A record current account deficit: causes and implications

The U.S. current account deficit was at a record level in 1999 and is expected to increase further in 2000. How large can this deficit get? Will an eventual adjustment in the deficit place the U.S. economy at risk? This article examines three arguments often put forth to explain the increase in the deficit--a consumption boom, the U.S. as a safe haven for short-term foreign capital and technological change affecting the U.S. economy. The authors find the strongest evidence in support of technological change and suggest why, under these conditions, an economic adjustment to the deficit need not to have as adverse an impact as some observes fear.Deficit financing ; Economic conditions - United States

GINA - A Polarized Neutron Reflectometer at the Budapest Neutron Centre

The setup, capabilities and operation parameters of the neutron reflectometer GINA, the recently installed "Grazing Incidence Neutron Apparatus" at the Budapest Neutron Centre, are introduced. GINA, a dance-floor-type, constant-energy, angle-dispersive reflectometer is equipped with a 2D position-sensitive detector to study specular and off-specular scattering. Wavelength options between 3.2 and 5.7 {\AA} are available for unpolarized and polarized neutrons. Spin polarization and analysis are achieved by magnetized transmission supermirrors and radio-frequency adiabatic spin flippers. As a result of vertical focusing by the five-element (pyrolytic graphite) monochromator the reflected intensity from a 20x20 mm sample has doubled. GINA is dedicated to studies of magnetic films and heterostructures, but unpolarized options for non-magnetic films, membranes and other surfaces are also provided. Shortly after its startup, reflectivity values as low as 3x10-5 have been measured on the instrument. The facility is now open for the international user community, but its development is continuing mainly to establish new sample environment options, the spin analysis of off-specularly scattered radiation and further decrease of the background

Organic fluorine as a polypeptide building element: in vivo expression of fluorinated peptides, proteins and proteomes

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Traditionally, the biological fluorination of complex biological systems like proteins is achieved through substitution of canonical amino acids or addition of fluorinated amino acids in the context of the standard genetic code. Ribosomal translation of monofluorinated amino acids into proteins often yields structures with minimal local changes in the interior but, on the same time, results in large global effects on characteristic features of the biopolymers (such as dramatically changed activity profile or folding stability). This is due to the novel and unique local interactions delivered by fluorine atoms such as (i) increase in the covalent radii (ii) changed polarities; (iii) changed hydrogen bond acceptor ability; (iv) altered water solubility as well as water ↔ organic solvent energy transfer. On the other hand, the biological incorporation of tri- or global fluorinated amino acids (such as trifluoroleucine, triflurovaline, and their hexafluoro counterparts, fluoromethionine and trifluoronorleucine etc.) represents still a challenge, as the natural structural scaffolds are optimized for hydrocarbon during evolution but not for fluorocarbon cores. Future work will be focused on the re-design of existing or de novo design of novel protein scaffolds capable of accommodating such building blocks into functional biologically active proteins and proteomes in the context of the viable cells

Masked millennial-scale climate variations in South West Africa during the last glaciation

To address the connection between tropical African vegetation development and high-latitude climate change we present a high-resolution pollen record from ODP Site 1078 (off Angola) covering the period 50–10 ka BP. Although several tropical African vegetation and climate reconstructions indicate an impact of Heinrich Stadials (HSs) in Southern Hemisphere Africa, our vegetation record shows no response. Model simulations conducted with an Earth System Model of Intermediate Complexity including a dynamical vegetation component provide one possible explanation. Because both precipitation and evaporation increased during HSs and their effects nearly cancelled each other, there was a negligible change in moisture supply. Consequently, the resulting climatic response to HSs might have been too weak to noticeably affect the vegetation composition in the study area. Our results also show that the response to HSs in southern tropical Africa neither equals nor mirrors the response to abrupt climate change in northern Africa

Generation of Arbitrary Frequency Chirps with a Fiber-Based Phase Modulator and Self-Injection-Locked Diode Laser

We present a novel technique for producing pulses of laser light whose frequency is arbitrarily chirped. The output from a diode laser is sent through a fiber-optical delay line containing a fiber-based electro-optical phase modulator. Upon emerging from the fiber, the phase-modulated pulse is used to injection-lock the laser and the process is repeated. Large phase modulations are realized by multiple passes through the loop while the high optical power is maintained by self-injection-locking after each pass. Arbitrary chirps are produced by driving the modulator with an arbitrary waveform generator