispersion, promoting a highly accurate overall solution. Numerical and fracture-related mechanical dispersions are compared in the realistic DFM models using second-order accurate runs as reference cases. With a CFL histogram, we establish target error criteria for CFL overstepping. This analysis indicates that for extreme fracture heterogeneity, only a few transport steps can be sufficient to analyse macro-dispersion. This makes our implicit method attractive for quick analysis of transport properties on multiple realisations of DFM models.     

Water‐based inorganic/polymer hybrid particles prepared via a multiple miniemulsion process

A universal method for the synthesis of water‐based inorganic–polymer hybrid particles was developed in which no organic solvent is required. To demonstrate the versatility of this process, zinc phosphate, calcium carbonate, and barium sulfate were chosen as different pigment examples which additionally can be utilized for functional coating applications. Furthermore, a complex polymeric composition based on epoxy–acrylic–styrene was chosen to illustrate the versatility from a soft matter point of view. The overall synthesis process was carried out by coemulsification of two inverse miniemulsions, containing two precursors, surrounded with a polymerizable continuous phase. This was then transferred to a direct miniemulsion by addition to a surfactant solution and subsequent homogenization followed by radical polymerization of the vinylic monomers. To our knowledge, this is the first work where a polymerizable continuous phase has been used in an inverse miniemulsion formation followed by transfer to a direct miniemulsion, followed by polymerization, so that the result is a water‐based dispersion. The resultant dispersion was characterized by dynamic light scattering; the particles were investigated via transmission electron microscopy with in situ determination of crystallinity using electron diffraction. Elemental analysis was also performed for the particles and the polymerized miniemulsions using X‐ray fluorescence and inductively coupled plasma‐optical emission spectroscopy, respectively. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011