Slow Decompression Research Articles

Effect of compression and decompression rates during high hydrostatic pressure processing on inactivation kinetics of bacterial spores at different temperatures

We investigated the effect of changing compression and decompression rates of High Hydrostatic Pressure (HHP) treatments on inactivation of spores. Bacillus subtilis (PS832) spores were inoculated in Tris buffer, skimmed milk and orange juice. The samples were subjected to HHP treatments of 600 MPa for 3 min at 60 °C and 70 °C. Microbiological analyses were carried out at 0, 1, 7 and 15 days of refrigeration storage (4–5 °C). Flow cytometery technique was used for the estimation of sublethally injured population. After 15 days, all pressure treated matrices at 70 °C showed higher spore inactivation caused by slower compression rates as compared to faster ones. However, at 60 °C, the inactivation caused by slower compression was not significantly different from faster rates. Slow decompression was found to be more lethal in 60 °C and 70 °C HHP treated samples. It is concluded that slow compression combined with slow decompression has a greater impact on inactivation of B. subtilis spores than any combination of fast compression and fast decompression at 60 °C and 70 °C processing temperatures. However the population of sub-lethally injured cells was found to be higher with fast compression and slow decompression rates.

An analog investigation of magma fragmentation and degassing: Effects of pressure, volatile content, and decompression rate

We conducted analog experiments using gum rosin–acetone (GRA) mixtures to approximate behavior of magmas containing dissolved and exsolved volatiles. The main objective was to investigate the role of pressure upon fragmentation behavior for GRA mixtures undergoing slow and fast decompressions. We found that under conditions of slow decompression (22–80 Pa s − 1 ), the GRA mixture never fragmented, exhibiting characteristic styles of surface degassing at different pressures. Under fast decompression (620–2400 kPa s − 1 ), fragmentation behavior was controlled principally by the initial volatile content of the GRA mixture, as well as by the extent and rate of decompression. Low-viscosity GRA mixtures with high levels of acetone fragmented efficiently at high final pressures, while viscous mixtures containing less acetone did not fragment except when subjected to small final pressures, high pressure differentials, and rapid decompression. Based on our observations, we propose that GRA mixtures near the fragmentation threshold are disrupted in a ductile fashion by intense vesiculation and bubble movements, while mixtures subject to elevated pressure differentials which are significantly higher than this threshold fragment in a brittle manner due to foam disruption. In non-fragmenting GRA mixtures, a form of stick–slip behavior was observed, the dynamics of which varied with the rheology of the mixture and the pressure differential applied during the decompression. In low-viscosity GRA mixtures, gas transfer occurred mainly in the form of gas bubbles and slugs which moved vertically upward through the material, creating permeable pathways to promote degassing and disruption of the mixture by bubble bursts. In viscous GRA mixtures dominated by foam development, vertical permeability gradients were observed, with a strongly degassed brittle foam at the top and a less degassed ductile foam beneath. Our observations have implications for submarine volcanism, volcanoes on Venus, and lava dome eruptions. For submarine volcanism, our experiments show that explosive fragmentation of magma may not be limited by water depth if the volatile content of the magma is sufficiently high (i.e., 4–6 wt.% H 2O). Our experimental results also suggest that the high-pressure atmospheric conditions of Venus (9300 kPa) are not an impediment to the explosive eruption of high volatile content magmas, which casts doubt on the interpretation of large-volume pancake lava domes on Venus as the high-pressure equivalent of terrestrial ignimbrite eruptions. Together with our experimental results, observations of actively growing lava domes demonstrate that explosive fragmentation is promoted by rapid, large-volume collapses of a dome, and by unroofed magma which is comparatively volatile-rich and vesicular.

Pressure-induced phase transitions inL-alanine andDL-alanine, revisited

The effect of pressure on L-alanine and DL-alanine has been studied by X-ray powder diffraction, single-crystal X-ray diffraction, Raman spectroscopy and optical microscopy. No previously reported structural phase transitions in L-alanine and DL-alanine have been observed up to 12.3 and 8.3 GPa, respectively. In both compounds at about 1.5-2 GPa (close to the pressure of the previously reported phase transition in L-alanine into a tetragonal phase, 2.3 GPa [1], [2]), the cell parameters a and b become accidentally equal to each other, but without a change in the space group symmetry. Neither could be a polymorphic transformation in L-alanine from tetragonal into a monoclinic phase at about 9 GPa confirmed, the changes in the cell parameters till the highest measured pressures being continuous and the cell metrics remaining orthorhombic. Our Raman experiments confirmed the effects described previously for the spectra of L-alanine [1] and DL-alanine [3], but we have shown that the spectral changes are continuous and are not related to structural phase transitions. During a slow decompression of L-alanine single crystal (in a methanol-ethanol 4:1 mixture as a pressure-transmitting liquid) from about 6 GPa, new phases crystallized in the diamond anvil cell in the pressure range between 0.8-4.7 GPa, which recrystallized into L-alanine below 0.8 GPa. These previously unknown phases were characterized by powder X-ray diffraction and Raman spectroscopy and seem to be a solvate of L-alanine. The study was supported by a grant from RFBR (09-03-00451), a BRHE grant RUX0-008-NO-06, a FASI Contract № 02.740.11.5102 and Integration Projects SB RAS (№13 & 109). [1] A.M.R. Teixeira, P.T.C. Freire, A.J.D. Moreno, J.M. Sasaki, A.P. Ayala, J. Mendes Filho, F.E.A. Melo, Solid State Commun., 2000, 116, 405-409. [2] J.S. Olsen, L. Gerward, P.T.C. Freire, J. Mendes Filho, F.E.A. Melo, A.G. Souza Filho, J. Phys. Chem. Solids, 2008, 69, 1641-1645. [3] E.A. Belo, J.A. Lima Jr., P.T.C. Freire, F.E.A. Melo, J. Mendes Filho, H.N. Bordallo, A. Polian, Vibr. Spectr., 2010, 54, 107-111.

THE LOW-TEMPERATURE AND HIGH-PRESSURE THERMOELASTIC AND STRUCTURAL PROPERTIES OF CHALCOPYRITE, CuFeS2

The thermoelastic properties of a sample of chalcopyrite from the Palabora mine, South Africa, have been investigated in the temperature range 4.2 – 330 K at ambient pressure, and between 0.22 and 6.81 GPa at ambient temperature. Magnetization measurements indicated a transition to a second antiferromagnetically ordered phase in the region of 53 K; however, all attempts to characterize this magnetic phase by introducing an ordered moment onto the copper site were unsuccessful owing to the small magnitude of the refined magnetic moment. In agreement with other low-temperature crystallographic measurements made on non-antiferromagnetically ordered adamantine-structured semiconducting materials (group IV; I–VII, II–VI, III–V, I–III–VI2, II–IV–V2 compounds), chalcopyrite exhibits negative linear and volumetric thermal expansion over a significant temperature interval. Calculation of the speeds of sound for a number of high-symmetry wave vectors is consistent with Blackman’s model for negative thermal expansion. The unit-cell volume and isochoric heat-capacity have been fitted assuming a two-term Debye internal energy function, with consistent values being found for the two characteristic temperatures. The temperature dependence of the thermodynamic Gruneisen parameter shows a deep minimum of ~−3 at T/θ ~0.55 (θ is the Debye temperature at 0 K) and a high-temperature limit of ~0.7; these results are the first demonstration that a chalcopyrite-structured phase behaves in the characteristic manner of the simpler adamantine-structured semiconducting materials. No systematic variation in either the nuclear nor the magnetic structure was found between 4.2 and 330 K, and the vibrational Debye temperatures derived by fitting the temperature dependence of the isotropic atomic displacement parameters show no relationship to features in the phonon density of states function. The bulk modulus of chalcopyrite is 77(2) GPa, in good agreement with that determined by ab initio calculations and a recent X-ray-diffraction study, and its pressure derivative is 2.0(6). At high pressure, chalcopyrite remains antiferromagnetically ordered until 6.7(2) GPa, at which point a transition to an amorphous phase is observed. Slow decompression of this phase leads to only a limited recovery of the crystalline phase.

A new type of high-pressure low-flow metering valve for continuous decompression: First experimental results on degassing of rhyodacitic melts

A novel type of high-pressure low-flow metering valve has been designed for experiments at continuous decompression in internally heated pressure vessels (IHPV) at pressures up to 500 MPa and temperatures up to 1500 °C. It consists of a modified high-pressure valve coupled with a piezoelectric nanopositioning system. The piezoelectric actuator (1) positions the needle of the valve statically with very high precision on a nanometer scale for infinitesimally slow decompression and, alternatively, (2) opens and closes the valve completely, within milliseconds, to achieve a fast pressure drop only limited by the diameter of the high-pressure tubing and the entire volume of the autoclave system. The valve connected to an IHPV has been successfully tested to simulate continuous decompression of volatile-bearing magma. Water saturated rhyodacitic melt was synthesized at 1050 °C and 300 MPa and subsequently decompressed to 50 MPa at an integrated decompression rate of 0.28 MPa/s using continuous decompression as well as single-step and multi-step decompression techniques. The experimental results of the three methods show significant differences, having important implications for the interpretation of textures observed in natural volcanic rocks. Bubble number density (BND) values increase from continuous to multi-step and to single-step decompression by two orders of magnitude. Bubble size distribution (BSD) also differs significantly. The BSD curve of the single-step decompression shows largest variation both in size and in population number density, whereas the BSD trend for the sample of multi-step decompression shows the smallest variation between size and population density of bubbles. The BSD of the continuously decompressed sample indicates similar proportions of bubbles with different size. Channel formation in the sample of single-step decompression may indicate fluid escape from over-pressurized bubbles through the melt. Single-step and continuous decompression style represent two extreme cases of magma degassing in which bubble nucleation and bubble growth are predominant processes, respectively, whereas multi-step decompression resembles the intermediate case.

Anesthetic Concerns for Large Intracranial Cyst Excision: Expect the Unexpected!

The management of neurosurgical procedures for infants is always challenging for the anesthesiologists. We hereby present a case of a large ICSOL (intracranial space occupying lesion), suspected to be a hydatid cyst, which later turned out to be an infected ventricular cyst and intraoperative problems. We faced an unexpected problem of massive blood loss intraoperatively due to disease pathology. We conclude that a thorough preparation prior to operation of infected cystic lesion of the brain is required including anticipation of massive blood loss and its management. A slow decompression of the large cystic lesion should be done. doi:10.4021/jnr20e

Decoding-Aware Compression of FPGA Bitstreams

Bitstream compression is important in reconfigurable system design since it reduces the bitstream size and the memory requirement. It also improves the communication bandwidth and thereby decreases the reconfiguration time. Existing research in this field has explored two directions: efficient compression with slow decompression or fast decompression at the cost of compression efficiency. This paper proposes a novel decode-aware compression technique to improve both compression and de compression efficiencies. The three major contributions of this paper are: 1) smart placement of compressed bitstreams that can significantly decrease the overhead of decompression engine; 2) selection of profitable parameters for bitstream compression; and 3) efficient combination of bitmask-based compression and run length encoding of repetitive patterns. Our proposed technique outperforms the existing compression approaches by 15%, while our decompression hardware for variable-length coding is capable of operating at the speed closest to the best known field-programmable gate array-based decoder for fixed-length coding.

Anesthetic Concerns for Large Intracranial Cyst Excision: Expect the Unexpected!

The management of neurosurgical procedures for infants is always challenging for the anesthesiologists. We hereby present a case of a large ICSOL (intracranial space occupying lesion), suspected to be a hydatid cyst, which later turned out to be an infected ventricular cyst and intraoperative problems. We faced an unexpected problem of massive blood loss intraoperatively due to disease pathology. We conclude that a thorough preparation prior to operation of infected cystic lesion of the brain is required including anticipation of massive blood loss and its management. A slow decompression of the large cystic lesion should be done. J Neurol Res. 2011;1(2):78-80 doi: https://doi.org/10.4021/jnr20e

A new humane method of stunning broilers using low atmospheric pressure

SUMMARY The use of toxic gas mixtures to stun broiler chickens before exsanguination continues to be controversial. This controversy concerns which gas mixture to use, the required structural modifications to the processing plant, and whether the methods are actually more humane than electrical stunning. In response to these criticisms, a system was designed and constructed to produce a controlled atmosphere by using reduced oxygen tension. In all these systems, the birds are rendered unconscious from a lack of oxygen. Low atmospheric pressure is achieved by using controlled slow decompression, which allows the body of the bird to adjust to changes in pressure and thus lose consciousness with minimal discomfort. Advantages include the absence of toxic gases, minimal plant modifications, and the ability to view the birds throughout the process via digital video feed, which can be recorded.

Effect of syneruptive decompression path on shifting intensity in basaltic sub-Plinian eruption: Implication of microlites in Yufune-2 scoria from Fuji volcano, Japan

To constrain the timing and conditions of syneruptive magma ascent that are responsible for shifting eruption intensity, we have investigated a basaltic sub-Plinian eruption that produced Yufune-2 scoria in Fuji volcano 2200 years ago. We deduced magmatic decompression conditions from groundmass microlite textures, including decompression path (i.e. evolution in decompression rate) and approximate decompression rate, in order to relate them to eruption intensity. The microlites revealed decompression conditions after water saturation at 700–1100 m depth. The temporal change in scoria size indicates that the magma discharge rate and resultant eruption intensity increased from unit a to unit b, and then declined toward ending units d and e. The overall decompression rate in each eruptive unit has a positive correlation with eruption intensity. The variation in decompression rate was enlarged in the final units, where the maximum remained the same as the peak through the eruption (0.13–0.22 MPa/s for units b and c), while the minimum was 0.025 MPa/s. The large variation here is due to 1) variation in flow velocity across conduit and 2) part of the erupted magma in unit d experienced remarkably slow decompression (0.002–0.003 MPa/s) resulting from decreased overpressure in the reservoir following the major eruption of unit b. Furthermore, crystal size distribution (CSD) of microlites implied that the earliest erupted magma (unit a) had once been decompressed slowly (0.005–0.012 MPa/s), having been arrested by material in the conduit–vent system, which was followed by an increase in decompression rate due to removal of the material at the initiation of the eruption. In addition, the magma that had been ascending slowly before the unit-d eruption may record the increase in decompression rate. This increased rate resulted from being pushed up by the successive magma at the start of that eruption. Two factors had a major impact on eruption intensity. First, magma decompression rate determined the degree of gas-phase separation from ascending magma. Judging from CSD, different decompression rates had been generated at least at the start of microlite crystallization. The second factor is the conduit radius that, in combination with magma ascent rate, controlled the magma discharge rate. Before the major eruption of unit b, the conduit radius likely increased, as evidenced by xenoliths of basaltic lava and lithic fragments with the same petrography as the xenoliths in unit a. In unit e, the conduit radius decreased through inward development of high-density magma from the conduit margin.

Pressure-induced phase transitions in L-alanine, revisited

The effect of pressure on L-alanine has been studied by X-ray powder diffraction (up to 12.3 GPa), single-crystal X-ray diffraction (up to 6 GPa), Raman spectroscopy and optical microscopy (up to 6.4 GPa). No structural phase transitions in L-alanine have been observed. At about 1.5-2 GPa (close to the pressure of the previously reported phase transition into a tetragonal phase, 2.3 GPa [1], [2]), the cell parameters a and b become accidentally equal to each other, but without a change in the space group symmetry. Neither could be a polymorphic transformation into a monoclinic phase at about 9 GPa confirmed, the changes in the cell parameters till the highest measured pressures being continuous and the cell metrics remaining orthorhombic. Our Raman experiments confirmed the effects described previously for the spectra of L-alanine [1], but we have shown that the spectral changes are continuous and are not related to structural phase transitions. During a slow decompression of L-alanine single crystal (in a methanol-ethanol 4:1 mixture as a pressure-transmitting liquid) from about 6 GPa, a new phase crystallized in the diamond anvil cell in the pressure range between 3-5 GPa, which dissolved at about 2 GPa. This previously unknown phase was characterized by powder X-ray diffraction and Raman spectroscopy and seems to be a solvate L-alanine. The study was supported by a grant from RFBR (09-03- 00451), a BRHE grant RUX0-008-NO-06) and a FASI Contract (№ 02.740.11.5102). [1] Teixeira, A.M.R., Freire, P.T.C., Moreno, A.J.D., Sasaki, J.M., Ayala, A.P., Mendes Filho, J., Melo, F.E.A. Solid State Commun., 116 (7), 405. [2] Olsen, J.S., Gerward, L., Freire, P.T.C., Mendes Filho, J., Melo, F.E.A., Souza Filho, A.G, J. Phys. Chem. Solids, 2008, 69 (7), 1641.

Development of High Pressure Research Instrument for Keeping of Deep-Sea Multicellular Organisms

In this article, recompression induced resuscitation and atmospheric pressure acclimation of deep-sea multicellular organisms were investigated. Despite captured deep-sea organisms at depths between 910 m and 1,300 m sustain serious damage on decompression and exposure to high temperature of surface seawater, the organisms recovered by immediate re-compression until 5 MPa within 30 minutes after submersible bring back to mother ship. The re-pressurized deep-sea organisms can acclimatize at atmospheric pressure condition for a few months after slow decompression at a rate of −0.025 MPa/h. Furthermore, negative potential application induced antirust effect of pressure-stat aquarium system, which composed of stainless steel, was also described.

A Universal Placement Technique of Compressed Instructions for Efficient Parallel Decompression

Instruction compression is important in embedded system design since it reduces the code size (memory requirement) and thereby improves the overall area, power, and performance. Existing research in this field has explored two directions: efficient compression with slow decompression, or fast decompression at the cost of compression efficiency. This paper combines the advantages of both approaches by introducing a novel bitstream placement method. Our contribution in this paper is a novel compressed bitstream placement technique to support parallel decompression without sacrificing the compression efficiency. The proposed technique enables splitting a single bitstream (instruction binary) fetched from memory into multiple bitstreams, which are then fed into different decoders. As a result, multiple slow decoders can simultaneously work to produce the effect of high decode bandwidth. We prove that our approach is a close approximation of the optimal placement scheme. Our experimental results demonstrate that our approach can improve the decode bandwidth up to four times with minor impact (less than 3%) on the compression efficiency.

Postoperative intracerebral and intraventricular hemorrhages following removal of a chronic subdural hematoma

We report a patient with multiple intracerebral and intraventricular hemorrhages after removal of bilateral chronic subdural hematomas (CSDH). Possible mechanisms include a sudden increase in cerebral blood flow within fragile cerebral vessels following decompression of CSDH, defective vascular autoregulation, and damage to the cerebral vascular tree. Clinical awareness of this complication and slow decompression of CSDH are stressed.

A viscosity measurement during the high pressure phase transition in triolein

The high-pressure properties of triolein, a subject of extensive research at the Faculty of Physics of Warsaw University of Technology (WUT) have been enhanced by the results of viscosity measurement within the pressure range up to 0.8 GPa. For the measurement the authors have adopted a new ultrasonic method based on Bleustein-Gulyaev waves, successfully developed earlier for the low pressures in the Section of Acoustoelectronics of the Institute of Fundamental Technological Research. The measurements have shown: 1. Exponential rise of viscosity with pressure up to 0.5 GPa. 2. Extraordinary increment of viscosity at constant pressure during phase transition. 3. Further exponential rise of viscosity with pressure of the high-pressure phase of triolein. 4. The pressure exponents of the viscosity of both phases were different (the high-pressure phase had much smaller exponent). 5. The decomposition of the high pressure phase due to the slow decompression have shown very large hysteresis of viscosity on pressure dependence.

Pressure-induced structural changes and densification of vitreous MgSiO 3

Compression of MgSiO 3 glass in a 6/8 multianvil apparatus to 10.0 ± 0.5 GPa results in demonstrable changes in density and silicon coordination. Under high-pressure, samples were heated over a range of temperatures from 300 to 773 K, quenched to room temperature and decompressed at rates of 10.4 and 0.08 GPa/min. Recovered glasses have bulk densities that are 2.6–11.0% higher than the non-compressed glass. 29Si MAS NMR spectra of compressed glasses show narrowing of the [4]Si peak resulting from a reduction in the spread of the Si–O–Si bond angle distribution. After heating and rapid decompression, 29Si MAS NMR spectra of recovered glasses exhibit peaks assignable to [4]Si, [5]Si, and [6]Si with relative fractions of 0.945, 0.045, and 0.008, respectively. These changes in Si coordination and in Si–O–Si bond angle distribution with pressure only represent part of the structural changes associated with permanent densification of heated and unheated samples. The abundance of [6]Si is found to be insensitive to decompression rate, while [5]Si reverts to [4]Si on slow decompression at room temperature. These observations demonstrate that high-coordinated silicon species in MgSiO 3 glass are formed on compression below glass transition temperatures and that pressure-induced structural changes can be preserved with rapid decompression. The ease with which [5]Si reverts to [4]Si during decompression suggests that the conversion of [4]Si → [5]Si principally involves short-range atomic displacement. The reversible and irreversible features of densification of MgSiO 3 glass, provide insights into the fundamental structural and rheological properties of refractory silicate melts similar to those found in the Earth’s mantle.

Cell biology of deep-sea multicellular organisms

Establishing tissue cultures derived from deep-sea multicellular organisms has been extremely difficult because of the serious damage they sustain upon decompression and exposure to the high temperature of surface seawater. We developed a novel pressure-stat aquarium system for the study of living deep-sea multicellular organisms under pressure. Using this system, we have succeeded in maintaining a variety of deep-sea multicellular organisms under pressure and atmospheric conditions after gradual, slow decompression. Furthermore, we successfully cultivated and freeze-stocked pectoral fin cells of the deep-sea eel Simenchelys parasiticus collected at a depth of 1,162 m under atmospheric pressure conditions. This review describes novel capture and maintenance devices for deep-sea organisms and cell culture studies of the organisms under atmospheric and pressure conditions.

生物と高圧科学 ― 深海生物の分子細胞生物学 ―

To investigate molecular and cellular biology of deep-sea multicellular organisms, the author has developed a novel piezo-stat aquarium system (Deep Aquarium System). Using this system, the author succeeded in maintaining a variety of deep-sea multicellular organisms under pressure and under atmospheric conditions after gradual and slow decompression. Furthermore, the author successfully cultivated pectoral fin cells of a living deep-sea fish that decompressed to atmospheric pressure. The deep-sea fish cells passaged more than 20 times and were succeeded in freeze storage under atmospheric condition. The deep-sea fish cells have greater pressure tolerance abilities than conger eel and mouse cells.

Effects of Supercritical Carbon Dioxide on Adhesive Strength between Micro-sized Photoresist Patterns and Silicon Substrates

AbstractAdhesive bend testing for micro-sized photoresist components has been performed to clarify the effects of supercritical CO2 (ScCO2) treatment. Multiple microsized cylindrical specimens were fabricated on a silicon substrate using epoxy-type photoresist. The specimens were ScCO2 treated at a temperature of 323K at a pressure of 15MPa for 30 min, and then, decompressed to atmospheric pressure at two different rates. Double refraction appeared in the SU-8 specimens near by the interface between the SU-8 specimens and a substrate after ScCO2 treatment. Adhesive bend strength of ScCO2 treated specimen with slow decompression process is approximately 60% higher than that of non- ScCO2 treated specimens, however, the strength of the microsized photoresist was slightly degraded by ScCO2 treatment with quick decompression process. All the results suggest that ScCO2 treatment improves the adhesive strength between microsized photoresist components and a silicon substrate by control of the decompression process.

Influence of decompression rate on the expansion velocity and expansion style of bubbly fluids

The decompression rate of magma is correlated with explosivity of volcanic eruptions. We present a series of decompression experiments in a shock tube apparatus to investigate the effect of decompression rate on the expansion and eruption style of bubbly fluids. We also consider the effects of the pressure change ΔP and initial vesicularity ϕi. As an analogue for magma we use viscoelastic polymer solutions. For fast decompression, we observe fragmentation and rupture of bubble walls only for large ΔP and large ϕi. For slow decompression, however, bubbles maintain spherical shapes, and the bubbly fluid does not fragment, irrespective of ΔP and ϕi. We consider two theoretical estimates for the expansion of bubbles, which we refer to as “equilibrium expansion,” in which the pressures inside and outside the bubbles are assumed to be equal, and “disequilibrium expansion,” in which the enthalpy change caused by the pressure change is converted into kinetic energy. The observed expansion velocity is governed by the slower estimate. For slow decompression, where bubbles expand while maintaining their spherical shape, the measured expansion is well explained by equilibrium expansion. In contrast, for fast decompression, in which we observe the rupture of bubble walls and fragmentation, the expansion follows disequilibrium expansion. We conclude that the disequilibrium estimate is an upper limit velocity for the bubble expansion and fragmentation and the rupture of bubble walls require disequilibrium expansion. The calculated threshold decompression rate for disequilibrium expansion is consistent with the estimated decompression rate for the explosive/effusive transition in natural basaltic eruptions.