Acetate ligands determine the crystal structure of CdSe nanoplatelets - a density functional theory study.

Cadmium selenide (CdSe) nanoplatelets of a few atomic layers thick exhibit extremely sharp photoluminescence peaks and are synthesized in the zinc blende crystal structure, whereas the most stable bulk polymorph of CdSe is the wurtzite structure. These platelets can be synthesized very monodispersely in thickness, and are covered with acetate ligands. Here, we show by means of density functional theory (DFT) calculations that these ligands play a pivoting role in the stabilization of 2D nanosheets as a whole, including the deviating crystal structure. The relative stability as a function of slab thickness, strong effects on electronic properties, and implications for synthesis are discussed.The Dutch science foundation NWO : a VIDI grant (grant number 723.012.006)

Structure and stability of hcp iron carbide precipitates: A first-principles study

Hexagonal close-packed(hcp)ironcarbidesplayanimportantroleinsteel processing andinsteelproducts.Therecentdiscoveryofnovelultrafine(2–5 nm) iron carbide(ε'-Fe2+xC) precipitatesinTRIPsteelshedsanewlightonthehcp family ofcarbides.Herewepresentafirst-principlesstudyontherelativestability, and theelectronic,magneticpropertiesofthe ε'-Fe2C phases.Differentstackingsof Fe-sheets andorderingsofCatomswereinvestigatedandcomparedwith experimental dataandwithJack’s model.Wefindveryfavorableformation enthalpies forthesenewmembersofthehcpfamily,andwepresentafirst- principles-refined modelforthecrystalstructureoftheultrafineFe(C)precipitates. These findingsareusefulforthecharacterizationofnano-sizedironcarbide precipitates, forunderstandingtheirroleinthemicrostructureofsteels,andforthe design ofnovelsteelshavingevenmoredesirableproperties.This workwas [9TD$DIF]funded byERC-CoGgrantnr.683076(NANO-INSITU)

Effectiveness and profitability of integrated pest management for improving yield on smallholder cocoa farms in Ghana

Many pests, especially capsid bugs, infest cocoa and contribute to low yields in producing countries. In Ghana, synthetic pesticides are recommended for controlling the insect pests, and a combination of synthetic pesticides and cultural practices for diseases and weeds. However, the farmers in Ghana are not motivated to adopt these recommendations due to the high cost of pesticides and low producer prices. There is also concern that use of synthetic pesticides on a wide scale can affect both human health and the environment. With the objective of improving cocoa yields through environmentally friendly pest control practices, evaluation of an integrated pest management (IPM) package based on aqueous neem (Azadirachta indica A. Juss.) seed extracts to control the insect pests and cultural practices to manage the diseases, weeds and parasitic plants was undertaken in farmers' fields with their active participation. The IPM package improved yields significantly and was found to be more profitable than the farmers' practices. However, there are two major constraints to adoption of the package by farmers: it is labour-intensive and currently, neem is not readily available to the community. The study recommends that these constraints must be tackled to motivate the farmers to adopt or adapt the IPM package

The nutritive value of black soldier fly larvae reared on common organic waste streams in Kenya

Open Access JournalIn Africa, livestock production currently accounts for about 30% of the gross value of agricultural production. However, production is struggling to keep up with the demands of expanding human populations, the rise in urbanization and the associated shifts in diet habits. High costs of feed prevent the livestock sector from thriving and to meet the rising demand. Insects have been identified as potential alternatives to the conventionally used protein sources in livestock feed due to their rich nutrients content and the fact that they can be reared on organic side streams. Substrates derived from organic by-products are suitable for industrial large-scale production of insect meal. Thus, a holistic comparison of the nutritive value of Black Soldier Fly larvae (BSFL) reared on three different organic substrates, i.e. chicken manure (CM), brewers’ spent grain (SG) and kitchen waste (KW), was conducted. BSFL samples reared on every substrate were collected for chemical analysis after the feeding process. Five-hundred (500) neonatal BSFL were placed in 23 × 15 cm metallic trays on the respective substrates for a period of 3–4 weeks at 28 ± 2 °C and 65 ± 5% relative humidity. The larvae were harvested when the prepupal stage was reached using a 5 mm mesh size sieve. A sample of 200 grams prepupae was taken from each replicate and pooled for every substrate and then frozen at −20 °C for chemical analysis. Samples of BSFL and substrates were analyzed for dry matter (DM), crude protein (CP), ether extracts (EE), ash, acid detergent fibre (ADF), neutral detergent fibre (NDF), amino acids (AA), fatty acids (FA), vitamins, flavonoids, minerals and aflatoxins. The data were then subjected to analysis of variance (ANOVA) using general linear model procedure. BSFL differed in terms of nutrient composition depending on the organic substrates they were reared on. CP, EE, minerals, amino acids, ADF and NDF but not vitamins were affected by the different rearing substrates. BSFL fed on different substrates exhibited different accumulation patterns of minerals, with CM resulting in the largest turnover of minerals. Low concentrations of heavy metals (cadmium and lead) were detected in the BSFL, but no traces of aflatoxins were found. In conclusion, it is possible to take advantage of the readily available organic waste streams in Kenya to produce nutrient-rich BSFL-derived feed

Host finding by Uscana lariophaga (Hymenoptera: Trichogrammatidae) in stored cowpea : the effect of distance, time interval, host patch size and spatial orientation

Host finding and parasitization by Uscana lariophaga Steffan, a potential biocontrol agent of the storage pest Callosobruchus maculatus (Fabricius), were investigated in stored cowpea. Host finding was shown to be a function of distance, time, host patch size and the spatial position of U. lariophaga relative to the host patch. Uscana lariophaga females were able to find hosts up to 75 cm horizontal distance from the host patch, which was the largest distance tested. The probability that a host patch was found when an individual U. lariophaga female was released at 2.5 cm horizontal distance from the host patch ranged from 0.6 after 2 h foraging time to 0.9 after 8 h foraging time. At 10 cm from the host patch, host finding probability ranged from 0.2 to 0.45 at these respective foraging times. Finding probabilities doubled compared to horizontal distances when U. lariophaga was released below the host patch, and halved when it was released above the host patch. The negative geotaxic response was shown not to be an artefact of the release method. The median net displacement rate in the direction of the host patch was two beans per hour (1.4 cm h-1). The results suggest that U. lariophaga females start searching for hosts regardless of the quality of the olfactory information they receive. Additional observations indicated that U. lariophaga is adapted to a host with a patchy distribution, which implies that host finding over larger distances is relevant for U. lariophag

The ACCOMPLISH study. A cluster randomised trial on the cost-effectiveness of a multicomponent intervention to improve hand hygiene compliance and reduce healthcare associated infections

Contains fulltext : 97410.pdf (publisher's version ) (Open Access)BACKGROUND: Public health authorities have recognized lack of hand hygiene in hospitals as one of the important causes of preventable mortality and morbidity at population level. The implementation strategy ACCOMPLISH (Actively Creating COMPLIance Saving Health) targets both individual and environmental determinants of hand hygiene. This study aims to evaluate the cost-effectiveness of a multicomponent implementation strategy aimed at the reduction of healthcare associated infections in Dutch hospital care, by promotion of hand hygiene. METHODS/DESIGN: The ACCOMPLISH package will be evaluated in a two-arm cluster randomised trial in 16 hospitals in the Netherlands, in one intensive care unit and one surgical ward per hospital. INTERVENTION: A multicomponent package, including e-learning, team training, introduction of electronic alcohol based hand rub dispensers and performance feedback. VARIABLES: The primary outcome measure will be the observed hand hygiene compliance rate, measured at baseline and after 6, 12 and 18 months; as a secondary outcome measure the prevalence of healthcare associated infections will be measured at the same time points. Process indicators of the intervention will be collected pre and post intervention. An ex-post economic evaluation of the ACCOMPLISH package from a healthcare perspective will be performed. STATISTICAL ANALYSIS: Multilevel analysis, using mixed linear modelling techniques will be conducted to assess the effect of the intervention strategy on the overall compliance rate among healthcare workers and on prevalence of healthcare associated infections. Questionnaires on process indicators will be analysed with multivariable linear regression, and will include both behavioural determinants and determinants of innovation. Cost-effectiveness will be assessed by calculating the incremental cost-effectiveness ratio, defined here as the costs for the intervention divided by the difference in prevalence of healthcare associated infections between the intervention and control group. DISCUSSION: This study is the first RCT to investigate the effects of a hand hygiene intervention programme on the number of healthcare associated infections, and the first to investigate the cost-effectiveness of such an intervention. In addition, if the ACCOMPLISH package proves successful in improving hand hygiene compliance and lowering the prevalence of healthcare associated infections, the package could be disseminated at (inter)national level. TRIAL REGISTRATION: NTR2448

Head-to-head comparison of 14 prediction models for postoperative delirium in elderly non-ICU patients:an external validation study

OBJECTIVES: Delirium is associated with increased morbidity, mortality, prolonged hospitalisation and increased healthcare costs. The number of clinical prediction models (CPM) to predict postoperative delirium has increased exponentially. Our goal is to perform a head-to-head comparison of CPMs predicting postoperative delirium in non-intensive care unit (non-ICU) elderly patients to identify the best performing models. SETTING: Single-site university hospital. DESIGN: Secondary analysis of prospective cohort study. PARTICIPANTS AND INCLUSION: CPMs published within the timeframe of 1 January 1990 to 1 May 2020 were checked for eligibility (Preferred Reporting Items for Systematic Reviews and Meta-Analyses). For the time period of 1 January 1990 to 1 January 2017, included CPMs were identified in systematic reviews based on prespecified inclusion and exclusion criteria. An extended literature search for original studies was performed independently by two authors, including CPMs published between 1 January 2017 and 1 May 2020. External validation was performed using a surgical cohort consisting of 292 elderly non-ICU patients. PRIMARY OUTCOME MEASURES: Discrimination, calibration and clinical usefulness. RESULTS: 14 CPMs were eligible for analysis out of 366 full texts reviewed. External validation was previously published for 8/14 (57%) CPMs. C-indices ranged from 0.52 to 0.74, intercepts from −0.02 to 0.34, slopes from −0.74 to 1.96 and scaled Brier from −1.29 to 0.088. Based on predefined criteria, the two best performing models were those of Dai et al (c-index: 0.739; (95% CI: 0.664 to 0.813); intercept: −0.018; slope: 1.96; scaled Brier: 0.049) and Litaker et al (c-index: 0.706 (95% CI: 0.590 to 0.823); intercept: −0.015; slope: 0.995; scaled Brier: 0.088). For the remaining CPMs, model discrimination was considered poor with corresponding c-indices <0.70. CONCLUSION: Our head-to-head analysis identified 2 out of 14 CPMs as best-performing models with a fair discrimination and acceptable calibration. Based on our findings, these models might assist physicians in postoperative delirium risk estimation and patient selection for preventive measures

Structural tale of two novel (Cr, Mn)C carbides in steel

Chromium (Cr), manganese (Mn) and carbon (C) are well known alloying elements used in technologically important alloy steels and advanced high strength steels. It is known that binary CrCx and MnCx carbides can be formed in steels, but in this study we reveal for the first time that Cr and Mn were found combined in novel ternary cementite type (Cr, Mn)C carbides. Electron diffraction experiments showed that Cr, Mn and C formed two distinct carbide phases possessing orthorhombic and monoclinic crystal structures. Density functional theory calculations were performed on these phases and excellent agreement was found between calculations and experiments on the lattice parameters and relative atomic positions. The calculations showed that the combination of Mn and Cr resulted in a very high thermodynamic stability of the (Cr, Mn)C carbides, and that local structural relaxations are associated with carbon additions. Possible implications of these ternary carbides for novel applications in steel design and manufacturing are discussed

Bridging the Gap: 3D Real-Space Characterization of Colloidal Assemblies via FIB-SEM Tomography

Insight in the structure of nanoparticle assemblies up to a single particle level is key to understand the collective properties of these assemblies, which critically depend on the individual particle positions and orientations. However, the characterization of large, micron sized assemblies containing small, 10-500 nanometer, sized colloids is highly challenging and cannot easily be done with the conventional light, electron or X-ray microscopy techniques. Here, we demonstrate that focused ion beam-scanning electron microscopy (FIB-SEM) tomography in combination with image processing enables quantitative real-space studies of ordered and disordered particle assemblies too large for conventional transmission electron tomography, containing particles too small for confocal microscopy. First, we demonstrate the high resolution structural analysis of spherical nanoparticle assemblies, containing small anisotropic gold nanoparticles. Herein, FIB-SEM tomography allows the characterization of assembly dimensions which are inaccessible to conventional transmission electron microscopy. Next, we show that FIB-SEM tomography is capable of characterizing much larger ordered and disordered assemblies containing silica colloids with a diameter close to the resolution limit of confocal microscopes. We determined both the position and the orientation of each individual (nano)particle in the assemblies by using recently developed particle tracking routines. Such high precision structural information is essential in the understanding and design of the collective properties of new nanoparticle based materials and processes.Comment: 17 pages, 4 figures, Supplemental Information at articles webpage: https://doi.org/10.1039/C8NR09753

Influence of temperature on selected life-history traits of black soldier fly (Hermetia illucens) reared on two common urban organic waste streams in Kenya

Open Access JournalIn sub-Saharan Africa, urban populations are projected to increase by 115% in the coming 15 years. In addition, economic growth and dietary shifts towards animal source foods have put high pressure and demand on agricultural production. The high ecological footprint of meat and dairy production, as well as high feed costs, prevent the livestock sector from meeting the increasing demand in a sustainable manner. Insects such as the black soldier fly (BSF) have been identified as potential alternatives to the conventionally used protein sources in livestock feed due to their rich nutrient content and the fact that they can be reared on organic side streams. Substrates derived from organic byproducts are suitable for industrial large-scale production of insect meal. Although efficient in waste management and in feed production, BSF larvae are very sensitive to the external environment such as temperature and rearing medium. Therefore, we studied the effect of temperature and substrate type, i.e., brewers’ spent grain (SG) and cow dung (CD), on the development and survival of BSF larvae. Both organic substrates were readily available in Nairobi, Kenya, the location of the experiments. In our experiment, 100 3–5-day-old BSF larvae were placed into containers that contained either SG or CD and further treated at temperatures of 15 °C, 20 °C, 25 °C, 30 °C, and 35 °C. The duration of larval development was recorded, and the prepupae were removed, weighed, and placed individually in separate, labeled, 35-mL plastic cups filled with moist sawdust. After emergence, 10 2-day-old adults (5 males and 5 females) from every replica per substrate were transferred into a cage (40 × 40 × 40 cm) and allowed to mate for 24 h at their respective temperatures. The laid egg batches were collected and counted, and the adult flies’ longevity was recorded. The data were subjected to a two-way analysis of variance (ANOVA) using the general linear model procedure. BSF larvae reared on SG developed faster than those reared on CD; the former also favored higher temperatures for their larval development and emergence into adults. The optimum range was 25–30 °C. With increasing temperatures, the longevity of adult BSF decreased, while the fecundity of females increased. Thus, it is possible to take advantage of the readily available SG waste streams in the urban environments of Kenya to produce BSF larvae-derived livestock feed within a short duration of time and at relatively high temperatures