Influence of doping with selected organic molecules on the magnetic and electronic properties of bare, surface terminated and defect patterned Ti2C MXene monolayers.

In this study, based on density functional theory, we examine the interaction between the bare, F-, OH-terminated as well as defect patterned Ti2C and selected neurotransmitter (NT) and amino acids (AA) such as dopamine, glutamate, glycine and serine. We found that these molecules are dissociated at a specific location in bare Ti2C monolayers and concomitantly they form Ti-H bonds. The adsorbed molecules give rise to significant charge transfer between the adsorbates and underlying substrates and generally the electronic energy states are affected, band gaps are tuned and magnetic moments are attained significantly. In particular, the bare antiferromagnetic-Ti2C monolayer undergoes an antiferromagnetic-ferromagnetic transition upon adsorption of the amino acids and nucleobase molecules due to bond dissociation of molecules. Moreover, the electronic and magnetic properties of bare Ti2C are crucially changed in the presence of a vacancy. While pristine Ti2C is an AFM semiconductor, mono- and di-vacancy structures become ferromagnetic semiconductors. When adsorbed by molecules, the defect patterned Ti2C is spin-polarized and hence the surface results in a metallic state. We also reveal that the Ti2C structure is transformed to the non-magnetic (NM) ground state in the presence of both F- and OH-surface termination groups. When adsorbed to these organic molecules on a terminated Ti2C surface, the binding of molecules to this surface is generally weak and arises from van der Waals interactions. We determine that the binding energy of dopamine, which is absorbed on bare Ti2C in equilibrium in a solvent, was found to be 2.31 eV and the magnetic moment per supercell was reduced to 2.91µB.

Interactions of selected organic molecules with a blue phosphorene monolayer: self-assembly, solvent effect, enhanced binding and fixation through coadsorbed gold clusters.

In this paper we investigate the interaction between a pristine blue phosphorene monolayer and selected organic molecules like amino acids and nucleic acid bases. These molecules are bound to the substrate by a weak van der Waals interaction leading to their physisorption. When isolated, they tend to orient themselves parallel to the surface and are located in flat minima with very low libration frequencies; thus the electronic structures of the substrate and physisorbed molecules are not affected except for relative shifts. Even though the regular self-assembly of these molecules on the pristine blue phosphorene cannot be realized under this weak interaction, only their irregular coating of the substrate can occur due to increased intermolecular coupling. In a solvent like water, the weak binding energy is further decreased. Gold adatoms and gold clusters can form strong chemical bonds with pristine blue phosphorene and modify its electronic and magnetic state depending on the coverage. While full coverage of a blue phosphorene monolayer by gold adatoms leads to instabilities followed by clustering, relatively lower coverage can attribute very interesting magnetic and electronic states, like a spin gapless semiconductor. When bound to the gold clusters already adsorbed on the blue phosphorene monolayer, amino acid and nucleic acid base molecules form relatively strong chemical bonds and hence can be fixed to the surface; they are reoriented to gain self-assembly character and the whole system acquires new functionalities.

Two dimensional ruthenium carbide: structural and electronic features.

The design and realization of novel 2D materials and their functionalities have been a focus of research inspired by the successful synthesis of graphene and many other 2D materials. In this study, in view of first principles calculations, we predict a novel 2D material ruthenium carbide (RuC) in graphene-like honeycomb hexagonal lattice with planar geometry. Phonon dispersion spectra display a dynamically stable structure. Comprehensive molecular dynamics calculations confirm the stability of the structure up to high temperatures as ≈1000 K. The system is a narrow gap semiconductor with a band gap of 53 meV (345 meV) due to GGA-PBE (HSE) calculations. Band gap exhibits significant changes by applied strain. Elastic and optical properties of the system are examined in monolayer form. RuC/RuC bilayer, RuC/graphene and RuC/h-BN heterostructures are also investigated. By calculating the phonon dispersion it is verified that RuC bilayer is the most stable in AA type-stacking configuration where Ru and C atoms of both layers have identical lateral coordinates. The effects of atomic substitutions on electronic band structures, acting as p-type and n-type doping, are revealed. A novel 3D RuCLi structure is also predicted to be stable and the isolation of its monolayer forms are discussed. Ruthenium carbide, as a 2D material which is dynamically and thermally stable, holds promise for applications in nanoelectronics.

Stable, one-dimensional suspended and supported monatomic chains of pnictogens: a metal-insulator framework.

Group-VA elements P, As, Sb, and Bi can construct free-standing, stable zigzag monatomic chain structures, which show unusual properties. They are normally semimetals with bands crossing at the Fermi level, but a very narrow gap opens due to spin-orbit coupling. They attain one quantum of conductance under a small bias potential; Bi, being an exception, attains two quanta of conductance. Finite size chains are magnetic semiconductors; their magnetic moments and the order of spin states show an even-odd disparity depending on the number of chain atoms. Variations of the HOMO-LUMO band gaps depending on the spin polarization and the size of the finite chains offer critical tunability. In the periodic, zigzag compound chains, a small band gap opens at the Fermi level. The mysterious zigzag geometry, cohesion, stability and band order of all these chains are well-explained by a simple bond model. When placed on the parent or other monolayers like graphene, h-BN and GaSe, these chains become weakly bound and construct a 1D metallic channel. The artificial grids or networks of these metallic chains on the insulating substrates can constitute metal-insulator frameworks of desired geometry. The zigzag phosphorene chain, having the highest stability, remains stable even at full coverage of adsorbates like H and OH, whereas other chains dissociate. While P-chains can be synthesized on GaSe and graphene substrates, phosphorene nanoribbons can transform into suspended chains under excessive tensile strain. Additionally, we showed that As, Sb, and Bi zigzag chains are weakly bound to their parent monolayers and remain stable. Nitrogen monatomic chains, on the other hand, are prone to instability. The diverse properties unveiled in this study based on the density functional method offer tunability through electric fields and strain.

Do ozonated water and boric acid affect the bond strength to dentin in different adhesive systems?

AIM: The aim of this in vitro study was to compare the effects of the application of three different cavity disinfecting agents to dentin on the micro-shear bond strength (µ-SBS) of one self-etch and two universal adhesive systems. MATERIALS AND METHODS: In total, 120 caries-free human permanent molar teeth were used in this study. Mid-coronal dentin surfaces were revealed by cutting occlusal enamel and a standard smear layer was obtained by using 600-800-1200 grid silicon carbide abrasive papers. Specimens were randomly assigned to four groups according to the disinfectant used: Group 1: Control (no disinfectant); Group 2: 2% chlorhexidine based (Consepsis); Group 3: 10 ppm ozonated water (TeknO3zone); Group 4: 5% boric acid (Handmade). Each group was divided into three subgroups according to the type of adhesive (Clearfil SE Bond, OptiBond XTR, and Tokuyama Universal). Specimens were bonded using either Clearfil SE Bond, OptiBond XTR or Tokuyama Universal, which were employed according to the manufacturer's instructions. Resin composite microcylinders were bonded using Tygon® tubes for µ-SBS testing. After specimens were stored for 24 h, at 37°C in distilled water, µ-SBS test was measured with a universal test machine (LF Plus, Lloyd, Instrument). µ-SBS results were analyzed by one-way analysis of variance (ANOVA) and Tukey's tests. RESULTS: When the mean microshear bond strength values of the control group were compared, the difference between the subgroups was not significant (P < 0.05). When the mean microshear bond strength values of the chx, ozonated water, and boric acid were compared, the difference between Clearfil SE Bond and Tokuyama Universal was significant (P < 0.05) and the difference between the other groups was not significant (P > 0.05). CONCLUSION: Ozonated water and boric acid may be as an alternative to other materials used as cavity disinfectants.

Influence of chalcogen composition on the structural transition and on the electronic and optical properties of the monolayer titanium trichalcogenide ordered alloys.

Based on first-principles spin-polarized density functional theory, we investigate the effects of chalcogen composition on the structural, electronic, and optical properties of monolayer (where X and X' = S, Se, Te) ordered alloys with values of x of 0, 0.167, 0.333, 0.500, 0.667, 0.833, and 1. We determine the optimized geometry for all possible substitutional adsorptions of chalcogen atoms for each x composition, and identify the energetically most stable allotropes as a function of composition. Our extensive analysis reveals that the structural and electronic properties depend on the chemical composition of the monolayers, and the band gap of TiX3 nanosheets can be tuned by adjusting the ratio of chalcogen compositions. While substitutional doping of tellurium atoms into TiS3 or TiSe3 monolayers results in a semiconductor-metal transition, the alloys remain a semiconductor under the transition from TiS3 to TiSe3 with band gaps which are very suitable for optical devices and infrared detectors. We also find that each TiS3(1-x)Se3x structure has an anisotropic dielectric function. Because of the anisotropy of the dielectric function, they can be useful materials for application in the transition metal trichalcogenide-based nanoelectronics industry in the future.

Electronic and magnetic properties of monolayer α-RuCl3: a first-principles and Monte Carlo study.

Recent experiments revealed that monolayer α-RuCl3 can be obtained by a chemical exfoliation method and exfoliation or restacking of nanosheets can manipulate the magnetic properties of the materials. In this paper, the electronic and magnetic properties of an α-RuCl3 monolayer are investigated by combining first-principles calculations and Monte Carlo simulations. From first-principles calculations, we found that the spin configuration of FM corresponds to the ground state for α-RuCl3, however, the other excited zigzag oriented spin configuration has an energy of 5 meV per atom higher than the ground state. The energy band gap is found to be 3 meV using PBE functionals. When the spin-orbit coupling effect is taken into account, the corresponding energy gap is determined to be 57 meV. We also investigate the effect of the Hubbard U energy terms on the electronic band structure of the α-RuCl3 monolayer and revealed that the band gap increases approximately linearly with increasing U value. Moreover, spin-spin coupling terms (J1, J2, and J3) have been obtained using first-principles calculations. By benefiting from these terms, Monte Carlo simulations with a single site update Metropolis algorithm have been implemented to elucidate the magnetic properties of the considered system. Thermal variations of magnetization, susceptibility and also specific heat curves indicate that monolayer α-RuCl3 exhibits a phase transition between ordered and disordered phases at the Curie temperature of 14.21 K. We believe that this study can be utilized to improve two-dimensional magnetic materials.

Lytic Activity of Various Phage Cocktails on Multidrug-Resistant Bacteria.

PURPOSE: A bacteriophage is a virus that infects and replicates within a bacterium following the injection of phage genome into the bacterial cytoplasm. They are seen as a possible therapy for multi-drug-resistant strains of many bacteria. The aim of this study is to evaluate the lytic activity of the Pyo, Intesti and Fersisi bacteriophage cocktails on P. aeruginosa and S. aureus. METHODS: Ten different S. aureus and P. aeruginosa strains, which were isolated from hospitalized patients in Turkey, were used in the study. The identification and antibiotic susceptibility of the isolates were performed using Vitec 2 system. The identities of the isolates were confirmed by a species-specific Polymerase Chain Reaction (PCR) assay. Lytic activity of the bacteriophage cocktails on bacteria was determined by spot test and plaque assay methods. RESULTS: The lytic activity of the Pyo phage cocktail was evaluated on P. aeruginosa and S. aureus strains. It was found that eight isolates of MDR S. aureus were susceptible to Pyo phage cocktail and two isolates were resistant. Nine isolates of antibiotic-resistant P. aeruginosa were found to be susceptible to this phage cocktail and one isolate was resistant. Thus, the Pyo, Intesti and Fersisi cocktails are very effective in treating clinical strains of multidrug-resistant P. aeruginosa and S. aureus isolated in Turkey. CONCLUSION: The Pyo, Intesti and Fersisi cocktails may prove useful in the treatment of various infections caused by those bacteria.

Long-Term Effect of Sublingual and Subcutaneous Immunotherapy in Dust Mite-Allergic Children With Asthma/Rhinitis: A 3-Year Prospective Randomized Controlled Trial.

BACKGROUND AND OBJECTIVE: Specific allergen immunotherapy is the only treatment modality that might change the natural course of allergic diseases in childhood. We sought to prospectively compare the long-term clinical and immunological effects of sublingual (SLIT) and subcutaneous (SCIT) immunotherapy compared with pharmacotherapy alone. METHODS: In this single-center, prospective randomized controlled trial, 48 children with mild persistent asthma with/without rhinitis, monosensitized to house dust mites (HDMs) were followed for 3 years. At baseline and years 1 and 3 of follow-up, patients were evaluated and compared for total rhinitis (TRSS) and asthma (TASS) symptom scores, total symptom scores (TSS), total medication scores (TMS), safety profiles, skin-nasal-bronchial reactivity, and immunological parameters. RESULTS: A significant reduction was observed in TASS for both HDM-SCIT and HDM-SLIT at year 3 of treatment compared with baseline and controls (P<.05 for both), with significant improvement in rhinitis symptoms for both groups compared with controls (P=.01 for both). TSS decreased significantly in both HDM-SCIT and HDM-SLIT at year 3 compared with baseline (P=.007 and P=.04, respectively) and controls (P<.01 for both). A significant reduction in TMS was observed in HDM-SCIT and HDM-SLIT compared with baseline and controls (P=.01 in all cases), with a reduction in skin reactivity to HDM (P<.05). Finally, a significant increase in allergen specific IgG4 was observed in the SCIT group at year 3 compared with baseline, the SLIT group, and controls (P<.001 in all cases). CONCLUSIONS: HDM-sensitized asthmatic children treated for at least 3 years with either SCIT or SLIT showed sustained clinical improvement.

Comparison of tumor markers and clinicopathological features in serous and mucinous borderline ovarian tumors.

OBJECTIVE: The aim of this study was to assess tumor markers and clinicopathological findings of patients with serous and mucinous borderline ovarian tumor (BOT) features. METHODS: The study consisted of 50 patients that were diagnosed with and treated for BOT between 2005-2010 in three centers. CA125, CA19-9, and CA125+CA19-9 levels and clinicopathological features were compared in serous and mucinous histotypes. In serous and mucinous BOTs, correlations between tumor markers and demographics such as age, menopausal status, parity, clinical findings (stage, relapse, adjuvant chemotherapy, cytology, lymph node involvement and tumoral morphology (cystic-solid content, papilla, septation) were evaluated. RESULTS: There were no significant differences between serous and mucinous tumors in the clinicopathological features such as stage, tumor markers, age, menopausal status, or cytology. In serous BOTs we found a significant relation between elevated CA125+ CA19-9, CA19-9 and recurrence (p < 0.05). Also there was a significant relation between elevated CA125+ CA19-9, CA19-9 and cytology positivity (p < 0.05). We found a significant relation in serous BOTs between elevated CA125+CA19-9, adjuvant chemotherapy and lymph node metastases (p < 0.05). Also In mucinous BOTs with papilla formation we found a significant relation between elevated CA125 and CA125+ CA19-9 (p < 0.05). There was significant relation between cytology positivity and elevated CA19-9 in mucinous BOTs (p < 0.05). CONCLUSION: Serum tumor markers of serous and mucinous BOTs were different in relation to their clinicopathological features. This may reflect differences of serous and mucinous BOTs.

Comparison of risk of malignancy indices; RMI 1-4 in borderline ovarian tumor.

PURPOSE: The aim of this study was to evaluate prognostic values of the risk of malignancy index (RMI)/1-4 in patients with borderline ovarian tumors (BOTs). METHODS: The study consisted of 50 patients with BOT diagnosed and treated between 2005-2010 and 50 patients with benign adnexal massses between 2009-2010 as a control comparison group in the retropsective study. Preoperative serum CA125, U score, tumor size (S), and menopausal status were recorded. The RMI 1-3 was calculated according to the formula; UxMxCA125 and RMI4 formulation was; UxMxCA125xS. S equaled 1 for tumor size <7 cm and was 2 when size a 7 cm. The RMI 1-4 indices were calculated for all patients together with the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy (DA). The performances of RMI indices were evaluated by McNemar's test and determined the best score cutoff value by the receiver operating characteristic (ROC) curve. RESULTS: The mean age, median value of CA125, ultrasound score, menopausal status, median values of RMI 1-4 of BOTs were statistically higher than benign adnexal masses. The sensitivity of RMI 1-4 was 26, 36, 62, and 60% at cutoff 200 level, respectively. The areas under curve of RMI 1-4 were found to be 0.676, 0.665, 0.668 and 0.734, respectively. DA of RMI 1-4 was found to be 56, 59, 50, and 71, respectively. When RMI 1-4 indices were compared with each other RMI 4 was the best RMI for BOTs. CONCLUSION: RMI 4 was the best predictive RMI for preoperative discrimination of BOT at a cutoff level of 200.

A new single-layer structure of MBene family: Ti2B.

In this manuscript, we have carried out a combined study of density functional theory and Monte Carlo (MC) simulations for a thorough examination of a single-layer (SL) Ti2B structure. On the basis of first-principles, spin-polarized density functional calculations, we showed that a free standing SL-Ti2B structure is dynamically and thermally stable. The atomic structure, phonon spectrum, electronic and magnetic properties of the SL-Ti2B structure are analyzed. In order to determine ground state, the structure of Ti2B is optimized for four types of spin oriented configurations, namely ferromagnetic (FM), antiferromagnetic Néel, antiferromagnetic Zigzag and antiferromagnetic Stripy and non-magnetic states. We found that the spin configuration FM corresponds to the ground state for SL-Ti2B. We also found that the Raman-active modes are softening in the antiferromagnetic cases. On the basis of these results, MC simulations show that the magnetic susceptibility, thermal variations of magnetization, and specific heat curves of Ti2B exhibit a phase transition between paramagnetic and FM phases at the Curie temperature of 39.06 K. While SL-Ti2B possess a little out-of-plane magnetic anisotropy, it has not any in plane magnetic anisotropy energy.

Electronic structure of BSb defective monolayers and nanoribbons.

In this paper, we investigate two- and one-dimensional honeycomb structures of boron antimony (BSb) using a first-principles plane wave method within the density functional theory. BSb with a two-dimensional honeycomb structure is a semiconductor with a 0.336 eV band gap. The vacancy defects, such as B, Sb, B + Sb divacancy, and B + Sb antisite disorder affect the electronic and magnetic properties of the 2D BSb sheet. All the structures with vacancies have nonmagnetic metallic characters, while the system with antisite disorder has a semiconducting band structure. We also examine bare and hydrogen-passivated quasi-one-dimensional armchair BSb nanoribbons. The effects of ribbon width (n) on an armchair BSb nanoribbon and hydrogen passivation on both B and Sb edge atoms are considered. The band gaps of bare and H passivated A-Nr-BSb oscillate with increasing ribbon width; this property is important for quantum dots. For ribbon width n = 12, the bare A-Nr-BSb is a nonmagnetic semiconductor with a 0.280 eV indirect band gap, but it becomes a nonmagnetic metal when B edge atoms are passivated with hydrogen. When Sb atoms are passivated with hydrogen, a ferromagnetic half-metallic ground state is observed with 2.09µB magnetic moment. When both B and Sb edges are passivated with hydrogen, a direct gap semiconductor is obtained with 0.490 eV band gap with disappearance of the bands of edge atoms.

Long-term effect of sublingual and subcutaneous immunotherapy in dust mite–allergic children with asthma/rhinitis: a 3-year prospective randomized controlled trial

Background and Objective: Specific allergen immunotherapy is the only treatment modality that might change the natural course of allergic diseases in childhood. We sought to prospectively compare the long-term clinical and immunological effects of sublingual (SLIT) and subcutaneous (SCIT) immunotherapy compared with pharmacotherapy alone. Methods: In this single-center, prospective randomized controlled trial, 48 children with mild persistent asthma with/without rhinitis, monosensitized to house dust mites (HDMs) were followed for 3 years. At baseline and years 1 and 3 of follow-up, patients were evaluated and compared for total rhinitis (TRSS) and asthma (TASS) symptom scores, total symptom scores (TSS), total medication scores (TMS), safety profiles, skin-nasal-bronchial reactivity, and immunological parameters. Results: A significant reduction was observed in TASS for both HDM-SCIT and HDM-SLIT at year 3 of treatment compared with baseline and controls (P<.05 for both), with significant improvement in rhinitis symptoms for both groups compared with controls (P=.01 for both). TSS decreased significantly in both HDM-SCIT and HDM-SLIT at year 3 compared with baseline (P=.007 and P=.04, respectively) and controls (P<.01 for both). A significant reduction in TMS was observed in HDM-SCIT and HDM-SLIT compared with baseline and controls (P=.01 in all cases), with a reduction in skin reactivity to HDM (P<.05). Finally, a significant increase in allergen specific IgG4 was observed in the SCIT group at year 3 compared with baseline, the SLIT group, and controls (P<.001 in all cases). Conclusions: HDM-sensitized asthmatic children treated for at least 3 years with either SCIT or SLIT showed sustained clinical improvement (AU)

Antecedentes: La inmunoterapia con alérgenos es el único tratamiento que podría cambiar el curso natural evolutivo de las enfermedades alérgicas en la infancia. Nuestro objetivo era comparar, de manera prospectiva, la eficacia a largo plazo de la inmunoterapia sublingual (SLIT) y subcutánea (SCIT), con el tratamiento exclusivo con farmacoterapia convencional. Métodos:En este ensayo clínico, prospectivo de tres años de duración, realizado en un solo centro y aleatorizado, se incluyeron 48 niños con asma leve persistente, con o sin rinitis asociada, monosensibilizados a los ácaros del polvo (HDM). Los pacientes fueron evaluados al inicio, al año y a los tres años de tratamiento, comparándose los cambios en la puntuación de síntomas nasales (TRSS), bronquiales (TASS), puntuación total de síntomas (TSS) y consumo de medicación (TMS), perfil de seguridad, reactividad frente al alérgeno cutánea, nasal y bronquial y diversos parámetros inmunológicos. Resultados: Se observó una reducción significativa del TASS tanto para el grupo HDM-SCIT como HDM-SLIT al final del tercer año de tratamiento, tanto cuando se comparaba con la situación basal como con los cambios observados en el grupo control (p<0.05, respectivamente). El TRSS también mejoró significativamente en ambos grupos HDM-SCIT y HDM-SLIT en el tercer año de tratamiento, cuando los cambios se compararon con los observados en el grupo control (p=0,01, en ambos). El TSS y el TMS disminuyeron también significativamente en ambos grupos HDM-SCIT y HDM-SLIT en el tercer año, comparado con la situación basal (p=0,007, p=0,04/ p=0,01, p=0,01 respectivamente) y con el grupo control (p<0,01,p<0,01/ p=0,01, p=0,01, respectivamente). Tras tres años de tratamiento la reactividad cutánea frente a los alérgenos de los ácaros disminuyó significativamente (p<0,05). Los niveles de IgG4 específica frente a ácaros se incrementaron en el grupo SCIT-HDM, comparados con la situación basal y con los cambios observados en el grupo SLIT-HDM y control (p<0,001, respectivamente). Conclusiones: El tratamiento durante tres años con inmunoterapia específica tanto SCIT como SLIT se acompañó de una eficacia clínica sostenida, en este grupo de niños asmáticos sensibilizados a los ácaros del polvo. Ambas rutas de administración de la inmunoterapia parecen tener mecanismos de acción similares (AU)

Two- and one-dimensional honeycomb structures of silicon and germanium.

First-principles calculations of structure optimization, phonon modes, and finite temperature molecular dynamics predict that silicon and germanium can have stable, two-dimensional, low-buckled, honeycomb structures. Similar to graphene, these puckered structures are ambipolar and their charge carriers can behave like a massless Dirac fermion due to their pi and pi(*) bands which are crossed linearly at the Fermi level. In addition to these fundamental properties, bare and hydrogen passivated nanoribbons of Si and Ge show remarkable electronic and magnetic properties, which are size and orientation dependent. These properties offer interesting alternatives for the engineering of diverse nanodevices.