Understanding the impact of ammonium ion substitutions on heterogeneous ice nucleation.

Understanding the mechanisms underpinning heterogeneous ice nucleation in the presence of ionic inclusions is important for fields such as cryopreservation and for improved models of climate and weather prediction. Feldspar and ammonium are both present in significant quantities in the atmosphere, and experimental evidence has shown that feldspar can nucleate ice from ammonium-containing solutions at temperatures warmer than water alone. In recent work, Whale hypothesised that this increase in nucleation temperature is due to an increase in configurational entropy when an ammonium ion is included in the ice hydrogen bond network (T.

Interplay of multiple clusters and initial interface positioning for forward flux sampling simulations of crystal nucleation.

Forward flux sampling (FFS) is a path sampling technique widely used in computer simulations of crystal nucleation from the melt. In such studies, the order parameter underpinning the progress of the FFS algorithm is often the size of the largest crystalline nucleus. In this work, we investigate the effects of two computational aspects of FFS simulations, using the prototypical Lennard-Jones liquid as our computational test bed.

The seven deadly sins: When computing crystal nucleation rates, the devil is in the details.

The formation of crystals has proven to be one of the most challenging phase transformations to quantitatively model-let alone to actually understand-be it by means of the latest experimental technique or the full arsenal of enhanced sampling approaches at our disposal. One of the most crucial quantities involved with the crystallization process is the nucleation rate, a single elusive number that is supposed to quantify the average probability for a nucleus of critical size to occur within a certain volume and time span. A substantial amount of effort has been devoted to attempt a connection between the crystal nucleation rates computed by means of atomistic simulations and their experimentally measured counterparts.

Soliton radiation beat analysis of optical pulses generated from two continuous-wave lasers.

We propose a fibre-based approach for generation of optical frequency combs (OFCs) with the aim of calibration of astronomical spectrographs in the low and medium-resolution range. This approach includes two steps: in the first step, an appropriate state of optical pulses is generated and subsequently moulded in the second step delivering the desired OFC. More precisely, the first step is realised by injection of two continuous-wave (CW) lasers into a conventional single-mode fibre, whereas the second step generates a broad OFC by using the optical solitons generated in step one as initial condition.

Timing and phase jitter suppression in coherent soliton transmission.

We have revisited soliton transmission in the new context of coherent optical detection optimizing and comparing digital backward propagation and in-line optical filtering as a means to suppress soliton timing and phase jitter. We find that in-line optical filtering allows one to improve the reach of the soliton system by up to the factor of 2. Our results show that nonlinear propagation can lead to performance beyond the nonlinear Shannon limit.

Nonlinear inverse synthesis and eigenvalue division multiplexing in optical fiber channels.

We scrutinize the concept of integrable nonlinear communication channels, resurrecting and extending the idea of eigenvalue communications in a novel context of nonsoliton coherent optical communications. Using the integrable nonlinear Schrödinger equation as a channel model, we introduce a new approach-the nonlinear inverse synthesis method-for digital signal processing based on encoding the information directly onto the nonlinear signal spectrum. The latter evolves trivially and linearly along the transmission line, thus, providing an effective eigenvalue division multiplexing with no nonlinear channel cross talk.

Power pre-emphasis for suppression of FWM in coherent optical OFDM transmission.

Four-wave-mixing (FWM) due to the fiber nonlinearity is a major limiting factor in coherent optical OFDM transmission. We propose to apply power pre-emphasis, i.e.

Random walks and random numbers from supercontinuum generation.

We report a numerical study showing how the random intensity and phase fluctuations across the bandwidth of a broadband optical super-continuum can be interpreted in terms of the random processes of random walks and Lévy flights. We also describe how the intensity fluctuations can be applied to physical random number generation. We conclude that the optical supercontinuum provides a highly versatile means of studying and generating a wide class of random processes at optical wavelengths.

Time domain all-optical signal processing at a RZ optical receiver.

We propose a new all-optical signal processing technique to enhance the performance of a return-to-zero optical receiver, which is based on nonlinear temporal pulse broadening and flattening in a normal dispersion fiber and subsequent slicing of the pulse temporal waveform. The potential of the method is demonstrated by application to timing jitter- and noise-limited transmission at 40Gbit/s.

All-optical binary counter.

We experimentally demonstrate an all-optical binary counter composed of four semiconductor optical amplifier based all-optical switching gates. The time-of-flight optical circuit operates with bit-differential delays between the exclusive-OR gate used for modulo-2 binary addition and the AND gate used for binary carry detection. A movie of the counter operating in real time is presented.

Nonlinear Optics for High-Speed Digital Information Processing.

Recent advances in developing nonlinear optical techniques for processing serial digital information at high speed are reviewed. The field has been transformed by the advent of semiconductor nonlinear devices capable of operation at 100 gigabits per second and higher, well beyond the current speed limits of commercial electronics. These devices are expected to become important in future high-capacity communications networks by allowing digital regeneration and other processing functions to be performed on data signals "on the fly" in the optical domain.

Experimental investigation of resonant enhancement of the acoustic interaction of optical pulses in an optical fiber.

The acoustic interaction of optical pulses in optical fibers is investigated directly by time-resolved pump-probe measurements of the transmission of a fiber Sagnac-loop interferometer. Resonant enhancement of the refractive-index change deltan(ac) induced by the acoustic waves is observed when the repetition frequency of the pulse train is close to a vibrational eigenfrequency of the fiber. For standard fiber deltan(ac) is enhanced by a factor of ~3 at the 465-MHz eigenmode frequency, and this factor increases to ~10 when the polymer jacket is removed from the fiber.

Measurement of the refractive-index modulation generated by electrostriction-induced acoustic waves in optical fibers.

The refractive-index modulation generated in optical fibers by electrostriction-induced acoustic waves is investigated directly by a pump-probe measurement technique in a 1-km-long fiber Sagnac-loop interferometer. Pump pulses propagating unidirectionally around the loop generate transverse acoustic waves that produce a time-dependent relative phase shift for the probe pulses. The consequent interferometer transmission changes are used as a measure of the acoustic interaction.

Suppression of soliton interactions by periodic phase modulation.

We study analytically and numerically the interaction of adjacent solitons under the influence of a phase modulator. Above a critical value, a bifurcation takes place and the interaction-free lengths are considerably increased.

Coronary artery fistulas: a review and case study.

Coronary artery fistula is a congenital abnormality that can present with a variety of cardiovascular complications. This article presents a patient with a coronary artery fistula outlining the pathophysiology and course of hospitalization, with particular emphasis on nursing management of a patient with coronary artery fistula.

Effect of dexmedetomidine, an alpha 2-adrenergic agonist, in the isolated heart.

Dexmedetomidine (DM) was studied in the isolated dog heart in the form of a Starling heart-lung preparation, (HLP). Hearts were subjected to increased loading by (a) increasing cardiac output, and (b) increasing systemic resistance. Results are depicted by cardiac function curves, prepared by plotting left atrial pressure against either systemic cardiac output or mean arterial pressure.

Average soliton dynamics of a high-gain erbium fiber laser.

Soliton propagation in a fiber described by the nonlinear Schrödinger equation in the presence of large periodic energy variations is examined. Stable propagation can be achieved provided that the soliton period is long compared with the period of energy variation and the (associated) average soliton (peak) pulse power equals the fundamental soliton (peak) pulse power. The result is used to interpret recent experiments on mode-locked, high-gain erbium fiber lasers.

Two-wavelength operation of the nonlinear fiber loop mirror.

We describe the two-wavelength operation of the nonlinear fiber loop mirror. In this mode of operation a high-power signal at one wavelength switches a low-power signal at another wavelength. This device is investigated both theoretically and experimentally.

Experimental demonstration of optical soliton switching in an all-fiber nonlinear Sagnac interferometer.

We demonstrate, for the first time to our knowledge, the switching of optical solitons. We observe switching of 93% of the total reflected energy in a partially transmitting integrated fiber loop mirror that makes up the interferometer. This result demonstrates the potential of solitons as the natural bits in ultrafast optical processing.