Amplification Dispersion Research Articles

Target-triggered hairpin-free chain-branching growth of DNA dendrimers for contrast-enhanced imaging in living cells by avoiding signal dispersion

The development of amplification strategies is one of the central challenges for detection of low-abundance targets. One-to-many (1:M) amplification strategies in which one target lights many signal probes, has improved the detection sensitivity in bulk solution, but with discounted contrast in cell imaging, because the lighted probes are dissociative and dispersible. In this work, a one-to-large (1:L) signaling mechanism, in which the lighted probes were orderly connected to each other, was conceptually proposed to enhance the contrast in cell imaging by avoiding signal dispersion in amplification. Accordingly, target-triggered hairpin-free chain-branching assembly (HFCBA) holds great potential to implement the 1:L mechanism, but using it in cell imaging has yet to be demonstrated. As a proof of concept, a group of probes were first programmed to implement miRNA-21-triggered HFCBA. After transfection of probes, gradually-growing signal flares in cells were monitored along with the growth of DNA dendrimers; and the in situ fluorescence accumulation in HFCBA resulted in highly-enhanced contrast to the surrounding by avoiding signal dispersion in amplification. The contrast-enhanced imaging with signal amplification is significant for biological analysis and molecular medicine. We expect the 1:L mechanism will provide a new thought for high-performance imaging of biomarkers in cells.

Rabi oscillations for subpicosecond pulses in quantum-well optical amplifiers: interplay of carrier heating, nonlinear, and spectral effects

Using the Foreman effective mass Hamiltonian for strained In/sub x/Ga/sub 1-x/As--In/sub y/Ga/sub 1-y/As/sub z/P/sub 1-z/ quantum wells, the propagation of subpicosecond pulses in a 1.55-/spl mu/m optical amplifier was calculated. The multisubband carrier dynamics as well as the polarization dynamics were taken into account. Carrier heating and coherent light-carrier interactions as well as the interplay of these nonlinear processes and the amplifier dispersion are studied. Strong Rabi oscillations occur in the optical field of a propagated pulse, its frequency chirp, as well as in the carrier density and temperature. While the Rabi oscillation imposes negative frequency chirp and hence red-shifts the pulse spectrum, positive frequency chirp can occur due to the local gain dispersion, where the higher frequency components of the pulse have larger gain. Due to the Rabi oscillation, the spectrum of the amplified pulse is considerably distorted and sidebands emerge. For a linearly chirped input pulse, the spectrum of the output pulse can be either red-shifted or blue-shifted with respect to its center frequency, depending on its initial chirp. For strong pulse propagation, a pronounced pulse break up occurs when a 175-fs pulse propagates in the gain regime, while a significant pulse compression occurs when the pulse propagates at the transparency point.

Effects of quintessence on observations of Type Ia supernovae in the clumpy universe

We discuss the amplification dispersion in the observed luminosity of standard candles, such as supernovae (SNe) of Type Ia, induced by gravitational lensing in a universe with dark energy (quintessence). We derive the main features of the magnification probability distribution function (pdf) of SNe in the framework of on average Friedmann-Lemaitre-Robertson-Walker (FLRW) models for both lensing by large-scale structures and compact objects. Analytic expressions, in terms of hypergeometric functions, for luminosity distance-redshift relations in a flat universe with homogeneous dark energy have been corrected for the effects of inhomogeneities in the pressureless dark matter (DM). The magnification pdf is strongly dependent on the equation of state, ω Q , of the quintessence. With no regard to the nature of DM (microscopic or macroscopic), the dispersion increases with the redshift of the source and is maximum for dark energy with very large negative pressure; the effects of gravitational lensing on the magnification pdf, i.e. the mode biased towards de-amplified values and the long tail towards large magnifications, are reduced for both microscopic DM and quintessence with an intermediate ω Q . Different equations of state of the dark energy can deeply change the dispersion in amplification for the projected observed samples of SNe Ia by future space-borne missions. The 'noise' in the Hubble diagram due to gravitational lensing strongly affects the determination of the cosmological parameters from SNe data. The errors on the pressureless matter density parameter, Ω M , and on ω Q are maximum for quintessence with not very negative pressure. The effect of the gravitational lensing is of the same order as the other systematics affecting observations of SNe Ia. As a result of the lensing by large-scale structures, in a flat universe with Ω M = 0.4, at z = 1 a cosmological constant (ω Q = -1) can be interpreted as dark energy with ω Q < -0.84 (at 2a confidence limit).

Gravitational lensing by smooth inhomogeneities in the Universe

The formalism developed by Gunn J. E. (1967, Astrophys. J., 150) on the gravitational lensing effect of smooth inhomogeneities in the Universe is reviewed and some new simple analytical expressions for the dispersion in amplification are derived. Two models for the distribution and evolution of density fluctuations are considered, namely a universe dominated by cold dark matter, and a scale-free universe with an initial density fluctuation spectrum corresponding to white noise.