Diatoms of Pilot Knob Sphagnum Bog, Hancock County, Iowa

The 47 diatom taxa listed here plus the 43 taxa in the genus Pinnularia reported earlier (Christensen 1976) constitute the numerically most important components of the diatom-flora of Pilot Knob Bog, the only known major Sphagnum bog in Iowa

Magneto-acoustic wave propagation and mode conversion in a magnetic solar atmosphere: comparing results from the CO5BOLD code with ray theory

We present simulations of magneto-acoustic wave propagation in a magnetic, plane-parallel stratified solar model atmosphere, employing the CO5BOLD-code. The tests are carried out for two models of the solar atmosphere, which are similar to the ones used by Cally (2007) and Schunker & Cally (2006). The two models differ only in the orientation of the magnetic field. A qualitative comparison shows good agreement between the numerical results and the results from ray theory. The tests are done in view of the application of the present numerical code for the computation of energy fluxes of propagating acoustic waves into a dynamically evolving magnetic solar atmosphere. For this, we consider waves with frequencies above the acoustic cut-off frequency.Comment: 4 pages, 4 figures, will appear in HELAS-IV Conference Proceedin

Long range axon tracing with NeuroTracker

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Kadison-Kastler stable factors

A conjecture of Kadison and Kastler from 1972 asks whether sufficiently close operator algebras in a natural uniform sense must be small unitary perturbations of one another. For n≥3 and a free, ergodic, probability measure-preserving action of SL<sub>n</sub>(Z) on a standard nonatomic probability space (X,μ), write M=(L<sup>∞</sup>(X,μ)⋊SL<sub>n</sub>(Z))⊗¯¯¯R, where R is the hyperfinite II1-factor. We show that whenever M is represented as a von Neumann algebra on some Hilbert space H and N⊆B(H) is sufficiently close to M, then there is a unitary u on H close to the identity operator with uMu∗=N. This provides the first nonamenable class of von Neumann algebras satisfying Kadison and Kastler’s conjecture. We also obtain stability results for crossed products L<sup>∞</sup>(X,μ)⋊Γ whenever the comparison map from the bounded to usual group cohomology vanishes in degree 2 for the module L<sup>2</sup>(X,μ). In this case, any von Neumann algebra sufficiently close to such a crossed product is necessarily isomorphic to it. In particular, this result applies when Γ is a free group

A remark on the similarity and perturbation problems

In this note we show that Kadison's similarity problem for C*-algebras is equivalent to a problem in perturbation theory: must close C*-algebras have close commutants?Comment: 6 Pages, minor typos fixed. C. R. Acad. Sci. Canada, to appea

Investigating Chemotherapeutic Resistance: Why is Glioblastoma So Deadly?

Glioblastoma multiforme (GBM), a malignancy of the glioblast stem cells of the brain, is one of the most aggressive and untreated forms of brain cancer. When an individual is diagnosed with GBM, depending on the location of the tumor, there are three treatment options including surgery, radiation, chemotherapy or the combination of these treatments. Many patients choose chemotherapy, however most GBM cases show little to no response to Temozolomide (TMZ), which is a common chemotherapy drug used for this type of cancer. In some recent studies, researchers have noticed an elevated amount or over production of an enzyme, Inosine 5\u27-monophosphate dehydrogenase (IMPDH). This enzyme 31 helps with DNA repair but in many GBM cases, due to its over production, it repairs at such a fast rate it does not allow TMZ to terminate the cancerous tumors. In our research we have been investigating whether the chemotherapeutic agent causes the increase in expression directly or whether it is a unique property of this cell type. Future directions involve: determining a molecular pathway that could lead to IMPDH expression at such high levels under chemotherapeutic stress and whether co-administering IMPDH inhibitors with TMZ can improve prognosis for those suffering from GBM.https://openriver.winona.edu/urc2019/1023/thumbnail.jp

Saturation and time dependence of geodynamo models

In this study we address the question under which conditions a saturated velocity field stemming from geodynamo simulations leads to an exponential growth of the magnetic field in a corresponding kinematic calculation. We perform global self-consistent geodynamo simulations and calculate the evolution of a kinematically advanced tracer field. The self-consistent velocity field enters the induction equation in each time step, but the tracer field does not contribute to the Lorentz force. This experiment has been performed by Cattaneo & Tobias (2009) and is closely related to the test field method by Schrinner et al. (2005, 2007). We find two dynamo regimes in which the tracer field either grows exponentially or approaches a state aligned with the actual self-consistent magnetic field after an initial transition period. Both regimes can be distinguished by the Rossby number and coincide with the dipolar and multipolar dynamo regimes identified by Christensen & Aubert (2006). Dipolar dynamos with low Rossby number are kinematically stable whereas the tracer field grows exponentially in the multipolar dynamo regime. This difference in the saturation process for dynamos in both regimes comes along with differences in their time variability. Within our sample of 20 models, solely kinematically unstable dynamos show dipole reversals and large excursions. The complicated time behaviour of these dynamos presumably relates to the alternating growth of several competing dynamo modes. On the other hand, dynamos in the low Rossby number regime exhibit a rather simple time dependence and their saturation merely results in a fluctuation of the fundamental dynamo mode about its critical state.Comment: 6 pages, 8 figure

Collection and Culture of Lower Animal Forms

The trend in secondary biology is to use living material in so far as it is possible. Biology instruction, as it has advanced beyond the descriptive level, has included more projects requiring living animals. The local collecting and culturing of some of these organisms adds just that much more biological experience to the course