207 research outputs found
A fuzzy qualitative model for the definition of redox potential and pH influence in the AMD of the Poderosa Mine System (Iberian Pyrite Belt SW Spain)
Molecular-orbital theory for the stopping power of atoms in the low velocity regime:the case of helium in alkali metals
A free-parameter linear-combination-of-atomic-orbitals approach is presented
for analyzing the stopping power of slow ions moving in a metal. The method is
applied to the case of He moving in alkali metals. Mean stopping powers for He
present a good agreement with local-density-approximation calculations. Our
results show important variations in the stopping power of channeled atoms with
respect to their mean values.Comment: LATEX, 3 PostScript Figures attached. Total size 0.54
Calibration of the length of a chain of single gold atoms
Using a scanning tunneling microscope or mechanically controllable break
junctions it has been shown that it is possible to control the formation of a
wire made of single gold atoms. In these experiments an interatomic distance
between atoms in the chain of ~3.6 Angstrom was reported which is not
consistent with recent theoretical calculations. Here, using precise
calibration procedures for both techniques, we measure length of the atomic
chains. Based on the distance between the peaks observed in the chain length
histogram we find the mean value of the inter-atomic distance before chain
rupture to be 2.6 +/- 0.2 A . This value agrees with the theoretical
calculations for the bond length. The discrepancy with the previous
experimental measurements was due to the presence of He gas, that was used to
promote the thermal contact, and which affects the value of the work function
that is commonly used to calibrate distances in scanning tunnelling microscopy
and mechanically controllable break junctions at low temperatures.Comment: 6 pages, 6 figure
Quantitative considerations in medium energy ion scattering depth profiling analysis of nanolayers
The high depth resolution capability of medium energy ion scattering (MEIS) is becoming increasingly relevant to the characterisation of nanolayers in e.g. microelectronics. In this paper we examine the attainable quantitative accuracy of MEIS depth profiling. Transparent but reliable analytical calculations are used to illustrate what can ultimately be achieved for dilute impurities in a silicon matrix and the significant element-dependence of the depth scale, for instance, is illustrated this way. Furthermore, the signal intensity-to-concentration conversion and its dependence on the depth of scattering is addressed. Notably, deviations from the Rutherford scattering cross section due to screening effects resulting in a non-coulombic interaction potential and the reduction of the yield owing to neutralization of the exiting, backscattered H+ and He+ projectiles are evaluated. The former mainly affects the scattering off heavy target atoms while the latter is most severe for scattering off light target atoms and can be less accurately predicted. However, a pragmatic approach employing an extensive data set of measured ion fractions for both H+ and He+ ions scattered off a range of surfaces, allows its parameterization. This has enabled the combination of both effects, which provides essential information regarding the yield dependence both on the projectile energy and the mass of the scattering atom. Although, absolute quantification, especially when using He+, may not always be achievable, relative quantification in which the sum of all species in a layer add up to 100%, is generally possible. This conclusion is supported by the provision of some examples of MEIS derived depth profiles of nanolayers. Finally, the relative benefits of either using H+ or He+ ions are briefly considered
ESMO management and treatment adapted recommendations in the COVID-19 era: gynaecological malignancies
The rapid spread of severe acute respiratory syndrome
coronavirus 2 infection and its related disease (COVID-19)
has required an immediate and coordinate healthcare
response to face the worldwide emergency and define
strategies to maintain the continuum of care for the
non-COVID-19 diseases while protecting patients and
healthcare providers. The dimension of the COVID-19
pandemic poses an unprecedented risk especially for the
more vulnerable populations. To manage patients with
cancer adequately, maintaining the highest quality of
care, a definition of value-based priorities is necessary
to define which interventions can be safely postponed
without affecting patientsâ outcome. The European
Society for Medical Oncology (ESMO) has endorsed a
tiered approach across three different levels of priority
(high, medium, low) incorporating information on the
value-based prioritisation and clinical cogency of the
interventions that can be applied for different disease
sites. Patients with gynaecological cancer are at particular
risk of COVID-19 complications because of their age and
prevalence of comorbidities. The definition of priority
level should be based on tumour stage and histology,
cancer-related symptoms or complications, aim (curative
vs palliative) and magnitude of benefit of the oncological
intervention, patientsâ general condition and preferences.
The decision-making process always needs to consider
the disease-specific national and international guidelines
and the local healthcare system and social resources,
and a changing situation in relation to COVID-19 infection.
These recommendations aim to provide guidance for the
definition of deferrable and undeferrable interventions
during the COVID-19 pandemic for ovarian, endometrial
and cervical cancers within the context of the ESMO
Clinical Practice Guidelines
Application of fast Fourier transforms to EPR spectra of free radicals in solution
A method of reducing EPR spectra of free radicals in solution is presented in detail. This method is based on the use of the fast Fourier transform algorithm and curve fitting in the Fourier space by weighted least-squares minimization. Comparison with previous work is shown for EPR spectra of methyl viologen.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23183/1/0000110.pd
Anisotropy studies around the galactic centre at EeV energies with the Auger Observatory
Data from the Pierre Auger Observatory are analyzed to search for
anisotropies near the direction of the Galactic Centre at EeV energies. The
exposure of the surface array in this part of the sky is already significantly
larger than that of the fore-runner experiments. Our results do not support
previous findings of localized excesses in the AGASA and SUGAR data. We set an
upper bound on a point-like flux of cosmic rays arriving from the Galactic
Centre which excludes several scenarios predicting sources of EeV neutrons from
Sagittarius . Also the events detected simultaneously by the surface and
fluorescence detectors (the `hybrid' data set), which have better pointing
accuracy but are less numerous than those of the surface array alone, do not
show any significant localized excess from this direction.Comment: Matches published versio
The Spanish Infrared Camera onboard the EUSO-BALLOON (CNES) flight on August 24, 2014
The EUSO-Balloon (CNES) campaign was held during Summer 2014 with a launch on August
24. In the gondola, next to the Photo Detector Module (PDM), a completely isolated Infrared
camera was allocated. Also, a helicopter which shooted flashers flew below the balloon. We have
retrieved the Cloud Top Height (CTH) with the IR camera, and also the optical depth of the nonclear atmosphere have been inferred with two approaches: The first one is with the comparison of the brightness temperature of the cloud and the real temperature obtained after the pertinent
corrections. The second one is by measuring the detected signal from the helicopter flashers by the IR Camera, considering the energy of the flashers and the location of the helicopter
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