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A Cretaceous ctenothrissiform fossil, Ctenothrissa sp. (order Ctenothrissiformes), on a limestone matrix found in Lebanon. Size: 90 mm (3.5 in.). (Photo courtesy of The Virtual Fossil Museum)

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from article Dewar flask

Two typical Dewar containers.

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from article Propagator (field theory)

Feynman diagrams for scattering processes. (a) Electron-proton scattering via photon exchange. (b) Proton-proton scattering via meson exchange.

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from article Conservation of energy

The conservation of energy allows energy to be interconverted among many different forms. In the use of wind power, for example, the kinetic energy of wind (movements of air) can be converted by turbine blades into electrical energy. (Credit: Ron…

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from article Electrical units and standards

Calculable capacitor. (a) Cross section of general cylindrical capacitor with four segments. (b) Cross section of symmetrical capacitor with cylindrical electrodes. (c) Calculable capacitor used in absolute determination of the ohm. (U.S. National…

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from article Electrical units and standards

Moving-coil balance. (a) Schematic diagram. (b) Equipment. (U.K. National Physical Laboratory)

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from article Electrical units and standards

Josephson effect. (a) Josephson junction characteristic. (b) Linear array of more than 2000 Josephson junctions in a folded microwave stripline, giving a total voltage step in the region of 1 volt. (U.S. National Institute of Standards and…

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from article Electrical units and standards

Quantum Hall effect. (a) Geometry of semiconductor. (b) Hall resistance characteristic. i = quantum number.

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from article Triple point

Phase diagram for water, showing gas, liquid, and several solid (ice) phases; triple points at A, B, and C. The pressure scale changes at 101 kilopascals from logarithmic scale at low pressure to linear at high pressure.

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from article Inertial confinement fusion

Ablative indirect drive and ablative direct drive. (a) In laser-illuminated, ablative indirect drive, the ICF target consists of a cylindrical hohlraum (hollow room) in which laser light is injected through the two holes in the end caps and heats…

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from article Inertial confinement fusion

X-ray images with a framing camera (developed at Lawrence Livermore National Laboratory) from a directly driven inertial confinement fusion capsule at the University of Rochester's Omega Facility. The camera has 80-ps exposure time and 55-ps time…

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from article Inertial confinement fusion

Deuterium–tritium fuel ion temperature and density at ignition, plotted against normalized radius, for a typical high-gain capsule.

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from article Inertial confinement fusion

The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL). Its driver is the world's largest laser. The 1.8 MJ of ultraviolet light (351-nm wavelength from frequency-tripled neodymium:glass laser light) is generated with…

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from article Inertial confinement fusion

Progress toward ignition on NIF is illustrated by the plot of no-burn D–T equivalent yield in number of neutrons versus the value of ρr inferred from the energy lost by fusion neutrons during passage out of the compressed fuel. These experiments…

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from article Inertial confinement fusion

View of the combined Z Machine and Z-Beamlet laser facility (lower left) with exploded view of the cross section of the Z Machine (upper left). Both will be used to drive the MagLIF capsule (right) at Sandia National Laboratories. The 10-kJ…

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from article Inertial confinement fusion

Computed capsule gains (energy yield divided by absorbed energy) from 1D simulations of the principal (radial) dynamics for ablative direct drive of a perfect capsule, which is irradiated by either 248-nm laser light or 351-nm laser light with…

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from article Inertial confinement fusion

Electra, an ∼500 J/pulse, electron-beam pumped KrF laser at the Naval Research Laboratory. It has achieved 90,000 shots in a continuous run and 330,000 shots in 8 days at 2.5–5 Hz.

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from article Inertial confinement fusion

Conceptual design of the X-target. (Credit: Heavy Ion Fusion Science Virtual National Laboratory)

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from article Macrocyclic compound

Macrocyclic structures. (a) Two crown ethers. (b) A basic structure for three cryptands. (c) A lariat ether. (d) All-aliphatic spherand. (e) All-aromatic spherand.

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from article Macrocyclic compound

Macrocycles with various structural features. (a) Bicyclic cryptand (ditopic receptor). (b) Calix[6]arene; R represents a functional group. (c) Cavitand. (d) Carcerand. (e) Cyclophanes.

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from article Macrocyclic compound

Tetramers. (a) Resorcinarene having the rctt conformation. (b) Pyrogallolarene having the rccc conformation.

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from article Macrocyclic compound

The metal cation is the guest and the organic structure is the host in (a) 18-crown-6 complex of potassium cation (K+) and (b) sodium (Na+) complexed by a calix[4]arene.

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from article Macrocyclic compound

Complexing species. (a) Dibinaphtho-22-crown-6. (b) R,R-dibinaphtho-22-crown-6 complex of phenethylammonium chloride.

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from article Macrocyclic compound

Affinities for anions and cations shown for (a) pyrrole and (b) furan-derived cyclic tetramers.

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from article Macrocyclic compound

Amphiphiles. (a) Crown ether-steroid amphiphile. (b) Crown ether bolaamphiphile.

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from article Renner-Teller effect

Bending potential function V for a degenerate electronic state of a linear molecule as a function of displacement r, and for three values (0, 0.5, 1.0) of the Renner parameter ε. In the absence of Renner-Teller splitting (ε = 0) there is a single…

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from article Capacitance

Parallel-plate capacitor P1, P2 with guard ring GG. Spacing between guard ring and plate is exaggerated. (a) Cross section with all parts of capacitor at ground potential. (b) Top view showing plate P1 surrounded by guard ring. (c) Cross section of…

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from article Capacitance

Variable air capacitor.

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from article Capacitance

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from article Capacitance

Wound-roll construction of plastic film and paper capacitors.

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from article Capacitance

Ceramic capacitor constructed in chip form, showing cutaway of finished chip.

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from article Capacitance

Tantalum electrolytic capacitor showing cross section. (General Electric Co.)

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from article Capacitance

Construction and polarity markings of aluminum electrolytic capacitor. (a) Cross section. (b Polarization markings for tabular capacitor with axial leads. (c) Polarization markings for capacitor with radial leads. (After A. Mottershead, Electricity…

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from article Capacitance

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from article Marcus equation

Free-energy plot for an electron-transfer reaction with zero standard free-energy change (an electron self-exchange reaction).

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from article Marcus equation

Free-energy plot for an electron-transfer reaction when the free-energy change (|Δ G °|) is less than the reorganization parameter (λ).

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from article Lead

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from article Lead

Galena (lead sulfide, PbS) is an ore mined for lead. (Credit: USGS)

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from article Oxygen toxicity

The dual effect of oxygen on biologic activity. Organisms that avail themselves of the enormous metabolic advantages provided by dioxygen (O2) must defend themselves against its toxicity. (Copyright © McGraw Hill)

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from article Transmission lines

Two common transmission lines for communication. (a) Coaxial cable. (b) Strip line.

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from article Transmission lines

Equivalent circuit that represents three sections of a lossless transmission line. Each section is of length Δz, and has an inductor (L) and capacitor (C). Voltages (V ) and currents (I ), and their differences (ΔV and ΔI ) between successive…

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from article Transmission lines

Signal detection on an oscilloscope. (a) Oscilloscope pictures of voltage pulses at three locations, z1, z2, and z3, on a transmission line, successively more distant from the signal generator. (b) Oscilloscope pictures of a periodic voltage sine…

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from article Transmission lines

Transmission line with characteristic impedance Zc, terminated in a load impedance ZL. A change of coordinate system (from z to ζ) is indicated.

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from article Transmission lines

Envelope of the voltage standing wave consisting of a wave propagating from z = −∞ and being reflected at z = 0. The wavelength, λ, and the maximum and minimum voltages, Vmax and Vmin , are indicated.

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from article Transmission lines

Two waveguides, with conventional coordinates. (a) Rectangular waveguide. (b) Cylindrical waveguide.

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from article Transmission lines

Dispersion curve for a rectangular waveguide of width a, showing relationship between the propagation constant, β, and the angular frequency, ω. Here, n specifies the mode of propagation, and c is the speed of light.

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from article Transmission lines

Equivalent circuit of a power transmission line. The single-phase circuit is used to represent balanced three-phase lines. Here, R and X are the resistance and reactance (at the operational frequency), and C is the capacitance of the entire…

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from article Curie temperature

Variation of spontaneous magnetization of a ferromagnetic material with temperature.

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from article Curie temperature

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from article Reactance

Circuit with a resistor and capacitor in parallel.

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from article Chicxulub impact crater

Bouguer gravity anomaly map over the Chicxulub impact crater. The coastline is designated by a thin white line, cenotes (natural pits) and sinkholes are designated by black dots, and the city of Mérida and the town of Chicxulub Puerto are designated…

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from article Chicxulub impact crater

Seismic line imaging of what lies beneath the seafloor, showing the Chicxulub impact crater. The crater includes many faults that can be grouped into an exterior ring fault, a series of outer ring faults, and a series of inner ring faults. Within…

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from article Bioassay

In conducting bioassays, researchers often employ laboratory culture tests, which use, for example, bacteria cultured in a petri dish (usually to model an effect on the organism of interest or on some basic cellular function). (Credit:…

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from article Surfactant

Foam blankets typically contain less than 1% surfactant to produce a stable foam that blocks oxygen for fire suppression. (Credit: U.S. Navy)

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from article Open channel

Types of open-channel flow. The inverted triangles denote the free surface of the flow. (a) Unsteady flow. (b) Steady, uniform flow. (c) Steady, gradually varied flow (GVF) and steady, rapidly varied flow (RVF). (After T. W. Sturm, Open Channel…

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from article Integrated optics

Optical waveguide. (a) Optical intensity of the fundamental guided mode. (b) Ray picture of the guided mode.

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from article Integrated optics

Two-dimensional transverse waveguiding. (a) Rib waveguide. (b) Diffused channel guide.

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from article Integrated optics

Prism input coupling and grating output coupling. With the ray directions reversed, the grating acts as an input coupler and the prism as an output coupler.

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from article Integrated optics

A “4 by 4” directional coupler switch.

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from article Integrated optics

Top view of an integrated optics spectrum analyzer.

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from article Integrated optics

A wavelength-division-multiplexed transmitter chip. DFB indicates distributed feedback.

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from article Muffler

Mufflers. (a) Reactive muffler for automobile exhaust system. (b) Dissipative muffler for industrial application.

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from article Muffler

Simple muffler elements and their representative transmission losses. (a) Helmholtz resonator. (b) Side-branch resonator. (c) Expansion chamber. (d) Expansion chamber with dissipative material.

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from article Conservation of mass

Charcoals burning. According to the principle of the conservation of mass, assuming the burning charcoals and the oxygen enabling their burning are all within a closed system, the total amount of mass in the system prior to the charcoals burning…

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from article Matrix isolation

Vacuum-vessel base cross section for matrix photoionization experiments. 10 K = −263°C or −442°F.

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from article Matrix isolation

Schematic plan view of the matrix assembly for pulsed-laser ablation.

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from article Matrix isolation

Infrared and Raman spectra of lithium superoxide, Li+O2−, using lithium-7 and 30% 18O2, 50% 16O18O, and 20% 16O2 at concentrations of Ar/O2 = 100. The Raman spectrum was recorded by using 200 mW of 488-nm excitation at the sample.

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from article Matrix isolation

Visible and ultraviolet absorption spectra of naphthalene samples in solid argon at 20 K. Upper curves show Ar/CCl4/N = 3000/4/1, and lower curves show the same sample after 15 s of irradiation at 220–1000 nm from a high-pressure mercury arc.

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from article Matrix isolation

Infrared spectra in the 2000–1200 cm−1 region for the products of the reactions of laser-ablated Al atoms with pure hydrogen co-deposited at 3.5 K. (a) Spectrum obtained from initial deposited sample. (b) Spectrum after >290 nm irradiation. (c)…

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from article Graptolithina

Sketches of portions of pterobranch and graptolite colonies showing the dwelling tubes and the constructional units of the graptolite skeleton. (a) Young Rhabdopleura compacta colony with founder zooid and first asexual bud (Recent). Benthic…

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from article Graptolithina

Scanning electron micrograph of a graptolite (Pseudoclimacograptus scharengergi) showing the fuselli (horizontal ridges) that compose graptolite thecae, and the cortical bandages (oblique strips) that were deposited on top of the fuselli (Middle…

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from article Graptolithina

Hypothetical form of zooids that inhabited colony tubes, based on a planktic graptolite. Large zooids are shown with possible oarlike swimming organs used to move the colony through the ocean water and tentacles for feeding. Also shown are two…

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from article Graptolithina

Examples of some planktic graptolites, reconstructed to show three-dimensional form.

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from article Aharonov-Bohm effect

Aharonov and Bohm's proposed experiments to demonstrate the effects of electromagnetic potentials in electron interference phenomena. (a) Experiment to verify the effect of a vector potential. (b) Experiment to demonstrate the effect of a scalar…

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from article Aharonov-Bohm effect

Very small ring fabricated from a gold film 38 nm thick. Lines forming the ring are 40 nm wide, and the average diameter is 0.82 μm. The electrical resistance is measured by applying a constant current through two of the leads connecting the sample…

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from article Aharonov-Bohm effect

Resistance oscillations observed in the ring of Fig. 1 at temperature of 0.01 K over a very small magnetic field range. Vertical scale measures deviation ΔR of resistance from its mean value R. The period of the h/e Aharonov-Bohm oscillations in…

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from article Optical fibers

Types of optical fiber designs. (a) Multimode, stepped-refractive-index-profile. (b) Multimode, graded-index-profile. (c) Single-mode, stepped-index. Graded-index is possible. (d) Microstructured optical fiber. (e) Hollow-core fiber for high-power…

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from article Optical fibers

Loss mechanisms in silica-based fibers.

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from article Platinum

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from article Overvoltage

Current density–potential curve.

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from article Overvoltage

Current density curves. (a) Experimental current–potential curve showing theoretical cathodic and anodic components. (b) Tafel plot.

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from article Crosstalk

Crosstalk in a space-division system. Z1, Z2, Z3, and Z4 designate impedances.

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from article Computer-aided circuit design

Four phases in creating a microelectronic chip. (a) Design. (b) Fabrication. (c) Testing. (d) Packaging. (After G. De Micheli, Synthesis and Optimization of Digital Circuits, McGraw-Hill, 1994)

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from article Computer-aided circuit design

Three abstraction levels of a circuit representation. (a) Architectural level. (b) Logic level. (c) Geometrical level. (After G. De Micheli, Synthesis and Optimization of Digital Circuits, McGraw-Hill, 1994)

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from article Radium

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from article Computer security

Applications such as power generation, stock trading, airplane navigation, and medical care have become so dependent on computing that loss of availability becomes a serious threat to life or society. Even on a less dramatic level, people have…

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from article Computer security

Smartphone with fingerprint identification. (Credit: Anatoliy Babiy/Getty Images)

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from article Auger electron spectroscopy

Schematic diagram of an Auger electron being ejected from a carbon atom for a KL2L2 transition. Round forms are electrons.

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from article Auger electron spectroscopy

Integral (upper) and differential (lower) mode spectra of sputter-cleaned copper with the most intense peaks identified: A, M2,3M4,5M4,5; B, L3M4,5M4,5; C, L3M2,3M4,5; D, L3M2,3M2,3.

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from article Intermediate vector boson

Observation of the W particle in the UA1 data from the electron transverse energy distribution. The solid curve is the expected distribution for the decay, W → eν, while the broken curve is the distribution expected for the decay of a different…

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from article Intermediate vector boson

Rates from the L3 experiment at LEP for the process e+e− → Z 0 as a function of total center-of-mass energy of the electron plus positron. The rate is measured as a total cross section. (After O. Adriani et al., Results from the L3 Experiment at…

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from article Palaeonisciformes

Mimia toombsi (Gardiner & Bartram, 1977), Late Devonian, Gogo, Australia. One of the earliest palaeonisciforms, reaching 15 cm (6 in.) long, and known by complete fossils. (Reprinted with permission from B. G. Gardiner, The relationships of the…

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from article Palaeonisciformes

Chirodus granulosus (Young, 1866) was a deep-bodied palaeonisciform that grew to 10 cm (4 in.) and lived in Carboniferous coal swamps of Britain. The teeth formed cutting blades that may have been used to crop vegetation. This reconstruction is…

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from article Electromotive force (cells)

Cross-section diagram of Daniell cell. (After W. J. Moore, Physical Chemistry, 5th ed., Longman, 1974)

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from article Programmable controllers

Functional architecture of a typical high-performance single-chip microcontroller used for control and signal processing. (National Semiconductor Corp.)

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from article Organosilicon compound

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from article Cladoselache

Cladoselache fyleri, from the Upper Devonian of Cleveland. (After S. E. Bendix-Algreen, 1975)

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from article Radiative transfer

Beam of light illuminating a slab of gas of thickness L, shown in cross section.

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from article Radiative transfer

Absorption of radiation in a slab of gas. The solid circles show the amount of radiation reaching each interface if each layer absorbs 50% of the radiation reaching it. The open circles are for 10 layers, each absorbing 25% of the radiation. The…

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from article Radiative transfer