Polytypic Two-Dimensional FeAs with High Anisotropy.

In the realm of two-dimensional (2D) crystal growth, the chemical composition often determines the thermodynamically favored crystallographic structures. This relationship poses a challenge in synthesizing novel 2D crystals without altering their chemical elements, resulting in the rarity of achieving specific crystallographic symmetries or lattice parameters. We present 2D polymorphic FeAs crystals that completely differ from bulk orthorhombic FeAs (Pnma), differing in the stacking sequence, i.e., polytypes. Preparing polytypic FeAs outlines a strategy for independently controlling each symmetry operator, which includes the mirror plane for 2Q-FeAs (I4/mmm) and the glide plane for 1Q-FeAs (P4/nmm). As such, compared to bulk FeAs, polytypic 2D FeAs shows highly anisotropic properties such as electrical conductivity, Young's modulus, and friction coefficient. This work represents a concept of expanding 2D crystal libraries with a given chemical composition but various crystal symmetries.

Effect of Residual Oxygen Concentration on the Lattice Parameters of Aluminum Nitride Powder Prepared via Carbothermal Reduction Nitridation Reaction.

Residual oxygen in wurtzite-type aluminum nitride (AlN) crystal, which significantly affects phonon transport and crystal growth, is crucial to thermal conductivity and the crystal quality of AlN ceramics. In this study, the effect of residual oxygen on the lattice of AlN was examined for as-synthesized and sintered samples. By controlling reaction time in the carbothermal reduction nitridation (CRN) procedure, AlN powder was successfully synthesized, and the amount of residual oxygen was systematically controlled. The evolution of lattice parameters of AlN with respect to oxygen conc. was carefully investigated via X-ray diffraction analysis. With increasing amounts of residual oxygen in the as-synthesized AlN, lattice expansion in the ab plane was induced without a significant change in the c-axis lattice parameter. The lattice expansion in the ab plane owing to the residual oxygen was also confirmed with high-resolution transmission electron microscopy, in contrast to the invariant lattice parameter of the sintered AlN phase. Micro-strain values from XRD peak broadening confirm that stress, induced by residual oxygen, expands the AlN lattice. In this work, the lattice expansion of AlN with increasing residual oxygen was elucidated via X-ray diffraction and HR-TEM, which is useful to estimate and control the lattice oxygen in AlN ceramics.

Direct Evidence on Effect of Oxygen Dissolution on Thermal and Electrical Conductivity of AlN Ceramics Using Al Solid-State NMR Analysis.

Aluminum nitride, with its high thermal conductivity and insulating properties, is a promising candidate as a thermal dissipation material in optoelectronics and high-power logic devices. In this work, we have shown that the thermal conductivity and electrical resistivity of AlN ceramics are primarily governed by ionic defects created by oxygen dissolved in AlN grains, which are directly probed using 27Al NMR spectroscopy. We find that a 4-coordinated AlN3O defect (ON) in the AlN lattice is changed to intermediate AlNO3, and further to 6-coordinated AlO6 with decreasing oxygen concentration. As the aluminum vacancy (VAl) defect, which is detrimental to thermal conductivity, is removed, the overall thermal conductivity is improved from 120 to 160 W/mK because of the relatively minor effect of the AlO6 defect on thermal conductivity. With the same total oxygen content, as the AlN3O defect concentration decreases, thermal conductivity increases. The electrical resistivity of our AlN ceramics also increases with the removal of oxygen because the major ionic carrier is VAl. Our results show that to enhance the thermal conductivity and electrical resistivity of AlN ceramics, the dissolved oxygen in AlN grains should be removed first. This understanding of the local structure of Al-related defects enables us to design new thermal dissipation materials.

Bulk Metamaterials Exhibiting Chemically Tunable Hyperbolic Responses.

Extraordinary properties of traditional hyperbolic metamaterials, not found in nature, arise from their man-made subwavelength structures causing unique light-matter interactions. However, their preparation requiring nanofabrication processes is highly challenging and merely provides nanoscale two-dimensional structures. Stabilizing their bulk forms via scalable procedures has been a sought-goal for broad applications of this technology. Herein, we report a new strategy of designing and realizing bulk metamaterials with finely tunable hyperbolic responses. We develop a facile two-step process: (1) self-assembly to obtain heterostructured nanohybrids of building blocks and (2) consolidation to convert nanohybrid powders to dense bulk pellets. Our samples have centimeter-scale dimensions typically, readily further scalable. Importantly, the thickness of building blocks and their relative concentration in bulk materials serve as a delicate means of controlling hyperbolic responses. The resulting new bulk heterostructured material system consists of the alternating h-BN and graphite/graphene nanolayers and exhibits significant modulation in both type-I and type-II hyperbolic resonance modes. It is the first example of real bulk hyperbolic metamaterials, consequently displaying the capability of tuning their responses along both in-plane and out-of-plane directions of the materials for the first time. It also distinctly interacts with unpolarized and polarized transverse magnetic and electronic beams to give unique hyperbolic responses. Our achievement can be a new platform to create various bulk metamaterials without complicated nanofabrication techniques. Our facile synthesis method using common laboratory techniques can open doors to broad-range researchers for active interdisciplinary studies for this otherwise hardly accessible technology.

Antireflective Transparent Conductive Oxide Film Based on a Tapered Porous Nanostructure.

A new architecture for antireflection (AR) has been developed to break the trade-off between the optical transmittance and the electrical conduction impeding the performance of transparent conductive oxide (TCO) films. The tapered porous nanostructure with a complex continuous refractive index effectively eliminates reflections from the interfaces between air and the TCO and TCO and the substrate. Compared to the conventional TCO film, the AR TCO film exhibited the same electrical conduction, with an average transmittance of 88.7% in the 400-800 nm range, a 10.3% increase. The new AR TCO film is expected to improve the performance of various optoelectronic devices.

Multi-Asymmetric Ion-Diode Membranes with Superior Selectivity and Zero Concentration Polarization Effect.

Biological ion channels exhibiting selective and rectified ion transport properties feature nanoscale asymmetries in their physical structure, chemical composition, and charge distribution. Inspired by this, a multi-asymmetric ion-diode membrane (IDM) having a heterojunction between a positively charged anodic aluminum oxide membrane with conical macropores and a negatively charged Nafion membrane with very narrow mesopores was designed and practically fabricated in this study. Experiments and theoretical calculations demonstrated that the proposed membrane has the highest selectivity among IDMs and provides complete suppression of the concentration polarization (CP) effect limiting the current density in ion-exchange membrane electrodialysis. These findings present direct evidence that the physical and chemical design of the channel structure can provide both superior selectivity and a zero CP effect to IDMs and practical fabrication methods of IDMs for diverse, promising membrane applications.

Fe-Doping Effect on Thermoelectric Properties of p-Type Bi0.48Sb1.52Te3.

The substitutional doping approach has been shown to be an effective strategy to improve ZT of Bi2Te3-based thermoelectric raw materials. We herein report the Fe-doping effects on electronic and thermal transport properties of polycrystalline bulks of p-type Bi0.48Sb1.52Te3. After a small amount of Fe-doping on Bi/Sb-sites, the power factor could be enhanced due to the optimization of carrier concentration. Additionally, lattice thermal conductivity was reduced by the intensified point-defect phonon scattering originating from the mass difference between the host atoms (Bi/Sb) and dopants (Fe). An enhanced ZT of 1.09 at 300 K was obtained in 1.0 at% Fe-doped Bi0.48Sb1.52Te3 by these synergetic effects.

Structurally nanocrystalline-electrically single crystalline ZnO-reduced graphene oxide composites.

ZnO, a wide bandgap semiconductor, has attracted much attention due to its multifunctionality, such as transparent conducting oxide, light-emitting diode, photocatalyst, and so on. To improve its performances in the versatile applications, numerous hybrid strategies of ZnO with graphene have been attempted, and various synergistic effects have been achieved in the ZnO-graphene hybrid nanostructures. Here we report extraordinary charge transport behavior in Al-doped ZnO (AZO)-reduced graphene oxide (RGO) nanocomposites. Although the most challenging issue in semiconductor nanocomposites is their low mobilities, the AZO-RGO nanocomposites exhibit single crystal-like Hall mobility despite the large quantity of nanograin boundaries, which hinder the electron transport by the scattering with trapped charges. Because of the significantly weakened grain boundary barrier and the proper band alignment between the AZO and RGO, freely conducting electrons across the nanograin boundaries can be realized in the nanocomposites. This discovery of the structurally nanocrystalline-electrically single crystalline composite demonstrates a new route for enhancing the electrical properties in nanocomposites based on the hybrid strategy.

Unoxidized graphene/alumina nanocomposite: fracture- and wear-resistance effects of graphene on alumina matrix.

It is of critical importance to improve toughness, strength, and wear-resistance together for the development of advanced structural materials. Herein, we report on the synthesis of unoxidized graphene/alumina composite materials having enhanced toughness, strength, and wear-resistance by a low-cost and environmentally benign pressure-less-sintering process. The wear resistance of the composites was increased by one order of magnitude even under high normal load condition (25 N) as a result of a tribological effect of graphene along with enhanced fracture toughness (KIC) and flexural strength (σf) of the composites by ~75% (5.60 MPa·m(1/2)) and ~25% (430 MPa), respectively, compared with those of pure Al2O3. Furthermore, we found that only a small fraction of ultra-thin graphene (0.25-0.5 vol%, platelet thickness of 2-5 nm) was enough to reinforce the composite. In contrast to unoxidized graphene, graphene oxide (G-O) and reduced graphene oxide (rG-O) showed little or less enhancement of fracture toughness due to the degraded mechanical strength of rG-O and the structural defects of the G-O composites.

Highly transparent and conducting graphene-embedded ZnO films with enhanced photoluminescence fabricated by aerosol synthesis.

Graphene/inorganic hybrid structures have attracted increasing attention in research aimed at producing advanced optoelectronic devices and sensors. Herein, we report on aerosol synthesis of new graphene-embedded zinc oxide (ZnO) films with higher optical transparency (>80% at visible wavelengths), improved electrical conductivity (>2 orders of magnitude, ∼ 20 kΩ/□), and enhanced photoluminescence (∼ 3 times), as compared to bare ZnO film. The ZnO/graphene composite films, in which reduced graphene oxide nanoplatelets (∼ 4 nm thick) are embedded in nanograined ZnO (∼ 50 nm in grain size), were fabricated from colloidal suspensions of graphene oxide with an aqueous zinc precursor. These new luminescent ZnO/graphene composites, with high optical transparency and improved electrical conductivity, are promising materials for use in optoelectronic devices.

Ethical modernization: research misconduct and research ethics reforms in Korea following the Hwang affair.

The Hwang affair, a dramatic and far reaching instance of scientific fraud, shocked the world. This collective national failure prompted various organizations in Korea, including universities, regulatory agencies, and research associations, to engage in self-criticism and research ethics reforms. This paper aims, first, to document and review research misconduct perpetrated by Hwang and members of his research team, with particular attention to the agencies that failed to regulate and then supervise Hwang's research. The paper then examines the research ethics reforms introduced in the wake of this international scandal. After reviewing American and European research governance structures and policies, policy makers developed a mixed model mindful of its Korean context. The third part of the paper examines how research ethics reform is proactive (a response to shocking scientific misconduct and ensuing external criticism from the press and society) as well as reactive (identification of and adherence to national or international ethics standards). The last part deals with Korean society's response to the Hwang affair, which had the effect of a moral atomic bomb and has led to broad ethical reform in Korean society. We conceptualize this change as ethical modernization, through which the Korean public corrects the failures of a growth-oriented economic model for social progress, and attempts to create a more trustworthy and ethical society.

The economic disease burden of measles in Japan and a benefit cost analysis of vaccination, a retrospective study.

BACKGROUND: During 1999-2003, Japan experienced a series of measles epidemics, and in Action Plans to Control Measles and the Future Problems, it was proposed that infants be immunized soon after their one-year birthday.In this study, we attempted to estimate the nationwide economic disease burden of measles based on clinical data and the economic effectiveness of this proposal using the benefit cost ratio. METHODS: Our survey target was measles patients treated at Chiba-Nishi general hospital from January 1999 to September 2001. Two hundred ninety-one cases were extracted from the database. The survey team composed of 3 pediatricians and 1 physician from Chiba-Nishi general hospital examined patient files and obtained additional information by telephone interview.We analyzed data based on a static model, which assumed that the number of measles patients would be zero after 100% coverage of single-antigen measles vaccine.Costs were defined as the direct cost for measles treatment, vaccination and transportation and the indirect cost of workdays lost due to the nursing of patients, hospital visits for vaccination or nursing due to adverse reactions. Benefits were defined as savings on direct and indirect costs. Based on these definitions, we estimated the nationwide costs of treatment and vaccination. RESULTS: Using our static model, the nationwide total cost for measles treatment was estimated to be US$ 404 million, while the vaccination cost was US$165 million. The benefit cost ratio of the base case was 2.48 and ranged from 2.21 to 4.97 with sensitivity analysis. CONCLUSIONS: Although the model has some limitations, we conclude that the policy of immunizing infants soon after their one-year birthday is economically effective.

Transcultural medicine: a multi-sited ethnography on the scientific-industrial networking of Korean medicine.

Through a multi-sited ethnography of three different types of organization--a traditional medical clinic, two laboratories, and a biotech company--this article examines how Korean medicine (KM) scientizes, globalizes, and industrializes its clinical knowledge. By tracing the complex networking process among multiple places, I aim to understand how KM reinvents its knowledge, identity, and boundaries in a global situation. In particular, I pay attention to how this process involves multiple dimensions of power relations, economic interests, and scientific authorities. This article concludes that heterogeneous and unequal encounters between KM, science, and industry lead to simultaneous productions of new culture and power without reducing them to a single logic or center in a global age.

Beyond paradigm: making transcultural connections in a scientific translation of acupuncture.

This paper examines the ways in which the acupuncture phenomenon is translated into scientific language through the mobilization of functional magnetic resonance imaging. In doing so, it explores how differences between science and traditional medicine are bridged and negotiated through an open-ended tuning process among heterogeneous elements. By showing the constructive interaction between traditional medicine and science, I aim to refute a conception of East Asian medicines as culturally bounded and to provide an interpretation of transculturalism that emphasizes its diverse and hybrid formations. Particularly, in order to explain the scientific translation of acupuncture, I refer to Andrew Pickering's "mangle of practice" as an alternative to Thomas Kuhn's paradigm. Adopting a performative perspective rather than a representational one with regard to science, I read the scientific interpretation of acupuncture as an interactive stabilization between the acupuncture phenomenon, neurological theory, and the material procedure of the MRI machine.

[(Th2F5)(NC7H5O4)2(H2O)][NO3]: an actinide-organic open framework.

We believe [(Th2F5)(NC7H5O4)2(H2O)][NO3] is the first three-dimensionally connected, actinide-organic framework solid. The structure is composed of thorium oxyfluoride chains, each of which connected to pyridinedicarboxylate groups to give a 3D cross-linked network with cavities containing nitrate anions.

The first organically templated thorium compounds, [C4N2H12]0.5[ThF5] and [C5N2H14][ThF6].0.5H2O.

Organically templated thorium compounds were synthesized for the first time under hydrothermal conditions; the piperazine containing compound consists of 2-D layers, while the 2-methylpiperazine phase contains unprecedented 1-D chains of face-sharing ThF9 polyhedra.