Tessellation of Chiral‐Nematic Cellulose Nanocrystal Films by Microtemplating

In biological architectures, material properties are optimized by the hierarchical structuring of components with a multiscaled order, from the nano‐ to the macroscales. Such designs enable, for instance, programmed yield points that maximize toughness. However, research efforts in biomimetic materials have focused on the assembly of nano‐ or macrostructures individually. In this study, high strength cellulose nanocrystals (CNCs), assembled into chiral‐nematically ordered structures, are tiled into a higher level, macro‐sized, architecture by topographical templating. As templates, two meshed architectures with distinct feature sizes are evaluated, and the optomechanical properties of the resulting films are compared to featureless, flat, CNC films. Controlling capillary stresses arising during CNC assembly is shown to enable control over the orientation of the chiral‐nematic director across the topography of the template. Tuning the specific reflections and multiscaled fracture propagation is demonstrated for the microtemplated CNC films. The latter phenomenon contributed to enhancing the toughness of the material through a high tortuosity of fracture propagation in all (x, y, z) directions. The presented findings are expected to pave the way towards the incorporation of current research in cellular metamaterials with the research focusing on the generation of nanoscaled biomimetic constructs.     

Defect theorems with compatibility relations

We consider words together with a compatibility relation induced by a relation on letters. Unique factorization with respect to two arbitrary word relations R and S defines the (R,S)-freeness of the semigroup considered. We generalize the stability theorem of Schützenberger and Tilson’s closure result for (R,S)-free semigroups. The inner and the outer (R,S)-unique factorization hull and the (R,S)-free hull of a set of words are introduced and we show how they can be computed. We prove that the (R,S)-unique factorization hulls possess a defect effect, which implies a variant of a cumulative defect theorem of word semigroups. In addition, a defect theorem of partial words is proved as a corollary.     

Thermal and X‐ray powder diffraction studies of aliphatic polyester dendrimers

The syntheses and thermal and X‐ray powder diffraction analyses of three sets of aliphatic polyester dendrimers based on 2,2‐bis(hydroxymethyl)propionic acid as a repeating unit and 2,2‐dimethyl‐1,3‐propanediol, 1,5‐pentanediol, and 1,1,1‐tris(hydroxymethyl)ethane as core molecules are reported. These dendritic polyesters were prepared in high yields with the divergent method. The thermal properties of these biodendrimers were evaluated with thermogravimetric analysis and differential scanning calorimetry. The thermal decomposition of the compounds occurred around 250 °C for the hydroxyl‐ended dendrimers and around 150 °C for the acetonide‐protected dendrimers. In addition, the crystallinity of the lower generation dendrimers was evaluated with X‐ray powder diffraction. The highest crystallinity and the highest melting points were observed for the first‐generation dendritic compounds. The higher generation dendrimers showed weaker melting transitions during the first heating scan. Only the glass‐transition temperatures were observed in subsequent heating scans. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5574–5586, 2004     

Analysis of band-to-band mixing distortion contributions in some usual circuit topologies

This paper uses hand analysis and a new fully numerical distortion contribution analysis technique to explain and optimize the nonlinear performance of analog circuits. Several example circuits are studied, where mixing of nonlinear distortion from one harmonic band to another is important. In some circuits the band-to-band mixing can be employed to reduce the overall distortion.     

Particulate and soluble Eu(III)-chelates as donor labels in homogeneous fluorescence resonance energy transfer based immunoassay

Many well-established homogeneous separation free immunoassays rely on particulate label technologies. Particles generally contain a high concentration of the embedded label and they have a large surface area, which enables conjugation of a large amount of protein per particle. Eu(III)-chelate dyed nanoparticles have been successfully used as labels in heterogeneous and homogeneous immunoassays. In this study, we compared the characteristics of two homogeneous competitive immunoassays using either soluble Eu(III)-chelates or polystyrene particles containing Eu(III)-chelates as donors in a fluorescence resonance energy transfer based assay. The use of the particulate label significantly increased the obtained sensitized emission, which was generated by a single binding event. This was due to the extremely high specific activity of the nanoparticle label and also in some extent the longer Förster radius between the donor and the acceptor. The amount of the binder protein used in the assay could be decreased by 10-fold without impairing the obtainable sensitized emission, which subsequently led to improved assay sensitivity. The optimized assay using particulate donor had the lowest limit of detection (calculated using 3 × S.D. of the 0 nM standard) 50 pM of estradiol in the assay well, which was approximately 20-fold more sensitive than assays using soluble Eu(III)-chelates.     

Versatile Synthetic Strategy for Coating Upconverting Nanoparticles with Polymer Shells through Localized Photopolymerization by Using the Particles as Internal Light Sources

We present a straightforward and generic strategy for coating upconverting nanoparticles (UCPs) with polymer shells for their protection, functionalization, conjugation, and for biocompatibility. UCPs are attracting much attention for their potential use as fluorescent labels in biological applications. However, they are hydrophobic and non‐compatible with aqueous media; thus prior surface modification is essential. Our method uses the internal UV or visible light emitted from UCPs upon photoexcitation with near‐infrared radiation, to locally photopolymerize a thin polymer shell around the UCPs. In this way, a large variety of monomers with different chemical functionalities can be incorporated. If required, a second layer can be added on top of the first. Our method can provide a large spectrum of surface functional groups rapidly and in one pot, hence offering a platform for the preparation of libraries of functional polymer‐encapsulated UCPs for applications in bioassays, biosensing, optical imaging, and theranostics.     

Optimal t-Edge-Robust r-Identifying Codes in the King Lattice

Locating faulty processors in a multiprocessor system gives a motivation for identifying codes. The concept of a t-edge-robust r-identifying code was introduced in [8]. We consider these codes in the king lattice and give several optimal densities. Research supported by the Academy of Finland under grants 207303 and 111940.     

Optimizing heuristic search in forest planning

Heuristic search methods are being used more and more in forest planning since the current formulations of exact methods such as linear programming are not suitable to all today's planning problems. A practical problem with most heuristics is that their performance greatly depends on the parameters that guide their search process. The effect of parameters is hard to know without extensive tests, but these tests cannot be conducted in forest planning practice, because of lacking time and experience. This study presented a method that uses Hooke and Jeeves direct search to optimize the parameters of a heuristic, taking into account the allowed computing time. The method was used to optimize three local-improvement heuristics in a non-spatial and a spatial forest planning problem, and with a short and long computing time. The heuristics were simulated annealing, threshold accepting, and tabu search, all of which are used in forestry. The results were logical and showed that while the optimal values of some parameters were rather constant the others were sensitive to problem type, allowed computing time, or problem size. The objective function value of the forest planning problem was not sensitive to small changes in the parameters of the heuristics. However, because computing time was very sensitive to many parameters, there was not much freedom to set the parameters if both the quality of the solution and speed of the algorithm had to be maintained.     

Low temperature nanoparticle sintering with continuous wave and pulse lasers

New manufacturing methods are being sought for electronics production. Printable electronics is a promising method for producing low cost and large-scale electronics. In printable electronics nanoparticle inks printed on the surface of substrate contain additives, such as dispersing agent and carrier fluids that provide good printing properties by changing the viscosity and separating the nanoparticles of the ink. In the sintering process ink particles are heated to a certain, ink-specific temperature. During the sintering process the carrier fluid and dispersing agents are evaporated from the ink. Additional heating after evaporation causes the nanoparticles to start to agglomerate. A small particle size allows the use of a considerably lower sintering temperature than with bulk silver, for example 220 °C. The sintering process is usually utilized with a convection oven, with a long sintering time, and the thermal load on the surrounding material can become too great as components and patterns are formed from layers of different type inks. Hence, alternative sintering methods are sought. This paper describes tests done with two different types of laser; pulsed and continuous wave lasers. Laser sintering enables short sintering times and selective sintering, making it possible for printed structures to contain fragile active components produced with other technologies.