Deep Scattering Layers of the Northern Gulf of Mexico Observed With a Shipboard 38-kHz Acoustic Doppler Current Profiler

Midwater sound-scattering layers containing aggregations of zooplankton and micronekton prey form in response to a trade-off between predator avoidance at depth and optimal foraging near the surface. Although the volume backscatter strength of zooplankton aggregations have been extensively studied in the past, fewer studies have specifically examined other descriptive characteristics of these layers such as depth of layers, timing of migrations, and the presence of secondary scattering layers below the main scattering layer. In the present study, patterns of deep scattering layers (DSLs) were characterized using relative acoustic backscatter from a ship-mounted 38-kHz phased-array, acoustic Doppler current profiler (ADCP) in the northern Gulf of Mexico in summers 2002 and 2003. Temporal patterns of scattering layers were analyzed with respect to the timing of the daytime and nighttime diel vertical migrations, and spatial patterns of scattering layers were analyzed with respect to their proximity to mesoscale circulation features associated with upwelling, downwelling, and water depth. The most prominent main scattering layer was consistently found at daytime depth of 450 to 550 m below the surface except during an unusual shoaling event in which a significant shallowing of the layer was observed at 200 to 300 m below the surface. This event coincided with the crossing of a strong frontal boundary between high salinity, blue water and low salinity, green water from the Mississippi River plume. Less prominent secondary scattering layers found deeper than the main scattering layer showed regional variability and appear to be more frequently associated with shallower shelf depths than in the deepwater basin. Variability among deep scattering layers in this region may have important implications for the behavior and interactions of higher trophic levels dependent on these prey layers

Spanning forests and the q-state Potts model in the limit q \to 0

We study the q-state Potts model with nearest-neighbor coupling v=e^{\beta J}-1 in the limit q,v \to 0 with the ratio w = v/q held fixed. Combinatorially, this limit gives rise to the generating polynomial of spanning forests; physically, it provides information about the Potts-model phase diagram in the neighborhood of (q,v) = (0,0). We have studied this model on the square and triangular lattices, using a transfer-matrix approach at both real and complex values of w. For both lattices, we have computed the symbolic transfer matrices for cylindrical strips of widths 2 \le L \le 10, as well as the limiting curves of partition-function zeros in the complex w-plane. For real w, we find two distinct phases separated by a transition point w=w_0, where w_0 = -1/4 (resp. w_0 = -0.1753 \pm 0.0002) for the square (resp. triangular) lattice. For w > w_0 we find a non-critical disordered phase, while for w < w_0 our results are compatible with a massless Berker-Kadanoff phase with conformal charge c = -2 and leading thermal scaling dimension x_{T,1} = 2 (marginal operator). At w = w_0 we find a "first-order critical point": the first derivative of the free energy is discontinuous at w_0, while the correlation length diverges as w \downarrow w_0 (and is infinite at w = w_0). The critical behavior at w = w_0 seems to be the same for both lattices and it differs from that of the Berker-Kadanoff phase: our results suggest that the conformal charge is c = -1, the leading thermal scaling dimension is x_{T,1} = 0, and the critical exponents are \nu = 1/d = 1/2 and \alpha = 1.Comment: 131 pages (LaTeX2e). Includes tex file, three sty files, and 65 Postscript figures. Also included are Mathematica files forests_sq_2-9P.m and forests_tri_2-9P.m. Final journal versio

(Re)framing a philosophical and epistemological framework for teaching and learning in STEM: Emerging pedagogies for complexity

Today’s learners are engaging in study where access to knowledge is easier than it ever has been in human history. Rapid advancement of technology and the increasing ease with which communication and interaction can occur has dramatically changed the landscape in which teachers of science, technology, engineering and mathematics (STEM) operate. The contemporary skills that students are required to possess include inter alia problem solving, creativity, teamwork abilities, communication skills and emotional intelligence. Despite the universal acceptance of their importance, these skills are commonly cited as underdeveloped and in addition, are still accompanied by outmoded ‘traditional’ forms of teaching and assessment. While the approaches of twentieth-century education were successful in developing knowledge stores, the ubiquity of access to knowledge—coupled with the constantly changing nature of the world today—requires alternative conceptions of teaching and learning. This article focuses primarily on an exploration of learning metaphors and teaching with the overall lens of creating self-regulated and furthermore, self-determined learners. The article begins with an exploration of learning in STEM education and a critique of the pedagogical perspective, discussing why this epistemology may be insufficient for contemporary STEM learning. The article then considers an alternative and potentially more contemporary notion; the emergent pedagogic space. The article presents a theoretical model to conceptualise learning in STEM education, with the goal of informing both practice and research. The realisation of this proposed emergent pedagogical space is explored through an applied case study from a design and technology context

Multihospital Outbreak of a Middle East Respiratory Syndrome Coronavirus Deletion Variant, Jordan: A Molecular, Serologic, and Epidemiologic Investigation

Background An outbreak of Middle East respiratory syndrome coronavirus (MERS-CoV) in Jordan in 2015 involved a variant virus that acquired distinctive deletions in the accessory open reading frames. We conducted a molecular and seroepidemiologic investigation to describe the deletion variant’s transmission patterns and epidemiology. Methods We reviewed epidemiologic and medical chart data and analyzed viral genome sequences from respiratory specimens of MERS-CoV cases. In early 2016, sera and standardized interviews were obtained from MERS-CoV cases and their contacts. Sera were evaluated by nucleocapsid and spike protein enzyme immunoassays and microneutralization. Results Among 16 cases, 11 (69%) had health care exposure and 5 (31%) were relatives of a known case; 13 (81%) were symptomatic, and 7 (44%) died. Genome sequencing of MERS-CoV from 13 cases revealed 3 transmissible deletions associated with clinical illness during the outbreak. Deletion variant sequences were epidemiologically clustered and linked to a common transmission chain. Interviews and sera were collected from 2 surviving cases, 23 household contacts, and 278 health care contacts; 1 (50%) case, 2 (9%) household contacts, and 3 (1%) health care contacts tested seropositive. Conclusions The MERS-CoV deletion variants retained human-to-human transmissibility and caused clinical illness in infected persons despite accumulated mutations. Serology suggested limited transmission beyond that detected during the initial outbreak investigation

Erratum: "A Gravitational-wave Measurement of the Hubble Constant Following the Second Observing Run of Advanced LIGO and Virgo" (2021, ApJ, 909, 218)

[no abstract available

GW190814: gravitational waves from the coalescence of a 23 solar mass black hole with a 2.6 solar mass compact object

We report the observation of a compact binary coalescence involving a 22.2–24.3 Me black hole and a compact object with a mass of 2.50–2.67 Me (all measurements quoted at the 90% credible level). The gravitational-wave signal, GW190814, was observed during LIGO’s and Virgo’s third observing run on 2019 August 14 at 21:10:39 UTC and has a signal-to-noise ratio of 25 in the three-detector network. The source was localized to 18.5 deg2 at a distance of - + 241 45 41 Mpc; no electromagnetic counterpart has been confirmed to date. The source has the most unequal mass ratio yet measured with gravitational waves, - + 0.112 0.009 0.008, and its secondary component is either the lightest black hole or the heaviest neutron star ever discovered in a double compact-object system. The dimensionless spin of the primary black hole is tightly constrained to �0.07. Tests of general relativity reveal no measurable deviations from the theory, and its prediction of higher-multipole emission is confirmed at high confidence. We estimate a merger rate density of 1–23 Gpc−3 yr−1 for the new class of binary coalescence sources that GW190814 represents. Astrophysical models predict that binaries with mass ratios similar to this event can form through several channels, but are unlikely to have formed in globular clusters. However, the combination of mass ratio, component masses, and the inferred merger rate for this event challenges all current models of the formation and mass distribution of compact-object binaries

Modelling the extreme hydrological event of Summer 2007 in the Severn Uplands from gauge and radar rainfall sources

This paper provides a comparison of gauge interpolated and radar derived precipitation data sources for an uplandcatchment in the UK for a time period when extreme hydrological conditions were prevalent. Subsequently,a performance measure was used to evaluate the accuracy of hydrological simulation of extreme conditions usingthe two independent precipitation data sources within a HEC-HMS modelling framework. Discrepancies betweengauge and radar time-series precipitation records were found to coincide with elevation, spatial distributionof precipitation and distance from the radar source. The Nash-Sutcliffe performance measure indicated thatdespite the higher temporal and spatial resolution of the radar data, interpolated gauging station records producedcomparative accuracy when replicating the extreme hydrological event of Summer 200

Deep Scattering Layers of the Northern Gulf of Mexico Observed With a Shipboard 38-kHz Acoustic Doppler Current Profiler

Midwater sound-scattering layers containing aggregations of zooplankton and micronekton prey form in response to a trade-off between predator avoidance at depth and optimal foraging near the surface. Although the volume backscatter strength of zooplankton aggregations have been extensively studied in the past, fewer studies have specifically examined other descriptive characteristics of these layers such as depth of layers, timing of migrations, and the presence of secondary scattering layers below the main scattering layer. In the present study, patterns of deep scattering layers (DSLs) were characterized using relative acoustic backscatter from a ship-mounted 38-kHz phased-array, acoustic Doppler current profiler (ADCP) in the northern Gulf of Mexico in summers 2002 and 2003. Temporal patterns of scattering layers were analyzed with respect to the timing of the daytime and nighttime diel vertical migrations, and spatial patterns of scattering layers were analyzed with respect to their proximity to mesoscale circulation features associated with upwelling, downwelling, and water depth. The most prominent main scattering layer was consistently found at daytime depth of 450 to 550 m below the surface except during an unusual shoaling event in which a significant shallowing of the layer was observed at 200 to 300 m below the surface. This event coincided with the crossing of a strong frontal boundary between high salinity, blue water and low salinity, green water from the Mississippi River plume. Less prominent secondary scattering layers found deeper than the main scattering layer showed regional variability and appear to be more frequently associated with shallower shelf depths than in the deepwater basin. Variability among deep scattering layers in this region may have important implications for the behavior and interactions of higher trophic levels dependent on these prey layers