To send content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about sending content to .
To send content items to your Kindle, first ensure firstname.lastname@example.org
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about sending to your Kindle.
Note you can select to send to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Mycoplasma gallisepticum causes disease in poultry and emerged as a novel pathogen in house finches resulting in a mycoplasmal conjunctivitis epidemic across North America after a single successful host jump from poultry to house finches. The rapid spread of the epidemic across eastern North America, causing a decline in host abundance, has been documented. Once established, disease prevalence showed regular seasonal variation: a late summer/early autumn peak, a mid-December minimum, followed by a late winter peak and a breeding season minimum, which requires seasonal reproduction (providing an autumn pulse of naïve hosts) and winter social aggregation as well as partial immunity of recovered birds. Virulence evolved rapidly: in eastern populations it increased once the disease had become endemic. In western North America the established strain was of much lower virulence, but once established also increased in virulence. We show that virulence may evolve in opposite directions depending on selection pressures. A detailed study showed that disease decreased survival and mobility and a high proportion of birds recovered; also that re-observation rates of clinically diseased birds are often different from those of asymptomatic birds; only calculations which include this effect allow an accurate estimate of disease prevalence.
Introduction: Collaborative Emergency Centres (CECs) provide access to care in rural communities. After hours, registered nurses (RNs) and paramedics work together in the ED with telephone support by an emergency medical services (EMS) physician. The safety of such a model is unknown. Relapse visits are often used as a proxy measure for safety in emergency medicine. The primary outcome of this study is to measure unscheduled relapses to emergency care. Methods: The electronic patient care record (ePCR) database was queried for all patients who visited two CECs from April 1, 2012 to April 1, 2013. Abstracted data included demographics, time, acuity score, clinical impression, chief complaint, and disposition. Records were searched for each discharged CEC patient to identify unscheduled relapses to emergency care, defined as presenting back to EMS, CEC, or any other ED within the Health Authority within 48 hours of CEC discharge. Results: There were 894 CEC visits, of which 66 were excluded due to missing data. The dispositions from CEC were: 131/828 (15.8%) transferred to regional ED; 264/828 (31.9%) discharged home; 488/828 (58.9%) discharged with follow up visit booked; and 11/82 (1.2%) left the CEC without being seen. There was 37/828 (4.5%) visits which relapsed back to emergency care, all of whom were discharged from CEC or left without being seen: 3/828 (0.4%) relapsed back to EMS (two taken to regional ED and one to CEC); 16/828 (1.9%) relapsed to regional ED (by walking-in); and 18/828 (2.2%) had a relapse to the CEC (walk-in). 516/828 (62.3%) CEC visits were resolved in a single visit. Conclusion: This study was based on only two of the 7 operating CECs due to accessing paper-based charts for multiple health regions. We also acknowledge the limitations of using relapse as a proxy for safety, and that low volumes and acuity will make detection of adverse events challenging. Albeit a proxy measure, the rate of patients who relapse to emergency care was under 5% in this case series of two CECs. Most patients had their concern resolved in a single visit to a CEC. Further research is underway to determine the effectiveness, optimal utilization and safety of this collaborative model of rural emergency care.
Trypanosoma cruzi, causative agent of Chagas disease, co-infects its triatomine vector with its sister species Trypanosoma rangeli, which shares 60% of its antigens with T. cruzi. Additionally, T. rangeli has been observed to be pathogenic in some of its vector species. Although T. cruzi–T. rangeli co-infections are common, their effect on the vector has rarely been investigated. Therefore, we measured the fitness (survival and reproduction) of triatomine species Rhodnius prolixus infected with just T. cruzi, just T. rangeli, or both T. cruzi and T. rangeli. We found that survival (as estimated by survival probability and hazard ratios) was significantly different between treatments, with the T. cruzi treatment group having lower survival than the co-infected treatment. Reproduction and total fitness estimates in the T. cruzi and T. rangeli treatments were significantly lower than in the co-infected and control groups. The T. cruzi and T. rangeli treatment group fitness estimates were not significantly different from each other. Additionally, co-infected insects appeared to tolerate higher doses of parasites than insects with single-species infections. Our results suggest that T. cruzi–T. rangeli co-infection could ameliorate negative effects of single infections of either parasite on R. prolixus and potentially help it to tolerate higher parasite doses.
Introduction: Hospitalization due to ambulatory care sensitive conditions (ACSC) is a proxy measure for access to primary care. Emergency medical services (EMS) are increasingly called when primary care cannot be accessed. A novel paramedic-nurse EMS Mobile Care Team (MCT) was implemented in an under-serviced community. The MCT responds in a non-transport unit to bookings from EMS, emergency and primary care and to low-acuity 911 calls in a defined geographic region. Our objective was to compare the prevalence of ACSC in ground ambulance (GA) responses before and after the introduction of the MCT. Methods: A cross-sectional analysis of GA and MCT patients with ACSC (determined by chief complaint, clinical impression, treatment protocol and medical history) one year pre- and one year post-MCT implementation was conducted for the period Oct. 1, 2012 to Sept. 30, 2014. Demographics were described. Predictors of ACSC were identified via logistic regression. Prevalence was compared with chi-squared analysis. Results: There were 975 calls pre- and 1208 GA/95 MCT calls post-MCT. ACSC in GA patients pre- and post-MCT was similar: n=122, 12.5% vs. n=185, 15.3%; p=0.06. ACSC in patients seen by EMS (GA plus MCT) increased in the post-period: 122 (12.5%) vs. 204 (15.7%) p=0.04. Pre vs post, GA calls differed by sex (p=0.007) but not age (65.38 ± 15.12 vs. 62.51 ± 20.48; p=0.16). Post-MCT, prevalence of specific ACSC increased for GA: hypertension (p<0.001) and congestive heart failure (p=0.04). MCT patients with ACSC were less likely to have a primary care provider compared to GA (90.2% and 87.6% vs. 63.2%; p=0.003, p=0.004). Conclusion: The prevalence of ACSC did not decrease for GA with the introduction of the MCT, but ACSC in the overall patient population served by EMS increased. It is possible more patients with ACSC call or are referred to EMS for the new MCT service. Given that MCT patients were less likely to have a primary care provider this may represent an increase in access to care, or a shift away from other emergency/episodic care. These associations must be further studied to inform the ideal utility of adding such services to EMS and healthcare systems.
In this paper we derive from first principles the expected body sizes of the parasite communities that can coexist in a mammal of given body size. We use a mixture of mathematical models and known allometric relationships to examine whether host and parasite life histories constrain the diversity of parasite species that can coexist in the population of any host species. The model consists of one differential equation for each parasite species and a single density-dependent nonlinear equation for the affected host under the assumption of exploitation competition. We derive threshold conditions for the coexistence and competitive exclusion of parasite species using invasion criteria and stability analysis of the resulting equilibria. These results are then used to evaluate the range of parasites species that can invade and establish in a target host and identify the ‘optimal’ size of a parasite species for a host of a given body size; ‘optimal’ is defined as the body size of a parasite species that cannot be outcompeted by any other parasite species. The expected distributions of parasites body sizes in hosts of different sizes are then compared with those observed in empirical studies. Our analysis predicts the relative abundance of parasites of different size that establish in the host and suggests that increasing the ratio of parasite body size to host body size above a minimum threshold increases the persistence of the parasite population.
Stable perovskite and metastable post-perovskite NaCoF3 were deformed in pure-shear geometry in a deformation-DIA press with radiographic monitoring of the sample strain. In isothermal experiments where there was no transformation, post-perovskite was found to be 5 times weaker than perovskite. In temperature-ramping experiments where post-perovskite transformed to perovskite during the deformation experiment the initial post-perovskite sample was 5–10 times weaker than perovskite under comparable conditions and their strengths converged during the transformation, being equal on completion of the transformation. These results confirm recent findings which show that postperovskite is weaker than perovskite, regardless of the prior history of the sample.
Here, the state of our knowledge regarding the interior dynamics and evolution of habitable terrestrial planets including Earth and super-Earths is reviewed, and illustrated using state-of-the-art numerical models. Convection of the rocky mantle is the key process that drives the evolution of the interior: it causes plate tectonics, controls heat loss from the metallic core (which generates the magnetic field) and drives long-term volatile cycling between the atmosphere/ocean and interior. Geoscientists have been studying the dynamics and evolution of Earth's interior since the discovery of plate tectonics in the late 1960s and on many topics our understanding is very good, yet many first-order questions remain. It is commonly thought that plate tectonics is necessary for planetary habitability because of its role in long-term volatile cycles that regulate the surface environment. Plate tectonics is the surface manifestation of convection in the 2900-km deep rocky mantle, yet exactly how plate tectonics arises is still quite uncertain; other terrestrial planets like Venus and Mars instead have a stagnant lithosphere- essentially a single plate covering the entire planet. Nevertheless, simple scalings as well as more complex models indicate that plate tectonics should be easier on larger planets (super-Earths), other things being equal. The dynamics of terrestrial planets, both their surface tectonics and deep mantle dynamics, change over billions of years as a planet cools. Partial melting is a key process influencing solid planet evolution. Due to the very high pressure inside super-Earths' mantles the viscosity would normally be expected to be very high, as is also indicated by our density function theory (DFT) calculations. Feedback between internal heating, temperature and viscosity leads to a superadiabatic temperature profile and self-regulation of the mantle viscosity such that sluggish convection still occurs.
The thermal diffusivity of diopside, jadeite and enstatite were measured at simultaneous pressures and temperatures of up to 7 GPa and 1200 K using the X-radiographic Ångström method. The measurements herein show that the pressure dependency of thermal diffusivity in pyroxenes is significantly greater than in olivine or garnet and that in the MORB-layer of a subducting slab the thermal diffusivity of pyroxenes are a factor of 1.5 greater than that of olivine. The temperature dependence of all the data sets is well described by a low-order polynomial fit to 1/K and the pressure dependence is exponential in 1/K, formulations which are consistent with the damped harmonic oscillator model for thermal properties.
Polypeptide sequences have an inherent tendency to self-assemble into filamentous nanostructures commonly known as amyloid fibrils. Such self-assembly is used in nature to generate a variety of functional materials ranging from protective coatings in bacteria to catalytic scaffolds in mammals. The aberrant self-assembly of misfolded peptides and proteins is also, however, implicated in a range of disease states including neurodegenerative conditions such as Alzheimer's and Parkinson's diseases. It is increasingly evident that the intrinsic material properties of these structures are crucial for understanding the thermodynamics and kinetics of the pathological deposition of proteins, particularly as the mechanical fragmentation of aggregates enhances the rate of protein deposition by exposing new fibril ends which can promote further growth. We discuss here recent advances in physical techniques that are able to characterise the hierarchical self-assembly of misfolded protein molecules and define their properties.
The peri-parturient period is crucial for controlling worms as the acquired immunity of ewes is disrupted, resulting in an increase in faecal worm egg counts. Two hypotheses were tested in this experiment – that ewes bred for worm resistance would have lower faecal worm egg counts than unselected control ewes, during late pregnancy and lactation, under similar but separate grazing areas; and also that numbers of infective nematode larvae would be lower on pastures grazed by resistant ewes than pastures grazed by unselected control ewes. Faecal samples were collected from resistant and unselected ewes in late pregnancy and early lactation, during the winter rainfall season, and analysed for numbers of Trichostrongylus colubriformis and Teladorsagia circumcincta. Pasture samples were taken 1 week before and 7 weeks after lambing started and analysed for infective larvae. In all sheep, worm egg counts rose 2 weeks prior to lambing and continued into lactation. Worm egg counts were significantly lower in the resistant ewes from 1 week before lambing to 2 weeks after lambing. There were no differences in egg counts between single- and twin-bearing ewes in the resistant line. However, twin-bearing control ewes had significantly higher egg counts than single-bearing control ewes. Following lactation, plots grazed by resistant ewes had substantially less contamination with T. colubriformis larvae, but there were no differences in numbers of T. circumcincta larvae. Our results demonstrate that sheep bred for worm resistance has lower worm burdens during the peri-parturient phase and that lambs born to resistant ewes face a lower larval challenge during their introduction to grazing. In our environment, selection for low worm egg counts has produced sheep highly resistant to T. colubriformis, but has had less impact on resistance towards T. circumcincta.
A new method to measure thermal diffusivity in samples at simultaneous high pressure and high temperature is presented. The sample is placed inside a cylindrical heater and subjected to a heater power that varies sinusoidally with time. The diffusion of the temperature variations into the sample is monitored using radiographic imaging of marker foils. This provides measurements of the phase lag and amplitude variation of the temperature cycle at a range of radii from the sample axis without the need for multiple thermocouples. The technique is tested using a NaCl sample at 4 GPa; the best-fit thermal diffusivity for NaCl at 4 GPa and 673 K is 2.4±0.5x10-6 m2/s.
A long-term objective of population biology is to explain the spatiotemporal variations in abundance of organisms by understanding the factors that limit both distribution and changes in abundance. In general, theory predicts that a major determinant of distribution and dynamics is the instantaneous population growth rate, presented as r (where r = ln(λ) = ln(Nt+1/Nt). Some models reveal the obvious, such that species will tend not to exist where their population growth is consistently negative and there is no immigration (see Chapter 2). But the models also expose intriguing dynamics; for example, simple single-species nonlinear models reveal that dynamics can vary from stability through oscillatory to chaotic behaviour simply by subtle changes in the population growth rate (May 1976). As such, it is not surprising that when we incorporate interspecific interactions, the stochastic vagaries of environmental conditions and dispersal, we reveal a Pandora's box of dynamical behaviours.
In the empirical literature, the population growth rate parameter does not enjoy the same importance as it does in the theoretical literature. Rarely do workers make an estimate of the intrinsic growth rate parameter (r) or its empirical equivalent, the maximum growth rate (rmax) which is simply the maximum rate of growth observed within a time-series. Changes in the observed growth rate at a specific time (rt) may be recorded along with the factors associated with the reproductive output of individuals, but studies tend not to estimate the extent to which the growth rate is reduced by density dependent regulatory factors.
CdTe etching was investigated using variable angle spectroscopic ellipsometry and glancing angle x-ray diffraction. Treatment with HNO3:H3PO4 (NP) based etches was shown to form amorphous-Te surface films which spontaneously crystallize following etching. Br2/methanol (BM) etching forms very thin amorphous-Te films. NP-etched surfaces are stable in ambient air for ∼1 hr before beginning to oxidize, while BM etched films oxidize immediately following treatment. CdTe grain boundary etching by NP was minimized using more acidic etches. Device analysis suggests that a higher Te content produces more stable back contacts by attenuating Cu diffusion. Mechanistic details of NP etching are discussed.
Both policy articles about US post-Cold War foreign policy and the recent rhetoric of US policymakers appears to be slipping back into the language of the ‘arrogance of power’, against which Senator Fulbright warned America in the 1960s. In what follows, the USA's style of foreign policy; its criteria for intervention; its invasion of Panama; its capabilities; its intervention in Bosnia; and the impact of contending theories about changes in the international sphere will be examined with a view to casting some light on how the USA has responded to the world outside its boundaries after the Cold War. Finally, in the light of Senator Fulbright's criticisms of US interventionism in the recent past, the essay draws towards its conclusion by specifically addressing the key questions of the whens, whys and wherefores of US intervention into and exits from international crises. It explores some of the problems posed by continuity and change in the struggle to adjust US foreign policy to a non-Cold War world and examines the wisdom of enthusiastic calls for the US to spread democracy abroad.
A novel process of pulse-heating copper films under high pressure has been developed for filling high-aspect-ratio vias and contact holes with copper. A copper film is sputter-deposited on to an oxidised silicon substrate containing an array of via holes with varied aspect ratios. The film, which is thick enough to bridge over the via holes, is then subjected to laser pulse heating under selected pressures of inert gas. Via filling has been achieved, up to an aspect ratio of 6 for 0.35 μm diameter holes. The microstructure of the pulse-heated copper films has been investigated by X-ray diffraction, and by focused ion beam microscopy (FIB) including sectioning. The FIB images of the film over a via pattern show a ‘chequer-board’ pattern of grains corresponding to the square pattern of via holes underneath. This pattern can be explained by transient melting of the film under pulse-heating and subsequent solidification in which each via hole acts as a nucleation site and has a crystal associated with it. Even though the as-deposited films are fine-grained and have (111) texture, the treated films can show (111) or (100) texture, depending on processing conditions. The origins of the final film texture and the possibilities for microstructural control are discussed.