Pressure-Induced Superconductivity up to 9 K in the Quasi-One-Dimensional KMn_{6}Bi_{5}.

The Mn-based superconductor is rare owing to the strong magnetic pair-breaking effect. Here we report on the discovery of pressure-induced superconductivity in KMn_{6}Bi_{5}, which becomes the first ternary Mn-based superconductor. At ambient pressure, the quasi-one-dimensional KMn_{6}Bi_{5} is an antiferromagnetic metal with T_{N}≈75 K. By measuring resistance and ac magnetic susceptibility under hydrostatic pressures up to 14.2 GPa in a cubic anvil cell apparatus, we find that its antiferromagnetic transition can be suppressed completely at a critical pressure of P_{c}≈13 GPa, around which bulk superconductivity emerges and displays a superconducting dome with the maximal T_{c}^{onset}=9.3 K achieved at about 14 GPa. The close proximity of superconductivity to a magnetic instability in the temperature-pressure phase diagram of KMn_{6}Bi_{5} and an unusually large µ_{0}H_{c2}(0) exceeding the Pauli paramagnetic limit suggests an unconventional magnetism-mediated paring mechanism. In contrast to the binary MnP, the flexibility of the crystal structure and chemical compositions in the ternary AMn_{6}Bi_{5} (A=alkali metal) can open a new avenue for finding more Mn-based superconductors.

The efficacy of metformin in pregnant women with polycystic ovary syndrome: a meta-analysis of clinical trials.

OBJECTIVES: The role of metformin in the treatment of pregnant women with polycystic ovary syndrome (PCOS) is controversial. Therefore, we evaluated whether the use of metformin during pregnancy in women with PCOS could reduce pregnancy-related complications. RESEARCH DESIGN AND METHODS: MEDLINE was searched to retrieve relevant trials. In addition, reviews and reference lists of the retrieved articles were scanned for further appropriate studies. The primary outcome measure was the incidence of complications of pregnancy, which included early pregnancy loss (EPL), gestational diabetes (GDM), pre-eclampsia (PE), and pre-term delivery (PD). RESULTS: In total, eight studies with 1106 patients were included. The pooled odds ratio (OR) (95% confidence interval) of outcome for pregnant women with PCOS prescribed metformin were 0.32 (0.19-0.55) for EPL, 0.37 (0.25-0.56) for GDM, 0.53 (0.30-0.95) for PE and 0.30 (0.13-0.68) for PD. CONCLUSIONS: Metformin therapy throughout pregnancy decreased the OR of EPL, GDM, PE, and PD in pregnant PCOS women with no serious detrimental side effects.

Age-related bone mineral density, osteoporosis rate and risk of vertebral fracture in mainland Chinese women with type 2 diabetes mellitus.

Few data are available regarding bone mineral density (BMD) and the risk of vertebral fracture among mainland Chinese women with type 2 diabetes mellitus (T2DM). A decrease in the bone projective area (BPA) can be an indirect marker reflecting compressed vertebral fracture. We investigated age-related BMD, BPA, and the prevalence of osteoporosis in women with T2DM in mainland China. BMD and BPA of the posteroanterior lumbar spine (L1-L4) and hip were measured by dual-energy X-ray absorptiometry in 1253 women with T2DM and 1194 control subjects without diabetes aged 40-80 yr. BMD of the lumbar spine and hip decreased with age. BMD of the lumbar spine was higher in T2DM than controls (p<0.05-0.001), as was BPA at some vertebral bodies (p<0.05-0.001), whereas no significant intergroup differences in BPA were observed at the hip. The prevalence of osteoporosis in the women with T2DM increased with age: 0-2.58% at age 40-49 yr, 6.94-28.4% at age 50-59 yr, 32.7-76.7% at age 70-80 yr, with the range reflecting differences between skeletal sites. In subjects over 60 yr, the rates of osteoporosis at posteroanterior spine were significantly lower in T2DM patients than in controls (p<0.05-0.001). In conclusion, women with T2DM had higher BMD and lower risk of osteoporosis. Higher BPA of the vertebrae indicated that women with T2DM in mainland China would have a lower risk of vertebral fracture than non-diabetic women.

Bone mineral content and bone mineral density at lumbar spine and forearm in Chinese girls aged 6-18 years.

We investigated the age-related bone mineral content (BMC), bone mineral density (BMD) and the tempo of growth in BMC and BMD at lumbar spine and forearm in 455 Chinese girls aged 6-18 yr. BMC and BMD at the anteroposterior lumbar spine (LS), the left forearm (radius+ulna ultradistal, R+UUD) and one-third region (R+U1/3) were measured using a dual-energy X-ray bone densitometer (DXA). BMC and BMD exhibited different change patterns with the age changes. There were significant correlations between age, height, weight and BMC and BMD at LS, R+UUD and R+U1/3 sites. BMC and BMD increased significantly with increments in pubertal stages at LS, R+UUD and R+U1/3 sites. In conclusion, our study showed that Tanner stage had a significant positive association with BMC and BMD of the lumbar spine and forearm. The differences were found in the growth tempo of BMC and BMD within a region and between the spine and forearm. Both BMD and BMC were recommended to evaluate the bone health in children and adolescents.

Relationship of circulating MMP-2, MMP-1, and TIMP-1 levels with bone biochemical markers and bone mineral density in postmenopausal Chinese women.

INTRODUCTION: Osteoblast-derived matrix metalloproteinase (MMP)-2, MMP-1 and tissue inhibitor of metalloproteinase (TIMP)-1 have been shown to play a role in bone metabolism by degrading the bone matrix. METHODS: The present study was performed to investigate the relationships between serum MMP-2, MMP-1, or TIMP-1 levels and bone mineral density (BMD), as well as bone biochemical markers, in 297 Chinese postmenopausal women aged 42-80 years. RESULTS: We found a significant negative weak correlation between MMP-2 and BMD at various skeletal regions. After adjustment for age and BMI, the correlation with BMD at the femoral neck and total hip disappeared. Multiple linear stepwise regression analysis showed that MMP-2 was not a determinant factor for BMD. The significant positive correlations between MMP-2 and bone cross-linked N-telopeptides of type I collagen (NTX), alkaline phosphatase (BAP), and osteocalcin (OC) and were found, and remained significant after adjustment for age and BMI. Moreover, serum MMP-2 concentrations were significantly higher in postmenopausal women with osteoporosis than in age-matched normal controls. There were no significant correlations between MMP-1, TIMP-1 and BMD. There were no significant relationships between MMP-1 and BAP, OC, and NTX. The associations between TIMP-1 and BAP and OC were not specific and constant. CONCLUSIONS: In conclusion, our results suggest that circulating MMP-2 and markers of bone turnover are correlated, and serum MMP-2 levels may rise with increase in bone turnover.