Atmosphere Behavior in Gas-Closed Mouse-Algal Systems: An Experimental and Modelling Study

A dual approach of mathematical modelling and laboratory experimentation aimed at examining the gas exchange characteristics of artificial animal/plant systems closed to the ambient atmosphere was initiated. The development of control techniques and management strategies for maintaining the atmospheric levels of carbon dioxide and oxygen at physiological levels is examined. A mathematical model simulating the atmospheric behavior in these systems was developed and an experimental gas closed system was constructed. These systems are described and preliminary results are presented

The Fiji Hydrographic Service 1970-1990 - A Working Example of the Challenges that Face Small Maritime States in Developing a Viable National Hydrographic Capability

The aim of this paper is to identify the major challenges that small maritime States can expect to face in developing a viable national hydrographic capability, with particular reference to the development of Fiji Hydrographic Service (FHS) in the period 1970-90

Imide and isatin derivatives as β-lactam mimics of β-lactam antibiotics

Activated γ-lactams, which are derivatives of succinimide, phthalimide and isatin with suitable elements of molecular recognition, have been synthesised as mimics of the ß-lactam antibiotics and their chemical and biological reactivity determined

Seasonal variations in Greenland Ice Sheet motion : Inland extent and behaviour at higher elevations

Peer reviewedPreprin

Modeling the effects of extracellular potassium on bursting properties in pre-Bötzinger complex neurons

There are many types of neurons that intrinsically generate rhythmic bursting activity, even when isolated, and these neurons underlie several specific motor behaviors. Rhythmic neurons that drive the inspiratory phase of respiration are located in the medullary pre-Bötzinger Complex (pre-BötC). However, it is not known if their rhythmic bursting is the result of intrinsic mechanisms or synaptic interactions. In many cases, for bursting to occur, the excitability of these neurons needs to be elevated. This excitation is provided in vitro (e.g. in slices), by increasing extracellular potassium concentration (K[subscript out]) well beyond physiologic levels. Elevated K[subscript out] shifts the reversal potentials for all potassium currents including the potassium component of leakage to higher values. However, how an increase in K[subscript out], and the resultant changes in potassium currents, induce bursting activity, have yet to be established. Moreover, it is not known if the endogenous bursting induced in vitro is representative of neural behavior in vivo. Our modeling study examines the interplay between K[subscript out], excitability, and selected currents, as they relate to endogenous rhythmic bursting. Starting with a Hodgkin-Huxley formalization of a pre-BötC neuron, a potassium ion component was incorporated into the leakage current, and model behaviors were investigated at varying concentrations of K[subscript out]. Our simulations show that endogenous bursting activity, evoked in vitro by elevation of K[subscript out], is the result of a specific relationship between the leakage and voltage-dependent, delayed rectifier potassium currents, which may not be observed at physiological levels of extracellular potassium.National Institutes of Health (U.S.) (National Center for Complementary and Integrative Health (U.S). Grant R01 AT008632)National Institutes of Health (U.S.) (National Institute of Neurological Disorders and Stroke (U.S.). Grant R01 NS069220

More Legumes for Green Manure = More Corn

Iowa State College experiments show that a lot of nitrogren can be cheaply produced by adding a legume seeding to the oats preceding corn. Research indicates every farmer could profitably make a legume seeding for green manure in every acre of oats in addition to meadow and rotation plantings

Mechanisms of Left-Right Coordination in Mammalian Locomotor Pattern Generation Circuits: A Mathematical Modeling View

The locomotor gait in limbed animals is defined by the left-right leg coordination and locomotor speed. Coordination between left and right neural activities in the spinal cord controlling left and right legs is provided by commissural interneurons (CINs). Several CIN types have been genetically identified, including the excitatory V3 and excitatory and inhibitory V0 types. Recent studies demonstrated that genetic elimination of all V0 CINs caused switching from a normal left-right alternating activity to a left-right synchronized “hopping” pattern. Furthermore, ablation of only the inhibitory V0 CINs (V0D subtype) resulted in a lack of left-right alternation at low locomotor frequencies and retaining this alternation at high frequencies, whereas selective ablation of the excitatory V0 neurons (V0V subtype) maintained the left–right alternation at low frequencies and switched to a hopping pattern at high frequencies. To analyze these findings, we developed a simplified mathematical model of neural circuits consisting of four pacemaker neurons representing left and right, flexor and extensor rhythm-generating centers interacting via commissural pathways representing V3, V0D, and V0V CINs. The locomotor frequency was controlled by a parameter defining the excitation of neurons and commissural pathways mimicking the effects of N-methyl-D-aspartate on locomotor frequency in isolated rodent spinal cord preparations. The model demonstrated a typical left-right alternating pattern under control conditions, switching to a hopping activity at any frequency after removing both V0 connections, a synchronized pattern at low frequencies with alternation at high frequencies after removing only V0D connections, and an alternating pattern at low frequencies with hopping at high frequencies after removing only V0V connections. We used bifurcation theory and fast-slow decomposition methods to analyze network behavior in the above regimes and transitions between them. The model reproduced, and suggested explanation for, a series of experimental phenomena and generated predictions available for experimental testing

Quantitatively ranking incorrect responses to multiple-choice questions using item response theory

Research-based assessment instruments (RBAIs) are ubiquitous throughout both physics instruction and physics education research. The vast majority of analyses involving student responses to RBAI questions have focused on whether or not a student selects correct answers and using correctness to measure growth. This approach often undervalues the rich information that may be obtained by examining students' particular choices of incorrect answers. In the present study, we aim to reveal some of this valuable information by quantitatively determining the relative correctness of various incorrect responses. To accomplish this, we propose an assumption that allow us to define relative correctness: students who have a high understanding of Newtonian physics are likely to answer more questions correctly and also more likely to choose better incorrect responses, than students who have a low understanding. Analyses using item response theory align with this assumption, and Bock's nominal response model allows us to uniquely rank each incorrect response. We present results from over 7,000 students' responses to the Force and Motion Conceptual Evaluation

Information and communication technology and climate change adaptation: Evidence from selected mining companies in South Africa

The mining sector is a significant contributor to the gross domestic product of many global economies. Given the increasing trends in climate-induced disasters and the growing desire to find lasting solutions, information and communication technology (ICT) has been introduced into the climate change adaptation mix. Climate change-induced extreme weather events such as flooding, drought, excessive fog, and cyclones have compounded the environmental challenges faced by the mining sector. This article presents the adoption of ICT innovation as part of the adaptation strategies towards reducing the mining sector’s vulnerability and exposure to climate change disaster risks. Document analysis and systematic literature review were adopted as the methodology. Findings from the study reflect how ICT intervention orchestrated changes in communication patterns which are tailored towards the reduction in climate change vulnerability and exposure. The research concludes with a proposition that ICT intervention must be part of the bigger and ongoing climate change adaptation agenda in the mining sector. Keywords: ICT; climate change; disaster risk reduction; mining; adaptation; South Afric

Critical Behavior of the Meissner Transition in the Lattice London Superconductor

We carry out Monte Carlo simulations of the three dimensional (3D) lattice London superconductor in zero applied magnetic field, making a detailed finite size scaling analysis of the Meissner transition. We find that the magnetic penetration length \lambda, and the correlation length \xi, scale as \lambda ~ \xi ~ |t|^{-\nu}, with \nu = 0.66 \pm 0.03, consistent with ordinary 3D XY universality, \nu_XY ~ 2/3. Our results confirm the anomalous scaling dimension of magnetic field correlations at T_c.Comment: 4 pages, 5 ps figure