Mechanisms explaining transitions between tonic and phasic firing in neuronal populations as predicted by a low dimensional firing rate model

Several firing patterns experimentally observed in neural populations have been successfully correlated to animal behavior. Population bursting, hereby regarded as a period of high firing rate followed by a period of quiescence, is typically observed in groups of neurons during behavior. Biophysical membrane-potential models of single cell bursting involve at least three equations. Extending such models to study the collective behavior of neural populations involves thousands of equations and can be very expensive computationally. For this reason, low dimensional population models that capture biophysical aspects of networks are needed. \noindent The present paper uses a firing-rate model to study mechanisms that trigger and stop transitions between tonic and phasic population firing. These mechanisms are captured through a two-dimensional system, which can potentially be extended to include interactions between different areas of the nervous system with a small number of equations. The typical behavior of midbrain dopaminergic neurons in the rodent is used as an example to illustrate and interpret our results. \noindent The model presented here can be used as a building block to study interactions between networks of neurons. This theoretical approach may help contextualize and understand the factors involved in regulating burst firing in populations and how it may modulate distinct aspects of behavior.Comment: 25 pages (including references and appendices); 12 figures uploaded as separate file

Spatio-temporal pattern of viral meningitis in Michigan, 1993-2001

To characterize Michigan’s high viral meningitis incidence rates, 8,803 cases from 1993–2001 were analyzed for standard epidemiological indices, geographic distribution, and spatio-temporal clusters. Blacks and infants were found to be high-risk groups. Annual seasonality and interannual variability in epidemic magnitude were apparent. Cases were concentrated in southern Michigan, and cumulative incidence was correlated with population density at the county level (r=0.45, p<0.001). Kulldorff’s Scan test identified the occurrence of spatio-temporal clusters in Lower Michigan during July–October 1998 and 2001 (p=0.01). More extensive data on cases, laboratory isolates, sociodemographics, and environmental exposures should improve detection and enhance the effectiveness of a Space-Time Information System aimed at prevention.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47932/1/10109_2005_Article_151.pd

The Iowa Homemaker vol.3, no.11

Table of Contents Identity by Ruth Elaine Wilson, page 2 The Responsibility of American Women to Citizenship by Marcia M. Roberts, page 3 Hearth and Home by Amanda Jacobsen, page 4 A Parent “That Needeth Not to be Ashamed” by Thomas F. Vance, page 5 Corn – Greatest Crop of Iowa by Gertrude E. Murray, page 6 American Home Economics Association Meets by Lela Johnson, page 7 The Evolution of Home Economics at Iowa State by Ruth Elaine Wilson, page 7 Hints for the Spring Wardrobe by Grace L. Heidbreder and Helen Brennan, page 8 Etiquette for College Girl by Marcella Dewell, page 9 Who’s There and Where by Dryden Quist, page 1

Crowdsourced assessment of surgical skill proficiency in cataract surgery

OBJECTIVE: To test whether crowdsourced lay raters can accurately assess cataract surgical skills. DESIGN: Two-armed study: independent cross-sectional and longitudinal cohorts. SETTING: Washington University Department of Ophthalmology. PARTICIPANTS AND METHODS: Sixteen cataract surgeons with varying experience levels submitted cataract surgery videos to be graded by 5 experts and 300+ crowdworkers masked to surgeon experience. Cross-sectional study: 50 videos from surgeons ranging from first-year resident to attending physician, pooled by years of training. Longitudinal study: 28 videos obtained at regular intervals as residents progressed through 180 cases. Surgical skill was graded using the modified Objective Structured Assessment of Technical Skill (mOSATS). Main outcome measures were overall technical performance, reliability indices, and correlation between expert and crowd mean scores. RESULTS: Experts demonstrated high interrater reliability and accurately predicted training level, establishing construct validity for the modified OSATS. Crowd scores were correlated with (r = 0.865, p \u3c 0.0001) but consistently higher than expert scores for first, second, and third-year residents (p \u3c 0.0001, paired t-test). Longer surgery duration negatively correlated with training level (r = -0.855, p \u3c 0.0001) and expert score (r = -0.927, p \u3c 0.0001). The longitudinal dataset reproduced cross-sectional study findings for crowd and expert comparisons. A regression equation transforming crowd score plus video length into expert score was derived from the cross-sectional dataset (r CONCLUSIONS: Crowdsourced rankings correlated with expert scores, but were not equivalent; crowd scores overestimated technical competency, especially for novice surgeons. A novel approach of adjusting crowd scores with surgery duration generated a more accurate predictive model for surgical skill. More studies are needed before crowdsourcing can be reliably used for assessing surgical proficiency

Modeling the breakage stage in spheronization of cylindrical paste extrudates

Funder: The University of QueenslandAbstract: Spheronization of cylindrical extrudates on a rotating friction plate involves breakage and rounding. Little attention has been given to the breakage stage and quantitative modeling of this process is scarce. Two simple models are compared with experimental data obtained for the early stages of spheronization of microcrystalline cellulose/water extrudates. Tests were conducted for different times (t), rotational speeds (ω), initial loadings, and on pyramidal friction plates with different dimensions. The first model, describing the number of pellets, validated ω3t as a characteristic time scale for the breakage stage. The kinetic parameters obtained by fitting showed a systematic dependence on plate dimensions expressed as a scaled gap width. The second model, a simple population balance, described the evolution of the number and length of pellets. The pseudo rate constants provided insights into the kinetics: extrudates tended to break near the middle, while breakage of smaller pellets was slowed down by more pellet–pellet collisions

Predicting potential global and future distributions of the African armyworm (Spodoptera exempta) using Species Distribution Models

Invasive species have historically been a problem derived from global trade and transport. To aid in the control and management of these species, Species Distribution Models (SDMs) have been used to help predict possible areas of expansion. Our focal organism, the African Armyworm (AAW), has historically been known as an important pest species in Africa, occurring at high larval densities and causing outbreaks that can cause enormous economic damage to staple crops. The goal of this study is to map the AAW’s present and potential distribution in three future scenarios for the region, and the potential global distribution if the species were to invade other territories, using 40 years of data on more than 700 larval outbreak reports from Kenya and Tanzania. The present distribution in East Africa coincides with its previously known distribution, as well as other areas of grassland and cropland, which are the host plants for this species. The different future climatic scenarios show broadly similar potential distributions in East Africa to the present day. The predicted global distribution shows areas where the AAW has already been reported, but also shows many potential areas in the Americas where, if transported, environmental conditions are suitable for AAW to thrive and where it could become an invasive species

Simulating the effect of perennialized cropping systems on nitrate-N losses using the SWAT model

Several newly released crop varieties, including the perennial intermediate wheatgrass (grain marketed as Kernza®), and the winter hardy oilseed crop camelina, have been developed to provide both economic return for farmers and reduced nutrient losses from agricultural fields. Though studies have indicated that these crops could reduce nitrate-nitrogen (N) leaching, little research has been done to determine their effectiveness in reducing nitrate-N loading to surface waters at a watershed scale, or in comparing their performance to more traditional perennial crops, such as alfalfa. In this study, nitrate-N losses were predicted using the Soil and Water Assessment Tool (SWAT) model for the Rogers Creek watershed located in south-central Minnesota, USA. Predicted looses of nitrate-N under three perennialized cropping systems were compared to losses given current cropping practices in a corn (Zea mays L.)-soybean (Glycine max L. Merr.) rotation. The perennialized systems included three separate crop rotations: intermediate wheatgrass (IWG) in rotation with soybean, alfalfa in rotation with corn, and winter camelina in rotation with soybean and winter rye. Model simulation of these rotations required creation of new crop files for IWG and winter camelina within SWAT. These new crop files were validated using measured yield, biomass, and nitrate-N data. Model results show that the IWG and alfalfa rotations were particularly effective at reducing nutrient and sediment losses from agricultural areas in the watershed, but smaller reductions were also achieved with the winter camelina rotation. From model predictions, achieving regional water-quality goals of a 30% reduction in nitrate-N load from fields in the watershed required converting approximately 25, 34, or 57% of current corn-soybean area to the alfalfa, IWG, or camelina rotations, respectively. Results of this study indicate that adoption of these crops could achieve regional water quality goals

Efficient Conversion of Astrocytes to Functional Midbrain Dopaminergic Neurons Using a Single Polycistronic Vector

Direct cellular reprogramming is a powerful new tool for regenerative medicine. In efforts to understand and treat Parkinson's Disease (PD), which is marked by the degeneration of dopaminergic neurons in the midbrain, direct reprogramming provides a valuable new source of these cells. Astrocytes, the most plentiful cells in the central nervous system, are an ideal starting population for the direct generation of dopaminergic neurons. In addition to their potential utility in cell replacement therapies for PD or in modeling the disease in vitro, astrocyte-derived dopaminergic neurons offer the prospect of direct in vivo reprogramming within the brain. As a first step toward this goal, we report the reprogramming of astrocytes to dopaminergic neurons using three transcription factors – ASCL1, LMX1B, and NURR1 – delivered in a single polycistronic lentiviral vector. The process is efficient, with 18.2±1.5% of cells expressing markers of dopaminergic neurons after two weeks. The neurons exhibit expression profiles and electrophysiological characteristics consistent with midbrain dopaminergic neurons, notably including spontaneous pacemaking activity, stimulated release of dopamine, and calcium oscillations. The present study is the first demonstration that a single vector can mediate reprogramming to dopaminergic neurons, and indicates that astrocytes are an ideal starting population for the direct generation of dopaminergic neurons