Morphology and photocatalytic activity of TiO2 Aerogels

In this paper we describe a methodology to form a data base that will allow us to investigate the correlation between the morphology of Ti?₂ aerogels and their photocatalytic activity with respect to photodecomposition of a water soluble organic compound. We start with a qualitative theoretical argument in which we show that any functionality that involves optimization of different length scale should require some kind of ramified structure. For photocatalytic activity we need to optimize substrate and light absorptions with diffusion of products and reactants. We proceed to describe the techniques that we use to analyze and parametrize the morphology of the aerogels, using nitrogen adsorption and Small Angle Neutron Scattering. The photocatalytic activity is monitored through the photodecomposition of salicylic acid. We compare the adsorption and photodegradation of salicylic acid on the aerogels to many other forms of TiO₂ and report that under our experimental conditions the photocatalytic activity of the aerogels is superior.     

A highly fluorescent nucleoside analog based on thieno[3,4-d]pyrimidine senses mismatched pairing

A highly emissive nucleobase analog, based on a thieno[3,4-d]pyrimidine core, is enzymatically incorporated into RNA oilgonucleotides that function as base discriminating fluorescent probes.     

Multiphase thermoplastic hybrid for controlled release of antimicrobial essential oils in active packaging film

Active packaging, a new technology concept in the field of food packaging, has been introduced in recent years in order to provide quality and safety, as well as extend the shelf life of food products. Antimicrobial (AM) agents can be incorporated directly into the active packaging and migrate in a controlled manner to the headspace between the food and the package, inhibiting bacteria growth on the food surface. Naturally derived AM agent, such as essential oils (EOs), has received considerable attention for food preservation purposes, because of their effective AM activity against various bacteria and fungi. In the present study, AM active film systems based on polypropylene/polyamide blends, montmorillonite nanoclays, and thymol EO were produced to investigate the feasibility of controlling the release rate of thymol from food packaging systems. Selective localization of thymol in a specific phase in the system that derives from thermodynamic affinity was assumed to be useful in controlling its migration rate from the film to the headspace. EO retention in the film under two different time conditions was measured by spectroscopic analysis. The release rate of EO was determined using Gas chromatography technique and analyzed by diffusion model approach. Inhibition of bacterial growth was periodically tested for Listeria and Escherichia coli bacteria. This study confirms the thermodynamic affinity of polyamide phase with thymol that has a positive effect in retaining the EO. Results show controlled AM behavior of the active packaging films, based on various blend compositions. Copyright © 2016 John Wiley & Sons, Ltd.     

Antimicrobial active packaging combining essential oils mixture: Migration and odor control study

Thymol is an essential oil (EO), known to have excellent antimicrobial (AM) properties and can potentially be used as an active agent in AM food packages. Mixing Thymol with other EOs may help to reduce the organoleptic impact of its strong odor. In the present study, the effect of thymol, carvacrol, citral, and eugenol binary mixtures on the AM activity, migration over time, and sensory properties of polypropylene (PP)/polyamide (PA)/nanoclays composite blends active package (AP) films was examined. The release of different EOs from the polymer film was found to have a direct correlation with the odor perception of thymol. Varied EOs bearing films have shown different capacity to inhibit bacterial growth over time (Escherichia coli). Lastly, the inhibition of fungal growth on food sample using EO‐loaded films was obtained for over 50 days, indicating the potential use of the developed films as active food packaging.     

Modified whey protein coatings for improved gas barrier properties of biodegradable films

As a result of environmental concern, there is an increasing interest in the development of biodegradable polymers for packaging with suitable properties, as an alternative to the synthetic petroleum‐based polymers. However, such biodegradable polymers are prevented for use in wide industrial and commercial packaging because of their limited gas and vapor barrier properties. This obstacle urges innovative strategies to achieve enhanced gas barrier properties using “bio‐layering” technologies. Whey protein isolate (WPI), a by‐product of the cheese industry, has quite promising properties for packaging purposes. It possesses good oxygen, aroma, and oil barrier properties; however, its permeability to water vapor is high. In this study, several WPI coatings were obtained, adding polyvinyl alcohol and pectin to improve the coated film properties; in addition, nanoclays were used to improve water vapor barrier properties. Comparison of neat poly (lactic acid) film versus poly (lactic acid) coated with WPI presented advantage of the later: improvement of about 90% in the oxygen barrier properties and about 27% in the water vapor barrier properties. Copyright © 2016 John Wiley & Sons, Ltd.     

Mitochondrial localization and photodamage during photodynamic therapy with tetraphenylporphines

The subcellular localization sites of TPPS4 and TPPS1 and the subsequent cellular site damage during photodynamic therapy were investigated in CT-26 colon carcinoma cells using spectroscopic and electron microscopy techniques. The association of both porphyrins with the mitochondria was investigated and the implications of this association on cellular functions were determined. Spectrofluorescence measurements showed that TPPS4 favors an aqueous environment, while TPPS1 interacts with lipophilic complexes. The subcellular localization sites of each sensitizer were determined using spectral imaging. Mitochondrial-CFP transfected cells treated with porphyrins revealed localization of TPPS1 in the peri-nuclear region, while TPPS4 localized in the mitochondria, inducing structural damage and swelling upon irradiation, as shown by transmission electron microscopy. TPPS4 fluorescence was detected in isolated mitochondria following irradiation. The photodamage induced a 38% reduction in mitochondrial activity, a 30% decrease in cellular ATP and a reduction in Na(+)/K(+)-ATPase activity. As a result, cytosolic concentrations of Na(+) and Ca(2+) increased, and the level of K(+) decreased. In contrast, the lipophilic TPPS1 did not affect mitochondrial structure or function and ATP content remained unchanged. We conclude that TPPS4 induces mitochondrial structural and functional photodamage resulting in an altered cytoplasmic ion concentration, while TPPS1 has no effect on the mitochondria.     

Designing new isomorphic fluorescent nucleobase analogues: the thieno[3,2-d]pyrimidine core

A convergent approach for a family of fluorescent nucleosides is described. It relies on thieno[3,2-d]pyrimidine-2,4(1H,3H)-dione that serves as a core heterocycle. This condensed pyrimidine is converted into an emissive pyrimidine nucleoside analogue by N-glycosylation and into an emissive purine nucleoside analogue by C-glycosidation at the thiophene's beta position. The design principles of this archetypical system are outlined together with the syntheses and photophysical properties of the resulting nucleosides.     

Melting and solidification behavior of laser-crystallized silicon thin-films studied by transient conductance measurements

In this paper we report on transient conductance measurements during melting and solidification of thin silicon films on foreign substrates, which were irradiated with an excimer laser. The silicon films were deposited on borosilicate float glass or single crystal silicon wafers that were coated with different intermediate layers. Our results show that the laser fluence required to melt the entire Si layer is mainly determined by the silicon–substrate interfacial thermal resistance and not by the heat conductivity of the bulk substrate. The solidification velocity, on the other hand, is strongly influenced by the heat conductivity of the bulk substrate and reaches a maximum value of 0.95 m/s for c-Si compared to 2.19 m/s for borosilicate float glass.     

A revised theorization of the relationship between teachers’ conceptions of mathematics and its teaching

We assembled the ideas about mathematics and about its teaching which were expressed by mathematicians and mathematics educators into two pairs of ‘official’ (collective) conceptions: mathematics is either static or dynamic, and mathematics teaching is either closed or open. These polar conceptions produce a 4-pair relationship between the conceptions of mathematics and its teaching. The adherence to official conceptions was tapped by a questionnaire encompassing 176 Israeli high school mathematics teachers, aimed at examining the relationship between their conceptions of mathematics and its teaching. The majority of these teachers either hold a single conception in one of the domains or do not adhere to any conception, and a quarter of them hold either the static-closed or dynamic-open pairs of conceptions that prevail among teachers in other countries. Consequently, we define a conception of an entity as a comprehensive and homogenous set of ideas about a particular characteristic or feature of that entity. Reality is that teachers practice their profession without adhering to any official conception, and perhaps are (/to be?/) praised for their reluctance to blindly adopt the clear-cut rigid official conceptions of mathematics and its teaching while maintaining their individual and independent blends of ideas.