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The Old Copper Complex (OCC) refers to the production of heavy copper-tool technology by Archaic Native American societies in the Lake Superior region. To better define the timing of the OCC, we evaluated 53 (eight new and 45 published) radiocarbon (14C) dates associated with copper artifacts and mines. We compared these dates to six lake sediment-based chronologies of copper mining and annealing in the Michigan Copper District. 14C dates grouped by archaeological context show that cremation remains, and wood and cordage embedded in copper artifacts have ages that overlap with the timing of high lead (Pb) concentrations in lake sediment. In contrast, dates in stratigraphic association and from mines are younger than those from embedded and cremation materials, suggesting that the former groups reflect the timing of processes that occurred post-abandonment. The comparatively young dates obtained from copper mines therefore likely reflect abandonment and infill of the mines rather than active use. Excluding three anomalously young samples, the ages of embedded organic material associated with 15 OCC copper artifacts range from 8500 to 3580 cal BP, confirming that the OCC is among the oldest known metalworking societies in the world.
Visible derivative spectroscopy (VDS) analysis of sediment from Cleland Lake, Southeastern British Columbia provides a reconstruction of paleolimnological productivity and hydrologic change during the past 14,000 calibrated 14C years before present (cal yr BP). The first five principal components (PC) of the VDS data explain 97% of the variance in the VDS data set. Four PCs correlate with standard reflectance derivative spectra for diatom, dinoflagellate algae, and cyanophyte pigments that record ecological change, while two PCs are paleohydrologic indicators. Dinoflagellate algae are predominant from 11,600 to 8600 cal yr BP then decrease to low levels after ~ 8500 cal yr BP. PCs 3–5 represent variations in cyanophyte abundance and exhibit peaks from 14,000 to 11,600, 14,000 to 9500, and 6100 to 5400 cal yr BP, respectively. Conditions shifted toward favoring diatoms around 9400 and lasted until 170 cal yr BP. Higher dinoflagellate-related pigment concentrations suggest a lower lake level from 11,600 to 8600 cal yr BP, followed by higher water levels and wetter conditions after 8500 cal yr BP. We propose that drier conditions transitioning from the late glacial into the Holocene were caused by summer insolation-driven, non-linear feedbacks between the northern hemisphere subtropical high-pressure systems, vegetation, and soil moisture.
Increasing breeding success in the giant panda requires a better understanding of its complex reproductive biology. We know that the female is typically mono-oestrus during a breeding season which occurs from February to May (within and outside China). Behavioural and physiological changes associated with pro-oestrus and oestrus last one to two weeks, during which the female exhibits proceptive behaviours, such as scent marking, to advertise her sexual receptivity (Lindburg et al., 2001). During the peri-ovulatory interval, receptive behaviours (e.g. tail-up lordotic posture) climax with copulation generally occurring over a one- to three-day interval. Birthing occurs from June to October with a gestation of 85 to 185 days (Zhu et al., 2001). This unusually wide gestation span is due to the phenomenon of delayed implantation, a varied interval before the conceptus implants in the uterus and begins foetal development. The driving force behind implantation in this species is unknown. The giant panda also experiences pseudopregnancy, whereby the female exhibits behavioural, physiological and hormonal changes similar to pregnancy.
Behavioural and physiological cues associated with both pregnancy and pseudopregnancy include decreased appetite, nest-building and cradling behaviours, vulvar swelling and colouration, mammary gland enlargement and lethargy. Additionally, temporal and quantitative progesterone patterns (tracked by assessing urinary hormone by-products and progestins) are indistinguishable between pregnancy and pseudopregnancy. Therefore, no definitive test currently exists for identifying pregnant from pseudopregnant giant pandas.
The photoluminescence band around 0.78 eV that is sometimes seen in strained layer SiGe samples or deformed silicon containing a high density of dislocations has been attributed to the presence of oxygen complexes. In this study we have prepared a set of Si0.9Ge0.1 samples by MBE which have then been implanted with iron, erbium, or oxygen in order to study the effect of implanted impurities on photoluminescence in the technologically important region around 1.5 microns.
Following implantation with oxygen, two luminescence bands appear around 0.85 eV and 0.78 eV, respectively. However, these bands are not present in either the unimplanted sample or those subject to Er or Fe implantation. The correlation between oxygen doping and the appearance of these bands supports the conjecture that they are associated with oxygen complexes.
Numerical and experimental techniques were used to study the physics of flow
separation for steady internal flow in a 45° junction geometry, such as that observed
between two pipes or between the downstream end of a bypass graft and an artery.
The three-dimensional Navier–Stokes equations were solved using a validated finite
element code, and complementary experiments were performed using the photochromic
dye tracer technique. Inlet Reynolds numbers in the range 250 to 1650 were considered.
An adaptive mesh refinement approach was adopted to ensure grid-independent
solutions. Good agreement was observed between the numerical results and the
experimentally measured velocity fields; however, the wall shear stress agreement was less
satisfactory. Just distal to the ‘toe’ of the junction, axial flow separation was observed
for all Reynolds numbers greater than 250. Further downstream (approximately 1.3
diameters from the toe), the axial flow again separated for Re [ges ] 450. The location and
structure of axial flow separation in this geometry is controlled by secondary flows,
which at sufficiently high Re create free stagnation points on the model symmetry
plane. In fact, separation in this flow is best explained by a secondary flow boundary
layer collision model, analogous to that proposed for flow in the entry region of a
curved tube. Novel features of this flow include axial flow separation at modest Re (as
compared to flow in a curved tube, where separation occurs only at much higher Re),
and the existence and interaction of two distinct three-dimensional separation zones.
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