A Note on the Parameters of PBIB Association Schemes

In an m-class partially balanced incomplete block (PBIB) design [3], any two distinct treatments are related as first, second, . . . ,or mth associates in accordance with certain rules, and the resulting classification of pairs of treatments is called an association scheme [1], [4]. Parameters, including v, ni, pijk, which depend only on the association relation between treatments and are common to all designs having a given association scheme, are called association scheme parameters. Other parameters, including b, r, k, λi, depend, in addition, on the arrangement of the treatments into blocks. Known results on two-class association scheme parameters, reviewed in this section with some changes in arrangement and notation, are used in Section 2 to prove some new relations. Dependent as they are on known necessary conditions, our theorems will not provide any new proofs of the nonexistence of particular designs. However, they are in a form which is convenient for application and are oriented toward the fundamental problem of the connection between number-theoretic properties of the parameters and combinatorial structure of the designs

Medical Device Technology: Does Federal Regulation of This New Frontier Preempt the Consumer\u27s State Common Law Claims Arising from Injuries Related to Defective Medical Devices?

The purpose of this paper is to explore the relationship between federal medical device regulation and state common law tort actions. Specifically, the issue to be addressed is whether the Medical Devices Act and regulations promulgated thereunder preempt state law damage actions brought by injured consumers against device manufacturers. An analysis of the preemptive provision of the Medical Devices Act and case law construing this provision is set forth below. The United States Supreme Court\u27s recent preemption analysis in Cipollone v. Liggett Group, Inc. will be used as a guide in establishing a useful method for determining whether state tort claims arising out of consumer injuries resulting from defective medical devices are preempted by the Medical Devices Act

On Linear Associative Algebras Corresponding to Association Schemes of Partially Balanced Designs

Given v objects 1, 2, .. , v, a relation satisfying the following conditions is said to be an association scheme with m classes: (a) Any two objects are either 1st, or 2nd, . . ,or mth associates, the relation of association being symmetrical, i.e., if the object α is the ith associate of the object β, then β is the ith associate of α. (b) Each object a has ni ith associates, the number ni being independent of α. (c) If any two objects α and β are ith associates, then the number of objects which are jth associates of α, and kth associates of β, is pijk and is independent of the pair of ith associates α and β. The numbers v, ni (i = 1, 2, . , m) and pijk (i, j, k = 1, 2, . . . , m) are the parameters of the association scheme. If we have an association scheme with m classes and given parameters, then we get a partially balanced design with r replications and b blocks if we can arrange the v objects into b sets (each set corresponding to a block) such that (i) each set contains k objects (all different) ; (ii) each object is contained in r sets; (iii) if two objects α and β are ith associates, then they occur together in λi sets, the number λi being independent of the particular pair of ith associates α and β

On Linear Associative Algebras Corresponding to Association Schemes of Partially Balanced Designs

Given v objects 1, 2, .. , v, a relation satisfying the following conditions is said to be an association scheme with m classes: (a) Any two objects are either 1st, or 2nd, . . ,or mth associates, the relation of association being symmetrical, i.e., if the object α is the ith associate of the object β, then β is the ith associate of α. (b) Each object a has ni ith associates, the number ni being independent of α. (c) If any two objects α and β are ith associates, then the number of objects which are jth associates of α, and kth associates of β, is pijk and is independent of the pair of ith associates α and β. The numbers v, ni (i = 1, 2, . , m) and pijk (i, j, k = 1, 2, . . . , m) are the parameters of the association scheme. If we have an association scheme with m classes and given parameters, then we get a partially balanced design with r replications and b blocks if we can arrange the v objects into b sets (each set corresponding to a block) such that (i) each set contains k objects (all different) ; (ii) each object is contained in r sets; (iii) if two objects α and β are ith associates, then they occur together in λi sets, the number λi being independent of the particular pair of ith associates α and β

On a matrix partition conjecture

AbstractIn 1977, Ganter and Teirlinck proved that any 2t × 2t matrix with 2t nonzero elements can be partitioned into four submatrices of order t of which at most two contain nonzero elements. In 1978, Kramer and Mesner conjectured that any mt × nt matrix with kt nonzero elements can be partitioned into mn submatrices of order t of which at most k contain nonzero elements. We show that this conjecture is true for some values of m, n, t and k but that it is false in general

Integrity of chromatin and replicating DNA in nuclei released from fission yeast by semi-automated grinding in liquid nitrogen

<p>Abstract</p> <p>Background</p> <p>Studies of nuclear function in many organisms, especially those with tough cell walls, are limited by lack of availability of simple, economical methods for large-scale preparation of clean, undamaged nuclei.</p> <p>Findings</p> <p>Here we present a useful method for nuclear isolation from the important model organism, the fission yeast, <it>Schizosaccharomyces pombe</it>. To preserve <it>in vivo </it>molecular configurations, we flash-froze the yeast cells in liquid nitrogen. Then we broke their tough cell walls, without damaging their nuclei, by grinding in a precision-controlled motorized mortar-and-pestle apparatus. The cryo-ground cells were resuspended and thawed in a buffer designed to preserve nuclear morphology, and the nuclei were enriched by differential centrifugation. The washed nuclei were free from contaminating nucleases and have proven well-suited as starting material for genome-wide chromatin analysis and for preparation of fragile DNA replication intermediates.</p> <p>Conclusions</p> <p>We have developed a simple, reproducible, economical procedure for large-scale preparation of endogenous-nuclease-free, morphologically intact nuclei from fission yeast. With appropriate modifications, this procedure may well prove useful for isolation of nuclei from other organisms with, or without, tough cell walls.</p

Reproducible doxycycline-inducible transgene expression at specific loci generated by Cre-recombinase mediated cassette exchange

Comparative analysis of mutants using transfection is complicated by clones exhibiting variable levels of gene expression due to copy number differences and genomic position effects. Recombinase-mediated cassette exchange (RMCE) can overcome these problems by introducing the target gene into pre-determined chromosomal loci, but recombination between the available recombinase targeting sites can reduce the efficiency of targeted integration. We developed a new LoxP site (designated L3), which when used with the original LoxP site (designated L2), allows highly efficient and directional replacement of chromosomal DNA with incoming DNA. A total of six independent LoxP integration sites introduced either by homologous recombination or retroviral delivery were analyzed; 70–80% of the clones analyzed in hamster and human cells were correct recombinants. We combined the RMCE strategy with a new, tightly regulated tetracycline induction system to produce a robust, highly reliable system for inducible transgene expression. We observed stable inducible expression for over 1 month, with uniform expression in the cell population and between clones derived from the same integration site. This system described should find significant applications for studies requiring high level and regulated transgene expression and for determining the effects of various stresses or oncogenic conditions in vivo and in vitro

Mouse genome-wide association and systems genetics identifies Lhfp as a regulator of bone mass.

Bone mineral density (BMD) is a strong predictor of osteoporotic fracture. It is also one of the most heritable disease-associated quantitative traits. As a result, there has been considerable effort focused on dissecting its genetic basis. Here, we performed a genome-wide association study (GWAS) in a panel of inbred strains to identify associations influencing BMD. This analysis identified a significant (P = 3.1 x 10-12) BMD locus on Chromosome [email protected] Mbp that replicated in two separate inbred strain panels and overlapped a BMD quantitative trait locus (QTL) previously identified in a F2 intercross. The association mapped to a 300 Kbp region containing four genes; Gm2447, Gm20750, Cog6, and Lhfp. Further analysis found that Lipoma HMGIC Fusion Partner (Lhfp) was highly expressed in bone and osteoblasts. Furthermore, its expression was regulated by a local expression QTL (eQTL), which overlapped the BMD association. A co-expression network analysis revealed that Lhfp was strongly connected to genes involved in osteoblast differentiation. To directly evaluate its role in bone, Lhfp deficient mice (Lhfp-/-) were created using CRISPR/Cas9. Consistent with genetic and network predictions, bone marrow stromal cells (BMSCs) from Lhfp-/- mice displayed increased osteogenic differentiation. Lhfp-/- mice also had elevated BMD due to increased cortical bone mass. Lastly, we identified SNPs in human LHFP that were associated (P = 1.2 x 10-5) with heel BMD. In conclusion, we used GWAS and systems genetics to identify Lhfp as a regulator of osteoblast activity and bone mass

CpG Islands: Starting Blocks for Replication and Transcription

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