Combined effects of shade and drought on physiology, growth, and yield of mature cocoa trees.

Climate models predict decreasing precipitation and increasing air temperature, causing concern for the future of cocoa in the major producing regions worldwide. It has been suggested that shade could alleviate stress by reducing radiation intensity and conserving soil moisture, but few on-farm cocoa studies are testing this hypothesis. Here, for 33 months, we subjected twelve-year cocoa plants in Ghana to three levels of rainwater suppression (full rainwater, 1/3 rainwater suppression and 2/3 rainwater suppression) under full sun or 40 % uniform shade in a split plot design, monitoring soil moisture, physiological parameters, growth, and yield. Volumetric soil moisture (Ï´w) contents in the treatments ranged between 0.20 and 0.45 m3m-3 and increased under shade. Rainwater suppression decreased leaf water potentials (ѱw), reaching -1.5 MPa in full sun conditions indicating severe drought. Stomatal conductance (gs) was decreased under the full sun but was not affected by rainwater suppression, illustrating the limited control of water loss in cocoa plants. Although pre-dawn chlorophyll fluorescence (Fv/Fm) indicated photoinhibition, rates of photosynthesis (Pn) were highest in full sun. On the other hand, litter fall was highest in the full sun and under water stress, while diameter growth and carbon accumulation increased in the shade but was negatively affected by rainwater suppression. Abortion of fruits and damage to pods were high under shade, but dry bean yield was higher compared to under the full sun. The absence of interactions between shade treatments and rainwater suppression suggests that shade may improve the performance of cocoa, but not sufficiently to counteract the negative effects of water stress under field conditions.

Ternary Mo2 NiB2 as a Superior Bifunctional Electrocatalyst for Overall Water Splitting.

Transition metal borides are considered as promising electrocatalysts for water splitting due to their metallic conductivity and good durability. However, the currently reported monometallic and noncrystalline multimetallic borides only show generic and monofunctional catalytic activity. In this work, the authors design and successfully synthesize highly crystalline ternary borides, Mo2 NiB2 , via a facile solid-state reaction from pure elemental powders. The as-synthesized Mo2 NiB2 exhibits very low overpotentials for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), that is, 280 and 160 mV to reach a current density of 10 mA cm-2 , in alkaline media. These values are much lower from the ones observed over monometallic borides, that is, Ni2 B and MoB, and the lowest among all nonprecious metal borides. By loading Mo2 NiB2 onto Ni foams as both cathode and anode electrode for overall water splitting applications, a low cell voltage of 1.57 V is required to achieve a current density of 10 mA cm-2 , comparable with the value required from the Pt/C||IrO2 /C couple (1.56 V). The proposed synthesis strategy can be used for the preparation of cost-effective, multi-metallic crystalline borides, as multifunctional electrocatalysts.

Ambient temperature sulfonated carbon fiber reinforced PEEK with hydroxyapatite and reduced graphene oxide hydroxyapatite composite coating.

30% carbon fiber reinforced polyetheretherketone (CFR-PEEK) has in recent times, become significant in the orthopedic industry because its elastic modulus can be engineered to match that of the human bone. But it is bioinert and does not integrate well with the immediate bone tissue environment. In this study, a combined surface modification technique involving ambient temperature sulfonation and surface coating of (hydroxyapatite (HA), 5%reduced graphene oxide hydroxyapatite(5%RGO/HA) and 10%reduced graphene oxide hydroxyapatite(10%RGO/HA) composites) on 30%CFR-PEEK was achieved with an appropriate temperature treatment at 345°C in nitrogen. The coatings adhered unto the surface of S30%CFR-PEEK with an improved hydrophilicity and bioactivity. With the sample S30%CFR-PEEK+HA, having the highest enhanced hydrophilicity from 112.5 ± 2.5° to 20 ± 2° and bioactivity. An improvement in hydrophilicity and bioactivity depicts a change in surface chemistry which will have a positive impact in the interaction of the materials surface with immediate bone environment for a successful application in the orthopedic industry.

3D mesoporous structure assembled from monoclinic M-phase VO2 nanoflakes with enhanced thermochromic performance.

Monoclinic M-phase VO2 is a promising candidate for thermochromic materials due to its abrupt change in the near infrared (NIR) transmittance along with the metal-to-insulator transition (MIT) at a critical temperature ∼68 °C. However, low luminous transmittance (T lum), poor solar energy modulation ability (ΔT sol), and high phase transition temperature (T c) can limit the application of VO2 for smart windows. To overcome these limitations, 3D mesoporous structure can be employed in VO2 films. Herein, 3D mesoporous structures assembled from monoclinic M-phase VO2 nanoflakes with a pore size of about 2-10 nm were synthesized by a hydrothermal method using Ensete ventricosum fiber (EF) as a template followed by calcination at 450 °C. The prepared film exhibited excellent thermochromic performance with balanced T lum = 67.3%, ΔT sol = 12.5%, and lowering T c to 63.15 °C. This is because the 3D mesoporous structure can offer the uniform dispersion of VO2 nanoflakes in the film to enhance T lum, ensure sufficient VO2 nanoflakes in the film for high ΔT sol and lower T c. Therefore, this work can provide a green approach to synthesize 3D mesoporous structures assembled from monoclinic M-phase VO2 nanoflakes and promote their application in smart windows.

Prevalence and attitude towards hepatitis B vaccination among healthcare workers in a tertiary hospital in Ghana.

INTRODUCTION: adequate knowledge on hepatitis B virus (HBV) infection is important among healthcare workers (HCWs) as this impacts the vaccination seeking behaviour. This study sought to assess the knowledge, vaccination status and related factors amongst HCWs in a tertiary facility in Ghana. METHODS: an analytical cross-sectional study was conducted amongst full-time HCWs of different categories at the Cape Coast Teaching Hospital, Ghana. Stratified sampling was used to arrive at the number needed for each category of HCW and then simple random sampling to recruit participants. A structured self-administered questionnaire was used. Descriptive statistics and logistics regression were carried out on the data. RESULTS: a total of 303 HCWs participated with 78.07% (n=235) being between 20-30 years, and majority being females (62.38%, n=189). A total of 186 (61.39%) participants had adequate knowledge, mean knowledge score was 4.73/7 (±0.97). About 80% (n=218) had received the 3 doses of HBV vaccine. Among the unvaccinated, cost was the major barrier (62.07%, n=18). Participants who did not know that HBV was more infectious than HIV (aOR=5.31, 95%CI: 1.91-14.77), p<0.001) and those who did not have knowledge that HBV vaccine was effective were more likely to be unvaccinated (aOR=8.63, 95%CI: 2.99-24.94), p<0.0001). The gender and cadre of staff did not show statistical evidence of an association with vaccination status. CONCLUSION: knowledge on HBV is paramount for all HCWs as well as the importance of receiving the full doses of the hepatitis B vaccines. Barriers to vaccination must be removed to ensure protection of HCWs.

3D Nitrogen-Doped Graphene Encapsulated Metallic Nickel-Iron Alloy Nanoparticles for Efficient Bifunctional Oxygen Electrocatalysis.

Invited for the cover of this issue is Liqiang Mai and co-workers at Wuhan University of Technology. The image depicts Ni3 Fe alloy nanoparticles encapsulated in N-doped graphene as an efficient bifunctional oxygen electrocatalyst toward rechargeable Zn-air batteries, which is expected to drive the electric vehicle. Read the full text of the article at 10.1002/chem.201904722.

3D Nitrogen-Doped Graphene Encapsulated Metallic Nickel-Iron Alloy Nanoparticles for Efficient Bifunctional Oxygen Electrocatalysis.

It is extremely desirable to explore high-efficient, affordable and robust oxygen electrocatalysts toward rechargeable Zn-air batteries (ZABs). A 3D porous nitrogen-doped graphene encapsulated metallic Ni3 Fe alloy nanoparticles aerogel (Ni3 Fe-GA1 ) was constructed through a facile hydrothermal assembly and calcination process. Benefiting from 3D porous configuration with great accessibility, high electrical conductivity, abundant active sites, optimal nitrogen content and strong electronic interactions at the Ni3 Fe/N-doped graphene heterointerface, the obtained aerogel showed outstanding catalytic performance toward the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Specifically, it exhibited an overpotential of 239 mV to attain 10 mA cm-2 for OER, simultaneously providing a positive onset potential of 0.93 V within a half-wave potential of 0.8 V for ORR. Accordingly, when employed in the aqueous ZABs, Ni3 Fe-GA1 achieved higher power density and superior reversibility than Pt/C-IrO2 catalyst, making it a potential candidate for rechargeable ZABs.

Bilayered microelectrodes based on electrochemically deposited MnO2/polypyrrole towards fast charge transport kinetics for micro-supercapacitors.

Micro-supercapacitors (MSCs) are promising power solution facilities for miniaturized portable electronic devices. Microfabrication of on-chip MSC with high specific capacitance and high energy density is still a great challenge. Herein, we report a high-performance MnO2/polypyrrole (PPy) microelectrode based MSC (MnO2/PPy-MSC) by modern micromachining technology. Interdigital Au micro current collectors were obtained by photolithography, physical vapor deposition and lift off. A layer of PPy was electrochemically deposited on Au current collectors followed by deposition of urchin-like MnO2 micro/nanostructures. The electrochemical performance of MnO2/PPy-MSC was explored employing LiClO4/PVA gel electrolyte. The assembled MSC demonstrated a high areal capacitance of 13 mF cm-2, an energy density of 1.07 × 10-3 mW h cm-2 and a power density of 0.53 mW cm-2. In addition, the MnO2/PPy-MSC showed an improved cycling stability, retaining 84% of the initial capacitance after 5000 CV cycles at a scan rate of 500 mV s-1. Our proposed strategy provides a versatile and promising method for the fabrication of high-performance MSCs with large-scale applications.

Strategies To Improve Linkage To HIV Care In Urban Areas Of Sub-Saharan Africa: A Systematic Review.

Of the 37 million people estimated to be living with HIV globally in 2017, about 24.7 million were in the sub-Saharan Africa region, which has been and remains worst affected by the epidemic. Enrolment of newly diagnosed individuals into care in the region, however, remains poor with up to 54% not being linked to care. Linkage to care is a very important step in the HIV cascade as it is the precursor to initiating antiretroviral therapy (ART), retention in care, and viral suppression. A systematic review was conducted to gather information regarding the strategies that have been documented to increase linkage to care of Persons living with HIV(PLHIV) in urban areas of sub-Saharan Africa. An electronic search was conducted on Scopus, Cochrane central, CINAHL Plus, PubMed and OpenGrey for linkage strategies implemented from 2006. A total of 189 potentially relevant citations were identified, of which 7 were eligible for inclusion. The identified strategies were categorized using themes from literature. The most common strategies included: health system interventions (i.e. comprehensive care, task shifting); patient convenience and accessibility (i.e. immediate CD4 count testing, immediate ART initiation, community HIV testing); behavior interventions and peer support (i.e. assisted partner services, care facilitation, mobile phone appointment reminders, health education) and incentives (i.e. non-cash financial incentives and transport reimbursement). Several strategies showed favorable outcomes: comprehensive care, immediate CD4 count testing, immediate ART initiation, and assisted partner services. Assisted partner services, same day home-based ART initiation, combination intervention strategies and point-of-care CD4 testing significantly improved linkage to care in urban settings of sub-Saharan African region. They can be delivered either in a health facility or in the community but should be facilitated by health workers. There is, however, the need to conduct more linkage-specific studies in the sub-region.

1D Carbon-Based Nanocomposites for Electrochemical Energy Storage.

Electrochemical energy storage (EES) devices have attracted immense research interests as an effective technology for utilizing renewable energy. 1D carbon-based nanostructures are recognized as highly promising materials for EES application, combining the advantages of functional 1D nanostructures and carbon nanomaterials. Here, the recent advances of 1D carbon-based nanomaterials for electrochemical storage devices are considered. First, the different categories of 1D carbon-based nanocomposites, namely, 1D carbon-embedded, carbon-coated, carbon-encapsulated, and carbon-supported nanostructures, and the different synthesis methods are described. Next, the practical applications and optimization effects in electrochemical energy storage devices including Li-ion batteries, Na-ion batteries, Li-S batteries, and supercapacitors are presented. After that, the advanced in situ detection techniques that can be used to investigate the fundamental mechanisms and predict optimization of 1D carbon-based nanocomposites are discussed. Finally, an outlook for the development trend of 1D carbon-based nanocomposites for EES is provided.

Macroscopic synthesis of ultrafine N-doped carbon nanofibers for superior capacitive energy storage.

Carbon nanofibers (CNFs) with excellent electric conductivity and high surface area have attracted immense research interests in supercapacitors. However, the macroscopic production of CNFs still remains a great challenge. Herein, ultrafine N-doped CNFs (N-CNFs) with a diameter of ∼20 nm are synthesized through a simple and scalable sol-gel method based on the self-assembly of phenolic resin and cetyltrimethylammonium bromide. When employed in aqueous supercapacitors, the obtained activated N-CNFs manifest a high gravimetric/areal capacitance (380 F g-1/1.7 F cm-2) as well as outstanding rate capability and cycling stability. Besides, the activated N-CNFs also demonstrate excellent capacitive performance (330 F g-1) in flexible quasi-solid-state supercapacitors. The remarkable electrochemical performance as well as the easy and scalable synthesis makes the N-CNFs a highly promising electrode material for supercapacitors.

Boosting oxygen reduction activity with low-temperature derived high-loading atomic cobalt on nitrogen-doped graphene for efficient Zn-air batteries.

High-loading atomic cobalt (12.8 wt%) dispersed on nitrogen-doped graphene was successfully synthesized via considerably low temperature pyrolysis. The catalyst exhibits excellent electrocatalytic performance towards the oxygen reduction reaction with a large limiting diffusion current density of 5.60 mA cm-2 (10% higher than that of commercial Pt/C), and when acting as the air catalyst of Zn-air batteries, a high open-circuit voltage of >1.40 V and excellent power density are also achieved.

Stepwise chelation-etching synthesis of carbon-confined ultrafine SnO2 nanoparticles for stable sodium storage.

A stepwise chelation-etching approach to synthesize carbon-confined ultrafine SnO2 nanoparticles was developed via conformal coating with polydopamine and chelation-etching with ethylenediaminetetraacetic acid (EDTA). EDTA plays a crucial role in the ordered removal of cobalt and tin. The obtained composite exhibits superior sodium storage performance.

Low-crystalline iron oxide hydroxide nanoparticle anode for high-performance supercapacitors.

Carbon materials are generally preferred as anodes in supercapacitors; however, their low capacitance limits the attained energy density of supercapacitor devices with aqueous electrolytes. Here, we report a low-crystalline iron oxide hydroxide nanoparticle anode with comprehensive electrochemical performance at a wide potential window. The iron oxide hydroxide nanoparticles present capacitances of 1,066 and 716 F g-1 at mass loadings of 1.6 and 9.1 mg cm-2, respectively, a rate capability with 74.6% of capacitance retention at 30 A g-1, and cycling stability retaining 91% of capacitance after 10,000 cycles. The performance is attributed to a dominant capacitive charge-storage mechanism. An aqueous hybrid supercapacitor based on the iron oxide hydroxide anode shows stability during float voltage test for 450 h and an energy density of 104 Wh kg-1 at a power density of 1.27 kW kg-1. A packaged device delivers gravimetric and volumetric energy densities of 33.14 Wh kg-1 and 17.24 Wh l-1, respectively.

Self-Organized 3D Porous Graphene Dual-Doped with Biomass-Sponsored Nitrogen and Sulfur for Oxygen Reduction and Evolution.

3D graphene-based materials offer immense potentials to overcome the challenges related to the functionality, performance, cost, and stability of fuel cell electrocatalysts. Herein, a nitrogen (N) and sulfur (S) dual-doped 3D porous graphene catalyst is synthesized via a single-row pyrolysis using biomass as solitary source for both N and S, and structure directing agent. The thermochemical reaction of biomass functional groups with graphene oxide facilitates in situ generation of reactive N and S species, stimulating the graphene layers to reorganize into a trimodal 3D porous assembly. The resultant catalyst exhibits high ORR and OER performance superior to similar materials obtained through toxic chemicals and multistep routes. Its stability and tolerance to CO and methanol oxidation molecules are far superior to commercial Pt/C. The dynamics governing the structural transformation and the enhanced catalytic activity in both alkaline and acidic media are discussed. This work offers a unique approach for rapid synthesis of a dual-heteroatom doped 3D porous-graphene-architecture for wider applications.

Porous Nickel-Iron Selenide Nanosheets as Highly Efficient Electrocatalysts for Oxygen Evolution Reaction.

Exploring non-noble and high-efficiency electrocatalysts is critical to large-scale industrial applications of electrochemical water splitting. Currently, nickel-based selenide materials are promising candidates for oxygen evolution reaction due to their low cost and excellent performance. In this work, we report the porous nickel-iron bimetallic selenide nanosheets ((Ni0.75Fe0.25)Se2) on carbon fiber cloth (CFC) by selenization of the ultrathin NiFe-based nanosheet precursor. The as-prepared three-dimensional oxygen evolution electrode exhibits a small overpotential of 255 mV at 35 mA cm(-2) and a low Tafel slope of 47.2 mV dec(-1) and keeps high stability during a 28 h measurement in alkaline solution. The outstanding catalytic performance and strong durability, in comparison to the advanced non-noble metal catalysts, are derived from the porous nanostructure fabrication, Fe incorporation, and selenization, which result in fast charge transportation and large electrochemically active surface area and enhance the release of oxygen bubbles from the electrode surface.

Three-Dimensional Crumpled Reduced Graphene Oxide/MoS2 Nanoflowers: A Stable Anode for Lithium-Ion Batteries.

Recently, layered transition-metal dichalcogenides (TMDs) have gained great attention for their analogous graphite structure and high theoretical capacity. However, it has suffered from rapid capacity fading. Herein, we present the crumpled reduced graphene oxide (RGO) decorated MoS2 nanoflowers on carbon fiber cloth. The three-dimensional framework of interconnected crumpled RGO and carbon fibers provides good electronic conductivity and facile strain release during electrochemical reaction, which is in favor of the cycling stability of MoS2. The crumpled RGO decorated MoS2 nanoflowers anode exhibits high specific capacity (1225 mAh/g) and excellent cycling performance (680 mAh/g after 250 cycles). Our results demonstrate that the three-dimensional crumpled RGO/MoS2 nanoflowers anode is one of the attractive anodes for lithium-ion batteries.