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Papers by Dan Dan

The field of electrochemistry can be defined as the set of physical and chemical phenomena involv... more The field of electrochemistry can be defined as the set of physical and chemical phenomena involved by the passage of an electric current in an ionic conductor. These phenomena involve the use of electrodes characterized by at least one interface common to two conductors of different nature. They manifest themselves in various ways in electrochemical reactors made up of two electronic conductors or electrodes separated by an ionic conductive medium. After having defined the main phenomena involved in the flow of current, the article presents the thermodynamic and kinetic aspects of electrochemistry (electrochemical cell). The main industrial applications of electrochemistry are briefly presented.

Frontiers in Physics, 2021

Fluorescence correlation spectroscopy (FCS) is a powerful technique for quantification of molecul... more Fluorescence correlation spectroscopy (FCS) is a powerful technique for quantification of molecular dynamics, and it has been widely applied in diverse fields, e.g., biomedicine, biophysics, and chemistry. By time-correlation of the fluorescence fluctuations induced by molecules diffusing through a focused light, FCS can quantitatively evaluate the concentration, diffusion coefficient, and interaction of the molecules in vitro or in vivo. In this review, the basic principle and implementation of FCS are introduced. Then, the advances of FCS variants are reviewed, covering dual-color FCCS, multi-focus FCS, pair correlation function (pCF), scanning FCS, focus-reduced FCS, SPIM-FCS, and inverse-FCS. Besides, the applications of FCS are demonstrated with the measurement of local concentration, hydrodynamic radius, diffusion coefficient, and the interaction of different molecules. Lastly, a discussion is given by summarizing the pros and cons of different FCS techniques, as well as the o...

Journal of the American College of Cardiology, 2002

We studied hemodynamic changes leading to orthostatic vasovagal presyncope to determine whether c... more We studied hemodynamic changes leading to orthostatic vasovagal presyncope to determine whether changes of cerebral artery blood flow velocity precede or follow reductions of arterial pressure. BACKGROUND Some evidence suggests that disordered cerebral autoregulation contributes to the occurrence of orthostatic vasovagal syncope. We studied cerebral hemodynamics with transcranial Doppler recordings, and we closely examined the temporal sequence of changes of cerebral artery blood flow velocity and systemic arterial pressure in 15 patients who did or did not faint during passive 70°head-up tilt. METHODS We recorded photoplethysmographic arterial pressure, RR intervals (electrocardiogram) and middle cerebral artery blood flow velocities (mean, total, mean/RR interval; Gosling's pulsatility index; and cerebrovascular resistance [mean cerebral velocity/mean arterial pressure, MAP]). RESULTS Eight men developed presyncope, and six men and one woman did not. Presyncopal patients reported light-headedness, diaphoresis, or a sensation of fatigue 155 s (range: 25 to 414 s) before any cerebral or systemic hemodynamic change. Average cerebral blood flow velocity (CBFV) changes (defined by an iterative linear regression algorithm) began 67 s (range: 9 to 198 s) before reductions of MAP. Cerebral and systemic hemodynamic measurements remained constant in nonsyncopal patients. CONCLUSIONS Presyncopal symptoms and CBFV changes precede arterial pressure reductions in patients with orthostatic vasovagal syncope. Therefore, changes of cerebrovascular regulation may contribute to the occurrence of vasovagal reactions.

The field of electrochemistry can be defined as the set of physical and chemical phenomena involv... more The field of electrochemistry can be defined as the set of physical and chemical phenomena involved by the passage of an electric current in an ionic conductor. These phenomena involve the use of electrodes characterized by at least one interface common to two conductors of different nature. They manifest themselves in various ways in electrochemical reactors made up of two electronic conductors or electrodes separated by an ionic conductive medium. After having defined the main phenomena involved in the flow of current, the article presents the thermodynamic and kinetic aspects of electrochemistry (electrochemical cell). The main industrial applications of electrochemistry are briefly presented.

Frontiers in Physics, 2021

Fluorescence correlation spectroscopy (FCS) is a powerful technique for quantification of molecul... more Fluorescence correlation spectroscopy (FCS) is a powerful technique for quantification of molecular dynamics, and it has been widely applied in diverse fields, e.g., biomedicine, biophysics, and chemistry. By time-correlation of the fluorescence fluctuations induced by molecules diffusing through a focused light, FCS can quantitatively evaluate the concentration, diffusion coefficient, and interaction of the molecules in vitro or in vivo. In this review, the basic principle and implementation of FCS are introduced. Then, the advances of FCS variants are reviewed, covering dual-color FCCS, multi-focus FCS, pair correlation function (pCF), scanning FCS, focus-reduced FCS, SPIM-FCS, and inverse-FCS. Besides, the applications of FCS are demonstrated with the measurement of local concentration, hydrodynamic radius, diffusion coefficient, and the interaction of different molecules. Lastly, a discussion is given by summarizing the pros and cons of different FCS techniques, as well as the o...

Journal of the American College of Cardiology, 2002

We studied hemodynamic changes leading to orthostatic vasovagal presyncope to determine whether c... more We studied hemodynamic changes leading to orthostatic vasovagal presyncope to determine whether changes of cerebral artery blood flow velocity precede or follow reductions of arterial pressure. BACKGROUND Some evidence suggests that disordered cerebral autoregulation contributes to the occurrence of orthostatic vasovagal syncope. We studied cerebral hemodynamics with transcranial Doppler recordings, and we closely examined the temporal sequence of changes of cerebral artery blood flow velocity and systemic arterial pressure in 15 patients who did or did not faint during passive 70°head-up tilt. METHODS We recorded photoplethysmographic arterial pressure, RR intervals (electrocardiogram) and middle cerebral artery blood flow velocities (mean, total, mean/RR interval; Gosling's pulsatility index; and cerebrovascular resistance [mean cerebral velocity/mean arterial pressure, MAP]). RESULTS Eight men developed presyncope, and six men and one woman did not. Presyncopal patients reported light-headedness, diaphoresis, or a sensation of fatigue 155 s (range: 25 to 414 s) before any cerebral or systemic hemodynamic change. Average cerebral blood flow velocity (CBFV) changes (defined by an iterative linear regression algorithm) began 67 s (range: 9 to 198 s) before reductions of MAP. Cerebral and systemic hemodynamic measurements remained constant in nonsyncopal patients. CONCLUSIONS Presyncopal symptoms and CBFV changes precede arterial pressure reductions in patients with orthostatic vasovagal syncope. Therefore, changes of cerebrovascular regulation may contribute to the occurrence of vasovagal reactions.