1,606 research outputs found
Alkylideneamino derivatives of some main group elements
This thesis describes the preparation of some alkylideneamino derivatives containing groups R(_2)C:N-attached to lithium, boron, aluminium, gallium, silicon and phosphorus, compounds which were prepared with the object of finding model systems for the study of dative N=M-bonding between nitrogen and these elements. Systems in which R = (^t)Bu proved particularly apt for this purpose. The new compounds di-t-butylmethyleneamine, (^t)BU(_2)C:NH, and its N-lithio and N-trimethylsilyl derivatives, (^t)BU(_2)C:NLi and (^t)Bu(_2)C:NSiMe(_3), were prepared (Chapter I) and used to synthesise di-t-butylmethyleneamino-boranes (Chapter III), -alanes (Chapter IV) and -silanes (Chapter VI), The infrared and (^1)H n.m.r. spectra of the boranes ((^t)Bu(_2)C:N)(_x)BX(_3-x) were consistent with allene-like geometries for these compounds, with the linear C=N=tB skeletons appropriate for significant (p → p) π-interaction between nitrogen and boron. Similar (p →p) and also (p →d) N=Al it-interactions were detected spectroscopically in 3- and 4-co-ordinate aluminium derivatives, and (p →d) N Si n-bonding was apparently indicated by the spectra of some di-t-butylmethyleneaminosilanes, (^t)Bu(_2)C:NSiR(_n)Cl(_3-n). Such interactions have subsequently been confirmed by X-ray crystallographic work on one boron and one aluminium compound. Studies on tetramethylguanidine adducts, (Me(_2)N)(_2)C:NH,AlX(_3) and on derivatives [(Me(_2)N)(_2)C:NAlX(_2)](_2) (X = Et, CI) (Chapter V) showed them to contain only single Al-N bonds, and apparently four-co-ordinate aluminium in each case. The spectroscopic effects of co-ordination of either a proton or boron trifluoride to various alkylideneamines R(^1)R(^2)C:NH, needed as reference systems for interpreting the spectra of derivatives R(^1)R(^2)C:NMX(_n), are described in Chapter II
The Hospital Anxiety And Depression Scale
There is a need to assess the contribution of mood disorder, especially anxiety and depression, in order to understand the experience of suffering in the setting of medical practice. Most physicians are aware of this aspect of the illness of their patients but many feel incompetent to provide the patient with reliable information. The Hospital Anxiety And Depression Scale, or HADS, was designed to provide a simple yet reliable tool for use in medical practice. The term 'hospital' in its title suggests that it is only valid in such a setting but many studies conducted throughout the world have confirmed that it is valid when used in community settings and primary care medical practice. It should be emphasised that self-assessment scales are only valid for screening purposes; definitive diagnosis must rest on the process of clinical examination
Steric engineering of metal-halide perovskites with tunable optical band gaps
Owing to their high energy-conversion efficiency and inexpensive fabrication
routes, solar cells based on metal-organic halide perovskites have rapidly
gained prominence as a disruptive technology. An attractive feature of
perovskite absorbers is the possibility of tailoring their properties by
changing the elemental composition through the chemical precursors. In this
context, rational in silico design represents a powerful tool for mapping the
vast materials landscape and accelerating discovery. Here we show that the
optical band gap of metal-halide perovskites, a key design parameter for solar
cells, strongly correlates with a simple structural feature, the largest
metal-halide-metal bond angle. Using this descriptor we suggest continuous
tunability of the optical gap from the mid-infrared to the visible. Precise
band gap engineering is achieved by controlling the bond angles through the
steric size of the molecular cation. Based on these design principles we
predict novel low-gap perovskites for optimum photovoltaic efficiency, and we
demonstrate the concept of band gap modulation by synthesising and
characterising novel mixed-cation perovskites.Comment: This manuscript was submitted for publication on March 6th, 2014.
Many of the results presented in this manuscript were presented at the
International Conference on Solution processed Semiconductor Solar Cells,
held in Oxford, UK, on 10-12 September 2014. The manuscript is 37 pages long
and contains 8 figure
ALTICORE: an initiative for coastal altimetry
ALTICORE (value-added ALTImetry for COastal REgions) is an international initiative whose main objective is to encourage the operational use of altimetry over coastal areas, by improving the quality and availability of coastal altimetry data. The ALTICORE proposal has recently been submitted for funding to the INTAS scheme (www.intas.be) by a consortium of partners from Italy, France, UK, Russia and Azerbaijan. ALTICORE is also meant as a contribution to the ongoing International Altimeter Service effort.
In this work we will describe the anticipated project stages, namely: 1) improvement of the most widely distributed, 1 Hz, data by analyzing the corrective terms and providing the best solutions, including those derived from appropriate local modelling; 2) development of a set of algorithms to automate quality control and gap-filling functions for the coastal regions; 3) development of testing strategies to ensure a thorough validation of the data.
The improved products will be delivered to ALTICORE users via Grid-compliant technology; this makes it easier to integrate the local data holdings, allows access from a range of services, e.g. directly into model assimilation or GIS systems and should therefore facilitate a widespread and complete assessment of the 1Hz data performance and limitations. We will also outline the design and implementation of the Grid-compliant system for efficient access to distributed archives of data; this consists of regional data centres, each having primary responsibility for regional archives, local corrections and quality control, and operating a set of web-services allowing access to the full functionality of data extraction.
We will conclude by discussing a follow-on phase of the project; this will investigate further improvements on the processing strategy, including the use of higher frequency (10 or 20 Hz) data. Phenomena happen at smaller spatial scales near the coast, so this approach is necessary to match the required resolution. The whole project will hopefully promote the 15-year sea surface height from altimetry to the rank of operational record for the coastal areas
Equivariant comparison of quantum homogeneous spaces
We prove the deformation invariance of the quantum homogeneous spaces of the
q-deformation of simply connected simple compact Lie groups over the
Poisson-Lie quantum subgroups, in the equivariant KK-theory with respect to the
translation action by maximal tori. This extends a result of Neshveyev-Tuset to
the equivariant setting. As applications, we prove the ring isomorphism of the
K-group of Gq with respect to the coproduct of C(Gq), and an analogue of the
Borsuk-Ulam theorem for quantum spheres.Comment: 21 page
On the spacing distribution of the Riemann zeros: corrections to the asymptotic result
It has been conjectured that the statistical properties of zeros of the
Riemann zeta function near z = 1/2 + \ui E tend, as , to the
distribution of eigenvalues of large random matrices from the Unitary Ensemble.
At finite numerical results show that the nearest-neighbour spacing
distribution presents deviations with respect to the conjectured asymptotic
form. We give here arguments indicating that to leading order these deviations
are the same as those of unitary random matrices of finite dimension , where is a well
defined constant.Comment: 9 pages, 3 figure
Randomized double-blind placebo-controlled trial of 40 mg/day of atorvastatin in reducing the severity of sepsis in ward patients (ASEPSIS Trial)
Introduction: Several observational studies suggest that statins modulate the pathophysiology of sepsis and may
prevent its progression. The aim of this study was to determine if the acute administration of atorvastatin reduces
sepsis progression in statin naïve patients hospitalized with sepsis.
Methods: A single centre phase II randomized double-blind placebo-controlled trial. Patients with sepsis were
randomized to atorvastatin 40 mg daily or placebo for the duration of their hospital stay up to a maximum of
28-days. The primary end-point was the rate of sepsis progressing to severe sepsis during hospitalization.
Results: 100 patients were randomized, 49 to the treatment with atorvastatin and 51 to placebo. Patients in the
atorvastatin group had a significantly lower conversion rate to severe sepsis compared to placebo (4% vs. 24% p =
0.007.), with a number needed to treat of 5. No significant difference in length of hospital stay, critical care unit
admissions, 28-day and 12-month readmissions or mortality was observed. Plasma cholesterol and albumin
creatinine ratios were significantly lower at day 4 in the atorvastatin group (p < 0.0001 and p = 0.049 respectively).
No difference in adverse events between the two groups was observed (p = 0.238).
Conclusions: Acute administration of atorvastatin in patients with sepsis may prevent sepsis progression. Further
multi-centre trials are required to verify these findings.
Trial Registration: International Standard Randomized Control Trial Registry ISRCTN64637517
Using remote substituents to control solution structure and anion binding in lanthanide complexes.
A study of the anion-binding properties of three structurally related lanthanide complexes, which all contain chemically identical anion-binding motifs, has revealed dramatic differences in their anion affinity. These arise as a consequence of changes in the substitution pattern on the periphery of the molecule, at a substantial distance from the binding pocket. Herein, we explore these remote substituent effects and explain the observed behaviour through discussion of the way in which remote substituents can influence and control the global structure of a molecule through their demands upon conformational space. Peripheral modifications to a binuclear lanthanide motif derived from α,α′-bis(DO3 Ayl)-m-xylene are shown to result in dramatic changes to the binding constant for isophthalate. In this system, the parent compound displays considerable conformational flexibility, yet can be assumed to bind to isophthalate through a well-defined conformer. Addition of steric bulk remote from the binding site restricts conformational mobility, giving rise to an increase in binding constant on entropic grounds as long as the ideal binding conformation is not excluded from the available range of conformers
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