17,557 research outputs found
Photoactivatable metal complexes : from theory to applications in biotechnology and medicine
This short review highlights some of the exciting new experimental and theoretical developments in the field of photoactivatable metal complexes and their applications in biotechnology and medicine. The examples chosen are based on some of the presentations at the Royal Society Discussion Meeting in June 2012, many of which are featured in more detail in other articles in this issue. This is a young field. Even the photochemistry of well-known systems such as metalâcarbonyl complexes is still being elucidated. Striking are the recent developments in theory and computation (e.g. time-dependent density functional theory) and in ultrafast-pulsed radiation techniques which allow photochemical reactions to be followed and their mechanisms to be revealed on picosecond/nanosecond time scales. Not only do some metal complexes (e.g. those of Ru and Ir) possess favourable emission properties which allow functional imaging of cells and tissues (e.g. DNA interactions), but metal complexes can also provide spatially controlled photorelease of bioactive small molecules (e.g. CO and NO)âa novel strategy for site-directed therapy. This extends to cancer therapy, where metal-based precursors offer the prospect of generating excited-state drugs with new mechanisms of action that complement and augment those of current organic photosensitizers
Non-Renormalization Properties of the Chern-Simons Action Coupled to Matter
We analyze an abelian gauge model in 3 dimensions which includes massless
scalar matter fields. By controlling the trace anomalies with a local
dilatation Ward identity, we show that, in perturbation theory and within the
BPHZL scheme, the Chern-Simons term has no radiative corrections. This implies,
in particular, the vanishing of the corresponding function in the
renormalization group equation.Comment: 11 page
Preformed metal crowns for decayed primary molar teeth
BackgroundPreformed metal crowns (PMCs) are recommended by the British Society of Paediatric Dentistry (BSPD) for restoring badly broken down primary molar teeth. However, few dental practitioners adopt this technique in clinical practice, citing cost and clinical difficulty as reasons for this. Whilst there is a subjective impression by clinical academics that PMCs provide a more durable restoration than filling materials, there appears to be little evidence within the literature to support this.ObjectivesThe primary aim of this systematic review was to compare clinical outcomes for primary molar teeth restored using PMCs compared to those restored with filling materials.Search methodsThe literature was searched using: the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2005, Issue 3); MEDLINE (1966 to August 2005); EMBASE (1980 to August 2005); System for Information on Grey Literature in Europe (SIGLE) (1976 to August 2005). Relevant publications' reference lists were reviewed for relevant articles. The most recent search was carried out on 24 August 2005.Selection criteriaRandomised controlled trials (RCTs) that assessed the effectiveness of PMCs compared with filling materials or where there had been no treatment in children with untreated tooth decay in one or more primary molar teeth.Data collection and analysisTwo review authors independently assessed the title and abstracts for each article from the search results to decide whether it was likely to be relevant. Full papers were obtained for relevant articles and all three review authors studied these.Main resultsFortyâseven records were retrieved by the search strategies of which some were duplicates. Of these, 14 studies were scrutinised. No studies met the inclusion criteria and six studies were excluded from the review as they were either retrospective in design or reported as prospective outcomes but not randomised. No data were available for extraction and analysis and therefore, no conclusion could be made as to whether PMCs were more successful than filling materials for restoring primary molar teeth.Authors' conclusionsNo RCTs were available for appraisal. Whilst this technique is recommended by the BSPD for use in clinical practice, the evidence to support this is not strong, consisting mainly of case reports and uncontrolled studies. It is important that the absence of evidence for PMCs is not misinterpreted as evidence for their lack of efficacy.There is a strong need for prospective RCTs comparing PMCs and fillings for managing decayed primary molar teeth. The lower levels of evidence that have been produced, however, have strength in that the clinical outcomes are consistently in favour of PMCs, despite many of the studies placing PMCs on the most damaged of the pair of teeth being analysed
Structure and energetics of solvated ferrous and ferric ions: Car-Parrinello molecular dynamics in the DFT+U formalism
We implemented a rotationally-invariant Hubbard U extension to
density-functional theory in the Car-Parrinello molecular dynamics framework,
with the goal of bringing the accuracy of the DFT+U approach to
finite-temperature simulations, especially for liquids or solids containing
transition-metal ions. First, we studied the effects on the Hubbard U on the
static equilibrium structure of the hexa-aqua ferrous and ferric ions, and the
inner-sphere reorganization energy for the electron-transfer reaction between
aqueous ferrous and ferric ions. It is found that the reorganization energy is
increased, mostly as a result of the Fe-O distance elongation in the hexa-aqua
ferrous ion. Second, we performed a first-principles molecular dynamics study
of the solvation structure of the two aqueous ferrous and ferric ions. The
Hubbard term is found to change the Fe-O radial distribution function for the
ferrous ion, while having a negligible effect on the aqueous ferric ion.
Moreover, the frequencies of vibrations between Fe and oxygen atoms in the
first-solvation shell are shown to be unaffected by the Hubbard corrections for
both ferrous and ferric ions.Comment: 13 pages, 2 figures, 1 table. Submitted to Journal of
Electroanalytical Chemistr
Dielectric Response of Periodic Systems from Quantum Monte Carlo Calculations
We present a novel approach that allows to calculate the dielectric response
of periodic systems in the quantum Monte Carlo formalism. We employ a many-body
generalization for the electric enthalpy functional, where the coupling with
the field is expressed via the Berry-phase formulation for the macroscopic
polarization. A self-consistent local Hamiltonian then determines the
ground-state wavefunction, allowing for accurate diffusion quantum Monte Carlo
calculations where the polarization's fixed point is estimated from the average
on an iterative sequence, sampled via forward-walking. This approach has been
validated for the case of an isolated hydrogen atom, and then applied to a
periodic system, to calculate the dielectric susceptibility of
molecular-hydrogen chains. The results found are in excellent agreement with
the best estimates obtained from the extrapolation of quantum-chemistry
calculations.Comment: 5 page 2figure
Perturbation Theory for Antisymmetric Tensor Fields in Four Dimensions
Perturbation theory for a class of topological field theories containing
antisymmetric tensor fields is considered. These models are characterized by a
supersymmetric structure which allows to establish their perturbative
finiteness.Comment: 23 page
Inhibitors of Bacterial \u3cem\u3eN\u3c/em\u3e-succinyl-L,L-diaminopimelic Acid Desuccinylase (DapE) and Demonstration of in vitro Antimicrobial Activity
The dapE-encoded N-succinyl-L,L-diaminopimelic acid desuccinylase (DapE) is a critical bacterial enzyme for the construction of the bacterial cell wall. A screen biased toward compounds containing zinc-binding groups (ZBGâs) including thiols, carboxylic acids, boronic acids, phosphonates and hydroxamates has delivered a number of micromolar inhibitors of DapE from Haemophilus influenzae, including the low micromolar inhibitor L-captopril (IC50 = 3.3 ÎŒM, Ki = 1.8 ÎŒM). In vitro antimicrobial activity was demonstrated for l-captopril against Escherichia coli
Mechanical properties of carbynes investigated by ab initio total-energy calculations
As sp carbon chains (carbynes) are relatively rigid molecular objects, can we
exploit them as construction elements in nanomechanics? To answer this
question, we investigate their remarkable mechanical properties by ab-initio
total-energy simulations. In particular, we evaluate their linear response to
small longitudinal and bending deformations and their failure limits for
longitudinal compression and elongation.Comment: 6 pages, 4 figures, 1 tabl
Transport properties of room temperature ionic liquids from classical molecular dynamics
Room Temperature Ionic Liquids (RTILs) have attracted much of the attention
of the scientific community in the past decade due the their novel and highly
customizable properties. Nonetheless their high viscosities pose serious
limitations to the use of RTILs in practical applications. To elucidate some of
the physical aspects behind transport properties of RTILs, extensive classical
molecular dynamics (MD) calculations are reported. Bulk viscosities and ionic
conductivities of butyl-methyl-imidazole based RTILs are presented over a wide
range of temperatures. The dependence of the properties of the liquids on
simulation parameters, e.g. system size effects and choice of the interaction
potential, is analyzed
A perceived gap between invasive species research and stakeholder priorities
Information from research has an important role to play in shaping policy and management responses to biological invasions but concern has been raised that research focuses more on furthering knowledge than on delivering practical solutions. We collated 449 priority areas for science and management from 160 stakeholders including practitioners, researchers and policy makers or advisors working with invasive species, and then compared them to the topics of 789 papers published in eight journals over the same time period (2009â2010). Whilst research papers addressed most of the priority areas identified by stakeholders, there was a difference in geographic and biological scales between the two, with individual studies addressing multiple priority areas but focusing on specific species and locations. We hypothesise that this difference in focal scales, combined with a lack of literature relating directly to management, contributes to the perception that invasive species research is not sufficiently geared towards delivering practical solutions. By emphasising the practical applications of applied research, and ensuring that pure research is translated or synthesised so that the implications are better understood, both the management of invasive species and the theoretical science of invasion biology can be enhanced
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