Oxygen vacancy formation in CeO2 and Ce(1-x)Zr(x)O2 solid solutions: electron localization, electrostatic potential and structural relaxation.

Ceria (CeO(2)) and ceria-based composite materials, especially Ce(1-x)Zr(x)O(2) solid solutions, possess a wide range of applications in many important catalytic processes, such as three-way catalysts, owing to their excellent oxygen storage capacity (OSC) through the oxygen vacancy formation and refilling. Much of this activity has focused on the understanding of the electronic and structural properties of defective CeO(2) with and without doping, and comprehending the determining factor for oxygen vacancy formation and the rule to tune the formation energy by doping has constituted a central issue in material chemistry related to ceria. However, the calculation on electronic structures and the corresponding relaxation patterns in defective CeO(2-x) oxides remains at present a challenge in the DFT framework. A pragmatic approach based on density functional theory with the inclusion of on-site Coulomb correction, i.e. the so-called DFT + U technique, has been extensively applied in the majority of recent theoretical investigations. Firstly, we review briefly the latest electronic structure calculations of defective CeO(2)(111), focusing on the phenomenon of multiple configurations of the localized 4f electrons, as well as the discussions of its formation mechanism and the catalytic role in activating the O(2) molecule. Secondly, aiming at shedding light on the doping effect on tuning the oxygen vacancy formation in ceria-based solid solutions, we summarize the recent theoretical results of Ce(1-x)Zr(x)O(2) solid solutions in terms of the effect of dopant concentrations and crystal phases. A general model on O vacancy formation is also discussed; it consists of electrostatic and structural relaxation terms, and the vital role of the later is emphasized. Particularly, we discuss the crucial role of the localized structural relaxation patterns in determining the superb oxygen storage capacity in kappa-phase Ce(1-x)Zr(1-x)O(2). Thirdly, we briefly discuss some interesting findings for the oxygen vacancy formation in pure ceria nanoparticles (NPs) uncovered by DFT calculations and compare those with the bulk or extended surfaces of ceria as well as different particle sizes, emphasizing the role of the electrostatic field in determining the O vacancy formation.

Heat maps present the spatial distribution of human papillomavirus infection in Zhejiang Province, China.

Determining the spatial distribution of human papillomavirus (HPV) and performing accurate public health analyses helps to distinguish areas of healthcare that require further research, and enables therapeutic techniques and approaches in healthcare to be focused more accurately. A total of 4,560 women were enrolled in the present study. Flow-through hybridization and gene chip assays were used to detect the genotypes of HPV infection. Heat maps were then generated to present the spatial distribution of HPV infections in Zhejiang Province according to genotype. Of the exfoliated cervical cell samples from the 4,560 women, HPV was detected in 1,886 samples. HPV-16, -58, -52 and -18 were the most prevalently identified genotypes in the population included in the present study. HPV-16 and -58 infections were mainly distributed in the northern and central regions of Zhejiang Province, such as in Hangzhou and Shaoxing, where the prevalence was higher than that in the southern regions (P<0.05). HPV-18 infection was widespread throughout Zhejiang Province, but had a much lower infection rate in Ningbo and Huzhou (P<0.05). High infection rates of HPV-52 were mainly detected in Hangzhou and the eastern coastal areas of Wenzhou, with a relatively low rate of infection in the center of the province (P<0.05). In conclusion, HPV-16, -58, -52 and -18 were the four most prevalent HPV genotypes observed in Zhejiang Province. Heat maps were created to display the spatial distribution of HPV infection according to genotype, which varied by geographical regions. The results indicate that for individuals in Ningbo or Wenzhou, bivalent or quadrivalent vaccines may be suitable, but for those in Hangzhou and Shaoxing, nonavalent vaccines are strongly recommended.

Prognostic value of serum α-fetoprotein in ovarian yolk sac tumors: A systematic review and meta-analysis.

This study was conducted to determine the prognostic value of serum α-fetoprotein (AFP) levels in patients with ovarian yolk sac tumor (OYST). We performed a systematic review and meta-analysis to assess the associations between serum AFP level and prognosis in OYST. A total of 12 quantitative studies met the inclusion criteria. Preoperative AFP was not found to be associated with overall survival (OS) [odds ratio (OR)=0.84, 95% confidence interval (CI): 0.43-1.62] in OYST. However, a high postoperative AFP level was associated with worse OS (OR=0.16, 95% CI: 0.05-0.48) and relapse-free survival (RFS) (OR=0.18, 95% CI: 0.08-0.43) compared to a low postoperative AFP level in patients with OYST. In addition, a postoperative AFP level of >1,000 ng/ml was associated with a decrease in OS (OR=0.16, 95% CI: 0.05-0.50) and RFS (OR=0.21, 95% CI: 0.08-0.57). In conclusion, the postoperative, but not the preoperative, AFP level was found to be a prognostic factor in patients with OYST. In particular, a postoperative AFP level of >1,000 ng/ml was an indicator of poor prognosis in patients with OYST.

Primary yolk sac tumor of the retroperitoneum: A case report and review of the literature.

Yolk sac tumor (YST), also known as an endodermal sinus tumor, is a rare malignant germ cell tumor. Primary retroperitoneal YST (PRYST) is extremely rare and, to the best of our knowledge, has only been described in case reports. The histogenesis of PRYST and the appropriate treatment strategy remain unclear due to the rarity of this type of tumor. The present study reports a case of YST in the retroperitoneum. A 19-year-old female presented with abdominal distension and edema of the lower limbs. A computed tomography scan revealed a large, solid mass located in the retroperitoneum. The tumor size was 20×25×30 cm and widespread metastasis was identified during the exploratory laparotomy. The postoperative histopathology report showed a malignant retroperitoneal tumor (although a YST was initially considered). The patient underwent three surgical procedures and 17 cycles of five different chemotherapy regimens. The patient succumbed to cachexia, which was due to tumor recurrence, and liver and spleen metastases 21 months after diagnosis. PRYST may relapse following surgical treatment; however, surgical resection is currently the optimal treatment method. In this case, bleomycin, etoposide and cisplatin; bleomycin, vincristine and cisplatin; and vincristine and cisplatin chemotherapy regimens were effective for the patient with PRYST, although the tumor was not completely resected. α-fetoprotein (AFP) is an important tumor marker for monitoring PRYST recurrence and observation of elevated serum AFP levels during chemotherapy indicates a poor prognosis.

Exchange between sub-surface and surface oxygen vacancies on CeO2(111): a new surface diffusion mechanism.

Using first principles calculations for O vacancy diffusion on CeO(2)(111), we locate a surface diffusion mechanism, the two-step O vacancy exchange one, which is more favored than the most common hopping mechanism. By analyzing the results, we identify quantitatively the physical origin of why the two-step exchange mechanism is preferred.

C-H bond activation over metal oxides: a new insight into the dissociation kinetics from density functional theory.

The C-H activation on metal oxides is a fundamental process in chemistry. In this paper, we report a density functional theory study on the process of the C-H activation of CH(4) on Pd(111), Pt(111), Ru(0001), Tc(0001), Cu(111), PdO(001), PdO(110), and PdO(100). A linear relationship between the C-H activation barrier and the chemisorption in the dissociation final state on the metal surfaces is obtained, which is consistent with the work in the literature. However, the relationship is poor on the metal oxide surfaces. Instead, a strong linear correlation between the barrier and the lattice O-H bond strength is found on the oxides. The new linear relationship is analyzed and the physical origin is identified.