32 research outputs found
Congested Traffic States in Empirical Observations and Microscopic Simulations
We present data from several German freeways showing different kinds of
congested traffic forming near road inhomogeneities, specifically lane
closings, intersections, or uphill gradients. The states are localized or
extended, homogeneous or oscillating. Combined states are observed as well,
like the coexistence of moving localized clusters and clusters pinned at road
inhomogeneities, or regions of oscillating congested traffic upstream of nearly
homogeneous congested traffic. The experimental findings are consistent with a
recently proposed theoretical phase diagram for traffic near on-ramps [D.
Helbing, A. Hennecke, and M. Treiber, Phys. Rev. Lett. {\bf 82}, 4360 (1999)].
We simulate these situations with a novel continuous microscopic single-lane
model, the ``intelligent driver model'' (IDM), using the empirical boundary
conditions. All observations, including the coexistence of states, are
qualitatively reproduced by describing inhomogeneities with local variations of
one model parameter.
We show that the results of the microscopic model can be understood by
formulating the theoretical phase diagram for bottlenecks in a more general
way. In particular, a local drop of the road capacity induced by parameter
variations has practically the same effect as an on-ramp.Comment: Now published in Phys. Rev. E. Minor changes suggested by a referee
are incorporated; full bibliographic info added. For related work see
http://www.mtreiber.de/ and http://www.helbing.org
Molecular and cellular aspects and regulation of intestinal lactase-phlorizin hydrolase
Carbohydrates are hydrolyzed in the
intestinal lumen by specific enzymes to monosaccharides
before transport across the brush border
membrane of epithelial cells into the cell interior. The
enzymes implicated in the digestion of carbohydrates in
the intestinal lumen are membrane-bound glycoproteins
that are expressed at the apical domain of the
enterocytes. Absent or reduced activity of one of these
enzymes is the cause of disaccharide intolerance and
malabsorption, the symptoms of which are abdominal
pain, cramps or distention, flatulence, nausea and
osmotic diarrhea. Lactose intolerance is the most
common intestinal disorder that is associated with an
absence or drastically reduced levels of an intestinal
enzyme, in this case lactase-phlorizin hydrolase (LPH).
The pattern of reduction of activity has been temed late
onset of lactase deficiency or adult type hypolactasia. It
was thought that the regulation of LPH was posttranslational
and was associated with altered structural
features of the enzyme. Recent studies, however, suggest
that the major mechanism of regulation of LPH is
transcriptional. Other forms of lactose intolerance
include the rare congenital lactase deficiency and
secondary forms, such as those caused by mucosa1
injury, due to infectious gastroenteritis, celiac disease,
parasitic infection, drug-induced enteritis and Crohn's disease. This review will shed light on important
strucural and biosynthetic aspects of LPH, the role
played by particular regions of the LPH protein in its
transport, polarized sorting, and function, as well as on
the gene expession and regulation of the activity of the
enzyme
Prostate-specific membrane antigen (PSMA) associates early in the endoplasmic reticulum with lipid microdomains
PSMA is an integral membrane glycoprotein that is overexpressed in prostate carcinomas rendering this cell surface marker an appropriate target for antibody-vehicled drugs and toxins. Here we report on the biosynthesis, processing and transport of PSMA in COS-1 cells transfected with a human cDNA encoding PSMA
The mouse Lyt-2/3 antigen complex--II. Structural analysis of the subunits.
Surface- or biosynthetically labeled Lyt-2/3 antigens were isolated from cell lysates by immunoprecipitation and affinity chromatography with a monoclonal antibody. Tryptic digests of the individual subunits of 37,000, 32,000 and 28,000 apparent mol. wts were analysed by reverse-phase high-performance liquid chromatography and by two-dimensional peptide mapping. The results indicate that the 37,000 and 32,000 mol. wt components are structurally very similar whereas the 28,000 mol. wt component appears as a different molecule
A mutation in a highly conserved region in brush-border sucrase-isomaltase and lysosomal alpha-glucosidase results in Golgi retention
Contains fulltext :
27832___.PDF (publisher's version ) (Open Access
A MUtation in a Highly Conserved Region in Brush Border Sucrase Isomaltase and Lysosomal Alpha Glucosidase Results in Golgi Retention.
Item does not contain fulltex
Routing and processing of lactase-phlorizin hydrolase in transfected Caco-2 cells
Contains fulltext :
216414.pdf (Publisher’s version ) (Open Access)6 p