8,255 research outputs found
Gamble mode: Resonance contact mode in atomic force microscopy
Active noise reduction has been accomplished in atomic force microscopy by applying a high frequency, low amplitude vibration to the cantilever while it is in contact with a surface. The applied excitation (>~ 200 kHz; ~ 1 nm) is acoustically coupled to the tip and dampens the resonance Q factors of the system. The applied frequency is well above the bandwidth of the acquisition system (50 kHz). We call this mode "gamble mode" or "resonance contact.
Why Two Renormalization Groups are Better than One
The advantages of using more than one renormalization group (RG) in problems
with more than one important length scale are discussed. It is shown that: i)
using different RG's can lead to complementary information, i.e. what is very
difficult to calculate with an RG based on one flow parameter may be much more
accessible using another; ii) using more than one RG requires less physical
input in order to describe via RG methods the theory as a function of its
parameters; iii) using more than one RG allows one to solve problems with more
than one diverging length scale. The above points are illustrated concretely in
the context of both particle physics and statistical physics using the
techniques of environmentally friendly renormalization. Specifically, finite
temperature theory, an Ising-type system in a film geometry, an
Ising-type system in a transverse magnetic field, the QCD coupling constant at
finite temperature and the crossover between bulk and surface critical
behaviour in a semi-infinite geometry are considered.Comment: 17 pages LaTex; to be published in the Proceedings of RG '96, Dubn
Noise reduction in atomic force microscopy: Resonance contact mode
Noise reduction has been accomplished in atomic force microscopy by applying a high frequency, low amplitude vibration to the cantilever while it is in contact with a surface. The applied excitation (>~200 kHz; ~1 nm) is acoustically coupled to the tip and dampens the resonance Q factors of the system. The applied frequency is well above the bandwidth of the acquisition system (50 kHz). We call this mode "resonance contact" mode. The nonlinear behavior of the tipâsample interaction allows the high frequency excitation to effectively broaden the frequency response of the system resonances
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The Adjudication and Enforcement of Rights After Brexit
This report records the inaugural meeting and roundtable of the Brexit and Rights Engagement Network (BREN) on Tuesday 3rd July 2018 at Edinburgh Law School. Attendees at the roundtable included network members, fellow academics, representatives of the Scottish Parliament, the Scottish Government, the Scottish Human Rights Commission, the Equality and Human Rights Commission, the legal professions, and NGOs. Two years after the EU Referendum and only a few days after the European Union (Withdrawal) Act 2018 (the 2018 Act) receiving Royal Assent, the Brexit and Rights Engagement Network met for the first time. The purpose of the roundtable was to ignite debate amongst legal scholars and policy makers, and others working in a rights environment relating to interpretation, adjudication and enforcement of rights in the lead up to, and following âBrexit Day,â (March 29, 2019). This report is split into two sections, Part A will consider the adjudication of EU rights, but also their enforcement under the 2018 Act and the Withdrawal Agreement, whilst âoptions for the futureâ will be broached in Part B
Information systems, software engineering, and systems thinking: challenges and opportunities
This article traces past research on the application of the systems approach to information systems development within the disciplines of information systems and software engineering. Their origins historically are related to a number of areas, including general systems theory. While potential improvement of software development practices is linked by some leading experts to the application of more systemic methods, the current state of the practice in software engineering and information systems development shows this is some way from being achieved. The authors propose possible directions for future research and practical work on bringing together both fields with systems thinking
Antimicrobial antagonists against food pathogens; a bacteriocin perspective
peer-reviewedEfforts are continuing to find novel bacteriocins with enhanced specificity and potency. Traditional plating techniques are still being used for bacteriocin screening studies, however, the availability of ever more bacterial genome sequences and the use of in silico gene mining tools have revealed novel bacteriocin gene clusters that would otherwise have been overlooked. Furthermore, synthetic biology and bioengineering-based approaches are allowing scientists to harness existing and novel bacteriocin gene clusters through expression in different hosts and by enhancing functionalities. The same principles apply to bacteriocin producing probiotic cultures and their application to control pathogens in the gut. We can expect that the recent developments on bacteriocins from Lactic Acid Bacteria (LAB) described here will contribute greatly to increased commercialisation of bacteriocins in food systems.This work was funded by the Alimentary Pharmabiotic Centre, a research centre funded by Science Foundation Ireland (SFI), through the Irish Governmentâs National Development Plan. The authors and their work were supported by SFI (grant no. 12/RC/2273
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Estimating drizzle drop size and precipitation rate using two-colour lidar measurements
A method to estimate the size and liquid water content of drizzle drops using lidar measurements at two wavelengths is described. The method exploits the differential absorption of infrared light by liquid water at 905 nm and 1.5 ÎŒm, which leads to a different backscatter cross section for water drops larger than â50 ÎŒm. The ratio of backscatter measured from drizzle samples below cloud base at these two wavelengths (the colour ratio) provides a measure of the median volume drop diameter D0. This is a strong effect: for D0=200 ÎŒm, a colour ratio of â6 dB is predicted. Once D0 is known, the measured backscatter at 905 nm can be used to calculate the liquid water content (LWC) and other moments of the drizzle drop distribution.
The method is applied to observations of drizzle falling from stratocumulus and stratus clouds. High resolution (32 s, 36 m) profiles of D0, LWC and precipitation rate R are derived. The main sources of error in the technique are the need to assume a value for the dispersion parameter ÎŒ in the drop size spectrum (leading to at most a 35% error in R) and the influence of aerosol returns on the retrieval (â10% error in R for the cases considered here). Radar reflectivities are also computed from the lidar data, and compared to independent measurements from a colocated cloud radar, offering independent validation of the derived drop size distributions
Topological Phase Transitions and Holonomies in the Dimer Model
We demonstrate that the classical dimer model defined on a toroidal hexagonal
lattice acquires holonomy phases in the thermodynamic limit. When all
activities are equal the lattice sizes must be considered mod 6 in which case
the finite size corrections to the bulk partition function correspond to a
massless Dirac Fermion in the presence of a flat connection with nontrivial
holonomy. For general bond activities we find that the phase transition in this
model is a topological one, where the torus degenerates and its modular
parameter becomes real at the critical temperature. We argue that these
features are generic to bipartite dimer models and we present a more general
lattice whose continuum partition function is that of a massive Dirac Fermion.Comment: 7 pages, 4 figures. Minor corrections with additional figure
The Specific Heat of a Ferromagnetic Film.
We analyze the specific heat for the vector model on a -dimensional
film geometry of thickness using ``environmentally friendly''
renormalization. We consider periodic, Dirichlet and antiperiodic boundary
conditions, deriving expressions for the specific heat and an effective
specific heat exponent, \alpha\ef. In the case of , for , by
matching to the exact exponent of the two dimensional Ising model we capture
the crossover for \xi_L\ra\infty between power law behaviour in the limit
{L\over\xi_L}\ra\infty and logarithmic behaviour in the limit
{L\over\xi_L}\ra0 for fixed , where is the correlation length in
the transverse dimensions.Comment: 21 pages of Plain TeX. Postscript figures available upon request from
[email protected]
In Vitro Activities of Nisin and Nisin Derivatives Alone and In Combination with Antibiotics against Staphylococcus Biofilms
peer-reviewedThe development and spread of pathogenic bacteria that are resistant to the existing
catalog of antibiotics is a major public health threat. Biofilms are complex, sessile
communities of bacteria embedded in an organic polymer matrix which serve to further
enhance antimicrobial resistance. Consequently, novel compounds and innovative
methods are urgently required to arrest the proliferation of drug-resistant infections in
both nosocomial and community environments. Accordingly, it has been suggested
that antimicrobial peptides could be used as novel natural inhibitors that can be used
in formulations with synergistically acting antibiotics. Nisin is a member of the lantibiotic
family of antimicrobial peptides that exhibit potent antibacterial activity against many
Gram-positive bacteria. Recently we have used bioengineering strategies to enhance
the activity of nisin against several high profile targets, including multi-drug resistant
clinical pathogens such as methicillin-resistant Staphylococcus aureus, vancomycinresistant
enterococci, staphylococci, and streptococci associated with bovine mastitis.
We have also identified nisin derivatives with an enhanced ability to impair biofilm
formation and to reduce the density of established biofilms of methicillin resistant
S. pseudintermedius. The present study was aimed at evaluating the potential of
nisin and nisin derivatives to increase the efficacy of conventional antibiotics and
to assess the possibility of killing and/or eradicating biofilm-associated cells of a
variety of staphylococcal targets. Growth curve-based comparisons established that
combinations of derivatives nisin V C penicillin or nisin I4V C chloramphenicol had
an enhanced inhibitory effect against S. aureus SA113 and S. pseudintermedius
DSM21284, respectively, compared to the equivalent nisin A C antibiotic combinations
or when each antimicrobial was administered alone. Furthermore, the metabolic activity
of established biofilms treated with nisin V C chloramphenicol and nisin I4V C
chloramphenicol combinations revealed a significant decrease in S. aureus SA113 and
S. pseudintermedius DSM21284 biofilm viability, respectively, compared to the nisin A C
antibiotic combinations as determined by the rapid colorimetric XTT assay. The results
indicate that the activities of the nisin derivative and antibiotic combinations represent a
significant improvement over that of the wild-type nisin and antibiotic combination and
merit further investigation with a view to their use as anti-biofilm agents.DF,CH,PC,RR are supported by the Irish Government under the National Development Plan, through a Science Foundation Ireland (SFI)Technology and Innovation Development Award
(TIDA14/TIDA/2286)to DF,a SFI Investigator awards to CH
and RR(10/IN.1/B3027),SFI-PI funding(11/PI/1137)to PC and the Alimentary Pharmabiotic Centre under Grant Number SFI/12/RC/2273
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