Dual-wavelength distributed feedback laser array based on four-phase-shifted sampled Bragg grating for terahertz generation.

We propose and experimentally demonstrate a dual-wavelength distributed feedback (DFB) laser array utilizing a four-phase-shifted sampled Bragg grating. By using this grating, the coupling coefficient is enhanced by approximately 2.83 times compared to conventional sampled Bragg gratings.

Alcohol and Apoptosis: Friends or Foes?

Alcohol abuse causes 79,000 deaths stemming from severe organ damage in the United States every year. Clinical manifestations of long-term alcohol abuse on the cardiac muscle include defective contractility with the development of dilated cardiomyopathy and low-output heart failure; which has poor prognosis with less than 25% survival for more than three years. In contrast, low alcohol consumption has been associated with reduced risk of cardiovascular disease, however the mechanism of this phenomenon remains elusive.

Calcitonin Gene-Related Peptide Regulates Cardiomyocyte Survival through Regulation of Oxidative Stress by PI3K/Akt and MAPK Signaling Pathways.

CGRP and specific CGRP receptors are found in the heart where they produce positive-inotropic and anti-apoptotic effects, key adaptations to exercise and cardiovascular disease. PI3K/Akt and MAPK signaling imbalances are associated with cardiomyocyte pathologies; however, the effects of CGRP on these pathways are unclear. Therefore, we hypothesized that CGRP modulates inotropic and apoptotic adaptations of cardiomyocytes by regulating PI3K/Akt and MAPK/ERK signaling balances.

Acute alcohol modulates cardiac function as PI3K/Akt regulates oxidative stress.

Background: Clinical manifestations of alcohol abuse on the cardiac muscle include defective contractility with the development of heart failure. Interestingly, low alcohol consumption has been associated with reduced risk of cardiovascular disease. Although several hypotheses have been postulated for alcoholic cardiomyopathy and for the low-dose beneficial cardiovascular effects, the precise mechanisms and mediators remain largely undefined.

Inotropic and lusitropic effects of calcitonin gene-related peptide in the heart.

Previous studies have demonstrated positive-inotropic effects of calcitonin gene-related peptide (CGRP), but the mechanisms remain unclear. Therefore, two experiments were performed to determine the physiological correlates of the positive-inotropic effects of CGRP. Treatments designed to antagonize the effects of physiologically active CGRP₁₋₃₇ included posttreatment with CGRP₈₋₃₇ and pretreatment with LY-294002 (LY, an inhibitor of phosphatidylinositol 3-kinase), 17β-estradiol (E), and progesterone (P) were also used to modulate the effects of CGRP₁₋₃₇.

The good, the bad, and the ugly with alcohol use and abuse on the heart.

Since its advent, alcohol has been utilized throughout history socially, for rituals, worship, and for its therapeutic, antibacterial, and analgesic properties. In moderation, alcohol consumption and its use are generally viewed as clinically beneficial. Excessive alcohol consumption on the other hand has been recognized as having several adverse implications.

Near-infrared center-of-intensity time gated imaging for detection of a target in a highly scattering turbid medium.

A near-infrared optical imaging approach for locating a target embedded in a turbid medium is introduced. The target localization is based on an analysis of the spatial variation of the transmitted-light intensity distribution for illumination at different positions on the sample boundary. The approach is used to detect, locate and generate images of absorbing targets embedded inside model scattering media of thickness approximately 50 times the transport mean free path of the medium, as well as, of ex vivo biological tissue specimens.

Determination of optical coefficients and fractal dimensional parameters of cancerous and normal prostate tissues.

Optical extinction and diffuse reflection spectra of cancerous and normal prostate tissues in the 750 to 860 nm spectral range were measured. Optical extinction measurements using thin ex vivo prostate tissue samples were used to determine the scattering coefficient (μ(s)), while diffuse reflection measurements using thick prostate tissue samples were used to extract the absorption coefficient (μ(a)) and the reduced scattering coefficient (μ'(s)). The anisotropy factor (g) was obtained using the extracted values of μ(s) and μ'(s).

Time reversal optical tomography: locating targets in a highly scattering turbid medium.

A time reversal optical tomography (TROT) method for near-infrared (NIR) diffuse optical imaging of targets embedded in a highly scattering turbid medium is presented. TROT combines the basic symmetry of time reversal invariance and subspace-based signal processing for retrieval of target location. The efficacy of TROT is tested using simulated data and data obtained from NIR imaging experiments on absorptive and scattering targets embedded in Intralipid-20% suspension in water, as turbid medium.

Optical tomographic image reconstruction from ultrafast time-sliced transmission measurements.

Optical imaging and localization of objects inside a highly scattering medium, such as a tumor in the breast, is a challenging problem with many practical applications. Conventional imaging methods generally provide only two-dimensional (2-D) images of limited spatial resolution with little diagnostic ability. Here we present an inversion algorithm that uses time-resolved transillumination measurements in the form of a sequence of picosecond-duration intensity patterns of transmitted ultrashort light pulses to reconstruct three-dimensional (3-D) images of an absorbing object located inside a slab of a highly scattering medium.

Two-dimensional near-infrared transillumination imaging of biomedical media with a chromium-doped forsterite laser.

Transillumination images of objects hidden in normal and cancerous human breast tissues and bovine, porcine, and gallinaceous (chicken) tissues as well as model-random-scattering media were recorded with 1250-nm light from a chromium-doped forsterite laser. A Fourier space gate and a polarization gate were used to sort out image-bearing photons and discriminate against multiply scattered image-blurring photons. Better contrast, higher spatial resolution, and deeper penetration of samples were achieved for imaging with 1250-nm light than those obtained at shorter wavelengths, such as 1064 nm from a neodymium-doped yttrium aluminum garnet (YAG) laser.

Optical imaging of turbid media using independent component analysis: theory and simulation.

A new imaging approach for 3-D localization and characterization of objects in a turbid medium using independent component analysis (ICA) from information theory is developed and demonstrated using simulated data. This approach uses a multisource and multidetector signal acquisition scheme. ICA of the perturbations in the spatial intensity distribution measured on the medium boundary sorts out the embedded objects.

Spectral and temporal near-infrared imaging of ex vivo cancerous and normal human breast tissues.

Cancerous and normal ex vivo human breast tissues were investigated using spectroscopic and time-sliced two-dimensional (2-D) transillumination imaging methods in order to demonstrate the importance and potential of spectral and temporal measurements in breast cancer detection and diagnosis. The experimental arrangement for time-sliced optical imaging used 120 fs, 1 kHz repetition-rate, 800 nm light pulses from a Ti:sapphire laser system for sample illumination, and a 80 ps resolution ultrafast gated intensified camera system for recording 2-D time-sliced images. The spectroscopic imaging arrangement used 1225-1300 nm tunable output of a Cr: forsterite laser for sample illumination, a Fourier space gate to discriminate against multiple-scattered light, and a near-infrared area camera to record 2-D images.

Three-dimensional localization and optical imaging of objects in turbid media with independent component analysis.

A new approach for optical imaging and localization of objects in turbid media that makes use of the independent component analysis (ICA) from information theory is demonstrated. Experimental arrangement realizes a multisource illumination of a turbid medium with embedded objects and a multidetector acquisition of transmitted light on the medium boundary. The resulting spatial diversity and multiple angular observations provide robust data for three-dimensional localization and characterization of absorbing and scattering inhomogeneities embedded in a turbid medium.

Aorta and skin tissues welded by near-infrared Cr4+:YAG laser.

Objective: The aim of our study was to explore the wavelength dependence of welding efficacy. Ex vivo samples of human and porcine aorta and skin tissues were investigated using a tunable Cr(4+):yttrium aluminum garnet (YAG) laser.

Background Data: Tissue welding is possible using laser light in the NIR spectral range.