Pulsed Inversion Research Articles

Separation of proteins by square-wave pulsed field and inversion field capillary electrophoresis

BackgroundCapillary electrophoresis (CE) is an effective method for protein analysis. Although previous researchers have proved that the separation performance of large DNA molecules was improved by pulsed field capillary electrophoresis (PFCE), there is lack of research about proteins separation by PFCE. MethodsHerein, we systematically investigated the separation performance of proteins sized from 44 kDa to 200 kDa under square wave and inversion electric field, respectively. FindingsResults showed that for pulsed electric field with same forward and backward time duration, there was a resonance frequency for protein molecule re-orientation and applied frequency, and the apparent mobility (μ) was the lowest at the resonance frequency. μ was positively correlated to modulation depth (M) if M was below 200%, while μ was negatively correlated to M if M was higher than 200%. For CE with same forward and backward voltage, it demonstrated that μ dropped as M went up, but the separation performance for proteins with high molecular mass improved. Through PFCE, albumin and α- globulins in human serum were also resolved within 7 min. Such a work may shed new light on the analysis of proteins by PFCE.

ЕЛЕКТРОХІМІЧНЕ ДОСЛІДЖЕННЯ ПРОЦЕСІВ ПОГЛИНАННЯ КОБАЛЬТУ ҐРУНТАМИ УКРАЇНИ

In this paper, the processes of cobalt absorption by soils of Ukraine are investigated by using the electrochemical method of pulsed inversion chronopotentiometry. It has been established that the absorption capacity of cobalt by soil varieties from complexing media is 64–98 %. In solutions of KNO3, NH4OH and CSN2H4 mobile compounds of cobalt are part of [Co(H2O)n]2+, [Co(NH3)n]2+,[Co(CSN2H4)n]2+, and in solutions of Na4P2O7, Na5P3O10 and ЕДТА4– anionic complexes [Co(P2O7)n]2–4n, [Co(P3O10)n]2–5n ³ [CoЕДТА]2– are formed. The cobalt cationic complexes [Co(H2O)n]2+, [Co(NH3)n]2+, [Co(CSN2H4)n]2+ are almost completely absorbed by the soils. Anionic complexes – [Co(P2O7) n] 2–4n, [Co(P3O10) n]2–5n ³ [CoЕДТА]2– largely remain mobile in the soil profile. The sorption effect depends on the charge of the complex ions, their strength and on the steriîìåtric parameters of the complex ions. A close positive relationship was established between the cobalt absorption by soils and the cation exchange capacity of soils, the correlation coefficient was 0,7976, and between the cobalt absorption by soils and the humus content (0,7034). In the study of biohumus, it was found that cobalt goes into the solution of 0,02M ЕДТАNa2 + 0,09M NH4Cl by the mechanism of competitive complexation, its transition to the HCl solution occurs due to the protonization of the functional groups of biohumus with which the metal is bound. Biohumus has rather high sorption properties of cobalt and may be promising for its use as an effective carrier matrix in various combinations with basic fertilizers. Isotherms of sorption or exchange of cobalt for exchange ions of biohumus in various solutions correspond to isotherms of Langmuir single layer adsorption. The method of IIHP analysis is important to use to control the content of trace elements at the level of their trace concentrations necessary for plant development.

Pulsed population inversion in recombination of positive metal ions with negative ions of sulfur, selenium, and tellurium

Ion-ion recombination of positive ions of 14 metals with negative ions of sulfur, selenium, and tellurium is considered. The energy levels of metal atoms predominantly populated in the process of ion-ion recombination are estimated. The possibility of creating the population inversion in the afterglow of a pulsed discharge on some atomic transitions is discussed along with realization of noncoherent sources of radiation.

Pulsed population inversion in recombination of positive metal ions with negative oxygen ion

We discuss the ion-ion recombination of positive metal ions and negative oxygen ion in a pulsed gas discharge for realization of the pulsed inversion population mechanism. The metal atom energy levels most populated in this process are estimated. The energy level diagrams with probable transitions for several metal atoms are presented.

Contrast-Enhanced Endoscopic Ultrasound with Low Mechanical Index: A New Technique

Recent advances in technology have supported the development of new endoscopic ultrasound systems making it possible to use low MI contrast-enhanced imaging techniques (wide band harmonic imaging done with endoscopic ultrasound is currently at a preliminary stage). We now report on the first use of contrast-enhanced, low mechanical index, real-time endoscopic ultrasound (CELMI-EUS) in six patients using prototype technology. CELMI-EUS was performed using an electronic echo-endoscope HITACHI/Pentax EG-3830UT and adapted dynamic contrast harmonic wide-band pulsed inversion software with low mechanical index (MI = 0.09 - 0.25) before and up to 180 seconds after injection of SonoVue (4.8 mL) in six patients. Adequate visualisation of the arterial and portal venous phases was achieved in all patients. The pancreas and liver were studied thereafter. In contrast to the satisfactory visualisation of these vessels, enhancement of the left liver lobe was sufficient only in 4 patients. In the remaining 2 patients with liver cirrhosis, the enhancement was less pronounced in contrast to the strong enhancement of the hepatic artery and portal vein. Recent advances in technology have supported the development of new echo-endoscopic systems making it possible to use real-time, low mechanical index, contrast-enhanced imaging techniques with endoscopic ultrasound. We have preliminarily shown that arterial, portal venous and parenchymal contrast enhancement is possible.

Contrast Enhanced Endoscopic Ultrasound With Low Mechanical Index, a New Technique-Preliminary Report

Introduction: Recent advances in technology have supported the development of new endoscopic systems making it possible to apply contrast enhanced low MI techniques with wide band harmonic imaging by endoscopic ultrasound at a preliminary stage. We report on the first use of real-time, contrast-enhanced, endoscopic ultrasound with low mechanical index technique in 6 patients. Methods: Endoscopic ultrasound was performed using an electronic echoendoscope HITACHI/Pentax EG-3830UT and adapted dynamic Contrast Harmonic Wideband Pulsed Inversion Software with low mechanical index (MI, 0.09–0.25) before and from up to 180 seconds after injection of BR1 4.8 mL. Results: Adequate visualization of the arterial and portal venous phase was sufficient in all patients. The pancreas and liver were studied thereafter. In contrast to the mentioned vessels enhancement of the liver was sufficient only in 4 patients. In the remaining 2 patients with liver cirrhosis the enhancement was less pronounced in contrast to the strong enhancement of the hepatic artery and portal vein. Discussion: Recent advances in technology have supported the development of new echoendoscopic systems making it possible to apply real-time, contrast-enhanced, low mechanical index techniques also by endoscopic ultrasound. We could preliminarily show that arterial, portal venous, and parenchymal contrast enhancement is possible.

A review of nonconventional ultrasound techniques and contrast-enhanced ultrasonography of noncardiac canine disorders.

Modern ultrasound contrast media are gas-containing stabilized microbubbles that remain intact in the circulating blood for several minutes after intravenous injection and increase the intensity of the backscattered ultrasound. When the microbubbles disappear from the blood, they can be detected in the parenchyma of the liver and the spleen for about 30 more minutes (late liver- and spleen-specific phase). The insonated microbubbles produce second harmonic ultrasound frequencies, whose detection requires nonconventional ultrasound modalities such as pulsed inversion imaging. Nonconventional ultrasound techniques can also be used without microbubbles because second harmonics can be generated by ultrasound in tissues as well. The physical principles and advantages of nonconventional ultrasound techniques are described. The circulating microbubbles can be used not only to enhance weak Doppler signals, but also to perform dynamic contrast studies. Contrast-enhanced dynamic ultrasound studies--similar to contrast-enhanced CT and MRI examinations--have been used in humans to characterize lesions noninvasively (i.e., without biopsies) found during conventional ultrasound examinations. To map the distribution of contrast medium in a nodule or in an organ, specific scanning techniques such as stimulated acoustic emission have been developed. Stimulated acoustic emission occurs when high acoustic pressure ultrasonic waves disrupt the stationary or slowly moving microbubbles. This results in the release of a large amount of harmonic ultrasound frequencies. When the stimulated acoustic emission technique is used for dynamic studies, scanning must be interrupted several times to allow the microvasculature of the lesion to refill with microbubbles (interval delay imaging). The contrast patterns of malignant and benign hepatic nodules in humans have been the most intensively studied. Another type of dynamic study in humans measures the transit time of the contrast medium; that is, how fast the peripherally injected microbubbles reach the hepatic veins. Hepatic cirrhosis can be differentiated from other diffuse parenchymal liver diseases by a shorter transit time. Introducing nonconventional ultrasound techniques and ultrasound contrast media in veterinary diagnostic imaging may have potential value; however, intensive research should be carried out before ultrasound contrast agents can routinely be used in clinical practice.

Interventional procedures

Interventional procedures

Electron spin-lattice relaxation studies of different forms of the S(2) state multiline EPR signal of the Photosystem II oxygen-evolving complex.

The pulsed EPR inversion recovery sequence has been utilized to monitor the temperature dependence of the electron spin-lattice relaxation rate of the Mn cluster of the Photosystem II oxygen evolving complex poised in a variety of S (2) state forms giving rise to g = 2 multiline EPR signals. A previous study (Lorigan and Britt (1994) Biochemistry 33: 12072-12076) showed that for PS II membranes treated with 5% ethanol, the S (2) state Mn cluster relaxes via the Orbach spin-lattice relaxation mechanism, where the relaxation is enhanced via phonon scattering off an excited state spin manifold, in this case at an energy of Delta = 36.5 cm(-1) above the S = 1/2 ground state giving rise to the multiline EPR signal. Parallel experiments are reported for PS II membranes with 5% methanol, treated with ammonia, and following short and long term dark adaptation. In each case, the temperature dependence of the electron spin-lattice relaxation rate is consistent with Orbach relaxation, and the range of excited state energies is relatively narrow (33.8 cm(-1) </= Delta </= 39.7 cm(-1)). In addition, short term dark adapted (6 min, 'active state') PS II membranes show biphasic recovery traces which indicate that a minority fraction of the oxygen evolving complexes are trapped in a form with greatly slowed spin-lattice relaxation.

Using Flow Relaxography to Elucidate Flow Relaxivity

We have investigated the theoretical and experimental linear dependence of the reciprocal of the apparent longitudinal relaxation time [(T*1)−1] of the NMR signal from spins in a flowing fluid on the volume flow rate,Fv, the so-calledinflow effect.We refer to the coefficient of this dependence as the longitudinalflow relaxivity, r1F. A very simple model predicts that, under a range of conditions pertinent to modern flow studies and perfusion imaging experiments,r1Fis controlled by the volume of the fluid in which the magnetization is perturbed by pulsed RF inversion or saturation, not the detection volume, and that it can be approximated as the reciprocal of half of the inversion volume. Phantom sample experiments, using a new, quantitative approach that we callflow relaxography,confirm the general predictions of this simple model. There are two intriguing implications of these findings for general NMR flow studies as well as for medical applications. It should be possible to vary the value ofr1Fby simply (noninvasively) adjusting the inversion slice thickness, and thus measure the value of (blood1H2O, for example)Fvin a vessel without changingFv, from the resultant varyingT*1values. Also, it should be possible to extrapolate to the intrinsicT1value of the fluid signal (as if it were stationary), without altering or stopping the flow. Again, these are quite successful in phantom sample studies. Imaging versions of the flow relaxographic experiments are also possible. The twin goals of flow studies in medical MRI are the quantitative discrimination of the signals from flowing and nonflowing spins, and the accurate measurement of the flow rate of the former.

Multislice imaging of quantitative cerebral perfusion with pulsed arterial spin labeling.

A method is presented for multislice measurements of quantitative cerebral perfusion based on magnetic labeling of arterial spins. The method combines a pulsed arterial inversion, known as the FAIR (Flow-sensitive Alternating Inversion Recovery) experiment, with a fast spiral scan image acquisition. The short duration (22 ms) of the spiral data collection allows simultaneous measurement of up to 10 slices per labeling period, thus dramatically increasing efficiency compared to current single slice acquisition protocols. Investigation of labeling efficiency, suppression of unwanted signals from stationary as well as intraarterial spins, and the FAIR signal change as a function of inversion delay are presented. The assessment of quantitative cerebral blood flow (CBF) with the new technique is demonstrated and shown to require measurement of arterial transit time as well as suppression of intraarterial spin signals. CBF values measured on normal volunteers are consistent with results obtained from H2O15 positron emission tomography (PET) studies and other radioactive tracer approaches. In addition, the new method allows detection of activation-related perfusion changes in a finger-tapping experiment, with locations of activation corresponding well to those observed with blood oxygen level dependent (BOLD) fMRI.

Multislice Imaging of Quantitative Cerebral Perfusion with Pulsed Arterial Spin-Labeling

A method is presented for multislice measurements of quantitative cerebral perfusion based on magnetic labeling of arterial spins. The method combines a pulsed arterial inversion, known as the FAIR (Flow-sensitive Alternating Inversion Recovery) experiment, with a fast spiral scan image acquisition. The short duration (22 ms) of the spiral data collection allows simultaneous measurement of up to 10 slices per labeling period, thus dramatically increasing efficiency compared to current single slice acquisition protocols. Investigation of labeling efficiency, suppression of unwanted signals from stationary as well as intraarterial spins, and the FAIR signal change as a function of inversion delay are presented. The assessment of quantitative cerebral blood flow (CBF) with the new technique is demonstrated and shown to require measurement of arterial transit time as well as suppression of intraarterial spin signals. CBF values measured on normal volunteers are consistent with results obtained from H2O15 positron emission tomography (PET) studies and other radioactive tracer approaches. In addition, the new method allows detection of activation-related perfusion changes in a finger-tapping experiment, with locations of activation corresponding well to those observed with blood oxygen level dependent (BOLD) fMRI.

Reduced transit-time sensitivity in noninvasive magnetic resonance imaging of human cerebral blood flow.

Herein, we present a theoretical framework and experimental methods to more accurately account for transit effects in quantitative human perfusion imaging using endogenous magnetic resonance imaging (MRI) contrast. The theoretical transit time sensitivities of both continuous and pulsed inversion spin tagging experiments are demonstrated. We propose introducing a delay following continuous labeling, and demonstrate theoretically that introduction of a delay dramatically reduces the transit time sensitivity of perfusion imaging. The effects of magnetization transfer saturation on this modified continuous labeling experiment are also derived, and the assumption that the perfusion signal resides entirely within tissue rather than the arterial microvasculature is examined. We present results demonstrating the implementation of the continuous tagging experiment with delay on an echoplanar scanner for measuring cerebral blood flow (CBF) in normal volunteers. By varying the delay, we estimate transit times in the arterial system, values that are necessary for assessing the accuracy of our quantification. The effect of uncertainties in the transit time from the tagging plane to the arterial microvasculature and the transit time to the tissue itself on the accuracy of perfusion quantification is discussed and found to be small in gray matter but still potentially significant in white matter. A novel method for measuring T1, which is fast, insensitive to contamination by cerebrospinal fluid, and compatible with the application of magnetization transfer saturation, is also presented. The methods are combined to produce quantitative maps of resting and hypercarbic CBF.

Optimal control of quantum systems by chirped pulses.

Research on optimal control of quantum systems has been severely restricted by the lack of experimentally feasible control pulses. Here, to overcome this obstacle, optimal control is considered with the help of chirped pulses. Simulated annealing is used as the optimizing procedure. The examples treated are pulsed population inversion between electronic levels, and optimization of vibronic excitation in the presence of another electronic level. In the problem of population inversion effective potentials of displaced harmonic oscillators are used. For optimizing vibronic excitation the CsI model potential is used.

Suitability of the maximum loss method for the determination of the gain of pulsed lasers

An analysis is made of the underestimate of the gain of pulse lasers measured by the method of maximum losses introduced into the laser resonator. The underestimate occurs because in the case of short lifetimes of pulsed inversion and low or moderate values of the gain the lasing is delayed. Moreover, the results of the measurements are affected by the lumped nature of the losses introduced into the resonator. An allowance is made for these two factors in the derivation of the relationships between the measured and real maximum unsaturated gain, which makes it possible to correct the measured gain and thus increase considerably the precision of the method when applied to pulsed lasers. Experiments are reported confirming the validity of the method proposed for measuring the gain.