292 research outputs found

    Normalization and Trace Element Contamination of Soils in a Karstic Polje - An Example from the Sinjsko Polje, Croatia

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    Estimation of the anthropogenic over natural contribution in the chemical content of soils and sediments is very important but not easy to measure. Normalization based on either aluminium or iron, as reference conservative elements having supposed natural distributions, is a useful tool in solving this problem. However, several independent factors can influence the normalization procedure, which if not taken into account could lead to completely erroneous conclusions about the origin of the particular elevated concentrations of certain elements. Therefore, a great deal of caution should be exercised during application of the normalization procedure. Analytical data from 95 soil samples from the Sinjsko polje enabled us to critically apply this procedure. Linear regression analysis, evaluation of enrichment factors and trend surface analysis with the construction of appropriate maps were used to test the procedure. Presuming an existing linear dependence between the conservative element and the heavy metal it is possible with the use of linear regression to simultaneously define the heavy metal geochemical background (baseline) and to isolate natural and/or anthropogenic outliers (anomalies). Coupled with geographic plotting facilities this type of outlier-screening is used to locate areas of man made pollution. Statistical treatment of selected elements included the calculation of means, standard deviations and other estimates of basic statistic parameters. Evaluation of enrichment factors reveals the dependence of this parameter upon four main factors: the choice of reference element; the choice of reference material; the homogeneity of reference element distribution in the study area; and correlation of particular element with reference element. Examination of trends is a common procedure in the analysis of geochemical maps. Its purpose is to segregate the underlying trend that possibly pervades the study area, from the local variations, that is, the “noise” or “background”. Statistical analysis, as suggested by the results in this work, would be more properly used over general areas in the karstic terrain, with different geological, geomorphologic and hydrogeological characteristics, rather than being focused on the relatively small phenomena such as poljes, with many local geologic, hydrogeological and geochemical constraints

    The influence of porosity on machinability of sintered fe foam elements

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    The aim of the experiment was to study the machinability of porous metal foams formed by reduction of metal oxides during sintering. The analysis focused on the machining process of metal foams with respect to their porosity and mechanical properties. The factors investigated included the geometry of the specimens, the surface condition depending on the machining parameters (milling) and the porosity of the metal foam. The metallic porous structure was obtained as a result of sintering the mixture of iron based powders ASC 100.29 and DISTALOY SE (DIST SE) with porosity from 67,9 % (SE 1) to 77,8 % (SE 2) for ASC base powder and 75,7 % to 80.3 % for DISTALOY SE were used

    Biocorrosion Behavior of High Noble Au-Pt Dental Alloy in Different Solutions and pH Values

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    Korozijska stabilnost i biokompatibilnost najvažniji su čimbenici za upotrebu neke slitine u ustima. Svrha ovoga rada bila je analizirati otpuštanje metalnih iona iz visoko plemenite zlatno-platinske (Au/Pt) slitine u različite otopine koje oponašaju različite uvjete u usnoj šupljini. Zlatno-platinska (Au/Pt) slitina bila je in vitro izložena otopini koja oponaša slinu (Saliva; fosfatni pufer pH 6.0), u jako kiselome mediju koji oponaša ekstremne uvjete u usnoj šupljini (Ekstrem; fosfatni pufer pH 3.5) i u mliječnoj kiselini pri pH 3,5 što oponaša uvjete ispod dentobakterijskoga plaka (Plak, mliječna kiselina pH 3.5). Po 6 uzoraka tvorničke slitine bilo je uronjeno u slinu, ekstrem i plak 1, 2, 3, 4, 5, 6, 7, 14, 21 i 30 dana. Otopine su analizirane na 15 metalnih iona s pomoću ICP-AES. Rezultati pokazuju da je otpuštanje iona Zn, Cu, Fe i Cr ovisno o vremenu izloženosti i o vrsti otopine i njezina pH (ANOVA, p<0.01 za vrstu otopine, vrijeme ekspozicije i interakcijske uporedbe). Krom i željezo nisu bili deklarirani u Au/Pt slitini, a pronađeni su u otopinama. Nedeklarirani ioni (npr. Cr) vjerojatno mogu biti uzrokom alergija koje se pripisuju zlatu.Corrosion stability and biocompatibility are basic factors for oral use of dental alloys. The aim of this study was to analyse the release of metal ions from Gold/platinum (Au/Pt) dental alloy in the different conditions that may be found in the oral cavity.Gold/platinum (Au/Pt) dental alloy was exposed in vitro to either simulated saliva (Saliva; phosphate buffer pH 6.0), highly acidic medium resembling the extreme conditions in the oral cavity (Acid; phosphate buffer pH 3.5), and in lactic acid at pH which occurs under the dental plaque (Plaque, lactic acid pH 3.5). The alloy was immersed in the Saliva, Acid, and Plaque solution for 1, 2, 3, 4, 5, 6, 7, 14, 21, and 30 days. The solution was analyzed for fifteen metals with the ICP-AES. The results revealed time and solution dependent leaching of Zn, Cu, Fe, and Cr (ANOVA, p<0.01 for solution, time, and interaction comparison). Chromium and iron were not declared in the Au/Pt dental alloy. Undeclared ions (eg. Cr) may be responsible for the allergy attributed to gold

    Živa u tlu i zraku kao element-indikator za boksitna ležišta u Istri - eksperimentalni istraživački model

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    ID order to find out a secondary dispersion halo of mercury and some other trace elements around the bauxite ore bodies, the authors sampled terra rossa along traverses over them. At the same time, mercury in air is measured and expressed by relative values (mA) using Zeeman mercury vapor analyser. Mercury in soil was determined by flameless atomic absorption method and Cd, Pb, Zn, Cu, Co and Mn by standard AA techniques. The results are equivocal since the natural vertical soil profiles are severely disturbed on traverses due to different land use, what should be taken into consideration during continuation of the survey.U radu je obrađeno istraživanje sekundarne disperzije žive i nekih drugih elemenata oko boksitnih rudnih tijela u Istri. U tu svrhu izvršeno je uzorkovanje terra rosse uzduž traversi položenih preko boksitnih rudnih tijela. Istovremeno s uzorkovanjem tla vršena su mjerenja pomoću Zeemanovog analizatora živinih para u zraku, a vrijednosti su izražavane u relativnim vrijednostima (mA). Živa u tlu je određivana pomoću metode besplamene atomske apsorpcije, a Cd, Pb, Zn, Cu, Co i Mn standardnom atomskom apsorpcijom. Rezultati ne pokazuju jednoznačnost na terenima s različitim stupnjem poremećenja prirodnog, vertikalnog profila tla (oranica, livada i Suma), što se mora uzeti u obzir prilikom nastavka istraživanja

    ŽIVA U ZRAKU IZNAD URBANIH I INDUSTRIJSKIH DIJELOVA GRADA ZAGREBA

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    In recent years Zagreb city encounters severe pollution problems in aquatic, terrrestrial and atmospheric environment. A random or permanent monitoring of some inorganic gaseous pollutants in atmosphere has already been organized and published alsewhere. By means of a sophisticated mercury vapor analyser with a Zeeman effect background corrector, however, continuous registration along two traverses (monitoring routes) over rural, urban and industrial parts of Zagreb has been elaborated for the first lime. Data show strong anthropogenic influence in the Žitnjak industrial area. The anomaly high 105 ngm Hg, on the 22 October moved slightly to downtown by change of wind direction on the 31 October. Intensity raised as much as 155 ngm Hg, 13 times augmented in comparison to a background value on the Medvednica mountain. Explanation should be sought in denser public traffic, change of wind direction and lowering of atmospheric pressure.Posljednjih godina grad Zagreb se susreće sa značajnim ekološkim problemima zagađenja svih medija; vode, zraka i tla. Povremena i stalna praćenja koncentracije određenih anorganskih zagađivača u atmosferi izvode se već duže vrijeme, a rezultati su publicirani u znanstvenim časopisima. Međutim, prvi put u našem gradu je korišten model suvremenog živinog analizatora s korektorom analitičkih šumova, baziranom na Zeemanovon efektu, koji omogućava kontinuirano registriranje vrijednosti koncentracija žive u zraku. Mjerenja su izvedena uzduž dviju trasa koje prolaze kroz ruralne, urbane i industrijske predjele grada Zagreba, Rezultati mjerenja su omogućili izradu grube geokemij-ske karte distribucije žive i lokaciju anomalnih koncentracija u najugroženijim područjima. Anomalija od 105 ngm Hg, registrirana 21. listopada (subota), vidljivo se pomakla u smjeru prema centru grada 31. listopada (utorak). Njezin intenzitet je porastao na 155 ngm Hg, 15 puta više od prosječnih vrijednosti na Medvednici, a položaj ukazuje na značajan antropogeni utjecaj u području industrijske zone Žitnjaka. Objašnjenje ove pojave treba tražiti u pojačanom utjecaju gradskog prometa, promjeni smjera vjetra i sniženju atmosferskog pritiska kao predznaka pogoršanja vremenskih uvjeta

    Karakterisasi Mekanik Biokomposit Klobot Jagung sebagai Bahan Dasar Plastik Biodegradable

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    The corn production in Indonesia, based on the data from Badan Pusat Statistik in 2012, amounted to 19.73 million tons, the cornhusk from the corn crop is about 38.38%. The utilization of cornhusk itself has not been maximized yet, so the research to maximize the utilization of cornhusk is required. The research has been made biocomposites cornhusk and Linear Low Density Polyethylene (LLDPE) with hot press method. Biocomposites made with the variation of cornhusk:LLDPE are 30:70, 40:60, 50:50, 60:40, 70:30, and it is characterized of the mechanical characteristics (tensile and tear) with Universal Testing Machine (UTM), biodegradation in a qualitative manner. Mechanical analysis showed the mechanical characteristics decrease with the addition of cornhusk concentration on biocomposites, and concentration 30:70 has the highest mechanical characteristics with tensile strength 24.77 MPa, elongation 19.10% and tear strength 53.94 N/mm. The result is contrast with the biodegradable analysis in which the bigger concentration cornhusk then the level of biodegradability is higher

    Raspodjela elemenata u tragovima u površinskim sedimentima Vranskog jezera i tlima otoka Cresa

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    This paper presents a study of major and trace element distribution and an evaluation of their environmental geochemical aspects in the surface sediments of Vrana Lake and the topsoil within its catchment area. The concentrations of 22 elements were determined in 30 lake sediment samples and 60 topsoil samples covering the lake catchment area and the whole island of Cres. The element to Al ratios fall into three main groups: the group of elements that show no difference in ratios in soils and lake sediments: Ni, Co, Mn, Th, Zn, Ba, Ti, K, V, Na, and H; elements that are enriched in the sediments: Ca, Sr, Cd, Pb, Ba and Mg; and elements that are depleted in the lake sediments: Cu, P, Fe, Cr, and La. Long-range air pollution is probably the main reason why the content of metals, especially lead, is increased in the lake sediments, although a local source, from road transport, as indicated by soil data from the catchment area, could also be an important source of Pb. Some pollutants in the soils of the catchment area, such as Cu and Hg from agro-chemical sources, were not determined in elevated concentrations in the lake sediments. Comparison of element/Al indexes from this study with the other studies of surface materials in the region show mutually similar sources, with loess and flysch as two geochemical end-members.U radu se daje pregled raspodjele glavnih elemenata i onih u tragovima u površinskim sedimentima Vranskog jezera i tlima na otoku Cresu, te se na temelju izra|enih analiza daje pregled mogućih geokemijskih promjena u okolišu. Određene su koncentracije 22 elementa u 30 uzoraka jezerskog sedimenta i 60 uzoraka tla koje pokriva slivno područje jezera i otoka Cresa. Na temelju omjera pojedinih elemenata i aluminija utvrđene su tri geokemijske grupe elemenata; prvu grupu čine elementi koji ne pokazuju razliku u omjerima element/Al u tlima i sedimentima: Ni, Co, Mn, Th, Zn, Ba, Ti, K, V, Na i H; elementi koji pokazuju obogaćenje u sedimentima: Ca, Sr, Cd, Pb, Ba i Mg, te grupa elemenata koja je obogaćena u tlima; Cu, P, Fe, Cr i La. Povišene koncentracije olova u jezerskim sedimentima moguće je tumačiti kao posljedicu atmosferskog taloženja iz udaljenih industrijskih izvora a koncentracije utvrđene u tlima, na lokacijama na širem području prometnice koja prolazi istočnom stranom slivnog područja jezera, upućuju i na mogućnost lokalnog utjecaja automobilskog prometa. Neki potencijalno toksični elementi (Hg i Cu) koji su utvrđeni u povišenim koncentracijama u tlima slivnog područja, nisu utvrđeni kao povišeni u samom jezerskom sedimentu. Usporedbom omjera element/Al dobivenih u ovom radu sa rezultatima istraživanja površinskih materijala drugih autora sa šireg područja pokazuju da detritični materijal potječe iz istih izvora sa lesom i naslagama fliša kao dva krajnja geokemijska člana

    Caregiver socioemotional health as a determinant of child wellâ being in schoolâ aged and adolescent Ugandan children with and without perinatal HIV exposure

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    ObjectiveCaregiver socioâ emotional attributes are major determinants of child wellâ being. This investigation in vulnerable schoolâ aged Ugandan children estimates relationships between children’s wellâ being and their caregiver’s anxiety, depression and social support.MethodsPerinatally HIVâ infected, HIVâ exposed uninfected and HIVâ unexposed Ugandan children and their caregivers were enrolled. Perinatal HIV status was determined by 18 months of age using DNAâ polymerase chainâ reaction test; status was confirmed via HIV rapid diagnostic test when children were 6â 18 years old. Five indicators of child wellâ being (distress, hopelessness, positive future orientation, esteem and quality of life (QOL)) and caregiversâ socioemotional status (depressive symptoms, anxiety and social support) were measured using validated, culturally adapted and translated instruments. Categories based on tertiles of each caregiver psychosocial indicator were defined. Linear regression analyses estimated percent differences (β) and corresponding 95% confidence intervals (CI) for child wellâ being in relation to caregiver’s psychosocial status.ResultsAs per tertile increment, caregiver anxiety was associated with 2.7% higher distress (95%CI:0.2%, 5.3%) and lower selfâ esteem/QOL (β = â 1.3%/â 2.6%; 95%CI: â 5.0%,â 0.2%) in their children. Child distress/hopelessness increased (β = 3.3%/7.6%; 95%CI:0.4%, 14.7%) and selfâ esteem/QOL decreased 2.3% (β = â 2.3%/â 4.4%; 95%CI: â 7.2%, â 1.3%) as per tertile increment in caregiver depression. Higher caregiver social support was associated with lower distress and higher positive outlook (β = 3%; 95%CI:1.4%, 4.5%) in their children. HIVâ infected/exposed children had most caregiver depressionâ related QOL deficit (β = â 5.2%/â 6.8%; 95%CI: â 12.4%, â 0.2%) and HIVâ unexposed children had most caregiver social supportâ related enhancements in positive outlook (β=4.5%; 95%CI:1.9%, 7.1%).ConclusionsCaregiver anxiety, depressive symptoms and low social support were associated with worse wellâ being in schoolâ aged and adolescent children. Improvement of caregiver mental health and strengthening caregiver social support systems may be a viable strategy for improving wellâ being of vulnerable children and adolescents in this setting.ObjectifLes attributs socioâ affectifs des responsables d’enfants sont des déterminants majeurs du bienâ être des enfants. Cette investigation menée auprès d’enfants ougandais vulnérables dâ âge scolaire a estimé les relations entre le bienâ être des enfants et l’anxiété, la dépression et le soutien social de leur responsable.MéthodesDes enfants ougandais infectés par le VIH de manière périnatale, exposés au VIH mais non infectés, et non exposés au VIH ainsi que leurs responsables ont été inscrits. Le statut VIH périnatal a été déterminé à lâ âge de 18 mois à l’aide du test de PCR de lâ ADN; le statut a été confirmé par un test de diagnostic rapide du VIH chez les enfants âgés de 6 à 18 ans. Cinq indicateurs du bienâ être de l’enfant (détresse, désespoir, orientation future positive, estime et qualité de vie (QV)), et le statut psychosocial des responsables (symptômes dépressifs, anxiété et soutien social) ont été mesurés à l’aide de méthodes validées, adaptées à la culture et respectées et d’outils traduits. Des catégories basées sur les tertiles de chaque indicateur psychosocial du responsable ont été définies. Des analyses de régression linéaire ont estimé les différences en pourcentage (β) et les intervalles de confiance (IC) à 95% correspondants pour le bienâ être de l’enfant par rapport au statut psychosocial de leurs responsables.RésultatsPar incrément de tertile, l’anxiété des responsables était associé à 2,7% de détresse plus élevé (IC95%: 0,2%, 5,3%) et de faible estime de soi/QV (β = â 1,3%/â 2,6%; IC95%: â 5,0%, â 0,2%) chez leurs enfants. La détresse et le désespoir des enfants augmentaient (β = 3,3%/7,6%; IC95%: 0,4%, 14,7%) et l’estime de soi/QV diminuait de 2,3% (β = â 2,3%/â 4,4%; IC95%: â 7,2%, â 1,3%) par incrément de tertile de la dépression chez le responsable. Un soutien social plus élevé des responsables était associé à une détresse moindre et à une perspective positive plus élevée (β = 3%; IC95%: 1,4%, 4,5%) chez leurs enfants. Les enfants infectés/exposés au VIH présentaient pour la plupart un déficit de QV lié à la dépression de leurs responsables (β = â 5,2%/â 6,8%; IC95%: â 12,4%, â 0,2%), et ceux non exposés au VIH présentaient pour la plupart des améliorations en perspective positive liées au soutien social de leurs responsables (β = 4,5%; IC95%: 1,9%, 7,1%).ConclusionsL’anxiété, les symptômes dépressifs et un faible soutien social du responsable étaient associés à un bienâ être précaire chez les enfants dâ âge scolaire et les adolescents. L’amélioration de la santé mentale des responsables et le renforcement des systèmes de soutien social pour les responsables peuvent constituer une stratégie viable pour améliorer le bienâ être des enfants et des adolescents vulnérables dans cette région.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149358/1/tmi13221.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149358/2/tmi13221_am.pd
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