Silica Glass Tube Research Articles

Synthesis and Characterization of Vanadium Doped Hexagonal Rubidium Tungsten Bronze

Attempts have been made to synthesize vanadium doped rubidium hexagonal tungsten bronzes with the nominal composition RbxVyW1-yO3 (x = 0.30, 0.25, and 0.0 ≤ y ≤ x). The samples were synthesized using the solid state synthesis method in a silica glass tube under vacuum at (10-2 Torr) 700°C. The X-ray diffraction measurements reveal that a pure hexagonal tungsten bronze (HTB) phase can be formed with a 60% replacement of W5+ by V5+. The systematic incorporation of vanadium into the HTB lattice, as well as the reduction of V/W-O bond lengths in the xy plane and the lengthening of these bonds in the crystallographic c direction, are also revealed by Rietveld structure refinement of XRD data. The XRD results are supported by FTIR absorption spectra of the oxidized phases. Furthermore, an absorption signature develops as a function of y and exhibits a considerable increase in intensity with the eventual replacement of W5+ by V5+, showing a large decrease in the metallic like contribution and revealing the compounds' nonmetallic nature. Elemental analysis indicates good agreement with nominal values, demonstrating that vanadium was systematically incorporated into the RbxVyW1-yO3 system. Dhaka Univ. J. Sci. 72(1): 77-84, 2024 (January)

One-atmosphere high-temperature CO–CO2–SO2 gas-mixing furnace: design, operation, and applications

Abstract. In this paper, we present a new design for a 1 atm gas-mixing furnace using the gas mixture CO–CO2–SO2. This furnace can simulate disequilibrium processes such as magmatic and volcanic degassing. Here, we present the technical aspects of the design. The furnace can sustain temperatures of up to 1650 ∘C and has a hot zone that spans 200 mm vertically, where the hotspot is determined to be ∼ 32 mm below the midpoint of the furnace enclosure. The four mass flow controllers are individually calibrated and accurate to within 0.8 % of the specified value. The fO2 is accurately reproduced in the furnace within ±0.002 log units, as calibrated by the Fe–FeO reaction across the iron–wüstite (IW) buffer at 1300 ∘C. The furnace can reliably simulate dynamic conditions, where the fO2 can be modulated at a maximum rate of 2.0 log units min−1 by varying the gas mixture. A delay of 40 s is observed to attain the fO2 calculated from the gas mixture, at the hotspot. A series of safety measures to protect the user from exposure to the toxic gases are detailed. In our experiments, the furnace is used to determine sulfur isotope fractionation factors among melt, sulfide, and the gas phase, within a magmatic context, using either crystals of olivine or silica glass tubes. The furnace has the potential to investigate various other dynamic high-temperature reactions occurring on Earth.

Single-crystal structure refinements and Debye temperatures of Ir2S3 kashinite and Rh2S3 bowieite.

Single crystals of Ir2S3 (diiridium trisulfide) and Rh2S3 (dirhodium trisulfide) were grown in evacuated silica-glass tubes using a chemical transport method and their crystal structures were determined by single-crystal X-ray diffraction analysis. These compounds have a unique sesquisulfide structure in which pairs of face-sharing octahedra are linked into a three-dimensional structure by further edge- and vertex-sharing. Ir2S3 and Rh2S3 had similar unit-cell parameters and bond distances. The atomic displacement parameter (MSD: mean-square displacement) of each atom in Ir2S3 was considerably smaller than that in Rh2S3. The Debye temperatures (ΘD) estimated from the observed MSDs for the Ir, S1 and S2 sites in Ir2S3 were 259, 576 and 546 K, respectively, and those for Rh, S1 and S2 in Rh2S3 were 337, 533 and 530 K, respectively. The bulk Debye temperature for Ir2S3 kashinite (576 K) was found to rank among the higher values reported for many known sulfides. The bulk Debye temperature for Rh2S3 bowieite (533 K) was lower than that for Ir2S3 kashinite, which crystallizes in the early sequences of mineral crystallization differentiation from the primitive magma in the Earth's mantle.

Slippery liquid-infused porous surface (SLIPS) with super-repellent and contact-killing antimicrobial performances

Slippery liquid-filled porous surfaces (SLIPS) have attracted extensive research attention for their unique repellent properties, but such surfaces typically lack essential bactericidal activity and cannot defend against the spread of bacteria once bacterial contamination occurs. Herein, a slippery liquid-infused porous surface (SLIPS), endowed with both super-repellent and contact-killing antimicrobial performances is reported. Firstly, polystyrene (PS) based porous structures are developed via a facile microphase separation technique with poly(ethylene glycol) (PEG) as the sacrifice template. The porous surface was then covalently modified by 3-(trimethoxysilyl)propyl dimethyl undecyl ammonium chloride (QAC-Silane) to get the contact-killing antimicrobial performances. After lubricant (silicone oil) is introduced to the porous structure, the SLIPS surface demonstrates remarkably high super-repellence against both Gram-positive and negative bacteria, and also maintains essential contact-killing antimicrobial activities from the fixed QAC-11 groups, once the infused lubricant was depleted. Also, this surface demonstrates a reduced coefficient of friction (COF) of ∼56% as compared to that of the control flat surface. Moreover, this SLIPS surface can be easily realized on various substrates, such as silica glass, polycarbonate (PC), polyethylene terephthalate (PET), polyethylene (PE) and silicone catheter tube. Owing to its simple, low-cost and fast fabrication approach, this kind of surface may find unique biomedical applications where an effective antibacterial performance and lubricity are highly needed.

An Accelerometer Based on All Silica In-Line Fiber Fabry-Perot Etalon for High Temperature up to 800 °C.

High-temperature accelerometers have been widely used in aerospace, nuclear reactors, automobile technologies, etc. In this paper, a fiber-optic Fabry–Perot accelerometer (FOFPA) with a cantilever beam for high temperature is designed and experimentally demonstrated. The FOFPA is formed by bonding an all-silica in-line fiber Fabry–Perot etalon (ILFFPE) to one surface of the uniform cantilever beam with the lumped mass at the free end for acceleration measurement. The all silica in-line fiber FP etalon is made by welding two gold-coat single-mode fiber (GSMF) and a hollow silica glass tube (HST). The research results indicate that the sensitivity of the FOFPA is 0.02328rad/g, and the resonance frequency is 1146.6 Hz in the range of 1 g ~ 10 g. The high-temperature performance of the FOFPA was also evaluated. From 20 °C to 800 °C, the temperature drift is about 0.3178 nm/°C. The FOFPA has the potential of being applicable in higher temperatures compared to conventional accelerometers.

A Rapid Method for the determination of Dehydrated alcohol (Ethanol) content in Clobetasol propionate foam by Non-polar Capillary Gas chromatography

Clobeatsol propionate foam is a topical class 1 corticosteroid used to treat itching and inflammatory arthritis on the skin occurred by allergic reactions, psoriasis and eczema. In the pharmaceutical aerosol products, Dehydrated alcohol (Ethanol) is the primary ingredient and its concentration level in the formulation composition plays a significant role in the regulation of aerosol rate, droplet shape and particle size. It can also act as solubilizer for active pharmaceutical ingredient, topical disinfectant and skin permeation enhancer. Hence accurate assay of Ethanol is a crucial quality control component. A simple and rapid gas chromatography method was developed to quantify Ethanol content in Clobetasol propionate foam drug product using fused silica glass tube non-polar capillary column (HP-5, 30 m, 0.53 mm, 1.5 µm). Ethanol in the sample was diluted with methanol after adding suitable amount of internal standard, the isopropyl alcohol solution.The developed method is precise, linear and accurate in the range of 5 mg/mL to 15 mg/mL of nominal concentration of ethanol i.e. 10 mg/mL . The presented method has an advantage of a very quick gas chromatographic separation (less than 16 min) and therefore is highly suitable for in-process and stability analysis of Ethanol content in Clobetasol propionate foam drug product.

Crystal synthesis and Debye temperature determination of PdSb2: Usefulness of single crystal precise structure analysis

Single crystals of pyrite-type PdSb2 were grown by sealing a stoichiometric proportion of the elements in an evacuated silica glass tube and heating the tube in a furnace at 930 K for 20 days. The crystal structure of PdSb2 [space groupPa3¯, a = 6.4659(2) Å, u = 0.37331(3), Z = 4] was refined to R1 = 0.0171 for 374 unique reflections obtained by single-crystal X-ray diffraction experiments. The lattice constant, a, and anion-anion distance of 2.8677(3) Å are slightly different from the previously reported values. The single crystal diffraction method has excellent advantages such that the Debye temperature can be determined for each crystallographically independent site. The obtained ΘD values for Pd and Sb in PdSb2 are 258 K and 214 K, respectively. Characteristically, the Debye temperatures, ΘD, of both atoms in PdSb2 were found to be very low among the pyrite-type transition metal pnictides and chalcogenides. Certain regularities between the cation–anion bonding distances and Debye temperatures were found in pyrite-type compounds. The vibration of anion contributes to the highest energy part of the normal mode of thermal vibration, when the cation–anion bonding distances in pyrite-type compounds are shorter than 2.6 Å.

Construction of a dual-core hollow waveguide for visible and mid-infrared light transmission based on PTFE tubing and UV gel

This work proposes a facile approach to fabricate a dual-core hollow waveguide based on two common and low-cost raw materials, namely polytetrafluoroethylene (PTFE) tube and ultraviolet (UV) gel. A silica glass tube is nested inside a heat-shrinkable PTFE tube. After heat treatment at 350 °C, the PTFE tube shrinks and then transforms into the low-index polymer on the outside of the silica tube. The PTFE-coated silica glass tubing is filled with UV gel followed by inserting a typical Ag/AgI mid-infrared (IR) hollow optical fiber. The UV gel is cured by UV radiation, forming a solid low-index layer between the PTFE-coated silica glass tubing and the Ag/AgI hollow optical fiber. A visible laser beam can be transmitted at a loss of 0.4 dB/m through the silica annulus between the low-index PTFE and UV gel layer. A 10.6-μm-wavelength CO2 laser beam is delivered through the Ag/AgI hollow optical fiber (core size 530 μm) and the transmission loss goes up from 1.63 to 3.22 dB/m as the bending angle increases from 0° to 90°.

Crystal structure refinements of stoichiometric Ni3Se2 and NiSe.

Single crystals of Ni3Se2 (trinickel diselenide) and NiSe (nickel selenide) with stoichiometric chemical compositions were grown in evacuated silica-glass tubes. The chemical compositions of the single crystals of Ni3Se2 and NiSe were determined by scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDS). The crystal structures of Ni3Se2 [rhombohedral, space group R32, a= 6.02813 (13), c= 7.24883 (16) Å, Z= 3] and NiSe [hexagonal, space group P63/mmc, a= 3.66147 (10), c= 5.35766 (16) Å, Z= 2] were analyzed by single-crystal X-ray diffraction and refined to yield R values of 0.020 and 0.018 for 117 and 85 unique reflections, respectively, with Fo > 4σ(Fo). R32 is a Sohncke type of space group where enantiomeric structures can exist; the single-domain structure obtained by the refinement was confirmed to be correct by a Flack parameter of -0.05 (2). The existence of Ni-Ni bonds was confirmed in both compounds, in addition to the Ni-Se bonds. The value of the atomic displacement parameter (mean-square displacement) of each atom in NiSe was larger than that in Ni3Se2. The larger amplitude of the atoms in NiSe corresponds to longer Ni-Se and Ni-Ni bond lengths in NiSe than in Ni3Se2. The Debye temperatures, θD, estimated from observed mean-square displacements for Ni and Se in Ni3Se2, were 322 and 298 K, respectively, while those for Ni and Se in NiSe were 246 and 241 K, respectively. The existence of large cavities in the structure and the weak bonding force are likely responsible for the brittle and soft nature of the NiSe crystal.

The effects of S, Cl and oxygen fugacity on the sublimation of volatile trace metals degassed from silicate melts with implications for volcanic emissions

Volatile trace metals emitted to the atmosphere by volcanism can be complexed with ligands in a gas phase that undergoes large changes in temperature (T) and oxygen fugacity (fO2). To study this effect, a modified vertical tube gas-mixing furnace was used to investigate the role of S and Cl on the degassing and sublimation of volatile trace metals from silicate melt at 100 kPa over a range of fO2 from FMQ+5 to FMQ−4.6 at the melt-gas interface (where FMQ is the fayalite-quartz-magnetite buffer). Analogue phonolitic melt compositions in the Na2O-Fe2O3-Al2O3-SiO2 systems containing trace metals (Li, V, Fe, Cu, Ni, Zn, As, Y, Mo, Cd, Sn, Yb, Rb, Cs, Ag, Pb and Bi) are degassed at 950 °C and form sublimates along a temperature gradient (25–900 °C) in a suspended silica glass tube. Silica polymorphs are ubiquitous sublimates at all temperatures; halite is common below 600 °C with other less-easily identified oxides, sulfides, sulfates, chlorides and molybdates in trace quantities. The trace metal concentrations in the sublimates show trends used to infer their transport and deposition with temperature, fO2 and ligand identity. The sublimation of metals is mainly controlled by T. Monovalent Rb, Cs, and Ag sublime in halides at 350 ± 50 °C with transport dominated by Cl. The effect of fO2 is only observed for Zn, As, Pb, Cd, Bi, Fe, and Ni below ∼FMQ−3, where they change their sublimation host from sulfates or sulfides at 500 ± 50 °C to halides at 350 ± 50 °C. Molybdates subliming at 600 ± 50 °C host Li and Mo. No discernible host phase for Cu and Sn is observed with decreasing temperature. The experiments suggest different suites of trace metals in volcanic systems are transported with either S (Zn, As, Pb, ±Cd, ±Bi) or Cl (Rb, Cs, Ag, Fe, Ni, ±Cd, ±Bi) depending on T and fO2. Eruptions rich in Cl make halide sublimates a likely significant source of volatile trace metals to the environment.

Novel method of determining the periodontal regenerative capacity of T‑PRF and L‑PRF: An immunohistochemical study.

Platelet-rich fibrin (PRF) plays an important role in the regeneration of the lost periodontal tissues. Immunohistochemistry (IHC) is the most sensitive staining technique for the identification and localization of specific cells. There are few studies in the available literature which use IHC to compare PRF prepared from titanium and silica glass tubes. The aim of the study was to use IHC to evaluate and compare cells present in the PRF membrane prepared from titanium and silica glass tubes. Blood was drawn from 10 healthy volunteers and PRF was prepared from titanium and silica glass tubes. Immunohistochemical staining for the localization, distribution and pattern of cells present in PRF with the CD 3, CD 15, CD 20, CD 34, CD 61, and CD 163 antibodies was carried out. A statistical analysis including the χ2 test, independent t-test and unpaired t-test was performed to determine significant differences. There were significantly more T cells, B‑lymphocytes and platelets, with a strongly positive staining in terms of the cell distribution and the labeling index in the T-PRF group in comparison with the L-PRF group. However, in terms of localization, a stronger positive staining was obtained with platelets in the T-PRF group and stem cells in the L-PRF group. In terms of the cell pattern, a significantly stronger positive staining was obtained by neutrophils in the L-PRF group and B‑lymphocytes in the T‑PRF group. Titanium PRF has the edge over PRF prepared from silica glass tubes, and emerged as a better alternative for use in the field of periodontal regeneration.

Experimental constraints on metal transport in fumarolic gases

Metals are efficiently transported in a gas phase and the gas composition strongly affects transport rates of these metals in the gas phase. Here we present a new approach to systematically investigate metal transport and deposition from volcanic gases of different compositions: We test the effect of sulfur and chlorine on the volatilization of 30 metal oxides and the phases deposited along a temperature gradient of 1250–300 °C in evacuated silica glass tubes in water-free systems. In total, we observe 30 different deposited phases, including oxides, sulfides and chlorides. The experimental results are compared with closed system and open system thermochemical equilibrium calculations. The closed system calculations provide insights into the metal speciation in the gas phase, and the open system calculations provide thermodynamic predictions of the temperature ranges over which metals deposited from the gas phase. Both approaches only partially reproduce the experimental observations of the deposited phases in the silica glass tubes. However, when we compare our experimental results with records from fumaroles on three different volcanoes (Kudriavy volcano, Russia, La Fossa crater on Vulcano, Italy, and Momotombo, Nicaragua), we find that our experiments agree very well with natural observations. We suggest that similar experimental investigations are powerful tools in the study of metal transport in ore forming systems involving gas phases, and results may be applied to various processes in terrestrial and planetary environments.

Investigation of the effect of Cl on the transport and sublimation of volatile trace metals in volcanic gases using benchtop fumarole experiments

Volatile trace metals emitted from volcanoes are frequently complexed with ligands and sublime from gases as halides, sulfides, sulfates and oxides. We investigate the effect of Cl as a ligand on the sublimation process by degassing broadly phonolitic composition melts with added trace metals (V, Cu, Zn, As, Y, Mo, Cd, Sn, Yb, Pb and Bi) and Cl in a benchtop fumarole apparatus at 100 kPa. Sublimates forming from the gas phase at 25–900 °C along a silica glass tube suspended above degassed melts are characterized by electron microscopy, Raman spectroscopy and solution nebulization inductively coupled plasma mass spectrometry (SN ICP-MS). Silica polymorphs are ubiquitous at all temperatures and halite forms below 600 °C. Szenicsite (Cu3(MoO4)(OH)4) and molybdofornacite (CuPb2(MoO4)(AsO4)(OH)) occur at ~500 °C. The latter phases may have formed from post-experiment hydration of original anhydrous molybates or arsenates, or alternatively are their Cl−-bearing analogues. Arsenate and vanadate minerals such as bradaczekite (NaCu4(AsO4)3) and leningradite (PbCu3(VO4)2Cl2), known in natural fumaroles, also occur in the experiments. Chloride sublimates can host substantial Pb, Tl, As, Cu, Bi and Zn. The addition of Cl to the melt in the experiments increases the concentration of Li, Rb, Cs, Ag, Cr, Cu, Mo and W in the sublimates compared to Cl-free experiments. In Cl-bearing volcanic gases, molybdates and chlorides are the most likely hosts of volatile trace metals, and when adhered to ash particles, are potential sources of trace metals to the atmosphere and oceans.

An In-Line Fiber Optic Fabry-Perot Sensor for High-Temperature Vibration Measurement.

An in-line fiber optic Fabry–Perot (FP) sensor for high-temperature vibration measurement is proposed and experimentally demonstrated in this paper. We constructed an FP cavity and a mass on single-mode fibers (SMFs) by fusion, and together they were inserted into a hollow silica glass tube (HST) to form a vibration sensor. The radial dimension of the sensor was less than 500 μm. With its all-silica structure, the sensor has the prospect of measuring vibration in high-temperature environments. In our test, the sensor had a resonance frequency of 165 Hz. The voltage sensitivity of the sensor system was about 11.57 mV/g and the nonlinearity was about 2.06%. The sensor could work normally when the temperature was below 500 °C, and the drift of the phase offset point with temperature was 0.84 pm/°C.

The central portions of the Cu–Fe–Se phase system at temperatures from 900 to 300 °C

ABSTRACTThe central portions of the condensed phase system Cu–Fe–Se were investigated by means of dry syntheses in evacuated silica glass tubes at 900, 750, 600, 500, 450, 350, and 300 °C. Synthesis products were studied by reflected-light microscopy and electron microprobe analyses. The field of sulfide melt is extensive at 900 °C and retreats progressively towards the Cu–Se side at 750 °C; residual selenide melt persists at 600 °C. The selenium analogue of iss was found only at and below 600 °C; eskebornite becomes individualized at and below 500 °C, whereas the selenium analogue of bornite solid solution is present at all investigated temperatures, although with reduced extent on temperature decrease. The three iron selenides (β, γ, δ) display considerable solubility of copper, which for the mackinawite-like β FeSe reaches 14 at.% Cu at 300 °C. FeSe2 displays an immiscibility gap with isotropic solid solution (Cu,Fe)Se2, the composition of which gradually changes towards Cu-rich with decreasing temperature. Similarities and differences with the sulfur-based system are highlighted.

The system Pd–Ag–S: phase relations and mineral assemblages

AbstractPhase equilibria in the system Pd–Ag–S were studied using the silica-glass tube method at 400°C and 550°C. In the system we synthesised three ternary phases: coldwellite (Pd3Ag2S), kravtsovite (PdAg2S) and a new phase Pd13Ag3S4. At 400°С, coldwellite forms a stable association with vysotskite (PdS) and vasilite (Pd16S7); vysotskite and kravtsovite; phase Pd4S and a Ag–Pd alloy; it also coexists with a new phase Pd13Ag3S4. Kravtsovite is stable up to 507°C; the presence of kravtsovite in the mineral assemblage reflects its formation below this temperature. The occurrence of coldwellite, vysotskite and Ag2S together in equilibrium reflects the formation of this mineral assemblage above this temperature (507°C). Coldwellite is stable up at 940°С. Mineral assemblages defined in this study can be expected in Cu–Ni–PGE mineral deposits, associated with mafic and ultramafic igneous rocks, in particular in mineralisations with known silver–palladium sulfides.

Single-frequency fibre laser with a cavity formed by Bragg gratings written in the core of an active composite fibre using KrF laser radiation (248 nm)

The possibility of producing a single-frequency fibre laser using a new type of fibre made by sintering phosphate glass in a silica glass tube (composite fibre) is demonstrated. In a fibre of this type, photosensitivity to laser radiation with a wavelength of 248 nm is detected. A fibre laser cavity is fabricated by writing fibre Bragg gratings directly in the core of the composite optical fibre activated by erbium ions. Stable single-frequency linearly polarised lasing regime is obtained at a wavelength of 1559.5 nm with a maximum output power of ∼3 mW.

Molybdenum isotope fractionation between Mo4+ and Mo6+ in silicate liquid and metallic Mo

Previous work has shown that Mo isotopes measurably fractionate between metal and silicate liquids, even at temperatures appropriate for core formation. However, the effect of variations in the structural environment of Mo in the silicate liquid, especially as a function of valence state, on Mo isotope fractionation remained poorly explored. We have investigated the role of valence state in metal-silicate experiments in a gas-controlled furnace at 1400 °C and at oxygen fugacities between 10−12.7 and 10–9.9, i.e. between three and 0.2 log units below the iron-wüstite buffer. Two sets of experiments were performed, both with a silicate liquid in the CaO-Al2O3-SiO2 system. One set used molybdenum metal wire loops as the metal source, the other liquid gold alloyed with 2.5 wt% Mo contained in silica glass tubes. X-ray absorption near-edge spectroscopy analysis indicates that Mo6+/ΣMo in the silicate glasses varies between 0.24 and 0.77 at oxygen fugacities of 10–12.0 and 10–9.9 in the wire loop experiments and between 0.15 and 0.48 at 10–11.4 and 10–9.9 in the experiments with Au-Mo alloys. Double-spiked analysis of Mo isotope compositions furthermore shows that Mo isotope fractionation between metal and silicate is a linear function of Mo6+/ΣMo in the silicate glasses, with a difference of 0.51‰ in 98Mo/95Mo between purely Mo4+-bearing and purely Mo6+-bearing silicate liquid. The former is octahedrally and the latter tetrahedrally coordinated. Our study implies that previous experimental work contained a mixture of Mo4+ and Mo6+ species in the silicate liquid. Our refined parameterisation for Mo isotope fractionation between metal and silicate can be described asΔ98/95Mometal–silicate=−1.43±0.14×106Mo6+/ΣMo+8±6×104T2Molybdenum isotope ratios therefore have potential as a proxy to constrain the oxygen fugacity during core formation on planetary bodies if the parameterisation of Mo6+/ΣMo variation with oxygen fugacity is expanded, for instance to include iron-bearing systems. On Earth literature data indicate that the upper mantle is depleted in heavy Mo isotopes relative to the bulk Earth, as represented by chondrites. As previously highlighted, this difference is most likely not caused by core formation, which either enriches the mantle in heavy Mo isotopes or causes no significant fractionation, depending on temperature and, as we determined here, Mo6+ content. We reaffirm that core formation does not account for the Mo isotope composition of the modern upper mantle, which may instead reflect the effect of fractionation during subduction as part of global plate recycling.

Preanalytical stability of [-2]proPSA in whole blood stored at room temperature before separation of serum and plasma: implications to Phi determination.

Background [-2]proPSA seems to outperform free/total prostate-specific antigen (PSA) ratio in prostate cancer diagnosis. However, [-2]proPSA stability remains an underestimated issue. We examined [-2]proPSA stability over time in whole blood before separation of serum and plasma and its implications for prostate health index (Phi) determination. Total PSA (tPSA) and free PSA (fPSA) stabilities were also assessed. Methods Blood was drawn from 26 patients and separated in two tubes for plasma (K2EDTA and K2EDTA plus protease inhibitors - P100) and one for serum (clot activator plus gel separator). Tubes were stored at room temperature before centrifugation 1, 3 and 5 h for serum and EDTA plasma or 1 and 5 h for P100 plasma. To investigate the influence of gel separator on markers' stability, blood was collected from 10 patients in three types of tubes to obtain serum: tubes with clot activator plus gel separator, with silica particles or glass tubes. Biomarkers were assayed with chemiluminescent immunoassays. Results [-2]proPSA and Phi levels significantly and progressively increased over time in serum (+4.81% and +8.2% at 3 h; +12.03% and +14.91% at 5 h, respectively, vs. 1 h; p<0.001). Conversely, [-2]proPSA levels did not change in plasma (EDTA or P100). tPSA levels did not change over time in serum or plasma, whereas fPSA decreased in serum. All markers were higher in plasma than in serum at any time point. This difference did not seem to be attributable to the use of gel for serum preparation. Conclusions EDTA prevented spurious in vitro modifications in PSA-related isoforms, confirming that a stabilized blood sample is a prerequisite for [-2]proPSA measurement and Phi determination.

An Experimental Protocol for Studying Mineral Effects on Organic Hydrothermal Transformations.

Organic-mineral interactions are widely occurring in hydrothermal environments, such as hot springs, geysers on land, and the hydrothermal vents in the deep ocean. Roles of minerals are critical in many hydrothermal organic geochemical processes. Traditional hydrothermal methodology, which includes using reactors made of gold, titanium, platinum, or stainless-steel, is usually associated with the high cost or undesired metal catalytic effects. Recently, there is a growing tendency for using the cost-effective and inert quartz or fused silica glass tubes in hydrothermal experiments. Here, we provide a protocol for carrying out organic-mineral hydrothermal experiments in silica tubes, and we describe the essential steps in the sample preparation, experimental setup, products separation, and quantitative analysis. We also demonstrate an experiment using a model organic compound, nitrobenzene, to show the effect of an iron-containing mineral, magnetite, on its degradation under a specific hydrothermal condition. This technique can be applied to study complex organic-mineral hydrothermal interactions in a relatively simple laboratory system.