System Designing of Transcritical CO2 Air Conditioning Systems using Ejector Performance Maps

Awareness about the climate impact of air conditioning systems has given impetus in developing environment-friendly solutions. The transcritical CO2 cycle with an ejector as a work recovery device has been reported as one of the green solutions in the literature. However, commercial applicability of these systems is limited so far despite their offered potential. One of the major impediments for limited commercial usage is unavailability of a systematic approach for system design that can help system designers in finding the optimum component combination for their application. For materializing system design approach, it is imperative to develop a system model that can accurately predict performance for wide range of operating conditions while considering different possible component combinations. In this paper, an ejector system model is developed using individual component models of ejector, evaporator, and compressor. The ejector is being modeled using the ejector performance maps, a recently developed methodology for representing ejector performance of a fixed-geometry ejector. The ejector performance maps are accurate, yet they can predict ejector performance for wide range of operation. The evaporator is modeled using geometric parameters, and the refrigerant and the air-side operating conditions, whereas other heat exchangers are modeled using thermodynamic state analysis. The compressor is modeled using semi-empirical correlations by curve-fitting ten-coefficient polynomial using compressor speed and pressure ratio as characterizing variables. The system analysis considers a total of eight component combinations for transcritical CO2 ejector cycle and helps in finding the combination that gives the optimum performance. The results are encouraging as the system analysis using ejector performance maps can help in designing new improved systems. The methodology can also be tested for designing ejector air conditioning systems using other refrigerants

Synthesis and Investigation of Chiral Poly(2,4-disubstituted-2-oxazoline)-Based Triblock Copolymers, Their Self-Assembly, and Formulation with Chiral and Achiral Drugs

Considering the largely chiral nature of biological systems, there is interest in chiral drug delivery systems. Here, we investigate for the first time polymer micelles based on poly(2-oxazoline) (POx) ABA-type triblock copolymers with chiral and racemic hydrophobic blocks for the formulation of chiral and achiral drugs. Specifically, poly(2-ethyl-4-ethyl-2oxazoline) (pEtEtOx) and poly(2-propyl-4-methyl-2-oxazoline) (pPrMeOx) were used as hydrophobic block B and poly(2-methyl-2-oxazoline) (pMeOx) as hydrophilic block A. Using these triblock copolymers, nanoformulations of curcumin (CUR), paclitaxel (PTX), and chiral (R and S) and racemic ibuprofen were prepared. For CUR and PTX, the maximum drug loading was significantly dependent on the structure of the hydrophobic repeat units, but not the chirality. In contrast, the maximum drug loading with chiral/racemic ibuprofen was affected neither by the polymer structure nor by chirality, but minor effects were observed with respect to the size and size distribution of the drug-loaded micelles.Peer reviewe

Triggered Assembly of a DNA-Based Membrane Channel

Chemistry is in a powerful position to synthetically replicate biomolecular structures. Adding functional complexity is key to increase the biomimetics' value for science and technology yet is difficult to achieve with poorly controlled building materials. Here, we use defined DNA blocks to rationally design a triggerable synthetic nanopore that integrates multiple functions of biological membrane proteins. Soluble triggers bind via molecular recognition to the nanopore components changing their structure and membrane position, which controls the assembly into a defined channel for efficient transmembrane cargo transport. Using ensemble, single-molecule, and simulation analysis, our activatable pore provides insight into the kinetics and structural dynamics of DNA assembly at the membrane interface. The triggered channel advances functional DNA nanotechnology and synthetic biology and will guide the design of controlled nanodevices for sensing, cell biological research, and drug delivery