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•NaYF4:Yb3+/Er3+ up-converting particles (UCPs) are processed via solvothermal route.•Either PEG or PVP are used as structure directing and coating agents.•There is α- and ...β-NaYF4:Yb3+/Er3+ phase coexistence in PEG assisted processing.•PVP leads to the prominent hexagonal β-NaYF4:Yb3+/Er3+ phase formation.•Yellow and green emissions are achieved in PEG and PVP coated NaYF4:Yb3+/Er3+ UCPs.
Owing to their unique optical properties, up-converting rare earth fluorides have attracted extensive attention in recent years. Varieties of synthesis procedures which generate nano- and micro-crystals with controllable compositions have been reported. In the vast majority, surfactants, complexing agents and solvents play essential role in controlling particles morphology and surface characteristics. Here we report on a rapid solvothermal synthesis (200°C, 2h) of either PEG or PVP capped NaYF4:Yb3+/Er3+ particles. Their structural, morphological and luminescence characteristics have been studied based on X-ray powder diffractometry (XRPD), Fourier transform infrared spectroscopy (FTIR), energy dispersive spectroscopy (EDS), high resolution transmission electron microscopy (HRTEM) and photoluminescence measurements. Both polymers proved to be a good structure directing agents enabling generation of the well crystalline polymer coated up-converting particles with efficient emissions in visible spectrum. It was shown that generation of the hexagonal P63/m β-NaYF4:Yb3+/Er3+ phase with the most efficient green emission (CIE 0.31, 0.66) is enhanced when PVP is used during synthesis, while promotion of the cubic Fm-3m α-NaYF4:Yb3+/Er3+ phase that has a yellowish spectral output (CIE 0.41, 0.56) was observed in the particles produced in the presence of PEG. Beneficial effect on the luminescence intensity was observed with additional particles annealing in argon atmosphere.
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•Yb3+/Er3+ doped YF3 and NaYF4 particles are processed via EDTA assisted hydrothermal route.•Particles exhibit compositional and morphological dependence on the nucleation rate.•With ...course of processing time transformation of α→β→α NaYF4:Yb3+/Er3+ is observed.•Up-conversion is phase dependent and can be tuned from green to yellowish-orange.
In this feature article, we highlight our works on compositional and structural dependence of up-converting rare earth (RE) fluorides obtained through ethylenediamine tetraacetic acid (EDTA) assisted hydrothermal synthesis. Various nanostructures were obtained by tuning of experimental conditions, such as precursor’s concentration, degree of doping, reaction time and solvent used during synthesis. We correlated in detail the structural, morphological and optical properties of YF3 and NaYF4 compounds co-doped with Yb3+ and Er3+ (introduced in total mol% of 8 and 20). For this purpose, X-ray powder diffraction, scanning and transmission electron microscopy, energy dispersive X-ray and Furrier transform infrared spectroscopy, as well as, the photoluminescence spectra and decay times were recorded and analyzed. The particle size and phase content were found to be dependent on the nucleation rate, which, in turn, was governed by the precursor concentration, degree of doping and solvent type. The transformation from cubic to hexagonal NaYF4:Yb3+/Er3+ phase was found to be sensitive to the reaction time and precursors concentration, while the crystallization of orthorhombic YF3:Yb3+/Er3+ phase is achieved through lowering of dopants concentration or by changing of solvent during hydrothermal treatment. The up-conversion photoluminescence demonstrated morphology and crystal phase dependence and is found to be superior in microcrystalline samples, independent on their phase composition.
Fluorescent nanoparticles have an important role in biological analyzes, and in the last ten years they are successfully applied in a visualization and characterization of biological processes at the ...cellular and molecular level, as well as, in the development of fluorescent lamps, displays, plasma screens and protective labels. The great interest is directed towards the development and implementation of the light up - converters containing rare earth ions which have the ability of a intense luminescence. In this paper we described the process of EDTA assisted hydrothermal synthesis of rare earth doped fluorides. Different structural forms of materials were obtained by changing the time of the hydrothermal reaction. Comparison of a structure, morphology and optical properties of NaYF4:Yb3+/Er3+ powders were done based on X-ray powder diffraction analysis (XRPD), scanning and transmission electron microscopy (SEM and TEM) and through measuring of the luminescence in a visible part of spectrum. It was shown that the transformation from cubic to hexagonal phase is affected by the reaction time, while the up - conversion luminescence is dependent of the particles morphology and the crystal structure.
Optički aktivne nanočestice fluorida elemenata retkih zemalja privlače veliku pažnju poslednjih godina zbog svoje uspešne primene u biološkim snimanjima, odnosno u vizualizaciji i karakterizaciji ...bioloških procesa na ćelijskom i molekulskom nivou. Optička aktivnost ovih materijala posledica je prisustva dopanata koji omogućavaju „Up“- konvertorsku (anti-štoks) emisiju svetlosti nakon pobude infracrvenim izvorom zračenja. U ovoj tezi, optički aktivne biokompatibilne čestice NaYF4 dopiranog iterbijumom i erbijumom, sintetisane su hidro/solvo-termalnim procesiranjem nitrata elemenata retkih zemalja uz upotrebu NaF kao precipitatora. Ispitan je uticaj koncentracije polaznih reaktanata, rastvarača (vode, etanola, etilen glikola i acetona) i prisustva različitih modifikatora površine (poletilenglikola - PEG, polivilinpirolidona - PVP, polilaktid-ko-glikolida - PLGA, hitozana - CS, poliakrilne kiseline - PAA, i etilendiamintetrasirćetne kiseline (etilendiamintetraacetat - EDTA) na proces nukleacije kubne i/ili heksagonalne NaY0.8Yb0.17Er0.03F4 faze, morfologiju i hemijske karakteristike površine čestica. U slučaju dobijanja čestica niske kristaliničnosti vršena je i dodatna kalcinacija praha u atmosferi argona, pri čemu je praćen proces konverzije kubne (α) u heksagonalnu (β) NaY0.8Yb0.17Er0.03F4 fazu. Efikasnost „up“- konverzije (UC), odnosno optička aktivnost čestica u vidljivom delu spektra, utvrđena je merenjem intenziteta i vremena emisije plave (na 408 nm, usled 2H9/2 →4I11/2 prelaza), zelene (na 520 i 540 nm, usled 2H11/2 →4I15/2 i 4S3/2 → 4I15/2 prelaza) i crvene (na 655 nm, usled 4F9/2 → 4I15/2prelaza) svetlosti nakon pobuđivanja infracrvenim izvorom zračenja (λ ~ 980 nm), definisanjem njihovog međusobnog odnosa, kao i izračunavanjem vrednosti hromatičnih koordinata x i y u CIE dijagramu.Rendgeno strukturna analiza praha pokazala je da korišćenje navedenih modifikatora površine u rastvorima niže koncentracije (5 i 10 mmol) dovodi primarno do kristalizacije α- NaY0.8 Yb0.17Er0.03F4 faze u sferičnim česticama nanometarskih dimenzija (<100 nm), osim u slučaju korišćenja PVP gde je postignuta in situ kristalizacija heksagonalne β faze. Utvrđeno je da na stabilizaciju heksagonalne kristalne strukture tokom procesa sinteze, pored izbora modifikatora površine, utiče i vreme hidro/solvo-termalnog tretmana, vrsta rastvarača i koncentracija polaznog rastvora. Kako heksagonalnu kristalnu strukturu odlikuje anizotropni rast kristala, ostvarena je i in situ kristalizacija monodisperznih heksagonalnih poliedarskih mikročestica u rastvorima veće koncentracije (100 mmol) korišćenjem EDTA modifikatora. U radu je pokazano da je dodatnim termičkim tretmanom nanočestica kubne kristalne strukture moguće dobiti čestice heksagonalne kristalne strukture, pri čemu čestice gube svoj sferičan oblik. Sve sintetisane čestice odlikuje visoka čistoća i hidrofilnost. Homogena raspodela jona dopanta u česticama pokazana je skenirajućom elektronskom mikroskopijom u kombinaciji sa energetskom disperzionom analizom X-zracima (SEM/EDAX). Prisustvo amino, karboksilnih ili hidroksilnih grupa na površini sintetisanih čestica, potvrđeno infracrvenom spektroskopijom sa Furijeovom transformacijom, što je ukazalo na formiranje biokompatibilnog sloja na površini čestica. U cilju ispitivanja mogućnosti njihovog korišćenja u biomedicinske svrhe antibakterijska aktivnost čestica je testirana prema Gram-negativnoj bakteriji Escherichia coli, Gram-pozitivnoj bakteriji Staphylococcus aureus i gljivici Candida albicans. Dodatno, za čestice koje se odlikuju najboljim morfološko-strukturnim karakteristikama (nanočestice α- NaY0.8Yb0.17Er0.03F4 faze dobijene u prisustvu PLGA i CS), ispitana je i citotoksičnost na primarnim ćelijama skvamoznog karcinoma jezika (eng. oral squamous cell carcinoma OSCC) i zdravim gingivalnim ćelijama korena pulpe (eng. human gingival cell, HGC) korišćenjem 3-(4,5-dimetiltiazol-2-il)-2,5-difenil tetrazolijum bromid (MTT) testa u opsegu koncentracija od 10-50 μg/mL. U oba slučaja, utvrđena je niža toksičnost nanočestica za HGC nego za OSCC te je dalje ispitana i mogućnost in vitro vizuelizacije ovih ćelija primenom nelinearne skenirajuće mikroskopije. Na osnovu dobijenih rezultata je utvrđeno da je vizuelizacija ćelija moguća i pri najnižim koncentracijama sintetisanih nanočestica, jer je njihovo prisustvo u citoplazmi potvrđeno jasnim svetlosnim odzivom pri pobudi laserom talasne dužine od 980 nm. Ovim istraživanjima je pokazano da je in situ sintezu biokompaktibilnih optički aktivnih nanočestica sastava NaY0.8Yb0.17Er0.03F4moguće izvesti u kontrolisanim uslovima hidro/solvo-termalne sinteze, kao i da dobijene čestice poseduju karakteristike potencijalnih biomarkera nove generacije.
During the treatment phase of active pulmonary tuberculosis (PTB), respiratory function impairment is usually restrictive. This may become obstructive, as a PTB-associated airflow obstruction (AFO) ...or as a later manifestation of underlying COPD.
The aim of the study was to examine the potential causes and risks for AFO development in PTB by exploring the aspects of spirometry limitations and clinical implications for the underlying COPD detection, taking into account various confounding factors.
Prospective, nest case-control study on 40 new cases of PTB with initial restrictive respiratory function impairment, diagnosed and treated according to the directly observed treatment short course (DOTS) strategy.
From all observed patients, 37.5% of them developed AFO upon the completion of PTB treatment, with significantly increased average of forced vital capacity (%) (P<0.01). Their changes in forced expiratory volume in the first second (%) during the PTB treatment were strongly associated with the air pollution exposure in living (0.474%-20.971% for 95% confidence interval CI; P=0.041) and working environments (3.928%-20.379% for 95% CI; P=0.005), initial radiological extent of PTB lesions (0.018%-0.700% for 95% CI; P=0.047), leukocyte count (0.020%-1.328% for 95% CI; P=0.043), and C-reactive protein serum level (0.046%-0.205% for 95% CI; P=0.003) compared to the other patients. The multivariate logistic regression analysis model shows initial radiological extent of pulmonary tuberculosis lesions (OR 1.01-1.05 for 95% CI; P=0.02) and sputum conversion rate on culture (OR 1.02-1.68 for 95% CI; P=0.04) as the most significant predictors for the risk of AFO development.
AFO upon PTB treatment is a common manifestation of underlying COPD, which mostly occurs later, during the reparative processes in active PTB, even in the absence of major risk factors, such as cigarette smoking and biomass fuel dust exposure. Initial spirometry testing in patients with active PTB is not a sufficient and accurate approach in the detection of underlying COPD, which may lead to their further potential health deterioration.
This paper presents some basic urban and architectural requirements regarding
the installation of solar panels for electricity production on buildings.
These requirements are usually design ? ...aesthetic and functional ?
constructive. However, from the thermal ambient aspect, constructor?s
solution is often not in accordance with requirements of architectural and
urban planning profession. It is a known fact that thermal environment
impacts the yield in the solar panels production. The aim of this paper is
to show, based on experience of solar power plant DOMIT, city of Leskovac,
Serbia, what is the expected effect in that aspect, in order to choose the
optimal solution with regard to the character of the building. The most
favorable production have solar power plants built on buildings where the
panels on the underside are completely open because they have the best
ventilation, and therefore cooling.
nema
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Introduction: Antibiotics are the most frequently used drugs in hospitalized patients, but studies have shown that the prescribed antibiotics may be inappropriate and may contribute to bacterial ...resistance. The aim of this work is the evaluation of antibiotic consumption in Clinical Centre Nis, Serbia from 2011 to 2014, with the focus on the monitoring of the ceftriaxone (CTX) and ciprofloxacin (CIP) utilization. Secondly, we screened bacterial resistance towards monitored antibiotics used for intra-abdominal infection (IAI) and urinary tract infection (UTI) in tertiary healthcare institution. Methods: Antibiotics consumption and antimicrobial resistance were monitored in the tertiary care university hospital-Clinical Centre Nis from 2011 to 2014. Data on the use of antibiotics in inpatients were obtained and expressed as defined daily doses per 100 bed days (DBD). Bacterial resistances were given as percentages of resistant isolates. Results: During the investigation period the use of cephalosporins increased by 6.39 %, from 2011 to 2013, but in 2014 there was a reduction in its consumption by 16.46 %. Penicillins consumption had a decreasing trend, whereas quinolones consumption was variable during observation period. The resistance of K. pneumoniae to CTX and CIP for the isolates from IAI, and resistance of E. coli to analyze antibiotics for isolates from UTI showed increasing trend within observed period of time. Conclusions: Our findings shows that cephalosporins were the most frequently used antibiotics in Clinical Centre Nis, and they were followed by penicillins and quinolones. Additionally, K. pneumoniae resistance to CTX and CIP increased markedly in IAI, while E. coli resistance showed an increasing trend to CTX and CIP in UTI over the study period.
Introduction: Two most common pharmaceutical formulation of tacrolimus (Tac) used after kidney transplantation (Tx) are immediate-release one, administered twice-daily (TacTD), and prolonged-release ...one, administered once-daily (Tac-OD). Aim: The aim of this study was to compare daily doses, trough concentrations (C0 ) and dose-adjusted trough concentrations (C0 /D) of Tac between patients who administered different drug formulations, Tac-TD or Tac-OD, during the first year after Tx. Additionally, the aim of the study was to compare the distribution of C0 within and beyond the target therapeutic range (8-12 ng/mL for the first 90 days and 6-10 ng/mL afterwards) after the administration of different drug formulations. Subjects and Methods: A retrospective pharmacokinetic study included 84 patients (56 on Tac-TD and 28 on Tac-OD), with a follow-up period between the first and twelfth month post-transplantation. Following pharmacokinetic data were used: daily dose, daily dose according to patient's body weight, concentration C0 and C0 /D of Tac. Results: The results of the study showed that patients on Tac-OD formulation had higher daily doses and higher C0 during 4-6 months (p<0.01) and 7-12 months (p<0.01) after Tx. Patients on Tac-OD had lower C0 /D during 4-6 months (p<0.05) and 7-12 months (p<0.01) after Tx. C0 in Tac-TD patients was significantly more frequently below the target range, whereas in Tac-OD patients C0 was more frequently above the target range, while both patient groups had equal distribution of C0 within the target range of Tac in the period between 4th and 12th month post-transplantation (p<0.01). Conclusions: The conducted research suggests that patients on Tac-OD preparation may require higher daily doses of Tac compared to patients on Tac-TD preparation in order to maintain optimal immunosuppression in the late post-transplant period.
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