Explore the vast range of titles available.

We report substantial improvements in the photoluminescence （PL） efficiency and Fabry-Perot （FP） resonance of individual GaAs nanowires through surface passivation and local field enhancement, enabling FP peaks to be observed even at room temperature. For bare GaAs nanowires, strong FP resonance peaks can be observed at 4 K, but not at room temperature. However, depositing the nanowires on gold substrates leads to substantial enhancement in the PL intensity （5X） and 3.7X to infinite enhancement of FP peaks. Finite-difference time-domain （FDTD） simulations show that the gold substrate enhances the PL spectra predominately through enhanced absorption （11X） rather than enhanced emission （1.3X）, predicting a total PL enhancement of 14X in the absence of non-radiative recombination. Despite the increased intensity of the FP peaks, lower Q factors are observed due to losses associated with the underlying gold substrate. As a means of reducing the non-radiative recombination in these nanowires, the surface states in the nanowires can be passivated by either an ionic liquid （1-ethyl-3-methylimidazolium bis（trifluoromethylsulfonyl）imide （EMIM TFSI）） or an A1GaAs surface layer to achieve up to 12X enhancement of the photoluminescence intensity and observation of FP peaks at room temperature without a gold substrate.

This work reports on recent advancements in the development of the Hg1−xCdxTe linear-mode, electron-initiated avalanche photodiode at Leonardo DRS. These detectors exhibit single-photon sensitivity from the visible to mid-wave infrared and have enabled several new NASA space LiDAR applications. In this paper, we first report on the issue of mitigating dark counts due to “ROIC glow.” By introducing a revised light-barrier in our detector design, we demonstrate a near factor of 4 reduction in glow-induced dark counts. We further present direct measurements of excess noise factor and describe post-analysis models that accurately extract this quantity from focal plane array performance data. All methods consistently reveal excess noise factors well below the McIntyre limit. Gain measurements are conducted on a smaller-format avalanche photodiode array and reveal gains of ~6100 (measured at a reverse bias of 14.9 V, operating temperature of 84 K and using a 1.55 µm illumination source), which is a new record for the mid-wave infrared technology at Leonardo DRS. Additional performance metrics such as false-event rate, photon-detection efficiency and timing jitter are presented for larger-format arrays (i.e. arrays with a greater number of pixels). We conclude with an examination of a non-fundamental, injection contact-induced breakdown phenomenon. Experimental data and modeling reveal that this breakdown is dependent on the gain and the photon signal level, and unrelated to classical avalanche breakdown.

This work reports on the prospect of using photonic crystal resonances to improve the performance of Leonardo DRS’s Hg1−xCdxTe high-density vertically integrated photodiodes. Close examination of Leonardo DRS’s unique photodiode architecture reveals that it is a photonic crystal by its very construction. As a result, by carefully tailoring the lattice parameters, it is possible to take advantage of guided-mode resonances to improve the performance in very thin film arrays. Of particular emphasis in this work is using such resonances to bolster the performance in thin-film arrays with a material cutoff in the longwave infrared. We begin the paper by describing guided-mode resonances and the benefits they afford. We continue by modeling both simplified and realistic high-density vertically integrated photodiodes using the finite-difference time-domain method. We present one structure with a longwave infrared material cutoff that, due to the presence of a guided-mode resonance, leads to near-perfect transmission into the Hg1−xCdxTe, even in the absence of an anti-reflective coating. Additionally, this same structure absorbs nearly 88% of the incident light even though the Hg1−xCdxTe material is only 1.0 µm thick. Following this theoretical study, we fabricated test structures and performed Fourier-transform infrared spectroscopy measurements. The measurements clearly revealed the presence of guided-mode resonances. Moreover, the measurements agree well with our modeling. Further modeling of the same structures suggests nearly 89% of the incident longwave infrared light can theoretically be absorbed near the presence of the guided-mode resonance. Being able to achieve similar quantum efficiencies in thinner longwave infrared materials would be a significant achievement, as the dark current should roughly decrease proportional to the volume of the absorber. Moreover, reducing our longwave infrared material thickness from nearly 6.0 µm to 1.0 µm has the added benefits of increasing material throughput and decreasing chamber downtime for material grown using molecular beam epitaxy.

Photonic structure plays a significant role in determining the brightness and efficiency of nanoemitter systems. Using photonic crystal slabs it is possible to affect these quantities in various ways. First, positioning a leaky mode near the emission frequency allows more light to be extracted from within the slab. Second, concentrating high electric field intensity near emitter locations significantly enhances the spontaneous emission rate. Improving the spontaneous emission rate is essential for systems inhibited by non-radiative recombination mechanisms, such as surface recombination. However, a large body of work has suggested these two contributing factors are in competition, making it difficult to simultaneously achieve high spontaneous emission and light extraction. Here, we begin by investigating the effects of guided-resonance modes on core-shell InGaN nanowire arrays. Using a guided-resonance mode ideal for a core-shell nanowire array, we are able to simultaneously enhance the spontaneous emission rate and light extraction efficiency. Our theoretical results predict nearly a 25× increase in external quantum efficiency, relative to an in-filled reference geometry. We build upon these theoretical findings by introducing quasi-aperiodic nanowire arrays: arrays that exhibit short-range aperiodicity, but themselves are periodic on a larger scale. Using an inverse design optimization procedure, we show that quasi-aperiodic arrays can be leveraged to bolster light extraction efficiency without sacrificing broadband spontaneous emission. Relative to the original, simple periodic geometry, our optimized quasi-aperiodic array improves the external quantum efficiency of the nanowire array up to 42%. Next, we experimentally investigate quasi-aperiodic geometries, fabricating highly-aniostropic nanowire arrays using a novel, top-down fabrication procedure. Room-temperature photoluminescence measurements support our theoretical findings and demonstrate the ability of quasi-aperiodic arrays to greatly improve upon the emitted far-field uniformity of uncoupled modes. Further, we illustrate how quasi-aperiodic arrays can be exploited to decrease in-plane distributed feedback, a quantity critical to the design of large-area photonic crystal surface-emitting lasers (PCSELs). We then turn our attention to the seamless, top-down synthesis of InGaN quantum dots (QDs). Using a quantum-size-controlled photoelectrochemical (QSC-PEC) etching technique we fabricate QDs within pre-fabricated nanowires. Low-temperature photoluminescence measurements reveal sharp spectral signatures within isolated nanowires and a 10× improvement in emitter efficiency following QSC-PEC etching. Second-order cross-correlation measurements of individual nanowires further confirm QD formation in addition to non-classical, anti-bunching emission behavior. Lastly, we show how photoelectrochemical etching can be used to selectively form membranes in complex heterostructures of pre-fabricated photonic crystal defect cavities. Our results offer exciting opportunity in improving the quantum efficiency of nanoemitter systems as well as spectrally and spatially coupling QDs within pre-fabricated nanophotonic structures.

Modern high-throughput molecular and analytical tools offer exciting opportunities to gain a mechanistic understanding of unique traits of weeds. During the past decade, tremendous progress has been made within the weed science discipline using genomic techniques to gain deeper insights into weedy traits such as invasiveness, hybridization, and herbicide resistance. Though the adoption of newer “omics” techniques such as proteomics, metabolomics, and physionomics has been slow, applications of these omics platforms to study plants, especially agriculturally important crops and weeds, have been increasing over the years. In weed science, these platforms are now used more frequently to understand mechanisms of herbicide resistance, weed resistance evolution, and crop–weed interactions. Use of these techniques could help weed scientists to further reduce the knowledge gaps in understanding weedy traits. Although these techniques can provide robust insights about the molecular functioning of plants, employing a single omics platform can rarely elucidate the gene-level regulation and the associated real-time expression of weedy traits due to the complex and overlapping nature of biological interactions. Therefore, it is desirable to integrate the different omics technologies to give a better understanding of molecular functioning of biological systems. This multidimensional integrated approach can therefore offer new avenues for better understanding of questions of interest to weed scientists. This review offers a retrospective and prospective examination of omics platforms employed to investigate weed physiology and novel approaches and new technologies that can provide holistic and knowledge-based weed management strategies for future.

Cardiosphere-derived cells (CDCs) ameliorate skeletal and cardiac muscle deterioration in experimental models of Duchenne muscular dystrophy. The HOPE-2 trial examined the safety and efficacy of sequential intravenous infusions of human allogeneic CDCs in late-stage Duchenne muscular dystrophy. In this multicentre, randomised, double-blind, placebo-controlled, phase 2 trial, patients with Duchenne muscular dystrophy, aged 10 years or older with moderate upper limb impairment, were enrolled at seven centres in the USA. Patients were randomly assigned (1:1) using stratified permuted blocks to receive CAP-1002 (1·5 × 108 CDCs) or placebo intravenously every 3 months for a total of four infusions. Clinicians, caregivers, patients, and clinical operations personnel were fully masked to treatment groups. The primary outcome was the change in mid-level elbow Performance of Upper Limb version 1.2 (PUL 1.2) score at 12 months, assessed in the intention-to-treat population. Safety was assessed in all individuals who received an investigational product. This trial is registered with ClinicalTrials.gov, NCT03406780. Between March 1, 2018, and March 31, 2020, 26 male patients with Duchenne muscular dystrophy were enrolled, of whom eight were randomly assigned to the CAP-1002 group and 12 to the placebo group (six were not randomised due to screening failure). In patients who had a post-treatment PUL 1.2 assessment (eight in the CAP-1002 group and 11 in the placebo group), the mean 12-month change from baseline in mid-level elbow PUL1.2 favoured CAP-1002 over placebo (percentile difference 36·2, 95% CI 12·7–59·7; difference of 2·6 points; p=0·014). Infusion-related hypersensitivity reactions without long-term sequelae were observed in three patients, with one patient discontinuing therapy due to a severe allergic reaction. No other major adverse reactions were noted, and no deaths occurred. CAP-1002 cell therapy appears to be safe and effective in reducing deterioration of upper limb function in patients with late-stage Duchenne muscular dystrophy. Various measures of cardiac function and structure were also improved in the CAP-1002 group compared with the placebo group. Longer-term extension studies are needed to confirm the therapeutic durability and safety of CAP-1002 beyond 12 months for the treatment of skeletal myopathy and cardiomyopathy in Duchenne muscular dystrophy. Capricor Therapeutics.

Despite the rapid rise in diversity and quantities of engineered nanomaterials produced, the impacts of these emerging contaminants on the structure and function of ecosystems have received little attention from ecologists. Moreover, little is known about how manufactured nanomaterials may interact with nutrient pollution in altering ecosystem productivity, despite the recognition that eutrophication is the primary water quality issue in freshwater ecosystems worldwide. In this study, we asked two main questions: (1) To what extent do manufactured nanoparticles affect the biomass and productivity of primary producers in wetland ecosystems? (2) How are these impacts mediated by nutrient pollution? To address these questions, we examined the impacts of a citrate-coated gold nanoparticle (AuNPs) and of a commercial pesticide containing Cu(OH)₂ nanoparticles (CuNPs) on aquatic primary producers under both ambient and enriched nutrient conditions. Wetland mesocosms were exposed repeatedly with low concentrations of nanoparticles and nutrients over the course of a 9-month experiment in an effort to replicate realistic field exposure scenarios. In the absence of nutrient enrichment, there were no persistent effects of AuNPs or CuNPs on primary producers or ecosystem productivity. However, when combined with nutrient enrichment, both NPs intensified eutrophication. When either of these NPs were added in combination with nutrients, algal blooms persisted for >50 d longer than in the nutrient-only treatment. In the AuNP treatment, this shift from clear waters to turbid waters led to large declines in both macrophyte growth and rates of ecosystem gross primary productivity (average reduction of 52% ± 6% and 92% ± 5%, respectively) during the summer. Our results suggest that nutrient status greatly influences the ecosystem-scale impact of two emerging contaminants and that synthetic chemicals may be playing an under-appreciated role in the global trends of increasing eutrophication. We provide evidence here that chronic exposure to Au and Cu(OH)₂ nanoparticles at low concentrations can intensify eutrophication of wetlands and promote the occurrence of algal blooms.

Increased urinary volume decreases recurrence rates of nephrolithiasis. Current recommendations for goal volumes are not adjusted to reflect individual risk factors, such as obesity. Our intent was to develop and evaluate a goal urine volume for stone prevention based on predictive calcium modeling. Stone formers with a 24-h urine study (6/2001-9/2010) were identified. Patients with inadequate collections or non-calcium stones were excluded. Multivariate and univariate predictive models for daily calcium were evaluated and a univariate (weight) model was selected. A target calcium concentration constant (2.5 mM) was determined from current recommendations. Individualized weight-based goal urine volumes (WGUV) were calculated. Measured calcium concentration and expected calcium concentrations using a 2-L goal volume and WGUV were compared. 185 of 399 patients met inclusion criteria. Body weight was a strong predictor of calcium excretion in each model (p < 0.0001). While a 2-L goal urine volume would be expected to improve mean calcium concentrations for the cohort from 3.53 to 2.96 mM, the benefit is unequal between subsets with nearly twofold expected concentration for the highest weight quartile (3.98 vs. 2.10 mM) and higher expected concentration for males (3.35 vs. 2.59 mM). By contrast, a WGUV model improves expected concentrations for all subsets to <2.9 mM and the overall cohort to 2.50 mM. This study demonstrates a strong relationship between body weight and urinary calcium excretion in stone formers. We introduce the novel concept of individualized goal urine output using statistical modeling, which may be preferable to current recommendations.[PUBLICATION ABSTRACT]

The subfamily Heteromyinae (spiny pocket mice) represents a well-defined monophyletic group within the rodent family Heteromyidae. Although 2 genera of spiny pocket mice, Heteromys and Liomys, are recognized in the subfamily, no phylogenetic analysis has demonstrated their reciprocal monophyly. A recent study using DNA-sequence data from the mitochondrial gene cytochrome b suggested that Liomys is paraphyletic but included few species of Heteromys. Here, we conduct phylogenetic analyses of the subfamily with dense taxonomic sampling using allozymic data from a previous study and external and cranial morphological data; our aim is to assess generic monophyly and elucidate phylogenetic structure within the genera, to the degree possible with these data. We also reidentify selected voucher specimens from the allozymic study. Parsimony-based analyses indicate 3 clades in the subfamily: (A) Liomys irroratus, L. pictus, and L. spectabilis; (B) L. adspersus and L. salvini; and (C) all examined species of Heteromys. However, the relationships among these clades are unresolved. The genus Heteromys is characterized by strong support and several unreversed morphological synapomorphies. In contrast, our analyses fail to indicate any synapomorphies for Liomys, but can neither demonstrate nor reject its monophyly. The 3 clades identified here match those recovered from a recent mitochondrial DNA–sequencing study, which found a resolved (B (A + C)) topology. Within Heteromys, we recover 5 lineages, but the relationships among them remain unresolved. The examined South American species of Heteromys formed a clade, but 2 species recently described from Ecuador and Venezuela were not included here. Samples referred to as H. desmarestianus crassirostris and H. d. planifrons were quite distinct from other samples of H. desmarestianus, emphasizing the need for alpha-level taxonomic revision of this species complex. Given the current results, future studies can now examine relationships among species of Heteromys using samples of Liomys as outgroups, but studies of Liomys must take into account its likely paraphyletic nature.