Discovery of ^{60}Ca and Implications For the Stability of ^{70}Ca

The discovery of the important neutron-rich nucleus _{20}^{60}Ca_{40} and seven others near the limits of nuclear stability is reported from the fragmentation of a 345  MeV/u ^{70}Zn projectile beam on ^{9}Be targets at the radioactive ion-beam factory of the RIKEN Nishina Center. The produced fragments were analyzed and unambiguously identified using the BigRIPS two-stage in-flight separator. The eight new neutron-rich nuclei discovered, ^{47}P, ^{49}S, ^{52}Cl, ^{54}Ar, ^{57}K, ^{59,60}Ca, and ^{62}Sc, are the most neutron-rich isotopes of the respective elements. In addition, one event consistent with ^{59}K was registered. The results are compared with the drip lines predicted by a variety of mass models and it is found that the models in best agreement with the observed limits of existence in the explored region tend to predict the even-mass Ca isotopes to be bound out to at least ^{70}Ca.

MT-ND5 Mutation Exhibits Highly Variable Neurological Manifestations at Low Mutant Load

Mutations in the m.13094T>C MT-ND5 gene have been previously described in three cases of Leigh Syndrome (LS). In this retrospective, international cohort study we identified 20 clinically affected individuals (13 families) and four asymptomatic carriers. Ten patients were deceased at the time of analysis (median age of death was 10years (range: 5·4months-37years, IQR=17·9years). Nine patients manifested with LS, one with mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS), and one with Leber hereditary optic neuropathy. The remaining nine patients presented with either overlapping syndromes or isolated neurological symptoms. Mitochondrial respiratory chain activity analysis was normal in five out of ten muscle biopsies. We confirmed maternal inheritance in six families, and demonstrated marked variability in tissue segregation, and phenotypic expression at relatively low blood mutant loads. Neuropathological studies of two patients manifesting with LS/MELAS showed prominent capillary proliferation, microvacuolation and severe neuronal cell loss in the brainstem and cerebellum, with conspicuous absence of basal ganglia involvement. These findings suggest that whole mtDNA genome sequencing should be considered in patients with suspected mitochondrial disease presenting with complex neurological manifestations, which would identify over 300 known pathogenic variants including the m.13094T>C.

Suggestion of the updated IVIS cut-off values for identifying non-ocular irritants in the bovine corneal opacity and permeability (BCOP) assay

The bovine corneal opacity and permeability (BCOP) assay is an alternative to the Draize test in rabbits. Although it can be used to evaluate ocular non-irritants and severe irritants, it is not used for the assessment of mild-irritating substances. In this assay, a chemical with an in vitro irritancy score (IVIS)≤3 is defined as a "non-irritant" while one with an IVIS>55 is defined as a "corrosive" or "severe irritant." We attempted to evaluate mild eye irritants by assessing the recovery of corneal lesions histopathologically. Our results indicated that chemicals with IVIS≤6 may be defined as "non-irritants," because the rapid recovery of lesions limited to the squamous layer was predicted by the histopathology. In cases where lesions extended to the wing and basal cell layers, when some intact basal cells remained, the lesions were also predicted to be reversible. Thus, chemicals which induce lesions in which basal cells remain intact can be considered to be mild irritants.

Remitted epilepsy with dysembryoplastic neuroepithelial tumor involving the thalamus

Dysembryoplastic neuroepithelial tumors (DNT) are benign hamartomatous tumors characterized by intractable epilepsy and common localization in the supratentorial cortex, but thalamic involvement in DNT is extremely rare. A 2-year 4-month-old boy presented with intractable epilepsy due to a tumorous lesion in the frontal lobe expanding to the thalamus. Under chronic intracranial electrocorticography guidance, partial lesionectomy with adjacent cortical resection was performed, and the lesion was pathologically diagnosed as DNT, complex form. Subsequently, the seizures completely disappeared without any neurological deficits despite the presence of full residual thalamic lesions. The epileptogenicity of DNT is closely associated with various clinicopathological factors, and the thalamic contribution to the seizure activity remains unclear. Due to the essential epileptogenic characteristics of DNT, the residual thalamic lesions and associated clinical features should be strictly observed in the future in the present case.

Quadrupole Order in the Frustrated Pyrochlore Tb_{2+x}Ti_{2-x}O_{7+y}

A hidden order that emerges in the frustrated pyrochlore Tb_{2+x}Ti_{2-x}O_{7+y} with T_{c}=0.53  K is studied using specific heat, magnetization, and neutron scattering experiments on a high-quality single crystal. Semiquantitative analyses based on a pseudospin-1/2 Hamiltonian for ionic non-Kramers magnetic doublets demonstrate that it is an ordered state of electric quadrupole moments. The elusive spin liquid state of the nominal Tb_{2}Ti_{2}O_{7} is most likely a U(1) quantum spin-liquid state.

Field-induced quantum criticality and universal temperature dependence of the magnetization of a spin-1/2 heisenberg chain

High-precision dc magnetization measurements have been made on Cu(C4H4N2) (NO3)2 in magnetic fields up to 14.7 T, slightly above the saturation field Hs=13.97  T, in the temperature range from 0.08 to 15 K. The magnetization curve and differential susceptibility at the lowest temperature show excellent agreement with exact theoretical results for the spin-1/2 Heisenberg antiferromagnet in one dimension. A broad peak is observed in magnetization measured as a function of temperature, signaling a crossover to a low-temperature Tomonaga-Luttinger-liquid regime. With an increasing field, the peak moves gradually to lower temperatures, compressing the regime, and, at Hs, the magnetization exhibits a strong upturn. This quantum critical behavior of the magnetization and that of the specific heat withstand quantitative tests against theory, demonstrating that the material is a practically perfect one-dimensional spin-1/2 Heisenberg antiferromagnet.

Spin-chirality-driven ferroelectricity on a perfect triangular lattice antiferromagnet

Magnetic field (B) variation of the electrical polarization P(c) (∥c) of the perfect triangular lattice antiferromagnet RbFe(MoO(4))(2) is examined up to the saturation point of the magnetization for B⊥c. P(c) is observed only in phases for which chirality is predicted in the in-plane magnetic structures. No strong anomaly is observed in P(c) at the field at which the spin modulation along the c axis, and hence the spin helicity, exhibits a discontinuity to the commensurate state. These results indicate that the ferroelectricity in this compound originates predominantly from the spin chirality, the explanation of which would require a new mechanism for magnetoferroelectricity. The obtained field-temperature phase diagram of ferroelectricity agree well with those theoretically predicted for the spin chirality of a Heisenberg spin triangular lattice antiferromagnet.

Unconventional magnetic and thermodynamic properties of S=1/2 spin ladder with ferromagnetic legs

We have succeeded in synthesizing single crystals of a new organic radical 3-Cl-4-F-V [3-(3-chloro-4-fluorophenyl)-1,5-diphenylverdazyl]. Through the ab initio molecular orbital calculation and the analysis of the magnetic properties, this compound was confirmed to be the first experimental realization of an S=1/2 spin-ladder system with ferromagnetic leg interactions. The field-temperature phase diagram indicated that the ground state is situated very close to the quantum critical point. Furthermore, we found an unexpected field-induced successive phase transition, which possibly originates from the interplay of low dimensionality and frustration.