Rapid Decompression Research Articles

Microbial cell disruption for improving lipid recovery using pressurized CO2 : Role of CO2 solubility in cell suspension, sugar broth, and spent media.

The study of in situ gas explosion to lyse the triglyceride-rich cells involves the solubilization of gas (e.g., carbon dioxide, CO2 ) in lipid-rich cells under pressure followed by a rapid decompression, which allows the gas inside the cell to rapidly expand and rupture the cell from inside out. The aim of this study was to perform the cell disruption using pressurized CO2 as well as to determine the solubility of CO2 in Rhodotorula glutinis cell suspension, sugar broth media, and spent media. Cell disruption of R. glutinis was performed at two pressures of 2,000 and 3,500 kPa, respectively, at 295.2 K, and it was found from both scanning electron microscopy (SEM) and plate count that a substantial amount of R. glutinis was disrupted due to the pressurized CO2 . We also found a considerable portion of lipid present in the aqueous phase after the disruption at P = 3,500 kPa compared to control (no pressure) and P = 2,000 kPa, which implied that more intracellular lipid was released due to the pressurized CO2 . Solubility of CO2 in R. glutinis cell suspension was found to be higher than the solubility of CO2 in both sugar broth media and spent media. Experimental solubility was correlated using the extended Henry's law, which showed a good agreement with the experimental data. Enthalpy and entropy of dissolution of CO2 were found to be -14.22 kJmol-1 and 48.10 kJmol-1 K-1 , 9.64 kJmol-1 and 32.52 kJmol-1 K-1 , and 7.50 kJmol-1 and 25.22 kJmol-1 K-1 in R. glutinis, spent media, and sugar broth media, respectively. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:737-748, 2017.

Like a cannonball: origin of dense spherical basaltic ejecta

Cannonballs are rare spherical to sub-spherical eruptive products associated with basaltic explosive activity. The origin of cannonballs is still debated and subjected to a wide spectrum of different interpretations. In order to better understand the physicochemical mechanisms controlling the formation of these explosive products, we investigated the textural and chemical features of cannonballs from the Cerro Chopo monogenetic volcano (Costa Rica). These explosive products ubiquitously show a core domain with coalesced bubbles (30–36% porosity) wrapped in a dense rim domain with small, isolated bubbles (20–27% porosity). Both domains are identical in terms of bulk rock composition and mineral chemistry and are portions of the same magma batch. Results from combined petrological and thermodynamic modeling indicate that a low-viscosity (~20 Pa s) melt containing early-formed olivine phenocrysts (~9 vol.%) ascended from storage at a decompression rate of 0.5 MPa s−1 until it reached a depth of 4.5 km (equivalent to a pressure of ~150 MPa). While rising from depth to 4.5 km, the melt underwent rapid decompression (0.5–2.6 MPa s−1) and H2O exsolution, driving late-stage crystallization of the groundmass. The fast ascent velocity (21–110 m s−1) while rising between 4.5 km and the surface induced turbulent (Re >103), annular flow development in the uppermost region of the conduit. We propose that cannonballs represent blebs of fluid magmas that underwent shear-driven detachment from the annulus of magma lining the conduit walls at depths lower than 4.5 km. The formation of such cannonballs is dictated by magma transport dynamics of low-viscosity, phenocryst-poor, and volatile-rich melts that rapidly accelerate within the shallow conduit.

Time Course of Endothelial Dysfunction Induced by Decompression Bubbles in Rats.

Decompression stress can cause endothelial injury, leading to systematic inflammation and prothrombotic phenomena. Our previous work found that endothelial injury following decompression correlated positively with bubble formation. This study aimed to investigate the time course of endothelial injury and the relationship with bubble amounts. Rats were subjected to a simulated air dive to 7 ATA for 90 min with rapid decompression. Bubbles were detected ultrasonically at the root of pulmonary arteries following decompression. Surviving rats were randomly divided into six groups according to sampling time following decompression (2, 6, 12, 24, 48, and 72 h). Three parameters, serum levels of malondialdehyde (MDA), endothelin-1 (ET-1), and intercellular cell adhesion molecule-1 (ICAM-1) were identified from our previous study and measured. The level of MDA reached a peak level at 12 h post decompression, and then decreased gradually to control level before 72 h. For both ET-1 and ICAM-1, the greatest expression appeared at 24 h following surfacing, and the increases lasted for more than 72 h. These changes correlated positively with bubble counts at most detection time points. This study reveals the progress of endothelial dysfunction following decompression which provides guidance for timing the determination at least for the current model. The results further verify that bubbles are the causative agents of decompression induced endothelial damage and bubble amounts are an objective and suitable parameter to predict endothelial dysfunction. Most importantly, levels of endothelial biomarkers post dive may serve as sensitive parameters for assessing bubble load and decompression stress.

Preventive effect of rosiglitazone on liver injury in a mouse model of decompression sickness.

Severe decompression sickness (DCS) is a multi-organ injury. This study investigated the preventive effects of rosiglitazone on liver injury following rapid decompression in mice and examined the underlying mechanisms. Mice were randomly divided into four groups: a control group, vehicle group, and rosiglitazone (5 and 10 mg·kg⁻¹) groups, the latter three being exposed to a pressure of 911 kPa. Haematoxylin and eosin staining, plasma levels of alanine transaminase (ALT), aspartate transaminase (AST) and lactate dehydrogenase and blood cell counts were used to evaluate liver injury at 30 min after rapid decompression. The expression of endothelial and inducible nitric oxide synthase (iNOS) and its phosphorylation were measured to uncover the underlying molecular mechanisms. A significant increase in plasma ALT, red blood cells and platelets, and a decrease in neutrophils were observed in the vehicle group. Furthermore, the expression of iNOS, E-selectin and the total level of NO in hepatic tissue, and soluble E-selectin in the plasma were significantly elevated in the vehicle group. Rosiglitazone pre-treatment prevented the increases in ALT (and AST), soluble E-selectin concentration, red blood cells and platelet counts. Moreover, rosiglitazone reduced over-expression of iNOS and the NO level, prevented the fall in neutrophil count and promoted the phosphorylation of iNOS in the liver. Pre-treatment with rosiglitazone ameliorated liver injury from severe DCS. This preventive effect may be partly mediated by stimulating endothelial NO production, improving endothelial function and limiting inflammatory processes.

A comparison of metrics to evaluate the effects of hydro-facility passage stressors on fish

Hydropower is the most common form of renewable energy, and countries worldwide are considering expanding hydropower to new areas. One of the challenges of hydropower deployment is mitigation of the environmental impacts including water quality, habitat alterations, and ecosystem connectivity. For fish species that inhabit river systems with hydropower facilities, passage through the facility to access spawning and rearing habitats can be particularly challenging. Fish moving downstream through a hydro facility can be exposed to a number of stressors (e.g., rapid decompression, cavitation, blade strike and collision, turbulence, and shear forces), which can affect fish survival in direct and indirect ways. Many studies have investigated the effects of hydroturbine passage on fish; however, the comparability among studies is limited by variation in the metrics and biological endpoints used. Future studies investigating the effects of hydroturbine passage should focus on using metrics and endpoints that are...

Pipeline Steels Strain Behaviour in High Mineralized Soils

The study of the features of corrosion degradation of the linear material underground pipelines in soils of different types is important to ensure the safe operation of gas pipelines and forecasting of resource (residual life) work correctly assesses operational risks. Our research aims at studying of long-acting and highly acidic medium term work on the deformation behaviour of the material pipelines. We have chosen main gas pipelines of large diameter made of steel 17HS that have been in operation for over 40 years as the object of the study. Test samples of pipelines material for air and liquid environments performed in static mode and re-load static pure bending with automatic registration trough design. To study the kinetics of deformation based on the results of previous studies and to improve their comparative analysis, we selected a similar level of nominal voltages that are 330, 420 and 510 MPa. In addition, in ME1, The pH of which is equal to 5, witnessing growth of strain from 5 to 15 percent, depending on the nominal stress fix and increase the angle of inclination of the final section of the curve, which indicates the danger of further loss of material's ability to resist prolonged stress. In the decreasing pH to 4 (ME2) fix significant deformation jumps occurred. Long term exploited steel deformation behavior in ME3 at pH 3 is more predictable. Cycles acceleration-deceleration strain are present, but their rate is lower than ME2. Furthermore, giving the significant aggressive environment, it is easy to predict significant risks due to rapid decompression of the metal in areas of damaged coating. Thus, the results of the research indicate significant risks of emergency situations in highly acidic soils, especially with simultaneous maintenance of chlorides and sulphates. This problem requires further investigation by physical simulation of processes of interaction of pipelines with soil electrolyte. Special attention should be paid to optimization of corrosion protection, including the value of the protective potential of cathodic stations.

Temporal evolution of magma flow and degassing conditions during dome growth, insights from 2D numerical modeling

Understanding magma degassing evolution during an eruption is essential to improving forecasting of effusive/explosive regime transitions at andesitic volcanoes. Lava domes frequently form during effusive phases, inducing a pressure increase both within the conduit and within the surrounding rocks. To quantify the influence of dome height on magma flow and degassing, we couple magma and gas flow in a 2D numerical model. The deformation induced by magma flow evolution is also quantified. From realistic initial magma flow conditions in effusive regime (Collombet, 2009), we apply increasing pressure at the conduit top as the dome grows. Since volatile solubility increases with pressure, dome growth is then associated with an increase in magma dissolved water content at a given depth, which corresponds with a decrease in magma porosity and permeability. Magma flow evolution is associated with ground deflation of a few μrad in the near field. However this signal is not detectable as it is hidden by dome subsidence (a few mrad). A Darcy flow model is used to study the impact of pressure and permeability conditions on gas flow in the conduit and surrounding rock. We show that dome permeability has almost no influence on magma degassing. However, increasing pressure in the surrounding rock, due to dome loading, as well as decreasing magma permeability in the conduit limit permeable gas loss at the conduit walls, thus causing gas pressurization in the upper conduit by a few tens of MPa. Decreasing magma permeability and increasing gas pressure increase the likelihood of magma explosivity and hazard in the case of a rapid decompression due to dome collapse.

Rapid versus gradual bladder decompression in acute urinary retention.

Objective:To demonstrate a benefit in diminished adverse events such as hypotension and hematuria with gradual drainage of the bladder when compared to rapid decompression in patients with acute urinary retention (AUR) due to benign prostatic hyperplasia in a case–control study.Methods:Sixty-two patients matched our selection criteria presenting with AUR. They were divided into two groups – the first was managed by rapid drainage of the bladder, the second was managed by gradual drainage through a urethral catheter (The first 100 mL immediately evacuated, then the rest evacuated gradually over 2 h).Results:The mean age was 64.4 and 63.2 years in the first and second group, respectively. Diagnosed cause was benign hyperplasia of the prostate. Hematuria occurred in two patients in the first group and none in the second group. The two cases of hematuria were mild and treated conservatively. After the relief of the obstruction, the mean blood pressure was noticed to decrease by 15 mmHg and 10 mmHg in the first and second group, respectively, however, no one developed significant hypotension. Pain relief was achieved after complete drainage in the first group and after the evacuation of 100 mL in the second group.Conclusions:We conclude that there is no significant difference between rapid and gradual decompression of the bladder in patients with AUR. Hematuria and hypotension may occur after rapid decompression of the obstructed urinary bladder, but these complications are rarely clinically significant.

Polarization of macrophages in the blood after decompression in mice.

The veins are a major site of bubble formation after decompression and the lung is a target organ of bubbles. Bubble-induced inflammation has been implicated in the pathogenesis of decompression sickness (DCS). Macrophages play a central role in the inflammation, and macrophage polarization is closely related to the pathogenesis of some lung diseases. This study aimed to investigate the blood macrophage polarization in mice after decompression. BALB/c mice were exposed to hyperbaric air for 60 minutes, and rapid decompression was performed to induce DCS. Slow decompression and hyperoxia (150 kPa, 60 minutes) served as control groups, and hyperbaric oxygen (HBO; 250 kPa, 60 minutes) was employed for DCS treatment. Macrophage phenotype was determined by flow cytometry, and cytokines related to macrophage polarization were measured by enzyme-linked immunosorbent assay. Our results showed rapid decompression significantly induced the shift to M1 phenotype, which was not observed in slow decompression group, HBO and hyperoxia groups. These changes were consistent with the change in blood tumor necrosis factor α level. Moreover, any treatment could significantly increase the M2 macrophages, but blood interleukin-10 remained unchanged after different treatments. In addition, the blood and lung levels of monocyte chemoattractant protein-1 and intercellular adhesion molecule-1 increased significantly after rapid decompression, but reduced markedly after HBO treatment. Taken together, rapid decompression is able to induce the shift to M1 phenotype in blood macrophages, which may then migrate into the lung involving decompression-induced lung injury.

The use of high-flow extracranial-intracranial artery bypass in pathology of the cerebral and brachiocephalic arteries: technical features and surgical outcomes

Poor outcomes of surgical treatment for complex cerebral aneurysms due to the development of cerebral ischemia were the cause to use cerebral revascularization surgery for this pathology. the study objective was to master a high-flow extracranial-intracranial (EC-IC) artery bypass technique and evaluate its application in surgical treatment of complex and giant cerebral aneurysms as well as complex lesions of the brachiocephalic arteries. Fifty two patients underwent high-flow IC-EC bypass surgery; of these, 34 patients had complex cerebral aneurysms, and 18 patients had complex stenotic occlusive lesions of the brachiocephalic arteries. After bypass placement, the patients with aneurysms underwent different variants of aneurysm exclusion (trapping or proximal clipping/ligation of the parent artery). All patients underwent follow-up studies of the bypass function and clinical condition in the early postoperative period and 6 and 12 months after surgery. High-flow IC-EC bypass surgery is routinely used in clinical practice of the Novosibirsk Federal Center of Neurosurgery. Fifty one out of the 52 patients were followed-up in a range of 4 to 56 months. According to the direct or CT angiography data, bypasses functioned in 51 (98.1%) patients in the early and long-term postoperative periods. The clinical efficacy (no ischemic changes and improved cerebral perfusion) of high-flow IC-EC bypasses was demonstrated in 31 (91.2%) of 34 patients with aneurysms and in 17 (94.4%) of 18 patients with complex lesions of the brachiocephalic arteries. The total number of surgical complications was 8 (15.4%) cases: 7 complications occurred in patients with aneurysms, and 1 complication developed in a patient with bilateral ICA occlusion. Of these, ischemic complications developed in 4 (7.7%) cases, hemorrhagic complications occurred in 2 (3.8%) cases, and cranial nerve complications were found in 2 (3.8%) cases. One (1.9%) female patient with a giant aneurysm died from hemispheric stroke due to insufficient blood flow through the bypass. Implementation of a large number of surgeries enabled improvement of the technique and clarification of the prerequisites for preoperative examination, intraoperative control, and postoperative management of patients. A low mortalits rate suggests this technique for use in clinical practice. The surgery is indicated for the treatment of giant aneurysms of the petrous, cavernous, and clinoid segments of the ICA. In the case of giant supraclinoid aneurysms, the surgery may be combined with removal of thrombotic masses from the aneurysm sac for rapid decompression of the cranial nerves. Application of this surgery for treatment of giant aneurysms of the trunk and bifurcation of the basilar artery is promising but requires further investigation. The surgery is also recommended for improving cerebral perfusion in the setting of complex stenotic occlusive lesions of the BCA: prolonged BCA stenoses, tandem ICA stenoses located in both the extracranial and intracranial segments, nonspecific vasculitis and arteriitis, subcranial aneurysms, kinking etc.

Energy‐Economic Analysis of Thermal‐Expansionary Pretreatment for Its Implementation at a Biogas Plant

AbstractThermal‐expansionary pretreatment is a novel environmentally friendly technology that has high potential to be installed in various industrial biofuel technologies where lignocellulosic biomass is processed. It is based on the boiling of biomass in water maintained by pressure in the liquid state, under a process temperature and a residence time with subsequent rapid batch decompression. The performance of the intensified pretreatment technology was shown in an intensified full‐scale biogas plant. Wheat straw was used as the model processing substrate. To show the improvement, the results were compared with the regular non‐intensified biogas plant. It was found that the intensified plant had a much higher power. The economic analysis and payback period were performed for both types of plant.

Significance of surgical management for cystic prolactinoma.

It is generally accepted that dopamine agonists (DA) represent the first-line treatment for most patients with prolactinoma, and patients become candidates for surgical intervention when DA is contraindicated. Surgical indication for cystic prolactinoma remains controversial. This study was performed to investigate the significance of surgery for cystic prolactinoma. A total of 28 patients that underwent transsphenoidal resection of prolactinoma between February 2004 and May 2016 were reviewed. Five consecutive patients with cystic prolactinoma were included in this study. Our surgical strategy for cystic prolactinoma was categorized as follows: first, when the purpose of surgical resection was normalization of the prolactin level, aggressive resection was performed; second, when volume reduction was essential to relieve the visual symptoms and headache, internal decompression was performed followed by DA therapy. The clinical outcomes were analyzed accordingly. All cystic prolactinoma were resected via the transsphenoidal approach without any complications, and all symptoms including visual impairment and hypogonadal activity were finally relieved combined with medication. Surgery for cystic prolactinoma could be a better option. Transsphenoidal surgery is relatively safe to remove the cystic prolactinoma, additionally it can normalize the prolactine level and achieve adequate and rapid decompression of optic chiasm. The risk of transsphenoidal surgery is highly dependent on the skill of the surgeon and treatment decision for cystic prolactinoma needs to be individualized for each patient.

Effects of the rapid decompression on intervention tourniquet on line via radial artery path of coronary artery

Objective To investigate the effect of the rapid decompression on intervention (TRI) of the TR Band tourniquet on line via radial artery path of coronary artery. Methods 270 postoperative patients with TRI were divided into A, B, C groups according to random number table. TR Band hemostat inflated 17 ml, group A deflated once every 30 min, group B deflated once every 1 hour, group C deflated once every 2 hours, inflated 2 ml each time, each group was deflated 6 times and removed oppression after 12 hours. The differences of postoperative bleeding, the local complications and comfort were observed 24 hours after surgery. Results The difference of patients with postoperative hemorrhage, degree of numbness among three groups was not statistical significant (χ2=0.25-0.78, P > 0.05). Difference of incidence on local fiber scleroma, palm and forearm swelling degree, pain intensity was statistical significant (χ2 =6.35, 7.70, 12.16, P < 0.05). Conclusions TRI rapid decompression does not increase the risk of bleeding in postoperative patients, which not only can reduce fiber scleroma local complications, still can improve the comfort. Key words: Radial artery; Intervention therapy; Oppression; TR Band

Endothelial dysfunction correlates with decompression bubbles in rats.

Previous studies have documented that decompression led to endothelial dysfunction with controversial results. This study aimed to clarify the relationship between endothelial dysfunction, bubble formation and decompression rate. Rats were subjected to simulated air dives with one of four decompression rates: one slow and three rapid. Bubble formation was detected ultrasonically following decompression for two hours, before measurement of endothelial related indices. Bubbles were found in only rapid-decompressed rats and the amount correlated with decompression rate with significant variability. Serum levels of ET-1, 6-keto-PGF1α, ICAM-1, VCAM-1 and MDA, lung Wet/Dry weight ratio and histological score increased, serum NO decreased following rapid decompression. Endothelial-dependent vasodilatation to Ach was reduced in pulmonary artery rings among rapid-decompressed rats. Near all the above changes correlated significantly with bubble amounts. The results suggest that bubbles may be the causative agent of decompression–induced endothelial damage and bubble amount is of clinical significance in assessing decompression stress. Furthermore, serum levels of ET-1 and MDA may serve as sensitive biomarkers with the capacity to indicate endothelial dysfunction and decompression stress following dives.

A geochemical contribution to the discussion about the genesis of impact-related pseudotachylitic breccias: Studies of PTB in the Otavi and Kudu Quarries of the Vredefort Dome support the“In Situ Formation”hypothesis

This work is aimed at contributing to the understanding of the formation of massive pseudotachylitic breccias (PTB) in impact structures. In the past this has been debated as being due to either melting of locally available country rocks or a combination of injection of impact melt from a higher level of the impact structure plus assimilation of other, including locally derived, material. Two occurrences of massive PTB in the Otavi and Kudu quarries of the outer crystalline core of the Vredefort Dome (South Africa) have been investigated petrographically and chemically. As shown in many previous studies of PTB, lithic and mineral clast populations only support derivation of PTB from local precursor material (granitic gneiss and amphibolite in the case of Kudu Quarry and various granitoids and a dolerite/amphibolite component in Otavi Quarry). The new major and trace element chemical systematics of melt rock and possible local precursors are fully consistent with this petrographic finding: in both cases PTB chemistry is readily explained by derivation from directly adjacent country rock, or mixtures of locally occurring granitoids and amphibolite. Harmonic least-squares mixing (HMX) calculations also do not indicate that additional components, such as a Vredefort Granophyre-like impact melt intrusive phase, contributed to the formation of these PTB. Absence of evidence (such as significant displacements along PTB developments) for the origin of PTB by friction melting along significant faults/shear zones is also recorded. As melting immediately after shock wave propagation (end of early compression stage of cratering), which is widely considered as the genetic process for shock vein formation in impact-affected rocks, including meteorites, does not apply to formation of such voluminous PTB, only local melting due to rapid decompression upon central uplift formation, followed by melt pooling in dilation sites, can be called upon to satisfactorily address PTB formation.

First-principles calculations of high-pressure phase transition of TiO2 during decompression: From baddeleyite-type TiO2 to α-PbO2-type TiO2

First-principles calculations were used to investigate the phase transition from baddeleyite-type to α-PbO2-type TiO2 during decompression. An intermediate structure was found, and its space group is Pbc21, which is polarized along [001]. The phase transition was mainly caused by oxygen diffusion, which has low activation energy for the phase transition. The activation energy increased as the pressure decreased. These results suggest that rapid decompression and preventing oxygen diffusion would be an effective way of recovering baddeleyite-type TiO2.

Experimental estimates of the energy budget of hydrothermal eruptions; application to 2012 Upper Te Maari eruption, New Zealand

Sudden hydrothermal eruptions occur in many volcanic settings and may include high-energy explosive phases. Ballistics launched by such events, together with ash plumes and pyroclastic density currents, generate deadly proximal hazards. The violence of hydrothermal eruptions (or explosive power) depends on the energy available within the driving-fluids (gas or liquid), which also influences the explosive mechanisms, volumes, durations, and products of these eruptions. Experimental studies in addition to analytical modeling were used here to elucidate the fragmentation mechanism and aspects of energy balance within hydrothermal eruptions. We present results from a detailed study of recent event that occurred on the 6th of August 2012 at Upper Te Maari within the Tongariro volcanic complex (New Zealand). The eruption was triggered by a landslide from this area, which set off a rapid stepwise decompression of the hydrothermal system. Explosive blasts were directed both westward and eastward of the collapsed area, with a vertical ash plume sourced from an adjacent existing crater. All explosions ejected blocks on ballistic trajectories, hundreds of which impacted New Zealand's most popular hiking trail and a mountain lodge, 1.4 km from the explosion locus. We have employed rocks representative of the eruption source area to perform rapid decompression experiments under controlled laboratory conditions that mimic hydrothermal explosions under controlled laboratory conditions. An experimental apparatus for 34 by 70 mm cylindrical samples was built to reduce the influence of large lithic enclaves (up to 30 mm in diameter) within the rock. The experiments were conducted in a temperature range of 250 °C–300 °C and applied pressure between 4 MPa and 6.5 MPa, which span the range of expected conditions below the Te Maari crater. Within this range we tested rapid decompression of pre-saturated samples from both liquid-dominated conditions and the vapor-dominated field. Further, we tested dry samples at the same pressure and temperature conditions. Results showed that host rock lithology and state of the interstitial fluid was a major influence on the fragmentation and ejection processes, as well as the energy partitioning. Clasts were ejected with velocities of up to 160 m/s as recorded by high-speed camera. In addition to rare large clasts (analogous to ballistics), a large amount of fine and very fine (<63 μm) ash was produced in all experiments. The efficiency of transformation of the total explosive energy into fragmentation energy was estimated between 10 to 15%, depending on the host rock lithology, while less than 0.1% of this was converted into kinetic energy. Our results suggest that liquid-to-vapor (flashing) expansion provides an order of magnitude higher energy release than steam expansion, which best explains the dynamics of the westward (and most energetic) directed blast at Te Maari. Considering the steam flashing as the primary energy source, the experiments suggested that a minimum explosive energy of 7×1010 to 2×1012 J was involved in the Te Maari blast.Experimental studies under controlled conditions, compared closely to a field example are thus highly useful in providing new insights into the energy release and hazards associated with eruptions in hydrothermal areas.

The Year Leading to a Supereruption.

Supereruptions catastrophically eject 100s-1000s of km3 of magma to the surface in a matter of days to a few months. In this study, we use zoning in quartz crystals from the Bishop Tuff (California) to assess the timescales over which a giant magma body transitions from relatively quiescent, pre-eruptive crystallization to rapid decompression and eruption. Quartz crystals in the Bishop Tuff have distinctive rims (<200 μm thick), which are Ti-rich and bright in cathodoluminescence (CL) images, and which can be used to calculate Ti diffusional relaxation times. We use synchrotron-based x-ray microfluorescence to obtain quantitative Ti maps and profiles along rim-interior contacts in quartz at resolutions of 1–5 μm in each linear dimension. We perform CL imaging on a scanning electron microscope (SEM) using a low-energy (5 kV) incident beam to characterize these contacts in high resolution (<1 μm in linear dimensions). Quartz growth times were determined using a 1D model for Ti diffusion, assuming initial step functions. Minimum quartz growth rates were calculated using these calculated growth times and measured rim thicknesses. Maximum rim growth times span from ~1 min to 35 years, with a median of ~4 days. More than 70% of rim growth times are less than 1 year, showing that quartz rims have mostly grown in the days to months prior to eruption. Minimum growth rates show distinct modes between 10−8 and 10−10 m/s (depending on sample), revealing very fast crystal growth rates (100s of nm to 10s of μm per day). Our data show that quartz rims grew well within a year of eruption, with most of the growth happening in the weeks or days preceding eruption. Growth took place under conditions of high supersaturation, suggesting that rim growth marks the onset of decompression and the transition from pre-eruptive to syn-eruptive conditions.

Primary and secondary fragmentation of crystal-bearing intermediate magma

Crystal-rich intermediate magmas are subjected to both primary and secondary fragmentation processes, each of which may produce texturally distinct tephra. Of particular interest for volcanic hazards is the extent to which each process contributes ash to volcanic plumes. One way to address this question is by fragmenting pyroclasts under controlled conditions. We fragmented pumice samples from Soufriere Hills Volcano (SHV), Montserrat, by three methods: rapid decompression in a shock tube-like apparatus, impact by a falling piston, and milling in a ball mill. Grain size distributions of the products reveal that all three mechanisms produce fractal breakage patterns, and that the fractal dimension increases from a minimum of ~2.1 for decompression fragmentation (primary fragmentation) to a maximum of ~2.7 by repeated impact (secondary fragmentation). To assess the details of the fragmentation process, we quantified the shape, texture and components of constituent ash particles. Ash shape analysis shows that the axial ratio increases during milling and that particle convexity increases with repeated impacts. We also quantify the extent to which the matrix is separated from the crystals, which shows that secondary processes efficiently remove adhering matrix from crystals, particularly during milling (abrasion). Furthermore, measurements of crystal size distributions before (using x-ray computed tomography) and after (by componentry of individual grain size classes) decompression-driven fragmentation show not only that crystals influence particular size fractions across the total grain size distribution, but also that free crystals are smaller in the fragmented material than in the original pumice clast. Taken together, our results confirm previous work showing both the control of initial texture on the primary fragmentation process and the contributions of secondary processes to ash formation. Critically, however, our extension of previous analyses to characterisation of shape, texture and componentry provides new analytical tools that can be used to assess contributions of secondary processes to ash deposits of uncertain or mixed origin. We illustrate this application with examples from SHV deposits.

Considerations in the management of giant frontal mucoceles with significant intracranial extension: A systematic review.

Giant frontal mucoceles, characterized by significant intracranial and/or intraorbital extension, can present with significant neurologic symptoms. Although typical mucoceles are managed endoscopically, giant mucoceles are often treated with an open or combined approach due to various concerns, including frontal lobe displacement, size, and rapid decompression of the intracranial component. The impact of significant intracranial extension on outcomes is not well described. This review studied key neurologic considerations in the management of giant frontal sinus mucoceles and analyzed outcomes of different management strategies. Systematic literature review by following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. Thirty-two articles, which represented 85 cases, met inclusion criteria. Neurologic symptoms on presentation ranged from headache (24.7%) and vision loss (12.9%) to extremity weakness (1.2%), frontal lobe syndrome (2.4%), and seizures (4.7%). Twenty-eight patients were treated endoscopically (34.1%), and 54 (65.9%) were treated with an external approach. Twenty-five of the open procedures included a craniotomy. Indications for the open approach included subdural empyema, enucleation, or large anterior table defects. Perioperative antibiotics were not consistently used. No perioperative seizures were reported with any approach. There were six cerebrospinal fluid leaks, all in the patients who underwent open procedures. The overall recurrence rate was 3.5%, with no recurrences reported in patients treated with an open approach. Follow-up ranged from 1 week to 8 years. Giant frontal mucoceles often present with various neurologic symptoms. Both open and endoscopic techniques offer excellent results. Endoscopic management is effective and preferred, except in special circumstances. An interdisciplinary team approach should be used to optimize surgical planning.