The Analysis of Two-Dimensional Laminar Flow Utilizing a Doubly Refracting Liquid

The optical characteristic exhibited by certain liquids known as flow double refraction offers attractive features in the analysis of two-dimensional laminar flow situations, especially those in which measuring probs are undesirable. Such liquids become anisotropic to the passage of light when set in motion; and when they are viewed in polarized light while flowing through a transparent channel, visible interference patterns are observed. These patterns may be related to the magnitude and direction of the shearing stresses set up by two-dimensional laminar flow, and from suitable calibration under down flow conditions they may be used to determine the stress distribution in an unknown flow situation. Attempts made by previous investigators to apply this technique to the analysis of flow have not yielded promising results. The doubly refracting test liquids used have been either very unstable or extremely viscous. Also, results have been analyzed under the assumption that doubly refracting properties could be correlated directly in terms of streamline directions and velocity gradients, rather than in terms of the direction and magnitude of the shearing stresses in the liquid. This assumption appears questionable in the light of certain experimental facts noted in this investigation, except for flow cases involving parallel streamlines. The objectives of the present investigation were two-fold: (a) the development of methods for predicting stream-line directions and velocity gradients from the stress distributions obtained from double refraction measurements, thus avoiding the necessity of any direct correlation between the gradients themselves and the doubly refracting properties, and (b) the experimental application of these methods to two-dimensional laminar flow situations, and the checking of results by independent means whenever possible. The desired analytical methods were developed, and experimental studies were carried out for the following situations: (a) flow between parallel plates, (b) converging and diverging flow between flat, non-parallel plates, and (c) flow about a cylindrical obstacle in a bounded channel. In case (a), streamlines were determined by the parallel channel walls. In case (b), streamlines were assumed to be straight lines emanating radically from the point of intersection of the non-parallel walls. In case (c), streamlines were determined from information on stress directions obtained from the flow double refraction patterns. The doubly refracting liquids employed were aqueous solutions of a commercial dye, milling yellow, which remain stable over a period of approximately two weeks, and which have viscosities in the neighborhood of twenty centipoises. They show Newtonian behavior under shearing stresses less than 5 dynes per swuare centimeter, the range of interest of this investigation. Correlation of doubly refracting properties with stress was obtained by observation of the known flow situation in the annular space between fixed and rotating concentric cylinders. The flow test channel was made of Plexiglass and was of rectangular cross section with a high aspect ratio (ratio of width to depth) in order to approximate two-dimensional flow. The channel was five inches wide and contained 1-inch and 1/2-inch deep sections joined by a converging section. A velocity profile obtained from double refraction measurements for plane parallel flow was checked with that predicted by the theoretical formula for flow between plane parallel plates, and all points agreed with 3.0 percent. Velocity profiles in plane parallel, converging, and diverging flow were integrated to yield total discharges for each case. Agreement was within a maximum deviation of 10.0 percent and a mean square deviation of 4.2 percent for all plane parallel flow cases, and within a maximum deviation of 13.5 percent and a mean square deviation of 7.8 percent for all converging and diverging flow cases. The experimental discharge was required in the analysis of flow about a cylindrical obstacle, and could not be used for comparison. However, the viscous drag coefficient for the cylinder was calculated from flow double refraction measurements and compared with theoretical and experimental literature values. Agreement was found within 2.0 percent with the theoretical value and within 10.5 percent with the experimental value. The range of flow rates covered was from 20 to 200 cu.cm./sec., and corresponded to Reynolds numbers from approximately 1 to 10. In conclusion, it appears that the technique offers attractive possibilities for the analysis of complex two-dimensional laminar flow situations, and with certain experimental refinements, should be capable of even better results that those reported above

Glyoxal observations in the global marine boundary layer

Glyoxal is an important intermediate species formed by the oxidation of common biogenic and anthropogenic volatile organic compounds such as isoprene, toluene and acetylene. Although glyoxal has been shown to play an important role in urban and forested environments, its role in the open ocean environment is still not well understood, with only a few observations showing evidence for its presence in the open ocean marine boundary layer (MBL). In this study, we report observations of glyoxal from ten field campaigns in different parts of the world's oceans. These observations together represent the largest database of glyoxal in the MBL. The measurements are made with similar instruments that have been used in the past, although the open ocean values reported here, average of about 25 pptv with an upper limit of 40 pptv, are much lower than previously reported observations that were consistently higher than 40 pptv and had an upper limit of 140 pptv, highlighting the uncertainties in the Differential Optical Absorption Spectroscopy (DOAS) method for the retrieval of glyoxal. Despite retrieval uncertainties, the results reported in this work support previous suggestions that the currently known sources of glyoxal are insufficient to explain the average MBL concentrations. This suggests that there is an additional missing source, more than a magnitude larger than currently known sources, which is necessary to account for the observed atmospheric levels of glyoxal. Therefore it could play a more important role in the MBL than previously considered

Multiscale, multimodal analysis of tumor heterogeneity in IDH1 mutant vs wild-type diffuse gliomas.

Glioma is recognized to be a highly heterogeneous CNS malignancy, whose diverse cellular composition and cellular interactions have not been well characterized. To gain new clinical- and biological-insights into the genetically-bifurcated IDH1 mutant (mt) vs wildtype (wt) forms of glioma, we integrated data from protein, genomic and MR imaging from 20 treatment-naïve glioma cases and 16 recurrent GBM cases. Multiplexed immunofluorescence (MxIF) was used to generate single cell data for 43 protein markers representing all cancer hallmarks, Genomic sequencing (exome and RNA (normal and tumor) and magnetic resonance imaging (MRI) quantitative features (protocols were T1-post, FLAIR and ADC) from whole tumor, peritumoral edema and enhancing core vs equivalent normal region were also collected from patients. Based on MxIF analysis, 85,767 cells (glioma cases) and 56,304 cells (GBM cases) were used to generate cell-level data for 24 biomarkers. K-means clustering was used to generate 7 distinct groups of cells with divergent biomarker profiles and deconvolution was used to assign RNA data into three classes. Spatial and molecular heterogeneity metrics were generated for the cell data. All features were compared between IDH mt and IDHwt patients and were finally combined to provide a holistic/integrated comparison. Protein expression by hallmark was generally lower in the IDHmt vs wt patients. Molecular and spatial heterogeneity scores for angiogenesis and cell invasion also differed between IDHmt and wt gliomas irrespective of prior treatment and tumor grade; these differences also persisted in the MR imaging features of peritumoral edema and contrast enhancement volumes. A coherent picture of enhanced angiogenesis in IDHwt tumors was derived from multiple platforms (genomic, proteomic and imaging) and scales from individual proteins to cell clusters and heterogeneity, as well as bulk tumor RNA and imaging features. Longer overall survival for IDH1mt glioma patients may reflect mutation-driven alterations in cellular, molecular, and spatial heterogeneity which manifest in discernable radiological manifestations