A-Site Cation Influence on the Structural and Optical Evolution of Ultrathin Lead Halide Perovskite Nanoplatelets.

Imposing quantum confinement has the potential to significantly modulate both the structural and optical parameters of interest in many material systems. In this work, we investigate strongly confined ultrathin perovskite nanoplatelets APbBr3. We compare the all-inorganic and hybrid compositions with the A-sites cesium and formamidinium, respectively. Compared to each other and their bulk counterparts, the materials show significant differences in variable-temperature structural and optical evolution. We quantify and correlate structural asymmetry with the excitonic transition energy, spectral purity, and emission rate. Negative thermal expansion, structural and photoluminescence asymmetry, photoluminescence full width at half-maximum, and splitting between bright and dark excitonic levels are found to be reduced in the hybrid composition. This work provides composition- and structure-based mechanisms for engineering of the excitons in these materials.

NAB2::STAT6 fusions and genome-wide DNA methylation profiling: Predictors of patient outcomes in meningeal solitary fibrous tumors.

Meningeal solitary fibrous tumors (SFT) are rare and have a high frequency of local recurrence and distant metastasis. In a cohort of 126 patients (57 female, 69 male; mean age at surgery 53.0 years) with pathologically confirmed meningeal SFTs with extended clinical follow-up (median 9.9 years; range 15 days-43 years), we performed extensive molecular characterization including genome-wide DNA methylation profiling (n = 80) and targeted TERT promoter mutation testing (n = 98). Associations were examined with NAB2::STAT6 fusion status (n = 101 cases; 51 = ex5-7::ex16-17, 26 = ex4::ex2-3; 12 = ex2-3::exANY/other and 12 = no fusion) and placed in the context of 2021 Central Nervous System (CNS) WHO grade. NAB2::STAT6 fusion breakpoints (fusion type) were significantly associated with metastasis-free survival (MFS) (p = 0.03) and, on multivariate analysis, disease-specific survival (DSS) when adjusting for CNS WHO grade (p = 0.03). DNA methylation profiling revealed three distinct clusters: Cluster 1 (n = 38), Cluster 2 (n = 22), and Cluster 3 (n = 20). Methylation clusters were significantly associated with fusion type (p < 0.001), with Cluster 2 harboring ex4::ex2-3 fusion in 16 (of 20; 80.0%), nearly all TERT promoter mutations (7 of 8; 87.5%), and predominantly an "SFT" histologic phenotype (15 of 22; 68.2%). Clusters 1 and 3 were less distinct, both dominated by tumors having ex5-7::ex16-17 fusion (respectively, 25 of 33; 75.8%, and 12 of 18; 66.7%) and with variable histological phenotypes. Methylation clusters were significantly associated with MFS (p = 0.027), but not overall survival (OS). In summary, NAB2::STAT6 fusion type was significantly associated with MFS and DSS, suggesting that tumors with an ex5::ex16-17 fusion may have inferior patient outcomes. Methylation clusters were significantly associated with fusion type, TERT promoter mutation status, histologic phenotype, and MFS.

Characteristics of ocular hypertension and uveitic glaucoma among patients with noninfectious uveitis.

OBJECTIVE: Ocular hypertension and uveitic glaucoma are important downstream sequela of noninfectious uveitis (NIU). Herein, we describe the clinical outcomes of NIU cases with ocular hypertension and uveitic glaucoma. DESIGN: Retrospective cohort study. PARTICIPANTS: All adults (≥18 years) with NIU under the care of uveitis subspecialty tertiary care clinics between 2010 and 2021 were included. METHODS: The primary outcomes were baseline and final visual acuity. RESULTS: A total of 216 patients out of 914 (23.6%) cases with NIU had ocular hypertension or uveitic glaucoma over the study period. Of all patients with ocular hypertension or uveitic glaucoma, 46% were corticosteroid responders. Baseline and last median visual acuities were better for the ocular hypertension patients compared with patients with uveitic glaucoma (p < 0.001). A higher proportion of patients with uveitic glaucoma than patients with ocular hypertension required glaucoma surgery (p < 0.001). The regression analyses suggested that baseline visual acuity and anatomical classification are significant predictors of last visual acuity, whereas diagnosis of ocular hypertension versus uveitic glaucoma were significant predictors of requirement for glaucoma surgery (p < 0.001). CONCLUSION: A quarter of patients with NIU in this study developed ocular hypertension or uveitic glaucoma. Approximately half of the patients with ocular hypertension or uveitic glaucoma were deemed to be corticosteroid responders. Baseline and last visual acuity outcomes are better amongst ocular hypertension patients compared with those with uveitic glaucoma. Poor baseline visual acuity and panuveitis are predictors of worse vision at last follow-up. Additionally, diagnosis of uveitic glaucoma was a significant predictor of requirement for glaucoma surgery.

Ensemble of deep convolutional neural networks is more accurate and reliable than board-certified ophthalmologists at detecting multiple diseases in retinal fundus photographs.

AIMS: To develop an algorithm to classify multiple retinal pathologies accurately and reliably from fundus photographs and to validate its performance against human experts. METHODS: We trained a deep convolutional ensemble (DCE), an ensemble of five convolutional neural networks (CNNs), to classify retinal fundus photographs into diabetic retinopathy (DR), glaucoma, age-related macular degeneration (AMD) and normal eyes. The CNN architecture was based on the InceptionV3 model, and initial weights were pretrained on the ImageNet dataset. We used 43 055 fundus images from 12 public datasets. Five trained ensembles were then tested on an 'unseen' set of 100 images. Seven board-certified ophthalmologists were asked to classify these test images. RESULTS: Board-certified ophthalmologists achieved a mean accuracy of 72.7% over all classes, while the DCE achieved a mean accuracy of 79.2% (p=0.03). The DCE had a statistically significant higher mean F1-score for DR classification compared with the ophthalmologists (76.8% vs 57.5%; p=0.01) and greater but statistically non-significant mean F1-scores for glaucoma (83.9% vs 75.7%; p=0.10), AMD (85.9% vs 85.2%; p=0.69) and normal eyes (73.0% vs 70.5%; p=0.39). The DCE had a greater mean agreement between accuracy and confident of 81.6% vs 70.3% (p<0.001). DISCUSSION: We developed a deep learning model and found that it could more accurately and reliably classify four categories of fundus images compared with board-certified ophthalmologists. This work provides proof-of-principle that an algorithm is capable of accurate and reliable recognition of multiple retinal diseases using only fundus photographs.

Motor cortex activation during visuomotor transformations: evoked potentials during overt and imagined movements.

Despite the prevalence of visuomotor transformations in our motor skills, their mechanisms remain incompletely understood, especially when imagery actions are considered such as mentally picking up a cup or pressing a button. Here, we used a stimulus-response task to directly compare the visuomotor transformation underlying overt and imagined button presses. Electroencephalographic activity was recorded while participants responded to highlights of the target button while ignoring the second, non-target button. Movement-related potentials (MRPs) and event-related desynchronization occurred for both overt movements and motor imagery (MI), with responses present even for non-target stimuli. Consistent with the activity accumulation model where visual stimuli are evaluated and transformed into the eventual motor response, the timing of MRPs matched the response time on individual trials. Activity-accumulation patterns were observed for MI, as well. Yet, unlike overt movements, MI-related MRPs were not lateralized, which appears to be a neural marker for the distinction between generating a mental image and transforming it into an overt action. Top-down response strategies governing this hemispheric specificity should be accounted for in future research on MI, including basic studies and medical practice.

Clinical characteristics of non-infectious uveitis treated with and without systemic immunomodulatory therapy.

OBJECTIVE: To compare the patient characteristics and long-term outcomes for those treated with and without systemic immunomodulatory therapy (IMT) for non-infectious uveitis (NIU). DESIGN: Retrospective cohort study. PARTICIPANTS: All consecutive adults with NIU receiving care at 5 uveitis subspecialty tertiary care clinics between 2010 and 2021. METHODS: Clinical outcomes were evaluated on initial presentation and at the last available follow-up. The main outcome measures were baseline characteristics and final visual acuity. RESULTS: A total of 914 NIU patients (418 IMT, 496 non-IMT) with a median age of 51.0 years and 57.4% female were identified. Over half the patients had bilateral disease, with a significantly higher proportion of bilateral cases in the IMT group compared with the non-IMT group (p < 0.001). The IMT group was more likely to have chronic uveitis (p < 0.001), with a higher proportion of patients experiencing cataracts and cystoid macular edema (p < 0.001 for both). A significantly higher proportion of non-IMT patients had anterior uveitis and an idiopathic etiology (p < 0.001). Overall, visual acuity improved significantly from baseline to last follow-up in the entire cohort (p < 0.001), with a slightly better improvement in the IMT group. Multivariable linear regression analysis suggested that baseline visual acuity and panuveitis were significant predictors of final visual acuity (p < 0.001 for both). CONCLUSIONS: NIU patients on IMT are often younger, suffer from bilateral and chronic uveitis, and are more likely to have ocular complications. Those in the non-IMT group are more likely to have anterior idiopathic NIU. Baseline visual acuity and panuveitis are the main predictors of final vision outcomes among patients with NIU.

Ultrafast dense DNA functionalization of quantum dots and rods for scalable 2D array fabrication with nanoscale precision.

Scalable fabrication of two-dimensional (2D) arrays of quantum dots (QDs) and quantum rods (QRs) with nanoscale precision is required for numerous device applications. However, self-assembly-based fabrication of such arrays using DNA origami typically suffers from low yield due to inefficient QD and QR DNA functionalization. In addition, it is challenging to organize solution-assembled DNA origami arrays on 2D device substrates while maintaining their structural fidelity. Here, we reduced manufacturing time from a few days to a few minutes by preparing high-density DNA-conjugated QDs/QRs from organic solution using a dehydration and rehydration process. We used a surface-assisted large-scale assembly (SALSA) method to construct 2D origami lattices directly on solid substrates to template QD and QR 2D arrays with orientational control, with overall loading yields exceeding 90%. Our fabrication approach enables the scalable, high fidelity manufacturing of 2D addressable QDs and QRs with nanoscale orientational and spacing control for functional 2D photonic devices.

Time-Resolved Line Shapes of Single Quantum Emitters via Machine Learned Photon Correlations.

Solid-state single-photon emitters (SPEs) are quantum light sources that combine atomlike optical properties with solid-state integration and fabrication capabilities. SPEs are hindered by spectral diffusion, where the emitter's surrounding environment induces random energy fluctuations. Timescales of spectral diffusion span nanoseconds to minutes and require probing single emitters to remove ensemble averaging. Photon correlation Fourier spectroscopy (PCFS) can be used to measure time-resolved single emitter line shapes, but is hindered by poor signal-to-noise ratio in the measured correlation functions at early times due to low photon counts. Here, we develop a framework to simulate PCFS correlation functions directly from diffusing spectra that match well with experimental data for single colloidal quantum dots. We use these simulated datasets to train a deep ensemble autoencoder machine learning model that outputs accurate, noiseless, and probabilistic reconstructions of the noisy correlations. Using this model, we obtain reconstructed time-resolved single dot emission line shapes at timescales as low as 10 ns, which are otherwise completely obscured by noise. This enables PCFS to extract optical coherence times on the same timescales as Hong-Ou-Mandel two-photon interference, but with the advantage of providing spectral information in addition to estimates of photon indistinguishability. Our machine learning approach is broadly applicable to different photon correlation spectroscopy techniques and SPE systems, offering an enhanced tool for probing single emitter line shapes on previously inaccessible timescales.

Investigating the influence of functional electrical stimulation on motor imagery related µ-rhythm suppression.

Background: Motor Imagery (MI) is a well-known cognitive technique that utilizes the same neural circuits as voluntary movements. Therefore, MI practice is widely used in sport training and post-stroke rehabilitation. The suppression of the µ-rhythm in electroencephalogram (EEG) is a conventional marker of sensorimotor cortical activation during motor imagery. However, the role of somatosensory afferentation in mental imagery processes is not yet clear. In this study, we investigated the impact of functional electrical stimulation (FES) on µ-rhythm suppression during motor imagery. Methods: Thirteen healthy experienced participants were asked to imagine their right hand grasping, while a 30-channel EEG was recorded. FES was used to influence sensorimotor activation during motor imagery of the same hand. Results: We evaluated cortical activation by estimating the µ-rhythm suppression index, which was assessed in three experimental conditions: MI, MI + FES, and FES. Our findings shows that motor imagery enhanced by FES leads to a more prominent µ-rhythm suppression. Obtained results suggest a direct effect of peripheral electrical stimulation on cortical activation, especially when combined with motor imagery. Conclusion: This research sheds light on the potential benefits of integrating FES into motor imagery-based interventions to enhance cortical activation and holds promise for applications in neurorehabilitation.

Single-Subject TMS Pulse Visualization on MRI-Based Brain Model: A precise method for mapping TMS pulses on cortical surface.

Highly accurate visualization of the points of transcranial magnetic stimulation (TMS) application on the brain cortical surface could provide anatomy-specific analysis of TMS effects. TMS is widely used to activate cortical areas with high spatial resolution, and neuronavigation enables site-specific TMS of particular gyrus sites. Precise control of TMS application points is crucial in determining the stimulation effects. Here, we propose a method that gives an opportunity to visualize and analyze the stimulated cortical sites by processing multi-parameter data.•This method uses MRI data to create a participant's brain model for visualization. The MRI data is segmented to obtain a raw 3D model, which is further optimized in 3D modeling software.•A Python script running in Blender uses the TMS coil's orientation data and participant's brain 3D model to define and mark the cortical sites affected by the particular TMS pulse.•The Python script can be easily customized to visualize TMS points task-specifically.

Event-Related Desynchronization Induced by Tactile Imagery: an EEG Study.

It is well known that both hand movements and mental representations of movement lead to event-related desynchronization (ERD) of the electroencephalogram (EEG) recorded over the corresponding cortical motor areas. However, the relationship between ERD in somatosensory cortical areas and mental representations of tactile sensations is not well understood. In this study, we employed EEG recordings in healthy humans to compare the effects of real and imagined vibrotactile stimulation of the right hand. Both real and imagined sensations produced contralateral ERD patterns, particularly in the µ-band and most significantly in the C3 region. Building on these results and the previous literature, we discuss the role of tactile imagery as part of the complex body image and the potential for using EEG patterns induced by tactile imagery as control signals in brain-computer interfaces (BCIs). Combining this approach with motor imagery (MI) could improve the performance of BCIs intended for rehabilitation of sensorimotor function after stroke and neural trauma.

Highly stable and pure single-photon emission with 250 ps optical coherence times in InP colloidal quantum dots.

Quantum photonic technologies such as quantum communication, sensing or computation require efficient, stable and pure single-photon sources. Epitaxial quantum dots (QDs) have been made capable of on-demand photon generation with high purity, indistinguishability and brightness, although they require precise fabrication and face challenges in scalability. By contrast, colloidal QDs are batch synthesized in solution but typically have broader linewidths, low single-photon purities and unstable emission. Here we demonstrate spectrally stable, pure and narrow-linewidth single-photon emission from InP/ZnSe/ZnS colloidal QDs. Using photon correlation Fourier spectroscopy, we observe single-dot linewidths as narrow as ~5 µeV at 4 K, giving a lower-bounded optical coherence time, T2, of ~250 ps. These dots exhibit minimal spectral diffusion on timescales of microseconds to minutes, and narrow linewidths are maintained on timescales up to 50 ms, orders of magnitude longer than other colloidal systems. Moreover, these InP/ZnSe/ZnS dots have single-photon purities g(2)(τ = 0) of 0.077-0.086 in the absence of spectral filtering. This work demonstrates the potential of heavy-metal-free InP-based QDs as spectrally stable sources of single photons.

Beyond passive observation: feedback anticipation and observation activate the mirror system in virtual finger movement control via P300-BCI.

Action observation (AO) is widely used as a post-stroke therapy to activate sensorimotor circuits through the mirror neuron system. However, passive observation is often considered to be less effective and less interactive than goal-directed movement observation, leading to the suggestion that observation of goal-directed actions may have stronger therapeutic potential, as goal-directed AO has been shown to activate mechanisms for monitoring action errors. Some studies have also suggested the use of AO as a form of Brain-computer interface (BCI) feedback. In this study, we investigated the potential for observation of virtual hand movements within a P300-based BCI as a feedback system to activate the mirror neuron system. We also explored the role of feedback anticipation and estimation mechanisms during movement observation. Twenty healthy subjects participated in the study. We analyzed event-related desynchronization and synchronization (ERD/S) of sensorimotor EEG rhythms and Error-related potentials (ErrPs) during observation of virtual hand finger flexion presented as feedback in the P300-BCI loop and compared the dynamics of ERD/S and ErrPs during observation of correct feedback and errors. We also analyzed these EEG markers during passive AO under two conditions: when subjects anticipated the action demonstration and when the action was unexpected. A pre-action mu-ERD was found both before passive AO and during action anticipation within the BCI loop. Furthermore, a significant increase in beta-ERS was found during AO within incorrect BCI feedback trials. We suggest that the BCI feedback may exaggerate the passive-AO effect, as it engages feedback anticipation and estimation mechanisms as well as movement error monitoring simultaneously. The results of this study provide insights into the potential of P300-BCI with AO-feedback as a tool for neurorehabilitation.

Uncovering temperature-dependent exciton-polariton relaxation mechanisms in hybrid organic-inorganic perovskites.

Hybrid perovskites have emerged as a promising material candidate for exciton-polariton (polariton) optoelectronics. Thermodynamically, low-threshold Bose-Einstein condensation requires efficient scattering to the polariton energy dispersion minimum, and many applications demand precise control of polariton interactions. Thus far, the primary mechanisms by which polaritons relax in perovskites remains unclear. In this work, we perform temperature-dependent measurements of polaritons in low-dimensional perovskite wedged microcavities achieving a Rabi splitting of [Formula: see text] = 260 ± 5 meV. We change the Hopfield coefficients by moving the optical excitation along the cavity wedge and thus tune the strength of the primary polariton relaxation mechanisms in this material. We observe the polariton bottleneck regime and show that it can be overcome by harnessing the interplay between the different excitonic species whose corresponding dynamics are modified by strong coupling. This work provides an understanding of polariton relaxation in perovskites benefiting from efficient, material-specific relaxation pathways and intracavity pumping schemes from thermally brightened excitonic species.

Elastic Phonon Scattering Dominates Dephasing in Weakly Confined Cesium Lead Bromide Nanocrystals at Cryogenic Temperatures.

Cesium lead halide perovskite nanocrystals (PNCs) have emerged as a potential next-generation single quantum emitter (QE) material for quantum optics and quantum information science. Optical dephasing processes at cryogenic temperatures are critical to the quality of a QE, making a mechanistic understanding of coherence losses of fundamental interest. We use photon-correlation Fourier spectroscopy (PCFS) to obtain a lower bound to the optical coherence times of single PNCs as a function of temperature. We find that 20 nm CsPbBr3 PNCs emit nearly exclusively into a narrow zero-phonon line from 4 to 13 K. Remarkably, no spectral diffusion is observed at time scales of 10 µs to 5 ms. Our results suggest that exciton dephasing in this temperature range is dominated by elastic scattering from phonon modes with characteristic frequencies of 1-3 meV, while inelastic scattering is minimal due to weak exciton-phonon coupling.

Antiviral therapy defiant mixed viral retinitis post hematopoietic allogeneic stem cell transplant.

Cytomegalovirus (CMV) retinitis is an uncommon presentation post allogeneic transplant and can be vision-threatening. Our case demonstrates the occurrence of polymerase chain reaction (PCR) proven mixed viral retinitis (cytomegalovirus and varicella zoster virus) post allogeneic stem cell transplant despite multiple prophylactic antiviral therapies, including letermovir, and in the documented absence of CMV DNAemia. A 21-year-old female with acute myeloid leukemia presented with mixed viral retinitis (cytomegalovirus and varicella zoster virus) post allogenic transplant. This presentation occurred despite ongoing standard prophylaxis for both of these viruses, as well as following two courses of treatment for CMV viremia, with a documented negative CMV PCR in the blood prior to the presentation with retinitis. The patient was treated with intravenous ganciclovir and subsequently transitioned to oral valganciclovir with durable resolution of the retinitis. We report a rare case of mixed viral retinitis occurring despite multiple antiviral prophylaxes including letermovir and with PCR-documented absence of preceding CMV viremia, in a post-allogeneic stem cell transplant patient, with PCR of the aqueous fluid demonstrating two viral populations. With very little existing literature on either mixed viral retinitis or CMV retinitis during letermovir prophylaxis, this case expands the literature on both topics. CMV retinitis is an uncommon potentially vision threatening presentation post hematopoietic stem cell transplant, and can occur due to early CMV reactivation, low CD4 count, and delayed CD4 lymphocyte recovery. Letermovir has poor CNS and retinal penetration. This case highlights the need for more research on secondary prophylaxis with letermovir.

Controlled Assembly and Anomalous Thermal Expansion of Ultrathin Cesium Lead Bromide Nanoplatelets.

Quantum confined lead halide perovskite nanoplatelets are anisotropic materials displaying strongly bound excitons with spectrally pure photoluminescence. We report the controlled assembly of CsPbBr3 nanoplatelets through varying the evaporation rate of the dispersion solvent. We confirm the assembly of superlattices in the face-down and edge-up configurations by electron microscopy, as well as X-ray scattering and diffraction. Polarization-resolved spectroscopy shows that superlattices in the edge-up configuration display significantly polarized emission compared to face-down counterparts. Variable-temperature X-ray diffraction of both face-down and edge-up superlattices uncovers a uniaxial negative thermal expansion in ultrathin nanoplatelets, which reconciles the anomalous temperature dependence of the emission energy. Additional structural aspects are investigated by multilayer diffraction fitting, revealing a significant decrease in superlattice order with decreasing temperature, with a concomitant expansion of the organic sublattice and increase of lead halide octahedral tilt.