Block Architecture Research Articles

Multiple Bit Upsets and Error Mitigation in Ultra-Deep Submicron SRAMS

Recent measurements of the SEU (single-event upset) cross-section for 6 T SRAMs fabricated in a nano-scale commercial CMOS process were performed. Results indicated that the dominant upset mechanism was associated with multiple-cell upsets (MCUs) strikes on PMOS transistors. The dominance of the MCU cross section favors the use of a block architecture with widely spaced word bits and the use of EDAC (error detect and correct) along with periodic memory scrubbing to prevent the integration of single-bit errors.

Genetic diversity and the structure of linkage disequilibrium in the methylenetetrahydrofolate reductase locus

Investigation of linkage disequilibrium block architecture in human genome is modern, intensely investigated field of molecular genetics. In the present study, genetic differentiation and linkage disequilibrium pattern in the methylenetetrahydrofolate reductase (MTHFR) locus was examined in the populations of Russians, Tuvinians, and Northern and Southern Kyrgyzes. Methylenetetrahydrofolate reductase is the key enzyme of folate cycle, responsible for reduction of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate. Decreased enzymatic activity of this protein often caused by certain associations of MTHFR alleles results in the increased plasma homocysteine levels. In the population groups examined, genotype and allele frequencies at five polymorphic MTHFR loci: rs17037397, rs4846052, rs1801133, rs1801131, and rs1537516 were evaluated. Statistically significant genetic differences between the population group of Southern Kyrgyzes and the other groups, as well as between Russians and Tuvinians, were demonstrated. In the MTHFR gene from the population of Southern Kyrgyzes one block was revealed; in the populations of Russians, Tuvinians, and Northern Kyrgyzes two blocks were detected. Thus, the structure of linkage disequilibrium in the MTHFR locus demonstrated population-specific pattern.

Influence of block composition on crack toughness behaviour of styrene- b–(styrene- random-butadiene)– b-styrene triblock copolymers

The deformation and fracture behaviour of symmetric and asymmetric styrene- b–(styrene- random-butadiene)– b-styrene (S–SB–S) triblock copolymers with variations in their molecular architectures in terms of their outer PS block and the random SB middle block composition ratios have been investigated using essential work of fracture approach based on post yield fracture mechanics concept. The present investigations on crack resistance behaviour of these S–(S/B)–S triblock copolymers where effective interaction parameter (χ eff) is systematically varied through the variation of block compositions and architecture is in continuation to our earlier communicated short article highlighting the phase behaviour-morphology and mechanical property interrelation. The crack initiation and propagation behaviours are correlated to morphology and dynamic mechanical properties as obtained from TEM, SAXS and DMA measurements. The influence of interaction parameter ( χ-parameter) space which has been manipulated through the variation of block compositions has clearly manifested in their morphologies and in their mechanical properties. Further the kinetic aspects of fracture mechanical response have also been investigated where all the materials have clearly revealed block composition dependence. SEM analysis was carried out to understand the fracture modes prior to failure.

A Tunable Analog Conditioning Circuit Applied to Magnetoresistive Sensors

This paper presents an adaptive processing system based on analog-digital circuits to extend the linear range of angular position sensors compensating the temperature-dependent drift. System-level simulations give a sensor output improvement higher than 70%, which drastically reduces deviations due to temperature. The building block architecture characteristics make these circuits suitable for implementing the ldquosmartnessrdquo part of smart sensors in embedded systems.

In Situ Cross-Linking of Elastin-like Polypeptide Block Copolymers for Tissue Repair

Rapid cross-linking of elastin-like polypeptides (ELPs) with hydroxymethylphosphines (HMPs) in aqueous solution is attractive for minimally invasive in vivo implantation of biomaterials and tissue engineering scaffolds. In order to examine the independent effect of the location and number of reactive sites on the chemical cross-linking kinetics of ELPs and the mechanical properties of the resulting hydrogels, we have designed ELP block copolymers comprised of cross-linkable, hydrophobic ELP blocks with periodic Lys residues (A block) and aliphatic, hydrophilic ELP blocks with no cross-linking sites (B block); three different block architectures, A, ABA, and BABA were synthesized in this study. All ELP block copolymers were rapidly cross-linked with HMPs within several minutes under physiological conditions. The inclusion of the un-cross-linked hydrophilic block, its length relative to the cross-linkable hydrophobic block, and the block copolymer architecture all had a significant effect on swelling ratios of the cross-linked hydrogels, their microstructure, and mechanical properties. Fibroblasts embedded in the ELP hydrogels survived the cross-linking process and remained viable for at least 3 days in vitro when the gels were formed from an equimolar ratio of HMPs and Lys residues of ELPs. DNA quantification of the embedded cells indicated that the cell viability within triblock ELP hydrogels was statistically greater than that in the monoblock gels at day 3. These results suggest that the mechanical properties of ELP hydrogels and the microenvironment that they present to cells can be tuned by the design of the block copolymer architecture.

Towards effective poster presentations: an annotated bibliography

PurposeThe aim of this paper is to introduce the topic of poster presentation as legitimate area of academic study and practice within the marketing discipline.Design/methodology/approachThe paper presents the output of one part of a research project that reviewed the state of knowledge and practice within poster presentation as a dissemination medium for research information. The results of the literature search are presented as an annotated bibliography.FindingsThe literature search reveals a sizeable body of material on the use of poster presentation as a dissemination media, indicative of a set of key themes that guide good practice in poster design, construction and presentation. It also includes material that has studied the use of poster design and presentation exercises as pedagogical devices.Research limitations/implicationsThe research on which the paper is based is limited by virtue of not offering a more complete survey of contemporary poster presentation practice across the sciences. It draws observations from the author's attendance at several marketing and management‐related conferences where poster presenters have been interviewed and examples of poster presentation have been collected. However, in the sciences, especially the medical sciences, poster practice is well‐established and in some cases moving towards digitisation.Practical implicationsThe aesthetics of poster design remain unclear in the case of poster design for the dissemination of scientific information. However, a set of templates has been produced based on the close study of a database of over 600 poster designs and ten years' experience of using posters as teaching tools for research training. A methodology for poster design has also been developed known as “The Block Architecture Method of Poster Design”. It uses the software Powerpoint and Photoshop to develop poster design electronically.Originality/valueThe bibliography will help interested teachers and students explore the various issues surrounding poster design, construction and presentation. It will also help to understand some of the advantages of using poster‐design exercises as creative and critical devices in a pedagogical context.

The Wegener’s granulomatosis quantitative trait locus on chromosome 6p21.3 as characterised by tagSNP genotyping

Background:A genomic region on chromosome 6p21.3, including HLA-DPB1, has been linked to Wegener’s granulomatosis (WG). The basis of this association is difficult to evaluate because of the complex haplotype block...

FPGA PLB Architecture Evaluation and Area Optimization Techniques Using Boolean Satisfiability

This paper presents a field-programmable gate array (FPGA) logic synthesis technique based upon Boolean satisfiability. This paper shows how to map any Boolean function into an arbitrary programmable logic block (PLB) architecture without any custom decomposition techniques. The authors illustrate several useful applications of this technique by showing how this technique can be used for architecture evaluation and area optimization. When evaluating the FPGA architecture, the authors focus on the basic building block of the FPGA, which they refer to as PLB. In order to illustrate the flexibility of their evaluation framework, several unrelated PLB architectures are evaluated in an automated fashion. Furthermore, the authors show that using their technique is able to reduce FPGA resource usage by 27% on average in common subcircuits found in digital design.

Sharing of SRAM Tables Among NPN-Equivalent LUTs in SRAM-Based FPGAs

This article introduces a novel lookup table (LUT) and its usage in the configurable logic block (CLB) architectures for SRAM-based field-programmable gate array (FPGA) architectures. The proposed CLB allows sharing of SRAM tables of LUTs among NPN-equivalent functions to reduce the size of memories used for storing the functions and also reduces the number of configuration bits required. We measured many different characteristics of FPGAs using our new CLB architecture, including area, delay, routing, and power requirements. We experimentally found that for many different FPGA architectures, CLBs can share one-fourth of their SRAM tables between two basic logic elements (BLEs), which reduced both power consumption and area without negatively affecting routing or wirelength, and there was only a negligible increase in critical path delay of 0.27%. Specifically, we find that FPGAs consisting of CLBs with 16 BLEs and 34 inputs can be implemented with eight normal SRAMs and four SRAMs shared between two BLEs, for an overall reduction of four out of sixteen SRAM tables per CLB. With this new CLB architecture, we measured an approximate reduction in overall power consumption of 2% and an estimated reduction in area of 3%

Effect of copolymer architecture on the response of pH sensitive fibers based on acrylonitrile and acrylic acid

Copolymers of acrylonitrile and acrylic acid with high acrylic acid feed ratio of 43 mol% were synthesized using free radical polymerization. The architecture of copolymers was modified by regulating the dosing of more reactive comonomer-acrylic acid. 13C NMR analysis confirmed that two copolymers – one (A) containing enriched blocks of individual monomer-residues (architecture close to a block copolymer) and the second (B) having nearly random distribution of the comonomers, could be successfully synthesized. The resultant acrylic acid content was determined to be nearly 50 mol% for both the copolymers. These copolymers were converted to fine fibers by solution spinning in DMF-water system, drawn in coagulation bath, and annealed at 120 °C for 2 h. The fibers were evaluated for pH response behavior, mechanical stability, and retracting stresses. The fiber A was found to have significantly higher swelling percentage (3300–3700%), faster response, and higher stability to repeated cycling compared to fiber B. Also, Fiber A showed lower thermal shrinkage, better mechanical properties during swelling and higher retracting forces during deswelling. These results indicate that the copolymer with enriched block architecture could possibly form segregated domain structure with acrylic acid domains facilitating enhanced pH response while acrylonitrile domains providing physical crosslinks for stronger mechanical strength. The study suggests that above approach may be more useful than chemically cross-linked gel rods in producing artificial muscles with faster response and good mechanical properties.

An insight into the phylogenetic history of HOX linked gene families in vertebrates

BackgroundThe human chromosomes 2q, 7, 12q and 17q show extensive intra-genomic homology, containing duplicate, triplicate and quadruplicate paralogous regions centered on the HOX gene clusters. The fact that two or more representatives of different gene families are linked with HOX clusters is taken as evidence that these paralogous gene sets might have arisen from a single chromosomal segment through block or whole chromosome duplication events. This would imply that the constituent genes including the HOX clusters reflect the architecture of a single ancestral block (before vertebrate origin) where all of these genes were linked in a single copy.ResultsIn the present study we have employed the currently available set of protein data for a wide variety of vertebrate and invertebrate genomes to analyze the phylogenetic history of 11 multigene families with three or more of their representatives linked to human HOX clusters. A topology comparison approach revealed four discrete co-duplicated groups: group 1 involves the genes from GLI, HH, INHB, IGFBP (cluster-1), and SLC4A families; group 2 involves ERBB, ZNFN1A, and IGFBP (cluster-2) gene families; group 3 involves the HOX clusters and the SP gene family; group 4 involves the integrin beta chain and myosine light chain families. The distinct genes within each co-duplicated group share the same evolutionary history and are duplicated in concert with each other, while the constituent genes of two different co-duplicated groups may not share their evolutionary history and may not have duplicated simultaneously.ConclusionWe conclude that co-duplicated groups may themselves be remnants of ancient small-scale duplications (involving chromosomal segments or gene-clusters) which occurred at different time points during chordate evolution. Whereas the recent combination of genes from distinct co-duplicated groups on different chromosomal regions (human chromosomes 2q, 7, 12q, and 17q) is probably the outcome of subsequent rearrangement of genomic segments, including syntenic groups of genes.

Dynamic combinatorial libraries of hydrazone-linked pseudo-peptides: dependence of diversity on building block structure and chirality

Expanding on our earlier building block architecture [(MeO)(2)CH-Linker-Pro-X-NHNH(2) where X = Phe, Cha], we have produced a series of new pseudo-dipeptides [(MeO)(2)CH-Linker-Pro-X-NHNH(2) where X = Val, Leu, Ile, Ala] for use in hydrazone-based dynamic combinatorial libraries (DCLs); reverse order analogues [Phe-Pro and Val-Pro] and two enantio-analogues [Pro-Phe and Pro-Val] were also prepared. The behaviours of these building blocks in DCLs, as single components and in mixtures, were studied systematically using HPLC and mass spectrometry in order to gain insight into the relationship between building block structure and good library diversity. Subtle changes in building block structure lead to significant changes in library distribution and in the ability to produce diverse libraries in mixtures.

Hydrogel Formation in Amphiphilic Triblock Copolypeptides

We report the synthesis of a variety of polylysine-b-polyleucine-b-polylysine, KmLnKo triblock copolypeptides and compare their gel forming properties to diblock copolypeptides. The architecture of the KmLnKo triblock copolypeptides forces the hydrophobic α-helical oligoleucine segments to pack perpendicular to extended fibrils in lamellar structure, and the similarity in properties between diblock and triblock copolymers supports the hypothesis that both systems assemble in a similar manner. The triblock architecture, however, allows preparation of samples with greater gel strength and better salt tolerance than diblock samples at similar concentrations. We have found that block architecture provides a means for fine adjustment of hydrogel properties beyond variation of polypeptide composition, concentration, and chain length.

A Monte Carlo simulation for the micellization of ABC 3-miktoarm star terpolymers in a selective solvent

We have used Monte Carlo simulation to study the micellization of ABC 3-miktoarm star terpolymers in a selective solvent (good to A segment, bad to B and C segments). The simulation results reveal that the self-assembled morphology is determined by the block length, molecular architecture, terpolymer concentration and insolubility of insoluble block in the solvent. In dilute solution, symmetric terpolymers ( N B = N C = 30) tend to aggregate into a novel wormlike pearl-necklace structure linked by an alternating arrangement of B and C spheres, whereas the asymmetric terpolymers ( N B = 10, N C = 50) are likely to aggregate into spherical or cylindrical micelles (formed by C blocks) connected with some small B spheres, when the concentration of terpolymer is relatively low (chain number is 100). However, when the concentration of terpolymer is relatively high (chain number is 250), the symmetric terpolymers tend to aggregate into a netlike structure linked by an alternation of B and C spheres, whereas the asymmetric terpolymers are likely to aggregate into wormlike micelles (formed by C blocks) connected with some of small spheres (formed by B blocks). Moreover, when the insolubility of insoluble block in the solvent is weak, the insoluble blocks aggregate into some incompact micelles. However, if we increase the insolubility of insoluble block, the resulting micelles will become more compact at first, and thereafter almost remain unchanged with further increasing the insolubility of insoluble blocks.

Microarray Glass Slides Coated with Block Copolymer Brushes Obtained by Reversible Addition Chain-Transfer Polymerization

The reversible addition-fragmentation chain-transfer polymerization was used to prepare microarray slides grafted with polymer brushes for DNA-based applications. Block copolymer brushes of N,N-dimethylacrylamide (DMA) and glycidyl methacrylate (GMA), poly(DMA-b-GMA) were prepared by extending living poly(dimethylacrylamide) chains. The functional surface was used as a substrate for oligonucleotide hybridization experiments. The results were compared to those provided by glass slides coated by a self-assembled monolayer made of (3-glycidyloxypropyl)trimethoxysilane. Surfaces coated with block polymer brushes bearing oxirane groups are more efficient as substrates for oligonucleotide hybridization than surfaces coated with nonpolymeric self-assembled monolayers containing the same functional group. The high probe grafting density and hybridization efficiency achieved with this polymeric coating reveal the importance of the block architecture to ensure good accessibility of the immobilized probe. The new surface was characterized by static angle measurements and diffuse reflectance FT-IR spectroscopy on a silica model system.

Discrete, Multiblock Isotactic–Atactic Stereoblock Polypropene Microstructures of Differing Block Architectures through Programmable Stereomodulated Living Ziegler–Natta Polymerization

Discrete, Multiblock Isotactic–Atactic Stereoblock Polypropene Microstructures of Differing Block Architectures through Programmable Stereomodulated Living Ziegler–Natta Polymerization

Discrete, Multiblock Isotactic–Atactic Stereoblock Polypropene Microstructures of Differing Block Architectures through Programmable Stereomodulated Living Ziegler–Natta Polymerization

Discrete, Multiblock Isotactic–Atactic Stereoblock Polypropene Microstructures of Differing Block Architectures through Programmable Stereomodulated Living Ziegler–Natta Polymerization

Metallopolymer−Peptide Conjugates: Synthesis and Self-Assembly of Polyferrocenylsilane Graft and Block Copolymers Containing a β-Sheet Forming Gly-Ala-Gly-Ala Tetrapeptide Segment

We describe the synthesis and self-assembly of two beta-sheet forming metallopolymer-peptide conjugates. The ability of the oligotetrapeptide sequence Gly-Ala-Gly-Ala (GAGA) to form antiparallel beta-sheets was retained in PFS-b-AGAG (PFS = polyferrocenylsilane) and PFS-g-AGAG conjugates with block and graft architectures, respectively. In the solid state, DSC experiments suggest a phase separation between the peptide and PFS domains. In toluene, PFS-b-AGAG interestingly forms a fibrous network which consists of a core containing the self-assembled antiparallel beta-sheet peptide and a corona of organometallic PFS. The self-assembly of the peptide into antiparallel beta-sheets is the driving force for the fiber formation, whereas PFS prevents uncontrolled lateral aggregation of the fibers. The use of an oligopeptide to self-assemble an otherwise random coiled organometallic polymer may be a useful strategy to enhance nanostructure formation. In the cases described here, the conjugates may be used to create nanopatterned ceramics, and the redox properties of the resulting supramolecular aggregates are of significant interest.

Self-association of block copoly(oxyalkylene)s in aqueous solution. Effects of composition, block length and block architecture

The article deals with the association behaviour in dilute aqueous solution of block copoly(oxyalkylene)s in which hydrophilic poly(ethylene oxide) is combined with hydrophobic poly(propylene oxide), poly(1,2-butylene oxide) or poly(styrene oxide). Polymers with three simple architectures are considered, i.e. copolymers of type EmAn, EmAnEm and AnEmAn, where E denotes an oxyethylene unit, A denotes a hydrophobic oxyalkylene unit, and the subscripts m and n denote number-average block lengths in repeat units. The aim is to examine how composition, block length and block architecture govern two fundamental properties, critical micelle concentration (cmc) and micelle association number (N), for systems which are in dynamic equilibrium. Copolymers with properties known to be greatly affected by heterogeneity in composition are excluded from consideration. A uniform pattern of behaviour emerges when log(cmc) is plotted against reduced hydrophobic block length (x), consistent with the micellisation equilibrium changing from one between unimers and multimolecular micelles at low values of x, to one between unimolecular micelles and multimolecular micelles at high values of x. Support for this model is provided by the enthalpy of micellisation, values of which fall effectively to zero as x is increased. Values of the micelle association number are used to define a critical hydrophobic block length for micellisation (n(cr)) for each class of diblock copolymers, values of which apply equally well to the half-length of the central block of corresponding EmAnEm triblock copolymers. Given these values, and irrespective of block architecture, the overall scaling law for the weight-average association number of the micelles is shown to be Nw = n'(1.07)m(-0.63) where m is the length (or half-length) of the hydrophilic block, and n' is the effective length of the hydrophobic block, equal to its length (or half-length) minus the critical length, i.e. n' = n-n(cr).

Effect of block architecture on the ability of polyalkylene oxides to overcome multidrug resistance of tumor cells

The relationship between the block architecture of copolymers consisting of poly(ethylene oxide) and poly(propylene oxide), their ability to induce disturbances in lipid bilayer membranes and cause chemosensitization of tumor cells was investigated. It was found that the ability of copolymers to induce disturbances in model membranes composed of egg lecithin increased with the volume of their hydrophobic blocks. Extremely high channel-forming and flippase activity was observed for the copolymer possessing a brush-like structure. The addition of cholesterol into lipid bilayers reduced the effects induced by copolymers, however, to different extents. The sensitivity of copolymer-induced effects to the addition of cholesterol increased with the growth of the critical packing parameter, which was estimated as a ratio of the volume of the whole copolymer chain to the water-accessible area of its polar headgroup and the distance between the hydrophilic and hydrophobic edges of the molecule. The comparison of the copolymers effect on multi-drug resistant human breast adenocarcinoma MCF7/DOX cells showed that two block copolymers RPE caused maximal chemosensitization, compromising between the shape of the amphiphile and the volume of its hydrophobic block.