Ultrahigh-efficient material informatics inverse design of thermal metamaterials for visible-infrared-compatible camouflage.

Multispectral camouflage technologies, especially in the most frequently-used visible and infrared (VIS-IR) bands, are in increasing demand for the ever-growing multispectral detection technologies. Nevertheless, the efficient design of proper materials and structures for VIS-IR camouflage is still challenging because of the stringent requirement for selective spectra in a large VIS-IR wavelength range and the increasing demand for flexible color and infrared signal adaptivity. Here, a material-informatics-based inverse design framework is proposed to efficiently design multilayer germanium (Ge) and zinc sulfide (ZnS) metamaterials by evaluating only ~1% of the total candidates. The designed metamaterials exhibit excellent color matching and infrared camouflage performance from different observation angles and temperatures through both simulations and infrared experiments. The present material informatics inverse design framework is highly efficient and can be applied to other multi-objective optimization problems beyond multispectral camouflage.

Directional Radiative Cooling via Exceptional Epsilon-Based Microcavities.

The advent of nanophotonics enables the regulation of thermal emission in the momentum domain as well as in the frequency domain. However, earlier attempts to steer thermal emission in a certain direction were restricted to a narrow spectrum or specific polarization, and thus their average (8-14 µm) emissivity (εav) and angular selectivity were nominal. Therefore, the practical uses of directional thermal emitters have remained unclarified. Here, we report broadband, polarization-irrelevant, amplified directional thermal emission from hollow microcavities covered with deep-subwavelength-thickness oxide shells. A hexagonal array of SiO2/AlOX (100/100 nm) hollow microcavities designed by Bayesian optimization exhibited εav values of 0.51-0.62 at 60°-75° and 0.29-0.32 at 5°-20°, yielding a parabolic antenna-shaped distribution. The angular selectivity peaked at 8, 9.1, 10.9, and 12 µm, which were identified as the epsilon-near-zero (via Berreman modes) and maximum-negative-permittivity (via photon-tunneling modes) wavelengths of SiO2 and AlOX, respectively, thus supporting phonon-polariton resonance mediated broadband side emission. As proof-of-concept experiments, we demonstrated that these exceptional epsilon-based microcavities could provide thermal comfort to users and practical cooling performance to optoelectronic devices.

High-index-contrast photonic structures: a versatile platform for photon manipulation.

In optics, the refractive index of a material and its spatial distribution determine the characteristics of light propagation. Therefore, exploring both low- and high-index materials/structures is an important consideration in this regard. Hollow cavities, which are defined as low-index bases, exhibit a variety of unusual or even unexplored optical characteristics and are used in numerous functionalities including diffraction gratings, localised optical antennas and low-loss resonators. In this report, we discuss the fabrication of hollow cavities of various sizes (0.2-5 µm in diameter) that are supported by conformal dielectric/metal shells, as well as their specific applications in the ultraviolet (photodetectors), visible (light-emitting diodes, solar cells and metalenses), near-infrared (thermophotovoltaics) and mid-infrared (radiative coolers) regions. Our findings demonstrate that hollow cavities tailored to specific spectra and applications can serve as versatile optical platforms to address the limitations of current optoelectronic devices. Furthermore, hollow cavity embedded structures are highly elastic and can minimise the thermal stress caused by high temperatures. As such, future applications will likely include high-temperature devices such as thermophotovoltaics and concentrator photovoltaics.

Music training modulates theta brain oscillations associated with response suppression.

There is growing interest in developing training programs to mitigate cognitive decline associated with normal aging. Here, we assessed the effect of 3-month music and visual art training programs on the oscillatory brain activity of older adults using a partially randomized intervention design. High-density electroencephalography (EEG) was measured during the pre- and post-training sessions while participants completed a visual GoNoGo task. Time-frequency representations were calculated in regions of interest encompassing the visual, parietal, and prefrontal cortices. Before training, NoGo trials generated greater theta power than Go trials from 300 to 500 ms post-stimulus in mid-central and frontal brain areas. Theta power indexing response suppression was significantly reduced after music training. There was no significant difference between pre- and post-test for the visual art or the control group. The effect of music training on theta power indexing response suppression was associated with reduced functional connectivity between prefrontal, visual, and auditory regions. These results suggest that theta power indexes executive control mechanisms in older adults. Music training affects theta power and functional connectivity associated with response suppression. These findings contribute to a better understanding of inhibitory control ability in older adults and the neuroplastic effects of music interventions.

Music and Visual Art Training Modulate Brain Activity in Older Adults.

Cognitive decline is an unavoidable aspect of aging that impacts important behavioral and cognitive skills. Training programs can improve cognition, yet precise characterization of the psychological and neural underpinnings supporting different training programs is lacking. Here, we assessed the effect and maintenance (3-month follow-up) of 3-month music and visual art training programs on neuroelectric brain activity in older adults using a partially randomized intervention design. During the pre-, post-, and follow-up test sessions, participants completed a brief neuropsychological assessment. High-density EEG was measured while participants were presented with auditory oddball paradigms (piano tones, vowels) and during a visual GoNoGo task. Neither training program significantly impacted psychometric measures, compared to a non-active control group. However, participants enrolled in the music and visual art training programs showed enhancement of auditory evoked responses to piano tones that persisted for up to 3 months after training ended, suggesting robust and long-lasting neuroplastic effects. Both music and visual art training also modulated visual processing during the GoNoGo task, although these training effects were relatively short-lived and disappeared by the 3-month follow-up. Notably, participants enrolled in the visual art training showed greater changes in visual evoked response (i.e., N1 wave) amplitude distribution than those from the music or control group. Conversely, those enrolled in music showed greater response associated with inhibitory control over the right frontal scalp areas than those in the visual art group. Our findings reveal a causal relationship between art training (music and visual art) and neuroplastic changes in sensory systems, with some of the neuroplastic changes being specific to the training regimen.

Different neural activities support auditory working memory in musicians and bilinguals.

Musical training and bilingualism benefit executive functioning and working memory (WM)-however, the brain networks supporting this advantage are not well specified. Here, we used functional magnetic resonance imaging and the n-back task to assess WM for spatial (sound location) and nonspatial (sound category) auditory information in musician monolingual (musicians), nonmusician bilinguals (bilinguals), and nonmusician monolinguals (controls). Musicians outperformed bilinguals and controls on the nonspatial WM task. Overall, spatial and nonspatial WM were associated with greater activity in dorsal and ventral brain regions, respectively. Increasing WM load yielded similar recruitment of the anterior-posterior attention network in all three groups. In both tasks and both levels of difficulty, musicians showed lower brain activity than controls in superior prefrontal frontal gyrus and dorsolateral prefrontal cortex (DLPFC) bilaterally, a finding that may reflect improved and more efficient use of neural resources. Bilinguals showed enhanced activity in language-related areas (i.e., left DLPFC and left supramarginal gyrus) relative to musicians and controls, which could be associated with the need to suppress interference associated with competing semantic activations from multiple languages. These findings indicate that the auditory WM advantage in musicians and bilinguals is mediated by different neural networks specific to each life experience.

The relationship between eye movements and subsequent recognition: Evidence from individual differences and amnesia.

There is consistent agreement regarding the positive relationship between cumulative eye movement sampling and subsequent recognition, but the role of the hippocampus in this sampling behavior is currently unknown. It is also unclear whether the eye movement repetition effect, i.e., fewer fixations to repeated, compared to novel, stimuli, depends on explicit recognition and/or an intact hippocampal system. We investigated the relationship between cumulative sampling, the eye movement repetition effect, subsequent memory, and the hippocampal system. Eye movements were monitored in a developmental amnesic case (H.C.), whose hippocampal system is compromised, and in a group of typically developing participants while they studied single faces across multiple blocks. The faces were studied from the same viewpoint or different viewpoints and were subsequently tested with the same or different viewpoint. Our previous work suggested that hippocampal representations support explicit recognition for information that changes viewpoint across repetitions (Olsen et al., 2015). Here, examination of eye movements during encoding indicated that greater cumulative sampling was associated with better memory among controls. Increased sampling, however, was not associated with better explicit memory in H.C., suggesting that increased sampling only improves memory when the hippocampal system is intact. The magnitude of the repetition effect was not correlated with cumulative sampling, nor was it related reliably to subsequent recognition. These findings indicate that eye movements collect information that can be used to strengthen memory representations that are later available for conscious remembering, whereas eye movement repetition effects reflect a processing change due to experience that does not necessarily reflect a memory representation that is available for conscious appraisal. Lastly, H.C. demonstrated a repetition effect for fixed viewpoint faces but not for variable viewpoint faces, which suggests that repetition effects are differentially supported by neocortical and hippocampal systems, depending upon the representational nature of the underlying memory trace.

Effects of short-term music and second-language training on executive control.

Separate lines of research have identified enhanced performance on nonverbal executive control (EC) tasks for bilinguals and those with music training, but little is known about the relation between them in terms of the specificity of the effects of each experience or the degree of exposure necessary to induce these changes. Using an intervention design, the current study pseudorandomly assigned 57 4- to 6-year-old children (matched on age, maternal education, and cognitive scores) to a 20-day training program offering instruction in either music or conversational French. The test battery consisted of verbal and nonverbal tasks requiring EC. All children improved on these tasks following training with some training-specific differences. No changes were observed on background or working memory measures after either training, ruling out simple practice effects. Children in both groups had better scores on the most challenging condition of a grammaticality sentence judgment task in which it was necessary to ignore conflict introduced through misleading semantic content. Children in both training groups also showed better accuracy on the easier condition of a nonverbal visual search task at post-test, but children in the French training group also showed significant improvement on the more challenging condition of this task. These results are discussed in terms of emergent EC benefits of language and music training.

The role of relational binding in item memory: evidence from face recognition in a case of developmental amnesia.

Current theories state that the hippocampus is responsible for the formation of memory representations regarding relations, whereas extrahippocampal cortical regions support representations for single items. However, findings of impaired item memory in hippocampal amnesics suggest a more nuanced role for the hippocampus in item memory. The hippocampus may be necessary when the item elements need to be bound within and across episodes to form a lasting representation that can be used flexibly. The current investigation was designed to test this hypothesis in face recognition. H.C., an individual who developed with a compromised hippocampal system, and control participants incidentally studied individual faces that either varied in presentation viewpoint across study repetitions or remained in a fixed viewpoint across the study repetitions. Eye movements were recorded during encoding and participants then completed a surprise recognition memory test. H.C. demonstrated altered face viewing during encoding. Although the overall number of fixations made by H.C. was not significantly different from that of controls, the distribution of her viewing was primarily directed to the eye region. Critically, H.C. was significantly impaired in her ability to subsequently recognize faces studied from variable viewpoints, but demonstrated spared performance in recognizing faces she encoded from a fixed viewpoint, implicating a relationship between eye movement behavior in the service of a hippocampal binding function. These findings suggest that a compromised hippocampal system disrupts the ability to bind item features within and across study repetitions, ultimately disrupting recognition when it requires access to flexible relational representations.

Short-term second language and music training induces lasting functional brain changes in early childhood.

Immediate and lasting effects of music or second-language training were examined in early childhood using event-related potentials. Event-related potentials were recorded for French vowels and musical notes in a passive oddball paradigm in thirty-six 4- to 6-year-old children who received either French or music training. Following training, both groups showed enhanced late discriminative negativity (LDN) in their trained condition (music group-musical notes; French group-French vowels) and reduced LDN in the untrained condition. These changes reflect improved processing of relevant (trained) sounds, and an increased capacity to suppress irrelevant (untrained) sounds. After 1 year, training-induced brain changes persisted and new hemispheric changes appeared. Such results provide evidence for the lasting benefit of early intervention in young children.

Efficient utilization of greenhouse gases in a gas-to-liquids process combined with CO2/steam-mixed reforming and Fe-based Fischer-Tropsch synthesis.

Two process models for carbon dioxide utilized gas-to-liquids (GTL) process (CUGP) mainly producing light olefins and Fischer-Tropsch (F-T) synthetic oils were developed by Aspen Plus software. Both models are mainly composed of a reforming unit, an F-T synthesis unit and a recycle unit, while the main difference is the feeding point of fresh CO2. In the reforming unit, CO2 reforming and steam reforming of methane are combined together to produce syngas in flexible composition. Meanwhile, CO2 hydrogenation is conducted via reverse water gas shift on the Fe-based catalysts in the F-T synthesis unit to produce hydrocarbons. After F-T synthesis, the unreacted syngas is recycled to F-T synthesis and reforming units to enhance process efficiency. From the simulation results, it was found that the carbon efficiencies of both CUGP options were successfully improved, and total CO2 emissions were significantly reduced, compared with the conventional GTL processes. The process efficiency was sensitive to recycle ratio and more recycle seemed to be beneficial for improving process efficiency and reducing CO2 emission. However, the process efficiency was rather insensitive to split ratio (recycle to reforming unit/total recycle), and the optimum split ratio was determined to be zero.

Broadly tuned face representation in older adults assessed by categorical perception.

Studies of face recognition in older adults (60 years of age and older) report increases in false alarms over younger adults (usually 18-30 years of age), but no age differences in hits. To examine this phenomenon, we compared older and younger adults in categorical perception of faces. We hypothesized that face representations in older adults would be broadly tuned, resulting in overlapping representations, manifested by a shallower slope in identity categorization than in younger adults, and age-related reductions in the advantage for between-categories, as compared with within-category, face discrimination. We morphed faces to change linearly from one identity to another. We used familiar or unfamiliar faces in separate conditions to examine the role of familiarity. Categorical perception was assessed in an identity-classification task and a discrimination task. Older adults showed a shallower slope and poorer discrimination compared with younger adults, and both groups exhibited better performance with familiar than unfamiliar faces. Enhanced discriminability for between-categories as compared with within-category faces was seen for both familiar and unfamiliar faces in younger adults, but only for familiar faces in older adults. The more broadly tuned representations of unfamiliar faces in older adults may lead to misidentification and greater false alarms for unfamiliar faces, but not for familiar faces.

Age-related dedifferentiation and compensatory changes in the functional network underlying face processing.

Recent evidence has shown that older adults fail to show adaptation in the right fusiform gyrus (FG) to the same face presented repeatedly, despite accurate detection of the previously presented face. We used functional magnetic resonance imaging to investigate whether this phenomenon is associated with age-related reductions in face specificity in brain activity and whether older adults compensate for these face-processing deficiencies by increasing activity in other areas within the face-processing network, or outside this network. A comparison of brain activity across multiple stimulus categories showed that, unlike young adults who engaged a number of brain regions specific to face processing, older adults generalized these patterns of activity to objects and houses. Also, young adults showed functional connectivity between the right FG and its homologous region during face processing, whereas older adults did not engage the left FG but showed a functional connection between the right FG and left orbitofrontal cortex. Finally, this frontotemporal functional connection was activated more strongly in older adults who performed better on a face-matching task (done outside of the scanner), suggesting increased involvement of this functional link for successful face recognition with increasing age. These findings suggest that 2 neural mechanisms, dedifferentiation and compensatory neural recruitment, underlie age differences in face processing.

Neural correlates of temporal integration in face recognition: an fMRI study.

Integration of temporally separated visual inputs is crucial for perception of a unified representation. Here, we show that regions involved in configural processing of faces contribute to temporal integration occurring within a limited time-window using a multivariate analysis (partial least squares, PLS) exploring the relation between brain activity and recognition performance. During fMRI, top and bottom parts of a famous face were presented sequentially with a varying interval (0, 200, or 800 ms) or were misaligned. The 800 ms condition activated several regions implicated in face processing, attention and working memory, relative to the other conditions, suggesting more active maintenance of individual face parts. Analysis of brain-behavior correlations showed that better identification in the 0 and 200 conditions was associated with increased activity in areas considered to be part of a configural face processing network, including right fusiform, middle occipital, bilateral superior temporal areas, anterior/middle cingulate and frontal cortices. In contrast, successful recognition in the 800 and misaligned conditions, which involve analytic and strategic processing, was negatively associated with activation in these regions. Thus, configural processing may involve rapid temporal integration of facial features and their relations. Our finding that regions concerned with configural and analytic processes in the service of face identification opposed each other may explain why it is difficult to apply the two processes concurrently.

Face processing changes in normal aging revealed by fMRI adaptation.

We investigated the neural correlates of facial processing changes in healthy aging using fMRI and an adaptation paradigm. In the scanner, participants were successively presented with faces that varied in identity, viewpoint, both, or neither and performed a head size detection task independent of identity or viewpoint. In right fusiform face area (FFA), older adults failed to show adaptation to the same face repeatedly presented in the same view, which elicited the most adaptation in young adults. We also performed a multivariate analysis to examine correlations between whole-brain activation patterns and behavioral performance in a face-matching task tested outside the scanner. Despite poor neural adaptation in right FFA, high-performing older adults engaged the same face-processing network as high-performing young adults across conditions, except the one presenting a same facial identity across different viewpoints. Low-performing older adults used this network to a lesser extent. Additionally, high-performing older adults uniquely recruited a set of areas related to better performance across all conditions, indicating age-specific involvement of this added network. This network did not include the core ventral face-processing areas but involved the left inferior occipital gyrus, frontal, and parietal regions. Although our adaptation results show that the neuronal representations of the core face-preferring areas become less selective with age, our multivariate analysis indicates that older adults utilize a distinct network of regions associated with better face matching performance, suggesting that engaging this network may compensate for deficiencies in ventral face processing regions.

Control of mode of crystal networking during monolayer assembly of microcrystals on water.

A series of hydrocarbon (HC)-coated cubic zeolite microcrystals (1.7 microm) was prepared. The HCs were n-octyl, n-dodecyl, methyl n-undecanoate, n-octadecyl, and n-heptadecafluorodecyl. The measured water contact angles (theta) of the corresponding HC-coated glass plates were 64, 77, 82, 102, and 105 degrees, respectively, indicating that the hydrophobicity of the surface-tethered hydrophobic chain (HC) increased in the above order. The HC-coated zeolite microcrystals readily formed closely packed monolayers at the air-water interface through interdigitation of surface-tethered HCs, and on glass plates after transferring onto glass plates by dip coating. Interestingly, while the mode of networking was face-to-face (FTF) contacting with n-octyl or n-dodecyl (theta < or =77 degrees) as HC, it changed to edge-to-edge (ETE) contacting mode with n-octadecyl or n-heptadecafluorodecyl (theta > or = 102 degrees) as HC. With methyl n-undecanoate (theta = 82 degrees) as HC, both modes appeared in the monolayers, with about equal populations. The resulting monolayers of cubic zeolite microcrystals with their three-fold axes oriented perpendicular to substrates would be useful for application of the zeolite monolayers for advanced materials.

Seeing an unfamiliar face in rotational motion does not aid identity discrimination across viewpoints.

Discriminating the identity of static face views is viewpoint-dependent (Lee, Matsumiya, & Wilson, 2006), yet the benefit of facial motion on improving cross-view discrimination remains unclear. We investigate here, whether seeing a face rotating in a single direction reduces the viewpoint dependence of neighboring views, in particular, along the trajectory of that motion direction. Results indicate that seeing an unfamiliar face rotating in a given direction does not aid identity discrimination of neighboring views regardless of the direction of rotation. These findings suggest that unfamiliar faces are represented in a view-specific manner.

Three cases of developmental prosopagnosia from one family: detailed neuropsychological and psychophysical investigation of face processing.

A number of reports have documented that developmental prosopagnosia (DP) can run in families, but the locus of the deficits in those cases remains unclear. We investigated the perceptual basis of three cases of DP from one family (67 year-old father FA, and two daughters, 39 year-old D1 and 34 year-old D2) by combining neuropsychological and psychophysical methods. Neuropsychological tests involving natural facial images demonstrated significant face recognition deficits in the three family members. All three members showed normal facial expression recognition and face detection, and two of them (D2, FA) performed well on within-class object recognition tasks. These individuals were then examined in a series of psychophysical experiments. Intermediate form vision preceding face perception was assessed with radial frequency (RF) patterns. Normal discrimination of RF patterns in these individuals indicates that their face recognition difficulties are higher in the cortical form vision hierarchy than the locus of contour shape processing. Psychophysical experiments requiring discrimination and memory for synthetic faces aimed to quantify their face processing abilities and systematically examine the representation of facial geometry across viewpoints. D1 showed deficits in perceiving geometric information from the face at a given view. D2's impairments seem to arise in later face processing stages involving transferring view-dependent descriptions into a view-invariant representation. FA performed poorly on face learning and recognition relative to the age-appropriate controls. These cases provide evidence for familial transmission of high-level visual recognition deficits with normal intermediate-level form vision.

Size-invariant but viewpoint-dependent representation of faces.

The present study investigated the role of size and view on face discrimination, using a novel set of synthetic face stimuli. Face discrimination thresholds were measured using a 2AFC match-to-sample paradigm, where faces were discriminated from a mean face. In Experiment 1, which assessed the effect of size alone, subjects had to match faces that differed in size up to four-fold. In Experiment 2 where only viewpoint was manipulated, a target face was presented at one of four different views (0 degree front, 6.7 degrees, 13.3 degrees, and 20 degrees side) and subsequent matches appeared either at the same or different view. Experiment 3 investigated how face view interacts with size changes, and subjects matched faces differing both in size and view. The results were as follows: (1) size changes up to four-fold had no effect on face discrimination; (2) threshold for matching different face views increased with angular difference from frontal view; (3) size differences across different views had no effect on face discrimination. Additionally, the present study found a perceptual boundary between 6.7 degrees and 13.3 degrees side views, grouping 0 degrees front and 6.7 degrees side views together and 13.3 degrees and 20 degrees side views together. This suggests categorical perception of face view. The present study concludes that face view and size are processed by parallel mechanisms.

Marked increase in the binding strength between the substrate and the covalently attached monolayers of zeolite microcrystals by lateral molecular cross-linking between the neighboring microcrystals.

Monolayers of cubic zeolite microcrystals (1.7 x 1.7 x 1.7 and 0.3 x 0.3 x 0.3 mum3) were assembled on glass plates through imine- or urethane-linkages between the zeolite-tethered 3-aminopropyl (AP) groups and the glass-bound benzaldehyde or isocyanate groups, which were prepared by treating AP-tethering glass plates with a large excess of terephthaldicarboxaldehyde (TPDA) or 1,4-diisocyanatobutane (DICB), respectively, in toluene. The additional treatment of the monolayers of zeolite microcrystals with TPDA or DICB led to lateral molecular cross-linking between the neighboring, closely packed zeolite microcrystals in the monolayers through AP-TPDA-AP imine or AP-DICB-AP urethane linkages between the zeolite-tethered AP groups and the newly introduced TPDA or DICB, respectively. The comparison of the binding strengths between the glass substrates and the monolayers revealed that the molecular cross-linking leads to as much as 7- and 38-fold (by average) increase in the binding strength in the cases of 1.7 x 1.7 x 1.7 and 0.3 x 0.3 x 0.3 mum3 crystals, respectively. We predict that the effect of lateral cross-linking on the binding strength will further increase with further decreasing the size of the building blocks to nanoparticles and to molecules.