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We present here an alternative, force-based measurement method for the detection of intracellular cytoskeletal proteins in the live cell. High aspect ratio nanoneedles of 200 nm in diameter were functionalized with anti-tubulin antibodies and inserted, using an atomic force microscope (AFM), into live NIH3T3 cells, without affecting cell viability. Force curves were recorded during insertion and evacuation of nanoneedles from the cells, and used to analyse intracellular interactions of the nanoneedles with the microtubule cytoskeleton during evacuation from the cell. Disruption of microtubules led to a correlated time-dependent decrease in the measured intracellular binding forces, pointing to the high-sensitivity and high-specificity of this detection method. This analytical technique allows for real-time evaluation of the microtubule network in the live cell, without the need to use potentially harmful molecular markers as do conventional detection methods, and may prove beneficial in the diagnosis and investigation of cytoskeleton-associated diseases. [Copyright &y& Elsevier]

Over the past decade, the Anderson localization of light and a wide variety of associated phenomena have come to the forefront of research. Numerous investigations have been made into the underlying physics of how disorder affects transport in a crystalline lattice incorporating disorder. The physics involved relies on the analogy between the paraxial equation for electromagnetic waves and the Schrödinger equation describing quantum phenomena. Experiments have revealed how wavefunctions evolve during the localization process, and have led to discoveries of new physics that are universal to wave systems incorporating disorder. This Review summarizes the phenomena associated with the transverse localization of light, with an emphasis on the history, new ideas and future exploration of the field. [ABSTRACT FROM AUTHOR]

Abstract: A cell diagnosis technique was developed, which uses an Atomic Force Microscope (AFM) and an ultra-thin AFM probe sharpened to a diameter of 200nm (nanoneedle). Due to the high aspect ratio of the nanoneedle, it was successfully inserted into a living cell without affecting its viability. Furthermore, by functionalizing the nanoneedle with specific antibodies and measuring the unbinding forces (‘fishing forces’) during evacuation of the nanoneedle from the cell, it was possible to measure specific mechanical interactions between the antibody-functionalized nanoneedle and the intracellular contents of the cell. In this study, an anti-actin-antibody-functionalized nanoneedle was used to evaluate the actin cytoskeleton state in living cells. To examine the effect of cytoskeleton condition on the measured fishing forces, the cytoskeleton-disrupting drugs cytochalasin D (cytD) and Y-27632 were used, showing a marked decrease in the measured fishing forces following incubation with either of the drugs. Furthermore, the technique was used to measure the time course changes in a single cell during incubation with cytD, showing a gradual time-dependent decrease in fishing forces. Even minute doses of the drugs, the effects of which were hardly evident by optical and fluorescence methods, could be clearly detected by the measurement of nanoneedle–protein fishing forces, pointing to the high sensitivity of this detection method. This technique may prove beneficial for the evaluation of cytoskeleton conditions in health and disease, and for the selection of specific cells according to their intracellular protein contents, without the need for introduction of marker proteins into the cell. [Copyright &y& Elsevier]

Complete population transfer in a four-coupled-modes system is analyzed from a geometrical point of view. An analytical solution of the dynamics is written by the use of two distinct frequencies, the generalization of the single Rabi frequency of the two-state dynamics. We also present its visualization on two separate Bloch spheres with two independent torque equations. With this scheme we analytically derive the requirements for complete population transfer in a four-state quantum system. Interestingly, the solutions are found to be linked to fundamental number theory, whereas complete population transfer occurs only if the ratios between coupling coefficients exactly match a set of Pythagorean triples. [ABSTRACT FROM AUTHOR]

The field of quantum coherent control, initially formulated with the goal of modifying and manipulating molecular systems, has had a number of applications in atomic and molecular spectroscopy in recent years. This review demonstrates how carefully designed fenitosecond pulses could be used to enhance resolution and improve detection in several areas of nonlinear spectroscopy. The two effects that are most intensively studied in this context are two-photon absorption and coherent anti-Stokes Ranian scattering. This article discusses the principles of the control of such processes and several possible applications in microscopy and remote sensing. [ABSTRACT FROM AUTHOR]

Mechanical stress affects and regulates many aspects of the cell, including morphology, growth, differentiation, gene expression and apoptosis. In this study we show how mechanical stress perturbs the intracellular structures of the cell and induces mechanical responses. In order to correlate mechanical perturbations to cellular responses, we used a combined fluorescence-atomic force microscope (AFM) to produce well defined nanomechanical perturbations of 10 nN while simultaneously tracking the real-time motion of fluorescently labelled mitochondria in live cells. The spatial displacement of the organelles in response to applied loads demonstrates the highly dynamic mechanical response of mitochondria in fibroblast cells. The average displacement of all mitochondrial structures analysed showed an increase of ∼40%, post-perturbation (∼160 nm in comparison to basal displacements of ∼110 nm). These results show that local forces can produce organelle displacements at locations far from the initial point of contact (up to ∼40 µm). In order to examine the role of the cytoskeleton in force transmission and its effect on mitochondrial displacements, both the actin and microtubule cytoskeleton were disrupted using Cytochalasin D and Nocodazole, respectively. Our results show that there is no significant change in mitochondrial displacement following indentation after such treatments. These results demonstrate the role of the cytoskeleton in force transmission through the cell and on mitochondrial displacements. In addition, it is suggested that care must be taken when performing mechanical experiments on living cells with the AFM, as these local mechanical perturbations may have significant structural and even biochemical effects on the cell. Copyright © 2008 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Demonstrates that changes on a femtosecond laser pulse using ultrashort pulse-shaping techniques to control two-photon transitions in cesium. Observations of predicted cancellation of the transitions due to destructive quantum interference; Power spectrum and energy of dark pulses observed to have no change.

We show that the nonlinear coupling between two waveguide modes can lead to both power exchange and nonlinear phase shifting between the modes. New applications of nonlinear phase shifting to all-optical devices are described. [ABSTRACT FROM AUTHOR]

Quantum coherent control techniques are applied to achieve high spectral resolution nonlinear vibrational spectroscopy using a single ultrashort laser source. By controlling the spectral phase of ∼10 fs pulses, we are able to obtain detailed coherent anti-Stokes Raman (CARS) spectra in the important fingerprint spectral region, which reflects the structural chemical information. A full theoretical analysis and an experimental demonstration of two alternative schemes leading to spectral resolution two orders of magnitude better than the pulse bandwidth are presented. The first involves selective excitation of vibrational levels within the pulse bandwidth by periodic modulation of the spectral phase of the pulse. In the second scheme an effective narrow probing of the vibrational level has been achieved by phase shifting of a narrow spectral band. Single-pulse CARS offers an attractive alternative to conventional multibeam nonlinear vibrational spectroscopy techniques. [ABSTRACT FROM AUTHOR]

The article presents a study carried out by researcher T. Ideguchi regarding the detection of molecules through specific vibration frequencies. Ideguchi has proposed a microscopy method which uses light sources called as frequency combs. It highlights that the study has solved a problem regarding the use of Raman spectroscopy in microscopy.

The article explores the experimentation regarding the construction of an optical switch operating with light pulses that contains a few photons. It notes a presentation of optical switching through a limitation to light and cold rubidium atoms in a hollow-core photonic band-gap fiber. It mentions that the demonstrators tackle an incoherent and coherent set-up consisting of an ultrahigh vacuum chamber wherein the atoms were collected and cooled using conventional laser-cooling methods.

Examines the limitations experienced by laser scientists when trying to drive quantum systems, such as atoms or molecules, into desired states. Ability of the linearly polarized laser pulses currently in use to drive the system along one axis only; Requirement of more complex light signals if full control should be implemented; Presentation of advances in ultrafast optics.

Reports the generation and use of attosecond laser pulses. Duration of the pulse; Basis on the research of high-order harmonics; Description of attosecond pulses.

There is a growing interest in perfusion or continuous processes to achieve higher productivity of biopharmaceuticals in mammalian cell culture, specifically Chinese hamster ovary (CHO) cells, towards advanced biomanufacturing. These intensified bioprocesses highly require concentrated feed media in order to counteract their dilution effects. However, designing such condensed media formulation poses several challenges, particularly regarding the stability and solubility of specific amino acids. To address the difficulty and complexity in relevant media development, the biopharmaceutical industry has recently suggested forming dipeptides by combining one from problematic amino acids with selected pairs to compensate for limitations. In this study, we combined one of the lead amino acids, L-tyrosine, which is known for its poor solubility in water due to its aromatic ring and hydroxyl group, with glycine as the partner, thus forming glycyl-L-tyrosine (GY) dipeptide. Subsequently, we investigated the utilization of GY dipeptide during fed-batch cultures of IgG-producing CHO cells, by changing its concentrations (0.125 × , 0.25 × , 0.5 × , 1.0 × , and 2.0 ×). Multivariate statistical analysis of culture profiles was then conducted to identify and correlate the most significant nutrients with the production, followed by in silico model-guided analysis to systematically evaluate their effects on the culture performance, and elucidate metabolic states and cellular behaviors. As such, it allowed us to explain how the cells can more efficiently utilize GY dipeptide with respect to the balance of cofactor regeneration and energy distribution for the required biomass and protein synthesis. For example, our analysis results uncovered specific amino acids (Asn and Gln) and the 0.5 × GY dipeptide in the feed medium synergistically alleviated the metabolic bottleneck, resulting in enhanced IgG titer and productivity. In the validation experiments, we tested and observed that lower levels of Asn and Gln led to decreased secretion of toxic metabolites, enhanced longevity, and elevated specific cell growth and titer. Key points: • Explored the optimal Tyr dipeptide for the enhanced CHO cell culture performance • Systematically analyzed effects of dipeptide media by model-guided approach • Uncovered synergistic metabolic utilization of amino acids with dipeptide [ABSTRACT FROM AUTHOR]

There is a growing interest in perfusion or continuous processes to achieve higher productivity of biopharmaceuticals in mammalian cell culture, specifically Chinese hamster ovary (CHO) cells, towards advanced biomanufacturing. These intensified bioprocesses highly require concentrated feed media in order to counteract their dilution effects. However, designing such condensed media formulation poses several challenges, particularly regarding the stability and solubility of specific amino acids. To address the difficulty and complexity in relevant media development, the biopharmaceutical industry has recently suggested forming dipeptides by combining one from problematic amino acids with selected pairs to compensate for limitations. In this study, we combined one of the lead amino acids, L-tyrosine, which is known for its poor solubility in water due to its aromatic ring and hydroxyl group, with glycine as the partner, thus forming glycyl-L-tyrosine (GY) dipeptide. Subsequently, we investigated the utilization of GY dipeptide during fed-batch cultures of IgG-producing CHO cells, by changing its concentrations (0.125 × , 0.25 × , 0.5 × , 1.0 × , and 2.0 ×). Multivariate statistical analysis of culture profiles was then conducted to identify and correlate the most significant nutrients with the production, followed by in silico model-guided analysis to systematically evaluate their effects on the culture performance, and elucidate metabolic states and cellular behaviors. As such, it allowed us to explain how the cells can more efficiently utilize GY dipeptide with respect to the balance of cofactor regeneration and energy distribution for the required biomass and protein synthesis. For example, our analysis results uncovered specific amino acids (Asn and Gln) and the 0.5 × GY dipeptide in the feed medium synergistically alleviated the metabolic bottleneck, resulting in enhanced IgG titer and productivity. In the validation experiments, we tested and observed that lower levels of Asn and Gln led to decreased secretion of toxic metabolites, enhanced longevity, and elevated specific cell growth and titer. Key points: • Explored the optimal Tyr dipeptide for the enhanced CHO cell culture performance • Systematically analyzed effects of dipeptide media by model-guided approach • Uncovered synergistic metabolic utilization of amino acids with dipeptide [ABSTRACT FROM AUTHOR]

Responds to a commentary on the article, titled `Nonlinear coupling of waveguide modes'. Vatarescu's claim that the nonlinear coupling between waveguide modes is not periodic; Analytical procedure that yields a solution for the variations of the mode power along the propagation direction.

The dynamics of filopodia interacting with the surrounding extracellular matrix (ECM) play a key role in various cell-ECM interactions, but their mechanisms of interaction with the ECM in 3D environment remain poorly understood. Based on first principles, here we construct an individual-based, force-based computational model integrating four modules of 1) filopodia penetration dynamics; 2) intracellular mechanics of cellular and nuclear membranes, contractile actin stress fibers, and focal adhesion dynamics; 3) structural mechanics of ECM fiber networks; and 4) reaction-diffusion mass transfers of seven biochemical concentrations in related with chemotaxis, proteolysis, haptotaxis, and degradation in ECM to predict dynamic behaviors of filopodia that penetrate into a 3D ECM fiber network. The tip of each filopodium crawls along ECM fibers, tugs the surrounding fibers, and contracts or retracts depending on the strength of the binding and the ECM stiffness and pore size. This filopodium-ECM interaction is modeled as a stochastic process based on binding kinetics between integrins along the filopodial shaft and the ligands on the surrounding ECM fibers. This filopodia stochastic model is integrated into migratory dynamics of a whole cell in order to predict the cell invasion into 3D ECM in response to chemotaxis, haptotaxis, and durotaxis cues. Predicted average filopodia speed and that of the cell membrane advance agreed with experiments of 3D HUVEC migration at r2 > 0.95 for diverse ECMs with different pore sizes and stiffness. [ABSTRACT FROM AUTHOR]

We measure ensemble-averaged quantum correlations of path-entangled photons, propagating in a disordered lattice and undergoing Anderson localization. These result in intriguing patterns, which show that quantum interference leads to unexpected dependencies of the location of one particle on the location of the other. These correlations are shared between localized and nonlocalized components of the twophoton wave function, and, moreover, yield information regarding the nature of the disorder itself. Such effects cannot be reproduced with classical waves, and are undetectable without ensemble averaging. [ABSTRACT FROM AUTHOR]

Proposed herein is a systematic media design framework that combines multivariate statistical approaches with in silico analysis of a genome-scale metabolic model of Chinese hamster ovary cell. The framework comprises sequential modules including cell culture and metabolite data collection, multivariate data analysis, in silico modeling and flux prediction, and knowledge-based identification of target media components. Two monoclonal antibody-producing cell lines under two different media conditions were used to demonstrate the applicability of the framework. First, the cell culture and metabolite profiles from all conditions were generated, and then statistically and mechanistically analyzed to explore combinatorial effects of cell line and media on intracellular metabolism. As a result, we found a metabolic bottleneck via a redox imbalance in the TCA cycle in the poorest growth condition, plausibly due to inefficient coenzyme q10-q10h2 recycling. Subsequent in silico simulation allowed us to suggest q10 supplementation to debottleneck the imbalance for the enhanced cellular energy state and TCA cycle activity. Finally, experimental validation was successfully conducted by adding q10 in the media, resulting in increased cell growth. Taken together, the proposed framework rationally identified target nutrients for cell line-specific media design and reformulation, which could greatly improve cell culture performance. • Developed a media design framework combining statistical and mechanistic approaches. • Identified target nutrients for cell line-specific media design and reformulation. • Mechanistically elucidated q10 metabolism for enhancing culture performance. • Provided virtual elements of bioreactor digital twin for deriving feeding strategy. [ABSTRACT FROM AUTHOR]

A new coherent anti-Stokes Raman spectroscopy (CARS) technique is reported for real-time detection and classification of several chemical constituents, utilizing a single detector and a single beam of shaped femtosecond pulses. The technique is based on rapidly switching between differently shaped pulses that either maximize or minimize the targeted vibrational lines excitation, thus creating temporally modulated ‘bright’ and ‘dark’ profiles in the total CARS signal that are measured by a single photomultiplier tube and demodulated by a multi-channel lock-in amplifier. Using a two-dimensional spatial light modulator displaying 24 different pulse shapes, we demonstrate pulse shaping at 80 kHz and chemically specific microscopy with pixel dwell times of less than 0.5 ms. [ABSTRACT FROM AUTHOR]

A quantum polarized light microscope using entangled NOON states with N = 2 and N = 3 is shown to provide phase supersensitivity beyond the standard quantum limit. We constructed such a microscope and imaged birefringent objects at a very low light level of 50 photons per pixel, where shot noise seriously hampers classical imaging. The NOON light source is formed by combining a coherent state with parametric down-converted light. We were able to show improved phase images with sensitivity close to the Heisenberg limit. [ABSTRACT FROM AUTHOR]

Imaging with optical resolution through turbid media is a long sought-after goal with important applications in deep tissue imaging. Although extensively studied, this goal was considered impractical until recently. Adaptive-optics techniques, which can correct weak aberrations, are inadequate for turbid samples, where light is scattered to complex speckle patterns with a number of modes greatly exceeding the number of degrees of control. This conception changed after the demonstration of coherent focusing through turbid media by wavefront-shaping, using spatial light modulators. Here, we show that wavefront-shaping enables wide-field imaging through turbid layers with incoherent illumination, and imaging of occluded objects using light scattered from diffuse walls. In contrast to the recently introduced schemes for imaging through turbid media, our technique does not require coherent sources, interferometric detection, raster-scanning or off-line reconstruction. Our results bring wavefront-shaping closer to practical applications and realize the vision of looking through 'walls' and around corners. [ABSTRACT FROM AUTHOR]

We experimentally show that two-photon path-entangled states can be coherently manipulated by multimode interference in multimode waveguides. By measuring the output two-photon spatial correlation function versus the phase of the input state, we show that multimode waveguides perform as nearly ideal multiport beam splitters at the quantum level, creating a large variety of entangled and separable multipath two-photon states. [ABSTRACT FROM AUTHOR]

Abstract: The tectorial membrane (TM) is a highly hydrated non-cellular matrix situated over the sensory cells of the cochlea. It is widely accepted that the mechanical coupling, between the TM and outer hair cells stereocilia bundles, plays an important role in the cochlea energy transduction mechanism. Recently, we provided supporting evidence for the existence of mechanical coupling by demonstrating that the mechanical properties of the TM change along its longitudinal direction. Since the biochemical composition of the TM is similar throughout its entire length, it is likely that structural differences induce the observed material properties changes. Presently, however, the structure of the TM under physiological environments remains unknown. In this work, the 3D structure of native TM samples is shown by using two-photon second-harmonic imaging microscopy. We find that the collagen fibers at the basal region are arranged in a parallel orientation while being tilted in an angle with respect to the plane of the TM surface at the apical region. Moreover, we find an intensified marginal band at the basal OHC zone which forms a shell-like structure which engulfs the stereocilium imprints surface of the TM. In supports of our previous mechanical characterization, the analysis presented here provides a structural basis for the changes in TM’s mechanical properties. [Copyright &y& Elsevier]

Abstract: The transition probability of a two-photon absorption (TPA) process in atomic Cesium, excited by phase-controlled temporally focused ultrashort pulses is shown to be spatially modulated in a controlled manner. In particular, we demonstrate the generation of a dark nonlinear focus. By controlling the excitation pulse shape along the propagation coordinate we create a region in space where the TPA rate vanishes which is flanked by bright regions. [Copyright &y& Elsevier]

Using a pulsed UV laser in a confocal scanning microscope, we present a relatively cheap, accurate and efficient method for fast UV laser flash photolysis of caged molecules in two-dimensional cultured neurons. The laser light is introduced through the imaging optics, can be localized by a parallel red laser and can photolyse a sphere of less than 1 μm2, and evoke local fluorescence changes in the imaged neurons. Caged glutamate and caged fluorescein are used to illustrate a disparity between spines and their parent dendrites at a sub-micron resolution. [Copyright &y& Elsevier]

Light propagating in linear and nonlinear waveguide lattices exhibits behaviour characteristic of that encountered in discrete systems. The diffraction properties of these systems can be engineered, which opens up new possibilities for controlling the flow of light that would have been otherwise impossible in the bulk: these effects can be exploited to achieve diffraction-free propagation and minimize the power requirements for nonlinear processes. In two-dimensional networks of waveguides, self-localized states-or discrete solitons-can travel along 'wire-like' paths and can be routed to any destination port. Such possibilities may be useful for photonic switching architectures. [ABSTRACT FROM AUTHOR]

Precision measurements can be brought to their ultimate limit by harnessing the principles of quantum mechanics. In optics, multiphoton entangled states, known as NOON states, can be use to obtain high-precision phase measurements, becoming more and more advantageous as the number of photons grows. We generated "high-NOON" states (N = 5) by multiphoton interference of quantum down-converted light with a classical coherent state in an approach that is inherently scalable. Super-resolving phase measurements with up to five entangled photons were produced with a visibility higher than that obtainable using classical light only. [ABSTRACT FROM AUTHOR]

We describe an advanced image reconstruction algorithm for pseudothermal ghost imaging, reducing the number of measurements required for image recovery by an order of magnitude. The algorithm is based on compressed sensing, a technique that enables the reconstruction of an N-pixel image from much less than N measurements. We demonstrate the algorithm using experimental data from a pseudothermal ghost-imaging setup. The algorithm can be applied to data taken from past pseudothermal ghost-imaging experiments, improving the reconstruction’s quality. [ABSTRACT FROM AUTHOR]

Provides information on a study which discussed single-pulse vibrational spectroscopy on several molecules in the liquid phase where both the excitation and the readout processes are performed by the same pulse in nonlinear coherent vibrational spectroscopy. Difficulty with single-pulse spectroscopy; Importance of the availability of ultrashort optical pulses; Ways to achieve high spectral resolution.

Filopodia have a key role in sensing both chemical and mechanical cues in surrounding extracellular matrix (ECM). However, quantitative understanding is still missing in the filopodial mechanosensing of local ECM stiffness, resulting from dynamic interactions between filopodia and the surrounding 3D ECM fibers. Here we present a method for characterizing the stiffness of ECM that is sensed by filopodia based on the theory of elasticity and discrete ECM fiber. We have applied this method to a filopodial mechanosensing model for predicting directed cell migration toward stiffer ECM. This model provides us with a distribution of force and displacement as well as their time rate of changes near the tip of a filopodium when it is bound to the surrounding ECM fibers. Aggregating these effects in each local region of 3D ECM, we express the local ECM stiffness sensed by the cell and explain polarity in the cellular durotaxis mechanism. [ABSTRACT FROM AUTHOR]

Focusing on intracellular targets, we propose a new cell separation technique based on a nanoneedle array (NNA) device, which allows simultaneous insertion of multiple needles into multiple cells. The device is designed to target and lift ("fish") individual cells from a mixed population of cells on a substrate using an antibody-functionalized NNA. The mechanics underlying this approach were validated by force analysis using an atomic force microscope. Accurate high-throughput separation was achieved using one-to-one contacts between the nanoneedles and the cells by preparing a single-cell array in which the positions of the cells were aligned with 10,000 nanoneedles in the NNA. Cell-type-specific separation was realized by controlling the adhesion force so that the cells could be detached in cell-type-independent manner. Separation of nestin-expressing neural stem cells (NSCs) derived from human induced pluripotent stem cells (hiPSCs) was demonstrated using the proposed technology, and successful differentiation to neuronal cells was confirmed. [ABSTRACT FROM AUTHOR]

Efficient and rapid delivery of macromolecule probes, such as quenchbodies and other large biomarkers that cannot readily pass through the plasma membrane, is necessary for live-cell imaging and other intracellular analyses. We present here an alternative, simple method for delivery of macromolecules into live cells. In this method, which we term here mechanoporation, a nanoneedle array is used for making transient pores in the plasma membrane to allow access of desired macromolecules into thousands of live cells, simultaneously. This rapid, 3-step method facilitates an efficient delivery by adding macromolecules into the medium, inserting nanoneedles into the cells and oscillating the nanoneedle array, a process that takes no more than 5 min in total. In addition, we demonstrate here how this method can repeatedly and reproducibly deliver molecules into specifically-selected locations on a given cell culture dish. The results presented here show how this unique mechanoporation method enables rapid and high-throughput bio-macromolecule delivery and live-cell imaging. [ABSTRACT FROM AUTHOR]

We experimentally demonstrate a method for creating broad bandwidth photon pairs in the visible spectral region, centered at a frequency that is higher than that of the initial pump source. Spontaneous down conversion of a narrowband 1053 nm pulsed Nd:YLF laser is followed by highly efficient upconversion in adiabatic nonlinear frequency-conversion process. Photon pairs are generated from 693 to 708 nm, and the complete conversion process occurs within a single monolithic 5-cm-long stoichiometric lithium tantalate nonlinear crystal. We have characterized the dependence of this structure with respect to pump intensity and crystal temperature. [ABSTRACT FROM AUTHOR]

We introduce a simple and flexible method to generate spatially non-Markovian light with tunable coherence properties in one and two dimensions. The unusual behavior of this light is demonstrated experimentally by probing the far field and by recording its diffraction pattern after a double slit: In both cases we observe, instead of a central intensity maximum, a line- or cross-shaped dark region, whose width and profile depend on the non-Markovian coherence properties. Because these properties can be controlled and easily reproduced in experiment, the presented approach lends itself to serving as a test bed to study and gain a deeper understanding of non-Markovian processes. [ABSTRACT FROM AUTHOR]

Vibrational modes are often localized in certain regions of a molecule, and so the coupling between these modes is sensitive to the molecular structure. Two-dimensional vibrational spectroscopy can probe the strength of this coupling in a manner analogous to two-dimensional NMR spectroscopy, but on ultrafast timescales. Here, we demonstrate how two-dimensional Raman spectroscopy, based on fifth-order optical nonlinearity, can be performed with a single beam of shaped femtosecond optical pulses. Our spectroscopy scheme offers not only a major simplification of the conventional set-up, but also an inherent elimination of a competing nonlinear signal, which overwhelms the desired signal in other schemes and carries no coupling information. [ABSTRACT FROM AUTHOR]

Quasiperiodic lattices have recently been shown to be a nontrivial topological phase of matter. Charge pumping-one of the hallmarks of topological states of matter-was recently realized for photons in a one-dimensional off-diagonal Harper model implemented in a photonic waveguide array. However, if the relationship between topological pumps and quasiperiodic systems is generic, one might wonder how to observe it in the canonical and most studied quasicrystalline system in one dimension-the Fibonacci chain. This chain is expected to facilitate a similar phenomenon, yet its discrete nature hinders the experimental study of such topological effects. Here, we overcome this obstacle by utilizing the topological equivalence of a family of quasiperiodic models which ranges from the Fibonacci chain to the Harper model. Implemented in photonic waveguide arrays, we observe the topological properties of this family, and perform a topological pumping of photons across a Fibonacci chain. [ABSTRACT FROM AUTHOR]

Controlling light through dynamically varying heterogeneous media is a sought-after goal with important applications ranging from free-space communication to nanosurgery. The underlying challenge is to control a large number of degrees of freedom of the optical wavefront, at timescales shorter than the medium dynamics. Many advances have been reported recently following the demonstration of focusing through turbid samples by wavefront shaping, where spatial light modulators with more than 1,000 degrees of freedom were used. Unfortunately, spatial light modulator-based wavefront shaping requires feedback from a detector or camera and is currently limited to slowly varying samples. Here, we demonstrate a novel approach for wavefront shaping utilizing all-optical feedback. We show that the complex wavefront required to focus light scattered by turbid samples (including thin biological tissues) can be generated at submicrosecond timescales by the process of field self-organization inside a multimode laser cavity, without requiring electronic feedback, spatial light modulators or phase-conjugation crystals. [ABSTRACT FROM AUTHOR]

An atomic force microscope probe can be formed into an ultra-sharp cylindrical shape (a nanoneedle) using micro-fabrication techniques such as focused ion beam etching. This nanoneedle can be effectively inserted through the plasma membrane of a living cell to not only access the cytosol, but also to penetrate through the nuclear membrane. This technique shows great potential as a tool for performing intranuclear measurements and manipulations. Repeated insertions of a nanoneedle into a live cell were previously shown not to affect cell viability. However, the effect of nanoneedle insertion on the nucleus and nuclear components is still unknown. DNA is the most crucial component of the nucleus for proper cell function and may be physically damaged by a nanoneedle. To investigate the integrity of DNA following nanoneedle insertion, the occurrence of DNA double-strand breaks (DSBs) was assessed. The results showed that there was no chromosomal DNA damage due to nanoneedle insertion into the nucleus, as indicated by the expression level of γ-H2AX, a molecular marker of DSBs. [ABSTRACT FROM AUTHOR]

We report here amethod for controlling cell adhesion, allowingsimple yet accurate cell detachment from the substrate, which is requiredfor the establishment of new cytometry-based cell processing and analyzingmethods. A biocompatible anchor for membrane (BAM) was conjugatedwith bovine serum albumin (BSA) to produce a cell-anchoring agent(BAM–BSA). By coating polystyrene substrates with a mixtureof BAM–BSA and BSA, controlled suppression of the substrate’sadhesive properties was achieved. Hook-shaped nanoneedles were usedto pick up cells from the substrate, while recording the cell–substrateadhesion force, using an atomic force microscope (AFM). Due to thelipid bilayer targeting property of BAM, the coated surface showedconstant adhesion forces for various cell lines, and controlling theBAM–BSA/BSA ratio enabled tuning of the adhesion force, rangingfrom several tens of nano-Newtons down to several nano-Newtons. Optimizedtuning of the adhesion force also enabled the detachment of cellsfrom BAM–BSA/BSA-coated dishes, using a shear flow. Moreover,the method was shown to be noncell type specific and similar resultswere observed using four different cell types, including nonadherentcells. The attenuation of cell adhesion was also used to enable thecollection of single cells by capillary aspiration. Thus, this versatileand relatively simple method can be used to control the adhesion ofvarious cell types to substrates. [ABSTRACT FROM AUTHOR]

Topological insulators and topological superconductors are distinguished by their bulk phase transitions and gapless states at a sharp boundary with the vacuum. Quasicrystals have recently been found to be topologically nontrivial. In quasicrystals, the bulk phase transitions occur in the same manner as standard topological materials, but their boundary phenomena are more subtle. In this Letter we directly observe bulk phase transitions, using photonic quasicrystals, by constructing a smooth boundary between topologically distinct one-dimensional quasicrystals. Moreover, we use the same method to experimentally confirm the topological equivalence between the Harper and Fibonacci quasicrystals. [ABSTRACT FROM AUTHOR]

Quantum lithography achieves phase superresolution using fragile, experimentally challenging entangled states of light. We propose a scalable scheme for creating features narrower than classically achievable with reduced use of quantum resources and, consequently, enhanced resistance to loss. The scheme is an implementation of interferometric lithography using a mixture of a spontaneous parametric down-converted entangled state with intense classical coherent light. We measure coincidences of up to four photons mimicking multiphoton absorption. The results show a narrowing of the interference fringes of up to 30% with respect to the best analogous classical scheme using only 10% of the nonclassical light required for creating NOON states. [ABSTRACT FROM AUTHOR]

Light scattering in inhomogeneous media induces wavefront distortions that pose an inherent limitation in many optical applications. Examples where this occurs include microscopy, nanosurgery and astronomy. In recent years, ongoing efforts have made the correction of spatial distortions possible using wavefront-shaping techniques. However, when ultrashort pulses are used, scattering also induces temporal distortions, which hinder the use of such pulses in nonlinear processes such as multiphoton microscopy and quantum control experiments. Here, we show that correction of both spatial and temporal distortions can be achieved by manipulating only the spatial degrees of freedom of the incident wavefront. By optimizing a nonlinear signal, we demonstrate spatiotemporal focusing and compression of chirped ultrashort pulses through scattering media, and refocusing in both space and time of 100 fs pulses through thick brain and bone samples. Our results open up new possibilities for optical manipulation and nonlinear imaging in scattering media. [ABSTRACT FROM AUTHOR]

Quantum walks of correlated particles offer the possibility of studying large-scale quantum interference; simulating biological, chemical, and physical systems; and providing a route to universal quantum computation. We have demonstrated quantum walks of two identical photons in an array of 21 continuously evanescently coupled waveguides in a SiOxNy chip. We observed quantum correlations, violating a classical limit by 76 standard deviations, and found that the correlations depended critically on the input state of the quantum walk. These results present a powerful approach to achieving quantum walks with correlated particles to encode information in an exponentially larger state space. [ABSTRACT FROM AUTHOR]

Patterning of semiconducting polymers on surfaces is important for various applications in nanoelectronics and nanophotonics. However, many of the approaches to nanolithography that are used to pattern inorganic materials are too harsh for organic semiconductors, so research has focused on optical patterning and various soft lithographies. Surprisingly little attention has been paid to thermal, thermomechanical and thermochemical patterning. Here, we demonstrate thermochemical nanopatterning of poly(p-phenylene vinylene), a widely used electroluminescent polymer, by a scanning probe. We produce patterned structures with dimensions below 28 nm, although the tip of the probe has a diameter of 5 µm, and achieve write speeds of 100 µm s−1. Experiments show that a resolution of 28 nm is possible when the tip–sample contact region has dimensions of ∼100 nm and, on the basis of finite-element modelling, we predict that the resolution could be improved by using a thinner resist layer and an optimized probe. Thermochemical lithography offers a versatile, reliable and general nanopatterning technique because a large number of optical materials, including many commercial crosslinker additives and photoresists, rely on chemical mechanisms that can also be thermally activated. [ABSTRACT FROM AUTHOR]

Abstract: We provide an overview of recent experimental and theoretical developments in the area of optical discrete solitons. By nature, discrete solitons represent self-trapped wavepackets in nonlinear periodic structures and result from the interplay between lattice diffraction (or dispersion) and material nonlinearity. In optics, this class of self-localized states has been successfully observed in both one- and two-dimensional nonlinear waveguide arrays. In recent years such photonic lattices have been implemented or induced in a variety of material systems, including those with cubic (Kerr), quadratic, photorefractive, and liquid-crystal nonlinearities. In all cases the underlying periodicity or discreteness leads to altogether new families of optical solitons that have no counterpart whatsoever in continuous systems. We first review the linear properties of photonic lattices that are key in the understanding of discrete solitons. The physics and dynamics of the fundamental discrete and gap solitons are then analyzed along with those of many other exotic classes — e.g. twisted, vector and multi-band, cavity, spatio-temporal, random-phase, vortex, and non-local lattice solitons, just to mention a few. The possibility of all-optically routing optical discrete solitons in 2D and 3D periodic environments using soliton collisions is also presented. Finally, soliton formation in optical quasi-crystals and at the boundaries of waveguide array structures are discussed. [Copyright &y& Elsevier]

Third harmonic generation microscopy is shown to be a robust method for obtaining structural information on a variety of biological specimens. Its nature allows depth-resolved imaging of inhomogeneities with virtually no background from surrounding homogeneous media. With an appropriate illumination geometry, third harmonic generation microscopy is shown to be particularly suitable for imaging of biogenic crystals, enabling extraction of the crystal orientation. [Copyright &y& Elsevier]