665 research outputs found
Structure Determination of Oligosaccharides Isolated from A + , H + and A â H â Hog-Submaxillary-Gland Mucin Glyoproteins, by 360-MHz 1 H-NMR Spectroscopy, Permethylation Analysis and Mass Spectrometry
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65915/1/j.1432-1033.1981.tb05545.x.pd
Sialic acid content of erythrocytes in normal individuals and patients with certain hematologic disorders
The sialic acid content of erythrocytes from healthy individuals of different blood types and of patients with known hematological disorders has been determined. The sialic acid was completely released enzymatically with sialidase and quantitated by the thiobarbituric acid method. The sialic acid content of erythrocytes was constant irrespective of ABO blood type, or anticoagulant used; viz, 0.85â0.92 mÌmoles/ml of packed erythrocytes or 46â53 Ă 10 6 sialyl residues per cell. Deviations from these normal values were obtained with erythrocytes from patients with a variety of hematological disorders. Patients with the following disorders have significantly (P < 0.01) lower sialic acid values compared to erythrocytes from healthy individuals (given in the order of decreasing sialic acid content): sickle cell anemia, acute lymphocytic leukemia, chronic lymphocytic leukemia, acute myelomonocytic leukemia, nonâHodgkin lymphocytic lymphoma, chronic granulocytic leukemia, acute myelocytic leukemia, leukemia, and Hodgkin disease.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/101840/1/2830090405_ftp.pd
Periodate oxidation studies in the elucidation of the structures of sialic acid containing oligosaccharides
The structures of sialo-oligosaccharide alditols as determined by 1H-NMR spectrometry together with methylation analysis did not correspond with those derived previously from quantitative periodate oxidation data alone. Possible causes of the discrepancy were explored in the periodate oxidation methodology. No free sialic acid was released by the acidity of the periodate in the course of oxidation at pH 4.5. The anionic properties of the sialic acid residues were therefore utilized to separate the periodate oxidation products and thereby establish the position of the sialic acid in the oligosaccharide chain.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24340/1/0000607.pd
T-cell cytotoxicity in the absence of viral protein synthesis in target cells
CYTOTOXIC T cells lyse only those virus infected target cells in vitro which express, in addition to the viral antigen(s), those K or D region products of the major histocompati-bility complex (MHC) which were present during anti-viral sensitisation in vivo. This 'associative recogniton' by cytotoxic T cells could reflect the interaction of two T-cell receptors with specificity for target K or D gene products and independently for the viral antigen, or one receptor with specificity for virally altered K or D region products (see ref. 1 and refs therein). There are various ways that the MHC antigens could be altered, including 'modification from within', where the virus modifies host protein synthesis by interfering with transcription2, translation or post-translational glycosylation; or 'modification from without' where enzymic or chemical alteration of cell membrane proteins are induced by virus activity at the cell surface. In this report we show that inactivated Sendai virus or isolated Sendai virus envelopes can serve to modify a cell and make it a specific target for Sendai-immune T-cell killing, thus excluding the possibility of 'modification from within' in this system
A quantum mechanical description of the experiment on the observation of gravitationally bound states
Quantum states in the Earth's gravitational field were observed, when
ultra-cold neutrons fall under gravity. The experimental results can be
described by the quantum mechanical scattering model as it is presented here.
We also discuss other geometries of the experimental setup which correspond to
the absence or the reversion of gravity. Since our quantum mechanical model
describes, particularly, the experimentally realized situation of reversed
gravity quantitatively, we can practically rule out alternative explanations of
the quantum states in terms of pure confinement effects.Comment: LaTeX, 10 pages, 4 figures, v2: references adde
Quantum Revivals in Periodically Driven Systems close to nonlinear resonance
We calculate the quantum revival time for a wave-packet initially well
localized in a one-dimensional potential in the presence of an external
periodic modulating field. The dependence of the revival time on various
parameters of the driven system is shown analytically. As an example of
application of our approach, we compare the analytically obtained values of the
revival time for various modulation strengths with the numerically computed
ones in the case of a driven gravitational cavity. We show that they are in
very good agreement.Comment: 14 pages, 1 figur
Creating a low-dimensional quantum gas using dark states in an inelastic evanescent-wave mirror
We discuss an experimental scheme to create a low-dimensional gas of
ultracold atoms, based on inelastic bouncing on an evanescent-wave mirror.
Close to the turning point of the mirror, the atoms are transferred into an
optical dipole trap. This scheme can compress the phase-space density and can
ultimately yield an optically-driven atom laser. An important issue is the
suppression of photon scattering due to ``cross-talk'' between the mirror
potential and the trapping potential. We propose that for alkali atoms the
photon scattering rate can be suppressed by several orders of magnitude if the
atoms are decoupled from the evanescent-wave light. We discuss how such dark
states can be achieved by making use of circularly-polarized evanescent waves.Comment: 8 pages, 4 figure
Diffusion Tensor Imaging and Tractography in Brown-Sequard Syndrome
This report illustrates the utility of DTI and DTT in delineating regions of cord injury in two patients with traumatic Brown-Sequard syndrome. Our results indicate that DTI provides clinically relevant information that supplements conventional MR imaging for patients with acute SCI
Substrate-based atom waveguide using guided two-color evanescent light fields
We propose a dipole-force linear waveguide which confines neutral atoms up to
lambda/2 above a microfabricated single-mode dielectric optical guide. The
optical guide carries far blue-detuned light in the horizontally-polarized TE
mode and far red-detuned light in the vertically-polarized TM mode, with both
modes close to optical cut-off. A trapping minimum in the transverse plane is
formed above the optical guide due to the differing evanescent decay lengths of
the two modes. This design allows manufacture of mechanically stable
atom-optical elements on a substrate. We calculate the full vector bound modes
for an arbitrary guide shape using two-dimensional non-uniform finite elements
in the frequency-domain, allowing us to optimize atom waveguide properties. We
find that a rectangular optical guide of 0.8um by 0.2um carrying 6mW of total
laser power (detuning +-15nm about the D2 line) gives a trap depth of 200uK for
cesium atoms (m_F = 0), transverse oscillation frequencies of f_x = 40kHz and
f_y = 160kHz, collection area ~ 1um^2 and coherence time of 9ms. We discuss the
effects of non-zero m_F, surface interactions, heating rate, the substrate
refractive index, and the limits on waveguide bending radius.Comment: 12 pages, 4 figures, revtex, submitted to Phys. Rev. A Replaced:
final version accepted by PRA v.61 Feb 2000. (2 paragraphs added
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