Transparent conductors are essential elements in an array of optoelectronic devices. The most commonly used transparent conductor – indium tin oxide (ITO) suffers from issues including poor ...mechanical flexibility, rising cost, and the need for annealing to achieve high conductivity. Consequently, there has been intensive research effort in developing ITO‐free transparent conductors over the recent years. This article gives a comprehensive review on the development of an important ITO‐free transparent conductor, that is based on thin metal films. It starts with the background knowledge of material selection for thin‐metal‐film‐based transparent conductors and then surveys various techniques to fabricate high‐quality thin metal films. Then, it introduces the spectroscopic ellipsometry method for characterizing thin metal films with high accuracy, and discusses the optical design procedure for optimizing transmittance through thin‐metal‐film‐based conductors. The review also summarizes diverse applications of thin‐metal‐film‐based transparent conductors, ranging from solar cells and organic light emitting diodes, to optical spectrum filters, low‐emissivity windows, and transparent electromagnetic interference coatings.
This review summarizes the recent development of thin‐metal‐film‐based transparent conductors. It starts with the general guidelines of material selection, and then surveys various techniques for preparing and characterizing high‐quality ultrathin metal films. Finally, it discusses relevant optical design procedures for maximizing the conductor's transmittance as well as classical and emerging applications of thin‐metal‐film‐based transparent conductors.
The main load-bearing network in the primary cell wall of most land plants is commonly depicted as a scaffold of cellulose microfibrils tethered by xyloglucans. However, a xyloglucan-deficient mutant ...(xylosyltransferase1/xylosyltransferase2 xxt1/xxt2) was recently developed that was smaller than the wild type but otherwise nearly normal in its development, casting doubt on xyloglucan's role in wall structure. To assess xyloglucan function in the Arabidopsis (Arabidopsis thaliana) wall, we compared the behavior of petiole cell walls from xxt1/xxt2 and wild-type plants using creep, stress relaxation, and stress/strain assays, in combination with reagents that cut or solubilize specific components of the wall matrix. Stress/strain assays showed xxt1/xxt2 walls to be more extensible than wild-type walls (supporting a reinforcing role for xyloglucan) but less extensible in creep and stress relaxation processes mediated by a-expansin. Fusicoccin-induced "acid growth" was likewise reduced in xxt1/xxt2 petioles. The results show that xyloglucan is important for wall loosening by α-expansin, and the smaller size of the xxt1/xxt2 mutant may stem from the reduced effectiveness of α-expansins in the absence of xyloglucan. Loosening agents that act on xylans and pectins elicited greater extension in creep assays of xxt1/xxt2 cell walls compared with wild-type walls, consistent with a larger mechanical role for these matrix polymers in the absence of xyloglucan. Our results illustrate the need for multiple biomechanical assays to evaluate wall properties and indicate that the common depiction of a cellulose-xyloglucan network as the major load-bearing structure is in need of revision.
Xyloglucan is widely believed to function as a tether between cellulose microfibrils in the primary cell wall, limiting cell enlargement by restricting the ability of microfibrils to separate ...laterally. To test the biomechanical predictions of this "tethered network" model, we assessed the ability of cucumber (Cucumis sativus) hypocotyl walls to undergo creep (long-term, irreversible extension) in response to three family-12 endo-β-1, 4-glucanases that can specifically hydrolyze xyloglucan, cellulose, or both. Xyloglucan-specific endoglucanase (XEG from Aspergillus aculeatus) failed to induce cell wall creep, whereas an endoglucanase that hydrolyzes both xyloglucan and cellulose (Cell2A from Hypocrea jecorina) induced a high creep rate. A cellulose-specific endoglucanase (CEG from Aspergillus niger) did not cause cell wall creep, either by itself or in combination with XEG. Tests with additional enzymes, including a family-5 endoglucanase, confirmed the conclusion that to cause creep, endoglucanases must cut both xyloglucan and cellulose. Similar results were obtained with measurements of elastic and plastic compliance. Both XEG and Cell2A hydrolyzed xyloglucan in intact walls, but Cell2A could hydrolyze a minor xyloglucan compartment recalcitrant to XEG digestion. Xyloglucan involvement in these enzyme responses was confirmed by experiments with Arabidopsis (Arabidopsis thaliana) hypocotyls, where Cell2A induced creep in wild-type but not in xyloglucan-deficient (xxt1/xxt2) walls. Our results are incompatible with the common depiction of xyloglucan as a load-bearing tether spanning the 20-to 40-nm spacing between cellulose microfibrils, but they do implicate a minor xyloglucan component in wall mechanics. The structurally important xyloglucan may be located in limited regions of tight contact between microfibrils.
The structural role of pectins in plant primary cell walls is not yet well understood because of the complex and disordered nature of the cell wall polymers. We recently introduced multidimensional ...solid-state nuclear magnetic resonance spectroscopy to characterize the spatial proximities of wall polysaccharides. The data showed extensive cross peaks between pectins and cellulose in the primary wall of Arabidopsis (Arabidopsis thaliana), indicating subnanometer contacts between the two polysaccharides. This result was unexpected because stable pectin-cellulose interactions are not predicted by in vitro binding assays and prevailing cell wall models. To investigate whether the spatial contacts that give rise to the cross peaks are artifacts of sample preparation, we now compare never-dried Arabidopsis primary walls with dehydrated and rehydrated samples. Onedimensional ¹³C spectra, two-dimensional ¹³C-¹³C correlation spectra, water-polysaccharide correlation spectra, and dynamics data all indicate that the structure, mobility, and intermolecular contacts of the polysaccharides are indistinguishable between never-dried and rehydrated walls. Moreover, a partially depectinated cell wall in which 40% of homogalacturonan is extracted retains cellulose-pectin cross peaks, indicating that the cellulose-pectin contacts are not due to molecular crowding. The cross peaks are observed both at −20°C and at ambient temperature, thus ruling out freezing as a cause of spatial contacts. These results indicate that rhamnogalacturonan I and a portion of homogalacturonan have significant interactions with cellulose microfibrils in the native primary wall. This pectin-cellulose association may be formed during wall biosynthesis and may involve pectin entrapment in or between cellulose microfibrils, which cannot be mimicked by in vitro binding assays.
This study reports that the noncentrosymmetry and phase synchronization requirements of the sum frequency generation (SFG) process can be used to distinguish the three-dimensional organization of ...crystalline cellulose distributed in amorphous matrices. Crystalline cellulose is produced as microfibrils with a few nanometer diameters by plants, tunicates, and bacteria. Crystalline cellulose microfibrils are embedded in wall matrix polymers and assembled into hierarchical structures that are precisely designed for specific biological and mechanical functions. The cellulose microfibril assemblies inside cell walls are extremely difficult to probe. The comparison of vibrational SFG spectra of uniaxially-aligned and disordered films of cellulose Iβ nanocrystals revealed that the spectral features cannot be fully explained with the crystallographic unit structure of cellulose. The overall SFG intensity, the alkyl peak shape, and the alkyl/hydroxyl intensity ratio are sensitive to the lateral packing and net directionality of the cellulose microfibrils within the SFG coherence length scale. It was also found that the OH SFG stretch peaks could be deconvoluted to find the polymorphic crystal structures of cellulose (Iα and Iβ). These findings were used to investigate the cellulose crystal structure and mesoscale cellulose microfibril packing in intact plant cell walls, tunicate tests, and bacterial films.
Understanding of ultrathin metal film's electrical and optical properties at sub‐10 nm thickness may provide important engineering insight on its application as a transparent conductor. Here, a rapid ...change is observed in the ultrathin metal film's electrical and optical scaling properties as the thickness shrinks to below a certain critical thickness dc. Below this thickness, the metal film's electrical properties are shown to be strongly influenced by the inhomogeneity of the film which can be modeled via general effective media theory by incorporating size‐effect contribution. As a result, below dc, carrier's scattering time rapidly decreases with a reduced mean free path leading to a rapid rise in resistivity. Also, the film's optical loss increases while the optical transmission plateaus below dc. As one promising application of thin metal film is transparent conductor where the film's electrical and optical properties are equally important, its maximum theoretical figure‐of‐merit is shown, which is determined at this dc serving as an important engineering metric.
It is observed that a rapid increase in electrical resistivity of ultrathin Ag film below its critical thickness where its resistivity is strongly influenced by film's morphology, which can be modeled by extended general effective media theory. The critical thickness of metal film can serve as an important engineering metric for its use as a transparent conductor application.
The introduction of inhaled corticosteroids (ICS) for the management of asthma has led to a decrease in acute exacerbation of asthma. However, there are concerns regarding the safety of long-term ICS ...use, particularly pneumonia. Growing evidence indicates that ICS use is associated with an increased risk of pneumonia in patients with chronic obstructive pulmonary disease, whereas the risk in patients with asthma remains unclear. This review discusses the effect of ICS on pneumonia among patients with asthma to update the existing literature. Asthma is associated with an increased risk of pneumonia. Several hypotheses have been proposed to explain this association, including that asthma impairs the clearance of bacteria owing to chronic inflammation. Therefore, controlling airway inflammation with ICS may prevent the occurrence of pneumonia in asthma. In addition, two meta-analyses investigating randomized control trials showed that ICS use was associated with a protective effect against pneumonia in asthma.
Abstract
Background and objective
Early identification of chronic obstructive pulmonary disease (COPD) in young individuals could be beneficial to attempt preventive interventions. The objective of ...this study was to investigate clinical features and outcomes of young individuals with COPD from the general population cohort.
Methods
We included individuals from the Korean National Health and Nutrition Examination Survey (KNHANES) with spirometry and identifiable smoking status. Young subjects with COPD were defined as aged between 40 and 50 years and had baseline forced expiratory volume in 1 s FEV
1
/forced vital capacity FVC ratio less than 0.7. Outcomes include the risk of exacerbation and medical expenses during 3 years of follow-up.
Results
Among 2236 individuals aged between 40 and 50 years, 95 (4.2%) had COPD, including 36 who were never-smokers and 59 who were ever-smokers. Approximately 98% of COPD subjects had mild to moderate airflow limitation. Inhaler treatment was given to only 6.3% patients in the COPD group. The risk of exacerbation for a 3-year period was analyzed using the never-smoker, non-COPD group as a comparator. Hazards ratio for exacerbation was 1.60 (95% confidence interval CI 0.18–14.20) in the never-smoker COPD group and 1.94 (95% CI 0.31–12.07) in the ever-smoker COPD group of young subjects. COPD related medical costs were not significantly different between non-COPD and COPD groups of young individuals.
Conclusions
The risk of exacerbation showed an increasing trend in COPD patients regardless of smoking status compared to non-COPD. More attention to early identification and provision of preventive measures are needed to reduce disease progression and improve outcome.
Arginine methylation is a posttranslational modification mediated by protein arginine methyltransferases (PRMTs). Although previous studies have shown that PRMT1 contributes to the severity of ...allergic airway inflammation or asthma, the underlying mechanism is poorly understood.
This study aimed to explore the role of PRMT1 and its relevant mechanism in the development of allergic rhinitis (AR).
The expression levels of PRMTs and cytokines were determined by RT-PCR, and the localization of PRMT1 was determined by immunohistochemistry and confocal microscopy. The levels of house dust mite (HDM)-specific immunoglobulins in serum and of cytokines in nasal lavage fluids were determined by ELISA. PRMT1 inhibition was achieved by siRNA and treatment with the pan PRMT inhibitor arginine N-methyltransferase inhibitor-1.
PRMT1 expression was significantly increased in the nasal mucosa of patients and mice with AR. The degree of eosinophilic infiltration in the nasal mucosa was reduced in PRMT1+/− AR mice compared with wild-type mice. PRMT1 haploinsufficiency reduced the levels of HDM-specific immunoglobulins in serum and those of TH2 (IL-4, IL-5, and IL-13) and epithelial (thymic stromal lymphopoietin TSLP, IL-25, and IL-33) cytokines in the nasal lavage fluids of AR mice. In nasal epithelial cells, HDM and IL-4 cooperate to enhance PRMT1 expression through a mitogen-activated protein kinase–dependent pathway. In addition, PRMT1 was essential for the production of TSLP, IL-25, and IL-33 in response to HDM and IL-4. Arginine N-methyltransferase inhibitor-1 treatment alleviated AR in the mouse model.
PRMT1 plays an important role in AR development by regulating epithelial-derived cytokine production and might be a new therapeutic target for AR.
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Structure determination of protein binding to noncrystalline macromolecular assemblies such as plant cell walls (CWs) poses a significant structural biology challenge. CWs are loosened during growth ...by expansin proteins, which weaken the noncovalent network formed by cellulose, hemicellulose, and pectins, but the CW target of expansins has remained elusive because of the minute amount of the protein required for activity and the complex nature of the CW. Using solid-state NMR spectroscopy, combined with sensitivity-enhancing dynamic nuclear polarization (DNP) and differential isotopic labeling of expansin and polysaccharides, we have now determined the functional binding target of expansin in the Arabidopsis thaliana CW. By transferring the electron polarization of a biradical dopant to the nuclei, DNP allowed selective detection of 13C spin diffusion from trace concentrations of 13C, 15N-labeled expansin in the CW to nearby polysaccharides. From the spin diffusion data of wild-type and mutant expansins, we conclude that to loosen the CW, expansin binds highly specific cellulose domains enriched in xyloglucan, whereas more abundant binding to pectins is unrelated to activity. Molecular dynamics simulations indicate short 13C-13C distances of 4–6 Å between a hydrophobic surface of the cellulose microfibril and an aromatic motif on the expansin surface, consistent with the observed NMR signals. DNP-enhanced 2D 13C correlation spectra further reveal that the expansin-bound cellulose has altered conformation and is enriched in xyloglucan, thus providing unique insight into the mechanism of CW loosening. DNP-enhanced NMR provides a powerful, generalizable approach for investigating protein binding to complex macromolecular targets.
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