Evaporation of liquids on chemically patterned surfaces

We studied evaporation rates of volatile liquids deposited onto chemically patterned surfaces by means of experiments and numerical simulations. We quantified the influence of the droplet geometry, in particular circular, triangular, rectangular and square shapes, as well as the influence of contact angles. We considered the two cases of vaporization both in stagnant atmospheres as well as in the presence of well-defined laminar airflows. While lateral air-convection enhances evaporation, it causes a dependence of the evaporation rate on the pattern orientation with respect to the airflow. Neighboring droplets and rivulets tend to mutually reduce their evaporation rate relative to isolated patterns.     

Aqueous two‐phase systems for the recovery of a recombinant viral coat protein from Escherichia coli

In this study the use of an aqueous two‐phase system (ATPS) following the direct chemical extraction of a recombinant viral coat protein, from the cytoplasm of Escherichia coli, is evaluated. The driving force is the need to establish an economically‐viable process for the manufacture of a vaccine against human papilloma infection. The partition behaviour of recombinant L1 protein, the major structural protein of the virus, and DNA was investigated in a polyethylene glycol (PEG)–phosphate system. An evaluation of system parameters including PEG molecular mass and the concentrations of PEG and phosphate was conducted, to estimate conditions under which the L1 protein and DNA partition to opposite phases. ATPS extraction comprising a volume ratio of 1.00, PEG 1000 (18.0%(w/w)) and phosphate (15.0%(w/w)) provided the conditions for accumulation of DNA into the bottom phase and concentration of L1 protein into the opposite phase (ie partition coefficient of DNA; ln K_DNA < 0.0 and partition coefficient of L1; ln K_L1 > 2.5). The findings reported here demonstrate the potential of ATPS to recover recombinant protein released from E coli by direct chemical extraction. © 2002 Society of Chemical Industry     

State multiplicity in CSTR-separator-recycle polymerisation systems

This article continues earlier work (Comput. Chem. Eng. 24 (2000) 209) concerning the design and control of isothermal reactor-separator-recycle systems. The multiplicity behaviour of six reaction systems of increasing complexity, from one-reactant, first-order reaction to chain-growth polymerisation, is investigated. Below a critical value of the plant Damkohler number, Da<Da^cr, the only steady state involves infinite flow rates. Feasible steady states become possible if the critical value is exceeded, Da>Da^cr. For one-reaction systems, one stable steady state is born at a transcritical bifurcation. For consecutive-reaction systems, including polymerisation, a fold bifurcation can lead to two feasible steady states. Moreover, the transcritical bifurcation is destroyed when two reactants are involved. If the gel-effect is included, a maximum of four steady states are possible. When multiple steady states exist, the achievable conversion is constrained by the instability of the low-conversion branch. This has practical importance for polymerisation systems when the radicals’ quasi-steady state assumption is not valid or the gel effect is significant.     

Synthesis and characterization of phenolic and amino resins based on α, β-unsaturated aldehydes

Phenolic and amino resins on the basis of α,β-unsaturated aldehydes were synthesized in bulk or solution. Catalysts were HCl, H₃PO₄, or formic acid, and in some cases NaOH. The course of the reactions was followed by GPC and NMR while the structure of the reaction products was determined by one- and two-dimensional NMR. The course of the reactions is influenced by experimental conditions: the type of monomers, their molar ratio, the type and quantity of the catalyst, the reaction time and temperature, and the reaction medium. At the beginning of the reaction the addition of a nucleophile to an aldehyde takes place through parallel 1,2-addition to and 1,4-addition to group. Oligomers with ? OH, , and ? CHO functional groups are able to add new monomer units or to react mutually to form higher molecular weight addition and condensation products. The overall rate constants for the beginning of the reactions were between 10^?3 L/mol s for the high reactive mixtures and 10^?7 L/mol s for the less reactive mixtures. The resins were cured by heating at temperatures above 135°C with the addition of hexamethylenetetramine.     

Elevated temperature impact on performance of Low Temperature Co-fired Ceramic dielectrics

The need for electronics to operate at temperatures of 200°C and above continues to grow. These applications include avionics, aerospace, automotive, downhole drilling, mining, and many others. To satisfy this demand, a significant amount of research and development has been conducted. Despite the efforts, the number of new electronic components designed specifically for high-temperature operation is still relatively limited. In Low Temperature Co-fired Ceramic (LTCC) packages, LTCC materials are generally used as the host media for a number of pre-fabricated semiconductor components. As a result, reliability of the entire LTCC package largely depends on the performance of the least robust component. Ferro A6M-E and Ferro L8 are the two well-established and recognized LTCC dielectrics widely used for mid and high frequency LTCC applications, including several high reliability aerospace and defense applications that require demanding Mil-Spec qualifications. This study is our first attempt to characterize and understand basic high-temperature dielectric properties of these two commercial LTCC materials. The secondary objective is to initiate a dialogue in attempt to establish reliability requirements for LTCC packages dedicated for high-temperature operation.     

Aging effect of atmospheric pressure plasma jet treated polycaprolactone polymer solutions on electrospinning properties

In previous work, an atmospheric pressure plasma jet was applied to successfully improve the electrospinnability of poly-ε-caprolactone (PCL) which enabled the fabrication of beadless nanofibers. In this paper, we report the aging effect of the plasma treatment to evaluate the robustness of the developed process. For this purpose, plasma-treated PCL polymer solutions with different exposure time were stored for 1 and 8 days and the aged solutions were analyzed in terms of conductivity, viscosity, surface tension, pH, and polymer molecular weight. During storage, the surface tension and acidity of the plasma-treated solutions were maintained constant. However, the viscosity was found to be significantly lower after 8 days which was attributed to PCL degradation. Electrospinning of all stored PCL solutions resulted in the generation of beadless PCL nanofibers. The plasma treatment effects were thus found to be highly stable over time and capable of producing high-quality PCL nanofibers up to 8 days. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48914.     

Lignin from Annual Plants as Raw Material Source for Flavors and Basic Chemicals

The enzymatic conversion of lignins, possibly in combination with electrochemical oxidation, makes aromatics such as syringol, guaiacol, vanillin and catechol available in the qualities required by the fragrance industry. The lignins were obtained by soda digestion from wheat straw and Miscanthus, characterized and then converted with laccases. The overall yield amounted up to 9 wt % with a product spectrum confined to four substances. Catechol was the major product, with a fraction of ≈75 %. It can easily be isolated by extraction with acetone.     

Cyclic distillation technology – a mini‐review

Process intensification in distillation systems has received much attention during past decades, with the aim of increasing both energy and separation efficiency. Various techniques, such as internal heat‐integrated distillation, membrane distillation, rotating packed bed, dividing‐wall columns and reactive distillation were studied and reported in the literature. All these techniques employ the conventional continuous counter‐current contact of vapor and liquid phases. Cyclic distillation technology is based on an alternative operating mode using separate phase movement which leads to key practical advantages in both chemical and biochemical processes. This article provides a mini‐review of cyclic distillation technology. The topics covered include the working principle, design and control methods, main benefits and limitations as well as current industrial applications. Cyclic distillation can be rather easily implemented in existing columns by simply changing the internals and the operating mode, thus bringing new life to old distillation towers by significantly increasing the column throughput, reducing the energy requirements and offering better separation performance. © 2016 Society of Chemical Industry     

Cloning and heterologous expression of three type II PKS gene clusters from Streptomyces bottropensis

Mensacarcin is a potent cytotoxic agent isolated from Streptomyces bottropensis. It possesses a high content of oxygen atoms and two epoxide groups, and shows cytostatic and cytotoxic activity comparable to that of doxorubicin, a widely used drug for antitumor therapy. Another natural compound, rishirilide A, was also isolated from the fermentation broth of S. bottropensis. Screening a cosmid library of S. bottropensis with minimal PKS-gene-specific primers revealed the presence of three different type II polyketide synthase (PKS) gene clusters in this strain: the msn cluster (mensacarcin biosynthesis), the rsl cluster (rishirilide biosynthesis), and the mec cluster (putative spore pigment biosynthesis). Interestingly, luciferase-like oxygenases, which are very rare in Streptomyces species, are enriched in both the msn cluster and the rsl cluster. Three cosmids, cos2 (containing the major part of the msn cluster), cos3 (harboring the mec cluster), and cos4 (spanning probably the whole rsl cluster) were introduced into the general heterologous host Streptomyces albus by intergeneric conjugation. Expression of cos2 and cos4 in S. albus led to the production of didesmethylmensacarcin (DDMM, a precursor of mensacarcin) and the production of rishirilide A and B (a precursor of rishirilide A), respectively. However, no product was detected from the expression of cos3. In addition, based on the results of isotope-feeding experiments in S. bottropensis, a putative biosynthesis pathway for mensacarcin is proposed.