Evidence Supporting Oral Hygiene Management by Owners through a Genetic Analysis of Dental Plaque Bacteria in Dogs.

With the increase in the number of households raising dogs and the reports of human-to-dog transmission of oral bacteria, concerns about dogs' oral health and the need for oral hygiene management are increasing. In this study, the owners' perceptions about their dogs' oral health and the frequency of oral hygiene were determined along with the analysis of dog dental plaque bacteria through metagenomic amplicon sequencing so as to support the need for oral hygiene management for dogs. Although the perception of 63.2% of the owners about their dogs' oral health was consistent with the veterinarian's diagnosis, the owners' oral hygiene practices regarding their dogs were very poor. The calculi index (CI) and gingiva index (GI) were lower in dogs who had their teeth brushed more than once a week (57.89%) than in dogs brushed less than once a month (42.10%); however, the difference was nonsignificant (CI: p = 0.479, GI: p = 0.840). Genomic DNA was extracted from dental plaque bacteria removed during dog teeth scaling, and metagenomic amplicons were sequenced. The 16S amplicons of 73 species were identified from among the plaque bacteria of the dogs. These amplicons were of oral disease-causing bacteria in humans and dogs. The 16S amplicon of Streptococcus mutans matched that of the human S. mutans, with type c identified as the main serotype. This result suggests that human oral bacteria can be transmitted to dogs. Therefore, considering the high frequency of contact between dogs and humans because of communal living and the current poor oral health of dogs, owners must improve the oral hygiene management of their dogs.

Voltage control of magnetism in Fe3-xGeTe2/In2Se3 van der Waals ferromagnetic/ferroelectric heterostructures.

We investigate the voltage control of magnetism in a van der Waals (vdW) heterostructure device consisting of two distinct vdW materials, the ferromagnetic Fe3-xGeTe2 and the ferroelectric In2Se3. It is observed that gate voltages applied to the Fe3-xGeTe2/In2Se3 heterostructure device modulate the magnetic properties of Fe3-xGeTe2 with significant decrease in coercive field for both positive and negative voltages. Raman spectroscopy on the heterostructure device shows voltage-dependent increase in the in-plane In2Se3 and Fe3-xGeTe2 lattice constants for both voltage polarities. Thus, the voltage-dependent decrease in the Fe3-xGeTe2 coercive field, regardless of the gate voltage polarity, can be attributed to the presence of in-plane tensile strain. This is supported by density functional theory calculations showing tensile-strain-induced reduction of the magnetocrystalline anisotropy, which in turn decreases the coercive field. Our results demonstrate an effective method to realize low-power voltage-controlled vdW spintronic devices utilizing the magnetoelectric effect in vdW ferromagnetic/ferroelectric heterostructures.

Interface-Induced Seebeck Effect in PtSe2/PtSe2 van der Waals Homostructures.

The Seebeck effect refers to the production of an electric voltage when different temperatures are applied on a conductor, and the corresponding voltage-production efficiency is represented by the Seebeck coefficient. We report a Seebeck effect: thermal generation of driving voltage from the heat flowing in a thin PtSe2/PtSe2 van der Waals homostructure at the interface. We refer to the effect as the interface-induced Seebeck effect. By exploiting this effect by directly attaching multilayered PtSe2 over high-resistance PtSe2 thin films as a hybridized single structure, we obtained the highly challenging in-plane Seebeck coefficient of the PtSe2 films that exhibit extremely high resistances. This direct attachment further enhanced the in-plane thermal Seebeck coefficients of the PtSe2/PtSe2 van der Waals homostructure on sapphire substrates. Consequently, we successfully enhanced the in-plane Seebeck coefficients for the PtSe2 (10 nm)/PtSe2 (2 nm) homostructure approximately 42% compared to that of a pure PtSe2 (10 nm) layer at 300 K. These findings represent a significant achievement in understanding the interface-induced Seebeck effect and provide an effective strategy for promising large-area thermoelectric energy harvesting devices using two-dimensional transition metal dichalcogenide materials, which are ideal thermoelectric platforms with high figures of merit.

Impact of H-Doping on n-Type TMD Channels for Low-Temperature Band-Like Transport.

Band-like transport behavior of H-doped transition metal dichalcogenide (TMD) channels in field effect transistors (FET) is studied by conducting low-temperature electrical measurements, where MoTe2 , WSe2 , and MoS2 are chosen for channels. Doped with H atoms through atomic layer deposition, those channels show strong n-type conduction and their mobility increases without losing on-state current as the measurement temperature decreases. In contrast, the mobility of unintentionally (naturally) doped TMD FETs always drops at low temperatures whether they are p- or n-type. Density functional theory calculations show that H-doped MoTe2 , WSe2 , and MoS2 have Fermi levels above conduction band edge. It is thus concluded that the charge transport behavior in H-doped TMD channels is metallic showing band-like transport rather than thermal hopping. These results indicate that H-doped TMD FETs are practically useful even at low-temperature ranges.

Growth and Simultaneous Valleys Manipulation of Two-Dimensional MoSe2-WSe2 Lateral Heterostructure.

The covalently bonded in-plane heterostructure (HS) of monolayer transition-metal dichalcogenides (TMDCs) possesses huge potential for high-speed electronic devices in terms of valleytronics. In this study, high-quality monolayer MoSe2-WSe2 lateral HSs are grown by pulsed-laser-deposition-assisted selenization method. The sharp interface of the lateral HS is verified by morphological and optical characterizations. Intriguingly, photoluminescence spectra acquired from the interface show rather clear signatures of pristine MoSe2 and WSe2 with no intermediate energy peak related to intralayer excitonic matter or formation of MoxW(1-x)Se2 alloys, thereby confirming the sharp interface. Furthermore, the discrete nature of laterally attached TMDC monolayers, each with doubly degenerated but nonequivalent energy valleys marked by (KM, K'M) for MoSe2 and (KW, K'W) for WSe2 in k space, allows simultaneous control of the four valleys within the excitation area without any crosstalk effect over the interface. As an example, KM and KW valleys or K'M and K'W valleys are simultaneously polarized by controlling the helicity of circularly polarized optical pumping, where the maximum degree of polarization is achieved at their respective band edges. The current work provides the growth mechanism of laterally sharp HSs and highlights their potential use in valleytronics.

Effect of graphene oxide ratio on the cell adhesion and growth behavior on a graphene oxide-coated silicon substrate.

Control of living cells on biocompatible materials or on modified substrates is important for the development of bio-applications, including biosensors and implant biomaterials. The topography and hydrophobicity of substrates highly affect cell adhesion, growth, and cell growth kinetics, which is of great importance in bio-applications. Herein, we investigate the adhesion, growth, and morphology of cultured breast cancer cells on a silicon substrate, on which graphene oxides (GO) was partially formed. By minimizing the size and amount of the GO-containing solution and the further annealing process, GO-coated Si samples were prepared which partially covered the Si substrates. The coverage of GO on Si samples decreases upon annealing. The behaviors of cells cultured on two samples have been observed, i.e. partially GO-coated Si (P-GO) and annealed partially GO-coated Si (Annealed p-GO), with a different coverage of GO. Indeed, the spreading area covered by the cells and the number of cells for a given culture period in the incubator were highly dependent on the hydrophobicity and the presence of oxygenated groups on GO and Si substrates, suggesting hydrophobicity-driven cell growth. Thus, the presented method can be used to control the cell growth via an appropriate surface modification.