Symmetric Breakage-Induced Semimetallic State: Polymorphism in Ruthenate Nanosheets.

Atomic arrangements and their symmetries govern the physical properties of materials, including nanosheets that are low-dimensional nanomaterials. Although they have the same composition, symmetric changes associated with atomic displacements sometimes induce unexpected physical properties. Herein, we report that symmetric breakage induces a semimetallic state in chemically exfoliated ruthenate nanosheets. The atomic arrangements and symmetries are determined by a pair distribution function (PDF); subsequently, the physical properties are discussed using ab initio calculations and resistivity measurements. Ruthenate nanosheets can adopt an electronic structure similar to that of graphene owing to symmetric breakage. We experimentally confirmed the polymorphism in ruthenate nanosheets that highlights the importance of symmetric analysis, even in low-dimensional materials.

Enhancement in the Charge-Transfer Kinetics of Pseudocapacitive Iridium-Doped Layered Manganese Oxide.

Birnessite manganese oxide is a promising candidate as an electrode material for aqueous supercapacitors owing to its pseudocapacitance associated with fast redox processes. While manganese oxides are semiconductive, the conductivity is much lower than that of typical materials used for capacitive electrodes such as activated carbon or ruthenium oxide. In an attempt to increase the electronic conductivity of birnessite, a new solid solution phase, Ky(Mn1-xIrx)O2, was synthesized, and the electrochemical charge storage capability of Ir-doped birnessite was studied in aqueous Li2SO4. Structural characterization revealed that the single-phase Ky(Mn1-xIrx)O2 could be synthesized up to x = 0.1. An increase in the pseudocapacitive charge was observed with the increase in Ir content. In addition to the increase in the pseudocapacitive charge, an unusual change in the peak potential was observed. The peak-to-peak difference for the Mn4+/Mn3+ redox decreased with increasing Ir content, indicating an increase in the reversibility of the pseudocapacitive process. The decrease in peak-to-peak difference was observed only by Ir substitution and was not observed for physical mixtures of K0.28MnO2 and IrO2, suggesting a strong electronic interaction between the host Mn ion and the substituting Ir ion.

Dopamine D2L Receptor Deficiency Causes Stress Vulnerability through 5-HT1A Receptor Dysfunction in Serotonergic Neurons.

Mental disorders are caused by genetic and environmental factors. We here show that deficiency of an isoform of dopamine D2 receptor (D2R), D2LR, causes stress vulnerability in mouse. This occurs through dysfunction of serotonin [5-hydroxytryptamine (5-HT)] 1A receptor (5-HT1AR) on serotonergic neurons in the mouse brain. Exposure to forced swim stress significantly increased anxiety- and depressive-like behaviors in D2LR knock-out (KO) male mice compared with wild-type mice. Treatment with 8-OH-DPAT, a 5-HT1AR agonist, failed to alleviate the stress-induced behaviors in D2LR-KO mice. In forced swim-stressed D2LR-KO mice, 5-HT efflux in the medial prefrontal cortex was elevated and the expression of genes related to 5-HT levels was upregulated by the transcription factor PET1 in the dorsal raphe nucleus. Notably, D2LR formed a heteromer with 5-HT1AR in serotonergic neurons, thereby suppressing 5-HT1AR-activated G-protein-activated inwardly rectifying potassium conductance in D2LR-KO serotonergic neurons. Finally, D2LR overexpression in serotonergic neurons in the dorsal raphe nucleus alleviated stress vulnerability observed in D2LR-KO mice. Together, we conclude that disruption of the negative feedback regulation by the D2LR/5-HT1A heteromer causes stress vulnerability.SIGNIFICANCE STATEMENT Etiologies of mental disorders are multifactorial, e.g., interactions between genetic and environmental factors. In this study, using a mouse model, we showed that genetic depletion of an isoform of dopamine D2 receptor, D2LR, causes stress vulnerability associated with dysfunction of serotonin 1A receptor, 5-HT1AR in serotonergic neurons. The D2LR/5-HT1AR inhibitory G-protein-coupled heteromer may function as a negative feedback regulator to suppress psychosocial stress.

Scalable Design of Two-Dimensional Oxide Nanosheets for Construction of Ultrathin Multilayer Nanocapacitor.

Large size of capacitors is the main hurdle in miniaturization of current electronic devices. Herein, a scalable solution-based layer-by-layer engineering of metallic and high-κ dielectric nanosheets into multilayer nanosheet capacitors (MNCs) with overall thickness of ≈20 nm is presented. The MNCs are built through neat tiling of 2D metallic Ru0.95 O2 0.2- and high-κ dielectric Ca2 NaNb4 O13 - nanosheets via the Langmuir-Blodgett (LB) approach at room temperature which is verified by cross-sectional high-resolution transmission electron microscopy (HRTEM). The resultant MNCs demonstrate a high capacitance of 40-52 µF cm-2 and low leakage currents down to 10-5 -10-6 A cm-2 . Such MNCs also possess complimentary in situ robust dielectric properties under high-temperature measurements up to 250 °C. Based on capacitance normalized by the thickness, the developed MNC outperforms state-of-the-art multilayer ceramic capacitors (MLCC, ≈22 µF cm-2 /5 × 104  nm) present in the market. The strategy is effective due to the advantages of facile, economical, and ambient temperature solution assembly.

Simplification of head and neck volumetric modulated arc therapy patient-specific quality assurance, using a Delta4 PT.

BACKGROUND/AIM: In many facilities, intensity-modulated radiation therapy (IMRT), and volumetric modulated arc therapy (VMAT) use intensity-modulated beams, formed by a multi-leaf collimator (MLC). In IMRT and VMAT, MLC and linear accelerator errors (both geometric and dose), can significantly affect the doses administered to patients. Therefore, IMRT and VMAT treatment plans must include the use of patient-specific quality assurance (QA) before treatment to confirm dose accuracy. MATERIALS AND METHODS: In this study, we compared and analyzed the results of dose verification using a multi-dimensional dose verification system Delta4 PT, an ionization chamber dosimeter, and gafchromic film, using data from 52 patients undergoing head and neck VMAT as the test material. RESULT: Based on the results of the absolute dose verification for the ionization chamber dosimeter and Delta4 PT, taking an axial view, the upper limit of the 95% confidence interval was 3.13%, and the lower limit was -3.67%, indicating good agreement. These results mean that as long as absolute dose verification for the axial view does not deviate from this range, Delta4 PT can be used as an alternative to an ionization chamber dosimeter for absolute dose verification. When we then reviewed dose distribution verification, the pass rate for Delta4 PT was acceptable, and was less varied than that of gafchromic film. CONCLUSION: This results in that provided the pass rate result for Delta4 PT does not fall below 96%, it can be used as a substitute for gafchromic film in dose distribution verification. These results indicate that patient-specific QA could be simplified.

The effect of rectal gas on dose distribution during prostate cancer treatment using full arc and partial arc Volumetric Modulated Arc Therapy (VMAT) treatment plans.

BACKGROUND/AIM: In this study, we investigated the effect of rectal gas on the dose distribution of prostate cancer using a volumetric modulated arc therapy (VMAT) treatment planning. MATERIALS AND METHODS: The first is the original structure set, clinical target volume (CTV), the rectum, and the bladder used clinically. The second is a structure set (simulated gas structure set) in which the overlapping part of the rectum and PTV is overwritten with Hounsfield Unit -950 as gas. Full arc and limited gantry rotation angle with VMAT were the two arcs. The VMAT of the full arc was 181°-179° in the clockwise (CW) direction and 179°-181° in the counterclockwise (CCW) direction. Three partial arcs with a limited gantry rotation angle were created: 200°-160 °CW and 160°-200 °CCW; 220°-140 °CW and 140°-220 °CCW; and finally, 240°-120 °CW and 120°-240 °CCW. The evaluation items were dose difference, distance to agreement, and gamma analysis. RESULT: In the CTV, the full arc was the treatment planning technique with the least effect of rectal gas. In the rectum, when the gantry rotation angle range was short, the pass rate tended to reduce for all evaluation indices. The bladder showed no characteristic change between the treatment planning techniques in any of the evaluation indices. CONCLUSIONS: The VMAT treatment planning with the least effect on dose distribution caused by rectal gas was shown to be a full arc.

Conductive Nanosized Magnéli-Phase Ti4O7 with a Core@Shell Structure.

Magnéli-phase Ti4O7, known for its high electrical conductivity and corrosion resistance, is typically prepared by hydrogen reduction at high temperatures (∼1000 °C), leading to large particles. Nanosized Ti4O7 have been explored for application toward high specific surface area electrode materials and electrocatalyst supports; nonetheless, the particle size of Ti4O7 is still insufficient for utilization as a support. In this study, we have pursued a novel synthetic approach for nanosized Ti4O7 platelets with a length of 10-80 nm and thickness of 3-10 nm even under high-temperature conditions. We herein describe the use of SiO2 beads as a core to obtain a SiO2 core coated with multilayers of TiO2 nanosheets exfoliated from layered H2Ti4O7 which is subsequently subjected to high-temperature reduction to prepare a SiO2-core@Ti4O7-shell structure. The pair distribution function technique has proven that the shell is transformed to single-phase Ti4O7. The electrical double layer capacitance of SiO2-core@Ti4O7-shell was much larger than that of conventionally synthesized Ti4O7 particles with a micrometer size. The results show the beneficial effects of the SiO2-core@Ti4O7-shell structure, and it is the first example of the synthesis for conductive Ti4O7 with a high specific surface area even under conditions of high-temperature synthesis.

DMPK is a New Candidate Mediator of Tumor Suppressor p53-Dependent Cell Death.

Tumor suppressor p53 plays an integral role in DNA-damage induced apoptosis, a biological process that protects against tumor progression. Cell shape dramatically changes when cells undergo apoptosis, which is associated with actomyosin contraction; however, it remains entirely elusive how p53 regulates actomyosin contraction in response to DNA-damaging agents. To identify a novel p53 regulating gene encoding the modulator of myosin, we conducted DNA microarray analysis. We found that, in response to DNA-damaging agent doxorubicin, expression of myotonic dystrophy protein kinase (DMPK), which is known to upregulate actomyosin contraction, was increased in a p53-dependent manner. The promoter region of DMPK gene contained potential p53-binding sequences and its promoter activity was increased by overexpression of the p53 family protein p73, but, unexpectedly, not of p53. Furthermore, we found that doxorubicin treatment induced p73 expression, which was significantly attenuated by downregulation of p53. These data suggest that p53 induces expression of DMPK through upregulating p73 expression. Overexpression of DMPK promotes contraction of the actomyosin cortex, which leads to formation of membrane blebs, loss of cell adhesion, and concomitant caspase activation. Taken together, our results suggest the existence of p53-p73-DMPK axis which mediates DNA-damage induced actomyosin contraction at the cortex and concomitant cell death.

Preparation of Mesoporous Bimetallic Au-Pt with a Phase-Segregated Heterostructure Using Mesoporous Silica.

Mesoporous bimetallic Au-Pt with a phase-segregated heterostructure has been prepared by using mesoporous silica SBA-15 as a template. Au nanoparticles were prepared as a seed metal within the mesopores, and subsequently Pt was deposited, sandwiching the Au seeds. Energy-dispersive X-ray (EDX) spectral mapping showed that the framework of mesoporous bimetallic Au-Pt, prepared by removing the silica template with HF, was composed of Au nanoparticles joined with Pt nanowires. The Au/Pt ratio of the mesoporous bimetallic Au-Pt could be varied by controlling the number of Au deposition cycles. Pre-adsorbed CO (COad) stripping voltammetry of the mesoporous bimetallic Au-Pt showed that the surfaces of the joined bimetallic structure were electrochemically active. This could be attributed to the open framework structure having a high ratio of exposed bimetallic mesopore surfaces. The described preparative approach, involving a mesoporous silica template and stepwise deposition within the mesopores, enables control of the nanostructure of the bimetallic material, which is greatly promising for the further development of synthetic methodologies for bimetallic structures.

Vertically aligned MXene bioelectrode prepared by freeze-drying assisted electrophoretic deposition for sensitive electrochemical protein detection.

Two-dimensional (2D) carbides, MXenes, have attracted attention as electrode materials of electrochemical biosensors because of their metallic conductivity, hydrophilicity, and mechanical stability. However, when fabricating electrodes, the nanosheets tend to re-stack and generally align horizontally with respect to the current collector due to the highly anisotropic nature of MXene, resulting in low porosity and poor utilization of the MXene surface. Here we report the electrochemical biosensing of antibody-antigen reactions with a vertically aligned Ti3C2Tx MXene (VA-MXene) electrode prepared by freeze-drying assisted electrophoretic deposition. The macroporous VA-MXene electrode exhibited a better electrochemical response towards the immunoreaction between the allergenic buckwheat protein (BWp16) and the antibody compared to a non-porous, horizontally (in-plane) stacked MXene (HS-MXene) and the sensors reported in the literature. The sensor responsiveness, defined as the ratio of the obtained current density of the electrode to the antigen concentration, was much higher for the VA-MXene electrode (238 µA cm-2 (ng mL-1) -1) than for the HS-MXene electrode. The proposed technique is applicable to other exfoliated nanosheets, and will open a new avenue for porous nanosheet electrodes to improve the sensing characteristics of electrochemical biosensors.