Quantum phenomena in a chirped parametric anharmonic oscillator.

Parametric ladder climbing and the quantum saturation of the threshold for the classical parametric autoresonance due to the zero point fluctuations at low temperatures are discussed. The probability for capture into the chirped parametric resonance is found by solving the Schrödinger equation in the energy basis and the associated resonant phase-space dynamics is illustrated via the Wigner distribution. The numerical threshold for capture into the resonance is compared with the classical and quantum theories in different parameter regimes.

Autoresonant generation of solitons in Bose-Einstein condensates by modulation of the interaction strength.

The autoresonant approach to generation of solitary structures in Bose-Einstein condensates by chirped frequency space-time modulation of the interaction strength is proposed. Both a spatially periodic case and a finite-size trap are studied numerically within a Gross-Pitaevskii equation. Weakly nonlinear theory of the process is developed in the spatially periodic case using Whitham's averaged variational principle. The theory also describes the threshold phenomenon setting the lowest bound on the amplitude of modulations of the interaction strength for autoresonant excitation.

Characterization of single-nucleotide polymorphisms in coding regions of human genes.

A major goal in human genetics is to understand the role of common genetic variants in susceptibility to common diseases. This will require characterizing the nature of gene variation in human populations, assembling an extensive catalogue of single-nucleotide polymorphisms (SNPs) in candidate genes and performing association studies for particular diseases. At present, our knowledge of human gene variation remains rudimentary. Here we describe a systematic survey of SNPs in the coding regions of human genes. We identified SNPs in 106 genes relevant to cardiovascular disease, endocrinology and neuropsychiatry by screening an average of 114 independent alleles using 2 independent screening methods. To ensure high accuracy, all reported SNPs were confirmed by DNA sequencing. We identified 560 SNPs, including 392 coding-region SNPs (cSNPs) divided roughly equally between those causing synonymous and non-synonymous changes. We observed different rates of polymorphism among classes of sites within genes (non-coding, degenerate and non-degenerate) as well as between genes. The cSNPs most likely to influence disease, those that alter the amino acid sequence of the encoded protein, are found at a lower rate and with lower allele frequencies than silent substitutions. This likely reflects selection acting against deleterious alleles during human evolution. The lower allele frequency of missense cSNPs has implications for the compilation of a comprehensive catalogue, as well as for the subsequent application to disease association.

Parametric autoresonant generation of dark solitons.

The autoresonant generation of dark solitons of the nonlinear Schrödinger (NLS) equation is discussed. The approach is based on capturing the system into a continuing resonance using a small, chirped frequency parametric driving. Adiabatic control of soliton parameters is achieved if the driving amplitude exceeds a threshold.

Autoresonant transition in the presence of noise and self-fields.

A sharp threshold for resonant capture of an ensemble of trapped particles driven by chirped frequency oscillations is analyzed. It is shown that at small temperatures T, the capture probability versus driving amplitude is a smoothed step function with the step location and width scaling as alpha(3/4) (alpha being the chirp rate) and (alphaT)(1/2), respectively. Strong repulsive self-fields reduce the width of the threshold considerably, as the ensemble forms a localized autoresonant macroparticle.

Narrow autoresonant magnetization structures in finite-length ferromagnetic nanoparticles.

The autoresonant approach to excitation and control of large-amplitude uniformly precessing magnetization structures in finite-length easy axis ferromagnetic nanoparticles is suggested and analyzed within the Landau-Lifshitz-Gilbert model. These structures are excited by using a spatially uniform, oscillating, chirped frequency magnetic field, while the localization is imposed via boundary conditions. The excitation requires the amplitude of the driving oscillations to exceed a threshold. The dissipation effect on the threshold is also discussed. The autoresonant driving effectively compensates the effect of dissipation but lowers the maximum amplitude of the excited structures. Fully nonlinear localized autoresonant solutions are illustrated in simulations and described via an analog of a quasiparticle in an effective potential. The precession frequency of these solutions is continuously locked to that of the drive, while the spatial magnetization profile approaches the soliton limit when the length of the nanoparticle and the amplitude of the excited solution increase.

Autoresonant excitation of Bose-Einstein condensates.

Controlling the state of a Bose-Einstein condensate driven by a chirped frequency perturbation in a one-dimensional anharmonic trapping potential is discussed. By identifying four characteristic time scales in this chirped-driven problem, three dimensionless parameters P_{1,2,3} are defined describing the driving strength, the anharmonicity of the trapping potential, and the strength of the particles interaction, respectively. As the driving frequency passes the linear resonance in the problem, and depending on the location in the P_{1,2,3} parameter space, the system may exhibit two very different evolutions, i.e., the quantum energy ladder climbing (LC) and the classical autoresonance (AR). These regimes are analyzed both in theory and simulations with the emphasis on the effect of the interaction parameter P_{3}. In particular, the transition thresholds on the driving parameter P_{1} and their width in P_{1} in both the AR and LC regimes are discussed. Different driving protocols are also illustrated, showing efficient control of excitation and deexcitation of the condensate.

Multiresonant control of two-dimensional dynamical systems.

It is shown that many two degree of freedom (2D) nonlinear dynamical systems can be controlled by continuous phase-locking (double autoresonance) between the two canonical angle variables of the system and two independent external oscillating perturbations having slowly varying frequencies. Conditions for stability of the 2D autoresonance and classification of systems with doubly autoresonant solutions in the vicinity of a stable equilibrium are outlined in terms of the Hessian matrix elements of the unperturbed system. The doubly autoresonant states in a generic, driven 2D system can be accessed by starting in equilibrium and simultaneous passage through two linear resonances in the system, provided that the driving amplitudes exceed a threshold scaling as alpha(3/4) , alpha being the characteristic chirp rate of the driving frequencies. The formation of nearly periodic trajectories in linearly nondegenerate, 2D driven systems with a single stable equilibrium is suggested as an application. Examples of autoresonant excitation and formation of nearly periodic states in other types of driven systems are presented, including a three-particle Toda chain, a particle in a 2D double-well potential, and a 3D oscillator.

Driven, autoresonant three-oscillator interactions.

An efficient control scheme of resonant three-oscillator interactions using an external chirped frequency drive is suggested. The approach is based on formation of a double phase-locked (autoresonant) state in the system, as the driving oscillation passes linear resonance with one of the interacting oscillators. When doubly phase locked, the amplitudes of the oscillators increase with time in proportion to the driving frequency deviation from the linear resonance. The stability of this phase-locked state and the effects of dissipation and of the initial three-oscillator frequency mismatch on the autoresonance are analyzed. The associated autoresonance threshold phenomenon in the driving amplitude is also discussed. In contrast to other nonlinear systems, driven, autoresonant three-oscillator excitations are independent of the sign of the driving frequency chirp rate.

Emergence and control of breather and plasma oscillations by synchronizing perturbations.

Large amplitude standing waves of spatially periodic sine-Gordon equations are excited and controlled by sweeping the frequency of a small, spatially modulated driving oscillation through resonances in the system. The approach is based on capturing the system into resonances and subsequent adiabatic, persistent phase locking (autoresonance) yielding control via a single external parameter (the driving frequency). Plasma oscillations in the system are excited by using a small amplitude drive in the form of a chirped frequency standing wave, while emergence of autoresonant breather oscillations requires driving by a combination of small amplitude oscillation and standing waves.

Parametric autoresonant excitation of the nonlinear Schrödinger equation.

Parametric excitation of autoresonant solutions of the nonlinear Schrodinger (NLS) equation by a chirped frequency traveling wave is discussed. Fully nonlinear theory of the process is developed based on Whitham's averaged variational principle and its predictions verified in numerical simulations. The weakly nonlinear limit of the theory is used to find the threshold on the amplitude of the driving wave for entering the autoresonant regime. It is shown that above the threshold, a flat (spatially independent) NLS solution can be fully converted into a traveling wave. A simplified, few spatial harmonics expansion approach is also developed for studying this nonlinear mode conversion process, allowing interpretation as autoresonant interaction within triads of spatial harmonics.

Excitation of multiphase waves of the nonlinear Schrödinger equation by capture into resonances.

A method for adiabatic excitation and control of multiphase ( N -band) waves of the periodic nonlinear Schrödinger (NLS) equation is developed. The approach is based on capturing the system into successive resonances with external, small amplitude plane waves having slowly varying frequencies. The excitation proceeds from zero and develops in stages, as an (N+1) -band (N=0,1,2,...) , growing amplitude wave is formed in the (N+1) th stage from an N -band solution excited in the preceding stage. The method is illustrated in simulations, where the excited multiphase waves are analyzed via the spectral approach of the inverse scattering transform method. The theory of excitation of 0- and 1-band NLS solutions by capture into resonances is developed on the basis of a weakly nonlinear version of Whitham's averaged variational principle. The phenomenon of thresholds on the driving amplitudes for capture into successive resonances and the stability of driven, phase-locked solutions in these cases are discussed.

Multiphase autoresonant excitations in discrete nonlinear Schrödinger systems.

Large amplitude, multiphase solutions of periodic discrete nonlinear Schrödinger (NLS) systems are excited and controlled by starting from zero and using a small perturbation. The approach involves successive formation of phases in the solution by driving the system with small amplitude plane wavelike perturbations (drives) with chirped frequencies, slowly passing through a system's resonant frequency. The system is captured into resonance and enters a continuing phase-locking (autoresonance) stage, if the drive's amplitude surpasses a certain sharp threshold value. This phase-locked solution is efficiently controlled by variation of an external parameter (driving frequency). Numerical examples of excitation of multiphase waves and periodic discrete breathers by using this approach for integrable (Ablowitz-Ladik) and nonintegrable NLS discretizations are presented. The excited multiphase waveforms are analyzed via the spectral theory of the inverse scattering method applied to both the integrable and nonintegrable systems. A theory of autoresonant excitation of 0- and 1-phase solutions by passage through resonances is developed. The threshold phenomenon in these cases is analyzed.

Anomalous autoresonance threshold for chirped-driven Korteweg-de-Vries waves.

Large amplitude traveling waves of the Korteweg-de-Vries (KdV) equation can be excited and controlled by a chirped frequency driving perturbation. The process involves capturing the wave into autoresonance (a continuous nonlinear synchronization) with the drive by passage through the linear resonance in the problem. The transition to autoresonance has a sharp threshold on the driving amplitude. In all previously studied autoresonant problems the threshold was found via a weakly nonlinear theory and scaled as α(3/4),α being the driving frequency chirp rate. It is shown that this scaling is violated in a long wavelength KdV limit because of the increased role of the nonlinearity in the problem. A fully nonlinear theory describing the phenomenon and applicable to all wavelengths is developed.

Autoresonant excitation of dark solitons.

Continuouslyphase-locked (autoresonant) dark solitons of the defocusing nonlinear Schrodinger equation are excited and controlled by driving the system by a slowly chirped wavelike perturbation. The theory of these excitations is developed using Whitham's averaged variational principle and compared with numerical simulations. The problem of the threshold for transition to autoresonance in the driven system is studied in detail, focusing on the regime when the weakly nonlinear frequency shift in the problem differs from the typical quadratic dependence on the wave amplitude. The numerical simulations in this regime show a deviation of the autoresonance threshold on the driving amplitude from the usual 3/4 power dependence on the driving frequency chirp rate. The theory of this effect is suggested.

Ocular and pericardial involvement in Legionnaires' disease.

Legionnaires' disease can exhibit protean extrapulmonary manifestations. Pericardial involvement is rare and has been described in three case reports. A patient is described with Legionnaires' disease and pericardial and ocular involvement, an entity that has not been reported previously. This patient was successfully treated with intravenous erythromycin with resolution of his pericardial effusion and ophthalmologic findings.

Development of a polymerase chain reaction assay to detect the presence of Streptococcus pneumoniae DNA.

In this study, we have developed a chemically sensitive and specific polymerase chain reaction (PCR) assay to detect the presence of Streptococcus pneumoniae genomic DNA. The target DNA sequence was a 322-base pair segment of the S. pneumoniae DNA polymerase I gene (pol I). PCR products of pure cultures of a set of pneumococcal serotypes commonly associated with human infection could be amplified in water and in blood cultures of clinical isolates containing S. pneumoniae. We were able to detect 2 fg of purified S. pneumoniae DNA. There were no false-positive reactions when the assay was performed on samples containing the following clinically encountered bacteria: Haemophilus influenzae type B, Neisseria meningitidis, Escherichia coli, Klebsiella pneumoniae, Pseudomonas spp. nontypeable H. influenzae, Staphylococcus aureus, coagulase-negative staphylococci, and Streptococcus pyogenes. The addition of EDTA and citrate-anticoagulated whole blood to the PCR reaction mixture inhibited the PCR assay, whereas the addition of lithium heparin, sodium heparin, and sodium polyanetholesulfonate-anticoagulated whole blood to PCR reaction mixture did not interfere with the ability to detect the presence of S. pneumoniae DNA.

Combination fentanyl and diazepam for pediatric conscious sedation.

OBJECTIVES: To evaluate the safety and to describe the use of combination IV diazepam and fentanyl in the pediatric emergency department (PED) as outpatient conscious sedation (CS) for orthopedic procedures. METHODS: A retrospective chart review of a standardized protocol for CS administered to 133 consecutive patients requiring CS for outpatient orthopedic procedures. The patients were continuously monitored for heart rate, respiratory rate, and arterial O2 saturation (Sao2) by pulse oximetry. The study was conducted at a large urban PED and regional referral center. RESULTS: A total of 133 children (mean age 8.5 years) received 138 orthopedic procedures. Mean (+/- SD) total diazepam dose was 0.12 +/- 0.05 mg/kg; mean total fentanyl dose was 3.18 +/- 1.04 micrograms/kg. Mean time intervals were 4.6 minutes from initial drug administration to start of procedure, 15.5 minutes to end of procedure, and 56 minutes to meeting criteria for release home. Complications included Sao2 < 90% for 15 patients (11%, 95% CI 6.4-17.4%), vomiting for one (0.7%, 95% CI 0.1-4.2%), and severe pruritus for one (0.7%, 95% CI 0.1-4.2%). An episode of Sao2 < 90% was associated with a higher initial mean fentanyl dose (2.60 vs 1.95 micrograms/kg; p = 0.0005), but was not associated with a higher initial mean diazepam dose (p = 0.28). Parenteral opioid use for pain management prior to CS was not associated with an increased risk for Sao2 < 90% (p = 0.42). Heart rate, respiratory rate, and blood pressure were stable during the observational period. No patient required naloxone, flumazenil, artificial airway control, or admission to the hospital. CONCLUSIONS: At the doses given in the study, the use of combination diazepam and fentanyl for outpatient CS of PED patients during orthopedic procedures was not associated with serious complications. A higher initial fentanyl dose was associated with episodes of Sao2 < 90%. Therefore, an initial dose of < or = 2.0 micrograms/kg fentanyl titrated to effect is recommended.

A pilot study of the predictive value of plasma tumor necrosis factor alpha and interleukin 1 beta for Streptococcus pneumoniae bacteremia in febrile children.

OBJECTIVE: To determine the value of tumor necrosis factor alpha (TNF) and interleukin 1 beta (IL1) levels in predicting Streptococcus pneumoniae bacteremia in nontoxic-appearing, febrile children who do not have a bacterial source for their fever on physical examination. METHODS: A prospective, nested case-control study was conducted in a children's hospital ED. All febrile children < 3 years old who were believed to be immunocompetent and not in shock, had no obvious bacterial source for their fever on physical examination, and had a blood culture obtained were eligible. Plasma obtained at the time of the blood culture was available for analysis by enzyme-linked immunosorbent assays for TNF and IL1. Children who had positive blood cultures for Streptococcus pneumoniae were the cases. The controls were selected from children who had negative blood cultures. RESULTS: During a 1-year period, 12 cases and 65 controls were identified. There was no significant difference in age, height or duration of fever, or illness acuity between the groups. The following were used as threshold values for positive test: white blood cell (WBC) count > 15.0 x 10(9) cells/L, TNF > 21.5 ng/mL, and IL1 > 9.0 ng/mL. Using an estimated prior probability of bacteremia of 4%, the positive predictive value (PPV) and the negative predictive value (NPV) for bacteremia were 11.7% and 98.6% using the WBC count, 11.1% and 98.6% using the IL1 level, and 9.0% and 98.9% using the TNF level. The combination of WBC count with either TNF or IL1 gave an NPV of 100%, with PPVs of 8.5% for TNF and 9.9% for IL1. CONCLUSIONS: Like the WBC count, TNF and IL1 are good negative but poor positive predictors of Streptococcus pneumoniae bacteremia in nontoxic-appearing, febrile children. At present, the addition of plasma TNF or IL1 levels would add little to emergency physicians' ability to predict Streptococcus pneumoniae bacteremia. However, as the quantification of these cytokines becomes more rapid, available, and standardized, and more knowledge of TNF and IL1 levels during various illnesses is gained, their utility in the clinical setting for ruling out bacteremia should be further assessed.

Multiphase control of a nonlinear lattice.

Large amplitude, multiphase excitations of the periodic Toda lattice (n-gap solutions) are created and controlled by small forcing. The approach uses passage through an ensemble of resonances and subsequent multiphase self-locking of the system with adiabatic wave-like perturbations. The synchronization of each phase in the excited lattice proceeds from the weakly nonlinear stage, where the problem can be reduced to that for a number of independent, driven, one-degree-of-freedom oscillatory systems. Due to this separability, the phase locking at this stage is robust, provided the amplitude of the corresponding forcing component exceeds a threshold, which scales as 3/4 power of the corresponding frequency chirp rate. The adiabatic synchronization continues into a fully nonlinear stage, as the driven lattice self-adjusts its state to remain in a persisting and stable multifrequency resonance with the driving perturbation. Thus, a complete control of the n-gap state becomes possible by slow variation of external parameters.