April

About: April is a based out in . It is known for research contribution in the topics: Population & Competence (human resources). The organization has 1424 authors who have published 1085 publications receiving 28875 citations. The organization is also known as: Apr & 4. month.

Molecular Structure of Nucleic Acids: A Structure for Deoxyribose Nucleic Acid

Abstract: The determination in 1953 of the structure of deoxyribonucleic acid (DNA), with its two entwined helices and paired organic bases, was a tour de force in X-ray crystallography. But more significantly, it also opened the way for a deeper understanding of perhaps the most important biological process. In the words of Watson and Crick: "It has not escaped our notice that the specific pairing that we have postulated immediately suggests a possible copying mechanism for the genetic material." [Obituary of Francis Crick:

The Infrared Array Camera (IRAC) for the Spitzer Space Telescope

Abstract: The Infrared Array Camera (IRAC) is one of three focal plane instruments on the Spitzer Space Telescope. IRAC is a four-channel camera that obtains simultaneous broadband images at 3.6, 4.5, 5.8, and 8.0 � m. Two nearly adjacent 5A2 ; 5A2 fields of view in the focal plane are viewed by the four channels in pairs (3.6 and 5.8 � m; 4.5 and 8 � m). All four detector arrays in the camera are 256 ; 256 pixels in size, with the two shorter wavelength channels using InSb and the two longer wavelength channels using Si:As IBC detectors. IRAC is a powerful survey instrument because of its high sensitivity, large field of view, and four-color imaging. This paper summarizes the in-flight scientific, technical, and operational performance of IRAC.

Business Models for Electronic Markets

Abstract: Electronic commerce over the Internet may be either complementary to traditional business or represent a whole new line of the new features of the Internet, critical questions to be answered include: ♦ what are the emerging business models; and related to this ♦ which strategic marketing approaches are applied, or emerging. This article addresses the first question above by providing a framework for the classification of Internet electronic commerce business models. This framework has been developed on the basis of current commercial Internet business and experimental work in European R&D programmes.

Body fluid flow control device

Abstract: A device to provide body fluid flow control in the form of a valve to be located within a duct or passageway. The device is controlled through pressure above a preselected threshold. Bulk resilience about a passageway in a valve body provides the mechanism for controlled flow. One-way valve operation may be provided through a flap or through a pressure differential on the valve body depending upon the direction of flow. A frame structure positioned within a resilient seal includes longitudinally elongate elements which may be of spring material, malleable material or heat recoverable material so as to accomplish an initial insertion state and an expanded anchoring state. A valve support transitions between the resilient seal portion and the valve body to insure that the states do not change the threshold opening pressure. Insertion devices may be employed to position and actuate a change of state of the frame in the body duct or passageway.

Transition from the tunneling regime to point contact studied using scanning tunneling microscopy

Abstract: Using scanning tunneling microscopy, we have studied local surface modifications induced by point contact of a tunnel tip with metallic surfaces. Two distinct types of topographical modification are found which correlate directly with the chemical condition of the tip as determined by tunneling spectroscopy. Observation of the dynamics of the transition from the tunneling regime to contact permits an evaluation of the gap distance prior to point contact. At gap spacings of s\ensuremath{\lesssim}3 A\r{} a significant decrease in the apparent tunnel barrier height is observed just before touching. Contact was found to initiate with the intimate contact of several atoms only. The implications of these results for lithography on a nanometer scale, and on the investigation of the mechanical properties of surfaces over ranges of a few nanometers are discussed.