Selection of conditions during tyrosinase isolation and purification from Agaricus bisporus

W ramach badań dobrano warunki izolacji i oczyszczania tyrozynazy z Agaricus bisporus: wybór źródła materiału wyjściowego, metody rozdrabniania, dezintegracja ultradźwiękami, wysalanie przy użyciu siarczanu amonu, chromatografia kolumnowa. W wyborze warunków kierowano się przede wszystkim możliwością zwiększenia skali procesuAll stages of mushroom tyrosinase isolation and purification were analyzed in details: choice of the method for cell disruption, ultrasonic disintegration, purification methods such as salting out and column chromatography. The possibility of process scale-up had a considerable influence on conditions selection

Tyrosinase operational stability in a batch reactor in the presence of substrates and organic solvents

Badając osadzanie cząstek w kanałach tchawicznych stwierdzono, że jest ono funkcją rozmiarów tych cząstek. Cząstki o rozmiarach mniejszych od 2 μm penetrują wszystkie dolne układy oddechowe. Zebrane informacje mogą posłużyć do produkcji leków dostarczanych do organizmu w postaci 3 aerozolu o odpowiednich rozmiarach cząstek w celu uniknięcia nadmiaru leku i niepożądanych efektów ubocznych.Particles deposition was examined in endotracheal tubes using CFD software. It was shown that deposition is a function of particle size. A particle of diameter smaller than 2 μm penetrates all lower airway systems. Obtained information may be used in the production of drugs that arc delivered in aerosol form with proper particles' diameter enabling the reduction of drug amount and preventing its side effects

Tyrosinase operational stability in the presence of organic solvents in a batch reactor

Głównym problemem enzymatycznego utleniania związków fenolowych jest tworzenie wolnych rodników, które są traktowano jako główna przyczyna in-aktywacji samobójczej ryrozynazy. Do badań wykorzystano 4 rozpuszczalniki organiczne mieszające się z wodą i na podstawie analizy kinetyki inaktywacji enzymu w obecności różnych stężeń ko-rozpuszczalników stwierdzono, że etanol i dimetyloformamid, w stężeniu 10%, mogą być zastosowane w bio-transformacjach jako potencjalne stabilizatory wolnych rodników.Four water miscible organic solvents of different concentrations were tested as potential co-solvents for phenolic compounds conversion with tyrosinase. A main problem in biotransformations with tyrosinase is its suicide inac- tivation that can be caused by free radicals formed by the enzyme during reaction. On basis of inactivation kinetics in the presence of co-solvents it was stated that ethanol and dimethylformamide in 10% concentration could be used as potential free radicals stabilizers

Silicon nitride for InP based planar photodiode applications

Przeprowadzono badania warstw azotku krzemu osadzonych na płytkach z fosforku indu metodą PECVD (Plasma Enhanced Chemical Yapor Deposition) z wykorzystaniem do wytwarzania plazmy dwóch generatorów pracujących na różnych częstotliwościach. Celem badań było ustalenie warunków wytwarzania warstw azotku krzemu stosowanych w technologii planarnych fotodiod wykonanych na bazie InP, w których obszarem absorpcyjnym są studnie kwantowe z InxGa1-xAs. Warstwy azotku krzemu były osadzane w temperaturach pomiędzy 250°C i 300°C. Podstawą do oceny wytworzonych warstw były wyniki badań: ich składu chemicznego, struktury, współczynnika załamania, poziomu naprężeń, rezystywności, wytrzymałości dielektrycznej, stałej dielektrycznej i efektywnej gęstości powierzchniowej ładunków elektrycznych. Stwierdzono, że warstwy osadzane w temperaturze 250°C mają najlepszą strukturę, dobrze spełniają rolę maski w procesie selektywnej dyfuzji cynku, a właściwości elektryczne umożliwiają wykorzystanie ich do pasywacji powierzchni bocznych złącz p-n, pod warunkiem zastosowania odpowiedniego cyklu wygrzewań po procesie osadzania.Silicon nitride films, deposited on InP wafers by the PECVD (Plasma Enhanced Chemical Vapor Deposition) method, have been investigated in terms of their applicability in the technology of InP based planar photodiodes with the InxGa1-xAs quantum well absorption region. In order to compensate the mechanical stress in the films, the plasma was excited by two radio-frequency sources operating at frequencies of 13,56 MHz and 100 kHz. The films were deposited at different temperatures in the range of 250 - 300°C. The chemical composition of all examined films, determined by the RBS (Rutherford Backscattering Spectrometry) method, is very close to that of stoichiometric Si3N4. The films contain a large amount of hydrogen. The hydrogen content, evaluated by the NRA (Nuclear Reactions Analysis) technique, exceeds 30 %. The silicon nitride films deposited at 300°C have grown much faster on InP wafers than on Si wafers placed beside these and the structure of both films is different. As the films deposited on Si are amorphous with smooth surfaces, the films deposited on InP are heterogeneous with rough surfaces. These last ones exhibit lower Si-N bond concentration, lower refractive index, higher extinction coefficient, lower resistivity and lower dielectric breakdown strength than the films deposited on silicon. Deterioration of the film quality is caused probably by the reaction of phosphorus, released from the InP substrate at the beginning of the deposition process, with deposited SiNx:H. Such films should not be used in the fabrication of InP based planar photodiodes. When the deposition temperature decreases, the properties of silicon nitride films improve. Their structure becomes more homogeneous and the Si-N bond concentration increases. The silicon nitride films deposited on InP at 250°C have the same amorphous structure and the same Si-N bond concentration, determined from FTIR (Fourier Transform Infrared Spectroscopy) absorption characteristics, as the films deposited on silicon. They exhibit the highest refractive index, the lowest extinction coefficient, the highest resistivity and the highest dielectric breakdown strength. These films are continuous, they do not crack during thermal processes and they can be applied as masking layers for the selective Zn diffusion used to form the p-n junctions. Unfortunately the films deposited at 250°C have the highest hydrogen content and the highest effective charge density. These films cannot be applied directly to passivate the p-n junction side surfaces. Measurements of hydrogen depth profiles and of FTIR absorption characteristics have revealed that the amount of hydrogen and of Si-N, Si-H and N-H bonds changed during annealing. An analysis of C-V characteristics of Al/Si3N4:H/InP MIS capacitors containing these films has shown, that annealing of the Si3N4:H films reduced the electronic defect state density at the Si3N4:H/InP interface. It is possible to take advantage of the thermal instability of silicon nitrides deposited by the PECVD method and to reduce the trap state density and the effective charge density by proper annealing processes. These investigations have enabled us to achieve reverse current values as low as 4 - 15 pA at the voltage of - 5 V and 200 - 500 pA at the voltage of -50 V for planar InP diodes with the 320 um diameter p-n junction. A high yield of 90 % is obtained. These results make a good base for development of planar photodiodes with InxGa1-xAs quantum wells inserted into the depletion region of the InP p-n junction

The application of semiconductor epitaxy supporting software in MOCVD technology

Celem artykułu jest przedstawienie oprogramowania komputerowego obejmującego szereg zadań związanych z epitaksją związków półprzewodnikowych. Wśród zadań tych znalazły miejsce: 1. zarządzanie przepływami prekursorów, 2. wspomaganie wytwarzania struktur ze studnią kwantową, 3. analiza struktur fotonicznych, 4. analiza potencjału elektrycznego w strukturach. Weryfikacja oprogramowania podczas pracy z systemem epitaksji MOCVD wykazała, że stanowi ono pozytywny przykład rozwiązania problemu numerycznego wspomagania procesu epitaksji.Several areas of semiconductor epitaxy can be efficiently assisted by computer recipes, some of these areas are already covered by well developed software units, other still needs such approach. The presentation of a software package combining most important tasks in one utility and some tests with MOCVD are included in this publication. The studied software overcomes following topics: 1. Flow corrections computing for ternary, quaternary or higher order compounds. 2. Analysis of quantum wells in semiconductor structures. 3. Analysis of Bragg reflectors and other 1- dimensional photonic structures. 4. Electrical potential profiling. 5. Calculators for minor epitaxy-related problems. Evaluation of flow corrections computing was tested on MOCVD with InGaAsP/InP, InGaAsP/GaAs, and other quaternaries and ternaries. Beside first order approximation, the process-flows response was exercised with application of "software-learning" empirical approach. Results indicated these functions as comfortable and efficient. The semiconductor quantum well structure analysis performed on AlGaAs/GaAs, InGaAs/GaAs, InGaAs/InP and other structures enabled to determine quantum well parameters with high accuracy. The algorithm developed for strained quantum wells was capable to resolve both QW thickness and composition in multiple PL test. The 1- dimensional photonic structure study with InGaAs/InP Bragg reflectors allowed to fit experimental data and resolve structure parameters and uniformity, technological problems with resonant cavities epitaxy have manifested as reduced by application of compiled numerical recipes. The next software area - electrical potential profiling - offered possibility to investigate HEMT structures, prepare potential data for semiconductor quantum well analysis or to forecast depletion regions of test structures. With few other numerical units all algorithms compose a solution of the problem of computer support for epitaxy

Enhancement of Nitrite and Nitrate Electrocatalytic Reduction through the Employment of Self-Assembled Layers of Nickel- and Copper-Substituted Crown-Type Heteropolyanions

Multilayer assemblies of two crown-type type heteropolyanions (HPA), [Cu20Cl(OH)24(H2O)12(P8W48O184)]25 12 and Ni4(P8W48O148)(WO2)]28 12, have been immobilized onto glassy carbon electrode surfaces via the layer-by-layer (LBL)technique employing polycathion-stabilized silver nanoparticles (AgNP) as the cationic layer within the resulting thin films characterized by electrochemical and physical methods. The redox behaviors of both HPA monitored during LBL assembly with cyclic voltammetry and impedance spectroscopy revealed significant changes by immobilization. The presence of AgNPs led to the retention of film porosity and electronic conductivity, which has been shown with impedance and voltammeric studies of film permeabilities toward reversible redox probes. The resulting films have been characterized by physical methods. Finally, the electrocatalytic performance of obtained films with respect to nitrite and nitrate electrocatalytic reduction has been comparatively studied for both catalysts. Nickel atoms trapped inside HPA exhibited a higher specific activity for reduction