Search results for "MINERALOGY"
showing 10 items of 1516 documents
Kalcīts un tā veidošanās apstākļi Franas stāva smilšakmeņos un dolomītos Latvijā
2019
Maģistra darbā “Kalcīts un tā veidošanās apstākļi Franas stāva smilšakmeņos un dolomītos Latvijā” raksturotas kalcīta fizikālās īpašības, ķīmiskais sastāvs un veidošanās apstākļi. Pētījumi veikti 16 Amatas, Pļaviņu, Daugavas un Stipinu svītas atradnēs un atsegumos. Dokumentēti ģeoloģiskie griezumi, pētītas kalcīta fluorescences izpausmes un citas fizikālās īpašības, attiecības ar smilšakmens un dolomīta komponentiem plānslīpējumos, noteikts kalcīta ķīmiskais sastāvs un oglekļa stabilo izotopu attiecības. Secināts, ka kalcīts Amatas svītas smilšakmeņos un Pļaviņu, Daugavas un Stipinu svītas dolomītos kristalizējies līdzīgos apstākļos – no atmosfēras izcelsmes pazemes ūdeņiem sauszemes apstāk…
Kalcīts un tā veidošanās apstākļi augšējā devona Daugavas svītas dolomītos Latvijas centrālajā un austrumu daļā
2017
Bakalaura darbā “Kalcīts un tā veidošanās apstākļi augšējā devona Daugavas svītas dolomītos Latvijas centrālajā un austrumu daļā” ir raksturotas minerāla kalcīta fizikālās īpašības, mikroelementu saturs un veidošanās apstākļi. Pētījumi veikti 8 dolomīta atradnēs; ģeoloģiskajā griezumā un atradņu teritorijā salīdzinātas kalcīta īpašības. Testētas kalcīta fluorescences izpausmes, pētīti plānslīpējumi, raksturoti kalcītā sastopamie mikroelementi un oglekļa stabilo izotopu attiecības tajā. Secināts, ka kalcīts kristalizējies no atmosfēras ūdeņiem sauszemes apstākļos. Šis minerāls veidojies paleokarsta procesa beigu stadijā pēc iegruvumu izveidošanās. Atslēgas vārdi: mineraloģija, paleokarsts, f…
Indirect chronology method employing rare earth elements to identify Sagunto Castle mortar construction periods
2017
A novel indirect chronology method has been developed to identify Sagunto Castle construction periods. The method is based on the use of inductively coupled plasma mass spectrometry (ICP-MS) to determine rare earth elements (REE) and other trace elements in mortars. Additionally, a no destructive geochemical analysis based on X-ray fluorescence (XRF) was employed for major elements determination. Collected chemical data were processed through Principal Component Analysis (PCA) to highlight any differences among the mortars belonging to different buildings and construction periods. The results show that PCA analysis permits to discriminate construction periods according to mortar sample REE …
Silicate modulates the cross-talk between osteoblasts (SaOS-2) and osteoclasts (RAW 264.7 cells): inhibition of osteoclast growth and differentiation
2012
It has been shown that inorganic monomeric and polymeric silica/silicate, in the presence of the biomineralization cocktail, increases the expression of osteoprotegerin (OPG) in osteogenic SaOS-2 sarcoma cells in vitro. In contrast, silicate does not affect the steady-state gene expression level of the osteoclastogenic ligand receptor activator of NF-κB ligand (RANKL). In turn it can be expected that the concentration ratio of the mediators OPG/RANKL increases in the presence of silicate. In addition, silicate enhances the growth potential of SaOS-2 cells in vitro, while it causes no effect on RAW 264.7 cells within a concentration range of 10-100 µM. Applying a co-cultivation assay system,…
Hydration process and rheological properties of cement pastes modified by orthophosphate addition
2005
Abstract The use of cement by nuclear industry for confining low radioactive waste knows a constant increase. The interest bore to this material is due to its mechanical and chemical properties. However, these properties may be modified by the nature and the amount of wastes introduced with the mixing solution especially with large amount of phosphate. Precipitation of hydroxylapatite in the cement paste at the very beginning after mixing was emphasized from a particular concentration of orthophosphate. It was also found that this phenomenon leads to an early rigidification of the cement paste. From a kinetics point of view, the evolution of hydration was both delayed and slowed down accord…
Impaired geometric properties of tibia in older women with hip fracture history.
2007
This study evaluated side-to-side differences in tibial mineral mass and geometry in women with previous hip fracture sustained on average 3.5 years earlier. Both tibial mineral mass and geometry were found to be reduced in the fractured leg. INTRODUCTION: The purpose of this study was to evaluate side-to-side differences in tibial mineral mass and geometry after hip fracture and to assess the determinants of such differences. METHODS: Thirty-eight 60- to 85-year-old women with a previous hip fracture and 22 same-aged control women without fractures participated in the study. Bone characteristics of the distal tibia and tibial shaft of both legs were assessed using pQCT in order to compare …
Tetragonal tungsten bronzes Nb8−xW9+xO47−δ: optimization strategies and transport properties of a new n-type thermoelectric oxide
2015
Engineering of nanoscaled structures may help controlling the electrical and thermal transport in solids, in particular for thermoelectric applications that require the combination of low thermal conductivity and low electrical resistivity. The tetragonal tungsten bronzes Nb8−xW9+xO47 (TTB) allow a continuous variation of the charge carrier concentration while fulfilling at the same time the concept of a “phonon-glass electron-crystal” through a layered nanostructure defined by intrinsic crystallographic shear planes. The thermoelectric properties of the tetragonal tungsten bronzes Nb8−xW9+xO47−δ (0 < x < 2) were studied in the temperature range from 373 to 973 K. Structural defects and the…
Preparation of Nd:YAG Nanopowder in a Confined Environment
2007
Nanopowder of yttrium aluminum garnet (YAG, Y3Al5O12) doped with neodymium ions (Nd:YAG) was prepared in the water/cetyltrimethylammonium bromide/1-butanol/n-heptane system. Aluminum, yttrium, and neodymium nitrates were used as starting materials, and ammonia was used as a precipitating agent. Coprecipitate hydroxide precursors where thermally treated at 900 degrees C to achieve the garnet phase. The starting system with and without reactants was characterized by means of the small-angle neutron scattering technique. The system, without reactants, is constituted by a bicontinuous structure laying near the borderline with the lamellar phase region. The introduction of nitrates stabilizes th…
Sistemi di tariffe di cubatura per le fustaie di pino d'Aleppo, pino laricio e pino domestico della Sicilia
2009
Obiettivo del presente lavoro e la messa a punto di sistemi di tariffe validi per la cubatura delle masse legnose dei principali soprassuoli di conifere della Sicilia: in particolare, i sistemi proposti si basano sull’elaborazione delle serie di inquadramento delle relazioni ipsodiametriche per il pino domestico, il pino d’Aleppo e il pino laricio. Per ciascuna specie e stato studiato l’andamento della distribuzione dei valori ipsodiametrici, risultato ben rappresentato da una forma funzionale di tipo semilogaritmico utilizzabile come «curva guida» delle serie di inquadramento delle relazioni ipsodiametriche. Adottando l’inclinazione stimata in base alla curva guida e adattando le singole s…
Solar radiative effects of a Saharan dust plume observed during SAMUM assuming spheroidal model particles
2011
The solar optical properties of Saharan mineral dust observed during the Saharan Mineral Dust Experiment (SAMUM) were explored based on measured size-number distributions and chemical composition. The size-resolved complex refractive index of the dust was derived with real parts of 1.51–1.55 and imaginary parts of 0.0008–0.006 at 550 nm wavelength. At this spectral range a single scattering albedo ω o and an asymmetry parameter g of about 0.8 were derived. These values were largely determined by the presence of coarse particles. Backscatter coefficients and lidar ratios calculated with Mie theory (spherical particles) were not found to be in agreement with independently measured lidar data.…