Overpressure Conditions Research Articles

Very high burnup spent fuel corrosion & leaching under hydrogen conditions

This paper concerns a very high burnup UO2 spent nuclear fuel leaching experiment performed under high hydrogen pressure conditions (5 MPa H2 initially) in simplified granitic groundwater. Following an initial release after start-up the results demonstrate that the concentrations of redox sensitive elements such as Tc, U, Np and Pu stabilize at the solubility limits of their reduced oxide forms. The release of non-redox sensitive elements such as Cs also ceased within a year. Together these observations indicate that the hydrogen overpressure resulted in reducing conditions that suppresses fuel matrix corrosion. Following an initially rather rapid release of fission gases Kr and Xe, the release also ceases towards the end of the experiment, although at a surprisingly high released fraction of the inventory. In this experiment the fuel was cut from the rod, crushed in a vice and pre-leached under semi aerated conditions for 9 days before transitioning to conditions of high hydrogen overpressure and the resulting apparent inhibition of further corrosion or dissolution of the fuel matrix. These results are in contrast to our previous experiments with other portions of fuel from the same rod under similar hydrogen conditions, but with extensive dry milling and fuel corrosion in aerated conditions, prior to the transitions to hydrogen conditions. The results thus tentatively support the conclusion that preceding oxidation of the fuel surfaces may limit the potential for hydrogen to suppress fuel corrosion and dissolution.

Effects of burial powder configuration on the microstructure, composition, and ion conductivity of perovskite Li3xLa1/3‐xTaO3 ion conductors

AbstractA combustion synthesis methodology for the preparation of perovskite Li3xLa1/3‐xTaO3 lithium‐ion conductors with x = 0.033 is presented. Bulk ceramic specimens were sintered under combinations of burial powder and cover crucibles to provide different lithium vapor overpressure conditions. A maximum total lithium ion conductivity of 6 × 10‐6 S cm‐1 at room temperature was found for the pellet covered by a crucible whose lip was sealed using parent powder (moderate overpressure), with agreement to the maximum in the intergranular ion conductivity. Intragranular conductivity was maximized at the low overpressure condition. The trend in ion conductivity was found to correspond to the lithium content in the samples through a combination nuclear reaction analysis and energy dispersive X‐ray spectroscopy phase constitution measurements. The mechanism impacting ion conductivity was determined to be changes in the amount of LaTaO4 secondary phase as driven by the processing conditions during sintering.

Growth interruption strategies for interface optimization in GaAsSb/GaAsN type-II superlattices

Recently, GaAsSb/GaAsN type II short-period superlattices (SLs) have been proposed as suitable structures to be implemented in the optimal design of monolithic multi-junction solar cells. However, due to strong surface Sb segregation, experimental Sb composition profiles differ greatly from the nominal square-wave design. In this work, the improvement of the interface quality of these SLs in terms of compositional abruptness and surface roughness has been evaluated by implementing different growth interruption times under Sb4/As4 (soaking) and As4 (desorption) overpressure conditions before and after the growth of GaAsSb layers, respectively. The combined effects of both processes enhance Sb distribution, achieving squarer compositional profiles with reduced surface roughness interfaces. It has been found that the improvement in compositional abruptness is quantitatively much higher at the lower interface, during soaking, than at the upper interface during desorption. Conversely, a larger decrease in surface roughness is achieved at the upper interface than at the lower interface. Fitting of the Sb segregation profiles using the 3-layer kinetic fluid model has shown that the increase in Sb incorporation rate is due to the decrease in segregation energy, presumably to changes in the surface reconstruction of the floating layer at the surface.

Nonsteady discharge of granular media from a silo driven by a pressurized gas

Motivated by an application to nuclear safety, we studied the effect of an imposed gas over-pressure on the discharge flow of granular media from a cylindrical silo. The size and type of particles and surrounding fluid where discharge occurs were varied, using air and water to test a coolant fluid for nuclear safety. Particle and air flow rates are found to increase during discharge with constant over-pressure conditions. A two-phase continuum model is used with a frictional rheology for particle-particle interactions. This model is solved numerically and we propose a simple quasi-steady analytical model with the air-pressure gradient at the orifice as a driving force in addition to gravity.

Overpressures Induced by Compaction Disequilibrium Within Structural Compartments of Murree Formation, Eastern Potwar, Pakistan

Overpressure conditions in Potwar Basin of Pakistan pose significant drilling and completion problems. Specifically, in eastern Potwar, abnormally high pressures are observed within structural compartments of Murree Formation of Neogene age. Compaction disequilibrium and tectonic stresses are considered as two major factors, controlling pore pressures in this foreland basin. Undercompaction of sediments due to high sediment influx affects the porosity-depth relationship as the rock deviates from the normal compaction trend. Demarcation of structural geometries is critical in understanding abnormal pressure conditions within thick molasse deposits of Murree Formation. Eastern Potwar is divided into three zones on the basis of structural geometries, including duplex thrust sheets, salt-cored anticlines, and triangular zones. Geohistory analysis and pore pressure prediction have been performed for determining the overpressuring mechanism. Log-based pressure prediction in different oil fields of eastern Potwar depicts anomalous pressure conditions in some of the wells. High-sedimentation rate during Miocene times resulted in a low porosity reduction rate due to the inability of fluid to escape out of the pores. Eaton’s method was used to predict the pore pressure, and these pressure curves were calibrated against measured pressure to validate the results. Pressures predicted in Qazian-1X well showed very good correlation with measured pressure data. Most of the wells with overpressure intervals exhibited high porosity values, showing deviation from the normal compaction trend. This pressure prediction revealed that compaction disequilibrium is the primary cause of overpressure conditions within Murree Formation, resulted in response to the rapid rate of sedimentation. The deformation mechanism and presence of different structural geometries also contributed in the development of abnormal pressures.

Effect of Diagenesis on the Quality of Sandstone Reservoirs Exposed to High-Temperature, Overpressure, and CO2-Charging Conditions: A Case Study of Upper Miocene Huangliu Sandstones of Dongfang District, Yinggehai Basin, South China Sea

The Upper Miocene Huangliu sandstones of the Dongfang district are currently regarded as an important exploration target in the Yinggehai Basin. Affected by the anomalous diagenetic environments of high temperature, overpressure, and CO2 fillings, the diagenetic evolution of the Huangliu sandstones appear complicated characteristics and subsequently exert a significant influence on reservoir development. Integrated methods employed in this study include an electron microscope, cathode luminescence, X-ray diffraction, scanning electron microscope, electron microprobe, stable isotope analysis, homogenization temperature, and physical property tests. By the comparative researches between the AF-1 and AF-2 areas of the Dongfang district, the aim of this study is to investigate the complex diagenetic modifications and their controlling effects on reservoir quality and development mechanism. With similar sedimentary features, the reservoirs in the AF-1 area exhibit slightly higher porosity than those of the AF-2 area. The permeability in the AF-1 area shows one or two orders of magnitude lower than that of the AF-2 area, and throats size distribution act as a critical factor to cause distinct diversities of permeability. In the AF-1 area, the later appearance of overpressure contributed to stronger compaction intensity and more loss of primary porosity. The dissolution induced by CO2-rich thermal fluids in late stage enhanced the secondary porosity significantly and improved the total porosity. However, extensive dissolution cause abundant precipitation including carbonate cement and authigenic illite in a closed diagenetic system, which lead to the decrease of reservoirs’ permeability. As for the AF-2 area, earlier occurrence of overpressure restrained mechanical compaction obviously and further retarded corrosion of organic acid, which preserved high proportions of primary porosity. Due to lesser impact by CO2 filling, the AF-2 area had a poor intensity of dissolution and cementation, and the authigenic illitization was also restrained significantly, which effectively prevented heavy damage on reservoir quality, and especially for permeability. Based on the diagenetic evolution pathways, two types of porosity evolution patterns are established. The effect degree on diagenesis by high temperature, overpressure, and CO2 filling vary significantly between the AF-1 and AF-2 areas. The two areas show different pathways of diagenetic evolution, forming two development patterns and exhibiting different reservoir types.

Dynamic characteristics analysis of pilot valves with different inlet diameters installed on the main steam valve set

The Main Steam Valve Set (MSVS) is the key protection device for nuclear power plants, whose dynamic characteristics are directly related to the security of the secondary circuit system especially under overpressure conditions. Dynamic mesh technology is used in this work to capture the dynamic characteristics of the interconnected pilot valves on the MSVS with different inlet diameters. The research results show that increasing inlet diameter can significantly reduce the opening time of the pilot valves, but it will also increase the fluid force of valve stem during the opening process as well as the movement speed at the maximum opening. The pressure of the pilot valves during the opening process is then analyzed. It can be seen that changing the inlet diameter will affect the inlet annular throttling area, thereby changing the pressure rise speed in the external chamber of the valve stem and the inner cavity of the valve body, thereby affecting the total response time. This work provides a reference for the selection of the pilot valve diameter in MSVS and helps to improve the overpressure protection capability of MSVS.

Wave Velocity in Sandstone and Mudstone under High Temperature and Overpressure in Yinggehai Basin

Wave velocity under different pressure and temperature (PT) conditions plays an important role in the exploration of oil and gas reservoirs. We obtained the mineral composition and porosity of 20 underground sandstone and mudstone samples in Yinggehai Basin via X-ray diffraction and porosity measurements. Using high-frequency ultrasound, the P- and S-wave velocities of four samples under high temperature and overpressure conditions were found to vary significantly, owing to the material composition and porosity. According to the comparison between the experimental conclusion and the well-logging data, the genesis of false bright spot and dark spot gas reservoirs in the study area was analyzed. The variation in P-wave velocity under different temperature and pressure conditions was explained with the PT coefficient. The traditional pressure–velocity and temperature–velocity prediction methods were improved and applied to well-logging data. Herein, the velocity of P- or S-waves of sand and mudstone under high temperature and overpressure via rock physics experiments and the genesis of false bright spot and dark spot gas reservoirs in the Yinggehai Basin was observed. Overall, the results serve as a theoretical basis for seismic exploration in the study area.

DEVELOPMENT OF FIBROUS CALCITE VEINS RELATED TO HYDROCARBON GENERATION AND OVERPRESSURING IN ORGANIC‐RICH SHALE SOURCE ROCKS: THE VACA MUERTA FORMATION, NEUQUÉN BASIN, ARGENTINA

Fibrous calcite bed‐parallel veins (BPVs) are a typical feature of the Upper Jurassic – Lower Cretaceous Vaca Muerta Formation in the subsurface of the Neuquén Basin (Argentina). The formation is considered to be the main source rock in the basin as well as an important unconventional play. This study examines the growth of BPVs through an analysis of core from three wells located along a transect extending for some 150 km from the NE Platform near the basin margin in the east to the Agrio fold‐and‐thrust belt at the Andean deformation front in the west. The main objective is to integrate fluid inclusion data with the palaeothermal and palaeopresure evolution obtained from a regional‐scale 2D basin and petroleum systems model to examine the timing of fracture development and its relationship with hydrocarbon generation in the Vaca Muerta Formation through time.The apertures of BPVs were measured in more than 360 m of core from three wells (wells A, D and E). This data was combined with optical petrography to investigate the number of calcite cementation events, and the temperature of cement precipitation based on fluid inclusion data. The organic geochemical and mineralogical characteristics of the Vaca Muerta source rock were also analysed. The integrated results were incorporated into a poro‐elastic basin model to investigate the impact of horizontal shortening due to Andean compression on pore pressure development and fracturing in the Vaca Muerta Formation. This framework allowed the timing of BPV formation to be determined together with possible mechanisms governing overpressure conditions through time.Near the Andean deformation front in the west of the modelled section where the Vaca Muerta Formation is in the wet gas window (well D) and dry gas window (well A), BPVs are characterized by two or more generations of calcite fibres indicating multiple growth phases. Calcite which precipitated during cementation event 1 (E1) in the internal zones of BPVs consists of crystals oriented perpendicular to fracture walls, indicating perpendicular vein opening. Calcite precipitated during cementation event 2 (E2) in the outer zones of BPVs includes curved and oblique crystals. During this phase, shear occurred between the opening vein walls as a result of horizontal shortening. Cementation event 3 (E3) is characterized by an equant mosaic of calcite crystals which preserve intracrystalline porosity. E1cements formed between 110 and 90 Ma with trapping temperatures of ∼112 °C (upper Vaca Muerta, well A) and ∼125 °C (lower Vaca Muerta, well D). Fracturing resulted from disequilibrium compaction and from volumetric expansion due to primary cracking of kerogen within the oil window. E2 cements record a trapping temperature of ∼159 °C and formed between 70 and 55 Ma (lower Vaca Muerta, well D) during maximum burial of the Vaca Muerta Formation, synchronous with the secondary cracking of retained liquid hydrocarbons and the beginning of Andean compression. E3 cements (upper Vaca Muerta, well A) have a trapping temperature of ∼162 °C, and formed between 65 Ma and 53 Ma synchronous with the generation of thermogenic gas.By contrast, in the east of the modelled section in the less deformed foreland area of the Neuquén Basin where the Vaca Muerta Formation is in the early oil window (well E), BPVs are composed of a single generation of calcite fibres (E1)with a trapping temperature of ∼118 °C. The E1 cement is characterized by calcite crystals which are oriented perpendicular to fracture walls with no evidence of shearing. According to model simulations, cementation here occurred between 64 Ma and 53 Ma during maximum burial and was related to overpressures which resulted from both disequilibrium compaction and primary transformation of kerogen into oil.The data presented suggests that in some intervals of the Vaca Muerta Formation, a slight increase in TOC content is accompanied by an increase in vein thickness, with the highest number of cementation events occurring towards the Andean deformation front in the west of the study area compared to the foreland in the east.

Circum-Tharsis wrinkle ridges at Lunae Planum: Morphometry, formation, and crustal implications

Wrinkle ridges are one of the most widespread tectonic landforms on Mars developed under a compressional stress regime within the lithosphere. In this study, we investigate the morphology and structure of wrinkle ridges at northern Lunae Planum, which belongs to the circum-Tharsis wrinkle ridge system. We use methods to construct balanced cross-sections of fold-and-thrust belts that are based on conservation of area and volume to assess the nature of deformation and to quantify the amount of shortening and the depth of detachment faulting. Our morphometric analyses indicate that height and width of wrinkle ridges at Lunae Planum systematically decrease with increasing distance from the center of the Tharsis rise from west to east. The results indicate that horizontal shortening decreases from 4.75% to 1.25%, or ~116 m to ~56 m from west to east, and this shortening is accommodated by the formation of complex asymmetric ridges. Sections through wrinkle ridges provided by an escarpment at Kasei Valles and steep walls of impact craters expose thrust faults beneath the wrinkle ridges that dip at 38° +/− 5°. We model wrinkle ridges as fault-propagation folds and show that the observed thrust faults form along the frontal fold axial planes of the anticlines. At depth these faults merge into more gentle thrust ramps of 20°+/− 5° dip. Kinematic modeling further implies that the thrust ramps transition into a sub-horizontal detachment, which rises from −4 km in the west to −2.6 km in the east, measured from the surface. The very gentle eastward dipping topographic slope of Lunae Planum and the eastward rising detachment define a narrow wedge that is interpreted as an incipient critical taper with a tectonic push induced by the Tharsis rise. We propose here that the mechanically weak detachment is localized in a water-bearing crustal layer underneath a crust whose pore space is sealed by ice. Fluid overpressure conditions may enable yielding and slip on the detachment. Hydrous mineral reactions on the slip planes and flood basalt layers that gently dip to the Tharsis center due to flexural loading may additionally weaken the basaltic rocks and contribute to detachment faulting.

Effect of Osmotic Pretreatment Combined with Vacuum Impregnation or High Pressure on the Water Diffusion Coefficients of Convection Drying: Case Study on Apples.

The paper presents water diffusion coefficients as providing a significant contribution to the creation of a comprehensive database and knowledge of weight variation during the drying process of raw plant materials that is used for modelling the technological process and designing innovative products. Dehydration is one of the most widely used methods for improving the stability and durability of fruit and vegetables because it reduces water activity and microbial activity, and minimises the physical and chemical changes during storage. The considerable impact of pressure on heat exchange and weight during the convection drying process of osmotically pretreated apples is demonstrated. The course of the drying curves and the drying rate is determined by the use of pressures of 0.02 and 500 MPa. Varied pressure applied during osmotic impregnation significantly influences the value of the diffusion coefficient: the average determined for the entire course of the drying curve and the average determined in the intervals of the reduced water content. The lowest values of the average water diffusion coefficient are obtained for apples preboiled under overpressure conditions and, at the same time, the determined diffusion coefficients in the water content are characterised on the drying curve by a clearly decreasing course until the reduced water content reaches approximately 0.2.

Overpressure on fingertips prevents state estimation of the pen grip force and movement accuracy.

We tested the hypothesis that the inability to move a pen accurately in a graphic task is partly due to a decrease of afferent somatosensory information resulting from overpressure on the tactile receptors of the fingers holding the pen. To disentangle the depressed somatosensory origin from an altered motor command, we compared a condition in which the participant actively produces pressure on the pen (active grip) with a condition in which pressure is passively applied (passive grip, no grip-related motor command). We expected that the response of the somatosensory cortex to electric stimulation of the wrist's tactile nerve (i.e., SEP) would be greater in the natural pen grip (baseline condition) than in the two overpressure conditions (actively or passively induced). Fifteen adults were required to trace a geometrical shape in the three grip conditions. The SEP amplitude was not significantly different between the baseline and both overpressure conditions. However, behavioral results showed that drawing accuracy is impaired when the pressure on the pen is increased (passively or actively). Cortical source analyses revealed that the activity of the superior parietal areas (SPL) increased in both overpressure conditions. Our findings suggest that the SPL is critical for sensorimotor integration, by maintaining an internal representation of pen holding. These cortical changes might witness the impaired updating of the finger-pen interaction force for such drawing actions under visual guidance.

Role of dyke geometry in understanding dyke-emplacement mechanisms and magma-chamber dynamics: A critical appraisal from the Chotanagpur Gneissic Complex, India

We present a detailed account of the structural aspects of dykes from the Chotanagpur Gneissic Complex (CGC) of eastern India, in order to understand dyke-emplacement mechanisms and magma-chamber dynamics. The study area comprises two temporally distinct parts of the CGC, namely the Proterozoic CGC and the Gondwana CGC. Dykes of the Gondwana CGC are divided into two types based on their intrusion into either sandstones or basalts. The size distributions of dyke lengths and of thicknesses respectively follow a power-law and an exponential distribution. Power law explains the nonlinear functional relationship between two quantities in which one quantity varies as the power of the other. The essential properties of power-law are that it is scale-invariant and represents the universality of a problem. An exponential distribution explains that a quantity sharply decreases with respect to other quantities over a period of time. We calculate the overpressure conditions for 60 selected dykes using their aspect ratios. Calculated overpressure is utilized to estimate the depth of magma origin, which in turn is used to estimate the magnitude of maximum and minimum principal stresses. Based on this collective information, we propose a conceptual model of dyke emplacement. Consequently, the results have critical implications in understanding magma chamber dynamics.

New insights on the petroleum migration and accumulation in the basal conglomerate reservoir of Cretaceous Qingshuihe Formation of Yongjin area, Central Junggar Basin

The Junggar Basin is one of the largest and most petroliferous superimposed petroleum basins in China. This study focussed on the characteristics of the unconformity between the Jurassic and Cretaceous (J/K) and its influence on hydrocarbon accumulation in the Yongjin area, Junggar Basin. Based on the seismic reflection characteristics and wireline well logging response, we identified the structure of the unconformity, which consists of three layers: the basal conglomerate layer, weathered clay layer, and semi‐leached layer. Geochemical studies show that the crude oils of the Lower Cretaceous Qingshuihe (K1q) Formation in the Yongjin area are mainly derived from Permian source rocks and partly from Cretaceous source rocks. The abnormally high value of acoustic time and the low value of resistivity of mudstone indicate that the overpressure condition is pervasive in the Yongjin area and may act as the driving force for the vertical migration of hydrocarbon‐containing palaeo‐fluids. The poor sealing ability of the weathered clay layer of the unconformity between the Jurassic and Cretaceous (J/K) and the high abnormal overpressure indicate that the petroleum from Permian source rocks may break through the sealing of the weathered clay layer and migrate upward to the Cretaceous conglomerate to accumulate. In addition, the combination of faults, sheet sand bodies, and unconformities constitutes a three‐dimensional petroleum migration pathway. The evolution of the Che‐Mo palaeo‐uplift also affected the formation of source rocks and petroleum migration. Accordingly, the hydrocarbon accumulation model of the Cretaceous in the Yongjin area indicated that Late Palaeogene is the first accumulation period. Permian source rocks have entered a mature to high‐mature stage, where a large amount of generated oil and gas migrated along faults and unconformities and accumulated in the braided river channel sand bodies of the K1q Formation. The second accumulation period was the Neogene. The basin experienced a regional tilt leading to a south‐inclined stratum. The oil and gas migrated upwards along the Late Hercynian deep reverse fault (Carboniferous–Permian) and then passed through the shallow faults and migrated to the bottom sandstone of Cretaceous reservoirs.

Characteristics and Genetic Mechanisms of Normal-Pressure Fractured Shale Reservoirs: A Case Study From the Wufeng–Longmaxi Formation in Southeastern Chongqing, China

Compared with the overpressure conditions of shale reservoirs in the Jiaoshiba area, exploring the controlling factors of changes in shale reservoir physical properties under normal-pressure accumulation is of great significance to shale gas exploration. To achieve this, X-ray powder diffraction, nitrogen adsorption, and scanning electron microscopy were carried out to determine mineral content, permeability, porosity, and pore structure for well core and outcrop samples of the Wufeng–Longmaxi Formation in southeastern Chongqing, China. Field observations and drilling cores revealed abundant structural fractures in southeastern Chongqing, offering potential main storage space for shale gas. Findings also determined that high-quality source rocks are located in the lower part of the Wufeng–Longmaxi Formation, which features low porosity and low permeability, yet existing structural fractures could potentially improve permeability to a certain extent. The main factors controlling the shale reservoir with the above characteristics include the depositional environment, mineral components, total organic carbon content, and tectonic movement. The deep-water anoxic depositional environment was conducive to the complete preservation of organic matter and sedimentation of the biogenic siliceous minerals, which had a strong effect on improving the porosity of organic matter and brittleness of the rocks. The high content of quartz was found to improve rock compression resistance and brittleness, and increasing clay proportion was found to enhance the interlayer pores of clay minerals. Total organic carbon content, specific surface area, pore volume, and fracture development were all found to have direct contributions to shale gas entrapment. Overall, the most important factor resulting in normal-pressure accumulation in southeastern Chongqing was the intense tectonic movements since the Late Jurassic period which destroyed the original overpressure accumulation conditions.

Hazard From Endogenous Gas Emissions and Phreatic Explosions in Rome City (Italy)

AbstractA gas blowout during an unauthorized well drilling occurred on June 9, 2020 at the Rome‐Ciampino boundary at the periphery of Colli Albani quiescent volcano. This zone hosts a shallow confined gas‐pressured aquifer, which recently produced further three gas blowouts. Dangerous atmospheric CO2 and H2S concentrations killed some birds, and 12 families were evacuated. The helium isotopic composition indicates that the gas has a magmatic origin. It rises toward the surface along leaky faults, pressurizing the shallow confined aquifer and creating a permanent gas blowout hazard. Colli Albani volcano is characterized by anomalous uplift, release of magmatic gas, and episodic seismic crises. Should a volcanic unrest occur, gas hazard would increase in this densely inhabited zone of Rome city, as the input of magmatic gas into the confined aquifer might create overpressure conditions leading to a harmful phreatic explosion, or increase the emission of hazardous gas through newly created fractures.

Intrusion fracturing and quartz sand-rich injections in thrust-related fault rocks within the basal shear zone of the Esla Nappe (Cantabrian Zone, NW Iberia)

The Esla Nappe, located in the Cantabrian Zone (Variscan Orogen, NW Iberia), has an estimated 19 km displacement to the NE accommodated in a thin (<2–3 m) shear zone (ENSZ) at least 4 km depth. Fault-rock assemblages record different deformation processes operating in the hangingwall and footwall. While the hangingwall was largely deformed through cataclastic flow localised in a <50 cm band, hangingwall-footwall intervening ultracataclasites and footwall lithologies preserve evidence for an interplay of cataclastic flow and pressure solution. Final hydrofracturing and calcite vein precipitation has contributed to the vertical dilation of the fault rock assemblages.In the late stages of emplacement, the ENSZ was breached through intrusion fracturing and associated clastic sills and dykes injected along re-opened previous discontinuities and anisotropies. Together, they conform an interconnected network of quartz sand-rich lithosomes reaching structural heights of 20 m over the ENSZ. Injections are formed by a mixture of injected quartz grains and host-derived fragments. Dyke orientations suggest that the injection process occurred under large fluid overpressure conditions exceeding lithostatic values in the footwall. Fluid overpressure may have been caused by progressive fluid accumulation beneath a low-permeability ultracataclasite layer at the base of the nappe. Breaching through the shear zone was favoured by a change in the stress regime following the Esla Nappe emplacement.

Effects of a Small Increase in Carbon Dioxide Pressure during Fermentation on Wine Aroma.

The present study tested the effect of a slight increase in pressure (from 0 to 1 bar) during the fermentation on the wine aroma profile. Fermentations were carried out with a commercial dry yeast on Sangiovese juice in the absence of berry skins. The wine samples fermented under slight overpressure conditions were found to be significantly different from the control samples produced at atmospheric pressure in relation to several chemical compounds. Concentrations of many esters (i.e., isoamyl acetate, ethyl acetate, ethyl hexanoate, hexyl acetate, ethyl dodecanoate, and ethyl tetradecanoate), and acids (i.e., hexanoic acid, octanoic acid, and decanoic acid) increased, while concentrations of two acids (i.e., isobutyric and isovaleric acid) decreased. These differences, notably the higher concentration of esters, are usually associated with a more intense fruity attribute. Triangular sensory tests revealed that the significant chemical differences were also perceivable; hence, introducing a slight pressure increase during the alcoholic fermentation could be a useful tool in managing the aroma profile of wine.

Influence of acetic and butyric acid and gas release modes on immobilized Clostridium acetobutylicum (DSMZ 792) in repeated batch experiments

The effects of supplementation of standard media with metabolic intermediates (2 g/L butyric acid, 2 g/L butyric acid + 1.5 g/L acetic acid) on butanol and hydrogen production/yield were evaluated. Fermentations were conducted with immobilized Clostridium acetobutylicum (DSMZ 792). Additionally, the influence of gas release modes (constant gas release vs. interval gas release) was tested in all setups to evaluate butanol and hydrogen production and yields. Fermentations were implemented in repeated batch mode (48 h, 37 °C, 100 rpm). Overpressure conditions had a negative impact on volumetric hydrogen production and hydrogen yield and a positive impact on butanol yield. Supplementation significantly increased the butanol concentrations in constant gas release mode, by 23.6%. When interval gas mode was applied in the supplemented fermentations, the butanol concentrations decreased by 8.4% when butyric acid was fed, and reached similar concentrations when both acids were added. The highest butanol concentration and volumetric butanol production rate of 9.6 ± 0.6 g/L and 0.2 ± 0.0 g/L*h, respectively, were reached with butyric acid supplementation and constant gas release mode. The highest volumetric hydrogen production was reached with the constant gas release mode in fermentations conducted with the addition of both acids, and reached 165 ± 9 mL/L*h.

Changes in phytosterol contents during rape seed storage under conditions simulating industrial silos

During seed storage in tall silos the low layers of rape seeds are exposed to static pressure exerted by the upper layers. This may cause deformation and damage of seeds found in the lower layers and losses of biologically active compounds. The aim of this study was to simulate under laboratory conditions the actual ecosystem found in industrial plants and to evaluate the effect of not only the temperature and moisture content, but also static pressure on degradation of phytosterols contained in rape seeds in the course of storage. Changes in phytosterol levels were assessed using GC-MS. During storage in all samples of seeds (7–16% moisture content) under the adopted conditions of overpressure (20–60 kPa) and temperature (25–35 °C) the total content of phytosterols decreased by 3–57%. The smallest losses in the total phytosterol contents (3–4%) were recorded during storage of seeds with a 7% moisture content, irrespective of the applied storage temperature (25–35 °C) and overpressure variants (20–60 kPa). The greatest losses of phytosterols (43–57%) were observed during storage of seeds with a 16% moisture content at a temperature of 35 °C, while the higher the applied overpressure, the greater these losses were. The study showed that the greatest influence on sterol content during storage was increased seed moisture, and subsequently the temperature and the pressure. Experimental results also showed that for seeds with higher moisture contents (13 and 16%) an increase in storage temperature from 30 to 35 °C intensifies losses of individual phytosterols much more markedly that an increase in temperature from 25 to 30 °C. Moreover it was observed that overpressure over 20 kPa enhanced losses of investigated phytosterols.