Integration of Prior Expectations and Suppression of Prediction Errors During Expectancy-Induced Pain Modulation: The Influence of Anxiety and Pleasantness.

Pain perception arises from the integration of prior expectations with sensory information. Although recent work has demonstrated that treatment expectancy effects (e.g., placebo hypoalgesia) can be explained by a Bayesian integration framework incorporating the precision level of expectations and sensory inputs, the key factor modulating this integration in stimulus expectancy-induced pain modulation remains unclear. In a stimulus expectancy paradigm combining emotion regulation in healthy male and female adults, we found that participants' voluntary reduction in anticipatory anxiety and pleasantness monotonically reduced the magnitude of pain modulation by negative and positive expectations, respectively, indicating a role of emotion. For both types of expectations, Bayesian model comparisons confirmed that an integration model using the respective emotion of expectations and sensory inputs explained stimulus expectancy effects on pain better than using their respective precision. For negative expectations, the role of anxiety is further supported by our fMRI findings that (1) functional coupling within anxiety-processing brain regions (amygdala and anterior cingulate) reflected the integration of expectations with sensory inputs and (2) anxiety appeared to impair the updating of expectations via suppressed prediction error signals in the anterior cingulate, thus perpetuating negative expectancy effects. Regarding positive expectations, their integration with sensory inputs relied on the functional coupling within brain structures processing positive emotion and inhibiting threat responding (medial orbitofrontal cortex and hippocampus). In summary, different from treatment expectancy, pain modulation by stimulus expectancy emanates from emotion-modulated integration of beliefs with sensory evidence and inadequate belief updating.

Enhancing the performance of AlGaN-based DUV-LEDs with multifocal laser stealth dicing.

In this study, AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs) processed via standard laser dicing (SLD) and multifocal laser stealth dicing (MFLSD) were investigated. Adopting the MFLSD technology would generate a roughing surface rather than the V-shaped grooves on the sidewall of 508 × 508 µm2 DUV-LEDs, which would reduce the forward operating voltage and increase the wall-plug efficiency, light output power, and far-field radiation patterns of these devices. In addition, the wavelength shift, far-field patterns, and light-tracing simulation results of the DUV-LEDs processed with SLD and MFLSD were clearly demonstrated and analyzed. Accordingly, it was observed that the MFLSD process provided more possibilities for photon escape to increase the light extraction efficiency (LEE) of DUV-LEDs, thus decreased the wavelength-redshift and junction temperature in DUV-LEDs. These results provide a reference for advanced nano-processing practices implemented during the fabrication of semiconductor devices.

Neural Basis of Somatosensory Spatial and Temporal Discrimination in Humans: The Role of Sensory Detection.

While detecting somatic stimuli from the external environment, an accurate determination of their spatial and temporal properties is essential for human behavior. Whether and how detection relates to human capacity for somatosensory spatial discrimination (SD) and temporal discrimination (TD) remains unclear. Here, participants underwent functional magnetic resonance imaging scanning when simply detecting vibrotactile stimuli of the leg, judging their location (SD), or deciding their number in time (TD). By conceptualizing tactile discrimination as consisting of detection and determination processes, we found that tactile detection elicited activation specifically involved in SD within the right inferior and superior parietal lobules, 2 regions previously implicated in the control of spatial attention. These 2 regions remained activated in the determination process, during which functional connectivity between these 2 regions predicted individual SD ability. In contrast, tactile detection produced little activation specifically related to TD. Participants' TD ability was implemented in brain regions implicated in coding temporal structures of somatic stimuli (primary somatosensory cortex) and time estimation (anterior cingulate, pre-supplementary motor area, and putamen). Together, our findings indicate a close link between somatosensory detection and SD (but not TD) at the neural level, which aids in explaining why we can promptly respond toward detected somatic stimuli.

Analytical Cryo-Scanning Electron Microscopy of Hydrated Polymers and Microgels.

Despite the fact that scanning electron microscopes (SEM) coupled with energy-dispersive X-ray microanalysis (EDS) has been commercially available for more than a half-century, SEM/EDS continues to develop and open new opportunities to study the morphology of advanced materials. This is particularly true in applications to hydrated soft matter. Developments in field-emission electron sources that enable low-voltage imaging of uncoated polymers, silicon-drift detectors that enable high-efficiency collection of X-rays characteristic of light elements, and cryogenic methods to effectively cryo-fix hydrated samples have opened new opportunities to apply techniques relatively well established in hard-materials applications to challenging new problems involving synthetic polymers. We have applied cryo-SEM imaging and spatially resolved EDS to collect new information characterizing polyelectrolyte microgels. These are charged gel particles with dimensions in the range of 0.1-100 µm. Perhaps most notable is the fact that the high hydration levels-the samples are mostly water-allow robust calibration curves to be generated using frozen-hydrated buffers with known salt and/or hydrocarbon compositions. Such calibration curves enable quantitative composition measurements in the low-concentration extremes associated with high-swelling hydrogels. We use an experimentally derived carbon calibration curve to determine the microgel swell ratio, Q. The swell ratio, arguably, is the single most important gel characteristic because it is directly related to the mesh size of the networked polymer, which in turn determines many of the gel's mechanical and transport properties. While Q can be experimentally measured in macroscopic gels based on weight measurements in the dry and hydrated states, it is very difficult to measure in a microgel, and the fact that EDS in a cryo-SEM can determine Q from a single X-ray spectrum is significant. Furthermore, because of the electrostatic charge distributed along the polymer chains, the presence and concentration of counter-ions play a critical role in polyelectrolyte systems. While conceptually understood for decades, experimental measurements of counter-ion concentrations have been largely limited to a relatively small set of materials that involve macroscopic samples. By developing calibration curves from frozen-hydrated buffer of known ionic strength, we measure the concentration of Na counter-ions in microgels of poly(acrylic acid) (PAA) with a limit of detection of ∼0.014 M. Such measurements may help resolve some long-standing questions in polyelectrolyte science concerning counter-ion condensation. Even in the absence of a calibration curve, we show that spatially resolved X-ray spectroscopy can map the spatial distribution of a cationic oligopeptide complexed within a hydrated PAA microgel because of the nitrogen fingerprint that, albeit at very low concentration, is unique to the peptide. We look specifically at the case of a microgel with a so-called core-shell structure, where, again, the underlying polyelectrolyte science responsible for core-shell formation remains incompletely understood. These examples highlight how a modern cryo-SEM can be exploited to quantitatively characterize hydrated soft matter. The approach is almost certain to continue its development and impact as the base of experienced practitioners, the accessibility to well-configured microscopes, and the abundance of challenging problems involving hydrated soft matter all continue to grow.

Thermal behavior of AlGaN-based deep-UV LEDs.

This study utilized thin p-GaN, indium tin oxide (ITO), and a reflective passivation layer (RPL) to improve the performance of deep ultra-violet light-emitting diodes (DUV-LEDs). RPL reflectors, which comprise HfO2/SiO2 stacks of different thickness to maintain high reflectance, were deposited on the DUV-LEDs with 40 nm-thick p-GaN and 12 nm-thick ITO thin films. Although the thin p-GaN and ITO films affect the operation voltage of DUV-LEDs, the highly reflective RPL structure improved the WPE and light extraction efficiency (LEE) of the DUV-LEDs, yielding the best WPE and LEE of 2.59% and 7.57%, respectively. The junction temperature of DUV-LEDs with thick p-GaN increased linearly with the injection current, while that of DUV-LEDs with thin p-GaN, thin ITO, and RPL was lower than that of the Ref-LED under high injection currents (> 500 mA). This influenced the temperature sensitive coefficients (dV/dT, dLOP/dT, and dWLP/dT). The thermal behavior of DUV-LEDs with p-GaN and ITO layers of different thicknesses with/without the RPL was discussed in detail.

Study on the performance of high-voltage deep ultraviolet light-emitting diodes.

This study fabricated high-voltage, low-current DUV-LEDs by connecting two devices. Due to better current spreading and the enhanced reflective mirror effect, high-voltage devices present a higher dynamic resistance, emission output power, wall-plug efficiency, external quantum efficiency, and view angle than single traditional devices. The study found that when the injection current was 320 mA, the maximum output power was exhibited at 47.1 mW in the HV sample. The maximum WPE and EQE of high-voltage DUV-LEDs were 2.46% and 5.48%, respectively. Noteworthily, the redshift wavelength shifted from 287.5 to 280.5 nm, less than the traditional device-from 278 to 282 nm. Further, due to the uniform emission patterns in high-voltage devices, the view angle presents 130 degrees at 100 mA input current. In this study, the high-voltage device showed more excellent properties than the traditional device. In particular, it presented a high potential application in high-voltage circuits, which can remove transformers to eliminate extra power consumption.

Sidewall geometric effect on the performance of AlGaN-based deep-ultraviolet light-emitting diodes.

In this study, deep-ultraviolet light-emitting diodes (DUV LEDs) with different chip sidewall geometries (CSGs) are investigated. The structure had two types of chip sidewall designs that combined DUV LEDs with the same p-GaN thickness. By comparing the differences of the characteristics such as the external quantum efficiency droops, light output power, light extraction efficiency (LEE), and junction temperature of these DUV LEDs, the self-heated effect and light-tracing simulation results have been clearly demonstrated to explain the inclined sidewalls that provide more possibility pathway for photons escape to increase the LEE of LEDs; thus, the DUV LEDs with the CSG presented improved performance. These results demonstrate the potential of CSG for DUV LED applications.

Trajectories of social support are associated with health outcomes and depressive symptoms among older Taiwanese adults with diabetes following hip-fracture surgery.

OBJECTIVE: This study examined trajectories of social support and their relationships with health outcomes over 2 years post hip-fracture surgery for older adults with diabetes mellitus (DM). METHODS: This was a secondary analysis of data derived from a clinical trial, which included 158 hip fractured older adults with DM who had completed the Medical Outcomes Study Social Support Survey at 1-, 12-, 18-, and 24-months following hospital discharge. Health outcomes for self-care, physical and nutritional status, mental health, and depression were assessed at 3-month intervals up to 24-months after hospital discharge. Trajectories of social support were derived with latent class analysis while hierarchical linear models were employed to assess the associations of social-support trajectory with health outcomes. RESULTS: Four social-support trajectories were derived for persons with DM following hip-fracture surgery: poor and declining (n = 18, 11.4%), moderate and stable (n = 29, 18.4%), high but declining (n = 34, 21.5%), and high and stable (n = 77, 48.7%). Relative to those in the poor and declining group, participants in the high and stable trajectory group performed better in Activities of Daily Living and quadriceps muscle power, had better mental Health-Related Quality of Life and nutritional status, and had fewer depressive symptoms. These differences persisted over the 2 years following hospital discharge. CONCLUSIONS: These results suggest social support for persons with DM should be continually assessed following hip-fracture surgery.

Impacts of the COVID-19 pandemic on household food waste behaviour: A systematic review.

Food waste has adverse economic, social, and environmental impacts and increases the prevalence of food insecurity. Panic buying at the beginning of the COVID-19 outbreak raised serious concerns about a potential rise in food waste levels and higher pressure on waste management systems. This article aims to investigate the impact of COVID-19 on food waste behaviour and the extent to which it occurs using the systematic review method. A total of 38 articles were identified and reviewed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The findings showed that the COVID-19 pandemic led to reductions in household food waste in most countries. Several changes in shopping and cooking behaviours, food consumption, and managing inventory and leftovers have occurred due to COVID-19. Based on these insights, we predicted that some desirable food-management habits would be retained, and others would roll back in the post-COVID-19 world. The review contributes to the food waste literature by offering a comprehensive overview of behavioural changes during the COVID-19 pandemic and future research directions.

Better nutrition trajectory improves recovery following a hip fracture surgery for older persons with diabetes mellitus.

BACKGROUND: Influences of nutritional status on hip fractured persons with diabetes mellitus (DM) following surgery have not been reported. AIMS: To explore the trajectory groups of nutritional status and their influences on post-operative recovery for older persons with hip fracture and DM. METHODS: A total of 169 patients with DM and hip fracture from a clinical trial were included in this analysis. Mini Nutritional Assessment was used to assess the nutritional status of the participants. Outcome variables included self-care ability, muscle strength, depressive symptoms, health related quality of life, and cognitive function, which were collected before discharge and 1-, 3-, 6-, 12-, 18-, and 24-months following hospital discharge. RESULTS: Among hip fractured older persons with DM, within two years following surgery there were three nutritional trajectory groups: malnourished (28.3%), at-risk of malnutrition (41.9%) and well-nourished (29.8%). A decline in nutritional status, especially for the malnourished group, was seen in the second year. A better nutritional trajectory was associated with better recovery outcomes, including self-care ability, health related quality of life, cognitive function and less depressive symptoms. DISCUSSION: Close to 30% of hip fractured persons with DM were considered to have a malnourished trajectory over 2 years following surgery. A poor nutritional trajectory was associated with poor mental health and physical recovery. CONCLUSIONS: Continuous nutrition assessment during the first 2 years following hip fracture surgery for older persons with DM is important. Development and implementation of interventions targeting the malnourished trajectory group are suggested.

Enhanced external quantum efficiencies of AlGaN-based deep-UV LEDs using reflective passivation layer.

In this study, deep ultraviolet light-emitting diodes (DUV-LEDs) with a reflective passivation layer (RPL) were investigated. The RPL consists of HfO2/SiO2 stacks as distributed Bragg reflectors, which are deposited on two DUV-LEDs with different p-GaN thicknesses. The RPL structure improved the external quantum efficiency droops of the DUV-LEDs with thick and thin p-GaN, thereby increasing their light output power by 18.4% and 39.4% under injection current of 500 mA and by 17.9% and 37.9% under injection current of 1000 mA, respectively. The efficiency droops of the DUV-LEDs with and without the RPL with thick p-GaN were 20.1% and 19.1% and with thin p-GaN were 18.0% and 15.6%, respectively. The DUV-LEDs with the RPL presented improved performance. The above results demonstrate the potential for development of the RPLs for DUV-LED applications.

Orienting and shaping organic semiconductor single crystals through selective nanoconfinement.

For organic semiconductor crystals exhibiting anisotropic charge transport along different crystallographic directions, nanoconfinement is a powerful strategy to control crystal orientation by aligning the fast crystallographic growth direction(s) with the unconfined axis(es) of nanoconfining scaffolds. Here, design rules are presented to relate crystal morphology, scaffold geometry, and orientation control in solution-processed small-molecule crystals. Specifically, organic semiconductor triisopropylsilylethynyl pyranthrene needle-like crystals with a dimensionality of n = 1 and perylene platelike crystals with n = 2 were grown from solution within nanoconfining scaffolds comprising cylindrical nanopores with a dimensionality of m = 1, representing one unconfined dimension along the cylinder axis, and those comprising nanopillar arrays with a dimensionality of m = 2. For m = n systems, native crystal growth habits were preserved while the crystal orientation in n = m direction(s) was dictated by the geometry of the scaffold. For n≠m systems, on the other hand, orientation control was restricted within a single plane, either parallel or perpendicular to the substrate surface. Intriguingly, control over crystal shape was also observed for perylene crystals grown in cylindrical nanopores (n > m). Within the nanopores, crystal growth was restricted along a single direction to form a needle-like morphology. Once growth proceeded above the scaffold surface, the crystals adopted their native growth habit to form asymmetric T-shaped single crystals with concave corners. These findings suggest that nanoporous scaffolds with spatially-varying dimensionalities can be used to grow single crystals of complex shapes.

Symptomatic cholelithiasis patients have an increased risk of pancreatic cancer: A population-based study.

BACKGROUND AND AIM: Pancreatic cancer is a fatal disease; currently, the risk factor survey is not suitable for sporadic pancreatic cancer, which has neither family history nor the genetic analysis data. The aim of the present study was to evaluate the roles of cholelithiasis and cholelithiasis treatments on pancreatic cancer risk. METHODS: Symptomatic adult patients with an index admission of cholelithiasis were selected from one million random samples obtained between January 2005 and December 2009. The control group was matched with a 1:1 ratio for sex, age, chronic pancreatitis, and pancreatic cystic disease. Subsequent pancreatic cancer, which we defined as pancreatic cancer that occurred ≥ 6 months later, and total pancreatic cancer events were calculated in the cholelithiasis and control groups. The cholelithiasis group was further divided into endoscopic sphincterotomy/endoscopic papillary balloon dilatation, cholecystectomy, endoscopic sphincterotomy/endoscopic papillary balloon dilatation and cholecystectomy, and no-intervention groups for evaluation. RESULTS: The cholelithiasis group and the matched control group included 8265 adults. The cholelithiasis group contained 86 cases of diagnosed pancreatic cancer, and the control group contained 8 cases (P < 0.001). The incidence rate ratio (IRR) of subsequent pancreatic cancer was significantly higher in the cholelithiasis group than in the control group (IRR: 5.28, P < 0.001). The IRR of subsequent pancreatic cancer was higher in the no-intervention group comparing with cholecystectomy group (IRR = 3.21, P = 0.039) but was similar in other management subgroups. CONCLUSION: Symptomatic cholelithiasis is a risk factor for pancreatic cancer; the risk is similar regardless of the intervention chosen for cholelithiasis.

Supply chain resilience reactive strategies for food SMEs in coping to COVID-19 crisis.

BACKGROUND: The ability of small- and medium-sized enterprises in the food industry (FSMEs) in cultivating resilience against the COVID-19 pandemic is vital food security. However, there is limited supply chain resilience literature to guide FSMEs in overcoming disruptions caused by pandemic. SCOPE AND APPROACH: This review aims to provide a broad view of SCRes reactive strategies for FSMEs in dealing with crises in the context of COVID-19. Attention is given to the literature on resilience in other types of supply chain and situated in the context of food settings. The factors are monitored or controlled to contribute to FSME resiliency.Key findings and conclusion: Four quadrants, i.e., (1) rapid with low cost, (2) rapid with high cost, (3) slow with low cost and (4) slow with high cost, are offered based on the limitations and the time needed to react, and the strategies of each quadrant are explained in depth. This review also provides a better understanding of and guidance on reactive strategies for SCRes as options for FSMEs in dealing with the COVID-19 pandemic. This review suggests future directions as extensions based on the logical flow of this review.

The Effectiveness of Betel Quid Cessation among Workers through the Adoption of the Five Action Areas of the Ottawa Charter.

OBJECTIVE: This study aimed to increase workers' awareness of betel quid cessation. Methods: Using community and workplace resources, a workplace health promotion program was developed in accordance with the five action areas of the Ottawa Charter. Questionnaires were administered to examine the changes in the knowledge and attitudes of 714 workers in different occupations before and three months after the intervention. Results: Regardless of subjects' pre-intervention chewing status, their knowledge and attitude scores relating to betel quid cessation increased significantly after the intervention. The effect of occupation was significant on the post-intervention knowledge and attitude scores among chewers. Furthermore, 16 (11.6%) of the 138 study subjects who chewed betel quid before the intervention and had no willingness to quit, did quit betel quid chewing following the intervention. The factors contributing to an unwillingness to quit among chewers with no intention to quit before the intervention were examined. Workers in the electronic material manufacturing industry had a greater willingness to quit compared to those in the metal, machinery, and related trades (odds ratio [OR] = 0.15; 95% confidence interval [CI] = 0.02-0.94). Travel attendants, tour guides, cleaners, and helpers were the least willing to quit (OR = 21.29; 95% CI = 2.51-180.81). Conclusions: This study promoted workers' awareness of betel quid cessation by adopting the five action areas of the Ottawa Charter framework, the effectiveness of the intervention varied in different occupations. Workers with a high-income and better education level had a higher awareness of betel quid cessation.

A causal eco-industrial park hierarchical transition model with qualitative information: Policy and regulatory framework leads to collaboration among firms.

Eco-industrial parks promise to reduce environmental and social impacts and improve the economic performance of industrial parks. However, the transition from industrial parks to eco-industrial parks is still not well understood. This study contributes to developing valid hierarchical eco-industrial park transition attribute sets with qualitative information, as prior studies lack an exploration of the attributes in the transition of eco-industrial parks in Hungary. In nature, eco-industrial park transition attributes have causal and hierarchical interrelationships and are described with qualitative information. The assessment involves an analysis of the industrial symbiosis principles by using linguistic preferences. However, multiple attributes are involved in the assessment; therefore, this study proposes the Delphi method to develop a valid attribute set and applies fuzzy set theory to translate qualitative information into crisp values. The fuzzy decision-making trial evaluation laboratory method is used to visualize the attributes' causal interrelationships under uncertainties. The results indicate that the policy and regulatory framework leads to collaboration among firms in the eco-industrial park transition model. In practice, price reforms, management commitment, strategic planning, cognitive barriers and the integration of external information are the practical criteria for improvement. Theoretical and practical implications are also discussed.

Effects of Positive and Negative Expectations on Human Pain Perception Engage Separate But Interrelated and Dependently Regulated Cerebral Mechanisms.

Expectations substantially influence pain perception, but the relationship between positive and negative expectations remains unclear. Recent evidence indicates that the integration between pain-related expectations and prediction errors is crucial for pain perception, which suggests that aversive prediction error-associated regions, such as the anterior insular cortex (aIC) and rostral anterior cingulate cortex (rACC), may play a pivotal role in expectation-induced pain modulation and help to delineate the relationship between positive and negative expectations. In a stimulus expectancy paradigm combining fMRI in healthy volunteers of both sexes, we found that, although positive and negative expectations respectively engaged the right aIC and right rACC to modulate pain, their associated activations and pain rating changes were significantly correlated. When positive and negative expectations modulated pain, the right aIC and rACC exhibited opposite coupling with periaqueductal gray (PAG) and the mismatch between actual and expected pain respectively modulated their coupling with PAG and thalamus across individuals. Participants' certainty about expectations predicted the extent of pain modulation, with positive expectations involving connectivity between aIC and hippocampus, a region regulating anxiety, and negative expectations engaging connectivity between rACC and lateral orbitofrontal cortex, a region reflecting outcome value and certainty. Interestingly, the strength of these certainty-related connectivities was also significantly associated between positive and negative expectations. These findings suggest that aversive prediction-error-related regions interact with pain-processing circuits to underlie stimulus expectancy effects on pain, with positive and negative expectations engaging dissociable but interrelated neural responses that are dependently regulated by individual certainty about expectations.SIGNIFICANCE STATEMENT Positive and negative expectations substantially influence pain perception, but their relationship remains unclear. Using fMRI in a stimulus expectancy paradigm, we found that, although positive and negative expectations engaged separate brain regions encoding the mismatch between actual and expected pain and involved opposite functional connectivities with the descending pain modulatory system, they produced significantly correlated pain rating changes and brain activation. Moreover, participants' certainty about expectations predicted the magnitude of both types of pain modulation, with the underlying functional connectivities significantly correlated between positive and negative expectations. These findings advance current understanding about cognitive modulation of pain, suggesting that both types of pain modulation engage different aversive prediction error signals but are dependently regulated by individual certainty about expectations.

Mechanistic Study of Pb(II) Removal by TiO2 and Effect of PO4.

As a commercial adsorbent, TiO2 shows a high adsorption capacity for lead (Pb(II)). However, the molecular structure of Pb(II) adsorption on TiO2 is still unknown. Meanwhile, as a widely used corrosion inhibitor, phosphate (PO4) is usually added into drinking water, and its influential mechanism on Pb(II) removal by TiO2 remains unknown. Here, the mechanisms of Pb(II) adsorption on TiO2 and the effect of PO4 were systematically investigated using a combination of spectroscopic analyses and surface complexation modeling. The adsorption structure of Pb(II) on TiO2 was revealed as a tridentate mononuclear configuration by the extended X-ray absorption fine structure (EXAFS) analysis. In the presence of 0.1-5 mg/L PO4, Pb(II) was removed mainly by adsorption on TiO2 rather than precipitation. Ternary complexation between Pb(II) and PO4 on TiO2 surfaces was found based on EXAFS and in situ Fourier transform infrared characterizations. These complexation structures were used to build a surface complexation model to accurately simulate and predict Pb(II) removal under different conditions. This study provides essential information about the mechanisms of Pb(II) removal by TiO2 and develops a model to predict adsorption behaviors, especially in the presence of PO4.

Generating Third Harmonic Vacuum Ultraviolet Light with a TiO2 Metasurface.

Dielectric metasurfaces have recently been shown to provide an excellent platform for the harmonic generation of light due to their low optical absorption and to the strong electromagnetic field enhancement that can be designed into their constituent meta-atoms. Here, we demonstrate vacuum ultraviolet (VUV) third harmonic generation from a specially designed dielectric metasurface consisting of a titanium dioxide (TiO2) nanostructure array. The metasurface was designed to enhance the generation of VUV light at a wavelength of 185 nm by tailoring its geometric design parameters to achieve an optical resonance at the fundamental laser wavelength of 555 nm. The metasurface exhibits an enhancement factor of nominally 180 compared to an unpatterned TiO2 thin film of the same thickness, evidence of strong field enhancement at the fundamental wavelength. Mode analysis reveals that the origin of the enhancement is an anapole resonance near the pump wavelength. This work demonstrates an effective strategy for the compact generation of VUV light that could enable expanded access to this useful region of the electromagnetic spectrum.

Counterion Exchange in Peptide-Complexed Core-Shell Microgels.

The complexation of polyvalent macroions with oppositely charged polyelectrolyte microgels can lead to core-shell structures. The shell is believed to be highly deswollen with a high concentration of counter-macroions. The core is believed to be relatively free of macroions but under a uniform compressive stress due to the deswollen shell. We use cryo-scanning electron microscopy (SEM) with X-ray microanalysis to confirm this understanding. We study poly(acrylic acid) (PAA) microgels which form a core-shell structure when complexed with a small cationic antimicrobial peptide (L5). We follow the spatial distribution of polymer, water, Na counterions, and peptide based on the characteristic X-ray intensities of C, O, Na, and N, respectively. Frozen-hydrated microgel suspensions include buffers of known composition from which calibration curves can be generated and used to quantify both the microgel water and sodium concentrations, the latter with a minimum quantifiable concentration less than 0.048 M. We find that as-synthesized PAA microgels are enriched in Na relative to the surrounding buffer as anticipated from established ideas of counterion shielding of electrostatic charge. The shell in L5-complexed microgels is depleted in Na and enriched in peptide and contains relatively little water. Our measurements furthermore show that shell/core interface is diffuse over a length scale of a few micrometers. Within the limits of detection, the core Na concentration is the same as that in as-synthesized microgels, and the core is free of peptide. The core has a slightly lower water concentration than as-synthesized controls, consistent with the hypothesis that the core is under compression from the shell.