3,162 research outputs found
Wolter Optics for Neutron Focusing
Focusing optics based on Wolter optical geometries developed for x-ray grazing incidence beams can be designed for neutron beams. Wolter optics are formed by grazing incidence reflections from two concentric conic sections (for example, a paraboloid and a hyperboloid). This has transformed observational X-ray astronomy by increasing the sensitivity by many orders of magnitude for research in astrophysics and cosmology. To increase the collection area, many reflecting mirrors of different diameters are nested with a common focal plane. These mirrors are fabricated using nickel-electroformed replication techniques. We apply these ideas to neutron focusing using nickel mirrors. We show an initial test of a conical mirror using a beam of cold neutrons. key words: electroformed nickel replication, focusing optics, grazing angle incidence, mirror reflection, neutron focusing, Wolter optic
Grazing-Incidence Neutron Optics based on Wolter Geometries
The feasibility of grazing-incidence neutron imaging optics based on the Wolter geometries have been successfully demonstrated. Biological microscopy, neutron radiography, medical imaging, neutron crystallography and boron neutron capture therapy would benefit from high resolution focusing neutron optics. Two bounce optics can also be used to focus neutrons in SANS experiments. Here, the use of the optics would result in lower values of obtainable scattering angles. The high efficiency of the optics permits a decrease in the minimum scattering vector without lowering the neutron intensity on sample. In this application, a significant advantage of the reflective optics over refractive optics is that the focus is independent of wavelength, so that the technique can be applied to polychromatic beams at pulsed neutron sources
Zwitterion Structure in Some 1-Carboxymethylimidazoles and Their Analgetic Activity
The ratio (R) of zwitterions to neutral molecule was determined
for the derivatives of 1-carboxymethylimidazole. 1-Carboxymethylimidazole (I) and its 2-methyl derivate (III) were found
to be entirely in the form of zwitterion. Of the two 1-carboxymethyl-
2-methyl-nitroimidazoles (V and VII) the 4-nitroisomer (V)
possesses no zwitterionic structure, but the 5-nitroisomer (VII) was
found to be about 65Q/o in the zwitterionic form. The results obtained
are discussed in view of the significant analgetic and sedative
effect observed with tlie compounds having a zwitterionic structure
From C-3PO to HAL: Opening The Discourse About The Dark Side of Multi-Modal Social Agents
The increasing prevalence of communicative agents raises questions about human-agent communication and the impact of such interaction on people's behavior in society and human-human communication. This workshop aims to address three of those questions: (i) How can we identify malicious design strategies - known as dark patterns - in social agents?; (ii) What is the necessity for and the effects of present and future design features, across different modalities and social contexts, in social agents?; (iii) How can we incorporate the findings of the first two questions into the design of social agents? This workshop seeks to conjoin ongoing discourses of the CUI and wider HCI communities, including recent trends focusing on ethical designs. Out of the collaborative discussion, the workshop will produce a document distilling possible research lines and topics encouraging future collaborations
Study of Cyclization Mechanism of N-Substituted-2-amino- benzophenones into 1,4-Benzodiazepines; B-Participation of an Vinylogous Amide Nitrogen
2-(N-B-Bromoalkyl)-amino-5-substiJtuted ben:oophenones 28, 32,
33 .and 38 have been i:nduced by treatment in ethanolic solution of
hexamethyleintetramine or rammonia ·to ring c1osure into 1,4-beinzcidiazepiines
39-46. Deuterium B-labe1ed compound 28 gave on
cyclization two 1,4-benzodfazepiines (39 and 40) in the rntio 45/55,
reveal1ng B-par!ticipation of :nitrogen atom. The neighbouri:ng grnup
participa·tion was further investigated by deternniniing the ratio
and configuration of the 2- and 3-substituted chiral 1,4-benzodi.
azepines 1resulting on ring closure: 32 gave (S)-41 and (S)-42
(ratio 82/18), 33 gave (S)-43 and {S)-44 ~rntio 92/8), 38 gave 45 and
46 (ratio 58/42). High regioselectiviity was also 1observed for recyclization of aziridines 36 in (S)-41 and (R)-42 (rntio 63/37), and
37 in (S)-43 and (R)-44 (ratio 76/24), respectively. Arn opposite
stereochemical course of formaition of 42 and 44 f.rom 32 and 33,
as :Dram 36 and 37 is observed. Absolute configurntfon of (-)- and
( + )-42 and 44 was determined by comparison of their CD spectra
with those of (S)-50, and mecha1nistic scheme is offered accountLng
for all exper-imental results
Book Reviews
J. Van Alphen: Rubber Chemicals (P. Mildner)
E. H. Rodd: Chemistry of Carbon Compounds. Vol. III B (K. Balenović)
F. Feigel: Spot Tests in Organic Analysis (K. Balenović)
F. R. Eirich: RheoLogy - Theory and Applications (J. Kratohvil)
Gmelins Handbuch der anorganischen Chemie: Calcium (V. J. Kovač)
Gmelins Handbuch der anorganischen Chemie: Platin (V. J. Kovač)
W. I. Perelman: Taschenbuch der Chemie (K. Weber)
H. Herold: Antibiotika (V. Johanides
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