A new channel pattern classification is presented based on theoretically derived channel pattern discriminant functions. The thresholds are formulated as power laws that relate the critical slope ...associated with a change in channel pattern to dimensionless discharge and relative bank strength. One threshold demarcates the boundary between stable single-thread channels (both straight and meandering) and stable multiple-thread channels (anabranching). Another threshold separates anabranching from braided channels, where braided channels are considered to be fundamentally unstable. The exponents of the thresholds are nearly identical to that in the threshold equation originally proposed by Leopold and Wolman (1957), and the coefficients are quite similar as well. An analysis of their data set using our dimensionless approach reveals that no fundamental difference exists between meandering and straight patterns, and thus data from both types are grouped together under the more general heading of single-thread channels. Furthermore, we demonstrate that over a limited range of conditions, an unstable single-thread channel can form stable multiple-threads; but that for systems far from the threshold bounding the single-thread channels, the number of divisions required to produce stable anabranches grows geometrically: this motivates a separation of multiple-thread channels into anabranching and braided types. Our theoretical thresholds are then compared against several large data sets of field data, and the results broadly confirm our proposed thresholds.
Remote sensing of laboratory rivers Leenman, Anya S.; Eaton, Brett C.
Earth surface processes and landforms,
January 2024, 2024-01-00, 20240101, Letnik:
49, Številka:
1
Journal Article
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Remote sensing enables us to measure fluvial systems without disrupting their dynamics. Small‐scale physical models of rivers allow us to observe their geomorphic evolution, but we need remote ...sensing methods to monitor these laboratory landscapes without altering their flow or topography, just as with field‐scale rivers. In this paper, we review how experimental geomorphologists have adapted remote sensing for the laboratory. We consider how remote methods to monitor model topography, flow depth, velocity and planform have been employed, enabling uninterrupted experimental evolution. We also explore the transfer of techniques between field‐scale and experimental remote sensing; the controlled conditions in the lab aided the development of some methods, while others benefited from airborne deployment. We consider recent developments offered by laboratory remote sensing, including through‐water laser scanning and adaptations of structure‐from‐motion photogrammetry; we also consider new challenges associated with these developments, such as computational power. Finally, we discuss new research problems that laboratory remote sensing is opening up to geomorphology. We hope this review will be useful for experimentalists seeking to collect data remotely, continuously and/or cost‐effectively.
Remote sensing can be adapted for the lab to monitor the evolution of physical experiments without disrupting their processes. We review ways to deploy ‘remote sensing’ for experiments in fluvial geomorphology. We hope this paper will be helpful for experimentalists who want to collect data both continuously and cost‐effectively.
We examine professionals’ use of telecommuting, perceptions of psychological job control, and boundary management strategies. We contend that work–family research should distinguish between ...descriptions of flexibility use (formal telecommuting policy user, amount of telecommuting practiced) and how the individual psychologically experiences flexibility (perceived control over where, when, and how one works, boundary management strategies regarding separation between work and family roles). Survey and interview data were collected from 245 professionals in two Fortune 500 firms with telework policies. Employees who perceived greater psychological job control had significantly lower turnover intentions, family–work conflict, and depression. Boundary management strategies higher on integration were positively related to family–work conflict. Although we found a main effect for formal policy use and higher depression, an interaction existed where women users with children had lower depression. Formal use positively related to supervisor performance ratings. Future research should distinguish between descriptive use and psychological experiences of flexibility.
To evaluate racial and ethnic disparities in utilization of total knee arthroplasty (TKA) in relation to demographic, health, and socioeconomic status variables.
Prospective study of 102,767 Women's ...Health Initiative postmenopausal women initially aged 50–79, examining utilization rates of primary TKA between non-Hispanic Black/African American, non-Hispanic White, and Hispanic/Latina women (hereafter referred to as Black, White, and Hispanic). A total of 8,942 Black, 3,405 Hispanic, and 90,420 White women with linked Medicare claims data were followed until time of TKA, death, or transition from fee-for-service coverage. Absolute disparities were determined using utilization rates by racial/ethnic group and relative disparities quantified using multivariable hazards models in adjusting for age, arthritis, joint pain, mobility disability, body mass index, number of comorbidities, income, education, neighborhood socioeconomic status (SES), and geographic region.
TKA utilization was higher among White women (10.7/1,000 person-years) compared to Black (8.5/1,000 person-years) and Hispanic women (7.6/1,000 person-years). Among women with health indicators for TKA including diagnosis of arthritis, moderate to severe joint pain, and mobility disability, Black and Hispanic women were significantly less likely to undergo TKA after adjusting for age Black: HR (95% confidence interval) = 0.70 (0.63–0.79); Hispanic: HR = 0.58 (0.44–0.77). Adjustment for SES modestly attenuated the measured disparity, but significant differences remained Black: HR = 0.75 (0.67–0.89); Hispanic: HR = 0.65 (0.47–0.89).
Compared to White women, Black and Hispanic women were significantly less likely to undergo TKA after considering need and appropriateness for TKA and SES. Further investigation into personal-level and provider-level factors that may explain these disparities is warranted.
Aldosterone activates the intercalated cell mineralocorticoid receptor, which is enhanced with hypokalemia. Whether this receptor directly regulates the intercalated cell chloride/bicarbonate ...exchanger pendrin is unclear, as are potassium's role in this response and the receptor's effect on intercalated and principal cell function in the cortical collecting duct (CCD).
We measured CCD chloride absorption, transepithelial voltage, epithelial sodium channel activity, and pendrin abundance and subcellular distribution in wild-type and intercalated cell-specific mineralocorticoid receptor knockout mice. To determine if the receptor directly regulates pendrin, as well as the effect of serum aldosterone and potassium on this response, we measured pendrin label intensity and subcellular distribution in wild-type mice, knockout mice, and receptor-positive and receptor-negative intercalated cells from the same knockout mice.
Ablation of the intercalated cell mineralocorticoid receptor in CCDs from aldosterone-treated mice reduced chloride absorption and epithelial sodium channel activity, despite principal cell mineralocorticoid receptor expression in the knockout mice. With high circulating aldosterone, intercalated cell mineralocorticoid receptor gene ablation directly reduced pendrin's relative abundance in the apical membrane region and pendrin abundance per cell whether serum potassium was high or low. Intercalated cell mineralocorticoid receptor ablation blunted, but did not eliminate, aldosterone's effect on pendrin total and apical abundance and subcellular distribution.
With high circulating aldosterone, intercalated cell mineralocorticoid receptor ablation reduces chloride absorption in the CCD and indirectly reduces principal cell epithelial sodium channel abundance and function. This receptor directly regulates pendrin's total abundance and its relative abundance in the apical membrane region over a wide range in serum potassium concentration. Aldosterone regulates pendrin through mechanisms both dependent and independent of the IC MR receptor.
We report catalytic silylation of dinitrogen to tris(trimethylsilyl)amine by a series of trinuclear first row transition metal complexes (M = Cr, Mn, Fe, Co, Ni) housed in our tris(β‐diketiminate) ...cyclophane (L3–). Yields are expectedly dependent on metal ion type ranging from 14 to 199 equiv. NH4+/complex after protonolysis for the Mn to Co congeners, respectively. For the series of complexes, the observed trend for the number of turnovers as a function of metal ion type is Co > Fe > Cr > Ni > Mn, consistent with prior reports of greater efficacy of Co over Fe in other ligand systems for this reaction.
Catalytic silylation of dinitrogen to tris(trimethylsilyl)amine by a series of trinuclear first row transition metal complexes (M = Cr, Mn, Fe, Co, Ni) is reported. Yields depend on metal ion type ranging from 14 to 199 equiv. NH4+/complex after protonolysis for the Mn to Co congeners, respectively.
Background: Quantitative magnetic resonance imaging (qMRI) may provide valuable measures of cartilage morphology in osteoarthritis (OA) but has been confined to sequences with relatively long ...acquisition times at 1.5 Tesla (T). Objective: To test the accuracy and precision of knee cartilage qMRI with a fast double echo, steady state (DESS) sequence with water excitation (we) at 3 T. Methods: As a pilot study for the Osteoarthritis Initiative, test-retest MR images were acquired in the knees of 19 participants with no OA to moderate degrees of clinical OA. Two double oblique coronal fast low angle shot (FLASHwe) sequences (1.5 mm slice thickness) were acquired at 3 T, and two sagittal DESSwe sequences (0.7 mm slice thickness). Double oblique coronal multiplanar reformats (MPR) were performed (1.5 mm slice thickness) from the sagittal DESSwe. Knee joint cartilage plates were quantified unpaired in random order with blinding to subject identification. Results: In the femorotibial joint, precision errors (root mean square coefficient of variation in % for unpaired analysis) for cartilage volume and thickness were 3.0–6.4% with coronal FLASHwe, 2.4–6.2% with coronal MPR DESSwe, and 2.3–8.2% with sagittal DESSwe. Correlation coefficients between DESSwe and FLASHwe ranged from r = 0.88 to 1.0. In the femoropatellar joint, precision errors (sagittal DESSwe) were 3.4–8.5%. Conclusions: DESSwe permits accurate and precise analysis of cartilage morphology in the femorotibial joint at 3 T. Further studies are needed to examine the accuracy of DESSwe in the femoropatellar joint and its ability to characterise sensitivity to longitudinal changes in cartilage morphology.
To examine the association of alcohol consumption with risk of incident knee osteoarthritis (OA) in a large prospective cohort study.
In the Osteoarthritis Initiative, 2,846 participants aged 45–79 ...years and free from radiographic knee OA in at least one knee at baseline were followed up to 96 months. Information on baseline alcohol consumption was obtained from the Block Brief Food Frequency Questionnaire. Incident cases of radiographic knee OA (ROA) were defined as Kellgren–Lawrence grade changing from zero or one to ≥ two during the follow-up time. Incident symptomatic OA (SxOA) was defined as ROA with knee pain worsening. The Cox proportional hazards models were used to assess the independent association between alcohol consumption and risk of knee.
During 96 months’ follow-up, we identified 691 knees with incident ROA, and 496 knees with incident SxOA among 2,846 subjects. Compared to non-drinkers, excessive alcohol consumption was significantly associated with increased risk of ROA (HR ≥ 30 g/d vs none = 1.93, 95% CI: 1.28–2.89) and SxOA (HR ≥ 30 g/d vs none = 1.61, 95% CI: 1.04–2.48). Similar association was observed for liquor consumption (HR liquor≥15 g/d vs none = 1.71, 95% CI: 1.16–2.52 for ROA; HR liquor≥15 g/d vs none = 1.59, 95% CI: 1.04–2.39 for SxOA). Light to moderate alcohol consumption was not associated with knee OA risk.
Our results suggest that excessive alcohol drinking was associated with an increased risk of knee OA. Further studies are needed in other populations.
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