412 research outputs found
Computing labs and Technology Classroom (ClTC) Initiative: A Model for Distributed Support
DePauw University is a small, liberal arts institution with 2200 undergraduate residential students and 222 faculty members, located in Greencastle, Indiana The challenges of supporting a campus with multiple and diverse facilities are further amplified by limited staff support resources. One of the strategies for addressing these challenges led to the formation of the Computing Labs and Technology Classrooms (CLTC) initiative. The CLTC recognizes and draws on the strengths of support specialists with a wide variety of professional training and experience, who regularly collaborate in the support and management of campus-wide labs and technology classrooms
Critical Casimir effect in classical binary liquid mixtures
If a fluctuating medium is confined, the ensuing perturbation of its
fluctuation spectrum generates Casimir-like effective forces acting on its
confining surfaces. Near a continuous phase transition of such a medium the
corresponding order parameter fluctuations occur on all length scales and
therefore close to the critical point this effect acquires a universal
character, i.e., to a large extent it is independent of the microscopic details
of the actual system. Accordingly it can be calculated theoretically by
studying suitable representative model systems.
We report on the direct measurement of critical Casimir forces by total
internal reflection microscopy (TIRM), with femto-Newton resolution. The
corresponding potentials are determined for individual colloidal particles
floating above a substrate under the action of the critical thermal noise in
the solvent medium, constituted by a binary liquid mixture of water and
2,6-lutidine near its lower consolute point. Depending on the relative
adsorption preferences of the colloid and substrate surfaces with respect to
the two components of the binary liquid mixture, we observe that, upon
approaching the critical point of the solvent, attractive or repulsive forces
emerge and supersede those prevailing away from it. Based on the knowledge of
the critical Casimir forces acting in film geometries within the Ising
universality class and with equal or opposing boundary conditions, we provide
the corresponding theoretical predictions for the sphere-planar wall geometry
of the experiment. The experimental data for the effective potential can be
interpreted consistently in terms of these predictions and a remarkable
quantitative agreement is observed.Comment: 30 pages, 17 figure
Leaf litter degradation in highly turbid transitional waters: preliminary results from litter-bag experiments in the Gironde Estuary
The rates of decomposition of oak (Quercus robur) leaves have been examined using litter bags in a very high turbidity macrotidal estuary, the Gironde Estuary (S.W. France). The first experiments show a marked decrease in the decomposition rate of oak leaves at the water-sediment interface (mud-contact: anoxic conditions, reduced physical fragmentation) in comparison to the water column. The results point out the impact of hydrodynamic conditions on leaf litter degradation in such fluvio-estuarine systems. Regarding the aquatic-terrestrial linkage, our observations suggest direct changes in leaf decomposition kinetics and then, a potential delay on the recycling and transport processes of coarse particulate organic matter, especially in a context of modification of the natural water flow, due to global and land use changes
The effects of administering different metaphylactic antimicrobials on growth performance and health outcomes of high-risk, newly received feedlot steers
Bovine respiratory disease (BRD) is the primary animal health concern facing feedlot producers. Many antimicrobial mitigation strategies are available, but few studies have compared feedlot performance during both the receiving and finishing periods following application of different antimicrobials used as metaphylaxis at arrival. The objective of this study was to compare antimicrobial metaphylaxis methods on clinical health and growth performance across both the receiving and finishing periods. A total of 238 multiple-sourced steers in two source blocks were used in a generalized complete block design. The four treatments included: 1) a negative control, 5 mL of sterile saline injected subcutaneously (CON); 2) subcutaneous administration of florfenicol at 40 mg/kg of BW (NUF); 3) subcutaneous administration of ceftiofur in the posterior aspect of the ear at 6.6 mg/kg of BW (EXC); and 4) subcutaneous administration of tulathromycin at 2.5 mg/kg of BW (DRA). The morbidity rate for the first treatment of BRD was decreased for the DRA and EXC treatments compared to CON and NUF (P \u3c 0.01). Additionally, average daily gain (ADG), dry matter intake (DMI), and gain-to-feed (G:F) were greater (P ≤ 0.02) in the DRA treatment during the receiving period compared to all other treatments. The ADG was also greater (P \u3c 0.05) for EXC than the CON treatment throughout the finishing period. Nonetheless, other growth performance variables did not differ among metaphylactic treatments during the finishing period (P ≥ 0.14). Likewise, no differences in carcass characteristics or liver abscess score were observed (P ≥ 0.18). All complete blood count (CBC) variables were affected by day (P ≤ 0.01) except mean corpuscular hemoglobin concentration (P = 0.29). Treatment × time interactions were observed for platelet count, white blood cell (WBC) count, monocyte count and percentage, and lymphocyte percentage (P ≤ 0.03). However, there were no observed hematological variables that differed among treatment (P ≥ 0.10). The results indicate that some commercially available antimicrobials labeled for metaphylactic use are more efficacious than others in decreasing morbidity rate
Critical Casimir forces and adsorption profiles in the presence of a chemically structured substrate
Motivated by recent experiments with confined binary liquid mixtures near
demixing, we study the universal critical properties of a system, which belongs
to the Ising universality class, in the film geometry. We employ periodic
boundary conditions in the two lateral directions and fixed boundary conditions
on the two confining surfaces, such that one of them has a spatially
homogeneous adsorption preference while the other one exhibits a laterally
alternating adsorption preference, resembling locally a single chemical step.
By means of Monte Carlo simulations of an improved Hamiltonian, so that the
leading scaling corrections are suppressed, numerical integration, and
finite-size scaling analysis we determine the critical Casimir force and its
universal scaling function for various values of the aspect ratio of the film.
In the limit of a vanishing aspect ratio the critical Casimir force of this
system reduces to the mean value of the critical Casimir force for laterally
homogeneous ++ and +- boundary conditions, corresponding to the surface spins
on the two surfaces being fixed to equal and opposite values, respectively. We
show that the universal scaling function of the critical Casimir force for
small but finite aspect ratios displays a linear dependence on the aspect ratio
which is solely due to the presence of the lateral inhomogeneity. We also
analyze the order-parameter profiles at criticality and their universal scaling
function which allows us to probe theoretical predictions and to compare with
experimental data.Comment: revised version, section 5.2 expanded; 53 pages, 12 figures, iopart
clas
Surface Termination of CsPbBr3 Perovskite Quantum Dots Determined by Solid-State NMR Spectroscopy
Cesium lead halide perovskite quantum dots (QDs) have gained significant attention as next-generation optoelectronic materials; however, their properties are highly dependent on their surface chemistry. The surfaces of cuboidal CsPbBr3 QDs have been intensively studied by both theoretical and experimental techniques, but fundamental questions still remain about the atomic termination of the QDs. The binding sites and modes of ligands at the surface remain unproven. Herein, we demonstrate that solid-state NMR spectroscopy allows the unambiguous assignments of organic surface ligands via 1H, 13C, and 31P NMR. Surface-selective 133Cs solid-state NMR spectra show the presence of an additional 133Cs NMR signal with a unique chemical shift that is attributed to Cs atoms terminating the surface of the particle and which are likely coordinated by carboxylate ligands. Dipolar dephasing curves that report on the distance between the surface ammonium ligands and Cs and Pb were recorded using double resonance 1H{133Cs} and 1H{207Pb} RESPDOR experiments. Model QD surface slabs with different possible surface terminations were generated from the CsPbBr3 crystal structure and theoretical RESPDOR dipolar dephasing curves considering all possible 1H-133Cs/207Pb spin pairs were then calculated. Comparison of the calculated and experimental RESPDOR curves indicates the particles are CsBr terminated (not PbBr2 terminated), with alkylammonium ligands situated within surface Cs vacancies, consistent with the surface-selective 133Cs NMR experiments. These results highlight the utility of high-resolution solid-state NMR spectroscopy for studying ligand binding and the surface structure of nanomaterials
Fertility, Living Arrangements, Care and Mobility
There are four main interconnecting themes around which the contributions in this book are based. This introductory chapter aims to establish the broad context for the chapters that follow by discussing each of the themes. It does so by setting these themes within the overarching demographic challenge of the twenty-first century – demographic ageing. Each chapter is introduced in the context of the specific theme to which it primarily relates and there is a summary of the data sets used by the contributors to illustrate the wide range of cross-sectional and longitudinal data analysed
Critical adsorption on curved objects
A systematic fieldtheoretic description of critical adsorption on curved
objects such as spherical or rodlike colloidal particles immersed in a fluid
near criticality is presented. The temperature dependence of the corresponding
order parameter profiles and of the excess adsorption are calculated
explicitly. Critical adsorption on elongated rods is substantially more
pronounced than on spherical particles. It turns out that, within the context
of critical phenomena in confined geometries, critical adsorption on a
microscopically thin `needle' represents a distinct universality class of its
own. Under favorable conditions the results are relevant for the flocculation
of colloidal particles.Comment: 52 pages, 10 figure
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