Computational wave-based photoacoustic imaging through an unknown thick aberrating layer

We introduce a physics-based computational reconstruction framework for non-invasive photoacoustic tomography through a thick aberrating layer. Our wave-based approach leverages an analytic formulation of diffraction to beamform a photoacoustic image, when the aberrating layer profile is known. When the profile of the aberrating layer is unknown, the same analytical formulation serves as the basis for an automatic-differentiation regularized optimization algorithm that simultaneously reconstructs both the profile of the aberrating layer and the optically absorbing targets. Results from numerical studies and proof-of-concept experiments show promise for fast beamforming that takes into account diffraction effects occurring in the propagation through thick, highly-aberrating layers.

Everything Seems So Illogical: Constructing Missingness Between Life and Death in Israel

This paper discusses the case of missing persons in Israel, to show how the category of "missingness" is constructed by the people who have been left behind, and how this may threaten the life-death dichotomy assumption. The field of missing persons in Israel is characterized not only by high uncertainty, but also by the absence of relevant cultural scripts. Based on a narrative ethnography of missingness in Israel, I claim that a new and subversive social category of "missingness" can be constructed following the absence of cultural scripts. The left-behinds fluctuate not only between different assumptions about the missing person's fate; they also fluctuate between acceptance of the life-death dichotomy, thus yearning for a solution to a temporary in-between state, and blurring this dichotomy, and thus constructing "missingness" as a new stable and subversive ontological category. Under this category, new rites of passage are also negotiated and constructed.

Image scanning lensless fiber-bundle endomicroscopy

Fiber-based confocal endomicroscopy has shown great promise for minimally-invasive deep-tissue imaging. Despite its advantages, confocal fiber-bundle endoscopy inherently suffers from undersampling due to the spacing between fiber cores, and low collection efficiency when the target is not in proximity to the distal fiber facet. Here, we demonstrate an adaptation of image-scanning microscopy (ISM) to lensless fiber bundle endoscopy, doubling the spatial sampling frequency and significantly improving collection efficiency. Our approach only requires replacing the confocal detector with a camera. It improves the spatial resolution for targets placed at a distance from the fiber tip, and addresses the fundamental challenge of aliasing/pixelization artifacts.

Towards passive non-line-of-sight acoustic localization around corners using uncontrolled random noise sources

Non-line-of-sight (NLoS) imaging is an important challenge in many fields ranging from autonomous vehicles and smart cities to defense applications. Several recent works in optics and acoustics tackle the challenge of imaging targets hidden from view (e.g. placed around a corner) by measuring time-of-flight information using active SONAR/LiDAR techniques, effectively mapping the Green functions (impulse responses) from several controlled sources to an array of detectors. Here, leveraging passive correlations-based imaging techniques (also termed 'acoustic daylight imaging'), we study the possibility of acoustic NLoS target localization around a corner without the use of controlled active sources. We demonstrate localization and tracking of a human subject hidden around a corner in a reverberating room using Green functions retrieved from correlations of broadband uncontrolled noise sources recorded by multiple detectors. Our results demonstrate that for NLoS localization controlled active sources can be replaced by passive detectors as long as a sufficiently broadband noise is present in the scene.

A flexible two-photon fiberscope for fast activity imaging and precise optogenetic photostimulation of neurons in freely moving mice

We developed a flexible two-photon microendoscope (2P-FENDO) capable of all-optical brain investigation at near cellular resolution in freely moving mice. The system performs fast two-photon (2P) functional imaging and 2P holographic photostimulation of single and multiple cells using axially confined extended spots. Proof-of-principle experiments were performed in freely moving mice co-expressing jGCaMP7s and the opsin ChRmine in the visual or barrel cortex. On a field of view of 250 μm in diameter, we demonstrated functional imaging at a frame rate of up to 50 Hz and precise photostimulation of selected groups of cells. With the capability to simultaneously image and control defined neuronal networks in freely moving animals, 2P-FENDO will enable a precise investigation of neuronal functions in the brain during naturalistic behaviors.

Massively degenerate coherent perfect absorber for arbitrary wavefronts

One of the key insights of non-Hermitian photonics is that well-established concepts such as the laser can be operated in reverse to realize a coherent perfect absorber (CPA). Although conceptually appealing, such CPAs are limited so far to a single, judiciously shaped wavefront or mode. Here, we demonstrate how this limitation can be overcome by time-reversing a degenerate cavity laser based on a unique cavity that self-images any incident light field onto itself. Placing a weak, critically coupled absorber into this cavity, any incoming wavefront, even a complex and dynamically varying speckle pattern, is absorbed with close to perfect efficiency in a massively parallel interference process. These characteristics open up interesting new possibilities for applications in light harvesting, energy delivery, light control, and imaging.

Flexible-type ultrathin holographic endoscope for microscopic imaging of unstained biological tissues

Ultrathin lensless fibre endoscopes offer minimally invasive investigation, but they mostly operate as a rigid type due to the need for prior calibration of a fibre probe. Furthermore, most implementations work in fluorescence mode rather than label-free imaging mode, making them unsuitable for general medical diagnosis. Herein, we report a fully flexible ultrathin fibre endoscope taking 3D holographic images of unstained tissues with 0.85-μm spatial resolution. Using a bare fibre bundle as thin as 200-μm diameter, we design a lensless Fourier holographic imaging configuration to selectively detect weak reflections from biological tissues, a critical step for label-free endoscopic reflectance imaging. A unique algorithm is developed for calibration-free holographic image reconstruction, allowing us to image through a narrow and curved passage regardless of fibre bending. We demonstrate endoscopic reflectance imaging of unstained rat intestine tissues that are completely invisible to conventional endoscopes. The proposed endoscope will expedite a more accurate and earlier diagnosis than before with minimal complications.

New constraints on axion-like dark matter using a Floquet quantum detector

Dark matter is one of the greatest mysteries in physics. It interacts via gravity and composes most of our universe, but its elementary composition is unknown. We search for nongravitational interactions of axion-like dark matter with atomic spins using a precision quantum detector. The detector is composed of spin-polarized xenon gas that can coherently interact with a background dark matter field as it traverses through the galactic dark matter halo. Conducting a 5-month-long search, we report on the first results of the Noble and Alkali Spin Detectors for Ultralight Coherent darK matter (NASDUCK) collaboration. We limit ALP-neutron interactions in the mass range of 4 × 10^-15 to 4 × 10^-12 eV/c² and improve upon previous terrestrial bounds by up to 1000-fold for masses above 4 × 10^-13 eV/c². We also set bounds on pseudoscalar dark matter models with quadratic coupling.

Guidestar-free image-guided wavefront shaping

Optical imaging through scattering media is a fundamental challenge in many applications. Recently, breakthroughs such as imaging through biological tissues and looking around corners have been obtained via wavefront-shaping approaches. However, these require an implanted guidestar for determining the wavefront correction, controlled coherent illumination, and most often raster scanning of the shaped focus. Alternative novel computational approaches that exploit speckle correlations avoid guidestars and wavefront control but are limited to small two-dimensional objects contained within the "memory-effect" correlation range. Here, we present a new concept, image-guided wavefront shaping, allowing widefield noninvasive, guidestar-free, incoherent imaging through highly scattering layers, without illumination control. The wavefront correction is found even for objects that are larger than the memory-effect range, by blindly optimizing image quality metrics. We demonstrate imaging of extended objects through highly scattering layers and multicore fibers, paving the way for noninvasive imaging in various applications, from microscopy to endoscopy.

Three-dimensional broadband light beam manipulation in forward scattering samples

Focusing light into highly disordered biological tissue is a major challenge in optical microscopy and biomedical imaging due to scattering. However, correlations in the scattering matrix, known as "memory effects", can be used to improve imaging capabilities. Here we discuss theoretically and numerically the possibility to achieve three-dimensional ultrashort laser focusing and scanning inside forward scattering media, beyond the scattering mean free path, by simultaneously taking advantage of the angular and the chromato-axial memory effects. The numerical model is presented in details, is validated within the state of the art theoretical and experimental framework and is finally used to propose a scheme for focusing ultra-short laser pulses in depth through forward scattering media.

100,000 frames-per-second compressive imaging with a conventional rolling-shutter camera by random point-spread-function engineering

We demonstrate an approach that allows taking videos at very high frame-rates of over 100,000 frames per second by exploiting the fast sampling rate of the standard rolling-shutter readout mechanism, common to most conventional sensors, and a compressive-sampling acquisition scheme. Our approach is directly applied to a conventional imaging system by the simple addition of a diffuser to the pupil plane that randomly encodes the entire field-of-view to each camera row, while maintaining diffraction-limited resolution. A short video is reconstructed from a single camera frame via a compressed-sensing reconstruction algorithm, exploiting the inherent sparsity of the imaged scene.

Using fiber-bending-generated speckles for improved working distance and background rejection in lensless micro-endoscopy

Lensless flexible fiber-bundle-based endoscopes allow imaging at depths beyond the reach of conventional microscopes with a minimal footprint. These multicore fibers provide a simple solution for wide-field fluorescent imaging when the target is adjacent to the fiber facet. However, they suffer from a very limited working distance and out-of-focus background. Here, we carefully study the dynamic speckle illumination patterns generated by bending a commercial fiber bundle and show that they can be exploited to allow extended working distance and background rejection, using a super-resolution fluctuations imaging analysis of multiple frames, without the addition of any optical elements.

Super-resolution photoacoustic and ultrasound imaging with sparse arrays

It has previously been demonstrated that model-based reconstruction methods relying on a priori knowledge of the imaging point spread function (PSF) coupled to sparsity priors on the object to image can provide super-resolution in photoacoustic (PA) or in ultrasound (US) imaging. Here, we experimentally show that such reconstruction also leads to super-resolution in both PA and US imaging with arrays having much less elements than used conventionally (sparse arrays). As a proof of concept, we obtained super-resolution PA and US cross-sectional images of microfluidic channels with only 8 elements of a 128-elements linear array using a reconstruction approach based on a linear propagation forward model and assuming sparsity of the imaged structure. Although the microchannels appear indistinguishable in the conventional delay-and-sum images obtained with all the 128 transducer elements, the applied sparsity-constrained model-based reconstruction provides super-resolution with down to only 8 elements. We also report simulation results showing that the minimal number of transducer elements required to obtain a correct reconstruction is fundamentally limited by the signal-to-noise ratio. The proposed method can be straigthforwardly applied to any transducer geometry, including 2D sparse arrays for 3D super-resolution PA and US imaging.

(Un) Natural Grief: Novelty, Tradition and Naturalization in Israeli Discourse on Posthumous Reproduction

This article examines Israeli discourse on posthumous reproduction (PR) and the related cultural construction of "(un)natural" grief. Based mainly on an analysis of in-depth interviews with family members who submitted a request for PR, we examine the regimes of justification used by supporters and opponents of this technology. With both sides using the notion of "nature" to support their claim, the dispute centers on whether PR constructs a new social expression of grief (and hence should be seen as unnatural) or is only a reflection of an age-old grieving process (and is thus natural). We argue that by employing a twofold, novel/traditional justification, PR supporters aim to go one step further, from a symbolic continuity of the dead to a so-called real one. This progression highlights the flexibility of the natural category at the intersection of technology and culture and the abandonment of such binary distinctions as life/death and nature/culture.

Compressive three-dimensional super-resolution microscopy with speckle-saturated fluorescence excitation

Nonlinear structured illumination microscopy (nSIM) is an effective approach for super-resolution wide-field fluorescence microscopy with a theoretically unlimited resolution. In nSIM, carefully designed, highly-contrasted illumination patterns are combined with the saturation of an optical transition to enable sub-diffraction imaging. While the technique proved useful for two-dimensional imaging, extending it to three-dimensions is challenging due to the fading of organic fluorophores under intense cycling conditions. Here, we present a compressed sensing approach that allows 3D sub-diffraction nSIM of cultured cells by saturating fluorescence excitation. Exploiting the natural orthogonality of speckles at different axial planes, 3D probing of the sample is achieved by a single two-dimensional scan. Fluorescence contrast under saturated excitation is ensured by the inherent high density of intensity minima associated with optical vortices in polarized speckle patterns. Compressed speckle microscopy is thus a simple approach that enables 3D super-resolved nSIM imaging with potentially considerably reduced acquisition time and photobleaching.

Noninvasive focusing through scattering layers using speckle correlations

Angular speckle correlations known as the "memory effect" have recently been exploited for noninvasive imaging through scattering layers. Here we show that the information obtained from speckle correlations can be used as a noninvasive feedback mechanism for wavefront shaping. We utilize this feedback to demonstrate noninvasive diffraction-limited focusing of coherent light through thin scattering layers.

Depth-resolved speckle-correlations imaging through scattering layers via coherence gating

Recently, novel imaging techniques based on the "memory-effect" speckle-correlations have enabled diffraction-limited imaging through scattering layers and around corners. These techniques, however, are currently limited to imaging only small planar objects contained within the angular and axial range of the memory effect. In addition, they do not provide depth information or depth-sectioning capability. Here, we extend speckle-correlation imaging to include high-resolution depth-sectioning capability in the reflection mode, by combining it with coherence gating via low-coherence holography. We demonstrate depth measurements of reflective targets through a scattering layer, and speckle-correlation imaging using coherence-gated scattered light.

Two-photon lensless micro-endoscopy with in-situ wavefront correction

Multi-core fiber-bundle endoscopes provide a minimally-invasive solution for deep tissue imaging and opto-genetic stimulation, at depths beyond the reach of conventional microscopes. Recently, wavefront-shaping has enabled lensless bundle-based micro-endoscopy by correcting the wavefront distortions induced by core-to-core inhomogeneities. However, current wavefront-shaping solutions require access to the fiber distal end for determining the bend-sensitive wavefront-correction. Here, we show that it is possible to determine the wavefront correction in-situ, without any distal access. Exploiting the nonlinearity of two-photon excited fluorescence, we adaptively determine the wavefront correction in-situ using only proximal detection of epi-detected fluorescence. We experimentally demonstrate diffraction-limited, three-dimensional, two-photon lensless microendoscopy with commercially-available ordered- and disordered multi-core fiber bundles.

Photoacoustic imaging beyond the acoustic diffraction-limit with dynamic speckle illumination and sparse joint support recovery

In deep tissue photoacoustic imaging the spatial resolution is inherently limited by the acoustic wavelength. Recently, it was demonstrated that it is possible to surpass the acoustic diffraction limit by analyzing fluctuations in a set of photoacoustic images obtained under unknown speckle illumination patterns. Here, we purpose an approach to boost reconstruction fidelity and resolution, while reducing the number of acquired images by utilizing a compressed sensing computational reconstruction framework. The approach takes into account prior knowledge of the system response and sparsity of the target structure. We provide proof of principle experiments of the approach and demonstrate that improved performance is obtained when both speckle fluctuations and object priors are used. We numerically study the expected performance as a function of the measurement's signal to noise ratio and sample spatial-sparsity. The presented reconstruction framework can be applied to analyze existing photoacoustic experimental data sets containing dynamic fluctuations.

Single-shot diffraction-limited imaging through scattering layers via bispectrum analysis

Recently introduced speckle correlations-based techniques enable noninvasive imaging of objects hidden behind scattering layers. In these techniques, the hidden object Fourier amplitude is retrieved from the scattered light autocorrelation, and the lost Fourier phase is recovered via iterative phase-retrieval algorithms, which suffer from convergence to wrong local minimums solutions and cannot solve ambiguities in object orientation. Here, inspired by notions used in astronomy, we experimentally demonstrate that in addition to Fourier amplitude, the object-phase information is naturally and inherently encoded in the scattered light bispectrum (the Fourier transform of triple correlation) and can also be extracted from a single high-resolution speckle pattern, based on which we present a single-shot imaging scheme to deterministically and unambiguously retrieve diffraction-limited images of objects hidden behind scattering layers.

Widefield lensless endoscopy with a multicore fiber

We demonstrate pixelation-free real-time widefield endoscopic imaging through an aperiodic multicore fiber (MCF) without any distal opto-mechanical elements or proximal scanners. Exploiting the memory effect in MCFs, the images in our system are directly obtained without any post-processing using a static wavefront correction obtained from a single calibration procedure. Our approach allows for video-rate 3D widefield imaging of incoherently illuminated objects with imaging speed not limited by the wavefront-shaping device refresh rate.

Widefield lensless imaging through a fiber bundle via speckle correlations

Flexible fiber-optic endoscopes provide a solution for imaging at depths beyond the reach of conventional microscopes. Current endoscopes require focusing and/or scanning mechanisms at the distal end, which limit miniaturization, frame-rate, and field of view. Alternative wavefront-shaping based lensless solutions are extremely sensitive to fiber-bending. We present a lensless, bend-insensitive, single-shot imaging approach based on speckle-correlations in fiber bundles that does not require wavefront shaping. Our approach computationally retrieves the target image by analyzing a single camera frame, exploiting phase information that is inherently preserved in propagation through convnetional fiber bundles. Unlike conventional fiber-based imaging, planar objects can be imaged at variable working distances, the resulting image is unpixelated and diffraction-limited, and miniaturization is limited only by the fiber diameter.

Spatiotemporal Coherent Control of Light through a Multiple Scattering Medium with the Multispectral Transmission Matrix

We report the broadband characterization of the propagation of light through a multiple scattering medium by means of its multispectral transmission matrix. Using a single spatial light modulator, our approach enables the full control of both the spatial and spectral properties of an ultrashort pulse transmitted through the medium. We demonstrate spatiotemporal focusing of the pulse at any arbitrary position and time with any desired spectral shape. Our approach opens new perspectives for fundamental studies of light-matter interaction in disordered media, and has potential applications in sensing, coherent control, and imaging.

Single-pulse CARS based multimodal nonlinear optical microscope for bioimaging

Noninvasive label-free imaging of biological systems raises demand not only for high-speed three-dimensional prescreening of morphology over a wide-field of view but also it seeks to extract the microscopic functional and molecular details within. Capitalizing on the unique advantages brought out by different nonlinear optical effects, a multimodal nonlinear optical microscope can be a powerful tool for bioimaging. Bringing together the intensity-dependent contrast mechanisms via second harmonic generation, third harmonic generation and four-wave mixing for structural-sensitive imaging, and single-beam/single-pulse coherent anti-Stokes Raman scattering technique for chemical sensitive imaging in the finger-print region, we have developed a simple and nearly alignment-free multimodal nonlinear optical microscope that is based on a single wide-band Ti:Sapphire femtosecond pulse laser source. Successful imaging tests have been realized on two exemplary biological samples, a canine femur bone and collagen fibrils harvested from a rat tail. Since the ultra-broad band-width femtosecond laser is a suitable source for performing high-resolution optical coherence tomography, a wide-field optical coherence tomography arm can be easily incorporated into the presented multimodal microscope making it a versatile optical imaging tool for noninvasive label-free bioimaging.

Deterministic control of broadband light through a multiply scattering medium via the multispectral transmission matrix

We present a method to measure the spectrally-resolved transmission matrix of a multiply scattering medium, thus allowing for the deterministic spatiospectral control of a broadband light source by means of wavefront shaping. As a demonstration, we show how the medium can be used to selectively focus one or many spectral components of a femtosecond pulse, and how it can be turned into a controllable dispersive optical element to spatially separate different spectral components to arbitrary positions.

Reference-less measurement of the transmission matrix of a highly scattering material using a DMD and phase retrieval techniques

This paper investigates experimental means of measuring the transmission matrix (TM) of a highly scattering medium, with the simplest optical setup. Spatial light modulation is performed by a digital micromirror device (DMD), allowing high rates and high pixel counts but only binary amplitude modulation. On the sensor side, without a reference beam, the CCD camera provides only intensity measurements. Within this framework, this paper shows that the TM can still be retrieved, through signal processing techniques of phase retrieval. This is experimentally validated on three criteria : quality of prediction, distribution of singular values, and quality of focusing.

Scanning-free imaging through a single fiber by random spatio-spectral encoding

We present an approach for 2D imaging through a single fiber without the need for scanners. A random scattering medium placed next to the distal end of the fiber is used to encode the collected light from every imaged pixel with a different random spectral signature. We demonstrate imaging of externally illuminated 2D objects from a single measured spectrum at the fiber's proximal end. The technique is insensitive to fiber bending, an advantage for endoscopic applications.

Improving photoacoustic-guided optical focusing in scattering media by spectrally filtered detection

We study the potential of photoacoustic guidance for light focusing through scattering samples via wavefront-shaping and iterative optimization. We experimentally demonstrate that the focusing efficiency on an extended absorber can be improved by iterative optimization of the high frequency components of the broadband photoacoustic signal detected with a spherically focused transducer. We demonstrate more than 12-fold increase in the photoacoustic signal generated by a 30 μm wire using a narrow frequency band around 60 MHz. By monitoring the speckle pattern evolution during the optimization process with a CCD camera, we experimentally confirm that such optimization leads to a smaller optical focus than what would be obtained by optimizing lower frequencies of the photoacoustic feedback.

Imaging with nature: compressive imaging using a multiply scattering medium

The recent theory of compressive sensing leverages upon the structure of signals to acquire them with much fewer measurements than was previously thought necessary, and certainly well below the traditional Nyquist-Shannon sampling rate. However, most implementations developed to take advantage of this framework revolve around controlling the measurements with carefully engineered material or acquisition sequences. Instead, we use the natural randomness of wave propagation through multiply scattering media as an optimal and instantaneous compressive imaging mechanism. Waves reflected from an object are detected after propagation through a well-characterized complex medium. Each local measurement thus contains global information about the object, yielding a purely analog compressive sensing method. We experimentally demonstrate the effectiveness of the proposed approach for optical imaging by using a 300-micrometer thick layer of white paint as the compressive imaging device. Scattering media are thus promising candidates for designing efficient and compact compressive imagers.

Light focusing and two-dimensional imaging through scattering media using the photoacoustic transmission matrix with an ultrasound array

We implement the photoacoustic transmission matrix approach on a two-dimensional photoacoustic imaging system, using a 15 MHz linear ultrasound array. Using a black leaf skeleton as a complex absorbing structure, we demonstrate that the photoacoustic transmission matrix approach allows to reveal structural features that are invisible in conventional photoacoustic images, as well as to selectively control light focusing on absorbing targets, leading to a local enhancement of the photoacoustic signal.

Improving visibility in photoacoustic imaging using dynamic speckle illumination

In high-frequency photoacoustic imaging with uniform illumination, homogeneous photoabsorbing structures may be invisible because of their large size or limited-view issues. Here we show that, by exploiting dynamic speckle illumination, it is possible to reveal features that are normally invisible with a photoacoustic system comprised of a 20 MHz linear ultrasound array. We demonstrate imaging of a ∅5 mm absorbing cylinder and a 30 μm black thread arranged in a complex shape. The hidden structures are directly retrieved from photoacoustic images recorded for different random speckle illuminations of the phantoms by assessing the variation in the value of each pixel over the illumination patterns.

Polarization control of multiply scattered light through random media by wavefront shaping

We show that the polarization state of coherent light propagating through an optically thick multiple scattering medium can be controlled by wavefront shaping, that is, by controlling only the spatial phase of the incoming field with a spatial light modulator. Any polarization state of light at any spatial position behind the scattering medium can be attained with this technique. Thus, transforming the random medium to an arbitrary optical polarization component becomes possible.

Spectral control of broadband light through random media by wavefront shaping

A random medium can serve as a controllable arbitrary spectral filter with spectral resolution determined by the inverse of the interaction time of the light in the medium. We use wavefront shaping to implement an arbitrary spectral response at a particular point in the scattered field. We experimentally demonstrate this technique by selecting either a narrow band or dual bands with a width of 5.5 nm each.

Spatiotemporal focusing through a thin scattering layer

We analyze the spatiotemporal distortions of an ultrashort pulse focused through a thin scattering surface. We show and experimentally verify that in such a scenario temporal distortions are proportional to the distance from the optical axis and are present only outside the focal point, as result of geometrical path length differences. We use wavefront shaping to correct for the spatiotemporal distortions and to temporally compress chirped input pulses through the scattering medium.

Structural and mechanical analysis of tectorial membrane Tecta mutants

The tectorial membrane (TM) is an extracellular matrix of the cochlea whose prominent role in hearing has been demonstrated through mutation studies. The C1509G mutation of the Tecta gene, which encodes for the α-tectorin protein, leads to hearing loss. The heterozygote TM only attaches to the first row of outer hair cells (OHCs), and the homozygote TM does not attach to any OHCs. Here we measured the morphology and mechanical properties of wild-type, heterozygous, and homozygous Tecta TMs. Morphological analyses conducted with second- and third-harmonic imaging, scanning electron microscopy, and immunolabeling revealed marked changes in the collagen architecture and stereocilin-labeling patterns of the mutant TMs. The mechanical properties of the mutant TM were measured by force spectroscopy. Whereas the axial Young's modulus of the low-frequency (apical) region of Tecta mutant TM samples was similar to that of wild-type TMs, it significantly decreased in the basal region to a value approaching that found at the apex. Modeling simulations suggest that a reduced TM Young's modulus is likely to reduce OHC stereociliary deflection. These findings argue that the heterozygote C1509G mutation results in a lack of attachment of the TM to the OHCs, which in turn reduces both the overall number of OHCs that are involved in mechanotransduction and the degree of mechanotransduction exhibited by the OHCs that remain attached to the TM.

Single-pulse stimulated Raman scattering spectroscopy

We demonstrate the acquisition of stimulated Raman scattering spectra with the use of a single femtosecond pulse. High-resolution vibrational spectra are obtained by shifting the phase of a narrow band of frequencies within the input pulse spectrum, using spectral shaping. The vibrational lines are resolved via amplitude features formed in the spectrum after interaction with the sample. Using this technique, low-frequency Raman lines (<100 cm⁻¹) are observed on both the Stokes and anti-Stokes sides.

Shot noise limited characterization of ultraweak femtosecond pulse trains

Ultrafast science is inherently, due to the lack of fast enough detectors and electronics, based on nonlinear interactions. Typically, however, nonlinear measurements require significant powers and often operate in a limited spectral range. Here we overcome the difficulties of ultraweak ultrafast measurements by precision time-domain localization of spectral components. We utilize this for linear self-referenced characterization of pulse trains having ∼ 1 photon per pulse, a regime in which nonlinear techniques are impractical, at a temporal resolution of ∼ 10 fs. This technique does not only set a new scale of sensitivity in ultrashort pulse characterization, but is also applicable in any spectral range from the near-infrared to the deep UV.

Mature teratoma, a rare cause of virilization in adolescence

Virilization in an adolescent patient can occur for multiple reasons (ovarian, suprarenal or exogenous reasons). We describe a 14-year-old patient with 1-year secondary amenorrhea, who had an ovarian mature teratoma as a cause of her clinical history.

Single-beam coherent Raman spectroscopy and microscopy via spectral notch shaping

We present a simple and easily implementable scheme for multiplexed Coherent Anti-Stokes Raman Scattering (CARS) spectroscopy and microscopy using a single femtosecond pulse, shaped with a narrow spectral notch. We show that a tunable spectral notch, shaped by a resonant photonic crystal slab, can serve as a narrowband, optimally time-delayed probe, resolving a broad vibrational spectrum with high spectral resolution in a single-shot measurement. Our single-source, single-beam scheme allows the simple transformation of any multiphoton microscope with adequate bandwidth into a nearly alignment-free CARS microscope.

Spatio-temporal X-wave

We introduce an illumination configuration which is a spatiotemporal analog of a non-diffracting X-wave. By interfering multiple ultrashort converging plane waves, we generate a tight central spot at which a transform limited ultrashort pulse is formed. Outside this tight focus a spatiotemporal speckle field with longer duration and reduced peak power is created. We investigate this spatiotemporal X-wave configuration analytically, numerically, and experimentally demonstrate the effect using two photon excitation fluorescence.

Multiple breakup of high-order spatial solitons

The breakup of high-order spatial solitons propagating in an AlGaAs slab waveguide is studied. We experimentally observe the breakup of such beams into multiple fragments and identify the mechanism of this breakup as the combined effect of two- and three-photon absorption. We show that the multiple breakup persists even when the value of two-photon absorption is reduced by an order of magnitude owing to the high value of three-photon absorption of AlGaAs at the half-bandgap. The experimental results extend known mechanisms of soliton breakup induced by two-photon absorption and agree well with numerical beam-propagation simulations.

In vitro activity of novel fluoroquinolones against Streptococcus pneumoniae isolated from children with acute otitis media

BACKGROUND

In recent years, novel fluoroquinolones with improved activity against gram-positive organisms have been introduced into clinical practice. These drugs may be of potential benefit for the treatment of pneumococcal otitis media, including infections caused by organisms resistant to conventional drugs.

METHODS

In vitro activity of 6 fluoroquinolones against 77 pneumococcal isolates from middle-ear fluid was determined by the E test.

RESULTS

Resistance to penicillin, co-trimoxazole, erythromycin, clindamycin, and tetracycline was present in 59 (76.6%), 47 (61.0%), 19 (24.7%), 11 (14.3%), and 17 (22.1%) isolates, respectively. Fluoroquinolone MIC(50) and MIC(90) (in microg/ml) were as follows: ciprofloxacin: 1.0 and 3.0, levofloxacin: 0.75 and 1.0, sparfloxacin: 0.25 and 0.38, grepafloxacin: 0.25 and 0.38, trovafloxacin: 0.094 and 0.125, and moxifloxacin: 0.19 and 0.25, respectively.

CONCLUSIONS

Novel fluoroquinolones and especially trovafloxacin and moxifloxacin appear to be of potential value for the treatment of acute otitis media caused by pneumococci resistant to traditional antibiotics.

Tailored chemosensors for chloroaromatic acids using molecular imprinted TiO2 thin films on ion-sensitive field-effect transistors

The SiO2 gate of an ion-sensitive field-effect transistor, (ISFET), is functionalized with a TiO2 film that includes imprinted molecular sites for 4-chlorophenoxy acetic acid, (1), or 2,4-dichlorophenoxy acetic acid, (2). The functionalized devices that include the imprinted interfaces reveal an impressive selectivity in the sensing of the imprinted substrates Na+ -1 or Na+ -2. The detection limit for Na+ -1 is (5+/-2) x 10(-4) M, which corresponds to 38 mV x dec(-1) in the concentration range of 0.5 to 6 mM. The detection limit for the analysis of Na+ -2 is (1.0+/-0.2) x 10(-5) M, which corresponds to 28 mV dec(-1) in the concentration range 0.1-9.0 mM. The equilibration time of the devices is ca. 5 min.