The soil geochemistry in the Beardmore Glacier Region, Antarctica: Implications for terrestrial ecosystem history

Although most models suggest continental Antarctica was covered by ice during the Last Glacial Maximum (LGM) it has been speculated that endemic species of soil invertebrates could have survived the Pleistocene at high elevation habitats protruding above the ice sheets. We analyzed a series of soil samples from different elevations at three locations along the Beardmore Glacier in the Transantarctic Mountains (in order of increasing elevation): Ebony Ridge (ER), Cloudmaker (CM), and Meyer Desert (MD). Geochemical analyses show the MD soils, which were exposed during the LGM, were the least weathered compared to lower elevations, and also had the highest total dissolved solids (TDS). MD soils are dominated by nitrate salts (NO₃/Cl ratios >10) that can be observed in SEM images. High δ¹⁷O and δ¹⁸O values of the nitrate indicate that its source is solely of atmospheric origin. It is suggested that nitrate concentrations in the soil may be utilized to determine a relative “wetting age” to better assess invertebrate habitat suitability. The highest elevation sites at MD have been exposed and accumulating salts for the longest times, and because of the salt accumulations, they were not suitable as invertebrate refugia during the LGM

Usporedba zrcalnog modela i modela prijenosnih linija u analizi horizontalne žičane strukture iznad dvoslojnog tla

The paper presents comparison between two approximate models of energized horizontal thin-wire conductors above two-layer soil. The formulation is posed in frequency domain by using two approaches. The first one is based on quasi-static image theory within Mixed Potential Integral Equation. The second one is based on transmission line theory with approximation of per unit length parameters. The authors compare currents computed by the both approximate models of a center fed wire to establish the computation errors over a wide frequency range. The main objective is to validate the proposed image and transmission line models for various lengths of wire conductors, and various cases of low and high conductivities of two-layer soil. The verification of the results is done by comparison with exact model based on full-wave theory. Detailed parametric analysis clearly illustrate validity domain and problems when using both approximate models with respect to their use in practical EMC studies.U radu je prikazana usporedba dviju približnih modela analize pobuđenog horizontalnog tankog žičanog vodiča iznad dvoslojnog tla. Formulacija problema je izvedena u frekvencijskoj domeni pomoću dva pristupa. Prvi pristup se temelji na kvazi-statičkom zrcalnom modelu unutar integralne jednadžbe s mješovitim potencijalima. Drugi se temelji na teoriji prijenosnih linija s aproksimacijom jediničnih parametara. Autori su usporedili distribucije struje izračunate s pomoću obje približne metode kako bi odredili pogrešku metoda u širokom rasponu frekvencija. Glavni cilj bio je potvrditi predloženi zrcalni i linijski model za različite duljine žičanog vodiča i razne slučajeve niske i visoke vodljivosti slojeva tla. Provjera rezultata obavljena je usporedbom s modelom bez aproksimacija temeljenog na punovalnoj teoriji. Detaljna parametarska analiza jasno pokazuju valjanosti domene i vrste problema uz korištenje obje približne metode s obzirom na njihovu primjenu u praktičnim EMC razmatranjima

The chemical compound 'Heatin' stimulates hypocotyl elongation and interferes with the Arabidopsis NIT1-subfamily of nitrilases

Temperature passively affects biological processes involved in plant growth. Therefore, it is challenging to study the dedicated temperature signalling pathways that orchestrate thermomorphogenesis, a suite of elongation growth-based adaptations that enhance leaf-cooling capacity. We screened a chemical library for compounds that restored hypocotyl elongation in the pif4-2-deficient mutant background at warm temperature conditions in Arabidopsis thaliana to identify modulators of thermomorphogenesis. The small aromatic compound 'Heatin', containing 1-iminomethyl-2-naphthol as a pharmacophore, was selected as an enhancer of elongation growth. We show that ARABIDOPSIS ALDEHYDE OXIDASES redundantly contribute to Heatin-mediated hypocotyl elongation. Following a chemical proteomics approach, the members of the NITRILASE1-subfamily of auxin biosynthesis enzymes were identified among the molecular targets of Heatin. Our data reveal that nitrilases are involved in promotion of hypocotyl elongation in response to high temperature and Heatin-mediated hypocotyl elongation requires the NITRILASE1-subfamily members, NIT1 and NIT2. Heatin inhibits NIT1-subfamily enzymatic activity in vitro and the application of Heatin accordingly results in the accumulation of NIT1-subfamily substrate indole-3-acetonitrile in vivo. However, levels of the NIT1-subfamily product, bioactive auxin (indole-3-acetic acid), were also significantly increased. It is likely that the stimulation of hypocotyl elongation by Heatin might be independent of its observed interaction with NITRILASE1-subfamily members. However, nitrilases may contribute to the Heatin response by stimulating indole-3-acetic acid biosynthesis in an indirect way. Heatin and its functional analogues present novel chemical entities for studying auxin biology

Learning Patterns in Noisy Data: The AQ Approach

Introduction In concept learning and data mining, a typical objective is to determine concept descriptions or patterns that will classify future data points as correctly as possible. If one can assume that the data contain no noise, then it is desirable that descriptions are complete and consistent with regard to all the data, i.e., they characterize all data points in a given class (positive examples) and no data points outside the class (negative examples). In real-world applications, however, data may be noisy, that is, they may contain various kinds of errors, such as errors of measurement, classification or transmission, and/or inconsistencies. In such situations, searching for consistent and complete descriptions ceases to be desirable. In the presence of noise, an increase in completeness (an increase of generality of a description) tends to cause a decrease in consistency and vice versa; therefore, the best strategy is to seek a description that represents the trade-off betw