11,388 research outputs found
RC J1148+0455 identification: gravitational lens or group of galaxies ?
The structure of the radio source RC B1146+052 of the ``Cold'' catalogue is
investigated by data of the MIT-GB-VLA survey at 4850 MHz. This source belongs
to the steep spectrum radio sources subsample of the RC catalogue. Its spectral
index is = -1.04. The optical image of this source obtained with 6m
telescope is analysed. The radio source center is situated in a group of 8
galaxies of about 24 in the R-filter. The possible explanations of the
complex structure of radio components are considered.Comment: 6 pages, 5 figures, uses psfig.sty. This was the poster as presented
on Gamow Memorial Internat. Conference GMIC'99 "Early Universe: Cosmological
Problems and Instrumental Technologies" in St.Petersburg, 23-27 Aug., 1999.
Submitted to Proceedings to be published in A&A Transaction
3,4,6-Tri-O-acetyl-2-(N-acetylacetamido )-1,2-dideoxy-o-Iyxohex- 1-enopyranose, an Acetamido-n-galactal Derivative, and the Mechanism of its Formation from 2-Acetamido-2-deoxy-D-galactose
The structure of an unsaturated amino sugar derivative, formed
in low yield when 2-acetamido-2-deoxy-o-galactose _is treated with
boiling isopropenyl acetate containing a trace of p-toluenesulfonic
acid, and formulated as 1,4,6-tri-0-acetyl-2-(N-acetylacetamido)-
2,3-dideoxy-o-threo-hex-2-enopyranose(II) in an earlier publication,
has been re-examined. Through a series of steps, including
catalytic hydrogenation, the substance has been converted into a
compound with an NMR spectrum which shows it to be 3,4,6-tri-
0-acetyl-2-(N -acetylbenzamido )-1,5-anhydro-2-deoxy-o-tali tol (X).
This fact, together with a re-examination of its NMR spectrum,
show the unsaturated compound to be 3,4,6-tri-0-acetyl-2-(N··
-acetylacetamido)-1,2-dideoxy-o-lyxo-hex-l-enopyranose (III), a
derivative of 2-acetamido-o-galactal (VI). The yield of III from
2-acetamido-2-deoxy-o-galactose has been substantially improved
through isolation of . 2-acetamido-1,3,4 , 6-tetra-0-acetyl-2-deoxy-~-
o-galactopyranose (XIII) as an intermediate and III has been
obtained in crystalline form. Evidence for the mechanism of its
formation is presented
The Behavior of 2-Acetamido-2-deoxy-o-galactose with Isopropenyl Acetate in the Presence of p-Toluenesulfonic Acid. Formation of an Unsaturated Aminosugar Derivative
Treatment of 2-acetamido-2-deoxy-n-galactose (III) with isopropenyl
acetate and p-toluenesulfonic acid gives 2-(n-glycero-1,2-
-diacetoxyethyl)-4-(N-acetylacetamido) furan (II), the anomeric 1,3,
4,6-te tra-O-acety 1- 2-(N -acetylacetamido )-2-d eoxy-o-gala ctopyranoses (IV and V), a mixture of the anomeric 1,3,5,6-te tra-0-acetyl-2- -(N-acetylacetamido) -2- deoxy-o-galactofuranoses (VII) and 1,4,6 - -tri -O-acetyl-2-(N-acetylacetamido)-2 ,3-dideoxy-o-threo-hex-2-enopyranose (X) . The anomeric 2-acetamido-1,3,4,6 -tetra-O-acetyl-2- -deo xy-n-galactopyranoses (VI) were also d etected ; they may be
primary products or artifacts arising from IV and V by spontaneous
de-N-acetylation in the course of the chromatography w hich was
used
3,4,6-Tri-O-acetyl-2-(N-acetylacetamido )-1,2-dideoxy-o-Iyxohex- 1-enopyranose, an Acetamido-n-galactal Derivative, and the Mechanism of its Formation from 2-Acetamido-2-deoxy-D-galactose
The structure of an unsaturated amino sugar derivative, formed
in low yield when 2-acetamido-2-deoxy-o-galactose _is treated with
boiling isopropenyl acetate containing a trace of p-toluenesulfonic
acid, and formulated as 1,4,6-tri-0-acetyl-2-(N-acetylacetamido)-
2,3-dideoxy-o-threo-hex-2-enopyranose(II) in an earlier publication,
has been re-examined. Through a series of steps, including
catalytic hydrogenation, the substance has been converted into a
compound with an NMR spectrum which shows it to be 3,4,6-tri-
0-acetyl-2-(N -acetylbenzamido )-1,5-anhydro-2-deoxy-o-tali tol (X).
This fact, together with a re-examination of its NMR spectrum,
show the unsaturated compound to be 3,4,6-tri-0-acetyl-2-(N··
-acetylacetamido)-1,2-dideoxy-o-lyxo-hex-l-enopyranose (III), a
derivative of 2-acetamido-o-galactal (VI). The yield of III from
2-acetamido-2-deoxy-o-galactose has been substantially improved
through isolation of . 2-acetamido-1,3,4 , 6-tetra-0-acetyl-2-deoxy-~-
o-galactopyranose (XIII) as an intermediate and III has been
obtained in crystalline form. Evidence for the mechanism of its
formation is presented
A dispersive wave pattern on Jupiter's fastest retrograde jet at S
A compact wave pattern has been identified on Jupiter's fastest retrograding
jet at 20S (the SEBs) on the southern edge of the South Equatorial Belt. The
wave has been identified in both reflected sunlight from amateur observations
between 2010 and 2015, thermal infrared imaging from the Very Large Telescope
and near infrared imaging from the Infrared Telescope Facility. The wave
pattern is present when the SEB is relatively quiescent and lacking large-scale
disturbances, and is particularly notable when the belt has undergone a fade
(whitening). It is generally not present when the SEB exhibits its usual
large-scale convective activity ('rifts'). Tracking of the wave pattern and
associated white ovals on its southern edge over several epochs have permitted
a measure of the dispersion relationship, showing a strong correlation between
the phase speed (-43.2 to -21.2 m/s) and the longitudinal wavelength, which
varied from 4.4-10.0 deg. longitude over the course of the observations.
Infrared imaging sensing low pressures in the upper troposphere suggest that
the wave is confined to near the cloud tops. The wave is moving westward at a
phase speed slower (i.e., less negative) than the peak retrograde wind speed
(-62 m/s), and is therefore moving east with respect to the SEBs jet peak.
Unlike the retrograde NEBn jet near 17N, which is a location of strong vertical
wind shear that sometimes hosts Rossby wave activity, the SEBs jet remains
retrograde throughout the upper troposphere, suggesting the SEBs pattern cannot
be interpreted as a classical Rossby wave. Cassini-derived windspeeds and
temperatures reveal that the vorticity gradient is dominated by the baroclinic
term and becomes negative (changes sign) in a region near the cloud-top level
(400-700 mbar) associated with the SEBs, suggesting a baroclinic origin for
this meandering wave pattern. [Abr]Comment: 19 pages, 11 figures, article accepted for publication in Icaru
Allylic Displacement Reactions of a 2-Acetamido-D-glucal Derivative with Acids and Phenols
Fusion of 3,4,6-tri-O-acetyl-2-(N-acetylacetamido)-1,2-dideoxy-
o-arabino-hex-1-enopyranose [I, 2-(N-acetylacetamido)-o-glucal
triacetate] with various acids and phenols in the presence of. a
trace of p-toluenesulfonic acid causes loss of the acetoxy group at
C-3, shift of the double bond to the C-2-C-3 position, and entry
of an acyloxy or aryloxy group at C-1 to give esters and glycosides,
respectively, of 4,6-di-0-acetyl-2-(N-acetylacetamido)-2,3-dideoxy-
a-o-erythro-hex-2-enopyranose (compounds III, V, VI, and
VII). In each case, the main product is accompanied by 1,4,6-tri-O-
acetyl-2- (N-acetylacetamido) -2,3-dideoxy-a-o-erythro-hex-2-enopyranose
(IV), a substance which is found to be readily accessible
through the deliberate rearrangement of I under acidic conditions.
While IV reacts with benzoic acid when boiled in benzene solution
containing hydrogen chloride, I is recovered unchanged after treatment
in this fashion. On the basis of these facts, a mechanism for
the acid-catalyzed reaction of I with carboxylic acids and phenols
is proposed. An improved preparation of I from 2-acetamido-2-deoxy-omannose via 2-acetamido-1,3,4,6-tetra-O-acetyl-2-deoxy-a-o-mannopyranose (II) is described. Phenyl 4,6-di-0-acetyl-2-(N -acetylacetamido )-2,3-dideoxy-a-D- eryth ro-hex-2-enopyranoside (VI) may be reduced by catalytic hydrogenation to the corresponding cyclohexyl glycoside (VIII), the double bond remaining unaffected
Allylic Displacement Reactions of a 2-Acetamido-D-glucal Derivative with Acids and Phenols
Fusion of 3,4,6-tri-O-acetyl-2-(N-acetylacetamido)-1,2-dideoxy-
o-arabino-hex-1-enopyranose [I, 2-(N-acetylacetamido)-o-glucal
triacetate] with various acids and phenols in the presence of. a
trace of p-toluenesulfonic acid causes loss of the acetoxy group at
C-3, shift of the double bond to the C-2-C-3 position, and entry
of an acyloxy or aryloxy group at C-1 to give esters and glycosides,
respectively, of 4,6-di-0-acetyl-2-(N-acetylacetamido)-2,3-dideoxy-
a-o-erythro-hex-2-enopyranose (compounds III, V, VI, and
VII). In each case, the main product is accompanied by 1,4,6-tri-O-
acetyl-2- (N-acetylacetamido) -2,3-dideoxy-a-o-erythro-hex-2-enopyranose
(IV), a substance which is found to be readily accessible
through the deliberate rearrangement of I under acidic conditions.
While IV reacts with benzoic acid when boiled in benzene solution
containing hydrogen chloride, I is recovered unchanged after treatment
in this fashion. On the basis of these facts, a mechanism for
the acid-catalyzed reaction of I with carboxylic acids and phenols
is proposed. An improved preparation of I from 2-acetamido-2-deoxy-omannose via 2-acetamido-1,3,4,6-tetra-O-acetyl-2-deoxy-a-o-mannopyranose (II) is described. Phenyl 4,6-di-0-acetyl-2-(N -acetylacetamido )-2,3-dideoxy-a-D- eryth ro-hex-2-enopyranoside (VI) may be reduced by catalytic hydrogenation to the corresponding cyclohexyl glycoside (VIII), the double bond remaining unaffected
The Rearrangement Reaction of Some Acetylated Unsaturated 2-Acetamidoaldose Derivatives. Selective Removal of one N-Acetyl Group from 2-(N-acetylacetamido) Compounds
Two pairs of anomers, the l ,4,6-tri-0-acetyl-2-(N-acetylacetamido)-
2,3-dideoxy-o-hex-2-enopyranoses of the erythro- (II and III)
and the threo- series (IV and VI) have been prepared and character;
ized. The molecular conformation of these substances has been
discussed on the basis of their NMR spectral characteristics. It is
suggested that the a-anomers II and IV adopt the H~ conformation
as the favorable one, while the B-anomers III and VI most probably
tend to take a slightly modified H~ conformation.
A convenient preparative method for selective removal of one
N-acetyl group from 0-acetylated N-acetylacetamido compounds is
described. The reaction can be carried out in aqueous dioxane solution
at room temperature in the presence of an ammonium salt
at pH ca. 9
The Rearrangement Reaction of Some Acetylated Unsaturated 2-Acetamidoaldose Derivatives. Selective Removal of one N-Acetyl Group from 2-(N-acetylacetamido) Compounds
Two pairs of anomers, the l ,4,6-tri-0-acetyl-2-(N-acetylacetamido)-
2,3-dideoxy-o-hex-2-enopyranoses of the erythro- (II and III)
and the threo- series (IV and VI) have been prepared and character;
ized. The molecular conformation of these substances has been
discussed on the basis of their NMR spectral characteristics. It is
suggested that the a-anomers II and IV adopt the H~ conformation
as the favorable one, while the B-anomers III and VI most probably
tend to take a slightly modified H~ conformation.
A convenient preparative method for selective removal of one
N-acetyl group from 0-acetylated N-acetylacetamido compounds is
described. The reaction can be carried out in aqueous dioxane solution
at room temperature in the presence of an ammonium salt
at pH ca. 9
The Physicist's Guide to the Orchestra
An experimental study of strings, woodwinds (organ pipe, flute, clarinet,
saxophone and recorder), and the voice was undertaken to illustrate the basic
principles of sound production in music instruments. The setup used is simple
and consists of common laboratory equipment. Although the canonical examples
(standing wave on a string, in an open and closed pipe) are easily reproduced,
they fail to explain the majority of the measurements. The reasons for these
deviations are outlined and discussed.Comment: 11 pages, 10 figures (jpg files). Submitted to European Journal of
Physic
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