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We consider the optimisation of the observing strategy (cadence, exposure time and filter choice) using medium size (2-m class) optical telescopes in the follow-up of kilonovae localised with arcminute accuracy to be able to distinguish among various kilonova models and viewing angles. To develop an efficient observation plan, we made use of the synthetic light curves obtained with the Monte Carlo radiative transfer code POSSIS for different kilonova models and as a function of different viewing angles and distances. By adding the appropriate photon counting noise to the synthetic light curves, we analysed four alternative sequences having the same total time exposure of 8 hours, with different time windows (0.5, 1, 2, 4 h), each with $i$, $r$, and $u$ filters, to determine the observing sequence that maximises the chance of a correct identification of the model parameters. We suggest to avoid $u$ filter and to avoid the use of colour curves. We also found that, if the error on distance is $\le$ 2%, 0.5, 1, 2-hour time window sequences are equivalent, so we suggest to use 2-hour one, because it has 1 day cadence, so it can be easily realised. When the distance of the source is unknown, 0.5 h time window sequence is preferable., Comment: 9 pages, 8 figures, published in MNRAS

Gamma-ray bursts (GRBs) are bright extragalactic flashes of gamma-ray radiation and briefly the most energetic explosions in the Universe. Their catastrophic origin (the merger of compact objects or the collapse of massive stars) drives the formation of a newborn compact remnant (black hole or magnetar) that powers two highly relativistic jets. To distinguish between magnetized and baryonic jet models and ultimately determine the power source for these energetic explosions, our team studies the polarization of the light during the first minutes after the explosion (using novel instruments on fully autonomous telescopes around the globe) to directly probe the magnetic field properties in these extragalactic jets. This technology allowed the detection of highly polarized optical light in GRB 120308A and confirmed the presence of mildly magnetized jets with large-scale primordial magnetic fields in a reduced sample of GRBs (e.g. GRB 090102, GRB 110205A, GRB 101112A, GRB 160625B). Here we discuss the observations of the most energetic and first GRB detected at very high TeV energies, GRB 190114C, which opens a new frontier in GRB magnetic field studies suggesting that some jets can be launched highly magnetized and that the collapse and destruction of these magnetic fields at very early times may have powered the explosion itself. Additionally, our most recent polarimetric observations of the jet of GRB 141220A indicate that, when the jetted ejected material is decelerated by the surrounding environment, the magnetic field amplification mechanisms at the front shock (needed to generate the observed synchrotron emission) produce small magnetic domains. These measurements validate theoretical expectations and contrast with previous observations that suggest large magnetic domains in collisionless shocks (i.e. GRB 091208B)., To appear in the Proceedings of the 16th Marcel Grossmann Meeting (July 5-10, 2021)

The contemporaneous detection of gravitational waves and gamma rays from GW170817/GRB 170817A, followed by kilonova emission a day after, confirmed compact binary neutron star mergers as progenitors of short-duration gamma-ray bursts (GRBs) and cosmic sources of heavy r-process nuclei. However, the nature (and life span) of the merger remnant and the energy reservoir powering these bright gamma-ray flashes remains debated, while the first minutes after the merger are unexplored at optical wavelengths. Here, we report the earliest discovery of bright thermal optical emission associated with short GRB 180618A with extended gamma-ray emission—with ultraviolet and optical multicolor observations starting as soon as 1.4 minutes post-burst. The spectrum is consistent with a fast-fading afterglow and emerging thermal optical emission 15 minutes post-burst, which fades abruptly and chromatically (flux density F ν ∝ t −α , α = 4.6 ± 0.3) just 35 minutes after the GRB. Our observations from gamma rays to optical wavelengths are consistent with a hot nebula expanding at relativistic speeds, powered by the plasma winds from a newborn, rapidly spinning and highly magnetized neutron star (i.e., a millisecond magnetar), whose rotational energy is released at a rate L th ∝ t −(2.22±0.14) to reheat the unbound merger-remnant material. These results suggest that such neutron stars can survive the collapse to a black hole on timescales much larger than a few hundred milliseconds after the merger and power the GRB itself through accretion. Bright thermal optical counterparts to binary merger gravitational wave sources may be common in future wide-field fast-cadence sky surveys.

The New Robotic Telescope (NRT) is an international collaboration to build and operate a 4m diameter fully robotic telescope. The telescope will take advantage of the superb atmospheric conditions at the Observatory of the Roque de los Muchachos (ORM). In conjunction with a large aperture, entirely robotic operation, quick response, and a set of versatile instrumentation in the optical and near-infrared this guarantees a high scientific impact focused mainly in the area of time domain astronomy. This paper presents the scientific motivation and the status of the project, discussing possible technical solutions under evaluation for the optics, mechanics and control system.

We present photometric and polarimetric measurements of gamma-ray burst (GRB) optical afterglows observed by the RINGO3 imaging polarimeter over its $\sim$7 year lifetime mounted on the Liverpool Telescope. During this time, RINGO3 responded to 67 GRB alerts. Of these, 28 had optical afterglows and a further ten were sufficiently bright for photometric and polarimetric analysis ($R\lessapprox{17}$). We present high quality multicolour light curves of ten sources: GRB 130606A, GRB 130610A, GRB 130612A, GRB 140430A, GRB 141220A, GRB 151215A, GRB 180325A, GRB 180618A, GRB 190114C, and GRB 191016A and polarimetry for seven of these (excluding GRB 130606A, GRB 130610A, and GRB 130612A, which were observed before the polarimetry mode was fully commissioned). Eight of these ten GRBs are classical long GRBs, one sits at the short-long duration interface with a $T_{90}$ $\sim$ 4 seconds and one is a classical short, hard burst with extended emission. We detect polarization for GRB 190114C and GRB 191016A. While detailed analyses of several of these GRBs have been published previously, here we present a uniform re-reduction and analysis of the whole sample and investigation of the population in a broad context relative to the current literature. We use survival analysis to fully include the polarization upper limits in the comparison with other GRB properties, such as temporal decay rate, isotropic energy and redshift. We find no clear correlation between polarization properties and wider sample properties and conclude that larger samples of early time polarimetry of GRB afterglows are required to fully understand GRB magnetic fields., 18 pages, 7 figures, Accepted for publication in MNRAS

The giant radio galaxy M 87, with its proximity (16 Mpc) and its very massive black hole ((3 - 6) \times 10^9 M_solar), provides a unique laboratory to investigate very high energy (E>100 GeV; VHE) gamma-ray emission from active galactic nuclei and, thereby, probe particle acceleration to relativistic energies near supermassive black holes (SMBH) and in relativistic jets. M 87 has been established as a VHE gamma-ray emitter since 2005. The VHE gamma-ray emission displays strong variability on timescales as short as a day. In 2008, a rise in the 43 GHz Very Long Baseline Array (VLBA) radio emission of the innermost region (core; extension of < 100 Rs ; Schwarzschild radii) was found to coincide with a flaring activity at VHE. This had been interpreted as a strong indication that the VHE emission is produced in the direct vicinity of the SMBH. In 2010 a flare at VHE was again detected triggering further multi-wavelength (MWL) observations with the VLBA, Chandra, and other instruments. At the same time, M 87 was also observed with the Fermi-LAT telescope at MeV/GeV energies, the European VLBI Network (EVN), and the Liverpool Telescope (LT). Here, preliminary results from the 2010 campaign will be reported., 6 pages, 2 figures; Procceedings of the workshop "High Energy Phenomena in Relativistic Outflows III" (HEPRO III), Barcelona, June 27 - July 1, 2011

We present a comprehensive multiwavelength temporal and spectral analysis of the FRED GRB 070419A. The early-time emission in the $\gamma$-ray and X-ray bands can be explained by a central engine active for at least 250 s, while at late times the X-ray light curve displays a simple power-law decay. In contrast, the observed behaviour in the optical band is complex (from 10$^2$ up to 10$^6$ s). We investigate the light curve behaviour in the context of the standard forward/reverse shock model; associating the peak in the optical light curve at $\sim$450 s with the fireball deceleration time results in a Lorenz factor $\Gamma \approx 350$ at this time. In contrast, the shallow optical decay between 450 and 1500 s remains problematic, requiring a reverse shock component whose typical frequency is above the optical band at the optical peak time for it to be explained within the standard model. This predicts an increasing flux density for the forward shock component until t $\sim$ 4 $\times$ 10$^6$ s, inconsistent with the observed decay of the optical emission from t $\sim$ 10$^4$ s. A highly magnetized fireball is also ruled out due to unrealistic microphysic parameters and predicted light curve behaviour that is not observed. We conclude that a long-lived central engine with a finely tuned energy injection rate and a sudden cessation of the injection is required to create the observed light curves - consistent with the same conditions that are invoked to explain the plateau phase of canonical X-ray light curves of GRBs., Comment: 9 pages, 10 figures, accepted for publication in MNRAS

The 2 m robotic Liverpool Telescope reacted promptly to the gamma-ray burst GRB 050502a, discovered by INTEGRAL, and started observing 3 minutes after the onset of the burst. The automatic identification of a bright afterglow with r' ~ 15.8 mag triggered, for the first time, an observation sequence in the BVr'i' filters during the first hour after a GRB. Observations continued for ~1 day using the RoboNet-1.0 network of 2 m robotic telescopes. The light curve in all filters can be described by a simple power law with index of 1.2 ± 0.1. We find evidence for a bump rising at t ~ 0.02 days in all filters. From the spectrum and the light curve, we investigate different scenarios and find possible evidence for a uniform circumburst medium with clumps in density, as in the case of GRB 021004. Other interpretations of such bumps, such as the effect of energy injection through refreshed shocks or the result of a variable energy profile, are less favored. The optical afterglow of GRB 050502a is likely to be the result of slow electron cooling, with the optical bands lying between the synchrotron peak frequency and the cooling frequency.

The crystal structure of barstowite (3PbCl2·PbCO3·H2O, P21/m, a = 4.2023(5), b = 9.2020(7), c = 16.6608(6)(Å), β = 91.829(9)°) from Bounds Cliff, St Endellion, Cornwall, has been determined to an R = 0.036. The structure can be described in terms of three layers stacked along [001] in the sequence …CACBCACBC… to give a 16.7 Å repeat. Layer A consists of face-sharing PbCl8 distorted square antiprisms. Layer B is composed of Pb coordinated to 5 Cl and 2 O each with two H to form H2O groups. Layer C is formed by Pb coordinated to 5 Cl and 3 O which are from CO3 groups. The H positions are deduced and are H-bonded to O from carbonates. The structural details were in agreement with previous deductions based on infrared spectra.

BACKGROUND—Resection is the treatment of choice for lung cancer, but may cause impaired cardiopulmonary function with an adverse effect on quality of life. Few studies have considered the effects of thoracotomy alone on lung function, and whether the operation itself can impair subsequent exercise capacity. METHODS—Patients being considered for lung resection (n = 106) underwent full static and dynamic pulmonary function testing which was repeated 3-6 months after surgery (n =53). RESULTS—Thoracotomy alone (n = 13) produced a reduction in forced expiratory volume in one second (FEV1; mean (SE) 2.10 (0.16) versus 1.87 (0.15) l; p

Background Patients with acute cardiac failure have excess body water, and it is commonly assumed that this is also so in patients with stable chronic cardiac failure (CCF). Methods To investigate this, we measured total body water (TBW) using stable isotope dilution and single-frequency bioelectrical impedance (BIA), and also extracellular volume (ECV) using bromide dilution in 12 patients with CCF and eight matched control subjects. Results TBW (kg−1 body weight) was similar in the two groups [median 18O dilution 53.2% (range 46.5–57.1%) in patients vs. 54.8% (47.9–62.7) in control subjects; BIA 56.6% (42.7–73.1) vs. 58.0% (52.0–68.6)]. ECV was also similar in the two groups [0.25 L kg−1 (0.20–0.29) vs. 0.25 (0.19–0.35)]. There was a strong correlation between stable isotope and BIA measurements of TBW for all subjects (r = 0.76), but BIA overestimated TBW by a mean difference of 2.4 kg (limits of agreement of –4.1 kg to +8.9 kg). Body fat content was similar in the two groups, whether measured by skinfold anthropometry, whole-body densitometry or by 18O dilution. Resting energy expenditure (REE), calculated from indirect calorimetry, and total energy expenditure (TEE), calculated from the ratio of 2H to 18O elimination rate after drinking doubly labelled water, were also similar in the two groups. Conclusion It is concluded that the patients with stable CCF in this study had normal ECV and TBW, and so excess body water did not account for their persistent symptoms.

OBJECTIVE The hemodynamic, respiratory, and metabolic responses to exercise were studied in IDDM patients and control subjects to detect diabetic cardiomyopathy. RESEARCH DESIGN AND METHODS Eight subjects aged 25–40 years with diabetes of at least 10 years' duration were compared with eight control subjects aged 21–46 years. All subjects underwent a progressive incremental bicycle exercise test with measurement of gas exchange, blood glucose, lactate, fat metabolite, and catecholamine levels and two steady-state exercise tests with measurement of cardiac output by a CO2 rebreathing method. A new first-pass radionuclide method was used to measure cardiac ejection fractions (EFs) at rest, peak exercise, and steady-state exercise. RESULTS The peak achieved oxygen consumption was similar in the diabetic and control subjects (29.9 [25.1–34.6] and 31.4 [26.9–35.9] ml . min−1 . kg−1, respectively; mean [95% CI]). There were no significant differences in heart rate, double product, ventilation, respiratory exchange ratio, or ventilatory equivalents for oxygen and CO2 during the incremental test. Glucose levels were higher in the diabetic subjects, but there were no significant differences in levels of lactate, catecholamines, free fatty acids, glycerol, or β-hydroxybutyrate. Left ventricular EF fell from rest to peak exercise within the diabetic group (66.0% [59.6–72.4] at rest; 53.6% [45.6–61.6] at peak; P < 0.05) but this did not differ significantly from the control group (58.7% [52.3–65.1] at rest; 60.3% [48.9–71.7] at peak). Right ventricular EFs were similar in each group, and there was no reduction in peak filling rate to suggest diastolic dysfunction. The cardiac output responses to exercise were also similar in the two groups. CONCLUSIONS There is no evidence of impairment of the exercise response in subjects with long-standing diabetes, and the apparent fall in left ventricular EF at peak exercise could be related to hemodynamic adaptation.

Peripheral circulating levels of atrial natriuretic peptide may exhibit short-term variation compatible with a pulsatile pattern of secretion. We obtained samples every 2 min for 90 min from the antecubital vein of 16 patients with chronic cardiac failure and 13 controls. Overall levels were higher in the patients (median and quartiles 230 (125,325) vs. 26 (16,48) ng l-1; P0.001). In both groups there was considerable variability, with 10 (2-12) peaks, 9 (7-15) troughs (both defined as2 SD from the mean) and 16 (13-18) pulses (defined by computer) during the sampling period in controls, and a similar number in patients. We then carried out simultaneous sampling in the pulmonary artery, femoral artery and peripheral vein in eight subjects with normal cardiac function and six patients with impaired function due to valvular heart disease. The pattern of variability was preserved in all three sites in both groups, suggesting intermittent secretion rather than variable breakdown of the peptide in the lung. No changes in right atrial pressure or heart rate were observed to coincide with the variations, but levels of the peptide in the pulmonary artery correlated with right atrial pressure in patients (r = 0.87; P0.05). The mechanism of such periodicity and its pathophysiological importance remain unknown.

Cardiac output was measured in 11 patients undergoing routine cardiac catheterization using a carbon dioxide rebreathing technique and compared with cardiac output measured by direct Fick and thermodilution. The carbon dioxide rebreathing technique gave consistently lower values for cardiac output than the other two methods (mean difference −0·73, 95% CI −0·95 to−0·511. min−1 with the direct Fick and −0·72. 95% CI −1·19 to −0·261. min−1 with thermodilution). The direct Fick and thermodilution methods gave similar results (mean dtfference −0·08, 95% CI −0·32 to 0·16a. min−1). Cardiac output was also measured in 10 healthy subjects at rest and during two steady-state levels of exercise using the carbon dioxide rebreathing technique. Measurements were made in triplicate on 3 separate days. The technique gave reproducible results between replicates at rest (coefficient of variation 91%) and became more reproducible on exercise (coefficients of variation 56% and 54% respectively at each exercise level). There was a good correlation between cardiac output and oxygen consumption (r=0·98 The carbon dioxide rebreathing technique is a feasible non-invasive way of measuring cardiac output. It tends to underestimate cardiac output at rest but is reproducible and becomes more so on exercise which is where it should be of most value.

During normal progressive exercise, the gas exchange anaerobic threshold occurs when CO2 production (VCO2) and ventilation (VE) increase so as to depart from a linear relationship to O2 consumption (VO2). This is thought to represent a gas exchange response to metabolic acidosis due to lactate accumulation. Patients with McArdle's disease have previously been reported to exhibit a steepened ventilatory response relative to VCO2, despite an inability to produce lactate. However, the VCO2 response has not been studied. We therefore investigated the VCO2-VO2 and VE-VO2 relationships in seven McArdle's disease patients and seven control subjects during symptom-limited maximal treadmill exercise. Analysis of gas exchange showed that whereas all control subjects had an easily identifiable anaerobic threshold, four of the patients had none and the other three displayed an attenuated threshold. The occurrence of the threshold in one patient was associated with a small rise in lactate and in another patient with an abrupt rise in leg discomfort, suggesting a pain response. Ammonia and the purine metabolite hypoxanthine were elevated during exercise in all patients, suggesting that ammonia may be a product of adenosine monophosphate degradation. Free fatty acid levels were also elevated, and a shift toward utilization of lipid may contribute to abnormal gas exchange responses. It is concluded that lactic acidosis contributes to the gas exchange anaerobic threshold but that other factors, such as discomfort, may be involved in the excess Ve seen during heavy exercise.

Using a new, comprehensive multiwavelength survey of 63 Gamma Ray Bursts (GRBs) with unprecedented temporal coverage, we classify the observed afterglows into four main classes and discuss the underlying physics that can explain them. The presence or absence of temporal breaks in X‐ray and optical bands is used to examine the emission in the context of the standard model; a number of GRBs are shown to deviate from the forward shock model even with the inclusion of energy injection or ambient density gradients. We show that additional emission in the early‐time X‐ray afterglow due to late‐time central engine activity is key and may explain both GRBs whose afterglows do not fit the standard model and those GRBs that appear to be optically dark even at early times.

The crystal structure of a novel variety {[(Mg0.81Fe0.19)(H2O)6](H2O)4}{(UO2)[(P0.67As0.33)O4]}2 of the mineral saleeite is determined using X-ray diffraction (Bruker Smart diffractometer, λMoKα, graphite monochromator, 2θmax = 56.62°, R = 0.0321 for 2317 reflections, T = 100 K). The main crystal data are as follows: a = 6.952(6) A, b = 19.865(5) A, c = 6.969(2) A, β = 90.806(4)°, space group P121/n1, Z = 2, and ρcalcd = 3.34 g/cm3. It is shown that the structure is formed by alternating (along the [010] direction) anionic layers, which are composed of uranium bipyramids and T(P,As) tetrahedra, and cation layers consisting of M(Mg,Fe) octahedra and water molecules, which are joined through a system of asymmetric hydrogen bonds. The hydrogen atoms are located, the scheme of hydrogen bonds is established, and their geometric characteristics are calculated.

Patients with acute cardiac failure have excess body water, and it is commonly assumed that this is also so in patients with stable chronic cardiac failure (CCF).To investigate this, we measured total body water (TBW) using stable isotope dilution and single-frequency bioelectrical impedance (BIA), and also extracellular volume (ECV) using bromide dilution in 12 patients with CCF and eight matched control subjects.TBW [kg(-1) bodyweight] was similar in the two groups [median 18O dilution 53.2% (range 46.5-57.1%) in patients vs. 54.8% (47.9-62.7) in control subjects; BIA 56.6% (42.7-73.1) vs. 58.0% (52.0-68.6)]. ECV was also similar in the two groups [0.25 Lkg(-1) (0.20-0.29) vs. 0.25 (0.19-0.35)]. There was a strong correlation between stable isotope and BIA measurements of TBW for all subjects (r = 0.76), but BIA overestimated TBW by a mean difference of 2.4 kg (limits of agreement of -4.1 kg to +8.9 kg). Body fat content was similar in the two groups, whether measured by skinfold anthropometry, whole-body densitometry or by 18O dilution. Resting energy expenditure (REE), calculated from indirect calorimetry, and total energy expenditure (TEE), calculated from the ratio of 2H to 18O elimination rate after drinking doubly labelled water, were also similar in the two groups.It is concluded that the patients with stable CCF in this study had normal ECV and TBW, and so excess body water did not account for their persistent symptoms.

1. The role of cardiac output limitation in the pathophysiology of exercise in patients with chronic failure remains undefined. During steady-state submaximal exercise, oxygen uptake is similar in patients and control subjects, but it is not known if cardiac output is also similar. We wished to determine if the reduced exercise tolerance of patients with chronic cardiac failure during such exercise is related to reduced cardiac output, or to peripheral factors. 2. Ten male patients with stable chronic failure and ten age-matched male normal controls were studied at rest and during exercise. Each subject performed a familiarization exercise test, a symptom-limited maximal exercise test and two submaximal exercise tests. Cardiac output was measured by a carbon dioxide rebreathing method. We also measured oxygen consumption, ventilation, Borg score of perceived exertion and venous lactate concentration, and ejection fractions. 3. As expected, patients had lower peak oxygen consumption [median (range) 1.18 (0.98–1.76) versus 1.935 (1.53–2.31) 1/min; P < 0.001], lower peak venous lactate concentration but a similar overall level of perceived exertion. At the same submaximal workload, patients and control subjects had similar oxygen consumption [0.67 (0.59–0.80) versus 0.62 (0.52–0.82) 1/min] and cardiac output [6.92 (5.79–9.76) versus 7.3 (5.99–10.38) 1/min] but the patients had a greater perceived level of exertion [Borg score: 4 (1–6) versus 3 (1–5); P < 0.005], higher venous lactate concentration [1.6 (1–3.3) versus 1.14 (0.7–1.7) mmol/l; P < 0.05] and higher heart rate [106 (89–135) versus 87 (69–112) beats/min;P < 0.005]. 4. During submaximal exercise at a similar absolute workload, patients with cardiac failure have a similar oxygen uptake and cardiac output but greater anaerobiosis and increased fatigue when compared with normal subjects. These findings appear to relate predominantly to changes that occur in the periphery rather than abnormalities of central cardiac function.

Atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) are known to be elevated in patients with chronic heart failure at rest. While it is known that during exercise the circulating level of ANP increases in patients with heart failure, the response of BNP to exercise in these patients relative to control subjects is unclear. Ten patients with stable chronic heart failure and 10 normal control subjects performed symptom-limited exercise with respired gas analysis. All patients had depressed left ventricular ejection fractions (LVEF). Patients had lower peak oxygen consumption PVo 2 ) than the control group [median (range) 1.18 (098-1.76) vs. 1.94 (1.53-2.31) L min -1 ; P < 0.001]. Circulating plasma levels of ANP and BNP were higher at rest in patients than in control subjects [ANP 335 (140-700) vs. 90 (25-500) pg mL -1 ; BNP 42 (25-50) vs. 20 (10-20) pg mL -1 ], and at peak exercise [ANP 400 (200-1000) vs. 130 (10-590); BNP 46 (40-51) vs. 20 (10-30)]. The rise in ANP at peak exercise was significant in patients compared with the resting level, but not in control subjects. For BNP, there was a significant rise in patients but no change in control subjects. The circulating plasma levels of both peptides showed a strong negative correlation with LVEF (ANP, P < 0.005; BNP, P < 00001) and, to a less extent, with RVEF. It is possible that BNP may give a better indication of cardiac function.

Elevated tumour necrosis factor (TNF- ) has been demonstrated in chronic cardiac failure (CCF) and may relate to severity of CCF and development of cachexia. We measured TNF receptor p55 in addition to TNF- in an attempt to improve the detection rate of TNF- activation, and simultaneously measured inter- leukin 6 (IL-6), interleukin 8 (IL-8) and C-reactive protein. Thirty-four patients with CCF and 24 control subjects were studied. Only TNF receptor p55 (6 . 95 (0 . 77 42 . 3) vs. 5 . 52 (1 . 50 13 . 36) ng mL 1 (median (range)) and IL-6 (0 . 335 (0 9 . 79) vs. 0 (0 14 . 71) pg mL 1 ) were significantly elevated in patients com- pared with control subjects (both P

Numerous hormonal and neuroendocrine changes have been described in patients with chronic cardiac failure. These affect the balance of vasodilator and vasoconstrictor factors in favour of the latter, to the detriment of the circulation. Whether this is a reaction to central cardiac (haemodynamic) abnormalities, or is an integral part of the syndrome of heart failure, remains to be determined. Catecholamine levels are increased, especially in severe heart failure, and contribute to the vasoconstriction and probably also to lethal ventricular arrhythmias. The renin-angiotensin-aldosterone system (RAAS) is also activated, causing fluid retention and further vasoconstriction. In the earlier stages, some of this increase may be iatrogenic due to the use of loop diuretics or inhibitors of angiotensin converting enzyme, but there is evidence for independent RAAS activation in more severe grades of heart failure. The role of vasoconstrictor peptides such as neuropeptide Y and endothelin is briefly considered. Counterbalancing these are vasodilator peptides, in particular atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP). The possibility of therapeutic interventions to increase circulating natriuretic hormone levels is discussed.

After the firm establishment of the English Atlantic colonies, and before the emergence of ‘the American identity’, these provinces participated with the metropolis in a political and economic ‘empire’. If ‘empire’ might be challenged as conveying too much political or economic meaning, it might also be challenged as conveying too little social meaning. Was the English Atlantic at the opening of the eighteenth century a civilization, a culture, a society, or a community? Though these terms are maddeningly ill-defined and somewhat interchangeable, they are suggested here as a scale of increasing social cohesiveness, from a relationship that is primarily inherited and parallel (civilization, culture) to a connexion that is primarily based upon the sharing of current ideas, institutions and interests (society, community). One essential pre-requisite for such sharing is a network of communications judged adequate by the people using it.

The textures and chemistry of silicates and oxides were investigated for 63 rocks from the Fiskenæsset complex, West Greenland, by light microscopy and electron microprobe analysis. Emphasis was placed on those chemical distributions known to depend on temperature.Photomicrographs are given for the following intergrowths: spinel-magnetite, chromite-rutile, Cr-magnetite-Al-chromite. Magnetite occurs dispersed throughout Fe-bearing silicates, probably the result of oxidation. Chromite grains in chromitites commonly have a centre rich in inclusions of rutile and amphibole and a clean margin; partial recrystallization of the chromite followed by metamorphic equilibration to give a uniform composition from core to rim is indicated. Magnetite associated texturally with sulphides is Cr-free, and apparently results from oxidation.Coexisting spinels outline a solvus between (Fe, Mg)Fe2O4 and (Fe, Mg)Al204 which has a critical point near (Mg, Fe)(Fe0.6Al0.6 Cr0.8)O4. The wide tie-lines for Cr-poor specimens indicate equilibration below 500°C.Coexisting ilmenite and ferromagnesian silicates apparently equilibrated in most rocks near 650 ± ∽100°C, but in ones with late serpentine or tremolite, equilibration was probably below ∽425°C. Coexisting pyroxenes apparently equilibrated at higher temperatures, either near 700 or 850°C depending on which laboratory calibration is used. The Cr-rich spinels from the Fiskenæsset complex are lower in Mg than ones from dry basaltic stratiform complexes, and other chemical features lead to a distinctive composition range as proposed by Ghisler. Further data for the silicates confirm most of the observations and conclusions in Part II, but (a) five specimens were found to contain tremolite apparently in compositional equilibrium with hornblende, (b) highly calcic plagioclase does not necessarily coexist with chromite as was proposed in Part II, (c) some specimens with unusually sodic plagioclase and unusually Fe-rich silicates may represent a cryptic differentiation trend. Although many problems remain for further study, the silicates and oxides are interpreted as the variously metamorphosed products in the granulite, amphibolite or greenschist facies of a moderately wet AI-rich basaltic magma which underwent crystal-liquid differentiation under fairly oxidizing conditions. The original igneous assemblage apparently involved early precipitation of Mg-AI-Ti-Cr-magnetite, prolonged crystallization of highly calcic plagioclase and tschermakitic-magnesiohornblende, and late crystallization of high-Fe, medium-Cr spinel.

(1980). The empire and provincial elites: An interpretation of some recent writings on the English Atlantic, 1675–1740. The Journal of Imperial and Commonwealth History: Vol. 8, The British Atlantic Empire Before the American Revolution, pp. 2-32.

The sol gel sol transformation of aqueous K-carrageenan occurs with complex changes in optical rotation which may be explained qualitatively in terms of the double helix model for junction zones. Evidence is given that the double helices in the gel are normally aggregated but can be kept separate within a narrow temperature range, and that gelation is a kinetic rather than an equilibrium process. An attempt has been made to predict the preferred conformations of irregular carrageenans by joining segments of simpler polysaccharides; the effect of certain structural variations on gel properties may then be explained. Model building in the computer does not exclude the possibility of double helices for the following polysaccharides which are structurally related to K- and i-carrageenan: hyaluronic acid, chondroitin, chondroitin 4-sulfate, chondroitin 6-sulfate, dermatan sulfate, keratan sulfate, agarose, porphyran, μ-carrageenan and furcellaran.