59,699 research outputs found

### A binary mixture of spinor atomic Bose-Einstein condensates

We study the ground state and classify its phase diagram for a mixture of two
spin-1 condensates in the absence of external magnetic (B-) field according to
atomic parameters for intra- and inter-species spin exchange coupling and
singlet pairing interaction. Ignoring the inter-species singlet pairing
interaction, the ground state phases are found analytically. Numerical approach
of simulated annealing is adopted when the singlet pairing interaction is
present. Our results on the phase diagram and the boundaries between phases
allow for easy identifications of quantum phase transitions, that can be
induced through the tuning of optical traps and atom numbers. They provide the
first insight and guidance for several ongoing experiments on mixtures of
spinor condensates.Comment: 5 pages, 4 figure

### Quantum entangled ground states of two spinor Bose-Einstein condensates

We revisit in detail the non-mean-field ground-state phase diagram for a
binary mixture of spin-1 Bose-Einstein condensates including quantum
fluctuations. The non-commuting terms in the spin-dependent Hamiltonian under
single spatial mode approximation make it difficult to obtain exact
eigenstates. Utilizing the spin z-component conservation and the total spin
angular momentum conservation, we numerically derive the information of the
building blocks and evaluate von Neumann entropy to quantify the ground states.
The mean-field phase boundaries are found to remain largely intact, yet the
ground states show fragmented and entangled behaviors within large parameter
spaces of interspecies spin-exchange and singlet-pairing interactions.Comment: 7 pages, 5 figure

### Quantum spin mixing in a binary mixture of spin-1 atomic condensates

We study quantum spin mixing in a binary mixture of spin-1 condensates
including coherent interspecies mixing process, using the familiar spinor
condensates of $^{87}$Rb and $^{23}$Na atoms in the ground lower hyperfine F=1
manifolds as prototype examples. Within the single spatial mode approximation
for each of the two spinor condensates, the mixing dynamics reduce to that of
three coupled nonlinear pendulums with clear physical interpretations. Using
suitably prepared initial states, it is possible to determine the interspecies
singlet-pairing as well as spin-exchange interactions from the subsequent
mixing dynamics.Comment: 6 pages, 3 figure

### Searching for high-$K$ isomers in the proton-rich $A\sim80$ mass region

Configuration-constrained potential-energy-surface calculations have been
performed to investigate the $K$ isomerism in the proton-rich $A\sim80$ mass
region. An abundance of high-$K$ states are predicted. These high-$K$ states
arise from two and four-quasi-particle excitations, with $K^{\pi}=8^{+}$ and
$K^{\pi}=16^{+}$, respectively. Their excitation energies are comparatively
low, making them good candidates for long-lived isomers. Since most nuclei
under studies are prolate spheroids in their ground states, the oblate shapes
of the predicted high-$K$ states may indicate a combination of $K$ isomerism
and shape isomerism

### Quantum states of a binary mixture of spinor Bose-Einstein condensates

We study the structure of quantum states for a binary mixture of spin-1
atomic Bose-Einstein condensates. In contrast to collision between identical
bosons, the s-wave scattering channel between inter-species does not conform to
a fixed symmetry. The spin-dependent Hamiltonian thus contains non-commuting
terms, making the exact eigenstates more challenging to obtain because they now
depend more generally on both the intra- and inter-species interactions. We
discuss two limiting cases, where the spin-dependent Hamiltonian reduces
respectively to sums of commuting operators. All eigenstates can then be
directly constructed, and they are independent of the detailed interaction
parameters.Comment: 5 pages, no figure

### Atomic number fluctuations in a mixture of two spinor condensates

We study particle number fluctuations in the quantum ground states of a
mixture of two spin-1 atomic condensates when the interspecies spin-exchange
coupling interaction $c_{12}\beta$ is adjusted. The two spin-1 condensates
forming the mixture are respectively ferromagnetic and polar in the absence of
an external magnetic (B-) field. We categorize all possible ground states using
the angular momentum algebra and compute their characteristic atom number
fluctuations, focusing especially on the the AA phase (when $c_{12}\beta >0$),
where the ground state becomes fragmented and atomic number fluctuations
exhibit drastically different features from a single stand alone spin-1 polar
condensate. Our results are further supported by numerical simulations of the
full quantum many-body system.Comment: 5 pages, 2 figures, in press PR

### Vacuolar ATPase depletion contributes to dysregulation of endocytosis in bloodstream forms of Trypanosoma brucei

BACKGROUND
Vacuolar H-ATPase (V-ATPase) is a highly conserved protein complex which hydrolyzes ATP and pumps protons to acidify vacuolar vesicles. Beyond its role in pH maintenance, the involvement of V-ATPase in endocytosis is well documented in mammals and plants but is less clear in Trypanosoma brucei.
METHODS
In this study, the subcellular localization of V-ATPase subunit B (TbVAB) of T. brucei was assessed via in situ N-terminal YFP-tagging and immunofluorescence assays. Transgenic bloodstream forms (BSF) of T. brucei were generated which comprised either a V-ATPase subunit B (TbVAB) conditional knockout or a V-ATPase subunit A (TbVAA) knockdown. Acridine orange and BCECF-AM were employed to assess the roles of V-ATPase in the pH regulation of BSF T. brucei. The endocytic activities of three markers were also characterized by flow cytometry analyses. Furthermore, trypanosomes were counted from trypanolysis treatment groups (either containing 1% or 5% NHS) and endocytosed trypanosome lytic factor (TLF) was also analyzed by an immunoblotting assay.
RESULTS
TbVAB was found to localize to acidocalcisomes, lysosomes and probably also to endosomes of BSF of T. brucei and was demonstrated to be essential for cell growth. TbVAB depletion neutralized acidic organelles at 24 hours post-tetracycline depletion (hpd), meanwhile the steady state intracellular pH increased from 7.016 ± 0.013 to 7.422 ± 0.058. Trypanosomes with TbVAB depletion at 24 hpd were found to take up more transferrin (2.068 ± 0.277 fold) but less tomato lectin (49.31 ± 22.57%) by endocytosis, while no significant change was detected in dextran uptake. Similar endocytic dysregulated phenotypes were also observed in TbVAA knockdown cells. In addition, TbVAB depleted trypanosomes showed a low uptake of TLF and exhibited less sensitive to lysis in both 1% and 5% NHS treatments.
CONCLUSIONS
TbVAB is a key component of V-ATPase and was found to play a key function in endocytosis as well as exhibiting different effects in a receptor/cargo dependent manner in BSF of T. brucei. Besides vacuolar alkalinization, the dysregulation of endocytosis in TbVAB depleted T. brucei is considered to contribute to the reduced sensitivity to lysis by normal human serum

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