GEOMETRIC OPTIMIZATION OF “+”-SHAPED CAVITY USING CONSTRUCTAL THEORY

In this work it is applied the Constructal Theory for the study of the geometry of an “+”-shaped isothermal cavity inserted in a conductive solid body. Main goal is to minimize the maximum temperature in the solid. The total volume of the solid and the total volume of the cavity are kept fixed while the dimensions of the cavity geometry vary according to constraints and degrees of freedom defined by the Constructal Design. The solid body has internal heat generation and its external surfaces are insulated. Cavity walls are isothermal with constant temperature Tmin. Obtained results indicate that the optimal performance of “+”-shape cavity is 37.2% better that the optimal performance of “C”-shape cavity and 10.8% better than the “T”-shaped cavity for the same thermal conditions

Vibrational, Electronic, and Structural Properties of 6‑Nitro- and 6‑Amino-2-Trifluoromethylchromone: An Experimental and Theoretical Study

Two 2-trifluoromethylchromones, 6-nitro-2-trifluoromethylchromone <b>(1)</b> and 6-amino-2-trifluoromethylchromone (<b>2</b>) were synthesized and characterized by NMR (¹H, ¹³C, and ¹⁹F), UV–vis, vibrational (IR and Raman) spectroscopy, MS spectrometry, and compound <b>1</b> also by single structural X-ray diffraction methods. This substance crystallizes in the monoclinic <i>P</i>2₁/<i>c</i> space group with <i>Z</i> = 4 molecules per unit cell. In the solid, the fused rings and the amino group of <b>1</b> are coplanar and the trifluoromethyl group adopts a nearly staggered conformation. The NMR, vibrational, and electronic spectra were discussed and assigned with the assistance of DFT calculations

Spectroscopic, Structural, and Conformational Properties of (<i>Z</i>)-4,4,4-Trifluoro-3-(2-hydroxyethylamino)-1-(2-hydroxyphenyl)-2-buten-1-one, C₁₂H₁₂F₃NO₃: A Trifluoromethyl-Substituted β-Aminoenone

The (<i>Z</i>)-4,4,4-trifluoro-3-(2-hydroxyethylamino)-1-(2-hydroxyphenyl)-2-buten-1-one (C₁₂H₁₂F₃NO₃) compound was thoroughly studied by IR, Raman, UV–visible, and ¹³C and ¹⁹F NMR spectroscopies. The solid-state molecular structure was determined by X-ray diffraction methods. It crystallizes in the <i>P</i>2₁/<i>c</i> space group with <i>a</i> = 12.1420(4) Å, <i>b</i> = 7.8210(3) Å, <i>c</i> = 13.8970(5) Å, β = 116.162(2)°, and <i>Z</i> = 4 molecules per unit cell. The molecule shows a nearly planar molecular skeleton, favored by intramolecular OH···O and NH···O bonds, which are arranged in the lattice as an OH···O bonded polymer coiled around crystallographic 2-fold screw-axes. The three postulated tautomers were evaluated using quantum chemical calculations. The lowest energy tautomer (I) calculated with density functional theory methods agrees with the observed crystal structure. The structural and conformational properties are discussed considering the effect of the intra- and intermolecular hydrogen bond interactions

Integration of High-Charge-Injection-Capacity Electrodes onto Polymer Softening Neural Interfaces

Softening neural interfaces are implanted stiff to enable precise insertion, and they soften in physiological conditions to minimize modulus mismatch with tissue. In this work, a high-charge-injection-capacity iridium electrode fabrication process is detailed. For the first time, this process enables integration of iridium electrodes onto softening substrates using photolithography to define all features in the device. Importantly, no electroplated layers are utilized, leading to a highly scalable method for consistent device fabrication. The iridium electrode is metallically bonded to the gold conductor layer, which is covalently bonded to the softening substrate via sulfur-based click chemistry. The resulting shape-memory polymer neural interfaces can deliver more than 2 billion symmetric biphasic pulses (100 μs/phase), with a charge of 200 μC/cm² and geometric surface area (GSA) of 300 μm². A transfer-by-polymerization method is used in combination with standard semiconductor processing techniques to fabricate functional neural probes onto a thiol–ene-based, thin film substrate. Electrical stability is tested under simulated physiological conditions in an accelerated electrical aging paradigm with periodic measurement of electrochemical impedance spectra (EIS) and charge storage capacity (CSC) at various intervals. Electrochemical characterization and both optical and scanning electron microscopy suggest significant breakdown of the 600 nm-thick parylene-C insulation, although no delamination of the conductors or of the final electrode interface was observed. Minor cracking at the edges of the thin film iridium electrodes was occasionally observed. The resulting devices will provide electrical recording and stimulation of the nervous system to better understand neural wiring and timing, to target treatments for debilitating diseases, and to give neuroscientists spatially selective and specific tools to interact with the body. This approach has uses for cochlear implants, nerve cuff electrodes, penetrating cortical probes, spinal stimulators, blanket electrodes for the gut, stomach, and visceral organs and a host of other custom nerve-interfacing devices

Positional Isomerism and Steric Effects in the Self-Assemblies of Phenylene Bis-Monothiooxalamides

The potential interplay of steric and substitution pattern effects of the monothiooxalamide side arms on the structure, conformational features, and self-assembly of a series of phenylene bis-monothiooxalamides was investigated. Herein we have demonstrated that phenylene bis-monothiooxalamides self-associate in the solid state, through intermolecular hydrogen bonding as <i>meso</i>-helices when the thioamide NR group is ^<i>s</i>Bu and through dispersive CO···CX (X = O, S, π), S···S, and C–H···S interactions when R is ^<i>t</i>Bu, independently from the substitution pattern in the phenyl ring. The helical structures are exclusively developed through N_CSH···O hydrogen bonding. The steric strain imposed by the <i>ortho</i>-substitution pattern has the effect of moving both monothiooxalyl units out of the phenyl plane enabling dimerization through strong N_COH···O intermolecular hydrogen bonds and promotes the formation of <i>meso</i>-helices. The steric demand of the thioamide NR group rules the conformation adopted by <i>meta</i>-substituted derivatives and the self-association arrangement of <i>para</i>-substituted derivatives. Infrared data support the blue-shifted nature of the N_CSH···O hydrogen bond. NMR data in solution agree with the extensive intramolecular hydrogen bonding scheme. Results are supported by density functional theory theoretical calculations. Monothiooxalamide unit offers considerable potential as a key moiety for crystal engineering