Letter to the Editor: Reply to the Comments on “Water Solubility of Cloud-Active Aerosols”

Please click here to find the Letter to the Editor to which this Response refers: http://dx.doi.org/10.1080/02786828508959062     

Letter to the Editor: On “Inversion” of Aerosol Size Distribution Data

Please click here to find the Original Article to which this Letter refers: http://dx.doi.org/10.1080/02786828208958576     

Ultrasound-Assisted Synthesis of a Novel Nano-Zigzag-Pattern Lead (II) Metal–Organic System: A New Precursor to Produce Nano-Sized PbO

A sonochemical method was used to synthesize a new nano Pb(II) 1D metal–organic zigzag chain [Pb(p-2-einh)NO₂]_n (1) (p-2-einh?=?(1-(pyridin-2-yl)ethylidene)isonicotinohydrazide). The compound was characterized by scanning electron microscopy (SEM), transmission electron microscopy, elemental analysis, IR spectroscopy, thermogravimetric analysis, X-ray powder diffraction, and single-crystal X-ray analysis. The X-ray analysis reveals a 1D zigzag-chain metal–organic polymer structure for 1 that is further extended to a 3D supramolecular structure by—interaction and other labile interactions. A coordination number of six was determined for the Pb(II) ions in PbN₃O₃. Lead oxide nanoparticles were prepared at 180?°C by thermolysis of 1. The average diameter of the nanoparticles was 20 nm. The size and morphology of the PbO samples were observed using SEM, and the structure of the system was optimized by DFT calculations. The calculated structural parameters and FT-IR spectra are consistent with the crystal structure.     

A Comparative Approach to the Application of a Physico‐Chemical and Advanced Oxidation Combined System to Natural Water Samples

Abstract

Natural organic matter removal (NOM) efficiencies of samples from three major drinking water sources (Elmali, Omerli, and Buyukcekmece) of Istanbul were compared using different treatment systems. Enhanced coagulation as a physico‐chemical method was applied using ferric chloride and aluminum sulphate as the coagulating agents. Moreover, the application of enhanced coagulation in combination with photocatalytic oxidation using TiO₂ was investigated. The efficiency of NOM removal relevant to each treatment step was assessed through DOC removal, UV₂₅₄ removal, and fluorescence measurements.

Irrespective of the treatment applied as enhanced coagulation, photocatalytic oxidation or their combinations, the highest removal efficiency was determined for Elmali followed by Omerli and Buyukcekmece samples both in terms of DOC and UV₂₅₄. Enhanced alum coagulation leads to significant variation in DOC removals as 44%, 28% and 26% for Elmali, Omerli, and Buyukcekmece water samples, respectively. Upon application of ferric chloride as the coagulant, the DOC removals achieved were found to be slightly higher as compared to alum. Moreover, the combined treatment incorporating photocatalytic oxidation subsequent to alum coagulation leads to 36%, 37%, and 50% of DOC removal for Omerli, Buyukcekmece, and Elmali respectively. The improvement of removal efficiencies in combined treatment systems were scrutinized with an emphasis on induced water properties as supported by the specific fluorescence intensities of the samples.     

Freeze-Drying Monitoring Using a New Process Analytical Technology: Toward a “Zero Defect” Process

This article presents a new process analytical technology to monitor a vial freeze-drying process taking into account the batch nonuniformity. It is based on a soft sensor, using a mathematical model of the process, and on the temperature measurement obtained using a new wireless device. It allows estimating the residual ice content in the monitored vials until the end of the primary drying stage and the values of the heat (and mass transfer) coefficients. Experiments carried out with aqueous solutions containing various excipients (sucrose, mannitol, polyvinylpyrrolidone) or with a pharmaceutical formulations show the effectiveness of the proposed system.     

Response from Authors to Comment on “Detection of Spatial Correlations Among Aerosol Particles”

This article reports the results of an optimization procedure for a semivolatile aerosol dichotomous sampler (SADS) and experimental confirmation of the instrument's performance with an optimized sampler. Using numerical model results, the relationships between four major design and operating parameters significantly affecting the performance of the SADS and four performance parameters were expressed in log polynomial equations. Utilizing an optimization procedure, values for the major parameters giving the best performance were determined and used as the base model for optimizing minor parameters. Five minor parameters were then investigated for their possible contribution to better performance of the SADS. The optimal dimensions found were as follows: the diameter ratio between the nozzle and the collection probe was 1.30 and the length ratio of the distance between the nozzle and the collection probe divided by the nozzle diameter was 0.6. Among the minor parameters, only the entrance angle of the nozzle made noticeable improvement at 45°. Experimental tests confirmed that the performance of the new sampler was improved although not as much as expected from the numerical simulation.     

Absolute Mass and Size Measurement of Monodisperse Particles Using a Modified Millikan's Method: Part I—Theoretical Framework of the Electro-Gravitational Aerosol Balance

A new method for accurate mass and size measurement of monodisperse particles is proposed. In this method, charged aerosol particles are introduced into parallel plate electrodes similar to the Millikan cell, and the number of particles left suspended after a certainty holding time has elapsed is measured. The particle survival rate as a function of the voltage applied to the electrodes is used to determine the particle mass. The particle size is deduced by using the particle density which is determined in a separate experiment. The expression of the particle survival function, which is defined as the survival rate as a function of the mass, for particles with and without Brownian diffusion is derived. The sensitivity of this method to the number average diameter, as well as other size distribution parameters, is analyzed on the basis of the survival function.     

From Oxadiazole to Triazole Analogues: Optimization toward a Dual Orexin Receptor Antagonist with Improved in vivo Efficacy in Dogs

The orexin system is responsible for regulating the sleep-wake cycle. Suvorexant, a dual orexin receptor antagonist (DORA) is approved by the FDA for the treatment of insomnia disorders. Herein, we report the optimization efforts toward a DORA, where our starting point was (5-methoxy-4-methyl-2-[1,2,3]triazol-2-yl-phenyl)-{(S)-2-[5-(2-trifluoromethoxy-phenyl)-[1,2,4]oxadiazol-3-yl]-pyrrolidin-1-yl}methanone ( 6 ), a compound which emerged from our in-house research program. Compound 6 was shown to be a potent, brain-penetrating DORA with in vivo efficacy similar to suvorexant in rats. However, shortcomings from low metabolic stability, high plasma protein binding (PPB), low brain free fraction (f_u brain), and low aqueous solubility, were identified and hence, compound 6 was not an ideal candidate for further development. Our optimization efforts addressing the above-mentioned shortcomings resulted in the identification of (4-chloro-2-[1,2,3]triazol-2-yl-phenyl)-{(S)-2-methyl-2-[5-(2-trifluoromethoxy-phenyl)-4H-[1,2,4]triazol-3-yl]-pyrrolidin-1-yl}l-methanone ( 42 ), a DORA with improved in vivo efficacy compared to 6 .     

Highly Porous Hybrid Metal–Organic Nanoparticles Loaded with Gemcitabine Monophosphate: a Multimodal Approach to Improve Chemo- and Radiotherapy

Nanomedicine recently emerged as a novel strategy to improve the performance of radiotherapy. Herein we report the first application of radioenhancers made of nanoscale metal-organic frameworks (nanoMOFs), loaded with gemcitabine monophosphate (Gem-MP), a radiosensitizing anticancer drug. Iron trimesate nanoMOFs possess a regular porous structure with oxocentered Fe trimers separated by around 5 Å (trimesate linkers). This porosity is favorable to diffuse the electrons emitted from nanoMOFs due to activation by γ radiation, leading to water radiolysis and generation of hydroxyl radicals which create nanoscale damages in cancer cells. Moreover, nanoMOFs act as “Trojan horses”, carrying their Gem-MP cargo inside cancer cells to interfere with DNA repair. By displaying different mechanisms of action, both nanoMOFs and incorporated Gem-MP contribute to improve radiation efficacy. The radiation enhancement factor of Gem-MP loaded nanoMOFs reaches 1.8, one of the highest values ever reported. These results pave the way toward the design of engineered nanoparticles in which each component plays a role in cancer treatment by radiotherapy.     

Engineering a Highly Active Sucrose Isomerase for Enhanced Product Specificity by Using a “Battleship” Strategy

The sucrose isomerase SmuA from Serratia plymuthica efficiently catalyses the isomerisation of sucrose into isomaltulose, an artificial sweetener used in the food industry. However, the formation of a hygroscopic by-product, trehalulose, necessitates additional separation to obtain a crystalline product. Therefore, we have improved the product specificity of SmuA by first introducing a few exploratory amino acid exchanges around the active site and investigating their influence. Then, we devised a second set of mutations, either at promising positions from the preceding cycle, but with a different side chain, or at alternative positions in the vicinity. After seven iterative cycles involving just 55 point mutations, we obtained the triple mutant Y219L/D398G/V465E which showed 2.3 times less trehalulose production but still had high catalytic efficiency (k_cat/K_M=11.8 mM⁻¹ s⁻¹). Not only does this mutant SmuA appear attractive as an industrial biocatalyst, but our semirational protein-engineering strategy, which resembles the battleship board game, should be of interest for other challenging enzyme optimization endeavours.     

One polymer,one layer,and two opposite functions: Using a pH-switchable polymer to fabricate a hydrophilic–hydrophobic fibrous membrane

Thanks to their permissibility of vapor transmitting and resistance to water penetration, hydrophilic–hydrophobic membranes (HHMs) are a critical factor in so many applications. Current strategies focus on electrospinning hybrid layers from two different hydrophilic–hydrophobic polymers. Here, we report a new generation of HHMs by electrospinning one layer of pH-switchable polymers followed by a simple post-treatment. In doing so, a hydrophobic poly(methyl methacrylate)-co-poly(N,N-diethylaminoethylmethacrylate) (PMMA-co-PDEAEMA) membrane is fabricated using the electrospinning method. Then, hydrochloric acid (HCl) vapor is used to convert one face of the membrane to a hydrophilic state. Field emission-scanning electron microscopy, drop test, water contact angle (WCA), moisture management test (MMT), t ensile strength, water vapor permeability (WVP), air permeability (AP), and cytotoxicity test were used to characterize the obtained membrane. The results show that by HCl vapor exposure, one side of the membrane gets successfully converted into a hydrophilic state, with the other side still remaining hydrophobic. The drop test and the WCA test showed that the optimal exposure time is only 5 min. This trigger has a small effect on the morphology and, subsequently, on water and air permeability as well as on the mechanical behavior of the membrane. This new generation of membranes can have applications in protective clothing and wound dressing.     

Resolving an Enhanced Oil Recovery Challenge: Optimum Formulation of a Surfactant-Oil–Water System Made Insensitive to Dilution

Upon dilution by the petroleum reservoir connate water, the anionic commercial surfactant blend often used in enhanced oil recovery by low tension, becomes more lipophilic at the interface because of so-called selective partitioning. Hence, the optimum formulation is not maintained when the injected slug moves through the reservoir. An opposite variation is found for ethoxylated nonionic surfactant systems. As a consequence of these antagonistic influences, the optimum formulation shift produced by dilution may be eliminated by using an appropriate mixture of anionic and nonionic commercial surfactants, so that the two effects exactly cancel out.