The Ultimate Halo Mass in a LCDM Universe

In the far future of an accelerating LCDM cosmology, the cosmic web of large-scale structure consists of a set of increasingly isolated halos in dynamical equilibrium. We examine the approach of collisionless dark matter to hydrostatic equilibrium using a large N-body simulation evolved to scale factor a = 100, well beyond the vacuum--matter equality epoch, a_eq ~ 0.75, and 53/h Gyr into the future for a concordance model universe (Omega_m ~ 0.3, Omega_Lambda ~ 0.7). The radial phase-space structure of halos -- characterized at a < a_eq by a pair of zero-velocity surfaces that bracket a dynamically active accretion region -- simplifies at a > 10 a_eq when these surfaces merge to create a single zero-velocity surface, clearly defining the halo outer boundary, rhalo, and its enclosed mass, mhalo. This boundary approaches a fixed physical size encompassing a mean interior density ~ 5 times the critical density, similar to the turnaround value in a classical Einstein-deSitter model. We relate mhalo to other scales currently used to define halo mass (m200, mvir, m180b) and find that m200 is approximately half of the total asymptotic cluster mass, while m180b follows the evolution of the inner zero velocity surface for a < 2 but becomes much larger than the total bound mass for a > 3. The radial density profile of all bound halo material is well fit by a truncated Hernquist profile. An NFW profile provides a somewhat better fit interior to r200 but is much too shallow in the range r200 < r < rhalo.Comment: 5 pages, 3 figures, submitted to MNRAS letter

Nutritive value of fishes of Lake Tanganyika: II. Mineral composition

The composition of the minerals in three economically important fish species of Lake Tanganyika was determined. From the analyses there does not appear to be significant difference in the composition for the three species. Beside the major elements: Ca, P, K, Na, Mg, Cl, Fe, Al and Zn, eighteen trace elements were determined. The presence of the bones in the fish is especially nutritionally important for the following elements: Ca, P, Br, Sr, Mn and Mg

Bistability patterns and nonlinear switching with very high contrast ratio in a 1550 nm quantum dash semiconductor laser

We report on the experimental observation of optical bistability (OB) and nonlinear switching (NS) in a nanostructure laser; specifically a 1550 nm quantum dash Fabry-Perot laser subject to external optical injection and operated in reflection. Different shapes of optical bistability and nonlinear switching, anticlockwise and clockwise, with very high on-off contrast ratio (up to 180:1) between output states were experimentally measured. These results added to the potential of nanostructure lasers for enhanced performance offer promise for use in fast all-optical signal processing applications in optical networks. © 2012 American Institute of Physics

Multiple solutions of the quasirelativistic Choquard equation

We prove existence of multiple solutions to the quasirelativistic Choquard equation with a scalar potential

Interleukin 2 restores CD3-zeta chain expression but fails to generate tumour-specific lytic activity in tumour-infiltrating lymphocytes derived from human colorectal hepatic metastases.

Metastatic colorectal cancer is usually progressive despite infiltration of the tumours by T lymphocytes, suggesting that these tumour-infiltrating lymphocytes (TILs) are functionally deficient. Recently, TILs from other tumours have been shown to express reduced levels of the T-cell receptor signal-transducing CD3-zeta chain. We were interested to determine whether a similar abnormality existed in TILs from human colorectal hepatic metastasis (CHM) and, if so, whether correcting the abnormality in vitro would restore anti-tumour activity and provide support for the development of immunotherapy for colorectal hepatic metastases. Twelve of 19 TILs from colorectal hepatic metastases were successfully expanded in vitro in high-dose recombinant interleukin 2 (rlL-2) and their specific anti-tumour cytolytic activity was determined. CD3-positive (CD3+) TILs were HLA-Drhigh and CD69high, suggesting that they had been activated by exposure to antigen but expressed low levels of CD25, CD71 and the nuclear proliferation antigen Ki-67. Furthermore, they showed reduced expression of CD3-zeta compared with autologous peripheral blood T cells (PBTs) and failed to proliferate in the absence of high-dose rIL-2. Expansion of TILs in rIL-2 resulted in restoration of CD3-zeta expression and the ability to lyse K562 and Daudi cells but not autologous tumour cells. The absence of autologous tumour-specific cytolytic T-cell (CTL) activity may be due to the poor immunogenicity of colorectal tumour cells, which we found expressed only low levels of MHC I antigens and CD54 and failed to express MHC II antigens or the co-stimulatory molecules CD80, CD86 or CD106. The inability of rIL-2 to generate tumour-specific CTLs despite restoration of CD3-zeta expression and the presence of an intact lytic mechanism suggests that successful immunotherapy may require the development of strategies to increase the immunogenicity of this tumour

Magnet Laboratory Research

Contains reports on three research projects

Orientability and energy minimization in liquid crystal models

Uniaxial nematic liquid crystals are modelled in the Oseen-Frank theory through a unit vector field $n$. This theory has the apparent drawback that it does not respect the head-to-tail symmetry in which $n$ should be equivalent to -$n$. This symmetry is preserved in the constrained Landau-de Gennes theory that works with the tensor $Q=s\big(n\otimes n- \frac{1}{3} Id\big)$.We study the differences and the overlaps between the two theories. These depend on the regularity class used as well as on the topology of the underlying domain. We show that for simply-connected domains and in the natural energy class $W^{1,2}$ the two theories coincide, but otherwise there can be differences between the two theories, which we identify. In the case of planar domains we completely characterise the instances in which the predictions of the constrained Landau-de Gennes theory differ from those of the Oseen-Frank theory