This work describes the application of nuclear magnetic resonance (NMR) in medicine and its influence on the work and life environment. Nuclear magnetic resonance, a powerful research tool, is based ...on the physical principle that cores of certain atoms (in this case hydrogen) can absorb or emit radiofrequency waves when placed in a magnetic field. This method is used for making high quality section pictures of the inside of the human body; in addition, it shows high sensitivity in revealing cancer, its position and its relation to the surrounding tissue. It is characterised by the use of non-ionizing radiation and a strong magnetic field, and, as explored by now, it does not have harmful effects on the human body. Therefore, it is completely noninvasive, comfortable and safe for patients as well for medical workers. / В данной работе описано применение в медицине ядерно- магнитного резонанса (ЯМР), являющегося мощным исследовательским средством в различных сферах, а также описано его влияние на рабочую и окружающую среду. Ядерно- магнитный резонанс основан на физическом явлении поглощения веществом электромагнитного излучения, атомных ядер, находящихся в постоянном магнитном поле. Данный метод используется для получения высококачественных изображений органов человеческого тела, а также для диагностики онкологических заболеваний и выявления опухолей. ЯМР отличается нейонизирующим излучением и сильным магнитным полем, не представляющих опасности для организма. Следовательно, применение ЯМР безболезненно, безвредно, удобно и безопасно, как для пациентов, так и для медсотрудников, проводящих процедуру. / U ovom radu opisana je primena nuklearne magnetne rezonance (NMR) u medicini, kao moćnog istraživačkog sredstva u različitim oblastima, i njen uticaj na radnu i životnu sredinu. Nuklearna magnetna rezonanca zasniva se na fizičkom fenomenu da jezgra određenih atoma (u ovom slučaju vodonika), postavljena u magnetno polje, mogu apsorbovati i emitovati radiofrekventne talase. Ova metoda koristi se za dobijanje visokokvalitetnih slika preseka unutrašnjosti tela, a pokazuje i visoku osetljivost u otkrivanju tumora, njihovog smeštaja i odnosa prema okolini. Odlikuje se korišćenjem nejonizujućeg zračenja i jakog magnetnog polja, a prema dosadašnjim istraživanjima nema štetno dejstvo na organizam. Potpuno je bezbolna, neinvazivna, konforna i bezopasna, kako za pacijenta, tako i za zdravstveno osoblje koje učestvuje u pregledu.
Methanol oxidation was studied in 0.1 M NaOH at supported Pt electrodes, and compared with the single crystal Pt electrodes, Pt(1
1
1), Pt(1
1
0) and Pt(3
3
2), chosen as model systems, and with a ...polycrystalline Pt electrode. The supported Pt electrodes were obtained by chemical (Pt–C/GC) and electrochemical (Pt/GC) deposition of the catalyst layer on glassy carbon resulting in the same metal loading of 20 μg
Pt
cm
−2. Using STM in air, the average particle size distributions, 3–6 nm at Pt–C/GC and 4–32 nm at Pt/GC were determined. Both supported Pt catalysts were less active than polycrystalline Pt. Negligible differences in the kinetics observed between Pt–C/GC and Pt(1
1
0) and also Pt/GC and Pt(1
1
1) suggested that the activities of supported Pt electrodes could be correlated with the activities of single crystal Pt electrodes oriented as the sites dominating in the Pt particles in catalyst deposits. The electrocatalytic activities of the electrodes studied increase in the sequence: Pt(3
3
2)
>
polycrystalline Pt
>
Pt–C/GC
∼
Pt(1
1
0)
>
Pt/GC
∼
Pt(1
1
1). On the basis of diagnostic criteria obtained, the chemical reaction between HCO
ad and OH
ad giving formate was proposed as the rate limiting step in methanol oxidation.
An injury to the central nervous system can result in a permanent loss of the voluntary motor function and sensation. However, the peripheral motor and sensory nerves below the level of lesion often ...remain intact, and so do the muscles. Functional Electrical Stimulation (FES) is a technique to restore motor and sensory functions after such injuries. The forces generated in muscles activated by FES can be graded by varying the stimulus pulses, but the relationship of the force to the stimulus pulse varies in a complex manner that depends on, for example, muscle length, electrode-nerve coupling, and activation history. Several studies have shown that the application of closed-loop control techniques can improve the regulation of the muscle activation. Natural sensors such as those found in the skin, muscles, tendons, and joints present an attractive alternative to artificial sensors for FES purposes because they are present throughout the body and contain information useful for feedback control. Moreover, the peripheral sensory apparatus is still viable after brain and spinal cord injuries. Electrical signals can be recorded using long-term implanted nerve cuff electrodes in the human peripheral nerves. Reliable detection of sensory nerve signals is essential if such signals are to be of use in sensory-based functional electrical stimulation neural prosthetics as a replacement for artificial sensory (switches, strain gauges, etc.) In this paper the signal characteristics of the sensors, the nerve interface, signal processing, and example of human applications to restore motor functions are described. In the second part of this presentation, stimulation of sensory nerves in CNS injured persons to improve their motor functions through neurorehabilitation will be addressed.
Energetics of Radical Transfer in DNA Photolyase Popović, Dragan M; Zmirić, Aleksandra; Zarić, Snežana D ...
Journal of the American Chemical Society,
04/2002, Letnik:
124, Številka:
14
Journal Article
Recenzirano
Charge separation and radical transfer in DNA photolyase from Escherichia coli is investigated by computing electrostatic free energies from a solution of the Poisson−Boltzmann equation. For the ...initial charge separation 450 meV are available. According to recent experiments Aubert et al. Nature 2000 , 405, 586−590 the flavin receives an electron from the proximal tryptophan W382, which consequently forms a cationic radical WH•+382. The radical state is subsequently transferred along the triad W382−W359−W306 of conserved tryptophans. The radical transfer to the intermediate tryptophan W359 is nearly isoenergetic (58 meV uphill); the radical transfer from the intermediate W359 to the distal W306 is 200 meV downhill in energy, funneling and stabilizing the radical state at W306. The resulting cationic radical WH•+306 is further stabilized by deprotonation, yielding the neutral radical W•306, which is 214 meV below WH•+306. The time scale of the charge recombination process yielding back the resting enzyme with FADH• is governed by reprotonation of W306, with a calculated lifetime of 1.2 ms that correlates well with the measured lifetime of 17 ms. In photolyase from Anacystis nidulans the radical state is partially transferred to a tyrosine Aubert et al. Proc. Natl. Acad. Sci. U.S.A. 1999 , 96, 5423−5427. In photolyase from Escherichia coli, there is a tyrosine (Y464) close to the distal tryptophan W306 that could play this role. We show that this tyrosine cannot be involved in radical transfer, because the electron transfer from tyrosine to W306 is much too endergonic (750 meV) and a direct hydrogen transfer is likely too slow. Coupling of specific charge states of the tryptophan triad with protonation patterns of titratable residues of photolyase is small.
The Arctic springtail, Megaphorura arctica, survives sub-zero temperatures in a dehydrated state via trehalose-dependent cryoprotective dehydration. Regulation of trehalose biosynthesis is complex; ...based in part on studies in yeast and fungi, its connection with oxidative stress caused by exposure of cells to oxidants, such as hydrogen peroxide (H sub(2)O sub(2)), or dehydration, is well documented. In this respect, we measured the amount of H sub(2)O sub(2) and antioxidant enzyme activities (superoxide dismutases: copper, zinc-CuZnSOD and manganese containing-MnSOD, and catalase-CAT), as the regulatory components determining H sub(2)O sub(2) concentrations, in Arctic springtails incubated at 5 degree C (control) versus -2 degree C (threshold temperature for trehalose biosynthesis). Because ecdysone also stimulates trehalose production in insects and regulates the expression of genes involved in redox homeostasis and antioxidant protection in Drosophila, we measured the levels of the active physiological form of ecdysone-20-hydroxyecdysone (20-HE). Significantly elevated H sub(2)O sub(2) and 20-HE levels were observed in M. arctica incubated at -2 degree C, supporting a link between ecdysone, H sub(2)O sub(2), and trehalose levels during cryoprotective dehydration. CAT activity was found to be significantly lower in M. arctica incubated at -2 degree C versus 5 degree C, suggesting reduced H sub(2)O sub(2) breakdown. Furthermore, measurement of the free radical composition in Arctic springtails incubated at 5 degree C (controls) versus -2 degree C by Electron Paramagnetic Resonance spectroscopy revealed melanin-derived free radicals at -2 degree C, perhaps an additional source of H sub(2)O sub(2). Our results suggest that H sub(2)O sub(2) and ecdysone play important roles in the cryoprotective dehydration process in M. arctica, linked with the regulation of trehalose biosynthesis.
The reported incidence of mitral regurgitation in relapsing polychondritis ranges from 2 to 3% and is associated with aortic regurgitation. There are no reports that mitral regurgitation can be an ...isolated cardiac complication of relapsing polychondritis. This case report demonstrates that partial chordal rupture and consequent severe mitral regurgitation can be the only features of cardiac involvement in relapsing polychondritis.
Patients with obstructive hypertrophic cardiomyopathy (HC) have various left ventricular (LV) shapes: reverse septal curvature (RSC, commonly familial), sigmoid septum (SS, common in hypertensives), ...and concentric hypertrophy (CH). Longitudinal (systolic and early diastolic) strain rate (SR) is sensitive in detecting regional myocardial dysfunction. We sought to determine differences in longitudinal SR of patients with obstructive HC, based on LV shapes. We studied 199 consecutive patients with HC (50% men) referred for surgical myectomy. Clinical and echocardiographic parameters were recorded. LV shapes were classified on echocardiography, using basal septal 1/3 to posterior wall ratio: RSC = ratio >1.3 (extending to mid and distal septum), SS = ratio >1.3 (extending only to basal 1/3), and concentric = ratio ≤1.3. Longitudinal systolic and early diastolic SRs were measured from apical 4- and 2-chamber views (VVI 2.0; Siemens, Erlangen). Distribution of RSC, SS, and CH was 50%, 28%, and 22%, respectively. Patients with RSC were significantly younger (47 ± 12 vs 64 ± 10 and 57 ± 11, respectively) with lower hypertension (40% vs71% and 67%, respectively) than patients with SS or CH (both p <0.001). Patients with RSC had lower global systolic (−0.99 ± 0.3 vs −1.05 ± 0.3 and −1.17 ± 0.3) and early diastolic SR (0.95 ± 0.4 vs 0.98 ± 0.3 and 1.16 ± 0.4) versus patients with SS and CH (in 1/s, both p <0.01), despite being much younger and less hypertensive. RSC was associated with abnormal global LV systolic (beta 0.16) and early diastolic (beta −0.17) SR (both p <0.01). In conclusion, patients with HC with RCS have significantly abnormal LV mechanics, despite being younger and less hypertensive. A combination of LV mechanics and shapes could help differentiate between genetically mediated and other causes of obstructive HC.
Resonant ion-pair formation from the collisions of NO{sup +} ions with electrons was studied using the heavy-ion storage ring CRYRING at the Manne Siegbahn Laboratory of Stockholm University. The ...total cross section is measured for the formation of N{sup +}+O{sup -} for electron energies 8--18 eV, and the results are compared with ion-pair formation in photoionization work. A peak in the cross section is observed at 12.5 eV, with a magnitude of 8.5 x 10{sup -19} cm{sup 2}. An attempt to extract the cross section for the reverse process of associative ionization is made.
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