Development of a dynamic model for ice-on-coil external melt storage systems

Ice storage systems are commonly used to balance the intermittency of renewable energy and decrease the peak load by switching to off-peak hours. An adequate model is necessary to predict the behaviour of these systems. However, there is a scarce in detailed models available used to describe the performance of an ice storage evaporator and its use in a refrigeration cycle. Most existing models approximate the working principles with a steady analysis, not considering the sub cooling of ice and thickness distribution along the length. The developed model in this article uses a discretisation in length and radial direction together with an adapted thermal resistance matrix method to limit the calculation time. It has a great variability of boundary conditions and the ability to implement different types of refrigerants. The simulation results are in good agreement with the data of the manufacturer. The model shows that switching from R404A to R449A reduces the total electricity consumption

Modeling Lewis acid catalyzed reactions in MOFs : how to solve the challenges?

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Modeling Lewis catalyzed reactions in Metal Organic Frameworks

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Structure, Organization, and Expression of the lct Gene for Lacticin 481, a Novel Lantibiotic Produced by Lactococcus lactis

The structural gene for the lactococcal lantibiotic lacticin 481 (lct) has been identified and cloned using a degenerated 20-mer DNA oligonucleotide based on the amino-terminal 7 amino acid residues of the purified protein. The transcription of the lct gene was analyzed, and its promoter was mapped. DNA sequence analysis of the lct gene revealed an open reading frame encoding a peptide of 51 amino acids. Comparison of its deduced amino acid sequence with the amino-terminal sequence and the amino acid composition of lacticin 481 indicates that the 61-residue peptide is prelacticin 481, containing a 27-residue carboxyl-terminal propeptide and a 24-residue amino-terminal leader peptide which lacks the properties of a typical signal sequence and which is significantly different from the leaders of other lantibiotics. The predicted amino acid sequence of prolacticin 481 contains 3 cysteines, 2 serines, and 2 threonines which were not detectable in amino acid analyses of mature lacticin 481. Based on these results and on characterization by two-dimensional NMR techniques, a structural model is proposed in which 2 cysteine residues are involved in lanthionine and one in β-methyllanthionine formation, and a 4th threonine residue is dehydrated. This model predicts a molecular mass for lacticin 481 of 2,901, which is in excellent agreement with that obtained from mass spectrometry.

Insights on the adsorption behavior of aromatics in MIL-47 and MIL-53 from a theoretical perspective

Recently, the spectrum of nanoporous materials like zeolites and zeotype structures has been further expanded through the discovery of a new class of hybrid porous solids [1, 2]. Those materials, nowadays also known as metal organic frameworks or MOFs, consist of both inorganic and organic moieties. Certain MOFs exhibit a very interesting adsorption and even catalytic behavior. Within this contribution, we will mainly focus on adsorption and separation of aromatic species in MIL-47 and MIL-53 [3, 4, 5]. Some of the presenting authors reported for first time on the successful use of MOFs as selective adsorbents for the extremely difficult and industrially relevant separations of para-xylene versus meta-xylene and para-xylene versus ethylbenzene [3]. Their study focuses on the MIL-47, which was first synthesized by Barthelet [4]. This separation behavior of MIL-47 could be better understood with adsorption studies [3, 5]. The packing of each C8-pair will be discussed on the basis of the interactions between those two aromatic compounds and MIL-47 [3]. In order to unravel the interaction between the guest molecules and the lattice, periodic Density Functional Theory calculations have been conducted. The DFT calculations were corrected for dispersion interaction [6] to include the long-range attractive forces. It seems that pi-pi stacking energies between pairs of aromatics but also with the walls of the MOF are crucial for the packing behavior in the pores