Relativistic particle motion in nonuniform electromagnetic waves

A charged particle moving in a strong nonuniform electromagnetic wave which suffers a net acceleration in the direction of the negative intensity gradient of the wave was investigated. Electrons will be expelled perpendicularly from narrow laser beams and various instabilities result

175 GHz, 400-fs-pulse harmonically mode-locked surface emitting semiconductor laser

We report a harmonically mode-locked vertical external cavity surface emitting laser (VECSEL) producing 400 fs pulses at a repetition frequency of 175 GHz with an average output power of 300 mW. Harmonic mode-locking was established using a 300 µm thick intracavity single crystal diamond heat spreader in thermal contact with the front surface of the gain sample using liquid capillary bonding. The repetition frequency was set by the diamond microcavity and stable harmonic mode locking was achieved when the laser cavity length was tuned so that the laser operated on the 117th harmonic of the fundamental cavity. When an etalon placed intracavity next to the gain sample, but not in thermal contact was used pulse groups were observed. These contained 300 fs pulses with a spacing of 5.9 ps. We conclude that to achieve stable harmonic mode locking at repetition frequencies in the 100s of GHz range in a VECSEL there is a threshold pulse energy above which harmonic mode locking is achieved and below which groups of pulses are observed

Do Firms Smooth the Seasonal in Production in a Boom? Theory and Evidence

Using disaggregated production data we show that the size of seasonal cycles changes significantly over the course of the business cycle. In particular, during periods of high economy-wide activity, some industries smooth seasonal fluctuations while others exaggerate them. We interpret this finding using a simple analytical model that describes the conditions under which seasonal and cyclical fluctuations can be separated. Our model implies that seasonal fluctuations can safely be disentangled from cyclical fluctuations only when the marginal cost of production is linear, and the variation in demand and cost satisfy certain (restrictive) conditions. The model also suggests that inventory movements can be used to isolate the role of demand shifts in generating any interaction between seasonal cycles and business cycles. Thus, the empirical analysis involves studying the variation in seasonally unadjusted patterns of production and inventory accumulation over different phases of the business cycle. Our finding that seasonals shrink during booms and that firms carry more inventories into high sales seasons during a boom leads us to conclude that for several industries, marginal cost slopes up at an increasing rate. Conversely, in a couple of industries we find that seasonal swings in production are exaggerated during booms and that inventories are drawn down prior to high sales seasons, suggesting that marginal costs curves flatten as production increases. Overall, we find considerable evidence that there are non-linear interactions between business cycles and seasonal cycles.

Development of high-emittance scales on thoriated nickel-chromium-aluminum-base alloys

The surface regions of a DSNiCrAl alloy have been doped, by a pack diffusion process, with small amounts of Mn, Fe, or Co, and the effect of these dopants on the total normal emissivity of the scales produced by subsequent high temperature oxidation has been measured. While all three elements lead to a modest increase in emissivity, (up to 23% greater than the undoped alloy) only the change caused by manganese is thermally stable. However, this increased emissivity is within 85 percent of that of TDNiCr oxidized to form a chromia scale. The maganese-doped alloy is some 50 percent weaker than undoped DSNiCrAl after the doping treatment, and approximately 30 percent weaker after oxidation

Chaucer and the politics of penance

Chaucer and the Politics of Penance argues for a Chaucerian fusion of penitential values with Wycliffite ideals in the 1390s. The historical setting for this study is the political crisis of 1388 and the political agenda that Richard II employs in the 1390s in an attempt to reassert an image of royal legitimacy and power. The case is made that Chaucer critiques Ricardian autocracy by employing penitential discourse as a possible corrective to Richard\u27s exemplarism or use of positive exempla to suppress political dissent. Chaucer is joined in this emphasis on the politics of penance by the Carmelite Richard Maidstone whose 1390s account of Richard II\u27s London re-entry pageant similarly employs penance to warn the king of the dangers inherent to exemplary politics or a political program that exaggerates the king\u27s virtues. In Chaucer\u27s Legend of Good Women penitential values merge with Lollard translation values to produce Chaucer\u27s concept of the naked text, a literary program that imagines how penance and heresy might be used to invent English as a literary language. This program finds further expression in Chaucer Canterbury Tales where the figure of the Parson combines Lollardy with penance to hopefully release Chaucer from both orthodox and heretical ideologies to pursue a literature of penitential humility and heretical independence

Studies in the mulga pastoral zone. 2. Some aspects of the value of the mulga scrub

THE mulga pastoral zone is so named since most of its area is dominated by Mulga (Acacia aneura). The mulga is found associated with shrubs and grasses in almost all plant habitats. In its various forms it can associate with spinifex (Triodia basedowi), Wandarrie Grasses (Danthonia, Eragostis and Eriachne spp.) and with low shrubs on flood plains, hills and breakaways. It may even attempt to become established in salty communities, though this is never completely successful. The scene the area offers from its low hills is one of a succession of low undulations, occasionally scarred by creeks or breakaways and completely dominated by the dull green or blue grey overmantle of the mulga tree

Range evaluation using aerial photography

The Department of Agriculture, in association with the University of Western Australia, recently undertook a study of the application of aerial photography to range condition monitoring in three rangeland types in the mulga zone of Western Australia. The project was financed by the Rural Credits Development Fund and the C.S.l.R.O. Rangelands Research Unit. This article deals in a general way with the possible use of aerial photography in rangeland administration