A novel barium oxide-based Iraqi sand glass to attenuate the low gamma-ray energies: Fabrication, mechanical, and radiation protection capacity evaluation

Al-Saeedi F.H.F.,Sayyed M.I.,Kapustin F.L.,Al-Ghamdi Hanan,Kolobkova E.V.,Tashlykov O.L.,Almuqrin Aljawhara H.,Mahmoud K.A. 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.8

In the present work, untreated Iraqi sand with grain sizes varied between 100 and 200 mm was used to produce a colored glass sample that has shielding features against the low gamma-ray energy. Therefore, a weight of 70e60 wt % sand was mixed with 9e14 wt% B2O3, 8e10 wt% Na2O, 4e6 wt% of CaO, 3e6 wt% Al2O3, in addition to 0.3% of Co2O3. After melting and annealing the glass sample, the X-ray diffraction spectrometry was applied to affirm the amorphous phase of the fabricated glass samples. Moreover, the X-ray dispersive energy spectrometry was used to measure the chemical composition, and the MH-300A densimeter was applied to measure the fabricated sample's density. The Makishima-Makinzie model was applied to predict the mechanical properties of the fabricated glass. Besides, the Monte Carlo simulation was used to estimate the fabricated glass sample's radiation shielding capacity in the low-energy region between 22.1 and 160.6 keV. Therefore, the simulated linear attenuation coefficient changed between 10.725 and 0.484 cm1 , raising the gamma-ray energy between 22.1 and 160.6 keV. Also, other shielding parameters such as a half-value layer, pure lead equivalent thickness, and buildup factors were calculated

The effect of Sn on the electronic state of M/γ-Al₂O₃(M = Pd, Pt) catalysts and the influence in the catalytic combustion of methane

Grisel Corro,O. Vázquez-Cuchillo,F. Bañuelos,A. Cruz-López,J.L.G. Fierro 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.6

Pd-Sn and Pt-Sn catalysts supported on γ-Al2O3 were prepared by co-precipitation and the Pt characterized dispersion of reduced samples was determined by H2 chemisorption for Pt and Pt-Sn catalysts, The Pd dispersion was determined by CO adsorption on Pd and Pd-Sn catalysts. The catalysts were characterized by the electron binding energy values determined by XPS. The results are explained on the basis of the Pt and Pd species electron binding energy changes due to the electronic properties of Sn. The catalytic activity in methane oxidation under lean burn conditions was measured. The results reveal that the tin addition causes a change in the catalytic activity of the supported catalysts, showing a greater catalytic activity on the CH4-O2 reaction for the bimetallic Pd-Sn/ γ-Al2O3. Pd-Sn and Pt-Sn catalysts supported on γ-Al2O3 were prepared by co-precipitation and the Pt characterized dispersion of reduced samples was determined by H2 chemisorption for Pt and Pt-Sn catalysts, The Pd dispersion was determined by CO adsorption on Pd and Pd-Sn catalysts. The catalysts were characterized by the electron binding energy values determined by XPS. The results are explained on the basis of the Pt and Pd species electron binding energy changes due to the electronic properties of Sn. The catalytic activity in methane oxidation under lean burn conditions was measured. The results reveal that the tin addition causes a change in the catalytic activity of the supported catalysts, showing a greater catalytic activity on the CH4-O2 reaction for the bimetallic Pd-Sn/ γ-Al2O3.

Particle Filtration Efficiency Testing of Sterilization Wrap Masks

Chau, Destiny F.,O'Shaughnessy, Patrick,Schmitz, Michael L. The Korean Society for Preventive Medicine 2021 Journal of Preventive Medicine and Public Health Vol.54 No.1

Objectives: Non-traditional materials are used for mask construction to address personal protective equipment shortages during the coronavirus disease 2019 (COVID-19) pandemic. Reusable masks made from surgical sterilization wrap represent such an innovative approach with social media frequently referring to them as "N95 alternatives." This material was tested for particle filtration efficiency and breathability to clarify what role they might have in infection prevention and control. Methods: A heavyweight, double layer sterilization wrap was tested when new and after 2, 4, 6, and 10 autoclave sterilizing cycles and compared with an approved N95 respirator and a surgical mask via testing procedures using a sodium chloride aerosol for N95 efficiency testing similar to 42 CFR 84.181. Pressure testing to indicate breathability was also conducted. Results: The particle filtration efficiency for the sterilization wrap ranged between 58% to 66%, with similar performance when new and after sterilizing cycles. The N95 respirator and surgical mask performed at 95% and 68% respectively. Pressure drops for the sterilization wrap, N95 and surgical mask were 10.4 mmH2O, 5.9 mmH2O, and 5.1 mmH2O, respectively, well below the National Institute for Occupational Safety and Health limits of 35 mmH2O during initial inhalation and 25 mmH2O during initial exhalation. Conclusions: The sterilization wrap's particle filtration efficiency is much lower than a N95 respirator, but falls within the range of a surgical mask, with acceptable breathability. Performance testing of non-traditional mask materials is crucial to determine potential protection efficacy and for correcting misinterpretation propagated through popular media.

STRONG CONVERGENCE OF A MODIFIED ISHIKAWA ITERATIVE ALGORITHM FOR LIPSCHITZ PSEUDOCONTRACTIVE MAPPINGS

Osilike, M.O.,Isiogugu, F.O.,Attah, F.U. The Korean Society for Computational and Applied M 2013 Journal of applied mathematics & informatics Vol.31 No.3

Let H be a real Hilbert space and let T : H ${\rightarrow}$ H be a Lipschitz pseudocontractive mapping. We introduce a modified Ishikawa iterative algorithm and prove that if $F(T)=\{x{\in}H:Tx=x\}{\neq}{\emptyset}$, then our proposed iterative algorithm converges strongly to a fixed point of T. No compactness assumption is imposed on T and no further requirement is imposed on F(T).

Effects of direct and indirect bonding techniques on bond strength and microleakage after thermocycling

F₁rat o''ztu''rk,Hasan Babacan,Ruhi Nalc.ac₁,Alper Kus.tarc₁ 대한치과교정학회 2009 대한치과교정학회지 Vol.39 No.6

Objective: The purpose of this study was to compare the shear bond strength (SBS) of brackets and microleakage of a tooth-adhesive-bracket complex bonded with a direct and an indirect bonding technique after thermocycling. Methods: Fifty non-carious human premolars were divided into two equal groups. In the direct bonding group a light-cured adhesive and a primer (Transbond XT) was used. In the indirect-bonding group, a light-cured adhesive (Transbond XT) and chemical-cured primer (Sondhi Rapid Set) were used. After polymerization, the teeth were kept in distilled water for 24 hours and thereafter subjected to thermal cycling (500 cycles). For the microleakage evaluation, 10 teeth from each group were further sealed with nail varnish, stained with 0.5% basic fuchsin for 24 hours, and examined under a stereomicroscope. Fifteen teeth from each group were used for SBS testing with the universal testing machine and adhesive remnant index (ARI) evaluation. Data were analyzed using the Mann-Whitney U test, Chi-square test, and Fisher's exact test. Results: There were no statistical differences on SBS and microleakage between the two bonding techniques. The indirect bonding group had a significantly lower ARI score. Bracket failures were obtained between enamel-resin interfaces. Conclusions: The type of bonding technique did not significantly affect the amount of microleakage and SBS. 본 연구는 직접 또는 간접 부착법으로 부착한 교정용 브라켓을 열순환 처리 후에 전단 결합 강도(shear bond strength, SBS)와 치아-접착제-브라켓 복합체의 미세 누출을 비교하기 위하여 시행하였다. 50개의 치아우식증이 없는 사람 소구치를 구하여 동등한 2개의 군으로 나누었다. 직접 부착군에서는 광중합 접착제 및 primer (Transbond XT)를 사용하였고 간접 부착군에서는 광중합 접착제와(Transbond XT) 화학중합 primer (Sondhi Rapid Set)를 사용하였다. 중합 후에 치아는 24시간 동안 증류수에 보관하였고 이후 500회 열순환 처리를 하였다. 미세누출의 평가를 위해 각 군에서 10개의 치아에 nail varnish로 추가 봉연을 실시하고 0.5% basic fuchsin에 24시간 동안 염색한 후 입체현미경으로 검경하였다. 만능시험기를 이용하여 각 군의 치아 15개로 SBS를 계측하였고 adhesive remnant index (ARI)를 평가하였다. 결과 자료는 Mann-Whitney U test, Chi-square test, Fisher's exact test로 통계 분석하였다. 직접 부착군과 간접 부착군 사이에 SBS 및 미세누출의 통계적으로 유의한 차이는 보이지 않았으며 간접 부착군에서 통계적으로 유의하게 ARI 점수가 낮았다. 브라켓의 탈락은 법랑질-레진 계면에서 발생하였다. 이상의 결과로 보아 부착법의 차이는 미세누출의 양과 SBS에 유의한 영향을 미치지 않는다.

Neutron-shielding behaviour investigations of some clay-materials

S.F. Olukotun,Kulwinder Singh Mann,S.T. Gbenu,F.I. Ibitoye,O.F. Oladejo,Amit Joshi,H.O. Tekin,M.I. Sayyed,M.K. Fasasi,F.A. Balogun,Turgay Korkut 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.5

The fast-neutron shielding behaviour (FNSB) of two clay-materials (Ball clay and Kaolin)of SouthwesternNigeria (7.49 N, 4.55 E) have been investigated using effective removal cross section, SRðcm 1Þ, massremoval cross section, SR=rðcm2g 1Þ and Mean free path, l (cm). These parameters decide neutronshielding behaviour of any material. A computer program - WinNC-Toolkit has been used for computationof these parameters. The toolkit evaluates these parameters by using elemental compositions anddensities of samples. The proficiency of WinNC-Toolkit code was probe by using MCNPX and GEANT4 tomodel fast neutron transmission of the samples under narrow beam geometry, intending to representthe actual experimental setup. Direct calculation of effective removal cross section (cm 1) of the sampleswas also carried out. The results from each of the methods for each types of the studied clay-materials(Ball clay and Kaolin) shows similar trend. The trend might be the fingerprint of water content retainedin each of the samples being baked at different temperature. The compositions of each sample have beenobtained by Particle-Induced X-ray Emission (PIXE) technique (Tandem Pelletron Accelerator: 1.7 MV,Model 5SDH). The FNSB of the selected clay-materials have been compared with standard concrete. Thecognizance of various factors such as availability, thermo-chemical stability and water retaining ability bythe clay-samples can be analyzed for efficacy of the material for their FNSB.

Effect of poly(ethylene oxide) and water on electrospun poly(vinylidene fluoride) nanofibers with enhanced mechanical properties as pre-filter for oil-in-water filtration

Agyemang, F.O.,Li, F.,Momade, F.W.Y.,Kim, H. Elsevier Science Publishers 2016 Materials chemistry and physics Vol.182 No.-

Poly(vinylidene fluoride) (PVDF) nanofibers were fabricated by combined electrospinning and selective removal of poly(ethylene oxide) PEO from a PVDF/(PEO)/water (H<SUB>2</SUB>O) composite. The method involved varying the concentration of PEO and H<SUB>2</SUB>O with respect to PVDF and N,N-dimethylformamide (DMF) respectively. The morphology and other properties of the nanofibers were characterized by SEM, FT-IR, UTM, CFP and AFM and showed improved properties that can be effectively utilized as a pre-filter for pretreatment of oil-in-water emulsion filtration. The as-electrospun PVDF nanofiber films exhibited high flux rate, higher porosity, high Young's modulus and tensile strength, and high surface roughness. Results showed that the nanofiber films can achieve a flux rate of 1172 Lm<SUP>-2</SUP> h<SUP>-1</SUP> with 96% filtration efficiency at a pressure as low as 0.2 bar in an oil-in-water emulsion system. The results indicate that these electrospun PVDF nanofiber films with high intra-pores can be used as a pre-filter in membrane filtration to reduce fouling on membranes. This will aid in cutting down cost since frequent cleaning of membranes shortens the membrane life span.

Investigation of gamma radiation shielding capability of two clay materials

S.F. Olukotun,S.T. Gbenu,F.I. Ibitoye,O.F. Oladejo,H.O. Shittu,M.K. Fasasi,F.A. Balogun 한국원자력학회 2018 Nuclear Engineering and Technology Vol.50 No.6

The gamma radiation shielding capability (GRSC) of two clay-materials (Ball clay and Kaolin)of SouthwesternNigeria (7.49 N, 4.55 E) have been investigated by determine theoretically and experimentallythe mass attenuation coefficient, m/r (cm2g 1) of the clay materials at photon energies of 609.31, 1120.29,1173.20, 1238.11, 1332.50 and 1764.49 keV emitted from 214Bi ore and 60Co point source. The massattenuation coefficients were theoretically evaluated using the elemental compositions of the claymaterialsobtained by Particle-Induced X-ray Emission (PIXE) elemental analysis technique as inputdata for WinXCom software. While gamma ray transmission experiment using Hyper Pure Germanium(HPGe) spectrometer detector to experimentally determine the mass attenuation coefficients, m/r(cm2g 1) of the samples. The experimental results are in good agreement with the theoretical calculationsof WinXCom software. Linear attenuation coefficient (m), half value layer (HVL) and mean free path(MFP) were also evaluated using the obtained m/r values for the investigated samples. The GRSC of theselected clay-materials have been compared with other studied shielding materials. The cognizance ofvarious factors such as availability, thermo-chemical stability and water retaining ability by the claysamplescan be analyzed for efficacy of the material for their GRSC.

Two-component analysis of the 4f multiplet of samarium hexaboride

Min, C.H.,Sommer, O.,Kang, B.Y.,Cho, B.K.,Bentmann, H.,Reinert, F. Elsevier Scientific Pub. Co 2015 Journal of electron spectroscopy and related pheno Vol.199 No.-

We present a detailed study on the temperature-dependence of the Sm 4f states in mixed-valent samarium hexaboride (SmB<SUB>6</SUB>) which, as a consequence of the hybridization with the conduction band states, largely determine the physical properties of the system. By comparing soft X-ray photoemission spectra of SmB<SUB>6</SUB> with those of Sm<SUB>0.35</SUB>La<SUB>0.65</SUB>B<SUB>6</SUB>, we discuss the apparent differences and similarities of the two systems. Based on our analyses we show that the 4f spectra of SmB<SUB>6</SUB> can be separated into two independent spectral contributions with the 4f peak maxima at different binding energies, representing two different electronic 4f configurations existing in the system.

Molecular characterization of Escherichia coli O157:H7 strains isolated from different sources and geographic regions

Adriana Hamond Regua-Mangia,Alice Gonçalves M. Gonzalez,Aloysio M. F. Cerqueira,João Ramos C.Andrade 대한수의학회 2012 Journal of Veterinary Science Vol.13 No.2

Escherichia (E.) coli serotype O157:H7 is a globally distributed human enteropathogen and is comprised of microorganisms with closely related genotypes. The main reservoir for this group is bovine bowels, and infection mainly occurs after ingestion of contaminated water and food. Virulence genetic markers of 28 O157:H7 strains were investigated and multilocus enzyme electrophoresis (MLEE) was used to evaluate the clonal structure. O157:H7 strains from several countries were isolated from food, human and bovine feces. According to MLEE, O157:H7 strains clustered into two main clonal groups designated A and B. Subcluster A1 included 82% of the O157:H7 strains exhibiting identical MLEE pattern. Most enterohemorrhagic E. coli (EHEC) O157:H7 strains from Brazil and Argentina were in the same MLEE subgroup. Bovine and food strains carried virulence genes associated with EHEC pathogenicity in humans.