Fitted Regression Line Research Articles

Relationship between positive clinical VTO and post-treatment soft tissue profile following phase l growth modification therapy

Introduction: Facial profile improvement is goal of cotemporary orthodontics and a reason to seek orthodontic therapy. The soft tissue profile plays a important role on orthodontic diagnosis and treatment planning. The objective of this study is to investigate the relationship between positive clinical VTO and actual post-treatment soft tissue profile after phase l therapy of growth modification in Class II.
 Materials & Method: Pretreatment simulation of post-treatment and actual post-treatment profile photographs of 30 class ll div l patients treated with twin block appliance were compared. Three profile photographs of each subject; pretreatment, positive clinical VTO and post-treatment were taken and on each photograph four angles; Nasofacial (NF), Nasomental (NM), Mentocervical (MC) and Nasolabial (NL) were drawn and measured. Mean, standard deviation, success and coefficient of determination of each angle was measured and linear regressions analysis was applied to find out the correlation.
 Result: Nasolabial and nasomental angles showed greater success i.e. 81.4% and 68.1% respectively showing greater correlation, while nasofacial and mentocervical angles showed less success i.e. 48.1% and 48.3% respectively showing less correlation. Linear regression analysis revealed that positive clinical VTO significantly predicted post-treatment profile whereas coefficient of determination for nasomental and mentocervical angles was 76.5% and 60% representing a better goodness of fit while nasolabial and nasofacial angles was 53.6% and 51.6% demonstrating poor fit of regression lines.
 Conclusion: Even though there is improved facial profile obtained by protracting the mandible into class l relation in a chair side maneuver in class ll div l malocclusions, yet the orthodontist should be tentative when predicting the outcome of growth modification to get benefit of this therapy.

FreeSurfer 5.3 versus 6.0: are volumes comparable? A Chronic Effects of Neurotrauma Consortium study

Automated neuroimaging methods like FreeSurfer ( https://surfer.nmr.mgh.harvard.edu/ ) have revolutionized quantitative neuroimaging analyses. Such analyses provide a variety of metrics used for image quantification, including magnetic resonance imaging (MRI) volumetrics. With the release of FreeSurfer version 6.0, it is important to assess its comparability to the widely-used previous version 5.3. The current study used data from the initial 249 participants in the ongoing Chronic Effects of Neurotrauma Consortium (CENC) multicenter observational study to compare the volumetric output of versions 5.3 and 6.0 across various regions of interest (ROI). In the current investigation, the following ROIs were examined: total intracranial volume, total white matter volume, total ventricular volume, total gray matter volume, and right and left volumes for the thalamus, pallidum, putamen, caudate, amygdala and hippocampus. Absolute ROI volumes derived from FreeSurfer 6.0 differed significantly from those obtained using version 5.3. We also employed a clinically-based evaluation strategy to compare both versions in their prediction of age-mediated volume reductions (or ventricular increase) in the aforementioned structures. Statistical comparison involved both general linear modeling (GLM) and random forest (RF) methods, where cross-validation error was significantly higher using segmentations from FreeSurfer version 5.3 versus version 6.0 (GLM: t = 4.97, df = 99, p value = 2.706e-06; RF: t = 4.85, df = 99, p value = 4.424e-06). Additionally, the relative importance of ROIs used to predict age using RFs differed between FreeSurfer versions, indicating substantial differences in the two versions. However, from the perspective of correlational analyses, fitted regression lines and their slopes were similar between the two versions, regardless of version used. While absolute volumes are not interchangeable between version 5.3 and 6.0, ROI correlational analyses appear to yield similar results, suggesting the interchangeability of ROI volume for correlational studies.

Kinetic modeling impacts of relative humidity, storage temperature, and air flow velocity on various indices of hen egg freshness

ABSTRACTStorage experiments were conducted to study the impacts of the environmental factors (temperature (T) (°C), relative humidity (RH) (%), and air flow velocity (VEL) (m/s)) on the hen egg quality indices and to develop kinetic model(s) for freshness prediction. VEL had negligible effect on relative weight loss (RWL). All factors had significant effect on Haugh unit (HU) but only T impacted S-ovalbumin content (SO). Fitted regression lines for the RWL and the HU had determination coefficient (R2) of 0.996 and 0.95, respectively. The HU equation reflected impacts of all factors, and the impact of temperature shift-up increases the HU decrease, where the impact decreases with RH and increases with flow velocity. Kinetic model for SO was developed using isothermal (5, 10, 20, 25, and 28.5°C) conditions and validated under dynamic (10 to 20 and 10 to 28.5°C) conditions. The accuracy and bias factor values were 1.091 and 0.917 at 10 to 20°C and 1.206 and 1.204 at 10 to 28.5°C, respectively, which indicates that the SO model performed well. The SO model can be used along with the HU model (as the HU model can reflect the combined effect of temperature, humidity, and air flow velocity) to predict hen egg freshness at 5 to 28.5°C storage condition.

Atherogenicity of diabetic rats administered single and combinatorial herbal extracts

ObjectiveThe present study sought to investigate atherogenicity of alloxan-induced diabetic rats administered single and combinatorial herbal formulations of Acanthus montanus, Asystasia gangetica, Gongronema latifolium and Solanum melongena. MethodsA single intra-peritoneal (i.p.) injection of 90 mg/kg b.w. of alloxan monohydrate was given to the rats to induce diabetes mellitus (DM). Serum lipid profiles were measured using standard spectrophotometric methods, whereas atherogenicity, serum lipid ratios and atherogenic coefficient/indices were calculated using standard formulae. ResultsSerum total cholesterol (TC) concentrations of experimental rat groups varied between 1.59 ± 0.10 mmol/L and 2.72 ± 0.16 mmol/L (p < 0.05). Serum high-density lipoprotein cholesterol (HDL-C) concentration of untreated DM rat (DM-r) group was significantly lower (p < 0.05) than those of treated DM-r groups. Atherogenic risk indices (ARIs) of treated DM-r groups were within the range of 0.74 ± 0.03 and 2.64 ± 0.21, whereas ARI of untreated DM-r was 4.04 ± 0.25. The linear regression analysis of atherognic index of plasma (AIP) versus serum low-density lipoprotein cholesterol (LDL-C) concentrations of the experimental rat groups gave a relatively close fitted regression line (R2 = 0.8275). Atherogenic protection of herbal extract treated DM-r groups was within the range of 33.4–81.7%. ConclusionThe present study showed that double herbal formulations (DHFs): A. gangetica + G. latifolium and A. gangetica + A. montanus offered comparatively high protection to DM-r against atherogenic outcomes, which paralleled the capacities of these DHFs to reverse dyslipidemia.

Source identification, geochemical normalization and influence factors of heavy metals in Yangtze River Estuary sediment

Sediment samples, including 40 surface samples and 12 sediment cores, were collected from 52 stations of the Yangtze River Estuary (YRE) in 2015 and 2016. The 95% linear prediction intervals (LPI) and principal components analysis (PCA), were conducted to evaluate the metal sources and grain-size effect (GSE). The in situ physico-chemical properties of pH, Eh, DO, salinity, temperature and turbidity were combined to elucidate the relationships between environmental factors and the fate of heavy metals in the river-estuary-shelf system. This study indicates a decreasing trend of metals in sediments from the estuary towards the adjacent shelf and the river channel and that Zn, Cu and Cr are mainly derived from natural processes throughout the catchment, whereas Pb appears to have anthropogenic inputs via atmospheric deposition. Furthermore, considering the best fit regression lines between the concentrations of Al and heavy metals as well as the deficiencies of the conventional Celements/CAl method, we introduce an approach (Al-SN: Al-scope normalization) that can eliminate the GSE on heavy metals and be applied to other estuaries. After Al-scope normalization, the relatively constant levels of Zn, Cu and Cr that remain in sediments from the river channel to the estuary and shelf confirmed that the variation of grain size in sediments almost entirely explained the distribution patterns of sediment toxicity in the YRE, while the enrichment of Pb in estuarine sediments could be attributed to its chemical species and physico-chemical properties. The results further suggest that the relationship between grain size and spatial behavior of sediment pollutants should be given priority over the contamination assessment and provenance discrimination in estuarine or similar environments with complex sediment compositions.

Importance of Considering the Middle Capillary Plexus on OCT Angiography in Diabetic Retinopathy.

PurposeTo quantify microvasculature changes in the superficial (SCP), middle (MCP), and deep capillary plexuses (DCP) in diabetic retinopathy (DR).MethodsRetrospective cross-sectional study at a tertiary academic referral center, in which 26 controls (44 eyes), 27 diabetic subjects without retinopathy (44 eyes), 32 subjects with nonproliferative retinopathy (52 eyes), and 27 subjects with proliferative retinopathy (40 eyes) were imaged with optical coherence tomography angiography (OCTA). Outcome measures included parafoveal vessel density (VD), percentage area of nonperfusion (PAN), and adjusted flow index (AFI) at the different plexuses.ResultsMCP VD and MCP AFI decreased with worsening DR, while PAN increased, mirroring changes within the DCP. The fitted regression line for MCP and DCP AFI were significantly different than the SCP, while DCP PAN differed from SCP PAN with disease progression. Higher SCP AFI and PAN were different in eyes with diabetes without retinopathy compared with controls. Unexpectedly, sex was found to independently influence MCP VD and AFI with worsening disease.ConclusionsOCTA parameters in the MCP and DCP displayed parallel changes with DR progression, different from the SCP, emphasizing the importance of physiologic considerations in the retinal capillaries. Thus, segmentation protocols that include the MCP within the SCP may be confounded. A difference in DCP PAN with worsening DR was unmasked relative to a prior study that included the MCP with SCP. We confirm that SCP AFI and PAN may serve as early indicators of microvascular changes in DR and identify an interaction between sex and the MCP deserving further study.

Least median of squares and iteratively re-weighted least squares as robust linear regression methods for fluorimetric determination of α-lipoic acid in capsules in ideal and non-ideal cases of linearity.

This study outlines two robust regression approaches, namely least median of squares (LMS) and iteratively re-weighted least squares (IRLS) to investigate their application in instrument analysis of nutraceuticals (that is, fluorescence quenching of merbromin reagent upon lipoic acid addition). These robust regression methods were used to calculate calibration data from the fluorescence quenching reaction (∆F and F-ratio) under ideal or non-ideal linearity conditions. For each condition, data were treated using three regression fittings: Ordinary Least Squares (OLS), LMS and IRLS. Assessment of linearity, limits of detection (LOD) and quantitation (LOQ), accuracy and precision were carefully studied for each condition. LMS and IRLS regression line fittings showed significant improvement in correlation coefficients and all regression parameters for both methods and both conditions. In the ideal linearity condition, the intercept and slope changed insignificantly, but a dramatic change was observed for the non-ideal condition and linearity intercept. Under both linearity conditions, LOD and LOQ values after the robust regression line fitting of data were lower than those obtained before data treatment. The results obtained after statistical treatment indicated that the linearity ranges for drug determination could be expanded to lower limits of quantitation by enhancing the regression equation parameters after data treatment. Analysis results for lipoic acid in capsules, using both fluorimetric methods, treated by parametric OLS and after treatment by robust LMS and IRLS were compared for both linearity conditions.

Trend Analysis of the Value Added Tax in Nepal

&lt;p&gt;Value added tax (VAT) is the recent one of the sales tax family. This article tries to estimate the share of VAT in Gross Domestic Product (GDP), total tax revenue and indirect tax revenue. Besides, it also estimates the growth rate of VAT. This comprises 2.80 percent and 16.01 percent share of GDP in fiscal year 2000/01 and 2014/15 respectively. It also ranges from 30.69 percent to 37.63 percent share of tax revenue. Likewise, its share ranges from39.94 percent to 50.05 percent. The regression equation has been used to estimate annual growth rate of VAT. The estimate of the annual growth rate of VAT is found to be Rs.6.63billion. From this result, it is obvious that VAT has been increased by Rs. 6.63 billion annually during study period of the fifteen years. The coefficient of determination (R2) shows 87.76% of the total variation in VAT is explained by the variation in time variable. Similarly, the adjusted coefficient of determination (R2) exhibits that 86.82% of the total variance in VAT is explained by the variance in time variable. The calculated value of F-distribution is found to be 93.204, which is greater than critical value of F i.e. F0.05 (1,13)=4.67. It is significant at 5% level, which exhibits the best fitted regression line. From the statistical analysis, the value of autocorrelation is found to be 0.54 and its d-statistic is also found, which is significant at 5 percent level. Thus, the analysis justifies that there is a positive autocorrelation among error terms. To remove the autocorrelation, the transformation data have been used. But, the value of autocorrelation is not found corrected which needs by incorporating other important explanatory variables to further research.&lt;/p&gt;&lt;p&gt; &lt;strong&gt;&lt;em&gt;Economic Literature&lt;/em&gt;&lt;/strong&gt;&lt;em&gt;, &lt;/em&gt;Vol. XIII August 2016, page 1-8&lt;/p&gt;&lt;p&gt; &lt;/p&gt;

Community structure and biovolume size spectra of mesozooplankton in the Pearl River estuary

The Pearl River estuary is the second largest estuary in China. This study reported the species composition and size structure of mesozooplankton in the upper and lower Pearl River estuary in the dry and wet seasons. The normalized biovolume size spectrum of mesozooplankton was constructed to analyze the trophic structure of the community. Copepods were the numerically predominant mesozooplankton group at all sampling stations. However, when converted into biovolume, medusae were dominant in the upper estuary in the dry season and Chaetognatha were dominant in the lower estuary in the wet season. There were apparent seasonal and spatial variations in the normalized biovolume size spectrum characteristics in the Pearl River estuary. In the dry season, the average fitted regression line of the normalized biovolume size spectrum had a slope of −1.02 in the upper estuary and −0.88 in the lower estuary. In the wet season, the average fitted regression line of the normalized biovolume size spectrum had a slope of −0.32 in the lower estuary, and no significant regression of the normalized biovolume size spectrum was found in the upper estuary. It is suggested that the mesozooplankton community was unstable in the upper estuary due to the strong freshwater perturbation in the wet season. The size diversity and normalized biovolume size spectrum slope indicated that the strength of top-down control and trophic efficiency was highest in the lower estuary in the wet season.

Measuring and Comparing Student Performance: A New Technique for Assessing Directional Associations

Measuring and comparing student performance have been topics of much interest for educators and psychologists. Particular attention has traditionally been paid to the design of experimental studies and careful analyses of observational data. Classical statistical techniques, such as fitting regression lines, have traditionally been utilized and far-reaching policy guidelines offered. In the present paper, we argue in favour of a novel technique, which is mathematical in nature, and whose main idea relies on measuring distance of the actual bivariate data from the class of all monotonic (increasing in the context of this paper) patterns. The technique sharply contrasts the classical approach of fitting least-squares regression lines to actual data, which usually follow non-linear and even non-monotonic patterns, and then assessing and comparing their slopes based on the Pearson correlation coefficient, whose use is justifiable only when patterns are (approximately) linear. We describe the herein suggested distance-based technique in detail, show its benefits, and provide a step-by-step implementation guide. Detailed graphical and numerical illustrations elucidate our theoretical considerations throughout the paper. The index of increase, upon which the technique is based, can also be used as a summary index for the LOESS and other fitted regression curves.

Assessing student understanding of measurement and uncertainty

The objectives of this study were to develop and assess student understanding of measurement and uncertainty. A test has been adapted and translated from the Laboratory Data Analysis Instrument (LDAI) test, consists of 25 questions focused on three topics including measures of central tendency, experimental errors and uncertainties, and fitting regression lines. The test was evaluated its content validity by three physics experts in teaching physics laboratory. In the pilot study, Thai LDAI was administered to 93 freshmen enrolled in a fundamental physics laboratory course. The final draft of the test was administered to three groups—45 freshmen taking fundamental physics laboratory, 16 sophomores taking intermediated physics laboratory and 21 juniors taking advanced physics laboratory at Chiang Mai University. As results, we found that the freshmen had difficulties in experimental errors and uncertainties. Most students had problems with fitting regression lines. These results will be used to improve teaching and learning physics laboratory for physics students in the department.

Identifying highly informative genetic markers for quantification of ancestry proportions in crossbred sheep populations: implications for choosing optimum levels of admixture

Understanding the relationship between genetic admixture and performances is crucial for the success of crossbreeding programs. Use of small sets of ancestry informative markers (AIMs) is a cost effective option to estimate the levels of admixture in situations where pedigree recording is difficult. In this study we select AIMs from Ovine 50KSNP data (SNP – single nucleotide polymorphism) and validate their ability in estimating the contributions of parental breeds to get information about optimum admixture levels for smallholders. We estimated admixture levels using ADMIXTURE software based on 74 AIMs selected from Ovine 50KSNP data. Awassi x Ethiopian fat-tailed crossbred sheep populations kept in government farms and farmer villages in different districts were included in the study. Mean Awassi levels estimated based on the selected AIMs were close to the Awassi levels obtained from pedigree information. Estimates from the 74 SNPs were compared to subsets of 65, 55, 45, 35, 25 and 15 SNPs selected based on both top and bottom fixation index (FST) rank using Spearman’s rank correlation (r = 0.862–0.996). A t-test comparison revealed that all SNP subsets had produced similar (P > 0.05) estimates with the 74 SNPs, except for the bottom 15 SNPs (P < 0.05). However estimates based on 45 and above SNP subsets were relatively close to the fitted regression line (r = 0.969–0.996). Association of admixture levels with lamb growth showed that Awassi level affected (P < 0.05) eight months weight in both farmer locations, lambs with higher Awassi levels were heavier. Lambing interval of ewes was longer as Awassi level increased, but this drawback was outweighed by the increased productivity of ewes in terms of eight months lamb weight per year. The results indicate that the Ovine 50KSNP array is a powerful tool to identify small sets of AIMs for admixture studies. The results of this study reveal about 45AIMs to accurately estimate admixture levels. If admixture estimation service with such low cost SNP chip would be available, farmers would have a clear market advantage without the need to rely on incomplete or possibly inaccurate pedigree records. Based on the results presented here, we were able to suggest optimum levels of breed composition for the two farmer environments investigated.

Improved Statistical Methods for Evaluation of Stability of In Vitro Diagnostic Reagents

ABSTRACTIn vitro diagnostic (IVD) reagent stability is typically evaluated using regression analysis of measurand drift across time following CLSI guideline EP25-A. The corresponding stability duration establishment has several limitations. The stability duration conclusion is based on a two-stage acceptance criteria using the p-value of the regression slope followed by the 95% confidence interval (CI) on the fitted regression line if the p-value <0.05. This analysis technique is based on traditional statistical hypothesis testing; however, the statistical equivalence testing framework better represents the goals of IVD reagent stability evaluation. The resulting stability duration CI does not achieve 95% coverage probability and the statistical properties of the estimated stability duration are substantially impacted by presence of common variance components not accounted for during power analysis and by not accounting for variability in the baseline estimate. The current proposal based on the equivalence testing framework uses a one-stage acceptance criteria based on the 95% CI for proportional measurand drift derived from the regression fit. The proposed methodology was applied to automated immunoassay data (Akbas, Budd, and Klee 2016). Monte Carlo simulation studies are presented to illustrate the improved statistical properties of the current proposal along with an example power analysis for study design. Supplementary materials for this article are available online.

Comparison of GOME-2 UVA Satellite Data to Ground-Based Spectroradiometer Measurements at a Subtropical Site

The ultraviolet A (UVA) (315–400 nm) daily exposures and maximum daily irradiances from the Global Ozone Monitoring Experiment (GOME)-2 satellite have been compared over three years to the corresponding data from a ground-based spectroradiometer for a subtropical Southern Hemisphere site. This is one of the first such comparisons for the GOME-2 UVA waveband in the Southern Hemisphere. For the UVA daily exposures and the maximum daily irradiances, the comparisons were undertaken for all sky conditions and for cloud-free conditions. Under cloud-free conditions the $R^{2}$ of the fit regression line for the comparisons was 0.93 for the exposures and the irradiances. The influence of cloud reduced the $R^{2}$ values to 0.86 and 0.70 for the daily exposures and maximum irradiances, respectively. The relative root-mean-square error (rRMSE), mean absolute bias error (MABE), and mean bias error (MBE) for the maximum daily UVA irradiances on the cloud-free days were 0.08, 6.59 ± 7.32%, and −1.04 ± 9.83%, respectively. Similarly, for the daily UVA exposures on the cloud-free days, the rRMSE, MABE, and MBE were 0.10, 5.19 ± 6.42%, and −0.79 ± 8.24%, respectively. For the all-sky conditions, the corresponding values were 0.20, 15.23 ± 14.90%, and −0.79 ± 8.24% for the maximum daily irradiances and 0.19, 14.17 ± 14.56%, and −4.63 ± 20.60% for the daily exposures. In all studies of the influence of UVA on human health, this can complement ground-based measurements that provide the higher temporal and spatial resolution available only at a limited number of surface monitoring sites.

Neck Muscle EMG-Force Relationship and Its Reliability During Isometric Contractions

BackgroundSusceptible to injury, the neck is subject to scientific investigations, frequently aiming to elucidate possible injury mechanisms via surface electromyography (EMG) by indirectly estimating cervical loads. Accurate estimation requires that the EMG-force relationship is known and that its measurement error is quantified. Hence, this study examined the relationship between EMG and isometric force amplitude of the anterior neck (AN), the upper posterior neck (UPN), and the lower posterior neck (LPN) and then assessed the relationships’ test-retest reliability across force-percentiles within and between days.MethodsEMG and force data were sampled from 18 participants conducting randomly ordered muscle contractions at 5–90% of maximal voluntary force during three trials over 2 days. EMG-force relationships were modeled with general linear mixed-effects regression. Overall fitted lines’ between-trial discrepancies were evaluated. Finally, the reliability of participants’ fitted regression lines was quantified by an intraclass correlation coefficient (ICC) and the standard error of measurement (SEM).ResultsA rectilinear model had the best fit for AN while positively oriented quadratic models had the best fit for UPN and LPN, with mean adjusted conditional coefficients of determination and root mean square errors of 0.97–0.98 and 4–5%, respectively. Overall EMG-force relationships displayed a maximum 6% between-trial discrepancy and over 20% of maximal force, and mean ICC was above 0.79 within day and 0.27–0.61 between days across areas. Corresponding SEM was below 12% both within and between days across areas, excluding UPN between days, for which SEM was higher.ConclusionsEMG-force relationships were elucidated for three neck areas, and provided models allow inferences to be drawn from EMG to force on a group level. Reliability of EMG-force relationship models was higher within than between days, but typically acceptable for all but the lowest contraction intensities, and enables adjustment for measurement imprecision in future studies.

Sufficient Protein Quality of Food Aid Varies with the Physiologic Status of Recipients

Protein quality scores use the amino acid (AA) requirements of a healthy North American child. AA requirements vary with physiologic status. We estimated AA requirements for healthy North American children, children with environmental enteric dysfunction, children recovering from wasting, and children with an acute infection. The protein quality of food aid products was then calculated to determine whether it was sufficient in all these groups, and we found that it may not be adequate for all of them. Physiologic status is important when assessing the protein quality of food aid. Rates of weight gain from 8 published trials treating children with moderate acute malnutrition were abstracted, and protein quality scores from the corresponding food aid products were calculated with the use of the digestible indispensable amino acid score (DIAAS). Two DIAAS values were calculated, one in healthy children aged 1-3 y as a reference population and the other in malnourished children aged 1-3 y as a reference population. These data were used to calculate the best fit regression line between weight gain and protein quality. The slope of the regression line was greater when malnourished children were used as a reference population than when healthy children were used (0.128; 95% CI: 0.118, 0.138 compared with 0.097; 95% CI: 0.090, 0.105 measured in g · kg-1 · d-1 · DIASS U-1). These findings suggest that adjusting AA requirements for physiologic status may more accurately estimate the minimum protein quality of food aid products.

Fertility Desires and the Course of Fertility Decline in sub‐Saharan Africa

This research has two main goals: (i) to examine fertility desires (number of children) in sub-Saharan Africa: levels as compared to other major regions and recent trends; and (ii) to assess the extent to which fertility decline in sub-Saharan Africa is contingent on decline in fertility desires (singly and in combination with other reproductive changes).

Spatial analysis of an intra-plate basaltic volcanic field in a compressional tectonic setting: South-eastern Australia

The Newer Volcanics Province (NVP) is a Pliocene to Recent intra-plate basaltic volcanic field (BVF) that has formed in a compressive tectonic setting (σv<σhmin<σHmax) and is not readily attributed to a single geodynamic process. A comprehensive spatial analysis of both monogenetic eruption centres and coeval vents of the NVP constrain factors that control the distribution and emplacement of volcanoes. A point-set of 434 eruption centres totalling 726 vents are divided into three geographical sub-provinces for analysis. Kernel density estimation and Poisson nearest neighbour analysis are used to scrutinize the distribution of eruption centres. A simple and novel fitted regression line method is used to determine the orientation of coeval vents, and Hough transform and two-point azimuth methods are used to identify alignments and alignment trends between eruption centres. The distribution of eruption centres and their relative spatial density corresponds with the extent of thinner lithosphere. Eruption centres of the NVP have a clustered distribution whilst smaller sub-sets of eruption centres are distributed more uniformly. The main alignment trends between coeval vents related to individual dikes and between eruption centres related to successive temporally discrete dikes are primarily oriented nearly parallel with pre-existing crustal fault trends. The frequency of volcanic alignments shows faults oriented nearly parallel to the orientation of the regional maximum horizontal compressive stress (σ1) are favourably utilised by intrusions over other fault trends. The depth from which pre-existing faults facilitate dike propagation is not constrained. We interpret they are likely important in preventing dikes from stalling and forming sills under a compressive stress field in the case of the NVP. It is also observed that coeval vent alignments are more strongly aligned in areas overlying consolidated basement relative to areas of poorly consolidated basin sediments. This could be explained by poorly aligned groups of vents being fed by shallow sills, preferentially forming in layered basin sediments.

Cosmogenic 26Al/10Be surface production ratio in Greenland

AbstractThe assumed value for the cosmogenic 26Al/10Be surface production rate ratio in quartz is an important parameter for studies investigating the burial or subaerial erosion of long‐lived surfaces and sediments. Recent models and data suggest that the production ratio is spatially variable and may be greater than originally thought. Here we present measured 26Al/10Be ratios for 24 continuously exposed bedrock and boulder surfaces spanning ~61–77°N in Greenland. Empirical measurements, such as ours, include nuclides produced predominately by neutron‐induced spallation with percent‐level contributions by muon interactions. The slope of a York regression line fit to our data is 7.3 ± 0.3 (1σ), suggesting that the 26Al/10Be surface production ratio exceeds the commonly used value of 6.75, at least in the Arctic. A higher 26Al/10Be production ratio has implications for multinuclide cosmogenic isotope studies because it results in greater modeled burial durations and erosion rates.

Hydration Control in Brain Extracellular Matrix:Astrocytes, Perycites, and Fibroblasts Adjust their Contractile Responses to Local Water Activity

Efficient brain function requires maintenance of optimal tissue hydration. For example, ex vivo, in mouse hippocampal slices, local brain interstitial dehydration impairs neuronal function, and mounting evidence indicates that, first, brain interstitial cells regulate transcapillary fluid exchange and, second, water flows in and out of brain tissue at speeds proportional to the aw (water activity) in the explant culture media, as expected from passive physical principles. We measured the responses of brain interstitial cells to changes in aw to find a common signal linking the passive adjustments to physiologic responses mediated by genetically programmed cell action. We obtained three types of primary cell cultures from human brain (Sciencell Research Laboratories), astrocytes, pericytes, and perivascular fibroblasts, expressing growth-factor astrocyte protein, α-smooth muscle actin, and fibronectin, respectively, and incorporated them into fully hydrated, 3D collagen gels floating in culture medium. We progressively decreased the cultures’ aw by adjusting the dissolved colloids to produce pressures of 4, 42, 100, and 200 mmHg, (corresponding to 0.9. The slopes of fitted regression lines were -0.99 ± .02 for astrocytes; −1.33 ± 0.23 for fibroblasts; and −1.90 ± 0 .19 µl/h/mmHg for pericytes (Means ± SE, n = 4-5). Rate increases with aw were significantly larger for pericytes than fibroblasts (p = 0.043) and astrocytes (p = 0.0048). These results show that brain interstitial cells can detect and respond to minute changes in hydration, adjusting contractile forces to prevent excessive hydration/dehydration in alignment with passive fluid-transfer along aw gradients.