357 research outputs found
Continuous Uniform Finite Time Stabilization of Planar Controllable Systems
Continuous homogeneous controllers are utilized in a full state feedback setting for the uniform finite time stabilization of a perturbed double integrator in the presence of uniformly decaying piecewise continuous disturbances. Semiglobal strong Lyapunov functions are identified to establish uniform asymptotic stability of the closed-loop planar system. Uniform finite time stability is then proved by extending the homogeneity principle of discontinuous systems to the continuous case with uniformly decaying piecewise continuous nonhomogeneous disturbances. A finite upper bound on the settling time is also computed. The results extend the existing literature on homogeneity and finite time stability by both presenting uniform finite time stabilization and dealing with a broader class of nonhomogeneous disturbances for planar controllable systems while also proposing a new class of homogeneous continuous controllers
Unique metabolites protect earthworms against plant polyphenols
All higher plants produce polyphenols, for defence against above-ground herbivory. These polyphenols also influence the soil micro- and macro-fauna that break down plant leaf litter. Polyphenols therefore indirectly affect the fluxes of soil nutrients and, ultimately, carbon turnover and ecosystem functioning in soils. It is unknown how earthworms, the major component of animal biomass in many soils, cope with high-polyphenol diets. Here, we show that earthworms possess a class of unique surface-active metabolites in their gut, which we term ‘drilodefensins’. These compounds counteract the inhibitory effects of polyphenols on earthworm gut enzymes, and high-polyphenol diets increase drilodefensin concentrations in both laboratory and field populations. This shows that drilodefensins protect earthworms from the harmful effects of ingested polyphenols. We have identified the key mechanism for adaptation to a dietary challenge in an animal group that has a major role in organic matter recycling in soils worldwide
Silicon-lattice-matched boron-doped gallium phosphide: A scalable acousto-optic platform
The compact size, scalability, and strongly confined fields in integrated
photonic devices enable new functionalities in photonic networking and
information processing, both classical and quantum. Gallium phosphide (GaP) is
a promising material for active integrated photonics due to its high refractive
index, wide band gap, strong nonlinear properties, and large acousto-optic
figure of merit. In this work we demonstrate that silicon-lattice-matched
boron-doped GaP (BGaP), grown at the 12-inch wafer scale, provides similar
functionalities as GaP. BGaP optical resonators exhibit intrinsic quality
factors exceeding 25,000 and 200,000 at visible and telecom wavelengths
respectively. We further demonstrate the electromechanical generation of
low-loss acoustic waves and an integrated acousto-optic (AO) modulator.
High-resolution spatial and compositional mapping, combined with ab initio
calculations indicate two candidates for the excess optical loss in the visible
band: the silicon-GaP interface and boron dimers. These results demonstrate the
promise of the BGaP material platform for the development of scalable AO
technologies at telecom and provide potential pathways toward higher
performance at shorter wavelengths
Resolving diverse oxygen transport pathways across Sr-doped lanthanum ferrite and metal-perovskite heterostructures
Perovskite structured transition metal oxides are important technological
materials for catalysis and solid oxide fuel cell applications. Their
functionality often depends on oxygen diffusivity and mobility through complex
oxide heterostructures, which can be significantly impacted by structural and
chemical modifications, such as doping. Further, when utilized within
electrochemical cells, interfacial reactions with other components (e.g. Ni-
and Cr-based alloy electrodes and interconnects) can influence the perovskite's
reactivity and ion transport, leading to complex dependencies that are
difficult to control in real-world environments. Here we use isotopic tracers
and atom probe tomography to directly visualize oxygen diffusion and transport
pathways across perovskite and metal-perovskite heterostructures, i.e. (Ni-Cr
coated) Sr-doped lanthanum ferrite (LSFO). Annealing in 18O2(g) results in
elemental and isotopic redistributions through oxygen exchange (OE) in the LSFO
while Ni-Cr undergoes oxidation via multiple mechanisms and transport pathways.
Complementary density functional theory (DFT) calculations at experimental
conditions provide rationale for OE reaction mechanisms and reveal a complex
interplay of different thermodynamic and kinetic drivers. Our results shed
light on the fundamental coupling of defects and oxygen transport in an
important class of catalytic materials.Comment: 39 pages, 10 figure
Interface properties and built-in potential profile of a LaCrO/SrTiO superlattice determined by standing-wave excited photoemission spectroscopy
LaCrO (LCO) / SrTiO (STO) heterojunctions are intriguing due to a
polar discontinuity along (001), two distinct and controllable interface
structures [(LaO)/(TiO) and (SrO)/(CrO)], and
interface-induced polarization. In this study, we have used soft- and hard
x-ray standing-wave excited photoemission spectroscopy (SW-XPS) to generate a
quantitative determination of the elemental depth profiles and interface
properties, band alignments, and the depth distribution of the
interface-induced built-in potentials in the two constituent oxides. We observe
an alternating charged interface configuration: a positively charged
(LaO)/(TiO) intermediate layer at the
LCO/STO interface and a negatively charged
(SrO)/(CrO) intermediate layer at the
STO/LCO interface. Using core-level SW data,
we have determined the depth distribution of species, including through the
interfaces, and these results are in excellent agreement with scanning
transmission electron microscopy and electron energy loss spectroscopy
(STEM-EELS) mapping of local structure and composition. SW-XPS also enabled
deconvolution of the LCO-contributed and STO- contributed
matrix-element-weighted density of states (MEWDOSs) from the valence band (VB)
spectra for the LCO/STO superlattice (SL). Monitoring the VB edges of the
deconvoluted MEWDOS shifts with a change in probing profile, the alternating
charge- induced built-in potentials are observed in both constituent oxides.
Finally, using a two-step simulation approach involving first core-level
binding energy shifts and then valence-band modeling, the built-in potential
gradients across the SL are resolved in detail and represented by the depth
distribution of VB edges.Comment: Main text: 29 pages, 5 figures; Supplementary Information: 20 pages,
10 figure
Waiting times for radiotherapy: variation over time and between cancer networks in southeast England
The aim of this study was to investigate variations in the length of time that patients with cancer wait from diagnosis to treatment with radiotherapy. A total of 57 426 men and 71 018 women diagnosed with cancer between 1992 and 2001 and receiving radiotherapy within 6 months of diagnosis were identified from the Thames Cancer Registry database. In total, 12 sites were identified for which a substantial number or proportion of patients received radiotherapy: head and neck, oesophagus, colon, rectum, lung, nonmelanoma skin cancer, breast, uterus, prostate, bladder, brain and non-Hodgkin's lymphoma. Median waiting times from diagnosis to radiotherapy were calculated, together with the proportion of patients who received radiotherapy within 60 days of diagnosis, and analysed by year of diagnosis, cancer site, deprivation quintile, age at diagnosis, sex and cancer network of either residence or treatment. Logistic regression was used to adjust the proportion receiving treatment within 60 days for the effects of the other factors. There were significant differences in the proportions receiving radiotherapy within 60 days between different networks and different cancer sites, which remained after adjustment. Median waiting times varied from 42 to 65 days across networks of residence, with the adjusted proportion treated within 60 days ranging from 44 to 71%. There was no difference between male and female patients after adjustment for the other factors, particularly site. There was a highly significant trend over time: the median wait increased from 45 days in 1992 to 76 days in 2001, while the adjusted proportion being treated within 60 days declined by almost a half, from 64 to 35%, over the same period
Optimising Psychoeducation for Transient Ischaemic Attack and Minor Stroke Management (OPTIMISM): Protocol for a feasibility randomised controlled trial
Background: A transient ischaemic attack (TIA) and minor stroke are medical emergencies and often a warning sign of future strokes if remain untreated. Few studies have investigated the long-term psychosocial effects of TIA and minor stroke. Secondary prevention and medical management are often the primary focus with limited access offered for further psychosocial support. Psychoeducational interventions can provide education and advice to people with physical health conditions and, with suitable tailoring, could be appropriate for people after TIA and minor stroke. This study aims to develop a group psychoeducational intervention for people after TIA and minor stroke and to test whether it is acceptable and feasible.
Methods: This mixed-methodology study involves two phases: Phase 1) A qualitative study to determine the content of a suitable intervention; Phase 2) A single-centre feasibility randomised controlled trial to evaluate the acceptability of this intervention. The overall study has ethical approval. Stroke survivors have been involved in designing and monitoring the trial. The aim is to recruit 30-40 participants from a Stroke/TIA Service, within 6 months following their diagnosis. Participants will be randomly allocated to either the usual care control group or the intervention group (psychoeducational programme). The programme will consist of six group sessions based on providing education, psychological and social support. The primary outcomes will relate to the feasibility aims of the study. Outcomes will be collected at 3 and 6 months to assess mood, quality of life, knowledge and satisfaction, and resource use.
Discussion: There is a need to develop and evaluate effective interventions that enhance the education provided to people after TIA and minor stroke and to promote their psychosocial wellbeing. Findings will indicate the acceptability of the intervention and parameters needed to conduct a definitive trial
Gene Expression Modifications by Temperature-Toxicants Interactions in Caenorhabditis elegans
Although organophosphorus pesticides (OP) share a common mode of action, there is increased awareness that they elicit a diverse range of gene expression responses. As yet however, there is no clear understanding of these responses and how they interact with ambient environmental conditions. In the present study, we investigated genome-wide gene expression profiles in the nematode Caenorhabditis elegans exposed to two OP, chlorpyrifos and diazinon, in single and combined treatments at different temperatures. Our results show that chlorpyrifos and diazinon induced expression of different genes and that temperature affected the response of detoxification genes to the pesticides. The analysis of transcriptional responses to a combination of chlorpyrifos and diazinon shows interactions between toxicants that affect gene expression. Furthermore, our combined analysis of the transcriptional responses to OP at different temperatures suggests that the combination of OP and high temperatures affect detoxification genes and modified the toxic levels of the pesticides
- …