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Search Results: 1 - 10 of 401102 matches for " Lewandowska-Szumiel M "
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Highly biocompatible, nanocrystalline hydroxyapatite synthesized in a solvothermal process driven by high energy density microwave radiation
Smolen D, Chudoba T, Malka I, Kedzierska A, Lojkowski W, Swieszkowski W, Kurzydlowski KJ, Kolodziejczyk-Mierzynska M, Lewandowska-Szumiel M
International Journal of Nanomedicine , 2013, DOI: http://dx.doi.org/10.2147/IJN.S39299
Abstract: hly biocompatible, nanocrystalline hydroxyapatite synthesized in a solvothermal process driven by high energy density microwave radiation Original Research (1184) Total Article Views Authors: Smolen D, Chudoba T, Malka I, Kedzierska A, Lojkowski W, Swieszkowski W, Kurzydlowski KJ, Kolodziejczyk-Mierzynska M, Lewandowska-Szumiel M Published Date February 2013 Volume 2013:8 Pages 653 - 668 DOI: http://dx.doi.org/10.2147/IJN.S39299 Received: 18 October 2012 Accepted: 28 November 2012 Published: 12 February 2013 Dariusz Smolen1, Tadeusz Chudoba1, Iwona Malka1, Aleksandra Kedzierska1, Witold Lojkowski1, Wojciech Swieszkowski2, Krzysztof Jan Kurzydlowski2, Malgorzata Kolodziejczyk-Mierzynska3, Malgorzata Lewandowska-Szumiel3 1Polish Academy of Science, Institute of High Pressure Physics, Warsaw, Poland; 2Faculty of Materials Engineering, Warsaw University of Technology, Warsaw, Poland; 3Department of Histology and Embryology, Center of Biostructure Research, Medical University of Warsaw, Warsaw, Poland Abstract: A microwave, solvothermal synthesis of highly biocompatible hydroxyapatite (HAp) nanopowder was developed. The process was conducted in a microwave radiation field having a high energy density of 5 W/mL and over a time less than 2 minutes. The sample measurements included: powder X-ray diffraction, density, specific surface area, and chemical composition. The morphology and structure were investigated by scanning electron microscopy as well as transmission electron microscopy (TEM). The thermal behavior analysis was conducted using a simultaneous thermal analysis technique coupled with quadruple mass spectrometry. Additionally, Fourier transform infrared spectroscopy tests of heated samples were performed. A degradation test and a biocompatibility study in vitro using human osteoblast cells were also conducted. The developed method enables the synthesis of pure, fully crystalline hexagonal HAp nanopowder with a specific surface area close to 240 m2/g and a Ca/P molar ratio equal to 1.57. TEM measurements showed that this method results in particles with an average grain size below 6 nm. A 28-day degradation test conducted according to the ISO standard indicated a 22% loss of initial weight and a calcium ion concentration at 200 μmol/dm3 in the tris(hydroxymethyl)aminomethane hydrochloride test solution. The cytocompatibility of the obtained material was confirmed in a culture of human bone derived cells, both in an indirect test using the material extract, and in direct contact. A quantitative analysis was based on the 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide. Viability assay as well as on DNA content measurements in the PicoGreen test. Indirect observations were performed at one point in time according to the ISO standard for in vitro cytotoxicity (ie, after 24 hours of cell exposure to the extracts). The direct contact tests were completed at three time points: after 24 hours, on day 7, and on day 14 of a cultu
A New Approach to Carbonate Alkalinity  [PDF]
Bogus?aw Pilarski, Anna M. Micha?owska-Kaczmarczyk, Agustin G. Asuero, Agnieszka Dobkowska, Monika Lewandowska, Tadeusz Micha?owski
Journal of Analytical Sciences, Methods and Instrumentation (JASMI) , 2014, DOI: 10.4236/jasmi.2014.42009
Abstract:

The article provides experimental data applied to the determination of carbonate alkalinity (CAM) according to modified Gran II functions. CAM is related to the mixtures NaHCO3 + Na2CO3 and Na2CO3 + NaOH. In addition to the determination of equivalence volumes, one of the main novelties of the proposed method is the possibility of determining the activity coefficient of hydrogen ions (γ). Moreover, CAM can be used to calculate the dissociation constants (K1, K2) for carbonic acid and the ionic product of water (KW) from a single pH titration curve. The parameters of the related functions are calculated according to the least squares method.

The capital barrier to innovation in the small and medium-sized enterprises
Lucyna Lewandowska
Comparative Economic Research , 2009, DOI: 10.2478/v10103-009-0006-7
Abstract: The article discusses SMEs' situation with reference to the process of creating an innovative economy. The presented discussion covers both non-material and financial barriers impeding the development of innovations. The examined range of new solutions designed to finance innovation includes types of capital support such as leasing, franchising, venture capital, Business Angels, NewConnect.
The Pulsar in the Crab Nebula
Natalia Lewandowska
Physics , 2015,
Abstract: The Crab pulsar belongs to one of the most studied stellar objects in the sky. Since its accidental detection in 1968, its pulsed emission has been observed throughout most of the electromagnetic spectrum. Although currently one of more than 2000 known pulsars, its way of work has remained not understood making the Crab pulsar an object of continuous studies and interest. Referring to the pulsed emission of the Crab pulsar only at radio wavelengths, it reveals a diversity of different phenomena. They range from deviations of the predicted slowing down process of the pulsar with time (long time phenomena) to an irregularity of its single pulse emission (short time phenomena). Similar and different kinds of deviations are observed at other wavelengths. Consequently, the Crab pulsar provides a large diversity of different emission characteristics which have remained difficult to interpret with a uniform theoretical approach including all observed properties. Since a review of all currently examined properties of the Crab pulsar is beyond the scope of this paper, its goal is to give an overview of previous studies of the Crab pulsar predominantly at radio and gamma-wavelengths with an emphasis on a possible connection to its radio single pulse emission. A discussion of a possible identification of common emission mechanisms is given.
Zespó jelita nadwra liwego - jedno schorzenie czy wiele chorób? Uwagi o ewolucji kryteriów diagnostycznych IBS
Agnieszka Lewandowska,Leszek Paradowski
Polish Gastroenterology , 2008,
Abstract: Objawy zespo u jelita nadwra liwego (irritable bowel syndrome - IBS) s opisywane ju od XIX wieku. Schorzenie to nale y do grupy zaburzeń czynno ciowych przewodu pokarmowego. Nie dysponujemy adnymi biologicznymi markerami tej choroby, dlatego diagnoza IBS jest cz sto ustalana dopiero po wykluczeniu przyczyny organicznej zg aszanych przez pacjenta dolegliwo ci. W artykule przedstawiono ewolucj kryteriów diagnostycznych IBS - od zaproponowanych w 1978 roku kryteriów Manninga, a do opublikowanych w 2006 roku najnowszych III Kryteriów Rzymskich.
Sulphates in particles of different sizes in the marine boundary layer over the southern Baltic Sea
Lucyna Falkowska,Anita Lewandowska
Oceanologia , 2004,
Abstract: Concentrations of sulphate ions and particle size distributions were measured in the marine boundary layer using a ten-cascade Berner impactor at Hel between December 1997 and March 1998, and with a filter pack in Gdynia from February to May 2001. In the marine boundary layer over the Hel Peninsula the presence of natural sea-salt and non-sea-salt sulphate ions (nssSO42-) was confirmed in the aerosols. The nssSO4 were present in all size ranges only in December 1997 and in the first half of January 1998, making up an average of 83.7 ± 2.4% of the total sulphate content. In the other winter months, nssSO42- were recorded only in aerosols of diameters from 0.4 to 1.5 μm, and their average contribution dropped by over 20%. The extended growing season in the Southern Baltic resulted in the formation of fine particles that appeared in the marine boundary layer in early winter. At that time the proportion of nssSO42- in ultra-fine particles ranged from 75.7% to 100%. The concentration of nssSO42-, which varied from 0.8 to 2.3 nmol m-3 in particles < 0.4 μm in size probably constituted the natural background aerosol population in the relatively clean coastal environment of the Southern Baltic Sea. In the coastal urbanised area of Gdynia, the sulphate concentration in aerosols was higher than at Hel (av. 75.3 nmol m-3) but the proportion of nssSO4 was low, of the order of 24%. Sea salt was then the dominant source of sulphate.
Ammonia and ammonium over the southern Baltic Sea. Part 1. Preparation of aerosol and air samples for the determination of ammonia by the indophenol method
Anita Lewandowska,Lucyna Falkowska
Oceanologia , 2004,
Abstract: 1997 saw the start of a study into the spatial and temporal changes in the chemical composition of the atmosphere over the littoral and offshore waters of the Baltic Sea. Collection of samples and their subsequent chemical analysis was preceded by meticulous laboratory experiments concerning the validation and adaptation of the analytical procedures. The colorimetric indophenol blue technique was used to analyse the aerosol samples for the concentration of ammonium ions and the air samples for their gaseous ammonia. The samples were collected with PTFE-filters and Whatman 41 filters coated with 5% orthophosphoric acid. This acid enhances the aerosol sampling efficacy but reduces the pH of the reaction in which indophenol is formed. The pH of the aerosol samples thus had to be raised, and this in turn required an alteration to the original procedure prior to ammonia determination. It was demonstrated that the addition of 0.1 N KOH to the filters coated with H3PO4 increases the pH of the reaction medium to the required level of pH = 8-11.5 and does not substantially influence the precision of the determination; the error of the modified procedure was of the order of 5.2%. Air samples for the determination of gaseous ammonia were collected with annular denuders. Oxalic acid and citric acid are the usual impregnating agents. In the present experiments oxalic acid was used for denuder impregnation; it turned out to be more effective than citric acid under the conditions of the southern Baltic Sea. The detection limit of the indophenol blue method in these laboratory experiments was 0.045 mmol dm-3. The respective relative standard deviations (RSD) within the range of higher and lower concentrations were 0.64% and 4.53%.
Effect of iron limitation on cells of the diatom Cyclotella meneghiniana Kützing
Jolanta Lewandowska,Alicja Kosakowska
Oceanologia , 2004,
Abstract: The response of the Baltic diatom Cyclotella meneghiniana to iron deficiency was examined. The following growth parameters were measured: cell number, chlorophyll a and protein content. The results demonstrate the ability of this diatom to grow well with minimal iron availability; however, the rate of growth fell markedly at the lowest iron(III) concentration. The results of spectrophotometric chlorophyll a measurements and protein assays using the Lowry and Bradford methods indicated a significant decrease in their quantities. Iron may therefore be an important regulatory factor controlling the growth of diatom C. meneghiniana in an aquatic ecosystem.
Kolonoskopia - czy istnieje optymalny sposób przygotowania do badania?
Agnieszka Lewandowska,El?bieta Poniewierka
Polish Gastroenterology , 2009,
Abstract: Kolonoskopia nale y do podstawowych procedur diagnostycznych w chorobach dolnego odcinka przewodu pokarmowego. Istniej okre lone wskazania oraz przeciwwskazania do wykonania tego badania. Dok adne przygotowanie jelita do kolonoskopii umo liwia pe n jego ocen i ustalenie w a ciwego rozpoznania. Obecnie w trakcie przygotowania do kolonoskopii najcz ciej stosowane s dwa rodki: preparaty fosforanu sodu oraz glikol polietylenowy. Przeprowadzone liczne badania wykazuj podobn skuteczno obu substancji i wskazuj zarówno na zalety, jak te na wady obu rodków przeczyszczaj cych. Nadal brak jest optymalnego preparatu s u cego do przygotowania do kolonoskopii.
Perturbation method to model enamel caries progress
Katarzyna D. Lewandowska,Tadeusz Kosztolowicz
Physics , 2007,
Abstract: We develop a theoretical model of the carious lesion progress caused by acids diffusing into the tooth enamel from the dental plaque. The acids react with static hydroxyapatite, which leads to demineralization of the enamel, and consequently to the development of the carious lesion. The model utilizes the diffusion-reaction equations with one static and one mobile reactant where the reaction term is proportional to the product of concentrations of acids and of mineral. The changes of concentrations are calculated approximately by means of a perturbation method. The analytical approximate solutions are compared with the numerical ones and experimental data.
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