Mapping the location of grafted PNIPAAM in mesoporous SBA-15 silica using gas adsorption analysis

The thermoresponsive polymer poly-N-isopropylacrylamide (PNIPAAM) was grafted in mesoporous SBA-15 silica. The grafting process consists of three steps: (i) increasing the amount of surface silanol groups of SBA-15 by hydroxylation, (ii) attachment of an anchor (1-(trichlorosilyl)-2-(m/p-(chloromethylphenyl)ethane) and finally (iii) the polymerization of the monomers (NIPAAM) onto the anchor. After each step, the materials were characterized regarding the porosity, using inert gas (argon, nitrogen) physisorption measurements. Also, the structure was investigated by small-angle X-ray diffraction analysis and thermogravimetric analysis was used for determination of the amount of grafted material. A total of 17% by weight of organic material was introduced in the porous host and the structure was preserved during the grafting process. Physisorption measurements revealed that the anchor is mainly located in the intrawall pores present in SBA-15. Consequently, the polymer is preferentially located in the intrawall pores or in the vicinity thereof. The final mesopore volume is 0.47 cm(3) g(-1) as compared to 0.96 cm(3) g(-1) for the pure SBA-15. The surprisingly large loss of mesopore volume and an almost constant mesopore diameter is consistent with a partial sealing of the mesopore volume in the composite materials. The potential thermocontrol combined with the large mesoporosity and the possible "storage space" provided by the sealed mesopore volume leads to a material with possibilities for various applications.     

The Size of Exponential Sums on Intervals of the Real Line

We prove that there is a constant c>0 depending only on M≥1 and μ≥0 such that

On the equivalence of Beukers-type and Sorokin-type multiple integrals

It is well known that a triple Beukers-type integral, as defined by G. Rhin and C. Viola, can be transformed into a suitable triple Sorokin-type integral. I will discuss possible extensions to the n-dimensional case of a similar equivalence between suitably defined Beukers-type and Sorokin-type multiple integrals, with consequences on the arithmetical structure of such integrals as linear combinations of zeta-values with rational coefficients.     

Network dilution and asymmetry in an efficient brain

ABSTRACT

The ultimate goal of neuroscience is to ultimately understand how the brain functions. The advancement of brain imaging shows us how the brain continuously alternates complex activity patterns and experimentally reveals how these patterns are responsible for memory, association, reasoning, and countless other tasks. Two fundamental parameters, dilution (the number of connections per node), and symmetry (the number of bidirectional connections of the same weight) characterise two fundamental features underlying the networks that connect the single neurons in the brain and generate these patterns. Mammalian brains show large variations of dilution, and mostly asymmetric connectivity, unfortunately the advantages which drove evolution to these state of network dilution and asymmetry are still unknown. Here, we studied the effects of symmetry and dilution on a discrete-time recurrent neural network with McCulloch–Pitts neurons. We use an exhaustive approach, in which we probe all possible inputs for several randomly connected neuron networks with different degrees of dilution and symmetry. We find an optimum value for the synaptic dilution and symmetry, which turns out to be in striking quantitative agreement with what previous researchers have found in the brain cortex, neocortex and hippocampus. The diluted asymmetric brain shows high memory capacity and pattern recognition speed, but most of all it is the less energy-consumptive with respect to fully connected and symmetric network topologies.     

Synthesis of bimodal mesoporous Ni oxide from octylamine

Mesoporous Ni hydroxynitrates were synthesized from a hydrothermal mixture of Ni nitrate, octylamine as the surfactant, ethanol and water at 25–100 °C for 24 h. Mesoporous Ni oxides were obtained by calcining the Ni hydroxynitrates in air at temperatures ranging from 200 to 500 °C for 2 h. The mesoporous Ni oxides have crystalline walls, a high surface area of 133 m²/g at 350 °C, high porosity up to 0.61 cm³/g, and a bimodal mesopore size distribution, with pores roughly 2 and 10–25 nm in diameter. With an increase in the synthesis temperature, the size of the larger pores and the total pore volume of the mesoporous Ni oxide increase, while the surface area decreases slightly from 133 (25 °C) to 111 m²/g (100 °C).     

Setting bounds on critical exponents with event-by-event analysis of nuclear fragmentation data

And analysis of recent ISiS data [1] is performed and a comparison with percolation-based theories is conducted. We pay particular attention to detector acceptance corrections as well as the role of sequential decays of excited pre-fragments. The corrected data are subjected to a scaling analysis. We find evidence for a continuous phase transition in these nuclear multi-fragmentation events and extract the value for the critical exponents: σ=0.5±0.1 and τ=2.35±0.05. In addition, we find T _c=8.3±0.2 MeV.     

Tests of the Laing and Morrison coalition models under different planning horizons

The research tested Laing and Morrison's myopic and hyperopic models for sequential, three‐person coalition games when the goal is maximizing rank position. The myopic model assumes that people behave as if the present trial were the last, while the hyperopic model assumes that people behave as if the coalition formed on the present trial will continue forever. The experiment involved three different planning horizon conditions: an indefinite number of trials (the condition specified by Laing and Morrison for their models), one trial remaining, and eight trials remaining. Four different accumulated point totals were used: 300–250–50, 350–150–100, 250–200–150, and 225–200–175. In general, the myopic model was more successful than the hyperopic model, though neither model was especially accurate. Changes in the myopic model were proposed, and the difficulties in developing a theory of social decision making involving long range planning were discussed.     

Design and Biocatalytic Synthesis of Pluronics-based Nanomicellar Self-assembly Systems for Drug Encapsulation Applications

Nano medicine is an emerging branch of pharmaceuticals, which is gaining considerable attention mainly due to its new and effective way of drug delivery. Various modes of drug delivery are still in their adolescent stage, polymer-based drug delivery system is one among these. In order to develop a novel and biocompatible nano-carrier for drug delivery through a “green” and, environmentally benign approach, herein, we report the design, synthesis and characterization of four novel pluronic-based amphiphilic copolymers. Candida antartica lipase was used to catalyze polymerization in the presence of molecular sieves under solventless conditions. The resulting copolymers were also investigated for their supramolecular organization and drug encapsulation capacity for biomedical applications.