221 research outputs found
Small values of signed harmonic sums
For every \u3c4 08R and every integer N, let mN(\u3c4) be the minimum of the distance of \u3c4 from the sums 11n=1Nsn/n, where s1,\u2026,sn 08 121,+1. We prove that mN(\u3c4
Mixed moments of characteristic polynomials of random unitary matrices
Following the work of Conrey, Rubinstein and Snaith and Forrester and Witte
we examine a mixed moment of the characteristic polynomial and its derivative
for matrices from the unitary group U(N) (also known as the CUE) and relate the
moment to the solution of a Painleve differential equation. We also calculate a
simple form for the asymptotic behaviour of moments of logarithmic derivatives
of these characteristic polynomials evaluated near the unit circle
Rapid identification of Burkholderia mallei and Burkholderia pseudomallei by intact cell Matrix-assisted Laser Desorption/Ionisation mass spectrometric typing
BACKGROUND: Burkholderia (B.) pseudomallei and B. mallei are genetically closely related species. B. pseudomallei causes melioidosis in humans and animals, whereas B. mallei is the causative agent of glanders in equines and rarely also in humans. Both agents have been classified by the CDC as priority category B biological agents. Rapid identification is crucial, because both agents are intrinsically resistant to many antibiotics. Matrix-assisted laser desorption/ionisation mass spectrometry (MALDI-TOF MS) has the potential of rapid and reliable identification of pathogens, but is limited by the availability of a database containing validated reference spectra. The aim of this study was to evaluate the use of MALDI-TOF MS for the rapid and reliable identification and differentiation of B. pseudomallei and B. mallei and to build up a reliable reference database for both organisms. RESULTS: A collection of ten B. pseudomallei and seventeen B. mallei strains was used to generate a library of reference spectra. Samples of both species could be identified by MALDI-TOF MS, if a dedicated subset of the reference spectra library was used. In comparison with samples representing B. mallei, higher genetic diversity among B. pseudomallei was reflected in the higher average Eucledian distances between the mass spectra and a broader range of identification score values obtained with commercial software for the identification of microorganisms. The type strain of B. pseudomallei (ATCC 23343) was isolated decades ago and is outstanding in the spectrum-based dendrograms probably due to massive methylations as indicated by two intensive series of mass increments of 14 Da specifically and reproducibly found in the spectra of this strain. CONCLUSIONS: Handling of pathogens under BSL 3 conditions is dangerous and cumbersome but can be minimized by inactivation of bacteria with ethanol, subsequent protein extraction under BSL 1 conditions and MALDI-TOF MS analysis being faster than nucleic amplification methods. Our spectra demonstrated a higher homogeneity in B. mallei than in B. pseudomallei isolates. As expected for closely related species, the identification process with MALDI Biotyper software (Bruker Daltonik GmbH, Bremen, Germany) requires the careful selection of spectra from reference strains. When a dedicated reference set is used and spectra of high quality are acquired, it is possible to distinguish both species unambiguously. The need for a careful curation of reference spectra databases is stressed
Towards defining reference materials for extracellular vesicle size, concentration, refractive index and epitope abundance
Accurate characterization of extracellular vesicles (EVs) is critical to
explore their diagnostic and therapeutic applications. As the EV research field
has developed, so too have the techniques used to characterize them. The
development of reference materials is required for the standardization of these
techniques. This work, initiated from the ISEV 2017 Biomarker Workshop in
Birmingham, UK, and with further discussion during the ISEV 2019
Standardization Workshop in Ghent, Belgium, sets out to elucidate which
reference materials are required and which are currently available to
standardize commonly used analysis platforms for characterizing EV size,
concentration, refractive index, and epitope expression. Due to their
predominant use, a particular focus is placed on the optical methods
nanoparticle tracking analysis and flow cytometry.Comment: 30 pages, 6 figures, 2 table
Equilibrium and dynamical properties of two dimensional self-gravitating systems
A system of N classical particles in a 2D periodic cell interacting via
long-range attractive potential is studied. For low energy density a
collapsed phase is identified, while in the high energy limit the particles are
homogeneously distributed. A phase transition from the collapsed to the
homogeneous state occurs at critical energy U_c. A theoretical analysis within
the canonical ensemble identifies such a transition as first order. But
microcanonical simulations reveal a negative specific heat regime near .
The dynamical behaviour of the system is affected by this transition : below
U_c anomalous diffusion is observed, while for U > U_c the motion of the
particles is almost ballistic. In the collapsed phase, finite -effects act
like a noise source of variance O(1/N), that restores normal diffusion on a
time scale diverging with N. As a consequence, the asymptotic diffusion
coefficient will also diverge algebraically with N and superdiffusion will be
observable at any time in the limit N \to \infty. A Lyapunov analysis reveals
that for U > U_c the maximal exponent \lambda decreases proportionally to
N^{-1/3} and vanishes in the mean-field limit. For sufficiently small energy,
in spite of a clear non ergodicity of the system, a common scaling law \lambda
\propto U^{1/2} is observed for any initial conditions.Comment: 17 pages, Revtex - 15 PS Figs - Subimitted to Physical Review E - Two
column version with included figures : less paper waste
Miglioramento della resistenza e della performance muscolare mediante trattamento con onde d’urto defocalizzate
Scopo di questo studio \ue8 la valutazione degli effetti di un trattamento con onde d\u2019urto defocalizzate sull\u2019attivit\ue0 del muscolo scheletrico in termini di resistenza e di performance.
Sono stati reclutati 60 soggetti sani, 30 maschi e 30 femmine. 40 pazienti sono stati sottoposti al protocollo di intervento, mentre 20 hanno partecipato al gruppo di controllo, senza ricevere il trattamento con onde d\u2019urto.
Al termine di un ciclo di quattro sedute di onde d\u2019urto si \ue8 osservato un aumento dell\u2019Endurance Time e una diminuzione della Frequenza Cardiaca Massimale durante il test da sforzo a carico costante su cicloergometro.
A 12 settimane dalla fine del trattamento i valori della Frequenza cardiaca Massimale non hanno subito variazioni statisticamente significative, mentre quelli dell\u2019Endurance Time hanno subito un ritorno ai valori basali.
Per quanto riguarda la performance muscolare si \ue8 visto un miglioramento significativo alla valutazione T1, subito dopo la terapia con onde d\u2019urto, e alla valutazione T2, 12 settimane dopo l\u2019ultima seduta di onde d\u2019urto, rispetto alla valutazione iniziale a T0. Non \ue8 stata evidenziata una differenza statisticamente significativa tra i valori rilevati a T1e quelli a T2.
I risultati di questo studio suggeriscono che il trattamento con onde d\u2019urto defocalizzate pu\uf2 portare a un miglioramento dell\u2019attivit\ue0 del muscolo scheletrico in termini di performance e di resistenza muscolare senza provocare alcun tipo di danno ai tessuti.
Questi risultati aprono possibilit\ue0 di applicazione di questa metodica sia in ambito clinico (per esempio per il recupero funzionale dell\u2019amiotrofia ex non usu), sia in ambito sportivo
Amount of substance and the mole in the SI
Abstract
Following the revision of the International System of Units (SI), that takes effect on 20 May 2019, the unit mole is defined by using a fixed number of elementary entities. This number is the fixed numerical value of the Avogadro constant, which is the defining constant of the unit mole. This definition was made possible because the determination of the Avogadro constant had reached a level of relative uncertainty that allowed its value to be fixed and, at the same time, safeguard continuity of measurement results before and after the definition. The motivation for the revision of the SI and the mole in particular will be explained and the experimental work that allowed it is summarized
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