Can boron form coordination complexes with diffuse electrons? Evidence for linked solvated electron precursors

Density functional theory and ab initio multi-reference calculations are performed to examine the stability and electronic structure of boron complexes that host diffuse electrons in their periphery. Such complexes (solvated electron precursors or SEPs) have been experimentally identified and studied theoretically for several s- and d-block metals. For the first time, we demonstrate that a p-block metalloid element can form a stable SEP when appropriate ligands are chosen. We show that three ammonia and one methyl ligands can displace two of the three boron valence electrons to a peripheral 1s-type orbital. The shell model for these outer electrons is identical to previous SEP systems (1s, 1p, 1d, 2s). Further, we preformed the first examination of a molecular system consisting of two SEPs bridged by a hydrocarbon chain. The electronic structure of these dimers is very similar to that of traditional diatomic molecules forming bonding and anti-bonding σ and π orbitals. Their ground state electronic structure resembles that of two He atoms, and our results indicate that the excitation energies are nearly independent of the chain length for four carbon atoms or longer. These findings pave the way for the development of novel materials similar to expanded metals and electrides.

Activated Sludge-Assisted Phytoremediation For Dye Removal

We report the biodegradation of dye pollutants by a green process that combines the microbial activity of activated sludge with phytoremediation ability of the aquatic plant L. gibba. The obtained results showed that the combination of the two processes when the pollutant was present at concentration of 50 mg/L, lead to a dye removal of 95 and 70% for VB-20 and DR-89, respectively. The biodegradability index based on COD and BOD5 measurement was equal to 3.1 for DR-89 and 2.0 for VB-20, confirming that DR-89 was removed by biosorption phenomena and only VB-20 was transformed into biodegradable compounds. UV-visible, FT-IR and LC/MS analysis were used as a tool for the monitoring of the biodegradation metabolite and the results showed that VB-20 biodegradation occurred by the cleavage of anthraquinone cycle and transformation of aromatic compounds to light hydrocarbon chain; this was further confirmed by the calculation of Fukui index using DFT method. This study highlighted the synergy between the phytoremediation and biodegradation process for organic dye removal.

N-Alkylmorpholines: Potent Dermal and Transdermal Skin Permeation Enhancers

Transdermal drug delivery is an attractive non-invasive method offering numerous advantages over the conventional routes of administration. The main obstacle to drug transport is, however, the powerful skin barrier that needs to be modulated, for example, by transdermal permeation enhancers. Unfortunately, there are still only a few enhancers showing optimum properties including low toxicity and reversibility of enhancing effects. For this reason, we investigated a series of new N-alkylmorpholines with various side chains as potential enhancers in an in vitro permeation study, using three model permeants (theophylline, indomethacin, diclofenac). Moreover, electrical impedance, transepidermal water loss, cellular toxicity and infrared spectroscopy measurements were applied to assess the effect of enhancers on skin integrity, reversibility, toxicity and enhancers’ mode of action, respectively. Our results showed a bell-shaped relationship between the enhancing activity and the hydrocarbon chain length of the N-alkylmorpholines, with the most efficient derivatives having 10–14 carbons for both transdermal and dermal delivery. These structures were even more potent than the unsaturated oleyl derivative. The best results were obtained for indomethacin, where particularly the C10-14 derivatives showed significantly stronger effects than the traditional enhancer Azone. Further experiments revealed reversibility in the enhancing effect, acceptable toxicity and a mode of action based predominantly on interactions with stratum corneum lipids.

Hydrocarbon Desaturation in Cyanobacterial Thylakoid Membranes Is Linked With Acclimation to Suboptimal Growth Temperatures

The ability to produce medium chain length aliphatic hydrocarbons is strictly conserved in all photosynthetic cyanobacteria, but the molecular function and biological significance of these compounds still remain poorly understood. This study gives a detailed view to the changes in intracellular hydrocarbon chain saturation in response to different growth temperatures and osmotic stress, and the associated physiological effects in the model cyanobacterium Synechocystis sp. PCC 6803. We show that the ratio between the representative hydrocarbons, saturated heptadecane and desaturated heptadecene, is reduced upon transition from 38°C toward 15°C, while the total content is not much altered. In parallel, it appears that in the hydrocarbon-deficient ∆ado (aldehyde deformylating oxygenase) mutant, phenotypic and metabolic changes become more evident under suboptimal temperatures. These include hindered growth, accumulation of polyhydroxybutyrate, altered pigment profile, restricted phycobilisome movement, and ultimately reduced CO2 uptake and oxygen evolution in the ∆ado strain as compared to Synechocystis wild type. The hydrocarbons are present in relatively low amounts and expected to interact with other nonpolar cellular components, including the hydrophobic part of the membrane lipids. We hypothesize that the function of the aliphatic chains is specifically associated with local fluidity effects of the thylakoid membrane, which may be required for the optimal movement of the integral components of the photosynthetic machinery. The findings support earlier studies and expand our understanding of the biological role of aliphatic hydrocarbons in acclimation to low temperature in cyanobacteria and link the proposed role in the thylakoid membrane to changes in photosynthetic performance, central carbon metabolism, and cell growth, which need to be effectively fine-tuned under alternating conditions in nature.

Novel Diazocrowns with Pyrrole Residue as Lead(II)Colorimetric Probes

Novel 18- and 23-membered diazomacrocycles were obtained with satisfactory yields by diazocoupling of aromatic diamines with pyrrole in reactions carried under high dilution conditions. X-ray structure of macrocycle bearing five carbon atoms linkage was determined and described. Compounds were characterized as chromogenic heavy metal ions receptors. Selective color and spectral response for lead(II) was found in acetonitrile and its mixture with water. Complexation properties of newly obtained macrocycles with a hydrocarbon chain were compared with the properties of their oligoether analogs. The influence of the introduction of hydrocarbon residue as a part of macrocycle on the lead(II) binding was discussed. Selective and sensitive colorimetric probe for lead(II) in aqueous acetonitrile with detection limit 56.1 mg/L was proposed.

Waste NR Latex Based-Precursors as Carbon Source for CNTs Eco-Fabrications

In this work, the potential of utilizing a waste latex-based precursor (i.e., natural rubber glove (NRG)) as a carbon source for carbon nanotube (CNT) fabrication via chemical vapor deposition has been demonstrated. Gas chromatography-mass spectroscopy (GC-MS) analysis reveals that the separation of the lightweight hydrocarbon chain from the heavier long chain differs in hydrocarbon contents in the NRG fraction (NRG-L). Both solid NRG (NRG-S) and NRG-L samples contain >63% carbon, <0.6% sulfur and <0.08% nitrogen content, respectively, as per carbon-nitrogen-sulfur (CNS) analysis. Growth of CNTs on the samples was confirmed by Raman spectra, SEM and TEM images, whereby it was shown that NRG-S is better than NRG-L in terms of synthesized CNTs yield percentage with similar quality. The optimum vaporization and reaction temperatures were 350 and 800 °C, respectively, considering the balance of good yield percentage (26.7%) and quality of CNTs (ID/IG = 0.84 ± 0.08, diameter ≈ 122 nm) produced. Thus, utilization of waste NRG as a candidate for carbon feedstock to produce value-added CNTs products could be a significant approach for eco-technology.

Appraising Security of Upstream Gas Supply of Complex Network via Integrated Modeling & Simulation for Minimizing Value Leakage for Hydrocarbon Chain for Malaysian Asset

Gas supply security plays a vital role in ensuring the continuity of the power generation and distribution for one of Malaysian State. Unplanned deferments at offshore facilities creates enormous impacts on gas quantity leading to loss/lowering of power generation. Such occurrences lead to value leakage and hinders the expansion strategies by non-firming of investment decisions. It therefore becomes imperative as prudent operator to sustain upstream gas supply by ensuring the security by appropriate strategies in occurrence of such events. Also, for complex facilities it is decisive to have comprehensive understanding of network characteristic, offshore supplies distributions and topology in terms of hydraulics & flow regimes from multiple fields to ensure security of gas supply to customers. This paper proposes an approach to endorse the security of gas supply during normal and ad hoc situations by aligning the relevant feeders to respective demand centers thru comprehensible network modeling and ensure the optimized system response operating envelope for such events. An innovative process was commenced to design, develop, validate, and deploy the network simulation model to cater for the technical characteristics in terms of ullage, hydraulic first principles, blending aspects and safety features during aligning of the respective feeders. The landscape includes around 100+ feeders, multiple export pipelines, several gas highways, and many demand centers with each of its specific requirement. The inline equipment such as pressure boosters with performance curves (compressors/pumps), pressure manipulators (control valves) also formed the integral portion of the model for resilient outputs. Also, the equation of state (for thermodynamic behavior) and appropriate flow co-relation (for pressure drop estimations) were embedded in the model for representative results. The model was validated thoroughly with the plant data by identifying critical junction points to have realistic consequences. Input to the model were classified as engineering input (static such as design capacity, pressure limits, maximum allowable operating pressure (MAOP)) and operational inputs (flow allocations, priority of supply, precedence in operation of demand centers). The process was looped to reallocate the feeders till the required intent is met for the supply as well as on technical aspects. The simulation model could decipher the pain points across the various intensity of the networks such as pressure choking, unintended flow distribution, violations of the resultant specifications and potential breach in the safety limitations. Several iterations could be accomplished in terms of permutations and combinations to align appropriate feeders. The scenarios could be also optimized for the optimal value ranking of the fields to be evacuated for designated demand centers. The simulation model could suggest amendments in the operating strategy such as clustering of sweet/sour fields, integrated contaminant management system, and addition of loop lines to ensure the hydrocarbon molecule travels the intended path. Also, model assisted in generating the heat maps in terms of pressure concentration, flow dispersal and other aspects to have the big picture of the asset which can be probed as required. Network Modeling could recommend the relevant swing fields or alteration in the configuration in case of unforeseen circumstances if it occurs to ensure the security of supply of gas is intact to cater necessities. The approach could recommend that the upstream security of gas supply could be enhanced or endorsed via usage of Network Modeling by either by apposite changes in the operating philosophy and/or configuration. It also resulted into nurture trust of the stakeholder to empower the power generation using gas as fuel and business continuity is ensured for upstream.

Zinc Recovery from Wulagen Sulfide Flotation Plant Tail by Applying Ether Amine Organic Collectors

Separating oxidized zinc minerals from flotation tailings is always a challenge. In this study, a flotation tailing from Wulagen zinc mine in China (Zn grade < 1%) was processed using froth flotation with combinations of amines (OPA 10, OPA 1214, OPA 13, DDA) and Na2S to study the effects of these amines on the zinc recovery as well as their interactions with other reagents, aiming to screen out a proper reagent scheme to improve zinc separation from extremely low-grade zinc flotation tailings. The results show that different amines led to different flotation performance, and the collectors were ranked as OPA 1214, OPA 13, OPA 10 and DDA in a decreasing order based on flotation collectivity and selectivity. An increase in the concentration of each collector increased the zinc recovery but reduced the concentrate zinc grade. Interactions were also observed between different amines and Na2S and Na2SiO3, and OPA 1214 outdid the others in saving the usage of both the Na2S and Na2SiO3. The measured adsorption of collector onto smithsonite was found to correlate well with flotation test results. It was concluded that hydrocarbon chains can be held accountable for the difference in the flotation performance with different amines. The longer the hydrocarbon chain, the stronger the hydrophobic association ability of amine, which is conducive to the selective amine adsorption onto sulfurized smithsonite particles and hence the smithsonite flotation.

Clotrimazole Fluidizes Phospholipid Membranes and Localizes at the Hydrophobic Part near the Polar Part of the Membrane

Clotrimazole (1-[(2-chlorophenyl)-diphenylmethyl]-imidazole) is an azole antifungal drug belonging to the imidazole subclass that is widely used in pharmacology and that can be incorporated in membranes. We studied its interaction with 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) phospholipid vesicles by using differential scanning calorimetry and found that the transition temperature decreases progressively as the concentration of clotrimazole increases. However, the temperature of completion of the transition remained constant despite the increase of clotrimazole concentration, suggesting the formation of fluid immiscibility. 1H-NMR and 1H NOESY MAS-NMR were employed to investigate the location of clotrimazole in 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) phospholipid membranes. In the presence of clotrimazole, all the resonances originating from POPC were shifted upfield, but mainly those corresponding to C2 and C3 of the fatty acyl, chains suggesting that clotrimazole aromatic rings preferentially locate near these carbons. In the same way, 2D-NOESY measurements showed that the highest cross-relaxation rates between protons of clotrimazole and POPC were with those bound to the C2 and C3 carbons of the fatty acyl chains. Molecular dynamics simulations indicated that clotrimazole is located near the top of the hydrocarbon-chain phase, with the nitrogen atoms of the imidazole ring of clotrimazole being closest to the polar group of the carbonyl moiety. These results are in close agreement with the NMR and the conclusion is that clotrimazole is located near the water–lipid interface and in the upper part of the hydrophobic bilayer.