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 email@example.com
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.
We report on an initial long-term study of dissolved inorganic and organic carbon (DIC) from Sabino Creek, located in Sabino Canyon, Pima County, Arizona. The purpose of this study was to monitor changes in dissolved radiocarbon (14C) with time and to understand the processes contributing to these variations. Our results span the period 2009–2016 and show a mixing trend between dissolved inorganic and organic carbon modern end-members with an older component. This study provides preliminary information for more detailed research on recycling of organic components in this stream system.
Horizontal density layers are commonly observed in stratified turbulence. Recent work (e.g. Taylor & Zhou, J. Fluid Mech., vol. 823, 2017, R5) has reinvigorated interest in the Phillips instability (PI), by which density layers form via negative diffusion if the turbulent buoyancy flux weakens as stratification increases. Theoretical understanding of PI is incomplete, in part because it remains unclear whether and by what mechanism the flux-gradient relationship for a given example of turbulence has the required negative-diffusion property. Furthermore, the difficulty of analysing the flux-gradient relation in evolving turbulence obscures the operating mechanism when layering is observed. These considerations motivate the search for an example of PI that can be analysed clearly. Here PI is shown to occur in two-dimensional Boussinesq sheared stratified turbulence maintained by stochastic excitation. PI is analysed using the second-order S3T closure of statistical state dynamics, in which the dynamics is written directly for statistical variables of the turbulence. The predictions of S3T are verified using nonlinear simulations. This analysis provides theoretical underpinning of PI based on the fundamental equations of motion that complements previous analyses based on phenomenological models of turbulence.
Culture-based studies, which focus on individual organisms, have implicated stethoscopes as potential vectors of nosocomial bacterial transmission. However, the full bacterial communities that contaminate in-use stethoscopes have not been investigated.
We used bacterial 16S rRNA gene deep-sequencing, analysis, and quantification to profile entire bacterial populations on stethoscopes in use in an intensive care unit (ICU), including practitioner stethoscopes, individual-use patient-room stethoscopes, and clean unused individual-use stethoscopes. Two additional sets of practitioner stethoscopes were sampled before and after cleaning using standardized or practitioner-preferred methods.
Bacterial contamination levels were highest on practitioner stethoscopes, followed by patient-room stethoscopes, whereas clean stethoscopes were indistinguishable from background controls. Bacterial communities on stethoscopes were complex, and community analysis by weighted UniFrac showed that physician and patient-room stethoscopes were indistinguishable and significantly different from clean stethoscopes and background controls. Genera relevant to healthcare-associated infections (HAIs) were common on practitioner stethoscopes, among which Staphylococcus was ubiquitous and had the highest relative abundance (6.8%–14% of contaminating bacterial sequences). Other HAI-related genera were also widespread although lower in abundance. Cleaning of practitioner stethoscopes resulted in a significant reduction in bacterial contamination levels, but these levels reached those of clean stethoscopes in only a few cases with either standardized or practitioner-preferred methods, and bacterial community composition did not significantly change.
Stethoscopes used in an ICU carry bacterial DNA reflecting complex microbial communities that include nosocomially important taxa. Commonly used cleaning practices reduce contamination but are only partially successful at modifying or eliminating these communities.
Simulations of strongly stratified turbulence often exhibit coherent large-scale structures called vertically sheared horizontal flows (VSHFs). VSHFs emerge in both two-dimensional (2D) and three-dimensional (3D) stratified turbulence with similar vertical structure. The mechanism responsible for VSHF formation is not fully understood. In this work, the formation and equilibration of VSHFs in a 2D Boussinesq model of stratified turbulence is studied using statistical state dynamics (SSD). In SSD, equations of motion are expressed directly in the statistical variables of the turbulent state. Restriction to 2D turbulence facilitates application of an analytically and computationally attractive implementation of SSD referred to as S3T, in which the SSD is expressed by coupling the equation for the horizontal mean structure with the equation for the ensemble mean perturbation covariance. This second-order SSD produces accurate statistics, through second order, when compared with fully nonlinear simulations. In particular, S3T captures the spontaneous emergence of the VSHF and associated density layers seen in simulations of turbulence maintained by homogeneous large-scale stochastic excitation. An advantage of the S3T system is that the VSHF formation mechanism, which is wave–mean flow interaction between the emergent VSHF and the stochastically excited large-scale gravity waves, is analytically understood in the S3T system. Comparison with fully nonlinear simulations verifies that S3T solutions accurately predict the scale selection, dependence on stochastic excitation strength, and nonlinear equilibrium structure of the VSHF. These results constitute a theory for VSHF formation applicable to interpreting simulations and observations of geophysical examples of turbulent jets such as the ocean’s equatorial deep jets.
Two 0.5 m cores from "Byrd" station, Antarctica have been studied in the laboratory, one from a shallow depth (155 m) and the other from the zone where recrystallization has given a vertical c-axis fabric, and the air in situ is thought to be in clathrate form (1 424 m). The dielectric response has been studied in the frequency range 60 Hz to 10 kHz, and in the temperature range — 6° C to —6o° C. The behaviour observed is markedly different from that of "pure" polycrystalline ice such as may be made by slowly freezing distilled de-ionized water and is thus at variance with the conclusions of Rogers (unpublished) who deduced, from measurements of the admittance of a dipole probe lowered through the fluid-filled drill hole at "Byrd", that the ice surrounding the hole had a dielectric response similar to that of "pure" ice. The Antarctic ice is shown to have properties similar to those of the ice from "Camp Century" and "Site 2" in Greenland studied by Paren (1973). In an attempt to discover what factors determine the difference in electrical behaviour between polar ice and pure ice, some samples were melted and subsequently refrozen slowly. Their dielectric response was similar to that of pure polycrystalline ice. These results are discussed in connection with the impurity content and growth conditions of the ices.
Herein, we demonstrate a facile, rapid, and scalable method to fabricate polymer-based gratings for surface-enhanced Raman spectroscopy (SERS) sensors. To accomplish this, epoxy nanostripe arrays on silicon substrates were prepared using thermal annealing and UV-cross-linking. After preparation of the nanostripe arrays, the surface was briefly treated with oxygen plasma, which decreased the surface energy and enabled the growth of AgNPs on the polymer surface using a simple, low-cost, aqueous-based synthesis procedure. The SERS substrates exhibited a detection limit of ∼1 pM using rhodamine 6G (R6G). In addition, preliminary work with E. coli DH5 showed that the nanoimprinted substrates can be used to obtain Raman spectra of washed bacteria cells.
Determining which biological traits affect taxonomic durations is critical for explaining macroevolutionary patterns. Two approaches are commonly used to investigate the associations between traits and durations and/or extinction and origination rates: analyses of taxonomic occurrence patterns in the fossil record and comparative phylogenetic analyses, predominantly of extant taxa. By capitalizing upon the empirical record of past extinctions, paleontological data avoid some of the limitations of existing methods for inferring extinction and origination rates from molecular phylogenies. However, most paleontological studies of extinction selectivity have ignored phylogenetic relationships because there is a dearth of phylogenetic hypotheses for diverse non-vertebrate higher taxa in the fossil record. This omission inflates the degrees of freedom in statistical analyses and leaves open the possibility that observed associations are indirect, reflecting shared evolutionary history rather than the direct influence of particular traits on durations. Here we investigate global patterns of extinction selectivity in Devonian terebratulide brachiopods and compare the results of taxonomic vs. phylogenetic approaches. Regression models that assume independence among taxa provide support for a positive association between geographic range size and genus duration but do not indicate an association between body size and genus duration. Brownian motion models of trait evolution identify significant similarities in body size, range size, and duration among closely related terebratulide genera. We use phylogenetic regression to account for shared evolutionary history and find support for a significant positive association between range size and duration among terebratulides that is also phylogenetically structured. The estimated range size–duration relationship is moderately weaker in the phylogenetic analysis due to the down-weighting of closely related genera that were both broadly distributed and long lived; however, this change in slope is not statistically significant. These results provide evidence for the phylogenetic conservatism of organismal and emergent traits, yet also the general phylogenetic independence of the relationship between range size and duration.
The present article on the recently excavated neolithic painted pottery fron Ta-ti-wan, Kansu, is intended as a follow-up to a comprehensive treatment of neolithic pottery published in the BMFEA 1981 and is written in light of a re-assessment by some Chinese scholars of the relationships between the Kansu and Central Plains styles. According to the view offered here, the Miao-ti-kou style is seen in its nascent phase at Ta-ti-wan and is explained as having developed from a combination of elements from the Pan-p'o and Wei River styles. The Wei River style is perceived to derive from Ma-chia-yao, although the later stages of Ma-chia-yao may have been coeval with the florescence of Miao-ti-kou.
This paper investigates the relationships between the Early Metal Age cultures of the Inner Mongolia and Gansu-Qinghai area with the Erlitou culture of the Central Plains region, and addresses the issue whether specific metal objects characteristic of these cultures may have their source of inspiration in areas as remote as southern Siberia and present-day Afghanistan and southern Turkmenistan. The proposal that China at the very beginning of its Bronze Age may have been affected by long-distance cultural transmissions depends upon recent reevaluations of the early history of the Eurasian steppe, in particular the advent of nomadic pastoralism and horse riding, and upon newly recalibrated carbon dates ascertained for specific Siberian sites and for the Bactrian-Margiana complex.
The question whether the Xia and the Shang signify a relatively homogeneous culture or relatively distinct cultures is approached through efforts both to determine whether the late Erlitou culture dates to the final years of dynastic Xia or to the beginning of Shang and to identify, in turn, those early Bronze Age sites most likely to correspond to the first recorded Shang capitals. By contrasting traditional chronologies with the developmental sequences of artifacts, the author reaches the conclusion that the Bronze Age remains at Erlitou represent the late Xia culture and the discoveries at Zhengzhou, the period of the Bo capital. A close affiliation between the Shang and the Xia rulers in the time prior to the conquest, revealed by the Bamboo Annals, is shown to be consistent with the archaeological evidence which Indicates that the transition between the two dynastic periods was characterized primarily by continuous development, rather than by disruption or radical change. The proposal is also made that the most significant influence from the eastcoast cultures upon those of the Zhong Yuan may have occurred during Xia times, instead of during Shang.
The main aim of the present study was to investigate the effects of dietary trans-10, cis-12-conjugated linoleic acid (t10c12-CLA) on intestinal microbiota composition and SCFA production. C57BL/6 mice (n 8 per group) were fed a standard diet either supplemented with t10c12-CLA (0·5 %, w/w) (intervention) or with no supplementation (control), daily for 8 weeks. Metabolic markers (serum glucose, leptin, insulin and TAG, and liver TAG) were assessed by ELISA commercial kits, tissue long-chain fatty acids and caecal SCFA by GC, and microbial composition by 16S rRNA pyrosequencing. Dietary t10c12-CLA significantly decreased visceral fat mass (P< 0·001), but did not affect body weight (intervention), when compared with no supplementation (control). Additionally, lipid mass and composition were affected by t10c12-CLA intake. Caecal acetate, propionate and isobutyrate concentrations were higher (P< 0·05) in the t10c12-CLA-supplemented group than in the control group. The analysis of the microbiota composition following 8 weeks of t10c12-CLA supplementation revealed lower proportions of Firmicutes (P= 0·003) and higher proportions of Bacteroidetes (P= 0·027) compared with no supplementation. Furthermore, t10c12-CLA supplementation for 8 weeks significantly altered the gut microbiota composition, harbouring higher proportions of Bacteroidetes, including Porphyromonadaceae bacteria previously linked with negative effects on lipid metabolism and induction of hepatic steatosis. These results indicate that the mechanism of dietary t10c12-CLA on lipid metabolism in mice may be, at least, partially mediated by alterations in gut microbiota composition and functionality.
We describe two cases of infant botulism due to Clostridium butyricum producing botulinum type E neurotoxin (BoNT/E) and a previously unreported environmental source. The infants presented at age 11 days with poor feeding and lethargy, hypotonia, dilated pupils and absent reflexes. Faecal samples were positive for C. butyricum BoNT/E. The infants recovered after treatment including botulism immune globulin intravenous (BIG-IV). C. butyricum BoNT/E was isolated from water from tanks housing pet ‘yellow-bellied’ terrapins (Trachemys scripta scripta): in case A the terrapins were in the infant's home; in case B a relative fed the terrapin prior to holding and feeding the infant when both visited another relative. C. butyricum isolates from the infants and the respective terrapin tank waters were indistinguishable by molecular typing. Review of a case of C. butyricum BoNT/E botulism in the UK found that there was a pet terrapin where the infant was living. It is concluded that the C. butyricum-producing BoNT type E in these cases of infant botulism most likely originated from pet terrapins. These findings reinforce public health advice that reptiles, including terrapins, are not suitable pets for children aged <5 years, and highlight the importance of hand washing after handling these pets.
A healthy gut microbiota plays many crucial functions in the host, being involved in the correct development and functioning of the immune system, assisting in the digestion of certain foods and in the production of health-beneficial bioactive metabolites or ‘pharmabiotics’. These include bioactive lipids (including SCFA and conjugated linoleic acid) antimicrobials and exopolysaccharides in addition to nutrients, including vitamins B and K. Alterations in the composition of the gut microbiota and reductions in microbial diversity are highlighted in many disease states, possibly rendering the host susceptible to infection and consequently negatively affecting innate immune function. Evidence is also emerging of microbially produced molecules with neuroactive functions that can have influences across the brain–gut axis. For example, γ-aminobutyric acid, serotonin, catecholamines and acetylcholine may modulate neural signalling within the enteric nervous system, when released in the intestinal lumen and consequently signal brain function and behaviour. Dietary supplementation with probiotics and prebiotics are the most widely used dietary adjuncts to modulate the gut microbiota. Furthermore, evidence is emerging of the interactions between administered microbes and dietary substrates, leading to the production of pharmabiotics, which may directly or indirectly positively influence human health.
It is essential to observe that Euripides' dramatization of the tragedy of Hippolytus is such as to reveal a striking disparity between word and action, between the values or motives professed by the leading characters and their actual behaviour, between the secondary characters' assessment of the events of the drama and the events themselves. At the basis of such an observation is the noticeable emphasis which Euripides accords to the fact that all the participants in the drama, including the chorus, are most concerned to proffer explanations of the situations and behaviour which confront them. Yet it becomes most apparent that all of these explanations fall far short of a proper assessment of the circumstances with which the play is concerned and the conclusions to which a responsive audience is directed by Euripides' particular organization of the constituents of the traditional story. The following paper is concerned with an examination of the nature and extent of this disparity between statement and performance, and with a determination of its function.
Feet and legs issues are some of the main causes for sow removal in the US swine industry. More timely lameness detection among breeding herd females will allow better treatment decisions and outcomes. Producers will be able to treat lame females before the problem becomes too severe and cull females while they still have salvage value. The objective of this study was to compare the predictive abilities and accuracies of weight distribution and gait measures relative to each other and to a visual lameness detection method when detecting induced lameness among multiparous sows. Developing an objective lameness diagnosis algorithm will benefit animals, producers and scientists in timely and effective identification of lame individuals as well as aid producers in their efforts to decrease herd lameness by selecting animals that are less prone to become lame. In the early stages of lameness, weight distribution and gait are impacted. Lameness was chemically induced for a short time period in 24 multiparous sows and their weight distribution and walking gait were measured in the days following lameness induction. A linear mixed model was used to determine differences between measurements collected from day to day. Using a classification tree analysis, it was determined that the mean weight being placed on each leg was the most predictive measurement when determining whether the leg was sound or lame. The classification tree’s predictive ability decreased as the number of days post-lameness induction increased. The weight distribution measurements had a greater predictive ability compared with the gait measurements. The error rates associated with the weight distribution trees were 29.2% and 31.3% at 6 days post-lameness induction for front and rear injected feet, respectively. For the gait classification trees, the error rates were 60.9% and 29.8% at 6 days post-lameness induction for front and rear injected feet, respectively. More timely lameness detection can improve sow lifetime productivity as well as animal welfare.
The effective use of model-based formal methods in the development of complex embedded systems requires the integration of discrete-event models of controllers with continuous-time models of their environments. This paper proposes a new approach to the development of such combined models (co-models), in which an initial discrete-event model may include approximations of continuous-time behaviour that can subsequently be replaced by couplings to continuous-time models. An operational semantics of co-simulation allows the discrete and continuous models to run on their respective simulators and managed by a coordinating co-simulation engine. This permits the exploration of the composite co-model's behaviour in a range of operational scenarios. The approach has been realised using the Vienna Development Method (VDM) as the discrete-event formalism, and 20-sim as the continuous-time framework, and has been applied successfully to a case study based on the distributed controller for a personal transporter device.