391 research outputs found
A genetic algorithm to design Laue lenses with optimal performance for focusing hard X- and gamma-rays
In order to focus hard X- and gamma-rays it is possible to make use of a Laue
lens as a concentrator. With this optical tool it would be possible to improve
the detection of radiation for several applications, spanning from the
observation of the most violent phenomena in the sky to nuclear medicine
applications, for diagnostic and therapeutic purposes. A code named LaueGen,
based on a genetic algorithm and aimed to designing optimized Laue lenses, has
been implemented. The genetic algorithm was selected because the optimization
of a Laue lens is a complex and discretized problem. The output of the code
consists in the design of a Laue lens composed of diffracting crystals selected
and arranged in such a way to maximize the performance of the lens. The code
allows one to manage crystals of any material and crystallographic orientation.
The program is structured in such a way that the user can control all the
initial parameters of the lens. As a result, LaueGen is highly versatile and
can be used for the design of very small lens, e.g. for nuclear medicine, to
very large lens, e.g. for satellite-borne astrophysical missions.Comment: 18 pages, 4 figure
Bent crystal selection and assembling for the LAUE project
For the first time, with the Laue project, bent crystals are being used for
focusing photons in the 80-300 keV energy range. The advantage is their high
reflectivity and better Point Spread Function with respect to the mosaic flat
crystals. Simulations have already shown their excellent focusing capability
which makes them the best candidates for a Laue lens whose sensitivity is also
driven by the size of the focused spot. Selected crystals are Germanium
(perfect, (111)) and Gallium Arsenide (mosaic, (220)) with 40 m curvature
radius to get a spherical lens with 20 m long focal length. A lens petal is
being built. We report the measurement technique by which we are able to
estimate the exact curvature of each tile within a few percent of uncertainty
and their diffraction efficiency. We also discuss some results.Comment: 9 pages, 15 figures, SPIE conference vol. 8861 (2013
AEI Student Design Competition: Value Engineering & Design Build
The Architectural Engineering Institute puts on a yearly student design competition that features interdisciplinary teams from colleges across the country. The project for the competition was the Jack H. Miller Center for Musical and Performing Arts on the Hope College campus in Holland Michigan. The main challenges in the problem statement address acoustics, using mass timber, and add alternative roof top space. Through a collaborative process, our team created a proposal that addressed the challenges and why we were the best fit for the job. I worked with a fellow construction management student, Shannon Wheeler, to produce our portion of the work. We created a multi-level estimate, schedule, site logistics plan, and other project management plans. We achieved this through our knowledge in the construction curriculum as well as being assisted from faculty and industry members. Overall, I learned that effective communication was a big key to success and that we had created a strong proposal by the date it was due
Steering efficiency of a ultrarelativistic proton beam in a thin bent crystal
Crystals with small thickness along the beam exhibit top performance for
steering particle beams through planar channeling. For such crystals, the
effect of nuclear dechanneling plays an important role because it affects their
efficiency. We addressed the problem through experimental work carried out with
400 GeV/c protons at fixed-target facilities of CERN-SPS. The dependence of
efficiency vs. curvature radius has been investigated and compared favourably
to the results of modeling. A realistic estimate of the performance of a
crystal designed for LHC energy including nuclear dechanneling has been
achieved.Comment: 16 pages, 6 figure
Insights into the Sensing Mechanism of a Metal-Oxide Solid Solution via Operando Diffuse Reflectance Infrared Fourier Transform Spectroscopy
Recently, the influence of Nb addition in the oxide solid solution of Sn and Ti was investigated with regard to the morphological, structural and electrical properties for the production of chemoresistive gas sensors. (Sn,Ti,Nb)xO2-based sensors showed promising features for ethanol monitoring in commercial or industrial settings characterized by frequent variation in relative humidity. Indeed, the three-metal solid solution highlighted a higher response level vs. ethanol than the most widely used SnO2 and a remarkably low effect of relative humidity on the film resistance. Nevertheless, lack of knowledge still persists on the mechanisms of gas reaction occurring at the surface of these nanostructures. In this work, operando Diffuse Reflectance Infrared Fourier Transform spectroscopy was used on SnO2- and on (Sn,Ti,Nb)xO2-based sensors to combine the investigations on the transduction function, i.e., the read-out of the device activity, with the investigations on the receptor function, i.e., compositional characterization of the active sensing element in real time and under operating conditions. The sensors performance was explained by probing the interaction of H2O and ethanol molecules with the material surface sites. This information is fundamental for fine-tuning of material characteristics for any specific gas sensing applications
Topical Issue "Dynamics of Systems on the Nanoscale (2021)". Editorial
Exploration of the structure formation and dynamics of animate and inanimate
matter on the nanometer scale is a highly interdisciplinary field of rapidly
emerging research. It is relevant for various molecular and nanoscale systems
of different origins and compositions and concerns numerous phenomena
originating from physics, chemistry, biology, and materials science. This
topical issue presents a collection of research papers devoted to different
aspects of the Dynamics of Systems on the Nanoscale. Some of the contributions
discuss specific applications of the research results in several modern and
emerging technologies, such as controlled nanofabrication with charged particle
beams or the design and practical realization of novel gamma-ray crystal-based
light sources. Most works presented in this topical issue were reported at the
joint Sixth International Conference "Dynamics of Systems on the Nanoscale" and
the tenth International Symposium "Atomic Cluster Collisions" (DySoN-ISACC
2021), which were held in Santa Margherita Ligure, Italy, in October 2021.Comment: Editorial for the topical issue "Dynamics of Systems on the Nanoscale
(2021)" of the European Physical Journal D; see
https://epjd.epj.org/component/toc/?task=topic&id=161
Relaxation of axially confined 400 GeV/c protons to planar channeling in a bent crystal
An investigation on the mechanism of relaxation
of axially confined 400 GeV/c protons to planar channeling
in a bent crystal was carried out at the extracted line H8 from
CERN Super Proton Synchrotron. The experimental results
were critically compared to computer simulations, showing
a good agreement. We identified a necessary condition for
the exploitation of axial confinement or its relaxation for
particle beam manipulation in high-energy accelerators. We
introduce the idea of using a short bent crystal, aligned with
one of its main axis to the beam direction, as a beam steerer
or a beam splitter with adjustable intensity in the field of particle
accelerators. In particular, in the latter case, a complete
relaxation from axial confinement to planar channeling takes
place, resulting in beam splitting into the two strongest skew
planar channels.An investigation on the mechanism of relaxation of axially confined 400 GeV/c protons to planar channeling in a bent crystal was carried out at the extracted line H8 from CERN Super Proton Synchrotron. The experimental results were critically compared to computer simulations, showing a good agreement. We identified a necessary condition for the exploitation of axial confinement or its relaxation for particle beam manipulation in high-energy accelerators. We introduce the idea of using a short bent crystal, aligned with one of its main axis to the beam direction, as a beam steerer or a beam splitter with adjustable intensity in the field of particle accelerators. In particular, in the latter case, a complete relaxation from axial confinement to planar channeling takes place, resulting in beam splitting into the two strongest skew planar channels
New Approach for the Detection of Sub-ppm Limonene: An Investigation through Chemoresistive Metal-Oxide Semiconductors
R-(+)-limonene, one of the major constituents of citrus oils, is a monoterpene that is widely used as a fragrance additive in cosmetics, foods, and industrial solvents. Nowadays, its detection mainly relies on bulky and expensive analytical methods and only a few research works proved its revelation through affordable and portable sensors, such as electrochemical and quartz crystal microbalance sensors. In response to the demand for effective miniaturized sensing devices to be integrated into Internet of Things systems, this study represents a pioneering investigation of
chemoresistive gas sensor capabilities addressed to R-(+)-limonene detection. An array of seven metal-oxide sensors was exploited to perform a complete electrical characterization of the target analyte. The experimental evidence allowed us to identify the WO3-based sensor as the most promising candidate for R-(+)-limonene detection. The material was highly sensitive already at sub-ppm concentrations (response of 2.5 at 100 ppb), consistent with applicative parameters, and it resulted in selective vs. different gases at a lower operating temperature (200 ◦C) than the other
sensors tested. Furthermore, it exhibited a humidity-independent behavior under real-life conditions (relative humidity > 20%). Finally, the WO3 sensor also demonstrated a remarkable cross-selectivity, thus enabling its exploitation in cutting-edge applications
Modelling soil water conent in a tomato field: proximal gamma ray spectroscopy and soil-crop system models
Proximal soil sensors are taking hold in the understanding of soil
hydrogeological processes involved in precision agriculture. In this context,
permanently installed gamma ray spectroscopy stations represent one of the best
space-time trade off methods at field scale. This study proved the feasibility
and reliability of soil water content monitoring through a seven-month
continuous acquisition of terrestrial gamma radiation in a tomato test field.
By employing a 1 L sodium iodide detector placed at a height of 2.25 m, we
investigated the gamma signal coming from an area having a ~25 m radius and
from a depth of approximately 30 cm. Experimental values, inferred after a
calibration measurement and corrected for the presence of biomass, were
corroborated with gravimetric data acquired under different soil moisture
conditions, giving an average absolute discrepancy of about 2%. A quantitative
comparison was carried out with data simulated by AquaCrop, CRITeRIA, and
IRRINET soil-crop system models. The different goodness of fit obtained in bare
soil condition and during the vegetated period highlighted that CRITeRIA showed
the best agreement with the experimental data over the entire data-taking
period while, in presence of the tomato crop, IRRINET provided the best
results.Comment: 18 pages, 9 Figures, 3 Table
Synchronous anal canal cancer and cervical cancer: report of a case and management implication
Background: This is the case report of a synchronous anal canal cancer and cervical cancer in a patient who underwent definitive chemoradiotherapy (CRT) and radical surgery for anal canal and cervical carcinoma, respectively. Case Report: A 55-year-old woman was diagnosed with cT4a cN1 Mx anal canal squamous cell carcinoma and stage IA2 cervical squamous cell carcinoma, based on biopsy and imaging. Definitive CRT consisted of radiotherapy (total dose of 59.4 Gy) and concomitant mitomycin (10 mg/m(2)) and 5-fluorouracil (750 mg/m(2)/5 daily continuous infusion) during the first and last week of radiation. The patient exhibited a complete clinical and radiological response. A radical hysterectomy with pelvic lymphadenectomy was then performed. At the last follow-up (30 months), the patient is still disease-free without any treatment-associated complications. Conclusion: There is limited information in the literature regarding treatment strategy and outcome of patients with synchronous anal canal and cervical cancer. A two-step treatment, including CRT and radical hysterectomy, is likely to be accepted as valid option
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