Longitudinal investigation of optic chiasm in patients with traumatic brain injury.

BACKGROUND: Traumatic brain injury (TBI) often precipitates a cascade of neurophysiological alterations, impacting structures such as the optic nerve and ocular motor system. However, the literature lacks expansive investigations into the longitudinal changes in the optic chiasm and its relationship with the clinical recovery of visual processing. This study aimed to scrutinize longitudinal changes in optic chiasm volume (OCV) and establish the relationship of OCV with process speed index at 12 months post-injury. Process speed index is derived from Wechsler Adult Intelligence Scale IV. METHODS: Thorough cross-sectional and longitudinal analyses were executed, involving 42 patients with moderate to severe TBI and 35 healthy controls. OCV was acquired at 3, 6, and 12 months post-injury using T1-weighted images. OCV of healthy controls and that of patients with TBI at 3, 6, and 12 months post-injury were compared using a Mann-Whitney U test. A multiple linear regression model was constructed to assess the association between OCV and PSI and to predict PSI at 12 months post-injury using OCV at 3 months post-injury. RESULTS: OCV of patients with TBI was significantly larger compared to healthy controls, persisting from 3 to 12 months post-injury (p < 0.05). This increased OCV negatively correlated with PSI at 12 months post-injury, indicating that larger OCV sizes were associated with decreased PSI (p = 0.031). Furthermore, the multiple linear regression model was significant in predicting PSI at 12 months post-injury utilizing OCV at 3 months post-injury (p = 0.024). CONCLUSION: For the first time, this study elucidates the increased OCV and the significant association between OCV in sub-chronic stage and PSI at 12 months post-injury, potentially providing clinicians with a tool for anticipatory cognitive rehabilitation strategies following TBI.

Integrated Chemical Vapor Sensor Based on Thin Wall Capillary Coupled Porous Glass Microsphere Optical Resonator.

A miniaturized chemical vapor sensor probe was developed using a porous glass microsphere (PGM) as the alignment-free optical microresonator. The porous microsphere was placed inside a thin wall silica capillary tube that was fusion-spliced to an optical fiber. The whispering gallery modes (WGMs) of the microsphere were excited by the evanescent field of the light propagating inside the capillary thin wall. Adsorption of chemical vapor molecules into the pores led to a refractive index change of the PGM and thus the resonance wavelength shift of the WGMs. To facilitate the in-taking of chemical vapor molecules into the PGM, a micro window was opened at the backend of the capillary tube using femtosecond laser micromachining. Ethanol vapor was used to demonstrate the probe for chemical vapor sensing. With a miniaturized size, integrated structure and reflection mode of operation, the proposed probe may find useful in many practical applications such as environmental monitoring and biomedical sensing.

Fiber pigtailed thin wall capillary coupler for excitation of microsphere WGM resonator.

In this paper, we demonstrate a fiber pigtailed thin wall capillary coupler for excitation of Whispering Gallery Modes (WGMs) of microsphere resonators. The coupler is made by fusion-splicing an optical fiber with a capillary tube and consequently etching the capillary wall to a thickness of a few microns. Light is coupled through the peripheral contact between inserted microsphere and the etched capillary wall. The coupling efficiency as a function of the wall thickness was studied experimentally. WGM resonance with a Q-factor of 1.14 × 10(4) was observed using a borosilicate glass microsphere with a diameter of 71 µm. The coupler operates in the reflection mode and provides a robust mechanical support to the microsphere resonator. It is expected that the new coupler may find broad applications in sensors, optical filters and lasers.

Optical microresonator based on hollow sphere with porous wall for chemical sensing.

A porous-wall hollow glass microsphere (PW-HGM) was investigated as an optical resonator for chemical vapor sensing. A single mode optical fiber taper was used to interrogate the microresonator. Adsorption of chemical molecules into the nanosized pores induced a refractive index change of the thin wall and thus a shift in its resonance spectrum. The PW-HGM resonator had shown higher vapor detection sensitivity in comparison with a solid microsphere under similar test conditions.

The determining factor of a preferred orientation of GaN domains grown on m-plane sapphire substrates.

Epitaxial lateral overgrowth in tandem with the first-principles calculation was employed to investigate the determining factor of a preferred orientation of GaN on SiO2-patterned m-plane sapphire substrates. We found that the (1100)-orientation is favored over the (1103)-orientation in the region with a small filling factor of SiO2, while the latter orientation becomes preferred in the region with a large filling factor. This result suggests that the effective concentration determines the preferred orientation of GaN: the (1100)- and (1103)-orientations preferred at their low and high concentrations, respectively. Our computational study revealed that at a low coverage of Ga and N atoms, the local atomic arrangement resembles that on the (1103) surface, although the (1100) surface is more stable at their full coverage. Such a (1103)-like atomic configuration crosses over to the local structure resembling that on the (1100) surface as the coverage increases. Based on results, we determined that high effective concentration of Ga and N sources expedites the growth of the (1103)-orientation while keeping from transition to the (1100)-orientation. At low effective concentration, on the other hand, there is a sufficient time for the added Ga and N sources to rearrange the initial (1103)-like orientation to form the (1100)-orientation.