Suchergebnisse

Objective:The study examines the factors determining the movement time (MT) of positioning an object in an immersive 3D virtual environment.Background:Positioning an object into a prescribed area is a fundamental operation in a 3D space. Although Fitts's law models the pointing task very well, it does not apply to a positioning task in an immersive 3D virtual environment since it does not consider the effect of object size in the positioning task.Method:Participants were asked to position a ball-shaped object into a spherical area in a virtual space using a handheld or head-tracking controller in the ray-casting technique. We varied object size (OS), movement amplitude (A), and target tolerance (TT). MT was recorded and analyzed in three phases: acceleration, deceleration, and correction.Results:In the acceleration phase, MT was inversely related to object size and positively proportional to movement amplitude. In the deceleration phase, MT was primarily determined by movement amplitude. In the correction phase, MT was affected by all three factors. We observed similar results whether participants used a handheld controller or head-tracking controller. We thus propose a three-phase model with different formulae at each phase. This model fit participants' performance very well.Conclusion:A three-phase model can successfully predict MT in the positioning task in an immersive 3D virtual environment in the acceleration, deceleration, and correction phases, separately.Application:Our model provides a quantitative framework for researchers and designers to design and evaluate 3D interfaces for the positioning task in a virtual space.

Beyond the scientific progress in assisted reproductive technologies (ART), it is necessary to discuss the ethical considerations behind these advances. Ethical issues concerning sperm donation have been considered and discussed by government and non-governmental agencies, the public, media and academic institutions in many countries. Recommendations and guidelines concerning sperm donation issues vary from country to country and between professional groups within countries. This paper attempts to present an overview of findings and reports from various agencies concerning the ethics of sperm donation. The following topics are considered: limiting the number of donor offspring; minimizing risk of infection and genetics from sperm donors; age requirements for sperm donors; and anonymity versus non-anonymity of sperm donors. The diversity of policies shows that each country has its unique set of guidelines tailored toward its own specific needs. Similarly, countries designing their own procedures and guidelines concerning reproductive medicine must tailor them toward their own needs and practical considerations. In Mainland China, the anonymous policy for sperm donation should still be carried out, and the number of donor offspring should be revaluated. ART procedures must be conducted in a way that is respectful of those involved. Ethical principles must respect the interests and welfare of persons who will be born as well as the health and psychosocial welfare of all participants, including sperm donors.

Ye Tao,1,* Zhen Yang,2,* Wei Fang,2 Zhao Ma,3 Yi Fei Huang,1 Zhengwei Li4 1Department of Ophthalmology, Key Lab of Ophthalmology and Visual Science, Chinese PLA General Hospital, Beijing, 2Department of Neurosurgery, Institute for Functional Brain Disorders, Tangdu Hospital, Fourth Military Medical University, Xi'an, 3Department of Neurosurgery, Central Hospital of Wuhan, Tongji Medical College, Huazhong University of Science and Technology, 4Department of Neurosurgery, Zhongnan Hospital of Wuhan University, Wuhan, People's Republic of China *These authors contributed equally to this work Abstract: Retinal degeneration (RD) is a heterogeneous group of inherited dystrophies leading to blindness. The N-methyl-N-nitrosourea (MNU)-administered mouse is used as a pharmacologically induced RD animal model in various therapeutic investigations. The present study found the retinal neuroglobin (NGB) expression in the MNU-administered mice was significantly lower than in normal controls, suggesting NGB was correlated with RD. Subsequently, an adeno-associated virus (AAV)-2-mCMV-NGB vector was delivered into the subretinal space of the MNU-administered mice. The retinal NGB expression of the treated eye was upregulated significantly in both protein and mRNA levels. Further, we found NGB overexpression could alleviate visual impairments and morphological devastations in MNU-administered mice. NGB overexpression could rectify apoptotic abnormalities and ameliorate oxidative stress in MNU-administered mice, thereby promoting photoreceptor survival. The cone photoreceptors in MNU-administered mice were also sensitive to AAV-mediated NGB overexpression. Taken together, our findings suggest that manipulating NGB bioactivity via gene therapy may represent a novel therapeutic strategy against RD. Future elucidation of the exact role of NGB would advance our knowledge about the pathological mechanisms underlying RD. Keywords: neuroglobin, retinal degeneration, photoreceptor

Urban green space (UGS) has gained increasing attention due to its environmental and social functions. However, the compound effects of climate change, population growth and economic development on UGS are largely unknown. We selected 107 medium-sized and large cities in China to investigate dynamics in the spatial pattern of UGS in relation to government policy and other drivers based on remote sensing data for the period 1990 to 2019. To explore the effect of different levels of urbanization on changes in green space, we develop a new Normalized Urban Development Index (NUDI) to classify urban-suburban-rural gradients, viz. Long-term Built-up, New Built-up and Non-Built-up. Then, we analysed changes over time in the annual peak value of fraction of vegetation cover (FVC) for 380,000 cloud-free Landsat images, and regional UGS dynamics were evaluated using the proposed Regional Greenness Dynamic Index (RGDI). Finally, to reveal the major driver(s) of changes in UGS and estimate the extent to which patterns of urban greening are due to differences in economic development, we compared the observed UGS spatio-temporal dynamics with data on several climatic, social-economic and land use related factors for the same period.