Natural hydroclimatic forcing of historical lake volume fluctuations at Devils Lake, North Dakota (USA)

Devils Lake, a terminal saline lake in eastern North Dakota, has experienced catastrophic flooding over the past two decades producing direct damages in excess of $1 billion ($USD). We use three long-term datasets to examine the temporal coherence between historical lake fluctuations and basic hydroclimatic drivers. Monthly precipitation and mean monthly air temperature data are used to characterize long-term precipitation delivery and evaporative demand. Monthly water balance data for a representative location are used to assess basin soil moisture conditions. A lake volume time series documents lake volume fluctuation in response to long-term precipitation and regional soil moisture conditions. Three variables are derived from the datasets, each characterizing a different aspect of the region’s hydroclimatology. A rescaling technique is applied to each variable to examine the temporal coherence and relative patterns of the variables and to identify distinct homogeneous hydroclimatic regimes during the historical period. The three rescaled variables show strong temporal coherence and confirm 1980 as an abrupt transition year between two distinct long-term hydroclimatic modes. Mode 1, a longer and drier phase, runs from 1907 to 1980, while mode 2, a shorter and wetter phase, extends from 1981 to the present. Multi-decadal and century-scale fluctuations between these two modes are the key drivers of long-term lake volume fluctuations, upon which interannual- and interdecadal-scale climatic variability are superimposed. The similar rates of change among the rescaled variables provides evidence in support of the conclusion that long-term natural hydroclimatological variability is the primary driver of observed lake volume changes at Devils Lake during the Twentieth Century and provides a foundation upon which to evaluate the potential contributing effects of anthropogenic climate change, and human alterations of the land use hydrology

A Response to Professor Poythress’s “Science as Allegory”

This paper critiques some of the arguments given by Vern Sheridan Poythress in his paper, Science as Allegory, particularly about the claims that the universe is poetry and that science is poetry

Stitching of near-nulled subaperture measurements

A metrology system for measuring aspheric test objects by subaperture stitching. A wavefront-measuring gauge having a limited capture range of wavefront shapes collects partially overlapping subaperture measurements over the test object. A variable optical aberrator reshapes the measurement wavefront with between a limited number of the measurements to maintain the measurement wavefront within the capture range of the wavefront-measuring gauge. Various error compensators are incorporated into a stitching operation to manage residual errors associated with the use of the variable optical aberrator

The Equilibrium in a Process for the Production of Sodium Cyanide

[Introduction]: The normally large demand for supplies of the various nitrogenous products of the industries has been greatly increased as a result of the war. The importation of nitrates to the United States from Chile would be stopped in case of a naval blockade. The problem of assuring an adequate supply of such materials is, therefore, a very pertinent one. This may best be solved by the improvement of the present commercial processes for the fixation of atmospheric nitrogen and by the development of new processes, not at present successful commercially. Apparently, the most promising known process of the latter class is based upon the formation of sodium cyanide by passing nitrogen gas over a mixture of sodium carbonate and carbon in the presence of a suitable catalyzer at high temperatures

Biochemical Systematics of Notothenioid Fishes from Antarctica

Genetic variation at 30 protein-coding loci was examined in seven forms of notothenioid fishes from Antarctica. Multilocus heterozygosity varied from 0.018 to 0.078 across taxa. An analysis of the allozyme data revealed the probable existence of an unrecognized cryptic species within Trematomu5 bemacchii. Pagothenia borchgrevinki is as closely related to some species of Trematomus as are some species of Trematomus to each other. Speciation among the species of Trematomus and Pagothenia appears to have taken place primarily after the separation of Antarctica from Australia

Computation in Classical Mechanics

There is a growing consensus that physics majors need to learn computational skills, but many departments are still devoid of computation in their physics curriculum. Some departments may lack the resources or commitment to create a dedicated course or program in computational physics. One way around this difficulty is to include computation in a standard upper-level physics course. An intermediate classical mechanics course is particularly well suited for including computation. We discuss the ways we have used computation in our classical mechanics courses, focusing on how computational work can improve students' understanding of physics as well as their computational skills. We present examples of computational problems that serve these two purposes. In addition, we provide information about resources for instructors who would like to include computation in their courses.Comment: 6 pages, 3 figures, submitted to American Journal of Physic

Functional and Morphological Correlates of Connexin50 Expressed in Xenopus laevis Oocytes

Electrophysiological and morphological methods were used to study connexin50 (Cx50) expressed in Xenopus laevis oocytes. Oocytes expressing Cx50 exhibited a new population of intramembrane particles (9.0 nm in diameter) in the plasma membrane. The particles represented hemichannels (connexin hexamers) because (a) their cross-sectional area could accommodate 24 ± 3 helices, (b) when their density reached 300–400/μm2, they formed complete channels (dodecamers) in single oocytes, and assembled into plaques, and (c) their appearance in the plasma membrane was associated with a whole-cell current, which was activated at low external Ca2+ concentration ([Ca2+]o), and was blocked by octanol and by intracellular acidification. The Cx50 hemichannel density was directly proportional to the magnitude of the Cx50 Ca2+-sensitive current. Measurements of hemichannel density and the Ca2+-sensitive current in the same oocytes suggested that at physiological [Ca2+]o (1–2 mM), hemichannels rarely open. In the cytoplasm, hemichannels were present in ∼0.1-μm diameter “coated” and in larger 0.2–0.5-μm diameter vesicles. The smaller coated vesicles contained endogenous plasma membrane proteins of the oocyte intermingled with 5–40 Cx50 hemichannels, and were observed to fuse with the plasma membrane. The larger vesicles, which contained Cx50 hemichannels, gap junction channels, and endogenous membrane proteins, originated from invaginations of the plasma membrane, as their lumen was labeled with the extracellular marker peroxidase. The insertion rate of hemichannels into the plasma membrane (80,000/s), suggested that an average of 4,000 small coated vesicles were inserted every second. However, insertion of hemichannels occurred at a constant plasma membrane area, indicating that insertion by vesicle exocytosis (60–500 μm2 membranes/s) was balanced by plasma membrane endocytosis. These exocytotic and endocytotic rates suggest that the entire plasma membrane of the oocyte is replaced in ∼24 h

Physiological Role of Gap-Junctional Hemichannels: Extracellular Calcium-Dependent Isosmotic Volume Regulation

Hemichannels in the overlapping regions of apposing cells plasma membranes join to form gap junctions and provide an intercellular communication pathway. Hemichannels are also present in the nonjunctional regions of individual cells and their activity is gated by several agents, including calcium. However, their physiological roles are unknown. Using techniques of atomic force microscopy (AFM), fluorescent dye uptake assay, and laser confocal immunofluorescence imaging, we have examined the extracellular calcium-dependent modulation of cell volume. In response to a change in the extracellular physiological calcium concentration (1.8 to ≤1.6 mM) in an otherwise isosmotic condition, real-time AFM imaging revealed a significant and reversible increase in the volume of cells expressing gap-junctional proteins (connexins). Volume change did not occur in cells that were not expressing connexins. However, after the transient or stable transfection of connexin43, volume change did occur. The volume increase was accompanied by cytochalasin D-sensitive higher cell stiffness, which helped maintain cell integrity. These cellular physical changes were prevented by gap-junctional blockers, oleamide and β-glycyrrhetinic acid, or were reversed by returning extracellular calcium to the normal level. We conclude that nongap-junctional hemichannels regulate cell volume in response to the change in extracellular physiological calcium in an otherwise isosmotic situation