663 research outputs found
ONBOARD CONTROL SYSTEM OF DRIVERâS HEALTH STATE
The method of driverâs health state determination by onboard ECG analysis system at vehicle driving is presented
COLON CAPSULE ENDOSCOPY: POSSIBILITIES OF NON-INVASIVE DIAGNOSTICS OF COLON DISEASES
Purpose. Evaluation of feasibility of colon capsule endoscopy (CCE), as non-invasive method of diagnostics of colon abnormalities.Patients and methods. From 31.01.2014 to 10.01.2017 we successfully performed 100 CCE in 101 (99,0%) patients (m-50, f-48, mean age 44,7 ± 14,8 years, range 22â81), including 2 twins aged 8 years (CCE was performed with pediatrician). The main indication for colonoscopy was colorectal cancer screening (73 (73,0%) pts). The indication for colonoscopy to 2 twins was complicated Peutz Jeghers syndrome in one of them. CCE was performed using the system PillCam (Given Imaging) and capsule PillCam Colon 2. For the bowel preparation we used two-stage regimen; for the evaluation of preparation â J.A. Leighton scale.Results. Preparation was adequate in 88 (88,0%) pts, non-adequate â in 12 (12,0%) pts. Total CCE was performed in 82 (82,0%) patients. The mean colon transit time was 4 hours 43 min ± 3 hours15 min. Total evaluation of the colon was performed in 82 (82,0%) pts. Mucosal lesions were revealed in 75 (75,0%) pts, including epithelial polyps in 52 (69,3%) pts. We also revealed comorbid lesions in 41 (54,6%) pts. Colonoscopy after CCE was recommended to 28 (37,3%) pts because of polyp detection, sized â„6 mm, and because of inflammatory changes of colon mucosa, but only 11 (39,3%) pts were performed colonoscopy.Conclusion. In this article the experience of colon capsule endoscopy demonstrates the principal possibility of noninvasive evaluation of the colon and detection of colon abnormalities
The evolution of multiple active site configurations in a designed enzyme
Developments in computational chemistry, bioinformatics, and laboratory evolution have facilitated the de novo design and catalytic optimization of enzymes. Besides creating useful catalysts, the generation and iterative improvement of designed enzymes can provide valuable insight into the interplay between the many phenomena that have been suggested to contribute to catalysis. In this work, we follow changes in conformational sampling, electrostatic preorganization, and quantum tunneling along the evolutionary trajectory of a designed Kemp eliminase. We observe that in the Kemp Eliminase KE07, instability of the designed active site leads to the emergence of two additional active site configurations. Evolutionary conformational selection then gradually stabilizes the most efficient configuration, leading to an improved enzyme. This work exemplifies the link between conformational plasticity and evolvability and demonstrates that residues remote from the active sites of enzymes play crucial roles in controlling and shaping the active site for efficient catalysis
Solvation and Protonation of Coumarin 102 in Aqueous Media - a Fluorescence Spectroscopic and Theoretical Study
The ground and excited state protonation of Coumarin 102 (C102), a fluorescent probe applied frequently in heterogeneous systems with an aqueous phase, has been studied in aqueous solutions by spectroscopic experiments and theoretical calculations. For the dissociation constant of the protonated form in the ground state, was obtained from the absorption spectra, for the excited state dissociation constant was obtained from the fluorescence spectra. These values were closely reproduced by theoretical calculations via a thermodynamic cycle â the value of also by calculations via the Förster cycle - using an implicit-explicit solvation model (polarized continuum model + addition of a solvent molecule). The theoretical calculations indicated that (i) in the ground state C102 occurs primarily as a hydrogen bonded water complex, with the oxo group as the binding site, (ii) this hydrogen bond becomes stronger upon excitation; (iii) in the ground state the amino nitrogen atom, in the excited state the carboxy oxygen atom is the protonation site. A comprehensive analysis of fluorescence decay data yielded the values kpr = 3.271010 M-1 s 1 for the rate constants of excited state protonation, and kdpr = 2.78108 s-1 for the rate constant of the reverse process (kpr and kdpr were treated as independent parameters). This, considering the relatively long fluorescence lifetimes of neutral C102 (6.02 ns) and its protonated form (3.06 ns) in aqueous media, means that a quasi-equilibrium state of excited state proton transfer is reached in strongly acidic solutions
Vapor grown carbon nanofiber based cotton fabrics with negative thermoelectric power
Vapor grown carbon nanofiber (CNF)
based ink dispersions were used to dip-coat woven
cotton fabrics with different constructional parameters, and their thermoelectric (TE) properties studied
at room temperature. Unlike the positive thermoelectric power (TEP) observed in TE textile fabrics
produced with similar carbon-based nanostructures,
the CNF-based cotton fabrics showed negative TEP,
caused by the compensated semimetal character of the
CNFs and the highly graphitic nature of their outer
layers, which hinders the p-type doping with oxygen
groups onto them. A dependence of the electrical
conductivity (r) and TEP as a function of the woven
cotton fabric was also observed. The cotton fabric with
the largest linear density (tex) showed the best
performance with negative TEP values around
- 8 lV K-1
, a power factor of 1.65 9 10-3
lW m-1 K-2
, and a figure of merit of 1.14 9 10-6
.
Moreover, the possibility of a slight e- charge transfer
or n-doping from the cellulose onto the most external
CNF graphitic shells was also analysed by computer
modelling. This study presents n-type carbon-based
TE textile fabrics produced easily and without any
functionalization processes to prevent the inherent
doping with oxygen, which causes the typical p-type
character found in most carbon-based TE materialsFEDER funds through
COMPETE and by national funds through FCT â Foundation for
Science and Technology within the project POCI-01-0145-
FEDER-007136. E. M. F. Vieira is grateful for financial support
through FCT with CMEMS-UMinho Strategic Project UIDB/
04436/202
Counteranion-Dependent Reaction Pathways in the Protonation of Cationic RutheniumâVinylidene Complexes
The tetraphenylborate salts of the cationic vinylidene complexes [Cp*Ru=C=CHR(iPr2PNHPy)]+ (R = p-C6H4CF3 (1a-BPh4), Ph (1b-BPh4), p-C6H4CH3 (1c- BPh4), p-C6H4Br (1d-BPh4), tBu (1e-BPh4), H (1f-BPh4)) have been protonated using an excess of HBF4·OEt2 in CD2Cl2, furnishing the dicationic carbyne complexes [Cp*RuâĄCCH2R(iPr2PNHPy)]2+ (R = p-C6H4CF3 (2a), Ph (2b), p-C6H4CH3 (2c), p-C6H4Br (2d), tBu (2e), H (2f)), which were characterized in solution at low temperature by NMR spectroscopy. The corresponding reaction of the chloride salts 1a-Cl, 1b-Cl, 1c-Cl, and 1d-Cl followed a different pathway, instead affording the novel alkene complexes [Cp*RuCl(Îș1(N),η2(C,C)-C5H4N-NHPiPr2CH=CHR)][BF4] (3aâd). In these species, the entering proton is located at the α- carbon atom of the former vinylidene ligand, which also forms a PâC bond with the phosphorus atom of the iPr2PNHPy ligand. To shed light on the reaction mechanism, DFT calculations have been performed by considering several protonation sites. The computational results suggest metal protonation followed by insertion. The coordination of chloride to ruthenium leads to alkenyl species which can undergo a PâC coupling to yield the corresponding alkene complexes. The noncoordinating nature of [BPh4]â does not allow the stabilization of the unsaturated species coming from the insertion step, thus preventing this alternative pathway
The Alkaline Hydrolysis of Sulfonate Esters: Challenges in Interpreting Experimental and Theoretical Data
Sulfonate ester hydrolysis has been the subject of recent debate, with experimental evidence interpreted in terms of both stepwise and concerted mechanisms. In particular, a recent study of the alkaline hydrolysis of a series of benzene arylsulfonates (Babtie et al., Org. Biomol. Chem. 10, 2012, 8095) presented a nonlinear BrĂžnsted plot, which was explained in terms of a change from a stepwise mechanism involving a pentavalent intermediate for poorer leaving groups to a fully concerted mechanism for good leaving groups and supported by a theoretical study. In the present work, we have performed a detailed computational study of the hydrolysis of these compounds and find no computational evidence for a thermodynamically stable intermediate for any of these compounds. Additionally, we have extended the experimental data to include pyridine-3-yl benzene sulfonate and its N-oxide and N-methylpyridinium derivatives. Inclusion of these compounds converts the BrĂžnsted plot to a moderately scattered but linear correlation and gives a very good Hammett correlation. These data suggest a concerted pathway for this reaction that proceeds via an early transition state with little bond cleavage to the leaving group, highlighting the care that needs to be taken with the interpretation of experimental and especially theoretical data
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