Nilpotent elements in integral representation rings of Hopf-algebra orders in group algebras of prime order

AbstractIn this paper we shall find necessary and sufficient conditions for integral representation rings of Hopf-algebra orders to have non-zero nilpotent elements, when the order is a module over a discrete valuation ring, and an order in a group of prime order

Assessing environmental impact on mass balance, carrying capacity and growth of exploited populations

Population models that have been applied for assessment of exploited populations are also useful for assessment of environmental impacts. Surplus production models have been applied for both fishery and environmental impact assessment; environmental impacts with three different modes of action can be incorporated into the surplus production model. For each of these possible modes of action the equilibrium relations among biomass, yield, level of fishing and level of environmental stress are developed. The resulting equations are applied to describe the results of laboratory experiments in which exploited populations were manipulated to alter the growth coefficient, carrying capacity, or mass balance. The models describe the experimental results.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24967/1/0000394.pd

The effect of concurrent infections with Pasteurella multocida and Ascaridia galli on free range chickens

Pasteurella multocida and Ascaridia galli are observed with high prevalences in free range chickens in Denmark, but the impact is unknown. A study was carried out to examine the interaction between A. galli and P. multocida in chickens and the impact on production. Five groups, each with 20 18-week-old Lohmann Brown chickens were infected. Group I was orally infected with 1000 +/- 50 embryonated A. galli eggs. Group 2 received 10(4) cfu p. multocida intratracheally. Group 3 was infected with A. galli and subsequently with P. multocida. Group 4 was infected with P. multocida followed by A. galli. Group 5 was the control. The study ran for I I weeks where clinical manifestations, weight gain and egg production were recorded. Excretion of P. multocida was determined on individual basis and blood smears were made for differential counts. At the end of the study pathological lesions and the number of adult worms, larvae and eggs in the faeces were recorded. The birds were more severely affected when infected with both pathogens compared to single infections with A. galli or P. multocida, respectively. A lower weight gain and egg production was observed with dual infections. A. galli infection followed by a secondary P. multocida infection resulted in more birds with pathological lesions and continued P. multocida excretion. In conclusion a negative interaction between A. galli and R multocida was observed and it is postulated that free range chickens are at higher risk of being subjected to outbreaks of fowl cholera when they are infected with A. galli

Multigenic lentiviral vectors for combined and tissue-specific expression of miRNA- and protein-based antiangiogenic factors.

Lentivirus-based gene delivery vectors carrying multiple gene cassettes are powerful tools in gene transfer studies and gene therapy, allowing coexpression of multiple therapeutic factors and, if desired, fluorescent reporters. Current strategies to express transgenes and microRNA (miRNA) clusters from a single vector have certain limitations that affect transgene expression levels and/or vector titers. In this study, we describe a novel vector design that facilitates combined expression of therapeutic RNA- and protein-based antiangiogenic factors as well as a fluorescent reporter from back-to-back RNApolII-driven expression cassettes. This configuration allows effective production of intron-embedded miRNAs that are released upon transduction of target cells. Exploiting such multigenic lentiviral vectors, we demonstrate robust miRNA-directed downregulation of vascular endothelial growth factor (VEGF) expression, leading to reduced angiogenesis, and parallel impairment of angiogenic pathways by codelivering the gene encoding pigment epithelium-derived factor (PEDF). Notably, subretinal injections of lentiviral vectors reveal efficient retinal pigment epithelium-specific gene expression driven by the VMD2 promoter, verifying that multigenic lentiviral vectors can be produced with high titers sufficient for in vivo applications. Altogether, our results suggest the potential applicability of combined miRNA- and protein-encoding lentiviral vectors in antiangiogenic gene therapy, including new combination therapies for amelioration of age-related macular degeneration

Radiative corrections to the excitonic molecule state in GaAs microcavities

The optical properties of excitonic molecules (XXs) in GaAs-based quantum well microcavities (MCs) are studied, both theoretically and experimentally. We show that the radiative corrections to the XX state, the Lamb shift $\Delta^{\rm MC}_{\rm XX}$ and radiative width $\Gamma^{\rm MC}_{\rm XX}$, are large, about $10-30$ of the molecule binding energy $\epsilon_{\rm XX}$, and definitely cannot be neglected. The optics of excitonic molecules is dominated by the in-plane resonant dissociation of the molecules into outgoing 1$\lambda$-mode and 0$\lambda$-mode cavity polaritons. The later decay channel, ``excitonic molecule $\to$ 0$\lambda$-mode polariton + 0$\lambda$-mode polariton'', deals with the short-wavelength MC polaritons invisible in standard optical experiments, i.e., refers to ``hidden'' optics of microcavities. By using transient four-wave mixing and pump-probe spectroscopies, we infer that the radiative width, associated with excitonic molecules of the binding energy $\epsilon_{\rm XX} \simeq 0.9-1.1$ meV, is $\Gamma^{\rm MC}_{\rm XX} \simeq 0.2-0.3$ meV in the microcavities and $\Gamma^{\rm QW}_{\rm XX} \simeq 0.1$ meV in a reference GaAs single quantum well (QW). We show that for our high-quality quasi-two-dimensional nanostructures the $T_2 = 2 T_1$ limit, relevant to the XX states, holds at temperatures below 10 K, and that the bipolariton model of excitonic molecules explains quantitatively and self-consistently the measured XX radiative widths. We also find and characterize two critical points in the dependence of the radiative corrections against the microcavity detuning, and propose to use the critical points for high-precision measurements of the molecule bindingenergy and microcavity Rabi splitting.Comment: 16 pages, 11 figures, accepted for publication in Phys. Rev.

PCB uptake and transfer to humans by lake trout

A mathematical model for contaminant uptake from food and water by fishes is combined with a model for yield as a function of fishing mortality in order to examine both the contaminant concentration in fishes and the amount of contaminant transferred to humans from fishes as functions of fishing mortality. The models are fitted to lake trout Salvelinus namaycush data from Lake Michigan, where there has been a persistent problem of PCB contamination. Transfer of contaminants from fishes to humans can be regulated through control of fishing. The concentration of contaminant decreases exponentially as fishing mortality increases because fishing reduces the number of older individuals in the population and concentration is a function of age. The amount of contaminant transferred from a fish population to humans increases to a maximum and then begins to decrease as fishing effort increases. The maximum rate of transfer occurs at a relatively low level of fishing.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24956/1/0000383.pd

Application of a surplus production model to assess environmental impacts on exploited populations of Daphnia pulex in the laboratory

The surplus production model is a simple and easily applied model for the assessment of environmental impacts on exploited fish populations. However, its application requires several assumptions about the relationships between the degree of impact and the population response that are difficult to test using field data. To examine these assumptions, the model is applied to exploited laboratory populations of Daphnia pulex exposed to chronic radiation stress. The model describes the observed relationship between equilibrium population size and the level of radiation exposure. It also describes the relationship between yield and population size.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23914/1/0000158.pd

Superradiation from Crystals of High-Spin Molecular Nanomagnets

Phenomenological theory of superradiation from crystals of high-spin molecules is suggested. We show that radiation friction can cause a superradiation pulse and investigate the role of magnetic anisotropy, external magnetic field and dipole-dipole interactions. Depending on the contribution of all these factors at low temperature, several regimes of magnetization of crystal sample are described. Very fast switch of magnetization's direction for some sets of parameters is predicted.Comment: 10 pages, 3 figure