Precisely Controlled Synthesis of Pt-Pd Octahedral Nanoframes as a Superior Catalyst towards Oxygen Reduction Reaction

Pt-based nanoframes represent a class of promising catalysts towards oxygen reduction reaction. Herein, we, for the first time, successfully prepared Pt-Pd octahedral nanoframes with ultrathin ridges less than 2 nm in thickness. The Pt-Pd octahedral nanoframes were obtained through site-selected deposition of Pt atoms onto the edge sites of Pd octahedral seeds, followed by selective removal of the Pd octahedral cores via chemical etching. Due to that a combination of three-dimensional opens geometrical structure and Pt-skin surface compositional structure, the Pt-Pd octahedral nanoframes/C catalyst shows a mass activity of 1.15 A/mgPt towards oxygen reduction reaction, 5.8 times enhancement in mass activity relative to commercial Pt/C catalyst （0.20 A/mgPt）. Moreover, even after 8000 cycles of accelerated durability test, the Pt-Pd octahedral nanoframes/C catalyst still exhibits a mass activity which is more than three times higher than that of pristine Pt/C catalyst.

Determination of vitamin D and analysis of risk factors for osteoporosis in patients with chronic pain

BACKGROUND Vitamin D deficiency is common in patients with chronic pain and healthy people,but the difference between the two has not been reported;thus,whether there is a relationship between vitamin D deficiency and chronic pain remains to be confirmed.Osteoporosis is a common disease in chronic pain disorders.Understanding the relationship between vitamin D and osteoporosis will provide a basis for the rational supplementation of vitamin D to prevent osteoporosis,and to understand the risk factors of bone mass change to provide a new treatment plan for early prevention of osteoporosis.AIM To determine 25 hydroxy vitamin D(25OHD)level in patients with chronic pain to clarify its clinical significance.The relationship between vitamin D and bone mineral density(BMD)and the risk factors for bone mass change were also evaluated.METHODS In this study,184 patients with chronic pain were included in the study group,and 104 healthy individuals who underwent routine health checkups during the same period were included in the control group.25OHD level was detected in both groups by enzyme-linked immunosorbent assay.According to the BMD test results,the patients in the study group were further classified into three subgroups:Normal BMD group,reduced BMD group,and osteoporosis group.Age,sex,ethnicity,living altitude,body mass index,25OHD level,parathyroid hormone(PTH),calcium(Ca)and phosphorus levels were analyzed statistically in both groups.RESULTS The vitamin D level in the study group was lower than that in the control group at 53.8%vs 57.7%,with no significant difference between the two groups.The proportion of patients with severe vitamin D deficiency in the study group was higher than that in the control group.The mean age was greater in the osteoporosis subgroup,and the youngest in the normal BMD subgroup.Vitamin D level in the osteoporosis subgroup was lower than that in the other two subgroups,and was not specific for the diagnosis of bone mass reduction and osteoporosis.The above results were analyzed statistically and showed significant differences(P<0.05).There was a positive correlation between age and BMD in patients with chronic pain(R=0.567,P<0.001).Age,PTH and Ca were risk factors for bone mass reduction,while age,ethnicity and altitude were risk factors for osteoporosis.CONCLUSION Vitamin D deficiency is a common phenomenon in patients with chronic pain,and severe vitamin D deficiency is not uncommon.Vitamin D level is not a risk factor for bone mass reduction and osteoporosis.Bone mass reduction is correlated with age,PTH and Ca,while osteoporosis is correlated with age,ethnicity and altitude.

The Libration Points in Photogravitational Restricted Three-Body Problem

The phologravilational restricled three-body problem in which the mass reduclionfactors of two primaries q_1 q_2( -∞, 1] are siudied and an analytic meihod toesli,;iale the number of libralion points ana io calculate lheir hoalion is given in thispaper. The results show lhal in phologravilalional reslricled three-body problem, thenumber of librafion poinis is .from one to seven for different q_1 and q_2. As application,the motion of dust grain like comet tail in the solar syslern is also discussed.