Past applications of one-dimensional advection, dispersion, and transient storage zone models have almost exclusively relied on a central differencing, Eulerian numerical approximation to the ...nonconservative form of the fundamental equation. However, there are scenarios where this approach generates unacceptable error. A new numerical scheme for this type of modeling is presented here that is based on tracking Lagrangian control volumes across a fixed (Eulerian) grid. Numerical tests are used to provide a direct comparison of the new scheme versus nonconservative Eulerian numerical methods, in terms of both accuracy and mass conservation. Key characteristics of systems for which the Lagrangian scheme performs better than the Eulerian scheme include: nonuniform flow fields, steep gradient plume fronts, and pulse and steady point source loadings in advection-dominated systems. A new analytical derivation is presented that provides insight into the loss of mass conservation in the nonconservative Eulerian scheme. This derivation shows that loss of mass conservation in the vicinity of spatial flow changes is directly proportional to the lateral inflow rate and the change in stream concentration due to the inflow. While the nonconservative Eulerian scheme has clearly worked well for past published applications, it is important for users to be aware of the scheme’s limitations.
Celotno besedilo
Dostopno za:
DOBA, FGGLJ, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A model for trace metals that considers in‐stream transport, metal oxide precipitation‐dissolution, and pH‐dependent sorption is presented. Linkage between a surface complexation submodel and the ...stream transport equations provides a framework for modeling sorption onto static and/or dynamic surfaces. A static surface (e.g., an iron‐ oxide‐coated streambed) is defined as a surface with a temporally constant solid concentration. Limited contact between solutes in the water column and the static surface is considered using a pseudokinetic approach. A dynamic surface (e.g., freshly precipitated metal oxides) has a temporally variable solid concentration and is in equilibrium with the water column. Transport and deposition of solute mass sorbed to the dynamic surface is represented in the stream transport equations that include precipitate settling. The model is applied to a pH‐modification experiment in an acid mine drainage stream. Dissolved copper concentrations were depressed for a 3 hour period in response to the experimentally elevated pH. After passage of the pH front, copper was desorbed, and dissolved concentrations returned to ambient levels. Copper sorption is modeled by considering sorption to aged hydrous ferric oxide (HFO) on the streambed (static surface) and freshly precipitated HFO in the water column (dynamic surface). Comparison of parameter estimates with reported values suggests that naturally formed iron oxides may be more effective in removing trace metals than synthetic oxides used in laboratory studies. The model's ability to simulate pH, metal oxide precipitation‐dissolution, and pH‐dependent sorption provides a means of evaluating the complex interactions between trace metal chemistry and hydrologic transport at the field scale.
Abstract
The local thermal conductivity, thermal diffusivity, and volumetric heat capacity of cesium lead chloride perovskite thin films are mapped simultaneously and with highest spatial resolution ...by a scanning near-field thermal microscope. Both, the 3D phase (CsPbCl
3
) and the 0D phase (Cs
4
PbCl
6
) are investigated. For CsPbCl
3
thin films the variation of the thermal properties across the phase transitions in the range from room-temperature to 65 °C are analyzed. While the thermal conductivity at room temperature is ultra-low, a significant increase of the thermal conductivity is found for the cubic phase of CsPbCl
3
(
T
> 46 °C). While only slight variations in the thermal conductivity are detectable for transitions from the monoclinic to the orthorhombic to the tetragonal phase, thermal diffusivity and volumetric heat capacity measurements are extremely sensitive to the amount of heat involved in the respective transition. It is shown that upon transition to the cubic phase of CsPbCl
3
thin films, the relative increase of the volumetric heat capacity is significantly higher than that of the thermal conductivity. Thus, the thermal diffusivity in the cubic phase becomes notably lower in comparison to that of the respective phase at room temperature. An increase of the volumetric heat capacity had been theoretically predicted earlier but could not be confirmed in previous experimental studies. The findings of our thermal analysis are of great general importance for fundamental material research and for the thermal design of thin-film devices based on CsPbCl
3
perovskites.
Within a two-country model with involuntary unemployment, this paper investigates corporate income taxation under separate accounting versus formula apportionment. In contrast to separate accounting, ...under formula apportionment the corporate tax policy causes a fiscal externality that results from unemployment. This externality is the highest when the apportionment formula contains the payroll factor only. It is minimized for the pure sales (property) formula, if the substitution elasticity is low (high). The unemployment externality tends to compensate other externalities such that tax rates become inefficiently low. The deviation from the efficient tax policy is minimized when the apportionment formula contains the sales factor only.
Ca-activated K (KCa) channels have been suggested to play a role in the control of endothelial functions such as regulation of vascular tone and cell proliferation. We established a method for ...single-cell reverse transcriptase–polymerase chain reaction analysis in combination with the patch-clamp technique to characterize KCa channel expression and function in single endothelial cells (ECs) within the endothelial monolayer of intact human mesenteric arteries (MAs) and in disease states. We tested whether endothelial KCa channel expression and function are altered in MAs obtained from patients with colonic adenocarcinoma (CA) compared with those in MAs from non–cancer patients with inactive diverticulitis. Expression of the intermediate-conductance KCa channel (hIK1) was detected in non–cancer and CA patients. In whole-cell patch-clamp measurements, only ECs expressing hIK1 exhibited corresponding KCa currents, whereas respective KCa currents were missing in hIK1-negative ECs. This heterogeneity of hIK1 expression patterns is indicative of a specialized subset of ECs within the endothelial monolayer. In CA patients, compared with non–cancer patients, a 2.5-fold increase in hIK1-expressing ECs per MA was observed (P <0.05). However, KCa current densities in hIK1-expressing ECs of both groups were similar. In addition to hIK1, expression of the large-conductance KCa channel (hSlo) was detected in single ECs from CA patients. The increased KCa channel expression in CA patients resulted in a 2.7-fold increase of bradykinin-induced endothelial hyperpolarization compared with controls (P <0.05). This increased expression and function of KCa channels might indicate an altered functional state of the endothelium in cancer patients and could play a role in tumor angiogenesis.
Acidic, metal-rich waters produced by the oxidative weathering and resulting leaching of major and trace elements from pyritic rocks can adversely affect water quality in receiving streams and ...riparian ecosystems. Five study areas in the southern Rocky Mountains with naturally acidic waters associated with porphyry mineralization were studied to document variations in water chemistry and processes that control the chemical variations. Study areas include the Upper Animas River watershed, East Alpine Gulch, Mount Emmons, and Handcart Gulch in Colorado and the Red River in New Mexico. Although host-rock lithologies in all these areas range from Precambrian gneisses to Cretaceous sedimentary units to Tertiary volcanic complexes, the mineralization is Tertiary in age and associated with intermediate to felsic composition, porphyritic plutons. Pyrite is ubiquitous, ranging from ∼1 to >5
vol.%. Springs and headwater streams have pH values as low as 2.6, SO
4 up to 3700
mg/L and high dissolved metal concentrations (for example: Fe up to 400
mg/L; Cu up to 3.5
mg/L; and Zn up to 14.4
mg/L). Intensity of hydrothermal alteration and presence of sulfides are the primary controls of water chemistry of these naturally acidic waters. Subbasins underlain by intensely hydrothermally altered lithologies are poorly vegetated and quite susceptible to storm-induced surface runoff. Within the Red River study area, results from a storm runoff study documented downstream changes in river chemistry: pH decreased from 7.80 to 4.83, alkalinity decreased from 49.4 to <1
mg/L, SO
4 increased from 162 to 314
mg/L, dissolved Fe increased from to 0.011 to 0.596
mg/L, and dissolved Zn increased from 0.056 to 0.607
mg/L. Compared to mine drainage in the same study areas, the chemistry of naturally acidic waters tends to overlap but not reach the extreme concentrations of metals and acidity as some mine waters. The chemistry of waters draining these mineralized but unmined areas can be used to estimate premining conditions at sites with similar geologic and hydrologic conditions. For example, the US Geological Survey was asked to estimate premining ground-water chemistry at the Questa Mo mine, and the proximal analog approach was used because a mineralized but unmined area was located adjacent to the mine property. By comparing and contrasting water chemistry from different porphyry mineralized areas, this study not only documents the range in concentrations of constituents of interest but also provides insight into the primary controls of water chemistry.
In the course of the current SARS-CoV-2 pandemic, antibody assays provide an important means for guidance of public health efforts. Thus, characterization of the course of antibody signals on ...different widely used assays is needed.
We selected 25 PCR-confirmed SARS-CoV-2 cases among 3,273 healthcare workers and measured the course of the antibody signal using the Abbott Architect SARS-CoV-2 IgG assay and the Roche Elecsys® Anti-SARS-CoV-2 immunoassay. The signal strength was then modelled using linear mixed models adjusted for age.
Since first sampling, the assay signal decreased per day in the Abbott assay (standardized slope (β) = -0.46, 95% CI = -0.54 to -0.39). In contrast, an increase in the signal was ascertained by the Roche immunoassay per day (β = 0.25, 95% CI = 0.09 to 0.41).
Roche Elecsys® Anti-SARS-CoV-2 immunoassay may exhibit greater sensitivity in detecting SARS-CoV-2-specific antibodies in individuals in late stages of postinfection.
The vast occurrence of mine drainage worldwide, documented in descriptive studies, presents a staggering challenge for remediation. Any tool that can move beyond descriptive study and helps to ...evaluate options for remediation in a way that maximizes improvements to the water quality of streams and minimizes cost of remediation could save valuable resources and time. A reactive solute transport model, calibrated from two detailed mass-loading studies in Little Cottonwood Creek (LCC), Utah, provides a tool to evaluate remediation options. Metal loading to LCC is dominated by discharge from two mine drainage tunnels. Discharge from an upstream tunnel has been treated by a fen to reduce metal loading. Discharge from the downstream tunnel (WDT) can be controlled because of a bulkhead that creates a mine pool. Simulations of remedial options for three compliance locations suggest that the water-quality standards for Cu and Zn at upstream and downstream compliance locations are met using various combinations of fen treatment and WDT regulation, but the complete compliance at the middle compliance location requires the highest level of fen treatment and the greatest regulation of WDT discharge. Reactive transport modeling is an useful tool for the evaluation of remedial alternatives in complex natural systems, where multiple hydrologic and geochemical processes determine metal fate.
A confocal imaging and image processing scheme is introduced to visualize and evaluate the spatial distribution of spectral information in tissue. The image data are recorded using a confocal ...laser-scanning microscope equipped with a detection unit that provides high spectral resolution. The processing scheme is based on spectral data, is less error-prone than intensity-based visualization and evaluation methods, and provides quantitative information on the composition of the sample. The method is tested and validated in the context of the development of dermal drug delivery systems, introducing a quantitative uptake indicator to compare the performances of different delivery systems is introduced. A drug penetration study was performed in vitro. The results show that the method is able to detect, visualize and measure spectral information in tissue. In the penetration study, uptake efficiencies of different experiment setups could be discriminated and quantitatively described. The developed uptake indicator is a step towards a quantitative assessment and, in a more general view apart from pharmaceutical research, provides valuable information on tissue composition. It can potentially be used for clinical in vitro and in vivo applications.
Background The young field of obesity surgery (bariatric surgery) in Germany expands as a consequence of the rapid increase of overweight and obesity. New surgical methods, minimal access techniques, ...and the enormous increase of scientific studies and evidence, all contribute to the success of bariatric surgery, which is the only realistic chance of permanent weight loss and regression of secondary diseases in many cases. Methods A systematic literature review, classification of evidence, graded recommendations, and interdisciplinary consensus. Results Obesity surgery is an integral component of the multimodal treatment of obesity, which consists of multidisciplinary evaluation and preparation, conservative and surgical treatment elements, and a life-long follow-up. The guideline confirms the body mass index (BMI)-based spectrum of indications (BMI > 40 kg/m² or >35 kg/m² with secondary diseases) and extends it through elimination of all age restrictions (>18 years and <60 years) and most of the contraindications. Precondition for surgery is the failure of a structured conservative program of 6-12 months or the expected futility of it. Type II diabetes mellitus becomes an independent indication criterion for BMI < 35 kg/m² (metabolic surgery). The standard techniques are gastric balloon, gastric banding, gastric bypass, gastric sleeve, and biliopancreatic diversion. The choice of procedure is based on profound knowledge of results, long-term effects, complications, and patient-specific circumstances. The after-care should be structured and organized long term. Conclusion The S3-guidelines contain evidence-based recommendations for the indication, selection of procedure, technique, and follow-up. Patient care should improve after implementation of these guidelines in clinical practice. Compliance by decision makers and health insurers is warranted.
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