The solar energy conversion properties of thin Si and GaP nanowire photoelectrodes in photoelectrochemical cells have been examined through sets of finite-element simulations. A discussion describing ...the motivation behind nanostructured, high aspect ratio semiconductor photoelectrode designs and a brief survey of current experimental results reported for nanostructured semiconductor photoelectrodes in photoelectrochemical cells are presented first. An analysis is then shown that outlines the primary recombination pathways governing the steady-state current-potential behaviors of thin, cylindrical nanowire photoelectrodes, with explicit expressions detailing the differences between planar and cylindrical photoelectrodes arising from the solution of carrier fluxes in planar and cylindrical geometries. Results from finite-element simulations used to model the key features of thin nanowire photoelectrodes under low-level injection conditions are shown that illustrate which recombination pathway(s) is operative under various experimental conditions. Specifically, the respective effects of non-uniform doping, tapering along the length, variation in charge carrier mobilities and lifetimes, changes in nanowire radius, and changes in the density of surface defects on the observable photocurrent-potential responses are reported. These cumulative results serve as guides for future experimental work aimed at improving the attainable solar energy conversion efficiencies of doped semiconductor nanowire photoelectrodes. Lastly, separate simulations that model lightly doped nanowire photoelectrodes under high-level injection conditions are discussed. These results suggest discrete, ohmic-selective contacts may afford a way to circumvent the stringent doping requirements discussed herein for thin nanowire photoelectrodes.
Macroporous GaP photoelectrodes with wall thicknesses of approximately 500 nm and pore depths ranging from 0 to 45 μm have been prepared from nondegenerately doped single-crystalline n-GaP(100) with ...a minority-carrier diffusion length of only 110 nm. The photoelectrochemical behaviors of planar and macroporous photoelectrodes have been assessed in nonaqueous regenerative photoelectrochemical cells operated under potentiostatic control and employing dry acetonitrile containing ferrocene/ferrocenium. Enhancements in the short-circuit photocurrents tracked increases in internal quantum yield measurements at long wavelengths for macroporous n-GaP. The observed photocurrent densities and spectral response measurements were consistent with values expected from GaP/liquid heterojunctions controlled by faradaic charge transfer to an outer-sphere, dissolved redox couple. Lower open-circuit photovoltages were observed with macroporous electrodes with increasing pore depth, consistent with distribution of the photocurrent across the entire macropore/solution interface. Fill factors observed under these conditions did not systematically track pore depth in macroporous photoelectrodes. The noted changes in short-circuit photocurrents, open-circuit photovoltages, and fill factors with increasing porosity resulted in more than an order of magnitude improvement in the photoelectrode efficiency of macroporous n-GaP with 45 μm deep pores at 100 mW cm−2 illumination. The presented data show the level and type of enhancement in energy conversion efficiency that high-aspect-ratio electrode architectures can provide carrier-collection-limited materials such as GaP.
Background and aims
The amount of nitrogen (N) derived from symbiotic N
2
fixation by legumes in grasslands might be affected by anthropogenic N and phosphorus (P) inputs, but the underlying ...mechanisms are not known.
Methods
We evaluated symbiotic N
2
fixation in 17 natural and semi-natural grasslands on four continents that are subjected to the same full-factorial N and P addition experiment, using the
15
N natural abundance method.
Results
N as well as combined N and P (NP) addition reduced aboveground legume biomass by 65% and 45%, respectively, compared to the control, whereas P addition had no significant impact. Addition of N and/or P had no significant effect on the symbiotic N
2
fixation per unit legume biomass. In consequence, the amount of N fixed annually per grassland area was less than half in the N addition treatments compared to control and P addition, irrespective of whether the dominant legumes were annuals or perennials.
Conclusion
Our results reveal that N addition mainly impacts symbiotic N
2
fixation via reduced biomass of legumes rather than changes in N
2
fixation per unit legume biomass. The results show that soil N enrichment by anthropogenic activities significantly reduces N
2
fixation in grasslands, and these effects cannot be reversed by additional P amendment.
Acinetobacter baumannii causes high mortality in ventilator-associated pneumonia patients, and antibiotic treatment is compromised by multidrug-resistant strains resistant to β-lactams, carbapenems, ...cephalosporins, polymyxins, and tetracyclines. Among COVID-19 patients receiving ventilator support, a multidrug-resistant A. baumannii secondary infection is associated with a 2-fold increase in mortality. Here, we investigated the use of the 8-hydroxyquinoline ionophore PBT2 to break the resistance of A. baumannii to tetracycline class antibiotics.
, the combination of PBT2 and zinc with either tetracycline, doxycycline, or tigecycline was shown to be bactericidal against multidrug-resistant A. baumannii, and any resistance that did arise imposed a fitness cost. PBT2 and zinc disrupted metal ion homeostasis in A. baumannii, increasing cellular zinc and copper while decreasing magnesium accumulation. Using a murine model of pulmonary infection, treatment with PBT2 in combination with tetracycline or tigecycline proved efficacious against multidrug-resistant A. baumannii. These findings suggest that PBT2 may find utility as a resistance breaker to rescue the efficacy of tetracycline-class antibiotics commonly employed to treat multidrug-resistant A. baumannii infections.
Within intensive care unit settings, multidrug-resistant (MDR) Acinetobacter baumannii is a major cause of ventilator-associated pneumonia, and hospital-associated outbreaks are becoming increasingly widespread. Antibiotic treatment of A. baumannii infection is often compromised by MDR strains resistant to last-resort β-lactam (e.g., carbapenems), polymyxin, and tetracycline class antibiotics. During the on-going COVID-19 pandemic, secondary bacterial infection by A. baumannii has been associated with a 2-fold increase in COVID-19-related mortality. With a rise in antibiotic resistance and a reduction in new antibiotic discovery, it is imperative to investigate alternative therapeutic regimens that complement the use of current antibiotic treatment strategies. Rescuing the efficacy of existing therapies for the treatment of MDR A. baumannii infection represents a financially viable pathway, reducing time, cost, and risk associated with drug innovation.
This study identified CD16+ DCs as the only blood DC subset distinctively activated during primary blood-stage human Plasmodium infection. As TNF/IL-10 coproducers, CD16+ DCs contribute to early ...inflammatory processes, yet P falciparum restimulation skewed cytokine responses further towards IL-10 production.
Abstract
Background
The malaria causing parasite Plasmodium subverts host immune responses by several strategies including the modulation of dendritic cells (DCs).
Methods
In this study, we show that Plasmodium falciparum skewed CD16+ DC cytokine responses towards interleukin (IL)-10 production in vitro, distinct to the cytokine profile induced by Toll-like receptor ligation. To determine CD16+ DC responsiveness in vivo, we assessed their function after induced P falciparum infection in malaria-naive volunteers.
Results
CD16+ DCs underwent distinctive activation, with increased expression of maturation markers human leukocyte antigen (HLA)-DR and CD86, enhanced tumor necrosis factor (TNF) production, and coproduction of TNF/IL-10. In vitro restimulation with P falciparum further increased IL-10 production. In contrast, during naturally acquired malaria episode, CD16+ DCs showed diminished maturation, suggesting increased parasite burden and previous exposure influence DC subset function.
Conclusions
These findings identify CD16+ DCs as the only DC subset activated during primary blood-stage human Plasmodium infection. As dual cytokine producers, CD16+ DCs contribute to inflammatory as well as regulatory innate immune processes.
Retrospective review of prospective, multicenter and international cohort study.
To describe the effect of gender on HRQoL, clinical outcomes and survival for patients with spinal metastases treated ...with either surgery and/or radiation.
Gender differences in health-related outcomes are demonstrated in numerous studies, with women experiencing worse outcomes and receiving lower standards of care than men, however, the influence that gender has on low health-related quality of life (HRQoL) and clinical outcomes after spine surgery remains unclear.
Patient demographic data, overall survival, treatment details, perioperative complications, and HRQoL measures including EQ-5D, pain NRS, the short form 36 version 2 (SF-36v2) and the Spine Oncology Study Group Outcomes Questionnaire (SOSGOQ2.0) were reviewed. Patients were stratified by sex, and a separate sensitivity analysis that excluded gender-specific cancers (i.e., breast, prostate, etc.) was performed.
The study cohort included 207 female and 183 male patients, with age, smoking status, and site of primary cancer being significantly different between the two cohorts (P<0.001). Both males and females experienced significantly improved SOSGOQ2.0, EQ-5D, and pain NRS scores at all study time points from baseline (P<0.001). Upon sensitivity analysis, (gender-specific cancers removed from analysis), the significant improvement in SOSGOQ physical, mental, and social subdomains and on SF-36 domains disappeared for females. Males experienced higher rates of postoperative complications. Kaplan-Meier survival analysis of both the overall and sensitivity analysis cohorts showed females lived longer than males after treatment (P=0.001 and 0.043, respectively).
Both males and females experienced significantly improved HRQoL scores after treatment, but females demonstrated longer survival and a lower complication rate. This study suggests that gender may be a prognostic factor in survival and clinical outcomes for patients undergoing treatment for spine metastases and should be taken into consideration when counseling patients accordingly.
Although most point sources of persistent organic pollutants (POPs), including polycyclic aromatic hydrocarbons (PAHs), are at lower latitudes, the Arctic region is contaminated. In particular, PAHs ...now dominate the POP body burden of the region’s marine biota at the lower trophic levels. Greenlandic Inuits have the most elevated levels of POPs in their blood compared to any other population, due to their consumption of seal meat and other marine mammals. PAHs, the by-products of the incomplete combustion of petroleum products, are known carcinogens and have been shown to affect the immune system, reproduction, endocrine functions, and the nervous system. With industrial activities and climate change set to increase local PAH emissions, it is paramount to document changes in atmospheric PAH deposition to further investigate PAH exposure in the region and attribute contaminations to their sources. As a measure of atmospheric pollution, we sampled bryophyte herbarium specimens of three common and widespread species collected in Greenland between the 1920s and 1970s after which time new collections were not available. They were analyzed for 19 PAHs using GC-MS (gas chromatography mass spectrometry). The presence of more low-molecular-weight PAHs than high-molecular-weight PAHs is evidence that the PAH contamination in Greenland is due to long-range transport rather than originating from local sources. The results show peaks in PAH atmospheric deposition in the first part of the 19th century followed by a trend of decrease, which mirror global trends in atmospheric pollution known from those periods. PAHs associated with wood and fossil-fuel combustion decrease in the 1970s coinciding with the disappearance of charcoal pits and foundries in Europe and North America, and a shift away from domestic heating with wood during the 19
th
century. The results highlight the value of bryophytes as bioindicators to measure PAH atmospheric pollution as well as the unrealized potential of herbaria as historical records of environmental change.
Protective malarial antibodies are acquired more rapidly in adults than children, independently of cumulative exposure, however the cellular responses mediating these differences are unknown. CD4 ...T-follicular helper (Tfh) cells have key roles in inducing antibodies, with Th2-Tfh cell activation associated with antibody development in malaria. Whether Tfh cell activation in malaria is age dependent is unknown and no studies have compared Tfh cell activation in children and adults with malaria.
We undertook a comprehensive study of Tfh cells, along with B cells and antibody induction in children and adults with malaria. Activation and proliferation of circulating Tfh (cTfh) cell subsets was measured ex vivo and parasite-specific Tfh cell frequencies and functions studied with Activation Induced Marker (AIM) assays and intracellular cytokine staining.
During acute malaria, the magnitude of cTfh cell activation was higher in adults than in children and occurred across all cTfh cell subsets in adults but was restricted only to the Th1-cTfh subset in children. Further, adults had higher levels of parasite-specific cTfh cells, and cTfh cells which produced more Th2-Tfh associated cytokine IL-4. Consistent with a role of higher Tfh cell activation in rapid immune development in adults, adults had higher activation of B cells during infection and higher induction of antibodies 7 and 28 days after malaria compared to children.
Our data provide evidence that age impacts Tfh cell activation during malaria, and that these differences may influence antibody induction after treatment. Findings have important implications for vaccine development in children.
This word was supported by the National Health and Medical Research Council of Australia, Wellcome Trust, Charles Darwin University Menzies School of Health Research, Channel 7 Children's Research Foundation, and National Health Institute.
Objectives
Malaria, caused by Plasmodium infection, remains a major global health problem. Monocytes are integral to the immune response, yet their transcriptional and functional responses in primary ...Plasmodium falciparum infection and in clinical malaria are poorly understood.
Methods
The transcriptional and functional profiles of monocytes were examined in controlled human malaria infection with P. falciparum blood stages and in children and adults with acute malaria. Monocyte gene expression and functional phenotypes were examined by RNA sequencing and flow cytometry at peak infection and compared to pre‐infection or at convalescence in acute malaria.
Results
In subpatent primary infection, the monocyte transcriptional profile was dominated by an interferon (IFN) molecular signature. Pathways enriched included type I IFN signalling, innate immune response and cytokine‐mediated signalling. Monocytes increased TNF and IL‐12 production upon in vitro toll‐like receptor stimulation and increased IL‐10 production upon in vitro parasite restimulation. Longitudinal phenotypic analyses revealed sustained significant changes in the composition of monocytes following infection, with increased CD14+CD16− and decreased CD14−CD16+ subsets. In acute malaria, monocyte CD64/FcγRI expression was significantly increased in children and adults, while HLA‐DR remained stable. Although children and adults showed a similar pattern of differentially expressed genes, the number and magnitude of gene expression change were greater in children.
Conclusions
Monocyte activation during subpatent malaria is driven by an IFN molecular signature with robust activation of genes enriched in pathogen detection, phagocytosis, antimicrobial activity and antigen presentation. The greater magnitude of transcriptional changes in children with acute malaria suggests monocyte phenotypes may change with age or exposure.
We investigate the transcriptional, functional and phenotypic changes in monocytes during an experimental blood‐stage P. falciparum infection in malaria naive healthy subjects and during an episode of clinical malaria in children and adults residing in a malaria‐endemic region. We specifically isolated monocytes for transcriptome analysis by RNA sequencing, to determine monocyte gene expression during subpatent and clinical malaria. Monocyte activation during subpatent malaria is driven by an inflammatory molecular signature and a greater magnitude of transcriptional changes in children with acute malaria suggest monocyte phenotypes may change with age or exposure.
Anemia is a major complication of malaria, driven largely by loss of uninfected RBCs during infection. RBC clearance through loss of complement regulatory proteins (CRPs) is a significant contributor ...to anemia in Plasmodium falciparum infection, but its role in Plasmodium vivax infection is unknown. CRP loss increases RBC susceptibility to macrophage clearance, a process that is also regulated by CD47. We compared CRPs and CD47 expression on infected and uninfected RBCs in adult patients with vivax and falciparum malaria and different anemia severities from Papua, Indonesia. Complement activation and parasite-specific complement-fixing antibodies were measured by ELISA. Levels of CR1 and CD55 were reduced in severe anemia in both falciparum and vivax malaria. Loss of CRPs and CD47 was restricted to uninfected RBCs, with infected RBCs having higher expression. There was no association among complement-fixing antibodies, complement activation, and CRP loss. Our findings demonstrate that CRP loss is a pan-species, age-independent mechanism of malarial anemia. Higher levels of CRP and CD47 expression on infected RBCs suggest that parasites are protected from complement-mediated destruction and macrophage clearance. Lack of associations between protective antibodies and CRP loss highlight that complement pathogenic and protective pathways are distinct mechanisms during infection.
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