2,404 research outputs found
Another Look at the Null of Stationary RealExchange Rates. Panel Data with Structural Breaks and Cross-section Dependence
This paper re-examines the null of stationary of real exchange rate for a panel of seventeen OECD developed countries during the post-Bretton Woods era. Our analysis simultaneously considers both the presence of cross-section dependence and multiple structural breaks that have not received much attention in previous panel methods of long-run PPP. Empirical results indicate that there is little evidence in favor of PPP hypothesis when the analysis does not account for structural breaks. This conclusion is reversed when structural breaks are considered in computation of the panel statistics. We also compute point estimates of half-life separately for idiosyncratic and common factor components and find that it is always below one year.Purchasing power parity, Half-lives, Panel unit roottests, Multiple structural breaks, Cross-section dependence.
Determining Factors that Influence Smooth Cordgrass (Spartina alterniflora Loisel) Transplant Success In Community-Based Living Shoreline Projects
Efforts to mitigate shoreline erosion through living shoreline methods along the USA Atlantic seaboard have often incorporated the cultivation and transplantation of smooth cordgrass, Spartina alterniflora. Assessments of these transplants at several sites in the Indian River Lagoon have shown that survival is variable after a year (survival: 10-93%). Lower survival has been attributed to environmental variables such as dislodgement by wave energy, and transplant shock due to salinity changes from cultivation to estuarine conditions. To improve living shoreline projects, we examined the effects of cultivation salinity (0 ppt, 15ppt) on transplantation success, and the success of anchoring plants to biodegradable mats (Jute mesh, 5 individuals per 50 cm2) and utilizing oyster bags as breakwaters in facilitating reestablishment of new transplants. Spartina alterniflora individuals were grown under salinity treatments for 20 weeks; plants grown in 15 ppt produced new shoots with significantly greater heights than those grown in freshwater. The plants were then transplanted to two sites in the IRL, and monitored after four weeks. After four weeks there was a greater net increase in stem density and larger decrease in plant height for plants grown in 15 ppt. Jute-mesh mats and oyster bags did not impact growth or survival of transplants. Low-saline (15 ppt) conditions increased shoot growth of the project by 50% in four weeks at a cost of 30 cents per additional shoot produced by an individual. Longer-term monitoring will determine if benefits persist or decrease over time, and if the cost is justified by the benefits
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Terahertz and Microwave Detection Using Metallic Single Wall Carbon Nanotubes
Carbon nanotubes (CNTs) are promising nanomaterials for high frequency applications due to their unique physical characteristics. CNTs have a low heat capacity, low intrinsic capacitance, and incredibly fast thermal time constants. They can also exhibit ballistic transport at low bias, for both phonons and electrons, as evident by their fairly long mean free paths. However, despite the great potential they present, the RF behavior of these nanostructures is not completely understood. In order to explore this high frequency regime we studied the microwave (MW) and terahertz (THz) response of individual and bundled single wall nanotube based devices. This thesis is an experimental study which attempts to understand the high frequency characteristics of metallic single walled carbon nanotubes, and to develop an ultra-fast and sensitive direct THz detector.
First, the appropriate high frequency detector background is introduced. CNTs previously measured behavior draws similarities to two types of detectors: diode and bolometer. Therefore, our CNT devices are geared towards those designs. Second the fabrication process of devices is reviewed. UV lithography is used to pattern THz coupling log periodic antennas, on top of which CNTs are deposited by using a dielectrophoretic process. Third, the fabricated devices are tested at DC, MW, and THz frequencies. All of these measurements are done as a function of temperature, power, and frequency. Finally, the physical processes that give rise to the diode and bolometric detections at MW and THz detection at different temperatures and under different bias regimes (i.e. low and high) are explained
Do students gain scientific inquiry knowledge and practices by participating in a school garden inquiry unit?
Since the turn of the century gardens have been spaces for learning to take place. Gardens allow for a variety of disciplines to be explored from horticulture to art. In the mid nineteen nineties a school garden movement began to grow, in the United States and by the early two thousands several states had implemented a school garden policy. The majority of school gardens focus on academic outcomes (e.g. science, math, or language arts) or health outcomes (e.g. nutrition, well-being, and self-esteem).
Currently, there is limited information about how school gardens can be places for scientific inquiry and practices to develop in students. Furthermore, more in-depth mixed-method research on school gardens and how school gardens can produce learning opportunities for scientific practices to develop need to be conducted. Future research should take a new direction. The scientific practices created by Next Generation Science Standards (NGSS) (LeadStates, 2013) need to be explored further in relation to how exposure to a school garden can affect these practices and knowledge about inquiry learning (Callahan, 2012; Chi, Dorph & Reisman, 2016; Kisiel & Anderson, 2010).
Through this dissertation, school gardens can be viewed as an extension of the traditional classroom. School gardens have the potential to foster learners’ abilities to construct real-life associations with science content due to engagement, free exploration, and scientific investigation. This study found school gardens as an out of class room setting where students have the ability to learn and develop their understanding about scientific inquiry and scientific practices. This new avenue may help develop better scientific literacy universally across learners. This research work created curriculum and assessment tools to use in conjunction with an out of classroom setting such as a school garden
G\"odel-type Spacetimes in Induced Matter Gravity Theory
A five-dimensional (5D) generalized G\"odel-type manifolds are examined in
the light of the equivalence problem techniques, as formulated by Cartan. The
necessary and sufficient conditions for local homogeneity of these 5D manifolds
are derived. The local equivalence of these homogeneous Riemannian manifolds is
studied. It is found that they are characterized by three essential parameters
, and : identical triads correspond to
locally equivalent 5D manifolds. An irreducible set of isometrically
nonequivalent 5D locally homogeneous Riemannian generalized G\"odel-type
metrics are exhibited. A classification of these manifolds based on the
essential parameters is presented, and the Killing vector fields as well as the
corresponding Lie algebra of each class are determined. It is shown that the
generalized G\"odel-type 5D manifolds admit maximal group of isometry
with , or depending on the essential parameters ,
and . The breakdown of causality in all these classes of homogeneous
G\"odel-type manifolds are also examined. It is found that in three out of the
six irreducible classes the causality can be violated. The unique generalized
G\"odel-type solution of the induced matter (IM) field equations is found. The
question as to whether the induced matter version of general relativity is an
effective therapy for these type of causal anomalies of general relativity is
also discussed in connection with a recent article by Romero, Tavakol and
Zalaletdinov.Comment: 19 pages, Latex, no figures. To Appear in J.Math.Phys.(1999
Mesenchymal stem cells for the treatment of systemic lupus erythematosus: is the cure for connective tissue diseases within connective tissue?
Mesenchymal stem cells (MSCs) are now known to display not only adult stem cell multipotency but also robust anti-inflammatory and regenerative properties. After widespread in vitro and in vivo preclinical testing in several autoimmune disease models, allogenic MSCs have been successfully applied in patients with severe treatment-refractory systemic lupus erythematosus. The impressive results of these uncontrolled phase I and II trials - mostly in patients with non-responding renal disease - point to the need to perform controlled multicentric trials. In addition, they suggest that there is much to be learned from the basic and clinical science of MSCs in order to reap the full potential of these multifaceted progenitor cells in the treatment of autoimmune diseases
Big brother is watching - using digital disease surveillance tools for near real-time forecasting
Abstract for the International Journal of Infectious Diseases 79 (S1) (2019).https://www.ijidonline.com/article/S1201-9712(18)34659-9/abstractPublished versio
Augmented Reality based monitoring of the remote-lab
© 2014 IEEE. Augmented Reality technology approach has been being adopted within the education sector. The advanced technology tools in many classes have the potential changed of users' attitudes toward the pedagogical and psychological objectives and goals. Moreover, augmented reality has not elicited so much attention within the corridors of education sector as it is now. In order to improve the interactive effectiveness in the smart classroom environment, there is a demand to tailor the innovation technology and align it with every changing requirements and capabilities of various users. Consequently, the educators are increasingly finding augmented reality suitable for deployment in education. In this paper, a project shows how Augmented Reality utilised with overlay Smart-Grid can support the learning process in attractive methods for monitoring events of captured scenes in remote-lab such as video stream, Web-link from smart devices' camera
Hysteresis-Free Nanosecond Pulsed Electrical Characterization of Top-Gated Graphene Transistors
We measure top-gated graphene field effect transistors (GFETs) with
nanosecond-range pulsed gate and drain voltages. Due to high-k dielectric or
graphene imperfections, the drain current decreases ~10% over time scales of
~10 us, consistent with charge trapping mechanisms. Pulsed operation leads to
hysteresis-free I-V characteristics, which are studied with pulses as short as
75 ns and 150 ns at the drain and gate, respectively. The pulsed operation
enables reliable extraction of GFET intrinsic transconductance and mobility
values independent of sweep direction, which are up to a factor of two higher
than those obtained from simple DC characterization. We also observe
drain-bias-induced charge trapping effects at lateral fields greater than 0.1
V/um. In addition, using modeling and capacitance-voltage measurements we
extract charge trap densities up to 10^12 1/cm^2 in the top gate dielectric
(here Al2O3). Our study illustrates important time- and field-dependent
imperfections of top-gated GFETs with high-k dielectrics, which must be
carefully considered for future developments of this technologyComment: to appear in IEEE Transactions on Electron Devices (2014
INTEGRATING OPTICAL AND RADAR IMAGERY TO ENHANCE RIVER DROUGHT MONITORING
Drought events are growingly affecting European and Italian territories, hampering local environments and biodiversity, such as the ones relying on rivers for their subsistence. Monitoring of rivers is becoming an important issue to face drought crisis and may be exploited with different tools. Among the most commons, satellite imagery is exploited to map water coverage, basing on optical or radar sources. This work proposes a combination of the two sensors to overcome possible limitations of the single dataset exploitation, reaching a reliable result. The methodology is applied to a stretch of Po River in Lombardy region (Italy). Through Google Earth Engine platform, optical satellite Sentinel-2 and radar satellite Sentinel-1 data are processed. The combination of the radar data and of the optical spectral indices is carried out through a pixel-based supervised classification, with a Random Forest classifier. Maps of water coverage are obtained, numerical outcomes of water surface evaluation are recorded and validated by the mean of reference hydrometric data. A multitemporal analysis is then reported, aiming to prove the efficiency of the procedure. All iterations show reliable accuracies and correlation among water surface estimation and water table measurements in two sections of interest. In perspective, the proposed methodology will be implemented in tools for supporting drought monitoring to be integrated in environmental public administration policies
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