µSR investigation of a new diluted magnetic semiconductor Li(Zn,Mn,Cu)As with Mn and Cu codoping at the same Zn sites.

We report the successful synthesis and characterization of a new type I-II-V bulk form diluted magnetic semiconductor (DMS) Li(Zn,Mn,Cu)As, in which charge and spin doping are decoupled via (Cu,Zn) and (Mn,Zn) substitution at the same Zn sites. Ferromagnetic transition temperature up to ∼33 K has been observed with a coercive field ∼40 Oe for the 12.5% doping level. µSR measurements confirmed that the magnetic volume fraction reaches nearly 100% at 2 K, and the mechanism responsible for the ferromagnetic interaction in this system is the same as other bulk form DMSs.

Changes of expression of estrogen and progestrone receptors, human epithelial growth factor receptor 2 and Ki-67 after neoadjuvant chemotherapy in the treatment of breast cancer.

Recent studies suggest that the development and prognosis of breast cancer is in close correlation to molecular subtype of breast cancer. Neoadjuvant chemotherapy has been extensively applied in the treatment of local breast cancer in advanced stage. In order to verify the correlation between expression changes of estrogen receptor, progestrone receptor, human epithelial growth factor receptor 2 and Ki-67 after neoadjuvant chemotherapy and neoadjuvant chemotherapy, we studied 120 patients with stage IIAIIIC breast cancer who underwent neoadjuvant chemotherapy in Binzhou Medical University Hospital, Shandong, China from February 2011 to February 2015. Clinical characteristics were retrospectively analyzed. The expression of estrogen receptor, progesterone receptor, human epithelial growth factor receptor 2 and Ki-67 of patients were detected using the immunohistochemical method before and after neoadjuvant chemotherapy. The results suggest that the overall remission rate of neoadjuvant chemotherapy was 76.7% (92/120) of which 16.7% (20/120) of cases had complete remission, 60% (72/120) had partial remission and 23.3% (28/120) were stable. There were no cases of progressive disease. The property of estrogen receptor and the expression of Ki-67 of primary tumor were correlated to the remission rate of neoadjuvant chemotherapy (P less than 0.05). The expression of Ki-67 had a significant decline after neoadjuvant chemotherapy, and the difference had statistical significance (P less than 0.05). The difference in expression of estrogen receptor, progesterone receptor and human epithelial growth factor receptor 2 before and after neoadjuvant chemotherapy had statistical significance (P > 0.05). Hence, it can be concluded that breast cancer patients with negative estrogen receptor expression and high Ki-67 expression before neoadjuvant chemotherapy can achieve better curative effects. Neoadjuvant chemotherapy cannot change the expression states of estrogen receptor, progesterone receptor and human epithelial growth factor receptor 2, but it can lower the expression level of Ki-67. Ki-67 can also be used for predicting the curative effect of neoadjuvant chemotherapy.

The synthesis and characterization of 1 1 1 1 type diluted ferromagnetic semiconductor (La(1-x)Ca(x))(Zn(1-x) Mn(x))AsO.

We report the synthesis and characterization of a bulk form diluted magnetic semiconductor, (La(1-x)Ca(x))(Zn(1-y) Mn(y))AsO, with a layered crystal structure isostructural to that of the 1 1 1 1 type Fe-based high-temperature superconductor LaFeAsO and the antiferromagnetic LaMnAsO. With Ca and Mn codoping into LaZnAsO, the ferromagnetic ordering occurs below the Curie temperature T(c) ∼30 K. Taking advantage of the decoupled charge and spin doping, we investigate the influence of carrier concentration on the ferromagnetic ordering state. For a fixed Mn concentration of 10%, T(c) increases from 24 K to 30 K when the Ca concentration increases from 5% to 10%. Further increase of Ca concentration reduces both the coercive field and saturation moment. Muon spin relaxation measurements confirm the ferromagnetically ordered state, and clearly demonstrate that La(1-x)Ca(x))(Zn(1-y) Mn(y))AsO shares a common mechanism for the ferromagnetic exchange interaction with (Ga,Mn)As. Neutron scattering measurements show no structural transition in (La(0.90)Ca(0.10))(Zn(0.90)Mn(0.10)) AsO below 300 K.

Ba(Zn(1-2x)MnxCux)2As2: A Bulk Form Diluted Ferromagnetic Semiconductor with Mn and Cu Codoping at Zn Sites.

We report the synthesis and characterization of a bulk form diluted magnetic semiconductor Ba(Zn(1-2x)MnxCux)2As2 (0.025 ≤ x ≤ 0.2) with the crystal structure identical to that of "122" family iron based superconductors and the antiferromagnet BaMn2As2. No ferromagnetic order occurs with (Zn, Mn) or (Zn, Cu) substitution in the parent compound BaZn2As2. Only when Zn is substituted by both Mn and Cu simultaneously, can the system undergo a ferromagnetic transition below TC ~ 70 K, followed by a magnetic glassy transition at Tf ~ 35 K. AC susceptibility measurements for Ba(Zn0.75Mn0.125Cu0.125)2As2 reveal that Tf strongly depends on the applied frequency with [formula in text] and a DC magnetic field dependence of [formula in text], demonstrating that a spin glass transition takes place at Tf. As large as -53% negative magnetoresistance has been observed in Ba(Zn(1-2x)MnxCux)2As2, enabling its possible application in memory devices.

NMR investigation of the quasi-one-dimensional superconductor K(2)Cr(3)As(3).

We report ^{75}As NMR measurements on the new quasi-one-dimensional superconductor K_{2}Cr_{3}As_{3} (T_{c}∼6.1 K) [J. K. Bao et al., Phys. Rev. X 5, 011013 (2015)]. We found evidence for strong enhancement of Cr spin fluctuations above T_{c} in the [Cr_{3}As_{3}]_{∞} double-walled subnanotubes based on the nuclear spin-lattice relaxation rate 1/T_{1}. The power-law temperature dependence, 1/T_{1}T∼T^{-γ} (γ∼0.25), is consistent with the Tomonaga-Luttinger liquid. Moreover, absence of the Hebel-Slichter coherence peak of 1/T_{1} just below T_{c} suggests an unconventional nature of superconductivity.

Compressibility, thermal expansion coefficient and heat capacity of CH4 and CO2 hydrate mixtures using molecular dynamics simulations.

Understanding the thermal and mechanical properties of CH4 and CO2 hydrates is essential for the replacement of CH4 with CO2 in natural hydrate deposits as well as for CO2 sequestration and storage. In this work, we present isothermal compressibility, isobaric thermal expansion coefficient and specific heat capacity of fully occupied single-crystal sI-CH4 hydrates, CO2 hydrates and hydrates of their mixture using molecular dynamics simulations. Eight rigid/nonpolarisable water interaction models and three CH4 and CO2 interaction potentials were selected to examine the atomic interactions in the sI hydrate structure. The TIP4P/2005 water model combined with the DACNIS united-atom CH4 potential and TraPPE CO2 rigid potential were found to be suitable molecular interaction models. Using these molecular models, the results indicate that both the lattice parameters and the compressibility of the sI hydrates agree with those from experimental measurements. The calculated bulk modulus for any mixture ratio of CH4 and CO2 hydrates varies between 8.5 GPa and 10.4 GPa at 271.15 K between 10 and 100 MPa. The calculated thermal expansion and specific heat capacities of CH4 hydrates are also comparable with experimental values above approximately 260 K. The compressibility and expansion coefficient of guest gas mixture hydrates increase with an increasing ratio of CO2-to-CH4, while the bulk modulus and specific heat capacity exhibit the opposite trend. The presented results for the specific heat capacities of 2220-2699.0 J kg(-1) K(-1) for any mixture ratio of CH4 and CO2 hydrates are the first reported so far. These computational results provide a useful database for practical natural gas recovery from CH4 hydrates in deep oceans where CO2 is considered to replace CH4, as well as for phase equilibrium and mechanical stability of gas hydrate-bearing sediments. The computational schemes also provide an appropriate balance between computational accuracy and cost for predicting mechanical and thermal properties of gas hydrates in the high temperature range (≥260 K), and the schemes may be useful for the study of other complex hydrate systems.

Association between p53 codon 72 polymorphisms and clinical outcome of nasopharyngeal carcinoma.

We conducted a cohort study to investigate whether polymorphisms in p53 at codon 72 are associated with tumor response and survival time of advanced nasopharyngeal carcinoma (NPC) patients treated with radiotherapy. The study population included 127 subjects with NPC who were enrolled at Binzhou Medical University between September 2008 and December 2009. Cox proportional hazard regression was used to assess the association between polymorphisms in the p53 gene and progression-free survival (PFS) and overall survival (OS) of NPC patients. During the follow-up period, 42 patients died and 72 patients showed progression at the end of the study. Of the 127 patients, median PFS was 22.5 ± 1.2 months (1-36 months), and the median OS time was 28.2 ± 1.1 months (2-36 months). The p53 codon 72 Pro/Pro genotype was associated with a longer median PFS time of 30.3 months compared with 18.2 months for patients with Arg/Arg variants. Moreover, the p53 codon 72 Pro/ Pro genotype was associated with a longer median OS time of 31.6 months compared with 25.8 months for those with Arg/Arg variants; the P value was marginally significant. We showed that variants in p53 codon 72 may be an independent predictor for PFS and OS of NPC patients.

NMR search for the spin nematic state in a LaFeAsO single crystal.

We report a (75)As single crystal NMR investigation of LaFeAsO, the parent phase of a pnictide high T(c) superconductor. We demonstrate that spin dynamics develop a strong twofold anisotropy within each orthorhombic domain below the tetragonal-orthorhombic structural phase transition at T(TO) ≈ 156 K. This intermediate state with a dynamical breaking of the rotational symmetry freezes progressively into a spin density wave below T(SDW) ≈ 142 K. Our findings are consistent with the presence of a spin nematic state below T(TO) with an incipient magnetic order.

Spin ice: magnetic excitations without monopole signatures using muon spin rotation.

Theory predicts the low temperature magnetic excitations in spin ices consist of deconfined magnetic charges, or monopoles. A recent transverse-field (TF) muon spin rotation (µSR) experiment [S. T. Bramwell et al., Nature (London) 461, 956 (2009)] reports results claiming to be consistent with the temperature and magnetic field dependence anticipated for monopole nucleation-the so-called second Wien effect. We demonstrate via a new series of µSR experiments in Dy(2)Ti(2)O(7) that such an effect is not observable in a TF µSR experiment. Rather, as found in many highly frustrated magnetic materials, we observe spin fluctuations which become temperature independent at low temperatures, behavior which dominates over any possible signature of thermally nucleated monopole excitations.

Contrasting spin dynamics between underdoped and overdoped Ba(Fe1-xCox)2As2.

We report the first NMR investigation of spin dynamics in the overdoped nonsuperconducting regime of Ba(Fe1-xCox)2As2 up to x=0.26. We demonstrate that the absence of interband transitions with large momentum transfer Q{AF} approximately (pi/a,0) between the hole and electron Fermi surfaces results in complete suppression of antiferromagnetic spin fluctuations for x greater than or approximately 0.15. Our experimental results provide direct evidence for a correlation between T{c} and the strength of Q{AF} antiferromagnetic spin fluctuations.

Why does undoped FeSe become a high-Tc superconductor under pressure?

Unlike the parent phases of the iron-arsenide high-Tc superconductors, undoped FeSe is not magnetically ordered and exhibits superconductivity with Tc approximately 9 K. Equally surprising is the fact that applied pressure dramatically enhances the modest Tc to approximately 37 K. We investigate the electronic properties of FeSe using 77Se NMR to search for the key to the superconducting mechanism. We demonstrate that the electronic properties of FeSe are very similar to those of electron-doped FeAs superconductors, and that antiferromagnetic spin fluctuations are strongly enhanced near Tc. Furthermore, applied pressure enhances spin fluctuations. Our findings suggest a link between spin fluctuations and the superconducting mechanism in FeSe.

59Co NMR evidence for charge ordering below T_(CO) approximately 51 K in Na0.5CoO2.

The CoO2 layers in NaxCoO2 may be viewed as a spin S=1/2 triangular-lattice doped with charge carriers. The underlying physics of the cobaltates is very similar to that of the high T_(c) cuprates. We will present unequivocal 59Co NMR evidence that below T_(CO) approximately 51 K, the insulating ground state of the itinerant antiferromagnet Na0.5CoO2 (T_(N) approximately 86 K) is induced by charge ordering.

17O NMR studies of a triangular-lattice superconductor NaxCoO2 x yH(2)O.

We report the first 17O NMR studies of a triangular-lattice superconductor Na(1/3)CoO2 x 4/3H(2)O and the host material Na(x)CoO2 (x=0.35 and 0.72). Knight shift measurements reveal that p-d hybridization induces sizable spin polarization in the O triangular-lattice layers. Water intercalation makes CoO2 planes homogeneous and enhances low frequency spin fluctuations near T(c)=4.5 K at some finite wave vectors different from both the ferromagnetic and "120 degree" modes.

Spin dynamics in the carrier-doped S=1/2 triangular lattice of NaxCoO2.yH2O.

We probed the local electronic properties of the mixed-valent Co+4-x triangular lattice in NaxCoO2.yH(2)O by 59Co NMR. We observed two distinct types of Co sites for x > or =1/2, but the valence seems averaged out for x approximately 1/3. Local spin fluctuations exhibit qualitatively the same trend down to approximately 100 K regardless of the carrier concentration x, and hence the nature of the electronic ground state. A canonical Fermi-liquid behavior emerges below approximately 100 K only for x approximately 1/3.