Diffusion-controlled evaporation of sodium dodecyl sulfate solution drops placed on a hydrophobic substrate

In this work, the effect of SDS anionic surfactant on the diffusion-controlled evaporation rate of aqueous solution drops placed on TEFLON-FEP substrate was investigated with 11 different SDS concentrations. Drop evaporation was monitored in a closed chamber having a constant RH of 54-57% by a video camera. The initial contact angle, θ(i) decreased from 104±2° down to 68±1° due to the adsorption of SDS both at the water-air and the solid-water interfaces. The adsorption of SDS on the solid surface was found to be 76% of that of its adsorption at the water-air interface by applying Lucassen-Reynders approach. An equation was developed for the comparison of the evaporation rates of drops having different θ(i) on the same substrate. It was found that the addition of SDS did not alter the drop evaporation rate considerably for the first 1200 s for all the SDS concentrations. The main difference was found to be the change of the mode of drop evaporation by varying the SDS concentration. The constant θ mode was operative up to 80 mM SDS concentration, whereas constant contact area mode was operative after 200 mM SDS concentrations due to rapid drop pining on the substrate.     

Synthesis of bishomoinositols and an entry for construction of a substituted 3-oxabicyclo[3.3.1]nonane skeleton

1,3,3a,7a-Tetrahydro-2-benzofuran was used as key compound for the synthesis of various bishomoinositol derivatives. The diene was subjected to an epoxidation reaction for further functionalization of the diene unit. The bisepoxide obtained was submitted to a ring-opening reaction with acid in the presence of water. Various bishomoinositols were synthesized. However, when the reaction was carried out in the presence of acetic anhydride, a substituted 3-oxabicyclo[3.3.1]nonane skeleton was formed. The mechanism of the formation of the products is discussed.     

Vector-valued multivariate conditional value-at-risk

In this study, we propose a new definition of multivariate conditional value-at-risk (MCVaR) as a set of vectors for arbitrary probability spaces. We explore the properties of the vector-valued MCVaR (VMCVaR) and show the advantages of VMCVaR over the existing definitions particularly for discrete random variables.     

Developing a Novel Platelet-Rich Plasma-Laden Bioadhesive Hydrogel Contact Lens for the Treatment of Ocular Surface Chemical Injuries

Permanent injury to corneal limbal stem cells after ocular surface chemical and thermal injuries is a major cause of corneal blindness. In this study, a PRP-laden GelMA hydrogel contact lens is manufactured which is aimed to support the limbal niche after ocular surface insults thereby preventing limbal stem cell failure. GelMA with varying platelet-rich plasma (PRP) concentrations (5%, 10%, and 20%) is photopolymerized using a visible light crosslinking system followed by characterizations of mechanical properties, growth factor release, enzymatic degradation, and in vitro cytotoxicity. The addition of 10% PRP into 10% GelMA hydrogel precursor solution results in the highest tensile and compressive modulus (38 and 110 kPa, respectively) and burst pressure (251±37.66 mmHg). Degradation time varies according to the concentration of the collagenase enzyme tested (0, 2.5, 5, and 40 µg/mL) and is most prolonged with 20% PRP. EGF and TGF-β release profiles suggest an initial burst release followed by sustained release, most consistent in the 10% PRP sample. Although cell viability decreases on day 1, rapid recovery is observed and is approximately 120% after day 21. PRP-laden GelMA in the form of a contact lens may be a promising biomaterial-based treatment approach for the maintenance of limbal epithelial stem cells after ocular surface insults.     

Substituent and heteroatom effects on the electrochromic properties of similar systems

Electrochromic polymers called poly(3,4‐dihydro‐3,3‐bis ((naphthalen‐1‐yl)methyl)‐2H‐thieno[3,4‐b][1,4]dioxepine) (PProDOT‐Np₂), poly(3,3‐dibenzyl‐3,4‐dihydro‐2H‐selenopheno[3,4‐b][1,4]dioxepine), and poly(3,3‐dibenzyl‐3,4‐dihydro‐2H‐thieno[3,4‐b][1,4]dioxepine) were synthesized electrochemically and the effect of substituents and heteroatoms on the electrochromic properties were investigated for the similar systems. All polymers show electrochromism from a colored state when neutralized to transmissive when oxidized. Although, increasing bulky size (PProDOT‐Np₂) causes lower coloration efficiency (CE) as well as lower optical contrast, the replacement of S atom by Se atom resulted in a lower band gap polymer with a higher CE than its thiophene analog. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Immobilization of Invertase in DAD Type Polymers: Combination of Benzothiadiazole Acceptor Unit and 3,4-Ethylenedioxythiophene and Thiophene Donor Units

Conductive polymers with donor-acceptor-donor (DAD) type units; benzothiadiazole acceptor unit and 3,4-ethylenedioxythiophene (EDOT) and thiophene (Th) donor units, were investigated for immobilization of invertase. The polymers were prepared potentiodynamically from their monomers, M₁ (Th-benzothiadiazole-Th), M₂ (EDOT-benzothiadiazole-EDOT), M₃ (Th-benzothiadiazole-EDOT) and a copolymer, which is a homolog to homopolymer of M₃, was prepared from M₁ and M₂. Invertase was trapped between a two layer-composite; DAD polymer and polypyrrole. The characterization of immobilized invertase was performed using a spectrophotometric method at 540 nm. Kinetic parameters, V _max, maximum reaction rate and K_m , Michaelis-Menten constant values of immobilized invertase in DAD type homopolymer (P₃), 0.95 μmol min^?1 and 22.7 mM, respectively, are found between those of homopolymers P₁ and P₂ and are better than the copolymer. Polymers and copolymers exhibited a broad optimal temperature profile between 30 and 50°C compared to the free enzyme. Optimum pH (5.0) is the same as for free invertase. The electrodes were found to be stable with 100% activity during one day for 40 consecutive measurements. As to the self-life, 25% of the initial activity was lost in the first ten days, then the electrodes were stable with 75% activity for a 40 day storage at 4°C.     

Syntheses and Optical Properties of Perfluorophenyl Containing Benzimidazole Derivatives: The Effect of Donor Units

Synthesis of two novel donor – acceptor – donor type monomers containing benzimidazole as the acceptor unit and thiophene and 3,4-ethylenedioxythiophene (EDOT) as the donor units were performed. 2-(Perfluorophenyl)-4,7-di(thiophen-2-yl)-1H-benzo[d]imidazole and 4,7-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-2-(perfluorophenyl)-1H-benzo[d]imidazole were synthesized successfully and polymerized electrochemically. The electrochemical and spectroelectrochemical studies of the polymers were studied. The effect of electron donating moieties on the optical properties of electrochemically polymerized polymers was investigated. Both polymers were p type dopable and possessed multi-chromic property. Optical studies demonstrated that the polymer based on EDOT unit (P2) resulted in lower band gap since EDOT is higher electron donating group than thiophene.     

3‐[(Diphenylphosphinothioyl)oxy]‐N‐methylpropan‐1‐aminium diphenylphosphanylthioate

The title salt, C₁₆H₂₁NOPS⁺·C₁₂H₁₀OPS, was synthesized from the reaction between 3‐(methylamino)propan‐1‐ol and PPh₂(S)Cl in the presence of Et₃N. Its structure has been identified using spectroscopic methods and X‐ray analysis. Single crystals were obtained from ethanol by slow evaporation. In the asymmetric unit, a cation–anion pair is formed through an intermolecular N—H...O [N...O = 2.6974 (18) Å] hydrogen bond. The molecules are packed through N—H...O and N—H...S hydrogen bonds in the crystal and these hydrogen bonds are responsible for the high melting point. The P atoms of the anion and cation both have distorted tetrahedral environments.     

Two-stage stochastic programming under multivariate risk constraints with an application to humanitarian relief network design

In this study, we consider two classes of multicriteria two-stage stochastic programs in finite probability spaces with multivariate risk constraints. The first-stage problem features multivariate stochastic benchmarking constraints based on a vector-valued random variable representing multiple and possibly conflicting stochastic performance measures associated with the second-stage decisions. In particular, the aim is to ensure that the decision-based random outcome vector of interest is preferable to a specified benchmark with respect to the multivariate polyhedral conditional value-at-risk or a multivariate stochastic order relation. In this case, the classical decomposition methods cannot be used directly due to the complicating multivariate stochastic benchmarking constraints. We propose an exact unified decomposition framework for solving these two classes of optimization problems and show its finite convergence. We apply the proposed approach to a stochastic network design problem in the context of pre-disaster humanitarian logistics and conduct a computational study concerning the threat of hurricanes in the Southeastern part of the United States. The numerical results provide practical insights about our modeling approach and show that the proposed algorithm is computationally scalable.