12 research outputs found
GEOMETRIC OPTIMIZATION OF ā+ā-SHAPED CAVITY USING CONSTRUCTAL THEORY
In this work it is applied the Constructal Theory for the study of the geometry of an ā+ā-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 ā+ā-shape cavity is 37.2% better that the optimal performance of āCā-shape cavity and 10.8% better than the āTā-shaped cavity for the same thermal conditions
Vibrational, Electronic, and Structural Properties of 6āNitro- and 6āAmino-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 (<sup>1</sup>H, <sup>13</sup>C, and <sup>19</sup>F), UVāvis, 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>2<sub>1</sub>/<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
Coloration Mechanism in Proton-Intercalated Electrochromic Hydrated NiO[sub y] and Ni[sub 1āx]V[sub x]O[sub y] Thin Films
Spectroscopic, Structural, and Conformational Properties of (<i>Z</i>)-4,4,4-Trifluoro-3-(2-hydroxyethylamino)-1-(2-hydroxyphenyl)-2-buten-1-one, C<sub>12</sub>H<sub>12</sub>F<sub>3</sub>NO<sub>3</sub>: A Trifluoromethyl-Substituted Ī²-Aminoenone
The (<i>Z</i>)-4,4,4-trifluoro-3-(2-hydroxyethylamino)-1-(2-hydroxyphenyl)-2-buten-1-one (C<sub>12</sub>H<sub>12</sub>F<sub>3</sub>NO<sub>3</sub>) compound was thoroughly studied by IR, Raman, UVāvisible, and <sup>13</sup>C and <sup>19</sup>F NMR spectroscopies. The solid-state molecular structure was determined by X-ray diffraction methods. It crystallizes in the <i>P</i>2<sub>1</sub>/<i>c</i> space group with <i>a</i> = 12.1420(4) Ć
, <i>b</i> = 7.8210(3) Ć
, <i>c</i> = 13.8970(5) Ć
, Ī² = 116.162(2)Ā°, and <i>Z</i> = 4 molecules per unit cell. The molecule shows a nearly planar molecular skeleton, favored by intramolecular OHĀ·Ā·Ā·O and NHĀ·Ā·Ā·O bonds, which are arranged in the lattice as an OHĀ·Ā·Ā·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 Ī¼s/phase), with
a charge of 200 Ī¼C/cm<sup>2</sup> and geometric surface area
(GSA) of 300 Ī¼m<sup>2</sup>. A transfer-by-polymerization method
is used in combination with standard semiconductor processing techniques
to fabricate functional neural probes onto a thiolāene-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 <sup><i>s</i></sup>Bu and through dispersive COĀ·Ā·Ā·CX
(X = O, S, Ļ), SĀ·Ā·Ā·S, and CāHĀ·Ā·Ā·S
interactions when R is <sup><i>t</i></sup>Bu, independently
from the substitution pattern in the phenyl ring. The helical structures
are exclusively developed through N<sub>CS</sub>HĀ·Ā·Ā·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<sub>CO</sub>HĀ·Ā·Ā·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<sub>CS</sub>HĀ·Ā·Ā·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