Apparatus for growing crystals

An improved apparatus and method for growing crystals from a melt employing a heat pipe, consisting of one or more sections, each section serving to control temperature and thermal gradients in the crystal as it forms inside the pipe

Recent Decisions

Comments on recent decisions by Ralph H. Witt, Raymond Brown, Thomas A. McNish, Daniel J. Manelli, Stanley B. Nelson, George A. Pelletier, Jr., David T. Link, and Thomas Kavadas, Jr

Properties of 3-manifolds for relativists

In canonical quantum gravity certain topological properties of 3-manifolds are of interest. This article gives an account of those properties which have so far received sufficient attention, especially those concerning the diffeomorphism groups of 3-manifolds. We give a summary of these properties and list some old and new results concerning them. The appendix contains a discussion of the group of large diffeomorphisms of the $l$-handle 3-manifold.Comment: 20 pages. Plain-TeX, no figures, 1 Table (A4 format

Modeling time delay in the NFκB signaling pathway following low dose IL-1 stimulation

Stimulation of human epithelial cells with IL-1 (10 ng/ml) + UVB radiation results in sustained NFκB activation caused by continuous IKKβ phosphorylation. We have recently published a strictly reduced ordinary differential equation model elucidating the involved mechanisms. Here, we compare model extensions for low IL-1 doses (0.5 ng/ml), where delayed IKKβ phosphorylation is observed. The extended model including a positive regulatory element, most likely auto-ubiquitination of TRAF6, reproduces the observed experimental data most convincingly. The extension is shown to be consistent with the original model and contains very sensitive processes which may serve as potential intervention targets

Vasoprotective effects of human CD34+ cells: towards clinical applications

<p>Abstract</p> <p>Background</p> <p>The development of cell-based therapeutics for humans requires preclinical testing in animal models. The use of autologous animal products fails to address the efficacy of similar products derived from humans. We used a novel immunodeficient rat carotid injury model in order to determine whether human cells could improve vascular remodelling following acute injury.</p> <p>Methods</p> <p>Human CD34+ cells were separated from peripheral buffy coats using automatic magnetic cell separation. Carotid arterial injury was performed in male Sprague-Dawley nude rats using a 2F Fogarty balloon catheter. Freshly harvested CD34+ cells or saline alone was administered locally for 20 minutes by endoluminal instillation. Structural and functional analysis of the arteries was performed 28 days later.</p> <p>Results</p> <p>Morphometric analysis demonstrated that human CD34+ cell delivery was associated with a significant reduction in intimal formation 4 weeks following balloon injury as compared with saline (I/M ratio 0.79 ± 0.18, and 1.71 ± 0.18 for CD34, and saline-treated vessels, respectively P < 0.05). Vasoreactivity studies showed that maximal relaxation of vessel rings from human CD34+ treated animals was significantly enhanced compared with saline-treated counterparts (74.1 ± 10.2, and 36.8 ± 12.1% relaxation for CD34+ cells and saline, respectively, P < 0.05)</p> <p>Conclusion</p> <p>Delivery of human CD34+ cells limits neointima formation and improves arterial reactivity after vascular injury. These studies advance the concept of cell delivery to effect vascular remodeling toward a potential human cellular product.</p

Europium Underneath Graphene on Ir(111): Intercalation Mechanism, Magnetism, and Band Structure

The intercalation of Eu underneath Gr on Ir(111) is comprehensively investigated by microscopic, magnetic, and spectroscopic measurements, as well as by density functional theory. Depending on the coverage, the intercalated Eu atoms form either a $(2 \times 2)$ or a $(\sqrt{3} \times \sqrt{3})$R$30^{\circ}$ superstructure with respect to Gr. We investigate the mechanisms of Eu penetration through a nominally closed Gr sheet and measure the electronic structures and magnetic properties of the two intercalation systems. Their electronic structures are rather similar. Compared to Gr on Ir(111), the Gr bands in both systems are essentially rigidly shifted to larger binding energies resulting in n-doping. The hybridization of the Ir surface state $S_1$ with Gr states is lifted, and the moire superperiodic potential is strongly reduced. In contrast, the magnetic behavior of the two intercalation systems differs substantially as found by X-ray magnetic circular dichroism. The $(2 \times 2)$ Eu structure displays plain paramagnetic behavior, whereas for the $(\sqrt{3} \times \sqrt{3})$R$30^{\circ}$ structure the large zero-field susceptibility indicates ferromagnetic coupling, despite the absence of hysteresis at 10 K. For the latter structure, a considerable easy-plane magnetic anisotropy is observed and interpreted as shape anisotropy.Comment: 18 pages with 14 figures, including Supplemental Materia

Petroleomic depth profiling of Staten Island salt marsh soil: 2ω detection FTICR MS offers a new solution for the analysis of environmental contaminants

Staten Island is located in one of the most densely populated regions of the US: the New York/New Jersey Estuary. Marine and industrial oil spills are commonplace in the area, causing the waterways and adjacent marshes to become polluted with a range of petroleum-related contaminants. Using Rock-Eval pyrolysis, the hydrocarbon impact on a salt marsh was assessed at regular intervals down to 90 cm, with several key sampling depths of interest identified for further analysis. Ultrahigh resolution data are obtained by direct infusion (DI) atmospheric pressure photoionization (APPI) on a 12 T solariX Fourier transform ion cyclotron resonance mass spectrometer (FTICR MS) allowing trends in the compositional profile with depth to be observed, such as changes in the relative hydrocarbon intensity and the relative contributions from oxygen- and sulfur-containing groups. These trends may correlate with the timing of major oil spills and leaks of petroleum and other industrial chemicals into the waterways. The use of gas chromatography (GC) coupled to a 7 T solariX 2XR FTICR MS equipped with an atmospheric pressure chemical ionization (APCI) ion source offers retention time resolved and extensive compositional information for the complex environmental samples complementary to that obtained by DI-APPI. The compositional profile observed using GC-APCI FTICR MS includes contributions from phosphorous-containing groups, which may be indicative of contamination from other anthropogenic source

Negative Energy Density in Calabi-Yau Compactifications

We show that a large class of supersymmetric compactifications, including all simply connected Calabi-Yau and G_2 manifolds, have classical configurations with negative energy density as seen from four dimensions. In fact, the energy density can be arbitrarily negative -- it is unbounded from below. Nevertheless, positive energy theorems show that the total ADM energy remains positive. Physical consequences of the negative energy density include new thermal instabilities, and possible violations of cosmic censorship.Comment: 25 pages, v2: few clarifying comments and reference adde