Surface passivation treatment is a widely used strategy to resolve trap-mediated nonradiative recombination toward high-efficiency metal-halide perovskite photovoltaics. However, a lack of passivation with mixture treatment has been investigated, as well as an in-depth understanding of its passivation mechanism. Here, a systematic study on a mixed-salt passivation strategy of formamidinium bromide (FABr) coupled with different F-substituted alkyl lengths of ammonium iodide is demonstrated. It is obtained better device performance with decreasing chain length of the F-substituted alkyl ammonium iodide in the presence of FABr. Moreover, they unraveled a synergistic passivation mechanism of the mixed-salt treatment through surface reconstruction engineering, where FABr dominates the reformation of the perovskite surface via reacting with the excess PbI2. Meanwhile, ammonium iodide passivates the perovskite grain boundaries both on the surface and top perovskite bulk through penetration. This synergistic passivation engineer results in a high-quality perovskite surface with fewer defects and suppressed ion migration, leading to a champion efficiency of 23.5% with mixed-salt treatment. In addition, the introduction of the moisture resisted F-substituted groups presents a more hydrophobic perovskite surface, thus enabling the decorated devices with excellent long-term stability under a high humid atmosphere as well as operational conditions. 相似文献
Chorismate and isochorismate constitute branch-point intermediates in the biosynthesis of many aromatic metabolites in microorganisms and plants. To obtain unnatural compounds, we modified the route to menaquinone in Escherichia coli. We propose a model for the binding of isochorismate to the active site of MenD ((1R,2S, 5S,6S)-2-succinyl-5-enolpyruvyl-6-hydroxycyclohex-3-ene-1-carboxylate (SEPHCHC) synthase) that explains the outcome of the native reaction with α-ketoglutarate. We have rationally designed variants of MenD for the conversion of several isochorismate analogues. The double-variant Asn117Arg–Leu478Thr preferentially converts (5S,6S)-5,6-dihydroxycyclohexa-1,3-diene-1-carboxylate (2,3-trans-CHD), the hydrolysis product of isochorismate, with a >70-fold higher ratio than that for the wild type. The single-variant Arg107Ile uses (5S,6S)-6-amino-5-hydroxycyclohexa-1,3-diene-1-carboxylate (2,3-trans-CHA) as substrate with >6-fold conversion compared to wild-type MenD. The novel compounds have been made accessible in vivo (up to 5.3 g L−1). Unexpectedly, as the identified residues such as Arg107 are highly conserved (>94 %), some of the designed variations can be found in wild-type SEPHCHC synthases from other bacteria (Arg107Lys, 0.3 %). This raises the question for the possible natural occurrence of as yet unexplored branches of the shikimate pathway. 相似文献
Overproduction of proteinase A by recombinant Saccharomyces cerevisiae was investigated by cultivations in a cell-recycling bioreactor. Membrane filtration was used to separate cells from the broth. Recycling ratios and dilution rates were varied and the effect on enzyme production was studied both experimentally and by computer simulations. Experiments and simulations showed that cell mass and product concentration were enhanced by high ratios of recycling. Additional simulations showed that the proteinase A concentration decreased drastically at high dilution rates and the optimal volumetric productivities were at high dilution rates just below washout and at high ratios of recycling. Cell-recycling fermentation gave much higher volumetric productivities and stable product concentrations in contrast to simple continuous fermentation. 相似文献
For new developments such as plasma surface technologies, it is first necessary to prove their scientific possibilities and limits. Therefore it is mainly questions of process understanding and process handling, quality of the substrate and coating as well as its interactions which are considered and discussed.
To use these technologies in industry it is also necessary to consider ecological aspects as well as economic and marketing aspects. For a scientist at first these aspects are not as important.
An overview of different economic aspects of the application of plasma surface technologies is presented by considering the following: investment and running costs of plants; costs of process development for special applications; comparison of different technologies; certainty and reproducibility of the coating technologies; cost and profit balance of coated work pieces; costs of marketing.
Recently, the importance of the ecological aspects of industrial technologies has increased greatly. In most cases these questions are closely linked to the economic aspects. Nearly all ecological problems can be solved and handled, but the costs for this are increasing greatly. Although the laws currently differ in different countries, in future the laws everywhere will become more strict. The main concerns of the application and handling of a plasma assisted process are for example the use or production of toxic media, security of plants for the staff and for the environment, and handling of used coated material. 相似文献
A comparative pharmacokinetic study has been performed in 19 healthy male volunteers in a single-dose, randomized, two way cross-over design with two preparations of gemfibrozil (CAS 25812-30-0) capsules each of them containing 300 mg active ingredient. The test preparation was Innogem 300 mg capsule. The plasma concentration of gemfibrozil was determined by a validated HPLC-UV analytical method. The statistical comparison of individual pharmacokinetic parameters (AUC0-16, AUC0-oc Cmax, tmax) of the two capsule preparations was performed by three-way analysis of variance (ANOVA), Wilcoxon's, Westlake's, Schuirmann's and Hanck-Anderson's method as well as by the calculation of confidence intervals on the ratio of test/reference. The relative bioavailability of the test preparation with respect to the reference preparation in terms of the AUC0-oc was 104.06 +/- 21.61%. No statistically significant difference was found between the pharmacokinetic parameters, calculated from plasma concentration-time curves, indicating that the two preparations were bioequivalent. 相似文献
OBJECTIVE: To find the reasons which determine failures to comply with anti-flu vaccinations, so that these can be corrected and the coverage of this preventive action be increased. DESIGN: Observational crossover study, done by means of a telephone survey of people over 65. A questionnaire with closed questions, composed after a pilot study and validated by Cronbach's alpha. SETTING: Primary Care Centre (PCC). PATIENTS: We calculated a population sample for qualitative variables (_ = 0.05; p = 0.60; e = 0.05) of 294 people over 65, chosen from the PCC records, by means of random sampling (K = 4) stratified for age and discounting the telephone selection bias. MEASUREMENTS AND RESULTS: The proportion of vaccinated patients (60.9%) obtained in our study did not significantly differ from that in the general population. The percentage of patients included in the programme for the first time was 14%. Level of satisfaction among those vaccinated was 89.4%, with 8.9% of problems detected being light. Main causes of non-vaccination were: thinking that they didn't need it (63.5%), ignorance of the campaign (35.7%), fear of the reaction (24.3%), forgetting (10.4%). The main form of access to the campaign information was from the PCC, both through individuals and posters. Lack of information was statistically significant (p < 0.00001) as a determinant of non-vaccination, without other factors (age, sex, associated pathologies...) explaining these differences. CONCLUSIONS: Individualised and on-going health education by the PCC is fundamental. This would enable the identification of the group not vaccinated due to their express refusal and the recovery of non-vaccinated patients. 相似文献
This paper presents a study of the structural and optical properties of strained GaInAs/ InP multiple quantum well (MQW) structures
fabricated by LP-MOVPE. The composition of the GaxIn1−xAs films ranged fromx = 0.17 tox = 1.0 and was determined by sputtered neutral mass spectrometry (SNMS) on thick layers. The structures of the MQW samples
with well widths from 1.5 to 5 nm were investigated by high resolution x-ray diffraction (HR-XRD). Simulations of the diffraction
patterns showed that transition layers of approximately 2 monolayer (ML) thickness with high lattice mismatch exist at the
interfaces. Photoluminescence (PL) measurements indicate well widths of a multiple of a monolayer with local variations of
one monolayer. The PL peak energies vary smoothly with the Ga concentration. These results were confirmed by optical absorption
measurements. 相似文献
This report reviews the analysis used to extract the complex conductivity of a compound from a microwave cavity perturbation measurement. We intend to present a generalized treatment valid for any spheroidally shaped sample of arbitrary conductivity which is placed at either the electric or magnetic field antinode of the cavity. To begin with, we establish the relationship between the measured parameters and the conductivity for a spherical sample. Next, we extend these results to the case of spheroids; and for the first time, we cover all different configurations that one can possibly use to study an arbitrary conducting sample inside a cavity: in particular, all possible orientations of the sample with respect to the applied field are solved. 相似文献
Droplet formation on Si surfaces bombarded by 10 keV beams from a liquid metal indium ion source has been observed. It has been verified that excess indium is transported in the ion beam, probably in the form of charged droplets. SIMS, SEM and RBS techniques have been used to study the distribution of droplets at the surface. At the specified ion source operating conditions, equilibrium droplet coverage is of the order of 25%. Individual droplets have an average diameter of 0.35 ωm and an average height of 2.2 nm. At a bombardment current density of 0.1 mA cm?2, equilibrium coverage is reached in about 1 s. 相似文献