The development of nanocrystals has been intensively pursued, not only for their fundamental scientific interest, but also for many technological applications. The synthesis of monodisperse nanocrystals (size variation <5%) is of key importance, because the properties of these nanocrystals depend strongly on their dimensions. For example, the colour sharpness of semiconductor nanocrystal-based optical devices is strongly dependent on the uniformity of the nanocrystals, and monodisperse magnetic nanocrystals are critical for the next-generation multi-terabit magnetic storage media. For these monodisperse nanocrystals to be used, an economical mass-production method needs to be developed. Unfortunately, however, in most syntheses reported so far, only sub-gram quantities of monodisperse nanocrystals were produced. Uniform-sized nanocrystals of CdSe (refs 10,11) and Au (refs 12,13) have been produced using colloidal chemical synthetic procedures. In addition, monodisperse magnetic nanocrystals such as Fe (refs 14,15), Co (refs 16-18), gamma-Fe(2)O(3) (refs 19,20), and Fe(3)O(4) (refs 21,22) have been synthesized by using various synthetic methods. Here, we report on the ultra-large-scale synthesis of monodisperse nanocrystals using inexpensive and non-toxic metal salts as reactants. We were able to synthesize as much as 40 g of monodisperse nanocrystals in a single reaction, without a size-sorting process. Moreover, the particle size could be controlled simply by varying the experimental conditions. The current synthetic procedure is very general and nanocrystals of many transition metal oxides were successfully synthesized using a very similar procedure.

CommunicationsMonodisperse magnetic iron oxide nanoparticles with a continuous size spectrum of 6-13 nm were produced by controlled growth on previously synthetisized monodisperse nanoparticle seeds. The detailed synthetic procedure and characterization is described in the communication by T. Hyeon et al. on the following pages.

Monodisperse spherical Ni nanoparticles with diameters of 2 nm, 5 nm, and 7 nm were synthesized from the thermal decomposition of a Ni–oleylamine complex. Ni nanocrystal superlattices were generated via the controlled evaporation of solvent (see Figure). The nanoparticles were successfully used as catalysts for the Suzuki coupling reaction, and were readily oxidized to produce NiO nanoparticles.

We have synthesized uniform and highly crystalline magnetite nanoparticles from the reaction of iron salts in microemulsion nanoreactors. The particle size can be controlled from 2 nm to 10 nm by varying the relative concentrations of the iron salts, surfactant, and solvent. Transmission electron microscope images of the nanoparticles reveal that they are very uniform in size distribution. Structural characterization using X‐ray diffraction and X‐ray magnetic circular dichroism shows that the nanoparticles are magnetite. The magnetic characterization of the nanoparticles showed that they are superparamagnetic at room temperature. Using a similar synthetic procedure, we have been able to synthesize nanoparticles of several mixed metal ferrites including cobalt ferrite, manganese ferrite, nickel ferrite, and zinc ferrite.

A Dirac fermion in a topological Dirac semimetal is a quadruple-degenerate quasi-particle state with a relativistic linear dispersion. Breaking either time-reversal or inversion symmetry turns this system into a Weyl semimetal that hosts double-degenerate Weyl fermion states with opposite chiralities. These two kinds of quasi-particles, although described by a relativistic Dirac equation, do not necessarily obey Lorentz invariance, allowing the existence of so-called type-II fermions. Recent theoretical discovery of type-II Weyl fermions evokes the prediction of type-II Dirac fermions in PtSe 2 -type transition metal dichalcogenides, expecting an experimental confirmation. Here, we report an experimental realization of type-II Dirac fermions in PdTe 2 by angle-resolved photoemission spectroscopy combined with ab-initio band calculations. Our experimental finding makes the first example that has both superconductivity and type-II Dirac fermions, which turns the topological material research into a new phase.

PurposeThe purpose of this study was to investigate the prognostic impact of pretreatment neutrophil to lymphocyte ratio (NLR) on breast cancer in view of disease-specific survival and the intrinsic subtype.MethodsWe retrospectively studied patients diagnosed with primary breast cancer that had completed all phases of primary treatment from 2000 to 2010. The association between pretreatment NLR and disease-specific survival was analyzed.ResultsA total of 442 patients were eligible for analysis. Patients with higher NLR (2.5 ≤NLR) showed significantly lower disease-specific survival rate than those with lower NLR (NLR <2.5). Higher NLR along with negative estrogen receptor status and positive nodal status were independently correlated with poor prognosis, with hazard ratio 4.08 (95% confidence interval [CI], 1.62-10.28), 9.93 (95% CI, 3.51-28.13), and 11.23 (95% CI, 3.34-37.83), respectively. Luminal A subtype was the only intrinsic subtype in which higher NLR patients showed significantly poor prognosis (87.7% vs. 96.7%, p=0.009).ConclusionPatients with an elevated pretreatment NLR showed poorer disease-specific survival than patients without elevated NLR, most evident in the luminal A subtype. Further validation and a feasibility study are required before it can be considered for clinical use.

Joo EY; Noh HJ; Kim JS; Koo DL; Kim D; Hwang KJ; Kim JY; Kim ST; Kim MR; Hong SB. Brain gray matter deficits in patients with chronic primary insomnia. 2013;36(7):999-1007.

We have investigated the electronic structure of graphite oxide using X-ray absorption spectroscopy at the carbon and oxygen K-edges. The unoccupied π * and σ * states associated with sp 2 hybridization in graphite, are also apparent in the graphite oxide, which indicates that it has a graphitic structure even though it experiences oxidation and annealing. Additional electronic states of the graphite oxide which are not present in its precursor, graphite, are ascribed to the functional groups such as epoxide, carboxyl, and hydroxyl groups.