Modular Building Block Approach Research Articles

Modular ceramic scaffolds for individual implants

Ideal artificial bone grafts aim for multiscale porosity, high mechanical strength and ensure rapid vascularization for bone ingrowth. In this work modular ceramic arteriovenous loops (AV-loops) with a hierarchical porosity approach were designed and manufactured to meet these criteria and to exceed the poor mechanical strength of monolithic scaffolds. Bioactive building blocks (β-TCP, HAp, BCP) with dimensions of 1.5–3.0 mm were prepared by injection molding and assembled to complex AV-loop scaffolds using a customized automated assembly technology (pick and place). The building blocks were bonded with a biocompatible adhesive. Single building blocks are characterized by a compressive strength of 112.4–134.5 MPa with a residual sintering porosity of 32.2–41.5%, matching the strength of cortical bone of 100–230 MPa. The compressive strength of the modular assemblies varied between 22.3 and 47.6 MPa primary depending on the building block arrangement. The achieved compressive strengths are superior to current monolithic AV-scaffolds and sufficient for the implantation as non-load-bearing AV-loop scaffolds in isolation chambers. The modular AV-loop scaffolds provide a hierarchical interconnected pore network (P = 58.8%) combining small macropores of 4.1–4.3 µm size for possible enhanced protein absorption and large gradient macropores of 200–1700 µm size for optimum vascularization and complete bone ingrowth. The modular building block approach allows to design patient individualized scaffolds with complex hierarchical pore networks. The pore volume, size and geometry as well as the biological response can effectively be tuned by changing the dimensions, shape and placing gap of the bioactive building blocks. Statement of SignificanceGold standard of bone replacement in case of surgery or cancer is still own bone material usually taken from the hip/arm or leg in second surgery with poor mechanical properties and limited amount. To avoid a second surgery and provide mechanical strong scaffold structures for fast patient regeneration a novel modular building block approach is used. This allows complex scaffold geometry with a hierarchical interconnection porosity for blood vessel ingrowth. The pore volume, size and geometry as well as the biological response can effectively be tuned by changing the dimensions, shape and placing gap of the bioactive building blocks.

A Modular Synthesis of Unsymmetrical Tetraarylazadipyrromethenes.

AbstractFor Abstract see ChemInform Abstract in Full Text.

A Modular Synthesis of Unsymmetrical Tetraarylazadipyrromethenes

[reaction: see text] A stepwise route to unsymmetrical tetraarylazadipyrromethenes by a condensation of 2,4-diaryl-5-nitroso-pyrroles with 2,4-diarylpyrroles is described. This modular building-block approach allows for the introduction of up to four different aryl substituents on the azadipyrromethene and is tolerant of a varied substituent set. An efficient synthesis of the 2,4-diarylpyrroles building blocks from 1,3-diaryl-4-nitro-butan-1-ones by nitro hydrolysis to a keto-aldehyde and subsequent ammonia condensation reaction has been achieved. The facile conversion of 2,4-diarylpyrroles into their alpha-nitroso analogues by their reaction with sodium nitrite generated the second building block required for the synthesis.

Clustering of Protein Structural Fragments Reveals Modular Building Block Approach of Nature

Structures of peptide fragments drawn from a protein can potentially occupy a vast conformational continuum. We co-ordinatize this conformational space with the help of geometric invariants and demonstrate that the peptide conformations of the currently available protein structures are heavily biased in favor of a finite number of conformational types or structural building blocks. This is achieved by representing a peptides' backbone structure with geometric invariants and then clustering peptides based on closeness of the geometric invariants. This results in 12,903 clusters, of which 2207 are made up of peptides drawn from functionally and/or structurally related proteins. These are termed “functional” clusters and provide clues about potential functional sites. The rest of the clusters, including the largest few, are made up of peptides drawn from unrelated proteins and are termed “structural” clusters. The largest clusters are of regular secondary structures such as helices and beta strands as well as of beta hairpins. Several categories of helices and strands are discovered based on geometric differences. In addition to the known classes of loops, we discover several new classes, which will be useful in protein structure modeling. Our algorithm does not require assignment of secondary structure and, therefore, overcomes the limitations in loop classification due to ambiguity in secondary structure assignment at loop boundaries.

Highly branched oligosaccharides: a general strategy for the synthesis of multiantennary N-glycans with a bisected motif.

Squeezing in a sugar: A modular building-block approach was the strategy used in a clever general synthesis of the sterically crowded triantennary N-glycans bearing an additional bisecting GlcNAc motif (see formula). Key steps include the use of the small trifluoroacetyl protective group and the late introduction of the α1,6-arm.

Structural design of modern steam turbine blades using ADINA ™

The present paper provides an overview of the structural design of modern steam turbine blades at Siemens power generation using the finite element code ADINA™. The different types of blades are described in detail regarding their geometry and loading. The modular building block approach of modelling is shown to be of essential importance. For the different analyses a fatigue post-processor has been implemented as well as an optimization tool. Both of these in-house codes will be briefly presented.

Design, Synthesis, and Photodynamics of Light-Harvesting Arrays Comprised of a Porphyrin and One, Two, or Eight Boron-Dipyrrin Accessory Pigments

Light-harvesting arrays containing one, two, or eight boron-dipyrrin (BDPY) pigments and one porphyrin (free base or Zn chelate) have been synthesized using a modular building block approach. The reaction of pyrrole and 4-(BDPY)benzaldehyde or 3,5-bis(BDPY)benzaldehyde, prepared by Pd-mediated ethynylation with the corresponding iodo-benzaldehydes, affords the desired BDPY-porphyrin array in yields of 10−58%. The arrays are soluble in organic solvents and have been characterized by static and time-resolved absorption and fluorescence spectroscopy. The blue-green BDPY absorption complements spectral coverage of the porphyrin chromophores and rivals the intensity of the porphyrin Soret band when eight BDPY accessory pigments are present. Efficient energy transfer from the BDPY pigment(s) to the porphyrin (free base or Zn-chelate) is observed in arrays containing one or two (>90%) or eight (>85%) accessory pigments per porphyrin. Biphasic excited-state decay behavior is exhibited by the BDPY pigments in isol...

Effects of central metal ion (Mg, Zn) and solvent on singlet excited-state energy flow in porphyrin-based nanostructures

F. Li, S. Gentemann, William A. Kalsbeck, J. Seth, Jonathan S. Lindsey, D. Holten and David F. Bocian, J. Mater. Chem., 1997, 7, 1245 DOI: 10.1039/A700146K

Synthesis of Linear Amphipathic Porphyrin Dimers and Trimers: An Approach to Bilayer Lipid Membrane Spanning Porphyrin Arrays.

A modular building-block approach has been developed for the construction of linear amphipathic porphyrin arrays. The reaction of meso-(trifluoromethyl)dipyrromethane and an aldehyde under the conditions of the two-step room temperature porphyrin synthesis affords the trans-substituted porphyrin (13-56% yields). A similar reaction with two different aldehydes provides access to porphyrins bearing two different functional groups. An ethyne porphyrin and an iodo porphyrin (either free base or zinc) are selectively joined via Pd(0)-catalyzed coupling reactions, affording a linear array with porphyrins in defined metalation states. Coupling of a zinc-porphyrin bearing iodo and ester groups with a free base porphyrin bearing ethyne and ester groups yielded the zinc-free base porphyrin dimer. Coupling of a bis-ethyne porphyrin with a porphyrin bearing iodo and ester groups afforded the porphyrin trimer. Cleavage of the esters yielded the amphipathic porphyrin dimer and trimer arrays. The arrays with adjacent zinc and free base porphyrins undergo efficient electronic energy transfer. Both amphipathic porphyrin arrays have been incorporated into L-alpha-phosphatidylcholine vesicles. This versatile synthetic strategy provides access to a family of porphyrin arrays for studies of photophysical processes in supramolecular assemblies.

Use of the slave emulator

In-circuit emulation is the ability to imitate electrically a target microprocessor, responding to system inputs or instructions, and producing accurately the expected outputs or responses to the instructions. A modular building block approach to microprocessor-based design is given, the Slave Emulator Control Unit (SECU) is described and its flexibility shown.