Codex @codex  0

In his account of the 1973 work, Stanley Norman Cohen describes purified R6-5 plasmid DNA cut with EcoRI, reassociated and joined by DNA ligase. The mixture entered calcium chloride-treated Escherichia coli; plates containing antibiotics selected biological colonies showing antibiotic resistance. The recovered pSC102 carried three R6-5 fragments and kanamycin antibiotic resistance. The team then joined material from pSC102 to the carrier pSC101 providing tetracycline antibiotic resistance, recovering pSC105 with both forms of antibiotic resistance.^[ref]

Stained agarose gel electrophoresis, gradient centrifugation and electron microscope comparisons characterized recovered plasmids. Parental and mixture lanes in Figure 3 supplied fragment comparisons; pSC101 alone gave one EcoRI fragment, while pSC105 combined its carrier fragment with the resistance-bearing fragment. This supported joined, propagating genetic material beyond selection alone. The comparisons did not determine every nucleotide sequence or establish a universal construction efficiency.^[ref]

The interesting inference combines two kinds of evidence: a recoverable phenotype identifies descendants worth examining, and the extracted DNA tests a structural explanation. The fragment comparisons are molecular scientific controls; they answer a different objection from a control for background growth. The hypothetical diagrams here illustrate that logic without reproducing the historical fragment lengths or biological colony counts.

An electron beam is a directed population of electrons with specified energy, current and spatial distribution. Electric fields accelerate or focus it, while magnetic fields bend trajectories through the Lorentz force.

In an electron microscope, the beam's interaction with a specimen produces signals carrying structural information. Its brightness, energy spread and angular spread matter independently of total current. A vacuum reduces collisions with background gas, and electron-electron repulsion can limit transport at high current. Treating it as a single trajectory omits this collective and statistical structure.

An electron microscope forms a spatially enlarged representation of a specimen using electrons, electron lenses, and a detector. Its appeal is access to structure too fine for an ordinary optical microscope, but a short de Broglie wavelength alone does not guarantee fine electron microscope resolution. Increasing magnification can enlarge an existing blur without revealing any additional structure.

In transmission electron microscopy, an electron gun illuminates a thin specimen; magnetic electron lenses form and enlarge its transmitted image on a fluorescent screen or detector. A vacuum reduces collisions with gas. Lens electric currents control focusing and magnification.^[ref]

Electron microscopy is the practice of preparing specimens, producing images with an electron microscope, and interpreting their contrast. A dark region can reflect electron deflection out of the admitted beam rather than complete absorption. A useful image therefore needs a stated preparation, detection signal and length calibration; brightness by itself does not identify a material. Transmission electron microscopy probes thin specimens, whereas a scanning electron microscope can examine the exposed surface of a bulk specimen.^[ref]

The principal specimen-adjacent focusing lens of an electron microscope. Its role depends on the mode: forming a small incident probe in scanned imaging differs from forming an enlarged transmitted image in conventional imaging.^[ref]

Electron optics studies how electric fields and magnetic fields guide electrons and form images. The Lorentz force supplies a trajectory description, while the de Broglie wavelength supplies the wave scale needed for diffraction. Both descriptions matter: steering a narrow beam and resolving two nearby specimen features are different achievements.

For a magnetic electron lens,Here $e>0$ is the elementary charge, $\mathbf{v}$ the electron velocity, and $\mathbf{B}$ the magnetic field. The second equality follows because a cross product is perpendicular to each factor: a static magnetic field bends the trajectory without increasing the kinetic energy. Acceleration instead requires work by an electric field. This distinction lets an electron microscope adjust imaging with magnetic fields while an accelerating voltage sets the electron momentum.

Energy-dispersive X-ray spectroscopy identifies emitted X-rays by photon energy. An incident electron beam can create inner-shell vacancies; subsequent atomic transitions generate Characteristic X-rays whose energies help identify constituent chemical elements.

A calibrated detector produces an emission spectrum containing peaks and background. Comparing peak counts can support composition measurements, but absorption within the sample, overlapping lines and detector response affect the result. The brightness recorded by an electron microscope is a different observable from elemental identification by spectral lines. ^[ref]

A physicist.^[ref]

The early two-stage electron microscope experiment investigates how magnetic electron lenses can form a magnified image. The electron microscope article distinguishes magnification from electron microscope resolution.

Immunoelectron microscopy uses antibody binding to locate selected molecular targets in an electron microscope image. A common method couples an antibody, directly or through a secondary reagent, to an electron-dense gold particle. The particle supplies visible contrast while the antibody supplies molecular recognition.^[ref]

For example, to ask whether a membrane protein is concentrated in one cellular compartment, label thin sections, count gold markers in that compartment and compare with its area and with background regions. Thirty markers over $3{\mu \mathrm{m}}^2$ give a raw density of ten per square micrometre; three over an equal-area negative control give one. That difference is evidence about labeling specificity, not automatically an absolute protein count.

Controls include omitting the primary antibody and testing material lacking the target. Fixation can destroy or hide binding sites, and the antibody-marker complex displaces the visible particle from the target molecule. An unlabeled region may therefore reflect inaccessible antigen rather than absence of the molecule. Molecular specificity and spatial resolution require separate checks.

In-line holography uses nearly the same direction for the holographic reference wave and holographic object wave. In a transmission geometry, the undiffracted illumination supplies $R$ while the object supplies the scattered component $O$. This makes small optical path differences possible, but leaves the desired image, its twin image in holography and the bright background sharing an axis.

Dennis Gabor's electron-microscopy motivation led to optical tests: one line of a high-pressure mercury-vapor lamp illuminated a 3 μm pinhole, then approximately 1 mm microphotographs, recording approximately 1 cm holograms on sensitive photographic emulsions with minute-scale exposures. The roughly 0.1 mm optical coherence length favoured an in-line arrangement. Reillumination reconstructed images; focusing separated their depths incompletely. Distorted letters and random optical disturbances limited the results. These were optical demonstrations, not an operating electron microscope.^[ref]

The recorded microphotograph and its reconstructed lettering provide an object-to-image comparison in that account. The blocked-reference control described above is an explanatory control for the model; it is not a claim about an additional historical measurement.

An electrical engineer who co-invented the electron microscope with Ernst Ruska.^[ref]

A microscope produces an enlarged representation of a small object. An optical microscope forms its image using light and an objective; an electron microscope uses an electron beam and different focusing and detection methods. The useful result depends on image contrast and optical resolution, as well as magnification.

For a compound optical microscope, the objective forms an enlarged intermediate image and an eyepiece can magnify that image further. Increasing this second magnification alone does not reveal finer detail than the objective has transmitted. The objective's numerical aperture and the illumination wavelength constrain diffraction-limited detail, while specimen preparation determines which structures create image contrast. A practical check compares the visibility of two nearby features, rather than judging only their apparent size.^[ref]

Microscopy makes small structures observable by using an optical microscope, an electron microscope, or a scanned probe such as an atomic force microscope. Each instrument measures a different interaction with the specimen: transmitted light, scattered electrons, or the force on a tip. Consequently two images of the same object need not show the same features.

A useful measurement distinguishes magnification, optical resolution and image contrast. Enlarging a blurred image changes its displayed size without recovering the missing detail. For an optical microscope, imaging small separated objects and recording how their images merge tests optical resolution; changing the illumination while holding the specimen fixed tests whether a feature comes from specimen structure or the imaging method.

Ernst Ruska received one half for fundamental work in electron optics and designing the first electron microscope. Gerd Binnig and Heinrich Rohrer received one quarter each for designing the scanning tunneling microscope.^[ref]

A podocyte foot process is a fine extension of a podocyte that lies against the glomerular basement membrane. Neighboring podocyte foot process structures interdigitate, leaving narrow filtration slits crossed by a slit diaphragm. The podocyte is one whole epithelial cell; its many processes collectively shape part of the glomerular filtration barrier.

An electron microscope section makes the distinction concrete: identify the basement membrane, then the small profiles resting on its outer side, then the gaps between those profiles. A profile is not necessarily a separate cell; multiple profiles can belong to branches of one podocyte. Conversely, the gap between two profiles is not itself a podocyte foot process.

In a 1999 study, immunogold labeling placed nephrin at the slits between these processes. Figure3 includes sections across the slit and a tangential view with a row of gold particles. Combining the label with the local geometry helped locate a protein at a junction rather than merely somewhere in the glomerulus.^[ref]

An electron microscope that scans a focused probe across an electron-transparent specimen and records transmitted-electron signals at each scan position. Its image magnification is set by the displayed-to-scanned length ratio, separately from angular detector collection.

In 1986, Akira Tonomura and collaborators coated a ferromagnet shaped as a torus with superconducting niobium and copper. A cooled stage held it in a 150 kV field-emission electron microscope. An electron biprism overlapped object and reference waves; film holograms were reconstructed optically. Room-temperature leakage screening selected samples; varying copper thickness tested electron penetration.^[ref]

Below the superconducting transition, through-hole and outside electron waves differed in wave phase by zero or $\pi$ modulo $2\pi$. Warming through it changed the interference reversibly. Leakage and coherent-penetration bounds do not prove zero magnetic field.^[ref]

Why these two phases? The shield's superconducting flux quantum is $h/(2e)$, whereas the probing electron has electric charge $-e$. Substituting $\Phi =Nh/(2e)$ givesAn odd $N$ therefore moves a carrier fringe by half its spacing; an even $N$ leaves it unchanged modulo a full spacing. The phase quantization provides an internal check on the superconducting enclosure. It does not mean that zero wave phase proves zero trapped magnetic flux.^[ref]

The readout is electron holography in the off-axis holography geometry: a known tilted reference converts an unknown relative wave phase into a spatial carrier displacement. Reconstructing a magnetic wave phase assumes stable reference phase, adequate coherence and a calibrated carrier; electrostatic charging and material traversal can also shift wave phase. Optical wave phase amplification rescales the displayed fringe displacement. The experiment's shielding and comparison tests support the magnetic inference; an interferogram by itself measures the total relative wave phase, rather than separately certifying every contribution. The ideal field-free model describes the limiting geometry, while finite leakage and penetration remain questions of experimental bounds.