Investigação de Er3+ nos dois sítios cristalográficos de Gd2SiO5 através da fotoluminescência resolvida no tempo

Gadolinium oxyortho-silicate, Gd2SiO5, presents a monoclinic structure with two crystallographic sites in which Gd3+ ions are equally distributed with coordination numbers CN, 7 and 9, respectively. By doping this host with Er3+ it is possible to distinguish and attribute the two sites by means of lifetime determination of the 4S3/2 state, (in this case, Er3+ substitutes Gd3+ ions). Samples doped with 0.1 and 5.0% molar Er3+ were prepared by solid state reaction and characterized by X-ray Diffractometry, Vibrational and Electronic Absorption Spectroscopies, and Time Resolved Photoluminescence. Based on the experimental results, it is possible to verify that, for the 5,0% doped sample, the lifetime value of the 4S3/2 state of the erbium ion inserted in site 1, (CN = 9), is 2.7 ± 0.1 mus, and for the one inserted in site 2, (CN = 7), it is 1.5 ± 0.1 mus.

A extração de cafeína em bebidas estimulantes: uma nova abordagem para um experimento clássico em química orgânica

Caffeine extraction procedures from water soluble and water insoluble materials for preparing stimulating beverages are described. Water soluble materials used were instant tea and coffee and water insoluble materials were, among others, guaraná powder and maté leaves. The extraction of caffeine from water soluble materials, especially instant tea, is more suitable for an organic chemistry teaching laboratory than the classic experiment using tea leaves, due to the economy of time and a larger amount of extracted caffeine. The procedure is time-saving and requires only a four-hour period. The experiments illustrate the extraction process as used in undergraduate organic chemistry laboratories.

Lukion opettajien ääni - Aineenopettajien käsityksiä muutoksista ja visioista lukiossa

Tulevaisuusorientaatio on tullut entistä tärkeämmäksi myös koulumaailmassa johtuen yhteiskunnassa nopeasti eteen tulevista muutoksista. On myös esitetty epäilyjä, että tulevaisuuteen reagoimisessa heikoin tilanne olisikin juuri kuntatason päätöksenteossa. Ymmärrys ja tieto opettajan työstä nimenomaan opettajan omasta perspektiivistä tarkasteltuna mahdollistavat lähtökohdan ja edellytykset todelliselle koulun uudistamiselle. Peruskysymys, johon tässä tutkimuksessa etsittiin vastausta oli: Millaisia ovat lukion aineenopettajien käsitykset lukion muutosprosesseista ja miten he visioivat oman lukionsa ja yleensä lukioiden tulevaisuutta? Aineiston keruu osui ajankohtaan, joka oli hyvin otollinen tulevaisuuden tarkasteluun, sillä uusi opetussuunnitelma otettiin käyttöön kaikissa Suomen lukioissa viimeistään lukuvuonna 2005-2006. Tutkimuksessa oli mukana kaksi hyvin erilaista lukiota Länsi-Suomen läänistä eli pieni maaseudun lukio ja hyvin suuri kaupunkilukio. Tutkimusaineiston keruu eteni kaksivaiheisesti: informoitu kysely ja teemahaastattelu. Tutkimusjoukon suuruus oli yhteensä 20, joista puolet oli miehiä ja puolet naisia. Aineenopettajien käsityksiä muutoksista ja visioista tutkittiin fenomenografisen tutkimusotteen avulla. Fenomenografiassa kiinnostuksen kohteena ovat ihmisten erilaiset käsitykset todellisuudesta ja näin saatava ymmärrys tavoista, joilla ihmiset kokevat tilanteita ja maailmaa. Organisaation muutosprosesseja voidaan kutsua myös oppimiseksi. Tutkimuksen oppivan organisaation näkökulmat perustuivat juuri yhteistyössä tapahtuvaan yhteisen toiminnan kehittämiseen. Aineenopettajien käsityksiä työyhteisöstään tarkasteltiin seuraavista oppivan organisaatiomallin näkökulmista: vuorovaikutus, päätöksenteko sekä rehtorin ja aineenopettajan rooli ja asema työyhteisössä. Aineenopettajien keskeisimmät käsitykset muutoksista lukiossa viime vuosina kohdistuivat aineenopettajan ammattirooliin ja lukio-opiskelijaan sekä opiskelijalta vaadittaviin lukio-opintoihin. Muutokset ammattiroolissa korostavat tutkimustulosten perusteella aineenopettajilta vaadittavia muitakin kuin opetettavien aineiden hallintataitoja. Suoranaista ammattitaidon puutetta opettajat kokivat varsinkin ryhmänohjaustehtävien yhteydessä, osittain myös uusien oppimisympäristöjen, esimerkiksi verkkopedagogisten taitojen, yhteydessä. Opettajien lisäkoulutuksen tarve koetaan konkreettisena, mutta sekä koulutusten sisältöihin, järjestelyihin ja ajankohtiin että koulun sijais- ym. järjestelyihin kaivattaisiin parannuksia. Verrattuna aikaisempiin tutkimuksiin näyttäisi siltä, että luokaton lukio on saanut opettajat enenevässä määrin huolestumaan opiskelijoiden syrjäytymisriskistä ja hyvinvoinnista. Opiskelijoiden syrjäytymisriskin kasvu lukio-opintojen aikana nouseekin yhdeksi lukion pessimistiseksi skenaarioksi. Muista pessimistisistä skenaarioista lukiolle, jotka saattoi johtaa tutkimustuloksista, voidaan mainita työyhteisön demokratiavajeen syveneminen sekä opetussuunnitelmasisältöjen ja ylioppilastutkintovaatimusten välisen kuilun syveneminen. Aineenopettajien käsitykset oman lukionsa visioista olivat sisällöiltään pääosin välineellisiä ja ne kohdentuivat kaikki opiskelijoihin. Esimerkiksi työyhteisöllisiä kehittämisajatuksia ei visioissa ilmennyt. Myöskään visioinnin dynaamisuus ei aineistossa korostunut. Aineenopettajien käsitykset visioiden arvopohjasta heijastivat perinteistä suomalaista arvomaailmaa eli itsekuria, velvollisuudentuntoa, kuuliaisuutta esivaltaa kohtaan ja perinteisten arvojen kunnioittamista. Sen sijaan antiikista perityviä Sokrateen edustamia keskustelua ja auktoriteettien kyseenalaistamista ei arvoissa ilmennyt, eikä myöskään uusliberalistista individualismia. Käsitykset visioiden synnystä näyttävät parhaiten selittävän opettajan muita käsityksiä liittyen visioon, visiointiin ja työyhteisöllisiin vaikutusmahdollisuuksiin sekä opettajan tulevaisuusorientoitumiseen.. Käsitykset vision syntytaustasta voidaan jakaa seuraaviin pää- ja alakategorioihin: 1. auktoriteettikeskeinen visiointi: johdon linjaus tai valtakunnallinen linjaus, 2. yhteisökeskeinen visiointi: yhteisöllinen linjaus tai toiminnallinen linjaus ja 3. yksilökeskeinen visiointi. Pessimistisimmiksi eli vähiten tulevaisuusorientoituneiksi opettajiksi työyhteisössä osoittautuivat ne opettajat, jotka pitivät oman lukionsa visiota koulun johdon sanelemana. Monet teoriat oppivasta organisaatiosta korostavat johtajuuden merkitystä työyhteisöä kehitettäessä. Johtajuuden merkitys nousi tämänkin tutkimuksen aineistosta keskeisesti esiin. Pyrkimystä kohti oppivaa organisaatiota opettajien puheista löytyy paljonkin, esimerkkeinä viittaukset johtajuuden ja vuorovaikutustapojen kehittämistarpeisiin. Sen sijaan opettajien puheet omista työyhteisöllisistä kehittymistarpeistaan, ns. alaistaidot, jäivät vähäisiksi. Tutkimustuloksista on luotu sovellusmalli kouluyhteisöjen visioinnin ja muun kehittämistyön tueksi.

Privatization and Regulation of Toll Motorways in Europe

The private sector plays an increasing and relevant role in highway funding and management. For that reason, the regulation designed and enforced by public authorities becomes even more important for the social welfare results generated by this process. In this study, we analyze the current trends in highway funding and management paying special attention on the recent process of privatization and its motivations. Since public ownership and regulation are substitutes for government intervention, we check the hypothesis that highways privatization induces more strict regulation. Indeed, we observe that as the private sector increases its size, toll regulation becomes more detailed.

Métodos para análise de ácido clorogênico

This paper describes the analytical methods for determination of total chlorogenic acid (CGA) and their individual isomers. Spectrofotometric methods are adequate for total CGA analysis in green coffee but they can provide inflated results for coffee products. High pressure liquid chromatography (HPLC) with gel permeation column and ultraviolet (UV) monitoring is adequate for the simultaneous analysis of total CGA, alkaloids and sugars in coffee products. HPLC-UV-reversed phase is a simple, rapid and precise method for the determination of the individual isomers of CGA. Gas chromatography (GC) also is applied to the analysis of the individual isomers but phenolic acids need to be derivatized before analysis. Both HPLC- and GC-mass spectrometry provide an unequivocal identification of the individual isomers. The capillary electrophoresis method is simple, rapid and adequate to the simultaneous analysis of polyphenols and xanthines. Advantages and limitations of each method are discussed throughout the text.

Determinação de compostos bioativos em amostras comerciais de café torrado

Coffee is a product consumed all around the world, Brazil being the biggest exporter. However, little is known about the difference in composition of the different brands in terms of bioactive substances. In the present study, ten of the most consumed brands of coffee in Rio de Janeiro were analyzed. Caffeine contents, trigonelline and total chlorogenic acid varied from 0.8 g/100g to 1.4 g/100g; 0.2 g/100g to 0.5 g/100g and from 3.5 g kg-1 to 15.9 g kg-1, respectively. The large heterogeneity observed in the amounts of the bioactive compounds can be attributed to different formulations of the various brands, as well as to different roasting conditions.

Análises quali- e quantitativa de cafés comerciais via ressonância magnética nuclear

Coffee is one of the beverages most widely consumed in the world and the "cafezinho" is normally prepared from a blend of roasted powder of two species, Coffea arabica and Coffea canephora. Each one exhibits differences in their taste and in the chemical composition, especially in the caffeine percentage. There are several procedures proposed in the literature for caffeine determination in different samples like soft drinks, coffee, medicines, etc but most of them need a sample workup which involves at least one step of purification. This work describes the quantitative analysis of caffeine using ¹H NMR and the identification of the major components in commercial coffee samples using 1D and 2D NMR techniques without any sample pre-treatment.

Efeito do processo de descafeinação com diclorometano sobre a composição química dos cafés arábica e robusta antes e após a torração

The decaffeinated coffee market has been expanding increasingly in the last years. During decaffeination, aroma precursors and bioactive compounds may be extracted. In the present study we evaluate the changes in the chemical composition of C. arabica and C. canephora produced by decaffeination using dichloromethane. A significant change in the chemical composition of both C. arabica and C. canephora species was observed, with differences between species and degrees of roasting. Major changes were observed in sucrose, protein and trigonelline contents after decaffeination. Changes in the levels of total chlorogenic acids and in their isomers distribution were also observed. Lipids and total carbohydrates were not affected as much. The sensory and biological implications of these changes need to be investigated.

Metodologia para análise simultânea de ácido nicotínico, trigonelina, ácido clorogênico e cafeína em café torrado por cromatografia líquida de alta eficiência

A reverse phase liquid chromatography method was developed for simultaneous determination of trigonelline, caffeine, nicotinic and chlorogenic (5-CQA) acids in roasted coffee. A gradient of acetic acid/acetonitrile was used as mobile phase and detection was carried out in the UV. The samples were extracted with acetonitrile/water (5:95 v/v) at 80 ºC/10 min. Good recovery (89 to 104%), repeatability and linearity were obtained. Detection limits of 0.01, 0.15, 0.04 and 0.04 mg mL-1 were observed for nicotinic acid, trigonelline, 5-CQA and caffeine. The method, applied to arabica and robusta coffees with different degrees of roasting, was efficient and fast (~35 min) and also allowed identification of cinnamic acids.

Determinação de açúcar total em café cru por espectroscopia no infravermelho próximo e regressão por mínimos quadrados parciais

In this work a fast method for the determination of the total sugar levels in samples of raw coffee was developed using the near infrared spectroscopy technique and multivariate regression. The sugar levels were initially obtained using gravimety as the reference method. Later on, the regression models were built from the near infrared spectra of the coffee samples. The original spectra were pre-treated according to the Kubelka-Munk transformation and multiplicative signal correction. The proposed analytical method made possible the direct determination of the total sugar levels in the samples with an error lower by 8% with respect to the conventional methodology.

Pectinases: aplicações industriais e perspectivas

Pectic substances are structural heteropolysaccharides that occur in the middle lamellae and primary cell walls of higher plants. They are composed of partially methyl-esterified galacturonic acid residues linked by alpha-1, 4-glycosidic bonds. Pectinolytic enzymes are complex enzymes that degrade pectic polymers and there are several classes of enzymes, which include pectin esterases, pectin and pectate lyases and polygalacturonases. Plants, filamentous fungi, bacteria and yeasts are able to produce pectinases. In the industrial world, pectinases are used in fruit juice clarification, in the production of wine, in the extraction of olive oil, fiber degumming and fermentation of tea, coffee and cocoa.

Determinação de zinco em solo utilizando colorimetria

In terms of soil fertility, zinc is a micronutrient that is very important in the culture of soy, maize, rice and coffee, because it is a structural and functional component of a great number of enzymes. Therefore, diverse methods have been used to determine zinc in soil. In this work we use colorimetry as a methods of zinc determination in soil using two methodologies of sample digesting, H2SO4/H2O2 and HNO3/H2O2. In order to compare the results, atomic absorption spectrometry (AAS) was used. Results show that colorimetric methods can be used due to good sensitivity and reproducibility, since the zinc calibration curve showed good linearity. Comparing colorimetric methods with AAS we observed that the results were equivalent, as proven by the statistical values of the F and t of Student tests. Furthermore, both methods of soil digesting can be used, leading to a flexible methodology of low-cost for routine zinc analyses in soil.

Influência do processamento e da torrefação sobre a atividade antioxidante do café (Coffea arabica)

The aim of this work is to evaluate the influence of processing (semi-dry and dry) and roasting (light, medium and dark) on the antioxidant activity of coffee brews, using tests to determine the reducing power and the DPPH scavenging, Fe+2 chelating and lipid peroxidation inhibition activities. All of the coffee brews presented concentration-dependent antioxidant activity. The light coffee samples presented the higher reducing power and DPPH scavenging activity. Its ion chelating capacity was similar to the medium samples, but was less than the green coffee chelating capacity. The semi-dry processing was more efficient than the dry processing only for the reducing power. All of the samples presented high lipid peroxidation inhibition activity. Based on the results the degree of coffee roasting seems to be more important than the processing to determine the antioxidant activity of brews.

Utilização do índice de retenção linear para caracterização de compostos voláteis em café solúvel utilizando GC-MS e coluna HP-Innowax

Gas chromatography coupled with mass spectrometry (GC-MS) is widely used for the characterization of volatile compounds. However, due to the complexity of the soluble coffee matrix, a complete identification of the components should not be based on mass spectra interpretation only. The linear index of retention (LRI) is frequently used to give support to mass spectra. The aim of this work is to investigate the characterization of the volatile compounds in soluble coffee samples by GC-MS using LRI values found with a HP-INNOWAX column. The method used allows a significant increase of the reliability of identifying compounds.

Preparação e caracterização de carvão ativado produzido a partir de resíduos do beneficiamento do café

Coffee fruit processing is one of the most polluting activities in agriculture due to the large amount of waste generated in the process. In this work, coffee parchment was employed as precursor for the production of carbons activated with ZnCl2 (CAP). The material was characterized using N2 adsorption/desorption at 77 K, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The material showed a surface area of 521.6 m²g-1 and microporous structure. CAP was applied as adsorbent for the removal of methylene blue dye in aqueous medium. The adsorption capacity was found to be about 188.7 mg g-1.