Springs–neaps cycles in daily total seabed light: Daylength-induced changes

AbstractIn shallow, tidal seas, daily total seabed light is determined largely by the interaction of the solar elevation cycle, the tidal cycle in water depth, and any temporal variability in turbidity. Since tidal range, times of low water, and often turbidity vary in regular ways over the springs–neaps cycle, daily total seabed light exhibits cycles of the same periodicity. Corresponding cycles are likely to be induced in the daily total primary production of benthic algae and plants, particularly those light-limited specimens occupying the lower reaches of a sub-tidal population. Consequently, this effect is an important control on the growth patterns, depth distribution and survival of, for example, macroalgal forests and seagrass meadows.Seasonal changes in daylength exert an important additional control on these cycles, as they alter the fraction of the tidal and turbidity cycles occurring within daylight hours. Bowers et al. (1997) modelled this phenomenon numerically and predicted that for a site with low water at about midday and midnight at neaps tides, 6am and 6pm at springs, daily total seabed light peaks at neaps in winter, but the ‘sense’ of the cycle ‘switches’ so that it peaks at springs in summer — the longer daylength permits the morning and evening low water springs to contribute substantially to the daily total. Observations for such a site in North Wales (UK), presented in this paper, show that no such ‘switch’ occurs, and neaps tides host the largest daily totals throughout the year. The predicted ‘switch’ is not observed because turbidity increases generally at spring tides, and specifically at low water springs, both of which were not accounted for in the model. Observations at a second site in Brittany (France), diametrically opposite in terms of the times of low water at neaps and at springs, indicate a peak at springs throughout the year.Analytical tools are developed to calculate the percentage of daily total sea surface irradiance reaching the bed at a site of interest on any given day, and to determine the sense of any springs–neaps cycle thereof for a given season. The conditions required for a ‘switch’ are explored graphically, resulting in the identification of criteria (and a useful parameter) for predicting their occurrence. Consequences for the growth patterns, depth limits and long-term survival of benthic algae and plants are discussed

Scale-dependent angle of alignment between velocity and magnetic field fluctuations in solar wind turbulence

Under certain conditions, freely decaying magnetohydrodynamic (MHD) turbulence evolves in such a way that velocity and magnetic field fluctuations delta v and delta B approach a state of alignment in which delta v proportional to delta B. This process is called dynamic alignment. Boldyrev has suggested that a similar kind of alignment process occurs as energy cascades from large to small scales through the inertial range in strong incompressible MHD turbulence. In this study, plasma and magnetic field data from the Wind spacecraft, data acquired in the ecliptic plane near 1 AU, are employed to investigate the angle theta(tau) between velocity and magnetic field fluctuations in the solar wind as a function of the time scale tau of the fluctuations and to look for the scaling relation similar to tau(1/4) predicted by Boldyrev. We find that the angle appears to scale like a power law at large inertial range scales, but then deviates from power law behavior at medium to small inertial range scales. We also find that small errors in the velocity vector measurements can lead to large errors in the angle measurements at small time scales. As a result, we cannot rule out the possibility that the observed deviations from power law behavior arise from errors in the velocity measurements. When we fit the data from 2 x 10(3) s to 2 x 10(4) s with a power law of the form proportional to tau(p), our best fit values for p are in the range 0.27-0.36

Mineral exploration in the Lower Palaeozoic rocks of south-west Cumbria. Part 1, regional surveys

The results of geochemical, geological and geophysical surveys over Lower Palaeozoic rocks in the south-western part of Cumbria are given in two reports. This report (Part 1) describes the results of a geochemical drainage survey and an examination of mineralised sites, and relates them to information from new geological mapping and an assessment of regional geophysical data. Part 2 contains details of follow-up surveys in the Black Combe inlier. The geochemical drainage survey, involving the collection and analysis of heavy mineral concentrates and stream sediment samples from 119 sites, found substantial antimony, arsenic, barium, bismuth, copper, iron, lead, tin, tungsten and zinc anomalies. Gold was reported for the first time from this part of the Lake District: small amounts were noted in panned concentrates from five sites. Other minerals identified in panned concentrates included arsenopyrite, baryte, bismutite, bismuthinite, cassiterite, chalcopyrite, cerussite, pyrite, pyromorphite, scheelite, sphalerite, stolzite and wolfram&e. The examination of old workings and outcrops revealed many undocumented occurrences of quartzsulphide vein-style mineralisation. The chemical analysis of samples taken from old workings and other occurrences confirmed field observations that locally, particularly in the Black Combe area, this mineralisation is polymetallic with variable amounts of arsenic, gold, bismuth, copper, lead, zinc and in a few cases antimony, barium, cobalt, nickel, tungsten and tin. Iron mineralisation occurs both as oxide (hematite) and sulphide deposits. Mercury was present in appreciable amounts in samples from the High Brow pyrite mine. The distribution of panned concentrate anomalies suggests that the vein-style mineralisation is polyphase and that individual phases may be zoned. Highest zinc anomalies occur near Torver and the highest lead on the west side of Black Combe. Tin and tungsten are restricted largely to the central part of Black Combe, and the most prominent arsenic and bismuth anomalies are found in the same area. Copper anomalies are widespread over the Skiddaw Group and the Borrowdale Volcanic Group. Barium anomalies indicate that baryte mineralisation is weak and localised, occurring principally within the Black Combe area and close to the Windermere Supergroup basal unconformity. Iron oxides from host rocks and hematite mineralisation are responsible for local enrichments of iron, antimony, arsenic and molybdenum in panned concentrates

The digestive morphophysiology of wild, free-living, giraffes

We have measured rumen-complex (rumen, reticulum, omasum, abomasum) and intestine (small and large combined) mass in 32 wild giraffes of both sexes with body masses ranging from 289 to 1441 kg, and parotid gland mass, tongue length and mass, masseter and mandible mass in 9 other giraffes ranging in body mass from 181 to 1396 kg. We have estimated metabolic and energy production rates, feed intake and home range size. Interspecific analysis of mature ruminants show that components of the digestive system increase linearly (Mb1) or positively allometric (MbN1)with bodymasswhile variables associatedwith feed intake scalewithmetabolic rate (Mb.75). Conversely, in giraffes ontogenetic increases in rumen-complex masswere negatively allometric (Mbb1), and increases in intestine mass, parotid gland mass, masseter mass, and mandible mass were isometric (Mb1). The relative masseter muscle mass (0.14% of Mb) and the relative parotid mass (0.03% of Mb) are smaller than in other ruminants. Increases in tongue length scale with head length0.72 andMb.32 and tongue mass with Mb.69. Absolute mass of the gastrointestinal tract increased throughout growth but its relative mass declined from 20% to 15% of Mb. Rumen-complex fermentation provides ca 43% of daily energy needs, large intestine fermentation 24% and 33% by digestion of soluble carbohydrates, proteins, and lipids. Dry matter intake (kg) was 2.4% of body mass in juveniles and 1.6% in adults. Energy requirements increased from 35 Mj/day to 190 Mj/day. Browse production rate sustains a core home range of 2.2–11.8 km2.Don Craib Trust and the University of Wyoming.http://www.elsevier.com/locate/cbpa2016-09-30hb201

Collapse dynamics of trapped Bose-Einstein condensates

We analyze the implosion and subsequent explosion of a trapped condensate after the scattering length is switched to a negative value. Our results compare very well qualitatively and fairly well quantitatively with the results of recent experiments at JILA.Comment: 4 pages, 3 figure