scatteR: Generating instance space based on scagnostics

Traditional synthetic data generation methods rely on model-based approaches that tune the parameters of a model rather than focusing on the structure of the data itself. In contrast, Scagnostics is an exploratory graphical method that captures the structure of bivariate data using graph-theoretic measures. This paper presents a novel data generation method, scatteR, that uses Scagnostics measurements to control the characteristics of the generated dataset. By using an iterative Generalized Simulated Annealing optimizer, scatteR finds the optimal arrangement of data points that minimizes the distance between current and target Scagnostics measurements. The results demonstrate that scatteR can generate 50 data points in under 30 seconds with an average Root Mean Squared Error of 0.05, making it a useful pedagogical tool for teaching statistical methods. Overall, scatteR provides an entry point for generating datasets based on the characteristics of instance space, rather than relying on model-based simulations.Comment: 17 pages. For the associated R package, see https://cran.r-project.org/package=scatte

Rhodium Complexes of a New Structurally Adaptive PNN-Pincer Type Ligand

A new PNN-pincer type ligand with pyrazolyl and diphenylphosphine flanking donors on a diarylamido anchor has been prepared. Its bis(tert-butyl isocyanide)rhodium(I) complex exhibits hemilabile behavior in solution, and its solid-state structure verified the elusive κ2P,N coordination mode for this type of ligand. Reactions between (PNN)Rh(CNtBu)2 and iodomethane afford both fac- and cis,mer-[(PNN)Rh(CNtBu)2(Me)](I), which further showcases the structural versatility of the ligand

SOil ORGANIC MAneR AND NUTRIENT STATUS OF SOME VEGETABLE GROWING SOilS IN MATARA DISTRICT

The main function of a soil from an agricultural perspective is to produce a bountifulcrop with minimum mputsrTherefore, the maintenance of soil fertility and productivityis important to obtain a sustainable yield. Though, farmers prefer that their soil support •ideal crop growth, poor soil management practices adopted by them have caused adecreasing trend of yield continuously. Therefore, it is important to investigate thenutrient status of such soils and make recommendation for sustainable land management.This study was conducted to assess organic matter and nutrient status of selectedvegetable growing soils in the Matara District, Sri Lanka.Ten vegetable growing fields were selected and soil samples were drawn randomly fromO-15cmdepth. Soil samples were analyzed to determine N, P, K and organic mattercontent using standard methods and soil samples were also taken from a forest on thesame soil type to compare cultivated and undisturbed soils.Results revealed that the average soil N, P and K contents for the vegetable growing soilwere 0.14%, 404 mglKg of soil and 106 mgIKg of soil respectively, and thecorresponding figures for the forest soil were 0.17%, 65 mg/Kg of soil and 30 mglKg ofsoil. The average organic matter content of the vegetable growing soils was 0.65%,whereas the corresponding figure for the reference forest soil was 2.5%. Results revealedthat the average P and K contents of Vegetable growing soils were higher than the forestsoil and possible reason may be the regular application of synthetic fertilizer to vegetablegrowing soils. Results further indicated that more than 50% samples collected fromvegetable growing soils had N and organic matter contents below the average value.According to the results, it can be concluded the most of the vegetable growing soils inMatara District are considerably low in N and organic matter contents. Hence preventingsoil erosion and sustaining or increasing soil organic matter levels by adding cropresidues, compost and organic manures may be the most important practices that growerscan adopt in managing soil nutrients status.

SEASONAL VARIATION OF SOIL INORGANIC NITROGEN IN AN ULTlSOL AS AFFECTED BY LAND USE

The importance of soil inorganic nitrogen (NH/-N plus N03--N) in plant nutrition andconcerns over the environmental impact of nitrate leaching and N20 emissions hasfocused attention on inorganic N in soils. Inorganic N in soils can originate from manysources including fertilizer additions and mineralization of organic N from soil organicmatter, crop residues/plant litter and organic wastes. This study was conducted in anUltisol in the low country wet zone of Sri Lanka to determine influence of land use onseasonal variation of soil inorganic N. Five contrasting land use types (mahoganywoodlot/forested area, grass, legume, cinnamon and vegetable cropping) wereperiodically monitored during the March-June, 2003 for soil inorganic N. Composite soilsamples were taken to 0-15cm depth from four separate blocks of each land use type.Sampling was done initially at weekly and later at biweekly intervals.Soil samples were analyzed for inorganic N and moisture content was measuredgravimetrically for each sample. Soil from forested area contained the highest content ofsoil inorganic N (39 mg N kg" soil) on average during the entire sampling period whilethe other land use types showed similar (around 25 mg N kg" soil) results. No distinctrelationship could be observed between the inorganic N and moisture content in soil. Theaverage ~ +-N content observed throughout the sampling period was higher in the soilfrom the forested area compared to all other land use types indicating the status of Nmineralization in soil. Vegetable field had relatively high average content of N03--N insoil compared to mahogany/forest and other land use types. Results revealed thatinorganic N in soil is highly variable during the season and all land use types had moreNH/-N than N03--N in soil at any given time.

Electronic Communication Across Diamagnetic Metal Bridges: A Homoleptic Gallium(III) Complex of a Redox-Active Diarylamido-Based Ligand and Its Oxidized Derivatives

Complexes with cations of the type [Ga(L)2]n+ where L = bis(4-methyl-2-(1H-pyrazol-1-yl)phenyl)amido and n = 1, 2, 3 have been prepared and structurally characterized. The electronic properties of each were probed by electrochemical and spectroscopic means and were interpreted with the aid of density functional theory (DFT) calculations. The dication, best described as [Ga(L–)(L0)]2+, is a Robin-Day class II mixed-valence species. As such, a broad, weak, solvent-dependent intervalence charge transfer (IVCT) band was found in the NIR spectrum in the range 6390–6925 cm–1, depending on the solvent. Band shape analyses and the use of Hush and Marcus relations revealed a modest electronic coupling, Hab of about 200 cm–1, and a large rate constant for electron transfer, ket, on the order of 1010 s–1 between redox active ligands. The dioxidized complex [Ga(L0)2]3+ shows a half-field ΔMs = 2 transition in its solid-state X-band electron paramagnetic resonance (EPR) spectrum at 5 K, which indicates that the triplet state is thermally populated. DFT calculations (M06/Def2-SV(P)) suggest that the singlet state is 21.7 cm–1 lower in energy than the triplet state

Homoleptic Nickel(II) Complexes of Redox-Tunable Pincer-type Ligands

Different synthetic methods have been developed to prepare eight new redox-active pincer-type ligands, H(X,Y), that have pyrazol-1-yl flanking donors attached to an ortho-position of each ring of a diarylamine anchor and that have different groups, X and Y, at the para-aryl positions. Together with four previously known H(X,Y) ligands, a series of 12 Ni(X,Y)2 complexes were prepared in high yields by a simple one-pot reaction. Six of the 12 derivatives were characterized by single-crystal X-ray diffraction, which showed tetragonally distorted hexacoordinate nickel(II) centers. The nickel(II) complexes exhibit two quasi-reversible one-electron oxidation waves in their cyclic voltammograms, with half-wave potentials that varied over a remarkable 700 mV range with the average of the Hammett σp parameters of the para-aryl X, Y groups. The one- and two-electron oxidized derivatives [Ni(Me,Me)2](BF4)n (n = 1, 2) were prepared synthetically, were characterized by X-band EPR, electronic spectroscopy, and single-crystal X-ray diffraction (for n = 2), and were studied computationally by DFT methods. The dioxidized complex, [Ni(Me,Me)2](BF4)2, is an S = 2 species, with nickel(II) bound to two ligand radicals. The mono-oxidized complex [Ni(Me,Me)2](BF4), prepared by comproportionation, is best described as nickel(II) with one ligand centered radical. Neither the mono- nor the dioxidized derivative shows any substantial electronic coupling between the metal and their bound ligand radicals because of the orthogonal nature of their magnetic orbitals. On the other hand, weak electronic communication occurs between ligands in the mono-oxidized complex as evident from the intervalence charge transfer (IVCT) transition found in the near-IR absorption spectrum. Band shape analysis of the IVCT transition allowed comparisons of the strength of the electronic interaction with that in the related, previously known, Robin–Day class II mixed valence complex, [Ga(Me,Me)2]2+

Syntheses and Electronic Properties of Rhodium(III) Complexes Bearing a Redox-Active Ligand

A series of rhodium(III) complexes of the redox-active ligand, H(L = bis(4-methyl-2-(1H-pyrazol-1-yl)phenyl)amido), was prepared, and the electronic properties were studied. Thus, heating an ethanol solution of commercial RhCl3·3H2O with H(L) results in the precipitation of insoluble [H(L)]RhCl3, 1. The reaction of a methanol suspension of [H(L)]RhCl3 with NEt4OH causes ligand deprotonation and affords nearly quantitative yields of the soluble, deep-green, title compound (NEt4)[(L)RhCl3]·H2O, 2·H2O. Complex 2·H2O reacts readily with excess pyridine, triethylphosphine, or pyrazine (pyz) to eliminate NEt4Cl and give charge-neutral complexes trans-(L)RhCl2(py), trans-3, trans-(L)RhCl2(PEt3), trans- 4, or trans-(L)RhCl2(pyz), trans-5, where the incoming Lewis base is trans- to the amido nitrogen of the meridionally coordinating ligand. Heating solutions of complexes trans-3 or trans-4 above about 100 °C causes isomerization to the appropriate cis-3 or cis-4. Isomerization of trans-5 occurs at a much lower temperature due to pyrazine dissociation. Cis-3 and cis- 5 could be reconverted to their respective trans- isomers in solution at 35 °C by visible light irradiation. Complexes [(L)Rh(py)2Cl](PF6), 6, [(L)Rh(PPh3)(py)Cl](PF6), 7, [(L)Rh(PEt3)2Cl](PF6), 8, and [(L)RhCl(bipy)](OTf = triflate), 9, were prepared from 2·H2O by using thallium(I) salts as halide abstraction agents and excess Lewis base. It was not possible to prepare dicationic complexes with three unidentate pyridyl or triethylphosphine ligands; however, the reaction between 2, thallium(I) triflate, and the tridentate 4′-(4-methylphenyl)-2,2′:6′,2″-terpyridine (ttpy) afforded a high yield of [(L)Rh(ttpy)]- (OTf)2, 10. The solid state structures of nine new complexes were obtained. The electrochemistry of the various derivatives in CH2Cl2 showed a ligand-based oxidation wave whose potential depended mainly on the charge of the complex, and to a lesser extent on the nature and the geometry of the other supporting ligands. Thus, the oxidation wave for 2 with an anionic complex was found at +0.27 V versus Ag/AgCl in CH2Cl2, while those waves for the charge-neutral complexes 3−5 were found between +0.38 to +0.59 V, where the cis- isomers were about 100 mV more stable toward oxidation than the trans- isomers. The oxidation waves for 6−9 with monocationic complexes occurred in the range +0.74 to 0.81 V while that for 10 with a dicationic complex occurred at +0.91 V. Chemical oxidation of trans-3, cis-3, and 8 afforded crystals of the singly oxidized complexes, [trans- (L)RhCl2(py)](SbCl6), cis-[(L)RhCl2(py)](SbCl4)·2CH2Cl2, and [(L)Rh(PEt3)2Cl](SbCl6)2, respectively. Comparisons of structural and spectroscopic features combined with the results of density functional theory (DFT) calculations between nonoxidized and oxidized forms of the complexes are indicative of the ligand-centered radicals in the oxidized derivatives

Bending-shear interaction of cold-formed stainless steel lipped channel sections

The bending-shear interaction response of cold-formed stainless steel lipped channel sections has been given inadequate attention in the past. Therefore, this paper investigates the bending and shear interaction behaviour of cold-formed stainless steel lipped channel sections using numerical studies. Finite element (FE) models were developed and validated against the experimental results found in the literature for three-point and four-point loading tests of lipped channel sections of both cold-formed stainless steel and cold-formed steel. The elaborated FE results were used for a comprehensive parametric study that was conducted comprising 60 FE models of three-point loading simulations of stainless steel lipped channels with five different aspect ratios to study the shear response and the bending-shear interaction response. Another 12 FE models of four-point bending simulations were developed to study the bending response. The numerical results were analysed and it is found that the sections with aspect ratios of 1.5 and 2.0 are subjected to the interaction of bending and shear while there is no interaction effect observed in the sections with other aspect ratios. Eurocode 3 and American specifications interaction equations were then evaluated using the numerical results. These design provisions are found to be too conservative for a higher level of applied shear force. Therefore, revised design equations for bending and shear interaction were proposed aiming better prediction accuracy. Further, a statistical evaluation was conducted for the proposed interaction equations and results suggest improved and consistent predictions

SOIL ORGANIC CARBON AS AN INDICATOR OF SOIL QUALITY: A STUDY IN SELECTED TEA PLANTATIONS IN GALLE DISTRICT

Assessment of soil quality in tea lands is important to determine the extent ofdegradation and introduce sustainable land management practices. A study wasundertaken in two stages to assess the suitability of soil organic carbon as a soil qualityindicator in tea lands. Soil samples were taken from 0-15 em tea estates in the GalleDistrict of Sri Lanka. In the first stage, soil samples were depth from selected taken from15 locations under four different field categories viz., under rehabilitation, rehabilitationcompleted, planted tea following rehabilitation and planted tea without rehabilitation.Second stage involved sampling of a tea field under rehabilitation and tea fields ofvarious ages (3, 7 and 11 year old) situated at one location. Soil samples were also takenfrom two forest sites to assess the impact of cultivation on soil organic carbon. Bulkdensity was measured at the field and soil samples were analyzed for total organiccarbon.Results revealed that land management has a significant impact on the quantity of soilcarbon in tea plantations. While rehabilitation process has increased the soil carboncontent, nearly 15% of the added carbon is lost during the initial years after planting tea.Forest soils had a soil organic carbon (in the O-15cmsoil layer) range of 3.39 to 4.42 kgm·2 compared to 3.02 to 3.18 kg m-2 observed in rehabilitated tea lands. The l l-year oldtea field has lost over 40% of its soil organic carbon since rehabilitated and planted withtea. Soil organic carbon can be considered as a robust indicator of soil quality and moreresearch is required to establish critical levels of soil carbon for tea lands in differentstages of the cultivation-rehabilitation cycle

Bending-shear interaction of cold-formed stainless steel lipped channel sections

The bending-shear interaction response of cold-formed stainless steel lipped channel sections has been given inadequate attention in the past. Therefore, this paper investigates the bending and shear interaction behaviour of cold-formed stainless steel lipped channel sections using numerical studies. Finite element (FE) models were developed and validated against the experimental results found in the literature for three-point and four-point loading tests of lipped channel sections of both cold-formed stainless steel and cold-formed steel. The elaborated FE results were used for a comprehensive parametric study that was conducted comprising 60 FE models of three-point loading simulations of stainless steel lipped channels with five different aspect ratios to study the shear response and the bending-shear interaction response. Another 12 FE models of four-point bending simulations were developed to study the bending response. The numerical results were analysed and it is found that the sections with aspect ratios of 1.5 and 2.0 are subjected to the interaction of bending and shear while there is no interaction effect observed in the sections with other aspect ratios. Eurocode 3 and American specifications interaction equations were then evaluated using the numerical results. These design provisions are found to be too conservative for a higher level of applied shear force. Therefore, revised design equations for bending and shear interaction were proposed aiming better prediction accuracy. Further, a statistical evaluation was conducted for the proposed interaction equations and results suggest improved and consistent predictions