Mortar properties obtained by dry premixing of cementitious materials and sand in a spout-fluid bed mixer

This study examines the efficacy of a pneumatic, dry premixing process for producing commercially acceptable, ternary-blend mortars, using less cementitious material. Data are presented comparing flowability, compressive and flexural strengths, drying shrinkage, and pore size distribution in the mortars using dry, premixed material with that prepared conventionally in a small-scale, high-shear, rotary mixer. A second generation, spout-fluid bed mixer was developed for dry premixing of sand and cementitious materials which is capable of being scaled to industrial size. This advance provides uniform particle distribution, improves the particle packing density leading to more reproducible mixes, and produces mortars equivalent to those produced with high shear, rotary mixers.Dry premixing allowed the production of commercially acceptable ternary-blend mortars using less cementitious material. At a sand-to-binder ratio of 3.2:1, the compressive strength of the dry premixed mortars was about 10% higher than that of the small-scale, high shear, rotary mixed mortars of the same composition. Other properties of the mortar were also positively affected, including a decrease in the shrinkage, and an increase in the workability.     

Multiple developmental stage-specific enhancers regulate CD8 expression in developing thymocytes and in thymus-independent T cells

We and others have recently identified a CD8 locus enhancer (E8) that directs expression in mature CD8 single-positive thymocytes and peripheral CD8+ T cells and in extrathymically derived intestinal intraepithelial lymphocytes (IEL). In this study, we show that deletion of E8, by homologous recombination results in reduced CD8alphaalpha homodimer expression on IEL. Since CD8 expression on thymus-derived T cells was normal, other enhancers regulate CD8 expression in these cells. By exploiting a transgenic reporter expression assay, we identified three additional enhancers that directed expression in diverse thymocyte subsets and mature T cells but not in CD8alphaalpha+ IEL. The results suggest that CD8alpha expression is primarily regulated by E8, in IEL and by the novel enhancers in the thymus-dependent lineages.     

Prediction of the maximum spoutable bed height in spout-fluid beds

A model for predicting the ratio of the maximum spoutable bed height in a spout-fluid bed to the maximum spoutable bed height in a spouted bed is presented and experimentally verified. The model is a further extension of the basic Mamuro and Hattori force balance model. The ratio H_mSF/H_m is found to be a function of the external annular fluid flowrate and a parameter C, which is the ratio of fluid velocity at the top of the annulus to that at minimum fluidization. C = 0.935 gives a best fit of our data.     

Antiviral immune responses in Itk-deficient mice

Mice lacking Itk, a T-cell-specific protein tyrosine kinase, have reduced numbers of T cells and reduced responses to allogeneic major histocompatibility molecules. This study analyzed antiviral immune responses in mice deficient for Itk. Primary cytotoxic T-lymphocyte (CTL) responses were analyzed after infection with lymphocytic choriomeningitis virus (LCMV), vaccinia virus (VV), and vesicular stomatitis virus (VSV). Ex vivo CTL activity was consistently reduced by a factor of two to six for the different viruses. CTL responses after restimulation in vitro were similarly reduced unless exogenous cytokines were added. In the presence of interleukin-2 or concanavalin A supernatant, Itk-deficient and control mice responded similarly. Interestingly, while LCMV was completely eliminated by day 8 in both Itk-deficient and control mice, VV cleared from itk-/- mice with delayed kinetics. Antibody responses were evaluated after VSV infection. Both the T-cell-independent neutralizing immunoglobulin M (IgM) and the T-cell-dependent IgG responses were similar in Itk-deficient and control mice. Taken together, the results show that CTL responses are reduced in the absence of Itk whereas antiviral B-cell responses are not affected.     

The classification of benign and malignant human prostate tissue by multivariate analysis of 1H magnetic resonance spectra

1H magnetic resonance spectroscopy studies (360 MHz) were performed on specimens of benign (n = 66) and malignant (n = 21) human prostate tissue from 50 patients, and the spectral data were subjected to multivariate analysis, specifically linear-discriminant analysis. On the basis of histopathological assessments, an overall classification accuracy of 96.6% was achieved, with a sensitivity of 100% and a specificity of 95.5% in classifying benign prostatic hyperplasia from prostatic cancer. Resonances due to citrate, glutamate, and taurine were among the six spectral subregions identified by our algorithm as having diagnostic potential. Significantly higher levels of citrate were observed in glandular than in stromal benign prostatic hyperplasia (P < 0.05). This method shows excellent promise for the possibility of in vivo assessment of prostate tissue by magnetic resonance.     

Convergence Results for Single-Step On-Policy Reinforcement-Learning Algorithms

An important application of reinforcement learning (RL) is to finite-state control problems and one of the most difficult problems in learning for control is balancing the exploration/exploitation tradeoff. Existing theoretical results for RL give very little guidance on reasonable ways to perform exploration. In this paper, we examine the convergence of single-step on-policy RL algorithms for control. On-policy algorithms cannot separate exploration from learning and therefore must confront the exploration problem directly. We prove convergence results for several related on-policy algorithms with both decaying exploration and persistent exploration. We also provide examples of exploration strategies that can be followed during learning that result in convergence to both optimal values and optimal policies.     

Most Relevant Explanation: computational complexity and approximation methods

Most Relevant Explanation (MRE) is the problem of finding a partial instantiation of a set of target variables that maximizes the generalized Bayes factor as the explanation for given evidence in a Bayesian network. MRE has a huge solution space and is extremely difficult to solve in large Bayesian networks. In this paper, we first prove that MRE is at least NP-hard. We then define a subproblem of MRE called MRE _k that finds the most relevant k-ary explanation and prove that the decision problem of MRE _k is NP^PPNP^{\it PP}-complete. Since MRE needs to find the best solution by MRE _k over all k, and we can also show that MRE is in NP^PPNP^{\it PP}, we conjecture that a decision problem of MRE is NP^PPNP^{\it PP}-complete as well. Furthermore, we show that MRE remains in NP^PPNP^{\it PP} even if we restrict the number of target variables to be within a log factor of the number of all unobserved variables. These complexity results prompt us to develop a suite of approximation algorithms for solving MRE, One algorithm finds an MRE solution by integrating reversible-jump MCMC and simulated annealing in simulating a non-homogeneous Markov chain that eventually concentrates its mass on the mode of a distribution of the GBF scores of all solutions. The other algorithms are all instances of local search methods, including forward search, backward search, and tabu search. We tested these algorithms on a set of benchmark diagnostic Bayesian networks. Our empirical results show that these methods could find optimal MRE solutions for most of the test cases in our experiments efficiently.     

A priori modelling of an adiabatic spouted bed catalytic reactor

An a priori reactor model for an adiabatic spouted bed reactor has been developed. This model uses first-principles mass and energy balances to predict the concentration and temperature profiles in the spout, annulus and fountain regions of the reactor. The particle circulation and voidage profiles in the spout are calculated using previously developed analytical techniques. Particle circulation patterns in the annulus are determined by a minimum path-length analysis. The spout and fountain are shown to contribute significantly to the overall conversion in the bed. Predicted and experimental conversions at flowrates up to 1.2U_ms show that extension of the fountain reaction zone and increased particle circulation with increasing inlet flow makes up for the higher average voidage in the spout and fountain. Experimental data confirm the calculated results for a stably spouting bed with CO oxidation over a Co₃O₄/αAl₂O₃ catalyst. The effects of flowrate and inlet reactant concentration are confirmed.     

A theory for predicting the maximum spoutable height in a spouted bed

A theory is presented for predicting the maximum spoutable height, in a spouted bed where fluidization of the annular solids limits the penetration of the fluid jet entering the bed. The quantity (H_md_s/(D – d) is found to be a function of d_s/D_c only for spherical particles and \[ \frac{{H_m d_S }} {{(D_c^2 - d_S^2 )}} = 0.345\left( {\frac{{d_S }} {{D_c }}} \right)^{ - 0.384} \] where the spout diameter is calculated using McNab's correlation⁽⁷⁾. Insertion of McNab's correlation into Equation (1) shows that H_m is proportional to D and the effect of d_p on H_m varies from d to d as the particle Reynolds number increases assuming 1 ≥ (d_s/D). Using experimental value of d_s, the calculated values of H_m differ from the experimental ones by 8.5% on average. When small particles are spouted with air, the penetration of the jet is limited by the formation of a slug in he spout and the theoretical value provides an upper limit for H_m.     

Binaural response patterns in subdivisions of the medial geniculate body

Auditory evoked potentials (AEPs) to binaural click stimulation were examined in the ventral (MGv) and caudomedial (MGcm) subdivisions of the medial geniculate body (MG) in guinea pigs. Binaural stimulation caused a decrease in amplitude for the response component recorded from the MGv, but an increase in amplitude for the AEP component recorded from the MGcm. Findings suggest that the evoked responses recorded from MGv and MGcm are functionally distinct. The inhibitory binaural response (BR) pattern seen in MGv was similar to that of the middle latency response (MLR) component recorded over the temporal cortex, while the additive BR pattern typical of the MGcm was similar to that of the surface midline MLR component. Furthermore, these data imply that the binaural response patterns seen in the primary and non-primary auditory cortex may be processed and encoded at the thalamic level. It is concluded that the distinct BR patterns noted for the two MG subdivisions reflect the predominant type of binaurally responsive neurons within the respective pathways.