The influence of forest reserve protection on the structure, stability, and functioning of dung-associated invertebrate communities

Communities are influenced by many factors, with anthropogenic impacts being one of the strongest. These factors can influence community structure and may cause non-random species loss by filtering certain traits of species, which may also determine how a species contributes to ecosystem functioning. The structure of a community can also be highly variable over short timescales and across seasons, as abiotic factors can alter a resource over the course of days and also alter intensity of competition within a community. These short-timescale influences are most noticeable in an ephemeral resource that is limited in both space and time. Changes in community structure and interactions can be represented as networks of interactions (links) among species (nodes). Interaction networks describe a community and incorporate non-trophic interactions, which can alter their structure. These are generally measured by counting the number of trophic interactions, ignoring non-trophic interactions such as competition. However, competitive interactions may be important for network dynamics, yet the most appropriate way to quantify competition remains unclear. The outcome of a competitive interaction could potentially be predicted by the body size ofcompeting individuals, and this would remove the need to observe individual interactions. These ideas were tested using the dung-associated community in an Afromontane forest reserve in Nigeria across variation in seasons and in areas that were protected from anthropogenic impacts by fencing. Trapping and recording of interactions within the community was used to assess community structure, and experiments were run to test how dung removal and secondary seed dispersal changed across seasons and in protected areas of the forest. The influence of competition was determined by altering the size and number of dung beetles present at the resource. The community structure was influenced by forest protection and varied across seasons. Additionally, the size and number of dung beetles present was higher in protected areas in the wet season, resulting in higher dung removal and secondary seed dispersal and indicating non-random species loss in unprotected areas. The attractiveness of the dung resource changed over short timescales and desiccation occurred rapidly in the dry season, which resulted in decreased insect abundance and diversity over the course of days. Individual dung removal rates were not additive, and could only be used to predict community-level dung removal when taking into account competitive interactions. The body-size ratio between winners and losers of a competition was a good predictor of an interaction outcome. Competition networks were highly connected and nested, with compartmentalisation occurring in the competition network. At the community level, effects of forest protection and changing seasons only altered network nestedness. Therefore, body size can be used to predict species responses to anthropogenic threats and community structure and function when taking into account density-dependent competitive interactions. Furthermore, when determining community responses to anthropogenic threats, sampling across changes in seasons and observing competitive interactions provides more information about a community structure and stability

Optical study of orbital excitations in transition-metal oxides

The orbital excitations of a series of transition-metal compounds are studied by means of optical spectroscopy. Our aim was to identify signatures of collective orbital excitations by comparison with experimental and theoretical results for predominantly local crystal-field excitations. To this end, we have studied TiOCl, RTiO3 (R=La, Sm, Y), LaMnO3, Y2BaNiO5, CaCu2O3, and K4Cu4OCl10, ranging from early to late transition-metal ions, from t_2g to e_g systems, and including systems in which the exchange coupling is predominantly three-dimensional, one-dimensional or zero-dimensional. With the exception of LaMnO3, we find orbital excitations in all compounds. We discuss the competition between orbital fluctuations (for dominant exchange coupling) and crystal-field splitting (for dominant coupling to the lattice). Comparison of our experimental results with configuration-interaction cluster calculations in general yield good agreement, demonstrating that the coupling to the lattice is important for a quantitative description of the orbital excitations in these compounds. However, detailed theoretical predictions for the contribution of collective orbital modes to the optical conductivity (e.g., the line shape or the polarization dependence) are required to decide on a possible contribution of orbital fluctuations at low energies, in particular in case of the orbital excitations at about 0.25 eV in RTiO3. Further calculations are called for which take into account the exchange interactions between the orbitals and the coupling to the lattice on an equal footing.Comment: published version, discussion of TiOCl extended to low T, improved calculation of orbital excitation energies in TiOCl, figure 16 improved, references updated, 33 pages, 20 figure

X-ray Nanodiffraction on a Single SiGe Quantum Dot inside a Functioning Field-Effect Transistor

For advanced electronic, optoelectronic, or mechanical nanoscale devices a detailed understanding of their structural properties and in particular the strain state within their active region is of utmost importance. We demonstrate that X-ray nanodiffraction represents an excellent tool to investigate the internal structure of such devices in a nondestructive way by using a focused synchotron X-ray beam with a diameter of 400 nm. We show results on the strain fields in and around a single SiGe island, which serves as stressor for the Si-channel in a fully functioning Si-metal-oxide semiconductor field-effect transistor

Mesoscale self organization of polydisperse magnetic nanoparticles at the water surface

In this study, we investigated the self ordering process in Langmuir films of polydisperse iron oxide nanoparticles on a water surface, employing in situ x ray scattering, surface pressure area isotherm analysis, and Brewster angle microscopy. X ray reflectometry confirmed the formation of a monolayer, while grazing incidence small angle x ray scattering revealed short range lateral correlations with a characteristic length equal to the mean particle size. Remarkably, our findings indicated that at zero surface pressure, the particles organized into submicrometer clusters, merging upon compression to form a homogeneous layer. These layers were subsequently transferred to a solid substrate using the Langmuir Schaefer technique and further characterized via scanning electron microscopy and polarized neutron reflectometry. Notably, our measurements revealed a second characteristic length in the lateral correlations, orders of magnitude longer than the mean particle diameter, with polydisperse particles forming circular clusters densely packed in a hexagonal lattice. Furthermore, our evidence suggests that the lattice constant of this mesocrystal depends on the characteristics of the particle size distribution, specifically the mean particle size and the width of the size distribution. In addition, we observed internal size separation within these clusters, where larger particles were positioned closer to the center of the cluster. Finally, polarized neutron reflectometry measurements provided valuable insights into the magnetization profile across the laye

The Motif Agony in the Garden in Poetry of GULAG Prisoners

Статья поступила в редакцию 13.01.2021 г.Предпринято исследование поэзии узников ГУЛАГа в аспекте функционирования в ней библейского мотива моления о чаше. Исходной научной гипотезой стало предположение о близости этого явления русской поэзии середины XX в. к традиции духовной поэзии, которая характеризуется, по определению Ф. И. Буслаева, тем, что соединяет в себе «поэтическое творчество и просвещенную христианскую мысль». Одновременно путем анализа творчества Н. Ануфриевой и А. Солодовникова показано, что поэтыузники, при всей приверженности к канонической трактовке библейского сюжета, позволяют себе индивидуальную интерпретацию его, оправданную как особенностями времени, так и личным опытом.The purpose of this study was to research the biblical motifs in the poetry of GULAG prisoners. The starting point for this work was a hypothesis that the phenomenon of GULAG poetry is in a close affi nity with the tradition of the spiritual poetry described by F. I. Byslaeva as poetry that connects “poetic art and an educated Christian thinking”. By analyzing poetry of N. Anyfrieva и А. Solodovnikovа the conclusion is drawn that even though poets-prisoners are trying to be adherent to the canonical understanding of the biblical plots they are inclined to have a very personal interpretation of the plots which is understandable given the circumstances of that historical time and their life experience