Ultrabroadband continuum amplification in the near infrared using BiB3O6 nonlinear crystals pumped at 800 nm

Ultrabroadband parametric amplification of a white-light continuum in the near IR (approximately 100 THz, 1.2-2.4 microm) is demonstrated in BiB3O6 pumped by 45 fs long pulses at 800 nm at a repetition rate of 1 kHz. The energy obtained with a 5 mm thick crystal reached 50 microJ, corresponding to external conversion efficiency of 20%.     

Superresolution in turbulent videos: making profit from damage

It is shown that one can make use of local instabilities in turbulent video frames to enhance image resolution beyond the limit defined by the image sampling rate. We outline the processing algorithm, present its experimental verification on simulated and real-life videos, and discuss its potentials and limitations.     

Periodic solitons in nonlocal nonlinear media

We identify periodic solitons in nonlocal nonlinear media: multi-hump soliton solutions propagating in a fully periodic fashion. We also demonstrate recurrences and breathers whose evolution is statistically periodic and discuss why some systems support periodic solitons while others do not.     

Gouy wave modes: undistorted pulse focalization in a dispersive medium

Gouy wave modes are linear waves with finite energy that propagate without distortion at any phase and group velocity through a focal region in a dispersive medium. These features make them potentially useful for the onset and control of nonlinear interactions.     

Diagnostic cellular organization features extracted from autofluorescence images

Depth-resolved NADH autofluorescence images are shown to differentiate between normal and precancerous engineered tissues. An inverse power law behavior of the power spectral density (PSD) of these images is observed, indicating a self-affine organization of mitochondrial NADH at length scales 1-10 microm. Power exponents of the PSD functions vary significantly with tissue depth and precancerous state, giving insight into the morphological changes associated with precancerous lesions and providing substantial potential for noninvasive clinical diagnosis of squamous epithelial lesions and tumors.     

Purkinje imaging system to measure anterior segment scattering in the human eye

We present an instrument based on Purkinje imaging that permits the objective measurement of the amount of scattering associated with the eye's anterior segment, avoiding the contribution from the retina. The experimental system records the fourth Purkinje image, and adequate processing is used to compute a parameter that quantifies the scattering. The method was first tested in an artificial eye and later in normal young eyes wearing customized contact lenses that induced different amounts of scatter. We were able to detect scattering increments, which indicates that this technique may be used as an objective tool to quantify the level of scattering in the anterior segment of the living human eye. The future use of this technique in clinical environments might help to estimate the level of corneal haze in eyes undergoing refractive surgery or/and scattering within the lens during cataract development.     

Umbilic point screening in random optical fields

Umbilic points--singular points of curvature characterized by a fractional topological charge q=+/-1/2--are the most numerous of all special points in the landscape of random optical fields (speckle patterns), outnumbering maxima, minima, saddle points, and optical vortices. To the best of our knowledge, we present the first experimental evidence that positive and negative umbilic points screen one another. Theory predicts that in the absence of screening the charge variance in a bounded region is proportional to the area of the region, whereas in the presence of screening the variance is drastically reduced and is proportional to the perimeter. Our data confirm this latter prediction and provide the first estimates of the screening lengths for umbilic points of the intensity and of the amplitude (field modulus).     

Integration of quantitative DCE-MRI and ADC mapping to monitor treatment response in human breast cancer: initial results

PURPOSE: The objective of this study was to assess changes in the water apparent diffusion coefficient (ADC) and in pharmacokinetic parameters obtained from the fast-exchange regime (FXR) modeling of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) during neoadjuvant chemotherapy in breast cancer. MATERIALS AND METHODS: Eleven patients with locally advanced breast cancer underwent MRI examination prior to and after chemotherapy but prior to surgery. A 1.5-T scanner was used to obtain T1, ADC and DCE-MRI data. DCE-MRI data were analyzed by the FXR model returning estimates of K(trans) (volume transfer constant), v(e) (extravascular extracellular volume fraction) and tau(i) (average intracellular water lifetime). Histogram and correlation analyses assessed parameter changes post-treatment. RESULTS: Significant (P < .05) changes or trends towards significance (P < .10) were seen in all parameters except tau(i), although there was qualitative reduction in tau(i) values post-treatment. In particular, there was reduction (P < .035) in voxels with K(trans) values in the range 0.2-0.5 min(-1) and a decrease (P < .05) in voxels with ADC values in the range 0.99 x 10(-3) to 1.35 x 10(-3) mm2/s. ADC and v(e) were negatively correlated (r = -.60, P < .02). Parameters sensitive to water distribution and geometry (T(1), v(e), tau(i) and ADC) correlated with a multivariable linear regression model. CONCLUSION: The analysis presented here is sensitive to longitudinal changes in breast tumor status; K(trans) and ADC are most sensitive to these changes. Relationships between parameters provide information on water distribution and geometry in the tumor environment.     

The anxiolytic effects of midazolam during anticipation to pain revealed using fMRI

BACKGROUND AND PURPOSE: Functional neuroimaging can distinguish components of the pain experience associated with anticipation to pain from those associated with the experience of pain itself. Anticipation to pain is thought to increase the suffering of chronic pain patients. Inappropriate anxiety, of which anticipation is a component, is also a cause of disability. We present a pharmacological functional magnetic resonance imaging (fMRI) study in which we investigate the selective modulation by midazolam of brain activity associated with anticipation to pain compared to pain itself. METHODS: Eight right-handed male volunteers underwent fMRI combined with a thermal pain conditioning paradigm and midazolam (30 mug/kg) or saline administration on different occasions, with order randomized across volunteers. Volunteers learned to associate a colored light with either painful, hot stimulation or nonpainful, warm stimulation to the back of the left hand. RESULTS: Comparison of the period during thermal stimulation (pain-warm) revealed a network of brain activity commonly associated with noxious stimulation, including activities in the anterior cingulate cortex (ACC), the bilateral insular cortices (anterior and posterior), the thalamus, S1, the motor cortex, the brainstem, the prefrontal cortex and the cerebellum. Comparison of the periods preceding thermal stimulation (anticipation to pain-anticipation to warm) revealed activity principally in the ACC, the contralateral anterior insular cortex and the ipsilateral S2/posterior insula. Detected by a region-of-interest analysis, midazolam reduced the activity associated specifically with anticipation to pain while controlling for anticipation to warm. This was most significant in the contralateral anterior insula (P<.05). There were no significant drug effects on the activity associated with pain itself. CONCLUSION: In identifying a pharmacological effect on activity preceding but not during pain, we have successfully demonstrated an fMRI assay that can be used to study the action of anxiolytic agents in a relatively small cohort of humans.     

The heterogeneous distribution of the liquid phase in partially filled porous glasses and its effect on self-diffusion

The spatial distribution of the liquid phase in a typical, partially filled, porous glass (VitraPor #5) has been examined with the aid of magnetic resonance microscopy and field gradient nuclear magnetic resonance diffusometry techniques. The correlation length of the material turned out to be long enough to permit the visualization of the microscopic heterogeneity of the material by magnetic resonance imaging. Contrasts are dominated by transverse relaxation depending on local filling degree, which in turn depends on local microstructure. The bimodal heterogeneity of the latter was also visualized by scanning electron microscopy. The effect of heterogeneity on an effective diffusion coefficient has been examined for polar (water) and nonpolar (cyclohexane) molecules.