Search

Ionized nebulae provide critical insights into the conditions of the interstellar medium (ISM). Their bright emission lines enable the measurement of physical properties, such as the gas-phase metallicity, across galaxy disks and in distant galaxies. The PHANGS--MUSE survey has produced optical spectroscopic coverage of the central star-forming discs of 19 nearby main-sequence galaxies. Here, we use the H{\alpha} morphology from this data to identify 30,790 distinct nebulae, finding thousands of nebulae per galaxy. For each nebula, we extract emission line fluxes and, using diagnostic line ratios, identify the dominant excitation mechanism. A total of 23,244 nebulae (75%) are classified as HII regions. The dust attenuation of every nebulae is characterised via the Balmer decrement and we use existing environmental masks to identify their large scale galactic environment (centre, bar, arm, interarm and disc). Using strong-line prescriptions, we measure the gas-phase oxygen abundances (metallicity) and ionization parameter for all HII regions. With this new catalogue, we measure the radial metallicity gradients and explore second order metallicity variations within each galaxy. By quantifying the global scatter in metallicity per galaxy, we find a weak negative correlation with global star formation rate and stronger negative correlation with global gas velocity dispersion (in both ionized and molecular gas). With this paper we release the full catalogue of strong line fluxes and derived properties, providing a rich database for a broad variety of ISM studies., Comment: 27 pages, accepted by MNRAS

Analyzing resolved stellar populations across the disk of a galaxy can provide unique insights into how that galaxy assembled its stellar mass over its lifetime. Previous work at ~1 kpc resolution has already revealed common features in the mass buildup (e.g., inside-out growth of galaxies). However, even at approximate kpc scales, the stellar populations are blurred between the different galactic morphological structures such as spiral arms, bars and bulges. Here we present a detailed analysis of the spatially resolved star formation histories (SFHs) of 19 PHANGS-MUSE galaxies, at a spatial resolution of ~100 pc. We show that our sample of local galaxies exhibits predominantly negative radial gradients of stellar age and [Z/H], consistent with previous findings, and a radial structure that is primarily consistent with local star formation, and indicative of inside-out formation. In barred galaxies, we find flatter [Z/H] gradients along the semi-major axis of the bar than along the semi-minor axis, as is expected from the radial mixing of material along the bar. In general, the derived assembly histories of the galaxies in our sample tell a consistent story of inside-out growth, where low-mass galaxies assembled the majority of their stellar mass later in cosmic history than high-mass galaxies. We also show how stellar populations of different ages exhibit different kinematics, with younger stellar populations having lower velocity dispersions than older stellar populations at similar galactocentric distances, which we interpret as an imprint of the progressive dynamical heating of stellar populations as they age. Finally, we explore how the time-averaged star formation rate evolves with time, and how it varies across galactic disks. This analysis reveals a wide variation of the SFHs of galaxy centers and additionally shows that structural features become less pronounced with age., 52 pages, 48 figures, accepted for publication in A&A

We present new HCN and HCO$^+$ ($J$=3-2) images of the nearby star-forming galaxies (SFGs) NGC 3351, NGC 3627, and NGC 4321. The observations, obtained with the Morita ALMA Compact Array, have a spatial resolution of $\sim$290-440 pc and resolve the inner $R_\textrm{gal} \lesssim$ 0.6-1 kpc of the targets, as well as the southern bar end of NGC 3627. We complement this data set with publicly available images of lower excitation lines of HCN, HCO$^+$, and CO and analyse the behaviour of a representative set of line ratios: HCN(3-2)/HCN(1-0), HCN(3-2)/HCO$^+$(3-2), HCN(1-0)/CO(2-1), and HCN(3-2)/CO(2-1). Most of these ratios peak at the galaxy centres and decrease outwards. We compare the HCN and HCO$^+$ observations with a grid of one-phase, non-local thermodynamic equilibrium (non-LTE) radiative transfer models and find them compatible with models that predict subthermally excited and optically thick lines. We study the systematic variations of the line ratios across the targets as a function of the stellar surface density ($\Sigma_\textrm{star}$), the intensity-weighted CO(2-1) ($\langle I_\text{CO}\rangle$), and the star formation rate surface density ($\Sigma_\text{SFR}$). We find no apparent correlation with $\Sigma_\text{SFR}$, but positive correlations with the other two parameters, which are stronger in the case of $\langle I_\text{CO}\rangle$. The HCN/CO-$\langle I_\text{CO}\rangle$ relations show $\lesssim$0.3 dex galaxy-to-galaxy offsets, with HCN(3-2)/CO(2-1)-$\langle I_\text{CO}\rangle$ being $\sim$2 times steeper than HCN(1-0)/CO(2-1). In contrast, the HCN(3-2)/HCN(1-0)-$\langle I_\text{CO}\rangle$ relation exhibits a tighter alignment between galaxies. We conclude that the overall behaviour of the line ratios cannot be ascribed to variations in a single excitation parameter (e.g. density or temperature)., Comment: Accepted for publication in A&A. 14 pages, 8 figures

One of the fundamental factors regulating the evolution of galaxies is stellar feedback. However, we still do not have strong observational constraints on the relative importance of the different feedback mechanisms (e.g. radiation, ionised gas pressure, stellar winds) in driving HII region evolution and molecular cloud disruption. In this letter, we constrain the relative importance of the various feedback mechanisms from young massive star populations by resolving HII regions across the disk of the nearby star-forming galaxy NGC 1672. We combine measurements of ionised gas nebular lines obtained by PHANGS-MUSE, with high-resolution imaging from the HST in both the narrow-band H{\alpha} and broad-band filters. We identify a sample of 40 isolated, compact HII regions in the HST H{\alpha} image, for which we measure the sizes that were previously unresolved in seeing-limited ground-based observations. Additionally, we identify the ionisation source(s) for each HII region from catalogues produced as part of the PHANGS-HST survey. We find that the HII regions investigated are mildly dominated by thermal or wind pressure, yet their elevation above the radiation pressure is within the expected uncertainty range. We see that radiation pressure provides a substantially higher contribution to the total pressure than previously found in the literature over similar size scales. In general, we find higher pressures within more compact HII regions, which is driven by the inherent size scaling relations of each pressure term, albeit with significant scatter introduced by the variation in the stellar population properties (e.g. luminosity, mass, age, metallicity). For nearby galaxies, here we provide a promising approach that could yield the statistics required to map out how the importance of different stellar feedback mechanisms evolve over the lifetime of an HII region., Comment: 5(+4) pages, 6 figures, 1 table (available online), accepted for publication in A&A Letters

As previously described, the absolute rate of photosynthesis due to a limited concentration of dissolved inorganic carbon at alkaline pH, where the rate of CO2 formation is strictly limited, plotted as a function of chlorophyll (Chl) concentration, will take the form of a rectangular hyperbola combined with a linear rate directly proportional to [Chl], which are, respectively, due to the contribution of CO2 and HCO3– to photosynthesis. This model represents that the mathematical asymptote of absolute rate of photosynthesis versus cell density is described by the whole-cell rate constant for HCO3– uptake and the maximum rate of CO2 formation in the extracellular space. This means that any trace modification of the CO2 formation rate outside the cell will alter the photosynthetic rate and should be detectable experimentally. In air-grown Chlorella ellipsoidea and C. kessleri and in high CO2-grown C. saccharophila, the graph of the absolute rate of photosynthesis against [Chl] clearly followed the mathematical model described above and the actual CO2 formation rates outside the cells were not significantly different from the calculated rates. It also indicated that the whole-cell rate constants for CO2 and HCO3– uptake in air-grown C. ellipsoidea and C. saccharophila were similar at ≈ 300 and 2·0 mm3μg–1 Chl min–1, respectively, whereas those in air-grown C. kessleri were ≈ 550 and 15 mm3μg–1 Chl min–1. These results indicate that no acidification of the periplasmic space occurs, and there is no trace activity of external carbonic anhydrase in these microalgae.

A mechanistic model has been used to examine the environmental regulation of photosynthetic gas exchange in moss. The effects of water content on conductance to CO 2 and on photosynthetic capacity during desiccation were calculated from the carbon isotope discrimination data of Williams & Flanagan (1996, Oecologia 108, pp. 38-46) and combined with the biochemical model of Farquhar et al. (1980, Planta 149, pp. 78-90). The model includes a simple light attenuation function that imparts curvature to the light response curve for net assimilation, enabling the use of physiologically realistic values for the biochemical parameters. Measurements of gas exchange for Sphagnum and Pleurozium were made in an old black spruce ecosystem over a growing season in order to assign values to parameters in the model. The calculated maximum rates of carboxylation by Rubisco (V max ) were 5, 14 and 6 μmol m -2 s -1 for Sphagnum during the spring, summer and autumn seasons of 1996, respectively. The increase in V max during the summer was consistent with an increased allocation of resources to the photosynthetic apparatus. In contrast, no seasonal variation in V max was observed in Pleurozium with average values of 7, 5 and 7 μmol m -2 s -1 during the spring, summer and autumn, respectively.

External carbonic anhydrase (CA) activity in Chlorella saccharophila is suppressed by growth at high dissolved inorganic carbon and at acid pH. External CA activity was shown to be suppressed by growth at pHs below 7.0, with total repression at pH5.0. Growth in the presence of the buffer 3-[N-Morpholino]propane-sulphonic acid (MOPS) between pH 7 and 8 suppressed CA activity. Cells grown at pH8.0 aerated at 6 dm3 h−1 exhibited external CA activity of 5 units mg−1 Chl once the dissolved inorganic carbon (DIC) was reduced to 300 mmol m−3, and this increased to 30 units mg−1 Chl over a period of 3d while the DIC dropped to 30mmol m−3. Cells aerated at 180 dm3 h−1 showed a similar trend in CA activity, although the onset was delayed by 1 d and the DIC did not drop below 300 mmol m−3. Cells grown at pH 7.8 near an air equilibrium DIC of 300 mmol m−3had no detectable external CA activity. It is probable that it is the CO2 supply to the cell, and not total DIC or HCO−3 which controls external CA activity. Cells grown at pH 5.0 had no detectable activity, although they reduced the CO2 concentration to 0.6 mmol m−3. The loss of CA upon transfer of air-grown cells to 10 mmol mol−1 CO2 took place over 48 h and was light dependent, while the loss upon transfer from alkaline pH to acid pH look place over 12 h and was independent of light. The effects of pH are independent of the response to CO2.

The effects of conventional, bole only harvesting (CH) and whole-tree harvesting (WTH) on major inorganic nutrient concentrations (K, NO3-N, NH4-N, PO4-P and Ca) in soil water are described from Beddgelert forest in North Wales. Monitoring of nutrient leaching losses, and the timing thereof, from brash through the soil and into streams draining the CH areas allowed assessments to be made of the value of brash as a nutrient source for second rotation crops. Most of the K (around 100 kg ha-1) and one-third of the P (10 out of 30 kg ha-1) leached out of the brash lying on the CH plots within one year of felling. A pulse of K passed through the soil profile, but less than half this K reached the streams. In contrast, the P was immobilized in the soil. The lack of brash resulted in the absence of K and P pulses on the WTH plots. On the CH plots, brash was a net sink for inorganic-N for 3 years after felling. However, in both CH and WTH, a pulse of nitrate was observed in the soil and also in streams draining CH areas. The source of this nitrate may have been death of fine tree roots, followed by rapid mineralization and nitrification. Calculation of a nutrient budget for a complete crop rotation indicates that P and Ca losses in harvested material are likely to result in long-term depletion of these elements, and that the effects will be significantly more severe if WTH is practised.

This paper describes the case of an industrial radiographer who was seriously overexposed to gamma radiation. The exact circumstances of this exposure were not established but it was concluded that he was repeatedly irradiated probably to a total average whole body dose of at least 10 Gy over several years. Also, a much larger dose to a hand required its partial amputation. He developed myelodysplasia, which progressed to acute myeloid leukaemia from which he died. Karyotypic examination of the leukaemic blasts showed changes very similar to those associated with secondary leukaemia that may develop after radio or chemotherapy. The paper describes his medical case history, the investigation of his workplace, and the attempts to estimate his radiation dose by chromosomal analysis of blood lymphocytes and electron spin resonance of dental enamel and bone.

The influence of forest development on soil solution and surface drainage water aluminium chemistry was investigated in Sitka spruce (Picea sitchensis) plantations in Wales. Comparisons with semi-natural grassland and moorland sites are described. A highly significant positive relationship was shown between increasing forest age and soilwater aluminium concentrations in the B horizons. Shortterm/episodic peaks in Al concentrations were strongly related to incidences of high concentrations of neutral, marine-derived, salts in the soilwater. Nitrification may be an important factor in soil acidification and the mobilization of Al in soilwaters beneath the older mature-forest plantations in Wales. Labile monomeric Al concentrations were largest in surface waters draining the oldest forestry plantations compared with younger forest catchments and moorland, although response to discharge of soilwater acidity to the surface waters at individual sites was dependent on the acid neutralizing capacity of the groundwater component of the surface waters.

External carbonic anhydrase (CA) was detected in whole cells of alkaline-grown Chlorella saccharophila but was suppressed by growth at acid pH or growth on elevated levels of CO2. Internal CA activity was measured potentiometrically as an increase in activity in cell extracts over that of intact cells. Cells grown under all conditions had equal levels of internal CA activity. Two isozymes were identified after electrophoretic separation of soluble proteins on cellulose acetate plates. The fast isozyme was found in cells grown under all conditions, whereas the slow isozyme was found only in cells grown at alkaline pH. Western blot analysis following sodium dodecyl sulfate-polyacrylamide gel electrophoresis using antibodies produced against the periplasmic form of CA from Chlamydomonas reinhardtii revealed a single band at 39 kD, which did not change in intensity between growth conditions and was associated only with proteins eluted from the fast band. The slow isozyme was inactivated by incubation of cell extract at 30[deg]C and by incubation in 10 mM dithiothreitol, whereas the internal form was unaffected. These results indicate that external and internal forms of CA differ in structure and their activities respond differently to environmental conditions.

SynopsisThe responses of clones of a range of willow species to waterlogging and total submersion were compared in glasshouse experiments using specially constructed perspex tanks. Up to 13 weeks of waterlogging had little effect on form and growth rates of above-ground parts of two clones of Salix caprea L. and one clone of S. cinerea L. A second clone of S. cinerea responded differently to the other three clones by significantly increasing its leaf area and stem dry weight, suggesting that it is likely to be more tolerant of waterlogging.Plant parts below the waterline in the waterlogging treatment responded very differently to the same parts on control plants. All waterlogged plants developed hypertrophied lenticels within four weeks, followed by significant increases in stem diameter. In each clone most of the pre-existing root system died by the end of the waterlogging treatment. All clones formed adventitious roots which varied considerably between the species and to a lesser extent between clones within each species. In S. cinerea many short, fine, much-branched roots grew vertically upwards until they reached the water surface. In S. cinerea clone 90 they originated from both the pre-existing woody roots and from the hypertrophied lenticels on the submerged portions of the stems. In S. cinerea clone 12 they developed only from the hypertrophied lenticels. New roots produced by waterlogged S. caprea clones were long, sparsely branched and floated on or near the surface of the water. As in S. cinerea clone 90 they originated from both the pre-existing woody roots and the submerged hypertrophied lenticels. Whereas roots of the control plants of all clones were mostly ectomycorrhizal, those of the waterlogged plants had no mycorrhizae. In a second waterlogging experiment S. × sericans, S. viminalis and S. fragilis produced adventitious roots more like those of S. caprea than S. cinerea. Plants of all clones removed from the waterlogging treatment after 16 days and kept with their soil at field capacity thereafter produced many new roots from their old root balls. After 32 days waterlogging no such recovery occurred.Total submersion caused much more severe damage to the aerial parts of all tested species than waterlogging. After eight days submersion the shoot tips of S. fragilis were beginning to rot and by day 25 those of S. × sericans and S. viminalis were rotting too. Subsequently shoots developed from axillary buds which remained unaffected by rot throughout the experiment. In S. cinerea shoot growth ceased after eight days and terminal buds were formed which remained dormant but healthy throughout the experiment. Submersion caused progressive loss of pre-existing leaves in all species. Some newly formed leaves of each species developed epinastic deformities after > 16 days of submersion. All species except S. cinerea showed significant reductions in root dry weight after 32 days of submersion.In a second submersion experiment responses of three clones each of S. purpurea and S. viminalis were compared. Shoot growth was reduced significantly in four of the six clones after 14 days. No further reductions occurred in the next 14 days of submersion. Root dry weight also decreased, but it took 28 days of submersion to produce the greatest effect. The faster growing clones of each species were more adversely affected by submersion in terms of both reduced shoot growth and root growth than those which grew more slowly.Considerable intraspecific variability in responses to waterlogging and submersion have been shown in these experiments by clones not selected for their variation in flooding tolerance. This suggests that selection and breeding could lead to the development of flood-tolerant cultivars of species such as S. cinerea and S. caprea which are not noted for their ability to withstand inundation.

A case is reported of duodenal perforation complicating laparoscopic cholecystectomy performed by laser dissection. The importance of investigating a patient with persistent shoulder-tip pain following this technique to exclude a subphrenic abscess is emphasised.

The European Commission fourth framework programme project ‘Assessment of passive safety injection systems of advanced light water reactors’ involved experiments on the PACTEL test facility and computer simulations of selected experiments. The experiments focused on the performance of passive safety injection systems (PSIS) of advanced light water reactors (ALWRs) in small break loss-of-coolant accident (SBLOCA) conditions. The PSIS consisted of a core make-up tank (CMT) and two pipelines. A pressure balancing line (PBL) connected the CMT to one cold leg. The injection line (IL) connected it to the downcomer. The project involved 15 experiments in three series. The experiments provided information about condensation and heat transfer processes in the CMT, thermal stratification of water in the CMT, and natural circulation flow through the PSIS lines. The project included validation of three thermal-hydraulic computer codes (APROS, CATHARE and RELAP5). The analyses showed the codes are capable of simulating the overall behaviour of the transients. The codes predicted accurately the core heatup, which occurred when the primary coolant inventory was reduced so much that the core top became free of water. The detailed analyses of the calculation results showed that some models in the codes still need improvements. Especially, further development of models for thermal stratification, condensation and natural circulation flow with small driving forces would be necessary for accurate simulation of the phenomena in the PSIS.

A multicentre trial for the treatment of dermatophyte onychomycosis of the toenails with terbinafine was carried out in Australia and New Zealand. Between eight and 12 nail samples were obtained from each of the 118 patients in the 48-week trial, and each sample was investigated by direct microscopy and culture for dermatophyte and non-dermatophyte fungi. Patients were randomized to treatment with terbinafine at 250 mg/day or placebo for the first 12 weeks of the study, then non-responders were offered a 12-week course of terbinafine from week 28. All patients had a dermatophyte infection. In 42 patients (36%) microscopy and mycological culture identified dermatophytes alone. In the remaining 76 patients (64%), a non-dermatophyte mould or yeast was also isolated at some stage during the trial, but in only three patients did the same non-dermatophyte persist in two or more successive nail specimens. The presence of a fungal contaminant in addition to a dermatophyte had no apparent effect on the efficacy of treatment with terbinafine. We conclude that non-dermatophyte moulds and yeasts are generally found as contaminating organisms in dermatophyte onychomycosis, secondary to the dermatophytes, and that they do not influence the outcome of treatment.

Successful implementation in a redesigning organization does not happen without a sound design, good implementation planning and effective leadership. The focus of the implementation preparation must change prior to and after the "go live" implementation date. Implementation preparation requires intentional steps to build systems, communicate effectively and develop operational understanding among clinicians, physicians and management. Early effort should focus on planning for efficient day-to-day operations, development of measurement systems and contingency planning. Immediately prior to and after implementation the focus should be on communication, goal setting, issues prioritization and fact-based issues resolution. After the first couple of months of implementation, the focus should move toward mentoring teams/individuals, building outcome measurement systems, identifying sources of future improvement and transferring more authority as appropriate to teams. Commit to comprehensive implementation preparation. Time spent on implementation preparation will pay large dividends during the challenging times of transitioning your organization to a redesigned world.

The physiological role of chloroplastic carbonic anhydrase (CA) was examined by antisense suppression of chloroplastic CA (on average 8% of wild type) in Nicotiana tabacum. Photosynthetic gas-exchange characteristics of low-CA and wild-type plants were measured concurrently with short-term, on-line stable isotope discrimination at varying vapor pressure deficit (VPD) and light intensity. Low-CA and wild-type plants were indistinguishable in the responses of assimilation, transpiration, stomatal conductance, and intercellular CO2 concentration to changing VPD or light intensity. At saturating light intensity, low-CA plants had lower discrimination against 13CO2 than wild-type plants by 1.2 to 1.8[per mille (thousand) sign]. Consequently, tissue of the low-CA plants was higher in 13C than the control plants. It was calculated that low-CA plants had chloroplast CO2 concentrations 13 to 22 [mu]mol mol-1 lower than wild-type plants. Discrimination against C18O16O in low-CA plants was 20% of that of the wild type, confirming a role of chloroplastic CA in the mechanism of discrimination against C18O16O ([delta]C18O16O). As VPD increased, stomatal closure caused a reduction in chloroplastic C02 concentration, and since VPD and chloroplastic CO2 concentration act in opposing directions on [delta]C18O16O, no effect of VPD was seen on [delta]C18O16O.

A bioassay protocol was optimized for measuring the potency of effluents or waterborne chemicals for inducing mixed-function oxygenase (MFO) activity of rainbow trout (Oncorhynchus mykiss). Measurements of ethoxyresorufin O-deethylase (EROD) can be made with an established endpoint assay using large volumes of reagents and tissue. However, a new kinetic microplate assay offers significant savings in time, reagents, and sample volumes. Data are distributed lognormally and must be log transformed before statistical analyses. EROD activity increases with exposure time to pulp mill effluent, and a 4-d exposure provides a near-maximal response. Optimum fish size conforms to standard practices in fish toxicology; loading rates should not exceed 1 g of fish per liter of test solution per day. Feed should be withheld from test fish 48 h before testing to reduce the variance of measured activity, and anaesthetizing fish with MS-222 does not affect their response to MFO inducers. Pulp mill effluents do not lose their potency during 2-3 wk of exposure at temperatures ranging from -20 to 13 degrees C, whether stored in plastic or glass. Steel containers were associated with slight losses in potency. Bioassays of MFO induction in fish exposed to liquid effluents are practical and conform to standard practice for testing the lethality of waterbone chemicals. The results are sufficiently precise that differences among means based on live fish per treatment can be discriminated statistically when activity changes by threefold or more.

An equation has been developed incorporating whole-cell rate constants for CO2 and HCO3- that describes accurately photosynthesis (Phs) in suspensions of unicellular algae at low dissolved inorganic carbon. At pH 8.0 the concentration of CO2 available to the algal cells depends on the rate of supply from, and the loss to, HCO3- and the rate of use by the cells. At elevated cell densities (>30 mg chlorophyll [Chl] L-1), at which CO2 use by the cells is high, the slope of a graph of absolute Phs versus Chl concentration approaches the rate of Phs on a milligram of Chl basis because of HCO3- use alone. The slope of a graph of Phs versus HCO3- will be the rate constant for HCO3-, and for Chlorella saccharophila it was 0.16 L mg-1 Chl h-1. The difference between the constants for dissolved inorganic carbon (measured in cells with external carbonic anhydrase) and HCO3-1 is the constant for CO2, which was 26 L mg-1 Chl h-1. This difference causes the half-saturation constant for Phs to increase 5- to 6-fold at high cell densities. The increase in CO2 use as a result of external carbonic anhydrase is described mathematically as a function of cell density.

An input-output budget for dissolved inorganic-N in a small forested catchment in North Wales is presented. From 1982 to 1990, bulk precipitation inputs averaged 10.3 kg ha(-1) year(-1), whereas throughfall inputs in 1983-1984 were 20.3 kg ha(-1) year(-1). Streamwater outputs were consistently larger than bulk precipitation inputs, averaging 14.6 kg ha(-1) year(-1). Inorganic-N in the forest stream was predominantly nitrate and concentrations were substantially higher than in a nearby moorland stream. Both streams showed seasonal trends in nitrate concentration, with highest concentrations occurring in summer in the forest stream but in winter in the moorland stream. Nitrate concentration in the forest stream increased with increasing soil temperature up to approximately 7 degrees C and decreased at higher temperatures. Nitrification is thought to be responsible for nitrate production at temperatures both below and above 7 degrees C, but root uptake becomes significant only at the higher temperatures. In the forest, dry deposition and cloudwater inputs of inorganic-N are responsible for increased nitrogen fluxes in throughfall compared with wet deposition. Mineralization and nitrification in excess of plant needs causes the organic soil horizons to act as a net source of dissolved inorganic-N. Nitrogen transformations in the soil lead to soil acidification at a rate of 1.0 keq ha(-1) year(-1).

Growth of selected clones of birch and willow obtained from nitrogen deficient soils was compared with that of unselected controls in pot experiments using three levels of nitrogen. Unselected controls of both genera continued shoot growth, albeit very slowly, with a very low level of nitrogen (5 ppm), while selected clones of birch grew significantly more than the controls. Selected clones of willow, on the other hand, ceased shoot growth after 10 weeks with this low nitrogen treatment. Nevertheless, they remained healthy, their leaves containing similar concentrations of nitrogen to those of the plants which continued stem growth throughout the experiment. Furthermore, they had very high root: shoot ratios compared with those of control willows and both selected and unselected birch. The two genera may have developed different mechanisms for tolerating low nitrogen, birch producing a small, relatively efficient root system; willow a larger but less efficient one. Both appear equally effective in ensuring survival on low-nitrogen sites in the field since all the selected clones were obtained from such sites and have survived well in field trials on similar sites. Both birch and willow responded toincreased nitrogen availability with increasing shoot growth and a relative decline in root growth. However, whereas in willow the unselected plants responded significantly more than selected clones, a similar but less markeddifference was found in birch. It appears that in both genera, as in herbaceous plants originating from nitrogen deficient sites, selected clones are less able to respond to increasing nitrogen supply than control plants from more fertile habitats. Attempts to correlate the response of the selected clones to nitrogen in this experiment with that to added nitrogen fertilizer in field trials has been unsuccessful. Further work is required to determine the importance of the many interacting factors which influence the response of young trees to nitrogen under the unusual field conditions associated with restored mineral workings.

Of four hangman's fractures of the axis, three occurred in road accidents and were stable, undisplaced and free of neurological signs, with full recovery after six to twelve weeks in a cervical collar. The fourth fracture occurred in a fall with profound tefraparesis from haemorrhage into the spinal cord, and the patient died a week later. There are two types of hangman's fracture: that of the axis pedicle, which results from more common than usually supposed because of the extension and compression of the cervical column, is slight symptoms it causes.

The constraint that extended molecules such as polymers cannot pass through each other is formulated in terms of a topological invariant. A simple model of the motion of a labelled loop entangled in a uniform background of amorphous loops is studied. A dynamical weighting factor is found which effectively removes configurational changes that would lead to the labelled loop passing through the strands of the background material. A perturbation treatment of this weighting factor is presented which describes the effects of the entanglements in terms of random environmental forces possessing considerable space and time correlations. A detailed analytic calculation is presented for the case of a labelled molecule with a rigid-ring configuration. This calculation illustrates the limited validity of perturbation theory in dealing with entanglements and suggests the existence of a transition in time to a random 'tube'-like behaviour, where the centre-of-mass motion of the ring depends on the time as t1/4 instead of the usual diffusive t1/2. The origin of this behaviour can be located in the long-time persistence of the bond vector correlation function of the labelled ring.

The effect of histamine on the uptake of radiosulphate by gastric tissue and gastric juice in guinea pigs was investigated. Radioactivity was recorded 4 hours after the administration of S35-labelled sulphate to normal controls and to histamine-treated animals.The radioactivity of fractions considered to contain sulphated mucopolysaccharides was also investigated.The uptake of radiosulphate by gastric tissue and juice was significantly higher in histamine-treated animals than in control guinea pigs.The S35 uptake by gastric sulphomucopolysaccharides was considered to represent the concentration of isotope by mucous cells and its secretion. This selective uptake was also markedly effected by histamine.Histamine may be a stimulant of the gastric mucous cells under the experimental conditions described.

A number of techniques have been used to diagnose aortic graft-enteric fistulae. These are reviewed and their value assessed. Three patients are described in whom the diagnosis was correctly made from characteristic appearances seen on a computed tomography (CT) scan. Further experience may show that CT scanning has an important role in the detection of this condition.

The solution of real-time sensor data processing problems with multi-microprocessor architectures of the multiple instruction multiple data stream (MIMD) class is limited by the structure of the interconnection network. A class of real-time sensor processing problems is analyzed to identify required network structures for use in evaluation of candidate interconnection networks. Several fundamental interconnection patterns are identified--macropipeline, K-nearest neighbors, binary search tree, one-n, n-one, one-n with groups of i, and random connection. A general model for a multi-microprocessor testbed is presented, and three candidate interconnection networks--ring, crossbar, and cube--are described for realizing the fundamental structures. Measures are identified for evaluating the candidate networks, and current results of the evaluation are presented.

The entire experience of in situ breast cancer in Alberta from 1953 to 1984 was examined. Of 243 patients coded, 226 were available for review by a panel of three pathologists. In 149 cases the diagnosis of in situ disease was confirmed. One hundred and eight patients had 109 ductal carcinomas in situ, 38 patients had lobular carcinomas in situ, with 3 patients having both. A multitude of treatments was used, ranging from local excision to radical mastectomy. Survival at a mean of 6 years follow-up was equal in all groups, with only two patients with a confirmed diagnosis of ductal carcinoma in situ dying from clinically suspected systemic disease. In patients treated by local excision, ipsilateral cancers were seen in 12% of ductal carcinoma in situ patients who had local excision and 13% of patients with lobular carcinoma in situ. Contralateral metachronous invasive cancers were seen in 6% of ductal carcinoma in situ patients and 3% of lobular carcinoma in situ patients. No lymph node involvement was seen in any of these patients, either with prophylactic dissection or in follow-up. The conclusion reached was that both in situ lesions are similar in their clinical course. Lymph node dissection is not necessary. Pathologic review is critical for accurate studies, with a change in diagnosis of 36% of diagnoses. Treatment does not appear to affect prognosis. The most appropriate treatment needs to be determined in prospective randomized trials.

We report on a patient who developed fatal respiratory distress two days after starting parenteral feeding for malnutrition complicating Crohn's disease. Post mortem examination revealed pulmonary collapse secondary to mediastinal leak of the infusion fluid due to an undiagnosed erosion of the vascular catheter tip through the brachiocephalic vein.

Summary Fatal spontaneous rupture of the lower abdominal aorta in a previously healthy 61-year-old woman is reported; the possibility that she had the Ehlers-Danlos syndrome is discussed.

Photosynthetic kinetics with respect to dissolved inorganic carbon were used to predict the outcome of competition for DIC between the green alga Selenastrum minutum and the cyanobacterium Synechococcus leopoliensis at pH 6.2, 7.5, and 10. Based on measured values of the maximum rate of photosynthesis, the half-saturation value of photosynthesis with respect to DIC (K 12/DIC ), and the DIC compensation point, it was predicted that S. leopoliensis would lower the steady-state DIC concentration below the DIC compensation point of S. minutum. This should result in competitive displacement of the green alga at a rate equivalent to the chemostat dilution rate. This prediction was validated by carrying out competition experiments over the range of pH. These results suggest that the low levels of DIC in air-equilibrated acidified lakes may be an important rate-limiting resource and hence affect phytoplankton community structure. Furthermore, the low levels of DIC in these systems may be below the DIC compensation point for some species, thereby precluding their growth at acid pH solely as a function of DIC limitation. The potential importance of DIC in shaping phytoplankton community structure in acidified systems is discussed.

Thermal annealing of defects in single-crystal GaP after 300 keV Ne+ irradiation at about 110°K to a dose of 6 • 1013 ions/cm2 has been studied at 110–500 °K by use of 275keV -channeled protons by measurement of back-scattering and gallium and phosphorus characteristic X-ray yields. The Ne+ dose was insufficient to produce any completely amorphous layer. Results indicate significant annealing at about 110°K, some further annealing at 200-350 °K and rapid annealing almost to completion in an annealing stage centred at 400 K. During both the neon irradiation and annealing, identical normalised gallium and phosphorus X-ray yields were observed. It was also found that irradiation of GaP at 103°K with 275 keV protons to doses of ~1016 H+/cm2 (unchanneled) caused significant lattice disorder.

We identify stellar structures in the PHANGS sample of 74 nearby galaxies and construct morphological masks of sub-galactic environments based on Spitzer 3.6 micron images. At the simplest level, we distinguish centres, bars, spiral arms, interarm and discs without strong spirals. Slightly more sophisticated masks include rings and lenses, publicly released but not explicitly used in this paper. We examine trends using PHANGS-ALMA CO(2-1) intensity maps and tracers of star formation. The interarm regions and discs without strong spirals dominate in area, whereas molecular gas and star formation are quite evenly distributed among the five basic environments. We reproduce the molecular Kennicutt-Schmidt relation with a slope compatible with unity within the uncertainties, without significant slope differences among environments. In contrast to early studies, we find that bars are not always deserts devoid of gas and star formation, but instead they show large diversity. Similarly, spiral arms do not account for most of the gas and star formation in disc galaxies, and they do not have shorter depletion times than the interarm regions. Spiral arms accumulate gas and star formation, without systematically boosting the star formation efficiency. Centres harbour remarkably high surface densities and on average shorter depletion times than other environments. Centres of barred galaxies show higher surface densities and wider distributions compared to the outer disc; yet, depletion times are similar to unbarred galaxies, suggesting highly intermittent periods of star formation when bars episodically drive gas inflow, without enhancing the central star formation efficiency permanently. In conclusion, we provide quantitative evidence that stellar structures in galaxies strongly affect the organisation of molecular gas and star formation, but their impact on star formation efficiency is more subtle., 28 pages, 11 figures, accepted for publication in A&A

Three etiological factors–ischemia, peripheral neuropathy, and infection–underlie the development of gangrene of the feet in diabetics. The emphasis on each factor varies from patient to patient. A clinical classification based on the temperature of the foot divides patients with gangrene of the feet into three groups that occur with equal frequency: (1) necrosis in a cold foot, (2) necrosis in a hot foot, and (3) necrosis in a warm foot. In the first group, a major amputation is the inevitable result. Local excision and preservation of part of the foot is possible in all patients in the second group. It is worth attempting a local excision in the third group, as healing will occur in half the cases.