Propagation of ultra-short, resonant, ionizing laser pulses in rubidium vapor

We investigate the propagation of ultra-short laser pulses in atomic rubidium vapor. The pulses are intensive enough to ionize the atoms and are directly resonant with the 780 nm $D_2$ line. We derive a relatively simple theory for computing the nonlinear optical response of atoms and investigate the competing effects of strong resonant nonlinearity and ionization in the medium using computer simulations. A nonlinear self-channeling of pulse energy is found to produce a continuous plasma channel with complete ionization. We evaluate the length, width and homogeneity of the resulting plasma channel for various values of pulse energy and initial focusing to identify regimes optimal for applications in plasma-wave accelerator devices such as that being built by the AWAKE collaboration at CERN. Similarities and differences with laser pulse filamentation in atmospheric gases are discussed.Comment: 8 figure

Composite pulses for high-fidelity population inversion in optically dense, inhomogeneously broadened atomic ensembles

We derive composite pulse sequences that achieve high-fidelity excitation of two-state systems in an optically dense, inhomogeneously broadened ensemble. The composite pulses are resistant to distortions due to the back-action of the medium they propagate in and are able to create high-fidelity inversion to optical depths $\alpha z>10$. They function well with smooth pulse shapes used for coherent control of optical atomic transitions in quantum computation and communication. They are an intermediary solution between single $\pi$-pulse excitation schemes and adiabatic passage schemes, being far more error tolerant than the former but still considerably faster than the latter.Comment: 9 pages, 4 figures, submitted to Phys. Rev.

Coherence rephasing combined with spin-wave storage using chirped control pulses

Photon-echo based optical quantum memory schemes often employ intermediate steps to transform optical coherences to spin coherences for longer storage times. We analyze a scheme that uses three identical chirped control pulses for coherence rephasing in an inhomogeneously broadened ensemble of three-level $\Lambda$-systems. The pulses induce a cyclic permutation of the atomic populations in the adiabatic regime. Optical coherences created by a signal pulse are stored as spin coherences at an intermediate time interval, and are rephased for echo emission when the ensemble is returned to the initial state. Echo emission during a possible partial rephasing when the medium is inverted can be suppressed with an appropriate choice of control pulse wavevectors. We demonstrate that the scheme works in an optically dense ensemble, despite control pulse distortions during propagation. It integrates conveniently the spin-wave storage step into memory schemes based on a second rephasing of the atomic coherences.Comment: 11 pages, 9 figure

Adiabatic passage in photon-echo quantum memories

Photon-echo based quantum memories use inhomogeneously broadened, optically thick ensembles of absorbers to store a weak optical signal and employ various protocols to rephase the atomic coherences for information retrieval. We study the application of two consecutive, frequency-chirped control pulses for coherence rephasing in an ensemble with a 'natural' inhomogeneous broadening. Although propagation effects distort the two control pulses differently, chirped pulses that drive adiabatic passage can rephase atomic coherences in an optically thick storage medium. Combined with spatial phase mismatching techniques to prevent primary echo emission, coherences can be rephased around the ground state to achieve secondary echo emission with close to unit efficiency. Potential advantages over similar schemes working with $\pi$-pulses include greater potential signal fidelity, reduced noise due to spontaneous emission and better capability for the storage of multiple memory channels.Comment: 12 pages, 13 figures, accepted for publication in Phys. Rev.

Central Venous-to-Arterial CO

Monitoring hypovolemia is an everyday challenge in critical care, with no consensus on the best indicator or what is the clinically relevant level of hypovolemia. The aim of this experiment was to determine how central venous oxygen saturation (ScvO(2)) and central venous-to-arterial carbon dioxide difference (CO(2) gap) reflect hypovolemia-caused changes in the balance of oxygen delivery and consumption. Anesthetized, ventilated Vietnamese minipigs (n = 10) were given a bolus followed by a continuous infusion of furosemide. At baseline and then in five stages hemodynamic, microcirculatory measurements and blood gas analysis were performed. Oxygen extraction increased significantly, which was accompanied by a significant drop in ScvO(2) and a significant increase in CO(2) gap. There was a significant negative correlation between oxygen extraction and ScvO(2) and significant positive correlation between oxygen extraction and CO(2) gap. Taking ScvO(2) < 73% and CO(2) gap >6 mmHg values together to predict an oxygen extraction >30%, the positive predictive value is 100%; negative predicted value is 72%. Microcirculatory parameters, capillary perfusion rate and red blood cell velocity, decreased significantly over time. Similar changes were not observed in the sham group. Our data suggest that ScvO(2) < 73% and CO(2) gap >6 mmHg can be complementary tools in detecting hypovolemia-caused imbalance of oxygen extraction

Central Venous-to-Arterial CO 2 Gap Is a Useful Parameter in Monitoring Hypovolemia-Caused Altered Oxygen Balance: Animal Study

Monitoring hypovolemia is an everyday challenge in critical care, with no consensus on the best indicator or what is the clinically relevant level of hypovolemia. The aim of this experiment was to determine how central venous oxygen saturation (ScvO 2 ) and central venous-to-arterial carbon dioxide difference (CO 2 gap) reflect hypovolemia-caused changes in the balance of oxygen delivery and consumption. Anesthetized, ventilated Vietnamese minipigs ( = 10) were given a bolus followed by a continuous infusion of furosemide. At baseline and then in five stages hemodynamic, microcirculatory measurements and blood gas analysis were performed. Oxygen extraction increased significantly, which was accompanied by a significant drop in ScvO 2 and a significant increase in CO 2 gap. There was a significant negative correlation between oxygen extraction and ScvO 2 and significant positive correlation between oxygen extraction and CO 2 gap. Taking ScvO 2 &lt; 73% and CO 2 gap &gt;6 mmHg values together to predict an oxygen extraction &gt;30%, the positive predictive value is 100%; negative predicted value is 72%. Microcirculatory parameters, capillary perfusion rate and red blood cell velocity, decreased significantly over time. Similar changes were not observed in the sham group. Our data suggest that ScvO 2 &lt; 73% and CO 2 gap &gt;6 mmHg can be complementary tools in detecting hypovolemiacaused imbalance of oxygen extraction

The synagogue in Subotica — resurrection or decay

The aim of this paper is to present the brief history of the Subotica Jewish Community, the circumstances of the construction of the synagogue building, as-well-as it’s architectural, structural and artistic character, and values. The paper addresses the reasons of the synagogue’s deterioration, the recent history and problems of the conservation and reconstruction process in brief and slightly touches the ideas and issues related to its new function, and rehabilitation. The paper will also describe the nature of the author’s participation in the reconstruction process of the synagogue in Subotica and how it has been evaluated so far by other experts in the field of conservation