New zinc lead borate glasses with (50B
2
O
3
–10ZnO–(40 −
y
) PbO)–
y
Fe
2
O
3
: 0 ≤
y
≤ 10 wt%) composition were synthesized by the conventional melt-quench technique. The amorphous nature of the ...glasses was tested by using X-ray diffraction spectroscopy. FTIR spectra for the glasses were recorded in the range of 4000–400 cm
−1
. Physical properties of the proposed glasses were evaluated. The mass attenuation coefficients (
μ
/
ρ
) for the glasses were calculated by the Geant4 simulation toolkit code and XCOM software within the photon energy range 365–2510 keV. Different γ-ray shielding parameters such as half-value layer, tenth value layer, and transmission fraction for the proposed glasses were evaluated using the obtained values of the (
μ
/
ρ
). Results reveal that for 1 cm glass thickness, the (50B
2
O
3
–10ZnO–30PbO)–10Fe
2
O
3
sample has the highest transmission, due to the lower amount of Pb, and thus poorer shielding capability among the other glass samples. In addition, the probabilities of γ-ray interaction with the studied glasses were investigated.
Structural, physical and gamma ray shielding properties of Dy3+ doped telluroborate glasses have been discussed. The molar volume of the glasses is proportional to the TeO2 content. The FTIR studies ...investigate the expansion of TeO2 content and the dynamic change of tetrahedral BO4 units into trigonal BO3 units. Using the absorption spectra, optical band gap (Eg) and Urbach's energy (ΔE) values are calculated. The molar volume of oxygen (VO) and boron‑boron separation (<dB–B>) values are increasing while there is a fall in oxygen packing density (OPD) from 0% to 40% of TeO2. The ionic nature of the present glasses is analyzed from the bonding parameter (δ), optical basicity (Λth), covalent and ionic characteristic factors. The gamma photon attenuation investigated employing GEANT4 code. The transmission factor (TF) shows that 0TBD sample (0 wt% of TeO2) has the highest TF, while the 4TBD sample (40 wt% of TeO2) has the lowest TF.
•The molar volume of oxygen increases with the TeO2 content.•All the glasses are highly ionic in nature.•More amount of TeO2 provides better photons attenuation in the glass network.•4TBD glass has the highest attenuation performance.
The important gamma and neutron radiation shielding parameters of the Dy3+ doped (65-x)Na2B4O7–15SiO2–20MoO3-xDy2O3 (x = 0, 5, 10, 15, 20 mol%) glass quaternary system were investigated to provide ...decisive information for their application in radiation environment. Gamma and neutron attenuation properties of the glass systems studied here were evaluated in terms of the mass attenuation coefficient (μm), transmission fraction (TF), half value layer (HVL), mean free path (MFP), effective atomic number (Zeff), exposure buildup factors (EBF) and fast neutron removal cross-section (∑R) parameters. Investigation of the each aforementioned parameter was performed thanks to the utilization of Monte Carlo simulations along with the Phy-X/PSD database. The photon attenuation characteristics were evaluated for gamma ray energies varying between 0.284 and 5.0 MeV. This study indicated that increase of the Dy2O3 content from 0% to 20% mole, enhances the gamma shielding capability due to the increase of the parameters μm and Zeff. In this study it was also observed that ∑R increases from 0.099 to 0.107 cm−1 as the molar fraction of Dy2O3 increases.
The Antarctic Peninsula is considered to be the last region of Antarctica to have been fully glaciated as a result of Cenozoic climatic cooling. As such, it was likely the last refugium for plants ...and animals that had inhabited the continent since it separated from the Gondwana supercontinent. Drill cores and seismic data acquired during two cruises (SHALDRIL I and II) in the northernmost Peninsula region yield a record that, when combined with existing data, indicates progressive cooling and associated changes in terrestrial vegetation over the course of the past 37 million years. Mountain glaciation began in the latest Eocene (approximately 37-34 Ma), contemporaneous with glaciation elsewhere on the continent and a reduction in atmospheric COâ concentrations. This climate cooling was accompanied by a decrease in diversity of the angiosperm-dominated vegetation that inhabited the northern peninsula during the Eocene. A mosaic of southern beech and conifer-dominated woodlands and tundra continued to occupy the region during the Oligocene (approximately 34-23 Ma). By the middle Miocene (approximately 16-11.6 Ma), localized pockets of limited tundra still existed at least until 12.8 Ma. The transition from temperate, alpine glaciation to a dynamic, polythermal ice sheet took place during the middle Miocene. The northernmost Peninsula was overridden by an ice sheet in the early Pliocene (approximately 5.3-3.6 Ma). The long cooling history of the peninsula is consistent with the extended timescales of tectonic evolution of the Antarctic margin, involving the opening of ocean passageways and associated establishment of circumpolar circulation.
The purpose of this study is the evaluation of radial collapse, based on the number of screws used in the metaphyseal region and by distal dorsal distance (DDD) and lunate facet distance (LFD) ...measurement.
Between 2015 and 2019, 60 patients who were being treated with volar locking plates due to isolated distal radius fracture were evaluated. Control radiographs were taken on the first day and at 3rd-, 6th- and 12th-month follow-ups. Distal dorsal cortex distance and lunate facet distance were measured in the lateral radiographs. The number of screws used in the metaphyseal region was also evaluated. According to the number of screws, the amount of collapse was analysed based on both the LFD and the DDD.
The mean age of patients was 43.5±12.7 years. Thirty-three of the patients included in the study were male and 27 were female, and the minimum follow-up period was one year. According to the mean number of screws, groups were defined as up to 6 screws or 7 screws and above. There was a statistically significant difference between the groups in terms of DDD collapse at the 6th-month and 12th-month follow-ups (p<0.005). It was observed that the radial collapse and decrease in DDD and LFD were lower in plates with seven screws and above.
Decreases in either DDD or LFD, or radial collapse were observed less in patients who had seven or more metaphyseal screws inserted. These findings might be useful for surgeons treating distal radius fractures to reduce radial collapse.
This survey was conducted to reveal the gamma and neutron stopping performance of the 30PbO–10ZnO—(60-x)TeO2—xB2O3 (x = 0, 10, 20, 30, 50% mole) glass quaternary. Gamma and neutron attenuation ...parameters including the linear attenuation coefficient (μ), transmission fraction (TF), half value layer (HVL), mean free path (MFP), effective atomic number (Zeff), exposure buildup factor (EBF) and fast neutron removal cross-section (∑R) were determined computationally using the Geant4 and Phy-X/PSD database tools and for photon energies ranging between 0.284 MeV and 2.510 MeV. It was found that increasing the B2O3 content from 0% to 50% mole and correspondingly decreasing the TeO2 content from 60% to 10% mole results in a degradation of μ by 18.2% and of Zeff by 28.6% at 0.284 MeV. Due to this decrease in μ and Zeff, the values of TF and HVL increased by 37.3% and 22.4% respectively. In the present study it was also observed that the density (ρ) of glass quaternary decreased with the decreasing content of TeO2, and that the density of glass has a remarkable effect on the photon attenuation characteristics. The Degradation of μ, Zeff, ρ and the increase of TF and HVL proves that the photon attenuation ability of the glasses investigated worsens with decreasing content of TeO2, as Tellurium's atomic number and atomic mass are high compared to those of boron. While the decrease of TeO2 weakens the photon attenuation performance, it was found that fast neutron attenuation increases as ∑R increases from 0.108 to 0.116 for the glass specimens containing 60% and 10% mole of TeO2 respectively.
Gamma and neutron shielding potential of the newly developed xAg2O-(35-x)0.5V2O5-0.5MoO3-65TeO2 (x = 0, 5, 10, 15, 20 and 25 mol%) quaternary tellurite glass system were investigated computationally ...by means of Geant4 Monte Carlo simulations and Phy-X software. Gamma ray shielding capabilities were studied via the mass attenuation coefficient (μm), transmission fractions (T), effective atomic number (Zeff), half value layer (HVL) and mean free path (MFP) parameters and for the photon energies of 0.284, 0.356, 0.511, 0.662, 1.173 and 1.330 MeV. Fast neutron removal cross-section (∑R) parameter of the glasses was calculated to assess the neutron shielding capabilities. The results of this study revealed that tellurite glass containing 25% moles of Ag2O has highest μm and Zeff and lowest T, HVL and MFP values due to the high atomic number of Ag. In this study it was also seen that the ∑R of the investigated glass system increases with the increase of Ag2O fraction and ∑R values of the studied glasses are higher than barite added concrete and close to the ∑R of the PbO added borate glasses.
In the current paper, glass samples were prepared from the composition
x
Gd
2
O
3
–(30-
x
)Y
2
O
3
–70B
2
O
3
(where
x
= 5, 10, 15, 20 and 25 mol%) via the technique of melt-quenching. Various ...optical parameters and inter-atomic separation were evaluated for the fabricated samples. The results showed that the inter-substitution of Y
2
O
3
content in replacement with Gd
2
O
3
content in the glass matrix shows structural variation in the glass. The density increases from 3.5521 to 4.1613 g/cm
3
with increase in Gd
2
O
3
content that signifies the role of Gd
2
O
3
being a glass modifier. The transmission spectra of the glass sample show more than 85% transmittance suggesting their superior transparency in the visible region. Also, several important shielding parameters of the prepared glass system have been computationally determined via the Geant4 model and the results were compared with Phy-X/PDS database software. The results revealed that the mass attenuation factor (
µ
/
ρ
) obtained by utilizing the two different toolkits are in agreement. The transmission fraction and the half value layer parameters of the glass system indicate that the glass sample with higher Gd concentration provides a better gamma blocking ability thanks to the high atomic number of Gd.
The XENON100 dark matter experiment Aprile, E.; Arisaka, K.; Arneodo, F. ...
Astroparticle physics,
April 2012, 2012-4-00, 20120401, Letnik:
35, Številka:
9
Journal Article
Recenzirano
Odprti dostop
► XENON100 is currently one of the most sensitive experiments to detect WIMP dark matter. ► Detector design and active/passive shielding reduce the radioactive background level. ► The event vertex of ...an interaction is reconstructed with a few mm precision. ► All position dependent signal corrections are presented in the paper. ► An energy scale exploiting the light-charge anti-correlation leads to an energy resolution competitive with NaI(Tl) crystals.
The XENON100 dark matter experiment uses liquid xenon (LXe) in a time projection chamber (TPC) to search for xenon nuclear recoils resulting from the scattering of dark matter Weakly Interacting Massive Particles (WIMPs). In this paper we present a detailed description of the detector design and present performance results, as established during the commissioning phase and during the first science runs.
The active target of XENON100 contains 62kg of LXe, surrounded by an LXe veto of 99kg, both instrumented with photomultiplier tubes (PMTs) operating inside the liquid or in xenon gas. The LXe target and veto are contained in a low-radioactivity stainless steel vessel, embedded in a passive radiation shield and is installed underground at the Laboratori Nazionali del Gran Sasso (LNGS), Italy. The experiment has recently published results from a 100 live-days dark matter search. The ultimate design goal of XENON100 is to achieve a spin-independent WIMP-nucleon scattering cross section sensitivity of σ=2×10−45cm2 for a 100GeV/c2 WIMP.
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