Herbivore-mediated effects on ecosystem processes in a near-Arctic salt marsh

Thesis (Ph.D.) University of Alaska Fairbanks, 2001Herbivores influence, and often regulate energy flow. I investigated interactions between herbivory and the foods on which geese rely while nesting and rearing their broods on the Yukon-Kuskokwim Delta in southwestern Alaska. In a captive Cackling Canada gosling (Branta Canadensis minima) experiment I decoupled the effects of seasonal declines in forage quality and availability on gosling development. An 11% decline in forage quality translated to goslings that were structurally smaller and 100 g lighter at 31 days of age. Forage availability had similar effects on gosling size, and the combined magnitude of these effects are similar to those observed in wild populations. I manipulated within-season grazing history of 'Carex subspathacea' swards within brood-rearing areas used by Black Brant geese (Branta bernicla nigricans). Spatial variation in forage quality and availability exceeded seasonal variation. Brant consumed over 95% of the annual aboveground production of these swards without any short- or apparent long-term effects on aboveground growth. Adding grazing pressure to 'C. ramenskii, ' or removing grazing pressure from 'C. subspathacea, ' resulted in a bi-directional shift in the morphology and nutritional characteristics of these sedges. The areal extent of 'C. subspathacea' increased 2 to 8% of the Tutakoke landscape with a concomitant decrease in 'C. ramenskii' meadows between 1991-1998. Brant have been increasing the carrying capacity of the Tutakoke River colony following a population decline in the early 1980's. The population has increased beginning in 1988, yet remains below historic numbers. Density-dependent effects on gosling growth accompanied the population increase initially. However, gosling mass has increased over the past decade due to herbivore-mediated increases in the areal extent of grazing lawns.Ch. 1. Cackling Canada gosling growth: separating variation in food quality from availability -- Ch. 2. Forage variation in brood-rearing areas used by pacific black brant geese on the Yukon-Kuskokwim delta, Alaska -- Ch. 3. Feedback dynamics of grazing lawns: coupling vegetation change with animal growth -- Ch. 4. Stability of a near-arctic saltmarsh: community resistance to tidal disturbance -- Conclusions -- Literature cited

Some results on fractional vs. expectation thresholds

A conjecture of Talagrand (2010) states that the so-called expectation and fractional expectation thresholds are always within at most some constant factor from each other. Expectation (resp. fractional expectation) threshold $q$ (resp. $q_f$) for an increasing nontrivial class $\mathcal{F}\subseteq 2^X$ allows to locate the threshold for $\mathcal{F}$ within a logarithmic factor (these are important breakthrough results of Park and Pham (2022), resp. Frankston, Kahn, Narayanan and Park (2019)). We will survey what is known about the relation between $q$ and $q_f$ and prove some further special cases of Talagrand's conjecture.Comment: 17 pages, 0 figure

The HLA-E Gene encodes two differentially regulated Transcripts and a Cell Surface Protein

An HLA-E-specific oligonucleotide probe was used to study the expressioonf HLA-E. This probed etects two HLA-E transcripts, 1.8 and 2.7 kb in size, which are present in varying ratios in allt issues and cell lines investigated. We demonstrate that alternative poly(A) site usage accounts for the differential regulation of the two HLA-E mRNA species. Sequence analysis of three cDNA clones, representing the two transcripts of HLA-E, and of anH LA-E gene encoded by cosmid cd3.14, revealed identity of gene and cDNA in the 3’ untranslated region. S1 nuclease protection assays confirmed that the two HLA-E transcripts are not alternative splicing products. Introduction of cd3.14, together with human ,&m into the murine myeloma cell line P3X63-Ag8.653, resulted in a cell surface expresosf ioan HLA-class I heavy chain detectablbey indirect immunofluorescence whereas transfection into the humBaznr n expressing mouse L cell line, 527 was negative with regard to cell surface expressionC. ell surface labeling of transfectants and immunoprecipitation with a monomorphic HLA class I-specific antibodyo r an antibody against human &m confirmed the presence of an HLA-E H chain on the cell surface. These results indicate that the HLA-E gene codes for a class I H chain that can be expressed on the cell surface

Putting aquifers into atmospheric simulation models: an example from the Mill Creek Watershed, northeastern Kansas

Aquifer–atmosphere interactions can be important in regions where the water table is shallow (\u3c2 m). A shallow water table provides moisture for the soil and vegetation and thus acts as a source term for evapotranspiration to the atmosphere. A coupled aquifer–land surface–atmosphere model has been developed to study aquifer–atmosphere interactions in watersheds, on decadal timescales. A single column vertically discretized atmospheric model is linked to a distributed soil-vegetation–aquifer model. This physically based model was able to reproduce monthly and yearly trends in precipitation, stream discharge, and evapotranspiration, for a catchment in northeastern Kansas. However, the calculated soil moisture tended to drop to levels lower than were observed in drier years. The evapotranspiration varies spatially and seasonally and was highest in cells situated in topographic depressions where the water table is in the root zone. Annually, simulation results indicate that from 5–20% of groundwater supported evapotranspiration is drawn from the aquifer. The groundwater supported fraction of evapotranspiration is higher in drier years, when evapotranspiration exceeds precipitation. A long-term (40 year) simulation of extended drought conditions indicated that water table position is a function of groundwater hydrodynamics and cannot be predicted solely on the basis of topography. The response time of the aquifer to drought conditions was on the order of 200 years indicating that feedbacks between these two water reservoirs act on disparate time scales. With recent advances in the computational power of massively parallel supercomputers, it may soon become possible to incorporate physically based representations of aquifer hydrodynamics into general circulation models (GCM) land surface parameterization schemes

Relational Symbolic Execution

Symbolic execution is a classical program analysis technique used to show that programs satisfy or violate given specifications. In this work we generalize symbolic execution to support program analysis for relational specifications in the form of relational properties - these are properties about two runs of two programs on related inputs, or about two executions of a single program on related inputs. Relational properties are useful to formalize notions in security and privacy, and to reason about program optimizations. We design a relational symbolic execution engine, named RelSym which supports interactive refutation, as well as proving of relational properties for programs written in a language with arrays and for-like loops

Thomas Knaus im Gespräch mit Gerhard Tulodziecki

Gerhard Tulodziecki (Universität Paderborn) ist bereits seit vielen Jahrzehnten einer der zentralen Akteure der Medienpädagogik. So geht beispielsweise das Konzept einer handlungs- und entwicklungsorientierten Medienpädagogik für die Schule auf ihn zurück. Auch nach seiner Emeritierung beteiligt er sich weiterhin sehr aktiv am medienpädagogischen Diskurs. Dies zeigt nicht zuletzt auch sein aktueller Beitrag für die vorliegende Ausgabe der LBzM. In den letzten Jahren hat er sich verstärkt der handlungstheoretischen Fundierung (medien-)pädagogischer Konzepte gewidmet und kürzlich auch ein weiteres Buch hierzu veröffentlicht. Um dieses Buch ging es im Gespräch mit Thomas Knaus (PH Ludwigsburg | FTzM Frankfurt am Main) – aber nicht nur: In dem freundschaftlich-kollegialen Austausch der beiden Medienpädagogen werden auch ganz aktuelle Medien- und Technikentwicklungen erörtert. In diesem Zuge greifen die beiden Kollegen auch gegenwärtige Diskussionen über KI-basierte Dialogsysteme und Textgeneratoren auf und beleuchten die mit ihnen verbundene gesellschaftlich-kulturelle Bedeutung nicht nur aus ihrer fachlichen Sicht als Medienpädagogen, sondern aufgrund ihrer technisch-informatischen Expertise auch multiperspektivisch. Dabei kommen die beiden Gesprächspartner auch auf mögliche Standortbestimmungen und Herausforderungen für die Medienpädagogik als Disziplin zu sprechen – passend zum Schwerpunkt unserer aktuellen Ausgabe auch im Hinblick auf gegenwärtige Kompetenzdiskurse. (DIPF/Orig.

The Mission Accessible Near-Earth Objects Survey: Four years of photometry

Over 4.5 years, the Mission Accessible Near-Earth Object Survey (MANOS) assembled 228 Near-Earth Object (NEO) lightcurves. We report rotational lightcurves for 82 NEOs, constraints on amplitudes and periods for 21 NEOs, lightcurves with no detected variability within the image signal to noise and length of our observing block for 30 NEOs, and 10 tumblers. We uncovered 2 ultra-rapid rotators with periods below 20s; 2016MA with a potential rotational periodicity of 18.4s, and 2017QG$_{18}$ rotating in 11.9s, and estimate the fraction of fast/ultra-rapid rotators undetected in our project plus the percentage of NEOs with a moderate/long periodicity undetectable during our typical observing blocks. We summarize the findings of a simple model of synthetic NEOs to infer the object morphologies distribution using the measured distribution of lightcurve amplitudes. This model suggests a uniform distribution of axis ratio can reproduce the observed sample. This suggests that the quantity of spherical NEOs (e.g., Bennu) is almost equivalent to the quantity of highly elongated objects (e.g., Itokawa), a result that can be directly tested thanks to shape models from Doppler delay radar imaging analysis. Finally, we fully characterized 2 NEOs as appropriate targets for a potential robotic/human mission: 2013YS$_{2}$ and 2014FA$_{7}$ due to their moderate spin periods and low $\Delta v$.Comment: Accepted for Publication, The Astrophysical Journal Supplement Serie