Rapid Signal Transmission Research Articles

Contactless Printing of Food Micro-Particles Controlled by Ultrasound

Traditional food 3D printing technology, which primarily relies on mechanical control, often faces challenges such as low resolution, stringent material requirements, limited flexibility, and cumbersome equipment. To overcome these limitations, we developed an innovative food 3D printing method utilizing ultrasonic phased arrays and subsequently designed a contactless printing device employing this advanced technology. The device effectively manipulates the phase and amplitude of the ultrasonic phased array to focus the sound field on a specific location. We have successfully demonstrated preliminary control over the suspension of small food particles, including popcorn, chocolate, honey, and marshmallows, using this apparatus. Following this, popcorn particles were selected for detailed practical printing and further analysis.Additionally, we established a software platform, Ultr_printing, based on Ultraino, for intelligent simulation and control of the printing process. Leveraging FPGA and Arduino controllers, this setup facilitates rapid signal transmission from personal computers to sensors, ensuring quick and adaptable movement of suspended particles. Experimental results confirm that the device consistently controls the food particles, irrespective of their motion state. Notably, it achieves a printing precision of 0.16 mm when handling popcorn particles measuring 1.5 mm in diameter. The process, entirely contactless and free from contamination, preserves the original flavor of the food particles. This technology is particularly effective for high-precision printing of micro-scale shapes and offers considerable benefits in assembly and precision manufacturing.

HYPERACTIVATION OF SPERMATOZOA AND ITS ROLE IN THE FERTILIZATION PROCESS

To date, according to the WHO estimates, every sixth person in the world faces the problem of infertility, while the contribution of the male factor is, according to various sources, from 30 to 50%. Understanding the cellular and molecular processes that lead to spermatozoa motility is necessary for accurate diagnosis and finding solutions to this problem. The purpose of the review is to analyze and evaluate current data on the problem of spermatozoa hyperactivation, the causes of its violation, molecular mechanisms and prognostic value. Materials and methods. Domestic and foreign sources of literature dated from 1987 to 2022 were used, they were taken from electronic libraries of scientific publications and medical databases, in particular "CyberLeninka", "Google Academy", "ScienceResearch", Elibrary.ru and PubMed. The review included the sources relevant to the topic of this review, which were searched using keywords such as spermatozoid, hyperactivation, infertility, fertilization. Research results. Hyperactivation of spermatozoa is one of the factors that ensure fertilization. This is a Ca2+ and energy-dependent process due to the normal operation of CatSper and KSper channels, as well as cAMP-, cGMP-dependent, potential-dependent channels. In the absence of the SLC9A10 gene in male mice, spermatozoa mature immobile, despite satisfactory spermatogenesis. The control units in the sperm flagella, consisting of CatSper, SLC9A10 and ABHD2, located on the surface, are necessary to ensure rapid signal transmission and coordinated control of complex cellular movement (hyperactivation and rotation). Conclusions. The motility of spermatozoa acquired during their hyperactivation is a vital functional characteristic that determines the ability of male germ cells to penetrate and migrate both into the cervical mucus and into the oocyte membrane (and ultimately fertilize it). Violation of hyperactivation processes or its absence can result in fertilization failure and, in consequence of, be one of the causes of infertility in a couple.

Hierarchical NiCo2O4/NiO mixed nanofibers for enhanced supercapacitor and ammonia gas sensor applications

In the present study, we investigated the NiCo2O4/NiO (NCO/NiO) composite nanofibers (NFs) synthesized via a facile electrospinning and solvothermal method as a future electrode material. The synthesized samples are characterized and their electrochemical and gas sensing properties are investigated. The morphology, structural, asymmetric vibrations and elemental compositions in the prepared samples are studied by Field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), Raman spectroscopy, Energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The prepared NCO/NiO NFs exhibit high specific capacitance (1212 Fg−1) and good cyclic performance (94%), showing promising supercapacitor properties. For NCO/NiO NFs, the continuity of the structure contributes to rapid signal transmission in gas detection. Ammonia gas measurement of NCO/NiO NFs operated at 100 °C showed fast response and recovery times of 17 and 11 s, respectively.

Calcium Signaling in Plant-Insect Interactions.

In plant–insect interactions, calcium (Ca2+) variations are among the earliest events associated with the plant perception of biotic stress. Upon herbivory, Ca2+ waves travel long distances to transmit and convert the local signal to a systemic defense program. Reactive oxygen species (ROS), Ca2+ and electrical signaling are interlinked to form a network supporting rapid signal transmission, whereas the Ca2+ message is decoded and relayed by Ca2+-binding proteins (including calmodulin, Ca2+-dependent protein kinases, annexins and calcineurin B-like proteins). Monitoring the generation of Ca2+ signals at the whole plant or cell level and their long-distance propagation during biotic interactions requires innovative imaging techniques based on sensitive sensors and using genetically encoded indicators. This review summarizes the recent advances in Ca2+ signaling upon herbivory and reviews the most recent Ca2+ imaging techniques and methods.

Small-world connectivity dictates collective endothelial cell signaling

Every blood vessel is lined by a single layer of highly specialized, yet adaptable and multifunctional endothelial cells. These cells, the endothelium, control vascular contractility, hemostasis, and inflammation and regulate the exchange of oxygen, nutrients, and waste products between circulating blood and tissue. To control each function, the endothelium processes endlessly arriving requests from multiple sources using separate clusters of cells specialized to detect specific stimuli. A well-developed but poorly understood communication system operates between cells to integrate multiple lines of information and coordinate endothelial responses. Here, the nature of the communication network has been addressed using single-cell Ca2+ imaging across thousands of endothelial cells in intact blood vessels. Cell activities were cross-correlated and compared to a stochastic model to determine network connections. Highly correlated Ca2+ activities occurred in scattered cell clusters, and network communication links between them exhibited unexpectedly short path lengths. The number of connections between cells (degree distribution) followed a power-law relationship revealing a scale-free network topology. The path length and degree distribution revealed an endothelial network with a “small-world” configuration. The small-world configuration confers particularly dynamic endothelial properties including high signal-propagation speed, stability, and a high degree of synchronizability. Local activation of small clusters of cells revealed that the short path lengths and rapid signal transmission were achieved by shortcuts via connecting extensions to nonlocal cells. These findings reveal that the endothelial network design is effective for local and global efficiency in the interaction of the cells and rapid and robust communication between endothelial cells in order to efficiently control cardiovascular activity.

Why and How the Bio-Electric Activity of Plant Roots is Awoken When the Leaves Need Water? A Very Rapid Signal Transmission from Aerial Part to Root

The simplest and scientific method to determine the bioelectric activity of a plant root is the measurement of the Trans-Root Electric Potential (TRP) i.e., the electric potential difference between the xylem apoplast and the earth surrounding the root.

Mechanisms underlying TARP modulation of the GluA1/2-\u03b38 AMPA receptor

AMPA-type glutamate receptors (AMPARs) mediate rapid signal transmission at excitatory synapses in the brain. Glutamate binding to the receptor’s ligand-binding domains (LBDs) leads to ion channel activation and desensitization. Gating kinetics shape synaptic transmission and are strongly modulated by transmembrane AMPAR regulatory proteins (TARPs) through currently incompletely resolved mechanisms. Here, electron cryo-microscopy structures of the GluA1/2 TARP-γ8 complex, in both open and desensitized states (at 3.5 Å), reveal state-selective engagement of the LBDs by the large TARP-γ8 loop (‘β1’), elucidating how this TARP stabilizes specific gating states. We further show how TARPs alter channel rectification, by interacting with the pore helix of the selectivity filter. Lastly, we reveal that the Q/R-editing site couples the channel constriction at the filter entrance to the gate, and forms the major cation binding site in the conduction path. Our results provide a mechanistic framework of how TARPs modulate AMPAR gating and conductance.

Signaling and transport processes related to the carnivorous lifestyle of plants living on nutrient-poor soil.

In Eukaryotes, long-distance and rapid signal transmission is required in order to be able to react fast and flexibly to external stimuli. This long-distance signal transmission cannot take place by diffusion of signal molecules from the site of perception to the target tissue, as their speed is insufficient. Therefore, for adequate stimulus transmission, plants as well as animals make use of electrical signal transmission, as this can quickly cover long distances. This update summarises the most important advances in plant electrical signal transduction with a focus on the carnivorous Venus flytrap. It highlights the different types of electrical signals, examines their underlying ion fluxes and summarises the carnivorous processes downstream of the electrical signals.

Xiaoyaosan exerts antidepressant-like effects by regulating the functions of astrocytes and EAATs in the prefrontal cortex of mice

BackgroundMounting evidence indicates that the cerebral cortex is an important physiological system of emotional activity, and its dysfunction may be the main cause of stress. Glutamate is the primary excitatory neurotransmitter in the central nervous system (CNS), which initiates rapid signal transmission in the synapse before its reuptake into the surrounding glia, specifically astrocytes (ASTs). The astrocytic excitatory amino acid transporters 1 (EAAT1) and 2 (EAAT2) are the major transporters that take up synaptic glutamate to maintain optimal extracellular glutamic levels, thus preventing accumulation in the synaptic cleft and ensuing excitotoxicity. Growing evidence has shown that excitotoxicity is associated with depression. Therefore, we hypothesized that the underlying antidepressant-like mechanism of Xiaoyaosan (XYS), a Chinese herbal formula, may be related to the regulation of astrocytic EAATs. Therefore, we studied the antidepressant mechanism of XYS on the basis of EAAT dysfunction in ASTs.MethodsEighty adult C57BL/6 J mice were randomly divided into 4 groups: a control group, a chronic unpredictable mild stress (CUMS) group, a Xiaoyaosan (XYS) treatment group and a fluoxetine hydrochloride (Flu) treatment group. Except for the control group, mice in the other groups all received chronic unpredictable mild stress for 21 days. Mice in the control and CUMS groups received gavage administration with 0.5 mL of normal saline (NS) for 21 days, and mice in the XYS and Flu treatment groups were administered dosages of 0.25 g/kg/d and 2.6 mg/kg/d by gavage. The effects of XYS on the depressive-like behavioral tests, including the open field test (OFT), forced swimming test (FST) and sucrose preference test (SPT), were examined. The glutamate (Glu) concentrations of the prefrontal cortex (PFC) were detected with colorimetry. The morphology of neurons in the PFC was observed by Nissl staining. The expression of glial fibrillary acidic protein (GFAP), NeuN, EAAT1 and EAAT2 proteins in the PFC of mice was detected by using Western blotting and immunohistochemistry. Quantitative real-time PCR (qPCR) was used to detect the expression of the GFAP, NeuN, EAAT1 and EAAT2 genes in the PFC of mice.ResultsThe results of behavioral tests showed that CUMS-induced mice exhibited depressive-like behavior, which could be improved in some tests with XYS and Flu treatment. Immunohistochemistry and Western blot analysis showed that the protein levels of GFAP, NeuN, EAAT1 and EAAT2 in the PFC of CUMS mice were significantly lower than those in the control group, and these changes could be reversed by XYS and Flu. The results of qPCR analysis showed that the expression of GFAP, NeuN, EAAT1 and EAAT2 mRNAs in the PFC of CUMS mice was not significantly changed, with the exception of EAAT2, compared with that of the control group, while the expression of the above mRNAs was significantly higher in the XYS and Flu groups than that in the CUMS group.ConclusionXYS may exert antidepressant-like effects by improving the functions of AST and EAATs and attenuating glutamate-induced neuronal damage in the frontal cortex.

Reorganization of Destabilized Nodes of Ranvier in βIV Spectrin Mutants Uncovers Critical Timelines for Nodal Restoration and Prevention of Motor Paresis.

Disorganization of nodes of Ranvier is associated with motor and sensory dysfunctions. Mechanisms that allow nodal recovery during pathological processes remain poorly understood. A highly enriched nodal cytoskeletal protein βIV spectrin anchors and stabilizes the nodal complex to actin cytoskeleton. Loss of murine βIV spectrin allows the initial nodal organization, but causes gradual nodal destabilization. Mutations in human βIV spectrin cause auditory neuropathy and impairment in motor coordination. Similar phenotypes are caused by nodal disruption due to demyelination. Here we report on the precise timelines of nodal disorganization and reorganization by following disassembly and reassembly of key nodal proteins in βIV spectrin mice of both sexes before and after βIV spectrin re-expression at specifically chosen developmental time points. We show that the timeline of nodal restoration has different outcomes in the PNS and CNS with respect to nodal reassembly and functional restoration. In the PNS, restoration of nodes occurs within 1 month regardless of the time of βIV spectrin re-expression. In contrast, the CNS nodal reorganization and functional restoration occurs within a critical time window; after that, nodal reorganization diminishes, leading to less efficient motor recovery. We demonstrate that timely restoration of nodes can improve both the functional properties and the ultrastructure of myelinated fibers affected by long-term nodal disorganization. Our studies, which indicate a critical timeline for nodal restoration together with overall motor performance and prolonged life span, further support the idea that nodal restoration is more beneficial if initiated before any axonal damage, which is critically relevant to demyelinating disorders.SIGNIFICANCE STATEMENT Nodes of Ranvier are integral to efficient and rapid signal transmission along myelinated fibers. Various demyelinating disorders are characterized by destabilization of the nodal molecular complex, accompanied by severe reduction in nerve conduction and the onset of motor and sensory dysfunctions. This study is the first to report in vivo reassembly of destabilized nodes with sequential improvement in overall motor performance. Our study reveals that nodal restoration is achievable before any axonal damage, and that long-term nodal destabilization causes irreversible axonal structural changes that prevent functional restoration. Our studies provide significant insights into timely restoration of nodal domains as a potential therapeutic approach in treatment of demyelinating disorders.

A High-Resolution 14C Chronology Tracks Pulses of Aggradation of Glaciofluvial Sediment on the Cormor Megafan between 45 and 20 ka BP

AbstractDuring the Last Glacial Maximum (LGM) the Tagliamento glacier delivered large amounts of sediment to the Cormor alluvial megafan on the southern Alpine foreland basin. To build a chronology of Late Pleistocene glacier fluctuations and assess the timing of the transition from interstadial to glacial conditions, we have performed radiocarbon (14C) dating on peat and macrofossil samples obtained from a drilling core from the distal Cormor megafan. Our chronology records fluvial and glaciofluvial aggradation from the end of MIS 3 until the end of the LGM. It shows a rapid transmission of signals of environmental change along the Cormor megafan, so that changes in the activity of the Tagliamento glacier directly affect glaciofluvial sedimentation. Our data demonstrate that the intrinsic heterogeneity of peat is most critical for the reliability and reproducibility of the obtained 14C ages. Macrofossil subsamples give evidence for significant mixing of organic components of different ages within single peat samples. Sample heterogeneity is also underlined by the results obtained from testing of different laboratory precleaning methods. Our results suggest that a rigorous ABA pretreatment is sufficient for peat cleaning. In contrast, the chemically stronger ABOX methods appear to rapidly degrade the peat, particularly destroying older organic components.

The Role of Potassium Channels in Arabidopsis thaliana Long Distance Electrical Signalling: AKT2 Modulates Tissue Excitability While GORK Shapes Action Potentials.

Fast responses to an external threat depend on the rapid transmission of signals through a plant. Action potentials (APs) are proposed as such signals. Plant APs share similarities with their animal counterparts; they are proposed to depend on the activity of voltage-gated ion channels. Nonetheless, despite their demonstrated role in (a)biotic stress responses, the identities of the associated voltage-gated channels and transporters remain undefined in higher plants. By demonstrating the role of two potassium-selective channels in Arabidopsis thaliana in AP generation and shaping, we show that the plant AP does depend on similar Kv-like transport systems to those of the animal signal. We demonstrate that the outward-rectifying potassium-selective channel GORK limits the AP amplitude and duration, while the weakly-rectifying channel AKT2 affects membrane excitability. By computational modelling of plant APs, we reveal that the GORK activity not only determines the length of an AP but also the steepness of its rise and the maximal amplitude. Thus, outward-rectifying potassium channels contribute to both the repolarisation phase and the initial depolarisation phase of the signal. Additionally, from modelling considerations we provide indications that plant APs might be accompanied by potassium waves, which prime the excitability of the green cable.

Orchestrating rapid long‐distance signaling in plants with Ca2+, ROS and electrical signals

Plants show a rapid systemic response to a wide range of environmental stresses, where the signals from the site of stimulus perception are transmitted to distal organs to elicit plant-wide responses. A wide range of signaling molecules are trafficked through the plant, but a trio of potentially interacting messengers, reactive oxygen species (ROS), Ca2+ and electrical signaling ('trio signaling') appear to form a network supporting rapid signal transmission. The molecular components underlying this rapid communication are beginning to be identified, such as the ROS producing NAPDH oxidase RBOHD, the ion channel two pore channel 1 (TPC1), and glutamate receptor-like channels GLR3.3 and GLR3.6. The plant cell wall presents a plant-specific route for possible propagation of signals from cell to cell. However, the degree to which the cell wall limits information exchange between cells via transfer of small molecules through an extracellular route, or whether it provides an environment to facilitate transmission of regulators such as ROS or H+ remains to be determined. Similarly, the role of plasmodesmata as both conduits and gatekeepers for the propagation of rapid cell-to-cell signaling remains a key open question. Regardless of how signals move from cell to cell, they help prepare distant parts of the plant for impending challenges from specific biotic or abiotic stresses.

Speed of saccade execution and inhibition associated with fractional anisotropy in distinct fronto-frontal and fronto-striatal white matter pathways.

Fast cancellation or switching of action plans is a critical cognitive function. Rapid signal transmission is key for quickly executing and inhibiting responses, and the structural integrity of connections between brain regions plays a crucial role in signal transmission speed. In this study, we used the search-step task, which has been used in nonhuman primates to measure dynamic alteration of saccade plans, in combination with functional and diffusion-weighted MRI. Functional MRI results were used to identify brain regions involved in the reactive control of gaze. Probabilistic tractography was used to identify white matter pathways connecting these structures, and the integrity of these connections, as indicated by fractional anisotropy (FA), was correlated with search-step task performance. Average FA from tracts between the right frontal eye field (FEF) and both right supplementary eye field (SEF) and the dorsal striatum were associated with faster saccade execution. Average FA of connections between the dorsal striatum and both right SEF and right inferior frontal cortex (IFC) as well as between SEF and IFC predicted the speed of inhibition. These relationships were largely behaviorally specific, despite the correlation between saccade execution and inhibition. Average FA of connections between the IFC and both SEF and the dorsal striatum specifically predicted the speed of inhibition, and connections between the FEF and SEF specifically predicted the speed of execution. In addition, these relationships were anatomically specific; correlations were observed after controlling for global FA. These data suggest that networks supporting saccade initiation and inhibition are at least partly dissociable. Hum Brain Mapp 37:2811-2822, 2016. © 2016 Wiley Periodicals, Inc.

Mural propagation of descending vasa recta responses to mechanical stimulation

To investigate the responses of descending vasa recta (DVR) to deformation of the abluminal surface, we devised an automated method that controls duration and frequency of stimulation by utilizing a stream of buffer from a micropipette. During stimulation at one end of the vessel, fluorescent responses from fluo4 or bis[1,3-dibutylbarbituric acid-(5)] trimethineoxonol [DiBAC₄(3)], indicating cytoplasmic calcium ([Ca²⁺]CYT) or membrane potential, respectively, were recorded from distant cells. Alternately, membrane potential was recorded from DVR pericytes by nystatin whole cell patch-clamp. Mechanical stimulation elicited reversible [Ca²⁺)]CYT responses that increased with frequency. Individual pericyte responses along the vessel were initiated within a fraction of a second of one another. Those responses were inhibited by gap junction blockade with 18 β-glycyrrhetinic acid (100 μM) or phosphoinositide 3 kinase inhibition with 2-morpholin-4-yl-8-phenylchromen-4-one (50 μM). [Ca²⁺]CYT responses were blocked by removal of extracellular Ca²⁺ or L-type voltage-gated channel blockade with nifedipine (10 μM). At concentrations selective for the T-type channel blockade, mibefradil (100 nM) was ineffective. During mechanostimulation, pericytes rapidly depolarized, as documented with either DiBAC4(3) fluorescence or patch-clamp recording. Single stimuli yielded depolarizations of 22.5 ± 2.2 mV while repetitive stimuli at 0.1 Hz depolarized pericytes by 44.2 ± 4.0 mV. We conclude that DVR are mechanosensitive and that rapid transmission of signals along the vessel axis requires participation of gap junctions, L-type Ca²⁺ channels, and pericyte depolarization.

Mitochondrial Colocalization with Ca2+ Release Sites is Crucial to Cardiac Metabolism

In cardiomyocyte subcellular structures, colocalization of mitochondria with Ca2+ release sites is implicated in regulation of cardiac energetics by facilitating Ca2+ influx into mitochondria to modulate the tricarboxylic acid (TCA) cycle. However, current experimental techniques limit detailed examination of this regulatory mechanism. Earlier, we developed a three-dimensional (3D) finite-element cardiomyocyte model featuring a subcellular structure that integrates excitation-contraction coupling and energy metabolism. Here, using this model, we examined the influence of distance between mitochondria and Ca2+ release sites by comparing a normal (50-nm) distance model and a large (200-nm) distance model (LD). The influence of distance was minimal under a low pacing rate (0.25 Hz), but under a higher pacing rate (2 Hz), lower levels of mitochondrial Ca2+ and NADH, elevated phosphate, and suppressed force generation became apparent in the LD model. Such differences became greater when functional impairments (reduced TCA cycle activity, uncoupling effect, and failing excitation-contraction coupling) were additionally imposed. We concluded that juxtaposition of the mitochondria and the Ca2+ release sites is crucial for rapid signal transmission to maintain cardiac-energy balance. The idealized 3D model of cardiac excitation-contraction and metabolism is a powerful tool to study cardiac energetics.

Biplexiform ganglion cells contact photoreceptors in the retina of the greenling Hexagrammos octogrammus

The biplexiform cell (bpxRGC) is a relatively and recently discovered type of retinal ganglion cells. Like "ordinary" ganglion cells, bpxRGCs have dendrites arborizing within the inner plexiform layer. However, as distinct from other ganglion cells, they have dendrites ascending to the outer plexiform layer. To date, bpxRGCs have been found in mammals, amphibians, and teleost fishes (Cook et al. [1996] Vis Neurosci 13:517-528). The mammalian and amphibian bpxRGCs form direct contacts with photoreceptors and may participate in rapid signal transmission to the brain (Mariani [1982] Science 216:1134-1136; Straznicky and Gábriel [1995] J Hirnforsch 36:135-141). The synaptic organization of teleost bpxRGCs has not been studied. We have studied the synaptic structure of bpxRGCs in the teleost fish Hexagrammos octogrammus. In the sclerad part of the outer plexiform layer, bpxRGC dendrites occurred among the elements in invaginated ribbon synapses (triads) in cone pedicles and rod spherules. Earlier, we showed that greenling bpxRGCs project to the optic tectum (Podugolnikova et al. [2002] Sensornye systemy 15:44-53). We suggest that greenling bpxRGCs participate in some of the tectum-mediated reactions requiring a quick launch of visuomotor reflexes.

ELLIOT S. VALENSTEIN. The War of the Soups and Sparks: The Discovery of Neurotransmitters and the Dispute over How Nerves Communicate. New York, Columbia University Press, 2005. 256 pp. (No price given).

Valenstein’s The War of the Soups and Sparks portrays an exceptionally polarizing debate that separated the emerging field of neuroscience into two camps: neurophysiologists and pharmacologists. The matter of their dispute was one of neuroscience’s most important questions: how do neurons communicate with one another? As we understand it today, the nervous system forms neural circuits by connecting individual neurons through a vast array of highly specialized cell-cell contact sites—called synapses—that use two different modes of operation. Electrical synapses have the obvious advantage of transmitting signals without substantial delay, while the degree of modulating signal strength is rather limited. In contrast, chemical signal transmission is delayed by the secretion of neurotransmitters, but nevertheless provides a better means of computing the encoded information. Valenstein’s book describes the long and remarkably controversial development of this understanding. Around 1900, it became generally accepted that neurons are connected by synapses that leave a physical gap between cells. Initially, almost all neurophysiologists believed that the main mode of signal transmission in the brain had to be electrical (sparks). The concept of chemical transmission was developed in stages, and its general acceptance in the scientific community was marked by the old mistake of unreasonable opposition to new ideas. The first hint came from the observation that acetylcholine and adrenalin affect the function of organs in a way similar to the stimulation of the innervating nerves; the famous example is the slower heart rate produced by stimulating the vagus nerve. Although this was firmly established by Henry Dale’s work, the idea that the innervating nerve might secrete chemicals was not seriously considered until Otto Loewi’s discovery of the “Vagusstoff” in 1921, which led to the concept of neurotransmitters (soups). Since Loewi’s work could not identify the origin of the secreted Vagusstoff, and because of the difficulties encountered in repeating his experiment, his work initially encountered vehement skepticism. Using a better system, Dale identified the Vagusstoff as acetylcholine and showed that it was indeed released from the nerve. However, despite the awarding of the Nobel Prize to Loewi and Dell in 1936, chemical transmission was still considered to be an isolated case. Neurophysiologists, like John Eccles, disputed the idea that transmitters might also mediate rapid signal transmission in the brain. For a number of years, the debate was fought vigorously but respectfully. A breakthrough occurred when Eccles, one of the staunchest opponents of chemical transmission, provided key evidence that synaptic transmission between motor nerves and skeletal muscles is indeed chemical, admitting that he and many others had been wrong all along. Ironically, just when the idea blossomed that all synapses might use neurotransmitters, a few electrical synapses were finally identified in the brain. In the end, less than one percent of all synapses turned out to rely on “sparks.”

Second order phase transition in neural rate coding: binary encoding is optimal for rapid signal transmission.

Here, we derive optimal tuning functions for minimum mean square reconstruction from neural rate responses subjected to Poisson noise. The shape of these tuning functions strongly depends on the length T of the time window within which action potentials (spikes) are counted in order to estimate the underlying firing rate. A phase transition towards pure binary encoding occurs if the maximum mean spike count becomes smaller than approximately three. For a particular function class, we prove the existence of a second-order phase transition. The analytically derived critical decoding time window length is in precise agreement with numerical results. Our analysis reveals that binary rate encoding should dominate in the brain wherever time is the critical constraint.

Copper On-Chip Interconnections: A Breakthrough in Electrodeposition to Make Better Chips

On-chip interconnections comprise a multilevel structure of fine wiring located on the top of the transistor circuitry of logic or memory chips, whose role is to connect circuits together as shown in Fig. 1. To avoid significant degradation of circuit speed, on-chip interconnections should permit rapid signal transmission among the various parts of the circuitry. Ever since the development of the integrated circuit about 40 years ago, the most pervasively used materials for the fabrication of the wiring structure have been aluminum as the conductor (or more recently an aluminum-copper alloy for better reliability) and silicon dioxide as the insulator. The transition to copper as the conductor and to a better insulator began with IBM’s announcement in September 1997 and product shipment since June 1998. This signals one of the most important changes in materials that the semiconductor industry has experienced since its creation. Copper metallization was implemented first since significant gains can be obtained by copper alone.