Terahertz field enhancement via coherent superposition of the pulse sequences after a single optical-rectification crystal

Terahertz electromagnetic pulses are frequently generated by optical rectification of femtosecond laser pulses. In many cases, the efficiency of this process is known to saturate with increasing intensity of the generation beam because of two-photon absorption. Here, we demonstrate two routes to reduce this effect in ZnTe(110) crystals and enhance efficiency, namely, by (i) recycling the generation pulses and by (ii) splitting each generation pulse into two pulses before pumping the crystal. In both methods, the second pulse arrives ∼1 ns after the first one, sufficiently long for optically generated carriers to relax. Enhancement is achieved by coherently superimposing the two resulting terahertz fields

An index to assess and monitor the progression of wasting disease in eelgrass Zostera marina

An index based on rapid visual determination of the relative amount of necrotic tissue on eelgrass shoots infected with wasting disease is described. The utility of the index for assessing and monitoring disease levels in natural and experimental populations of eelgrass is illustrated with examples from the field and a mesocosm experiment. Using the Wasting Index, monitoring of the disease along with environmental variables provided correlational data that aided understanding of the disease progression and linked disease severity with salinity. Once salinity increased above a threshold, disease spread rapidly and was inversely correlated with leave are

An index to assess and monitor the progression of wasting disease in eelgrass Zostera marina

An index based on rapid visual determination of the relative amount of necrotic tissue on eelgrass shoots infected with wasting disease is described. The utility of the index for assessing and monitoring disease levels in natural and experimental populations of eelgrass is illustrated with examples from the field and a mesocosm experiment. Using the Wasting Index, monitoring of the disease along with environmental variables provided correlational data that aided understanding of the disease progression and linked disease severity with salinity. Once salinity increased above a threshold, disease spread rapidly and was inversely correlated with leave are

Estimating Potential Ground and Surface Water Pollution from Land Application of Poultry Litter - II

In Arkansas, approximately 1 Tg of poultry (Gallus gallus domesticus) manure and litter is produced annually. These waste products are commonly applied to pastures as a soil amendment or fertilizer, but excessive application rates and poor management practices could result in nutrient contamination of ground and surface water. The purpose of this study was to: (1) assess the nutrient concentrations in poultry manure and (2) evaluate the nitrogen loss from land-applied poultry litter and manure due to ammonia volatilization and denitrification. Analyses for total Kjeldahl nitrogen (TKN), inorganic nitrogen (Ni), phosphorus (P), and potassium (K) were compared in 12 wet and dry hen manure samples. Drying the manure reduced the TKN from 57 to 40 g N/kg on a dry weight basis in wet and dry manure, respectively. The Ni in the manure was in the ammoniacal form with values of 19 and 2 g N/kg for wet and dry manure, respectively. The P and K levels were not influenced by drying the manure and had values of 24 and 21 g/kg, respectively. The results indicate that the nitrogen content of hen manure can be significantly reduced by drying the sample prior to analysis. In a 10-day laboratory study and an 11-day field study to evaluate ammonia volatilization from surface-applied hen manure, results indicated that 37% of the total nitrogen content of the manure was lost. The results indicated that a substantial amount of nitrogen in surface-applied poultry waste can be lost due to ammonia volatilization. Laboratory studies to evaluate denitrification in a Captina silt loam amended with 9 Mg/ha of poultry litter were conducted. When the soil was aerobically incubated for 168 h and then flooded for 66 h, the nitrate-nitrogen level decreased a net of 17 mg N/kg. The results indicated that, if the ammoniacal nitrogen in the litter is oxidized to nitrate under aerobic conditions and then the soil is flooded and available carbon is present, denitrification can occur rapidly. Results from these studies indicate that soil and environmental conditions playa critical role in determining the potential for nitrate pollution of ground and surface water when poultry manure and litter are surface-applied to pastures

Ultrabroadband single-cycle terahertz pulses with peak fields of 300 kV cm−1^{-1} from a metallic spintronic emitter

To explore the capabilities of metallic spintronic thin-film stacks as a source of intense and broadband terahertz electromagnetic fields, we excite a W/CoFeB/Pt trilayer on a large-area glass substrate (diameter of 7.5 cm) by a femtosecond laser pulse (energy 5.5 mJ, duration 40 fs, wavelength 800 nm). After focusing, the emitted terahertz pulse is measured to have a duration of 230 fs, a peak field of 300 kV cm$^{-1}$ and an energy of 5 nJ. In particular, the waveform exhibits a gapless spectrum extending from 1 to 10 THz at 10% of amplitude maximum, thereby facilitating nonlinear control over matter in this difficult-to-reach frequency range and on the sub-picosecond time scale.Comment: 7 pages, 4 figure

Linearisable third order ordinary differential equations and generalised Sundman transformations

We calculate in detail the conditions which allow the most general third order ordinary differential equation to be linearised in X'''(T)=0 under the transformation X(T)=F(x,t), dT=G(x,t)dt. Further generalisations are considered.Comment: 33 page

Review and evaluation of past solar cell development efforts

Bibliography on photovoltaic effect and solar cell developmen

Review and evaluation of past solar cell development efforts Semiannual report, Jun. 1 - Nov. 30, 1967

Historical review of scientific work on photovoltaic effects and on energy conversion devices using this effec