Superatomic-Charge-Density-Wave in Cluster-Assembled Au6Te12Se8 Superconductors.

Superatomic crystals are a class of hierarchical materials composed of atomically precise clusters assembled via van der Waals or covalent-like interactions. Au6Te12Se8, an all-inorganic superatomic superconductor exhibiting superatomic-charge-density-wave (S-CDW), provides the first platform to study the response of its collective quantum phenomenon to the external pressure in superatomic crystals. We reveal a competition between S-CDW and superconductivity in an ultra-narrow pressure range. Distinct from conventional CDW ordering, S-CDW shows the lowest threshold (0.1 GPa) toward external pressure that is 1-2 orders of magnitude lower than other atomic compounds. Prominently, a second superconducting phase emerges above 7.3 GPa with a threefold enhancement in the transition temperature (Tc) to 8.5 K, indicating a switch of the conduction channel from the a- to b-axis. In situ synchrotron diffractions and theoretical calculations reveal a pressure-mediated mesoscopic slip of the superatoms and a 2D-3D transition of the Fermi surface topology, which well explains the observed dimensional crossover of conductivity and re-entrant superconductivity.

Structure, phase transition and properties of the one-dimensional antiferromagnet Cu(2,6-dimethylpyrazine)Br2.

We report the crystal structure and properties of the one-dimensional S = 1/2 antiferromagnet Cu(2,6-dimethylpyrazine)Br2 with strong intra-chain exchange. At room temperature, its linear spin chains are formed by Cu2+ ions via the non-bonding Br⋯Br contacts. Interestingly, a phase transition from Pmmn to P21/n structure occurs at T S ≈ 248 K below which the [CuBr2] n spin chains become non-linear and the magnetic susceptibility abruptly increases, reflecting the weakening of antiferromagnetic exchange strength. This result evidences the Goodenough-Kanamori rules which claim that a linear super-exchange pathway produces stronger antiferromagnetic coupling. From magnetic susceptibility measurements we find the average intra-chain exchange strength is J/k B ≈ -88.18 K in the low temperature phase. Both magnetic and specific measurements show the absence of magnetic ordering down to 2 K, implying the excellent magnetic one-dimensionality of Cu(2,6-dimethylpyrazine)Br2. We also performed ultra-violet (UV) absorption and photoluminescence measurements which give a semiconducting band gap Δ ≈ 2.79 eV which is consistent with theoretical calculations.

Coexistence of Ferromagnetic and Stripe-Type Antiferromagnetic Spin Fluctuations in YFe_{2}Ge_{2}.

We report neutron scattering measurements of single-crystalline YFe_{2}Ge_{2} in the normal state, which has the same crystal structure as the 122 family of iron pnictide superconductors. YFe_{2}Ge_{2} does not exhibit long-range magnetic order but exhibits strong spin fluctuations. Like the iron pnictides, YFe_{2}Ge_{2} displays anisotropic stripe-type antiferromagnetic spin fluctuations at (π, 0, π). More interesting, however, is the observation of strong spin fluctuations at the in-plane ferromagnetic wave vector (0, 0, π). These ferromagnetic spin fluctuations are isotropic in the (H, K) plane, whose intensity exceeds that of stripe spin fluctuations. Both the ferromagnetic and stripe spin fluctuations remain gapless down to the lowest measured energies. Our results naturally explain the absence of magnetic order in YFe_{2}Ge_{2} and also imply that the ferromagnetic correlations may be a key ingredient for iron-based materials.

Examining income-related inequality in health literacy and health-information seeking among urban population in China.

BACKGROUND: Health literacy and health-information seeking behaviour (HISB) play vital roles in health outcome improvements. This study examines the extent of income-related inequality in health literacy and health-information seeking as well as the contributions of the main socioeconomic determinants in China. METHODS: We analysed representative data of participants aged over 18 years as well as older adults from the Guangzhou Community Health Survey. A concentration index (CI) was used to quantify the degree of income-related inequity in health literacy and health-information seeking. Probit regression models were employed to decompose the CI into the contributions to each factor. RESULTS: Results showed a significant pro-rich distribution of adequate health literacy (CI: 0.0602, P < 0.001; horizontal index [HI]: 0.0562, P < 0.001) and HISB from healthcare professionals (CI: 0.105, P < 0.001; HI: 0.0965, P < 0.001). The pro-rich distribution of health literacy was mainly attributable to education background (contribution: 54.76%), whereas income inequalities contributed most to the pro-rich distribution of health-information seeking among an urban population (contribution: 62.53%). CONCLUSION: Public interventions in China to reduce inequality in health literacy and HISBs among the urban population, coupled with easily accessible information sources on health, warrant further attention from policymakers.

The Risk of Hypertension Doubles Every 10 Years in China: Age, Period, and Birth Cohort Effects on the Prevalence of Hypertension From 2004 to 2013.

BACKGROUND: Hypertension is a growing problem worldwide and can often result in a variety of negative health outcomes. The aim of this study was to assess the effects of age at diagnosis, calendar period, and birth cohort on the change in the prevalence rate of hypertension in Guangzhou from 2004 to 2013. METHODS: We used data from the Guangzhou Community Health Survey, a population-based study designed by the National Health and Family Planning Commission of the PRC every 5 years. A total of 27,299, 23,467, and 18,362 participants aged 15-79 years completed the survey in 2004, 2009, and 2013, respectively. RESULTS: Age effects increased slowly before the age of 42 years but increased rapidly after the age of 42 years, peaking at 79 years. Cohort effects grew slowly before the end of the 1960s but grew quickly after the end of the 1960s. The risk of suffering from hypertension among people born in 1962, 1972, 1982, and 1992 was 1.39, 2.68, 5.55, and 11.53 times, respectively, than that of people born in 1952. The period effects increased 25% from 2004 to 2009 and later declined 27% from 2009 to 2013 in the entire population. There was no gender difference in age effects and period effects, but strong cohort effects on hypertension were observed among males compared with females. CONCLUSIONS: For Chinese individuals, the later one is born, the higher the risk is of suffering from hypertension. Strong cohort effects for hypertension were observed among males compared with females, indicating that males are more easily affected by hypertension based on the change in birth cohort.

Trends and Associated Factors of Hypertension among Residents Aged ≥15 Years in Guangzhou, China, 2004-2013.

BACKGROUND: We aimed to describe the trends and associated factors of hypertension among residents aged ≥15 yr in Guangzhou, China. METHODS: Three standardized cross-sectional health surveys were conducted in 2004, 2009 and 2013 using a multi-stage cluster sampling method, and a total of 69128 qualified participants were included in the study. The data were obtained through physical health examination and questionnaire survey. RESULTS: The age-standardised prevalence of hypertension increased from 12.5% to 16.0% between 2004 and 2009 and declined from 16.0% to 14.0% between 2009 and 2013, and crude prevalence respectively was 14.6%, 19.1% and 18.8% in 2004, 2009 and 2013. The proportion of optimal blood pressure dropped from 51.1% to 33.2%, high-normal blood pressure increased from 20.1% to 28.9%, grade 1 hypertension and grade 2 or 3 hypertension increased from 11.5% to 13.6% and 3.9% to 5.8% between 2004 and 2013. The average age was significantly increased (P<0.001) from 42.8 to 47.5 yr, and the average body mass index slightly increased (P<0.001) from 22.4 to 23.0. Logistic regression analysis shows that higher age, male, higher body mass index, smoking and drinking alcohol were potential risk factors for hypertension. CONCLUSION: Both crude and age-standardized prevalence of hypertension were initially increased, but subsequently decreased in Guangzhou during 2004-2013. The optimal blood pressure population decreased significantly while the high-normal blood pressure population increased substantially during the survey period.

Structure of spin excitations in heavily electron-doped Li0.8Fe0.2ODFeSe superconductors.

Heavily electron-doped iron-selenide high-transition-temperature (high-T c) superconductors, which have no hole Fermi pockets, but have a notably high T c, have challenged the prevailing s ± pairing scenario originally proposed for iron pnictides containing both electron and hole pockets. The microscopic mechanism underlying the enhanced superconductivity in heavily electron-doped iron-selenide remains unclear. Here, we used neutron scattering to study the spin excitations of the heavily electron-doped iron-selenide material Li0.8Fe0.2ODFeSe (T c = 41 K). Our data revealed nearly ring-shaped magnetic resonant excitations surrounding (π, π) at ∼21 meV. As the energy increased, the spin excitations assumed a diamond shape, and they dispersed outward until the energy reached ∼60 meV and then inward at higher energies. The observed energy-dependent momentum structure and twisted dispersion of spin excitations near (π, π) are analogous to those of hole-doped cuprates in several aspects, thus implying that such spin excitations are essential for the remarkably high T c in these materials.The microscopic mechanism underlying an enhanced superconductivity in electron-doped iron selenide superconductor remains unclear. Here, Pan et al. report the spin excitations of Li0.8Fe0.2ODFeSe, revealing analogous momentum structure and dispersion to hole-doped cuprates.

Effects of ambient temperature on stroke hospital admissions: Results from a time-series analysis of 104,432 strokes in Guangzhou, China.

BACKGROUND: Stroke is a main cause of death and public health burden in China. The evidence on the burden of different strokes attack attribute to ambient temperature in China is limited. This study aimed to show the characteristics of stroke attack and the attributable risk due to temperature based on hospital admission data in Guangzhou, one of the most developed cities in China. MATERIAL AND METHODS: From January 1, 2013 to December 31, 2015, 104,432 stroke hospitalizations in Guangzhou residents from 67 hospitals for stroke sentinel surveillance were registered. Characteristics of hospital admissions by gender, age group, calendar year and stroke subtype were analyzed, and distributed lag non-linear models were applied to evaluate the effects of temperature on stroke attack admissions. RESULTS: Stroke attack admissions increased from 31,851 to 36,755 through 2013 to 2015, increasing by 15.4%. An increasing trend in the risk of stroke attack with age was observed, irrespectively of stroke subtype and calendar year. People with hypertension were more likely to have an associated stroke than people without that. The effects of cold temperature on attack admissions for CBI and ICH strokes were significant. Overall, the percentages of CBI and ICH attack admissions attribute to cold temperature were 9.06% (95% CI: 1.84, 15.00) and 15.09% (95% CI: 5.86, 21.96), respectively. Besides, elderly people were more vulnerable to cold temperature than the young. CONCLUSIONS: Measures should be taken to increase public awareness about the ill effects of cold temperature on stroke attack, and educate the public about self-protection.

Evidence for a spinon Fermi surface in a triangular-lattice quantum-spin-liquid candidate.

A quantum spin liquid is an exotic quantum state of matter in which spins are highly entangled and remain disordered down to zero temperature. Such a state of matter is potentially relevant to high-temperature superconductivity and quantum-information applications, and experimental identification of a quantum spin liquid state is of fundamental importance for our understanding of quantum matter. Theoretical studies have proposed various quantum-spin-liquid ground states, most of which are characterized by exotic spin excitations with fractional quantum numbers (termed 'spinons'). Here we report neutron scattering measurements of the triangular-lattice antiferromagnet YbMgGaO4 that reveal broad spin excitations covering a wide region of the Brillouin zone. The observed diffusive spin excitation persists at the lowest measured energy and shows a clear upper excitation edge, consistent with the particle-hole excitation of a spinon Fermi surface. Our results therefore point to the existence of a quantum spin liquid state with a spinon Fermi surface in YbMgGaO4, which has a perfect spin-1/2 triangular lattice as in the original proposal of quantum spin liquids.

Magnetic ground state of FeSe.

Elucidating the nature of the magnetism of a high-temperature superconductor is crucial for establishing its pairing mechanism. The parent compounds of the cuprate and iron-pnictide superconductors exhibit Néel and stripe magnetic order, respectively. However, FeSe, the structurally simplest iron-based superconductor, shows nematic order (Ts=90 K), but not magnetic order in the parent phase, and its magnetic ground state is intensely debated. Here we report inelastic neutron-scattering experiments that reveal both stripe and Néel spin fluctuations over a wide energy range at 110 K. On entering the nematic phase, a substantial amount of spectral weight is transferred from the Néel to the stripe spin fluctuations. Moreover, the total fluctuating magnetic moment of FeSe is ∼60% larger than that in the iron pnictide BaFe2As2. Our results suggest that FeSe is a novel S=1 nematic quantum-disordered paramagnet interpolating between the Néel and stripe magnetic instabilities.

Transition from Sign-Reversed to Sign-Preserved Cooper-Pairing Symmetry in Sulfur-Doped Iron Selenide Superconductors.

An essential step toward elucidating the mechanism of superconductivity is to determine the sign or phase of the superconducting order parameter, as it is closely related to the pairing interaction. In conventional superconductors, the electron-phonon interaction induces attraction between electrons near the Fermi energy and results in a sign-preserved s-wave pairing. For high-temperature superconductors, including cuprates and iron-based superconductors, prevalent weak coupling theories suggest that the electron pairing is mediated by spin fluctuations which lead to repulsive interactions, and therefore that a sign-reversed pairing with an s_{±} or d-wave symmetry is favored. Here, by using magnetic neutron scattering, a phase sensitive probe of the superconducting gap, we report the observation of a transition from the sign-reversed to sign-preserved Cooper-pairing symmetry with insignificant changes in T_{c} in the S-doped iron selenide superconductors K_{x}Fe_{2-y}(Se_{1-z}S_{z})_{2}. We show that a rather sharp magnetic resonant mode well below the superconducting gap (2Δ) in the undoped sample (z=0) is replaced by a broad hump structure above 2Δ under 50% S doping. These results cannot be readily explained by simple spin fluctuation-exchange pairing theories and, therefore, multiple pairing channels are required to describe superconductivity in this system. Our findings may also yield a simple explanation for the sometimes contradictory data on the sign of the superconducting order parameter in iron-based materials.

Strong interplay between stripe spin fluctuations, nematicity and superconductivity in FeSe.

In iron-based superconductors the interactions driving the nematic order (that breaks four-fold rotational symmetry in the iron plane) may also mediate the Cooper pairing. The experimental determination of these interactions, which are believed to depend on the orbital or the spin degrees of freedom, is challenging because nematic order occurs at, or slightly above, the ordering temperature of a stripe magnetic phase. Here, we study FeSe (ref. )-which exhibits a nematic (orthorhombic) phase transition at Ts = 90 K without antiferromagnetic ordering-by neutron scattering, finding substantial stripe spin fluctuations coupled with the nematicity that are enhanced abruptly on cooling through Ts. A sharp spin resonance develops in the superconducting state, whose energy (∼4 meV) is consistent with an electron-boson coupling mode revealed by scanning tunnelling spectroscopy. The magnetic spectral weight in FeSe is found to be comparable to that of the iron arsenides. Our results support recent theoretical proposals that both nematicity and superconductivity are driven by spin fluctuations.

Structure and thermodynamic properties of (C5H12N)CuBr3: a new weakly coupled antiferromagnetic spin-1/2 chain complex lying in the 1D-3D dimensional cross-over regime.

Single crystals of a metal organic complex (C5H12N)CuBr3 (C5H12N = piperidinium, pipH for short) have been synthesized, and the structure was determined by single-crystal X-ray diffraction. (pipH)CuBr3 crystallizes in the monoclinic group C2/c. Edging-sharing CuBr5 units link to form zigzag chains along the c axis, and the neighboring Cu(II) ions with spin-1/2 are bridged by bibromide ions. Magnetic susceptibility data down to 1.8 K can be well fitted by the Bonner-Fisher formula for the antiferromagnetic spin-1/2 chain, giving the intrachain magnetic coupling constant J ≈ -17 K. At zero field, (pipH)CuBr3 shows three-dimensional (3D) order below TN = 1.68 K. Calculated by the mean-field theory, the interchain coupling constant J' = -0.91 K is obtained and the ordered magnetic moment m0 is about 0.23 µB. This value of m0 makes (pipH)CuBr3 a rare compound suitable to study the 1D-3D dimensional cross-over problem in magnetism, since both 3D order and one-dimensional (1D) quantum fluctuations are prominent. In addition, specific heat measurements reveal two successive magnetic transitions with lowering temperature when external field µ0H ≥ 3 T is applied along the a' axis. The µ0H-T phase diagram of (pipH)CuBr3 is roughly constructed.

Prevalence of noncommunicable diseases and their risk factors in Guangzhou, China.

INTRODUCTION: This article reports on the prevalence of noncommunicable diseases (NCDs) and their risk factors in the city of Guangzhou, China, and shows a trend toward epidemic proportions when municipal data are compared with provincial data. METHODS: We conducted the Guangzhou Community Health Survey in the 12 administrative districts of Guangzhou to learn about NCDs and their risk factors. A community-based, face-to-face survey with a stratified multistage cluster sampling was used. Information was gathered on 27,743 respondents, aged 0 to 108 years, with a male to female ratio of 1 to 1. All participants completed a questionnaire, and those aged 15 years or older had a physical examination. Survey results were compared with the provincial results of the 2002 Guangdong Nutrition and Health Survey (GNHS). RESULTS: The data were weighted to the respondent's probability of selection and to the age- and sex-specific population. Prevalence estimate of self-reported NCDs was 16.0%. Hypertension and diabetes were reported as the most important NCDs. Of those who responded, 6.8% reported having more than 2 chronic conditions. The adjusted prevalence of hypertension decreased by 13.3% since 2002. Awareness, treatment, and control of hypertension and diabetes were improved. The estimated prevalence of current smoking decreased, and the prevalence of former smoking increased from 2002. However, the prevalence of overweight and obesity, especially central obesity, increased. CONCLUSION: Results were encouraging with regard to hypertension and diabetes. However, the unfavorable trends, especially for overweight, central obesity, and passive smoking, call for additional action.

Useful information for hypertension management reform in community health care: prevalence, awareness, treatment and control among Guangzhou adults.

BACKGROUND: Objective data on hypertension prevalence and management in local areas are scarce. We assessed the prevalence of hypertension and its management in Guangzhou adult population. METHODS: A stratified multistage cluster sampling with probability proportional to size method was used in this survey. Information on a total of 23 939 respondents, aged 15 years old or above, having a gender ratio of 0.997 (male versus female) with completed questionnaire and blood pressure measurement, was obtained. Hypertension was defined as having a mean SBP of at least 140 mm Hg, a DBP of at least 90 mm Hg, and/or the prescription of antihypertensive drugs. Information related to the history of hypertension and treatment of hypertension was collected through a questionnaire. RESULTS: The prevalence of hypertension was 11.8%. Among patients with hypertension, 54.4% were aware of their elevated BP, 49.3% had treatment, and 23.3% achieved targeted BP control. Among those who were aware of their hypertension, 90.4% underwent treatment, and among those who were treated, 43.6% were well controlled. Although the prevalence, awareness and treatment of hypertension varied significantly among adults with several social economics status, the control of hypertension did not show significant differences. Among treated patients, the control of hypertension showed significant differences among adults with education, occupation, insurance and income. CONCLUSIONS: It is the first time for Guangzhou to describe epidemic and management of hypertension. A baseline was established, which could provide useful information not only to policymakers but also to developing countries with a close urbanization and aging rate similar to Guangzhou.

Gender difference in association of NEDD4L gene variants among southern Han Chinese with essential hypertension - a population-based case-control study.

Genetic variation of NEDD4L has been associated with hypertension and related phenotypes with conflicting results, probably attributable to gender-, age- and ethnicity-related variations in its phenotypic expression. We evaluated the association of three representative polymorphisms in NEDD4L (rs2288774, rs3865418 and rs4149601) with essential hypertension (EH) in a community-based sample of men (n = 1029) and women (n = 869) belonging to Han Chinese, Southern China, to probe whether gender interacts with NEDD4L in contributing to the risk of EH. In this population sample, rs4149601 was excluded from further analysis due to deviation from Hardy-Weinberg equilibrium. For two other variants tested, the allele frequencies and genotype distributions did not differ between cases and controls (p > 0.05) when both genders were combined. However, sex-stratified analysis revealed that the distribution of the dominant model of rs2288774 (TC + CC versus TT) and the additive and dominant (CT + TT versus CC) models of rs3865418 differed significantly between cases and controls in men (p = 0.044, 0.041 and 0.016, respectively) but not in women. After adjusting for confounding factors, logistic regression analysis showed that rs2288774 and rs3865418 (in the dominant model) were still significantly associated with EH (rs2288774: OR = 0.73, 95% CI = 0.57-0.95, p = 0.017 and rs3865418: OR = 0.71, 95% CI = 0.55-0.92, p = 0.009) in men. There was a significant interaction between the NEDD4L genotype and gender (p for interaction: 0.046 for rs2288774 and 0.033 for rs3865418). Genetic variation in NEDD4L may have sex-dependent effects in the development of EH in Han Chinese. Previous studies that ignore gender-specific effects in their design and interpretation could have failed to identify a uniform conclusion.

The metabolic syndrome among postmenopausal women in rural Canton: prevalence, associated factors, and the optimal obesity and atherogenic indices.

OBJECTIVES: This research aimed to (i) determine the prevalence of metabolic syndrome (MetS) and its components; (ii) assess factors associated with MetS, and (iii) define optimal ethnic-specific cutoffs of obesity- and atherogenic-based markers to predict MetS among postmenopausal women in rural Canton. METHODOLOGY/PRINCIPAL FINDINGS: The Rural Canton Diabetes and Metabolic Disorders Study, a population based cross-sectional study, was conducted during 2011-2012 in Canton. In person interviews, blood glucose and lipid measurements were completed for 4,706 postmenopausal women who did not receive hormone replacement therapy. MetS was diagnosed using criteria of the Joint-Interim-Statement (JIS), the International-Diabetes-Federation (IDF) and the Modified-Third-Adult-Treatment-Panel (M-ATPIII). Age-standardized prevalence of MetS was 38.4%, 28.8%, and 37.1% according to JIS, IDF, and M-ATPIII criteria, respectively. Excellent agreement was observed between three definitions (κ ≥ 0.79), in particular between JIS and ATPIII (κ = 0.98, 95%CI: 0.97-0.98). Factors positively associated with MetS were living in Southern Canton, personal income, current smoking, higher BMI, and family history of cardiovascular disease. However, regular leisure-time physical activity can have protective effects. The optimal cutoff values for waist-circumference (WC), waist-to-hip ratio (WHR), waist-to-height ratio(WHtR), BMI, HDL-cholesterol to total cholesterol ratio (HDL/TC), HDL-cholesterol to LDL-cholesterol ratio (HDL/LDL), and triglyceride to HDL-cholesterol ratio (TG/HDL) that predicted the presence of MetS were 79.5 cm, 0.86, 0.53, 22.47 kg/m(2), 0.33, 0.68, and 0.88, respectively. CONCLUSIONS: This study highlights the importance of MetS among postmenopausal women in rural Canton. Our findings contribute to help selecting Cantonese-specific markers to predict MetS and support the need to establish educational program for promoting healthy-lifestyles among this population.

A functional variant of NEDD4L is associated with obesity and related phenotypes in a Han population of Southern China.

NEDD4L is a candidate gene for hypertension, both functionally and genetically. Recently, studies showed evidence for the association of NEDD4L with obesity, a key intermediate phenotype in hypertension. To further investigate the relationship between NEDD4L and body mass-related phenotypes, we genotyped three common variants (rs2288774, rs3865418 and rs4149601) in a population-based study of 892 unrelated Han Cantonese using the Sequenom MALDI-TOF-MS platform. Allele frequencies and genotype distribution were calculated in lean controls and overweight/obese cases and analyzed for association by the Chi-squared test and Logistic regression. Linear regression analysis was used to analyze the effect of individual genotypes on quantitative traits. Multivariate analyses demonstrated that the minor allele of rs4149601(A = 20.9%) was associated with a 2.60 kg, 2.78 cm and 0.97 kg/m2 decrease per allele copy in weight, waist and BMI, respectively. Carriers of this allele also had a significant lower risk of overweight/obesity (p < 0.0001, OR = 0.52, 95% CI: 0.37-0.74) as compared to non-carriers. However, no significant association between genotypes at rs2288774 and rs3865418 and covariate-adjusted overweight/obesity or any related phenotypes was observed. These results suggested that the functional variant of NEDD4L, rs4149601, may be associated with obesity and related phenotypes, and further genetic and functional studies are required to understand its role in the manifestation of obesity.