The Raman Effect: A Large-Scale Lecture Demonstration

This article describes a lecture demonstration of the Raman effect. It presents a method for using a simple arrangement of optical components to project Raman lines from liquid samples. The Raman lines are visible as different colors of light projected on a screen several meters away. The demonstration is appropriate for physical, analytical or instrumental analysis courses.     

Natrium und Kalium

Ohne Zusammenfassung     

Determination of cadmium residues in bee products using a ‘lab-made’ bismuth bulk electrode

Raw propolis and bee pollen has been widely used in different areas such as medicine, food and apitherapy because they have biological and medicinal properties. The beneficial effects of both bee products for human health include antibacterial, antiviral, antimicrobial and anti-inflammatory properties. However, hives exposure to heavy metals, due beekeeping practices and environment, is one of the problems facing beekeepers. The presence of cadmium in bee products should be controlled, because of its high toxicity. A lab-made Bismuth Bulk Electrode (BiBE) was developed for cadmium residue determination in Argentinean bee products such as raw propolis and bee pollen employing square wave anodic stripping voltammetry (SWASV) as electrochemical technique. The SWASV parameters were optimised based on a 2 ⁵ factorial design. The method presents a linear range from 2.00 to 100.0 µg L^?1 of Cd (II) with a limit of detection (LOD) and a limit of quantitation (LOQ) of 0.78 µg L^?1 and 2.61 µg L^?1, respectively. The repeatability was 8.03%, calculated as the relative standard deviation. Recovery experiments were performed using spiked raw propolis and bee pollen samples with standard deviation values from 1.16% to 7.20%. The BiBE is easy and fast to elaborate and the propose method is environmentally friendly and low cost. Then, it can be considered as a good alternative to the quality control of bee products due to its importance in the beekeeping industry.     

Magnetic cellulosic materials based on TEMPO-oxidized viscose fibers

A simple method for preparation of magnetic cellulose fibers by coating (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO)-oxidized viscose with oleic-acid-coated or uncoated, freshly prepared magnetic nanoparticles (MNp) is presented. MNp attachment was facilitated by chemical activation of the cellulose fibers through introduction of negatively charged carboxylic groups using the well-established TEMPO-mediated oxidation protocol. The resulting composite materials preserved the intrinsic properties of the cellulose fibers, but gained notable specific features due to the presence of magnetic nanoparticles. The obtained composite materials were characterized using spectral (Fourier-transform infrared spectroscopy) and microscopic (scanning electron microscopy) methods. Thermogravimetric analyses were carried out to evaluate the thermal stability of the magnetic fibers. The magnetic properties were evaluated using vibrating-sample magnetometry.     

Dual‐emissive polydiphenylsilane nanocomposite: effect of N,N′‐bis(4‐hydroxysalicylidene)‐1,2‐phenylenediamine‐Zn complex

The fluorescence properties of polysilane can be strongly influenced by creating new excited states that involve electronic transitions and the relaxation to the ground state. This work presents the optical effects obtained by doping a specially designed polydiphenylsilane copolymer with Zn complex of N,N′‐bis(4‐hydroxysalicylidene)‐1,2‐phenylenediamine. The nanocomposites have been prepared in solution by mixing the polymer with low amounts of Zn–salophen and using tetrahydrofuran as solvent. The ultraviolet–visible spectrum has shown the occurrence of an intermolecular charge transfer between polysilane and the metal complex. Photoluminescence studies have revealed an interesting dual emission profile of nanocomposite. The origin of this phenomenon has been evidenced by molecular modeling and simulation of the electronic transitions. The modeling results have unveiled a new low‐lying excited state due to intermolecular interactions. The thin films of nanocomposites have been drop‐casted from solutions. The obtained films have been studied by Transmission Electron Microscopy (TEM)‐Scanning Transmission Electron Microscopy (STEM)‐Energy Dispersive X‐ray analysis (EDX) to gain information on the film‐forming capacity and surface morphology. The results have revealed a high potential of such materials for fluorescence sensing applications. Copyright © 2015 John Wiley & Sons, Ltd.     

Anthocyanins profile,total phenolics and antioxidant activity of two Romanian red grape varieties: Fetească neagră and Băbească neagră (<Emphasis Type="Italic">Vitis vinifera</Emphasis>)

The phenolic composition of Feteasc? neagr?and B?beasc? neagr? grapes from Dealul Bujorului vineyard (south-east Romania) was studied using the spectrophotometric and high-performance liquid chromatographic (HPLC) methods. The results revealed significant differences between these cultivars. Total anthocyanins ranged from 0.22–5.98 mg g^?1 DW berries in B?beasc? neagr? grapes to 0.54–18.54 mg g^?1 DW berries in Feteasc? neagr?. Both cultivars were characterised by an interesting anthocyanin profile for winemaking with a prevalence of malvidin-3-glucoside. The skins and seeds both had small amounts of flavonoids. In contrast with B?beasc? neagr?, Feteasc? neagr? had more flavonoids in the seeds (69 %) than in the skins. Statistically significant correlations were observed between antioxidant activity and total anthocyanin content in both varieties. The antioxidant activity was also found to be highly correlated to the total phenolic compounds content.     

Organoantimony(III)‐Containing Tungstoarsenates(III): From Controlled Assembly to Biological Activity

A family of three sandwich‐type, phenylantimony(III)‐containing tungstoarsenates(III), [(PhSb^III){Na(H₂O)}As^III₂W₁₉O₆₇(H₂O)]^11? ( 1 ), [(PhSb^III)₂As^III₂W₁₉O₆₇(H₂O)]^10? ( 2 ), and [(PhSb^III)₃(B‐α‐As^IIIW₉O₃₃)₂]^12? ( 3 ), have been synthesized by one‐pot procedures and isolated as hydrated alkali metal salts, Cs₃K_3.5Na_4.5[(PhSb^III){Na(H₂O)}As^III₂W₁₉O₆₇(H₂O)]?41H₂O ( CsKNa ‐ 1 ), Cs_4.5K_5.5[(PhSb^III)₂As^III₂W₁₉O₆₇(H₂O)]?35H₂O ( CsK‐2 ), and Cs_4.5Na_7.5[(PhSb^III)₃(B‐α‐As^IIIW₉O₃₃)₂]?42H₂O ( CsNa ‐ 3 ). The number of incorporated {PhSb^III} units could be selectively tuned from one to three by careful control of the reaction parameters. The three compounds were characterized in the solid state by single‐crystal XRD, IR spectroscopy, and thermogravimetric analysis. The aqueous solution stability of sandwich polyanions 1 – 3 was also studied by multinuclear (¹H, ¹³C, ¹⁸³W) NMR spectroscopy. Effective inhibitory activity against six different kinds of bacteria was identified for all three polyanions, for which the activity increased with the number of incorporated {PhSb^III} groups.     

New Polylactic Acid Composites for Packaging Applications: Mechanical Properties,Thermal Behavior,and Antimicrobial Activity

The interest in antimicrobial packaging materials based on polylactic acid (PLA) polymers has increased due to the need to improve food safety and environment quality and also to find alternatives to synthetic polymers made from petrochemicals. PLA films by addition of different fillers (grape wastes and celery fibers) were obtained. The mechanical, thermal, surface, and antimicrobial properties of the films were evaluated. The incorporation of inexpensive fillers into the PLA matrix could reduce costs and the studied formulations offer approaches to realize composites with high performances and antimicrobial response, suitable for film food-active packaging materials, especially by use of grape wastes.     

Characterization of Vegetables by Stable Isotopic and Elemental Signatures

ABSTRACT

109 Romanian parsley, celery and parsnip root, cucumber, vegetable marrow, onion, and pepper samples were characterized by their stable isotope ratios and elemental concentrations in comparison to imported varieties. Organic and conventional agriculture practices were also compared as well as a differentiation between eggplant and peppers grown in greenhouses and those in the field. δ²H values were between ?70.8 and 5.6‰, while the δ¹⁸O values were between ?9.0 and 4.1‰. The δ¹⁵N values for white onions were from 2.8 to 11.1‰. For Romanian organic onions, the carbon isotopic values were lower (?29.2 to ?28.2‰) compared to conventional onions from other countries (?27.8‰ to ?23.8%). Linear discriminant analysis was used to characterize agricultural practices and the geographic origin of the vegetables.     

Integration of Temperature and Blue‐Light Sensing in Acinetobacter baumannii Through the BlsA Sensor

BlsA is a BLUF photoreceptor present in Acinetobacter baumannii, responsible for modulation of motility, biofilm formation and virulence by light. In this work, we have combined physiological and biophysical evidences to begin to understand the basis of the differential photoregulation observed as a function of temperature. Indeed, we show that blsA expression is reduced at 37°C, which correlates with negligible photoreceptor levels in the cells, likely accounting for absence of photoregulation at this temperature. Another point of control occurs on the functionality of the BlsA photocycle itself at different temperatures, which occurs with an average quantum yield of photoactivation of the signaling state of 0.20 ± 0.03 at 15°C < T < 25°C, but is practically inoperative at T > 30°C, as a result of conformational changes produced in the nanocavity of FAD. This effect would be important when the photoreceptor is already present in the cell to avoid almost instantaneously further signaling process when it is no longer necessary, for example under circumstances of temperature changes possibly faced by the bacteria. This complex interplay between light and temperature would provide the bacteria clues of environmental location and dictate/modulate light photosensing in A. baumannii.