We propose a widegap II–VI semiconductor alloy, MgxZn1−xO, for the fabrication of heteroepitaxial ultraviolet light emitting devices based on ZnO. The c-axis oriented MgxZn1−xO films were epitaxially grown by pulsed laser deposition on ZnO epitaxial films and sapphire (0001) substrates using ceramic targets. Solid solution films were prepared with Mg content up to x=0.33, achieving a band gap of 3.99 eV at room temperature. MgO impurity phase segregated at x⩾0.36. Lattice constants of MgxZn1−xO films changed slightly (∼1%), increasing in a axis and decreasing in c-axis direction with increasing x. These films showed ultraviolet photoluminescence at energies from 3.36 (x=0) to 3.87 eV (x=0.33) at 4.2 K.

We describe the structural and optical properties of II-VI oxide alloys, Mg x Zn 1Ϫx O and Cd y Zn 1Ϫy O, grown by pulsed-laser deposition. Single-phase alloyed films of ͑Mg,Zn͒O and ͑Cd,Zn͒O with c-axis orientations were epitaxially grown on sapphire ͑0001͒ substrates. The maximum magnesium and cadmium concentrations ͑xϭ0.33 and yϭ0.07, respectively͒ were significantly larger than the thermodynamic solubility limits. The band gap energies systematically changed from 3.0 (yϭ0.07) to 4.0 eV (xϭ0.33) at room temperature. The photoluminescence peak energy deduced at 4.2 K could be tuned from 3.19 to 3.87 eV by using Cd 0.07 Zn 0.93 O and Mg 0.33 Zn 0.67 O at both ends, respectively. The lattice constants of the a axis were monotonically increasing functions of the concentrations of both alloys. The exciton-phonon coupling strength was determined in Cd 0.01 Zn 0.99 O grown on a lattice-matched ScAlMgO 4 substrate.

Backgrounds No confirmatory randomized controlled trials (RCTs) have evaluated the efficacy of laparoscopy-assisted distal gastrectomy (LADG) compared with open distal gastrectomy (ODG). We performed an RCT to confirm that LADG is not inferior to ODG in efficacy. Methods We conducted a multi-institutional RCT. Eligibility criteria included histologically proven gastric adenocarcinoma in the middle or lower third of the stomach, clinical stage I tumor. Patients were preoperatively randomized to ODG or LADG. This study is now in the follow-up stage. The primary endpoint is relapse-free survival (RFS) and the primary analysis is planned in 2018. Here, we compared the surgical outcomes of the two groups. This trial was registered at the UMIN Clinical Trials Registry as UMIN000003319.Results Between March 2010 and November 2013, 921 patients (LADG 462, ODG 459) were enrolled from 33 institutions. Operative time was longer in LADG than in ODG (median 278 vs. 194 min, p \ 0.001), while blood loss was smaller (median 38 vs. 115 ml, p \ 0.001). There was no difference in the overall proportion with in-hospital grade 3-4 surgical complications (3.3 %: LADG, 3.7 %: ODG). The proportion of patients with elevated serum AST/ALT was higher in LADG than in ODG (16.4 vs. 5.3 %, p \ 0.001). There was no operation-related death in either arm. Conclusions This trial confirmed that LADG was as safe as ODG in terms of adverse events and short-term clinical outcomes. LADG may be an alternative procedure in clinical IA/IB gastric cancer if the noninferiority of LADG in terms of RFS is confirmed.

ZnO/Mg 0.2 Zn 0.8 O superlattices with a band-gap offset of about 0.5 eV were epitaxially grown by laser molecular-beam epitaxy on a sapphire͑0001͒ substrate using a ZnO buffer layer. The superlattice structure with a period ranging from 8 to 18 nm was clearly verified by cross-sectional transmission electron microscopy, Auger depth profile, and x-ray diffraction. As the well layer thickness decreased below 5 nm, the photoluminescence peak and absorption edge in the photoluminescence excitation spectra showed a blueshift, indicating a quantum-size effect.

The superconducting gap structure of recently discovered heavy fermion CePt3Si without spatial inversion symmetry was investigated by thermal transport measurements down to 40 mK. In zero field a residual T -linear term was clearly resolved as T → 0, with a magnitude in good agreement with the value expected for a residual normal fluid with a nodal gap structure, together with a T 2 -dependence at high temperatures. With an applied magnetic fields, the thermal conductivity grows rapidly, in dramatic contrast to fully gapped superconductors, and exhibits one-parameter scaling with T / √ H. These results place an important constraint on the order parameter symmetry, that is CePt3Si is most likely to have line nodes.PACS numbers: 74.20. Rp, 74.25.Bt, 74.25.Fy, 74.70.Tx @ In heavy fermion (HF) compounds containing Ce, Pr and U atoms, the strong Coulomb repulsion within the atomic f -shells leads to a notable many-body effect and often gives rise to unconventional superconductivity, in which the superconducting gap function has line or point nodes along certain directions in the Brillouin zone. Since the gap structure is closely related to the pairing mechanism of the electrons, the gap structure of HF superconductors is very important in understanding the physics of unconventional superconductivity in strongly correlated systems [1,2].Very recently a new HF superconductor CePt 3 Si with T c =0.75 K has been discovered [3]. CePt 3 Si has aroused great interest because it possesses quite unique properties. The most noticeable feature is the absence of spatial inversion symmetry, in contrast to most unconventional superconductors. It is well known that in the presence of strong spin-orbit interaction, the absence of inversion symmetry gives rise to a splitting of the two spin degenerate bands. It has been shown that the lifted spin degeneracy strongly influences the pairing symmetry of Cooper pairs [3,4,5,6,7,8,9,10,11,12]. For example, Rashba-type spin-orbit interaction dramatically changes the paramagnetic effect, which breaks up Cooper pairs [5,6,7,8,9]. According to a subsequent band structure calculation, the band splitting energy near the Fermi level in CePt 3 Si is more than a thousand times larger than k B T c , indicating strong spin-orbit coupling [10]. The special interest in the symmetry of CePt 3 Si has arisen with the observation that the upper critical field H c2 ∼ 4 T drastically exceeds the Pauli paramagnetic limit H P ∼ 1.3k B T c /µ B ∼1 T [3]. Moreover, recent NMR measurements have reported no change of the Knight shift below T c for H c [13]. These results indicate that the paramagnetic effect on Cooper pairs is absent or is strongly reduced in CePt 3 Si. Generally in the system without inversion symmetry the gap function is a mixture of spin-singlet and -triplet channels in the pres-

We report on novel antiferromagnetic (AFM) and superconducting (SC) properties of noncentrosymmetric CePt3Si through measurements of the 195Pt nuclear spin-lattice relaxation rate 1/T(1). In the normal state, the temperature (T) dependence of 1/T(1) unraveled the existence of low-lying levels in crystal-electric-field multiplets and the formation of a heavy-fermion (HF) state. The coexistence of AFM and SC phases that emerge at T(N)=2.2 K and T(c)=0.75 K, respectively, takes place on a microscopic level. CePt3Si is the first HF superconductor that reveals a peak in 1/T(1) just below T(c) and, additionally, does not follow the T3 law that used to be reported for most unconventional HF superconductors. We remark that this unexpected SC characteristic may be related to the lack of an inversion center in its crystal structure.

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We have studied the superconducting property by measuring the electrical resistivity under the magnetic field and pressure for CePt 3 Si, which is the first antiferromagnetic heavy fermion superconductor without inversion symmetry in its tetragonal crystal structure. The upper critical field H c2 ð0Þ is found to be approximately isotropic: H c2 ð0Þ ¼ 2:7 T for H k ½100 and 3.2 T for H k ½001. The Néel temperature T N ¼ 2:3 K and the zero resistivity superconducting transition temperature T sc ' 0:65 K decrease markedly with increasing pressure, suggesting that the present superconductivity is correlated to the antiferromagnetic state.A recently discovered superconductor CePt 3 Si is unique, possessing a few characteristics. 1) Superconductivity with the transition temperature T sc ¼ 0:75 K is realized in the long-range antiferromagnetic state with the Néel temperature T N ¼ 2:2 K. Both transitions were observed clearly in the specific heat measurement. The electronic specific heat coefficient is large, 300-400 mJ/K 2 Ámol. In the previous cerium-based heavy fermion superconductors including a prototype superconductor CeCu 2 Si 2 and a quasi-two-dimensional superconductor CeCoIn 5 with a large value of 1000 mJ/K 2 Ámol, superconductivity occurs in the nonmagnetic state or the antiferromagnetically spin-fluctuating state. 2-4) Another example is CeIn 3 under pressure. 4-6) At ambient pressure, the Néel temperature in CeIn 3 is T N ¼ 10 K and the ordered moment is 0.5 B /Ce. With increasing pressure P, T N decreases smoothly as a function of pressure and becomes zero at around a critical pressure P c ' 2:7 GPa where superconductivity sets in below 0.2 K.Moreover, it is noted that CePt 3 Si is the first heavy fermion superconductor lacking a center of symmetry. The crystal structure of CePt 3 Si is tetragonal, space group P4mm (No. 99) with a ¼ 4:072 # A and c ¼ 5:442 # A. The existence of inversion symmetry in the crystal structure is believed to be a favorable factor for superconductivity. The absence of superconductivity in, for example, ferromagnet MnSi was tentatively attributed to the lack of inversion symmetry in its crystal structure. 7) Theoretically it was, however, argued that spin-triplet pairing is not entirely excluded in MnSi and CePt 3 Si because the lack of inversion symmetry reduces the effect of paramagnetic limiting for spin-singlet pairing. 8) In fact we have very recently observed superconductivity in the vicinity of a critical pressure for ferromagnet UIr without inversion symmetry. 9) The relationship between superconductivity and lack of inversion symmetry is the most crucial issue to be clarified at present.We have studied an effect of magnetic field and pressure on the superconducting state for a single crystal with high quality. The electrical resistivity has been measured to investigate the anisotropy of the upper critical field and the relationship between antiferromagnetic ordering and superconductivity.Single crystals of CePt 3 Si and non-4f reference compound LaPt 3 Si were grown by t...