ABSTRACT
Chemical adsorption of non-metal atoms may lead to the emergence of novel features in two-dimensional (2D) materials. In this work, the electronic and magnetic properties of graphene-like XC (X = Si and Ge) monolayers with adsorbed H, O, and F atoms are investigated using spin-polarized first-principles calculations. Deeply negative adsorption energies suggest strong chemical adsorption on XC monolayers. Despite the non-magnetic nature of both host monolayer and adatom, SiC is significantly magnetized by H adsorption inducing the magnetic semiconductor nature. Similar features are observed in GeC monolayers upon adsorbing H and F atoms. In all cases, an integer total magnetic moment of 1 µB is obtained, originating mainly from adatoms and their neighbor X and C atoms. In contrast, O adsorption preserves the non-magnetic nature of SiC and GeC monolayers. However, the electronic band gaps exhibit significant reduction of the order of 26% and 18.84%, respectively. These reductions are consequences of the middle-gap energy branch generated by the unoccupied O-pz state. The results introduce an efficient approach to develop d0 2D magnetic materials to be applied in spintronic devices, as well as to widen the working region of XC monolayers in optoelectronic applications.
ABSTRACT
In this work, the structural, electronic, and magnetic properties of arsenene monolayer doped with germanium (Ge) and nitrogen (N) atoms are investigated using density functional theory calculations. Pristine monolayer is dynamically stable and it possesses a wide indirect band gap. Ge doping induces magnetic semiconductor (MS) nature generated by the semiconductor behavior in both spin channels with significant spin asymmetry around the Fermi level. The dopant produces mainly magnetic properties. Upon increasing the doping concentration, different doping configurations along armchair, zigzag edges, and hexagonal ring have been proposed. The MS nature is retained with an odd number of Ge atoms, meanwhile an eVen number leads to the disappearance of magnetism. In contrast, N doping induces a gap reduction of 11.80%, preserving the non-magnetic nature. At higher doping level, different electronic features including semiconductor, nearly semimetallic, and metallic natures are obtained depending on the doping concentration and configurations. In addition, the formation energy and cohesive energy are calculated to analyze the systems' stability. Our results show that different doping arrangements induce novel features in arsenene monolayer for applications in spintronic and optoelectronic devices.
ABSTRACT
Surgical sperm retrieval (SSR) is currently one of the most common procedures in in vitro fertilization (IVF). However, a gap between the guidelines and routine clinical practice regarding antibiotic use in SSR, which might lead to antibiotic resistance, is a challenging problem worldwide. A cross-sectional survey was conducted from May 1, 2021, to July 15, 2021, to investigate antibiotic usage by medical professionals when performing SSR in IVF centers in Vietnam. The confidential questionnaire comprised 12 items, including characteristics of the study population, awareness of antimicrobial resistance, attitude toward prescribing antibiotics, and current practice of prescribing antibiotics when performing SSR. Surveys were completed by 30 of 45 registered IVF centers (66.7%). Among 67 physicians working at those centers, the age and work-experience years (mean ± standard deviation [s.d.]) were 38.6 ± 6.6 years and 11.2 ± 7.0 years, respectively. Over 60% of them held a degree in Obstetrics and Gynecology, and over four-fifths were men. Most respondents "often/very often/always" raised awareness of antimicrobial resistance to their patients (83.3%), but only half of them "often/occasionally" prescribed antibiotics to patients with SSR in cases where the prescription would be optional. About one-tenth of respondents followed the recommendation from the American Urological Association using "prophylaxis only" for SSR patients. For more invasive SSR, physicians tended to prescribe more complicated and sometimes inappropriate regimens. In conclusion, antibiotic usage in SSR was not always appropriate among IVF centers. Further studies may define specific recommendations for regimens, intervention strategies, and programs to promote appropriate antibiotic use for SSR patients among IVF specialists.