Rapid Pressure Changes Research Articles

A New Method to Record Subglottal Pressure Waves: Potential Applications

Summary: Rapid subglottal pressure changes related to the glottal cycles influence the aerodynamics of phonation. Various methods to measure these have been developed, but are not practical for routine phoniatric use. For that reason, a noninvasive measurement tool is necessary. This article presents a technique that uses a microphone positioned at the skin of the jugular fossa to record the signal which arises in the subglottal spaces and is transmitted through the soft tissue to the surface of the skin. Using the program Glottal Segmentation of Voice and Speech, jugular microphone recordings from two healthy subjects were compared with simultaneously recorded direct intratracheal measurements during the same phonation. A systematic error arising from the transmission properties of the microphone and the soft tissue leads to phase and amplitude deviations. These must be taken into account and require correction. This correction procedure leads to high correlations and a good agreement between the two signals. Even without this correction the jugular microphone measurements proved to be useful as a diagnostic and a therapeutic tool in cases where chest resonance specific processes appear affected. In addition, they offer material for research purposes. Although based on a small number of subjects, the new method shows a good validity; testing on a larger number of subjects will probably strengthen the validity.

Viscoelastic effects in dynamics of concentration fluctuations in dynamically asymmetric polymer blends

Relaxation processes of the concentration fluctuations induced by a rapid pressure change were investigated for a dynamically asymmetric polymer blend (deuterated polybutadiene (DPB) / polyisoprene (PI)) with a composition of 50/50 by weight in one phase region by using time-resolved small-angle neutron scattering. The theoretical analysis yielded the wave-number q-dependence of Onsager kinetic coefficient which is characterized by a q -2-dependence at qξ ve >1 with the characteristic length ξ ve being much larger than radius of gyration of DPB or PI. The estimated ξ ve agrees well with that calculated using the theory by Doi & Onuki, which takes into account viscoelastic effects.

Constraints on the composition of ore fluids and implications for mineralising events at the Cleo gold deposit, Eastern Goldfields Province, Western Australia

The Cleo gold deposit, 55 km south of Laverton in the Eastern Goldfields Province of Western Australia, is characterised by banded iron‐formation (BIF)‐hosted ore zones in the gently dipping Sunrise Shear Zone and high‐grade vein‐hosted ore in the Western Lodes.There is evidence that gold mineralisation in the Western Lodes (which occurred at ca 2655 Ma) post‐dates the majority of displacement along the Sunrise Shear Zone, but it remains uncertain if the ore in both structures formed simultaneously or separately. Overall, the Pb, Nd, Sr, C, O and S isotopic compositions of ore‐related minerals from both the Western Lodes and ore zones in the Sunrise Shear Zone are similar. Early low‐salinity aqueous‐carbonic fluids and late high‐salinity fluids with similar characteristics are trapped in inclusions in quartz veins from both the Sunrise Shear Zone and the Western Lodes. The early CO2, CO2–H2O, and H2O‐dominant inclusions are interpreted as being related to ore formation, and to have formed from a single low‐salinity aqueous‐carbonic fluid as a result of intermittent fluid immiscibility. Homogenisation temperatures indicate that these inclusions were trapped at approximately 280°C and at approximately 4 km depth, in the deeper epizonal range. Differences between the ore zones are detected in the trace‐element composition of gold samples, with gold from the Sunrise Shear Zone enriched in Ni, Pb, Sn, Te and Zn, and depleted in As, Bi, Cd, Cu and Sb, relative to gold from the Western Lodes. Although there are differences in gold composition between the Sunrise Shear Zone and Western Lodes, and hence the metal content of ore fluids may have varied slightly between the different ore zones, no other systematic fluid or solute differences are detected between the ore zones. Given the fact that the ore fluids in each zone have very similar bulk properties, the considerable differences in gold grade, sulfide mineral abundance, and ore textures between the two ore zones most likely result from different gold‐deposition mechanisms. The association of ore zones in the Sunrise Shear Zone with pyrite‐replaced BIF suggests that wall‐rock sulfidation was the most significant mechanism of gold precipitation, through the destabilisation of gold‐bisulfide complexes. The Western Lodes, however, do not exhibit any host‐rock preference and multistage veins commonly contain coarse‐grained gold. Fluid‐inclusion characteristics and breccia textures in veins in the Western Lodes suggest that rapid pressure changes, brought about by intermittent release of overpressured fluids and concomitant phase separation, are likely to have caused the destabilisation of gold‐thiocomplexes, leading to formation of higher‐grade gold ore zones.

Unsteady Combustion of Layered Condensed Systems. Parallel Burning of Components

A model of unsteady combustion of a “sandwich”:‐type layered condensed system consisting of parallel layers of simultaneously burning components capable of self‐sustaining combustion is considered. The response function of the mass burning rate of the system to periodic pressure oscillations with allowance for the interaction between the components caused by the difference between their burning rates is found. In the linear approximation, combustion of such systems under a rapid change in pressure is analyzed. It is shown that the pattern and duration of these processes depend on the ratio of the layer thickness of the slowly burning component and the thickness of its heated layer. It is found that bending of the burning surface of components in the course of unsteady combustion of the layered condensed system can substantially affect the pattern of its unsteady combustion as a whole, in particular, enhance or reduce its stability.

Cerebral haemodynamics in obstructive sleep apnoea and Cheyne-Stokes respiration.

Obstructive sleep apnoeas are common among stroke patients and, as different from central apnoeas, they do not decline during stroke rehabilitation. Cerebral and cardiovascular changes display a different pattern during central and obstructive sleep apnoeas. The cerebral blood flow velocity according to transcranial Doppler increases during an obstructive apnoea and decreases after apnoea termination concomitant with changes in arterial pressure. The changes in cerebral circulation during obstructive apnoeas could be an immediate effect of rapid changes in blood pressure because cerebral autoregulation is overridden. Low cerebral blood flow, low arterial pressure and hypoxemia after apnoea termination may predispose to nocturnal cerebral ischaemia. The opposite pattern is seen during a central apnoea, with a decrease in cerebral blood flow velocity during apnoea and an increase after apnoea termination. Changes during obstructive apnoeas are probably hazardous, with adverse cardiovascular effects including stroke. This may not be the case during central apnoeas, as Cheyne-Stokes respiration with central apnoeas is a result of an underlying disorder such as heart failure and stroke and is not a disease entity in itself. It is suggested that obstructive sleep apnoea is a risk factor for stroke as it is common among stroke victims and cerebral hypoperfusion occurs after an obstructive apnoea. The treatment of sleep apnoea should also be taken into account among stroke patients. Large cohort studies, treatment studies and further studies of possible mechanisms for apnoea-induced stroke are, however, essential in order to evaluate whether obstructive sleep apnoea is an independent risk factor for stroke.

A novel pressure-jump apparatus for the microvolume analysis of protein-ligand and protein-protein interactions: its application to nucleotide binding to skeletal-muscle and smooth-muscle myosin subfragment-1.

Reactions involving proteins frequently involve large changes in volume, which allows the equilibrium position to be perturbed by changes in pressure. Rapid changes in pressure can thus be used to initiate relaxation in pressure; however, this approach is seldom used, because it requires specialized equipment. We have built a microvolume (50 microl) pressure-jump apparatus, powered by a piezoelectric actuator, based on the original design of Clegg and Maxfield [(1976) Rev. Sci. Instrum. 47, 1383-1393]. This equipment can apply pressure changes of +/-20 MPa (maximally) in time periods as short as 80 micros and follow the resulting change in fluorescence signals. The system is relatively simple to use with fast (approx. 1 min) exchange of samples. In the present study, we show that this system can perturb the binding of 2'(3')-O-(N-methylanthraniloyl)-ADP to myosin subfragment-1(S1) from skeletal and smooth muscles. The kinetic data are consistent with previous work, and in addition show that, although 2'(3')-O-(N-methylanthraniloyl)-ADP binds with a similar affinity to both proteins, the increase in molar volume for the skeletal-muscle S1 binding to ADP is half of that for the smooth-muscle protein. This high-volume change for smooth-muscle S1 may be related to the ability of ADP to induce a 23 degrees tilt in the tail of S1 bound to actin.

Role of central command in carotid baroreflex resetting in humans during static exercise.

The purpose of the experiments was to examine the role of central command in the exercise-induced resetting of the carotid baroreflex. Eight subjects performed 30 % maximal voluntary contraction (MVC) static knee extension and flexion with manipulation of central command (CC) by patellar tendon vibration (PTV). The same subjects also performed static knee extension and flexion exercise without PTV at a force development that elicited the same ratings of perceived exertion (RPE) as those observed during exercise with PTV in order to assess involvement of the exercise pressor reflex. Carotid baroreflex (CBR) function curves were modelled from the heart rate (HR) and mean arterial pressure (MAP) responses to rapid changes in neck pressure and suction during steady state static exercise. Knee extension exercise with PTV (decreased CC activation) reset the CBR-HR and CBR-MAP to a lower operating pressure (P < 0.05) and knee flexion exercise with PTV (increased CC activation) reset the CBR-HR and CBR-MAP to a higher operating pressure (P < 0.05). Comparison between knee extension and flexion exercise at the same RPE with and without PTV found no difference in the resetting of the CBR-HR function curves (P > 0.05) suggesting the response was determined primarily by CC activation. However, the CBR-MAP function curves were reset to operating pressures determined by both exercise pressor reflex (EPR) and central command activation. Thus the physiological response to exercise requires CC activation to reset the carotid-cardiac reflex but requires either CC or EPR to reset the carotid-vasomotor reflex.

Pregnancy and acute baroreflex resetting in conscious rabbits.

To test the hypothesis that acute resetting of baroreflex control of heart rate (HR) is enhanced during pregnancy, we determined whether the rightward shift in the baroreflex relationship between arterial pressure and HR after arterial pressure is raised [~25 mmHg for 30 min, due to infusion of phenylephrine (PE) or methoxamine (Meth)] is greater in late pregnant compared with nonpregnant conscious rabbits. Baroreflex function was assessed by monitoring HR responses to both stepwise steady-state changes (n = 14) and rapid ramp changes (n = 10) in arterial pressure. Pregnancy decreased reflex gain, increased reflex minimum HR, and shifted the curves to a lower pressure level, when either the steady-state or ramp method was used (all changes, P < 0.05). When PE was used to increase pressure, resetting of steady-state curves was observed both before and during pregnancy, but the magnitude of the resetting was less in the pregnant rabbits. Further inspection of the data revealed that the size of the shift in pregnant rabbits was inversely related to the dose of PE. Because the pressure rise was the same in all experiments, PE appears to nonspecifically counteract acute resetting. When Meth was used instead to increase pressure, resetting of steady-state curves was similar in pregnant and nonpregnant rabbits and was unrelated to dose. Similarly, when reflex curves were generated using the ramp method, and either Meth or low doses of PE were used to increase pressure, no differences in the degree of resetting were observed between pregnant and nonpregnant rabbits. In summary, high doses of PE counteract acute resetting of baroreflex control of HR. More importantly, while baroreflex function is depressed, the ability of the baroreflex to reset appears to be preserved during pregnancy.

Effect of Bearing Surroundings on the High-Speed Spindle-Bearing Compliance

This paper investigates the effect of bearing assembly tolerance on spindle-bearing compliance. In a high-speed spindle system, the bearing characteristics are influenced significantly by the initial assembly tolerances and the thermal deformation of the bearing surroundings. In the very early stage of spindle operation, spindle bearings could be under hazardous conditions owing to the rapid change of the internal pressure resulting from thermal deformation or centrifugal force-oriented deformation. The bearing's internal clearance also may be changed by the operating conditions such as external load, rotational speed, and operating cycle time. To determine the initial tolerance and the optimal cooling regimen, a comprehensive dynamic modelling and analysis of a high-speed spindle system in terms of bearing pressure, bearing compliance, and heat generation is required with consideration of those effects. Moreover, in order to predict spindle characteristics in operation, all of these parameters should be monitored and recalculated in real-time. For this purpose, very simple and effective equations are suggested, representing the bearing stiffness in accordance with the thermal deformation. Most former bearing analyses were based on the Hertzian contact model, without considering the radial elastic deformation of the races. In this paper, analytical and experimental investigations of the bearing compliance are conducted with consideration of both the elastic deformation of the race and the thermal deformation of the housing in terms of the bearing stiffness. The experimental results show the effectiveness of the proposed equations, which are simple and useful for fast calculation of the bearing stiffness by dynamic simulation.

A Survey of large, rapid solar wind dynamic pressure changes observed by Interball-1 and IMP 8

Abstract. The high time-resolution solar wind ion flux measurements from Interball-1 and IMP 8 show about one hundred large, rapid dynamic the pressure changes each year. We cataloged these events by the size and transition time of the pressure changes and present a statistical survey of these events. We find that the majority of the pressure changes of more than 1–2 nPa occur over a very short time period, on the order of a few minutes or less. Most of the large pressure changes not associated with shocks are due solely to density changes with speed remaining constant. We find that pressure balance between the thermal and magnetic pressures is not maintained across most of these events, so these events are still evolving.Key words. Interplanetary physics (solar wind plasma)

Blending Information and Communication Technology with Accounting Research

INTRODUCTION The purpose of this commentary is to explore how information and communication technologies (ICT) have forever changed many aspects of business and accounting practice and, as a result, offer new and exciting research opportunities to accounting professionals and academics. In today's computerized, interconnected, global business environment, the accounting profession must deal with a host of complex issues that never existed in the past--for instance, how to capture and record new business transactions and events, develop value-added business and information processes, create new value-chain and supply-chain opportunities, disseminate useful knowledge to a wide array of information consumers, and provide assurance services across the entire spectrum of economic activities reflect some of the more compelling topics of interest. Accounting researchers can add value to the profession by investigating these issues, among others, and presenting scientific results in a clear and understandable fashion to practicin g accountants. An important message of this commentary is that researchers in accounting information systems (AIS) and other areas of accounting, such as financial, auditing, tax, and managerial, should work together on projects, as each party can learn a great deal from the other. Synergistic relationships arising from such teamwork hold great potential to yield high-quality research results that can have notable impact on the accounting profession. THE NEW BUSINESS AND ACCOUNTING LANDSCAPE Over the past centuries, business practices and accounting procedures developed and matured a great deal, yet at a relatively predictable, slow, and controlled rate. We stand squarely, proudly, and respectfully on the broad shoulders of those who came before us, as their guidance, wisdom, and insight masterfully steered us to this place and time in the profession. However, in the apparent twinkling of an eye, ICT has disrupted our peaceful existence by radically transforming the manner in which business is conducted across the world and alerting us to the many challenges that lay ahead. How Technology Affects Business Practice There is little doubt that ICT has contributed immensely to the magnitude, speed, and acceleration of change in business practice over the past three decades. Rapid changes in the business world place immense pressure on business executives to stay ahead of the competition by leveraging JOT to dramatically and continually redesign business processes and models. Using ICT to Create a Digitally Integrated Entity Figure 1 depicts an JOT infrastructure that envelopes and permeates the inputprocess-output value chain of a business entity. Encapsulated by this JOT infrastructure, digitally integrated business entities capture economic events as they unfold, process information with instantaneous speed and ubiquitous availability, and disseminate valuable decision-making information and knowledge throughout the organization. The blending of JOT and business process integration manifests itself in enterprise resource planning (ERP) systems, which serve as the foundation for linking multiple, related business entities into integrated supply chains. Using ICT to Integrate the Conventional Supply Chain When related entities link their internally integrated information systems to one another, the value of the interconnected network potentially becomes greater than the sum of the participating firms' isolated systems. The supply chain illustrated in Figure 2 depicts how a digitally integrated business environment might look, assuming that conventional relationships among upstream and downstream partners remain intact. Suppliers can monitor upcoming production schedules of manufacturers to ensure that the proper amount and mix of raw materials arrive on time where needed. Upon receipt of raw materials, the manufacturer could send electronic payment to the suppliers. …

Viscoelastic effects in relaxation processes of concentration fluctuations in dynamically asymmetric polymer blends.

Relaxation processes of the concentration fluctuations induced by a rapid pressure change were investigated for a dynamically asymmetric polymer blend [deuterated polybutadiene (DPB)/polyisoprene (PI)] with a composition of 50-50 by weight by using time-resolved small-angle neutron scattering. The pressure change was carried out inside the single-phase of the blend with the cell designed for polymeric systems under high pressure and temperature. Time change in the scattered intensity distribution with wave number (q) during the relaxation processes was found to be approximated by Cahn-Hilliard-Cook linearized theory. The theoretical analysis yielded the q dependence of Onsager kinetic coefficient that is characterized by the q(-2) dependence at q(xi)(ve)>1 with the characteristic length xi(ve) (with xi(ve) being the viscoelastic length) being much larger than radius of gyration of DPB or PI. The estimated xi(ve) agrees well with that calculated using the Doi and Onuki theory that takes into account the viscoelastic effects arising from the dynamical asymmetry between the component polymers in the relaxation of concentration fluctuations.

108 エレベーター用気圧制御システムの開発

When the passenger goes up and down a skyscraper by elevator, over 600m speed in a minute, he feels unpleasant by rapid atmospheric pressure change, sometimes he may feel a ache of tympanic membrance even. In order to soften it, a system which controls the atmospheric pressure inside the elevator car is proposed. To investigate which pattern of atmospheric pressure change is the most effective, we provided the atmospheric pressure control chamber and using the chamber we did some monitor examination. In this report, I will describe about the result and the validity of air pressure control of car. And moreover I will mention about the structure of cage which can realize the air pressure Control system.

Effect of bearing support structure on the high-speed spindle bearing compliance

This paper investigates the effect of bearing assembly tolerance on the spindle–bearing compliance. In a high-speed spindle system, the bearing characteristics are significantly influenced by the initial assembly tolerance and the thermal deformation of the bearing support structure. In particular, in the very early stage of spindle operation, spindle–bearings could be under hazardous conditions due to the rapid change of the internal pressure resulting from the thermal deformation or the centrifugal force-oriented deformation. The bearing's internal clearance may be also changed with the operating conditions such as external load, rotational speed and operating cycle time. To determine the initial tolerance and the optimal cooling regimen, a comprehensive dynamic modeling and analysis of the high speed spindle system in terms of bearing pressure, bearing compliance and heat generation is required with consideration to those effects. Furthermore, in order to predict spindle characteristics in operation, all of these parameters should be monitored and recalculated in real time. For this purpose, simple and effective equations have been suggested, representing the bearing stiffness in accordance with the thermal deformation. Moreover, contrast to the former bearing analyses which are mostly based on the Hertzian contact model without considering the radial elastic deformation of the races, this paper presents the analytical and experimental investigations on the bearing compliance with additional consideration to both the elastic deformation of the race and the thermal deformation of the housing in terms of the bearing stiffness. The experimental results show the effectiveness of the proposed equations, which will provide a very simplified calculation of the bearing stiffness in dynamic simulation.

Geomagnetic field response along the Polar orbit to rapid changes in the solar wind dynamic pressure

Magnetometer observations on board the Polar spacecraft have been used to measure the magnetospheric response to rapid changes in the dynamic pressure of the solar wind. Over much of the magnetosphere the magnetic field increases when the solar wind dynamic pressure increases, roughly in proportion to the square root of the change of the solar wind dynamic pressure with a proportionality similar to that seen in ground‐based data. Nevertheless, dynamic pressure increases can lead to reductions in the magnitude of the magnetic field. These reductions occur on the dayside polar field lines, where the magnetospheric field points southward while the perturbation field due to the magnetopause current is northward. Throughout most of the magnetosphere these changes occur slowly over ∼ 5–10 min as the interplanetary shock envelopes the dayside magnetosphere and near tail. Compressions of the magnetosphere generally lead to increases in the intensity of the ULF waves along the field lines, but in one case the wave intensity decreased upon compression of the field. This decrease occurred in the predawn sector while the increases occurred in the noon to postdusk sector.

Fluid transients and fluid-structure interaction in flexible liquid-filled piping

Fluid-structure interaction in piping systems (FSI) consists of the transfer of momentum and forces between piping and the contained liquid during unsteady flow. Excitation mechanisms may be caused by rapid changes in flow and pressure or may be initiated by mechanical action of the piping. The interaction is manifested in pipe vibration and perturbations in velocity and pressure of the liquid. The resulting loads imparted on the piping are transferred to the support mechanisms such as hangers, thrust blocks, etc. The phenomenon has recently received increased attention because of safety and reliability concerns in power generation stations, environmental issues in pipeline delivery systems, and questions related to stringent industrial piping design performance guidelines. Furthermore, numerical advances have allowed practitioners to revisit the manner in which the interaction between piping and contained liquid is modeled, resulting in improved techniques that are now readily available to predict FSI. This review attempts to succinctly summarize the essential mechanisms that cause FSI, and present relevant data that describe the phenomenon. In addition, the various numerical and analytical methods that have been developed to successfully predict FSI will be described. Several earlier reviews regarding FSI in piping have been published; this review is intended to update the reader on developments that have taken place over the last approximately ten years, and to enhance the understanding of various aspects of FSI. There are 123 references cited in this review article.

Spontaneous arousals during quiet sleep in piglets: a visual and wavelet-based analysis.

The objectives of the study were to characterize spontaneous arousals during NREM sleep in piglets and to compare two methods of identifying these events: a "visual" technique using spectral analysis and an automated technique using wavelets. Our goal was to understand the benefits and limits of these methods when applied to sleep in human infants. Arousals were identified by evaluating rapid changes in EEG low frequency activity, blood pressure (BP), and heart rate (HR). A cortical arousal was defined as a rapid decrease in EEG low frequency activity. An autonomic arousal was defined by a transient increase in heart rate or a transient change in mean arterial BP (MAP). Laboratory study in sleeping and awake piglets. Five 1-2 week old piglets. Chronically instrumented with a femoral arterial line, EEG, EOG, EMG electrodes, and a micro-dialysis probe with its tip located in the rostral ventral medulla. Artificial CSF (aCSF) was dialyzed into the RVM throughout the experiments Measurements: For the visual analysis, the average delta power (0.5-4 Hz) for each 5-second epoch was determined using spectral analysis. MAP and HR were analyzed in 1-second bins. Video images were analyzed for body movements and eye openings. Transient changes in blood pressure, HR, and delta power were then visually identified. For the wavelet analysis, a quantitative, automated technique with a defined "wakefulness threshold" was used to identify rapid decreases in EEG low frequency activity and the rate of change of MAP. Using the visual method, 117 episodes associated with stereotypical hemodynamic, EEG, and behavioral changes (startle) were identified. Seventy five events occurred in isolation or were first in a series of "multiple" events, 41 "multiple" events were defined as events occurring <20 seconds following a previous event. Eighteen events were associated with the termination of apnea. In isolated events or those occurring first in a series, the onset of changes in HR and BP clearly preceded the decrease in EEG amplitude and delta power. Using wavelet analysis, 73 EEG arousals and 115 MAP transients were identified independently; 62% of the EEG events were associated with a transient change in MAP and HR, and in these cases the onset of the hemodynamic events preceded EEG arousals. EEG arousals and MAP transients, however, also occurred alone and not associated with a stereotypical pattern of a startle, changes in MAP and HR and the EEG. Many of these spontaneous arousals represent integrated EEG, hemodynamic, and behavioral processes similar to arousal phenomena described in adult rats and human infants, but the pattern of spontaneous arousals appears to be more heterogeneous than has been described for arousals induced by exogenous stimuli. Both the visual and wavelet analysis identified these events, but the wavelet technique has the potential advantage of better time resolution and automation of the analysis.

Topographic Distortion of a Cold Front over the Snake River Plain and Central Idaho Mountains

The topographic distortion of a cold front over the Snake River Plain (SRP) and central Idaho Mountains on 3 December 1998 is described using high-density surface observations from MesoWest, a collection of meteorological networks over the western United States. Although relatively unperturbed upstream of central Idaho, the cold front became distorted as it was deflected and accelerated up the low-elevation SRP, where a pronounced frontal bulge developed. The speed of the cold front over the SRP was comparable to the magnitude of the postfrontal winds that, due to terrain channeling, were oriented normal to the front. Meanwhile, the front advanced more slowly over the central Idaho mountains and southwest Montana, becoming increasingly diffuse over the former. Eventually, cold air surrounded the central Idaho Mountains and the two portions of the cold front merged over eastern Idaho. The cold front intensified as it moved from the eastern to central SRP, with rapid changes in temperature and pressure observed at locations in the southern half of the SRP. Intensification of the cross-frontal temperature gradient in this region appeared to be the result of confluence between southerly prefrontal winds, which experienced downslope warming to the lee of the Jarbidge–Caribou Highlands, and terrain-channeled postfrontal winds. Although the rapid changes in temperature and pressure suggested that the front developed the local structure of a gravity current, the frontal motion over the SRP was not consistent with gravity current theory and instead appeared to be the result of advection of the front by the terrain-induced flow field. The case study illustrates the value of high-density and multielevation MesoWest observations for advancing knowledge of frontal evolution over the western United States and improving operational surface analyses. Such observations aid in the identification of large-scale airmass and circulation changes that can be masked by boundary layer processes, valley inversions, and local and mesoscale terrain-induced wind systems.

Linking of regional and local hydrothermal systems in the mid-crust by shearing and faulting

The concentration of mass during regional metamorphism and metallogenesis requires interactions between regional and local hydrothermal systems that are scale- and time-dependent. During regional low- to medium-temperature metamorphism in which fluid flow is driven by broad thermal or mechanical gradients, fluid flow rates are (on average) <10 −8 m/s, and are limited by restricted permeabilities and gentle gradients in hydraulic head. In contrast, coseismic fluid flow rates in major fault zones may reach ≥10 −2 m/s. As a consequence, there may be a limited capacity for individual faults to substantially control fluid flow in the region because of the large contrast in flow rates and permeabilities between faults and low permeability rocks. To produce a major epigenetic ore deposit in overpressured crust, fluid flow systems with such diverse flow rates must interact in such a way that metal dissolution and transport from regional fluid flow systems culminate in focused fluid flow with metal deposition. This is best achieved through two steps; one in which km-scale hydrothermal systems channel into 100 m-scale ductile shear zones largely by reaction- and deformation-enhanced permeability in the shear zone; and a second one in which rapid fluid pressure changes accompanying brittle faulting (or intense shearing) within the broader shear zones causes metal deposition and ore genesis.

Kinetic methods in studying the defect concentration and their mobility in non-stoichiometric metal sulphides

The chemical diffusion coefficient and point defect concentration in metal-deficit manganous sulphide (Mn1−yS) has been studied using re-equilibration kinetics and Rosenburg's method. Measurements have been carried out in a microthermogravimetric apparatus of a new generation, enabling to make rapid changes of sulphur vapour pressure in the reaction chamber and determine the mass changes of a given sample with the high accuracy, up to 10−7 g. Using this device deviations from stoichiometry, chemical diffusion in metal-deficit manganous sulphide was investigated, as a function of temperature (973–1273 K) and sulphur activity (10−2–104 Pa). From obtained data, the self-diffusion coefficient of cations in Mn1−yS has been calculated as a function of temperature and sulphur activity.