Channeling of Charged Particles Through Periodically Bent Crystals: on the Possibility of a Gamma Laser

We discuss radiation generated by positrons channeling in a crystalline undulator. The undulator is produced by periodically bending a single crystal with an amplitude much larger than the interplanar spacing. Different approaches for bending the crystal are described and the restrictions on the parameters of the bending are established. We present the results of numeric calculations of the spectral distributions of the spontaneous emitted radiation and estimate the conditions for stimulated emission. Our investigations show that the proposed mechanism provides an efficient source for high energy photons, which is worth to be studied experimentally.Comment: contributed to the conference ``Fundamental and Applied Aspects of Modern Physics'' in Luederitz, Namibia, 200

ACREAGE RESPONSES TO EXPECTED REVENUES AND PRICE RISK FOR MINOR OILSEEDS AND PROGRAM CROPS IN THE NORTHERN PLAINS

Wheat, barely, flaxseed, and oilseed sunflower acreage respond to different economic variables. Wheat and barely acreage must be divided among program-complying, program-planted, and nonprogram-planted acreage because these categories respond to different variables and respond to own expected-revenue and price-risk variables in opposite ways. Flaxseed, sunflower, and nonprogram-planted acreage of wheat and barley have highly significant, positive responses to their own expected revenue and negative responses to their own-price risk. Flaxseed and sunflower acreage have been more responsive to their lagged values than to expected revenues for wheat.Crop Production/Industries,

An engineering feasibility study of an orbiting scanning radiometer

Engineering feasibility study of lunar orbiting optical scanning radiometer

Anatomy of relativistic pion loop corrections to the electromagnetic nucleon coupling

We present a relativistic formulation of pion loop corrections to the coupling of photons with nucleons on the light front. Vertex and wave function renormalization constants are computed to lowest order in the pion field, including their nonanalytic behavior in the chiral limit, and studied numerically as a function of the ultraviolet cutoff. Particular care is taken to explicitly verify gauge invariance and Ward-Takahashi identity constraints to all orders in the mπ expansion. The results are used to compute the chiral corrections to matrix elements of local operators, related to moments of deep-inelastic structure functions. Finally, comparison of results for pseudovector and pseudoscalar coupling allows the resolution of a longstanding puzzle in the computation of pion cloud corrections to structure function moments.Chueng-Ryong Ji, W. Melnitchouk, and A.W. Thoma

WORLD FEED BARLEY TRADE UNDER ALTERNATIVE TRADE POLICY SCENARIOS

A spatial equilibrium model based on a quadratic programming algorithm was developed to analyze world feed barley trade and international competition among major exporters (Australia, Canada, the European Union, and the United States) under the current and alternative trade policy scenarios. The U.S. Export Enhancement Program (EEP) plays an important role to maintain U.S. market share in importing countries. Eliminating Canadian rail subsidy decreases Canadian offshore exports, but greatly increases its exports to the United States. The North American Free Trade Agreement (NAFTA) increases feed barley trade within North America, but has little impact on world trade flows for feed barley. Canada benefits most under the Uruguay Round Agreement of GATT and the world free trade through significantly higher exports to offshore markets and the United States. Australia also gains from free trade. The European Union is worse off under free trade.feed barley, international grain trade, trade policy, spatial equilibrium model, International Relations/Trade,

PROGRAM AND NONPROGRAM WHEAT ACREAGE RESPONSES TO PRICES AND RISK

Wheat acreage responses to expected wheat price and price risk are reversed for program and nonprogram-planted acreage in the northern plains, central plains, southern plains, and U.S. Expected wheat price has a strong negative effect on program-complying wheat acreage. Government support prices have a positive effect on program-complying and program-planted acreage. Price risk has a positive effect on program-complying wheat acreage and a negative effect on nonprogram-planted acreage. Estimated price elasticities are higher than in studies where risk was ignored.Demand and Price Analysis, Risk and Uncertainty,

Kaonic hydrogen and K^- p scattering

Chiral SU(3) effective field theory in combination with a relativistic coupled channels approach is used to perform a novel analysis of the strong interaction shift and width in kaonic hydrogen in view of the new accurate DEAR measurements. Questions of consistency with previous K^- p data are examined. Coulomb and isospin breaking effects turn out to be important and are both taken into account in this work.Comment: 4 pages, 4 figure

Scanning Photo-Induced Impedance Microscopy - Resolution studies and polymer characterization

Scanning Photo-Induced Impedance Microscopy (SPIM) is an impedance imaging technique that is based on photocurrent measurements at field-effect structures. The material under investigation is deposited onto a semiconductor-insulator substrate. A thin metal film or an electrolyte solution with an immersed electrode serves as the gate contact. A modulated light beam focused into the space charge region of the semiconductor produces a photocurrent, which is directly related to the local impedance of the material. The absolute impedance of a polymer film can be measured by calibrating photocurrents using a known impedance in series with the sample. Depending on the wavelength of light used, charge carriers are not only generated in the focus but also throughout the bulk of the semiconductor. This can have adverse effects on the lateral resolution. Two-photon experiments were carried out to confine charge carrier generation to the spacecharge layer. The lateral resolution of SPIM is also limited by the lateral diffusion of charge carriers in the semiconductor. This problem can be solved by using thin silicon layers as semiconductor substrates. A resolution of better than 1 mu m was achieved using silicon on sapphire (SOS) substrates with a I l.Lm thick silicon layer

Pregnancy-associated breast cancer - Special features in diagnosis and treatment

For obvious psychological reasons it is difficult to associate pregnancy - a life-giving period of our existence with life-threatening malignancies. Symptoms pointing to malignancy are often ignored by both patients and physicians, and this, together with the greater difficulty of diagnostic imaging, probably results in the proven delay in the detection of breast cancers during pregnancy. The diagnosis and treatment of breast cancer are becoming more and more important, as the fulfillment of the desire to have children is increasingly postponed until a later age associated with a higher risk of carcinoma, and improved cure rates of solid tumors no longer exclude subsequent pregnancies. The following article summarizes the special features of the diagnosis and primary therapy of pregnancy-associated breast cancer with particular consideration of cytostatic therapy