233 research outputs found
Two types of bone necrosis in the Middle Triassic Pistosaurus longaevus bones: the results of integrated studies
Avascular necrosis, diagnosed on the basis of either a specific pathological modification of the articular surfaces of bone or its radiologic appearance in vertebral centra, has been recognized in many Mesozoic marine reptiles as well as in present-day marine mammals. Its presence in the zoological and paleontologic record is usually associated with decompression syndrome, a disease that affects secondarily aquatic vertebrates that could dive. Bone necrosis can also be caused by infectious processes, but it differs in appearance from decompression syndrome-associated aseptic necrosis. Herein, we report evidence of septic necrosis in the proximal articular surface of the femur of a marine reptile, Pistosaurus longaevus, from the Middle Triassic of Poland and Germany. This is the oldest recognition of septic necrosis associated with septic arthritis in the fossil record so far, and the mineralogical composition of pathologically altered bone is described herein in detail. The occurrence of septic necrosis is contrasted with decompression syndrome-associated avascular necrosis, also described in Pistosaurus longaevus bone from Middle Triassic of Germany
Computer faceted thermal model of helicopter
The paper presents a computer Faceted Thermal Target Model of helicopter (FTTM) describing radiative properties of target in the infrared. The model is predestined for target simulation in analyses of influence of thermal-scene conditions on the possibilities of target detection by a thermodetection system. This is a faceted model describing the target as a set of facets. The set of data for the model of helicopter requires information on the shape and dimensions of the target as well as on temperature distribution and emissivity coefficient of its surface. The model enables to determine emission of radiation from the target surface for various directions and distances of detection. It makes possible to obtain the data necessary to design devices for infrared recognition with a limited application of costly experimental investigations. 1
Different route of hydroxide incorporation and thermal stability of new type of water clathrate : X-ray single crystal and Raman investigation
Chlormayenite Ca12Al14O32[♦4Cl2] (♦-vacancy) is partially hydrated micro porouss mineral with hydroxide groups situated at various crystallographic sites. There are few mechanisms describing its hydration. The first one assumes Cl- substitution by OH- at the center of the structural cages (W-site). The second one determines the converting a T1O4 tetrahedron to a T1O3(OH)3 octahedron due to the replacement of oxygen at the O2 site by three OH-groups according to the scheme: (O2O2- + W Cl-) → 3 × O2aOH. The third mechanism, not considered so far in the case of zeolite-like minerals, includes the hydroxide incorporation in form of hydrogarnet defect due to the arrangement of tetrahedral (OH)4 in vacant cages. This yields a strong hydrated phase containing even up to 35% of water more than in any currently known mineral applicable to Portland cement. Moreover, water molecules present in different structural cages are stable up to 355 K while dehydroxylation linked to the gradual loss of only 8% of OH- groups according to 3 O2aOH- → O2O2- + W OH- + gH2O occurs at temperature range from 355 K to 598 K
Unexpected Crossover in the kinetics of mutarotation in the supercooled region : the role of H-bonds
Intra- and intermolecular studies on the molten L-sorbose have been carried out at variable temperature
conditions to determine the crosover temperature (Tc). In addition, isothermal time-dependent
FTIR and Raman measurements were performed to probe the pace of mutarotation and activation
energy of this reaction in the studied saccharide, which varied from 53–62 kJ/mol up to 177–192 kJ/mol
below and above Tc, respectively. To explain the change in activation barrier for the mutarotation a
complementary analysis using difference FTIR spectra collected around Tc = 365 K in the hydroxyl region
has been done. It was found that the alteration of kinetic parameters and molecular dynamics around Tc
are strictly related to the variation in the strength of H-bonds which above Tc are significantly weaken,
increasing the freedom of rotation of functional groups and movement of individual molecules. That
phenomenon most likely affects the proton transfer, underlying molecular mechanism of mutarotation,
which may lead to the significant increase in activation barrier. The new insight into a molecular aspect
of the mutarotation around Tc has created an opportunity to better understanding the relationship
between physics of condensed matter and the potential role of H-bonds dynamics on the progress of
the chemical reaction in highly viscous systems
Microstructural and magnetic characterization of Ni0.5Zn0.5Fe2O4 ferrite nanoparticles
International audienc
Leveraging Case Study Research: A Mechanism to Measure Teaching Effectiveness
This article shares findings from a descriptive, multiple case study assessing graduate outcomes 2.5 years after the completion of a teacher education program. Case study was used as an alternative to value-added measures to holistically examine complex attributes of effective teaching. Mixed methods data collection included graduate and supervisor surveys, self and supervisor evaluation of skills and dispositions, interviews, and classroom observations. Results indicated participants effectively applied the knowledge, skills, and dispositions the program was designed to achieve in the areas of Learner and Learning, Content, Instructional Practice, and Professional Responsibility. Three major recommendations emerged: 1) the necessity to develop established proficiency levels for new teachers related to diverse learners, 2) the need for shared responsibility of outcomes and targeted induction support, and 3) support for supervisor evaluation as a viable mechanism for education program accountability of teaching effectiveness of graduates
A feasibility study of ortho-positronium decays measurement with the J-PET scanner based on plastic scintillators
We present a study of the application of the Jagiellonian Positron Emission
Tomograph (J-PET) for the registration of gamma quanta from decays of
ortho-positronium (o-Ps). The J-PET is the first positron emission tomography
scanner based on organic scintillators in contrast to all current PET scanners
based on inorganic crystals. Monte Carlo simulations show that the J-PET as an
axially symmetric and high acceptance scanner can be used as a multi-purpose
detector well suited to pursue research including e.g. tests of discrete
symmetries in decays of ortho-positronium in addition to the medical imaging.
The gamma quanta originating from o-Ps decay interact in the plastic
scintillators predominantly via the Compton effect, making the direct
measurement of their energy impossible. Nevertheless, it is shown in this paper
that the J-PET scanner will enable studies of the o-Ps decays with
angular and energy resolution equal to and
keV, respectively. An order of magnitude shorter decay
time of signals from plastic scintillators with respect to the inorganic
crystals results not only in better timing properties crucial for the reduction
of physical and instrumental background, but also suppresses significantly the
pileups, thus enabling compensation of the lower efficiency of the plastic
scintillators by performing measurements with higher positron source
activities
Commissioning of the J-PET detector for studies of decays of positronium atoms
The Jagiellonian Positron Emission Tomograph (J-PET) is a detector for
medical imaging of the whole human body as well as for physics studies
involving detection of electron-positron annihilation into photons. J-PET has
high angular and time resolution and allows for measurement of spin of the
positronium and the momenta and polarization vectors of annihilation quanta. In
this article, we present the potential of the J-PET system for background
rejection in the decays of positronium atoms.Comment: Presented at the 2nd Jagiellonian Symposium on Fundamental and
Applied Subatomic Physics, Krak\'ow, Poland, June 4-9, 2017. To be published
in Acta Phys. Pol.
J-PET: a new technology for the whole-body PET imaging
The Jagiellonian Positron Emission Tomograph (J-PET) is the first PET built
from plastic scintillators. J-PET prototype consists of 192 detection modules
arranged axially in three layers forming a cylindrical diagnostic chamber with
the inner diameter of 85 cm and the axial field-of-view of 50 cm. An axial
arrangement of long strips of plastic scintillators, their small light
attenuation, superior timing properties, and relative ease of the increase of
the axial field-of-view opens promising perspectives for the cost effective
construction of the whole-body PET scanner, as well as construction of MR and
CT compatible PET inserts. Present status of the development of the J-PET
tomograph will be presented and discussed.Comment: Presented at the 2nd Jagiellonian Symposium on Fundamental and
Applied Subatomic Physics, Krak\'ow, Poland, June 4-9, 2017. To be published
in Acta Phys. Pol.
Multichannel FPGA based MVT system for high precision time (20~ps~RMS) and charge measurement
In this article it is presented an FPGA based ulti-oltage hreshold
(MVT) system which allows of sampling fast signals ( ns rising and falling
edge) in both voltage and time domain. It is possible to achieve a precision of
time measurement of ps RMS and reconstruct charge of signals, using a
simple approach, with deviation from real value smaller than 10.
Utilization of the differential inputs of an FPGA chip as comparators together
with an implementation of a TDC inside an FPGA allowed us to achieve a compact
multi-channel system characterized by low power consumption and low production
costs. This paper describes realization and functioning of the system
comprising 192-channel TDC board and a four mezzanine cards which split
incoming signals and discriminate them. The boards have been used to validate a
newly developed Time-of-Flight Positron Emission Tomography system based on
plastic scintillators. The achieved full system time resolution of
(TOF) ps is by factor of two better with respect to the
current TOF-PET systems.Comment: Accepted for publication in JINST, 10 pages, 8 figure
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