Field Equations of Massless Fields in the New Interpretation of the Matrix Model

Recently, some of the authors have introduced a new interpretation of matrix models in which covariant derivatives on any curved space can be expressed by large-N matrices. It has been shown that the Einstein equation follows from the equation of motion of IIB matrix model in this interpretation. In this paper, we generalize this argument to covariant derivatives with torsion. We find that some components of the torsion field can be identified with the dilaton and the $B$-field in string theory. However, the other components do not seem to have string theory counterparts. We also consider the matrix model with a mass term or a cubic term, in which the equation of motion of string theory is exactly satisfied.Comment: 21 page

Multiple hydrothermal sources along the south Tonga arc and Valu Fa Ridge

Quantifying hydrothermal venting at the boundaries of tectonic plates is an outstanding geoscience problem. Considerable progress has been made by detailed surveys along mid-ocean ridges (MORs), but until recently little was known about fluid venting along volcanic arcs. We present the first systematic survey for hydrothermal venting along the 425-km-long south Tonga arc and new chemistry data for particle and thermal plumes previously reported along an adjacent 88-km-long section of the back-arc Valu Fa Ridge (VFR). Eleven hydrothermal plumes, recognized by their anomalous light backscattering, Eh, temperature, pH, dissolved 3He, CH4, and total dissolvable Fe and Mn, were identified arising from seven volcanic centers along the arc. Five plumes on the VFR were characterized chemically. Vent field density for the south Tonga arc was 2.6 sites/100 km of arc front, comparable to that found by surveys of the Kermadec arc (1.9 to 3.8 sites/100 km) and to MORs in the eastern Pacific (average value for 2280 km of surveyed ridgecrest: 3.2 sites/100 km). A "vent gap" occurs along a 190 km section of the arc closest to the VFR, and a site density twice the average for MORs on the eastern edge of the Pacific plate was found on this part of the VFR (6.6 sites/100 km). We suggest magmas ascending under the adjacent south Tonga arc have been captured by the VFR. While chemical enrichments of plumes on the south Tonga arc were, in general, slightly less than those on the Kermadec arc, several instances of excessive anomalies in pH suggest a similar presence of fluids enriched in magmatic volatiles (CO2-SO2-H2S). Locally, venting on the VFR has contributed to accumulations of 3He, Fe, and Mn within the southern Lau basin. On a broader scale, our results provide considerable support for the notion that venting from intraoceanic arcs on the convergent margin of the Pacific plate adds significantly to the total hydrothermal input into the Pacific Ocean

Vasculature-driven stem cell population coordinates tissue scaling in dynamic organs

Stem cell (SC) proliferation and differentiation organize tissue homeostasis. However, how SCs regulate coordinate tissue scaling in dynamic organs remain unknown. Here, we delineate SC regulations in dynamic skin. We found that interfollicular epidermal SCs (IFESCs) shape basal epidermal proliferating clusters (EPCs) in expanding abdominal epidermis of pregnant mice and proliferating plantar epidermis. EPCs consist of IFESC-derived Tbx3⁺–basal cells (Tbx3⁺-BCs) and their neighboring cells where Adam8–extracellular signal–regulated kinase signaling is activated. Clonal lineage tracing revealed that Tbx3⁺-BC clones emerge in the abdominal epidermis during pregnancy, followed by differentiation after parturition. In the plantar epidermis, Tbx3⁺-BCs are sustained as long-lived SCs to maintain EPCs invariably. We showed that Tbx3⁺-BCs are vasculature-dependent IFESCs and identified mechanical stretch as an external cue for the vasculature-driven EPC formation. Our results uncover vasculature-mediated IFESC regulations, which explain how the epidermis adjusts its size in orchestration with dermal constituents in dynamic skin

Non-abelian Action for Multiple Five-Branes with Self-Dual Tensors

We construct an action for non-abelian 2-form in 6-dimensions. Our action consists of a non-abelian generalization of the abelian action of Perry and Schwarz for a single five-brane. It admits a self-duality equation on the field strength as the equation of motion. It has a modified 6d Lorentz symmetry. On dimensional reduction on a circle, our action gives the standard 5d Yang-Mills action plus higher order corrections. Based on these properties, we propose that our theory describes the gauge sector of multiple M5-branes in flat space.Comment: LaTeX, 26 pages. v2: improved discussion of Lorentz symmetry. ref added. v3: add comments in the discussion section on the inclusion of scalar fields and supersymmetry; title changed to a more suitable one; version published in JHE

Pur alpha and Sp8 as opposing regulators of neural gata2 expression

AbstractGata2 is an essential hematopoietic transcriptional factor that is also expressed prominently in the nervous system. The early lethality of knockout mice due to severe anemia has largely precluded studies of gata2 neural regulation and function. In this report, we describe the identification of zebrafish Pur alpha and Sp8 orthologs as two factors that function to regulate neuronal expression of gata2. During embryogenesis, Pur alpha is expressed widely, whereas Sp8 has an overlapping pattern of expression with gata2 in the nervous system. Knockdown and ectopic expressions of Pur alpha and Sp8 indicate that these factors function, respectively, as a repressor and an activator of gata2 gene expression in the nervous system. With consideration given to the previously established roles for these factors, we propose a model for how the transcriptional regulation of neural gata2 expression may be involved in controlling cellular proliferation in the nervous system

Dynamic Behavior of Salmonella-Induced Membrane Tubules in Epithelial Cells

Salmonella Typhimurium is a facultative intracellular pathogen that causes acute gastroenteritis in man. Intracellular Salmonella survive and replicate within a modified phagosome known as the Salmonella-containing vacuole (SCV). The onset of intracellular replication is accompanied by the appearance of membrane tubules, called Salmonella-induced filaments (Sifs), extending from the SCV. Sifs are enriched in late endosomal/lysosomal membrane proteins such as lysosome-associated membrane protein 1, but their formation and ability to interact with endosomal compartments are not characterized. In this study, we use live cell imaging techniques to define the dynamics of Sif formation in infected epithelial cells. At early time-points, Sifs are simple tubules extending from the surface of SCVs. These tubules are highly dynamic and exhibit bidirectional, microtubule-dependent movement. At the distal ends of individual Sif tubules, furthest from the SCV, a distinct ‘leader’ domain was often observed. At later times, Sifs develop into highly complex tubular networks that extend throughout the cell and appear less dynamic than nascent Sifs; however, individual tubules continue to display bidirectional dynamics. Sifs can acquire endocytic content by fusion, indicating a sustained interaction with the endocytic pathway. Together, these results show that these Salmonella-induced tubules form a highly dynamic network that involves both microtubule-dependent motility and interactions with endosomal compartments