scholarly journals Determination of Gold Particle Characteristics for Sampling Protocol Optimisation

Minerals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1109
Author(s):  
Simon C. Dominy ◽  
Ian M. Platten ◽  
Hylke J. Glass ◽  
Saranchimeg Purevgerel ◽  
Brian W. Cuffley
Keyword(s):  
Particle Size ◽  
Gold Particle ◽  
Low Grade ◽  
Large Sample Size ◽  
High Grade ◽  
Sampling Protocol ◽  
Gold Particles ◽  
Sampling Protocols ◽  
Very High

Sampling, sample preparation, and assay protocols aim to achieve an acceptable estimation variance, as expressed by a relatively low nugget variance compared to the sill of the variogram. With gold ore, the typical heterogeneity and low grade generally indicate that a large sample size is required, and the effectiveness of the sampling protocol merits attention. While sampling protocols can be optimised using the Theory of Sampling, this requires determination of the liberation diameter (dℓAu) of gold, which is linked to the size of the gold particles present. In practice, the liberation diameter of gold is often represented by the most influential particle size fraction, which is the coarsest size. It is important to understand the occurrence of gold particle clustering and the proportion of coarse versus fine gold. This paper presents a case study from the former high-grade Crystal Hill mine, Australia. Visible gold-bearing laminated quartz vein (LV) ore was scanned using X-ray computed micro-tomography (XCT). Gold particle size and its distribution in the context of liberation diameter and clustering was investigated. A combined mineralogical and metallurgical test programme identified a liberation diameter value of 850 µm for run of mine (ROM) ore. XCT data were integrated with field observations to define gold particle clusters, which ranged from 3–5 mm equivalent spherical diameter in ROM ore to >10 mm for very high-grade ore. For ROM ore with clusters of gold particles, a representative sample mass is estimated to be 45 kg. For very-high grade ore, this rises to 500 kg or more. An optimised grade control sampling protocol is recommended based on 11 kg panel samples taken proportionally across 0.7 m of LV, which provides 44 kg across four mine faces. An assay protocol using the PhotonAssay technique is recommended.

scholarly journals Gold Particle Size Determination on Au/TiO2-CeO2 Catalysts by Means of Carbon Monoxide, Hydrogen Chemisorption and Transmission Electron Microscopy

2009 ◽  
Vol 5 ◽  
pp. 13-23 ◽  
Author(s):  
C. Guzmán ◽  
Gloria Del Angel ◽  
Ricardo Gómez ◽  
F. Galindo ◽  
R. Zanella ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Carbon Monoxide ◽  
Particle Size ◽  
Gold Particle ◽  
Precipitation Method ◽  
Hydrogen Chemisorption ◽  
Gold Particles ◽  
Transmission Electron ◽  
Gold Particle Size

Au/TiO2 and Au/TiO2-CeO2 catalysts were prepared by the sol-gel method and carbon monoxide, hydrogen chemisorption and TEM spectroscopy have been exploited to determine the size of gold particles. The gold nanoparticles (8.1 to 2.1 nm) were deposited by using the deposition-precipitation method. The XRD characterization shows the presence of anatase as the TiO2 crystalline phase; while by XPS spectroscopy, the presence of Au°, Au2O3, Ce3+ and Ce4+ species co-existing in the Au/TiO2-CeO2 catalysts is shown. The characterizations by TPD-CO as well as by TPD-H2 (temperature programmed desorption) showed that on catalysts containing cerium, the gold particle size can be determined with great accuracy by using these chemisorption methods. The gold particle size calculated from either the CO or H2 thermodesorption values is in good agreement with that obtained by High Resolution Transmission Electron Microscopy (HRTEM) and Scanning Transmission Electron Microscopy (STEM) analyses. It was proposed that the TPD-CO and/or TPD-H2 techniques could be helpful for the characterization of the gold particles by TEM; especially when the high contrast in the pictures of the supports containing CeO2 prevents the particle size from being determined.

scholarly journals Effective diameters of protein A-gold and goat anti-rabbit-gold conjugates visualized by field emission scanning electron microscopy.

1992 ◽  
Vol 40 (6) ◽  
pp. 751-758 ◽  
Author(s):  
P Lea ◽  
D K Gross
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Particle Size ◽  
Field Emission ◽  
Gold Particle ◽  
Protein A ◽  
Gold Complexes ◽  
Gold Particles ◽  
Gold Particle Size ◽  
Scanning Electron

High-voltage (15-30 kV) field emission scanning electron microscopy (FESEM) was used to evaluate the effects of gold particle size and protein concentration on the formation of protein-gold complexes. Six colloidal gold sols were prepared, ranging in diameter from 7.6 to 39.8 nm. The minimal protecting amounts (m.p.a.) of protein A and goat anti-rabbit antibody (GAR) were experimentally determined. Gold particles were conjugated at the m.p.a., one half the m.p.a., and ten times the m.p.a. for both proteins, and protein-gold complexes prepared for FESEM. The smallest colloidal gold particles required the most protein per milliliter of gold suspension for stabilization. Transmission electron microscopy was found to be the preferred method for accurate sizing of gold particles, whereas FESEM of protein-gold complexes permitted visualization of a protein halo around a spherical gold core. Protein halo width varied significantly with changes in gold particle size. Measurements of protein halos indicated that conjugation with the m.p.a. of protein A resulted in the thickest protein layers for all gold sizes. GAR conjugation with the m.p.a. again produced the thickest protein layers. However, GAR halos were significantly smaller than those obtained with protein A conjugation. The proteins used showed similar adsorption patterns for the larger gold particles. For smaller gold particles, proteins may act differently, and these complexes should be further characterized by low-voltage FESEM.

Determination of expression of platelet derived growth factor receptors (PDGFR) in astrocitic tumors

2006 ◽  
Vol 24 (18_suppl) ◽  
pp. 11518-11518 ◽  
Author(s):  
C. H. Barrios ◽  
F. S. Viola ◽  
L. M. Coutinho ◽  
E. Paglioli
Keyword(s):  
Tumor Vasculature ◽  
Molecular Target ◽  
Platelet Derived Growth Factor ◽  
Low Grade ◽  
High Grade ◽  
Santa Cruz ◽  
Cell Compartment ◽  
Oncology Unit

11518 Background: PDGF and its receptors (α and β) are frequently expressed together in gliomas raising the possibility that an autocrine/paracrine loop could contribute to the pathogenesis of these tumors. Studies with immunohistochemistry (IHC) and in situ hybridization have clarified that PDGF-α receptors (PDGF-R α) are preferentially expressed in tumor cells, whereas PDGF-β receptors (PDGF-R β) are preferentially expressed in proliferating endotelial cells within the tumor vasculature. Objective: Determine the expression of PDGF-R α and β in astrocitic tumors. Methods: Paraffin blocks samples from patients with a diagnosis of low-grade astrocitoma, anaplastic astrocitoma, and glioblastoma were obtained from the Neuro-Oncology Unit at Hospital São Lucas-PUCRS. These patients presented and were treated from 1996 through 2001. We collected a total of 130 cases: 57 Low-grade astrocitomas (LGA), 13 Anaplastic Astrocitomas (AA), and 60 Glioblastomas (GBM). All cases were studied with standard IHC techniques using antibodies for PDGFR α and β (Santa Cruz Biotechnology). Results: See table . Conclusion: The expression of PDGF-R α and β in low-grade tumors reflects the possible role these receptors may have in the evolution of these neoplasms. More importantly we documented that over 60% of high-grade gliomas (61% in AA; 65% in GBM) show expression of PDGF-R β predominantly in the endothelial cell compartment of the tumors. This is consistent with and reflects the extensive angiogenesis observed in these diseases. The level of expression we encountered identifies an attractive molecular target to explore. [Table: see text] No significant financial relationships to disclose.

scholarly journals Determination of human papillomavirus 16 physical status through E1/E6 and E2/E6 ratio analysis

2014 ◽  
Vol 63 (12) ◽  
pp. 1716-1723 ◽  
Author(s):  
Dimitris Tsakogiannis ◽  
Zaharoula Kyriakopoulou ◽  
Irina Georgia Anna Ruether ◽  
Grigoris D. Amoutzias ◽  
Tilemachos G. Dimitriou ◽  
...  
Keyword(s):  
Human Papillomavirus ◽  
Present Report ◽  
Target Selection ◽  
Low Grade ◽  
High Grade ◽  
Physical Status ◽  
Major Step ◽  
Significant Information ◽  
Host Chromosome

Human papillomavirus (HPV) 16 genome integration into the host chromosome is a crucial event during the life cycle of the virus and a major step towards carcinogenesis. The integration of HPV16 DNA promotes a constitutive high expression level of E6 and E7 oncoproteins, resulting in the extensive proliferation of the infected epithelial cells. In the present report the physical status of the HPV16 genome was studied, through determination of E1/E6 and E2/E6 DNA copy number ratios in 61 cervical samples of low- and high-grade malignancy and 8 cervical cancer samples, all of them associated with HPV16 infection. The selection of E1, E2 and E6 amplification target regions was performed according to the most prevalent deleted/disrupted sites of E1 and E2 genes. For this target selection we also considered the most conserved regions of E1, E2 and E6 genes among the same HPV16 isolates that were recently reported by our group. The analysis of HPV16 DNA form revealed a significant association among the mixed DNA forms in low-grade and high-grade malignancies, (χ2, P<0.01). The comparative analysis of E1/E6 and E2/E6 in the same cervical samples provides an accurate picture of HPV16 DNA form and may reveal whether different HPV16 DNA integrants coexist in the same cervical sample or not. This study proposes that E1/E6 and E2/E6 ratios determine with accuracy the HPV16 DNA integration pattern and may predict multiple integration events in the examined sample, thus providing significant information about the progression of cervical dysplasia.

Patterns in the care of oligodendrogliomas and oligoastrocytomas: A single center experience

2009 ◽  
Vol 27 (15_suppl) ◽  
pp. e13034-e13034
Author(s):  
S. H. Kizilbash ◽  
L. Nadeau
Keyword(s):  
Radiation Therapy ◽  
Surgical Resection ◽  
Progression Free Survival ◽  
Low Grade ◽  
High Grade ◽  
Single Center Experience ◽  
Data Collection And Analysis ◽  
Unique Identity

e13034 Background: Although rare, oligodendrogliomas (ODs) and oligoastrocytomas (OAs) have established a unique identity due to their sensitivity to chemotherapy, especially if they exhibit combined loss of heterozygosity (LOH) of 1p and 19q. However, optimal management is still controversial and data is lacking on actual practice patterns. This study describes the epidemiology of ODs/OAs at a community based hospital in Michigan and evaluates the management of these tumors, especially with respect to 1p/19q LOH. Methods: A retrospective review was conducted of all cases of OD and OA that were managed at our institution from 1975 to 2007. 135 patients were isolated. Of these, 48 patients had already been evaluated for 1p/19q LOH. This latter subset underwent data collection and analysis. Results: 31 patients had low-grade tumors (either ODs or OAs) while 17 had high grade tumors (anaplastic ODs or anaplastic OAs). Of the low grade tumors, 35% had combined 1p/19q LOH. 71% underwent surgical resection, 35% received chemotherapy, and 26% received radiation therapy. As for the high grade tumors, 47% had combined 1p/19q LOH. 88% underwent surgical resection, 76% received chemotherapy, and 59% received radiation therapy. At a mean of 29 months of follow up, eight patients had tumor progression while 12 died. Median progression free survival (MPFS) for patients receiving chemotherapy was increased in patients with combined 1p/19q LOH, for both low-grade tumors (34 vs. 20 months) and high-grade tumors (14 vs. 8 months). Also, significantly more patients with low-grade tumors and combined 1p/19q LOH were offered chemotherapy when compared to those without 1p/19q LOH (64% vs 20%, p = 0.04, Fisher exact). However, in patients with high-grade tumors, knowledge of 1p/19q LOH did not significantly impact the choice to administer chemotherapy (88% vs. 67%, p = 0.67). Conclusions: Patients with ODs/OAs and combined 1p/19q LOH who have been treated with chemotherapy demonstrate increased MPFS when compared with those without this genotype. Despite this, determination of 1p/19q LOH significantly affects physician choice to offer chemotherapy only in patients with low-grade tumors, but not in those with high-grade tumors. A future study is in development to determine 1p/19q LOH status for the remaining 87 patients. No significant financial relationships to disclose.

Coexisting sodic and calcic amphiboles from high-pressure metamorphic belts and the stability of barroisitic amphibole

1979 ◽  
Vol 43 (326) ◽  
pp. 269-278 ◽  
Author(s):  
W. G. Ernst
Keyword(s):  
Local Equilibrium ◽  
Miscibility Gap ◽  
Back Reaction ◽  
Low Grade ◽  
Lower Grade ◽  
High Grade ◽  
Ligurian Alps ◽  
Show Evidence ◽  
A Site ◽  
Very High

SummaryCompositions of glaucophanes and actinolite-hornblende solid solutions occurring in chemically similar metabasaltic rocks from blueschist terranes in east-central Shikoku, W. California, Valtournanche (W. Alps), and W. Liguria are compared. Chemical contrasts among coexisting Na and Ca amphibole pairs, which reflect disparate P-T histories under the presumed attendance of local equilibrium, include: Na contents are rather high among barroisitic hornblendes from the western and Ligurian Alps, as well as among high-grade tectonic blocks from California; in contrast, actinolitic amphiboles from both lower-grade Franciscan tectonic blocks and in situ schists and the blueschists of Shikoku are impoverished in Na relative to blue-green hornblendes. Sodic amphiboles contain less than 0. 5 Aliv per formula unit, whereas Alvi is very high; a situation reversed among calcic amphiboles. The Na + Ca contents ofglaucophanes are strongly clustered around the sum of 2.0 (i.e. A site vacant) whereas calcic amphiboles have a wider range with the A site variably occupied. No solvus has been detected within either sodic or calcic amphiboles under blueschist facies conditions. For low-grade metabasaltic parageneses, a miscibility gap separates these two amphibole groups; at relatively high grade such compositions have sodic calcic amphiboles of barroisitic type; this may mean that glaucophane + hornblende assemblages are metastable, accounting for textural relations indicating that the sodic amphibole typically did not grow at the same time as the barroisite. Ti, Mn, and K appear to be concentrated in calcic amphibole compared to coexisting glaucophane, probably in the M2, M4, and A sites, respectively.Contrasts in coexisting amphibole tie lines are thought to be a consequence of the fact that the parageneses of Shikoku and California reflect high P and very high P prograde P-T paths respectively, whereas those from Valtournache and W. Liguria show evidence of decompression recrystallization (or back-reaction) of high P (i.e. eclogitic) protoliths. Comparison of the inferred physical conditions operating during the production of these four contrasting paragenetic sequences allows the provisional assignment of a P-T stability region for barroisitic amphibole in metabasaltic rocks as: P 4–5 kb at c. 350°; P 5–7 kb at c. 450 °C.

scholarly journals Advances in the management of osteosarcoma

F1000Research ◽  
2016 ◽  
Vol 5 ◽  
pp. 2767 ◽  
Author(s):  
Stefan S. Bielack ◽  
Stefanie Hecker-Nolting ◽  
Claudia Blattmann ◽  
Leo Kager
Keyword(s):  
Limb Salvage ◽  
Bone Cancer ◽  
Postoperative Treatment ◽  
Surgical Reconstruction ◽  
Low Grade ◽  
Lower Grade ◽  
High Grade ◽  
Treatment Standards ◽  
High Doses ◽  
Very High

Osteosarcoma, a bone cancer most commonly seen in adolescents and young adults, is usually a high-grade malignancy characterized by a very high risk for the development of pulmonary metastases. High-grade osteosarcomas are usually treated by preoperative and postoperative chemotherapy and surgery, with a very limited number of active agents available. Rarer lower-grade variants such as parosteal and periosteal osteosarcoma or low-grade central osteosarcoma are treated by surgery only. Imaging to search for possible metastases focuses on the lung. Computed tomography is the most sensitive method but cannot reliably distinguish small metastases from benign lesions. Advances of local imaging and surgical reconstruction now allow the use of limb-salvage in an ever-increasing proportion of patients. While still troubled by complications, non-invasive endoprosthesis-lengthening mechanisms have led to an increased uptake of limb-salvage, even for young, skeletally immature patients. Radiotherapy is employed when osteosarcomas cannot be removed with clear margins, but very high doses are required, and both proton and carbon-ion radiotherapy are under investigation. Unfortunately, the past 30 years have witnessed few, if any, survival improvements. Novel agents have not led to universally accepted changes of treatment standards. In patients with operable high-grade osteosarcomas, the extent of histological response to preoperative chemotherapy is a significant predictive factor for both local and systemic control. Attempts to improve prognosis by adapting postoperative treatment to response, recently tested in a randomized, prospective setting by the European and American Osteosarcoma Study Group, have not been proven to be beneficial. Many agree that only increased knowledge about osteosarcoma biology will lead to novel, effective treatment approaches and will be able to move the field forward.

Deformational behaviour of migmatites and problems of structural analysis in migmatite terrains

1984 ◽  
Vol 121 (4) ◽  
pp. 339-345 ◽  
Author(s):  
Eileen McLellan
Keyword(s):  
Structural Analysis ◽  
Low Grade ◽  
High Grade ◽  
Metamorphic History ◽  
Fold Type ◽  
History Of ◽  
Deformation Processes ◽  
Geometrically Complex ◽  
Fold Formation ◽  
Very High

AbstractAn understanding of the response of migmatites to deformation is crucial to an interpretation of their structures, and in anatectic and intrusive migmatite terrains due consideration must be given to the modification of deformation processes imposed by melts. In partially molten systems containing more than 30% melt the classical theories of fold formation are inapplicable; the folds produced are of the ‘viscous fold’ type. Their geometry is unpredictable and may mimic structures due to refolding; this is particularly true at very high degrees of melting where flow of melt carrying rafts of solids begins. Failure to distinguish ‘viscous folds’ from the products of refolding will lead to errors in interpreting the structural and metamorphic history of an area, and to consequent misinterpretation of the true structural relations between geometrically complex high-grade and more regularly deformed low-grade areas.

Klinische Wertigkeit der Positronen-Emissions-Tomographie (PET) bei onkologischen Fragestellungen: Ergebnisse einer interdisziplinären Konsensuskonferenz

1996 ◽  
Vol 35 (02) ◽  
pp. 42-52 ◽  
Author(s):  
R. Bares ◽  
U. Bull ◽  
A. Guhlmann ◽  
E. Moser ◽  
M. F. Wannenmacher ◽  
...  
Keyword(s):  
Low Grade ◽  
High Grade ◽  
Klinische Anwendung ◽  
Wissenschaftliche Studien

Zusammenfassung Ziel: Es ist das Ziel der vorliegenden Arbeit, an Hand bisher publizierter Studienergebnisse eine Beurteilung des klinischen Stellenwertes von PET in der Onkologie zu erarbeiten. Methoden: Im Rahmen einer interdisziplinären Konferenz mit namhaften Experten wurde eine Wertung des gegenwärtigen Stands von PET in der Onkologie an Hand der in der Literatur dokumentierten Studienergebnisse erarbeitet. Angestrebt wurde eine differenzierte Bewertung von PET für die klinische Anwendung in fünf Klassen (1a, 1b, 2a, 2b, 3) von »angemessen« (1a), »akzeptabel« (1b), »hilfreich« (2a), »noch keine Bewertung möglich« (2b), »ohne Nutzen« (3). Ergebnisse: Für den klinischen Einsatz in der Onkologie ist 2-F18-Fluorodeoxyglukose (FDG) das Radiopharmakon der Wahl. PET ist klinisch in der Patientenversorgung zur Rezidivdiagnostik von high-grade Gliomen (FDG), low-grade Gliomen (C-11 Methionin oder F-18 Tyrosin), für die Dignitätsdiagnostik des peripheren Lungenrundherdes bei Risikopatienten sowie für die Diagnostik des Pankreaskarzioms indiziert (Indikation 1a). PET kann in der Patientenversorgung bei folgenden Indikationen (1b) eingesetzt werden: »low-grade« Gliome, Suche nach unbekanntem Primärtumor bei Kopf-Hals-Tumoren, Rezidivdiagnostik des nicht kleinzelligen Bronchialkarzinoms sowie des Rektumkarzinoms, Lymphknotenstaging beim nicht kleinzelligen Bronchial-Karzinom, Pan-kreas-Karzinom, muskelinvasiven Blasen-Karzinom und Hoden-Karzinom. Staging bei M. Hodgkin (Stad. I/II versus III), frühe Therapiekontrolle bei Resttumor und Rezidivdiagnostik bei M. Hodgkin und hochmalignen Non-Hodgkin-Lymphomen, Lymphknoten-Staging und Fern-metastasensuche beim malignen Melanom (Breslow >1,5 mm), Lymphknoten- und Fernmetastasen-Nachweis beim Schilddrüsen-Karzinommit erhöhtem hTg und nicht radiojodspeichernden Metastasen. Zahlreiche weitere Indikationen zeichnen sich bereits jetzt ab, sind jedoch noch weniger gut durch wissenschaftliche Studien belegt. Für die meisten Indikationen außerhalb wissenschaftlicher Studien ist eine individuelle Kosten-Nutzen-Betrachtung durch den verantwortlichen Arzt geboten. Schlußfolgerungen: Die metabolische Bildgebung von PET besitzt für eine Vielzahl onkologischer Fragestellungen prinzipielle Vorteile gegenüber der anatomisch-morphologisch orientierten Schnittbilddiagnostik. Für die klinische Indikationsstellung ist allerdings eine differenzierte Betrachtung der spezifischen Leistungsfähigkeit von PET geboten.

Sign in / Sign up

Export Citation Format

Share Document