Ion channels play a crucial role in the physiology of complex biological systems because of their... more Ion channels play a crucial role in the physiology of complex biological systems because of their influence on the electrical equilibrium between the cells and their environment. From an engineering viewpoint, ion chan- nels will be the key components of the design and the production of a new generation of biosensors integrat- ing the selectivity of ion channels with
We consider Brownian motion in a bounded domain $\Omega$ on a two-dimensional Riemannian manifold... more We consider Brownian motion in a bounded domain $\Omega$ on a two-dimensional Riemannian manifold $(\Sigma,g)$. We assume that the boundary $\p\Omega$ is smooth and reflects the trajectories, except for a small absorbing arc $\p\Omega_a\subset\p\Omega$. As $\p\Omega_a$ is shrunk to zero the expected time to absorption in $\p\Omega_a$ becomes infinite. The narrow escape problem consists in constructing an asymptotic expansion of
We applied a periodic magnetic field of frequency 16 Hz and amplitude 16 nT to a human I_Ks chann... more We applied a periodic magnetic field of frequency 16 Hz and amplitude 16 nT to a human I_Ks channel, expressed in a Xenopus oocyte and varied the membrane depolarization between -100 mV and +100 mV. We observed a maximal increase of about 9% in the potassium current at membrane depolarization between 0 mV and 8 mV (see Figure 3). A
A dendritic spine is an intracellular compartment in synapses of central neurons. The role of the... more A dendritic spine is an intracellular compartment in synapses of central neurons. The role of the fast twitching of spines, brought about by a transient rise of internal calcium concentration above that of the parent dendrite, has been hitherto unclear. We propose an explanation of the cause and effect of the twitching and its role in the functioning of the
Abstract-We consider two parallel M/M/l queueing systems where a new arrival (customer, job, mess... more Abstract-We consider two parallel M/M/l queueing systems where a new arrival (customer, job, message) joins the shorter of the two queues. Such problems arise naturally in computer communications and packet switched data networks. An asymptotic approach is ...
... 17S. Glasstone, K. Laidler, and H. Eyring, The Theory of Rate Processes (McGraw-Hill, New Yor... more ... 17S. Glasstone, K. Laidler, and H. Eyring, The Theory of Rate Processes (McGraw-Hill, New York, 1966). 18H. Suzuki, J. Stat. Phys. 16, 11 (1977). 19H. ... 25H. Risken and HD Vollmer, Phys. Lett. 69A, 387 (1979). 26E. Ben-Jacob, DJ Bergman, and Z. Schuss, Phys. Rev. ...
MILCOM 1987 - IEEE Military Communications Conference - Crisis Communications: The Promise and Reality, 1987
The relative motion of the transmitter and receiver or a clock rate mismatch lead to the introduc... more The relative motion of the transmitter and receiver or a clock rate mismatch lead to the introduction of a Doppler (or offset) term in a first order non-coherent code tracking loop equation (in DS-SPSP systems). The combined effect of both noise (jamming) and the Doppler shift on the mean time to loss of lock is analyzed for two types of
Flux between regions of different concentration occurs in nearly every device involving diffusion... more Flux between regions of different concentration occurs in nearly every device involving diffusion, whether an electrochemical cell, a bipolar transistor, or a protein channel in a biological membrane. Diffusion theory has calculated that flux since the time of Fick (1855), and the flux has been known to arise from the stochastic behavior of Brownian trajectories since the time of Einstein
Ionic diffusion through and near small domains is of considerable importance in molecular biophys... more Ionic diffusion through and near small domains is of considerable importance in molecular biophysics in applications such as permeation through protein channels and diffusion near the charged active sites of macromolecules. The motion of the ions in these settings depends on the specific nanoscale geometry and charge distribution in and near the domain, so standard continuum type approaches have obvious
Permeation of ions from one electrolytic solution to another, through a protein channel, is a bio... more Permeation of ions from one electrolytic solution to another, through a protein channel, is a biological process of considerable importance. Permeation occurs on a time scale of micro- to milliseconds, far longer than the femtosecond time scales of atomic motion. Direct simulations of atomic dynamics are not yet possible for such long-time scales; thus, averaging is unavoidable. The question is
We present a theoretical study of two ultrasmall-capacitance normal tunnel junctions connected in... more We present a theoretical study of two ultrasmall-capacitance normal tunnel junctions connected in series and driven by a dc voltage source, using the semiclassical junction approach. We show that the two junctions in series display a voltage offset similar to that of a single junction ...
We first study noncoherent Bloch oscillations in ultrasmall-capacitance normal tunnel junctions u... more We first study noncoherent Bloch oscillations in ultrasmall-capacitance normal tunnel junctions using the semiclassical approach. We then study coherent Bloch oscillations in other systems showing an energy spectrum similar to the ''nearly-free-electron''model in ...
We consider two parallel, infinite capacity,M/G/1queues characterized by (U_{1}(t), U_{2}(t)) wit... more We consider two parallel, infinite capacity,M/G/1queues characterized by (U_{1}(t), U_{2}(t)) withU_{j}(t)denoting the unfinished work (buffer content) in queuej. A new arrival is assigned to the queue with the smaller buffer content. We construct formal (as opposed to rigorous) asymptotic approximations to the Joint stationary distribution of the Markov process (U_{1}(t), U_{2}(t)), treating separately the asymptotic limits of heavy traffic, light traffic, and large buffer contents. In heavy traffic, the stochastic processesU_{1}(t) + U_{2}(t)andU_{2}(t) - U_{1}(t)become independent, with the distribution ofU_{1}(t) + U_{2}(t)identical to the heavy traffic waiting time distribution in the standardM/G/2queue, and the distribution ofU_{2}(t) - U_{1}(t)closely related to the tail of the service time density. In light traffic, we obtain a formal expansion of the stationary distribution in powers of the arrival rate.
... v, which together with (3.17) implies that aqt/an = bv at points of maximum. Therefore fan e ... more ... v, which together with (3.17) implies that aqt/an = bv at points of maximum. Therefore fan e 0~/s2 wofb ii dS (3.21) CO = lim an e e/S2 wob vdS We note that the function wo is nonnegative on the boundary, since (3.18) may be written as a first order ordinary differential ...
Ion channels play a crucial role in the physiology of complex biological systems because of their... more Ion channels play a crucial role in the physiology of complex biological systems because of their influence on the electrical equilibrium between the cells and their environment. From an engineering viewpoint, ion chan- nels will be the key components of the design and the production of a new generation of biosensors integrat- ing the selectivity of ion channels with
We consider Brownian motion in a bounded domain $\Omega$ on a two-dimensional Riemannian manifold... more We consider Brownian motion in a bounded domain $\Omega$ on a two-dimensional Riemannian manifold $(\Sigma,g)$. We assume that the boundary $\p\Omega$ is smooth and reflects the trajectories, except for a small absorbing arc $\p\Omega_a\subset\p\Omega$. As $\p\Omega_a$ is shrunk to zero the expected time to absorption in $\p\Omega_a$ becomes infinite. The narrow escape problem consists in constructing an asymptotic expansion of
We applied a periodic magnetic field of frequency 16 Hz and amplitude 16 nT to a human I_Ks chann... more We applied a periodic magnetic field of frequency 16 Hz and amplitude 16 nT to a human I_Ks channel, expressed in a Xenopus oocyte and varied the membrane depolarization between -100 mV and +100 mV. We observed a maximal increase of about 9% in the potassium current at membrane depolarization between 0 mV and 8 mV (see Figure 3). A
A dendritic spine is an intracellular compartment in synapses of central neurons. The role of the... more A dendritic spine is an intracellular compartment in synapses of central neurons. The role of the fast twitching of spines, brought about by a transient rise of internal calcium concentration above that of the parent dendrite, has been hitherto unclear. We propose an explanation of the cause and effect of the twitching and its role in the functioning of the
Abstract-We consider two parallel M/M/l queueing systems where a new arrival (customer, job, mess... more Abstract-We consider two parallel M/M/l queueing systems where a new arrival (customer, job, message) joins the shorter of the two queues. Such problems arise naturally in computer communications and packet switched data networks. An asymptotic approach is ...
... 17S. Glasstone, K. Laidler, and H. Eyring, The Theory of Rate Processes (McGraw-Hill, New Yor... more ... 17S. Glasstone, K. Laidler, and H. Eyring, The Theory of Rate Processes (McGraw-Hill, New York, 1966). 18H. Suzuki, J. Stat. Phys. 16, 11 (1977). 19H. ... 25H. Risken and HD Vollmer, Phys. Lett. 69A, 387 (1979). 26E. Ben-Jacob, DJ Bergman, and Z. Schuss, Phys. Rev. ...
MILCOM 1987 - IEEE Military Communications Conference - Crisis Communications: The Promise and Reality, 1987
The relative motion of the transmitter and receiver or a clock rate mismatch lead to the introduc... more The relative motion of the transmitter and receiver or a clock rate mismatch lead to the introduction of a Doppler (or offset) term in a first order non-coherent code tracking loop equation (in DS-SPSP systems). The combined effect of both noise (jamming) and the Doppler shift on the mean time to loss of lock is analyzed for two types of
Flux between regions of different concentration occurs in nearly every device involving diffusion... more Flux between regions of different concentration occurs in nearly every device involving diffusion, whether an electrochemical cell, a bipolar transistor, or a protein channel in a biological membrane. Diffusion theory has calculated that flux since the time of Fick (1855), and the flux has been known to arise from the stochastic behavior of Brownian trajectories since the time of Einstein
Ionic diffusion through and near small domains is of considerable importance in molecular biophys... more Ionic diffusion through and near small domains is of considerable importance in molecular biophysics in applications such as permeation through protein channels and diffusion near the charged active sites of macromolecules. The motion of the ions in these settings depends on the specific nanoscale geometry and charge distribution in and near the domain, so standard continuum type approaches have obvious
Permeation of ions from one electrolytic solution to another, through a protein channel, is a bio... more Permeation of ions from one electrolytic solution to another, through a protein channel, is a biological process of considerable importance. Permeation occurs on a time scale of micro- to milliseconds, far longer than the femtosecond time scales of atomic motion. Direct simulations of atomic dynamics are not yet possible for such long-time scales; thus, averaging is unavoidable. The question is
We present a theoretical study of two ultrasmall-capacitance normal tunnel junctions connected in... more We present a theoretical study of two ultrasmall-capacitance normal tunnel junctions connected in series and driven by a dc voltage source, using the semiclassical junction approach. We show that the two junctions in series display a voltage offset similar to that of a single junction ...
We first study noncoherent Bloch oscillations in ultrasmall-capacitance normal tunnel junctions u... more We first study noncoherent Bloch oscillations in ultrasmall-capacitance normal tunnel junctions using the semiclassical approach. We then study coherent Bloch oscillations in other systems showing an energy spectrum similar to the ''nearly-free-electron''model in ...
We consider two parallel, infinite capacity,M/G/1queues characterized by (U_{1}(t), U_{2}(t)) wit... more We consider two parallel, infinite capacity,M/G/1queues characterized by (U_{1}(t), U_{2}(t)) withU_{j}(t)denoting the unfinished work (buffer content) in queuej. A new arrival is assigned to the queue with the smaller buffer content. We construct formal (as opposed to rigorous) asymptotic approximations to the Joint stationary distribution of the Markov process (U_{1}(t), U_{2}(t)), treating separately the asymptotic limits of heavy traffic, light traffic, and large buffer contents. In heavy traffic, the stochastic processesU_{1}(t) + U_{2}(t)andU_{2}(t) - U_{1}(t)become independent, with the distribution ofU_{1}(t) + U_{2}(t)identical to the heavy traffic waiting time distribution in the standardM/G/2queue, and the distribution ofU_{2}(t) - U_{1}(t)closely related to the tail of the service time density. In light traffic, we obtain a formal expansion of the stationary distribution in powers of the arrival rate.
... v, which together with (3.17) implies that aqt/an = bv at points of maximum. Therefore fan e ... more ... v, which together with (3.17) implies that aqt/an = bv at points of maximum. Therefore fan e 0~/s2 wofb ii dS (3.21) CO = lim an e e/S2 wob vdS We note that the function wo is nonnegative on the boundary, since (3.18) may be written as a first order ordinary differential ...
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