Analysis of tumor as an inverse problem provides a novel theoretical framework for understanding tumor biology and therapy

We use a novel “inverse problem” technique to construct a basic mathematical model of the interacting populations at the tumor-host interface. This approach assumes that invasive cancer is a solution to the set of state equations that govern the interactions of transformed and normal cells. By considering the invading tumor edge as a traveling wave, the general form of the state equations can be inferred. The stability of this traveling wave solution imposes constraints on key biological quantities which appear as parameters in the model equations. Based on these constraints, we demonstrate the limitations of traditional therapeutic strategies in clinical oncology that focus solely on killing tumor cells or reducing their rate of proliferation. The results provide insights into fundamental mechanisms that may prevent these approaches from successfully eradicating most common cancers despite several decades of research. Alternative therapies directed at modifying the key parameters in the state equations to destabilize the propagating solution are proposed

Local disorder and optical properties in V-shaped quantum wires : towards one-dimensional exciton systems

The exciton localization is studied in GaAs/GaAlAs V-shaped quantum wires (QWRs) by high spatial resolution spectroscopy. Scanning optical imaging of different generations of samples shows that the localization length has been enhanced as the growth techniques were improved. In the best samples, excitons are delocalized in islands of length of the order of 1 micron, and form a continuum of 1D states in each of them, as evidenced by the sqrt(T) dependence of the radiative lifetime. On the opposite, in the previous generation of QWRs, the localization length is typically 50 nm and the QWR behaves as a collection of quantum boxes. These localization properties are compared to structural properties and related to the progresses of the growth techniques. The presence of residual disorder is evidenced in the best samples and explained by the separation of electrons and holes due to the large in-built piezo-electric field present in the structure.Comment: 8 figure

Viral Retinitis following Intraocular or Periocular Corticosteroid Administration: A Case Series and Comprehensive Review of the Literature.

Abstract Purpose: To describe viral retinitis following intravitreal and periocular corticosteroid administration. Methods: Retrospective case series and comprehensive literature review. Results: We analyzed 5 unreported and 25 previously published cases of viral retinitis following local corticosteroid administration. Causes of retinitis included 23 CMV (76.7%), 5 HSV (16.7%), and 1 each VZV and unspecified (3.3%). Two of 22 tested patients (9.1%) were HIV positive. Twenty-one of 30 (70.0%) cases followed one or more intravitreal injections of triamcinolone acetonide (TA), 4 (13.3%) after one or more posterior sub-Tenon injections of TA, 3 (10.0%) after placement of a 0.59-mg fluocinolone acetonide implant (Retisert), and 1 (3.3%) each after an anterior subconjunctival injection of TA (together with IVTA), an anterior chamber injection, and an anterior sub-Tenon injection. Mean time from most recent corticosteroid administration to development of retinitis was 4.2 months (median 3.8; range 0.25-13.0). Twelve patients (40.0%) had type II diabetes mellitus. Treatments used included systemic antiviral agents (26/30, 86.7%), intravitreal antiviral injections (20/30, 66.7%), and ganciclovir intravitreal implants (4/30, 13.3%). Conclusions: Viral retinitis may develop or reactivate following intraocular or periocular corticosteroid administration. Average time to development of retinitis was 4 months, and CMV was the most frequently observed agent. Diabetes was a frequent co-morbidity and several patients with uveitis who developed retinitis were also receiving systemic immunosuppressive therapy

A quadtree-polygon-based scaled boundary finite element method for image-based mesoscale fracture modelling in concrete

A quadtree-polygon scaled boundary finite element-based approach for image-based modelling of concrete fracture at the mesoscale is developed. Digital images representing the two-phase mesostructure of concrete, which comprises of coarse aggregates and mortar are either generated using a take-and-place algorithm with a user-defined aggregate volume ratio or obtained from X-ray computed tomography as an input. The digital images are automatically discretised for analysis by applying a balanced quadtree decomposition in combination with a smoothing operation. The scaled boundary finite element method is applied to model the constituents in the concrete mesostructure. A quadtree formulation within the framework of the scaled boundary finite element method is advantageous in that the displacement compatibility between the cells are automatically preserved even in the presence of hanging nodes. Moreover, the geometric flexibility of the scaled boundary finite element method facilitates the use of arbitrary sided polygons, allowing better representation of the aggregate boundaries. The computational burden is significantly reduced as there are only finite number of cell types in a balanced quadtree mesh. The cells in the mesh are connected to each other using cohesive interface elements with appropriate softening laws to model the fracture of the mesostructure. Parametric studies are carried out on concrete specimens subjected to uniaxial tension to investigate the effects of various parameters e.g. aggregate size distribution, porosity and aggregate volume ratio on the fracture of concrete at the meso-scale. Mesoscale fracture of concrete specimens obtained from X-ray computed tomography scans are carried out to demonstrate its feasibility

Thiophene-based poly(arylene ether ketone)s: 2. Thermal and mechanical properties of amorphous systems using bis(p-fluorobenzoyl)aryl monomers

A series of high molar mass and controlled molar mass poly(aryl ether ketone)s were synthesized based on bis(p-fluoro-benzoyl)aryl monomers and 4,4'-isopropylidenediphenol. The central aromatic unit of the activated bishalide was varied to include 1,4 phenylene, 2,5 thiophene, and 1,3 phenylene to systematically change the exocyclic bond angle from 180˚ to 148˚ to 120˚, respectively. The thermal, dynamic mechanical and mechanical properties of the three polymers were determined for the controlled molar mass materials. The glass transition temperature of the controlled molar mass 2,5-thiophene based polymer was 147˚ C compared to 149˚ C for 1,3-phenylene based polymer and 162˚ C for the 1,4-phenylene based polymer. The thermal stability of poly(BFTh-BisA) was similar to that of poly(1,3-BFBBisA) and poly(1,4-BFB-BisA). Two sub T loss dispersions were measured for each of the three polymers. The pronounced y relaxation for poly(BFTh-BisA), poly(1,4- BFB-BisA), and poly(1,3-BFB-BisA), has an activation energy of 7.5, 9.0, and 10 kcal/mole, respectively. The activation energy of β dispersion for poly(BFTh-BisA) is 16 kcal/mole. The Young's modulus is 2.9 GPa, 3.1 GPa and 3.6 GPa for poly(1,4-BFB-BisA), poly(2,5-BFTh-BisA) and poly(1,3-BFB-BisA), respectively

Self-consistent stability analysis of spherical shocks.

In this paper, we study self-similar solutions, and their linear stability as well, describing the flow within a spherical shell with finite thickness, expanding according to a power law of time, t q , where q>0. The shell propagates in a medium with initially uniform density and it is bounded by a strong shock wave at its outer border while the inner face is submitted to a time-dependent uniform pressure. For q=2/5, the well-known Sedov–Taylor solution is recovered. In addition, although both accelerated and decelerated shells can be unstable against dynamic perturbations, they exhibit highly different behaviors. Finally, the dispersion relation derived earlier by Vishniac (Vishniac, E.T. in Astrophys. J. 274:152, 1983) for an infinitely thin shell is obtained in the limit of an isothermal shock wave

Scaling and self-averaging in the three-dimensional random-field Ising model

We investigate, by means of extensive Monte Carlo simulations, the magnetic critical behavior of the three-dimensional bimodal random-field Ising model at the strong disorder regime. We present results in favor of the two-exponent scaling scenario, $\bar{\eta}=2\eta$, where $\eta$ and $\bar{\eta}$ are the critical exponents describing the power-law decay of the connected and disconnected correlation functions and we illustrate, using various finite-size measures and properly defined noise to signal ratios, the strong violation of self-averaging of the model in the ordered phase.Comment: 8 pages, 6 figures, to be published in Eur. Phys. J.

Efecto de la inoculación con Glomus intraradices y de la fertilización nitrogenada en el crecimiento de plantas de fresa

The white-tailed deer (Odocoileus virginianus peruvianus) is a ruminant of the family Cervidae that is managed as a game species in the Sauce Grande area of Coto de Caza El Angolo (CCEA), Piura, Peru. The aim of this study was to propose a health protocol for the white-tailed deer of CCEA as an essential component of their management work plans as well as to serve as a model for other wildlife in protected natural areas. For the development of this protocol a literature review was done on the species, along with five visits to CCEA for the evaluation of the area and the standardization of some procedures, where biological samples were collected from white-tailed deers and domestic mammals in the area for microbiologic analysis.El objetivo de este trabajo fue evaluar el efecto de la inoculación del HMA Glomus intraradices en el crecimiento de las plantas de fresa variedad Camino Real, fertirrigadas con 0, 1, 3 y 10 mM de N en forma de NH4+ ó NO3-. Se realizó un experimento en condiciones de invernadero, en el que se evaluó el porcentaje de colonización, el peso seco de las raíces (PSR) y de la parte aérea (PSPA), a los 33 y 48 dias después del establecimiento (dde). El porcentaje de colonización se redujo conforme al incremento de la concentración de NH4+ ó NO3- en la solución de riego; a los 33 dde, la inoculación de G. intraradices incrementó el PSR y el PSPA en las plantas fertilizadas con NH4+; y a los 48 dde se observó el mismo efecto en las plantas que recibieron NO3-. En ambos casos, los valores más altos de biomasa aérea y radical se registraron en las plantas fertirrigadas con bajas concentraciones de N. Estos resultados indican que la inoculación con G. intraradices tiene el potencial de reducir la aplicación de fertilizantes nitrogenados en el cultivo de fresa. Además, el exceso de N inhibe la colonización de HMA sin incrementar el crecimiento de la planta. Así mismo, el efecto de la inoculación de G. intraradices, forma y dosis de fertilizante nitrogenado depende de la fase de crecimiento de la planta