690 research outputs found
Suppression of anchorage-independent growth after gene transfection.
A novel procedure for isolating anchorage-dependent cells has been developed. It involves negative selection of cells growing in suspension followed by clonal replica screening for anchorage-dependent growth. Cells which have regained anchorage-dependent growth have been isolated from a library of the Chinese hamster ovary cell line, CHO-K1, transfected with pSV2neo and human genomic DNA. One anchorage-dependent clone, 1042AC, has been studied in detail. Anchorage-dependent growth of 1042AC is stable when cultured as adherent monolayers, but revertants appear rapidly when cultured in suspension. Suppression is unlikely to be due to loss or mutation of hamster genes conferring anchorage-independent growth as hybrids between 1042AC and CHO-K1 have the suppressed phenotype of 1042AC. Furthermore, a population of cells obtained from the hybrid by selecting for revertants to anchorage-independent growth showed selective loss of the transgenome derived from 1042AC. The growth suppression was not due to transfection of the human Krev-1 gene, which has previously been shown to restore anchorage-dependent growth, nor was there any evidence of alteration in the endogenous hamster Krev-1 gene. However, evidence for a human gene being responsible for the suppressed phenotype has not been obtained yet
Establishment and characterization of primary human pancreatic carcinoma in continuous cell culture and in nude mice.
Primary human panceratic exocrine adenocarcinoma has been established in tissue culture and as xenografts in immune-deficient nu/nu mice. The cell line has a doubling time of 36 h and grows as a confluent monolayer together with a constant population of free-floating cells. Evidence of tumourigenicity was provided by growth on an early diploid fibroblast monolayer and in soft agar, and as solid tumours in immune-deficient nu/mu mice. Chromosome analysis of the cultured cells confirmed their tumour origin. Xenografts established from the cell line or directly from primary tumour tissue have retained a similar histology to the original tumour on serial transplantation. An electrophoretic study of exportable pancreatic digestive enzymes and a number of intracellular enzymes has shown that the cell line and xenografts maintain a human intracellular enzyme profile, but do not produce pancreatic digestive enzymes
57-Fe Mossbauer study of magnetic ordering in superconducting K_0.85Fe_1.83Se_2.09 single crystals
The magnetic ordering of superconducting single crystals of
K_0.85Fe_1.83Se_2.09 has been studied between 10K and 550K using 57-Fe
Mossbauer spectroscopy. Despite being superconducting below T_sc ~30K, the iron
sublattice in K_0.85Fe_1.83Se_2.09 clearly exhibits magnetic order from well
below T_sc to its N\'eel temperature of T_N = 532 +/- 2K. The iron moments are
ordered perpendicular to the single crystal plates, i.e. parallel to the
crystal c-axis. The order collapses rapidly above 500K and the accompanying
growth of a paramagnetic component suggests that the magnetic transition may be
first order, which may explain the unusual temperature dependence reported in
recent neutron diffraction studies.Comment: 6 pages, 4 figures Submitted to Phys.Rev.
How to Spread a Rumor: Call Your Neighbors or Take a Walk?
We study the problem of randomized information dissemination in networks. We
compare the now standard PUSH-PULL protocol, with agent-based alternatives
where information is disseminated by a collection of agents performing
independent random walks. In the VISIT-EXCHANGE protocol, both nodes and agents
store information, and each time an agent visits a node, the two exchange all
the information they have. In the MEET-EXCHANGE protocol, only the agents store
information, and exchange their information with each agent they meet.
We consider the broadcast time of a single piece of information in an
-node graph for the above three protocols, assuming a linear number of
agents that start from the stationary distribution. We observe that there are
graphs on which the agent-based protocols are significantly faster than
PUSH-PULL, and graphs where the converse is true. We attribute the good
performance of agent-based algorithms to their inherently fair bandwidth
utilization, and conclude that, in certain settings, agent-based information
dissemination, separately or in combination with PUSH-PULL, can significantly
improve the broadcast time.
The graphs considered above are highly non-regular. Our main technical result
is that on any regular graph of at least logarithmic degree, PUSH-PULL and
VISIT-EXCHANGE have the same asymptotic broadcast time. The proof uses a novel
coupling argument which relates the random choices of vertices in PUSH-PULL
with the random walks in VISIT-EXCHANGE. Further, we show that the broadcast
time of MEET-EXCHANGE is asymptotically at least as large as the other two's on
all regular graphs, and strictly larger on some regular graphs.
As far as we know, this is the first systematic and thorough comparison of
the running times of these very natural information dissemination protocols.The authors would like to thank Thomas Sauerwald and Nicol\'{a}s Rivera for helpful discussions.
This research was undertaken, in part, thanks to funding from
the ANR Project PAMELA (ANR-16-CE23-0016-01),
the NSF Award Numbers CCF-1461559, CCF-0939370 and CCF-18107,
the Gates Cambridge Scholarship programme,
and the ERC grant DYNAMIC MARCH
HBIM FOR THE SURVEYING, ANALYSIS AND RESTORATION OF THE SAINT JOHN THE THEOLOGIAN CATHEDRAL IN NICOSIA (CYPRUS)
Abstract. The present study illustrates the results of an interdisciplinary collaboration between the Mediterranean Laboratory of Survey and Diagnostics for Architecture (RDA) of the Department of Civil Engineering and Architecture (DICAR) of the University of Catania in Italy and the Andreas Pittas Laboratories for Art Characterisation (APAC) of the Science and Technology in Archaeology Research Center (STARC) of the Cyprus Institute in Cyprus. The research focused on the application of an H-BIM approach in the study of a Mediterranean iconic heritage asset, the St. John Cathedral of Nicosia, built in 1662 on the remains of a monastery from the 15th century. The adopted methodology has provided the framework for a dynamic investigation, constantly evolving along several dimensions: historical, geometric spatial, architectural-constructive identification and mapping of degrade, interpretation of degenerative causes and design proposals.</p
Cigarette smoking and urinary oestrogen excretion in premenopausal and post-menopausal women.
Cigarette smoking is associated with a reduction in the risk for endometrial cancer in post-menopausal women and it has been suggested that this is because smoking has an anti-oestrogenic effect. To investigate this, concentrations of oestrone, oestradiol and oestriol were measured in 24 h urine samples from 167 premenopausal women (53 smokers, 114 non-smokers) and 200 post-menopausal women (54 smokers, 146 non-smokers). Among premenopausal women there were no significant differences in oestrogen excretion between smokers and non-smokers. Among post-menopausal women, geometric mean excretion rates for oestrone and oestradiol did not differ significantly between groups, but oestriol excretion was 19% lower (95% confidence interval -34% to -1%) in smokers than in non-smokers. This may partly explain the reduced risk for endometrial cancer among post-menopausal smokers
Localization Properties of Electronic States in Polaron Model of poly(dG)-poly(dC) and poly(dA)-poly(dT) DNA polymers
We numerically investigate localization properties of electronic states in a
static model of poly(dG)-poly(dC) and poly(dA)-poly(dT) DNA polymers with
realistic parameters obtained by quantum-chemical calculation. The randomness
in the on-site energies caused by the electron-phonon coupling are completely
correlated to the off-diagonal parts. In the single electron model, the effect
of the hydrogen-bond stretchings, the twist angles between the base pairs and
the finite system size effects on the energy dependence of the localization
length and on the Lyapunov exponent are given. The localization length is
reduced by the influence of the fluctuations in the hydrogen bond stretchings.
It is also shown that the helical twist angle affects the localization length
in the poly(dG)-poly(dC) DNA polymer more strongly than in the
poly(dA)-poly(dT) one. Furthermore, we show resonance structures in the energy
dependence of the localization length when the system size is relatively small.Comment: 6 pages, 6 figure
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