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Volume 6, Year 2015, Issue 4, October-December

Influence of junction temperature on the spectral power distribution of Light Emitting Diodes
Author:
Łukasz Budzyński
Downloads:
48 x
 

Abstract: This article describes electrical method for measuring junction temperature of high power LEDs. Measurement system consisting of a temperature controller and a thermostatic chamber was designed and constructed. A number of studies of LEDs in a typical thermal conditions that exist in luminaries were performed. Basing on these results, influence of junction temperature on luminous flux and spectral power distribution of LED was determined. Obtained results allow to optimize the construction of LED lighting fixtures, in the ambient temperature range from 0°C to 100°C, especially in the aspect of improving the photometric properties of the luminaire.

Keywords: LED, junction temperature, spectral power, measurement

Area: Electronics, Telecomunications and Informatics

Spectral analysis of parametric two degrees- of-freedom system
Author:
Juliusz Krzyżkowski, Yuriy Pyryev
Downloads:
14 x
 

Abstract: In this paper model of a vibrating system of two rotating, stressed to each other and periodically losing contact cylinders is presented. The model is described by two-degrees-of-freedom Hill's differential equations system, which was numerically solved. Spectra of the vibrations were analyzed in here.

Keywords: parametric vibrations, Hill equations, TDOF system, spectral analysis

Area: Mechanics, Automation and Robotics

The Effect of Ascorbic Acid Supplementation on Betacyanin Stability in Purple Pitaya (Hylocereus polyrhizus) Juice
Author:
Anna Skopińska, Dominika Szot, Karolina Starzak, Yosef Mizrahib, Sławomir Wybraniec
Downloads:
24 x
 

Abstract: Current studies on betalains are focused on searching of new plant sources of these pigments. In this light, purple pitaya (Hylocereus polyrhizus) is a valuable batalain-containing fruit. Betalains are known to be sensitive at elevated temperatures conditions. Nevertheless, addition of specific food stabilizers (EDTA, ascorbic acid, citric acid) as well as natural matrix compounds may exert stabilizing effect on maintenance of pigments. Therefore, in presented study, the stability of betalains in Hylocereus polyrhizus juices with protective addition of ascorbic acid at 85 ̊C was examined. Spectrophotometric analyses enable monitoring of reaction during heating of solutions. The hypsochromic shift of λmax to 460 nm is observed in more acidic media without ascorbic acid, suggesting the generation of new reaction products. These absorption bands in solutions with ascorbic acid are not detected, indicating on retaining of the basic structure of betalain chromophore. Generally, pigment retention is diminishing with prolonged heating and depends on pH-values of tested solutions. The addition of ascorbic acid significantly affects the betalain stability. After 60 min of heating, more than 60% of the initial pigment is retained at pH 3-4 in samples of purple pitaya with ascorbic acid. In summary, betacyanins in purple pitaya juice are shown to exhibit proper heat stability, when are stabilized with ascorbic acid. However, a protective effect of natural juice matrix and ascorbic acid is more significant at acidic pH.

Keywords: betalains, betacyanins, Hylocereus polyrhizus, thermal treatment of natural pigments, ascorbic acid

Area: Chemistry and Pharmacy

Profiles of products generated during betacyanins reduction by 2-methylpyridine borane
Author:
Dominika Szot, Karolina Starzak, Anna Skopińska, Sławomir Wybraniec
Downloads:
16 x
 

Abstract: Betanin and neobetanin (14,15-dehydrogenated betanin), natural betacyanin pigments were subjected to a gentle reduction by 2-methylpyridine borane. During each reduction reaction, the visible spectra were collected. The results were tentatively confirmed by LC-DAD-ESI-MS. In comparison to a previous study with sodium borohydride, various types of products were obtained. Depending on pH, one or two double bonds are reduced. Interestingly, a preliminary decarboxylation of the pigments is also noticed. Betacyanins are plant red-violet pigments applied as colorants in food and pharmaceutical industry which are proven to have an antioxidant activity. They are confirmed to be beneficial for human health as free radical scavengers. Therefore, betacyanins can prevent from many diseases which would be induced by an excessive accumulation of free radicals in the human body. There are more and more reports of their pro-health properties. However, the mechanism of betacyanins oxidation remains not completely elucidated. It is postulated that the rearrangement in the chromophoric system is a significant part of this mechanism. The products obtained as a result of reduction of betanin and neobetanin can be useful in oxidation investigations. Betacyanins with partially destroyed chromophoric system by reduction of the double bonds would by perfect models for further studies on their oxidation.

Keywords: betanin, neobetanin, betacyanins, reduction, 2-methylpyridine borane, LC-MS

Area: Chemistry and Pharmacy

Dynamic bubble tensiometry as a useful tool for assessment of physicochemical interactions of liposomal drug carriers with respiratory tract
Author:
Katarzyna Kramek-Romanowska, Tomasz R. Sosnowski
Downloads:
12 x
 

Abstract: This article presents an experimental investigation of physicochemical interactions of novel liposomal drug carriers intended for inhalation with model lung surfactant system. The research was done with the use of maximum bubble pressure (MBP) method to measure changes of dynamic surface tension of pulmonary surfactant system after contact with liposomal colloids made of lecithin and lecithin/cholesterol (3:1 w/w) before and after 5 and 10 minutes of nebulisation by pneumatic nebulizer. What is important to point, MBP method allows the discussion of measured phenomena with reference to the time scales characteristic for the changes of alveolar surface area during the breathing cycle. Obtained results may have a potential application during design and development of new therapeutic liposomal formulations for treatment of respiratory as well as systemic diseases.

Keywords: pulmonary surfactant, liposomes, inhalation, surface tension, adsorption

Area: Chemistry and Pharmacy

Reactive extraction of citric acid using supercritical CO2 and trioctylamine
Author:
Małgorzata Djas, Marek Henczka, Karolina Potocka, Jowita Wawer
Downloads:
27 x
 

Abstract: The paper is dedicated to the integrated process of the reactive extraction of citric acid from aqueous solution using supercritical CO2 and trioctylamine. The aim of this study is to investigate the influence of process parameters (concentration of reactants in phases, pressure, temperature, mixing rate, mixing time) on the course of the reactive extraction process. The increase of the initial concentration of amine (0.04-0.07 mol∙dm-3) results in the higher efficiency of reactive extraction. The influence of pressure (12-18 MPa) on the process is negligible. The process efficiency decreases with temperature (308-328 K). The increase of stirrer speed (250-500 rpm) leads to increase of process rate, so the final efficiency is obtained in shorter time.

Keywords: reactive extraction, supercritical CO2, citric acid, trioctylamine

Area: Chemistry and Pharmacy

Investigation on the course of complex processes carried out in vortex impinging jet reactors
Author:
Krzysztof Wojtas, Anna Rybałtowska, Damian Witkowski, Łukasz Makowski
Downloads:
7 x
 

Abstract: The paper presents an application of CFD simulations to predict a course of complex processes carried out in jet reactors. In this work the simulations results were verified with PIV and PLIF techniques and validated by comparing model predictions with experimental data for fast parallel chemical test reactions. Experimental results of BaSO4 precipitation in jet reactors are also discussed.

Keywords: jet reactors, mixing, chemical reaction, precipitation, numerical simulation

Area: Chemistry and Pharmacy

Cosmetic Wastewater Treatment Using Coagulation and Fenton Processes
Author:
Jan Bogacki, Piotr Marcinowski, Jeremi Naumczyk
Downloads:
16 x
 

Abstract: The cosmetic wastewater was treated by coagulation and Fenton process. COD of raw wastewater was 2888 mg/l. The effectiveness of these processes, defined as a decrease of COD was 66.4% for coagulation for a FeCl3 dose 900 mg/l and 87.7% (to 295mg/l COD) for Fenton process for H2O2/Fe2+ doses 3000/1000mg/l. The contribution of coagulation in Fenton process was defined as 71.3% of the total treatment effect. The calculated H2O2 efficiency is high and for optimal doses reached 149.3%. The optimal pH of Fenton process is 3.0. Even a small change in its value leads to a rapid decrease in the efficiency of oxidation and hence in the effects of the process. The kinetics of the Fenton process can be described as d[COD]/dt =-a tm [COD], where t stands for time, while the a and m are constants, depending on the initial concentration of the reagents. It has been proved that the cosmetic wastewater is susceptible to purification by means of coagulation and Fenton process.

Keywords: cosmetic wastewater, wastewater treatment, coagulation, Fenton process

Area: Environmental Sciences

Architecture as an Indicator of Territorial Conflicts, Globalisation and Unification
Author:
Anna P. Gawlikowska
Downloads:
20 x
 

Abstract: The paper discusses architecture as a marker of two selected types of conflicts. The first type described are conflicts rooted in a dispute over a territory. Territorial conflicts result in the transpositions of architectural styles, their merges and evolutions. Based on colonial architecture, the author gives examples of the aggressors’ architectural practices, which are treating the local design in various manners: elimination, acceptance or conscious use. Subsequently to colonialism, the paper discusses decolonisation and globalisation, which lead to the unification of architecture all over the world. This, as the article shows, is related to the transformations of global economy. The paper discusses examples of architectural styles and tendencies, which are triggered by economic factors, including the architecture of international corporations, and modular container building. Finally, the paper comments on architecture portraying economic discrepancies, reflecting extreme luxury and poverty. The author comments on the clash between elitist skyscrapers and slums in large metropolises. The article discusses social phenomena that stem from this clash and, most importantly, portrays architecture as an agent and a victim of territorial and economic conflicts.

Keywords: architecture, territorial conflicts, economic conflicts, globalisation, colonial architecture, decolonisation, hybrid architecture

Area: Town and Urban Planning, Architecture and Building Engineering

 
 
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