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Soil microbial communities in restored and unrestored coastal dune ecosystems in California
Most restoration projects involving invasive plant eradication tend to focus on plant removal with little consideration given to how these invasives change soil microbial communities. However, soil microorganisms can determine invasibility of habitats and, in turn, be altered by invasives once established, potentially inhibiting native plant establishment. We studied soil microbial communities in coastal dunes with varying invasion intensity and different restoration approaches (herbicide, mechanical excavation) at Point Reyes National Seashore. Overall, we found evidence of a strong link between bacterial and fungal soil communities and the presence of invasives and restoration approach. Heavily invaded sites were characterized by a lower abundance of putatively identified nitrifiers, fermentative bacteria, fungal parasites, and fungal dung saprotrophs and a higher abundance of cellulolytic bacteria and a class of arbuscular mycorrhizal fungi (Archaeosporomycetes). Changes in soil microbiota did not fully dissipate following removal of invasives using herbicide, with exception of reductions in cellulolytic bacteria and Archaeosporomycetes abundance. Mechanical restoration effectively removed both invasives and soil legacy effects by inverting or “flipping” rhizome-contaminated surface soils with soils from below and may have inadvertently induced other adverse effects on soils that impeded reestablishment of native dune plants. Land managers should consider additional measures to counteract lingering legacy effects and/or focus restoration efforts in areas where legacy effects are less pronounced
Generalization of Child-Langmuir Law for Non-Zero Injection Velocities in a Planar Diode
The Child-Langmuir law relates the voltage applied across a planar diode to
the saturation value J_CL of current density that can be transmitted through it
in case the injection velocity of electrons into the diode is zero. The
Child-Langmuir current density J_CL is, at the same time, (i) the maximum
current density that can be transmitted through a planar diode, (ii) the
current density below which the flow is steady and unidirectional in the long
time limit and (iii) the average transmitted current density for {\em any}
value of injected current density above J_CL. Existing generalizations of
Child-Langmuir law to non-zero velocities of injection are based on the
characteristics (i) and (ii) of J_CL. This paper generalizes the law to
non-zero velocities of injection based on the characteristic (iii) by deriving
an analytical expression for the saturation value of current density. The
analytical expression for the saturation current density is found to be well
supported by numerical computations. A reason behind preferring the saturation
property of the Child-Langmuir current density as the basis for its
generalization is the importance of that property in numerical simulations of
high current diode devices.Comment: revtex, 4 figure
Book Reviews in The Great Plains Sociologist: The Continuation of a Regional Tradition
On the tenth anniversary of publication of The Great Plains Sociologist, we examine the book section for content and for participation by residents of the Great Plains. Since the inception of this journal feature in 1991, women have published 57 percent (N=57) of all book reviews. Moreover, women at masters and doctoral degree granting institutions have published a greater number of book reviews (52%. N=52) than their male counterparts (41%, N=41) and than women or men at 2-year,four-year, and tribal colleges (5%, N=5 and 2%, N=2 respectively). While there are differences in the topical areas evaluated by women and men, the primary area of interest for both is rural issues(16%, N=16). We conclude that the journal has met its goal of providing opportunities for regional scholars to publish their work and that The Great Plains Sociologist clearly plays a unique role in the region and in the discipline
Radiotherapy planning for glioblastoma based on a tumor growth model: Improving target volume delineation
Glioblastoma are known to infiltrate the brain parenchyma instead of forming
a solid tumor mass with a defined boundary. Only the part of the tumor with
high tumor cell density can be localized through imaging directly. In contrast,
brain tissue infiltrated by tumor cells at low density appears normal on
current imaging modalities. In clinical practice, a uniform margin is applied
to account for microscopic spread of disease.
The current treatment planning procedure can potentially be improved by
accounting for the anisotropy of tumor growth: Anatomical barriers such as the
falx cerebri represent boundaries for migrating tumor cells. In addition, tumor
cells primarily spread in white matter and infiltrate gray matter at lower
rate. We investigate the use of a phenomenological tumor growth model for
treatment planning. The model is based on the Fisher-Kolmogorov equation, which
formalizes these growth characteristics and estimates the spatial distribution
of tumor cells in normal appearing regions of the brain. The target volume for
radiotherapy planning can be defined as an isoline of the simulated tumor cell
density.
A retrospective study involving 10 glioblastoma patients has been performed.
To illustrate the main findings of the study, a detailed case study is
presented for a glioblastoma located close to the falx. In this situation, the
falx represents a boundary for migrating tumor cells, whereas the corpus
callosum provides a route for the tumor to spread to the contralateral
hemisphere. We further discuss the sensitivity of the model with respect to the
input parameters. Correct segmentation of the brain appears to be the most
crucial model input.
We conclude that the tumor growth model provides a method to account for
anisotropic growth patterns of glioblastoma, and may therefore provide a tool
to make target delineation more objective and automated
Quantum Spin Lenses in Atomic Arrays
We propose and discuss `quantum spin lenses', where quantum states of
delocalized spin excitations in an atomic medium are `focused' in space in a
coherent quantum process down to (essentially) single atoms. These can be
employed to create controlled interactions in a quantum light-matter interface,
where photonic qubits stored in an atomic ensemble are mapped to a quantum
register represented by single atoms. We propose Hamiltonians for quantum spin
lenses as inhomogeneous spin models on lattices, which can be realized with
Rydberg atoms in 1D, 2D and 3D, and with strings of trapped ions. We discuss
both linear and non-linear quantum spin lenses: in a non-linear lens, repulsive
spin-spin interactions lead to focusing dynamics conditional to the number of
spin excitations. This allows the mapping of quantum superpositions of
delocalized spin excitations to superpositions of spatial spin patterns, which
can be addressed by light fields and manipulated. Finally, we propose
multifocal quantum spin lenses as a way to generate and distribute entanglement
between distant atoms in an atomic lattice array.Comment: 13 pages, 9 figure
Precision of maxillo-mandibular registration with intraoral scanners in vitro
Purpose: To compare the precision of maxillo-mandibular registration and resulting full arch occlusion produced by three intraoral scanners in vitro.
Methods: Six dental models (groups A–F) were scanned five times with intraoral scanners (CEREC, TRIOS, PLANMECA), producing both full arch and two buccal maxillo-mandibular scans. Total surface area of contact points (defined as regions within 0.1 mm and all mesh penetrations) was measured, and the distances between four pairs of key points were compared, each two in the posterior and anterior.
Results: Total surface area of contact points varied significantly among scanners across all groups. CEREC produced the smallest contact surface areas (5.7–25.3 mm2), while PLANMECA tended to produce the largest areas in each group (22.2–60.2 mm2). Precision of scanners, as measured by the 95% CI range, varied from 0.1–0.9 mm for posterior key points. For anterior key points the 95% CI range was smaller, particularly when multiple posterior teeth were still present (0.04–0.42 mm). With progressive loss of posterior units (groups D–F), differences in the anterior occlusion among scanners became significant in five out of six groups (D–F left canines and D, F right canines, p < 0.05).
Conclusions: Maxillo-mandibular registrations from three intraoral scanners created significantly different surface areas of occlusal contact. Posterior occlusions revealed lower precision for all scanners than anterior. CEREC tended towards incorrect posterior open bites, whilst TRIOS was most consistent in reproducing occluding units
Geometric predictors of abdominal aortic aneurysm maximum wall stress
Abdominal aortic aneurysm (AAA) is a dilation of the abdominal aorta (above 50 % of its original diameter), which can cause death upon rupturing. It usually grows asymptomatically leading to late clinical intervention. The medical criteria to indicate surgery are based on measuring the diameter and growth rate, but in many cases aneurysms fail at uncharacterized critical values. In search of a more efficient technique in predicting AAA failure, there is consensus on the importance of studying its geometric characteristics and estimation of the wall stress, but no fully successful correlation has been found between the two yet. This work examines the relationship between a parameterized geometry (18 input variables and 10 dependent indices) and 1 output variable: the maximum wall stress
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