Pressure Pockets Research Articles

Deciphering cometary outbursts: linking gas composition changes to trigger mechanisms

ABSTRACT Dust and gas outbursts are recurrent cometary phenomena, playing a crucial role in shaping the coma. Proposed outburst trigger mechanisms include cliff collapse, pressure pockets, and amorphous-to-crystalline phase transition of water ice; however, the underlying processes remain inadequately understood. In this study, we analyse Rosetta/ROSINA data from multiple outbursts on comet 67P/Churyumov-Gerasimenko and present the evolution of the gas composition in the comet’s coma during outburst events. We distinguish two distinct categories of cometary outbursts on the comet: water-driven events characterized by rapid (minutes to hours) changes in coma composition, and CO2-driven events displaying a slow, prolonged (hours to days) increase in highly volatile species. We tentatively associate these different gas composition patterns with different trigger mechanisms. Exposure of fresh ice due to cliff collapse leads to a notable water enhancement, while most perihelion outbursts coincide with substantial density increases of CO2. We propose that these CO2-driven events originate from subsurface gas-filled cavities, whose walls are suggested to have been sealed by earlier refreezing of CO2 migrating from warmer spots, hence increasing the cavity pressure required to burst.

Effect of rotor blade position on Vertical Axis Wind Turbine performance

In this paper a numerical study is presented with the aim of evaluating the performance output of three Vertical Axis Wind Turbine (VAWT) configurations. Here using Computational Fluid Dynamics (CFD) a two-dimensional Multi Reference Frame (MRF) approach has been used to perform steady state simulations. For this purpose an inlet velocity of 4m/s has been used along with rotor blade tip speed ratios (λ) in the range of 0 to 0.6. The effects of varying rotor blade position on the global and local flow fields have been quantified. Furthermore, the influence of rotor blade position on performance has been computed. It has been found that within a typical rotor blade passage, maximum torque is obtained at a unique rotor angle. It can be seen that the torque output of the turbine decreases with an increase in rotor tip speed ratio (λ) for all rotor blade positions. From the data obtained it can be concluded that the VAWT power curve characteristics vary with relative rotor blade position.

Spatio-temporal changes in degassing behavior at Stromboli volcano derived from two co-exposed SO2 camera stations

Improving volcanic gas monitoring techniques is central to better understanding open-vent, persistently degassing volcanoes. SO2 cameras are increasingly used in volcanic gas studies, but observations are commonly limited to one single camera alone viewing the volcanic plume from a specific viewing direction. Here, we report on high frequency (0.5 Hz) systematic measurements of the SO2 flux at Stromboli, covering a 1-year long observation period (June 2017-June 2018), obtained from two permanent SO2 cameras using the same automated algorithm, but imaging the plume from two different viewing directions. Our aim is to experimentally validate the robustness of automatic SO2 camera for volcano monitoring and to demonstrate the advantage of using two co-exposed SO2 camera stations to better capturing degassing dynamics at open-vent volcanoes. The SO2 flux time-series derived from the two SO2 camera stations exhibit good match, demonstrating the robustness of the automatic SO2 camera method. Our high-temporal resolution SO2 records resolve individual Strombolian explosions as transient, repetitive gas bursts produced by the sudden release of over pressurized gas pockets and scoriae. Calculations show that explosive degassing activity accounts for ∼10% of the total SO2 emission budget (dominated by passive degassing) during mild regular open-vent activity. We show that the temporal variations of the explosive SO2 flux go in tandem with changes in total SO2 flux and VLP seismicity, implicating some commonality in the source processes controlling passive degassing and explosive activity. We exploited the spatial resolution of SO2 camera to discriminate degassing at two distinct regions of the crater area, and to minimize biases due by the station position respect to the target plume. We find that the SO2 fluxes from southwest-central (SWCC) and northeast (NEC) crater areas oscillate coherently but those from the NEC are more sensitive to the changes in the volcanic intensity. We interpret this as due to preferential gas/magma channeling into the structurally weaker north-eastern portion of the crater terrace in response to increasing supply rate of buoyant, bubble-rich magma in the shallow plumbing system.

Finite Element Analysis of Soccer Ball-Related Ocular and Retinal Trauma and Comparison with Abusive Head Trauma.

PurposeTrauma to the eye resulting from a soccer ball is a common sports-related injury. Although the types of ocular pathologic features that result from impact have been documented, the underlying pathophysiologic mechanics are not as well studied. The purpose of this study was to evaluate the biomechanical events after the collision of a soccer ball with the eye to better understand the pathophysiology of observed ocular and retinal injuries and to compare them with those observed in abusive head trauma (AHT).DesignComputer simulation study.ParticipantsNone.MethodsA finite element model of the eye was used to investigate the effects of a collision of a soccer ball on the eye.Main Outcome MeasuresIntraocular pressure and stress.ResultsImpact of the soccer ball with the eye generated a pressure wave that traveled through the vitreous, creating transient pockets of high and negative pressure. During the high-frequency phase, pressure in the vitreous near the posterior pole ranged from 39.6 to –30.9 kPa. Stress in ocular tissue was greatest near the point of contact, with a peak of 66.6 kPa. The retina experienced the greatest stress at the vasculature, especially at distal branches, where stress rose to 15.4 kPa. On average, retinal stress was greatest in the subretinal layer, but was highest in the preretinal layer when considering only vascular tissue.ConclusionsThe high intraocular pressure and stress in ocular tissue near the point of soccer ball impact suggest that injuries to the anterior segment of the eye can be attributed to direct transmission of force from the ball. The subsequent propagation of a pressure wave may cause injuries to the posterior segment as the positive and negative pressures exert compressive and tractional forces on the retina. The linear movement of the pressure wave likely accounts for localization of retinal lesions to the posterior pole or superior temporal quadrant. The primarily linear force in soccer ball trauma is the probable cause for the more localized injury profile and lower retinal hemorrhage incidence compared with AHT, in which repetitive angular force is also at play.

Endoscopic resection of superficial non-ampullary duodenal epithelial tumor.

Although superficial non‐ampullary duodenal epithelial tumor (SNADET) was previously considered a rare disease, in recent years, the opportunities to detect and treat SNADET are increasing. Considering the high morbidity of pancreatoduodenectomy, endoscopic resection can be a treatment option that preserves the organs and contributes maintain patients’ quality of life. Endoscopic mucosal resection (EMR) is a standard treatment for relatively small lesions in gastrointestinal tracts, however, it is difficult because submucosal fibrosis frequently occurs due to the previous biopsy. Recently, some modified EMR techniques including underwater EMR (UEMR) and cold polypectomy (CP) have been proposed. In UEMR, the duodenal lumen is filled with water or saline and resected the targe lesion with a snare without injection into the submucosa. It would be a treatment option that could reduce candidates for ESD especially SNADET less than 20 mm. CP was reported as a safe and convenient means for SNADET. It would also be one of the standard treatments for diminutive lesions, though there remain some concerns on its resectability. ESD for SNADET is technically challenging, especially with an extremely high risk of adverse event (AE) with a reported bleeding rate of more than 20% and perforation rate up to about 40%. However, modified treatment techniques including the water pressure method and pocket creation method have been reported to potentially contribute to improving outcomes of ESD. Moreover, accumulated evidence shows closing the mucosal defect significantly reduces delayed adverse events after duodenal endoscopic treatments. Further studies are warranted to elucidate curative criteria, long‐term outcomes, and appropriate surveillance strategy.

Experimental Validation of a New Design Concept for the Increase of Efficiency of the Hydraulic Drive System in Mobile Working Machines

In mobile working machines like excavators, hydraulic actuators and drives are indispensable due to their advantages of a high power to weight ratio, robustness and the good power transmission over medium distances by the hydraulic fluid. Axial piston machines can deliver a large volume flow at a high operation pressure with high efficiency and are therefore widely used as system pump or drive motor. The three essential tribological contacts piston / bushing, sliding shoe / swash plate and valve plate / cylinder block strongly influence the machine’s efficiency and so the complete drive system. The paper on hand focuses on the experimental validation of a new design concept to increase the efficiency of the tribological contact between valve plate and cylinder block in an axial piston pump. Due to the different pressure forces at the high- and low-pressure side, the cylinder block tilts and holds this preferred position almost constant. Therefore, the gap height is not constant. In the area of minimum gap height, the danger of solid body contact increases. In addition, the heat dissipation is decreased, which can lead to local constant high temperature hot-spots. Both can destroy the surface structure or the coating. A new design concept has been developed to reduce these risks, thus increasing the efficiency, the lifetime and making it possible to dispense of leaded coating materials. In this design concept, pressure pockets are added in the area of minimum gap height. The simulation study shows a high potential of this concept. The experimental results of the prototype parts, which are measured on a special test rig and presented in this paper, confirm the simulations and validate the potential of the new design concept in this way.

An innovative approach to assess comprehensive care: Temple University's patient wellness report.

The transition from a paper-based to an all-electronic patient health record took a major step forward in 2018, with the implementation of an electronic health record that supports the School's patient-centered comprehensive care model and facilitates outcomes assessment. The Patient Wellness Report (PWR) summarizes findings of the patient assessment, and it does so automatically by locating data already entered in axiUm forms. This study aimed to describe the PWR implementation procedures and to examine outcomes and characteristics among patients with completed treatment plans during an 18-month period. Outcome data were extracted from axiUm for patients aged ≥16 years who completed comprehensive care treatment plans. Each PWR contained 14 metrics related to "dimensions" of wellness (quality of life, general health factors, oral hygiene, caries risk, and degree of periodontal inflammation and pocketing), each of which is rated on a 3-point scale based on best available scientific evidence. A total of 2074 patients completed planned procedures between July 2018 and January 2020, and met the study eligibility criteria. Improvement of several conditions was observed between baseline and follow-up in caries lesions (21%), blood pressure (9%), and periodontal pocket (3.2%). A majority of patients rated in good condition at baseline had their scores unchanged at follow-up in the following areas: dental anxiety (92%), speaking (88%), smoking (87%), and alcohol consumption (79%). Improvements in dental caries and blood pressure metrics were easily monitored using the PWR. In addition, disparities exist in improvement of patient outcomes by race/ethnicity.

Designing liveable urban open spaces in high density cities

Hong Kong is one of the densest cities compared to other metropolitan cities with population density in some districts exceeding 57,250 persons per sqkm. Hong Kong’s liveability has been affected by factors such as escalating urban density, lack of open spaces, congested living environments, air pollution concentration and high proneness to pandemics.Due to extremely high land premiums, some residents in Hong Kong live in nano flats small as 15sqm in high-rise towers. Given the congested nature of apartments, open spaces a play a vital role contributing to residents’ psychological and physical well-being. Due to peculiar topography and extreme high density, Hong Kong open space per capita is far from the WHO recommended standards of 9 sqm per person. Most urban open spaces are pocket spaces located among developments or adjacent to traffic roads with a high ratio of hardscape compared to vegetation. Due to challenging Summer conditions in Hong Kong with high temperature, humidity and stagnant wind most urban open spaces are underutilized.This research investigates the factors effecting enjoyment of open spaces and design factors that could contribute to improve their liveability as public amenities. Exploration is based on liveability parameters such as user comfort, user behaviour, and spatial attributes of urban open spaces. Field data was collected on seven urban open spaces within Tsuen Wan district during dry Summer days. Field data analysis was supplemented by simulation methods, photographic survey of users’ movement within open spaces and user interviews.All open spaces are located amidst of high-density urban environment facilitating easy access to residents in the neighbourhood proving sense of security. Findings indicate tendencies in using these open spaces in the afternoon after 4pm when these open spaces cool off from solar radiation. Majority of open spaces benefited from shading effect from surrounding buildings, however the seating arrangements have not benefited from the shading. Satisfactory wind speed could be observed in four open spaces out of the seven that benefited from South and SE wind directions providing desirable thermal comfort to users. The park that consisted of the highest ratio of greenery received the lowest wind speed due walled effect created by surrounding buildings. Ironically open spaces with high percentage of hardscape areas reported better wind performance indicating the possibility of high emissivity material creating low pressure pockets drawing winds in particularly in the afternoons.

Mould design for clutch housing parts using a casting simulation of high pressure die casting

To manufacture automotive clutch housing parts in application of high pressure die casting, the following three gating system designs were taken into account. Since adopting these gating system designs in actual experiment would require too much cost and time, a casting simulation program was used instead: Analyzed were flow behaviors as elements filled the mould. Based on the air pressure and air pocket after the melt was completely filled in mould, the final gating system design was selected. The third gating system design with 5 gates was expected to involve less defects than others was even and uniform. A cooling channel and a chill vent were designed. In a real casting test, five products in total were produced. All of them were sound and involved neither any spot of insufficient filling nor defect on the surface. The real test expected to involve shrinkage porosities based on the analysis and those of the manufactured products that actually involved shrinkage porosities did not exactly correspond to each other but were similar. The hardness was about 84 HV regardless of location.

Validation of the Instant Blood Pressure Smartphone App.

Mobile health (mHealth) technologies include unregulated consumer smartphone apps.1 The Instant Blood Pressure app (IBP; AuraLife) estimates blood pressure (BP) using a technique in which the top edge of the smartphone is placed on the left side of the chest while the individual places his or her right index finger over the smartphone’s camera. Between its release on June5, 2014, and removal on July 30, 2015 (421 days), the IBP app spent 156 days as one of the top 50 best-selling iPhone apps; at least 950 copies of this $4.99 app were sold on each of those days.2 Validation of this popular app or any of the similar iPhone apps still available (eg, Blood Pressure Pocket, Quick Blood Pressure Measure and Monitor), have not been performed. Using a protocol based on national guidelines,3 we investigated the accuracy and precision of IBP.

Prevalence of substance abuse among regular degree health science students in Sheba University College in Mekelle Town, Tigray - Ethiopia.

Background:Substance abuse (SA) refers to the harmful or hazardous use of psychoactive substances, including alcohol and illicit drugs. The most common substances which are usually abused are alcohol and tobacco. Herein, we assessed the prevalence of SA among regular degree health science students of the Sheba University College (SUC).Materials and Methods:A cross-sectional survey was carried out among 1076 SUC students using self-administered structured questionnaire. The simple sampling technique was used to select students. Descriptive statistics, bivariate, and multivariate analysis were done.Results:The overall prevalence of “ever used substance” for at least one was 45.5%. The most commonly used drugs in descending order were alcohol (25.1%), cigarette (11.4%), and khat (9.2%). Male participants, urban setting, peer pressure, personal pleasure, and academic dissatisfaction and pocket money were highly associated with SA.Conclusion:This study showed a lower magnitude (45.6% ever use and 21% still using) of SA among students' compared to other studies. Even if a considerable decrease in SA among study subjects, the creation of awareness and health education should be continued to fully combat the problem of abuse.

Gas blowout from shallow boreholes near Fiumicino International Airport (Rome): Gas origin and hazard assessment

In summer 2013 a toxic and polluting gas blowout (19tonnesday−1 CO2, 95kgday−1 CH4) occurred from two shallow boreholes drilled at only 50m from the International Airport of Rome (Italy), in the town of Fiumicino. Another gas blowout occurred in the same period from a borehole located offshore, 2km away, also generating sea-water acidification; it lasted only a couple of days. Onshore, CO2 was also diffusing from holes within the soil, particularly toward the airport, generating a soil flux up to 1.8tonnesday−1. In 3.5months ~1500tonnes of CO2 and 5.4tonnes of CH4 were emitted in the atmosphere. Temporal monitoring of gas geochemistry indicates that in this area a mixing occurs between shallow and pressurized gas pockets, CO2-dominated, but with different chemical (i.e., He/CH4 ratio) and isotopic (3He/4He, δ13C-δDCH4) characteristics. Numerical simulation of CO2 dispersion in the atmosphere showed that dangerous air CO2 concentrations, up to lethal values, were only found near the vents at a height of 0.2m. Fiumicino is a high blowout risk area, as CO2 rising through deep reaching faults pressurizes the shallow aquifer contained in gravels confined underneath shales of the Tiber delta deposits. The Fiumicino blowout is a typical example of dangerous phenomenon that may occur in urban context lying nearby active or recent volcanoes and requires quick response on hazard assessment by scientists to be addressed to civil protection and administrators.

Petrology of ultramafic xenoliths in Cenozoic alkaline rocks of northern Madagascar (Nosy Be Archipelago)

Late Miocene basanites of Nosy Be and Nosy Sakatia islands (Nosy Be Archipelago, northern Madagascar) carry spinel-facies anhydrous ultramafic xenoliths (lherzolites, harzburgites and wehrlites). Geothermobarometric estimates indicate that these xenoliths derive from shallow mantle depths of 35–40 km, with those from Nosy Be island showing equilibration T (averages in the range of 945–985 °C) lower than the Nosy Sakatia analogues (averages ranging from 1010 to 1110 °C). One Nosy Sakatia mantle xenolith exhibits relatively fertile lherzolite composition, with trace and major element mineral chemistry consistent with a residual character after low degrees (1–2%) of mafic melt extraction. We interpret this composition as that resembling a depleted mantle (DM)-like lithospheric composition before metasomatic overprints. The other lherzolites and harzburgites display petrochemical characters consistent with variable extent of partial melting (up to 18%), associated with pronounced metasomatic overprints caused by migrating melts, as highlighted by enrichments in highly incompatible trace elements (e.g. light rare earth elements, LREE and Sr), together with the abundant occurrence of wehrlitic lithologies.The variability of petrochemical features points to different styles of metasomatism and metasomatic agents. The estimated composition of the parental melts of wehrlites matches that of host basanites. The combination of this evidence with the petrographic features, characterized by coarse-granular to porphyroclastic textures and by the presence of olivine without kink-banding, suggests that wehrlites are veins or pockets of high pressure cumulates within the mantle peridotite. The same melts also metasomatized via porous-flow percolation some lherzolites and harzburgites. Distinctly, a group of lherzolites and harzburgites was metasomatized by a different alkaline melt having markedly lower incompatible trace element contents.Late infiltration of metasomatic fluids is responsible for the spongy texture of some clinopyroxenes of lherzolites, harzburgites and wehrlites.

Hazardous gas emissions from the flanks of the quiescent Colli Albani volcano (Rome, Italy)

Abstract Gas hazard was evaluated in the three most important cold gas emission zones on the flanks of the quiescent Colli Albani volcano. These zones are located above structural highs of the buried carbonate basement which represents the main regional aquifer and the main reservoir for gas rising from depth. All extensional faults affecting the limestone reservoir represent leaking pathways along which gas rises to the surface and locally accumulates in shallow permeable horizons forming pressurized pockets that may produce gas blowout when reached by wells. The gas, mainly composed of CO 2 (>90 vol.%), contains appreciable quantities of H 2 S (0.35–6 vol.%), and both represent a potentially high local hazard. Both gases are denser than air and accumulate near ground where they may reach hazardous concentrations, and lethal accidents frequently occur to animals watering at local ponds. In order to evaluate the rate of degassing and the related hazard, CO 2 and H 2 S diffuse soil flux surveys have been repeatedly carried out using an accumulation chamber. The viscous gas flux of some important discrete emissions has been evaluated and the CO 2 and H 2 S air concentration measured by portable devices and by Tunable Diode Laser profiles. The minimum potential lethal concentration of the two gases (250 ppm for H 2 S and 8 vol.% for CO 2 ) is 320 times higher for CO 2 , whereas the CO 2 /H 2 S concentration ratio in the emitted natural gas is significantly lower (15–159). This explains why H 2 S reaches hazardous, even lethal, concentrations more frequently than CO 2 . A relevant hazard exists for both gases in the depressed zones (channels, excavations) particularly in the non-windy early hours of the day.

Hydrodynamics of the bluegill sunfish C-start escape response: three-dimensional simulations and comparison with experimental data

In this work we study the hydrodynamics of a bluegill sunfish performing a C-start maneuver in unprecedented detail using 3-D numerical simulations guided by previous laboratory experiments with live fish. The 3-D fish body geometry and kinematics are reconstructed from the experiments using high-speed video and prescribed as input to the numerical simulation. The calculated instantaneous flow fields at various stages of the C-start maneuver are compared with the two-dimensional particle image velocimetry measurements, and are shown to capture essentially all flow features observed in the measurements with good quantitative accuracy; the simulations reveal the experimentally observed three primary jet flow patterns whose momentum time series are in very good agreement with the measured flow field. The simulations elucidate for the first time the complex 3-D structure of the wake during C-starts, revealing an intricate vortical structure consisting of multiple connected vortex loops at the end of the C-start. We also find that the force calculated based on the 3-D flow field has higher magnitudes than that implied by the jet momentum on the midplane, and it exhibits large and rapid fluctuations during the two stages of the C-start. These fluctuations are physical and are related to the change in the direction of the acceleration of the fish body, which changes the location of the high and low pressure pockets around the fish.

Formation of uncapped nanometre-sized metal particles by decomposition of metal carbonyls in carbon nanotubes

Carbonyl complexes of transition metals (Mx(CO)y, where x = 1, 2, or 3 and y = 6, 10, or 12 for M = W, Re, or Os, respectively) inserted into single walled carbon nanotubes (SWNT, diameter 1.5 nm) transform into metallic nanoparticles (MNPs) under heat treatment or electron beam irradiation. The host-nanotube acts as an efficient template, controlling the growth of MNPs to ∼1 nm in diameter. The only co-product of nanoparticle formation, carbon monoxide (CO) gas, creates pockets of high pressure between nanoparticles, thus preventing their collision and coalescence into larger structures. As a result, the MNPs stay largely spheroidal in shape and are uniformly distributed throughout the entire length of the SWNT. Despite their extremely small size (on average each MNP contains 30–90 atoms) and no protection of their surface by a capping layer of molecules, the metallic nanoparticles encapsulated in nanotubes are very stable under ambient conditions and even at elevated temperatures. Aberration-corrected high-resolution transmission electron microscopy reveals the crystalline nature of the MNPs, probes their interactions with the nanotube interior and illustrates the complex dynamics of confined MNPs in real-time and direct-space.

High‐speed imaging of Strombolian explosions: The ejection velocity of pyroclasts

Explosive volcanic eruptions are defined as the violent ejection of gas and hot fragments from a vent in the Earth's crust. Knowledge of ejection velocity is crucial for understanding and modeling relevant physical processes of an eruption, and yet direct measurements are still a difficult task with largely variable results. Here we apply pioneering high‐speed imaging to measure the ejection velocity of pyroclasts from Strombolian explosive eruptions with an unparalleled temporal resolution. Measured supersonic velocities, up to 405 m/s, are twice higher than previously reported for such eruptions. Individual Strombolian explosions include multiple, sub‐second‐lasting ejection pulses characterized by an exponential decay of velocity. When fitted with an empirical model from shock‐tube experiments literature, this decay allows constraining the length of the pressurized gas pockets responsible for the ejection pulses. These results directly impact eruption modeling and related hazard assessment, as well as the interpretation of geophysical signals from monitoring networks.

AUTOMATIC DETECTION OF LEARNER'S AFFECT FROM GROSS BODY LANGUAGE

We explored the reliability of detecting learners' affect by monitoring their gross body language (body position and arousal) during interactions with an intelligent tutoring system called AutoTutor. Training and validation data on affective states were collected in a learning session with AutoTutor, after which the learners' affective states (i.e., emotions) were rated by the learner, a peer, and two trained judges. An automated body pressure measurement system was used to capture the pressure exerted by the learner on the seat and back of a chair during the tutoring session. We extracted two sets of features from the pressure maps. The first set focused on the average pressure exerted, along with the magnitude and direction of changes in the pressure during emotional experiences. The second set of features monitored the spatial and temporal properties of naturally occurring pockets of pressure. We constructed five data sets that temporally integrated the affective judgments with the two sets of pressure features. The first four datasets corresponded to judgments of the learner, a peer, and two trained judges, whereas the final data set integrated judgments of the two trained judges. Machine-learning experiments yielded affect detection accuracies of 73%, 72%, 70%, 83%, and 74%, respectively (chance = 50%) in detecting boredom, confusion, delight, flow, and frustration, from neutral. Accuracies involving discriminations between two, three, four, and five affective states (excluding neutral) were 71%, 55%, 46%, and 40% with chance rates being 50%, 33%, 25%, and 20%, respectively.

Advances in Canadian Peatland Hydrology, 2003-2007

Peatlands represent over 90% of Canadian wetlands and are the focus of considerable hydrological and biogeochemical research. Research on evapotranspiration (ET) has shown that it can exceed annual precipitation (P) where there are replenishing flood events. Evaporation from open water ponds in boreal peatlands exceeds ET from vegetated riparian zones by about two times, but surrounding forests can shelter small ponds by reducing turbulence. In an open bog, evaporation was modelled by separating the surface into vascular vegetation, hummock moss and hollow moss surfaces, and showed that vascular plants contribute 60-80% of ET, mosses making up the remainder with hummock mosses dominant over hollows. Runoff from peatlands is enhanced by features ranging from headwater swamps, ice-cored peat plateaus, patchy arctic wetlands and even sections of riverine peatlands. Groundwater fluxes can be quite erratic, and depend on transient properties of the peat that depend on moisture content (e.g., unsaturated hydraulic conductivity) to unsteady saturated hydraulic properties (e.g., hydraulic conductivity, specific yield) caused by peat compression and dilation associated with water storage changes. Surface elevation adjustments can result in a more stable depth to water table, increase evaporation losses, increase methane emission, and attenuate pore-water concentration of contaminants. Research on Canadian peatlands has also made significant methodological advances, including measurement of hydraulic properties of living mosses and peat pore-water and pore dimension characteristics. A considerable multi-annual effort has also been made in evaluating carbon dynamics from Canadian peatlands. Summer moisture availability is important to determining carbon fluxes with some peatlands experiencing enhanced productivity following drought (water table drawdown). Sudden changes in water table elevation promote DOC production and export. Methane bubbles confound hydraulic gradients and flows by creating local pockets of pressure, which are then released episodically when the entrapped gas reaches a threshold content. Canadian peatland hydrology continues to be actively researched in lab, field and modelling studies.

Association between High Blood Pressure and Deep Periodontal Pockets

A hypertension screening project was performed jointly at a dental clinic and a primary health care centre. In this report the hypothesis that there is an association between high diastolic blood pressure and deep periodontal pockets was tested. A total of 1,239 consecutive patients aged 35–65 years had their blood pressure measured before the dental examination or had a known hypertension. Information on medical history and tobacco use was obtained by interview and dental status was recorded. Fifty-four subjects had known hypertension and 141 had previously unknown diastolic blood pressure >90 mmHg (cases). For each case an age, sex and tobacco-use matched referent was chosen from those with diastolic blood presure < 90 mmHg.Significantly more cases than referents had periodontal pckets >5 millimeters deep.In multivariate analyses the prevalence of deep periodontal pockets was associated with blood pressure status also after adjustment for the small differences between the groups in age, sex, tobacco use and number of teeth. In conclusion there was an association between diastolic blood pressure and prevalent deep periodontal pockets. Whether the relationship is a causal one remains to be explored. Screening for high blood pressure at regulary visits at the dental clinic may give the dental care a new important role in the public health field.