Parametric CR-umbilical Locus of Ellipsoids in C2\mathbb{C}^2

For every real numbers $a \geqslant 1$, $b \geqslant 1$ with $(a,b) \neq (1,1)$, the curve parametrized by $\theta \in \mathbb{R}$ valued in $\mathbb{C}^2 \cong \mathbb{R}^4$ $$\gamma\, \colon \ \ \ \theta \,\,\,\longmapsto\,\,\, \big( x(\theta)+{\scriptstyle{\sqrt{-1}}}\,y(\theta),\,\, u(\theta)+{\scriptstyle{\sqrt{-1}}}\,v(\theta) \big)$$ with components: $$x(\theta) \,:=\, {\textstyle{\sqrt{\frac{a-1}{a\,(ab-1)}}}}\, \cos\,\theta, \ \ \ \ \ y(\theta) \,:=\, {\textstyle{\sqrt{\frac{b\,(a-1)}{ab-1}}}}\, \sin\,\theta, \ \ \ \ \ u(\theta) \,:=\, {\textstyle{\sqrt{\frac{b-1}{b\,(ab-1)}}}}\, \sin\,\theta, \ \ \ \ \ v(\theta) \,:=\, -\, {\textstyle{\sqrt{\frac{a\,(b-1)}{ab-1}}}}\, \cos\,\theta,$$ has image contained in the CR-umbilical locus: $$\gamma(\mathbb{R}) \,\subset\, {\sf UmbCR} \big({\sf E}_{a,b}\big) \,\subset\, {\sf E}_{a,b}$$ of the ellipsoid ${\sf E}_{a,b} \subset \mathbb{C}^2$ of equation $a\,x^2+y^2+b\,u^2+y^2 = 1$

Thermal generation of spin current in epitaxial CoFe2O4 thin films

The longitudinal spin Seebeck effect (LSSE) has been investigated in high-quality epitaxial CoFe2O4 (CFO) thin films. The thermally excited spin currents in the CFO films are electrically detected in adjacent Pt layers due to the inverse spin Hall effect (ISHE). The LSSE signal exhibits a linear increase with increasing temperature gradient, yielding a LSSE coefficient of ~100 nV/K at room temperature. The temperature dependence of the LSSE is investigated from room temperature down to 30 K, showing a significant reduction at low temperatures, revealing that the total amount of thermally generated magnons decreases. Furthermore, we demonstrate that the spin Seebeck effect is an effective tool to study the magnetic anisotropy induced by epitaxial strain, especially in ultrathin films with low magnetic moments.Comment: 17 pages, 4 figure

Influence of thickness and interface on the low-temperature enhancement of the spin Seebeck effect in YIG films

The temperature dependent longitudinal spin Seebeck effect (LSSE) in heavy metal (HM)/Y3Fe5O12 (YIG) hybrid structures is investigated as a function of YIG film thickness, magnetic field strength, and different HM detection material. The LSSE signal shows a large enhancement with reducing the temperature, leading to a pronounced peak at low temperatures. We find the LSSE peak temperature strongly depends on the film thickness as well as on the magnetic field. Our result can be well explained in the framework of magnon-driven LSSE by taking into account the temperature dependent effective propagation length of thermally excited magnons in bulk. We further demonstrate that the LSSE peak is significantly shifted by changing the interface coupling to an adjacent detection layer, revealing a more complex behavior beyond the currently discussed bulk effect. By direct microscopic imaging of the interface, we correlate the observed temperature dependence with the interface structure between the YIG and the adjacent metal layer. Our results highlight the role of interface effects on the temperature dependent LSSE in HM/YIG system, suggesting that the temperature dependent spin current transparency strikingly relies on the interface conditions

Star Formation and Clumps in Cosmological Galaxy Simulations with Radiation Pressure Feedback

Cosmological simulations of galaxies have typically produced too many stars at early times. We study the global and morphological effects of radiation pressure (RP) in eight pairs of high-resolution cosmological galaxy formation simulations. We find that the additional feedback suppresses star formation globally by a factor of ~2. Despite this reduction, the simulations still overproduce stars by a factor of ~2 with respect to the predictions provided by abundance matching methods for halos more massive than 5E11 Msun/h (Behroozi, Wechsler & Conroy 2013). We also study the morphological impact of radiation pressure on our simulations. In simulations with RP the average number of low mass clumps falls dramatically. Only clumps with stellar masses Mclump/Mdisk <= 5% are impacted by the inclusion of RP, and RP and no-RP clump counts above this range are comparable. The inclusion of RP depresses the contrast ratios of clumps by factors of a few for clump masses less than 5% of the disk masses. For more massive clumps, the differences between and RP and no-RP simulations diminish. We note however, that the simulations analyzed have disk stellar masses below about 2E10 Msun/h. By creating mock Hubble Space Telescope observations we find that the number of clumps is slightly reduced in simulations with RP. However, since massive clumps survive the inclusion of RP and are found in our mock observations, we do not find a disagreement between simulations of our clumpy galaxies and observations of clumpy galaxies. We demonstrate that clumps found in any single gas, stellar, or mock observation image are not necessarily clumps found in another map, and that there are few clumps common to multiple maps.Comment: 13 pages, 6 figures, submitted to MNRA

The preprophase band-associated kinesin-14 OsKCH2 is a processive minus-end-directed microtubule motor.

In animals and fungi, cytoplasmic dynein is a processive minus-end-directed motor that plays dominant roles in various intracellular processes. In contrast, land plants lack cytoplasmic dynein but contain many minus-end-directed kinesin-14s. No plant kinesin-14 is known to produce processive motility as a homodimer. OsKCH2 is a plant-specific kinesin-14 with an N-terminal actin-binding domain and a central motor domain flanked by two predicted coiled-coils (CC1 and CC2). Here, we show that OsKCH2 specifically decorates preprophase band microtubules in vivo and transports actin filaments along microtubules in vitro. Importantly, OsKCH2 exhibits processive minus-end-directed motility on single microtubules as individual homodimers. We find that CC1, but not CC2, forms the coiled-coil to enable OsKCH2 dimerization. Instead, our results reveal that removing CC2 renders OsKCH2 a nonprocessive motor. Collectively, these results show that land plants have evolved unconventional kinesin-14 homodimers with inherent minus-end-directed processivity that may function to compensate for the loss of cytoplasmic dynein