Idealised modelling of offshore-forced sea level hot spots and boundary waves along the North American East Coast

Hot spots of sea level variability along the North American East Coast have been shown to shift in latitude repeatedly over the past 95 years and connections with a number of forcing phenomena, including the North Atlantic Oscillation (NAO) and Atlantic Meridional Overturning Circulation (AMOC), have been suggested. Using a barotropic 1/12° NEMO model of the North American East Coast (to represent the upper ocean and a homogeneous shelf), we investigate the coastal sea level response to remote sea surface height (SSH) variability along the upper continental slope. Hilbert transform Complex EOF analysis is used to investigate the responses to interannual changes in the strength of the mean winds and an idealised NAO. Variability in the mean winds produces in-phase coastal sea level variability along the entire coastline and is driven by a SSH anomaly in the subpolar gyre. Variability due to the NAO forcing is in phase along the coast south of Cape Hatteras. Interannual coastal sea level variability at a given latitude is found to be driven by off-shore SSH anomalies originating many degrees of latitude (100s km) further north, and linear barotropic trapped wave theory is used to explain the mechanism. A comparison of the results from an analytical model with those from the numerical model is used to suggest that the boundary wave mechanism is also relevant for understanding the coastal response to interior sea level change over longer time periods. Nonlinear effects are found not to significantly modify the character of the linear solution

Assessing the Impact of Relational Governance on the Supply Chain Performances of Manufacturing Firms in Ghana

Over the years, there have been many challenges in supply chain management across the globe especially in the developing countries. There were challenges of quality control, risk management, finding right distributors to handle distribution, fragmented markets and many others. The most challenging issue in the supply chain management is the unpleasant relationship between the firms and their partners leading to many inconsistencies, uncertainties and losses in their operations and transactions leading to the assessment of both the direct and indirect impact of relational governance on supply chain performance of the manufacturing firms in Ghana. The study sought to assess the impact relational governance has directly and indirectly on supply chain performance. Data were collected and gathered through a survey questionnaire responded by 147 manufacturing firms in Ghana. The structural equation modelling was used to test the hypothesis and also validate the results. Findings indicate that the relational governance has a positive effect on supply chain performance and at the same time has an indirect effect on supply chain performance through both information sharing and quality of information. The study provides a hard evidence that the higher levels of information sharing and quality of information can lead to enhanced effect of relational governance on supply chain performance. Keywords - Relational Governance, Information Sharing, Quality of Information, Supply Chain Performance, Manufacturing Firms. DOI: 10.7176/EJBM/12-12-01 Publication date: April 30th 202

Time-Resolved Intraband Relaxation of Strongly-Confined Electrons and Holes in Colloidal PbSe Nanocrystals

The relaxation of strongly-confined electrons and holes between 1P and 1S levels in colloidal PbSe nanocrystals has been time-resolved using femtosecond transient absorption spectroscopy. In contrast to II-VI and III-V semiconductor nanocrystals, both electrons and holes are strongly confined in PbSe nanocrystals. Despite the large electron and hole energy level spacings (at least 12 times the optical phonon energy), we consistently observe picosecond time-scale relaxation. Existing theories of carrier relaxation cannot account for these experimental results. Mechanisms that could possibly circumvent the phonon bottleneck in IV-VI quantum dots are discussed

Bathymetric influence on the coastal sea level response to ocean gyres at western boundaries

It is our aim with this paper to investigate how the presence of a continental shelf and slope alters the relationship between interior ocean dynamics and western boundary (coastal) sea level. The assumption of a flat-bottomed basin with vertical sidewall at the coast is shown to hide the role that depth plays in the net force acting on the coast. A linear β-plane theory is then developed describing the transmission of sea level over variable depth bathymetry as analogous to the steady advection–diffusion of a thermal fluid. The parameter , relating the friction parameter r to the bathymetry depth H and width , is found to determine the contribution of interior sea level to coastal sea level, with small giving maximum penetration and large maximum insulation. In the small (infinite friction) limit the frictional boundary layer extends far offshore, and coastal sea level tends toward the vertical sidewall solution. Adding simple stratification produces exactly the same result but with reduced effective depth and hence enhanced penetration. Penetration can be further enhanced by permitting weakly nonlinear variations of thermocline depth. Wider and shallower shelves relative to the overall scales are also shown to maximize penetration for realistic values of . The theory implies that resolution of bathymetry and representation of friction can have a large impact on simulated coastal sea level, calling into question the ability of coarse-resolution models to accurately represent processes determining the dynamic coastal sea level

Gamma-Ray Bursts in Circumstellar Shells: A Possible Explanation for Flares

It is now generally accepted that long-duration gamma ray bursts (GRBs) are due to the collapse of massive rotating stars. The precise collapse process itself, however, is not yet fully understood. Strong winds, outbursts, and intense ionizing UV radiation from single stars or strongly interacting binaries are expected to destroy the molecular cloud cores that give birth to them and create highly complex circumburst environments for the explosion. Such environments might imprint features on GRB light curves that uniquely identify the nature of the progenitor and its collapse. We have performed numerical simulations of realistic environments for a variety of long-duration GRB progenitors with ZEUS-MP, and have developed an analytical method for calculating GRB light curves in these profiles. Though a full, three-dimensional, relativistic magnetohydrodynamical computational model is required to precisely describe the light curve from a GRB in complex environments, our method can provide a qualitative understanding of these phenomena. We find that, in the context of the standard afterglow model, massive shells around GRBs produce strong signatures in their light curves, and that this can distinguish them from those occurring in uniform media or steady winds. These features can constrain the mass of the shell and the properties of the wind before and after the ejection. Moreover, the interaction of the GRB with the circumburst shell is seen to produce features that are consistent with observed X-ray flares that are often attributed to delayed energy injection by the central engine. Our algorithm for computing light curves is also applicable to GRBs in a variety of environments such as those in high-redshift cosmological halos or protogalaxies, both of which will soon be targets of future surveys such as JANUS or Lobster.Comment: 12 pages, 5 figures, Accepted by Ap

What Does a PROMIS T-score Mean for Physical Function?

Introduction/Purpose: The use of patient-reported outcomes (PRO) continues to expand beyond research to involve standard of care assessments. Although the PROMIS physical function (PF) is normalized to a T-score it is unclear how to interpret and apply this information in the daily care of patients. The T-score is abstract and unanchored to patient abilities impairing its clinical utility when shared with the patient. Patient questions are concrete such as “when will I be able to run again after this procedure?” The purpose of this research was to link PROMIS PF T-scores with physical function activities and provide a visual map of this linkage to aid in treatment assessment and address concrete patient education

Shape control and whole-life energy assessment of an ‘infinitely stiff’ prototype adaptive structure

A previously developed design methodology produces optimum adaptive structures that minimise the whole-life energy which is made of an embodied part in the material and an operational part for structural adaptation. Planar and complex spatial reticular structures designed with this method and simulations showed that the adaptive solution achieves savings as high as 70% in the whole-life energy compared to optimised passive solutions. This paper describes a large-scale prototype adaptive structure built to validate the numerical findings and investigate the practicality of the design method. Experimental results show that (1) shape control can be used to achieve 'infinite stiffness' (i.e. to reduce displacements completely) in real-time without predetermined knowledge regarding position, direction and magnitude (within limits) of the external load; (2) the whole-life energy of the structure is in good agreement with that predicted by numerical simulations. This result confirms the proposed design method is reliable and that adaptive structures can achieve substantive total energy savings compared to passive structures

An integrated design of Drexel’s formula SAE chassis

The handling performance of a racecar is dependent on the torsional rigidity of the chassis. A chassis test rig for Formula SAE racecars will be designed and manufactured. The test rig will be used to statically measure the strains and rigidity of the current Formula SAE racecar chassis. Utilizing Finite element Analysis (FEA) and experimental test data, the chassis design will be evaluated for torsional rigidity and strain. The comparison of data from both FEA and testing will validate the structural integrity and design of the existing and future chassis. Therefore, a general testing procedure, employing a re-useable methodology, will be generated for the use of future teams. A document regarding test procedures and relating the test results to the chassis will be generated for the use of future teams. A validated FEA will be submitted to Formula SAE Drexel Racing for presentation at competition

A Wideband Polarization Study of Cygnus A with the JVLA. I: The Observations and Data

We present results from deep, wideband, high spatial and spectral resolution observations of the nearby luminous radio galaxy Cygnus A with the Jansky Very Large Array. The high surface brightness of this source enables detailed polarimetric imaging, providing images at 0.75\arcsec, spanning 2 - 18 GHz, and at 0.30\arcsec (6 - 18 GHz). The fractional polarization from 2000 independent lines of sight across the lobes decreases strongly with decreasing frequency, with the eastern lobe depolarizing at higher frequencies than the western lobe. The depolarization shows considerable structure, varying from monotonic to strongly oscillatory. The fractional polarization in general increases with increasing resolution at a given frequency, as expected. However, there are numerous lines of sight with more complicated behavior. We have fitted the 0.3\arcsec images with a simple model incorporating random, unresolved fluctuations in the cluster magnetic field to determine the high resolution, high-frequency properties of the source and the cluster. From these derived properties, we generate predicted polarization images of the source at lower frequencies, convolved to 0.75\arcsec. These predictions are remarkably consistent with the observed emission. The observations are consistent with the lower-frequency depolarization being due to unresolved fluctuations on scales $\gtrsim$ 300 - 700 pc in the magnetic field and/or electron density superposed on a partially ordered field component. There is no indication in our data of the location of the depolarizing screen or the large-scale field, either, or both of which could be located throughout the cluster, or in a boundary region between the lobes and the cluster.Comment: 24 pages, 13 figures. The manuscript has been accepted for publication in The Astrophysical Journa