Abstract
The lack of solubility and the high degree of volatility of essential oils present significant problems to determining the biological effects of these oils. The activity of 10 essential oils ...and 4 essential oil blends against a Gram-positive bacterium, Staphylococcus aureus., and a yeast, Candida albicans., was compared using a dilution assay and two diffusion methods. The tube dilution assay, using a 0.2% agar solution to provide a stable homogeneous dispersion of oils, was used to measure minimum inhibitory concentrations (MICs). The relative merits of using p.-iodonitro tetrazolium dye (INT) or optical density (OD) in measuring MIC of essential oils also were evaluated. All 14 oils were active against both microorganisms. Thyme, mountain savory, and Turkish oregano were the most active oils against S. aureus. with MICs of 0.31-0.42 µl/ml. Thyme, Turkish oregano, and mountain savory also were the most active against C. albicans. with MICs of 0.31-0.42 µl/ml. The MIC values as determined by INT or OD methods are strongly correlated for both microorganisms, and both give an accurate estimation of MIC. In the disk diffusion assay, thyme, Turkish oregano, Melissa, mountain savory, and the Exodus II (E2) blend were most active against S. aureus.. In the hole-plate assay, the same oils were active against S. aureus. except for Melissa. For C. albicans., thyme, Melissa, mountain savory, Turkish oregano, rosewood, E2 blend, and the T1 blend were most active in the disk diffusion assay. The same oils were active against C. albicans. in the hole-plate diffusion assay except for the T1 blend. Of the methods tested, the tube dilution assay best addresses the solubility and volatility concerns of essential oils. We favor the determination of MIC using INT because of several eliminated steps. Although there were differences in the way in which some essential oils responded in the two diffusion methods, the correlations between the disk and hole-plate diffusion methods were high and yielded comparable results. However, results from the dilution assay were weakly correlated with agar diffusion results. Diffusion assays are useful as a qualitative assessment of biological activity of essential oils but are not appropriate in assessing quantitative effects.
We report on a precise measurement of double-polarization asymmetries in electron-induced breakup of He3 proceeding to pd and ppn final states, performed in quasi-elastic kinematics at ...Q2=0.25(GeV/c)2 for missing momenta up to 250MeV/c. These observables represent highly sensitive tools to investigate the electromagnetic and spin structure of He3 and the relative importance of two- and three-body effects involved in the breakup reaction dynamics. The measured asymmetries cannot be satisfactorily reproduced by state-of-the-art calculations of He3 unless their three-body segment is adjusted, indicating that the spin-dependent part of the nuclear interaction governing the three-body breakup process is much smaller than previously thought.
We have measured the beam-normal single-spin asymmetry $A_n$ in the elastic scattering of 1-3 GeV transversely polarized electrons from $^1$H and for the first time from $^4$He, $^{12}$C, and ...$^{208}$Pb. For $^1$H, $^4$He and $^{12}$C, the measurements are in agreement with calculations that relate $A_n$ to the imaginary part of the two-photon exchange amplitude including inelastic intermediate states. Surprisingly, the $^{208}$Pb result is significantly smaller than the corresponding prediction using the same formalism. These results suggest that a systematic set of new $A_n$ measurements might emerge as a new and sensitive probe of the structure of heavy nuclei.
Superconducting nanowire single photon detectors are capable of single-photon detection across a large spectral range with near unity detection efficiency, picosecond timing jitter, and sub-10 mu m ...position resolution, at rates as high as 10(9) counts/s. In an effort to bring this technology into nuclear physics experiments, we fabricate niobium nitride (NbN) nanowire detectors using ion beam assisted sputtering and test their performance in strong magnetic fields. We demonstrate that these devices are capable of detection of 400 nm wavelength photons with saturated internal quantum efficiency at temperatures of 3 K and in magnetic fields of up to 5 T at high count rates and with nearly zero dark counts.
The last decade has seen a marked shift in how the internal structure of hadrons is understood. Modern experimental facilities, new theoretical techniques for the continuum bound-state problem and ...progress with lattice-regularised QCD have provided strong indications that soft quark+quark (diquark) correlations play a crucial role in hadron physics. For example, theory indicates that the appearance of such correlations is a necessary consequence of dynamical chiral symmetry breaking, viz. a corollary of emergent hadronic mass that is responsible for almost all visible mass in the universe; experiment has uncovered signals for such correlations in the flavour-separation of the proton's electromagnetic form factors; and phenomenology suggests that diquark correlations might be critical to the formation of exotic tetra- and penta-quark hadrons. Therefore, a broad spectrum of such information is evaluated herein, with a view to consolidating the facts and therefrom moving toward a coherent, unified picture of hadron structure and the role that diquark correlations might play.
Nucleon form factor studies at JLab Giusa, A.; Bellini, V.; Mammoliti, F. ...
Applied radiation and isotopes,
08/2011, Letnik:
69, Številka:
8
Journal Article
Recenzirano
The ratio of the electromagnetic proton elastic form factors,
G
p
E
/
G
p
M
, has been measured at Jefferson Lab up to
Q
2
≈
9
(
GeV
/
c
)
2
, by using the CEBAF 6
GeV electron beam, and revealing an ...unexpected and challenging physical behaviour. The 2014 scheduled 12
GeV upgrade will allow the measurement of
G
p
E
/
G
p
M
up to
Q
2
≈
15
(
GeV
/
c
)
2
, by taking advantage of the new large-acceptance forward spectrometer Super BigBite (SBS) in Hall A. Measurements of neutron form factors in the region around 10
(GeV/
c)
2, where quark confinement plays an important role, are expected to show the behaviour already observed in the proton case.
We demonstrate a method for simulating restricted diffusion of hyperpolarized gases in lung airspaces that does not rely on an idealized analytic model of alveolar structure. Instead, the restricting ...geometry was generated from digital representations of histological sections of actual lung tissue obtained from a rabbit model of emphysema. Monte-Carlo simulations of restricted diffusion were performed in the short-time-scale regime, for which the time-dependent diffusivity is quantitatively related to the surface-to-volume ratio (S/V) of the pore space. In each of the eight samples studied, the S/V extracted from the simulated time-dependent diffusivity curves differed by less than 3% from direct assessment of S/V using image-processing methods. Simulated MRI measurements of apparent diffusion coefficients (ADCs) were performed in three representative lung sections to determine the effect of realistic gradient pulse shapes on the extracted S/V values. It was confirmed that ADCs measured at short diffusion times using either narrow or square gradient pulses yield accurate S/V values based on previously derived theoretical relationships. Simulations of triangular and sinusoidal diffusion-sensitizing gradients were then used to quantify the modifications required to extract accurate S/V values from ADC measurements obtained using more realistic gradient waveforms.
We have measured the neutron spin asymmetry A{sub 1}{sup n} with high precision at three kinematics in the deep inelastic region at x = 0.33, 0.47 and 0.60, and Q{sup 2} = 2.7, 3.5 and 4.8 ...(GeV/c){sup 2}, respectively. Our results unambiguously show, for the first time, that A{sub 1}{sup n} crosses zero around x = 0.47 and becomes significantly positive at x = 0.60. Combined with the world proton data, polarized quark distributions were extracted. Our results, in general, agree with relativistic constituent quark models and with perturbative quantum chromodynamics (pQCD) analyses based on the earlier data. However they deviate from pQCD predictions based on hadron helicity conservation.
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