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Surface debris covers much of the western portion of the McMurdo Ice Shelf and has a strong influence on the local surface albedo and energy balance. Differential ablation between debris-covered and debris-free areas creates an unusual heterogeneous surface of topographically low, high-ablation, and topographically raised (‘pedestalled’), low-ablation areas. Analysis of Landsat and MODIS satellite imagery from 1999 to 2018, alongside field observations from the 2016/2017 austral summer, shows that pedestalled relict lakes (‘pedestals’) form when an active surface meltwater lake that develops in the summer, freezes-over in winter, resulting in the lake-bottom debris being masked by a high-albedo, superimposed, ice surface. If this ice surface fails to melt during a subsequent melt season, it experiences reduced surface ablation relative to the surrounding debris-covered areas of the ice shelf. We propose that this differential ablation, and resultant hydrostatic and flexural readjustments of the ice shelf, causes the former supraglacial lake surface to become increasingly pedestalled above the lower topography of the surrounding ice shelf. Consequently, meltwater streams cannot flow onto these pedestalled features, and instead divert around them. We suggest that the development of pedestals has a significant influence on the surface-energy balance, hydrology and flexure of the ice shelf.
On 2 March 2016, several small en échelon tabular icebergs calved from the seaward front of the McMurdo Ice Shelf, and a previously inactive rift widened and propagated by ~3 km, ~25% of its previous length, setting the stage for the future calving of a ~14 km2 iceberg. Within 24 h of these events, all remaining land-fast sea ice that had been stabilizing the ice shelf broke-up. The events were witnessed by time-lapse cameras at nearby Scott Base, and put into context using nearby seismic and automatic weather station data, satellite imagery and subsequent ground observation. Although the exact trigger of calving and rifting cannot be identified definitively, seismic records reveal superimposed sets of both long-period (>10 s) sea swell propagating into McMurdo Sound from storm sources beyond Antarctica, and high-energy, locally-sourced, short-period (<10 s) sea swell, in the 4 days before the fast ice break-up and associated ice-shelf calving and rifting. This suggests that sea swell should be studied further as a proximal cause of ice-shelf calving and rifting; if proven, it suggests that ice-shelf stability is tele-connected with far-field storm conditions at lower latitudes, adding a global dimension to the physics of ice-shelf break-up.
Material extrusion 3D printing (ME3DP) based on fused deposition modeling (FDM) technology is currently the most commonly used additive manufacturing method. However, ME3DP suffers from a limitation of compatible materials and typically relies upon amorphous thermoplastics, such as acrylonitrile butadiene styrene (ABS). The work presented here demonstrates the development and implementation of binary and ternary polymeric blends for ME3DP. Multiple blends of acrylonitrile butadiene styrene (ABS), styrene ethylene butadiene styrene (SEBS), and ultrahigh molecular weight polyethylene (UHMWPE) were created through a twin screw compounding process to produce novel polymer blends compatible with ME3DP platforms. Mechanical testing and fractography were used to characterize the different physical properties of these new blends. Though the new blends possessed different physical properties, compatibility with ME3DP platforms was maintained. Also, a decrease in surface roughness of a standard test piece was observed for some blends as compared with ABS.
Although what drives the abundance and habitat selection of ungulates is a long-standing question, coherent datasets investigating the influences of rainfall, competition and fire on ungulates are unusual. Over 4 y we carried out extensive monthly road transects in Ithala Game Reserve, South Africa, to determine the demographics and habitat occupancy of the region's prevalent grazer (wildebeest) and mixed-feeder (impala). Habitat occupancy was determined using a GIS-based approach. We obtained 8742 sighting records, encompassing 8400 wildebeest and 10071 impala. Annual rainfall did not significantly correlate with population sizes of either species. Fecundity of wildebeest, but not of impala, showed a significant positive relationship with rainfall specifically over the perinatal period (November–December), whilst no significant relationships were found for either species between fecundity and rainfall over the previous year, 2 y, rut (February–April) or height of the dry season (June–August). Impala unexpectedly favoured browse habitats to grassland year round, probably consequent on competition for grass with wildebeest. Dry-season grass flushes attracted both wildebeest and impala. The study emphasized how rainfall, competition and fire regimes may affect differently grazers compared with mixed-feeders.
Resource depletion and associated increases in interspecific competition are likely to influence differential habitat usage amongst a guild. We tested some prominent theoretical concepts using observed differences in seasonal habitat use amongst the savanna browser guild (elephant, giraffe, impala, kudu and nyala) in Hluhluwe-iMfolozi Park, South Africa. Herbivore locations (n = 3108) were recorded over 2 y using repeated road transects and, for elephant, GPS collars (187 254 downloads). Densities were calculated using a novel GIS approach designed to be a cost-effective method for annual censuses, but also able to cope with abrupt changes in visibility. Selectivity for (Manly's α) vegetation types, and overlap (Schoener's index) in vegetation type usage were calculated. Resource depletion in the dry season resulted in all members of the guild increasing selectivity for vegetation types (sum of absolute values away from the neutral value for Manly's alpha for the guild: dry seasons 3.97, 5.16; corresponding wet seasons 3.12, 3.68), but decreasing interspecific overlap (80% of Schoener's indices lower in dry season versus wet season). These effects were more marked over the second, more severe, dry season. We found support for the niche overlap hypothesis and the niche compression hypothesis. The Jarman–Bell principle was generally supported, although unexpectedly during the severe dry season elephant showed the most selectivity for vegetation type. The greater the resource depletion, the more relevant interspecific differences in habitat usage become in relation to the differential impacts of guild members.
Research has increasingly established that mesoherbivores influence the regeneration of woody plants. However the relationship between mesoherbivore density and degree of impact, and the spatial component of this impact, has not been well established. Using a novel sampling design, we assessed in iMfolozi Park, South Africa, the impact of impala (Aepyceros melampus) across the full complement of woody species within the home range, evaluating its spatial component and relationship to impala density. We used four GPS collars, in separate breeding herds, and a GIS to detect zones of different density of impala in the landscape, thus defining a fine-grain browsing gradient. We assessed impact on woody recruits (≤ 0.5 m height) across this gradient by means of 1600 random 1 × 1-m quadrats. Densities of woody seedlings, and mean percentage of remaining canopy, were significantly less in areas of high impala density versus low-density areas. There was a significant correlation between increasing impala density and decreasing density of favoured woody recruits. We propose a hypothesis of impala-induced patch dynamics. It seems likely that the ubiquitous impala may create and sustain a shifting mosaic of patches, and thus function as a key determinant of landscape heterogeneity.
The Canadian Association of Emergency Physicians (CAEP) sepsis guidelines created by the CAEP Critical Care Practice Committee (C4) and published in the Canadian Journal of Emergency Medicine (CJEM) form the most definitive publication on Canadian emergency department (ED) sepsis care to date. Our intention was to identify which of the care items in this document are specifically necessary in the ED and then to provide these items in a tiered checklist that can be used by any Canadian ED practitioner.
Practice points from the CJEM sepsis publication were identified to create a practice point list. Members of C4 then used a Delphi technique consensus process over May to October 2009 via e-mail to create a tiered checklist of sepsis care items that can or could be completed in a Canadian ED when caring for the septic shock patient. This checklist was then assessed for use by a survey of ED practitioners from varying backgrounds (rural ED, community ED, tertiary ED) from July to October 2010.
Twenty sepsis care items were identified in the CAEP sepsis guidelines. Fifteen items were felt to be necessary for ED care. Two levels of checklists were then created that can be used in a Canadian ED. Most ED physicians in community and tertiary care centres could complete all parts of the level I sepsis checklist. Rural centres often struggle with the ability to obtain lactate values and central venous access. Many items of the level II sepsis checklist could not be completed outside the tertiary care centre ED.
Sepsis care continues to be an integral and major part of the ED domain. Practice points for sepsis care that require specialized monitoring and invasive techniques are often limited to larger tertiary care EDs and, although heavily emphasized by many medical bodies, cannot be reasonably expected in all centres. When the resources of a centre limit patient care, transfer may be required.
Les directives de l'Association canadienne des médecins d'urgence (ACMU) relatives à la sepsie, créées par le Critical Care Practice Committee de l'ACMU (C4) et publiées dans le Canadian Journal of Emergency Medicine (CJEM), constituent la plus importante publication consacrée à la prise en charge de la sepsie au sein des services des urgences (SU) canadiens. Notre intention consistait à identifier lesquels, parmi les éléments de prise en charge proposés dans ce document, sont spécifiquement nécessaires au sein du SU et de présenter ensuite ces éléments sous la forme d'une liste de contrôle à plusieurs niveaux pouvant être utilisée par n'importe quel praticien d'un SU canadien.
Les points pratiques de la publication du CJEM consacrée à la sepsie ont été identifiés afin de générer une liste pratique en plusieurs points. Les membres du C4 ont ensuite eu recours, de mai à octobre 2009, à une procédure de consensus selon la technique Delphi, par courriel, en vue de créer une liste de contrôle à plusieurs niveaux relatives aux eléménts de la prise en charge de la sepsie pouvant ou non être assurés au sein d'un SU canadien lors de la prise en charge d'un patient victime d'un choc septique. Cette liste de contrôle a ensuite été évaluée en vue de son utilisation par le biais d'un questionnaire adressé à des praticiens de SU travaillant dans divers contextes (SU rural, SU communautaire, SU tertiaire), cela de juillet à octobre 2010.
Vingt éléments de la prise en charge de la sepsie ont été identifiés dans les directives de l'ACMU relatives à la sepsie. Quinze eléménts ont été jugés nécessaires pour la prise en charge dans le cadre d'un SU. On a ensuite crée deux niveaux de liste de contrôle pouvant être utilisés dans un SU canadien. La plupart des médecins urgentistes travaillant dans des centres de soins communautaires et tertiaires ont pu réaliser toutes les parties de la liste de contrôle de niveau I pour le sepsis. Les centres ruraux rencontrent souvent des difficultés en ce qui concerne la possibilité d'obtention d'un dosage du lactate valeurs et d'un accès veineux central. Un grand nombre d'éléments de la liste de contrôle de niveau II pour le sepsis n'ont pas pu être réalisés en dehors des SU de centres de soins tertiaires.
La prise en charge de la sepsie fait toujours partie intégrante et constitue un élément majeur du domaine des SU. Les points pratiques pour la prise en charge de la sepsie qui requièrent un monitorage spécialisé et des techniques invasives sont souvent limités aux SU de soins tertiaires plus importants et, bien que bon nombre de corps médicaux soulignent leur importance, ne peuvent pas raisonnablement être attendus dans tous les centres. Lorsque les ressources d'un centre limitent la prise en charge du patient, un transfert peut s'avérer nécessaire.
To clarify the potential influence of different browsers in the same guild on woody vegetation, dietary overlap and separation between elephant, giraffe, kudu, nyala and impala was assessed in Hluhluwe-iMfolozi Park, South Africa. Woody species browsed, browsing heights, plant-parts browsed and browsing versus grazing were recorded over 2 y by direct observation. We obtained 3068 browse records. Niche breadth (Levins' measure) and overlap (Schoener's index) in species browsed and browsing heights were calculated. Annual and seasonal differences in these measurements, plant-part use and browsing versus grazing were assessed. Elephant utilized the largest number (n = 78) of different woody plant species. Overlap in species browsed was lower between elephant and other browsers than amongst the latter. Seasonal rainfall influenced the range of woody plants utilized, niche breadth in terms of species browsed and browsing versus grazing. Marked resource depletion caused elephant, contrary to theoretical predictions, to narrow niche breadth in terms of species browsed. However, resource depletion rarely had a significant effect on interspecific overlap in species browsed or overlap in browsing heights, on actual browsing heights or plant-parts utilized. A small suite (n = 8) of woody species formed the core diet of all guild members, implying the potential for synergistic impacts by guild members on these species and for competition between populations of different guild members.
Sediment records from two lakes in the east-central Sierra Nevada, California, provide evidence of cooling and hydrological shifts during the Younger Dryas stade (YD; ~ 12,900–11,500 cal yr BP). A chironomid transfer function suggests that lake-water temperatures were depressed by 2°C to 4°C relative to maximum temperatures during the preceding Bølling–Allerød interstade (BA; ~ 14,500–12,900 cal yr BP). Diatom and stable isotope records suggest dry conditions during the latter part of the BA interstade and development of relatively moist conditions during the initiation of the YD stade, with a reversion to drier conditions later in the YD. These paleohydrological inferences correlate with similar timed changes detected in the adjacent Great Basin. Vegetation response during the YD stade includes the development of more open and xeric vegetation toward the end of the YD. The new records support linkages between the North Atlantic, the North Pacific, and widespread YD cooling in western North America, but they also suggest complex hydrological influences. Shifting hydrological conditions and relatively muted vegetation changes may explain the previous lack of evidence for the YD stade in the Sierra Nevada and the discordance in some paleohydrological and glacial records of the YD stade from the western United States.
Evidence for the efficacy of cognitive–behavioural therapy for schizophrenia is promising but evidence for clinical effectiveness is limited.
To test the effectiveness of cognitive–behavioural therapy delivered by clinical nurse specialists in routine practice.
Of 274 referrals, 66 were allocated randomly to 9 months of treatment as usual (TAU), cognitive–behavioural therapy plus TAU (CBT) or supportive psychotherapy plus TAU (SPT) and followed up for 3 months.
Treatment effects were modest but the CBT condition gave significantly greater improvement in overall symptom severity than the SPT or TAU conditions combined (F (1,53)=4.14; P=0.05). Both the CBT and SPT conditions combined gave significantly greater improvement in severity of delusions than did the TAU condition (F (1,53)=4.83; P=0.03). Clinically significant improvements were achieved by 7/21 in the CBT condition (33%), 3/19 in the SPT condition (16%) and 2/17 in the TAU condition (12%).
Cognitive–behavioural therapy delivered by clinical nurse specialists is a helpful adjunct to routine care for some people with chronic psychosis.
We report survival and pretreatment prognostic factors for survival and chemosensitivity in 53 oligodendrogliomas treated with PCV (procarbazine, lomustine and vincristine) chemotherapy.
A total of 53 patients with histologically proven oligodendroglioma, anaplastic oligodendroglioma or oligo-astrocytoma and treated with PCVwere extracted from the London Regional Cancer Center database. A retrospective review was conducted to evaluate overall survival and pretreatment prognostic factors for survival and chemosensitivity.
The median survival time from diagnosis was 123.6 months. The overall five- and ten-year survival rates were 72.7% and 52.7% respectively. Age <40, seizure as an initial symptom, absence of cognitive deficit and presence of a homogeneous hypodense lesion without contrast enhancement on the initial pretreatment CT scan were all factors independently associated with favorable outcome. The presence of increased cellularity, pleomorphism, mitosis, vascular proliferation and grading as an anaplastic lesion using these surrogates on pathological assessment, were all associated with an unfavorable outcome in univariable analysis. In multivariable analysis, only the anaplastic grading and presence of increased cellularity were significant determinants of unfavorable survival. The only factor adversely associated with chemosensitivity was the presence of a focal symptom at presentation.
Overall survival is significantly longer in oligodendroglial lesions than in fibrillary astrocytic tumors. A two tier grading system using standard morphological features seems accurate in predicting outcome in these patients. The presence of a neoplastic astrocytic component does not seem to impact the outcome. No clinical, radiological or pathological factor could be identified to reliably predict chemotherapy response.
We considered the problem of conserving small populations of prey by reviewing observational and field experiments in search of general answers to the question of how predators impact upon their prey. We then explored the likely effectiveness of predator control as a conservation tool by simulating a small, fragmented population of prey. We chose red grouse in Britain as an example of this general predicament. An individual-based population simulation model was used to simulate the fate of a small red grouse population. The model was used to investigate the relative impacts of predation, habitat changes and stochastic factors associated with small population size on the viability of the population. Although most predator–prey studies have been undertaken in temperate regions and only four studies found evidence of regulation, some generalizations arose. Predation can limit populations but generally did not drive the prey population to extinction. Extinction was more likely in cases involving an introduced predator on islands or in isolated prey populations. The simulation model showed that at small population sizes the stochastic factors were always significant, whereas environmental variation and habitat change had the greatest impact on large populations over the long term; predation was only a significant threatening factor when it occurred at a high rate, was more severe over the long term when predators took a constant proportion of the prey base, and when predation was across all age classes.