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  • Life and Medical Sciences  (33)
  • GEOPHYSICS  (24)
  • STRUCTURAL MECHANICS
  • 2005-2009
  • 1995-1999  (15)
  • 1990-1994  (59)
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  • 1
    Publication Date: 2013-08-31
    Description: The objective of this paper is to describe current results from an on-going study of the mechanisms that led to the failure of the TIBB. Experimental and analytical results are presented. Experimental results include load, strain, and deflection data for the TIBB (Technology Integration Box Beam). An analytical investigation was conducted to compliment the experimental investigation and to gain additional insight into the TIBB structural response. Analytical results include strain and deflection results from a global analysis of the TIBB. A local analysis of the failure region is being completed. These analytical results are validated through comparisons with the experimental results from the TIBB tests. The experimental and analytical results from the TIBB tests are used to determine a sequence of events that may have resulted in failure of the TIBB. A potential cause of failure is high stresses in a stiffener runout region. Typical analytical results are presented for a stiffener runout specimen that is being defined to simulate the TIBB failure mechanisms. The results of this study are anticipated to provide better understanding of potential failure mechanisms in composite aircraft structures, to lead to future design improvements, and to identify needed analytical tools for design and analysis.
    Keywords: STRUCTURAL MECHANICS
    Type: FAA, Ninth DOD(NASA)FAA Conference on Fibrous Composites in Structural Design, Volume 2; p 673-68
    Format: application/pdf
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  • 2
    Publication Date: 2013-08-31
    Description: Composite structures have the potential to be cost-effective, structurally efficient primary aircraft structures. The Advanced Composites Technology (ACT) Program has the goal to develop the technology to exploit this potential for heavily loaded aircraft structures. As part of the ACT Program, Lockheed Aeronautical Systems Company completed the design and fabrication of the Technology Integration Box Beam (TIBB). The TIBB is an advanced composite prototype structure for the center wing section of the C-130 aircraft. Lockheed subjected the TIBB to downbending, upbending, torsion and combined upbending and torsion load conditions to verify the design. The TIBB failed at 83 percent of design ultimate load for the combined upbending and torsion load condition. The objective of this paper is to describe the mechanisms that led to the failure of the TIBB. The results of a comprehensive analytical and experimental study are presented. Analytical results include strain and deflection results from both a global analysis of the TIBB and a local analysis of the failure region. These analytical results are validated by experimental results from the TIBB tests. The analytical and experimental results from the TIBB tests are used to determine a sequence of events that resulted in failure of the TIBB. A potential cause of failure is high stresses in a stiffener runout region. Analytical and experimental results are also presented for a stiffener runout specimen that was used to simulate the TIBB failure mechanisms.
    Keywords: STRUCTURAL MECHANICS
    Type: Third NASA Advanced Composites Technology Conference, Volume 1, Part 2; p 951-965
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  • 3
    ISSN: 0886-1544
    Keywords: actomyosin ; smooth muscle contraction ; nonmuscle cell motility ; microinjection ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The effects of monoclonal anti-caldesmon antibodies, C2, C9, C18, C21, and C23, on the binding of caldesmon to F-actin/F-actin-tropomyosin filaments and to Ca++/calmodulin were examined in an in vitro reconstitution system. In addition, the antibody epitopes were mapped by Western blot analysis of NTCB (2-nitro-5-thiocyanobenzoic acid) and CNBr (cyanogen bromide) fragments of caldesmon. Both C9 and C18 recognize an amino terminal fragment composed of amino acid residues 19 to 153. The C23 epitope lies within a fragment ranging from residues 230 to 386. Included in this region is a 13-residue repeat sequence. Interestingly this repetitive sequence shares sequence similarity with a sequence found in nuclear lamin A, a protein which is also recognized by C23 antibody. Therefore, it is likely that the C23 epitope corresponds to this 13-residue repeat sequence. A carboxyl-terminal 10K fragment contains the epitopes for antibodies C2 and C21. Among these antibodies, only C21 drastically inhibits the binding of caldesmon to F-actin/F-actin-tropomyosin filaments and tc Ca++/calmodulin. When the molar ratio of monoclonal antibody C21 to caldesmon reached 1.0, a maximal inhibition (90%) on the binding of caldesmon to F-actin filaments was observed. However, it required double amounts of C21 antibody to exhibit a maximal inhibition of 70% on the binding of caldesmon to F-actin-tropomyosin filaments. These results suggest that the presence of tropomyosin in F-actin enhances caldesmon's binding. Furthermore, C21 antibody also effectively inhibits the caldesmon binding to Ca++/calmodolin. The kinetics of C21 inhibition on caldesmon's binding to Ca++/calmodulin is very similar to the inhibition obtained by preincubation of caldesmon with free Ca++/calmodulin. This result suggests that there is only one Ca++/calmodulin binding domain on caldesmon and this domain appears to be very close to the C21 epitope. Apparently, the Ca++/calmodulin-binding domain and the actin-binding domain are very close to each other and may interfere with each other. In an accompanying paper, we have further demonstrated that microinjection of C21 antibody into living chicken embryo fibroblasts inhibit intracellular granule movement, suggesting an in vivo interference with the functional domains [Hegmann et al., 1991: Cell Motil. Cytoskeleton 20:109-120].
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 30 (1995), S. 285-300 
    ISSN: 0886-1544
    Keywords: microtubule dynamics ; β-tubulin ; mitosis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Microtubule (MT) dynamics vary both spatially and temporally within cells and are thought to be important for proper MT cellular function. Because MT dynamics appear to be closely tied to the guanosine triphosphatase (GTPase) activity of β-tubulin subunits, we examined the importance of MT dynamics in the budding yeast S. cerevisiae by introducing a T107K point mutation into a region of the single β-tubulin gene, TUB2, known to affect the assembly-dependent GTPase activity of MTs in vitro. Analysis of MT dynamic behavior by video-enhanced differential interference contrast microscopy, revealed that T107K subunits slowed both the growth rates and catastrophic disassembly rates of individual MTs in vitro. In haploid cells tub2-T107K is lethal; but in tub2-T107K/tub2-590 heterozygotes the mutation is viable, dominant, and slows cell-cycle progression through mitosis, without causing wholesale disruption of cellular MTs. The correlation between the slower growing and shortening rates of MTs in vitro, and the slower mitosis in vivo suggests that MT dynamics are important in budding yeast and may regulate the rate of nuclear movement and segregation. The slower mitosis in mutant celis did not result in premature cytokinesis and cell death, further suggesting that cell-cycle control mechanisms “sense” the mitotic slowdown, possibly by monitoring MT dynamics directly. © 1995 Wiley-Liss, Inc.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 44 (1990), S. 199-205 
    ISSN: 0730-2312
    Keywords: polyamine synthesis ; polyamine transport ; ornithine decarboxylase control ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The management of polyamine synthesis and polyamine pools differs fundamentally from that of most other small molecular-weight endproducts. The polyamines are vital to growth and important cellular functions, but they are toxic in excess. I argue here that their multivalent cationic character, leading to binding to cell constituents, precludes fluent feedback inhibition of synthesis. This has led to the development of elaborate alternative regulatory mechanisms controlling ornithine decarboxylase, the key initial enzyme of the pathway. Poorly regulated polyamine synthesis and the toxicity of polyamines impose upon cells a need to control uptake and to dispose of excess polyamines. Recent data on polyamine transport suggest unorthodox mechanisms of accomplishing these functions.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 64 (1997), S. 499-504 
    ISSN: 0730-2312
    Keywords: protein kinase CK2 ; nuclear matrix ; cytoskeleton ; chromatin ; intermediate filaments ; core filaments ; carcinoma ; prostate ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Nuclear matrix (NM) plays roles of fundamental structural and functional significance as the site of replication, transcription, and RNA processing and transport, acting as an anchor or attachment site for a variety of enzymes and other proteins involved in these activities. We have previously documented that protein kinase CK2 translocates from the cytosol to the nucleus, where it associates preferentially with chromatin and NM, in response to certain growth stimuli. Considering that characteristics of the isolated NM can depend on the procedure employed for its isolation, we compared three standard methods for NM preparation to confirm the association of intrinsic CK2 with this structure. Our data suggest that the method used for isolating the NM can quantitatively influence the measurable NM-associated CK2. However, all three methods employed yielded qualitatively similar results with respect to the stimulus-mediated modulation of NM-associated CK2, thus further supporting the notion that NM is an important site for physiologically relevant functions of CK2. In addition, core filaments and cytoskeleton that were isolated by two of the preparative methods had a small but significant level of associated CK2 activity. J. Cell. Biochem. 64:499-504. © 1997 Wiley-Liss, Inc. This article is a U.S. Government work and, as such, is in the public domain in the United States of America.
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  • 7
    ISSN: 0730-2312
    Keywords: phosphorylation ; interferon regulatory factor 2 ; transcription factor ; oncogene ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: IRF2 is a transcription factor, possessing oncogenic potential, responsible for both the repression of growth-inhibiting genes (interferon) and the activation of cell cycle-regulated genes (histone H4). Surprisingly little is known about the post-translational modification of this factor. In this study, we analyze the phosphorylation of IRF2 both in vivo and in vitro. Immunoprecipitation of HA-tagged IRF2 expressed in 32P-phosphate labelled COS-7 cells demonstrates that IRF2 is phosphorylated in vivo. Amino acid sequence analysis reveals that several potential phosphorylation sites exist for a variety of serine/threonine protein kinases, including those of the mitogen activated protein (MAP) kinase family. Using a battery of these protein kinases we show that recombinant IRF2 is a substrate for protein kinase A (PKA), protein kinase C (PKC), and casein kinase II (CK2) in vitro. However, other serine/threonine protein kinases, including the MAP kinases JNK1, p38, and ERK2, do not phosphorylate IRF2. Two-dimensional phosphopeptide mapping of the sites phosphorylated by PKA, PKC, and CKII in vitro demonstrates that these enzymes are capable of phosphorylating IRF2 at multiple distinct sites. Phosphoaminoacid analysis of HA-tagged IRF2 immunoprecipitated from an asynchronous population of proliferating, metabolically phosphate-labelled cells indicates that this protein is phosphorylated exclusively upon serine residues in vivo. These results suggest that the oncogenic protein IRF2 may be regulated via multiple pathways during cellular growth. J. Cell. Biochem. 66:175-183, 1997. © 1997 Wiley-Liss, Inc.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 65 (1997), S. 308-324 
    ISSN: 0730-2312
    Keywords: PO-B ; HL-60 ; differentiation ; AP-1 ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: PO-B was originally characterized as a transcriptional regulatory factor of the pro-opiomelanocortin (POMC) gene; however, it has become increasingly clear that this protein may be active in tissues outside the pituitary, since it is present in diverse cell types, including differentiated HL-60 promyelocytic leukemia cells. We previously showed that PO-B DNA-binding is progressively induced during differentiation of promyelomonocytic leukemia HL-60 cells to the macrophage-like lineage (with phorbol esters). We now report that PO-B DNA-binding in HL-60 cells is similarly induced during differentiation to the granulocytic lineage (with either retinoic acid or dimethylsulfoxide). Either a genetic or pharmacologic blockade of HL-60 differentiation prohibited these inductive effects. These studies have prompted our interest in the dynamics of other transcription factor changes during HL-60 differentiation. Of these, we observed that another transcription factor (AP-1) is also robustly induced at the DNA-binding level during macrophagelike HL-60 differentiation, but not during granulocytic differentiation. Conversely, the DNA-binding of the transcription factor AP-2 was slightly reduced by TPA-induced HL-60 differentiation but unchanged during granulocyte differentiation. From these data, we conclude that the induction of PO-B DNA binding is a general marker of HL-60 myelomonocytic differentiation, but that qualitative aspects of the induction of additional distinct transcription factors, such as AP-L may contribute to lineage-specific determinants of cell fate. J. Cell. Biochem. 65:308-324. © 1997 Wiley-Liss, Inc.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 69 (1998), S. 211-220 
    ISSN: 0730-2312
    Keywords: nuclear matrix ; protein kinase CK2 ; disulfide bonds ; sodium tetrathionate ; iodoacetamide ; sulfhydryl crosslinking ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Nuclear matrix (NM) appears to be an intranuclear locale for significant and dynamic association of the ubiquitous multifunctional messenger-independent serine/threonine protein kinase CK2 that has been implicated in growth control [Tawfic et al. (1996): J Cell Biochem 61:165-171]. We have examined the nature of the association of CK2 with the NM. Nuclei prepared in the presence of a sulfhydryl-blocking reagent such as iodoacetamide demonstrate a reduction in the amount of CK2 associated with the NM to less than 5% of the control. On the other hand, when nuclei are treated with the sulfhydryl crosslinking reagent sodium tetrathionate, NM-associated CK2 increases severalfold. Treatment of nuclei with sodium tetrathionate followed by 2-mercaptoethanol blocks this increase. Nuclei isolated from rat liver and prostate behaved similarly, suggesting an identical mode of association of CK2 with the NM regardless of the organ. These results indicate a role of sulfhydryl interactions such that NM anchoring of CK2 occurs via its β subunit, which contains several vicinal cysteine residues. Further, various sulfhydryl-blocking reagents inhibited CK2 activity in a concentration-dependent manner, and the inhibitory effect was reversed by agents such as dithiothreitol, implying that cysteine residues in the CK2 play a role in its catalytic activity. J. Cell. Biochem. 69:211-220, 1998. Published 1998 Wiley-Liss, Inc.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 67 (1997), S. 1-12 
    ISSN: 0730-2312
    Keywords: DPP ; Drosophila ; mutations ; dorsal closure signaling pathway ; JNK pathway ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The dorsal surface of the Drosophila embryo is formed by the migration of the lateral epithelial cells to cover the amnioserosa. The Drosophila cJun-N-terminal kinase (DJNK) is essential for this process. Mutations in DJNK or the DJNK activator hemipterous (HEP) lead to incomplete dorsal closure, resulting in a hole in the dorsal cuticle. The molecules downstream of DJNK in this signaling pathway have not been established. Here we demonstrate that the basket1 (bsk1) mutation of DJNK causes decreased interaction with DJUN. Expression of decapentaplegic (DPP), a TGF-β homologue, in the leading edge of the dorsal epithelium, is identified as a genetic target of the JNK pathway. A constitutive allele of JUN is able to rescue the dorsal closure defect of bsk1 and restores DPP expression. Furthermore, ectopic DPP rescues the defects in dorsal closure caused by bsk1. These data indicate that the interaction of DJNK with DJUN contributes to the dorsal closure signaling pathway and targets DPP expression. J. Cell. Biochem. 67:1-12, 1997. © 1997 Wiley-Liss, Inc.
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