Fourier Transforms of Lorentz Invariant Functions

Fourier transforms of Lorentz invariant functions in Minkowski space, with support on both the timelike and the spacelike domains are performed by means of direct integration. The cases of 1+1 and 1+2 dimensions are worked out in detail, and the results for 1+n dimensions are given.Comment: 15 pages, 1 figur

Sorghum Ergot: New Disease Threat to the Sorghum Industry

2 pp., 1 color photoSorghum ergot is caused by a fungus that infects the ovaries of sorghum flowers, converting each into a white fungal mass. First discovered in Texas in March 1997, the fungus can produce large amounts of honeydew that interferes with harvest and supports soprophytic fungal growth

Coherence of femtosecond single electrons exceeds biomolecular dimensions

Time-resolved diffraction and microscopy with femtosecond electron pulses provide four-dimensional recordings of atomic motion in space and time. However, the limited coherence of electron pulses, reported in the range of 2–3 nm, has so far prevented the study of complex organic molecules with relevance to chemistry and biology. Here we characterize the coherence of femtosecond single-electron pulses that are generated by laser photoemission. We show how the absence of space charge and the minimization of the source size allow the transverse coherence to be extended to 20 nm at the sample position while maintaining a useful beam diameter. The extraordinary coherence is experimentally demonstrated by recording singleelectron diffraction snapshots from a complex organic molecular crystal and identifying more than 80 sharp Bragg reflections. Further optimization affords promise for coherences of 100 nm. These advances will allow time-resolved imaging of functional dynamics in biological systems, uniting picometre and femtosecond resolutions in a compact, table-top instrumentation.publishe

Take-All Root Rot of Turfgrass

2 pp., 2 color photosTake-all root rot (patch) is a serious disease caused by a soil-borne fungus. This leaflet covers symptoms and diagnosis, disease cycle, cultural disease management and fungicides

Picosecond imaging of low-density plasmas by electron deflectometry

We have imaged optical-field ionized plasmas with electron densities as low as 1013 cm−3 on a picosecond timescale using ultrashort electron pulses. Electric fields generated by the separation of charges are imprinted on a 20 keV probe electron pulse and reveal a cloud of electrons expanding away from a positively charged plasma core. Our method allows for a direct measurement of the electron energy required to escape the plasma and the total charge. Simulations reproduce the main features of the experiment and allow determination of the energy of the electrons

Relativistic Doppler effect: universal spectra and zeptosecond pulses

We report on a numerical observation of the train of zeptosecond pulses produced by reflection of a relativistically intense femtosecond laser pulse from the oscillating boundary of an overdense plasma because of the Doppler effect. These pulses promise to become a unique experimental and technological tool since their length is of the order of the Bohr radius and the intensity is extremely high $\propto 10^{19}$ W/cm$^2$. We present the physical mechanism, analytical theory, and direct particle-in-cell simulations. We show that the harmonic spectrum is universal: the intensity of $n$th harmonic scales as $1/n^{p}$ for $n < 4\gamma^2$, where $\gamma$ is the largest $\gamma$--factor of the electron fluid boundary, $p=3$ and $p=5/2$ for the broadband and quasimonochromatic laser pulses respectively.Comment: 4 figure

Sorghum Ergot: New Disease Threat to the Sorghum Industry

2 pp., 1 color photoSorghum ergot is caused by a fungus that infects the ovaries of sorghum flowers, converting each into a white fungal mass. First discovered in Texas in March 1997, the fungus can produce large amounts of honeydew that interferes with harvest and supports soprophytic fungal growth