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The technique of backside thinning is used to obtain thinner freestanding GaN membrane. This technique is helpful for producing stronger reflectance peaks and to reduce the reflectance spectra quantity and reflectance interference in the visible light range. Ion beam etching (IBE) was used to fabricate a GaN membrane grating, and the size of the tapered angle of which has an important affect on the reflectance spectra modes. Therefore, we presented a GaN membrane grating model with tapered angle which is built based on a GaN-on-silicon wafer structure. The influence of the varied tapered angle on the reflectance spectra of grating was investigated. Meanwhile, affects of different parameters like the grating thickness, membrane thickness, grating period, filling factor, incident beam based on a certain tapered angle were also analyzed on reflectance spectra of the GaN grating. Rigorous coupled wave analysis (RCWA) was used as theoretical principle for numerical simulations on the GaN grating model in this study. The results of this report are very useful for fabricating GaN reflectance photonic devices, such as refractive index sensor, couplers and so on. [ABSTRACT FROM AUTHOR]

Introduction: Although depression is commonly accompanied by cognitive deficits, the underlying mechanism remains unclear. One possibility is that such deficits are related to abnormal brain network connections. The purpose of this study was thus to investigate changes in brain functional connectivity (FC) in depression and its relationship with cognitive deficits.Methods: We enrolled 37 first-episode MDD patients and 53 matched healthy controls (HC). All participants completed clinical and neurocognitive assessments and underwent resting-state functional MRI. Seed-based analysis was used to define the dorsolateral prefrontal cortex (DLPFC) and FC analysis was then performed. We used bias correlation to analyze the correlation between FC and clinical and neurocognitive scores.Results: MDD patients showed increased FC of the right DLPFC with the left inferior temporal gyrus, left cuneus, right inferior frontal gyrus, right anterior cingulate cortex, left BA39, right angular gyrus, right precuneus, left middle frontal gyrus, and right precentral gyrus. MDD patients also showed stronger FC in the left thalamus and reduced FC between the left superior occipital gyrus and left DLPFC seed region. Interestingly, increased FC was related to disease severity (with the right precentral gyrus) and social cognitive dysfunction (with the right angular gyrus) in MDD patients.Limitations: The sample size was relatively small and it is unclear how age may influence FC changes in patients with depression.Conclusions: These findings support changes in FC of the DLPFC in early MDD patients related to cognitive function. FC is a potential biomarker for the diagnosis of MDD. [ABSTRACT FROM AUTHOR]

The spectral characteristics of carbon nanotubes is essential for the development of optoelectronic components and sensors with application in many fields. The linear polarizability absorption spectra of the carbon nanotube with a twisted angle have been calculated by using the tight-binding model and sum-over-state method. First, a structural model of carbon nanotubes based on PPP(Pariser-Parr_Pople) was established, then a certain carbon atom was moved to a position where the carbon nanotubes are angled, and the torsional carbon nanotube structure model was calculated based on the change in bond length. Finally, the absorption spectrum at different twisted angles based on SOS(Sum-over-State) was calculated, and then the detailed analysis was made. It is found that the twisted angle has real impact on the absorption spectra of different types carbon nanotubes. The torsional angle leads to changes in the position and number of absorption peaks of the carbon nanotubes. Its influence on absorption spectra of different types of carbon nanotubes is different, but mainly concentrated in the low frequency region. Exactly, altering the twisted angle has an important effect on the absorption spectra of the carbon nanotube. This work offers a guidance of fabricating carbon nanotubes in the applications of photonic device in many fields. [ABSTRACT FROM AUTHOR]