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 CeO2(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.

A Model to Understand the Oxygen Vacancy Formation in Zr-Doped CeO2:Electrostatic Interaction and Structural Relaxation

Using density functional theory with the inclusion of on-site Coulomb Correction, the O vacancy formation energies of CexZr1-xO2 solid solutions with a series of Ce/Zr ratios are calculated, and a model to understand the results is proposed. It consists of electrostatic and structural relaxation terms, and the latter is found to play a vital role in affecting the O vacancy formation energies. Using this model, several long-standing questions in the field, such as why ceria with 50% ZrO2 usually exhibit the best oxygen storage capacity, can be explained. Some implications of the new interpretation are also discussed.

Using dispersive delay lines and time reversal for low contrast tumour detection

On the basis of the technique of time reversal (TR), through adding dispersive delay lines to each element of a TR mirror, a method for low contrast tumour detection is proposed. When compared with a conventional detection method, the proposed method improves refocusing onto a low dielectric contrast tumour. The method does not require an accurate estimate of the position of the tumour. The theoretical basis for the approach is given and numerical simulated results demonstrate the capability of the proposed method.

Relationship between Laves phase and the impact brittleness of P92 steel reevaluated

Laves phase has been widely accepted to cause the impact brittleness of 9–12Cr martensitic heat-resistant steels after long time aging at elevated temperatures. However, in the present research, the impact toughness of the already brittle P92 steel aged at 600 °C for 2035 h could be restored to the original level by reheating at 700 °C for 1 h, with Laves phase barely changed. This interesting result strongly indicated that the presence of Laves phase might not be the real reason for the impact brittleness.

Local atomic structure modulations activate metal oxide as electrocatalyst for hydrogen evolution in acidic water

Modifications of local structure at atomic level could precisely and effectively tune the capacity of materials, enabling enhancement in the catalytic activity. Here we modulate the local atomic structure of a classical but inert transition metal oxide, tungsten trioxide, to be an efficient electrocatalyst for hydrogen evolution in acidic water, which has shown promise as an alternative to platinum. Structural analyses and theoretical calculations together indicate that the origin of the enhanced activity could be attributed to the tailored electronic structure by means of the local atomic structure modulations. We anticipate that suitable structure modulations might be applied on other transition metal oxides to meet the optimal thermodynamic and kinetic requirements, which may pave the way to unlock the potential of other promising candidates as cost-effective electrocatalysts for hydrogen evolution in industry.

A survey of perceived training differences between ophthalmology residents in Hong Kong and China.

Background: To study the differences in ophthalmology resident training between China and the Hong Kong Special Administrative Region (HKSAR).Methods: Training programs were selected from among the largest and best-known teaching hospitals. Ophthalmology residents were sent an anonymous 48-item questionnaire by mail. Work satisfaction, time allocation between training activities and volume of surgery performed were determined.Results: 50/75 residents (66.7 %) from China and 20/26 (76.9 %) from HKSAR completed the survey. Age (28.9 ± 2.5 vs. 30.2 ± 2.9 years, p = 0.15) and number of years in training (3.4 ± 1.6 vs. 2.8 ± 1.5, p = 0.19) were comparable between groups. The number of cataract procedures performed by HKSAR trainees (extra-capsular, median 80.0, quartile range: 30.0, 100.0; phacoemulsification, median: 20.0, quartile range: 0.0, 100.0) exceeded that for Chinese residents (extra-capsular: median = 0, p < 0.0001; phacoemulsification: median = 0, p < 0.0001). Chinese trainees spent more time completing medical charts (>50 % of time on charts: 62.5 % versus 5.3 %, p < 0.0001) and received less supervision (≥90 % of training supervised: 4.4 % versus 65 %, p < 0.0001). Chinese residents were more likely to feel underpaid (96.0 % vs. 31.6 %, p < 0.0001) and hoped their children would not practice medicine (69.4 % vs. 5.0 %, p = 0.0001) compared HKSAR residents.Conclusions: In this study, ophthalmology residents in China report strikingly less surgical experience and supervision, and lower satisfaction than HKSAR residents. The HKSAR model of hands-on resident training might be useful in improving the low cataract surgical rate in China.

Phacoemulsification combined with posterior capsulorhexis and anterior vitrectomy in the management of malignant glaucoma in phakic eyes

Purpose: To describe sequential phacoemulsification-intraocular lens (IOL) implantation-posterior capsulorhexis-anterior vitrectomy in the management of phakic malignant glaucoma. Methods: Twenty consecutive patients (25 eyes) with phakic malignant glaucoma were enrolled at the Zhongshan Ophthalmic Center, Sun Yat-sen University. All patients underwent phacoemulsification, IOL implantation and posterior capsulorhexis together with anterior vitrectomy via a clear corneal paracentesis. Visual acuity, intraocular pressure (IOP), anterior chamber depth (ACD), surgical complications and medications required after the surgery were recorded. Results: After surgery, the mean LogMAR visual acuity and ACD increased significantly (visual acuity from -1.56 ± 1.17 to -0.54 ± 0.81, p < 0.001; ACD from 0.367 ± 0.397 mm to 2.390 ± 0.575 mm, p < 0.001), and mean IOP decreased significantly (from 39.6 ± 10.6 mm Hg to 14.5 ± 4.1 mmHg, p < 0.001). No serious perioperative complications occurred, and only five eyes required topical glaucoma medications after surgery. Conclusion: Combined phacoemulsification-IOL implantation-posterior capsulorhexis-anterior vitrectomy surgery is a safe and effective method for treating patients with phakic malignant glaucoma. © 2012 The Authors. Acta Ophthalmologica © 2012 Acta Ophthalmologica Scandinavica Foundation.