Four geosynthetic clay liners (GCLs) serving as single liners were exhumed from below 0.7 m of silty sand on a 3:1 (horizontal:vertical) north-facing slope at the QUELTS site in Godfrey, Ontario, ...after 5 and 7 years. The 300 mm GCL overlaps with 0.4 kg/m supplemental bentonite were all physically intact. The exchangeable bound sodium was completely replaced with divalent cations. The GCL with the smallest needle-punched bundle size (average of 0.7 mm) and percentage area covered by bundles (4%) maintained low hydraulic conductivity (k) when tested under 0.07–1.2 m head with 10 mmol/L CaCl
2
solution as the permeant. For GCLs with larger bundles (1.1–1.6 mm) and higher percentage area covered by bundles (9%–14%), k was low when the head was low (0.07 m). Once the applied head increased, k increased by 1–4 orders of magnitude depending on the (i) hydraulic gradient, (ii) size and number of the needle-punched bundles, and (iii) structure and mass of the bentonite per unit area. The results suggest that the GCLs can perform effectively as a single hydraulic barrier in covers providing that the head above the GCL is kept low (e.g., by a suitable drainage layer above the GCL).
Celotno besedilo
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Solution-based combinatorial samples of lithium manganese nickel oxide were synthesized and studied by X-ray diffraction in order to map out the entire pseudoternary system. The samples were made by ...heating to 800 °C in an oxygen atmosphere, and two cooling methods were tested: quenching and a slower cooling rate. This article focuses on the areas of the Gibbs triangle that lie between the layered and spinel structures as well as the single-phase layered region. The layered region is much larger than previously reported in the literature, and lattice parameters throughout the solid solution are reported. The complex coexistence region includes a two-phase region as well as two 3-phase regions. Supporting evidence demonstrating the 3-phase regions and careful identification of their corners is included here. The 3-phase regions also undergo a transformation during slow cooling that can be attributed to high entropy phases no longer being favored. In order to confirm that the findings for the small combinatorial samples are relevant to bulk samples, we present XRD patterns from a few bulk samples synthesized in oxygen as well as some heated in air. The results show that though the boundaries in the phase diagram move with synthesis conditions, the main features of the coexistence regions remain the same.
Most studies to assess effort intolerance in patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) have used questionnaires. Few studies have compared questionnaires with ...objective measures like an actometer or an exercise test. This study compared three measures of physical activity in ME/CFS patients: the physical functioning scale (PFS) of the SF-36, the number of steps/day (Steps) using an actometer, and the %peak VO
of a cardiopulmonary stress test.
Female ME/CFS patients were selected from a clinical database if the three types of measurements were available, and the interval between measurements was ≤ 3 months. Data from the three measures were compared by linear regression.
In 99 female patients the three different measures were linearly, significantly, and positively correlated (PFS vs Steps, PFS vs %peak VO
and Steps vs %peak VO
: all P < 0.001). Subgroup analysis showed that the relations between the three measures were not different in patients with versus without fibromyalgia and with versus without a maximal exercise effort (RER ≥ 1.1). In 20 patients re-evaluated for symptom worsening, the mean of all three measures was significantly lower (P < 0.0001), strengthening the observation of the relations between them. Despite the close correlation, we observed a large variation between the three measures in individual patients.
Given the large variation in ME/CFS patients, the use of only one type of measurement is inadequate. Integrating the three modalities may be useful for patient care by detecting overt discrepancies in activity and may inform studies that compare methods of improving exercise capacity.
•Doppler imaging to measure cerebral blood flow is feasible during tilt testing.•Cerebral blood flow in ME/CFS patients is reduced during tilt testing.•90% of ME/CFS patients show abnormal cerebral ...blood flow reduction on tilt testing.•Cerebral blood flow reduction correlates with symptoms of orthostatic intolerance.
The underlying hypothesis in orthostatic intolerance (OI) syndromes is that symptoms are associated with cerebral blood flow (CBF) reduction. Indirect CBF measurements (transcranial Doppler flow velocities), provide inconsistent support of this hypothesis. The aim of the study was to measure CBF during a 30 min head-up tilt test (HUT), using Doppler flow imaging of carotid and vertebral arteries, in individuals with chronic fatigue syndrome/myalgic encephalomyelitis (ME/CFS), a condition with a high prevalence of OI.
429 ME/CFS patients were studied: 247 had a normal heart rate (HR) and blood pressure (BP) response to HUT, 62 had delayed orthostatic hypotension (dOH), and 120 had postural orthostatic tachycardia syndrome (POTS). We also studied 44 healthy controls (HC). CBF measurements were made at mid-tilt and end-tilt. Before mid-tilt, we administered a verbal questionnaire to ascertain for 15 OI symptoms.
End-tilt CBF reduction was 7% in HC versus 26% in the overall ME/CFS group, 24% in patients with a normal HR/BP response, 28% in those with dOH, and 29% in POTS patients (all P < .0005). Using a lower limit of normal of 2SD of CBF reduction in HC (13% reduction), 82% of patients with normal HR/BP response, 98% with dOH and 100% with POTS showed an abnormal CBF reduction. There was a linear correlation of summed OI symptoms with the degree of CBF reduction at mid-tilt (P < .0005).
During HUT, extracranial Doppler measurements demonstrate that CBF is reduced in ME/CFS patients with POTS, dOH, and even in those without HR/BP abnormalities.
This study shows that orthostatic intolerance symptoms are related to CBF reduction, and that the majority of ME/CFS patients (90%) show an abnormal cerebral flow reduction during orthostatic stress testing. This may have implications for the diagnosis and treatment of ME/CFS patients.
The Li–Mn–Ni-O system has received much attention for potential positive electrode materials in lithium-ion batteries. Recent work mapping the phase diagrams of the entire pseudo-ternary system ...showed that the layered solid-solution region extends to compositions with both less and more lithium than the well-known lithium-rich layered composition line that joins Li2MnO3 to LiNi0.5Mn0.5O2. The part of this solid-solution region that is lithium deficient has a “bump” feature in the single-phase boundary, which could not be explained until now. The current study explores this part of the phase diagram with the use of X-ray diffraction, helium pycnometry measurements, redox titrations, and a Monte Carlo simulation. Results show that metal site vacancies are present in the structures in increasing amounts as the lithium content of the samples decreases. A Ni2+ ion and a vacancy can replace two Li+ ions in LiLi1/3Mn2/3O2 to make the solid solution series LiLi(1/3)–x Ni x/2□ x/2Mn2/3O2 with 0 < x < 1/3. The most lithium-deficient structures contain sufficient vacancies to allow manganese to form on two-thirds (2/3) of the transition-metal layer, such that the ordering of manganese on two √3 × √3 lattices yields a structure with low internal energy and sharp superlattice peaks in XRD patterns. The material with the maximum theoretical vacancy fraction that still has two-thirds of the transition-metal layer filled with manganese, LiNi1/6□1/6Mn2/3O2, was also synthesized. Both XRD and electrochemical data regarding this new material are presented.
Field observations of downslope bentonite erosion from a geosynthetic clay liner (GCL) covered by only a black geomembrane are reported for a composite liner left exposed without a protective soil ...cover for much longer than recommended by the GCL manufacturer. A new nondestructive, light-transmission technique developed to investigate bentonite erosion features in the field is presented. A classification system is developed to describe the type of erosion features observed. Results from five field investigations at the Queen’s University Environmental Liner Test Site (QUELTS II) are reported to quantify the onset, progression, and severity of downslope erosion for one particular geotextile-encased, needle-punched GCL for exposure periods of between 7 weeks and 1.3 years. The first significant erosion feature (type “E”with bentonite loss narrower than 2.5 cm) was observed after 6 months of exposure. Irrecoverable erosion features (type “EE” with bentonite loss wider than 2.5 cm) were observed after 12 months of exposure. These findings highlight the need to follow the manufacturer’s recommendations for timely covering of a composite liner with soil following liner installation.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The hydration of different GCLs from the pore water of the underlying foundation soil is investigated for isothermal conditions at room temperature. Results are reported for three different ...reinforced (needle punched) GCL products. Both a silty sand (SM) and sand (SP) foundation soil are examined. GCL hydration is shown to be highly dependant on the initial moisture content of the foundation soil. GCLs on a foundation soil with a moisture content close to field capacity hydrated to a moisture content essentially the same as if immersed in water while those on soil at an initial moisture content close to residual only hydrated to a gravimetric moisture content of 30–35%. The method of GCL manufacture is shown to have an effect on the rate of hydration and the final moisture content. The presence or absence of a small (2 kPa) seating pressure is shown to affect the rate of hydration but not the final moisture content. The GCL hydration did not change significantly irrespective of whether a nonwoven cover or woven carrier GCL rested on the foundation soil.
Orthostatic intolerance (OI) is common among individuals with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Cognitive dysfunction has been demonstrated during head-up tilt testing ...(HUT) in those with ME/CFS: worse scores on cognitive tests occur with increasing tilt angles and increasing complexity of the cognitive challenge. The aim of our study was to determine whether cognitive impairment persists after completion of HUT.
Eligible participants were consecutive individuals satisfying criteria for ME/CFS who underwent HUT because of OI. The 2- and 3-back tests were performed before the start of HUT and within 5 min after completion of HUT. We measured the percentage of correct responses and raw reaction times before and after HUT for both the 2- and 3-back tests. We studied 128 ME/CFS patients who underwent HUT and had a complete set of N-back data before and after HUT. Compared to pre-tilt responses, the percentage of correct responses on the 2-back test decreased post-HUT from 77(18) to 62(21) and of the 3-back test from 57(17) to 41(17) (both
< 0.0001). The raw reaction time of the 2-back test increased post-HUT from 783(190) to 941(234) m/s and of the 3-back test from 950(170) to 1102(176) (both
< 0.0001). There was no difference in the N-back test data for subgroups dichotomized based on disease severity, the presence of co-morbid fibromyalgia, or the presence of postural orthostatic tachycardia syndrome.
As measured by the N-back test, working memory remains impaired in adults with ME/CFS following a 30-min head-up tilt test.
The variation in length of the longest hydraulic features (connected wrinkles) formed in an exposed black high-density polyethylene (HDPE) geomembrane liner observed at different times of the day and ...in different seasons over multiple years is presented for both a 3% base slope and 3H:1V side slope at the Queen’s University Experimental Liner Test Site (latitude of 44°34′N and longitude 76°39′W). The longest wrinkle observed on the 0.15 ha base was about 1500 m. The longest wrinkle observed on the 0.17 ha slope was about 2000 m. The length of connected wrinkles is shown to be primarily related to solar radiation, although the soil and ambient temperature played a role in maintaining wrinkles in the afternoon as solar radiation decreased. Wrinkles of less than 20 m connected length were observed for geomembrane surface temperatures of less than 30 °C and solar radiation of less than 600 W/m
2
. Wrinkles exceeding 500 m in connected length were observed for geomembrane temperatures between about 30 and 62 °C and solar radiation between 600 and 1100 W/m
2
. The vast majority (about 85%) of wrinkle heights were between 0.04 and 0.08 m with the average wrinkle height being 0.06 m and a maximum wrinkle height of about 0.18 m. The manually measured wrinkle widths around noon (when there was the greatest number of wrinkles) ranged between about 0.20 and 0.43 m, but most of the wrinkles were between 0.23 and 0.36 m with a mean of 0.29 m (standard deviation 0.05 m). The data from this study suggest that a reasonable estimate of mean wrinkle width would be about 0.2 to 0.3 m. The size of the area constraining the geomembrane is shown to affect the connected wrinkle length. Calculations of leakage for the wrinkle lengths and widths observed are reported to be consistent with what has been reported for landfills in North America.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
AbstractWrinkles are buckles or waves that develop from restrained thermal expansion when the geomembrane is left exposed to solar heating. Wrinkles can substantially reduce the effectiveness of the ...geomembrane as a hydraulic barrier if a hole is at or near a wrinkle, depending on the number, length, and width of wrinkles. Low altitude aerial photography and digital image analysis are used to quantify the nature and extent of wrinkles that developed over one hot and sunny day in a smooth, black, 1.5-mm-thick high-density polyethylene (HDPE) geomembrane over a 55 m by 140 m area. Wrinkles were found to significantly vary over the course of the day, increasing from the fewest wrinkles in the morning to a maximum just after noon before decreasing toward the late afternoon. For the specific conditions examined, wrinkles were found to occupy 3%, 21%, and 7% of the entire area surveyed at 8:45, 12:25, and 17:15, respectively. Connections between adjacent wrinkles were observed to create significant interconnected wrinkle features greater than 2,000 m long. The shortest maximum interconnected wrinkle feature of 80 m/ha was measured at 8:45 while the longest such feature was 6,600 m/ha at 13∶45. The observations and results provide data to support the approach that limiting the time of day when cover is placed on geomembrane can be effective at reducing the extent of wrinkling.
Celotno besedilo
Dostopno za:
DOBA, FGGLJ, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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