High Resolution Remote Sensing Observations of Summer Sea Ice

During the Arctic summer melt season, the sea ice transitions from a consolidated ice pack with a highly reflective snow-covered surface to a disintegrating unconsolidated pack with melt ponds spotting the ice surface. The albedo of the Arctic decreases by up to 50%, resulting in increased absorption of solar radiation, triggering the positive sea ice albedo feedback that further enhances melting. Summer melt processes occur at a small scale and are required for melt pond parameterization in models and quantifying albedo change. Arctic-wide observations of melt features were however not available until recently. In this work we develop original techniques for the analysis of high-resolution remote sensing observations of summer sea ice. By applying novel algorithms to data acquired from airborne and satellite sensors onboard IceBridge, Sentinel-2, WorldView and ICESat-2, we derive a set of parameters that describe melt conditions on Arctic sea ice in summer. We present a new, pixel-based classification scheme to identify melt features in high-resolution summer imagery. We apply the classification algorithm to IceBridge Digital Mapping System data and find a greater melt pond fraction (25%) on sea ice in the Beaufort and Chukchi Seas, a region consisting of predominantly first year ice, compared to the Central Arctic, where the melt pond fraction is 14% on predominantly multiyear ice. Expanding the study to observations acquired by the Sentinel-2 Multispectral Instrument, we track the variability in melt pond fraction and sea ice concentration with time, focusing on the anomalously warm summer of 2020. So as to obtain a three-dimensional view of the evolution of summer melt we also exploit ICESat-2 surface elevation measurements. We develop and apply the Melt Pond Algorithm to track ponds in ICESat-2 photon cloud data and derive their depth. Pond depth measurements in conjunction with melt pond fraction and sea ice concentration provide insights into the regional patterns and temporal evolution of melt on summer sea ice. We found mean melt pond fraction increased rapidly in the beginning of the melt season, peaking at 16% on 24 June 2020, while median pond depths increased steadily from 0.4 m at the beginning of the melt season, to peaking at 0.97 m on 16 July, even as melt pond fraction had begun to decrease. Our findings may be used to improve parameterization of melt processes in models, quantify freshwater storage, and study the partitioning of under ice light

Memory retrieval : the effects of retrieval-induced forgetting on tertiary law assessments

Empirical support for the idea that successful retrieval of momentarily wanted information depends to some extent on the inhibition of unwanted, competing information, comes from a phenomenon termed retrieval-induced forgetting (RIP). Cmrent research examining the effects of RIF in everyday learning experiences indicates that retrieval practice strategies, which involve answering a sub-set of topic-related questions, may actually be detrimental to exam preparation. The present study examined whether law students engaging in retrieval practice of evidential facts and statute provisions in a criminal case produce RIF. A second research question explored whether an instruction to take a certain perspective when encoding the facts and provisions would reduce or eliminate RIF. Pichert and Anderson (1977) hypothesised that by imposing a perspective, the resulting high-level schema may work as an effective retrieval framework for retrieving learned text elements. A third research question examined whether requiring the retrieval practice task to be more active would result in a significant difference between the recall of the retrieval-practiced items and the unrelated items that received no retlieval practice, as was unexpectedly, not the case in Experiments 1 and 2. The overall findings showed the occurrence of RIF in the context of tertiary law exam preparation, lending support to previous studies examining the effects of retrieval practice. However, there was no support for Pichert and Anderson's schema theory relating to perspective taking. The results for Experiments 1 and 2 produced an intriguing finding that suggests that law students show a strong propensity to generate counterarguments that complement the retrieval practice items while practicing evidential facts and statute provisions in a criminal case. It appears that in contrast to university students in other RIF studies, the law students engage in a type of recall strategy that enhances their pelformance on unpracticed information when that information consists of the direct counterarguments to the arguments they are actually practicing. When the retrieval practice task was modified to reduce participants' ability to generate such counterarguments in Experiment 3, the standard RIF effects emerged

Potential use of the black soldier fly larvae in faecal sludge management: a study in Durban, South Africa

This study was performed to determine the bioconversion and waste reduction capabilities using the Black Soldier Fly larvae (BSFL) on treating Urine Diversion Toilet (UDT) sludge on a full-scale plant. A bioconversion of 10 % wet basis and a mean relative waste reduction of 41 % wet basis was achieved over a period of 13 days using 6-day-old larvae. The study is a preliminary study to identify and quantify useful design parameters and material flows, which would assist in improving the system by increasing the bioconversion and waste reduction of UDT sludge

Assessing the effect of organic residue quality on active decomposing fungi in a tropical Vertisol using 15N-DNA stable isotope probing

15N-DNA stable isotope probing (15N-DNA-SIP) combined with 18S rRNA gene-based community analysis was used to identify active fungi involved in decomposition of 15N-labeled maize and soybean litter in a tropical Vertisol. Phylogenetic analysis of 15N-labeled DNA subjected to 18S rRNA gene-based community fingerprinting showed that organic residue quality promoted either slow (i.e. Penicillium sp., Aspergillus sp.) or fast growing (i.e. Fusarium sp., Mortierella sp.) fungal decomposers in soils treated with maize or soybean residues, respectively, whereas Chaetomium sp. were found as dominant decomposers in both residue treatments. Therefore, we have clear evidence that specific members of the fungal community used 15N derived from the two different organic resources for growth and stimulated early decomposition of maize or soybean decomposition. In conclusion, our study showed that 15N-DNA-SIP-based community analyses cannot only follow the flow of N from organic resources into bacteria, but also into the actively decomposing fungal communities of soils

Traveling Waves for Conservation Laws with Cubic Nonlinearity and BBM Type Dispersion

Scalar conservation laws with non-convex fluxes have shock wave solutions that violate the Lax entropy condition. In this paper, such solutions are selected by showing that some of them have corresponding traveling waves for the equation supplemented with dissipative and dispersive higher-order terms. For a cubic flux, traveling waves can be calculated explicitly for linear dissipative and dispersive terms. Information about their existence can be used to solve the Riemann problem, in which we find solutions for some data that are different from the classical Lax-Oleinik construction. We consider dispersive terms of a BBM type and show that the calculation of traveling waves is somewhat more intricate than for a KdV-type dispersion. The explicit calculation is based upon the calculation of parabolic invariant manifolds for the associated ODE describing traveling waves. The results extend to the p-system of one-dimensional elasticity with a cubic stress-strain law.Comment: 17 pages, 5 figure

A quality control check to ensure comparability of stereophotogrammetric data between session and systems

Optoelectronic stereophotogrammetric (SP) systems are widely used in human movement research for clinical diagnostics, interventional applications, and as a reference system for validating alternative technologies. Regardless of the application, SP systems exhibit different random and systematic errors depending on camera specifications, system setup and laboratory environment, which hinders comparing SP data between sessions and across different systems. While many methods have been proposed to quantify and report the errors of SP systems, they are rarely utilized due to their complexity and need for additional equipment. In response, an easy-to-use quality control (QC) check has been designed that can be completed immediately prior to a data collection. This QC check requires minimal training for the operator and no additional equipment. In addition, a custom graphical user interface ensures automatic processing of the errors in an easy-to-read format for immediate interpretation. On initial deployment in a multicentric study, the check (i) proved to be feasible to perform in a short timeframe with minimal burden to the operator, and (ii) quantified the level of random and systematic errors between sessions and systems, ensuring comparability of data in a variety of protocol setups, including repeated measures, longitudinal studies and multicentric studies