145 research outputs found
Density correlations in ultracold atomic Fermi gases
We investigate density fluctuations in a coherent ensemble of interacting
fermionic atoms. Adapting the concept of full counting statistics, well-known
from quantum optics and mesoscopic electron transport, we study second-order as
well as higher-order correlators of density fluctuations. Using the mean-field
BCS state to describe the whole interval between the BCS limit and the BEC
limit, we obtain an exact expression for the cumulant-generating function of
the density fluctuations of an atomic cloud. In the two-dimensional case, we
obtain a closed analytical expression. Poissonian fluctuations of a molecular
condensate on the BEC side are strongly suppressed on the BCS side. The size of
the fluctuations in the BCS limit is a direct measure of the pairing potential.
We also discuss the BEC-BCS crossover of the third cumulant and the temperature
dependence of the second cumulant.Comment: 4 pages, 4 figures. To appear in Phys. Rev. A. New calculation of the
bin statistics of a free Bose gas; updated and extended bibliograph
Biomaterial and biocompatibility evaluation of tunicate nanocellulose for tissue engineering
Extracellular matrix fibril components, such as collagen, are crucial for the structural properties of several tissues and organs. Tunicate-derived cellulose nanofibrils (TNC) combined with living cells could become the next gold standard for cartilage and soft-tissue repair, as TNC fibrils present similar dimensions to collagen, feasible industrial production, and chemically straightforward and cost-efficient extraction procedures. In this study, we characterized the physical properties of TNC derived from aquaculture production in Norwegian fjords and evaluated its biocompatibility regarding induction of an inflammatory response and foreign-body reactions in a Wistar rat model. Additionally, histologic and immunohistochemical analyses were performed for comparison with expanded polytetrafluoroethylene (ePTFE) as a control. The average length of the TNC as determined by atomic force microscopy was tunable from 3 mu m to 2.4 mu m via selection of a various number of passages through a microfluidizer, and rheologic analysis showed that the TNC hydrogels were highly shear-thinning and with a viscosity dependent on fibril length and concentration. As a bioink, TNC exhibited excellent rheological and printability properties, with constructs capable of being printed with high resolution and fidelity. We found that post-print cross-linking with alginate stabilized the construct shape and texture, which increased its ease of handling during surgery. Moreover, after 30 days in vivo, the constructs showed a highly-preserved shape and fidelity of the grid holes, with these characteristics preserved after 90 days and with no signs of necrosis, infection, acute inflammation, invasion of neutrophil granulocytes, or extensive fibrosis. Furthermore, we observed a moderate foreign-body reaction involving macrophages, lymphocytes, and giant cells in both the TNC constructs and PTFE controls, although TNC was considered a nonirritant biomaterial according to ISO 10993-6 as compared with ePTFE. These findings represent a milestone for future clinical application of TNC scaffolds for tissue repair. One sentence summary: In this study, the mechanical properties of tunicate nanocellulose are superior to nanocellulose extracted from other sources, and the biocompatibility is comparable to that of ePTFE
Interplay between SIN3A and STAT3 Mediates Chromatin Conformational Changes and GFAP Expression during Cellular Differentiation
BACKGROUND: Neurons and astrocytes are generated from common neural precursors, yet neurogenesis precedes astrocyte formation during embryogenesis. The mechanisms of neural development underlying suppression and de-suppression of differentiation-related genes for cell fate specifications are not well understood. METHODOLOGY/PRINCIPAL FINDINGS: By using an in vitro system in which NTera-2 cells were induced to differentiate into an astrocyte-like lineage, we revealed a novel role for Sin3A in maintaining the suppression of GFAP in NTera-2 cells. Sin3A coupled with MeCP2 bound to the GFAP promoter and their occupancies were correlated with repression of GFAP transcription. The repression by Sin3A and MeCP2 may be an essential mechanism underlying the inhibition of cell differentiation. Upon commitment toward an astrocyte-like lineage, Sin3A- MeCP2 departed from the promoter and activated STAT3 simultaneously bound to the promoter and exon 1 of GFAP; meanwhile, olig2 was exported from nuclei to the cytoplasm. This suggested that a three-dimensional or higher-order structure was provoked by STAT3 binding between the promoter and proximal coding regions. STAT3 then recruited CBP/p300 to exon 1 and targeted the promoter for histone H3K9 and H3K14 acetylation. The CBP/p300-mediated histone modification further facilitates chromatin remodeling, thereby enhancing H3K4 trimethylation and recruitment of RNA polymerase II to activate GFAP gene transcription. CONCLUSIONS/SIGNIFICANCE: These results provide evidence that exchange of repressor and activator complexes and epigenetic modifications are critical strategies for cellular differentiation and lineage-specific gene expression
GLUCOSE-6-PHOSPHATE DEHYDROGENASE AND 6-PHOSPHOGLUCONATE DEHYDROGENASE ACTIVITY IN ADRENALS OF MICE WITH SPONTANEOUS ADRENOCORTICAL LIPID DEPLETION
Histometric studies on the adrenal cortex of mice with spontaneous adrenocortical lipid depletion. A comparaison with dexamethasone- and acth-treated c57bl mice.
Autoradiographic studies on the incorporation of 3h-uridine into the adrenal glands of mice with spontaneous adrenocortical lipid depletion. A comparison with c57bl mice.
The adrenal weight of mice with spontaneous adrenocortical lipid depletion. A comparison with untreated, acth- and dexamethasone- treated c57bl mice.
Gonadectomy and testosterone-substitution in male mice with spontan- eous adrenocortical lipid depletion. A comparison with c57bl mice.
Incorporation of 3h-uridine into the adrenal cortex of mice after stimulation and inhibition. An autoradiographic study.
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