ALBERT

Description: Alginate hydrogel beads are widely used as an encapsulation medium for biomedical, bioprocessing, and pharmaceutical applications. The size and shape of the beads are often critically controlled since in many usages the beads are monodisperse in size and spherical in shape. Extrusion dripping is a well-known method to produce alginate beads. Nevertheless, the production of beads of desired size and spherical shape is often achieved based on one's experience or trial and error. An overview is provided on alginate properties, formulation and preparation of alginate and gelling solutions, production conditions, and post-production treatment that may influence the bead size and shape. Various methods of bead size and shape measurement are also discussed. The influence of significant process variables like alginate properties, formulation and preparation of alginate and gelling solutions, production conditions, and post-production treatment on size and shape of Ca-alginate beads is reviewed. Various methods for bead size determination and shape analysis are described in detail and discussed.

Description: Abstract We performed the first systematic analysis of pickup ion (PUI) cutoff speed variations, across compression regions and due to fast fluctuations in solar wind (SW) speed and magnetic field strength. This study is motivated by the need to remove or correct for systematic effects on the determination of the interstellar flow longitude based on the longitudinal variation of the PUI cutoff. Using 2007–2014 STEREO A PLASTIC observations, we identified SW compression regions and accumulated the contained PUI velocity distributions in a superposed epoch analysis. The shift of the cutoff in velocity, interpreted as PUI energization, varies systematically across the compression region and increases approximately linearly with the speed gradient of the compression. Additionally, the shift remains positive into the negative speed gradient at the beginning of the rarefaction region. A similar response is found when PUI distributions are sorted according to the strength of fast fluctuations in SW speed, density, and magnetic field strength. These parameters remain high in the first part of the rarefaction region, suggesting a possible PUI energization through compressive turbulence. Based on these results, we removed the strongest compression regions from the interstellar flow analysis, finding no significant change in direction or uncertainty. Thus, we have revealed the influence of adiabatic compression and compressive turbulence, increasing the PUI cutoff energy, and we have demonstrated that the determination of the interstellar inflow direction via analysis of PUI distributions is robust for a multiyear data set, even in the presence of SW interaction regions.

Description: Silicic volcanic rocks at Hadjer el Khamis, near Lake Chad, are considered to be an extension of the Cameroon volcanic line (CVL) but their petrogenetic association is uncertain. The silicic rocks are divided into peraluminous and peralkaline groups with both rock types chemically similar to within-plate granitoids. In situ U/Pb zircon dating yielded a mean 206 Pb/ 238 U age of 74.4 ± 1.3 Ma indicating the magmas erupted ∼10 million years before the next oldest CVL rocks (i.e. ∼66 Ma). The Sr isotopes (i.e. I Sr = 0.7021 to 0.7037) show a relatively wide range but the Nd isotopes (i.e. 143 Nd/ 144 Nd i = 0.51268 to 0.51271) are uniform and indicate that the rocks were derived from a moderately depleted mantle source. Thermodynamic modeling show that the silicic rocks likely formed by fractional crystallization of a mafic parental magma but that the peraluminous rocks were affected by low temperature alteration processes. The silicic rocks are isotopically similar to Late Cretaceous basalts identified within the Late Cretaceous basins (i.e. 143 Nd/ 144 Nd i = 0.51245 to 0.51285) of Chad than the uncontaminated CVL rocks (i.e. 143 Nd/ 144 Nd i = 0.51270 to 0.51300). The age and isotopic compositions suggest the silicic volcanic rocks of the Lake Chad region are related to Late Cretaceous extensional volcanism in the Termit basin. It is unlikely that the silicic volcanic rocks are petrogenetically related to the CVL but it is possible that, in both cases, magmatism was structurally controlled by suture zones that formed during the opening of the Central Atlantic Ocean and/or the Pan-African Orogeny. This article is protected by copyright. All rights reserved.

Description: Aqueous chemistry can play a vital role in secondary organic aerosol (SOA) formation and aging. A novel analytical approach that allows for simultaneous photo-oxidation and atomization of reacting bulk solutions coupled to an aerosol mass spectrometer (AMS) investigates aqueous OH oxidation of ambient biogenic SOA, cloud water from a biogenic environment, glyoxal, and mixtures of glyoxal with α-pinene SOA components. This is the first study of aqueous oxidative aging of ambient SOA and cloud water organics. Starting with an AMS-based observational framework, we show that aqueous oxidation of biogenic SOA in the presence of glyoxal can better represent observed atmospheric aging than when glyoxal is absent. Oxidation of glyoxal alongside semi-volatile SOA components leads to the production of highly oxidized SOA.

Description: The magnetopause is the boundary where the reduced solar wind dynamic pressure is equal to the magnetic pressure of the Earth's outer magnetosphere. With hundreds of magnetopause crossings identified from the THEMIS data, we estimate a ratio (f) of the compressed magnetic field just inside the subsolar magnetopause to the purely dipolar magnetic field. Previous theoretical studies reported that the ratio f was nearly independent of the subsolar standoff distance (r0). Here we report that the ratio f is linearly proportional to r0 for both northward and southward interplanetary magnetic field (IMF). The proportionality constant for southward IMF is larger than that for northward IMF, implying that the compression level of the magnetic field by inward magnetopause for southward IMF is smaller than that for northward IMF.

Description: Abstract Traditional methods of carbon monitoring in mountainous regions are challenged by complex terrain. Recently, solar‐induced fluorescence (SIF) has been found to be an indicator of gross primary production (GPP), and the increased availability of remotely‐sensed SIF provides an opportunity to estimate GPP across the Western US. Although the empirical linkage between SIF and GPP is strong, the current mechanistic understanding of this linkage is incomplete, and depends upon changes in leaf biochemical processes in which absorbed sunlight leads to photochemistry, heat (via non‐photochemical quenching, NPQ), fluorescence, or tissue damage. An improved mechanistic understanding is necessary to leverage SIF observations to improve representation of ecosystem processes within land surface models. Here, we included an improved fluorescence model within the Community Land Model, Version 4.5 (CLM 4.5) to simulate seasonal changes in SIF at a subalpine forest in Colorado. We found that when the model accounted for sustained NPQ this provided a larger seasonal change in fluorescence yield leading to simulated SIF that more closely resembled the observed seasonal pattern (GOME‐2 satellite platform and a tower‐mounted spectrometer system). We found that an acclimation model based on mean air temperature was a useful predictor for sustained NPQ. Although light intensity was not an important factor for this analysis, it should be considered before applying the sustained NPQ and SIF to other cold climate evergreen biomes. More leaf level fluorescence measurements are necessary to better understand the seasonal relationship between sustained and reversible components of NPQ and to what extent that influences solar‐induced fluorescence.

Description: The characterization of geologic heterogeneity that affects flow and transport phenomena in the subsurface is essential for cost-effective and reliable decision-making in applications such as groundwater supply and contaminant cleanup. In the last decades, geostatistical inversion approaches have been widely used to tackle subsurface characterization problems and quantify their corresponding uncertainty. Some well-established geostatistical methods use models that assume gradually varying parameters. However, in many cases, the subsurface can often be better represented as consisting of a few relatively uniform geologic facies or zones with abrupt changes at their boundaries. We advance a Bayesian inversion approach with the gradient represented not through a Gaussian but a Laplace prior, also known as total variation prior, for the case that there are reasons to believe that discrete geologic structures with relatively homogeneous properties predominate in the subsurface but their number, locations, and shapes are unknown a priori. Structural parameters (or hyperparameters of the inversion scheme) are determined in a Bayesian framework by maximizing the marginal distribution of these parameters using an expectation-maximization approach; this allows proper weighting of prior versus data information and produces results with realistic uncertainty quantification. We present here three applications of the method: a time-varying extraction rate estimation at a well, a linear cross-well seismic tomography, and a nonlinear hydraulic tomography. These results are compared with those achieved in the classical geostatistical method and it is shown that the Bayesian inversion approach with total variation prior can be a useful tool to identify discrete geologic structures.

Description: Using electric and magnetic field data from Thermal Emission Imaging System (THEMIS) probes (TH-A, TH-D, and TH-E) acquired in the inner magnetosphere (L 〈 4) and low-latitude ground magnetic field data from Bohyun (BOH, L = 1.35) and Hermanus (HER, L = 1.83) stations, we studied longitudinal variations of Pi2-associated fast mode waves away from midnight. We selected 48 nightside Pi2 events at BOH identified when THEMIS probes were in the inner magnetosphere for 1 month (February 2008). During that period the probes were located between 4.0 and 20.0 magnetic local time (MLT), i.e., at and on either side of the dayside sector. This choice was motivated by our interest in studying loss of Pi2 wave energy away from its nominal source at the nightside, all the way to the dayside. Between 4.0 and 8.0 MLT the probes often observed poloidal oscillations in space during BOH Pi2 events. The poloidal oscillations had high coherence (〉0.6) with BOH Pi2s and radially standing fast mode structures. Thus, these fast mode waves are explained by plasmaspheric resonance. On the duskside, however, few events at THEMIS probes had high coherence with BOH Pi2s. Furthermore, the THEMIS probe data showed no evidence of Pi2 signals at 9.0–18.0 MLT, which is consistent with previous studies. Most of the high-coherence events were detected when the local time separation between the THEMIS probes and BOH was less than 3 h. These observations suggest that Pi2 wave energy is lost as it propagates azimuthally from a source region localized in longitude. From longitudinally separated simultaneous multipoint observations at THEMIS probes and BOH and HER stations, we found that the Pi2 frequency varies with longitude both in space and on the ground. This implies that although plasmaspheric fast mode waves establish a standing wave structure on a given meridional plane, their frequency changes with longitude if the plasmasphere is not axisymmetric. Finally, we show that a low-latitude daytime Pi2 is not a fast mode wave propagating to the dayside through the magnetosphere.

Description: Previous work have shown that sea ice variability in the south Pacific is associated with extra-tropical atmospheric anomalies linked to the Southern Oscillation (SO). Over a 32-year period (1982-2013), our study shows that the trend in Southern Oscillation index (SOI) is also able to quantitatively explain the trends in sea-ice edge, drift, and surface winds in this region. On average two-thirds of the winter ice-edge trend in this sector, linked to ice drift and surface winds, could be explained by the positive SOI trend thus subjecting the ice edge to strong decadal SO variability. If this relationship holds, the negative SOI trend prior to the recent satellite era suggests ice edge trends opposite to that of the recent record over a similar time scale. Significant low frequency ice edge trends, linked to the natural variability of SO, are superimposed upon any trends expected of anthropogenic forcing.