- Chemical Structure, Ensemble and Single-Particle Spectroscopy of Thick-Shell InP-ZnSe Quantum Dots. [Journal Article]
- NLNano Lett 2018 Feb 14; 18(2):709-716
- Thick-shell (>5 nm) InP-ZnSe colloidal quantum dots (QDs) grown by a continuous-injection shell growth process are reported. The growth of a thick crystalline shell is attributed to the high temperat...
Thick-shell (>5 nm) InP-ZnSe colloidal quantum dots (QDs) grown by a continuous-injection shell growth process are reported. The growth of a thick crystalline shell is attributed to the high temperature of the growth process and the relatively low lattice mismatch between the InP core and ZnSe shell. In addition to a narrow ensemble photoluminescence (PL) line-width (∼40 nm), ensemble and single-particle emission dynamics measurements indicate that blinking and Auger recombination are reduced in these heterostructures. More specifically, high single-dot ON-times (>95%) were obtained for the core-shell QDs, and measured ensemble biexciton lifetimes, τ2x∼ 540 ps, represent a 7-fold increase compared to InP-ZnS QDs. Further, high-resolution energy dispersive X-ray (EDX) chemical maps directly show for the first time significant incorporation of indium into the shell of the InP-ZnSe QDs. Examination of the atomic structure of the thick-shell QDs by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) reveals structural defects in subpopulations of particles that may mitigate PL efficiencies (∼40% in ensemble), providing insight toward further synthetic refinement. These InP-ZnSe heterostructures represent progress toward fully cadmium-free QDs with superior photophysical properties important in biological labeling and other emission-based technologies.
- Content validation of behaviours and autonomic responses for the assessment of pain in critically ill adults with a brain injury. [Journal Article]
- ACAust Crit Care 2017 Nov 13
- CONCLUSIONS: Facial expressions, movements towards the pain site, and vocalisation of pain were the most relevant pain-related behaviours rated by critical care clinicians. The relevance of some behaviours (e.g., moaning and verbal complaints of pain) varied across LOCs, thereby calling forth adaptations of behavioural pain scales to allow for interpretation in the context of a patient's LOC and ability to express specific behaviours.
- Influence of exercise on the structure of the anterior chamber of the eye. [Journal Article]
- AOActa Ophthalmol 2018; 96(2):e247-e253
- CONCLUSIONS: The blinking rate did not change significantly during exercise, while ACA, AOD500 and TISA500 increased after exercise. Exercise also induced or increased IC. These changes in anterior chamber structure were only associated with exercise, but not with the postexercise change in PD or IOP.
- Shell thickness effects on quantum dot brightness and energy transfer. [Journal Article]
- NNanoscale 2017 Nov 02; 9(42):16446-16458
- Heterostructured core/shell quantum dots (QDs) are prized in biomedical imaging and biosensing applications because of their bright, photostable emission and effectiveness as Förster resonance energy...
Heterostructured core/shell quantum dots (QDs) are prized in biomedical imaging and biosensing applications because of their bright, photostable emission and effectiveness as Förster resonance energy transfer (FRET) donors. However, as nanomaterials chemistry has progressed beyond traditional QDs to incorporate new compositions, ultra-thick shells, and alloyed structures, few of these materials have had their optical properties systematically characterized for effective application. For example, thick-shelled QDs, also known as 'giant' QDs (gQDs) are useful in single-particle tracking microscopy because of their reduced blinking, but we know only that CdSe/CdS gQDs are qualitatively brighter than thin-shelled CdSe/CdS in aqueous media. In this study, we quantify the impact of shell thickness on the nanoparticle molar extinction coefficient, quantum yield, brightness, and effectiveness as a FRET donor for CdSe/xCdS core/shell and CdSe/xCdS/ZnS core/shell/shell QDs, with variable thicknesses of the CdS shell (x). Molar extinction coefficients up to three orders of magnitude higher than conventional dyes and forty-fold greater than traditional QDs are reported. When thick CdS shells are combined with ZnS capping, quantum yields following thiol ligand exchange reach nearly 40%-5-10× higher than either the commercially available QDs or gQDs without ZnS caps treated the same way. These results clearly show that thick CdS shells and ZnS capping shells work in concert to provide the brightest possible CdSe-based QDs for bioimaging applications. We demonstrate that thicker shelled gQDs are over 50-fold brighter than their thin-shelled counterparts because of significant increases in their absorption cross-sections and higher quantum yield in aqueous milieu. Consistent with the point-dipole approximation commonly used for QD-FRET, these data show that thick shells contribute to the donor-acceptor distance, reducing FRET efficiency. Despite the reduction in FRET efficiency, even the thickest-shell gQDs exhibited energy transfer. Through this systematic study, we elucidate the tradeoffs between signal output, which is much higher for the gQDs, and FRET efficiency, which decreases with shell thickness. This study serves as a guide to nanobiotechnologists striving to use gQDs in imaging and sensing devices.
- Visual Fatigue Induced by Viewing a Tablet Computer with a High-resolution Display. [Journal Article]
- KJKorean J Ophthalmol 2017; 31(5):388-393
- CONCLUSIONS: Visual fatigue and discomfort were significantly induced by viewing smart mobile devices, even though the devices were equipped with state-of-the-art display technology.
- A Single-Channel EOG-Based Speller. [Journal Article]
- ITIEEE Trans Neural Syst Rehabil Eng 2017; 25(11):1978-1987
- Electrooculography (EOG) signals, which can be used to infer the intentions of a user based on eye movements, are widely used in human-computer interface (HCI) systems. Most existing EOG-based HCI sy...
Electrooculography (EOG) signals, which can be used to infer the intentions of a user based on eye movements, are widely used in human-computer interface (HCI) systems. Most existing EOG-based HCI systems incorporate a limited number of commands because they generally associate different commands with a few different types of eye movements, such as looking up, down, left, or right. This paper presents a novel single-channel EOG-based HCI that allows users to spell asynchronously by only blinking. Forty buttons corresponding to 40 characters displayed to the user via a graphical user interface are intensified in a random order. To select a button, the user must blink his/her eyes in synchrony as the target button is flashed. Two data processing procedures, specifically support vector machine (SVM) classification and waveform detection, are combined to detect eye blinks. During detection, we simultaneously feed the feature vectors extracted from the ongoing EOG signal into the SVM classification and waveform detection modules. Decisions are made based on the results of the SVM classification and waveform detection. Three online experiments were conducted with eight healthy subjects. We achieved an average accuracy of 94.4% and a response time of 4.14 s for selecting a character in synchronous mode, as well as an average accuracy of 93.43% and a false positive rate of 0.03/min in the idle state in asynchronous mode. The experimental results, therefore, demonstrated the effectiveness of this single-channel EOG-based speller.
- Neural mechanisms underlying sound-induced visual motion perception: An fMRI study. [Journal Article]
- APActa Psychol (Amst) 2017; 178:66-72
- Studies of crossmodal interactions in motion perception have reported activation in several brain areas, including those related to motion processing and/or sensory association, in response to multim...
Studies of crossmodal interactions in motion perception have reported activation in several brain areas, including those related to motion processing and/or sensory association, in response to multimodal (e.g., visual and auditory) stimuli that were both in motion. Recent studies have demonstrated that sounds can trigger illusory visual apparent motion to static visual stimuli (sound-induced visual motion: SIVM): A visual stimulus blinking at a fixed location is perceived to be moving laterally when an alternating left-right sound is also present. Here, we investigated brain activity related to the perception of SIVM using a 7T functional magnetic resonance imaging technique. Specifically, we focused on the patterns of neural activities in SIVM and visually induced visual apparent motion (VIVM). We observed shared activations in the middle occipital area (V5/hMT), which is thought to be involved in visual motion processing, for SIVM and VIVM. Moreover, as compared to VIVM, SIVM resulted in greater activation in the superior temporal area and dominant functional connectivity between the V5/hMT area and the areas related to auditory and crossmodal motion processing. These findings indicate that similar but partially different neural mechanisms could be involved in auditory-induced and visually-induced motion perception, and neural signals in auditory, visual, and, crossmodal motion processing areas closely and directly interact in the perception of SIVM.
- 4D ultrasound study of fetal facial expressions in the third trimester of pregnancy. [Journal Article]
- JMJ Matern Fetal Neonatal Med 2017 May 29; :1-9
- CONCLUSIONS: Our results suggest that 4D ultrasound assessment of fetal facial expressions may be a useful modality for evaluating fetal brain maturation and development. The decreasing frequency of fetal yawning after 30 weeks of gestation may explain the emergence of distinct states of arousal.
- Qualitative assessment of tear dynamics with fluorescein profilometry. [Journal Article]
- CLCont Lens Anterior Eye 2017; 40(4):208-212
- CONCLUSIONS: Fluorescein profilometry allows clinicians to follow dynamic changes in the tear film on the entire ocular surface and may be used for qualitative assessment of the tear film dynamics.
New Search Next
- iTrack: instrumented mobile electrooculography (EOG) eye-tracking in older adults and Parkinson's disease. [Journal Article]
- PMPhysiol Meas 2017; 38(1):N16-N31
- Detection of saccades (fast eye-movements) within raw mobile electrooculography (EOG) data involves complex algorithms which typically process data acquired during seated static tasks only. Processin...
Detection of saccades (fast eye-movements) within raw mobile electrooculography (EOG) data involves complex algorithms which typically process data acquired during seated static tasks only. Processing of data during dynamic tasks such as walking is relatively rare and complex, particularly in older adults or people with Parkinson's disease (PD). Development of algorithms that can be easily implemented to detect saccades is required. This study aimed to develop an algorithm for the detection and measurement of saccades in EOG data during static (sitting) and dynamic (walking) tasks, in older adults and PD. Eye-tracking via mobile EOG and infra-red (IR) eye-tracker (with video) was performed with a group of older adults (n = 10) and PD participants (n = 10) (⩾50 years). Horizontal saccades made between targets set 5°, 10° and 15° apart were first measured while seated. Horizontal saccades were then measured while a participant walked and executed a 40° turn left and right. The EOG algorithm was evaluated by comparing the number of correct saccade detections and agreement (ICC2,1) between output from visual inspection of eye-tracker videos and IR eye-tracker. The EOG algorithm detected 75-92% of saccades compared to video inspection and IR output during static testing, with fair to excellent agreement (ICC2,1 0.49-0.93). However, during walking EOG saccade detection reduced to 42-88% compared to video inspection or IR output, with poor to excellent (ICC2,1 0.13-0.88) agreement between methodologies. The algorithm was robust during seated testing but less so during walking, which was likely due to increased measurement and analysis error with a dynamic task. Future studies may consider a combination of EOG and IR for comprehensive measurement.