trapping sites
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2021 ◽  
Author(s):  
Jinggang Lan ◽  
Yo-ichi Yamamoto ◽  
Toshinori Suzuki ◽  
Vladimir Rybkin

We present condensed-phase first-principles molecular dynamics simulations to elucidate the presence of different electron trapping sites in liquid methanol and their roles in the formation, electronic transitions, and relaxation of solvated electrons (e−met) in methanol. Excess electrons injected into liquid methanol are most likely trapped by methyl groups, but rapidly diffuse to more stable trapping sites with dangling OH bonds. After localization at the sites with one free OH bond (1OH trapping sites), reorientation of other methanol molecules increases the OH coordination number and the trap depth, and ultimately four OH bonds become coordinated with the excess electrons under thermal conditions. The simulation identified four distinct trapping states with different OH coordination numbers. The simulation results also revealed that electronic transitions of e−met are primarily due to charge transfer between electron trapping sites (cavities) formed by OH and methyl groups and that these transitions differ from hydrogenic electronic transitions involving aqueous solvated electrons (e−aq). Such charge transfer also explains the alkyl-chain-length dependence of the photoabsorption peak wavelength and the excited-state lifetime of solvated electrons in primary alcohols.


Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7269
Author(s):  
Luis Borja Peral ◽  
Inés Fernández-Pariente ◽  
Chiara Colombo ◽  
Cristina Rodríguez ◽  
Javier Belzunce

The influence of hydrogen on the fracture toughness and fatigue crack propagation rate of two structural steel grades, with and without vanadium, was evaluated by means of tests performed on thermally precharged samples in a hydrogen reactor at 195 bar and 450 °C for 21 h. The degradation of the mechanical properties was directly correlated with the interaction between hydrogen atoms and the steel microstructure. A LECO DH603 hydrogen analyzer was used to study the activation energies of the different microstructural trapping sites, and also to study the hydrogen eggresion kinetics at room temperature. The electrochemical hydrogen permeation technique was employed to estimate the apparent hydrogen diffusion coefficient. Under the mentioned hydrogen precharging conditions, a very high hydrogen concentration was introduced within the V-added steel (4.3 ppm). The V-added grade had stronger trapping sites and much lower apparent diffusion coefficient. Hydrogen embrittlement susceptibility increased significantly due to the presence of internal hydrogen in the V-free steel in comparison with tests carried out in the uncharged condition. However, the V-added steel grade (+0.31%V) was less sensitive to hydrogen embrittlement. This fact was ascribed to the positive effect of the precipitated nanometric (Mo,V)C to alleviate hydrogen embrittlement. Mixed nanometric (Mo,V)C might be considered to be nondiffusible hydrogen-trapping sites, in view of their strong hydrogen-trapping capability (~35 kJ/mol). Hence, mechanical behavior of the V-added grade in the presence of internal hydrogen was notably improved.


2021 ◽  
pp. 1-12
Author(s):  
S. Labu ◽  
S. Subramanian ◽  
F.M. Khamis ◽  
P. Akite ◽  
P. Kasangaki ◽  
...  

This study investigated the relative abundance and identity of microbial contaminants of the edible long-horned grasshopper (Ruspolia differens) harvested from the wild and traded in informal markets in Uganda, to reveal high health risk points. Raw samples of whole R. differens were collected from wild vegetation, trapping sites and markets. Additionally, samples of plucked and deep-fried ready-to-eat R. differens were collected from the markets. The samples were cultured on standard media for microbial quantification, and pure cultures were characterised using molecular techniques. Bacterial and fungal counts in deep fried ready-to-eat R. differens were ~3- and 2-fold lower, respectively, than in raw samples. Loads of these microbes in deep fried insects were within recommended food safety limits. The highest bacterial counts were detected in whole R. differens samples from the market followed by trapping points. The fungal counts in the raw R. differens were comparable across the sampling points. The bacterial and fungal counts in R. differens in Kampala were not influenced by district of origin. Seven species of bacteria and seven species of fungi were recorded in R. differens samples. The microbial species were most diverse in samples from trapping points and least diverse in the deep-fried insects. The key pathogenic bacteria detected in marketed R. differens were Staphylococcus sciuri, Acinetobacter baumannii and Serratia marcescens, all of which were absent in wild-caught whole insects. Our results demonstrate that R. differens obtained at the trapping sites and markets are contaminated with potentially harmful microbes, therefore they require processing through deep frying to minimise health risks associated with their consumption. Further studies are warranted to elucidate specific handling practices at distribution and trapping points which may prevent introduction of microbes into R. differens.


Polymers ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1567
Author(s):  
Adam Luczak ◽  
Angélina Ruiz ◽  
Simon Pascal ◽  
Adrian Adamski ◽  
Jarosław Jung ◽  
...  

The interface between the semiconductor and the dielectric layer plays a crucial role in organic field-effect transistors (OFETs) because it is at the interface that charge carriers are accumulated and transported. In this study, four zwitterionic benzoquinonemonoimine dyes featuring alkyl and aryl N-substituents were used to cover the dielectric layers in OFET structures. The best interlayer material, containing aliphatic side groups, increased charge carrier mobility in the measured systems. This improvement can be explained by the reduction in the number of the charge carrier trapping sites at the dielectric active layer interface from 1014 eV−1 cm−2 to 2 × 1013 eV−1 cm−2. The density of the traps was one order of magnitude lower compared to the unmodified transistors. This resulted in an increase in charge carrier mobility in the tested poly [2,5-(2-octyldodecyl)-3,6-diketopyrrolopyrrole-alt-5,5-(2,5-di(thien-2-yl)thieno [3,2-b]thiophene)] (DPPDTT)-based transistors to 5.4 × 10−1 cm2 V−1 s−1.


2021 ◽  
Vol 1024 ◽  
pp. 135-144
Author(s):  
Takuya Kamimura ◽  
Hayato Yamashita ◽  
Koichi Sato ◽  
Tsunakazu Ohyama ◽  
Yoshinori Kimoto ◽  
...  

Herein, we compared thermal desorption analysis (TDA) curves obtained by conducting experiments and simulations. In addition, we discussed the validation of our simulations and trapping sites of hydrogen atoms. In as-received F82H, when the samples contained solute atoms, grain boundaries, dislocations, and precipitates, the experimental curve corresponded to the simulated curve. In positron annihilation lifetime (PAL) measurements, di-vacancies were detected in the electron-irradiated F82H. When we changed the growth and the concentration of vacancy-type defects during temperature increase using the rate theory, the simulation results agreed with experiment results. In creep-ruptured Fe, only dislocations were detected by the PAL measurements. However, the existence of a type of defect, which was related to grain boundaries, must be assumed to fit the simulation curve to the experimental one. In the next step, the diffusion of hydrogen atoms on grain boundaries should be added to simulation program.


2021 ◽  
Vol 7 ◽  
Author(s):  
Yi-Ting Lin ◽  
Hong Liang Yi ◽  
Zhi Yuan Chang ◽  
Hsin-Chih Lin ◽  
Hung-Wei Yen

This work investigated hydrogen trapping and hydrogen embrittlement (HE) in two press-hardened steels, 22MnB5 for 1,500 MPa grade and 34MnB5V for 2000 MPa grade, respectively. Superior to the 22MnB5 steel, the newly developed 34MnB5V steel has an ultimate tensile strength of over 2000 MPa without sacrificing ductility due to the formation of vanadium carbides (VCs). Simulated press hardening was applied to two steels, and hydrogen was induced by cathodic charging. Susceptibility to HE was validated by slow strain-rate tensile test. When hydrogen content was high, the 34MnB5V steel fractured in elastic regime. However, when hydrogen content was 0.8–1.0 ppmw, the 34MnB5V steel bore much higher stress than the 22MnB5 steel before fracture. The behavior of hydrogen trapping was investigated by thermal desorption analyses. Although the two steels trapped similar amounts of hydrogen after cathodic charging, their trapping mechanisms and effective trapping sites were different. In summary, a finer prior austenite grain size due to the pinning effect of VCs can also improve the toughness of 34MnB5V steel. Moreover, trapping hydrogen by grain boundary suppresses the occurrence of hydrogen-enhanced local plasticity. Microstructural refinement enhanced by VCs improves the resistance to HE in 34MnB5V steel. Importantly, the correlation between hydrogen trapping by VCs and improvement of HE is not significant. Hence, this work presents the challenge in designing irreversible trapping sites in future press-hardened steels.


2021 ◽  
Vol 63 (4) ◽  
pp. 483
Author(s):  
Э.И. Рау ◽  
А.А. Татаринцев

The goal of this paper is first to critical review the charging phenomena occurring during electron deposition in insulating materials. In this research we focus on the elucidation of the charging kinetics including the effects of the electron emission increasing and the electron-radiation defect creation. In order to avoid some misinterpretation and contradiction of the experimental results we include three fundamental key factors. The first, in the consideration we include the density of the initial (intrinsic) and radiation-induced trapping sites, second, we take into account the role of the primary thermalized electrons in the emission, and third, the charging phenomena in steady-state phase is regulated by the electronic filed, generated during charging.


Author(s):  
André Antonio Cutolo ◽  
Gabriela Motoie ◽  
Ingrid Menz ◽  
Vera Lucia Pereira-Chioccola

Abstract American cutaneous leishmaniasis (ACL) is a neglected zoonotic disease caused mainly by Leishmania (Viannia) braziliensis, which is endemic throughout Brazil. Canine ACL cases were investigated in a rural area of Monte Mor, São Paulo, where a human ACL case had been confirmed. Dogs were evaluated through clinical and laboratory diagnosis including serology, cytological tissue preparations and PCR on skin lesions, lymph node and bone marrow samples. Entomological investigations on sandflies trapped in the surroundings of the study area were performed for 14 months. Nyssomyia neivai was the predominant phlebotomine species, comprising 94.65% of the captured specimens (832 out of 879). This species was the most abundant in all trapping sites, including human homes and dog shelters. Ny. whitmani, Migonemyia migonei, Pintomyia monticola, Evandromyia cortellezzii, Pi. fischeri and Expapilata firmatoi were also captured. Two of the three dogs examined were positive for anti-Leishmania IgG in ELISA using the antigen Fucose mannose ligand and skin samples were positive for L. (V.) braziliensis in PCR, but all the samples collected were negative for L. (L.) infantum. One of the dogs had a confirmed persistent infection for more than one year.


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