In their 1946 letter, Felix Bloch, William Webster Hansen, and Martin Packard reported water at room temperature. A steady magnetic field along $z$ and an oscillating field along $x$ produced a signal in a pickup coil along $y$, displayed on an oscilloscope. Some samples included paramagnetic additives to accelerate thermal equilibrium. Resonance fields at two frequencies gave the same field-to-frequency ratio, consistent with the proton value.^[ref]

The detailed paper describes glass water bulbs inside tuned receiving coils. Transmitter coils, shields and a conducting paddle controlled leakage. Field modulation at 60 Hz drove the horizontal oscilloscope sweep. A diode and audio amplification supplied the vertical trace. Vibration changed coupling: their largest difficulty. Coil tuning capacitors formed tank circuits. The actual receiver omitted the conceptual diagram's radiofrequency amplifier.^[ref]

The orthogonal coil axes suppress direct transmitter pickup, but do not eliminate it. A field-dependent signal at the nuclear resonance must be distinguished from leakage and noise; merely detecting a radiofrequency voltage is insufficient. This is why the field sweep and the independently checked field-to-frequency ratio matter.

The molecular mass is the mass of a molecule; relative molecular mass compares it with a reference mass.

A colloid contains dispersed particles in a continuous medium. A fine particle suspension can form a colloid; the particles in the Perrin sedimentation experiment illustrate this case.

A unit of measurement is a chosen reference for comparing magnitudes of a physical quantity. A value written as a number times a measurement unit changes its numerical part when the measurement unit changes, while representing the same physical quantity.

Measurement resolution is the smallest change in an instrument indication that its reading method can distinguish. It contributes to measurement uncertainty, but does not by itself establish accuracy or remove systematic error. The manometer height-to-pressure calibration shows how a height scale affects the inferred pressure.

Measurement of length and geometrical dimensions. A length standard supplies a reference; a differential length comparator measures the difference between two lengths rather than treating its own structure as perfectly invariant.

An infinite conducting cylinder of radius $a$ at centre height $d>a$ above a grounded plane has the same exterior electric potential as opposite line charges $\pm \lambda$ at heights $\pm c$. If $R_{+}$ and $R_{-}$ are distances from the positive and negative lines, $V=\lambda \ln (R_{-}/R_{+})/(2\pi {\epsilon }_0)$. The plane has $R_{-}=R_{+}$; the cylinder has $R_{-}/R_{+}=(d+c)/a$. Its voltage is therefore $\lambda \mathrm{arcosh}(d/a)/(2\pi {\epsilon }_0)$, giving the displayed capacitance per unit length. The Uniqueness of the Dirichlet problem fixes the exterior field. A Gaussian contour surrounding the cylinder encloses the positive image line, so $\lambda$ is also its physical charge per unit length.

For $b>0$, the Poisson equation $\Delta V=q{\delta }^{(2)}(x,y)$ in $-b<x<b$ with homogeneous Neumann boundary conditions on both edges admits the even-in-$y$ method of images solution in the title, where $r_n^2=(x-2nb{)}^2+y^2$. All image strengths are $q$. Pairing the images at $\pm 2nb$ and subtracting their constant logarithms makes each summand $O(n^{-2})$, giving local uniform convergence away from the source. The unrenormalized sum of logarithms does not converge.

Differentiating givesThe corresponding $x$-derivatives cancel in reflected pairs on $x=\pm b$. For $y>0$, integration across the strip yields a telescoping arctangent sum:One closed form, up to an additive constant, is $V=(q/4\pi )\log [\cosh (\pi y/b)-\cos (\pi x/b)]$. Its near-source logarithmic singularity has coefficient $q/(2\pi )$. Conditions at large $|y|$ or a symmetry class must be specified for a uniqueness claim; side Neumann boundary conditions alone allow additional homogeneous harmonic functions.

A device that regulates a fluid flow by opening, closing or restricting a passage.

A gasket is a deformable component that closes a leakage path between contacting surfaces. In a diamond anvil cell, its hole also confines the sample laterally.

By Georges Matheron. Economic Geology 58(8), 1246–1266; published 1 December 1963. DOI 10.2113/gsecongeo.58.8.1246.

Cited passages: p. 1246, abstract and introduction, on mining estimation. Primary text was inspected through a scan mirror; the mirror is not the author or publisher.

By Skip Thompson. Scholarpedia 2(3):2367, 2007; DOI 10.4249/scholarpedia.2367. Publication year is distinguished from later online revisions.

Cited passages: opening definition and equation (1); Initial History Function; Derivative Discontinuities. Relevant text was inspected through indexed Scholarpedia results when the direct page was unavailable.

By Paul Lévy. Compositio Mathematica 7, 283–339; Numdam catalogs the volume as 1940. Received 29 March 1939 (p. 339).

Digitized paper: www.numdam.org/article/CM_1940__7__283_0.pdf

Cited passage: §5, pp. 301–302, especially the circle-projection paragraph on p. 302.

By Scott Kirkpatrick, Charles Daniel Gelatt Jr. and Mario P. Vecchi. Science 220(4598), 671–680 (13 May 1983).

DOI: doi.org/10.1126/science.220.4598.671

Inspected scan: hedibert.org/wp-content/uploads/2013/12/1983KirkpatrickGelattVecchi.pdf

Cited passages: pp. 672–673 and 675.