University of Maine

About: University of Maine is a education organization based out in Orono, Maine, United States. It is known for research contribution in the topics: Population & Ice sheet. The organization has 8637 authors who have published 16932 publications receiving 590124 citations. The organization is also known as: University of Maine at Orono.

Larval settlement preferences and post-settlement survival of the threatened Caribbean corals Acropora palmata and A. cervicornis

Abstract: The settlement specificity of two threatened Caribbean corals, Acropora palmata and A. cervicornis, was tested by measuring their rates of larval metamorphosis in response to crustose coralline algae (CCA) and other substrata. In the no-choice experiments, the coral larvae were placed in six treatments: filtered seawater (FSW), a fragment of biofilmed dead skeleton of A. palmata, or a fragment of one of four species of CCA (Hydrolithon boergesenii, Porolithon pachydermum, Paragoniolithon solubile, and Titanoderma prototypum). Within each CCA treatment, there were three different substrata on which to settle and metamorphose: (1) the CCA surface, (2) the rock under the CCA, or (3) the plastic dish. The 5-day-old larvae of both A. palmata and A. cervicornis had similar rates of total metamorphosis (all substrata combined) in every treatment (excluding FSW) even in the absence of CCA. However, there were differences in larval behavior among the CCA species since the larvae settled and metamorphosed on different substrata in the presence of different CCA species. In the no-choice experiments the larvae of both corals had higher rates of metamorphosis on the top surfaces of H. boergesenii and/or T. prototypum than on P. pachydermum. In the choice experiments, the coral larvae were offered two species of CCA in the same dish. When given a choice, both species of coral larvae had more settlement and metamorphosis on the surface of H. boergesenii or T. prototypum or clean rock than onto the surface of P. solubile. After 6 weeks in the field, transplanted A. palmata recruits had approximately 15% survival on both T. prototypum and H. boergesenii, but A. cervicornis recruits only survived on T. prototypum (13%). Some, but not all, CCA species facilitated the larval settlement and post-settlement survival of these two threatened corals, highlighting the importance of benthic community composition for successful coral recruitment.

Israeli acute paralysis virus: epidemiology, pathogenesis and implications for honey bee health.

Abstract: Israeli acute paralysis virus (IAPV) is a widespread RNA virus of honey bees that has been linked with colony losses. Here we describe the transmission, prevalence, and genetic traits of this virus, along with host transcriptional responses to infections. Further, we present RNAi-based strategies for limiting an important mechanism used by IAPV to subvert host defenses. Our study shows that IAPV is established as a persistent infection in honey bee populations, likely enabled by both horizontal and vertical transmission pathways. The phenotypic differences in pathology among different strains of IAPV found globally may be due to high levels of standing genetic variation. Microarray profiles of host responses to IAPV infection revealed that mitochondrial function is the most significantly affected biological process, suggesting that viral infection causes significant disturbance in energy-related host processes. The expression of genes involved in immune pathways in adult bees indicates that IAPV infection triggers active immune responses. The evidence that silencing an IAPV-encoded putative suppressor of RNAi reduces IAPV replication suggests a functional assignment for a particular genomic region of IAPV and closely related viruses from the Family Dicistroviridae, and indicates a novel therapeutic strategy for limiting multiple honey bee viruses simultaneously and reducing colony losses due to viral diseases. We believe that the knowledge and insights gained from this study will provide a new platform for continuing studies of the IAPV–host interactions and have positive implications for disease management that will lead to mitigation of escalating honey bee colony losses worldwide.

Au(110) (1×2)-to-(1×1) phase transition: A physical realization of the two-dimensional Ising model

Abstract: We report the first measurements of the critical exponents of a phase transition at the surface of a clean metal, the Au(110) (1 \ifmmode\times\else\texttimes\fi{} 2) \ensuremath{\leftrightarrow} (1 \ifmmode\times\else\texttimes\fi{} 1) transition. The exponents $\ensuremath{\beta}$, $\ensuremath{\gamma}$, and $\ensuremath{ u}$ and the amplitudes were measured by LEED and place the phase transition in the two-dimensional Ising universality class. The critical scattering is observed to peak above ${T}_{c}$, signaling the breakdown of the Ornstein-Zernike theory, and is in numerical accord with predictions of Fisher and Burford.

Diffusion in nanoporous materials: fundamental principles, insights and challenges

Abstract: Following a brief review of Fick's laws and the theory of diffusion in a homogeneous medium, we consider the application of the Fickian model to diffusion in nanoporous materials. If the pore system is statistically uniform the simple Fickian model is directly applicable. Inhomogeneities such as surface or internal barriers require some adjustments to the model but Fick's equations still provide a valid approach. Hierarchical pore systems present a more serious challenge. When there is rapid exchange between the different regions such systems conform to the simple Fickian model, with a diffusivity corresponding to the mean of the diffusivities in the different regions. In contrast, when the condition of rapid exchange is not fulfilled the simple Fickian model is not applicable and the situation becomes more complicated. Simple hierarchical pore structures such as the micropore/macropore system typically found in commercial adsorbents and catalysts can still be described by a dual resistance Fickian model but for more complex hierarchical pore structures Monte Carlo or MD simulations offer the only realistic approach. The measurement of self-diffusion by PFG NMR and by microimaging (notably by interference microscopy) is also reviewed and selected examples are presented to show the detailed information that can be extracted from such measurements, especially when accompanied by molecular simulations. Examples highlighting the relevance of a detailed knowledge of the various steps of mass transfer for a transport-optimized technological application of nanoporous materials, notably for molecular separations and mass conversions, are provided.

Three-Dimensional Simulation of Scour-Inducing Flow at Bridge Piers

Abstract: Presently available formulas for estimating the maximum depth of scour near bridge piers often lead to unreliable results. A fully three-dimensional hydrodynamic model is therefore used in this study to simulate the flow occurring at the base of a cylindrical bridge pier within a scour hole. The results of the numerical simulation are compared with laboratory observations by Melville and Raudkivi (1977). Quantitative and qualitative agreement between the studies is quite good. Discrepancies between the results of the two studies are of an order that may be attributed to choices in numerical model parameters. The simulations may be supplemented by Lagrangian particle-tracking to estimate the depth of the equilibrium scour condition.