Bandgap-Engineered HgCdTe Infrared Detector Structures for Reduced Cooling Requirements.

State-of-the-art mercury cadmium telluride (HgCdTe) high performance infrared (IR) p-n heterojunction technology remains limited by intrinsic, thermal Auger generation- recombination (G-R) mechanisms which necessitate strict cooling requirements, and challenges related to processing technology, particularly those associated with achieving stable, controllable in situ p-type doping in molecular beam epitaxy (MBE) grown HgCdTe. These limitations motivate the need to firstly, increase device operating temperatures, and secondly, address material processing issues. This work investigates three alternative HgCdTe IR device architectures as proposed solutions: 1) the high operating temperature (HOT) detector, 2) the nBn detector, and 3) the NBnuN detector. The HOT detector is designed to suppress Auger processes, in turn, reducing the detector noise and cryogenic cooling requirements. A simulation study comparing the device behavior and performance metrics of the Auger-suppressed HOT structure to those obtained for the conventional double layer planar heterostructure (DLPH) device predicts the HOT detector can provide a significant advantage over conventional detectors with an increased operating temperature of ~40-50 K for devices with cutoff wavelengths in the range of 5-12 um. In a related study, a series of experiments is conducted to examine arsenic (As) deep diffusion in HgCdTe with the goal of achieving controllable low p-type doping in the HOT absorber layer to reduce Auger G-R processes by increasing minority carrier lifetimes. Furthermore, a unipolar, barrier-integrated nBn detector structure is proposed to address the challenges associated with p-type doping in MBE grown HgCdTe. Numerically simulated performance characteristics of the HgCdTe nBn device predict values similar to comparable DLPH structures for a range of temperatures, motivating the experimental demonstration of mid- and long-wave IR HgCdTe nBn detectors. Fabricated nBn detectors successfully exhibit barrier-influenced current-voltage and photoresponse characteristics, but are limited by perimeter leakage currents which must be resolved in future work. Finally, this work culminates with the simulation study of the novel, hybrid NBnuN structure which addresses both technology limitations by combining the advantages and designs of the Auger-suppressed HOT and unipolar nBn detectors in a single configuration.Ph.D.Electrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/91390/1/aitsuno_1.pd

Design of peptide-containing N5-unmodified neutral flavins that catalyze aerobic oxygenations

Simulation of the monooxygenation function of flavoenzyme (Fl-Enz) has been long-studied with N5-modified cationic flavins (FlEt+), but never with N5-unmodified neutral flavins (Fl) despite the fact that Fl is genuinely equal to the active center of Fl-Enz. This is because of the greater lability of 4a-hydroperoxy adduct of Fl, FlOOH, compared to those of FlEt+, FlEtOOH, and Fl-Enz, FlOOH-Enz. In this study, Fl incorporated into a short peptide, flavopeptide (Fl-Pep), was designed by a rational top-down approach using a computational method, which could stabilize the corresponding 4a-hydroperoxy adduct (FlOOH-Pep) through intramolecular hydrogen bonds. We report catalytic chemoselective sulfoxidation as well as Baeyer–Villiger oxidation by means of Fl-Pep under light-shielding and aerobic conditions, which are the first Fl-Enz-mimetic aerobic oxygenation reactions catalyzed by Fl under non-enzymatic conditions

Experimental-Induced Colitis in Rats by Ethanolic Solution of Trinitrobenzene Sulfonic Acid and Ethanol Alone : A Comparative Study

Epidemiological data suggest an increase in both developed and undeveloped countries of inflammatory bowel disease. Furthermore, its etiology and pathophysiology remain unknown. Appropriated animal models are needed. We have studied a rat model of hapten-induced chronic colitis. In Wistar rats, intracolonic instillation of 20 mg or 42 mg of the hapten trinitrobenzene sulfonic acid in 30 % and 40 % ethanol proved to induce chronic colitis after 14 to 21 days of administration, in dose-dependent fashion when compared with ethanol alone that induced only acute colitis after three days of administration. This chronic colitis shares some characteristics with inflammatory bowel disease in humans, specially with Crohn\u27s disease, such as transmural inflammation, development of strictures, ulcerations and infiltration of inflammatory cells throughout the colonic wall. These features make this model suitable for further studies of intestinal inflammation

Distribution and Localization of Endocrine Cells in the Human Gastro-intestinal Tract -In Relation to Histogenesis of Rectal Carcinoid-

The distribution of endocrine cells in the human intestine was studied by immunostaining using the labeled avidinbiotin technique. The total number of endocrine cells was abundant in the proximal portion of the small intestine and the distal portion of the large intestine. Gastrin, cholecystokinin, and motilin immunoreactive cells were localized in the proximal portion of the small intestine. Peptide YY, serotonin, and glucagon/glicentin immunoreactive cells were distributed more abundantly in the lower large intestine. The serotonin and somatostatin concentrations in the colonic mucosa determined by high-performance liquid chromatography and radioimmunoassay were higher in the distal than proximal portion of the large intestine, being in correlation with the distribution of serotonin and somatostatin immunoreactive cells estimated by immunostaining. Therefore, the regional differences in the number of endocrine cells and the mucosal concentrations of the hormones probably reflect differences in the physiological functions of different regions of the gut. Not many endocrine cells with unknown peptides and animes and immature endocrine cells were present in the lower large intestine. Therefore, the frequent occurrence of carcinoids in the rectum is difficult to explain by the quantitative dominance of endocrine cells alone in the rectal mucosa, and other factors are considered to need evaluation

A Clinico-pathological Study of Gastric Polyps Treated with Endoscopic Polypestomy

181 gastric polyps obtained by endoscopic polypectomy were studied clinico-pathologically. The polyps occurred most frequently in the lower portion, and the incidence of the polyps tended to increase with age. 91% (164/181) of the polyps were occupied by hyperplastic polyps, and 3 polyps and one polyp respectively with dysplastic and carcinomatous foci were detected in 164 hyperplastic polyps. Although hyperplastic polyps rarely transform into dysplasia or carcinoma, careful follow-up is recommended

Design, Synthesis and Evaluation of Novel Tyrosine-Based DNA Gyrase B Inhibitors

Peer reviewe

A Journey from Thermally Tunable Synthesis to Spectroscopy of Phenylmethanimine in Gas Phase and Solution

Phenylmethanimine is an aromatic imine with a twofold relevance in chemistry: organic synthesis and astrochemistry. To tackle both aspects, a multidisciplinary strategy has been exploited and a new, easily accessible synthetic approach to generate stable imine-intermediates in the gas phase and in solution has been introduced. The combination of this formation pathway, based on the thermal decomposition of hydrobenzamide, with a state-of-the-art computational characterization of phenylmethanimine laid the foundation for its first laboratory observation by means of rotational electric resonance spectroscopy. Both E and Z isomers have been accurately characterized, thus providing a reliable basis to guide future astronomical observations. A further characterization has been carried out by nuclear magnetic resonance spectroscopy, showing the feasibility of this synthetic approach in solution. The temperature dependence as well as possible mechanisms of the thermolysis process have been examined. © 2020 The Authors. Published by Wiley-VCH Gmb

Continuous Flow Asymmetric Transfer Hydrogenation with Long Catalyst Lifetime and Low Metal Leaching

Homogenous iridium complexes with asymmetric ligands and different tether lengths have been solid‐supported and prepared in multi‐gram quantities. Packed in a fixed‐bed, they have been used in continuous flow for up to 120 hours in the asymmetric transfer hydrogenation of APs in 2‐propanol to make 1‐phenethyl alcohols in > 95 % conversion and ee. The CsDPEN ligand and C5 tether showed higher performance than TsDPEN and the C14 tether, whilst the ketone feed concentration and reaction temperature were optimized to enable the catalyst to be used at 5 mol‐% loading with a residence time of 39 minutes. The total amount iridium leaching of from the support during sustained operation was 58–147 ppm. The flow system gives higher catalyst turnover numbers than the related batch reactions, but the nature and concentration of the base were found to influence strongly the catalyst's performance, with the finding that triethylamine maintains high enantioselectivity but slowly deactivates the catalyst, whilst potassium tert‐butoxide does the opposite. The utility of the system is shown in the high ee's and good conversions achieved for a range of aryl alcohols