Quartz Sheets Research Articles

Optimization of Laser Micro/Nano Processing of Silicon and Quartz

This research paper explores the application of three laser systems, namely the Nd:YAG laser, fiber laser, and CO2 laser, for the micro/nano machining of silicon and quartz materials. The experimental results demonstrate the successful formation of stable silicon nanoparticles with reduced dimensions. Additionally, a quartz sheet was utilized to create a microlens array. The laser microprocessing technique was enhanced through the implementation of design of experiments (DOE) analysis. A Box-Behnken design (BBD) software was employed to conduct 17 tests, investigating the influence of laser parameters on the microprocessing outcomes. The COMSOL software was utilized for theoretical calculations to determine the distribution of surface temperatures and subsurface temperatures of silicon and quartz. The maximum temperatures achieved were approximately 5700 K for silicon and 2630 K for quartz. Numerical optimization using DOE software improved the production of silicon nanoparticles and quartz microlens, producing silicon nanoparticles wavelength peak and absorption peak values of 318.2 nm and 0.39, respectively. Additionally, quartz microlens numerical aperture and surface roughness improved to 0.494 and 4.64 nm, respectively. Due to the precise control offered by the laser micro/nano machining process, the findings of this study hold potential for diverse applications in optoelectronics and biological imaging that can leverage the unique characteristics of silicon nanoparticles and microlens arrays.

Selective Detection of Erythrocytes with QCMs-ABO Blood Group Typing.

Blood transfusion, as well as organ transplantation, is only possible after prior blood group (BG) typing and crossmatching. The most important blood group system is that of Landsteiner's ABO classification based on antigen presence on the erythrocyte surfaces. A mass sensitive QCM (quartz crystal microbalance) sensor for BG typing has been developed by utilizing molecular imprinting technology. Polyvinylpyrrolidone (crosslinked with N,N-methylenebisacrylamide) is a favorable coating that was imprinted with erythrocytes of different blood groups. In total, 10 MHz quartz sheets with two resonators, one for MIP (molecularly imprinted polymer) and the other for NIP (non-imprinted polymer) were fabricated and later used for mass-sensitive measurements. The structure of erythrocyte imprints resembles a donut, as identified by AFM (atomic force microscope). All the erythrocytes of the ABO system were chosen as templates and the responses to these selective coatings were evaluated against all blood groups. Each blood group can be characterized by the pattern of responses in an unambiguous way. The results for blood group O are remarkable given that all types of erythrocytes give nearly the same result. This can be easily understood as blood group O does not possess neither antigen A nor antigen B. The responses can be roughly related to the number of respective antigens on the erythrocyte surface. The imprints generate hollows, which are used for reversible recognition of the erythrocytes. This procedure is based on molecular recognition (based on supramolecular strategies), which results from size, shape and enthalpic interactions between host and guest molecules.

Effects of Impurity Barrier Layer on the Red Zone at the Bottom of Cast Monocrystalline Si Ingot for Solar Cells

A technique to prepare low‐cost high‐purity quartz sheets as impurity barrier layers between the crucible and the seed crystal is proposed herein to improve the casting process of monocrystalline Si (mono‐Si) ingots. The results show that the diffusion of metal impurities from the crucible toward a cast mono‐Si ingot can be hindered, increasing the minority carrier lifetime of Si crystals and reducing the height of the red zone at the bottom of the ingot. Solar cell devices assembled from cast mono‐Si ingots exhibit the enhancement in their overall photoelectric conversion efficiency (η) by 0.76% in comparison to those based on conventional mono‐Si ingots. Therefore, high‐purity quartz sheets as impurity barrier layers for the casting of mono‐Si ingots have great application potential in the photovoltaic industry.

CO2-Repurification Microemulsion Detergent for Oil-Based Slurry Cleaning

In order to solve problems such as environmental pollution and pipeline blockage caused by oily wastewater after washing, N,N-dimethylcyclohexylamine (DMCHA) with CO2 response was selected as the oil phase, and an O/W microemulsion wellbore cleaning fluid with CO2 switching characteristics was successfully prepared with erucamide propyl betaine (EAB-40), sodium dodecyl benzene sulfonate (SDBS), n-butanol, silicone defoamer, and water. The water content of the microemulsion was 89.99%, and it had good stability at 40 and -5 °C. The emulsion was rapidly demulsified after being injected with CO2 in the CO2-repurification microemulsion detergent, and CO2 was removed with a N2 detergent. The emulsion was restored to its original state, which demonstrated the CO2/N2 switching properties of the emulsion. It is proven that the switching microemulsion has a good wetting transformation ability by cleaning the steel sheet and quartz sheet contaminated by oil-based slurry. The switching microemulsion system can clean the simulated wellbore contaminated by oil-based slurry, and the cleaning efficiency is above 99%. CO2 can be used at room temperature to separate oil and water from oily wastewater after cleaning.

Material priority engineered metal-polyphenol networks: mechanism and platform for multifunctionalities

Engineering the surface of materials with desired multifunctionalities is an effective way to fight against multiple adverse factors during tissue repair process. Recently, metal-polyphenol networks (MPNs) have gained increasing attention because of their rapid and simple deposition process onto various substrates (silicon, quartz, gold and polypropylene sheets, etc.). However, the coating mechanism has not been clarified, and multifunctionalized MPNs remain unexplored. Herein, the flavonoid polyphenol procyanidin (PC) was selected to form PC-MPN coatings with Fe3+, and the effects of different assembly parameters, including pH, molar ratio between PC and Fe3+, and material priority during coating formation, were thoroughly evaluated. We found that the material priority (addition sequence of PC and Fe3+) had a great influence on the thickness of the formed PC-MPNs. Various surface techniques (e.g., ultraviolet–visible spectrophotometry, quartz crystal microbalance, X-ray photoelectron spectroscopy, atomic force microscopy, and scanning electron microscopy) were used to investigate the formation mechanism of PC-MPNs. Then PC-MPNs were further engineered with multifunctionalities (fastening cellular attachment in the early stage, promoting long-term cellular proliferation, antioxidation and antibacterial activity). We believe that these findings could further reveal the coating formation mechanism of MPNs and guide the future design of MPN coatings with multifunctionalities, thereby greatly broadening their application prospects, such as in sensors, environments, drug delivery, and tissue engineering.Graphical

Quartz crystal based sensor head design and analysis for robot torque sensor application

Background: In recent years, with the gradual development of robot human-computer interaction, robots need to meet the precise control of more complex motion. Torque sensors play an important role. The traditional strain gauge sensor uses a metal strain gauge as the sensitive element, which means that the sensor has a slow response, low resolution and can easily be affected by external signal noise. Aiming at these deficiencies of strain gauge sensors, a sensor with cutting quartz square sheet as the sensor head is proposed. Methods: In order to study the application of quartz square sensing head in the sensor, firstly, COMSOL (5.6) simulation modeling is used to obtain the stress relationship between square quartz sheet and circular quartz sheet. Then the calculation formula of the force frequency coefficient of the circular quartz sheet is modified to obtain the calculation formula of the force frequency coefficient of the square quartz sheet, and the feasibility of the formula is verified by practical experiments. Next, the theoretical simulation and experimental research on the buckling limit force of quartz wafer are carried out, and the formula of buckling limit force in the process of quartz wafer installation is modified. Finally, the designed sensitive head is installed on the elastomer structure for verification. The frequency signal is collected by SGS-THOMSON Microelectronics 32 with a sampling rate of 1000Hz. Results: The main performances of the sensor are range 150nm, sensitivity 350Hz / nm, linearity 98.14%, hysteresis 0.51%, repeatability 98.44%, resolution 0.02%. Conclusions: As the sensitive unit of the torque sensor, the designed quartz wafer can obtain high response time and high resolution, solve the problems of low resolution and slow response time of the traditional strain gauge torque sensor, and reduce the use cost of the sensor.

Ultra sensitive detection of malachite green in fish muscle with gold nanoparticles and graphene oxide hybrid as a substrate for surface enhanced Raman scattering

Malachite green (MG) is a banned fish drug, but is often found in various aquatic food products. In this study, Au nanoparticles (NPs) were incorporated with graphene oxide (GO) to fabricate Au NPs-GO hybrid films as surface enhanced Raman scattering (SERS) substrate for MG detection. The enhancement effect of the hybrid substrate for SERS signal of MG as influenced by GO concentration, size of Au NPs and pretreatment method for quartz sheets were evaluated. The optimal Au NPs-GO substrate was used to detect MG in fish muscle with SERS technology. The lowest detectable concentration for MG standard solution was 0.01 ng/mL, and the concentration of 0.25 ng/g could be detected in the muscle extracts of two different fish. SERS combined with Au NPs-GO hybrid substrate shows great potential for detection of trace amounts of MG in aquatic products.

Effect of downward vapor stream on falling film evaporation of R134a in a tube bundle

The influence of downward vapor stream on the falling film evaporation with nucleate boiling outside a horizontal enhanced tube bundle arrayed in a vertical column is experimentally investigated. The variations in local and bundle averaged heat transfer coefficients with vapor velocity are presented. To simulate the practical condition in a falling film evaporator, the flow passages of the liquid/vapor are constructed using two quartz glass sheets and two columns of dummy half tubes. The test ranges are saturation temperature of 6 °C, film flow rate of 0.035–0.1 kgm–1s–1, heat flux of 20, 30, 40 kWm–2. It is found that (1) the downward vapor effects are either positive or negative depending on the tube position, film flow rate, heat flux and vapor velocity; (2) the bundle effect becomes stronger under the effect of downward vapor stream; (3) the downward vapor has a significant effect on the heat transfer of the lower tubes than the upper tubes; and (4) the vapor stream effect on the bundle averaged heat transfer coefficient varies with the levels of film flow rate and heat flux. The experimental results provide significant guidance in the design of the vapor escape channel in a falling film evaporator.

Carbon nanotube synthesis via the catalytic chemical vapor deposition of methane in the presence of iron, molybdenum, and iron–molybdenum alloy thin layer catalysts

In this study, we documented the catalytic chemical vapor deposition synthesis of carbon nanotubes (CNTs) using ferrocene and molybdenum hexacarbonyl as catalyst nanoparticle precursors and methane as a nontoxic and economical carbon source for the first time. Field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, wavelength dispersive X-ray spectrometry and transmission electron microscopy of the thin layer catalyst as a simple and cost effective catalyst preparation after methane decomposition reaction, along with Fourier transform infrared spectroscopy and Raman spectroscopy confirmed the growth of CNTs, from bimetallic nanoparticles, which are converted into iron–molybdenum alloy nanoparticles at 700 °C for pretreatment by hydrogen after chemical vapor deposition of thin layers. An investigation of the weight percentages of the chemical elements present in the CNTs synthesized from iron–molybdenum catalyst using quartz sheet substrate at 750 °C, confirmed a significant carbon yield of 75.4% which represents high catalyst activity. Additionally, multi-walled carbon nanotubes (∼16–55 nm in diameter and 1.2 µm in length) were observed in the iron–molybdenum alloy sample after methane decomposition reaction at 750 °C for 35 min. To show the role of iron and molybdenum coated on silicon substrate as two thin layer catalysts, samples were considered for CNTs growth (diameter ∼47–69 nm) at 800 °C and 830 °C, respectively. Moreover, the effect of hydrogen pretreatment was evaluated in terms of active metal coating properly. The best graphitic structure due to Raman spectroscopy outcomes (ID/IG ratio) was obtained for iron coated on a quartz sheet, which was estimated at 0.8505. Thermogravimetric analysis proved the thermal stability of the synthesized CNTs using iron thin-layer catalyst up to 350 °C.

A Novel Strategy to Eliminate the Influence of Water Adsorption on Quartz Surfaces on Piezoelectric Dynamometers.

Piezoelectric dynamometers are out of use in high humidity. Experimental results showed that piezoelectric coefficients measured by the force-induced charges method initially fluctuated in a small range and then was unstable, and they could not be measured at high relative humidity (RH). The traditional shielding method-insulation paste was not quiet convenient, and it even added the weight of piezoelectric dynamometers. In this paper, a novel strategy that eliminates the influence of water adsorption with quartz surfaces on piezoelectric dynamometers was proposed. First, a water-quartz model was developed to analyze the origin of the RH effect. In the model, water vapor, which was adsorbed by the quartz sheet side surface, was considered. Second, equivalent sheet resistor of the side surface was researched, while the relationship of the three R’s (Roughness, RH, and Resistor) was respectively discussed based on the adsorption mechanism. Finally, fluorination technology was skillfully adapted to each surface of quartz sheets to shield the water vapor. The experiment verified the fluorination strategy and made piezoelectric dynamometers work in high humidity up to 90%RH successfully. The results showed that the presented model above was reasonable. In addition, these observations also drew some useful insights to change the structure of piezoelectric dynamometers and improve the properties.

Application of picene thin-film semiconductor as a photocatalyst for photocatalytic hydrogen formation from water

Interesting photocatalytic properties of a picene thin film on quartz (PTF/Q) have been demonstrated for photocatalytic hydrogen formation from water using several sacrificial agents. Hydrogen is produced in the presence of PTF/Q catalysts under light irradiation, indicating that PTF/Q works as a photocatalyst. The catalyst retains its activity under light irradiation and addition of sacrificial agents enhanced the rate of photocatalytic hydrogen formation from water, similar to the condition when a traditional inorganic photocatalyst is used. Moreover, PTF/Q catalysts comprising picene films of different thickness have been fabricated, and PTF/Q with the thinnest film (50nm) exhibits the highest activity for hydrogen formation. X-ray diffraction patterns show that the picene crystals are vertically aligned on the surface of the quartz sheet, and that PTF/Q with the thinnest film has a nonuniform film phase. The difference of picene thin-film surface in morphology probably influences the photocatalytic activity. The absorption edge and optical gap energies of the prepared PTF/Q catalyst are determined and the optical gap of the picene film is calculated to be 3.2eV.

Dramatic changes of optical nonlinearity and ultrafast dynamics of palladium nanoparticles caused by hydriding

Pd nanoparticles are deposited on one surface of a quartz sheet. Their optical nonlinearity and ultrafast dynamics in air and in hydrogen environment are investigated. The Pd nanoparticles exhibit self focusing and saturable absorption in air. In hydrogen environment with increasing hydrogen, the NPs maintain self focusing, however their nonlinear refraction index increases; and their nonlinear absorption changes from saturable absorption to reverse saturable absorption. In hydrogen environment, the acoustic breathing movement of these NPs damps more obviously and the contact between the NPs and quartz sheet is looser, comparing to that in air.

Photocatalytic Degradation of Reactive Brilliant Red X-3B Based on Microwave Electrodeless Lamp and Long Lifetime Immobilized TiO<sub>2</sub>

A novel photocatalytic system (MEL/TiO2/QS) based on microwave electrodeless lamp (MEL) and TiO2 films supported on quartz sheets (TiO2/QS) was established for high photocatalytic efficiency and long catalyst life. The results showed that the degradation efficiency for reactive brilliant red X-3B in MEL/TiO2/QS was equally as that in a suspended TiO2 system. Furthermore, under the microwave irradiation, the TiO2/QS had high catalytic activity after successively used 10 times without additional separation and regeneration. The pseudo-first-order kinetics was employed to describe decomposition of the dye and reaction rates at different initial dye concentrations, followed by the Langmuir– Hinshelwood kinetic model. The mineralization process and final products were also analyzed by total organic carbon (TOC) and ion chromatography (IC). The research might be useful in the commercial scale application of low cost and high efficiency photocatalytic process. Keywords: Catalyst regeneration, microwave electrodeless lamp, reactive brilliant red X-3B, TiO2 films.

New Transparent Laser-Drilled Fluorine-doped Tin Oxide covered Quartz Electrodes for Photo-Electrochemical Water Splitting

A new-designed transparent, conductive and porous electrode was developed for application in a compact laboratory-scale proton exchange membrane (PEM) photo-electrolyzer. The electrode is made of a thin transparent quartz sheet covered with fluorine-doped tin oxide (FTO), in which an array of holes is laser-drilled to allow water and gas permeation. The electrical, morphological, optical and electrochemical characterization of the drilled electrodes is presented in comparison with a non-drilled one. The drilled electrode exhibits, in the visible region, a good transmittance (average value of 62%), a noticeable reflectance due to the light scattering effect of the hole-drilled internal region, and a higher effective surface area than the non-drilled electrode. The proof-of-concept of the applicability of the drilled electrode was achieved by using it as a support for a traditional photocatalyst (i.e. commercial TiO2 nanoparticles). The latter, coupled with a polymeric electrolyte membrane (i.e.Nafion 117) and a Pt counter electrode, forms a transparent membrane electrode assembly (MEA), with a good conductivity, wettability and porosity. Electrochemical impedance spectroscopy (EIS) was used as a very powerful tool to gain information on the real active surface of the new drilled electrode and the main electrochemical parameters driving the charge transfer reactions on it. This new electrode architecture is demonstrated to be an ideal support for testing new anodic and cathodic photoactive materials working in tandem configuration for solar fuels production by water photo-electrolysis.

UVA-activated synthesis of metalloproteinases 1, 3 and 9 is prevented by a broad-spectrum sunscreen

Specific sunscreens against ultraviolet (UV) A and B radiations are essential to prevent matrix degradation and the activation of intracellular signaling pathways involved in photoaging and photocarcinogenesis. Matrix degradation results from UVA-induced production of matrix metalloproteinases (MMP) and activation of intracellular pathways in fibroblasts and keratinocytes. In particular, in keratinocytes, UVA radiation induces β-catenin nuclear translocation and stimulates MMP gene transcription. Our study was aimed at assessing the efficacy of a specific broad-spectrum sunscreen in preventing β-catenin translocation and MMPs enhanced expression in cultured keratinocytes after UVA irradiation. Sunscreen or the vehicle was spread on quartz sheet. Irradiation of HaCaT cells with 6 J/cm(2) UVA was performed through the sheet, and cells were collected for β-catenin immunostaining then visualization by confocal microscopy, and quantitative real-time polymerase chain reaction analysis of MMP-1, -3 and -9 gene expression. As shown by immunostaining and confocal microscopy, the sunscreen abrogated UVA-induced beta-catenin translocation to the nucleus, in comparison with control groups. MMP-1, -3 and -9 mRNA expression was enhanced by 7, 7 and 4 folds (P < 0.0001, P < 0.001 and P < 0.01, respectively) in unprotected UVA-irradiated cells compared to the non-irradiated control. Sunscreen protection of the cells significantly reduced UVA-induced expression of MMP-1, -3 and -9 by 83% (P < 0.01), 80% (P < 0.01) and 65% (P < 0.05), respectively. This study demonstrated the efficacy of this broad-spectrum sunscreen in preventing UVA-induced effects on the markers of photoaging and photocarcinogenesis in vitro. It was able to protect HaCaT keratinocytes from UVA-induced β-catenin translocation to the nucleus and MMPs expression.

Quartz cementation in mudstones: sheet-like quartz cement from clay mineral reactions during burial

ABSTRACT Petrographic evidence of thin sheet-like or platelet-shaped quartz cement parallel to bedding is documented in deeply buried, originally smectite-rich, Late Cretaceous mudstones from well 6505/10-1 in the Voring Basin, offshore Norway. The platelets are mainly built up of areas of patchy continuous quartz cement with various amounts of earlier-formed interlocking microquartz crystals. Cathode luminescence (CL) spectra confirm an authigenic origin for the quartz cement. The quartz platelets may originate as flakes (at c . 90–100 °C) that may evolve into well-developed near-continuous patchy quartz cement identified at 4300 m/150 °C. The quartz cement is probably sourced from silica released by the clay dissolution-precipitation processes (smectite and smectite/illite to illite and kaolinite to illite). At temperatures above about 90–100 °C, the continuous supply of silica from these clay mineral reactions results in precipitation of quartz flakes and sheet-like quartz cement. The quartz sheets may act as a mudrock stiffening agent, reinforcing and further cementing together the microquartz networks and aggregates and possibly also enhancing the schistosity and anisotropy of these mudstones during increasing burial. The quartz sheets may also act as vertical permeability barriers in the sediment possibly contributing to overpressure formation during chemical compaction.

Experimental investigation of the dissolution of quartz by a muscovite mica surface: Implications for pressure solution

Using the surface forces apparatus, which can measure small changes in thickness occurring even at essentially geological timescales, we have measured dissolution of quartz sheets when pressed against muscovite mica surfaces in aqueous electrolyte solution, but no dissolution is observed under dry conditions. It is postulated that the dissolved quartz may reprecipitate outside the contact junction as a fragile silica gel, which could be the main factor limiting the rate of further dissolution.

EIS study of niobium films sputtered at different target–substrate angles

Nb films have been magnetron sputtered onto quartz sheets oriented with respect to the target at angles varying between 0° and 90°, with 15° steps. Impedance plots have been obtained by contacting these films with aqueous Na 2SO 4, either at the open circuit potential or at a potential where Nb is covered by an anodic passive Nb 2O 5 film. As the target–substrate angle θ increases, the shape of the impedance plots changes from that of a smooth electrode to that of a porous one, characterised in the high frequency range by a straight line forming a 45° angle with the real axis. The surface roughness of the Nb deposits, calculated from their double layer capacity, is low and constant at low θ, significantly increases at θ = 45°, goes through a maximum in the range 60–75° and drops at θ = 90°. AFM surface profiling confirms this trend, but estimates a lower surface roughness. Attempts to obtain Nb deposits with a surface roughness less strongly dependent on θ have been made by performing the depositions under pulsed conditions or by heating the substrates at 400–600 °C. Heating at the higher temperature was a fairly effective method for decreasing the roughness of deposits formed at large θ.

Langmuir–Schäfer films of a new calix[4]pyrrole-based macrocycle exhibiting induced chirality upon binding with chiral alcohol vapours

A new calix[4]pyrrole-based macrocycle, meso-tetra(methyloctyl)calix[4]pyrrole (MTP), has been synthesized and fully characterized. Thin films of MTP have been transferred onto hydrophobized quartz and silicon oxide sheets by using the Langmuir–Schafer (LS) method (horizontal lifting). Scanning force microscopy (SFM) investigation showed that the LS films are almost homogeneous and are consistent with the X-type configuration with the hydrophobic tails of MTP disposed almost perpendicularly with respect to the substrate. Induced circular dichroism (ICD) measurements have been performed in the presence of chiral alcohol vapours, such as (−)-(R)-2-butanol, (−)-(R)-2-pentanol and (−)-(R)-2-hexanol. The results showed that although not chiral by themselves the MTP molecules within the film exhibit chirality induced by binding with the chiral guests. The appearance of ICD signals is accounted for by the close proximity of the alcohol molecules to the pyrrole moieties of MTP. The reversibility of the binding event, coupled with the differentiated response observed towards the alcohols investigated, makes the LS films promising active layers for the chemical recognition of short-chain polar neutral molecules.

Evolution of bulk composition, mineralogy, strain style and fluid flow during an HT–LP metamorphic event: sillimanite zone of the Catalan Coastal Ranges Variscan basement, NE Iberia

Metamorphic rocks in the Osor complex (Guilleries massif, NE Iberian Peninsula) show the following structural and compositional features: strong differentiation into quartz-rich gneissic semipelitic and quartz-absent, mica-rich schistose bands, higher density of igneous (both basic and leucogranitic) and quartz veins in the schistose domains and strong strain partitioning in the pelitic bands. Garnet is present in both kinds of lithologies, showing also differential textural and chemical features interpreted to be dependent on bulk composition, deformation and fluid interaction histories. Textures, mineral composition and thermobarometry suggest the operation of concurrent mechanical, mass transfer and thermal phenomena such as: (1) variations in strain style, (2) fluid infiltration, (3) magmatic injection and (4) HT–LP metamorphic and metasomatic episodes. The following sequence of events is suggested: initially the cooling of syntectonic high- T basic quartz diorite sheets promoted high strain rates, low d P/d T thermobaric evolution, incipient anatexis in the pelitic bands and devolatilization through a pervasive to vein-channelized prograde fluid flow. The prograde flow enhanced an ongoing compositional tectono-metamorphic differentiation and produced metasomatism through depletion of the Osor rocks in alkalis and calcium. Later injection and cooling of peraluminous leucogranitoid sheets, preferentially along pelitic bands, increased the ratio of magmatic/metamorphic components in the fluids and strongly enriched them in alkalis producing a second metasomatic episode. During crystallization of quartz and leucogranitoid veins, the pelitic bands were strongly enriched back again in alkalis, promoting the blastesis of big crystals of post-peak muscovite and albite as well as the retrogression of garnet. The metasomatic mica-rich levels must have been the preferred locus for development of a new deformation style dominated by shear band fabrics in metapelites and related to a release of the gravitational instability originated previously due to crustal thickening. The increasing decompressional component of the retrograde P– T path also suggests that this style of deformation was prevalent during, if not responsible for, a phase of exhumation of the metamorphic complex. It is suggested that similar patterns of thermomechanical and mass transfer phenomena could well be a fundamental characteristic common to all HT–LP metamorphic belts.