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A new technique to analyze the energy flow in liquid-phase dynamics is described. Some of the energy in the transition is transferred from the reaction coordinate to other internal degrees of the solute. The rate at which the remaining energy is transferred to the solvent is a function of the reaction of coordinate phase space point and its time derivative as well as other velocities characterizing a trajectory of the system.

Water is one of the most important, yet least understood, liquids in nature. Many anomalous properties of liquid water originate from its well-connected hydrogen bond network.sup.1, including unusually efficient vibrational energy redistribution and relaxation.sup.2. An accurate description of the ultrafast vibrational motion of water molecules is essential for understanding the nature of hydrogen bonds and many solution-phase chemical reactions. Most existing knowledge of vibrational relaxation in water is built upon ultrafast spectroscopy experiments.sup.2-7. However, these experiments cannot directly resolve the motion of the atomic positions and require difficult translation of spectral dynamics into hydrogen bond dynamics. Here, we measure the ultrafast structural response to the excitation of the OH stretching vibration in liquid water with femtosecond temporal and atomic spatial resolution using liquid ultrafast electron scattering. We observed a transient hydrogen bond contraction of roughly 0.04 Å on a timescale of 80 femtoseconds, followed by a thermalization on a timescale of approximately 1 picosecond. Molecular dynamics simulations reveal the need to treat the distribution of the shared proton in the hydrogen bond quantum mechanically to capture the structural dynamics on femtosecond timescales. Our experiment and simulations unveil the intermolecular character of the water vibration preceding the relaxation of the OH stretch. Liquid ultrafast electron scattering measures structural responses in liquid water with femtosecond temporal and atomic spatial resolution to reveal a transient hydrogen bond contraction then thermalization preceding relaxation of the OH stretch., Author(s): Jie Yang [sup.1] [sup.2] [sup.11] , Riccardo Dettori [sup.3] , J. Pedro F. Nunes [sup.4] , Nanna H. List [sup.1] [sup.2] [sup.5] , Elisa Biasin [sup.1] [sup.2] , Martin [...]

Chemical vapour deposition of carbon-containing precursors on metal substrates is currently the most promising route for the scalable synthesis of large-area, high-quality graphene films.sup.1. However, there are usually some imperfections present in the resulting films: grain boundaries, regions with additional layers (adlayers), and wrinkles or folds, all of which can degrade the performance of graphene in various applications.sup.2-7. There have been numerous studies on ways to eliminate grain boundaries.sup.8,9 and adlayers.sup.10-12, but graphene folds have been less investigated. Here we explore the wrinkling/folding process for graphene films grown from an ethylene precursor on single-crystal Cu-Ni(111) foils. We identify a critical growth temperature (1,030 kelvin) above which folds will naturally form during the subsequent cooling process. Specifically, the compressive stress that builds up owing to thermal contraction during cooling is released by the abrupt onset of step bunching in the foil at about 1,030 kelvin, triggering the formation of graphene folds perpendicular to the step edge direction. By restricting the initial growth temperature to between 1,000 kelvin and 1,030 kelvin, we can produce large areas of single-crystal monolayer graphene films that are high-quality and fold-free. The resulting films show highly uniform transport properties: field-effect transistors prepared from these films exhibit average room-temperature carrier mobilities of around (7.0 [plus or minus] 1.0) × 10.sup.3 centimetres squared per volt per second for both holes and electrons. The process is also scalable, permitting simultaneous growth of graphene of the same quality on multiple foils stacked in parallel. After electrochemical transfer of the graphene films from the foils, the foils themselves can be reused essentially indefinitely for further graphene growth. Restricting the initial growth temperatures used for chemical vapour deposition of graphene on metal foils produces optimum conditions for growing large areas of fold-free, single-crystal graphene., Author(s): Meihui Wang [sup.1] [sup.2] , Ming Huang [sup.1] [sup.5] , Da Luo [sup.1] , Yunqing Li [sup.1] [sup.3] , Myeonggi Choe [sup.1] [sup.3] , Won Kyung Seong [sup.1] , [...]

Out of equilibrium, a lack of reciprocity is the rule rather than the exception. Non-reciprocity occurs, for instance, in active matter.sup.1-6, non-equilibrium systems.sup.7-9, networks of neurons.sup.10,11, social groups with conformist and contrarian members.sup.12, directional interface growth phenomena.sup.13-15 and metamaterials.sup.16-20. Although wave propagation in non-reciprocal media has recently been closely studied.sup.1,16-20, less is known about the consequences of non-reciprocity on the collective behaviour of many-body systems. Here we show that non-reciprocity leads to time-dependent phases in which spontaneously broken continuous symmetries are dynamically restored. We illustrate this mechanism with simple robotic demonstrations. The resulting phase transitions are controlled by spectral singularities called exceptional points.sup.21. We describe the emergence of these phases using insights from bifurcation theory.sup.22,23 and non-Hermitian quantum mechanics.sup.24,25. Our approach captures non-reciprocal generalizations of three archetypal classes of self-organization out of equilibrium: synchronization, flocking and pattern formation. Collective phenomena in these systems range from active time-(quasi)crystals to exceptional-point-enforced pattern formation and hysteresis. Our work lays the foundation for a general theory of critical phenomena in systems whose dynamics is not governed by an optimization principle. A theoretical study of non-reciprocity in collective phenomena reveals the emergence of time-dependent phases heralded by exceptional points in contexts ranging from synchronization and flocking to pattern formation., Author(s): Michel Fruchart [sup.1] , Ryo Hanai [sup.1] [sup.2] [sup.3] , Peter B. Littlewood [sup.1] , Vincenzo Vitelli [sup.1] [sup.4] Author Affiliations: (1) James Franck Institute and Department of Physics, [...]

Coherent control of quantum dynamics is key to a multitude of fundamental studies and applications.sup.1. In the visible or longer-wavelength domains, near-resonant light fields have become the primary tool with which to control electron dynamics.sup.2. Recently, coherent control in the extreme-ultraviolet range was demonstrated.sup.3, with a few-attosecond temporal resolution of the phase control. At hard-X-ray energies (above 5-10 kiloelectronvolts), Mössbauer nuclei feature narrow nuclear resonances due to their recoilless absorption and emission of light, and spectroscopy of these resonances is widely used to study the magnetic, structural and dynamical properties of matter.sup.4,5. It has been shown that the power and scope of Mössbauer spectroscopy can be greatly improved using various control techniques.sup.6-16. However, coherent control of atomic nuclei using suitably shaped near-resonant X-ray fields remains an open challenge. Here we demonstrate such control, and use the tunable phase between two X-ray pulses to switch the nuclear exciton dynamics between coherent enhanced excitation and coherent enhanced emission. We present a method of shaping single pulses delivered by state-of-the-art X-ray facilities into tunable double pulses, and demonstrate a temporal stability of the phase control on the few-zeptosecond timescale. Our results unlock coherent optical control for nuclei, and pave the way for nuclear Ramsey spectroscopy.sup.17 and spin-echo-like techniques, which should not only advance nuclear quantum optics.sup.18, but also help to realize X-ray clocks and frequency standards.sup.19. In the long term, we envision time-resolved studies of nuclear out-of-equilibrium dynamics, which is a long-standing challenge in Mössbauer science.sup.20. Suitably shaped X-ray pulses are used to coherently steer the quantum dynamics of atoms' nuclei rather than their electrons, with few-zeptosecond temporal stability of the phase control., Author(s): Kilian P. Heeg [sup.1] , Andreas Kaldun [sup.1] , Cornelius Strohm [sup.2] , Christian Ott [sup.1] , Rajagopalan Subramanian [sup.1] , Dominik Lentrodt [sup.1] , Johann Haber [sup.2] , [...]

Current hardware approaches to biomimetic or neuromorphic artificial intelligence rely on elaborate transistor circuits to simulate biological functions. However, these can instead be more faithfully emulated by higher-order circuit elements that naturally express neuromorphic nonlinear dynamics.sup.1-4. Generating neuromorphic action potentials in a circuit element theoretically requires a minimum of third-order complexity (for example, three dynamical electrophysical processes).sup.5, but there have been few examples of second-order neuromorphic elements, and no previous demonstration of any isolated third-order element.sup.6-8. Using both experiments and modelling, here we show how multiple electrophysical processes--including Mott transition dynamics--form a nanoscale third-order circuit element. We demonstrate simple transistorless networks of third-order elements that perform Boolean operations and find analogue solutions to a computationally hard graph-partitioning problem. This work paves a way towards very compact and densely functional neuromorphic computing primitives, and energy-efficient validation of neuroscientific models. Electrophysical processes are used to create third-order nanoscale circuit elements, and these are used to realize a transistorless network that can perform Boolean operations and find solutions to a computationally hard graph-partitioning problem., Author(s): Suhas Kumar [sup.1] , R. Stanley Williams [sup.2] , Ziwen Wang [sup.3] Author Affiliations: (1) Hewlett Packard Labs, Palo Alto, USA (2) Texas A&M University, College Station, USA (3) [...]

The rate of cell growth is crucial for bacterial fitness and drives the allocation of bacterial resources, affecting, for example, the expression levels of proteins dedicated to metabolism and biosynthesis.sup.1,2. It is unclear, however, what ultimately determines growth rates in different environmental conditions. Moreover, increasing evidence suggests that other objectives are also important.sup.3-7, such as the rate of physiological adaptation to changing environments.sup.8,9. A common challenge for cells is that these objectives cannot be independently optimized, and maximizing one often reduces another. Many such trade-offs have indeed been hypothesized on the basis of qualitative correlative studies.sup.8-11. Here we report a trade-off between steady-state growth rate and physiological adaptability in Escherichia coli, observed when a growing culture is abruptly shifted from a preferred carbon source such as glucose to fermentation products such as acetate. These metabolic transitions, common for enteric bacteria, are often accompanied by multi-hour lags before growth resumes. Metabolomic analysis reveals that long lags result from the depletion of key metabolites that follows the sudden reversal in the central carbon flux owing to the imposed nutrient shifts. A model of sequential flux limitation not only explains the observed trade-off between growth and adaptability, but also allows quantitative predictions regarding the universal occurrence of such tradeoffs, based on the opposing enzyme requirements of glycolysis versus gluconeogenesis. We validate these predictions experimentally for many different nutrient shifts in E. coli, as well as for other respiro-fermentative microorganisms, including Bacillus subtilis and Saccharomyces cerevisiae. A model of sequential flux bottlenecks explains a universal trade-off between steady-state growth and physiological adaptation time in bacteria exposed to fluctuating growth conditions., Author(s): Markus Basan [sup.1] [sup.2] , Tomoya Honda [sup.3] , Dimitris Christodoulou [sup.2] , Manuel Hörl [sup.2] , Yu-Fang Chang [sup.1] , Emanuele Leoncini [sup.1] , Avik Mukherjee [sup.1] , [...]

Somatic TP53 mutations are highly prevalent in therapy-related acute myeloid leukaemia and myelodysplastic syndrome, which arise as complications of cytotoxic chemotherapy or radiotherapy; although it was believed that these TP53 mutations are directly induced by cytotoxic therapy, new data indicate that they predate cytotoxic therapy and that haematopoietic progenitors harbouring these pre-existing mutations may selectively expand after exposure to chemotherapy or radiotherapy. TP53 mutations predate cytotoxic therapy The clonal haematopoietic disorders known as therapy-related acute myeloid leukaemia (t-AML) and therapy-related myelodysplastic syndrome (t-MDS) typically develop 1 to 5 years after exposure to chemotherapy or radiotherapy. TP53 mutations are selectively enriched in t-AML/t-MDS, and were thought to be directly induced by cytotoxic therapy. Now Daniel Link and colleagues present genome sequencing data that suggest the TP53 mutations predate cytotoxic therapy. It appears that rare haematopoietic stem/progenitor cells in blood or bone marrow carry age-related TP53 mutations, and that these cells undergo clonal expansion only after selective pressure applied by chemotherapy. Therapy-related acute myeloid leukaemia (t-AML) and therapy-related myelodysplastic syndrome (t-MDS) are well-recognized complications of cytotoxic chemotherapy and/or radiotherapy.sup.1. There are several features that distinguish t-AML from de novo AML, including a higher incidence of TP53 mutations.sup.2,3, abnormalities of chromosomes 5 or 7, complex cytogenetics and a reduced response to chemotherapy.sup.4. However, it is not clear how prior exposure to cytotoxic therapy influences leukaemogenesis. In particular, the mechanism by which TP53 mutations are selectively enriched in t-AML/t-MDS is unknown. Here, by sequencing the genomes of 22 patients with t-AML, we show that the total number of somatic single-nucleotide variants and the percentage of chemotherapy-related transversions are similar in t-AML and de novo AML, indicating that previous chemotherapy does not induce genome-wide DNA damage. We identified four cases of t-AML/t-MDS in which the exact TP53 mutation found at diagnosis was also present at low frequencies (0.003-0.7%) in mobilized blood leukocytes or bone marrow 3-6 years before the development of t-AML/t-MDS, including two cases in which the relevant TP53 mutation was detected before any chemotherapy. Moreover, functional TP53 mutations were identified in small populations of peripheral blood cells of healthy chemotherapy-naive elderly individuals. Finally, in mouse bone marrow chimaeras containing both wild-type and Tp53.sup.+/- haematopoietic stem/progenitor cells (HSPCs), the Tp53.sup.+/- HSPCs preferentially expanded after exposure to chemotherapy. These data suggest that cytotoxic therapy does not directly induce TP53 mutations. Rather, they support a model in which rare HSPCs carrying age-related TP53 mutations are resistant to chemotherapy and expand preferentially after treatment. The early acquisition of TP53 mutations in the founding HSPC clone probably contributes to the frequent cytogenetic abnormalities and poor responses to chemotherapy that are typical of patients with t-AML/t-MDS., Author(s): Terrence N. Wong [sup.1] , Giridharan Ramsingh [sup.2] , Andrew L. Young [sup.3] , Christopher A. Miller [sup.4] , Waseem Touma [sup.1] , John S. Welch [sup.1] [sup.5] , [...]

Therapy-related acute myeloid leukaemia (t-AML) and therapy-related myelodysplastic syndrome (t-MDS) are well-recognized complications of cytotoxic chemotherapy and/or radiotherapy (1). There are several features that distinguish t-AML from denovo AML, including a higher incidence of TP53 mutations (2,3), abnormalities of chromosomes 5 or 7, complex cytogenetics and a reduced response to chemotherapy (4). However, it is not clear how prior exposure to cytotoxic therapy influences leukaemogenesis. In particular, the mechanism by which TP53 mutations are selectively enriched in t-AML/t-MDS is unknown. Here, by sequencing the genomes of 22 patients with t-AML, we show that the total number of somatic single-nucleotide variants and the percentage of chemotherapy-related transversions are similar in t-AML and denovo AML, indicating that previous chemotherapy does not induce genome-wide DNA damage. W e identified four cases of t-AML/ t-MDS in which the exact TP53 mutation found at diagnosis was also present at low frequencies (0.003-0.7%) in mobilized blood leukocytes or bone marrow 3-6 years before the development of t-AML/tMDS, including two cases in which the relevant TP53 mutation was detected before any chemotherapy. Moreover, functional TP53 mutations were identified in small populations of peripheral blood cells of healthy chemotherapy-naive elderly individuals. Finally, in mouse bone marrow chimaeras containing both wild-type and [Tp53.sup.+/-] haematopoietic stem/progenitor cells (HSPCs), the [Tp53.sup.+/-] HSPCs preferentially expanded after exposure to chemotherapy. These data suggest that cytotoxic therapy does not directly induce TP53 mutations. Rather, they support a model in which rare HSPCs carrying age-related TP53 mutations are resistant to chemotherapy and expand preferentially after treatment. The early acquisition of TP53 mutations in the founding HSPC clone probably contributes to the frequent cytogenetic abnormalities and poor responses to chemotherapy that are typical of patients with t-AML/t-MDS., t-AML and t-MDS are clonal haematopoietic disorders that typically develop 1-5 years after exposure to chemotherapy or radiotherapy (1). To understand better how prior cytotoxic therapy contributes to the high [...]

Whisking and sniffing are predominant aspects of exploratory behaviour in rodents. Yet the neural mechanisms that generate and coordinate these and other orofacial motor patterns remain largely uncharacterized. Here we use anatomical, behavioural, electrophysiological and pharmacological tools to show that whisking and sniffing are coordinated by respiratory centres in the ventral medulla. We delineate a distinct region in the ventral medulla that provides rhythmic input to the facial motor neurons that drive protraction of the vibrissae. Neuronal output from this region is reset at each inspiration by direct input from the pre-Botzinger complex, such that high-frequency sniffing has a one-to-one relationship with whisking, whereas basal respiration is accompanied by intervening whisks that occur between breaths. We conjecture that the respiratory nuclei, which project to other premotor regions for oral and facial control, function as a master clock for behaviours that coordinate with breathing., Active sensing is an essential component of orofacial behaviour. Animals rhythmically sniff to smell, lick to taste, and whisk to touch. The muscles involved in these patterned sensory behaviours overlap [...]

Interference is fundamental to wave dynamics and quantum mechanics. The quantum wave properties of particles are exploited in metrology using atom interferometers, allowing for high-precision inertia measurements (1,2). Furthermore, the state-of-the-art time standard is based on an interferometric technique known as Ramsey spectroscopy. However, the precision of an interferometer is limited by classical statistics owing to the finite number of atoms used to deduce the quantity of interest (3). Here we show experimentally that the classical precision limit can be surpassed using nonlinear atom interferometry with a Bose-Einstein condensate. Controlled interactions between the atoms lead to non-classical entangled states within the interferometer; this represents an alternative approach to the use of non-classical input states (4-8). Extending quantum interferometry (9) to the regime of large atom number, we find that phase sensitivity is enhanced by 15 per cent relative to that in an ideal classical measurement. Our nonlinear atomic beam splitter follows the 'one-axis-twisting' scheme (10) and implements interaction control using a narrow Feshbach resonance. We perform noise tomography of the quantum state within the interferometer and detect coherent spin squeezing with a squeezing factor of - 8.2 dB (refs 11-15). The results provide information on the many-particle quantum state, and imply the entanglement of 170 atoms (16)., The concept of interferometry relies on the splitting of a quantum state into two modes, a period of free evolution and, finally, the recombination of the modes for readout. The [...]

Quantum measurement in a tangle Atom interferometers, which rely on the wave properties of particles, are used in a variety of ultra-high-precision measurements, from determining the gravitational constant to defining the time standard. The precision of interferometers is generally limited by classical statistics, arising from the finite number of atoms used in the experiment. Two papers in this issue demonstrate the potential of 'spin-squeezing' in Bose-Einstein condensates (BECs) to facilitate measurements that are more precise than classical statistics allow. Using a specially prepared BEC as the input to an interferometer, Gross et al. beat the classical precision limit. In the second study, Riedel et al. create similar 'spin-squeezed' states in a BEC confined to an 'atom chip' by controlling elastic collisional interactions with a state-dependent potential. This demonstration of multi-particle entanglement on a chip raises the prospect of chip-based portable atomic clocks that also beat the classical precision limits. The precision of interferometers -- used in metrology and in the state-of-the-art time standard -- is generally limited by classical statistics. Here it is shown that the classical precision limit can be beaten by using nonlinear atom interferometry with Bose-Einstein condensates. Interference is fundamental to wave dynamics and quantum mechanics. The quantum wave properties of particles are exploited in metrology using atom interferometers, allowing for high-precision inertia measurements.sup.1,2. Furthermore, the state-of-the-art time standard is based on an interferometric technique known as Ramsey spectroscopy. However, the precision of an interferometer is limited by classical statistics owing to the finite number of atoms used to deduce the quantity of interest.sup.3. Here we show experimentally that the classical precision limit can be surpassed using nonlinear atom interferometry with a Bose-Einstein condensate. Controlled interactions between the atoms lead to non-classical entangled states within the interferometer; this represents an alternative approach to the use of non-classical input states.sup.4,5,6,7,8. Extending quantum interferometry.sup.9 to the regime of large atom number, we find that phase sensitivity is enhanced by 15 per cent relative to that in an ideal classical measurement. Our nonlinear atomic beam splitter follows the 'one-axis-twisting' scheme.sup.10 and implements interaction control using a narrow Feshbach resonance. We perform noise tomography of the quantum state within the interferometer and detect coherent spin squeezing with a squeezing factor of -8.2 dB (refs 11-15). The results provide information on the many-particle quantum state, and imply the entanglement of 170 atoms.sup.16., Author(s): C. Gross [sup.1] , T. Zibold [sup.1] , E. Nicklas [sup.1] , J. Estève [sup.1] [sup.2] , M. K. Oberthaler [sup.1] Author Affiliations: (1) Kirchhoff-Institut für Physik, Universität Heidelberg, [...]

Theta oscillations clock hippocampal activity during awake behaviour and rapid eye movement (REM) sleep. These oscillations are prominent in the local field potential, and they also reflect the subthreshold membrane potential and strongly modulate the spiking of hippocampal neurons. The prevailing view is that theta oscillations are synchronized throughout the hippocampus, despite the lack of conclusive experimental evidence. In contrast, here we 'how that in freely behaving rats, theta oscillations in area CA1 are travelling waves that propagate roughly along the septotemporal axis of the hippocampus. Furthermore, we find that spiking in the CA1 pyramidal cell layer is modulated in a consistent travelling wave pattern. Our results demonstrate that theta oscillations pattern hippocampal activity not only in time, but also across anatomical space. The presence of travelling waves indicates that the instantaneous output of the hippocampus is topographically organized and represents a segment, rather than a point, of physical space., Theta oscillations are a prominent 4-10-Hz rhythm in the hippocampal local field potential (LFP) of all mammals studied to date (1-3), including humans (4). During wakefulness they are associated with [...]

The development of X-ray and electron diffraction methods with ultrahigh time resolution has made it possible to map directly, at the atomic level, structural changes in solids induced by laser excitation (1-8). This has resulted in unprecedented insights into the lattice dynamics of solids undergoing phase transitions. In aluminium, for example, femtosecond optical excitation hardly affects the potential energy surface of the lattice; instead, melting of the material is governed by the transfer of thermal energy between the excited electrons and the initially cold lattice (1). In semiconductors, in contrast, exciting ~10 per cent of the valence electrons results in non-thermal lattice collapse owing to the anti-bonding character of the conduction band (2-5,9,10). These different material responses raise the intriguing question of how Peierls-distorted systems (11) such as bismuth (12) will respond to strong excitations. The evolution of the atomic configuration of bismuth upon excitation of its [A.sub.1g] lattice mode, which involves damped oscillations of atoms along the direction of the Peierls distortion of the crystal, has been probed (6-8), but the actual melting of the material has not yet been investigated. Here we present a femtosecond electron diffraction study of the structural changes in crystalline bismuth as it undergoes laser-induced melting. We find that the dynamics of the phase transition depend strongly on the excitation intensity, with melting occurring within 190 fs (that is, within half a period of the unperturbed [A.sub.1g] lattice mode (6-8)) at the highest excitation. We attribute the surprising speed of the melting process to laser-induced changes in the potential energy surface of the lattice, which result in strong acceleration of the atoms along the longitudinal direction of the lattice and efficient coupling of this motion to an unstable transverse vibrational mode. That is, the atomic motions in crystalline bismuth can be electronically accelerated so that the solid-to-liquid (13) phase transition occurs on a sub-vibrational timescale., The crystalline structure of bismuth (Bi) is derived from a face-centred-cubic lattice rombohedrically distorted along the body diagonal (12) by the well-known Peierls-Jones mechanism (11). A seminal study (6) used [...]

The response of terrestrial vegetation to a globally changing environment is central to predictions of future levels of atmospheric carbon dioxide (1,2). The role of tropical forests is critical because they are carbon-dense and highly productive (3,4). Inventory plots across Amazonia show that old-growth forests have increased in carbon storage over recent decades (5-7), but the response of one-third of the world's tropical forests in Africa (8) is largely unknown owing to an absence of spatially extensive observation networks (9,10). Here we report data from a ten-country network of long-term monitoring plots in African tropical forests. We find that across 79 plots (163 ha) above-ground carbon storage in live trees increased by 0.63 Mg C [ha.sup.-1] [yr.sup.-1] between 1968 and 2007 (95% confidence interval (CI), 0.22-0.94; mean interval, 1987-96). Extrapolation to unmeasured forest components (live roots, small trees, necromass) and scaling to the continent implies a total increase in carbon storage in African tropical forest trees of 0.34 Pg C [yr.sup.-1] (CI, 0.15-0.43). These reported changes in carbon storage are similar to those reported for Amazonian forests per unit area (6,7), providing evidence that increasing carbon storage in old-growth forests is a pan-tropical phenomenon. Indeed, combining all standardized inventory data from this study and from tropical America and Asia (5,6,11) together yields a comparable figure of 0.49 Mg C [ha.sup.-1] [yr.sup.-1] (n = 156; 562 ha; CI, 0.29-0.66; mean interval, 1987-97). This indicates a carbon sink of 1.3 Pg C [yr.sup.-1] (CI, 0.8-1.6) across all tropical forests during recent decades. Taxon-specific analyses of African inventory and other data (12) suggest that widespread changes in resource availability, such as increasing atmospheric carbon dioxide concentrations, may be the cause of the increase in carbon stocks (13), as some theory (14) and models (2,10,15) predict., Tropical forests cover 7-10% of the global land area, store 40-50% of carbon in terrestrial vegetation and annually process approximately six times as much carbon via photosynthesis and respiration as [...]

A central question in ecology with great importance for management, conservation and biological control is how changing connectivity affects the persistence and dynamics of interacting species. Researchers in many disciplines [...]

Author(s): L. Ian Schmitt [1]; Ralf D. Wimmer [1]; Miho Nakajima [1]; Michael Happ [1]; Sima Mofakham [1]; Michael M. Halassa (corresponding author) [1, 2] Although interactions between the thalamus [...]

Low-dimensional systems provide beautiful examples of manybody quantum physics (1). For one-dimensional (1D) systemm (2), the Luttinger liquid approah (3) provides insight into universal properties. Much is known of the [...]

Author(s): Kazuki Horikawa (corresponding author) [1, 3]; Kana Ishimatsu [1, 3]; Eiichi Yoshimoto [2, 3]; Shigeru Kondo [2]; Hiroyuki Takeda (corresponding author) [1] Synchronized oscillation is a universal feature of [...]

Author(s): Kenneth D. Harris; Darrell A. Henze; Hajime Hirase; Xavier Leinekugel; George Dragoi; Andras Czurkó; György Buzsáki (corresponding author) According to the temporal coding hypothesis [1], neurons encode information by [...]

Author(s): Hugh R. Wilson (corresponding author) [1]; Randolph Blake [2]; Sang-Hun Lee [2] Nonlinear wave propagation is ubiquitous in nature, appearing in chemical reaction kinetics [1], cardiac tissue dynamics [1, [...]

Author(s): Steven H. Strogatz (corresponding author) Networks are on our minds nowadays. Sometimes we fear their power -- and with good reason. On 10 August 1996, a fault in two [...]

Author(s): A. Sørensen (corresponding author) [1]; L.-M. Duan [2]; J. I. Cirac [2]; P. Zoller [2] The possibility of creating and manipulating entangled states of systems of many particles is [...]

In 1665, the Dutch scientist Christiaan Huygens discovered that two pendulum clocks mounted on the same wall synchronize with one another--their pendulums swing with the same frequency but exactly out [...]

Author(s): Peter Turchin [1] Ecologists studying population dynamics prefer not to bother with the possibility of evolutionary change affecting their study organisms. This is sensible, because understanding the results of [...]

Author(s): Toshiyuki Nakagaki (corresponding author) [1, 2]; Hiroyasu Yamada [1, 2, 3]; Ãgota Tóth [4] The plasmodium of the slime mould Physarum polycephalum is a large amoeba-like cell consisting of [...]

Author(s): Dudley Herschbach (corresponding author) [illus. 1] Kent Wilson, who died on 27 March, developed innovative laser techniques to probe the molecular dynamics of chemical and biochemical reactions. A remarkably [...]