13,587 research outputs found
Integrable models for shallow water with energy dependent spectral problems
We study the inverse problem for the so-called operators with energy
depending potentials. In particular, we study spectral operators with quadratic
dependance on the spectral parameter. The corresponding hierarchy of integrable
equations includes the Kaup-Bousinesq equation. We formulate the inverse
problem as a Riemann-Hilbert problem with a Z2 reduction group. The soliton
solutions are explicitly obtained.Comment: 17 pages, 3 figure
Safer healthcare at home: Detecting, correcting and learning from incidents involving infusion devices
OBJECTIVE:
Complex medical devices such as infusion pumps are increasingly being used in patientsâ homes with little known about the impact on patient safety. Our aim was to better understand the risks to patient safety in this situation and how these risks might be minimised, by reference to incident reports.
DESIGN:
We identified 606 records of incidents associated with infusion devices that had occurred in a private home and were reported to the UK National Reporting and Learning Service (2005â2015 inclusive). We used thematic analysis to identify key themes.
RESULTS:
In this paper we focus on two emergent themes: detecting and diagnosing incidents; and locating the patient, lay caregivers and their family in incident reports. The majority of incidents were attributed to device malfunction, and resulted in the patient being under-dosed. Delays in recognising and responding to problems were identified, alongside challenges in identifying the cause. We propose a process model for fault diagnosis and correction.
Patients and caregivers did not feature strongly in reports; we highlight how the device is in the home but of the care system, and propose an agent model to describe this; we also identify ways of mitigating this disjoint.
CONCLUSION:
Devices need to be appropriately tailored to the setting in which they are employed, and within a system of care that ensures they are used optimally and safely. Suggested features to improve patient safety include devices that can provide better feedback to identify problems and support resolution, alongside greater monitoring and technical support by care providers for both patients and frontline professionals. The proposed process and agent models provide a structure for reviewing safety and learning from incidents in home health care
Critical percolation of free product of groups
In this article we study percolation on the Cayley graph of a free product of
groups.
The critical probability of a free product of groups
is found as a solution of an equation involving only the expected subcritical
cluster size of factor groups . For finite groups these
equations are polynomial and can be explicitly written down. The expected
subcritical cluster size of the free product is also found in terms of the
subcritical cluster sizes of the factors. In particular, we prove that
for the Cayley graph of the modular group (with the
standard generators) is , the unique root of the polynomial
in the interval .
In the case when groups can be "well approximated" by a sequence of
quotient groups, we show that the critical probabilities of the free product of
these approximations converge to the critical probability of
and the speed of convergence is exponential. Thus for residually finite groups,
for example, one can restrict oneself to the case when each free factor is
finite.
We show that the critical point, introduced by Schonmann,
of the free product is just the minimum of for the factors
A socio-ecological model of agency: The role of structure and agency in shaping education and employment transitions in England
This study examines the role of structural and agentic resources in shaping school-to-work transitions in England. We ask to what extent are young people able to steer the course of their lives despite the constraining forces of social structure, and how satisfied are they with their lives following the completion of compulsory schooling. Drawing on data from the Longitudinal Study of Young People in England we use sequence analysis of monthly activity data to identify differences in the timing and sequencing of education and employment transitions. We identified six distinct pathways, differentiating between an academic track, three pathways involving further education and training, as well as a work-focused transition and a group of young people who were over a long period not in education or training (NEET). The findings suggest that not all young people are inclined to follow an academic track and instead select into pathways involving vocational training or further education, enabling them to experience competence and life satisfaction. For others (about one in 10), however, the lack of socioeconomic and psycho-social resources is too overwhelming and they encounter long-term experience of NEET or are not able to transform their educational credentials into employment opportunities. The findings highlight that in addition to
considering structural constraints it is important to conceptualise the role of the agent for a better understanding of variations in youth transitions
Microwave properties of DyBa_2Cu_3O_(7-x) monodomains and related compounds in magnetic fields
We present a microwave characterization of a DyBaCuO
single domain, grown by the top-seeded melt-textured technique. We report the
(a,b) plane field-induced surface resistance, , at 48.3 GHz,
measured by means of a cylindrical metal cavity in the end-wall-replacement
configuration. Changes in the cavity quality factor Q against the applied
magnetic field yield at fixed temperatures. The temperature
range [70 K ; T_c] was explored. The magnetic field 0.8 T was
applied along the c axis. The field dependence of does not
exhibit the steep, step-like increase at low fields typical of weak-links. This
result indicates the single-domain character of the sample under investigation.
exhibits a nearly square-root dependence on H, as expected for
fluxon motion. From the analysis of the data in terms of motion of Abrikosov
vortices we estimate the temperature dependences of the London penetration
depth and the vortex viscosity , and their zero-temperature
values 165 nm and 3 10 Nsm, which are
found in excellent agreement with reported data in YBaCuO
single crystals. Comparison of microwave properties with those of related
samples indicate the need for reporting data as a function of T/T_c in order to
obtain universal laws.Comment: 6 pages, 4 figures, LaTeX, submitted to Journal of Applied Physic
Future mobility in an ageing society:Where are we heading?
The demographic profile of UK society is changing as people live longer. Maintaining the wellbeing and quality of life of an ageing society is set to be extremely challenging. To what extent can the state afford to meet a potentially burgeoning demand for social care? What expectations will be placed upon informal carers to enable the system to cope? In what ways and to what extent might assistive technologies have a part to play in supporting people both in terms of active ageing and in relation to coping with failing health? Beyond these questions is one which is more explicitly pertinent to transport policy: how and where will older people live and how will this affect patterns of mobility and levels of travel demand? This paper reports on a scenario planning exercise which has examined four different futures for living in later life, defined by considering two critical uncertainties: the extent to which older people in society engage with new healthcare technologies; and the extent to which the state provides care for people living in later life. The scenarios, explored with transport, ageing and assistive technology experts, serve to highlight how social practices may be shaped in very different ways both for older people and for those with whom they interact. The paper goes on to examine the implications for future mobility â such as the role of the home as a trip attractor as well as a trip generator â as well as to explore the extent to which transport policymakers are equipped to address the uncertainties for the transport system of an ageing society
Major features and forcing of highâlatitude northern hemisphere atmospheric circulation using a 110,000âyearâlong glaciochemical series
The Greenland Ice Sheet Project 2 glaciochemical series (sodium, potassium, ammonium, calcium, magnesium, sulfate, nitrate, and chloride) provides a unique view of the chemistry of the atmosphere and the history of atmospheric circulation over both the high latitudes and midâlow latitudes of the northern hemisphere. Interpretation of this record reveals a diverse array of environmental signatures that include the documentation of anthropogenically derived pollutants, volcanic and biomass burning events, storminess over marine surfaces, continental aridity and biogenic source strength plus information related to the controls on both highâ and lowâfrequency climate events of the last 110,000 years. Climate forcings investigated include changes in insolation of the order of the major orbital cycles that control the longâterm behavior of atmospheric circulation patterns through changes in ice volume (sea level), events such as the Heinrich events (massive discharges of icebergs first identified in the marine record) that are found to operate on a 6100âyear cycle due largely to the lagged response of ice sheets to changes in insolation and consequent glacier dynamics, and rapid climate change events (massive reorganizations of atmospheric circulation) that are demonstrated to operate on 1450âyear cycles. Changes in insolation and associated positive feedbacks related to ice sheets may assist in explaining favorable time periods and controls on the amplitude of massive rapid climate change events. Explanation for the exact timing and global synchroneity of these events is, however, more complicated. Preliminary evidence points to possible solar variabilityâclimate associations for these events and perhaps others that are embedded in our iceâcoreâderived atmospheric circulation records
Dynamical percolation on general trees
H\"aggstr\"om, Peres, and Steif (1997) have introduced a dynamical version of
percolation on a graph . When is a tree they derived a necessary and
sufficient condition for percolation to exist at some time . In the case
that is a spherically symmetric tree, H\"aggstr\"om, Peres, and Steif
(1997) derived a necessary and sufficient condition for percolation to exist at
some time in a given target set . The main result of the present paper
is a necessary and sufficient condition for the existence of percolation, at
some time , in the case that the underlying tree is not necessary
spherically symmetric. This answers a question of Yuval Peres (personal
communication). We present also a formula for the Hausdorff dimension of the
set of exceptional times of percolation.Comment: 24 pages; to appear in Probability Theory and Related Field
Non-parametric pricing and hedging of exotic derivatives
In the spirit of ArrowâDebreu, we introduce a family of financial derivatives that act as primitive securities in that exotic derivatives can be approximated by their linear combinations. We call these financial derivatives signature payoffs. We show that signature payoffs can be used to non-parametrically price and hedge exotic derivatives in the scenario where one has access to price data for other exotic payoffs. The methodology leads to a computationally tractable and accurate algorithm for pricing and hedging using market prices of a basket of exotic derivatives that has been tested on real and simulated market prices, obtaining good results
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