Mutants of the human PAI-1 protein are described which are inhibitors of neutrophil elastase or are inhibitors of vitronectin (Vn)-dependent cell migration These mutants preferably comprise one or two amino acid substitutions in the reactive center loop of PAI-1, particularly at positions 331 and 346 of the mature protein. These mutants are notable in being resistant to inactivation by elastase, having high affinity for Vn, or both properties. These mutant proteins as pharmaceutical compositions are used to inhibit elastase in a subject, thereby treating a number of disorders associated with elastase activity, most notably emphysema, ARDS, inflammatory lung injury and cystic fibrosis. The mutants which interact with Vn are used to inhibit cell migration in a subject, thereby treating diseases or conditions associated with undesired cell migration and proliferation, particularly of smooth muscle cells. Such conditions include atherosclerosis, post angioplasty restenosis, fibrosis associated with chronic inflammation or chemotherapy, tumor invasion and metastasis and conditions in which angiogenesis is pathogenic. Also disclosed are peptides of such mutant proteins, mutant-specific antibodies, nucleic acid molecules, particularly DNA, encoding the mutant protein and host cells transformed by such nucleic acids.

1. Field of the Invention
The invention in the field of biochemistry and medicine relates to compositions comprising mutant proteins of plasminogen activator inhibitor-type 1 (PAI-1) which have the capacity to inhibit the enzyme elastase and to inhibit vitronectin (Vn)-dependent migration of cells. This invention also relates to uses of these proteins for the treatment of diseases and disorders associated with elastase activity or in which migration and migration-driven proliferation of cells have pathophysiologic consequences.
2. Description of the Background Art
Plasminogen activators (PAs) are specific serine proteinases that activate the proenzyme plasminogen, by cleavage of a single Arg-Val peptide bond, to the enzyme plasmin (Saksela O, Biochim Biophys Acta (1985) 823:35-65). Two plasminogen activators are found in mammals, tissue-type PA (tPA) and urokinase-type PA (uPA) (Saksela O et al, Annu Rev Cell Biol (1988) 4:93-126). These enzymes are thought to influence critically many biological processes, including vascular fibrinolysis (Bachmann E, Thromb Haemost (1987) 10:227-265), ovulation (Hsuch A J W et al, In: Haseltine FP et al, eds, Meiotic Inhibition: Molecular Control of Meiosis New York: Liss 1988:227-258), inflammation (Pollanen J et al., Adv Cancer Res (1991) 57:273-328), tumor metastasis (Dano K et al., Adv Cancer Res (1985) 44:139-266), angiogenesis (Moscatelli D et al., Biochim Biophys Acta (1988) 948:67-85), and tissue remodeling (Saksela, supra).
The regulation of PAs is a complex process controlled on many levels. The synthesis and release of PAs are governed by various hormones, growth factors, and cytokines (Saksela, supra; Dano et al., supra). Following secretion, PA activity can be regulated both positively and negatively by a number of specific protein-protein interactions. Activity can be enhanced or concentrated by interactions with fibrin (Hoylaerts M et al., J Biol Chem (1982) 257:2912-2919), the uPA receptor (uPAR) (Ellis V et al., Semin Thromb Hemost (1991) 17:194-200), the tPA receptor (tPAR) (Hajjar K A et al, J Biol Chem (1990) 265:2908-2916), or the plasminogen receptor (Plow E F et al., Thromb Haemost (1991) 66:32-36).
PA activity can be downregulated by specific PA inhibitors (PAIs) (Lawrence, D. A et al., In: Molecular Biology of Thrombosis and Hemostasis, Roberts, H. R. et al., (Eds.), Marcel Dekker Inc., New York, chapter 25, pp. 517-543 (1995)). In addition, PA activity is dependent on its location or microenvironment and may be different in solution (e.g., circulating blood) as compared to a solid-phase (e.g., on a cell surface or in the extracellular matrix (ECM)). The overall activity of the PA system is determined by the interactions among these various elements and the balance between the opposing activities of enzymes and inhibitors.
The PAIs have become recognized as critical regulators of the PA system. The identification of an efficient inhibitor of tPA in endothelial cells (ECs) was first reported in 1983 (Loskutoff D J et al., Proc Natl Acad Sci USA (1983) 80:2956-2960). Four kinetically relevant PAIs are currently recognized: PAI type 1 (PAI-1), initially described as the endothelial cell PAI; PAI type 2 (PAI-2), also referred to as placental PAI, PAI type 3 (PAI-3), also. known as activated protein C (APC) inhibitor and proteinase nexin 1 (PN-1), also called glia-derived neurite-promoting factor. The present invention is directed in particular to PAI-1.
Elastase is a serine proteinase released by activated neutrophils and macrophages and monocytes. During inflammatory responses, neutrophils are activated and release elastase leading to tissue destruction through proteolysis. In the lung, elastase degrades elastic tissues and leads to emphysema. Elastase is also a compounding factor in cystic fibrosis (CF) and in both adult and infant acute respiratory distress syndrome (ARDS). Elastase has also been implicated in TNF-mediated inflammation (Massague, J. et al., Annu. Rev. Biochem. 62:515-541 (1993) and HIV infection (Bristow, C. L. et al., International Immunol. 7:239-249 (1995)).
Elastase has a broader spectrum of reactivity than plasminogen activators each of which acts preferentially on a precursor substrate to activate it.
The natural defense to elastase is a protein called xcex11 anti-trypsin (xcex11AT) or xcex11 proteinase inhibitor ((xcex11PI). Patients who are deficient in xcex11AT are prone to emphysema, especially smokers. Furthermore, smoking provokes inflammation. In such xcex11AT deficiencies, the enzyme is present (CRM+) but is functionally impaired. In addition, even in individuals with normal enzyme, smoking directly inactivates xcex11AT. Therefore, an improved inhibitor of elastase would be highly desirable for the prevention of emphysema in susceptible subjects or for reversal of the pathophysiological process leading to this an other related diseases.
The major PAIs belong to the serine proteinase inhibitor (serpin) gene superfamily which includes many proteinase inhibitors in blood as well as other proteins with unrelated or unknown function (Huber R et al., Biochemistry (1989) 28:8951-8966). The serpins share a common tertiary structure and have evolved from a common ancestor. Serpins regulate many processes including coagulation, fibrinolysis, complement activation, ovulation, angiogenesis, inflammation, neoplasia, viral pathogenesis and allergic reactivity.
Current models of serpin structure are based on x-ray crystallographic studies of one member of the family, xcex11AT (reviewed in Huber et al., supra). An interesting feature of the structure of a modified form of xcex11AT, cleaved in its reactive center (Loebermann H et al., J Mol Biol (1984) 177:531-557), is that the two amino acid residues that normally constitute the reactive center (Met-Ser bond), are found on opposite ends of the molecule, separated by almost 70 xc3x85. This is shown for PAI-1 in FIG. 2 and can be compared to the active structure modeled in FIG. 1. Relaxation of a strained configuration takes place upon cleavage of the reactive-center peptide bond, rather than a major rearrangement of the inhibitor structure. In this model, the reactive center is part of an exposed loop, also called the strained loop. Upon cleavage, this loop moves or xe2x80x9csnaps back,xe2x80x9d becoming one of several central strands in a major xcex2 sheet structure. This transformation is accompanied by a large increase in thermal stability, presumably as a result of the reconstitution of the six-stranded xcex2 sheet A.
Synthetic peptides homologous to the reactive-center loops of serpins, when added in trans, incorporate into their respective molecules, presumably as a central strand of the major xcex2 sheet structure and increase the thermal stability of the molecule like that observed after cleavage at the reactive center. This structural change converts the serpin from an inhibitor to a substrate for its target proteinase (Carrell R W et al., Nature (1991) 353:576-578, Bjork I et al., J Biol Chem (1992) 267:1976-1982).
Serpins act as suicide inhibitors, reacting only once with their target proteinase to form a sodium dodecyl sulfate (SDS)-stable complex. These complexes can dissociate to yield free active enzyme together with a cleaved inhibitor similar to that seen in the xcex11AT crystal structure (Carrell R W et al., In: Barrett A J, et al. eds., Proteinase Inhibitors. Amsterdam: Elsevier Science Publishers 1986:403-420) and modeled in FIGS. 1 and 2 for PAI-1.
Serpins interact with their target proteinase by providing a xe2x80x9cbaitxe2x80x9d amino acid residue in the reactive center which is thought to mimic the normal substrate of the enzyme and to associate via its side-chain atoms with the specificity crevice, or S1 site, of the enzyme (Huber et al., supra.; Carrell et al., supra; Shubeita H E et al., J Biol Chem (1990) 265:18379-18385; York J D et al., J. Biol Chem (1991) 266:8495-8500; Sherman P M et al., J Biol Chem (1992) 267:7588-7595). The bait amino acid is designated the P1 residue. The amino acids toward the N-terminal side of the scissile reactive-center bond are labeled in order P1, P2, P3, etc., and the amino acids on the carboxyl side are labeled P1xe2x80x2, P2xe2x80x2, etc. (Carrell et al., 1986, supra). The amino acid residues in the reactive center loop of PAI-1 (residues 332-351) are shown below labeled according to the foregoing naming convention. Also noted are the numerical positions in the full sequence of mature PAI-1 (SEQ ID NO:11): 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 P15 P14 P13 P12 P11 P10 P9 P8 P7 P6 P5 P4 P3 P2 P1 P1xe2x80x2 P2xe2x80x2 P3xe2x80x2 P4xe2x80x2 P5xe2x80x2 Gly Thr Val Ala Ser Ser Ser Thr Ala Val Ile Val Ser Ala Arg Met Ala Pro Glu Glu
The complex between serpins and their target proteinases is thought to be covalently linked via an ester bond between the active-site serine residue of the proteinase and the new C-terminal end of the P1 residue, forming an acyl-enzyme complex (Lawrence D A et al., J Biol Chem (1995) 279:25309-25312). The association between inhibitor and proteinase also involves regions other than the P1 residue of the serpin and other than the catalytic site of the proteinase, based on the characterization of two recombinant PA mutants in which six or seven amino acids were deleted from the catalytic domains. These mutant PAs were almost completely refractory to inhibition by PAI-1, suggesting that the residues distant from the active site are nevertheless critical for the interaction with PAI-1 (Madison E L et al., Nature (1989) 339:721-724; Adams D S et al., J Biol Chem (1991) 266:8476-8482).
PAI-1 (see Table 1) is considered one of the principal regulators of the PA system. It is a single chain glycoprotein with a molecular weight of 50 kDa (Van Mourik J A et al., J Biol Chem (1984) 259:14914-14921) and is the most efficient inhibitor known of the single- and two-chain forms of tPA and of uPA (Table 1) (Lawrence D et al., Eur J Biochem (1989) 186:523-533). PAI-1 also inhibits plasmin and trypsin (Hekman C M et al., Biochemistry (1988) 27:2911-2918) and also inhibits thrombin and activated protein C, though with much lower efficiency.
PAI-1 is present in plasma at very low concentrations, ranging from 0 to 60 ng/ml (average of about 20 ng/ml or 0.5 nM) (Declerck P J et al., Blood (1988) 71:220-225) and a reported half-life of about 6-7 minutes (Vaughan D E et al., Circ Res (1990) 67:1281-1286). In a study comparing the clearance of two distinct forms of PAI-1 (active and latent; see below), the active form was cleared biphasically (half-lives of 6 and 25 minutes), whereas latent PAI-1 was cleared with a half-life of only 1.7. minutes (Mayer E J et al., Blood (1990) 76:1514-1520).
PAI-1 is present in platelets and other tissues and is produced by many cell types in culture (Erickson L A et al., J Clin Invest (1984) 74:1465-1472; Sawdey M S et al., J Clin Invest (1991) 88:1346-1353; Krishnamurti C et al., Semin Thromb Hemost (1992) 18:67-80). In vivo, the primary extravascular source of PAI-1 appears to be vascular smooth muscle cells (SMCs) (Loskutoff D J, Fibrinolysis (1991) 5:197-206). During endotoxemia or other pathological conditions, ECs become a major site of PAI-1 synthesis (Pyke C et al., Cancer Res (1991) 51:4067-4071; Schneiderman J et al., Proc Natl Acad Sci USA (1992) 89:6998-7002 Keeton M et al., Am J Pathol (1993) 142:59-70).
Plasma PAI-1 is present as a complex with vitronectin (Vn) or S protein (Declerck P J et al., J Biol Chem (1988) 263:15454-15461). PAI-1 is also associated with Vn in the ECM in culture and may be involved in maintaining the integrity of the cell substratum in vivo (Mimuro J et al., Blood (1987) 70:721-728, Mimuro J et al., J Biol Chem (1989) 264:5058-5063).
The major source of plasma PAI-1 is not known but is likely to be vascular SMCs, though a contribution from the platelet pool cannot be excluded. PAI-1 functions efficiently in solution and when bound to surfaces (xe2x80x9csolid phasexe2x80x9d), and it is likely that PAI-1 regulates fibrinolysis in both environments.
(a) PAI-1 Protein Structure and Function (See FIGS. 1-4)
PAI-1 cDNA encodes a protein of 402 amino acids that includes a typical secretion signal sequence (Ny et al., supra; Ginsburg et al., 1986, supra). Mature human PAI-1 isolated from cell culture is composed of two variants of 381 and 379 amino acids in approximately equal proportions. These two forms, likely arising from alternative cleavage of the secretion signal sequence, provide proteins with overlapping amino-terminal sequences of (SEQ ID NO:12) Ser-Ala-Val-His-His and (SEQ ID NO:13) Val-His-His-Pro-Pro (portion of SEQ ID NO:2 and 3) (Lawrence et al., 1989, supra). This latter sequence is generally referred to as mature PAI-1.
PAI-1 is a glycoprotein with three potential N-linked glycosylation sites containing between 15 and 20% carbohydrate (Van Mourik J A et al., supra). Mature PAI-1 contains no cysteine residues, facilitating efficient expression and isolation of recombinant PAI-1 from E. coli. PAI-1 produced in E. coli, although nonglycosylated, is functionally very similar to native PAI-1. Recombinant PAI-1 can be isolated from E. coli in an inherently active form (see below), which contrasts with PAI-1 purified from mammalian cell culture (Lawrence et al., 1989, supra; Hekman et al., 1988, supra).
(b) Active and Latent Conformation
PAI-1 exists in an active form as it is produced by cells and secreted into the culture medium and an inactive or latent form that accumulates in the culture medium over time (Hekman C M et al, J Biol Chem (1985) 260:11581-11587, Levin E G et al, Blood (1987) 70:1090-1098). The active form spontaneously converts to the latent form with a half-life of about 1 h at 37xc2x0 C. (Lawrence et al., supra, Hekman et al., supra; Levin E G et al, 1987, supra).
The latent form can be converted into the active form by treatment with denaturants, negatively charged phospholipids or Vn (Lambers et al, supra, Hekman et al, supra; Wun T-C et al, J Biol Chem (1989) 264:7862-7868). Latent PAI-1 infused into rabbits became reactivated in vivo by an unknown mechanism. The reversible interconversion between the active and latent structures, presumably due to a conformational change, is a unique feature of PAI-1 as compared to other serpins. The latent form appears to be more energetically favored.
The three-dimensional structure of the latent form of PAI-1 has been solved. In this structure the entire N-terminal side of the reactive center loop is inserted as the central strand into xcex2 sheet A (FIG. 2) (Mottonen et al., supra) which explains the increased stability (Lawrence, D. A. et al., Biochemistry 33:3643-3648 (1994)) as well as the lack of inhibitory activity. The structure of active PAI-1 is still unknown. It has been proposed that the reactive center in active PAI-1 is exposed as a surface loop, in contrast to its position in the latent structure (FIG. 1).
(c) The Reactive-Center Loop (RCL)
The RCL region of PAI-1 has been the subject of extensive mutational analysis which demonstrated the importance of the P1 bait residue in inhibitor function, whereas the surrounding amino acids play a less critical role. Random mutagenesis of the P3, P2, and P1 residues and the P1 and P1xe2x80x2 residues, respectively, clearly demonstrated that either arginine or lysine at P1 is essential for PAI-1 to function as an effective inhibitor of uPA (York et al., 1991, supra; Sherman et al., 1992, supra). Residues surrounding P1can modulate PAI-1 inhibitor activity by up to two orders of magnitude and can alter target proteinase specificity. The P1xe2x80x2 site is surprisingly tolerant of amino acid substitutions with the exception of proline which caused almost total loss of function. When an 18 amino acid segment of PAI-1 encompassing most of the RCL was replaced with the same region from PAI-2, antithrombin III, or a serpin consensus sequence, most of the requirements for PAI-1 specificity (apart from the P1 residue), were found to lie outside the RCL sequence. All three chimeras remained efficient inhibitors of tPA and uPA, and the antithrombin III chimera was not a significantly improved inhibitor of thrombin. Furthermore, the specific sequence of the RCL, the region inserted into xcex2 sheet A in the latent PAI-1 structure (FIG. 1, see above), was not critical for the conversion between the active and latent conformations of PAI-1. Hence, loop insertion depends more on the flexibility of xcex2 sheet A than on the specific amino acid residues in the loop. Finally, binding to Vn was not affected by these substitutions in the RCL. The P4xe2x80x2 and P5xe2x80x2 residues on the C-terminal side of the reactive-center bond have also been replaced with only a small effect on PAI-1 activity.
(d) Interactions with Vitronectin (Vn)
The adhesive glycoprotein Vn is a 72 kDa glycoprotein present in plasma at micromolar concentrations and associated with many tissues. Like PAI-1, Vn can exist in multiple conformational states. Vn is involved in a wide variety of physiological responses, including cell adhesion, complement activation, thrombosis, and plasma clearance of proteinase-inhibitor complexes (Tomasini, B. R. et al. (1991) Prog. Hemost. Thromb. 10, 269-305).
PAI-1 in plasma or in the subcellular matrix is stabilized by Vn. Vn-bound PAI-1 in solution is approximately twice as stable as unbound PAI-1. On ECM the half-life of PAI-1 can be  greater than 24 h (Mimuro et al., supra). Most of the PAI-1 found in platelets appears to be latent, although this point is controversial (Lang I M et al., Blood (1992) 80:2269-2274). Platelets contain Vn (Preissner K T et al., Blood (1989) 74:1989-1996), which could act to reactivate latent platelet PAI-1 (Wun et al, supra). Platelet PAI-1 may be a major factor in the resistance of platelet-rich thrombi to thrombolysis (Fay W P et al., Blood (1994) 84:351-356). Consistent with this, anti-PAI-1 antibodies enhance clot lysis when contacted with platelet-rich thrombi in vitro (Levi M et al., Circulation (1992) 85: 305-312, Braaten J V et al., Blood (1993) 81:12901299).
Vn is thought to localize PAI-1 to the ECM where it regulates local proteolytic activity (Mimuro et al., 1987, supra). Views concerning the interaction of PAI-1 with Vn are controversial probably due to the conformational variability of both proteins. The controversy is directed to both the nature and affinity of binding of these two molecules (Sigurdardottir O et al., Biochim Biophys Acta (1990) 1035:56-61, Kost C et al., J Biol Chem (1992) 267: 12098-12105, Seiffert D et al., Biochim Biophys Acta (1991) 1078:23-30; Salonen E-M et al., J Biol Chem (1989) 264:6339-6343). Controversy also surrounds the Vn binding site for PAI-1, which has been localized to the somatomedin B domain at the N-terminus (Seiffert D et al., J Biol Chem (1991) 266:2824-2830) and to the C terminus of Vn between residues 348 and 370 (Kost et al., supra). Some of these conflicts may be explained by differences in affinity of binding of the active vs. latent form of PAI-1 with Vn and/or by differences in the relative abundance of PAI-1 conformers in various PAI-1 preparations.
Recent studies of the serpin mechanism of inhibition indicate that it follows a multi-step process that requires an exposed RCL (Shore, J. D. et al., (1994) J Biol. Chem. 270, 5395-5398; Lawrence, D. A. et al., (1995) J. Biol. Chem. 270, 25309-25312; Fa, M. et al., (1995) Biochem. 34:13833-13840, Wilczynska, M. et al., (1995) J. Biol. Chem. 270:29652-29655). Upon association with a target proteinase the serpin RCL is cleaved at its P1-P1xe2x80x2, bond and this is followed by a rapid insertion of the RCL into xcex2-sheet A yielding the stable serpin-proteinase complex. As shown by the present inventors (see Examples) a PAI-1 Vn binding epitope on the edge of xcex2-sheet A is sensitive to this conformational change in xcex2-sheet A, as well as to similar changes associated with conversion of PAI-1 to the latent form or cleavage in the RCL by a non-target proteinase. This sensitivity may provide a way to ensure the expression of PAI-1 activity at specific sites of action. For example, Vn is thought to localize PAI-1 to the ECM where it regulates local proteolytic activity (Mimuro et al., supra). In this situation it may be beneficial to permit only functionally active PAI-1 to bind to Vn. On a cell surface an inactive ligand it can be internalized and degrades. However, this type of regulation may not be as efficient on the less dynamic ECM. Therefore, to prevent Vn from becoming saturated with inactive forms of inhibitor, a system may have evolved that is sensitive to the conformational state of PAI-1, which is closely linked to its activity state.
In addition to stabilizing active PAI-1, Vn alters PAI-1 specificity, converting it to an efficient inhibitor of thrombin (Ehrlich et al., supra; Keijer, J. et al., Blood (1991) 78:1254-1261). Vn-bound PAI-1 has a 270-fold greater rate constant toward thrombin than does free PAI-1, dependent upon the source of the Vn. Although all forms of Vn can bind PAI-1, only Vn isolated under physiological conditions is able to stimulate PAI-1 to inhibit thrombin (Naski, M. C. et al., J Biol Chem (1993) 268:12367-12372). Vn also enhances the clearance of PAI-1-thrombin complexes by the low density lipoprotein receptor-related protein (LRP) (Stefansson, S. et al., (1996) J Biol. Chem. 271:8215). PAI-1 does not appear to contribute significantly to thrombin inhibition in plasma in vivo, although local concentrations of PAI-1 may have significant effects. Vn also stimulates the inhibition of tPA by PAI-1, but to a much less dramatic extent (Keijer et al, supra; Edelberg J M et al., J Biol Chem (1991) 266:7488-7493). Vn can partially restore the reduced inhibitory activity of PAI-1 RCL mutants toward tPA.
(e) Interactions with Thrombin
Given that PAI-1 is expressed at sites of inflammation and released from platelet granules upon activation, it may under these conditions be a relevant inhibitor of thrombin. While PAI-1 alone is a rather poor inhibitor of thrombin, PAI-1-Vn complexes have greatly augmented ability to inhibit thrombin (Naski. et al, supra). Vn is present in connective tissue extracellular matrices and released from platelets upon their activation. Thrombin-PAI-1 complexes form on endothelial cell ECM, which can be inhibited with antibodies to Vn (Ehrlich, H. J. et al, (1991) J. Cell Biol. 115, 1773-1781). While these authors speculated that the thrombin:PAI-1 interaction might promote PA activity by neutralizing PAI-1, this interaction may also mediate cellular clearance of thrombin. Such clearance would resemble that of tPA and uPA whose endocytosis and degradation via several members of the LDL receptor family are promoted after complex formation with PAI-1 (Nykjaer, A. et al., (1992) J. Biol. Chem. 267, 14543-14546 (Orth, K. et al., (1992) Proc. Natl. Acad. Sci. USA 89, 7422-7426, Stefansson, S. et al., (1995) J. Cell Sci. 108: 2361-2369).
(f) Clinical Significance of PAI-1 and its Interactions
Increased levels of circulating PAI-1 are associated with thrombotic disease, including myocardial infarction and deep vein thrombosis (Juhan-Vague I et al., Thromb Res (1984) 33:523-530; Hamsten A et al., N Engl J Med (1985) 313:15571563; Wiman B et al., J Lab Clin Med (1985) 105:265-270, Paramo J A et al., BMJ (1985) 291:573-574; Nilsson I M et al., BMJ (1985) 290:1453-1456; Aznar J et al., Br Heart J (1988) 59:535-541; Angles-Cano E et al., J Lab Clin Med (1993) 121:646-653). Reduced postoperative fibrinolytic activity has been correlated with increased PAI-1 activity immediately following surgery (Kluft C et al., Scand J Clin Lab Invest (1985) 45:605-610), apparently mediated by a plasma factor that stimulates PAI-1 production and secretion from vascular ECs (Kassis J et al, Blood (1992) 80:1758-1764). Consistent with these observations, the overproduction of PAI-1 in transgenic mice results in venous thrombosis primarily in the extremities (Erickson L A et al., Nature (1990) 346:74-76). In contrast, a prospective study found no correlation between PAI-1 levels and vascular disease (Ridker P M et al., Circulation (1992) 85:1822-1827).
Three cases of partial or complete PAI-1 deficiency have been reported in humans and were associated with abnormal bleeding. In one case, normal PAI-1 antigen was detected, but PAI-1 activity was significantly reduced (Schleef R R et al., J Clin Invest (1989) 83:1747-1752), whereas in another, both PAI-1 antigen and activity levels in plasma were markedly reduced with normal levels in platelets (Dieval J et al., Blood (1991) 77:528-532). A complete deficiency of platelet and plasma PAI-1 in a 9-year-old Amish girl was associated with a moderate bleeding disorder. The patient was homozygous for a 2 base pair insertion at the end of exon 4 of the PAI-1 gene (Fay W P et al., N Engl J Med (1992) 327:1729-1733) which results in a frameshift leading to a truncated PAI-1 protein and an unstable mRNA. The deficiency is inherited as an autosomal recessive disorder. Although heterozygous parents and siblings all had plasma PAI-1 activity and antigen in the normal range, they were consistently lower than homozygous normal family members. The lack of developmental and other abnormalities in this patient was considered surprising. The correlation of complete PAI-1 deficiency with abnormal bleeding clearly demonstrates that importance of PAI-1 in the regulation of hemostasis. Given the young age of the above patient, however, an additional important in vivo role of PAI-1 in the control of ovulation or tumor metastasis cannot yet be excluded (Pollanen et al., supra Liu Y-X et al., Eur J Biochem (1991) 195:549-555).
(g) Clearance Receptors
The LDL receptor-related protein (LRP) is a cell surface receptor (family with four members) which acts as a general clearance receptor for a diverse set of ligands, including proteinase inhibitor complexes. For review, see Strickland, D. K. et al, FASEB J. 9:890-898 (1995)) Binding to LRP results in the uptake of PAI-1-proteinase complexes into cells and destruction in the lysosomal compartment. While LRP is found on all cells, these receptors are present at higher levels in liver and on the epithelial lining of the lungs.
(h) Cell Migration
Cell migration is a tightly controlled process which depends on the coordination of many factors. Migrating cells and cells with invasive phenotypes express high levels of uPA. Processes such as angiogenesis and metastasis can be blocked by proteinase inhibitors. Inactivation of the gene for uPA in mice prevents arterial stenosis due to neointima formation following vascular trauma (Carmeliet, P. et al. Circulation 90: 1-144 (1994)). During wound healing vascular cells exhibit an increase in the expression of the Vn receptor (VnR) integrin xcex1vxcex23 (Liaw L et al., Circ Res 77:665-72 (1995)). VnR permits cell motility on matrix proteins deposited at the wound. Specifically, migration into the wound area is facilitated by Vn which is deposited at the site by activated platelets or derived from plasma. Migrating vascular cells also show elevated expression of uPA and its receptor uPAR which co-localize with the VnR at focal contacts. As previously understood in the art, the PAs were thought to activate a generalized proteolytic cascade resulting in matrix destruction necessary for cellular migration and invasion. However, results obtained by the present inventors and presented herein suggest a more subtle role for PAs in regulating the expression of cryptic cell attachment sites.
The present invention provides mutants and variants of wild-type human PAI-1 (wtPAI-1) that have improved properties in the inhibition of serine proteinases, in particular elastase. These mutant PAI-1 molecules are more resistant to destruction by the proteinases to which they bind and therefore have improved therapeutic properties.
The nucleotide sequence (SEQ ID NO:1; the complementary strand is SEQ ID NO:10)) and amino acid sequence (including the signal sequence) (SEQ ID NO:2) of human PAI-1 is shown in FIGS. 3 and 4A. The full mature protein sequence (SEQ ID NO:3) is shown in FIG. 4B.
The present invention is further directed to the use of PAI-1 and mutants and variants thereof for the inhibition of elastase activity. PAI-1 and its mutants are used to treat any of a number of diseases associated with elastase activity, including emphysema, CF and ARDS. Mutants of this invention are also used to inhibit Vn-dependent cell attachment, migration and subsequent proliferation, which processes are associated with diseases ranging from atherosclerosis and restenosis to tumor growth and metastasis and neovascularization.
Thus, the present invention is directed to a mutant protein of PAI-1 protein, which wild-type sequence of which is SEQ ID NO:3, which mutant inhibits neutrophil elastase or other elastase-like proteinases. Preferably the inhibition is such that no more than about one mole of the mutant protein are required to inhibit 1 mole of the elastase. More preferably no more than about two moles, four moles, ten moles, or most preferably 100 moles, of the mutant protein are required to inhibit 1 mole of the elastase.
Also provided is the above mutant protein having at least one amino acid substitution in the sequence from amino acid position 343 to 350 of SEQ ID NO:3, more preferably in positions 331-350. Preferred substitutions are at position 343, position 346 or both. A preferred substitutions at position 346 is Ala, Val, Asp, Phe or Gly. A preferred substitution at position 343 is Ala, Asp, Gly, Leu or Ile. In a preferred embodiment the mutant protein has both a substitution position 343 and 343 as above. Another preferred mutant protein differs from SEQ ID NO:3 by a single substitution of Val at position 346, a single substitution of Ala at position 343, or both. Also provided is a mutant protein having a substitution at 343, 346 or both, wherein the amino acid substituting at position 343: (a) renders the mutant protein resistant to cleavage by elastase after position 343, and (b) has side chains which do not interfere with the binding of the mutant protein to the elastase to form a mutant PAI-1:elastase complex.
A mutant protein as above may further include between one and four of the following additional amino acid substitutions in SEQ ID NO:3 which stabilize the protein: (a) His at position 150; (b) Thr at position 154; (c) Leu at position 319; and (d) Ile at position 354. A preferred mutant includes all four of the above additional substitutions. Additional stabilizing substitutions include Leu at position 91 and Ile at position 372. Also preferred are mutants having additionally Arg at position 333 and/or 335 or at both 333 and 335. An additional substitution in this region is Gly at 331. PAI-1 mutants including any combination of the foregoing substitutions may be used as a stabilized form of the protein, in particular for use in vivo
In another embodiment, the present invention is directed to a mutant protein of PAI-1 protein (SEQ ID NO:3) which is particularly useful for inhibiting the binding of PAI-1 to Vn. Such as mutant is characterized as being resistant to inactivation by the following proteinases: elastase, a plasminogen activator, plasmin, thrombin, cathepsin G, chymase, gelatinase A and B, stromelysin and a collagenase. Such an inhibitory PAI-1 mutant protein preferably has high affinity for Vn such that the binding of the mutant protein to a proteinase does not decrease the affinity of binding of the mutant protein to Vn more than about 100-fold relative to the affinity of wtPAI-1 to Vn.
The above mutant protein preferably has at least one amino acid substitution in the fragment from amino acid position 343 to position 350 of SEQ ID NO:3, more preferably from 331 to 350. One or more of the abovementioned substitutions at positions 343 and 346 (as well as at 331, 333 and 335) are preferably included in this embodiment. The mutant protein may have between one and four, preferably all four, of the following additional amino acid substitutions in SEQ ID NO:3:(i) His at position 150; (ii) Thr at position 154; (iii) Leu at position 319; and (iv) Ile at position 354.
In another embodiment is provided any mutant protein of PAI-1 protein (SEQ ID NO:3) which has a higher affinity for Vn than does wtPAI-1.
Shorter peptides which include at least the PAI-1 reactive center loop with the amino acid substitutions described above are also intended to be within the scope of this invention. Such peptides may be used a elastase inhibitors or cell migration inhibitors in vitro or in vivo. As elastase inhibitors, such peptides (or full length mutant proteins) are useful in methods of measuring or titrating elastase activity.
The present invention is also directed to a pharmaceutical composition useful for inhibiting elastase activity in a subject, comprising (a) a mutant protein (or peptide) as described above, and (b) a pharmaceutically acceptable carrier or excipient.
Also provided is a pharmaceutical composition useful for inhibiting Vn-dependent cell attachment, migration and/or migration-induced cell proliferation in a subject, comprising (a) a mutant PAI-1 protein as described above and (b) a pharmaceutically acceptable carrier or excipient.
This invention is further directed to a method for inhibiting elastase in a subject having a disease or condition associated with pathogenic elastase activity, comprising administering to the subject an effective amount of a pharmaceutical composition as above. The disease or condition is preferably one selected from the group consisting of emphysema, acute respiratory distress syndrome, acute inflammatory lung injury, congenital alpha-1-antitrypsin deficiency, cystic fibrosis, atopic dermatitis, pancreatitis, periodontal disease, arthritis and HIV infection.
Also provided is a method for inhibiting cell attachment, migration and/or migration-induced cell proliferation in a subject having a disease or condition associated with undesired Vn-dependent cell attachment, migration and/or migration-induced proliferation, comprising administering to the subject an effective amount of (a) a pharmaceutical composition comprising wtPAI-1 protein and a pharmaceutically acceptable carrier or excipient; or (b) a pharmaceutical composition comprising a mutant PAI-1 protein as described above.
In the foregoing method, the inhibition is preferably directed to smooth muscle cells. In the foregoing method, the disease or condition is preferably atherosclerosis, post-balloon angioplasty vascular restenosis, neointima formation following vascular trauma, vascular graft restenosis, fibrosis associated with a chronic inflammatory condition, lung fibrosis, chemotherapy-induced fibrosis, wound healing with scarring and fibrosis, primary tumor growth, invasion or growth of a tumor metastasis, psoriasis, deep venous thrombosis, or a disease or condition in which angiogenesis is pathogenic.
This invention is further directed to a nucleic acid molecule, preferably, DNA encoding a mutant PAI-1 protein or peptide as described above. The nucleic acid molecule is preferably a variant of SEQ ID NO:1 or of a coding portion thereof. Also provided is a host cell transformed or transfected with a DNA molecule as above which encodesa mutant PAI-1 protein or peptide. The invention includes methods for producing the mutant PAI-1 protein comprising culturing the transformed or transfected host cells under conditions wherein the mutant PAI-1 protein or peptide is expressed.
Also provided is an antibody, polyclonal or monoclonal, specific for an epitope of a mutant PAI-1 protein as described above, which epitope is not present on wtPAI-1 protein.

Mutant plasminogen activator-inhibitor type 1 (PAI-1) proteins


A contour rope saw for stones and similar workpieces has a slide (3) mounted displaceably in one direction (x) for taking up the workpiece (4) and an endlessly circulating rope (17) with a horizontal strand (17') between two deflection rolls (14, 15) that are vertically movable on a supporting structure (5). A further deflection roll (16) is spaced from the supporting structure (5) in the sliding direction (x) of the slide (6). The rotational axes (20 to 22) of the deflection rolls (14 to 16) are substantially vertical.

Contour rope saws are known in the prior art. Typically, rotational axes of the two deflection rolls between which the cutting strand of the rope extends are horizontal and parallel to the sliding direction of the slide. Although the known saw has largely proven to work excellently it requires considerable space.
The present invention is based on the problem of substantially reducing the space required by the known apparatus without impairing its performance in any way.

Contour rope saw for stones or similar workpieces


A microelectronic assembly and method for fabricating the same are described. In an example, a microelectronic assembly includes a microelectronic device having a surface with one or more areas to receive one or more solder balls, the one or more areas having a surface finish comprising Ni. A solder material comprising Cu, such as flux or paste, is applied to the Ni surface finish and one or more solder balls are coupled to the microelectronic device by a reflow process that forms a solder joint between the one or more solder balls, the solder material comprising Cu, and the one or more areas having a surface finish comprising Ni.

Solder joints such as ball-grid array (BGA) and bump interconnects are often employed to mechanically and electrically join microelectronic devices during microelectronic packaging such as integrated circuit (IC) packaging. These solder joints may fail when placed under mechanical stresses such as shock, vibration, or drop tests compromising the reliability of microelectronic packages. The most common drop test failure mechanism occurs at weaker defect-rich layers that are created during the soldering reaction.
Current methods to address such solder joint failure include using an underfill to provide additional structural support between the joined microelectronic devices. However, underfill requires costly additional process steps that could be circumvented with strengthened solder joints. Solutions that locally strengthen the joints between solder balls and microelectronic devices by reducing the size of weaker layers while accommodating traditional bulk solder materials for solder balls are needed in the microelectronic packaging industry to reduce solder joint reliability problems and avoid costly process development associated with new bulk solder materials for solder balls.

Solder joint reliability in microelectronic packaging


A vinyl chloride polymer composition that contains a mixture of an alkylene-bridged bisphosphate composition, as a fire retardant, and a polyester plasticizer, which is the reaction product of an aliphatic diol and a dicarboxylic acid.

Blends of certain polymeric plasticizers with an alkylene-bridged aryl bis-phosphate compositions have shown low levels of smoke generation and of heat release rate as measured in combustion studies.
Additives which act as flame retardants can contribute significantly to smoke generation because they decrease the efficiency of the fuel source and as a result, create a sooty combustion. It has been found that blends of an alkylene-bridged aryl bis-phosphate and a polymeric plasticizer contribute significantly to flame retardancy while maintaining a very low level of smoke evolution.

Alkyl-aryl oligomeric phosphate ester and polymeric plasticizer blends for vinyl resins


An image forming apparatus using a plurality of laser beams having the same characteristic in order to form a predetermined color image. The predetermined color image consists of a plurality of image colors. The laser beams are shifted with respect to each other in a vertical scanning direction by a diameter of each laser beam divided by the number of the laser beams. Since a rotating of a polygon mirror which deflects the laser beams is asynchronous with a rotating of a photosensitive body on which each laser beam is radiated so as to form a latent image, image colors are shifted with respect to each other. According to the present invention, one of the laser beams is selected for each image color, based on a timing difference between the polygon mirror and the photosensitive body, so that image colors can be superimposed on each other.

The present invention relates to image forming apparatuses, such as a laser printer, a digital copier, etc., which generate a color image.
In a general conventional image forming apparatus a laser beam, representing a predetermined image, is reflected on a rotating polygon mirror and then radiated to a rotating photosensitive body to form a latent image thereon. The photosensitive body is then charged with electricity, and the latent image thereon is developed and transferred onto a piece of recording paper via a transfer charger. The above process is repeated for each image color, and thus each image color is superimposed on the paper. Hereupon, the photosensitive body rotates indifferent to the input of the laser beam transmitted to it from the rotating polygon mirror, and to properly form the latent image on the photosensitive body, it is desirable to synchronize the rotation of the photosensitive body with the input of the laser beam transmitted thereto. However, an image forming apparatus having such a synchronizer shown in Japanese Laid-Open Patent Application No.57-19764 has a complicated circuitry construction and is expensive. On the other hand, without such a synchronizer, the rotation of the photosensitive body cannot be completely synchronous with the input of the laser beam and the image colors cannot be completely superimposed on each other. Thus, the image colors are shifted with respect to each other by at worst one dot, even if a recording timing of the laser beam, at which timing the laser beam is radiated on the photosensitive body, is controlled based on a position signal of the photosensitive body. In addition, a dot position of an end of a line cannot be always constant

Color image forming apparatus having means for properly superimposing image colors on each other


An enhanced duct apparatus provides enhanced re-establishment of ink fluid flow between an ink reservoir and printheads when, for example, ink supply tubing located therebetween is filled with slugs of ink which prevent the flow from being established. The apparatus requires minimal head pressure, thus reducing reservoir depth, by including a high surface energy material within the tubing. Preferably, the material is in the form of a spring which may be of stainless steel. This inclusion of a high surface energy material is more readily wetted by the ink and allows substantially instantaneous overcoming of impedance, including adhesive, surface tension, and wetting forces, upon initiating opening of fluid flow from the reservoir through the duct.

1. Field of the Invention
The present invention relates to enhancement of fluid flow through a duct by the inclusion of a high surface energy material, and more specifically to enhancement of ink flow through tubing of thermal ink jet printing devices.
2. Description of Related Art
In thermal ink jet printing devices, it is necessary to be able to turn ink flow on and off between an ink supply reservoir and a printhead. In a typical ink supply system, when the ink flow shuts off, slugs of ink, separated by air pockets, form in the duct or supply tube communicating the ink between the reservoir and the printhead. These slugs of ink prevent ink flow from being re-established. This is due to the forces of wetting and surface tension acting on the inner walls of the duct and the slugs.
A possible solution to the problem would be to pressurize the ink reservoir. This however requires extra cost and complexity.
The force of adhesion, i.e., wetting of the tube walls, could also be reduced by coating the walls of the tube with a low surface energy material, such as RAIN-X, however such a solution will not be perfect and will not produce much benefit because the wetting forces are small compared with surface tension forces.
Another option would be to make the walls of the tube as smooth as possible in order to minimize the forces of wetting. This option is time consuming, costly, and still does not substantially reduce forces.
There is a need for a simple, low cost device which enhances the re-establishment of fluid flow in the duct.

Enhancement of ink flow ducts with high surface energy material inclusions


The invention provides a multi-wavelength optical batch amplification apparatus wherein, upon batch amplification of a multi-wavelength input optical signal, the powers of optical signals on the input and output sides of an optical amplifier are monitored totally or individually to control the powers of optical signals of the output optical signal of the optical amplifier so that they may be fixed equally. The apparatus includes an entire input light detection section for monitoring the power of the entire input optical signals on the input side of the optical amplifier, an individual output light detection section for monitoring the powers of the output optical signals on the output side of the optical amplifier, an optical amplifier output adjustment section for adjusting the output of the optical amplifier, and a control section for controlling the optical amplifier output adjustment section based on results of detection by the entire input light detection section and the individual output light detection section so that the powers of the output optical signals on the output side of the optical amplifier may be fixed equally.

1. Field of the Invention
This invention relates to a multi-wavelength optical batch amplification apparatus.
2. Description of the Related Art
In an optical communication field in recent years, a technique of multiplexing and transmitting a plurality of input optical signals of different wavelengths has been and is being investigated energetically, and also development of a multi-wavelength optical batch amplification apparatus which amplifies a plurality of input optical signals of different wavelengths in a batch has been and is being performed rapidly.
Actually, however, the gain to input optical signal wavelength characteristic of an optical amplifier is not flat, and when a plurality of input optical signals having different wavelengths are amplified in a batch, the gains of the wavelengths of the input optical signals rely upon the total number, the wavelengths, the powers and so forth of input optical signals. Consequently, the optical amplifier exhibits a very complicated behavior.
Therefore, a multi-wavelength optical batch amplification apparatus is demanded which can amplify input optical signals having different wavelengths from each other in a batch so that the powers of output optical signals may equally exhibit a desired output value without being influenced by the conditions of the input optical signals.
FIG. 33 shows in block diagram a construction of an ordinary multi-wavelength optical batch amplification apparatus. Referring to FIG. 33, the multi-wavelength optical batch amplification apparatus shown includes a plurality of optical signal sources (E/O) 100-1 to 100-N (N is a natural number), a wavelength multiplexing (WDM) wave combiner 101, two couplers (CPL) 102 and 107, two isolators (ISO) 103 and 106, an erbium doped fiber (EDF) optical amplifier 104, a wave combiner 105, two photodiodes (PD) 109 and 110, a laser diode (LD) 111, and an automatic level control (ALC) circuit 112.
The optical signal sources 100-1 to 100-N output optical signals having different wavelengths .lambda.1 to .lambda.n (n being a natural number) from each other. The WDM wave combiner 101 combines the optical signals of the different wavelengths from the optical signal sources 100-1 to 100-N to multiplex them in wavelength. Each of the couplers 102 and 107 branches an optical signal inputted thereto.
Each of the isolators 103 and 106 removes, from an optical signal from the WDM wave combiner 101 or the wave combiner 105, noise components caused by an insertion loss of the WDM wave combiner 101 or the wave combiner 105 or by reflected light during transmission of the optical signal. The EDF optical amplifier 104 amplifies component optical signals of a wavelength multiplexed signal from the WDM wave combiner 101 in a batch to a desired power. The wave combiner 105 combines the output of the EDF optical amplifier 104 and the output of the laser diode 111.
Further, each of the photodiodes 109 and 110 produces an electric signal corresponding to the power of an optical signal branched by the coupler 102 or 107. The laser diode 111 generates pumping light to be combined with the output of the EDF optical amplifier 104 by the wave combiner 105. The ALC circuit 112 performs feedback control of the EDF optical amplifier 104 based on the outputs of the photodiodes 109 and 110 so that the output of the EDF optical amplifier 104 may be fixed.
In the multi-wavelength optical batch amplification apparatus having the construction described above, a plurality of optical signals having different wavelengths (.lambda.1 to .lambda.n) from the optical signal sources 100-1 to 100-N are multiplexed in wavelength by the WDM wave combiner 101 and inputted by way of the coupler 102 and the isolator 103 to the EDF optical amplifier 104, by which the component optical signals of the wavelength multiplexed optical signal are amplified in a batch to a desired power.
The optical signal amplified by the EDF optical amplifier 104 in this manner is combined with pumping light from the laser diode 111 by the wave combiner 105 so that a wavelength multiplexed optical signal (.lambda.1+.lambda.2+ . . . +.lambda.n) wherein the optical signals are individually amplified to the desired power is obtained by way of the isolator 106 and the coupler 107.
By the way, the optical signal branched by the coupler 107 is converted into an electric signal corresponding to the total power of the component optical signals of the output optical signal then by the photodiode 110, and the electric signal is inputted to the ALC circuit 112. The ALC circuit 112 controls the output of the laser diode 111 based on the output of the photodiode 110, that is, based on the total power of the output optical signal, to perform feedback control so that the output of the EDF optical amplifier 104 may be fixed. It is to be noted that also the optical signal branched by the coupler 102 is converted into an electric signal in accordance with the power of the optical signal by the photodiode 109, and the electric signal is inputted to the ALC circuit 112. In this instance, the electric signal is supplied as input light interruption information of the output of zero when an input optical signal or signals are interrupted.
However, with the multi-wavelength optical batch amplifier described above, since the power control of an output optical signal is formed by way of ALC control of the total power of the component optical signals of the output optical signal having the wavelengths from .lambda.1 to .lambda.n, when some of the input optical signals enter into an interrupted condition, the output optical signal varies per one wave by EQU .DELTA.P=10.multidot.logK/(K-F)!(1)
where K is an initial number of signals, and F is a number of interrupted signals. In this instance, it is assumed that the EDF optical amplifier 104 has no wavelength characteristic.
In particular, for example, when three optical signals of wavelengths .lambda.1 to .lambda.3 are being outputted equally with a desired output power as seen in FIG. 34(a), if the input optical signal of the wavelength .lambda.3 enters into an interrupted condition, then the powers of the other output optical signals of the wavelengths .lambda.1 and .lambda.2 rise as seen in FIG. 34(b). Then, if also the input optical signal of the wavelength 12 enters into an interrupted condition, then the power of the output optical signal of the wavelength .lambda.1 further rises as seen in FIG. 34(c). Consequently, no output optical signal of the desired power can be obtained any more.
Also multi-wavelength optical batch amplification apparatus have been proposed which can suppress such variation of the output optical signal power per one wave as described above. An exemplary one of multi-wavelength optical batch amplification apparatus of the type just mentioned is shown in FIG. 35. Referring to FIG. 35, the multi-wavelength optical batch amplification apparatus shown includes, in addition to a plurality of optical signal sources 100-1 to 100-N, an optical signal source 100-M (M>N) which outputs a control optical signal having a wavelength .lambda.m (m>n). When one of the input optical signals enters into an interrupted condition, the variation of the output optical signal power per one wave is suppressed using the control optical signal from the optical signal source 100-M. It is to be noted that, in FIG. 35, those elements denoted by like reference characters to those of FIG. 33 are similar to those described hereinabove with reference to FIG. 33.
However, the multi-wavelength optical batch amplification apparatus described hereinabove with reference to FIG. 33 as well as the multi-wavelength optical batch amplification apparatus described hereinabove with reference to FIG. 35 are disadvantageous in several points. In particular, the multi-wavelength optical batch amplification apparatus shown in FIG. 33 is disadvantageous in that it is low in resisting property to a power variation (including an interrupted condition) of input optical signals. In particular, if all of the input optical signals of the wavelengths from .lambda.1 to .lambda.n exhibit variations by an equal level, then the output powers of the component optical signals of the output optical signals can be made equal to each other to some degree, but in any other case, it is almost impossible to make the output powers of the component optical signals of the output optical signal equal to each other.
Meanwhile, with the multi-wavelength optical batch amplification apparatus shown in FIG. 35, the output power variations of component optical signals of an output optical signal which occur when some of input optical signals enter into an interrupted condition can be suppressed to some degree using the control input optical signal (wavelength .lambda.m) from the optical signal source 100-M. However, if the control optical signal enters into an interrupted condition, then the power control of the output optical signal is still disabled.
It seems a possible idea to use the control optical signal of the wavelength .lambda.m as an optical signal for exclusive use for controlling the output optical signal power. However, from the object of wavelength multiplexing which is employed in order to assure an enlarged transmission capacity, it should be avoided to use one wavelength only for output control in this manner.
Further, the multi-wavelength optical batch amplification apparatus are effective only when it is assumed that, upon multi-wavelength batch amplification by the EDF optical amplifier 104, the gain tilt thereof is free from input optical signal wavelength dependency, input optical signal power dependency and pumping light power dependency. In any other case, however, it is very difficult to control the output optical signal powers of different wavelengths strictly equal to each other.

Multi-wavelength optical batch amplification apparatus


The present invention relates to a styrene-butadiene latex, a preparation method thereof and a coating liquid containing the same, more precisely a styrene-butadiene latex binder for ink-jet paper containing ethylenically unsaturated monomer by 0.1-1.5 weight parts with lowering surface negative charge density, a preparation method thereof and a coating liquid containing the same. The present invention provides a coating liquid for ink-jet paper having excellent price competitiveness and coating work-ability and at the same time reducing energy cost for drying process and thereby provides an ink-jet paper with excellent printing quality.

Cultural paper which has been a medium for the delivery of information and advertisement, gradually hands over its position to the digital media as popularization of computer and commercialization of internet are realized and innovative development of other electric communication apparatus advance. The method of publishing books and magazines changes from 'printing and distribution' into 'distribution and printing,' and big demand for an adequate paper is expected with the growth of digital system. Unlike the conventional system (printed and bound books are sold in bookstores), the recent digital system sends the information through internet and then a dealer or a consumer searches the information and if wanted the dealer or the consumer prints the information directly by formatted digital printing method. And this digital printing system is expected to be generalized in near future.
The digital printing can be divided largely into two different methods; toner type and ink-jet type. In the late 2000, the digital printing already held 41% of the market in the case that required copies were up to 2000. And its market sharing will be soon as high as the conventional offset printing.
The ink-jet type, the most universal type for digital printing, has been generally used for multiple color printing, which will extend its market sharing according to the generalization of digital camera and the use of images on internet. Up to date, silica has been used as a major material and polyvinyl alcohol and polyvinyl acetate have been used as a binder for the production of ink-jet paper. To increase preservation and image reproducibility, more upgraded materials are multi-layered for photopapers.
The reason of using polyvinyl alcohol and polyvinyl acetate as a binder is that the major material silica has a very wide specific surface area asking a high adhesive force and they have excellent compatibility with ink-jet ink comprising soluble dye. In addition, polyvinyl acetate has a weak ionic strength, suggesting that it does not interact with polydiallyldimethylammonium chloride (polyDADMAC) which is a cation additive used for the production of a coating liquid for ink-jet paper, so that quantum properties for ink-jet paper can be well preserved. However, these water-soluble binders, polyvinyl alcohol and polyvinyl acetate, are very expensive materials and intensively increase the viscosity of a coating liquid, resulting in the decrease of coating workability, the increase of energy cost for drying process and deterioration of the quality of ink-jet paper. In particular, it has been pointed that polyvinyl acetate causes irregularity of a product and has insufficient functions as an ink-jet binder.

Styrene-butadiene latex binder for ink-jet paper, preparation method thereof and coating liquid containing the same


A network device for selecting a port from a trunk group to transmit a unicast packet on the selected port. The network device includes at least one trunk group including a plurality of physical ports. The network device also includes a table with a plurality of entries. Each entry is associated with one trunk group and includes a plurality of fields that are associated with ports in the trunk group. Each entry also includes a hash field that is used to select bits from predefined fields of an incoming unicast packet to obtain an index bit for accessing one of the plurality of fields. The network device transmits the unicast packet to a port associated with an accessed one of the plurality of fields.

1. Field of the Invention
The present invention relates to a network device in a data network and more particularly to a system and method of creating a logical port by logically linking multiple ports and for transmitting unicast packets through the logical port.
2. Description of the Related Art
A packet switched network may include one or more network devices, such as a Ethernet switching chip, each of which includes several modules that are used to process information that is transmitted through the device. Specifically, the device includes an ingress module, a Memory Management Unit (MMU) and an egress module. The ingress module includes switching functionality for determining to which destination port a packet should be directed. The MMU is used for storing packet information and performing resource checks. The egress module is used for performing packet modification and for transmitting the packet to at least one appropriate destination port. One of the ports on the device may be a CPU port that enables the device to send and receive information to and from external switching/routing control entities or CPUs.
A current network device may support physical ports and logical/trunk ports, wherein each trunk port includes a set of physical external ports and the trunk port acts as a single link layer port. Ingress and destination ports on the device may be physical external ports or trunk ports. By logically combining multiple physical ports into a trunk port, the network may provide greater bandwidth for connecting multiple devices. If one port in the trunk fails, information may still be sent between connected devices through other active ports of the trunk. Therefore, trunk ports enable the network to provide greater redundancy between connected network devices.
In order to transmit information from one network device to another, the sending device has to determine if the packet is being transmitted to a trunk destination port. If a destination port is a trunk port, the sending network device must dynamically select a physical external port in the trunk on which to transmit the packet. The dynamic selection must account for load sharing between ports in a trunk so that outgoing packets are adequately distributed across the trunk.
Typically, each packet entering a network device may be one of a unicast packet, a broadcast packet, a muliticast packet, or an unknown unicast packet. The unicast packet is transmitted to a specific destination address that can be determined by the receiving network device. However, the sending network device must select one port from the trunk group and adequately distribute packets across ports of the trunk group.


Disclosed is a method of processing an exposed presensitized planographic printing plate employing an automatic processor, the method comprising the steps of developing the exposed presensitized planographic printing plate with a developer; and washing the developed printing plate with a washing water, wherein the ratio W/D of the washing time W to the cross-over time D taken from completion of the developing step to the beginning of the washing step is 3 or more.

In preparing a planographic printing plate from a presensitized planographic printing plate (hereinafter referred to also as a PS plate), a light sensitive layer of the PS plate is marked by a ball point pen in order to register an original through which image wise exposure is carried out, and then imagewise exposed. Thereafter, the exposed PS plate is developed with an alkaline developer to remove the light sensitive layer at non-image portions to obtain a planographic printing plate. However, the ball point pen ink on the light sensitive layer at non-image portions to be removed is not removed by the developer, but remains on the support of the planographic printing plate, resulting in a problem of stain occurrence in printing. This phenomenon is called residual ball point pen ink.

Method of processing presensitized planographic printing plate


A frame container support is formed from a substantially planar rectangular section and a plurality of corner sections attached to the corners of the rectangular section. Each corner section has a container framing section extending a predetermined distance from one side of the rectangular section's plane and downwardly depending segments, which may be loop-shaped, extending a predetermined distance from the opposite side of the plane. The frame may also have a plurality of container support sections which join two adjacent sides of the rectangular peripheral portion. A container is supported within the frame. Plural frame container supports may be placed one on top of another to form a stack by fitting the downwardly depending segments snugly over the outside surface of the container framing segments of the frame disposed immediately below. Lateral movement of the frames with respect to each other is inhibited by this stacking technique. The downwardly depending segments of the lower-most frame may be braced against and/or slotted into a pallet, thereby permitting placement of the entire stack on the pallet. A shroud may be placed over the stack during shipping. The containers may be constructed of corrugated board with a relief portion formed in the corners of the container to inhibit buckling due to the weight of contents of containers above.

Stackable containers which form vertically stable stacks are known in the art. However, stackable container systems wherein a frame supports a container, and wherein the frame includes a corner section that provides framing the container corners within the frame and which simultaneously provides bracing for the container below, are not known.
There is a need for a stackable container system and a container support that is easy to fabricate, inexpensive to manufacture, lightweight but strong, easily stackable to any desired height, quickly and easily set up and broken down, and which can be placed on a shipping pallet so that it will not shift laterally on the pallet as the pallet is moved during shipping and handling. The present invention fills these needs.

Frame container support and stackable container system using same


A method of fabricating a flash memory device includes defining a high voltage region and a low voltage region on a substrate. The high voltage region provides an area for one or more first transistors configured to operation at a first voltage, the low voltage region providing an area for one or more second transistors configured to operation at a second voltage that is lower than the first voltage, each first transistor having a gate and a source/drain region on each side of the gate. A first impurity region is formed as part of the source/drain region, the first impurity region having a first depth from an upper surface of the substrate, the first impurity region being of first conductivity having a first impurity concentration. A second impurity is formed as part of the source/drain region, the second impurity region having a second depth from the upper surface of the substrate that is less than first depth, the second impurity region being of the first conductivity and having a second impurity concentration that is greater than the first impurity concentration. Impurities of second conductivity are implanted into the source/drain region.

The present invention relates to a flash memory device, and more specifically to a method of fabricating a flash memory device, in which the junction breakdown voltage (JBV) and the on-current margin of a high-voltage PMOS transistor can be improved.
In a NAND flash memory device, a high-voltage bias is used upon program/erase. In order to supply the high-voltage bias to a cell, a high-voltage transistor must be located at the end of the wordline and the bitline, so that a high-voltage can be smoothly applied.
In a single-level cell (hereinafter referred to as "SLC") in which 1 bit is stored per cell, programming is performed in steps of 500 mV, from 16V to 19.5V. In a multi-level cell (hereinafter, referred to as "MLC") in which two or more bits are stored per cell, however, cell distribution must be smaller than that of the SLC. Accordingly, a problem is presented by the narrowness of the process margin.
In order to solve this problem, a high-voltage PMOS transistor is used in the MLC in order to improve the cell threshold voltage distribution.
FIGS. 1a-1d are sectional views for illustrating a method of fabricating a flash memory device in the related art. The same reference numerals will be used to identify like or similar parts having the same function.
In order to fabricate the conventional flash memory device, an N-well is formed in a high-voltage PMOS transistor region of a P-type conductive semiconductor substrate. The semiconductor has two regions, a high-voltage PMOS transistor region and a low-voltage element region (or cell region). The semiconductor substrate 10 is divided into an active region and a field region by an isolation process.
Referring next to FIG. 1a, a tunnel oxide film 11a, a polysilicon film 11b for a floating gate, an interlayer dielectric film 11c, and a polysilicon film 11d for a control gate are laminated on the semiconductor substrate 10. The polysilicon film 11d for a control gate, the interlayer dielectric film 11c, and the polysilicon film 11b for a floating gate are selectively etched by photolithography, so that gates 11 are formed on the high-voltage PMOS transistor region and the low-voltage element region.
Thereafter, in order to mitigate damage to the gates 11 caused by the etch process, a re-oxide film 12 is formed on the lateral sides and the top surface of the gates 11 by a re-oxidation process.
As shown in FIG. 1b, a first photoresist layer PR1 is coated on the entire surface and is patterned by an exposure and development process, so that the high-voltage PMOS transistor region is exposed.
P− ions are then implanted using the patterned first photoresist layer PR1 as a mask, thus forming low-concentration P-type ion implant regions 13 in the N-well on both sides of the gate 11 of the high-voltage PMOS transistor region.
The low-concentration P-type ion implant region 13 functions to mitigate a JBV reduction phenomenon, which is generated due to a difference in the concentration between the N-well and a high-concentration P-type ion implant region to be formed later. At this time, the region 13 is formed at a low-concentration doping level.
Thereafter, as shown in FIG. 1c, P+ ions are implanted using the first photoresist layer PR1 as a mask, thus forming high-concentration P-type ion implant regions 14 in the low-concentration P-type ion implant region 13.
A source and drain junction of a Double Doped Drain (DDD) structure having the high-concentration P-type ion implant regions 14 surrounded by the low-concentration P-type ion implant regions 13 is completed thereby.
After the first photoresist layer PR1 is removed, a deep UV photoresist is coated on the entire surface as a second photoresist layer PR2. The second photoresist layer PR2 is then patterned to expose the low-voltage element region, as shown in FIG. 1d.
An N-type ions, such as P31 and As75 ions, having a concentration of 1E13 ions/cm3 or less, is then implanted using the patterned second photoresist layer PR2 as a mask, thus forming low-concentration N-type ion implant regions 15 in the semiconductor substrate 10 on both sides of the gate 11 of the low-voltage element region.
Thereafter, though not shown in the drawing, the second photoresist layer PR2 is removed and a spacer is formed on both sides of the gate 11 of the high-voltage PMOS transistor region and the low-voltage element region. N+ ions are implanted into the semiconductor substrate 10 on both sides of the gate 11 and the spacer of the low-voltage element region, thus forming a high-concentration N-type ion implant region.
In order for a high-concentration PMOS transistor to maintain a high junction breakdown (JBV), the concentration of the low-concentration P-type ion implant region 13 needs to be low. However, if the concentration of the P-type ion implant region 13 is low, there are less charge carriers available for current and results in reducing the on-current of the high-voltage PMOS transistor.

Method of fabricating flash memory device


Provided is a grease composition which contains (A) a mixed base oil containing (A1) a low-viscosity base oil having a kinematic viscosity at 40° C. of 10 to 50 mm2/s and (A2) a high-viscosity base oil having a kinematic viscosity at 40° C. of 200 to 700 mm2/s, (B) a lithium-based thickener and (C) a polymer having a kinematic viscosity at 100° C. of 1,000 to 100,000 mm2/s, and has an apparent viscosity at −10° C., as measured according to JIS K2220:2013 and at a shear rate of 10 s−1, of 50 to 250 mPa·s. The grease composition is excellent in pumpability and is also excellent in wear resistance under poor lubrication conditions.

In various machines, grease may be used in lubrication parts such as bearings, slide parts and joint parts.
For example, construction machines and mining machines such as hydraulic shovels are equipped with a slewing mechanism for swirling an upper revolving superstructure or a mechanism for operating a boom, an arm or a packet, on a frame that connects right and left lower traveling bodies.
Grease is also used in such a sliming mechanism of hydraulic shovels (for example, see PTL 1).

Grease composition and use of grease composition


A mobile electronic apparatus functions as an image medium reproducer, and, in particular, a moving image, such as a DVD reproducer. The mobile electronic apparatus has a mobile body, and a mobile stand detachably connectable with the mobile body. While the mobile apparatus body is connected to the mobile apparatus stand, the mobile apparatus body performs auralization and visualization of at least one A/V (Audio/Video) signal based on at least one input A/V signal from an A/V storage medium and at least one input body control signal output from the mobile apparatus stand, and outputs at least one stand control signal controlling the A/V signal output by the mobile apparatus stand. When the mobile apparatus body is disconnected from the mobile apparatus stand, the mobile apparatus body operates as an independent mobile electronic apparatus.

1. Field of the Invention
The present invention relates to a mobile electronic apparatus functioning as an image reproduction medium, and a reproduction method thereof, and more particularly to a mobile electronic apparatus including a detachable mobile apparatus stand, in which the mobile electronic apparatus operates as an independent mobile electronic apparatus when being disconnected from the mobile apparatus stand, and functions as an image reproduction medium (i.e., an image medium, typically, a moving image medium reproducer), such as a DVD (Digital Video Disc) reproducer (player) when being connected to the mobile apparatus stand, as well as a reproduction method of such an image reproduction medium.
2. Description of the Related Art
With the development of recent digital technology, various functional mobile electronic apparatuses have been released in the market. In general, these mobile electronic apparatuses have a characteristic of convenient portability, but they also have functional restrictions resulting from limitations in size and weight. To be specific, they are suitable for access to Internet or reproduction (execution) of various application programs, but they place several restrictions on the exerting (execution or availability) of functions for reproducing multimedia, such as a DVD and so on. Generally, conventional mobile electronic apparatuses include a detachable mobile apparatus stand. This mobile apparatus stand has typical functions, and in particular main functions, such as, for example, a power supply function for supplying electric power to the mobile electronic apparatus, an interface function for allowing the mobile electronic apparatuses to perform data communication with others, and so forth.

Mobile electronic apparatus capable of functioning as image reproduction medium and reproduction method thereof


A structural configuration for rapidly assembling walls and linings of insulating firebricks and prefabricated insulating modules that aligns the bricks or modules during assembly with grooves and inserts, minimizes the amount of through joints in the completed structure, and allows the full height of each brick or module to be utilized in the completed structure is provided.

Walls and linings constructed from insulating firebrick are utilized in numerous applications in furnaces, kilns and high temperature applications as primary hot face refractory linings or as insulation behind other refractories. Such walls and linings are typically assembled on-site from smooth sided insulating firebrick and mortar and are laid down in courses.
In industrial furnace and kiln application having walls or linings constructed of insulating firebrick, the furnaces and kilns must be periodically rebuilt. As productivity and profitability are directly impacted by the amount of time taken to rebuild the furnace or kiln, any reduction in the time necessary for a rebuild is desirable.
As an example, insulating firebrick is utilized in the construction of side wall and bottom insulation in carbon anode baking furnaces. Carbon anode baking furnaces are utilized to fire carbon anodes used in the Hall process of smelting aluminum. As 0.4 to 0.5 pounds of anode are consumed in the production of each pound of aluminum, the ability to produce carbon anodes is critical for the production of aluminum. When it becomes necessary for an aluminum smelter to rebuild its carbon anode baking furnace, it must stock pile carbon anodes in order to continue aluminum production during rebuild. Occasionally this is not possible as the carbon anode baking furnace is sized to the needs of the smelter; therefore during a rebuild a smelter must purchase anodes from another source or pause aluminum production.
Attempts have been made in the prior art to supply tongue and groove interlocking insulating firebrick in an attempt to reduce the rebuild time of carbon anode baking furnaces; such attempts have met with limited success as the manufacturing cost of such insulating firebricks is greatly increased. Unlike the tongue and groove in thermally conductive bricks utilized in constructing the flue walls, the tongue and groove in insulating firebricks may not be pressed into the brick's shape during the process of manufacture, but rather must be machined into the fired brick. To machine a tongue into an insulating firebrick is an expensive and time consuming process with the further drawback that the effective height of the insulating firebrick is reduced by the height of the tongue machined into it.
Attempts have also been made in the prior art to provide large prefabricated sidewall insulating modules constructed from insulating firebrick; however difficulties are encountered in aligning and handling such large modules.
Finally, in the prior art, attempts have been made to provide pre-cast modules of tongue and groove design. Such pre-cast modules have been constructed from refractory castable insulating material. Refractory castable insulating material is considerably less durable than insulating firebrick having the same insulating value; as a result, modules constructed from refractory castable insulating material are particularly susceptible to damage in transportation and handling. If a stronger insulating castable is used to produce the modules, the insulating value of the modules is significantly inferior to that of insulating firebrick.
Accordingly, it is an objective of the present invention to provide a method of rapidly assembling durable kiln and furnace linings, and further to provide durable preassembled insulating wall modules, constructed from insulating firebrick, that are self-aligning and interlocking and allow accurate and rapid assembly of side wall insulation.
Other objects and advantages of the present invention will be apparent to those skilled in the art from the following description of the invention.


A novel IC chip packaging construction in which the chip package materials are selected such that their thermal linear expansion curves are closely matched over the full operating temperature range of the IC chip. The IC chip packaging construction includes a metal base and cover for enclosing the IC chip and a pair of insulating frames for hermetically sealing the IC chip in the chip package. A plurality of input/output leads make electrical connections with the IC chip through fine wires that are soldered to the leads and to contact areas on the IC chip. The metal base and cover and the input/output leads are fabricated from copper and the insulating frames are fabricated from Fotoceram.RTM. 160, which has a thermal linear expansion curve that closely matches that of copper over the full operating temperature range of the chip. Accordingly, the problems of differential expansion rates due to temperature variations for wafer size or very large scale IC chips are greatly minimized.

This invention relates generally to techniques for packaging integrated-circuit (IC) chips and, more particularly, to techniques for packaging wafer size or very large scale IC chips.
Conventional integrated-circuit (IC) chip packaging techniques involve hermetically sealing IC chips in individual chip packages to protect the chips from the environment. The chip packages are generally fabricated from a ceramic material, such as alumina (Al.sub.2 O.sub.3) or beryllia (BeO), or from a metal, such as copper. However, ceramic materials have relatively low thermal conductivities when compared with metals and are generally unsuitable for packaging wafer size or very large scale IC chips. This is because these chips draw large amounts of current and generate considerable amounts of heat that must be dissipated through the chip package. The use of ceramic materials for packaging these chips would either cause the chips to operate at excessively high temperatures or severely limit the density of the circuit elements that could be formed on the chips.
In contrast, metals have relatively high thermal conductivities and are quite suitable for packaging large scale IC chips. Conventional metal chip packages, such as the chip package disclosed in U.S. Pat. No. 4,524,238 to Butt, have a metal base, to which an IC chip is bonded, and a metal cover. The chip is hermetically sealed in the metal package by a solder glass or ceramic material having a coefficient of thermal expansion (CTE) that closely matches that of the metal base and cover. The coefficients of thermal expansion are matched to prevent any cracking of the solder glass or ceramic material due to temperature variations that occur during operation of the chip. Several solder glass materials, which have coefficients of thermal expansion in the range of approximately 160 to 170.times.10.sup.-7 /.degree.C., are suggested in the Butt patent for use in a copper or copper alloy chip package. Copper has a coefficient of thermal expansion of approximately 165.times.10.sup.-7 /.degree.C., from 0 to 100.degree. C.
However, as IC chips become very large and approach the size of a semiconductor wafer, in the range of 5 to 6 inches, differences in the thermal linear expansion curves of the copper and solder glass materials over the full operating temperature range of the chip become extremely critical. A thermal linear expansion curve is to be compared with a coefficient of thermal expansion which is the slope of the expansion curve at a specified temperature, such as room temperature (25.degree. C.). Even very small differences in the thermal expansions of these materials at some temperatures can cause cracking of a large scale chip package, resulting in the chip being ruined. The solder glass materials listed in the Butt patent generally do not have thermal linear expansion curves that closely match the thermal expansion curve of copper over the full operating temperature range of the chip. Accordingly, there has been a need for an improved packaging material for use with wafer size or large scale IC chips. The present invention is directed toward this end.

Packaging construction for very large scale integrated-circuit chips


The invention relates to an electric power generation system for a water storage tank and a storage structure system for a water storage tank wherein the electric power generation system for the water storage tank according to the invention comprises: a water storage tank for storing rainwater or water underground for a specific purpose; an electricity generation part for generating electricity by utilizing water stored in the water storage tank; a cooling part for cooling heat generated at the time of generating electricity by the electricity generation part; and a cooling water supply part for supplying the cooling part with the water stored in the water storage tank. Thereby, dispersed electricity generation facilities can be secured by utilizing open underground spaces of the water storage tank.

Conventional regeneration or power generation systems are a fueled power generation facility, a solar heat power generation facility or a wind power facility, etc. and have mainly been installed on the ground, which is very costly. Accordingly, due to this problem, they had much difficulties in being widely used as an urban power generation plant. Thus, recently the inventors began to review the method of using a power generation system for generating electric power by utilizing water, as an urban power generation plant.
The sewerage system is a generic term for conduits installed to collect and process home foul water, industrial water waste, rain and underground water, etc., discharged from various areas, and for other structures and facilities. Recently water storage facilities for storing water underground are being used in such sewerage system in order to prevent flood damage due to rain, etc., and to prevent temporal overflow of the river in case heavy rain falls intensively.
Example of these water storage facilities is disclosed in Japanese patent application publication No. 2000-352080. Example of a unit member of Japanese patent application publication No. 2000-352080 is illustrated in FIG. 1. The unit member (A), as shown in FIG. 1, includes a base portion 110 of a rectangular shape and a container portion 120 arranged such that it is integrally projected from the base portion 110. In addition, the unit member (A) has four container portions 120 formed symmetrically relative to a center. Example showing the configuration in which such unit members (A) are assembled in the top and bottom manner is illustrated in FIG. 2.
However, in case a water storage tank is configured by utilizing such unit member (A) only, the water storage tank is likely to collapse due to the load of soil, etc., and an installation space for generating electricity cannot be secured.

Power production apparatus and structure block system for water storage facility


An object of this invention is to present a thermal printer for printing at high speed the data with the drive at a low voltage of around 5 V while preventing the printing problems attributable to the voltage drop due to internal impedance and to the loss inside the head coming from the common conductor inside the head. The thermal printer has a plurality of heating elements.. The thermal printer comprises a print head consisting of the print blocks which have divided the heating elements at every stipulated quantity and a heating means for electrically heating the heating elements on the basis of the stipulated data at every print block wherein the heating means has been structured to simultaneously heat the heating elements against a plurality of print blocks to color the thermosensitive paper in contact with the heating elements of the print block.

1. Field of the Invention
The present invention relates to a line thermal printer, and in particular relates to a line thermal printer which is suitable, for example, to be used with a terminal etc. and which is to be connected to a compact type portable equipment driven by batteries, for example.
2. Description of the Related Art
In recent years, a number of so called thermal printers have been developed, which print by electrically heating the print head corresponding to the letters and graphics on to a thermosensitive paper which develops colors if heat is sensed.
These thermal printers, especially a thermal printer driven by batteries are roughly classified into 2 groups,
(1) a serial thermal printer of a low voltage system (about 5 V), and
(2) a line thermal printer of a high voltage system (about 12 V) and generally, a thermal printer working with a low voltage is slow in print speed while a thermal printer high in print speed requires a high voltage.
In other words, compact portable equipment, for example, a terminal and the like can not print at a high speed because the equipment is driven by a battery in the order of 4.5 to 6.5 V or with a low voltage in a 5 V single power source.
Therefore, a line thermal printer that can be operated with a low voltage, for example, around 5 V is required.
On the other hand, there exist a variety of thermosensitive papers being used with this thermal printer, such as red/black paper the color of which changes, for example of example, different temperatures are sensed, different print energies, are given and a 2-ply paper is sensed. A 2-ply paper does not develop colors unless a greater print energy is provided than the usual print energy, which makes a 1-ply thermosensitive paper.
Consequently, in order to obtain favorable print quality for a variety of thermosensitive papers, a line thermal printer is necessary that can change the print energy per unit area in accordance with the thermosensitive papers to be used.
In the past, a line thermal printer as shown in FIG. 1, for example, is available as this type of thermal printer.
The print head 1 of this line thermal printer is structured of 4 print blocks, 3a to 3d, whose heating element 2 of 320 dots per dot line has been divided at every 80 dots.
In the aforesaid structure, if the printing is made on a given thermosensitive paper, the heating element 2 in the print block 3a is electrified for a stipulated time, for example, with a high voltage of around 12 V, first based on the stipulated data, the printing is made at the thermosensitive paper position (shaded area (1)) corresponding to the print block 3a as shown in FIG. 2, and then the paper is fed out very slightly.
Thereafter, the heating elements 2 in the print blocks 3b, 3c and 3d are sequentially electrified in a similar way, the printing is made on the thermosensitive paper positions (shaded areas (2), (3) and (4)) corresponding to the print blocks 3b, 3c and 3d, and thus the printing of 1 dot line is ended.
However, this type of conventional line thermal printer has been structured such that the printer is electrified for the stipulated time with a high voltage of around 12 V, so if the printing has been made at every line with a low voltage, for example, from 4.8 V to 5.0 V, there is the problematic point that a favorable print quality or print density can not be obtained and the printing can not be made at a high speed as a result because the print energy is small. This is because, compact portable a terminal and like, for example, need to be driven by a low voltage, or by a single power source of around 4.8 V. Sufficient print energy can not be produced with this type of low voltage.
In addition, there is the problematic point that the printing can not be made at a high speed with the drive at a low voltage.
In other words, to obtain the necessary to color the thermosensitive paper with a low voltage, the resistance value needs to be made lower and the current value needs to be made larger, but in general, the energy needed for printing is expressed by the following formula: ##EQU1## where .epsilon.=Energy per unit area.
v: Impressed voltage. PA0 Vs: Saturation voltage. PA0 R: Heating element resistance value. PA0 t: Pulse width. PA0 S: Heating element area,
and for enlarging the print energy,
(1) the saturation voltage "Vs" must be made smaller,
(2) the heating element resistance value "R" must be made smaller,
(3) the heating element area "S" must be made smaller, or
(4) the pulse width "t" must be made larger.
However, there is a limit to decrease the heating element resistance value "R" because of the material of print head. If the heating element resistance value "R" should become smaller, the current "i" flowing to the heating element 2 becomes greater, so the saturation voltage "VS" is enlarged. The saturation voltage "Vs" becomes an ineffective energy and has no effect on the print coloring.
This can be explained as EQU Current "i"=(V-Vs)/R,
but this is the current flowing to a single heating element, and the total current flowing to the actual print head 1 will become as follows: ##EQU2##
Namely, the saturation voltage Vs depends on the current "i" and becomes approximately as follows: EQU Vs=ai+b.
(For information, the voltage actually becomes non-linear from the saturation characteristics of the switching transistor).
Therefore, if the current "i" becomes greater, the saturation voltage Vs is increased, and because the formula V-Vs becomes smaller, the print energy ".epsilon." becomes smaller.
In addition, if a battery is used, it generates the new problematic point that the presence of internal impedance from using the battery becomes a printing problem as the drop in voltage because the impressed voltage "V" itself depends on the current "i" and therefore fluctuates with the loss inside the head due to the common conductor inside the head. For this reason, the optimum range of heating element resistance "R" is determined by itself, and consequently the pulse width "t" must essentially be set to relatively narrow value.
Enlarging the pulse width "t" results generally in enlarging the print cycle, so the print speed becomes slow. The pulse width "t" can not be set to a high value because realize a high speed printing is desirable.
Decreasing the pulse width generally results in decreasing the print cycle, so that the print speed can be accelerated. However, decreasing the pulse width involves the problematic point that the print energy ".epsilon." essentially becomes smaller.
Therefore, an object of this invention is to present a thermal printer to print at high speed with the drive of low voltage of around 4.8 to 5 V while preventing the printing troubles attributable to the fall in voltage coming from the internal impedance and to the loss in head due to the common conductor inside the head. and moreover,
it is another object to present a line thermal printer capable of obtaining the favorable print quality against a variety of thermosensitive papers while preventing the drop in print speed even in the case of low voltage, for example, of around 4.8 to 5.0 V.