Variable transmission optical filter based on an actuated origami structure.

A variable transmission thin film for visible light is proposed based on a mechanically actuated origami structure coated with metallic nanoparticles. The transmissivity can be tuned continuously from 0 to >90% for unpolarized incident light. Power is only required for switching and is not necessary to maintain the desired transmittance state. The asymmetric metal nanorods create two distinct plasmon resonances. Controlling the orientation of the nanorods with respect to the direction of the incident light changes the optical transmittance. The switching speed is only limited by the mechanical actuation and not by the optical response of the materials. The applicability of the proposed film for smart glass applications is investigated. Good image transmission clarity with minimal distortion is shown.

An in vitro evaluation of Icon resin infiltrant penetration into demineralized enamel lesions using an indirect staining technique with confocal laser scanning microscope analysis in dual fluorescence mode.

Context: White spot lesion is the first clinical sign of a caries lesion and represents mineral loss from the enamel subsurface. Aim: The aim of this study was to evaluate the penetration depth (PD) of Icon resin infiltrant into artificially demineralized enamel lesions using confocal laser scanning microscope (CLSM) analysis in dual fluorescence mode. Settings and Designs: The design of the study was an in vitro study. Materials and Methods: 22 extracted human permanent maxillary central incisor teeth were collected, and enamel sections were obtained from the coronal middle third. All enamel specimens were exposed to demineralization and remineralization solutions for 14 days. On positive confirmation of enamel demineralization by scanning electron microscope analysis, 20 specimens were then subjected to Icon resin infiltration following manufacturer instructions. Specimens were processed with indirect staining technique using rhodamine B and sodium fluorescein dyes and examined under CLSM at ×10 magnification in dual fluorescence mode using ImageJ software to evaluate PD of resin infiltrant into demineralized enamel lesions. Statistical Analysis Used: Obtained data were analyzed using an independent t-test. P ≤0.05 was considered statistically significant. Results: The maximum depth of demineralized enamel lesion was 590 µm, and the mean depth was 290.78 ± 14.80 µm. The maximum depth of resin infiltrant penetration was 580 µm, and the mean depth was 279.08 ± 13.88 µm; P = 0.006. The percentage penetration of resin infiltrant was 95.99%. Conclusion: Icon resin infiltrant was highly effective in its depth of penetration into demineralized enamel lesions. The use of indirect staining and CLSM analysis in dual fluorescence mode is more reliable and accurate technique to evaluate the PD of resin infiltrant.

In-Vitro Evaluation of Dental Adhesive Bond Strength With Diode Laser Irradiation Before Photopolymerization.

AIM: In-vitro evaluation of shear bond strength, mode of failure, and adaptation of fifth-generation (etch-and-rinse), seventh-generation,and eighth-generation self-etch dental adhesives to human dentin with or without diode-laser irradiation before photopolymerization. MATERIALS AND METHODS: Seventy-two extracted human maxillary premolar teeth were collected. The buccal and lingual surfaces of teeth were grounded until dentin was exposed. Test areas of 4 mm diameter were created on both surfaces of teeth to standardize the area of treatment. The samples were then randomly allocated into three groups (n = 24): Group 1 Adper Single Bond 2 Etch-and-Rinse; Group 2 Tetric-N-Bond Universal Self-Etch; Group 3 Prime and Bond Universal Self-Etch dental adhesives were used. Buccal surfaces (sub-groups 'a') of all specimens were irradiated with diode laser before photopolymerization of the adhesive material, and palatal surfaces (sub-groups 'b') were directly photopolymerized without prior diode laser irradiation and restored with composite resin. All specimens were thermocycled. Four specimens from each group were then subjected to scanning electron microscopy (SEM) analysis to examine the adaptation of adhesive to dentin, and the remaining 60 specimens were evaluated for shear bond strength tests, modes of failure at the adhesive-dentin interface, and values were recorded, tabulated, and used for data analysis. A one-way ANOVA test and the Student's t-test were used for statistical analysis. A P value ≤ 0.05 was considered statistically significant. RESULTS: The mean shear bond strength for the groups was: Group 1a (13.96 MPa), 1b (14.95 MPa); Group 2a (10.06 MPa), 2b (10.30 MPa); Group 3a (12.03 MPa), and 3b (10.44 MPa). No statistically significant difference was seen among sub-groups 1a and 3a, 2a and 3a, 2b and 3b as P > 0.05. A significant difference was seen among sub-groups 1b and 3b (P<0.05), 1a and 2a, and 1b and 2b (P<0.01). CONCLUSION: Adper Single Bond 2 without diode-laser irradiation before photopolymerization showed the highest shear bond strength, followed by Adper Single Bond 2 irradiated with diode laser before photopolymerization, with the maximum adaptation of dental adhesive to dentin compared to other adhesives used either with or without diode-laser irradiation.

Cell-type-specific cholinergic control of granular retrosplenial cortex with implications for angular velocity coding across brain states.

Cholinergic receptor activation enables the persistent firing of cortical pyramidal neurons, providing a key cellular basis for theories of spatial navigation involving working memory, path integration, and head direction encoding. The granular retrosplenial cortex (RSG) is important for spatially-guided behaviors, but how acetylcholine impacts RSG neurons is unknown. Here, we show that a transcriptomically, morphologically, and biophysically distinct RSG cell-type - the low-rheobase (LR) neuron - has a very distinct expression profile of cholinergic muscarinic receptors compared to all other neighboring excitatory neuronal subtypes. LR neurons do not fire persistently in response to cholinergic agonists, in stark contrast to all other principal neuronal subtypes examined within the RSG and across midline cortex. This lack of persistence allows LR neuron models to rapidly compute angular head velocity (AHV), independent of cholinergic changes seen during navigation. Thus, LR neurons can consistently compute AHV across brain states, highlighting the specialized RSG neural codes supporting navigation.

Running speed and REM sleep control two distinct modes of rapid interhemispheric communication.

Rhythmic gamma-band communication within and across cortical hemispheres is critical for optimal perception, navigation, and memory. Here, using multisite recordings in both rats and mice, we show that even faster ∼140 Hz rhythms are robustly anti-phase across cortical hemispheres, visually resembling splines, the interlocking teeth on mechanical gears. Splines are strongest in superficial granular retrosplenial cortex, a region important for spatial navigation and memory. Spline-frequency interhemispheric communication becomes more coherent and more precisely anti-phase at faster running speeds. Anti-phase splines also demarcate high-activity frames during REM sleep. While splines and associated neuronal spiking are anti-phase across retrosplenial hemispheres during navigation and REM sleep, gamma-rhythmic interhemispheric communication is precisely in-phase. Gamma and splines occur at distinct points of a theta cycle and thus highlight the ability of interhemispheric cortical communication to rapidly switch between in-phase (gamma) and anti-phase (spline) modes within individual theta cycles during both navigation and REM sleep.

Instantaneous amplitude and shape of postrhinal theta oscillations differentially encode running speed.

Hippocampal theta oscillations have a temporally asymmetric waveform shape, but it is not known if this theta asymmetry extends to all other cortical regions involved in spatial navigation and memory. Here, using both established and improved cycle-by-cycle analysis methods, we show that theta waveforms in the postrhinal cortex are also temporally asymmetric. On average, the falling phase of postrhinal theta cycles lasts longer than the subsequent rising phase. There are, however, rapid changes in both the instantaneous amplitude and instantaneous temporal asymmetry of postrhinal theta cycles. These rapid changes in amplitude and asymmetry are very poorly correlated, indicative of a mechanistic disconnect between these theta cycle features. We show that the instantaneous amplitude and asymmetry of postrhinal theta cycles differentially encode running speed. Although theta amplitude continues to increase at the fastest running speeds, temporal asymmetry of the theta waveform shape plateaus after medium speeds. Our results suggest that the amplitude and waveform shape of individual postrhinal theta cycles may be governed by partially independent mechanisms and emphasize the importance of employing a single cycle approach to understanding the genesis and behavioral correlates of cortical theta rhythms. (PsycInfo Database Record (c) 2021 APA, all rights reserved).