117 research outputs found
Current advances in tissue repair and regeneration: the future is bright
The fifth EMBO conference on ‘The Molecular and Cellular Basis of Regeneration and Repair’ took place in the peaceful coastal town of Sant Feliu de Guixols (Spain) on September 2014. The meeting was organised by Emili Saló (U. Barcelona, Spain), Kimberly Mace (U. Manchester, UK), Patrizia Ferretti (University College London, UK) and Michael Brand (Centre for Regenerative Therapies Dresden, Germany) and received the generous support of Society for Developmental Biology, The Company of Biologists, Centre for Regenerative Therapies Dresden, Garland Science and the journals Regeneration and Cell Signalling. The natural surroundings provided an inspiring setting for 185 researchers from all over the world to share their latest findings and views on the field. The conference showcased the great diversity of model organisms used for studying regeneration and tissue repair, including invertebrate and vertebrate species (Fig. 1). Importantly, this diversity in animal models allowed for a global overview of the mechanisms that promote regeneration. In addition, it highlighted some of the unique aspects that confer differences in regenerative capacities among different species. These differences might lie in each of the different steps involved in performing regeneration, including triggering the regenerative response, controlling cellular plasticity, re-stablishing the correct tissue patterns, as well as determining the roles of extrinsic factors, such as the role of inflammation in regeneration. A deeper understanding of these processes in the naturally regenerating species is a prerequisite for advancing the field of regenerative medicine and tissue repair in humans
Simultaneous lineage tracing and cell-type identification using CRISPR-Cas9-induced genetic scars
A key goal of developmental biology is to understand how a single cell is transformed into a full-grown organism comprising many different cell types. Single-cell RNA-sequencing (scRNA-seq) is commonly used to identify cell types in a tissue or organ. However, organizing the resulting taxonomy of cell types into lineage trees to understand the developmental origin of cells remains challenging. Here we present LINNAEUS (lineage tracing by nuclease-activated editing of ubiquitous sequences)-a strategy for simultaneous lineage tracing and transcriptome profiling in thousands of single cells. By combining scRNA-seq with computational analysis of lineage barcodes, generated by genome editing of transgenic reporter genes, we reconstruct developmental lineage trees in zebrafish larvae, and in heart, liver, pancreas, and telencephalon of adult fish. LINNAEUS provides a systematic approach for tracing the origin of novel cell types, or known cell types under different conditions
Cross Section Limits for the Pb(Kr,n)118 Reaction
In April-May, 2001, the previously reported experiment to synthesize element
118 using the Pb(Kr,n)118 reaction was repeated. No
events corresponding to the synthesis of element 118 were observed with a total
beam dose of 2.6 x 10 ions. The simple upper limit cross sections (1
event) were 0.9 and 0.6 pb for evaporation residue magnetic rigidities of 2.00
and 2.12 , respectively. A more detailed cross section calculation,
accounting for an assumed narrow excitation function, the energy loss of the
beam in traversing the target and the uncertainty in the magnetic rigidity of
the Z=118 recoils is also presented. Re-analysis of the primary data files from
the 1999 experiment showed the reported element 118 events are not in the
original data. The current results put constraints on the production cross
section for synthesis of very heavy nuclei in cold fusion reactions.Comment: 7 pages, 2 figures. Submitted to EPJ
Semiempirical Shell Model Masses with Magic Number Z = 126 for Superheavy Elements
A semiempirical shell model mass equation applicable to superheavy elements
up to Z = 126 is presented and shown to have a high predictive power. The
equation is applied to the recently discovered superheavy nuclei Z = 118, A =
293 and Z = 114, A = 289 and their decay products.Comment: 7 pages, including 2 figures and 2 table
The structure of superheavy elements newly discovered in the reaction of Kr with Pb
The structure of superheavy elements newly discovered in the
Pb(Kr,n) reaction at Berkeley is systematically studied in the
Relativistic Mean Field (RMF) approach. It is shown that various usually
employed RMF forces, which give fair description of normal stable nuclei, give
quite different predictions for superheavy elements. Among the effective forces
we tested, TM1 is found to be the good candidate to describe superheavy
elements. The binding energies of the 118 nucleus and its
decay daughter nuclei obtained using TM1 agree with those of FRDM
within 2 MeV. Similar conclusion that TM1 is the good interaction is also drawn
from the calculated binding energies for Pb isotopes with the Relativistic
Continuum Hartree Bogoliubov (RCHB) theory. Using the pairing gaps obtained
from RCHB, RMF calculations with pairing and deformation are carried out for
the structure of superheavy elements. The binding energy, shape, single
particle levels, and the Q values of the decay are
discussed, and it is shown that both pairing correlation and deformation are
essential to properly understand the structure of superheavy elements. A good
agreement is obtained with experimental data on . %Especially, the
atomic number %dependence of %seems to match with the experimental
observationComment: 19 pages, 5 figure
Competition of fusion and quasi-fission in the reactions leading to production of the superheavy elements
The mechanism of fusion hindrance, an effect observed in the reactions of
cold, warm and hot fusion leading to production of the superheavy elements, is
investigated. A systematics of transfermium production cross sections is used
to determine fusion probabilities. Mechanism of fusion hindrance is described
as a competition of fusion and quasi-fission. Available evaporation residue
cross sections in the superheavy region are reproduced satisfactorily. Analysis
of the measured capture cross sections is performed and a sudden disappearance
of the capture cross sections is observed at low fusion probabilities. A
dependence of the fusion hindrance on the asymmetry of the projectile-target
system is investigated using the available data. The most promising pathways
for further experiments are suggested.Comment: 8 pages, 7 figures, talk presented at 7th International
School-Seminar on Heavy-Ion Physics, May 27 - June 1, 2002, Dubna, Russi
Colocalization of different neurotransmitter transporters on synaptic vesicles is sparse except for VGLUT1 and ZnT3
Vesicular transporters (VTs) define the type of neurotransmitter that synaptic vesicles (SVs) store and release. While certain mammalian neurons release multiple transmitters, it is not clear whether the release occurs from the same or distinct vesicle pools at the synapse. Using quantitative single-vesicle imaging, we show that a vast majority of SVs in the rodent brain contain only one type of VT, indicating specificity for a single neurotransmitter. Interestingly, SVs containing dual transporters are highly diverse (27 types) but small in proportion (2% of all SVs), excluding the largest pool that carries VGLUT1 and ZnT3 (34%). Using VGLUT1-ZnT3 SVs, we demonstrate that the transporter colocalization influences the SV content and synaptic quantal size. Thus, the presence of diverse transporters on the same vesicle is bona fide, and depending on the VT types, this may act to regulate neurotransmitter type, content, and release in space and time
Semiempirical Shell Model Masses with Magic Number Z=126 for Translead Elements with N smaller or equal to 126
A semiempirical shell model mass equation based on magic number Z=126 and
applicable to translead elements with N smaller or equal to 126 is presented.
For alpha decay energies the equation is shown to have a high predictive power
and an rms deviation from the data of about 100 keV. The rms deviations for
masses and other mass differences are between about 200 and 300 keV.Comment: 8 pages including 3 figures and 3 table
Shell Corrections of Superheavy Nuclei in Self-Consistent Calculations
Shell corrections to the nuclear binding energy as a measure of shell effects
in superheavy nuclei are studied within the self-consistent Skyrme-Hartree-Fock
and Relativistic Mean-Field theories. Due to the presence of low-lying proton
continuum resulting in a free particle gas, special attention is paid to the
treatment of single-particle level density. To cure the pathological behavior
of shell correction around the particle threshold, the method based on the
Green's function approach has been adopted. It is demonstrated that for the
vast majority of Skyrme interactions commonly employed in nuclear structure
calculations, the strongest shell stabilization appears for Z=124, and 126, and
for N=184. On the other hand, in the relativistic approaches the strongest
spherical shell effect appears systematically for Z=120 and N=172. This
difference has probably its roots in the spin-orbit potential. We have also
shown that, in contrast to shell corrections which are fairly independent on
the force, macroscopic energies extracted from self-consistent calculations
strongly depend on the actual force parametrisation used. That is, the A and Z
dependence of mass surface when extrapolating to unknown superheavy nuclei is
prone to significant theoretical uncertainties.Comment: 14 pages REVTeX, 8 eps figures, submitted to Phys. Rev.
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