Low Transport Rates Research Articles

Drag Coefficient of Emergent Vegetation in a Shallow Nonuniform Flow Over a Mobile Sand Bed

AbstractWidely distributed in natural rivers and coasts, vegetation interacts with fluid flows and sediments in a variable and complicated manner. Such interactions make it difficult to predict associated drag forces during sediment transport. This paper investigates the drag coefficient for an emergent vegetated patch area under nonuniform flow and mobile bed conditions, based on an analytical model solving the momentum equation following our previous work (Zhang et al., 2020, https://doi.org/10.1029/2020WR027613). Emergent vegetation was modeled with rigid cylinders arranged in staggered arrays of different vegetation coverage ∅. Laboratory flume tests were conducted to measure variations in both the water and bed surfaces along a vegetated patch on a sand bed. Based on the experimental and theoretical analyses, a dimensionless drag model integrating both terms of flow properties and bed effects is proposed to predict the drag coefficient Cd over a mobile bed. The calculated values of Cd exhibit two different trends, that is, nonmonotonically or monotonically increasing along the streamwise direction, due to the combined effect of water surface gradient and bed slope. The morphodynamic response of the mobile bed to nonuniform flow manifests as an evolution in the bed slope within the vegetated patch. Ongoing scouring directs the flow's energy toward overcoming the rising Cd and bed slope, leading to a relatively stable stage with a low sediment transport rate. This study advances the existing understanding of the drag coefficient's role over a mobile bed within nonuniform flows. It also enhances the applicability of vegetation drag models in riverine restoration.

Polydopamine supporting method fabricating vanadium nitride nanoparticle enclosed into hierarchical hollow carbon nanospheres for supercapacitors

Nanostructure is crucial for achieving electrode materials with high capacity and high-power ascribing to pleasing specific surface area, intrinsic safety, and satisfactory ion transport pathways; nevertheless, the structural collapse that occurs during high-temperature treatment may lead to a decrease in the specific surface area of the electrode material, causing technical obstacles, and hence affecting its practical applicability. Vanadium nitride has become a promising electrode material since its superior conductivity and desirable theoretical capacity; unfortunately, its practical application is hindered by its limited rate capability, cycle stability, and tendency to dissolve in alkaline solutions. In this study, a template-free method is employed to prepare hollow nanosphere structures through the self-supporting effect of dopamine. When subjected to high-temperatures, it can successfully hinder the collapse of the hollow nanostructures. Graded vanadium nitride nanoparticles are generated in this process and encapsulated in hollow nanostructures. The issues of vanadium nitride dissolution and low transport rate in alkaline electrolytes can be efficiently resolved by leveraging the self-supporting action of dopamine and the subsequent formation of hierarchical vanadium nitride nanoparticles. The anode material endows a capacity of 387.14 F g−1 at a current density of 0.5 A g−1, as well as a coulombic efficiency of 98.28 % even after 10, 000 cycles at a current density of 3 A g−1. Additionally，the assembled device can achieve a maximum power density of 4, 000 W kg−1 and an energy density of 22.89 Wh Kg−1. This anode material displays potential applications in energy storage devices and offers a novel approach to material preparation.

Solvation structure regulation of deep eutectic solvents: stabilization of the zinc anode in rechargeable zinc–air batteries

A novel water-free ZnCl2-based DES that achieves an effective regulation of the solvation structure of [ZnClx]2−x by simply controlling the concentration of ZnCl2 was developed.

Ambulance deployment without transport: a retrospective difference analysis for the description of emergency interventions without patient transport in Bavaria

BackgroundNot all patients who call the ambulance service are subsequently transported to hospital. In 2018, a quarter of deployments of an emergency ambulance in Bavaria were not followed by patient transport. This study describes factors that influence patient transport rates.MethodThis is a retrospective cross-sectional study based on data from all Integrated Dispatch Centres of the Free State of Bavaria in 2018. Included were ambulance deployments without emergency physician involvement, which were subdivided into ambulance deployments without transport and ambulance deployments with transport. The proportion of transported patients were determined for the primary reasons for deployment and for the different community types. On-scene time was compared for calls with and without patient transport. Differences were tested for statistical significance using Chi2 tests and the odds ratio was calculated to determine differences between groups.ResultsOf 510,145 deployments, 147,621 (28.9%) could be classified as ambulance deployments without transport and 362,524 (71.1%) as ambulance deployments with transport.The lowest proportion of patients transported was found for activations where the fire brigade was involved (“fire alarm system” 0.6%, “fire with emergency medical services” 5.4%) and “personal emergency response system active alarm” (18.6%). The highest transport rates were observed for emergencies involving “childbirth/delivery” (96.9%) and “trauma” (83.2%). A lower proportion of patients is transported in large cities as compared to smaller cities or rural communities; in large cities, the odds ratio for emergencies without transport is 2.02 [95% confidence interval 1.98–2.06] referenced to rural communites. The median on-scene time for emergencies without transport was 20.8 min (n = 141,052) as compared to 16.5 min for emergencies with transport (n = 362,524). The shortest on-scene times for emergencies without transport were identified for activations related to “fire alarm system” (9.0 min) and “personal emergency response system active alarm” (10.6 min).ConclusionThis study indicates that the proportion of patients transported depends on the reason for deployment and whether the emergency location is urban or rural. Particularly low transport rates are found if an ambulance was dispatched in connection with a fire department operation or a personal emergency medical alert button was activated. The on-scene-time of the rescue vehicle is increased for deployments without transport. The study could not provide a rationale for this and further research is needed.Trial registration This paper is part of the study “Rettungswageneinsatz ohne Transport” [“Ambulance deployment without transport”] (RoT), which was registered in the German Register of Clinical Studies under the number DRKS00017758.

Moisture Migration and Recharge Pattern of Low-Permeability Thick Cohesive Soil in Northern Margin of the Jianghan Plain

An extremely low hydraulic conductivity of cohesive soil causes a low transport rate of water and solute, with a time-consuming result, as we all know. Stable isotopes (δD and δ18O) and in situ monitoring systems of the data about soil water, rainfall, and groundwater were used to analyze the soil moisture migration pattern, using a conceptual model in the field test site, simulated by Hydrus 1D. The results show that multiple rainfalls’ accumulations can cause the water to recharge from soil moisture to micro-confined groundwater, gradually. The soil moisture dynamic change is composed of a dehydration period and absorption period; the cohesive soil water content below 5.0 m was affected by the micro-confined groundwater level and dehydrated in advance due to the level decline. The thick cohesive soil profile can be divided into a shallow mixing zone (0–2 m), steady zone (2–5 m), and deep mixing zone (5–15 m). The effective precipitation recharge was 234 mm and the average infiltration recharge coefficient (Rc) was 0.1389, but the water exchange between the cohesive soil moisture and groundwater was 349 mm in two hydrological years. This paper reveals the moisture migration and recharge pattern of low-permeability thick cohesive soil in a humid area with a micro-confined groundwater aquifer; this is of great significance for groundwater resources evaluation and environmental protection in humid climate plain areas.

Exploring Volatile Precursors: Synthesis, Characterization and Thermal Properties of Thulium Fluoroacetylacetonate Complexes

Five trifluoroacetylacetonate (tfaa−) complexes [Tm(tfaa)3(H2O)]2, [Tm(tfaa)3(H2O)2], [Tm(tfaa)3(H2O)2] · diglyme, [Tm(tfaa)3(DME)] (DME = 1,2-dimethoxyethane) and [TmCl2(tfaa)(diglyme)] (diglyme = bis(2-methoxyethyl) ether) of thulium have been synthesized and characterized by X-ray single-crystal structure analysis and spectroscopic techniques. Thermoanalytical studies at elevated temperatures provide information about their volatility. The results are compared with the hexafluoroacetylacetonate (hfaa−) complexes of thulium known in the literature, which were reported as volatile precursors for CVD application. The reported high volatility of [Tm(hfaa)3(DME)] was confirmed and compared with those of the aqueous complexes which show a lower transport rate. In addition, the new crystal structures of the hexafluoroacetylacetonate complexes [Tm(hfaa)3(H2O)2], [Tm(hfaa)2(tfa)(H2O)2]2 (tfa− = trifluoroacetate), [Tm(hfaa)3(DME)NaCl]2 and Na[Tm(hfaa)4] are presented.

Monitoring sediment transport pathways from an artificial nearshore berm, South Padre Island, Texas, USA, August 2018 to November 2019—Implications for coastal management

During August 2018 – November 2019, the transport pathways of dredge material from a specially constructed nearshore feeder berm were investigated as part of a collaborative study by the City of South Padre Island, U.S. Army Corps of Engineers–Galveston District, U.S. Geological Survey, Partrac GeoMarine Inc., and Texas A&M University, into the efficacy of beneficial use dredge material (BUDM) as a method of replenishing the beach profile and shoreface at South Padre Island, Texas with sediment. Dual-signature (fluorescent and ferrimagnetic) tracer particles, designed to be hydraulically equivalent to the dredge material, were placed on the berm, and a sampling program was initiated to monitor the spatiotemporal movement of tracer particles under the influence of the prevailing hydrodynamic regime. Wave and current data were collected and were used together with available metocean data to identify the forcing mechanisms of sediment transport; improved understanding garnered from the consideration of multiple datasets can be used to inform future coastal management decisions.Tracer analysis results indicated low magnitude, shoreward transport of dredge material from the berm and along shore transport in both northerly and southerly directions. Small amounts of tracer detected in beach face samples demonstrated connectivity between the constructed feeder berm and the shoreface. However, the generally low tracer concentration within beach face samples indicated low rates of sediment transport for berm sediments, and a low magnitude sediment transport pathway from the berm directly to the beach face, with possible storage of sediment in the nearshore bar system.Given that the berm was at or beyond the closure depth and considering the relatively weak prevailing near bottom hydrodynamic conditions, the potential for sediment to be mobilized and transported during the study period was generally low. Periods of higher energy waves, driven by north-northwest winds, were identified as a key driver of sediment transport but due to the infrequent nature of these events the sediment transport regime across the area of interest was temporally limited. Longshore movement of sediment was both north and south, mainly dependent on prevailing wind directions and resulting longshore currents.We discuss implications for coastal zone management and the use of feeder berms as an artificial beach nourishment mechanism to replenish sediments lost by coastal erosional processes. The insight into nearshore emplacement of material can be used by local governments and coastal managers to optimize the efficacy of berm emplacement and implement such schemes as a cost-effective nourishment option, or when onshore placement of material is not feasible.

Development of the Gravel Pressure and Voice Synchronous Observation System and Application in Bedload Transport Measurement

Bedload sediment transport is critical in the natural river environmental and ecological system. It is quite challenging to measure the bedload sediment transport rate in rivers with any degree of accuracy. In this study, the authors developed the Gravel Pressure and Voice Synchronous observation system (GPVS) to estimate the bedload sediment transport rate in rivers. The core of the GPVS includes an underwater high-fidelity audio recorder and pressure sensor. The audio recorder is intended to monitor the low bedload sediment transport rate, whereas the pressure sensor is utilized to detect relatively substantial bedload sediment transport. The GPVS is tested by running flume experiments with natural gravel to evaluate the system’s reliability and feasibility. Results reveal that the GPVS has a very high sensitivity for detecting bedload transport. When the bedload sediment transport rate is relatively low, the audio recorder can measure it quantitatively, showing that the system is not impacted by ambient noise.

Gigantic and Continuous Output Power in Ionic Thermo-Electrochemical Cells by Using Electrodes with Redox Couples.

The main obstacle of ionic thermo-electrochemical cells (TECs) in continuous power supply lies in a low heat-to-electricity energy conversion efficiency because most TECs work in thermodiffusion mode in which the ions are confined in a liquid/electrolyte media. The introduction of the redox couple onto the electrode surface may overcome the obstacle by resolving the low mass transport rate of ions caused by the redox process occurring near but not on the electrode surface. Herein, the authors demonstrate enhancement of TECs by integrating the redox couple directly onto the electrode surface to maximize the mass transport efficiency. A discontinuous interfacial modification strategy is developed by using a carbon cloth/iron (II/III) phytate as the symmetric electrodes. The gelled electrolyte consisting of a polyacrylamide matrix and phytic acid is shown to promote selective ion diffusion. A synergistic combination consisting of the thermodiffusion effect and redox reactions on the electrode is established in a pre-treated layout. Such TEC affords a high output voltage of 0.4 V, an excellent instantaneous output power density (20.26 mW m-2 K-2 ) and a record-high 2 h output energy density (2451 J m-2 ) under TH = 30 °C with TC = 15 °C, with an ultrahigh Carnot-relative efficiency of 1.12%.

Pre-Hospital Emergency Medical Services Utilization Amid COVID-19 in 2020: Descriptive Study Based on Routinely Collected Dispatch Data in Bavaria, Germany.

The COVID-19 pandemic affected the utilization of health care services and posed organizational challenges. While many previous studies focused on the misuse of pre-hospital EMS for low-urgency health problems, the pandemic has put more emphasis on the avoidance of medically necessary calls. To compare the utilization of pre-hospital emergency medical services before and after specific pandemic periods. This was a retrospective, descriptive analysis of routine data from 26 dispatch centers in Bavaria, Germany. We investigated the number of emergencies per 100,000 population, as well as the relative change in the emergency rates and transport rates in 2020, compared to the two previous years. Boxplots showed the distributions across the Bavarian districts per calendar week. The mean rates and standard deviations as well as the relative changes were presented for the specific periods. A paired samples t-test was used to compare the rates. Compared to the average of the two previous years, the emergency rates in 2020 were lower in 35 out of 52 calendar weeks. The strongest reductions were observed during the first wave, where the average emergency rate declined by 12.9% (SD 6.8, p < 0.001). There was no statistically significant difference in the overall emergency rate during the summer holidays. Lower transport rates were observed throughout the year, especially during the first wave. Utilization of pre-hospital emergency medical services decreased in 2020, especially during the periods with strict measures. This could be due to the lower morbidity from the behavioral changes during the pandemic, but also to the avoidance of medical services for both less urgent and severe conditions. While a reduction in unnecessary care would be beneficial, patients must be encouraged to seek necessary urgent care, even during a pandemic.

Coaly Graphite as an Eco-Friendly Material in the Microporous Layer of Proton Exchange Membrane Fuel Cells

Proton exchange membrane (PEM) fuel cells, which can directly convert chemical energy to electricity, are promising as the next-generation energy harvesting method. Among all of the components, the microporous layer (MPL) controls the water and gas transport between the gas diffusion layer and the catalysis layer, where carbon black is one of the traditional materials for fabrication. However, owing to its energy-intensive preparation method, high capitalized cost, and low water transport rate features, the realization of carbon black on a large scale still faces obstacles. Here, we demonstrate a combination of three carbon materials for synthesizing the MPL using carbon black (CB), coaly graphite (CG), and graphene oxide (GO), whose synergistic effect ensures a high output in PEM fuel cells. CB is partially replaced by CG, which reduces the carbon and toxic gas footprint while still maintaining a high power density. This work for designing membrane structures for the MPL opens opportunities for developing highly efficient PEM fuel cells.

Loss of CpFTSY Reduces Photosynthetic Performance and Affects Insertion of PsaC of PSI in Diatoms.

The chloroplast signal recognition particle (CpSRP) receptor (CpFTSY) is a component of the CpSRP pathway that post-translationally targets light-harvesting complex proteins (LHCPs) to the thylakoid membranes in plants and green algae containing chloroplasts derived from primary endosymbiosis. In plants, CpFTSY also plays a major role in the co-translational incorporation of chloroplast-encoded subunits of photosynthetic complexes into the thylakoids. This role has not been demonstrated in green algae. So far, its function in organisms with chloroplasts derived from secondary endosymbiotic events has not been elucidated. Here, we report the generation and characterization of mutants lacking CpFTSY in the diatom Phaeodactylum tricornutum. We found that this protein is not involved in inserting LHCPs into thylakoid membranes, indicating that the post-translational part of the CpSRP pathway is not active in this group of microalgae. The lack of CpFTSY caused an increased level of photoprotection, low electron transport rates, inefficient repair of photosystem II (PSII), reduced growth, a strong decline in the PSI subunit PsaC and upregulation of proteins that might compensate for a non-functional co-translational CpSRP pathway during light stress conditions. The phenotype was highly similar to the one described for diatoms lacking another component of the co-translational CpSRP pathway, the CpSRP54 protein. However, in contrast to cpsrp54 mutants, only one thylakoid membrane protein, PetD of the Cytb6f complex, was downregulated in cpftsy. Our results point to a minor role for CpFTSY in the co-translational CpSRP pathway, suggesting that other mechanisms may partially compensate for the effect of a disrupted CpSRP pathway.

Termination of resuscitation in out-of-hospital cardiac arrest in women and men: An ESCAPE-NET project

AimWomen have less favorable resuscitation characteristics than men. We investigated whether the Advanced Life Support Termination of Resuscitation rule (ALS-TOR) performs equally in women and men. Additionally, we studied whether adding or removing criteria from the ALS-TOR improved classification into survivors and non-survivors. MethodsWe analyzed 6,931 female and 14,548 male out-of-hospital cardiac arrest (OHCA) patients from Dutch and Swedish registries, and validated in 10,772 female and 21,808 male Danish OHCA patients. Performance measures were calculated for ALS-TOR in relation to 30-day survival. Recursive partitioning analysis was performed with the ALS-TOR criteria, as well as age, comorbidities, and additional resuscitation characteristics (e.g. initial rhythm, OHCA location). Finally, we explored if we could reduce the number of ALS-TOR criteria without loss of prognostic value. ResultsThe ALS-TOR had a specificity and positive predictive value (PPV) of ≥99% in both women and men (e.g. PPV 99.9 in men). Classification by recursive partitioning analysis showed a high sensitivity but a PPV below 99%, thereby exceeding the acceptable miss rate of 1%. A combination of no return of spontaneous circulation (ROSC) before transport to the hospital and unwitnessed OHCA resulted in nearly equal specificity and PPV, higher sensitivity, and a lower transport rate to the hospital than the ALS-TOR. ConclusionFor both women and men, the ALS-TOR has high specificity and low miss rate for predicting 30-day OHCA survival. We could not improve the classification with additional characteristics. Employing a simplified version may decrease the number of futile transports to the hospital.

Amorphous antimony sulfide nanoparticles construct multi-contact electron transport layers for efficient carbon-based all-inorganic CsPbI2Br perovskite solar cells

Titanium dioxide (TiO2) layers usually have been applied in perovskite solar cells (PSCs) as traditional electron transport layers (ETLs). However, it has some flaws such as charge recombination and low electron transport rate. Herein, we synthesize amorphous antimony sulfide nanoparticles (Sb2S3 NPs) with uniform distribution of elements and the particle size is about 20 nm by hot injection method, and the nanoparticles are ligand-exchanged with mercaptopropionic acid (MPA). After detailed concentration adjustment, the surface of TiO2 ETL is modified and a multi-contact ETL is prepared. Compared to the conventional TiO2 ETL, the multi-contact ETL exhibits better conductivity, which gives suppressed charge recombination and more effective charge transport at the ETL/perovskite interface. Moreover, the multi-contact ETL can assist to form high quality of CsPbI2Br films. At the same time, the best efficiency of the prepared carbon-based CsPbI2Br PSC achieves as high as 14.59 %, and it still can maintain the initial efficiency of about 96.4 % after continuously heating at 85 °C for 28 days under nitrogen condition.

Boosting Industrial‐Level CO2 Electroreduction of N‐Doped Carbon Nanofibers with Confined Tin‐Nitrogen Active Sites via Accelerating Proton Transport Kinetics

AbstractThe development of highly efficient robust electrocatalysts with low overpotential and industrial‐level current density is of great significance for CO2 electroreduction (CO2ER), however the low proton transport rate during the CO2ER remains a challenge. Herein, a porous N‐doped carbon nanofiber confined with tin‐nitrogen sites (Sn/NCNFs) catalyst is developed, which is prepared through an integrated electrospinning and pyrolysis strategy. The optimized Sn/NCNFs catalyst exhibits an outstanding CO2ER activity with the maximum CO FE of 96.5%, low onset potential of −0.3 V, and small Tafel slope of 68.8 mV dec−1. In a flow cell, an industrial‐level CO partial current density of 100.6 mA cm−2 is achieved. In situ spectroscopic analysis unveil the isolated SnN site acted as active center for accelerating water dissociation and subsequent proton transport process, thus promoting the formation of intermediate *COOH in the rate‐determining step for CO2ER. Theoretical calculations validate pyrrolic N atom adjacent to the SnN active species assisted reducing the energy barrier for *COOH formation, thus boosting the CO2ER kinetics. A Zn‐CO2 battery is designed with the cathode of Sn/NCNFs, which delivers a maximum power density of 1.38 mW cm−2 and long‐term stability.

Experimental and molecular dynamics study on the deterioration mechanism of GFRP bars in distilled water and salt solution environments

The deterioration speed of glass-fibre-reinforced polymer (GFRP) bars plays an important role in their long-term application in concrete. The deterioration mechanism of GFRP bars in different salt solutions and distilled water (DW) environments was determined by conducting a combination of water uptake, microscopic, Fourier transform infrared spectroscopy, and tensile strength (TS) tests. The interaction between the epoxy resin and water molecules and the effect of salt ions on the interior of the epoxy resin system were revealed by performing molecular dynamics (MD) simulation. The results showed that the water uptake and TS losses of the GFRP bars in DW were higher than those in the salt solution environments. Moreover, the TS losses of the GFRP were mainly due to the water uptake swelling and plasticization of the resin. In addition, the MD simulation, revealed that as the moisture uptake increased, the water molecule diffusion coefficient increased and the water-water hydrogen bonding dominated, leading to the occurrence of the water-clustering phenomenon. However, the presence of salt ions led to a low transport rate of water molecules inside the resin, thereby reducing the water-molecule-clustering phenomenon. Compared with monovalent cations (Na+ and K+), multivalent Ca2+ is more likely to bind to COO− ions inside the network system, reducing the electrostatic repulsion between the COO− ions and hindering the swelling of GFRP.

Endothelial Cell Transcytosis Assay as an In Vitro Model to Evaluate Inner Blood-Retinal Barrier Permeability.

Dysfunction of the blood-retinal barrier (BRB) contributes to the pathophysiology of several vascular eye diseases, often resulting in retinal edema and subsequent vision loss. The inner blood-retinal barrier (iBRB) is mainly composed of retinal vascular endothelium with low permeability under physiological conditions. This feature of low permeability is tightly regulated and maintained by low rates of paracellular transport between adjacent retinal microvascular endothelial cells, as well as transcellular transport (transcytosis) through them. The assessment of retinal transcellular barrier permeability may provide fundamental insights into iBRB integrity in health and disease. In this study, we describe an endothelial cell (EC) transcytosis assay, as an in vitro model for evaluating iBRB permeability, using human retinal microvascular endothelial cells (HRMECs). This assay assesses the ability of HRMECs to transport transferrin and horseradish peroxidase (HRP) in receptor- and caveolae-mediated transcellular transport processes, respectively. Fully confluent HRMECs cultured on porous membrane were incubated with fluorescent-tagged transferrin (clathrin-dependent transcytosis) or HRP (caveolae-mediated transcytosis) to measure the levels of transferrin or HRP transferred to the bottom chamber, indicative of transcytosis levels across the EC monolayer. Wnt signaling, a known pathway regulating iBRB, was modulated to demonstrate the caveolae-mediated HRP-based transcytosis assay method. The EC transcytosis assay described here may provide a useful tool for investigating the molecular regulators of EC permeability and iBRB integrity in vascular pathologies and for screening drug delivery systems.

Effect of Nitrate via CVD Coating on Hydrogen Embrittlement in High Strength Steel Treated with Zinc PVD Coating

High strength low alloy steel (HSLAS) is quite sensitive to hydrogen embrittlement due to its different phases. This study investigated the hydrogen embrittlement (HE) behavior of uncoated, physically vapor deposition (PVD) coated, and chemically vapor deposition (CVD) coated HSLAS. The XRD indicates the formation of ZnO, Zn(N3)2, γN and C3N4 phases at the outer coating layer. The results show that combination of surface nitriding and zinc deposition are efficient method against hydrogen embrittlement. This could be attributed to the reduction of hydrogen that is generated by the reaction of surface Zn) N3)2 phase and the low rate of hydrogen transport through the γN phase. The coatings were tested by immersing the tensile samples in a diluted H2SO4 solution with water for 24 hours. Additionally, the result shows that combined coating resulting in higher tensile strength, yield stress, and tensile elongation compared to uncoated samples. Hardness results indicate that the combined coatings (PVD + CVD) has the higher value of about 258 HV, followed by the uncoated sample of about 218 HV, while the PVD only coated sample have the lower hardness value of about 175 HV.

First-principles study of the crystal structure, electronic and optical properties of Cu2O1-xMx (M = S, Se, Te)

Cu2O has the advantages of low price, stable chemical properties, and high visible light absorption rate. It is a very promising hole transport material in solar cells. However, the pure phase Cu2O has a low hole transport rate, which can be improved it by means of doping or something else. In this paper, based on the first-principles, the performance of different amounts of S, Se, and Te doped Cu2O are calculated, it is found that the Te-doped Cu2O performance is pronounced, with the energy gap reduction (1.871 eV), there appear free electron generating, the valence band maximum enables energy level is matched (−5.463 eV), and the absorption coefficient in the ultraviolet and visible range improved, nearly 103.07% at 3.26 eV, the reflectance increased to, for the point 11.7 eV, 76%, and the loss function value is very small in the visible light region (less than 0.1).

Enhancing tryptophan production by balancing precursors in Escherichia coli.

Tryptophan, an essential aromatic amino acid, is widely used in animal feed, food additives, and pharmaceuticals. Although sustainable and environmentally friendly, microbial tryptophan production from renewable feedstocks is limited by low biosynthesis and transport rates. Here, an Escherichia coli strain capable of efficient tryptophan production was generated by improving and balancing the supply of precursors and by engineering membrane transporters. Tryptophan biosynthesis was increased by eliminating negative regulatory factors, blocking competing pathways, and preventing tryptophan degradation. Promoter engineering balanced the supply of the precursors erythrose-4-phosphate and phosphoenolpyruvate, as well as the availability of serine. Finally, the engineering of tryptophan transporters prevented feedback inhibition and growth toxicity. Fed-batch fermentation of the final strain (TRP12) in a 5 L bioreactor produced 52.1 g·L-1 of tryptophan, with a yield of 0.171 g·g-1 glucose and productivity of 1.45 g·L-1 ·h-1 . The metabolic engineering strategy described here paves the way for high-performance microbial cell factories aimed at the production of tryptophan as well as other valuable chemicals.