Simultaneous Nodal Superconductivity and Time-Reversal Symmetry Breaking in the Noncentrosymmetric Superconductor CaPtAs.

By employing a series of experimental techniques, we provide clear evidence that CaPtAs represents a rare example of a noncentrosymmetric superconductor which simultaneously exhibits nodes in the superconducting gap and broken time-reversal symmetry (TRS) in its superconducting state (below T_{c}≈1.5 K). Unlike in fully gapped superconductors, the magnetic penetration depth λ(T) does not saturate at low temperatures, but instead it shows a T^{2} dependence, characteristic of gap nodes. Both the superfluid density and the electronic specific heat are best described by a two-gap model comprising of a nodeless gap and a gap with nodes, rather than by single-band models. At the same time, zero-field muon-spin relaxation spectra exhibit increased relaxation rates below the onset of superconductivity, implying that TRS is broken in the superconducting state of CaPtAs, hence indicating its unconventional nature. Our observations suggest CaPtAs to be a new remarkable material that links two apparently disparate classes, that of TRS-breaking correlated magnetic superconductors with nodal gaps and the weakly correlated noncentrosymmetric superconductors with broken TRS, normally exhibiting only a fully gapped behavior.

Two-Gap Superconductivity in LaNiGa_{2} with Nonunitary Triplet Pairing and Even Parity Gap Symmetry.

The nature of the pairing states of superconducting LaNiC_{2} and LaNiGa_{2} has to date remained a puzzling question. Broken time reversal symmetry has been observed in both compounds and a group theoretical analysis implies a nonunitary triplet pairing state. However, all the allowed nonunitary triplet states have nodal gap functions but most thermodynamic and NMR measurements indicate fully gapped superconductivity in LaNiC_{2}. Here we probe the gap symmetry of LaNiGa_{2} by measuring the London penetration depth, specific heat, and upper critical field. These measurements demonstrate two-gap nodeless superconductivity in LaNiGa_{2}, suggesting that this is a common feature of both compounds. These results allow us to propose a novel triplet superconducting state, where the pairing occurs between electrons of the same spin, but on different orbitals. In this case the superconducting wave function has a triplet spin component but isotropic even parity gap symmetry, yet the overall wave function remains antisymmetric under particle exchange. This model leads to a nodeless two-gap superconducting state which breaks time reversal symmetry, and therefore accounts well for the seemingly contradictory experimental results.

Superconductivity and structural distortion in BaPt2As2.

We report the synthesis of BaPt2As2 single crystals and the discovery of superconductivity and a structural phase transition in this compound by measuring the electrical resistivity, magnetic susceptibility and specific heat as well as the x-ray diffraction at low temperatures. BaPt2As2 crystallizes in the CaBe2Ge2-type tetragonal structure (P4/nmm) at room temperature and undergoes a first-order structural transition at TS ≃ 275 K, which is likely to be associated with a charge-density-wave (CDW) instability. BCS-like superconductivity with two subsequent transitions Tc1 ≃ 1.67 K and Tc2 ≃ 1.33 K is observed. Our results demonstrate that BaPt2As2 may serve as a new system for studying the interplay of superconductivity and the CDW order.

Helicobacter pylori infection and chronic active gastritis.

Helicobacter pylori (H. pylori) is an S-Shaped, gram-negative bacillus that recently has been implicated in the pathogenesis of chronic active gastritis and other peptic ulcer disease. These findings have encouraged gastroenterologists to provide a new rationale for patient management, with hope of providing more successful treatment of peptic ulcer disease, particularly gastritis. Therefore, a cooperative diagnostic effort was made at the pathology laboratory of St Francis Medical Center to adopt a simple and reliable method for the identification of H. pylori in tissue sections of endoscopic biopsies of stomach and duodenum. We attempted to estimate the prevalence of H. pylori infection in patients biopsied for upper Gl disorders who were refractory to medication. A prevalence of H. pylori infection among different ethnic groups also was studied.

[Studies on new triterpenoids of Tripterygium regelii].

Four triterpenoids were isolated from the root of Tripterygium regelii collected in Fusong Prefecture, Jilin Province. III was confirmed as methyl 3-oxo-22 alpha-acetoxy-23-hydroxy-urs-12-ene-30-oate, named regelin C, V and VI were a pair of isomers identified as methyl 3 beta, 22 alpha-dihydroxy-urs-12-ene-30-oate and methyl 3 beta, 22 alpha-dihydroxy-olean-12-ene-29-oate, named regelindiol A and regelindiol B respectively. VII was represented as methyl 3-oxo-22 alpha-hydroxy-olean-12-ene-29-oate, named regelin D. III, V and VII were new compounds, and VI was isolated for the first time as a natural compound.