Structural network heterogeneities and network dynamics: a possible dynamical mechanism for hippocampal memory reactivation

The hippocampus has the capacity for reactivating recently acquired memories [1-3] and it is hypothesized that one of the functions of sleep reactivation is the facilitation of consolidation of novel memory traces [4-11]. The dynamic and network processes underlying such a reactivation remain, however, unknown. We show that such a reactivation characterized by local, self-sustained activity of a network region may be an inherent property of the recurrent excitatory-inhibitory network with a heterogeneous structure. The entry into the reactivation phase is mediated through a physiologically feasible regulation of global excitability and external input sources, while the reactivated component of the network is formed through induced network heterogeneities during learning. We show that structural changes needed for robust reactivation of a given network region are well within known physiological parameters [12,13].Comment: 16 pages, 5 figure

ALD grown zinc oxide with controllable electrical properties

The paper presents results for zinc oxide films grown at low temperature regime by Atomic Layer Deposition (ALD). We discuss electrical properties of such films and show that low temperature deposition results in oxygen-rich ZnO layers in which free carrier concentration is very low. For optimized ALD process it can reach the level of 10^15 cm-3, while mobility of electrons is between 20 and 50 cm2/Vs. Electrical parameters of ZnO films deposited by ALD at low temperature regime are appropriate for constructing of the ZnO-based p-n and Schottky junctions. We demonstrate that such junctions are characterized by the rectification ratio high enough to fulfill requirements of 3D memories and are deposited at temperature 100degC which makes them appropriate for deposition on organic substrates.Comment: 29 pages, 9 figures, 64 references, review pape

Identification of strong photometric activity in the components of LHS 1070

Activity in low-mass stars is an important ingredient in the evolution of such objects. Fundamental physical properties such as age, rotation, magnetic field are correlated with activity. Aims: We show that two components of the low-mass triple system LHS 1070 exhibit strong flaring activity. We identify the flaring components and obtained an improved astrometric solution for the LHS 1070 A/(B+C) system. Methods: Time-series CCD observations were used to monitor LHS 1070 in the B and I_C bands. H-band data were used to obtain accurate astrometry for the LHS 1070 A/(B+C) system. Results: We have found that two components of the triple system LHS 1070 exhibit photometric activity. We identified that components A and B are the flaring objects. We estimate the total energy, ~2.0 x 10^{33} ergs, and the magnetic field strength, ~5.5 kG, of the flare observed in LHS 1070 B. This event is the largest amplitude, \Delta B > 8.2 mag, ever observed in a flare star.Comment: 5 pages, 5 figures, accepted for publication in A&

Randomized trial of polychromatic blue-enriched light for circadian phase shifting, melatonin suppression, and alerting responses.

Wavelength comparisons have indicated that circadian phase-shifting and enhancement of subjective and EEG-correlates of alertness have a higher sensitivity to short wavelength visible light. The aim of the current study was to test whether polychromatic light enriched in the blue portion of the spectrum (17,000 K) has increased efficacy for melatonin suppression, circadian phase-shifting, and alertness as compared to an equal photon density exposure to a standard white polychromatic light (4000 K). Twenty healthy participants were studied in a time-free environment for 7 days. The protocol included two baseline days followed by a 26-h constant routine (CR1) to assess initial circadian phase. Following CR1, participants were exposed to a full-field fluorescent light (1 × 10 14 photons/cm 2 /s, 4000 K or 17,000 K, n = 10/condition) for 6.5 h during the biological night. Following an 8 h recovery sleep, a second 30-h CR was performed. Melatonin suppression was assessed from the difference during the light exposure and the corresponding clock time 24 h earlier during CR1. Phase-shifts were calculated from the clock time difference in dim light melatonin onset time (DLMO) between CR1 and CR2. Blue-enriched light caused significantly greater suppression of melatonin than standard light ((mean ± SD) 70.9 ± 19.6% and 42.8 ± 29.1%, respectively, p \u3c 0.05). There was no significant difference in the magnitude of phase delay shifts. Blue-enriched light significantly improved subjective alertness (p \u3c 0.05) but no differences were found for objective alertness. These data contribute to the optimization of the short wavelength-enriched spectra and intensities needed for circadian, neuroendocrine and neurobehavioral regulation

Mirax: A Brazilian X-Ray Astronomy Satellite Mission

We describe the ``Monitor e Imageador de Raios-X'' (MIRAX), an X-ray astronomy satellite mission proposed by the high energy astrophysics group at the National Institute for Space Research (INPE) in Brazil to the Brazilian Space Agency. MIRAX is an international collaboration that includes, besides INPE, the University of California San Diego, the University of Tuebingen in Germany, the Massachusetts Institute of Technology and the Space Research Organization Netherlands. The payload of MIRAX will consist in two identical hard X-ray cameras (10 -200 keV) and one soft X-ray camera (2-28 keV), both with angular resolution of ~ 5-6 arcmin. The basic objective of MIRAX is to carry out continuous broadband imaging spectroscopy observations of a large source sample (~ 9 months/yr) in the central Galactic plane region. This will allow the detection, localization, possible identification, and spectral/temporal study of the entire history of transient phenomena to be carried out in one single mission. MIRAX will have sensitivities of ~ 5 mCrab/day in the 2-10 keV band (~2 times better than the All Sky Monitor on Rossi X-ray Timing Explorer) and 2.6 mCrab/day in the 10-100 keV band (~40 times better than the Earth Occultation technique of the Burst and Transient Source Experiment on the Compton Gamma-Ray Observatory). The MIRAX spacecraft will weigh about 200 kg and is expected to be launched in a low-altitude (~ 600 km) circular equatorial orbit around 2007/2008.Comment: 6 pages, 1 table, 3 figures, presented at 2002 COSPAR meeting in Houston. Submitted to Adv. Space Re

Genetic Predictors of Weight Loss and Weight Regain After Intensive Lifestyle Modification, Metformin Treatment, or Standard Care in the Diabetes Prevention Program

OBJECTIVE: We tested genetic associations with weight loss and weight regain in the Diabetes Prevention Program, a randomized controlled trial of weight loss–inducing interventions (lifestyle and metformin) versus placebo. RESEARCH DESIGN AND METHODS: Sixteen obesity-predisposing single nucleotide polymorphisms (SNPs) were tested for association with short-term (baseline to 6 months) and long-term (baseline to 2 years) weight loss and weight regain (6 months to study end). RESULTS: Irrespective of treatment, the Ala12 allele at PPARG associated with short- and long-term weight loss (−0.63 and −0.93 kg/allele, P ≤ 0.005, respectively). Gene–treatment interactions were observed for short-term (LYPLAL1 rs2605100, P$_{lifestyle*SNP}$ = 0.032; GNPDA2 rs10938397, P$_{lifestyle*SNP}$ = 0.016; MTCH2 rs10838738, P$_{lifestyle*SNP}$ = 0.022) and long-term (NEGR1 rs2815752, P$_{metformin*SNP}$ = 0.028; FTO rs9939609, P$_{lifestyle*SNP}$ = 0.044) weight loss. Three of 16 SNPs were associated with weight regain (NEGR1 rs2815752, BDNF rs6265, PPARG rs1801282), irrespective of treatment. TMEM18 rs6548238 and KTCD15 rs29941 showed treatment-specific effects (P$_{lifestyle*SNP}$ < 0.05). CONCLUSIONS: Genetic information may help identify people who require additional support to maintain reduced weight after clinical intervention

Evolution of spectral function in a doped Mott insulator : surface vs. bulk contributions

We study the evolution of the spectral function with progressive hole doping in a Mott insulator, $La_{1-x}Ca_xVO_3$ with $x$ = 0.0 - 0.5. The spectral features indicate a bulk-to-surface metal-insulator transition in this system. Doping dependent changes in the bulk electronic structure are shown to be incompatible with existing theoretical predictions. An empirical description based on the single parameter, $U/W$, is shown to describe consistently the spectral evolution.Comment: Revtex, 4 pages, 3 postscript figures. To appear in Phys. Rev. Let

He II λ\lambda4686 emission from the massive binary system in η\eta Car: constraints to the orbital elements and the nature of the periodic minima

{\eta} Carinae is an extremely massive binary system in which rapid spectrum variations occur near periastron. Most notably, near periastron the He II $\lambda 4686$ line increases rapidly in strength, drops to a minimum value, then increases briefly before fading away. To understand this behavior, we conducted an intense spectroscopic monitoring of the He II $\lambda 4686$ emission line across the 2014.6 periastron passage using ground- and space-based telescopes. Comparison with previous data confirmed the overall repeatability of EW(He II $\lambda 4686$), the line radial velocities, and the timing of the minimum, though the strongest peak was systematically larger in 2014 than in 2009 by 26%. The EW(He II $\lambda 4686$) variations, combined with other measurements, yield an orbital period $2022.7\pm0.3$ d. The observed variability of the EW(He II $\lambda 4686$) was reproduced by a model in which the line flux primarily arises at the apex of the wind-wind collision and scales inversely with the square of the stellar separation, if we account for the excess emission as the companion star plunges into the hot inner layers of the primary's atmosphere, and including absorption from the disturbed primary wind between the source and the observer. This model constrains the orbital inclination to $135^\circ$-$153^\circ$, and the longitude of periastron to $234^\circ$-$252^\circ$. It also suggests that periastron passage occurred on $T_0 = 2456874.4\pm1.3$ d. Our model also reproduced EW(He II $\lambda 4686$) variations from a polar view of the primary star as determined from the observed He II $\lambda 4686$ emission scattered off the Homunculus nebula.Comment: The article contains 23 pages and 17 figures. It has been accepted for publication in Ap

Skill of managers and the wisdom of herds: examining an alternative approach to grazing management in larkspur habitat, The

2019 Spring.Includes bibliographical references.The many species of larkspur (Delphinium spp. L.) are among the most dangerous poisonous plants on rangelands in the western United States, causing death losses estimated at 2-5% (up to 15%) per year for cattle grazing in larkspur habitat. Research has estimated the value of these losses at $234 million per year. Other effects, such as altered grazing management practices and consequent lost forage quantity and quality, are significant but poorly understood. Current best management practice recommendations stress seasonal avoidance of pastures with larkspur present, with little evidence that this is practical or ultimately effective. Alternative approaches to addressing this complex challenge are difficult to design, test, and apply due to the threat of dead livestock. In this dissertation I explore an alternative approach based on the idea that it may be possible to manage cattle grazing such that no individual consumes a lethal dose, regardless of timing of grazing or larkspur density. This idea was inspired by producers past and present who have reported such success. I examine this hypothesis using agent-based models and a field experiment with Geyer's larkspur (D. geyeri Greene), the focal species throughout this research. Chapter 2 presents a conceptual model that situates this work within the broader context of livestock grazing management and rangeland science. This synthesis also highlights the potential for conceptual models to aid in the design, application, communication, and consilience of research in rangelands. Drawing on a wide range of work, this model challenges the discipline of rangeland science to integrate a broader array of methods and epistemologies to create knowledge sufficient to the complexity of the systems under study. Agent-based models (ABMs) provide an effective method of testing alternate management strategies without risk to livestock. ABMs are especially useful for modeling complex systems such as livestock grazing management and allow for realistic bottom-up encoding of cattle behavior. In Chapter 3, I introduce a spatially-explicit, behavior-based ABM of cattle grazing in a pasture with a dangerous amount of D. geyeri. This model tests the role of herd cohesion and stocking density in larkspur intake, finds that both are key drivers of larkspur-induced toxicosis, and indicates that alteration of these factors within realistic bounds can mitigate risk. Crucially, the model points to herd cohesion, which has received little attention in the discipline, as playing an important role in reducing lethal acute toxicosis. As the first agent-based model to simulate grazing behavior at realistic scales, this study also demonstrates the tremendous potential of ABMs to illuminate grazing management dynamics, including fundamental aspects of livestock behavior amidst ecological heterogeneity. Chapter 3 raises the question of the potential response of larkspur to being grazed. In Chapter 4, I examine the response of D. geyeri to two seasons of 25% or 75% aboveground plant mass removal. The 75% treatment led to significantly lower alkaloid concentrations (mg•g-1) and pools (mg per plant), while the 25% treatment had a lesser effect. Combined with lessons from previous studies, this indicates that Geyer's larkspur plants subject to aboveground mass removal such as may occur via grazing can be expected to become significantly less dangerous to cattle. We suggest that the mechanisms for this reduction are both alkaloid removal and reduced belowground root mass, as significant evidence indicates that alkaloids are synthesized and stored in the roots. The most common explanations for the evolution and persistence of herd behavior in large herbivores relate to decreased risk of predation. However, poisonous plants such as larkspur can present a threat comparable to predation. Chapters 3 and 4 point to the cattle herd itself as the potential solution to this seemingly intractable challenge and suggest that larkspur and forage patchiness may drive deaths. In Chapter 5, I present an agent-based model that incorporates neutral landscape models to assess the interaction between plant patchiness and herd behavior within the context of poisonous plants as predator and cattle as prey. The simulation results indicate that larkspur patchiness is indeed a driver of toxicosis and that highly cohesive herds can greatly reduce the risk of death in even the most dangerous circumstances. By placing the results in context with existing theories about the utility of herds, I demonstrate that grouping in large herbivores can be an adaptive response to patchily distributed poisonous plants. Lastly, the results hold significant management-relevant insight, both for cattle producers managing grazing in larkspur habitat and in general as a call to reconsider the manifold benefits of herd behavior among domestic herbivores. The findings in this dissertation build a strong case for an alternative approach to grazing management in larkspur habitat but fall short of actionable recommendations. For one, this is because a one-size-fits-all solution that would work across the great diversity of habitats and management systems in which larkspur is found is unlikely. Instead, these findings must be placed in context with existing knowledge and the complex multiscale decision-making processes of producers. Future work will thus focus on improving our understanding of the diverse set of management circumstances under which the many species of problematic larkspur are found