Influence of heat transfer across the wall of dividing wall columns on energy demand

The implementation of a vertical dividing wall (DW) into a distillation column is a well‐known concept which can result in considerable energy savings for the separation of multicomponent mixtures. It is commonly known that heat streams across the DW, which are present due to temperature differences between both sides, may either increase or decrease the energy demand for a certain separation task. However, no work has been published so far which explains the maximum influence on energy demand. This article derives the maximum extent to which the minimum energy demand for a given column design can change due to heat transfer across the DW. Additionally, it is illustrated how energy‐efficient column operation can be assured even if the total amount of transferred heat is unknown. These results show that the phenomenon of heat transfer across the DW can be handled very well with a suitable control strategy. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1648–1662, 2015     

Polymorphic calcium carbonate phases as adsorbents for allergens in natural rubber latex

Natural rubber latex contains different allergenic proteins and peptides that restrict its application in consumer products. Small mineral particles have a comparatively high specific surface area and are therefore well suited to adsorb such biomolecules. The adsorption of such biomolecules onto different polymorphic phases of calcium carbonate, i.e., calcite, aragonite, and vaterite, was quantitatively determined, both from solution as well as from cured natural rubber latex. All phases were able to adsorb the allergens, with slight differences between the different allergens. Desorption experiments showed differences between the allergens of natural rubber latex, but only small differences between the polymorphic phases of calcium carbonate. The release of the allergens from latex objects with incorporated calcium carbonate particles showed that a retention of allergens is possible by adding calcium carbonate as a filler material. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41271.     

2021 Update on Diagnostic Markers and Translocation in Salivary Gland Tumors

Salivary gland tumors are a rare tumor entity within malignant tumors of all tissues. The most common are malignant mucoepidermoid carcinoma, adenoid cystic carcinoma, and acinic cell carcinoma. Pleomorphic adenoma is the most recurrent form of benign salivary gland tumor. Due to their low incidence rates and complex histological patterns, they are difficult to diagnose accurately. Malignant tumors of the salivary glands are challenging in terms of differentiation because of their variability in histochemistry and translocations. Therefore, the primary goal of the study was to review the current literature to identify the recent developments in histochemical diagnostics and translocations for differentiating salivary gland tumors.     

A threshold heating rate for single-stage heat treatments in glass-ceramics containing seed formers

The development of glass-ceramic materials is often achieved using an elementary microstructural strategy that splits the tasks of seed formation and functionality between two types of crystals. This strategy requires customized time-temperature ceramization protocols, which have been so far implemented using empirical parameters. Here, a more fundamental approach is proposed: the extent of overlap O_e between seed formation and volume crystallization is evaluated by calorimetric and dilatometric measurements, targeting the computation of a threshold heating rate q_t for effective single-stage heat treatments. The applicability of this novel parameter is tested in TiO₂-doped lithium magnesium aluminosilicate glass-ceramics, whose seed formation stage is thoroughly characterized by Raman spectroscopy and STEM. High-temperature X-ray diffraction demonstrates that insufficient seeding results in potentially weaker performances of the final products, due to large sizes and silica deficiency of the functional quartz solid solution crystals.     

Synthesis and Metabolic Fate of 4-Methylthiouridine in Bacterial tRNA

Ribonucleic acid (RNA) is central to many life processes and, to fulfill its function, it has a substantial chemical variety in its building blocks. Enzymatic thiolation of uridine introduces 4-thiouridine (s⁴U) into many bacterial transfer RNAs (tRNAs), which is used as a sensor for UV radiation. A similar modified nucleoside, 2-thiocytidine, was recently found to be sulfur-methylated especially in bacteria exposed to antibiotics and simple methylating reagents. Herein, we report the synthesis of 4-methylthiouridine (ms⁴U) and confirm its presence and additional formation under stress in Escherichia coli. We used the synthetic ms⁴U for isotope dilution mass spectrometry and compared its abundance to other reported tRNA damage products. In addition, we applied sophisticated stable-isotope pulse chase studies (NAIL-MS) and showed its AlkB-independent removal in vivo. Our findings reveal the complex nature of bacterial RNA damage repair.     

Rapid Estimation of Membrane Protein Orientation in Liposomes

The topological organization of proteins embedded in biological membranes is crucial for the tight interplay between these enzymes and their accessibility to substrates in order to fulfil enzymatic activity. The orientation of a membrane protein reconstituted in artificial membranes depends on many parameters and is hardly predictable. Here, we present a convenient approach to assess this important property independent of the enzymatic activity of the reconstituted protein. Based on cysteine-specific chemical modification of a target membrane protein with a cyanine fluorophore and a corresponding membrane-impermeable fluorescence quencher, the novel strategy allows rapid evaluation of the distribution of the two orientations after reconstitution. The assay has been tested for the respiratory complexes bo₃ oxidase and ATP synthase of Escherichia coli and the results agree well with other orientation determination approaches. Given the simple procedure, the proposed method is a powerful tool for optimization of reconstitution conditions or quantitative orientation information prior to functional measurements.     

Efficient Synthesis of Benzothiazinone Analogues with Activity against Intracellular Mycobacterium tuberculosis

8-Nitrobenzothiazinones (BTZs) are a promising class of antimycobacterial agents currently under investigation in clinical trials. Starting from thiourea derivatives, a new synthetic pathway to BTZs was established. It allows the formation of the thiazinone ring system in one synthetic step and is applicable for preparation of a wide variety of BTZ analogues. The synthetic procedure furthermore facilitates the replacement of the sulphur atom in the thiazinone ring system by oxygen or nitrogen to afford the analogous benzoxazinone and quinazolinone systems. 36 BTZ analogues were prepared and tested in luminescence-based assays for in vitro activity against Mycobacterium tuberculosis (Mtb) using the microdilution broth method and a high-throughput macrophage infection assay.     

Europium(III)‐Doped MgAl2O4 Spinel Nanophosphor Prepared by CO2 Laser Co‐Vaporization

Photoluminescent nanoparticles (NPs) are of specific interest for biomedical applications, bioimaging, and cell tracking. Here, we report on the synthesis of europium(III)‐doped MgAl₂O₄ spinel NPs by the CO₂ laser co‐vaporization of a homogeneous raw powder mixture consisting of micrometer‐sized MgAl₂O₄ and Eu₂O₃ (2 and 4 mol%, respectively). The resulting NPs are spherically shaped, show a narrow size distribution (mean diameter: ~30 nm), and are well dispersed. The as‐prepared NPs are highly crystalline and consist of MgAl₂O₄ with small amounts of the secondary phases MgO (~10 mass%) and Eu₂O₃ (<0.5 mass%). The photoluminescence spectra of the doped spinel nanopowders show an intense red emission (λ_em = 615 nm) resulting from the ⁵D₀→⁷F₂ transition with a maximum intensity at an excitation wavelength of 470 nm.     

Predicting the occurrence and effects of defects in castings

Casting designs are generally based on strength of materials calculations and the experience of the designer. This process leads to incremental development of designs utilizing factors of safety, which lead to increased component weights and inefficient use of materials. In castings, unquantifiable factors (such as shrinkage, porosity, hot tears, and inclusions) lead to conservative design rules. Non-destructive testing does not give the designer a way to assess the effect of indications on part performance. This article describes recent work to predict the occurrence and nature of defects in castings and determine their effect on performance. For more information, contact Christoph Beckermann, University of Iowa, Department of Mechanical and Industrial Engineering, 2412 SC, Iowa City, IA 52242-1527; (319) 335-5681; fax (319) 335-5669; e-mail becker@engineering.uiowa.edu.