643 research outputs found
Boss/Sev Signaling from Germline to Soma Restricts Germline-Stem-Cell-Niche Formation in the Anterior Region of Drosophila Male Gonads
SummaryDrosophila germline stem cells are regulated by the somatic microenvironment, or “niche,” which ensures that the stem cells can both self-renew and produce functional gametes throughout adult life. However, despite its prime importance, little is known about how niche formation is regulated during gonadal development. Here, we demonstrate that a receptor tyrosine kinase, Sevenless (Sev), is required to ensure that the niche develops in the anterior region of the male embryonic gonads. Sev is expressed in somatic cells within the posterior region of the gonads. Sev is activated by a ligand, Bride of sevenless (Boss), which is expressed by the germline, to prevent ectopic niche differentiation in the posterior gonadal somatic cells. Thus, we propose that signal transduction from germline to soma restricts expansion of the germline-stem-cell niche in the gonads
Optical trapping with structured light : a review
Funding: This work was supported by the National Natural Science Foundation of China (11874102 and 61975047), the Sichuan Province Science and Technology Support Program (2020JDRC0006), and the Fundamental Research Funds for the Central Universities (ZYGX2019J102). M.C. and Y.A. thank the UK Engineering and Physical Sciences Research Council for funding.Optical trapping describes the interaction between light and matter to manipulate micro-objects through momentum transfer. In the case of 3D trapping with a single beam, this is termed optical tweezers. Optical tweezers are a powerful and noninvasive tool for manipulating small objects, and have become indispensable in many fields, including physics, biology, soft condensed matter, among others. In the early days, optical trapping was typically accomplished with a single Gaussian beam. In recent years, we have witnessed rapid progress in the use of structured light beams with customized phase, amplitude, and polarization in optical trapping. Unusual beam properties, such as phase singularities on-axis and propagation invariant nature, have opened up novel capabilities to the study of micromanipulation in liquid, air, and vacuum. We summarize the recent advances in the field of optical trapping using structured light beams.Publisher PDFPeer reviewe
Electronic structure of Fe1.04(Te0.66Se0.34)
We report the electronic structure of the iron-chalcogenide superconductor,
Fe1.04(Te0.66Se0.34), obtained with high resolution angle-resolved
photoemission spectroscopy and density functional calculations. In
photoemission measurements, various photon energies and polarizations are
exploited to study the Fermi surface topology and symmetry properties of the
bands. The measured band structure and their symmetry characters qualitatively
agree with our density function theory calculations of Fe(Te0.66Se0.34),
although the band structure is renormalized by about a factor of three. We find
that the electronic structures of this iron-chalcogenides and the
iron-pnictides have many aspects in common, however, significant differences
exist near the Gamma-point. For Fe1.04(Te0.66Se0.34), there are clearly
separated three bands with distinct even or odd symmetry that cross the Fermi
energy (EF) near the zone center, which contribute to three hole-like Fermi
surfaces. Especially, both experiments and calculations show a hole-like
elliptical Fermi surface at the zone center. Moreover, no sign of spin density
wave was observed in the electronic structure and susceptibility measurements
of this compound.Comment: 7 pages, 9 figures. submitted to PRB on November 15, 2009, and
accepted on January 6, 201
Gate-Tuned Thermoelectric Power in Black Phosphorus
The electric field effect is a useful means of elucidating intrinsic material
properties as well as for designing functional devices. The
electric-double-layer transistor (EDLT) enables the control of carrier density
in a wide range, which is recently proved to be an effective tool for the
investigation of thermoelectric properties. Here, we report the gate-tuning of
thermoelectric power in a black phosphorus (BP) single crystal flake with the
thickness of 40 nm. Using an EDLT configuration, we successfully control the
thermoelectric power (S), and find that the S of ion-gated BP reached +510
V/K at 210 K in the hole depleted state, which is much higher than the
reported bulk single crystal value of +340 V/K at 300 K. We compared this
experimental data with the first-principles-based calculation and found that
this enhancement is qualitatively explained by the effective thinning of the
conduction channel of the BP flake and non-uniformity of the channel owing to
the gate operation in a depletion mode. Our results provide new opportunities
for further engineering BP as a thermoelectric material in nanoscale.Comment: 17 pages, 4 figure
Experimental verification of PbBiTe as a 3D topological insulator
The first experimental evidence is presented of the topological insulator
state in PbBiTe. A single surface Dirac cone is observed by
angle-resolved photoemission spectroscopy (ARPES) with synchrotron radiation.
Topological invariants are calculated from the {\it ab initio}
band structure to be 1; (111). The observed two-dimensional iso-energy contours
in the bulk energy gap are found to be the largest among the known
three-dimensional topological insulators. This opens a pathway to achieving a
sufficiently large spin current density in future spintronic devices.Comment: 5 pages, 5 figures, accepted for publication in Phys. Rev. Let
Chaperones as integrators of cellular networks: Changes of cellular integrity in stress and diseases
Cellular networks undergo rearrangements during stress and diseases. In
un-stressed state the yeast protein-protein interaction network (interactome)
is highly compact, and the centrally organized modules have a large overlap.
During stress several original modules became more separated, and a number of
novel modules also appear. A few basic functions, such as the proteasome
preserve their central position. However, several functions with high energy
demand, such the cell-cycle regulation loose their original centrality during
stress. A number of key stress-dependent protein complexes, such as the
disaggregation-specific chaperone, Hsp104, gain centrality in the stressed
yeast interactome. Molecular chaperones, heat shock, or stress proteins form
complex interaction networks (the chaperome) with each other and their
partners. Here we show that the human chaperome recovers the segregation of
protein synthesis-coupled and stress-related chaperones observed in yeast
recently. Examination of yeast and human interactomes shows that (1) chaperones
are inter-modular integrators of protein-protein interaction networks, which
(2) often bridge hubs and (3) are favorite candidates for extensive
phosphorylation. Moreover, chaperones (4) become more central in the
organization of the isolated modules of the stressed yeast protein-protein
interaction network, which highlights their importance in the de-coupling and
re-coupling of network modules during and after stress. Chaperone-mediated
evolvability of cellular networks may play a key role in cellular adaptation
during stress and various polygenic and chronic diseases, such as cancer,
diabetes or neurodegeneration.Comment: 13 pages, 3 figures, 1 glossar
Impact of Heterogeneity of Human Peripheral Blood Monocyte Subsets on Myocardial Salvage in Patients With Primary Acute Myocardial Infarction
ObjectivesWe examined whether distinct monocyte subsets contribute in specific ways to myocardial salvage in patients with acute myocardial infarction (AMI).BackgroundRecent studies have shown that monocytes in human peripheral blood are heterogeneous.MethodsWe studied 36 patients with primary AMI. Peripheral blood sampling was performed 1, 2, 3, 4, 5, 8, and 12 days after AMI onset. Two monocyte subsets (CD14+CD16−and CD14+CD16+) were measured by flow cytometry. The extent of myocardial salvage 7 days after AMI was evaluated by cardiovascular magnetic resonance imaging as the difference between myocardium at risk (T2-weighted hyperintense lesion) and myocardial necrosis (delayed gadolinium enhancement). Cardiovascular magnetic resonance imaging was also performed 6 months after AMI.ResultsCirculating CD14+CD16−and CD14+CD16+monocytes increased in AMI patients, peaking on days 3 and 5 after onset, respectively. Importantly, the peak levels of CD14+CD16−monocytes, but not those of CD14+CD16+monocytes, were significantly negatively associated with the extent of myocardial salvage. We also found that the peak levels of CD14+CD16−monocytes, but not those of CD14+CD16+monocytes, were negatively correlated with recovery of left ventricular ejection fraction 6 months after infarction.ConclusionsThe peak levels of CD14+CD16−monocytes affect both the extent of myocardial salvage and the recovery of left ventricular function after AMI, indicating that the manipulation of monocyte heterogeneity could be a novel therapeutic target for salvaging ischemic damage
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