Explore the vast range of titles available.

An ultrarapid camera Ultrafast real-time optical imaging is used in many areas of science, from biological imaging to the study of shockwaves. But in systems that undergo changes on very fast timescales, conventional technologies such as CCD (charge-coupled-device) cameras are compromised. Either imaging speed or sensitivity has to be sacrificed unless special cooling or extra-bright light is used. This is because it takes time to read out the data from sensor arrays, and at high frame rates only a few photons are collected. Now a UCLA team has developed an imaging method that overcomes these limitations and offers frame rates at least a thousand times faster than those of conventional CCDs, making this perhaps the world's fastest continuously running camera, with a shutter speed of 440 picoseconds. The technology — serial time-encoded amplified microscopy or STEAM — maps a two-dimensional image into a serial time-domain data stream and simultaneously amplifies the image in the optical domain. A single-pixel photodetector then captures the entire image. Ultrafast real-time optical imaging is used in diverse areas of science, but conventional imaging devices such as CCDs are incapable of capturing fast dynamical processes with high sensitivity and resolution. This imaging method overcomes these limitations and offers frame rates that are at least 1,000 times faster than those of conventional CCDs. The approach is applied to continuous real-time imaging of microfluidic flow and phase-explosion effects that occur during laser ablation. Ultrafast real-time optical imaging is an indispensable tool for studying dynamical events such as shock waves 1 , 2 , chemical dynamics in living cells 3 , 4 , neural activity 5 , 6 , laser surgery 7 , 8 , 9 and microfluidics 10 , 11 . However, conventional CCDs (charge-coupled devices) and their complementary metal–oxide–semiconductor (CMOS) counterparts are incapable of capturing fast dynamical processes with high sensitivity and resolution. This is due in part to a technological limitation—it takes time to read out the data from sensor arrays. Also, there is the fundamental compromise between sensitivity and frame rate; at high frame rates, fewer photons are collected during each frame—a problem that affects nearly all optical imaging systems. Here we report an imaging method that overcomes these limitations and offers frame rates that are at least 1,000 times faster than those of conventional CCDs. Our technique maps a two-dimensional (2D) image into a serial time-domain data stream and simultaneously amplifies the image in the optical domain. We capture an entire 2D image using a single-pixel photodetector and achieve a net image amplification of 25 dB (a factor of 316). This overcomes the compromise between sensitivity and frame rate without resorting to cooling and high-intensity illumination. As a proof of concept, we perform continuous real-time imaging at a frame speed of 163 ns (a frame rate of 6.1 MHz) and a shutter speed of 440 ps. We also demonstrate real-time imaging of microfluidic flow and phase-explosion effects that occur during laser ablation.

In the present study, a CMOS high speed camera system was employed for two-dimensional thermographic phosphor thermometry. By the pixelwise evaluation of the luminescence lifetimes, a temperature map of a phosphor layer can be obtained. Using spatially and temporally isothermal conditions in a tube furnace, a temperature lifetime characteristic was determined for the phosphor Mg 4 FGeO 6 : Mn and was compared with data obtained by point measurements using a photomultiplier tube. Both, the pixel-to-pixel and the shot-to-shot standard deviation were evaluated at different temperatures. Non-linearities and pixel-to-pixel inhomogeneities of the CMOS chip were characterised and corrected employing a homogeneous light source.

Advances in high-speed laser and camera technology have made scientific kHz repetition rate combustion and flow laser diagnostics feasible. While quantitative flow-field results have been shown to be possible via PIV, measuring scalars relevant to combustion such as mixture fraction, temperature and species concentrations is still a significant challenge. Tracer-LIF has proven to be a useful tool for imaging of mixture fraction. This paper highlights recent success at extending this technique for use at 9.5 kHz acquisition rate. The measurements are taken near the exit of an isothermal round jet seeded with acetone. Results taken at both maximum possible signal and a practical configuration for reacting flows are contrasted. Data are fully quantified and corrected for not only absorption, optical uniformity and laser pulse variation, but also for individual CMOS pixel offset and sensitivity.

The diverse physiology of the brain is reflected in its complex organization at regional, cellular, and subcellular levels. Sjöstedt et al. combined data—both newly acquired and from other large-scale brain mapping projects—from transcriptomics, single-cell genomics, in situ hybridization, and antibody-based protein profiling to map the molecular profiles in human, pig, and mouse brain. The analysis is consistent with a conserved basic brain architecture during mammalian evolution, but it does show differences in regional gene expression profiles. Science , this issue p. eaay5947 The Brain Atlas compares the expression of protein-coding genes in the mammalian brain. The brain, with its diverse physiology and intricate cellular organization, is the most complex organ of the mammalian body. To expand our basic understanding of the neurobiology of the brain and its diseases, we performed a comprehensive molecular dissection of 10 major brain regions and multiple subregions using a variety of transcriptomics methods and antibody-based mapping. This analysis was carried out in the human, pig, and mouse brain to allow the identification of regional expression profiles, as well as to study similarities and differences in expression levels between the three species. The resulting data have been made available in an open-access Brain Atlas resource, part of the Human Protein Atlas, to allow exploration and comparison of the expression of individual protein-coding genes in various parts of the mammalian brain.

The linear Doppler shift is widely used to infer the velocity of approaching objects, but this shift does not detect rotation. By analyzing the orbital angular momentum of the light scattered from a spinning object, we observed a frequency shift proportional to product of the rotation frequency of the object and the orbital angular momentum of the light. This rotational frequency shift was still present when the angular momentum vector was parallel to the observation direction. The multiplicative enhancement of the frequency shift may have applications for the remote detection of rotating bodies in both terrestrial and astronomical settings.

Knowing when a physical system has reached sufficient size for its macroscopic properties to be well described by many-body theory is difficult. We investigated the crossover from few-to many-body physics by studying quasi-one-dimensional systems of ultracold atoms consisting of a single impurity interacting with an increasing number of identical fermions. We measured the interaction energy of such a system as a function of the number of majority atoms for different strengths of the interparticle interaction. As we increased the number of majority atoms one by one, we observed fast convergence of the normalized interaction energy toward a many-body limit calculated for a single impurity immersed in a Fermi sea of majority particles.

Temporally resolved measurements of transient phenomena in turbulent flames, such as extinction, ignition or flashback, require cinematographic sampling of two-dimensional scalar fields. Hereby, repetition rates must exceed typical flame-inherent frequencies. The high sensitivity planar laser-induced fluorescence (PLIF) has already proved to be a practical method for scalar imaging. The present study demonstrates the feasibility of generating tuneable narrowband radiation in the ultraviolet (UV) spectral range at repetition rates up to 5 kHz. Pulse energies were sufficiently high to electronically excite hydroxyl radicals (OH) produced in a partially-premixed turbulent opposed jet (TOJ) flame. Red-shifted fluorescence was detected two-dimensionally by means of an image-intensified CMOS camera. Sequences comprising up to 4000 frames per run were recorded. Besides statistically stationary conditions, extinction of a turbulent flame due to small Damköhler numbers is presented showing the potential of the technique.

In this paper we present the first comprehensive study of the role of spectral phase on cross-polarized wave (XPW) generation using sub-30 femtosecond (fs) laser pulses. XPW generation improves the temporal contrast and shortens the pulse duration of fs chirped pulse amplification (CPA) lasers. For Ti:Sa lasers, compression below 30 fs is non-trivial and therefore never perfect. We therefore systematically analyze the effect of an arbitrary input spectral phase on the output spectrum and efficiency of the XPW process, both theoretically and experimentally. We derive the maximum acceptable value of residual phase for a given initial pulse duration in order to efficiently drive the XPW process for pulse shortening and contrast improvement.

This paper proposes a combined method for two-dimensional temperature and velocity measurements using temperature sensitive particles (TSParticles), a pulsed ultraviolet (UV) laser and a single high-speed camera. TSParticles were synthesized using ion-exchange particles and Eu(TTA) luminescent dye. The size and material of the particles for synthesizing TSParticles are selectable. TSParticles respond to temperature changes in a flow and can also serve as tracers for the velocity field. TSParticles were seeded into a heated water flow in a complex-shaped channel constructed of MEXFLON resin, which has a refractive index exactly equal to that of water. Particle images of flow beyond the structure can be recorded without any distortion. The TSParticles were excited by the UV pulsed laser and the luminescence from the TSParticles were recorded at 40,000 frames per second as sequential images for a lifetime-based temperature analysis. Another advantage of our approach is that high time-resolved PIV can be carried out without a high-frequency laser. The recorded images were also used for the particle image velocimetry (PIV) calculation.

There are few phenomena in condensed matter physics that are defined only by the fundamental constants and do not depend on material parameters. Examples are the resistivity quantum, h/e2 (h is Planck's constant and e the electron charge), that appears in a variety of transport experiments and the magnetic flux quantum, h/e, playing an important role in the physics of superconductivity. By and large, sophisticated facilities and special measurement conditions are required to observe any of these phenomena. We show that the opacity of suspended graphene is defined solely by the fine structure constant, a = e2/hc 1/137 (where c is the speed of light), the parameter that describes coupling between light and relativistic electrons and that is traditionally associated with quantum electrodynamics rather than materials science. Despite being only one atom thick, graphene is found to absorb a significant (pa = 2.3%) fraction of incident white light, a consequence of graphene's unique electronic structure.