Inverse design of crystals and quasicrystals in a non-additive binary mixture of hard disks.

The development of new materials typically involves a process of trial and error, guided by insights from past experimental and theoretical findings. The inverse design approach for soft-matter systems has the potential to optimize specific physical parameters, such as particle interactions, particle shape, or composition and packing fraction. This optimization aims to facilitate the spontaneous formation of specific target structures through self-assembly. In this study, we expand upon a recently introduced inverse design protocol for monodisperse systems to identify the required conditions and interactions for assembling crystal and quasicrystal phases within a binary mixture of two distinct species. This method utilizes an evolution algorithm to identify the optimal state point and interaction parameters, enabling the self-assembly of the desired structure. In addition, we employ a convolutional neural network (CNN) that classifies different phases based on their diffraction patterns, serving as a fitness function for the desired structure. Using our protocol, we successfully inverse design two-dimensional crystalline structures, including a hexagonal lattice and a dodecagonal quasicrystal, within a non-additive binary mixture of hard disks. Finally, we introduce a symmetry-based order parameter that leverages the encoded symmetry within the diffraction pattern. This order parameter circumvents the need for training a CNN and is used as a fitness function to inverse design an octagonal quasicrystal.

A deep-learning approach to realizing functionality in nanoelectronic devices.

Many nanoscale devices require precise optimization to function. Tuning them to the desired operation regime becomes increasingly difficult and time-consuming when the number of terminals and couplings grows. Imperfections and device-to-device variations hinder optimization that uses physics-based models. Deep neural networks (DNNs) can model various complex physical phenomena but, so far, are mainly used as predictive tools. Here, we propose a generic deep-learning approach to efficiently optimize complex, multi-terminal nanoelectronic devices for desired functionality. We demonstrate our approach for realizing functionality in a disordered network of dopant atoms in silicon. We model the input-output characteristics of the device with a DNN, and subsequently optimize control parameters in the DNN model through gradient descent to realize various classification tasks. When the corresponding control settings are applied to the physical device, the resulting functionality is as predicted by the DNN model. We expect our approach to contribute to fast, in situ optimization of complex (quantum) nanoelectronic devices.

Mixed Monolayers of Spiropyrans Maximize Tunneling Conductance Switching by Photoisomerization at the Molecule-Electrode Interface in EGaIn Junctions.

This paper describes the photoinduced switching of conductance in tunneling junctions comprising self-assembled monolayers of a spiropyran moiety using eutectic Ga-In top contacts. Despite separation of the spiropyran unit from the electrode by a long alkyl ester chain, we observe an increase in the current density J of a factor of 35 at 1 V when the closed form is irradiated with UV light to induce the ring-opening reaction, one of the highest switching ratios reported for junctions incorporating self-assembled monolayers. The magnitude of switching of hexanethiol mixed monolayers was higher than that of pure spiropyran monolayers. The first switching event recovers 100% of the initial value of J and in the mixed-monolayers subsequent dampening is not the result of degradation of the monolayer. The observation of increased conductivity is supported by zero-bias DFT calculations showing a change in the localization of the density of states near the Fermi level as well as by simulated transmission spectra revealing positive resonances that broaden and shift toward the Fermi level in the open form.

A Remarkable Multitasking Double Spiropyran: Bidirectional Visible-Light Switching of Polymer-Coated Surfaces with Dual Redox and Proton Gating.

Smart or functional surfaces that exhibit complex multimodal responsivity, e.g., to light, heat, pH, etc., although highly desirable, require a combination of distinct functional units to achieve each type of response and present a challenge in achieving combinations that can avoid cross-talk between the units, such as excited-state quenching. Compounds that exhibit multiple switching modalities help overcome this challenge and drastically reduce the synthetic cost and complexity. Here we show that a bis-spiropyran photochrome, which is formed through coupling at the indoline 5-position using redox chemistry, exhibits pH-gated photochromism, with opening of the spiro moiety by irradiation with UV light and the expected reversion by either heating or irradiation with visible light gated by protonation/deprotonation. Remarkably, when the photochrome is oxidized to its dicationic form, bis-spiropyran(2+), visible light can be used instead of UV light to switch between the spiro and merocyanine forms, with locking and unlocking of each state achieved by protonation/deprotonation. The formation of the bis-spiropyran unit by electrochemical coupling is exploited to generate "smart surfaces", i.e., polymer-modified electrodes, avoiding the need to introduce an ancillary functional group for polymerization and the concomitant potential for cross-talk. The approach taken means not only that the multiresponsive properties of the bis-spiropyran are retained upon immobilization but also that the effective switching rate can be enhanced dramatically.

A dithienylethene-based rewritable hydrogelator.

Dithienylethene photochromic switching units have been incorporated into a hydrogelating system based on a tripeptide motif. The resulting hybrid system provided both a photochromic response and the ability to gelate water under acidic and neutral conditions. Fluorescence spectroscopy shows that the dithienylethene units are in sufficient proximity to each other to stack in gel fibers, with the tripeptide unit determining solubility. TEM measurements provided insight into the microscopic structure of the fibers formed.

Light-controlled formation of vesicles and supramolecular organogels by a cholesterol-bearing amphiphilic molecular switch.

A new responsive material composed of an amphiphilic light-switchable dithienylethene unit functionalized with a hydrophobic cholesterol unit and a hydrophilic poly(ethylene glycol)-modified pyridinium group has been designed. This unique single-molecule system shows responsive light-switchable self-assembly in both water and organic solvents. Light-triggered reversible vesicle formation in aqueous solutions is reported. The molecule shows a different behavior in apolar aromatic solvents, in which light-controlled formation of organogel fibers is observed. The light-triggered aggregation behavior of this molecule demonstrates that control of a supramolecular structure with light can be achieved in both aqueous and organic media and that this ability can be present in a single molecule. This opens the way toward the effective development of new strategies in soft nanotechnology for applications in controlled chemical release systems.

Mechanically induced gel formation.

Mechanical triggering of gelation of an organic solution by a carbazole-based bisurea organogelator is described. Both the duration of the mechanical stimulation and the gelator concentration control the gelation process and the characteristics of the gel obtained.

Oxidative electrochemical aryl C-C coupling of spiropyrans.

The isolation and definitive assignment of the species formed upon electrochemical oxidation of nitro-spiropyran (SP) is reported. The oxidative aryl C-C coupling at the indoline moiety of the radical cation to form covalent dimers of the ring-closed form is demonstrated. The coupling is blocked with a methyl substituent para to the indoline nitrogen.

UV/vis and NIR light-responsive spiropyran self-assembled monolayers.

Self-assembled monolayers of a 6-nitro BIPS spiropyran (SP) modified with a disulfide-terminated aliphatic chain were prepared on polycrystalline gold surfaces and characterized by UV/vis absorption, surface-enhanced Raman scattering (SERS), and X-ray photoelectron spectroscopies (XPS). The SAMs obtained are composed of the ring-closed form (i.e., spiropyran) only. Irradiation with UV light results in conversion of the monolayer to the merocyanine form (MC), manifested in the appearance of an N(+) contribution in the N 1s region of the XPS spectrum of the SAMs, the characteristic absorption band of the MC form in the visible region at 555 nm, and the C-O stretching band in the SERS spectrum. Recovery of the initial state of the monolayer was observed both thermally and after irradiation with visible light. Several switching cycles were performed and monitored by SERS spectroscopy, demonstrating the stability of the SAMs during repeated switching between SP and MC states. A key finding in the present study is that ring-opening of the surface-immobilized spiropyrans can be induced by irradiation with continuous wave NIR (785 nm) light as well as by irradiation with UV light. We demonstrate that ring-opening by irradiation at 785 nm proceeds by a two-photon absorption pathway both in the SAMs and in the solid state. Hence, spiropyran SAMs on gold can undergo reversible photochemical switching from the SP to the MC form with both UV and NIR and the reverse reaction induced by irradiation with visible light or heating. Furthermore, the observation of NIR-induced switching with a continuous wave source holds important consequences in the study of photochromic switches on surfaces using SERS and emphasizes the importance of the use of multiple complementary techniques in characterizing photoresponsive SAMs.

Interpersonal behaviors and complementarity in interactions between teachers and kindergartners with a variety of externalizing and internalizing behaviors.

The present study investigated whether the complementarity principle (mutual interactive behaviors are opposite on control and similar on affiliation) applies to teacher-child interactions within the kindergarten classroom. Furthermore, it was examined whether interactive behaviors and complementarity depended on children's externalizing and internalizing behaviors, interaction time, and interaction frequency. A total of 48 teachers and 179 selected kindergartners with a variety of externalizing and internalizing behaviors were observed in a small group task setting in the natural ecology of the classroom. Teachers' and children's interactive behaviors were rated by independent observers. Teachers reported about children's externalizing and internalizing behaviors. Multilevel analyses indicated that both teachers and children reacted complementarily on the control dimension but not on the affiliation dimension. Teachers showed more control and more affiliation toward children with higher levels of internalizing behavior. In addition, teachers displayed less affiliation toward children with higher levels of externalizing behavior, whereas those children did not show less affiliation themselves. Teachers' and children's complementarity tendencies on control were weaker if children had higher levels of externalizing behavior.

Supporting teachers' relationships with disruptive children: the potential of relationship-focused reflection.

A relationship-focused reflection program (RFRP) was developed that targeted teachers' mental representations of relationships with specific children. Relative effectiveness was examined in a randomized comparative trial with repeated measures. Thirty-two teachers were assigned to the RFRP or the comparison intervention directly aimed at teacher behavior. Per teacher, two children (N = 64) were selected with above-median levels of externalizing behavior. Multilevel growth modeling was used to explore intervention effects on teacher-reported Closeness and Conflict, and observed Teacher Sensitivity and Behavior Management Quality. Teaching Efficacy was included as a moderator. The RFRP yielded changes over time in closeness for about half of the teacher-child dyads. In addition, teachers with high efficacy beliefs were more likely to report declines in conflict than low-efficacy teachers. Lastly, significant increases were found in observed sensitivity. These effects were different from those found in the comparison condition and provided preliminary evidence for the potential of in-depth reflection on specific relationships to promote teacher-child relationships.

[Tumor regression in malignant choroidal melanomas after transpupillary thermotherapy (TTT) versus ruthenium brachytherapy and sandwich therapy - a comparative analysis]. / Tumorregression maligner Aderhautmelanome nach Transpupillarer Thermotherapie (TTT) versus Ruthenium-Brachytherapie und Sandwichtherapie - eine vergleichende Analyse.

PURPOSE: The aim of this study was to evaluate tumour regression in a large series of choroidal melanomas, which were treated with three different eye-sparing treatment modalities. PATIENTS AND METHODS: Retrospective review of the treatment results in all eyes with malignant choroidal melanoma, which were treated in the University Eye Clinic of Mainz consecutively in the time span 1.1992 to 12.2000 with transpupillary thermotherapy (TTT, standard protocol Oosterhuis JA 1995), ruthenium brachytherapy (RB, tumor apex dose 150 Gy) or sandwich therapy (ST). One-step ST was defined as TTT followed by RB with 100 Gy tumor apex dose within 48 hours. The treatment of residual prominences with TTT secondary to RB after different time spans was called two-step ST. Follow-up was 2 years. RESULTS: 131 eyes with malignant choroidal melanoma (mean tumour thickness: 4.5 mm) were treated with RB (66 eyes), TTT (26 eyes) or ST (39 eyes). Preservation of the globe was achieved in 109 eyes (81 %). Local tumour control was found in small melanomas (prominence up to 3 mm) in 89 %, in large tumors (prominence 8 mm and higher) in 50 %. In a subgroup of small posterior melanomas (n = 70 eyes, prominence up to 4.5 mm, located posterior to the equator) local tumour control was noted in 91 %. The time span to reach local tumour control (Kaplan-Meier estimates) was the shortest after TTT (median: 20 weeks), compared with RB (48 weeks) and one-step ST (29 weeks). CONCLUSIONS: In choroidal melanomas the chance of local tumour control and preservation of the globe decreases with increase of the tumour prominence. In small choroidal melanomas with posterior location local tumour control was achieved significantly faster after TTT than after RB.

Internalizing behaviors among kindergarten children: measuring dimensions of social withdrawal with a checklist.

Three studies examined whether different types of withdrawal among young children could be assessed with a short checklist. In Study 1, kindergarten teachers rated 487 children on a modified version of the Behavior Questionnaire for Two- to Six-Year-Olds (BQTSYO). Exploratory factor analyses yielded 2 withdrawal factors, Social Inhibition and Solitary Behavior, and a factor of Emotional Dysregulation. In Study 2, an adjusted version of the checklist was completed for 858 kindergartners. The 3 factors of Social Inhibition, Solitary Behavior, and Emotional Dysregulation were identified in one half of the sample and confirmed in the other. They could be measured with 3 internally consistent scales. No gender differences were found on the scales. Their content validity was supported by unique associations with teachers' free descriptions of children's behaviors in Study 3. Results suggest that the instrument is adequate for the assessment of different types of withdrawal.