Giant Beaver (Castoroides) Palaeoecology Inferred from Stable Isotopes

Stable isotope analysis was used to explore unresolved questions about the palaeoecology of the extinct Pleistocene giant beaver (Castoroides). The δ13C, δ15N, and δ18O of bone collagen and structural carbonate from enamel served as proxies for palaeodiet and palaeoclimate. A new baseline for freshwater and terrestrial plant δ13C and δ15N was utilized in a mixing model (SIAR) to assess rodent feeding niche. SIAR analysis indicated that Castoroides’ consumed a diet of predominantly macrophytes, making them reliant on wetland habitat for food. Based on isotopic data for potential modern analog species (Castor and Ondatra), SIAR also indicated that Castor and Castoroides occupied complementary dietary niches, allowing them to share habitat space throughout the Pleistocene. The δ13C and δ18O of Castoroides’ ever-growing incisors also recorded seasonal fluctuations in diet and climate. Wetland loss due to climate change during the Last Glacial Maximum, and increased competition for habitat, probably factored into Castoroides’ extinction

Clastic Sediment Partitioning in a Cretaceous Delta System, Western Canada: Responses to Tectonic and Sea-Level Controls

The early–mid Cenomanian Dunvegan Formation represents a large delta complex that prograded at least 400 km from NW to SE. A regional stratigraphy based on marine transgressive surfaces and equivalent subaerial interfluves allows the formation to be subdivided into ten transgressive–regressive allomembers, labelled J to A in ascending order, each with an average duration of <200 ky. Analysis of stacking patterns and facies distributions of parasequences within allomembers allows transgressive, highstand, falling stage and lowstand systems tracts to be identified. Extensive valley systems that average 1–2 km wide and 21 m deep can be traced for up to 320 km across the top surfaces of allomembers H to E. In their lower 20–40 km, valleys are filled with muddy heterolithic tidal facies but this changes to fluvial-dominated multi-storey channel-fills further up-valley. Interfluve surfaces are marked by palaeosols, the character of which indicate a protracted hiatus with extensive physical, chemical and biological modification of the parent material. Changes in flexural subsidence rate are indicated by isopach patterns. Allomembers J–F have a sigmoidal prismatic geometry, successively offlapping to the SE. There is no evidence of thickening toward the orogen. In contrast, overlying allomembers E–A show progressive development of a depocentre along the western margin of the basin. The increasing accommodation rate on the updip coastal plain caused marine deltas to be starved of sediment, leading to progressive backstep of shorelines. Simultaneously, alluvial deposits within the depocentre show an upward increase in the proportion of subaqueous to subaerial facies, culminating in the incursion of brackish and finally marine waters. Thus tectonic subsidence rate had a first-order affect on both the volume of sediment available to build marine deltas and also on the local character of facies that accumulated on the coastal plain. The onset of flexural subsidence in allomember E appears to have resulted in subtle uplift of a forebulge, resulting in dramatic deflection of river systems. Despite the clear tectonic signature, successive transgressions and regressions involved similar horizontal displacements of the shoreline, regardless of subsidence rate. This suggests that modest eustatic changes also influenced the accommodation available. Based on the measured horizontal excursions of the shoreline, the vertical thickness of alluvial strata, and realistic alluvial gradients, an average eustatic excursion of about 24 m is calculated. The incision of valley systems is attributed in part to periods of eustatic fall. However, valleys seem too long to be explained by eustasy alone, and hence secular changes in discharge are postulated as an additional forcing factor. Climatic cycles in the Milankovitch band may have been responsible for both eustatic and discharge variations

Deriving the ideal ore texture for microwave treatment of metalliferous ores

High power density microwave treatments on metalliferous ores have historically been shown to reduce ore competency prior to beneficiation at economically feasible energy inputs. However, the relationship between mineralogical textural features and the extent of the microwave-induced fracturing had previously been limited to qualitative descriptions or simplistic two-phase numerical models, which could not account for the complex mineral assemblages in real ores. In this paper, mineralogy, grain size, dissemination, textural consistency and mineral associations were determined for 13 commercially exploited nickel, copper and lead-zinc ores using a Mineral Liberation Analyser (MLA). The ores were subjected to high power density microwave treatments at up to 25kW in a single mode cavity with microwave energy inputs of approximately 0.5-10kWh/t, and the subsequent reductions in ore competency were measured by the Point Load Test. The ores that demonstrated the greatest reductions in strength typically contained between approximately 2%wt to 20%wt of highly microwave-absorbing minerals, with a native grain size d50 greater than approximately 500µm, constrained by hard matrix minerals such as quartz and feldspar. Texturally consistent ores with a high proportion of amenable textures also demonstrated the highest average reductions in strength. These findings support the qualitative descriptions and numerical modelling results available in the literature and provide a baseline for selecting likely candidate ores for microwave treatments in the future

Giant Beaver Palaeoecology Inferred from Stable Isotopes

This is a multi-individual (n = 11), stable carbon and nitrogen isotope study of bone collagen (δ13Ccol and δ15Ncol) from the giant beaver (genus Castoroides). The now-extinct giant beaver was once one of the most widespread Pleistocene megafauna in North America. We confirm that Castoroides consumed a diet of predominantly submerged aquatic macrophytes. These dietary preferences rendered the giant beaver highly dependent on wetland habitat for survival. Castoroides’ δ13Ccol and δ15Ncol do not support the hypothesis that the giant beaver consumed trees or woody plants, which suggests that it did not share the same behaviours as Castor (i.e., tree-cutting and harvesting). The onset of warmer, more arid conditions likely contributed to the extinction of Castoroides. Six new radiocarbon dates help establish the chronology of the northward dispersal of the giant beaver in Beringia, indicating a correlation with ice sheet retreat

Increasing the grind size for effective liberation and flotation of a porphyry copper ore by microwave treatment

In this paper, mineralogy, grain size, dissemination, textural consistency and mineral associations were determined for a commercially exploited porphyry copper ore using a Mineral Liberation Analyser (MLA). The ore was subjected to high power density microwave treatments in a single mode cavity at 15 kW and approximately 2 kW h/t. The untreated and microwave-treated samples were subsequently milled to two grind sizes near the nominal plant grind size and a size-by-liberation analysis performed. The analysis revealed that equivalent liberation could be obtained at a grind size approximately 50–60 μm coarser than the nominal plant grind due to the microwave treatment. Flotation testing indicated that an increase in copper recovery of approximately 1% could be achieved, or that a grind size increase of approximately 30 μm may potentially yield equivalent copper recovery due to the microwave-enhanced liberation observed. However, statistical analyses demonstrated that it is difficult to attain confidence in recovery increases of approximately 1% even when conducting batch flotation tests in triplicate. The ore under investigation had previously been shown to produce only modest average reductions in strength (∼8%) under similar microwave treatment conditions due to a prevalence of many unfavourable textures. However, the preferential association of copper minerals with a hard matrix mineral (quartz) and a hard microwave-absorbent mineral (pyrite) resulted in a significant change in liberation behaviour

Comparison of clinical and biochemical markers of dehydration with the clinical dehydration scale in children: A case comparison trial

Background: The clinical dehydration scale (CDS) is a quick, easy-to-use tool with 4 clinical items and a score of 1-8 that serves to classify dehydration in children with gastroenteritis as no, some or moderate/severe dehydration. Studies validating the CDS (Friedman JN) with a comparison group remain elusive. We hypothesized that the CDS correlates with a wide spectrum of established markers of dehydration, making it an appropriate and easy-to-use clinical tool.Methods: This study was designed as a prospective double-cohort trial in a single tertiary care center. Children with diarrhea and vomiting, who clinically required intravenous fluids for rehydration, were compared with minor trauma patients who required intravenous needling for conscious sedation. We compared the CDS with clinical and urinary markers (urinary electrolytes, proteins, ratios and fractional excretions) for dehydration in both groups using receiver operating characteristic (ROC) curves to determine the area under the curve (AUC).Results: We enrolled 73 children (male = 36) in the dehydration group and 143 (male = 105) in the comparison group. Median age was 32 months (range 3-214) in the dehydration and 96 months (range 2.6-214 months, p \u3c 0.0001) in the trauma group. Median CDS was 3 (range 0-8) within the dehydration group and 0 in the comparison group (p \u3c 0.0001). The following parameters were statistically significant (p \u3c 0.05) between the comparison group and the dehydrated group: difference in heart rate, diastolic blood pressure, urine sodium/potassium ratio, urine sodium, fractional sodium excretion, serum bicarbonate, and creatinine measurements. The best markers for dehydration were urine Na and serum bicarbonate (ROC AUC = 0.798 and 0.821, respectively). CDS was most closely correlated with serum bicarbonate (Pearson r = -0.3696, p = 0.002).Conclusion: Although serum bicarbonate is not the gold standard for dehydration, this study provides further evidence for the usefulness of the CDS as a dehydration marker in children.Trial registration: Registered at ClinicalTrials.gov (NCT00462527) on April 18, 2007. © 2014 Tam et al.; licensee BioMed Central Ltd

Anatomy and origin of authochthonous late Pleistocene forced regression deposits, east Coromandel inner shelf, New Zealand: implications for the development and definition of the regressive systems tract

High-resolution seismic reflection data from the east Coromandel coast, New Zealand, provide details of the sequence stratigraphy beneath an autochthonous, wave dominated inner shelf margin during the late Quaternary (0-140 ka). Since c. 1 Ma, the shelf has experienced limited subsidence and fluvial sediment input, producing a depositional regime characterised by extensive reworking of coastal and shelf sediments during glacio-eustatic sea-level fluctuations. It appears that only one complete fifth-order (c. 100 000 yr) depositional sequence is preserved beneath the inner shelf, the late Pleistocene Waihi Sequence, suggesting any earlier Quaternary sequences were mainly cannibalised into successively younger sequences. The predominantly Holocene-age Whangamata Sequence is also evident in seismic data and modern coastal deposits, and represents an incomplete depositional sequence in its early stages of formation. A prominent aspect of the sequence stratigraphy off parts of the east Coromandel coast is the presence of forced regressive deposits (FRDs) within the regressive systems tract (RST) of the late Pleistocene Waihi Sequence. The FRDs are interpreted to represent regressive barrier-shoreface sands that were sourced from erosion and onshore reworking of underlying Pleistocene sediments during the period of slow falling sea level from isotope stages 5 to 2 (c. 112-18 ka). The RST is volumetrically the most significant depositional component of the Waihi Sequence; the regressive deposits form a 15-20 m thick, sharp-based, tabular seismic unit that downsteps and progrades continuously across the inner shelf. The sequence boundary for the Waihi Sequence is placed at the most prominent, regionally correlative, and chronostratigraphically significant surface, namely an erosional unconformity characterised in many areas by large incised valleys that was generated above the RST. This unconformity is interpreted as a surface of maximum subaerial erosion generated during the last glacial lowstand (c. 18 ka). Although the base of the RST is associated with a prominent regressive surface of erosion, this is not used as the sequence boundary as it is highly diachronous and difficult to identify and correlate where FRDs are not developed. The previous highstand deposits are limited to subaerial barrier deposits preserved behind several modern Holocene barriers along the coast, while the transgressive systems tract is preserved locally as incised-valley fill deposits beneath the regressive surface of erosion at the base of the RST. Many documented late Pleistocene RSTs have been actively sourced from fluvial systems feeding the shelf and building basinward-thickening, often stacked wedges of FRDs, for which the name allochthonous FRDs is suggested. The Waihi Sequence RST is unusual in that it appears to have been sourced predominantly from reworking of underlying shelf sediments, and thus represents an autochthonous FRD. Autochthonous FRDs are also present on the Forster-Tuncurry shelf in southeast Australia, and may be a common feature in other shelf settings with low subsidence and low sediment supply rates, provided shelf gradients are not too steep, and an underlying source of unconsolidated shelf sediments is available to source FRDs. The preservation potential of such autochthonous FRDs in ancient deposits is probably low given that they are likely to be cannibalised during subsequent sea-level falls

New machine-marked tests for selection into core medical training: evidence from two validation studies

The objective of this study was to examine whether two machine-marked tests (MMTs), a clinical problem-solving test (CPS) and a situational judgement test (SJT, focusing on professional dilemmas), previously validated for selection into general practice (GP) training in the UK, could provide a valid selection methodology for shortlisting into core medical training (CMT). An exploratory longitudinal design was used to examine the psychometric properties of the MMTs for CMT applicants, and the correlation between MMT scores (time 1) and subsequent CMT interview outcomes (time 2). Independent samples from two consecutive years were used: in 2008 a retrospective analysis of data was used, while in 2009, doctors applying for CMT were asked to complete the MMTs for evaluation purposes. In 2008, a total of 1,711 doctors applied to both CMT and GP training and completed the MMTs. In 2009, a total of 2,265 doctors who applied for CMT completed the MMTs for evaluation purposes. The main outcome measure was the CMT applicants’ interview score. Both the CPS and SJT had good reliability and score distributions for 2008 and 2009 CMT samples, similar to the GP comparison samples. The MMTs were good predictors of performance in the CMT interviews (r0.56, p0.001 in 2008, and r0.61, p0.001 in 2009 for both MMTs combined) and offered incremental validity over the current shortlisting process. The GP MMTs offer an appropriate measurement methodology for selection into CMT, representing a significant innovation for developing selection methodology for CMT. Longer-term studies should be undertaken to assess the validity of all selection techniques used, in terms of CMT training outcome

Within-wing isotopic (δ2H, δ13C, δ15N) variation of monarch butterflies: implications for studies of migratory origins and diet

Increasingly, stable isotope measurements are being used to assign individuals to broad geographic origins based on established relationships between animal tissues and tissue-specific isoscapes. In particular, the eastern North American population of the monarch butterfly (Danaus plexippus) has been the subject of several studies using established δ2H and δ13C wing-tissue isoscapes to infer natal origins of migrating and overwintering individuals. However, there has been no study investigating potential variance that can derive from sub-sampling different regions of the wings, especially those regions differing in pigmentation (orange versus black). Within-wing isotopic (δ2H, δ13C, δ15N) variance of 40 monarch butterflies collected from natural overwinter mortality on Mexican roost sites were split evenly into two groups: unwashed samples and those washed in a 2:1 chloroform:methanol solvent. Isotopic variance in δ2H and δ13C was related to pigment (within-wing range 5‰ and 0.5‰, respectively), but not region of subsampling. This variance was reduced 3 to 4 fold through solvent washing that removed pigmented surface scales and any adhered oils. Wing δ15N was similarly influenced by pigment (range 0.3‰), but this effect was not reduced through washing. We recommend future isotopic studies of monarchs and other butterflies for migration research to use the same region for sub-sampling consistently and to wash samples with solvent to reduce isotopic variance related to uncontrolled variance in discrimination (δ2H, δ13C, δ15N) and/or adsorbed water vapor (δ2H). These data also need to be included in description of methods

Validating an inertial measurement unit for cricket fast bowling: a first step in assessing the feasibility of diagnosing back injury risk in cricket fast bowlers during a tele-sport-and-exercise medicine consultation

This study aimed to validate an array-based inertial measurement unit to measure cricket fast bowling kinematics as a first step in assessing feasibility for tele-sport-and-exercise medicine. We concurrently captured shoulder girdle relative to the pelvis, trunk lateral flexion, and knee flexion angles at front foot contact of eight cricket medium-fast bowlers using inertial measurement unit and optical motion capture. We used one sample t-tests and 95% limits of agreement (LOA) to determine the mean difference between the two systems and Smallest Worth-while Change statistic to determine whether any differences were meaningful. A statistically significant (p < 0.001) but small mean difference of −4.7° ± 8.6° (95% Confidence Interval (CI) [−3.1° to −6.4°], LOA [−22.2 to 12.7], SWC 3.9°) in shoulder girdle relative to the pelvis angle was found between the systems. There were no statistically significant differences between the two systems in trunk lateral flexion and knee flexion with the mean differences being 0.1° ± 10.8° (95% CI [−1.9° to 2.2°], LOA [−22.5 to 22.7], SWC 1.2°) and 1.6° ± 10.1° (95% CI [−0.2° to 3.3°], LOA [−19.2 to 22.3], SWC 1.9°) respectively. The inertial measurement unit-based system tested allows for accurate measurement of specific cricket fast bowling kinematics and could be used in determining injury risk in the context of tele-sport-and-exercise-medicine