Heat transfer from a high temperature safety rod placed in a perforated guide tube and surrounded by an array of cold tubes

In this paper, a simple natural convection heat-transfer model for a safety rod placed in a perforated guide tube is proposed. The geometry is typical of the Savannah River K reactor. The proposed model for the rod and the perforated guide-tube assembly is benchmarked against prototypical test data obtained by Idaho National Engineering Laboratory. The results showed that the proposed model was in good agreement with the experimental data except at very high temperatures where the model slightly underpredicted the rod and tube temperatures. By evaluating the thermal conductivity of the fluid (air) at the wall temperature, the prediction of the high temperature natural convection data was further improved.     

Propensity of raw victorian brown coal for physical adsorption of nitrogen, oxygen, carbon dioxide and wat

A brief investigation of the relative propensity of untreated Victorian brown coal for physical adsorption of oxygen, nitrogen, carbon dioxide and water has been made. Due to the similarities between the physical properties of nitrogen and those of oxygen, nitrogen has been taken as a non-reacting oxygen model. The measurements show that physical and reversible adsorption of water occurs to a significant extent under the conditions usually applied in low temperature coal oxidation studies.     

Functional connectivity in the rodent trigeminal pathway grown in vitro

In explant cocultures of the rat trigeminal pathway, embryonic trigeminal ganglion cells grow their axons into peripheral cutaneous and central nervous system targets (R.S. Erzurumlu, S. Jhaveri, Target influences on the morphology of trigeminal axons, Exp. Neurol, 135 (1995) 1-16; R.S. Erzurumlu, S. Jhaveri, H. Takahashi, R.D.G. McKay, Target-derived influences on axon growth modes in explant cocultures of trigeminal neurons, Proc. Natl. Acad. Sci. USA 90 (1993) 7235-7239). In heterochronic cocultures, composed of embryonic trigeminal ganglion, embryonic whisker pad and postnatal brainstem slice, trigeminal axons develop arbors and terminal boutons in the brainstem trigeminal nuclei. To determine whether these terminal arbors establish functional connections with the brainstem neurons, we examined the electrophysiological properties of brainstem neurons and their responsiveness to trigeminal ganglion stimulation. Intracellular recordings were done in vitro on cells of the trigeminal subnucleus interpolaris (SPI) in trigeminal pathway cocultures (E15 whisker pad, E15 trigeminal ganglion, and postnatal day (PND) 0-2 brainstem slice) or in the SPI of acutely prepared brainstem slices. Electrophysiological properties of SPI cells in both preparations were virtually identical. The voltage responses of SPI neurons to intracellular current injection were highly linear suggesting they lacked a number of voltage-dependent conductances. Depolarizing current injection produced trains of action potentials with a frequency that varied with stimulus intensity. In explant cocultures, electrical activation of the trigeminal ganglion evoked EPSPs, and EPSPs coupled with IPSPs in SPI cells. Bicuculline blockade of IPSP activity resulted in long lasting EPSPs whose duration increased with membrane depolarization. These results show that brainstem trigeminal neurons can retain their functional properties in culture and establish functional connections with primary sensory afferents.     

Use of solutions of organic acids to produce low friction anodised surfaces

The properties of anodic films produced by anodising aluminium in aqueous solutions of organic acids at room temperature at commercially interesting current densities were investigated with particular emphasis on the wear index, micro hardness, surface roughness and pore structure. Voltage time curves obtained using 10% w./v. solutions of the pure acids showed a rapid rise in voltage at commercially realistic current densities of 1–2 A dm^?2 but this problem could be overcome by the addition of 1–2% v./v. sulphuric acid. The films obtained under these conditions using sulphosuccinic acid (SSA), sulphosalicylic (SCA) or sulphophthalic acids (SPHA) had properties closely resembling those obtained under hard anodising conditions in 10% sulphuric acid at 0–4°C. Films were not formed using para-toluenesulphonic acid (PTSA) and the use of maleic acid (MA) resulted in the formation of substantial quantities of fumaric acid. The oxide films exhibited a structure made up of densely packed columns suffused by narrow pores. The films fall into two categories. On the one hand films produced using sulphur containing organic acids have very narrow pores of less than 10 nm diameter resembling those produced by the conventional low temperature sulphuric acid process, and on the other hand films produced using maleic or citric acids exhibit much larger pores with diameters of the order of 20 nm. Attempts to incorporate PTFE particles from aqeous dispersions of this polymer into the films were unsuccessful due to their large size (~200 nm). Duplex films with a highly porous outer layer (~100 nm diameter) on top of a dense hard layer were produced and evidence is presented which shows that some of the smaller PTFE particles can enter the mouths of these pores.     

Acid Functionalized Multiwall Carbon Nanotube/Magnetite (MWCNT)-COOH/Fe3O4 Hybrid: Synthesis, Characterization and Conductivity Evaluation

A functionalized multiwall carbon nanotube (MWCNT)–COOH/Fe₃O₄ hybrid was fabricated by co-precipitation method. Fe₃O₄ nanoparticles were stably attached to the surface of carboxyl groups (COOH). The presence of Fe₃O₄ nanoparticles and their surface conjugation to MWCNT have been confirmed by XRD, TEM and FT-IR techniques. Magnetic evaluation revealed a superparamagnetic character of the hybrid and therefore the attached Fe₃O₄ nanoparticles. The crystallite size (9 ± 3 nm), particle size (9 ± 2 nm) and magnetic domain size estimated for Fe₃O₄ are consistent with each other, which reveal the single crystalline character of the nanoparticles. Electrical conductivity and dielectric behavior have also been characterized by utilizing impedance spectroscopy up to 3 MHz for an isotherm line varying from 293 to 393 K by 10 K steps. Electrical characteristics and its complex dielectric approaches might be elucidated with the existence of a conventional tunneling conduction mechanism of temperature-independency. The AC conductivity of MWCNT–COOH/Fe₃O₄ hybrid could also be a consequence of the estimations of the universal dynamic response.     

Tumor-Cut: segmentation of brain tumors on contrast enhanced MR images for radiosurgery applications

In this paper, we present a fast and robust practical tool for segmentation of solid tumors with minimal user interaction to assist clinicians and researchers in radiosurgery planning and assessment of the response to the therapy. Particularly, a cellular automata (CA) based seeded tumor segmentation method on contrast enhanced T1 weighted magnetic resonance (MR) images, which standardizes the volume of interest (VOI) and seed selection, is proposed. First, we establish the connection of the CA-based segmentation to the graph-theoretic methods to show that the iterative CA framework solves the shortest path problem. In that regard, we modify the state transition function of the CA to calculate the exact shortest path solution. Furthermore, a sensitivity parameter is introduced to adapt to the heterogeneous tumor segmentation problem, and an implicit level set surface is evolved on a tumor probability map constructed from CA states to impose spatial smoothness. Sufficient information to initialize the algorithm is gathered from the user simply by a line drawn on the maximum diameter of the tumor, in line with the clinical practice. Furthermore, an algorithm based on CA is presented to differentiate necrotic and enhancing tumor tissue content, which gains importance for a detailed assessment of radiation therapy response. Validation studies on both clinical and synthetic brain tumor datasets demonstrate 80%-90% overlap performance of the proposed algorithm with an emphasis on less sensitivity to seed initialization, robustness with respect to different and heterogeneous tumor types, and its efficiency in terms of computation time.     

Synthesis and Characterization of Multiwall-Carbon Nanotubes Decorated with Nickel Ferrite Hybrid

Acid functionalized multiwall carbon nanotube, (MWCNT)-COOH/nickel ferrite (NiFe₂O₄), magnetic hybrids were synthesized by a co-precipitation method. X-ray diffraction, Fourier transform infrared spectrometry, thermal gravimetry, transmission electron microscopy, vibrating sample magnetometry and Impedance Spectroscopy were used to characterize the physical and electrical properties of the MWCNT-COOH/NiFe₂O₄ hybrid. NiFe₂O₄ NPs are stably attached to the surface of via carboxyl groups (COOH). The magnetic saturation value of the product was found as 8 emu/g. A tunneling conduction mechanism was believed to occur in the hybrid. The real modules (M′) of the product illustrate power law variation with a power exponent of approximately unity. These magnetic MWCNT-COOH/NiFe₂O₄ hybrids exhibit a promising prospective in the application of bio-nanoscience and technology.     

Modeling the behavior of longwall coal mine gate roadways subjected to dynamic loading

In order to characterize the behavior of a main gate during retreating of longwall faces and to evaluate the performances of five different support types, including rock bolts and steel sets, a total of 21 convergence and 18 floor-heave stations were installed. Consequently, about 11,500 convergence and 7200 floor-heave data points were obtained over a period of 14 months. In order to simulate the behavior of a supported main gate roadway, a convergence model, represented by an exponential function, was developed on the basis of statistical analyses. In addition to the convergence model, convergence–velocity and convergence–acceleration models were also derived and interpreted in terms of gate road behavior. It was determined that the convergence depends on the loading region, the time, the location of the upper and lower longwall faces, the support type and pattern, and the static and dynamic support loads. Convergence–velocity and acceleration curves provide better means to interpret the performance of supports and gate roadway behavior.     

Translation, Scale, and Deformation Weighted Polar Active Contours

Polar active contours have proven to be a powerful segmentation method for many medical as well as other computer vision applications, such as interactive image segmentation or tracking. Inspired by recent work on Sobolev active contours we derive a Sobolev-type function space for polar curves, which is endowed with a metric that allows us to favor origin translations and scale changes over smooth deformations of the curve. The resulting translation, scale, and deformation weighted polar active contours inherit the coarse-to-fine behavior of Sobolev active contours as well as their robustness to local minima and are thus very useful for many medical applications, such as cross-sectional vessel segmentation, aneurysm analysis, or cell tracking.