An investigation on the synthesis of borazine

Borazine is a promising precursor for boron nitride. A detailed investigation on the reaction of sodium borohydride and ammonium sulfate from 40 °C to 120 °C for synthesis of borazine was performed. The reaction was monitored by means of ¹¹B nuclear magnetic resonance (¹¹B NMR) and Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), mass spectroscopy (MS). The reaction produces mainly ammonia borane (AB), but not borazine at temperatures below 60 °C. Increases of temperature promote yield of borazine, which reaches the maximum around 110 °C. Whereas further increased temperature causes severe polymerization of borazine, and hence holds back yields of borazine.     

Quantum chemical studies on substitution effects within silyl group in the silylative coupling of olefins

In this study quantum chemical calculations based on the density functional theory (DFT) have been carried out to examine the effects of methoxy substituent attached to a silicon atom on the reaction of silylative coupling of olefins. It has been shown, that substituted substrate undergoes the reaction according to the recently proposed insertion-rotation-elimination mechanism. During the rotation around C-C single bond additional stabilization by oxygen-ruthenium interaction was observed. Similarly to the (trimethylsilyl)ethene the rate determining step of the reaction is the insertion of the alkene into Ru-Si single bond. The substitution of SiMe₃ by Si(OMe)₃ decreases the energy span of the reaction by almost 3 kcal mol^-1 that is from 21 kcal mol^-1 to 18 kcal mol^-1. The decrease of the energy barrier of the reaction seems to be the result of the increase of point charge differences between the Ru and Si atoms which increases electrostatic attraction between these atoms. Moreover, for Si(OMe)₃ the rate-determining transition state is closer to the alkene interacting with the Ru centre side of the reaction.     

Full assessment of Sida (Sida hermaphrodita) biomass as a solid fuel

Due to an increased awareness of climate change and limited fossil resources, the demand for alternative energy carriers such as biomass has risen significantly during the past years. This development is supported by the idea of a transition to a bio‐based economy reducing fossil‐based carbon dioxide emissions. Based on this trend, biomass for energy is expected to be used in the EU mainly for heating until the end of the decade. The perennial herbaceous mallow plant Sida hermaphrodita (L.) Rusby (‘Sida’) has high potential as an alternative biomass plant for energy purposes. Different density cultivation scenarios of Sida accounting for 1, 2, or 4 plants per m² resulted in a total biomass yield of 21, 28, and 34 tons dry matter/ha, respectively, over a 3‐year period under agricultural conditions while the overall investment costs almost doubled from 2 to 4 plants per m². Subsequently, Sida biomass was used as SI) chips, SII) pellets, and SIII) briquettes for combustion studies at pilot plant scale. Pellets outcompeted chips and briquettes by showing low CO emission of 40 mg/Nm³, good burnout, and low slagging behavior, however, with elevated NO_x and SO₂ levels. In contrast, combustion of chips and briquettes displayed high CO emissions of >1,300 mg/Nm³, while SO₂ values were below 100 mg/Nm³. Contents of HCl in the flue gas ranged between 32 and 52 mg/Nm³ for all Sida fuels tested. High contents of alkaline earth metals such as CaO resulted in high ash melting points of up to 1,450°C. Life cycle assessment results showed the lowest ecological impact for Sida pellets taking all production parameters and environmental categories into consideration, showing further advantages of Sida over other alternative biomasses. Overall, the results indicate the improved applicability of pelletized Sida biomass as a renewable biogenic energy carrier for combustion.     

Theoretical study of borazine and its derivatives

The density functional theory is used to study the geometries, electronic structures, and aromaticity of borazine and its fused ring derivatives. Some new evidences for the ionic nature of B-N bond are found. Geometry studies show that the B-N bond lengths are equal. The lone pair VSCCs of the N atoms are found. As shown, the B-N bonds are of ionic nature based on their positive Laplacian. Magnatic shielding constants also are computed. The shielding and deshielding contributions are divided into Lewis and non-Lewis parts by the NCS-NBO method. It is demonstrated in the NICS studies that there are the ring current effects on borazine and its derivatives are very weak. The aromaticity of borazine is weakened with the fused ring number increasing.     

Theoretical study of the effects of substituents (F,Cl, Br,CH<Subscript>3</Subscript>, and CN) on the aromaticity of borazine

This paper presents a theoretical study of the effects of substituents (F, Cl, Br, CH₃, and CN) on the aromaticity of borazine (B₃N₃H₆), using density functional theory (DFT) and the Hartree-Fock (HF) method. The calculations to optimize the geometries, structural properties, and vibrational frequencies were performed using the same 6–311G(d,p) and 6–311++G(d,p) basis sets, comparing the methods with experimental results. In the analysis of the NICS_ZZ values, it was found that that replacing the hydrogen atoms by halogen atoms (F, Cl, and Br) and CH₃ reduced the aromaticity of the borazine molecule, while use of the CN group resulted in NICS_ZZ values (0.9–2.0 Å) very close to those of borazine, presenting the following order of increasing aromaticity: B₃N₃H₃-(Br)₃?<?B₃N₃H₃-(Cl)₃?<?B₃N₃H₃-(F)₃?<?B₃N₃H₃-(CH₃)₃?<?B₃N₃H₆ ~ B₃N₃H₃-(CN)₃. All the spectra of the compounds showed only the presence of transition peaks distant from the UV region, reflecting the large energy difference between the HOMO and LUMO orbitals. After the substitution of the borazine ring, all the compounds presented an intensification of the spectrum, with a shift of the maximum absorbance toward red, indicative of a bathochromic effect. There was a direct inverse relation between the energy gap and the maximum wavelength of the compounds.     

Energy potential for combustion and anaerobic digestion of biomass from low-input high-diversity systems in conservation areas

In this study, we assessed the potential for bioenergy production of Low-Input High-Diversity (LIHD) systems in temperate West-European conservation areas. A wide range of seminatural ecosystems (wet and dry grasslands, marshes, tall-herb vegetation and heathlands) was sampled. Because LIHD biomass is often scattered and discontinuously available, we only considered the potential for anaerobic digestion and combustion. Both technologies are suitable for decentralized biomass utilization. The gross energy yield showed a promising range between 46–277  GJ per hectare per mowing cycle (MC). The energy efficiency of the anaerobic digestion process was rather low (10–30%) with a methane energy yield of 5.5–35.5 GJ ha⁻¹ MC⁻¹, experimentally determined by batch digestion tests. The water content, functional group composition and biochemical composition (hemicellulose, cellulose, lignin and Kjeldahl nitrogen) of the biomass were analyzed to assess the suitability of different valorization pathways. On the basis of the results, we were able to propose recommendations regarding the appropriate conversion techniques. Biomass from plant communities with ‘late’ harvest dates (August–October) or a high fraction of woody species like heathland and dune slacks, is best valorized through combustion, while herbaceous biomass of ‘early’ harvested grasslands (June–July) and tall-herb vegetation can better be digested. The main advantages of the production of bioenergy from LIHD biomass originating from conservation management are the minimization of the competition with food production and its potential to reconcile renewable energy policies and biodiversity goals.     

Chemical composition and tissue energy density of the cuttlefish (Sepia apama) and its assimilation efficiency by Diomedea albatrosses

The cuttlefish Sepia apama Gray (Mollusca: Cephalopoda) is a seasonally abundant food resource exploited annually by moulting albatrosses throughout winter and early spring in the coastal waters of New South Wales, Australia. To assess its nutritional value as albatross forage, we analysed S. apama for water, lipid protein, ash contents, energy density and amino acid composition. Because albatrosses consistently consume S. apama parts preferentially in the order of head, viscera and mantle, we analysed these sections separately, but did not identify any nutritional basis for this selective feeding behaviour. The gross energy value of S. apama bodies was 20.9 kJ/g dry mass, but their high water content (>83%; cf <70% for fish) results in a relatively low energy density of 3.53 kJ/g. This may contribute to a need to take large meals, which subsequently degrade flight performance. Protein content was typically >75% dry mass, whereas fat content was only about 1%. Albatrosses feed on many species of cephalopods and teleost fish, and we found the amino acid composition of S. apama to be comparable to a range of species within these taxa. We used S. apama exclusively in feeding trials to estimate the energy assimilation efficiency for Diomedea albatrosses. We estimated their nitrogen-corrected apparent energy assimilation efficiency for consuming this prey to be 81.82 ± 0.72% and nitrogen retention as 2.90 ± 0.11 g N kg⁻¹ d⁻¹. Although S. apama has a high water content and relatively low energy density, its protein composition is otherwise comparable to other albatross prey species. Consequently, the large size and seasonal abundance of this prey should ensure that albatrosses remain replete and adequately nourished on this forage while undergoing moult.     

A DFT study of adsorption and decomposition of hexahydro-1,3,5-trinitro-1,3,5-triazine on Mg(0001) surface

The adsorption and decomposition of hexogen (RDX) molecule on the Mg(0001) surface were investigated by the generalized gradient approximation (GGA) of density functional theory (DFT). The calculations employed a supercell (4?×?4?×?4) slab model and three-dimensional periodic boundary conditions. The strong attractive forces between RDX molecule and magnesium atoms induce the RDX’s N???O bond breaking. Subsequently, the dissociated oxygen atoms and radical fragment of RDX oxidize the Mg surface. The largest adsorption energy is ?2104.0 kJ mol^-1. We also investigated the decomposition mechanism of RDX molecule on the Mg(0001) surface. The activation energy for the dissociation step of configuration V4 is as small as 2.5 kJ mol^-1, while activation energies of other configurations are much larger, in the range of 964.9–1375.1 kJ mol^-1. Mg powder is more active than Al powder, and Mg powder performs better in increasing the combustion exothermicity of RDX as well.     

Single Ru Atoms Stabilized by Hybrid Amorphous/Crystalline FeCoNi Layered Double Hydroxide for Ultraefficient Oxygen Evolution

In view of the sluggish kinetics suppressing the oxygen evolution reaction (OER), developing efficient and robust OER catalysts is urgent and essential for developing efficient energy conversion technologies. Herein, hybrid amorphous/crystalline FeCoNi layered double hydroxide (LDH)-supported single Ru atoms (Ru SAs/AC-FeCoNi) are developed for enabling a highly efficient electrocatalytic OER. The amorphous outer layer in Ru SAs/AC-FeCoNi is composed of abundant defect sites and unsaturated coordination sites, which can serve as anchoring sites to stabilize single Ru atoms. The crystalline inner has a highly symmetric rigid structure, thereby strengthening the stability of support for a long-lasting OER. The synergistic effects endow this hybrid catalyst with extremely low overpotential (205 mV at 10 mA cm⁻²). Density functional theory calculation indicates that single Ru atoms stabilized by hybrid amorphous/crystalline FeCoNi LDH facilitate the formation of Ru–O* (rate-determining step), thus accelerating the OER process.     

NiCo2O4 Nanofibers as Carbon‐Free Sulfur Immobilizer to Fabricate Sulfur‐Based Composite with High Volumetric Capacity for Lithium–Sulfur Battery

Both the energy density and cycle stability are still challenges for lithium–sulfur (Li–S) batteries in future practical applications. Usually, light‐weight and nonpolar carbon materials are used as the hosts of sulfur, however they struggle on the cycle stability and undermine the volumetric energy density of Li–S batteries. Here, heavy NiCo₂O₄ nanofibers as carbon‐free sulfur immobilizers are introduced to fabricate sulfur‐based composites. NiCo₂O₄ can accelerate the catalytic conversion kinetics of soluble intermediate polysulfides by strong chemical interaction, leading to a good cycle stability of sulfur cathodes. Specifically, the S/NiCo₂O₄ composite presents a high gravimetric capacity of 1125 mAh g^?1 at 0.1 C rate with the composite as active material, and a low fading rate of 0.039% per cycle over 1500 cycles at 1 C rate. In particular, the S/NiCo₂O₄ composite with the high tap density of 1.66 g cm^?3 delivers large volumetric capacity of 1867 mAh cm^?3, almost twice that of the conventional S/carbon composites.     

Coordination Engineering of N,O Co-Doped Cu Single Atom on Porous Carbon for High Performance Zinc Metal Anodes

Traditional challenges of poor cycling stability and low Coulombic efficiency in Zinc (Zn) metal anodes have limited their practical application. To overcome these issues, this work introduces a single metal-atom design featuring atomically dispersed single copper (Cu) atoms on 3D nitrogen (N) and oxygen (O) co-doped porous carbon (CuNOC) as a highly reversible Zn host. The CuNOC structure provides highly active sites for initial Zn nucleation and further promotes uniform Zn deposition. The 3D porous architecture further mitigates the volume changes during the cycle with homogeneous Zn²⁺ flux. Consequently, CuNOC demonstrates exceptional reversibility in Zn plating/stripping processes over 1000 cycles at 2 and 5 mA cm⁻² with a fixed capacity of 1 mAh cm⁻², while achieving stable operation and low voltage hysteresis over 700 h at 5 mA cm⁻² and 5 mAh cm⁻². Furthermore, density functional theory calculations show that co-doping N and O on porous carbon with atomically dispersed single Cu atoms creates an efficient zincophilic site for stable Zn nucleation. A full cell with the CuNOC host anode and high loading V₂O₅ cathode exhibits outstanding rate-capability up to 5 A g⁻¹ and a stable cycle life over 400 cycles at 0.5 A g⁻¹.     

Operation of a bioelectrochemical system as a polishing stage for the effluent from a two-stage biohydrogen and biomethane production process

Anaerobic bioenergy production processes including fermentative biohydrogen (BioH₂), anaerobic digestion (AD) and bioelectrochemical system have been investigated for converting municipal waste or various biomass feedstock to useful energy carriers. However, the performance of a microbial fuel cell (MFC) fed on the effluent from a two-stage biogas production process has not yet been investigated extensively in continuous reactor operation on complex substrates. In this study we have investigated the extent to which a microbial fuel cell (MFC) can reduce COD and recover further energy from the effluent of a two-stage biohydrogen and biomethane system. The performance of a four-module tubular MFC was determined at six different organic loadings (0.036–6.149 g sCOD L⁻¹ d⁻¹) in terms of power generation, COD removal efficiency, coulombic efficiency (CE) and energy conversion efficiency (ECE). A power density of 3.1 W m⁻³ was observed at the OLR = 0.572 g sCOD L⁻¹ d⁻¹, which resulted in the highest CE (60%) and ECE (0.8%), but the COD removal efficiency decreased at higher organic loading rates (35.1–4.4%). The energy recovery was 92.95 J L⁻¹ and the energy conversion efficiency, based on total influent COD was found to be 0.48–0.81% at 0.572 g sCOD L⁻¹ d⁻¹. However, the energy recovery by the MFC is only reported for a four-module reactor and improved performance can be expected with an extended module count, as chemical energy remained available for further electrogenesis.     

Construction of Ordered Atomic Donor–Acceptor Architectures in bcc IrGa Intermetallic Compounds toward Highly Electroactive and Stable Overall Water Splitting

Benefiting from ordered atomic structures and strong d-orbital interactions, intermetallic compounds (IMCs) are promising electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, the body-centered cubic IrGa IMCs with atomic donor–acceptor architectures are synthesized and anchored on the nitrogen-doped reduced graphene oxide (i.e., IrGa/N-rGO). Structural characterizations and theoretical calculations reveal that the electron-rich Ir sites are atomically dispersed in IrGa/N-rGO, facilitating the electron transfer between Ir atoms and adsorbed species, which can efficiently decrease the energy barriers of the potential determining step for both HER and OER. Impressively, the IrGa/N-rGO||IrGa/N-rGO exhibits excellent performance for overall water splitting in alkaline medium, requiring a low cell voltage of 1.51 V to achieve 10 mA cm⁻², meanwhile, exhibiting no significant degradation for 100 h. This work demonstrates that the rational design of noble metal electrocatalysts with donor–acceptor architectures is beneficial for catalytic reactions in energy conversion applications.     

Phenanthrene biodegradation by immobilized microbial consortium in polyvinyl alcohol cryogel beads

Removal of polycyclic aromatic hydrocarbons (PAHs), a group of widespread toxic compounds, has been one of the environmental issues in wastewater treatment systems for many years. In this study, biodegradation of phenanthrene (PHE), as a model contaminant, by a microbial consortium entrapped in polyvinyl alcohol (PVA) cryogel prepared by freeze-thaw method was investigated. The effect of inoculum size (300–900 mg of cell dry weight per liter) and initial PHE concentration (100–2000 ppm) as well as bead cell density (5 and 10 mg ml⁻¹) on PHE biodegradation by freely suspended cell (FC) and immobilized cell (IC) systems in aqueous phase was examined. Results showed that although both IC and FC systems were capable of complete removal of 100 and 250 ppm of initial PHE (as sole carbon and energy sources), incomplete PHE removals were observed at higher initial PHE concentrations up to 2000 ppm after 7 days. IC system resulted in the maximum PHE removal of 400 ppm at initial PHE concentration of 750 ppm and inoculum size of 600 mg l⁻¹, while under these conditions FC system removed 310 ppm of PHE. Moreover, bead cell density was shown to affect the performance of IC system, with the lower density of 5 mg ml⁻¹ leading to a higher PHE removal due to the enhanced transport phenomena in the culture. Additionally, a correlation was proposed to predict PHE biodegradation at a range of initial PHE concentrations.     

Boosting Thermoelectric Performance of Thermogalvanic Hydrogels by Structure Engineering Induced by Liquid Nitrogen Quenching

Quasi-solid thermogalvanic hydrogels hold great promise in harvesting low-grade thermal energy, yet, they are still far from practical application owing to relatively low power output. Herein, through liquid nitrogen quenching-induced structure engineering, a high-performance stretchable thermogalvanic hydrogel thread with a high specific output power density of 2227.5 µW m⁻² K⁻² and a large thermopower of 4.5 mV K⁻¹ is designed. After liquid nitrogen quenching, both the thermopower and electrical conductivity have been greatly improved compared to natural cooling. The excellent properties are attributed to liquid nitrogen quenching-induced grain refinement and precipitation inhibition. It is a novel and general preparation method for high-performance and homogeneous thermogalvanic hydrogels. Finally, a thermogalvanic hydrogel array is demonstrated to be capable of driving a low-power motor and charging a mobile phone by low-grade thermal energy harvesting, indicating a great potential for practical applications in human daily life.     

Estimation of Boron Intake and its Relation with Bone Mineral Density in Free-Living Korean Female Subjects

In this study, the status of boron intake was evaluated and its relation with bone mineral density was examined among free-living female subjects in Korea. Boron intake was estimated through the use of the database of boron content in frequently consumed foods by Korean people as well as measuring bone mineral density, taking anthropometric measurements, and surveying dietary intake of 134 adult females in order to relatively evaluate the intake of boron as a nutrient to supplement the low level of calcium intake and to verify its relationship with bone mineral density. Average age, height, and weight of the subjects were respectively 40.84 years, 157.62 cm and 59.70 kg. Also, average bone mineral density of lumbar spine L1–L4 and average bone mineral density of the femoral neck were 0.92 g/cm² and 0.80 g/cm², respectively. Their average intakes of energy and boron per day were 6,538.53 kJ and 926.94 μg. Intake of boron through vegetables, fruits, and cereals accounted for 61.72% of the overall boron intake. The food item that contributed most to their daily boron intake was rice. Also, 65.41% of overall boron intake was from 30 varieties of other food items, such as soybean paste, soybeans, red beans, watermelons, oriental melons, pears, Chinese cabbage Kimchi, soybean sprouts and soybean milk, etc. Boron intake did not show significant relation to bone mineral density in lumbar vertebra and femoral region. In summary, the average daily intake of boron was 926.94 μg and did not display significant relation to bone mineral density in 134 free-living female subjects. The continuous evaluation of boron consumption by more diverse targets will need to be conducted in the future.     

Low-Friction Graphene Oxide-Based Ion Selective Membrane for High-Efficiency Osmotic Energy Harvesting

Graphene-based laminate membranes with selective ion-transport capability show great potential in renewable osmotic energy harvesting. One of the great challenges is to reduce the overall energy barriers while remain the high ion selectivity in the transmembrane ion transport process. Here, a strategy is proposed to break the trade-off between ion selectivity and permeability in laminar nanochannels using amphiphilic molecules as modifier, which enhances the surface charge density of nanochannel by loading more ion polymer with polar head and lows the frictional force of ion transport with hydrophobic tail. The conversion efficiency can reach to 32% in osmotic energy harvesting (0.5 m /0.01 m concentration gradient) after adopting this modifier. During the process of mixing real river water and seawater, the maximum power density can reach to 13.38 W m⁻². The amphiphilic molecules also bind adjacent nanosheets, endowing the membrane's strong mechanical strength and high stability in aqueous solution. This work can open up a new way to regulate the transmembrane ion transport in 2D laminate membranes.     

Low-dose photodynamic therapy effect on closure of scratch wounds of normal and diabetic fibroblast cells: An in vitro study

Chronic wounds such as diabetic ulcers are a serious public health problem. Extensive research is needed to find new alternatives for wound treatment. Photodynamic therapy (PDT) is a non-invasive method, which has been studied for several decades to treat cancer, infections, and other diseases. PDT involves the administration of a photosensitizer compound followed by irradiation with using light at specific wavelength to produce reactive oxygen species (ROS) using molecular oxygen. It is possible that low dose photodynamic therapy (LDPDT) could improve wound healing and stimulates the cell repair process. This study we explored the effect of LDPDT on wound healing in vitro using normal and diabetic cellular wound models. The effects of different concentrations of 5-ALA and different energy densities (dark or light) on the cell viability of human fibroblast cells were studied using the MTT assay. After ascertaining the optimum parameters, a scratch wound assay was performed on both normal and diabetic cells and then cells treated with 1 and 5 μg/mL of 5-ALA at 1 J/cm² energy density. ROS production and morphological alteration of the cells were studied. The mortality of normal fibroblast cells increased with increasing 5-ALA concentration and also increasing energy density (up to 3 J/cm²). However, in diabetic cells, the mortality rate did not decrease. Diabetic cells showed increased migration and closure of the scratch compared to normal cells under similar conditions. A low concentration of 5-ALA (5 μg/mL) and low energy density of 1 J/cm² in both normal and diabetic cells gave a small increase in ROS levels compared to controls. This may explain the positive effects of LDPDT on wound healing. The findings of this study suggest that LDPDT may have a potential effect on the wound healing of diabetic wounds.     

Process development for production of human granulocyte-colony stimulating factor by high cell density cultivation of recombinant <Emphasis Type="Italic">Escherichia coli</Emphasis>

The fed-batch process using glucose as the sole source of carbon and energy with exponential feeding rate was carried out for high cell density cultivation of recombinant Escherichia coli BL21 (DE3) expressing human granulocyte-colony stimulating factor (hG-CSF). IPTG was used to induce the expression of hG-CSF at 48 g dry cell wt l⁻¹ during high cell density culture of recombinant E. coli BL21 (DE3) [pET23a-g-csf]. The final cell density, specific yield and overall productivity of hG-CSF were obtained as ~64 g dry cell wt l⁻¹, 223 mg hG-CSF g⁻¹ dry cell wt and 775 mg hG-CSF l⁻¹ h⁻¹, respectively. The resulting purification process used cell lysis, inclusion body (IB) preparation, refolding, DEAE and Butyl-Sepharose. Effects of different process conditions such as cell lysis and washing of IB were evaluated. The results reveal that the cells lyzed at 1,200 bar, 99.9% and Triton removed about 64% of the LPS but sarcosyl had no effect on removal of nucleic acids and LPS. Further analysis show that DEAE column removes DNA about 84%. Cupper concentration was identified as parameter that could have a significant impact on aggregation, as an unacceptable pharmaceutical form that decrease process yields. The purity of purified hG-CSF was more than 99%. Also the comparison of activity between purified hG-CSF and commercial form do not show valuable decrease in activity in purified form.