649 research outputs found
Aluminium Nanowires: Influence of Work Hardening on Conductance Histograms
Conductance histograms of work-hardened Al show a series up to 11 equidistant
peaks with a period of 1.15 +/- 0.02 of the quantum conductance unit G_0 =
2e^2/h. Assuming the peaks originate from atomic discreteness, this agrees with
the value of 1.16 G_0 per atom obtained in numerical calculations by Hasmy et
al.Comment: 4 pages, 4 figure
Network theory approach for data evaluation in the dynamic force spectroscopy of biomolecular interactions
Investigations of molecular bonds between single molecules and molecular
complexes by the dynamic force spectroscopy are subject to large fluctuations
at nanoscale and possible other aspecific binding, which mask the experimental
output. Big efforts are devoted to develop methods for effective selection of
the relevant experimental data, before taking the quantitative analysis of bond
parameters. Here we present a methodology which is based on the application of
graph theory. The force-distance curves corresponding to repeated pulling
events are mapped onto their correlation network (mathematical graph). On these
graphs the groups of similar curves appear as topological modules, which are
identified using the spectral analysis of graphs. We demonstrate the approach
by analyzing a large ensemble of the force-distance curves measured on:
ssDNA-ssDNA, peptide-RNA (system from HIV1), and peptide-Au surface. Within our
data sets the methodology systematically separates subgroups of curves which
are related to different intermolecular interactions and to spatial
arrangements in which the molecules are brought together and/or pulling speeds.
This demonstrates the sensitivity of the method to the spatial degrees of
freedom, suggesting potential applications in the case of large molecular
complexes and situations with multiple binding sites
Atomic size oscillations in conductance histograms for gold nanowires and the influence of work hardening
Nanowires of different nature have been shown to self-assemble as a function
of stress at the contact between two macroscopic metallic leads. Here we
demonstrate for gold wires that the balance between various metastable nanowire
configurations is influenced by the microstructure of the starting materials
and we discover a new set of periodic structures, which we interpret as due to
the atomic discreteness of the contact size for the three principal crystal
orientations.Comment: This version corrects an error in attributing the three observed
periods, and includes a comparison with recent model calculation
Correlative Microscopy of Morphology and Luminescence of Cu porphyrin aggregates
Transfer of energy and information through molecule aggregates requires as
one important building block anisotropic, cable-like structures. Knowledge on
the spatial correlation of luminescence and morphology represents a
prerequisite in the understanding of internal processes and will be important
for architecting suitable landscapes. In this context we study the morphology,
fluorescence and phosphorescence of molecule aggregate structures on surfaces
in a spatially correlative way. We consider as two morphologies, lengthy
strands and isotropic islands. It turns out that phosphorescence is quite
strong compared to fluorescence and the spatial variation of the observed
intensities is largely in line with the amount of dye. However in proportion,
the strands exhibit more fluorescence than the isotropic islands suggesting
weaker non-radiative channels. The ratio fluorescence to phosphorescence
appears to be correlated with the degree of aggregation or internal order. The
heights at which luminescence saturates is explained in the context of
attenuation and emission multireflection, inside the dye. This is supported by
correlative photoemission electron microscopy which is more sensitive to the
surface region. The lengthy structures exhibit a pronounced polarization
dependence of the luminescence with a relative dichroism up to about 60%,
revealing substantial perpendicular orientation preference of the molecules
with respect to the substrate and parallel with respect to the strands
A novel methodology for in vivo endoscopic phenotyping of colorectal cancer based on real-time analysis of the mucosal lipidome: a prospective observational study of the iKnife
Background: This pilot study assessed the diagnostic accuracy of rapid evaporative ionization mass spectrometry (REIMS) in colorectal cancer (CRC) and colonic adenomas. Methods: Patients undergoing elective surgical resection for CRC were recruited at St. Mary’s Hospital London and The Royal Marsden Hospital, UK. Ex vivo analysis was performed using a standard electrosurgery handpiece with aspiration of the electrosurgical aerosol to a Xevo G2-S iKnife QTof mass spectrometer (Waters Corporation). Histological examination was performed for validation purposes. Multivariate analysis was performed using principal component analysis and linear discriminant analysis in Matlab 2015a (Mathworks, Natick, MA). A modified REIMS endoscopic snare was developed (Medwork) and used prospectively in five patients to assess its feasibility during hot snare polypectomy. Results: Twenty-eight patients were recruited (12 males, median age 71, range 35–89). REIMS was able to reliably distinguish between cancer and normal adjacent mucosa (NAM) (AUC 0.96) and between NAM and adenoma (AUC 0.99). It had an overall accuracy of 94.4 % for the detection of cancer versus adenoma and an adenoma sensitivity of 78.6 % and specificity of 97.3 % (AUC 0.99) versus cancer. Long-chain phosphatidylserines (e.g., PS 22:0) and bacterial phosphatidylglycerols were over-expressed on cancer samples, while NAM was defined by raised plasmalogens and triacylglycerols expression and adenomas demonstrated an over-expression of ceramides. REIMS was able to classify samples according to tumor differentiation, tumor budding, lymphovascular invasion, extramural vascular invasion and lymph node micrometastases (AUC’s 0.88, 0.87, 0.83, 0.81 and 0.81, respectively). During endoscopic deployment, colonoscopic REIMS was able to detect target lipid species such as ceramides during hot snare polypectomy. Conclusion: REIMS demonstrates high diagnostic accuracy for tumor type and for established histological features of poor prognostic outcome in CRC based on a multivariate analysis of the mucosal lipidome. REIMS could augment endoscopic and imaging technologies for precision phenotyping of colorectal cancer
Evaluating the performance of ionic liquid coatings for mitigation of spacecraft surface charges
To reduce the impact of charging effects on satellites, cheap and lightweight
conductive coatings are desirable. We mimic space-like charging environments in
ultra-high vacuum (UHV) chambers during deposition of charges via the electron
beam of a scanning electron microscope (SEM). We use the charge induced
signatures in SEM images of a thin ionic liquid (IL) film on insulating
surfaces such as glass, to assess the general performance of such coatings. In
order to get a reference structure in SEM, the samples were structured by
nanosphere lithography and coated with IL. The IL film (we choose BMP DCA, due
to its beneficial physical properties) was applied ex situ and a thickness of
10 to 30 nm was determined by reflectometry. Such an IL film is stable under
vacuum conditions. It would also only lead to additional mass of below 20
mg/m. At about 5 A/m e/(sm), a typical
sample charging rate in SEM, imaging is possible with no noticeable contrast
changes over many hours; this electron current density is already 6 orders of
magnitudes higher than "worst case geosynchronous environments" of
A/m. Measurements of the surface potential are used for
further insights in the reaction of IL films to the electron beam of a SEM.
Participating mechanisms such as polarization or reorientation will are
discussed.Comment: Submitted to Proceedings of the 14th IAA Symposium on Small
Satellites for Earth System Observatio
Initial teacher training to promote health and well-being in schools – a systematic review of effectiveness and barriers and facilitators
Objectives: to conduct a systematic review of effectiveness, and barriers and facilitators, of initial teacher training to promote health and wellbeing in schools. Design: systematic review of the literature Method: a total of 20 bibliographic databases were searched, including Medline, Embase, and the Social Science Citation Index. Studies were included if they reported research into the processes and/or outcomes of initial (pre?service) teacher training to promote health. Results: a total of 20 studies met the inclusion criteria, mainly from the UK and Australia. Twelve studies assessed outcomes, commonly using uncontrolled before and after assessment designs. Sixteen studies evaluated the processes of training. Training was diverse in terms of content, format and health topics. The studies demonstrated short?term increases in trainee teachers’ factual knowledge of health issues, a general increase in teachers’ confidence to teach about health and to identify and help children with specific health issues. There was an increase in teachers’ positive beliefs about their role in promoting children’s health. None of the studies assessed changes in pupil outcomes. The training was generally considered acceptable and adequate by trainee teachers. However, some of trainees felt that they still lacked knowledge and confidence to address sensitive health issues on entering teaching practice. Conclusion: this systematic review identified some evidence for the effectiveness of teacher training for health, and highlighted factors which facilitate and inhibit effective training. Further evaluation, using controlled trial designs with long?term follow?up of teacher and pupil outcomes, may enable teachers to effectively address the health and education needs of school pupils <br/
Correlations in nano-scale step fluctuations: comparison of simulation and experiments
We analyze correlations in step-edge fluctuations using the
Bortz-Kalos-Lebowitz kinetic Monte Carlo algorithm, with a 2-parameter
expression for energy barriers, and compare with our VT-STM line-scan
experiments on spiral steps on Pb(111). The scaling of the correlation times
gives a dynamic exponent confirming the expected step-edge-diffusion
rate-limiting kinetics both in the MC and in the experiments. We both calculate
and measure the temperature dependence of (mass) transport properties via the
characteristic hopping times and deduce therefrom the notoriously-elusive
effective energy barrier for the edge fluctuations. With a careful analysis we
point out the necessity of a more complex model to mimic the kinetics of a
Pb(111) surface for certain parameter ranges.Comment: 10 pages, 9 figures, submitted to Physical Review
DeamiDATE 1.0:Site-specific deamidation as a tool to assess authenticity of members of ancient proteomes
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