152 research outputs found
Dispersal distances and migration rates at the arctic treeline in Siberia – a genetic and simulation-based study
A strong
temperature increase in the Arctic is expected to lead to latitudinal
treeline shift. This tundra–taiga turnover would cause a positive
vegetation–climate feedback due to albedo decrease. However, reliable
estimates of tree migration rates are currently lacking due to the complex
processes involved in forest establishment, which depend strongly on seed
dispersal.
We aim to fill this gap using LAVESI, an individual-based and spatially
explicit Larix vegetation simulator. LAVESI was designed to simulate plots within
homogeneous forests. Here, we improve the implementation of the seed
dispersal function via field-based investigations. We inferred the effective
seed dispersal distances of a typical open-forest stand on the southern
Taymyr Peninsula (northern central Siberia) from genetic parentage analysis
using eight nuclear microsatellite markers.
The parentage analysis gives effective seed dispersal distances (median ∼10 m) close to the seed parents. A comparison between simulated and
observed effective seed dispersal distances reveals an overestimation of
recruits close to the releasing tree and a shorter dispersal distance
generally. We thus adapted our model and used the newly parameterised version
to simulate south-to-north transects; a slow-moving treeline front was
revealed. The colonisation of the tundra areas was assisted by occasional
long-distance seed dispersal events beyond the treeline area. The treeline
(∼1 tree ha−1) advanced by ∼1.6 m yr−1, whereas the
forest line (∼100 trees ha−1) advanced by only ∼0.6 m yr−1.
We conclude that the treeline in northern central Siberia currently lags behind
the current strong warming and will continue to lag in the near future.</p
Implementing spatially explicit wind-driven seed and pollen dispersal in the individual-based larch simulation model: LAVESI-WIND 1.0
It is of major interest to estimate the feedback of arctic ecosystems to the
global warming we expect in upcoming decades. The speed of this response is
driven by the potential of species to migrate, tracking their climate
optimum. For this, sessile plants have to produce and disperse seeds to newly
available habitats, and pollination of ovules is needed for the seeds to be
viable. These two processes are also the vectors that pass genetic
information through a population. A restricted exchange among subpopulations
might lead to a maladapted population due to diversity losses. Hence, a
realistic implementation of these dispersal processes into a simulation model
would allow an assessment of the importance of diversity for the migration of
plant species in various environments worldwide. To date, dynamic global
vegetation models have been optimized for a global application and
overestimate the migration of biome shifts in currently warming temperatures.
We hypothesize that this is caused by neglecting important fine-scale
processes, which are necessary to estimate realistic vegetation trajectories.
Recently, we built and parameterized a simulation model LAVESI for larches
that dominate the latitudinal treelines in the northernmost areas of Siberia.
In this study, we updated the vegetation model by including seed and pollen
dispersal driven by wind speed and direction. The seed dispersal is modelled
as a ballistic flight, and for the pollination of ovules of seeds produced,
we implemented a wind-determined and distance-dependent probability
distribution function using a von Mises distribution to select the pollen
donor. A local sensitivity analysis of both processes supported the
robustness of the model's results to the parameterization, although it
highlighted the importance of recruitment and seed dispersal traits for
migration rates. This individual-based and spatially explicit implementation
of both dispersal processes makes it easily feasible to inherit plant traits
and genetic information to assess the impact of migration processes on the
genetics. Finally, we suggest how the final model can be applied to
substantially help in unveiling the important drivers of migration dynamics
and, with this, guide the improvement of recent global vegetation models.</p
Standard and Embedded Solitons in Nematic Optical Fibers
A model for a non-Kerr cylindrical nematic fiber is presented. We use the
multiple scales method to show the possibility of constructing different kinds
of wavepackets of transverse magnetic (TM) modes propagating through the fiber.
This procedure allows us to generate different hierarchies of nonlinear partial
differential equations (PDEs) which describe the propagation of optical pulses
along the fiber. We go beyond the usual weakly nonlinear limit of a Kerr medium
and derive an extended Nonlinear Schrodinger equation (eNLS) with a third order
derivative nonlinearity, governing the dynamics for the amplitude of the
wavepacket. In this derivation the dispersion, self-focussing and diffraction
in the nematic are taken into account. Although the resulting nonlinear
may be reduced to the modified Korteweg de Vries equation (mKdV), it also has
additional complex solutions which include two-parameter families of bright and
dark complex solitons. We show analytically that under certain conditions, the
bright solitons are actually double embedded solitons. We explain why these
solitons do not radiate at all, even though their wavenumbers are contained in
the linear spectrum of the system. Finally, we close the paper by making
comments on the advantages as well as the limitations of our approach, and on
further generalizations of the model and method presented.Comment: "Physical Review E, in press
Bodies on the margins: regulating bodies, regulatory bodies
Sport is all about bodies, but some bodies are seen as on the margins and policies are directed at re-situating them into the mainstream. This article explores some of the ways in which embodied selves are the target of diversity policies and practices, especially those implemented by fan-based, anti-racist organisations. I use the phenomenological concepts of lived bodies and embodied selves to explore some of the processes involved in addressing 'bodies on the margins' in sport. Sport has long been considered a site for the creation of healthy citizens, a tradition which has been rearticulated to encompass diverse groups of people who are seen as under-represented in sport. This article looks at which embodied selves are encouraged to participate by non-governmental regulatory bodies in sport, to investigate the tension between the positive and negative dimensions of diversity politics in sport, as an example of what Paul Gilroy calls 'conviviality'
Limits of JT gravity
We construct various limits of JT gravity, including Newton-Cartan and
Carrollian versions of dilaton gravity in two dimensions as well as a theory on
the three-dimensional light cone. In the BF formulation our boundary conditions
relate boundary connection with boundary scalar, yielding as boundary action
the particle action on a group manifold or some Hamiltonian reduction thereof.
After recovering in our formulation the Schwarzian for JT, we show that
AdS-Carroll gravity yields a twisted warped boundary action. We comment on
numerous applications and generalizations.Comment: 41 pages, 3 figures, 1 table; v2: Matches published version +
Footnote 11; v3: Corrected typo in Carrollian/Galilean generalized dilaton
potentia
Self-assembled nanogel made of mannan : synthesis and characterization
Amphiphilic mannan (mannan-C16) was synthesized by the Michael addition of hydrophobic 1-hexadecanethiol (C16)
to hydroxyethyl methacrylated mannan (mannan-HEMA). Mannan-C16 formed nanosized aggregates in water by selfassembly
via the hydrophobic interaction among C16molecules as confirmed by hydrogen nuclearmagnetic resonance (1H
NMR), fluorescence spectroscopy, cryo-field emission scanning electron microscopy (cryo-FESEM), and dynamic light
scattering (DLS). The mannan-C16 critical aggregation concentration (cac), calculated by fluorescence spectroscopy with
Nile red and pyrene, ranged between 0.04 and 0.02mg/mL depending on the polymer degree of substitution ofC16 relative
to methacrylated groups. Cryo-FESEM micrographs revealed that mannan-C16 formed irregular spherical macromolecular
micelles, in this work designated as nanogels, with diameters ranging between 100 and 500 nm. The influence of the
polymer degree of substitution, DSHEMA andDSC16, on the nanogel size and zeta potential was studied byDLS at different
pH values and ionic strength and as a function of mannan-C16 and urea concentrations. Under all tested conditions, the
nanogel was negatively charged with a zeta potential close to zero. Mannan-C16 with higher DSHEMA and DSC16
values
formed larger nanogels andwere also less stable over a 6month storage period and at concentrations close to the cac.When
exposed to solutions of different pH and aggressive conditions of ionic strength and urea concentration, the size of
mannan-C16 varied to some extent but was always in the nanoscale range.International Iberian
Nanotechnology Laboratory (INL)Fundação para a Ciência e a Tecnologia (FCT
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Pharmacists in general practice: a qualitative interview case study of stakeholders’ experiences in a West London GP Federation
Background
Increased patient demand for healthcare services coupled with a shortage of general practitioners necessitates changes in professional roles and service delivery. In 2016, NHS England began a three year pilot study of pharmacists in general practice, however, this is not an entirely new initiative. There is limited, current, evidence-based, UK research to inform the pilot so studies of pre-existing services must suffice until findings from a formal national evaluation are available.
Methods
The aim of this exploratory, descriptive interview study was to explore the experiences of stakeholders in eight general practices in the Ealing GP Federation, West London, where pharmacy services have been provided for several years. Forty-seven participants, including pharmacy team members (pre-registration and clinical pharmacists, independent prescribers and pharmacy technicians), general practitioners, patients, practice managers, practice nurses and receptionists took part in semi-structured, audio-recorded qualitative interviews which were transcribed verbatim, coded and analysed thematically to extract the issues raised by participants and the practicalities of providing pharmacy services in general practice.
Results
Findings are reported under the themes of Complementarity (incorporating roles, skills, education and workloads); Integration (incorporating relationships, trust and communication) and Practicalities (incorporating location and space, access, and costs). Participants reported the need for time to develop and understand the various roles, develop communication processes and build inter-professional trust. Once these were established, however, experiences were positive and included decreased workloads, increased patient safety, improved job satisfaction, improved patient relationships, and enhanced cost savings. Areas for improvement included patients’ awareness of services; pharmacists’ training; and regular, onsite access for practice staff to the pharmacy team.
Conclusions
Recommendations are made for the development of clear role definitions, identification of training needs, dedication of time for team building, production of educational materials for practice staff members and patients, and provision of on-site, full-time pharmacy services. Future work should focus on evaluation of various models of employing pharmacy teams in general practice; integration of pharmacists and pharmacy technicians into multidisciplinary general practice teams; relationships between local community pharmacy and general practice personnel and patients’ service and information needs. A formal national evaluation of the pilot scheme is overdue
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