Periodic minimal surfaces of cubic symmetry

A survey of cubic minimal surfaces is presented, based on the concept of fundamental surface patches and their relation to the asymmetric units of the space groups. The software Surface Evolver has been used to test for stability and to produce graphic displays. Particular emphasis is given to those surfaces that can be generated by a finite piece bounded by straight lines. Some new varieties have been found and a systematic nomenclature is introduced, which provides a symbol (a ‘gene’) for each triply-periodic minimal surface that specifies the surface unambiguously

Packing defects and the width of biopolymer bundles

The formation of bundles composed of actin filaments and cross-linking proteins is an essential process in the maintenance of the cells' cytoskeleton. It has also been recreated by in-vitro experiments, where actin networks are routinely produced to mimic and study the cellular structures. It has long been observed that these bundles seem to have a well defined width distribution, which has not been adequately described theoretically. We propose here that packing defects of the filaments, quenched and random, contribute an effective repulsion that counters the cross-linking adhesion energy and leads to a well defined bundle width. This is a two-dimensional strain-field version of the classic Rayleigh instability of charged droplets

Annotation of SBML Models Through Rule-Based Semantic Integration

*Motivation:* The creation of accurate quantitative Systems Biology Markup Language (SBML) models is a time-intensive, manual process often complicated by the many data sources and formats required to annotate even a small and well-scoped model. Ideally, the retrieval and integration of biological knowledge for model annotation should be performed quickly, precisely, and with a minimum of manual effort. Here, we present a method using off-the-shelf semantic web technology which enables this process: the heterogeneous data sources are first syntactically converted into ontologies; these are then aligned to a small domain ontology by applying a rule base. Integrating resources in this way can accommodate multiple formats with different semantics; it provides richly modelled biological knowledge suitable for annotation of SBML models.
*Results:* We demonstrate proof-of-principle for this rule-based mediation with two use cases for SBML model annotation. This was implemented with existing tools, decreasing development time and increasing reusability. This initial work establishes the feasibility of this approach as part of an automated SBML model annotation system.
*Availability:* Detailed information including download and mapping of the ontologies as well as integration results is available from "http://www.cisban.ac.uk/RBM":http://www.cisban.ac.uk/RB

Sedimentology and Stratigraphy of Glacial Lake Souris, North Dakota: effects of a glacial-lake outburst

Glacial-lake outbursts commonly occurred along the southern margin of the Laurentide Ice Sheet as ice-marginal lakes suddenly drained. These outbursts released huge volumes of water with tremendous erosive potential, forming large trench-shape channels. Although glacial-lake spillways have been studied in detail, the effects of outbursts on downstream lakes have not. The purpose of this study was to demonstrate the effects of the Glacial Lake Regina outburst on the lake that received the flows, Glacial Lake Souris. Glacial Lake Souris, located in what is now North Dakota, was inundated by about 74 km3 of water carrying 25 km3 of sediment from the outburst of Lake Regina (Saskatchewan). Prior to the outburst, the bottom of Lake Souris was irregular with two shallow depressions and comprised of diamicton overlain by silt and clay rhythmites. Quiet-water lake sedimentation was abruptly halted by coarse-grained outburst sedimentation. Based on surficial mapping, subsurface sample collection, and textural analyses, the outburst sediments have been grouped into three lithofacies: 1) matrix-rich gravel, commonly with lignite, that generally occurs at the base of the outburst sediments; 2) matrix deficient gravel, generally without lignite, that occurs near the ground surface adjacent to the Souris spillway; and 3) sand, the most widespread lithofacies, that tends to overlie other lithofacies. Lignite particles are abundant in much of the sand; at depth, outsize lignite clasts are common. Three major depositional processes probably are responsible for deposition of the outburst sediments: braided rivers, low-density turbidity currents (the dominant process), and high-density turbidity currents or modified grain flows. Most high-density flows resulted directly from the influx of the outburst or from continuous avalanching due to rapid sedimentation. Low-density turbidity currents occurred for the entire duration of the outburst and were caused by the continuous influx of sediment-laden flows and by residual currents from high-density flows. The emptying of Lake Souris was triggered by inundation of the lake by outburst waters before silt- and clay-size sediment had time to settle out. Incision of the lake bottom by outburst flows occurred concurrently with falling lake level

Bulletin 47 - Information for Prospective Students

https://thekeep.eiu.edu/eiu_bulletin/1147/thumbnail.jp

Paleohydraulics of pleistocene drainage development of the Souris, Des Lacs, and Moose Mountain spillways, Saskatchewan and North Dakota

Recent recognition of the rapid draining of numerous glacial lakes, including some in the Northern Plains, has revealed \u27a need for further research concerning this process. Geomorphic interpretation of the Souris, Des Lacs, and Moose Mountain Valleys, and the gravel deposits in them, has resulted in the recognition of five phases in the development of the drainageways. Textural analyses and paleohydraulic methods were applied to the sediments associated with each phase to distinguish and characterize the discharges. Four of the five phases of development involved short-lived, high velocity (\u3e4 m/s) discharges resulting from the rapid draining of glacial lakes; the other phase (2) involved deposition by glacial meltwater. Phase 1 discharges (3 x 104 m3/s) initiated the development of the Des Lacs Valley; the source probably was a supraglacial lake in the vicinity of Bowbells, North Dakota. Deposits of generally unstructured sandy gravel occur relatively high on the valley walls and are confined to the lower Des Lacs and Souris spillways. Phase 2 discharges (2.1 x 103 m3/s) deposited outwash sediment, consisting of cross-bedded gravelly sand, in the Moose Mountain and lower Souris Valley. Glacial meltwater from the Moose Mountains, which commenced when the ice sheet divided around the Moose Mountains, was the source of these flows. Phase 3 and 4 discharges (1.9 x 104 m3/s) probably each resulted from the rapid draining of Glacial Lake Arcola. Phase 3 was an erosional stage that incised the Moose Mountain and lower Souris Valley and induced landslides along the valley walls. Deposition of unstructured pebble gravel throughout much of the lower Souris spillway occurred during phase 4. The deposits commonly are inset into the valley walls, indicating that they were later truncated by erosion. The upper Souris Valley was developed and the lower Souris and Des Lacs spillways were enlarged during the cataclysmic discharges of phase 5 (2.0 x 105 m3 /s) from Glacial Lake Regina. Huge bars of unstructured pebbly cobble gravel were deposited during this event. Several geomorphic features associated with this phase are similar to features described in the Channeled Scabland. Phase 5 concluded the development of the spillways. A glacial chronology proposed by Clayton and Moran (1982) indicates that the drainage described in this study occurred between 11,700 BP and 11,300 BP. Although active ice is generally assumed to have been northeast of the spillways during the time of drainage development, the presence of stagnant ice is indicated by streamlined collapse topography within a fluvially scoured zone, several inconsistencies in paleohydraulic calculations, and the abundance of landslides in the lower Souris Valley. The information developed from this study, and the relatively recent recognition of other floods resulting from the rapid draining of glacial lakes, indicates that this form of \u27instantaneous\u27 drainage development may have been common during the Pleistocene Epoch, especially in areas of ice stagnation