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Night-migratory songbirds appear to sense the direction of the Earth's magnetic field via radical pair intermediates formed photochemically in cryptochrome flavoproteins contained in photoreceptor cells in their retinas. It is an open question whether this light-dependent mechanism could be sufficiently sensitive given the low-light levels experienced by nocturnal migrants. The scarcity of available photons results in significant uncertainty in the signal generated by the magnetoreceptors distributed around the retina. Here we use results from Information Theory to obtain a lower bound estimate of the precision with which a bird could orient itself using only geomagnetic cues. Our approach bypasses the current lack of knowledge about magnetic signal transduction and processing in vivo by computing the best-case compass precision under conditions where photons are in short supply. We use this method to assess the performance of three plausible cryptochrome-derived flavin-containing radical pairs as potential magnetoreceptors.
The Stokes equation system and Ohm's law were solved numerically for fluid in periodic bicontinuous porous media of simple cubic (SC), body-centred cubic (BCC) and face-centred cubic (FCC) symmetry. The Stokes equation system was also solved for fluid in porous media of SC arrays of disjoint spheres. The equations were solved by Galerkin's method with finite element basis functions and with elliptic grid generation. The Darcy permeability k computed for flow through SC arrays of spheres is in excellent agreement with predictions made by other authors. Prominent recirculation patterns are found for Stokes flow in bicontinuous porous media. The results of the analysis of Stokes flow and Ohmic conduction through bicontinuous porous media were used to test the permeability scaling law proposed by Johnson, Koplik & Schwartz (1986), which introduces a length parameter Λ to relate Darcy permeability k and the formation factor F. As reported in our earlier work on the SC bicontinuous porous media, the scaling law holds approximately for the BCC and FCC families except when the porespace becomes nearly spherical pores connected by small orifice-like passages. We also found that, except when the porespace was connected by the small orifice-like passages, the permeability versus porosity curve of the bicontinuous media agrees very well with that of arrays of disjoint and fused spheres of the same crystallographic symmetry.
The production of highly charged ions in a CO2
laser-generated plasma is compared for different laser pulse-time
structures. The work was performed at the CERN Laser Ion Source,
which has the aim of developing a high current, high charge-state
ion source for the Large Hadron Collider (LHC). When an intense
laser pulse is focused onto a high-Z metal target,
the ions expanding in the plasma plume are suitable for extraction
from the plasma and matching into a synchrotron. For the first
time, a comparison is made between free-running pulses with
randomly fluctuating intensity, and mode-locked pulse trains
with a reproducible structure and the same energy. Despite the
lower power density with respect to the mode-locked pulse train,
the free-running pulse provides higher charge states and higher
Twenty-four middle-aged healthy men were given a low-fat high-carbohydrate (5.5 g fat; L), or a moderately-fatty, (25.7 g fat; M) breakfast of similar energy contents for 28 d. Other meals were under less control. An oral glucose tolerance test (OGTT) was given at 09.00 hours on day 1 before treatment allocation and at 13.30 hours on day 29. There were no significant treatment differences in fasting serum values, either on day 1 or at the termination of treatments on day 29. The following was observed on day 29: (1) the M breakfast led to higher OGTT C-peptide responses and higher areas under the curves (AUC) of OGTT serum glucose and insulin responses compared with the OGTT responses to the L breakfast (P < 0.05); (2) treatment M failed to prevent OGTT glycosuria, eliminated with treatment L; (3) serum non-esterified fatty acid (NEFA) AUC was 59% lower with treatment L than with treatment M, between 09.00 and 13.20 hours (P <0.0001), and lower with treatment L than with treatment M during the OGTT (P = 0.005); (4) serum triacylglycerol (TAG) concentrations were similar for both treatments, especially during the morning, but their origins were different during the afternoon OGTT when the Svedberg flotation unit 20–400 lipid fraction was higher with treatment L than with treatment M (P = 0.016); plasma apolipoprotein B-48 level with treatment M was not significantly greater than that with treatment L (P = 0.086); (5) plasma tissue plasminogen-activator activity increased after breakfast with treatment L (P = 0.0008), but not with treatment M (P = 0.80). Waist:hip circumference was positively correlated with serum insulin and glucose AUC and with fasting LDL-cholesterol. Waist:hip circumference and serum TAG and insulin AUC were correlated with factors of thrombus formation; and the OGTT NEFA and glucose AUC were correlated. A small difference in fat intake at breakfast has a large influence on circulating diurnal NEFA concentration, which it is concluded influences adversely glucose tolerance up to 6 h later.
An experiment was conducted in twelve healthy middle-aged volunteers, six of each sex, with a mean BMI of 27kg/m2 to detect differences between morning and afternoon in postprandial blood glucose, insulin and C-peptide concentrations. These responses were measured following the consumption of isoenergetic meals that were high or low in fat content, at breakfast and at lunch. Over 4d each subject received the high-carbohydrate (L, 5·5 g mixed fat/meal) and moderately high-fat (M, 33 g mixed fat/meal) breakfasts and lunches, in three combinations (LL, MM, LM), or they fasted at breakfast time and received a moderately high-fat lunch (NM), in three Latin squares. Each evening a standard meal was given. Plasma glucose, insulin and C-peptide responses were greater following L than M meals and within both MM and LL treatments insulin and C-peptide responses were greater following breakfast than following lunch. The incremental C-peptide response to a fatty lunch following a fast at breakfast time (NM) was similar to that to a fatty breakfast, but the incremental insulin response for the same comparison was marginally lower at lunch (P=0·06). The relationship of C-peptide and insulin concentrations was assessed. Plasma glucose response to a fatty lunch was increased by a fatty breakfast. The relationships of these metabolic events with fat metabolism are discussed.
The lower part of the post-Variscan succession around Exeter,
south Devon, England, comprises some 800 m of breccias, with
subordinate sandstones and mudstones, which rest upon Devonian and
Carboniferous rocks folded during the Variscan Orogeny and are
overlain, disconformably, by the Aylesbeare Mudstone Group (Early
Triassic?). These deposits comprise the most westerly of the early
post-Variscan successions preserved onshore in northwest Europe and
lie to the south of the Variscan Deformation Front; they are assigned
to the Exeter Group (new term). Geochronological and palaeontological
studies, in conjunction with detailed geological mapping, show that
the constituent formations comprise a lower (Late
Carboniferous(?)–Early Permian) sequence separated from an
upper (Late Permian) sequence by an unconformity which represents an
hiatus with a duration of at least 20 m.y. The lower sequence
contains volcanic rocks dated at between 291 and 282 Ma (Early
Permian) and pre-dates intrusion of the nearby Dartmoor Granite (280
Ma). In the overlying, palynologically-dated, Late Permian sequence,
older breccias contain clasts of the Dartmoor Granite aureole rocks,
and younger ones contain clasts of that granite. The lower sequence
occurs mainly within the Crediton Trough, an east–west
trending, partly fault-bounded, sedimentary basin that probably
formed by extensional reactivation of a Variscan thrust. Breccias in
this sequence formed largely on alluvial fans; the common occurrence
of debris flows and a down-fan passage from gravity flows into
fluvially deposited sediments is typical of deposition on semi-arid
fans. The upper (Late Permian) sequence is more widespread but
includes similar deposits overlain, at the top of the Exeter Group,
by aeolian dune and interdune deposits. Correlation within the
laterally variable facies associations which comprise these sequences
has been achieved using a combination of sedimentary facies analysis,
sedimentary geochemistry, and petrographical and geochemical clast
typing. The stratigraphy revealed within the Exeter Group is broadly
comparable with that recognized in the early post-Variscan Rotliegend
successions elsewhere in Europe. This similarity may, however, be
deceptive; the upper part of the Exeter Group may be coeval with the
Zechstein, and apparently correlatable major unconformities in the
group and the Rotliegend may reflect different events in the Variscan
fold-belt and Variscan Foreland areas, respectively.
Three experiments were conducted in healthy middle-aged volunteers (six males and six females in Expt 1, six males and two females in Expt 2 and twelve males in Expt 3) with a mean BMI of 27 kg/m2 to determine whether there is a difference between morning and afternoon dietary fat clearance and utilization, and to determine in what way the fat and starch contents of the meal influence postprandial blood lipid metabolites over 4·5 h. Over 4 days in Expt 1 each subject received isoenergetic, high-carbohydrate (L, 5·5 g mixed fat/meal) and moderately high-fat (M, 33 g mixed fat/meal) breakfasts and lunches, in three combinations (LL, MM, LM), or they fasted at breakfast time and received a high fat lunch (NM) in a randomized and balanced arrangement. Each evening a standard meal was given. The following effects were significant (P<0·05): plasma triacylglycerol (TAG) responses were greater following M meals; plasma TAG concentrations were greater in the afternoon than in the morning, following two meals of the same composition, although the postprandial incremental response was less following lunch than following breakfast and peak responses were reached much earlier than after breakfast; a low-fat breakfast, or fasting at breakfast time, delayed the peak TAG response to a M lunch. The plasma concentrations of non-esterified fatty acids (NEFA) and of free glycerol were higher in the afternoon following M meals at breakfast and lunch, especially in males. This response was reduced, by the L breakfast preceding the M lunch. Two M meals in succession lowered plasma HDL-cholesterol concentration. In Expt 2 each subject received a very low-fat (VL) breakfast, followed by a lunch of the same composition. Each of these meals was followed, 110 min from the start of eating, by an infusion of Intralipid 10% emulsion at the rate of 1 ml/kg body weight over 60 s. Clearance rates of Intralipid were faster in the afternoon than in the morning (P= 0·024). In Expt 3 twelve subjects were randomly allocated to either treatment MM or LM meal patterns, as given in Expt 1. These were given daily for a period of 17 d, during which the change in fasting plasma TAG concentration was similar in both treatments. On days 1, 16 and 17 responses were measured to the M lunch and to a glucose tolerance test (GTT), conducted 2 h 17 min after lunch. The post-lunch responses confirmed those found in Expt 1; but immediately following the glucose dose there was an abrupt increase in plasma TAG that was greater in treatment LM than in treatment MM (P= 0·025), whereas plasma NEFA concentration decreased rapidly in both treatments at that time (P = 0·00066)
This paper describes the first results of a feasibility study undertaken at CERN to determine whether a laser-produced plasma can be used as a source of intense highly charged heavy ion beams. A variety of important measurements have been made, and the results are encouraging. Furthermore, a beam of highly charged light ions produced by the laser ion source has been accelerated successfully in a radio frequency quadrupole (RFQ) structure.
Polyethylene trisiloxane surfactants M(D′En)M (n=6, 8, 10, 12) self assemble into sheet-like structure and form various lyotropic cubic, hexagonal and lamellar liquid crystal phases in ternary trisiloxane surfactant - silicone oil - water systems. Small angle X-ray scattering (SAXS) was used to identify and characterize the liquid crystal phases. Cyclic octamethylcyclotetrasiloxane (D4), decamethyl-cyclopentasiloxane(D5) and short linear decamethyltetrasiloxane (MD2M) silicone oils facilitate the formation of liquid crystals. The structures in liquid crystals (LC) progress from zero curvature lamellar liquid crystals to higher curvature cubic liquid crystals with increasing the surfactant hydrophilic head group size. The effects of surfactant and oil concentration on the lamellar bilayer thickness and molecular packing were studied with small angle X-ray scattering.
Liquid and colloidal microstructures can be imaged at high resolution with cryo-TEM and cryo-SEM by fast-freezing with a Controlled Environment Vitrification System. Frozen bare-films can be directly imaged by TEM, while films sandwiched between metal plates can be frozen, fractured, and directly imaged with cryo-SEM or indirectly imaged by TEM after replication. We describe sample preparation techniques and report cryo-SEM studies of particle distributions and fracture patterns in such specimens.
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