This knit is produced on the basis of a biocompatible polymer material monofilament, whose pattern is defined by a front lap and a rear lap of yarns knitted together and determines a plurality of cells each having a substantially polygonal shape. The pattern gives the knit a multidirectional tensile behavior such as obtained by a front lap capable of being obtained by knitting according to a scheme 5-4/4-3/2-1/0-1/1-2/3-4 and by a rear lap capable of being obtained by knitting according to a scheme 0-1/1-2/3-4/5-4/4-3/2-1.

1. Field of the Invention
The present invention relates to an isoelastic open knit useful in particular in parietal and/or visceral surgery, but which can also be used in other areas of surgery.
2. Description of Related Art
The present invention will be described more particularly by referring to a prosthetic knit of said type, intended to be used for the repair of hernias or eventrations. The abdominal wall consists of muscles which are physiologically deformable in all directions, and therefore an ideal reinforcement must follow these physiological deformations whilst providing additional strength to a weakened wall. Even though there is a lack of published data, the lower limit of tensile strength of a prosthetic knit for the repair of hernias or eventrations is in the region of 10 kg, when tested according to the NFG 07-001 standard.
In the present application, the expressions given below have the following meanings:
the term xe2x80x9cfabricxe2x80x9d means an assembly of yarns, obtained in particular by knitting and/or weaving;
the term xe2x80x9cbiocompatible polymer materialxe2x80x9d means a material, or its possible products of degradation in a biological medium, which induces no effect which is toxic or contrary to the sought effect, once implanted in the body.
For a long time, surgeons have used flat prosthetic fabrics, that is to say two-dimensional ones, to repair or replace any part of the body, such as an aponeurosis or a muscular wall, destroyed or damaged, for example as a result of a traumatism. Consequently there are now a large number of such prosthetic fabrics manufactured or obtained according to various processes, for example weaving, knitting or molding, and which have often been designed to carry out specific functions within the body in which they are implanted. Such prosthetic fabrics are described for example in documents U.S. Pat. No. 5,569,273, WO-A-96/03091 and EP-A-0797962, which divulge the knitting of monofilaments or multifilaments of polypropylene or of polyester.
Patent application PCT WO-A-97/02789 describes an open knit based on a monofilament of a biocompatible polymer material, the pattern of said knit defining a plurality of cells having a substantially polygonal shape. The fabric is intended in particular for the repair of hernias, and is based on a polypropylene monofilament, of diameter 0.15 mm, whose knitting pattern is defined by two laps of yarns knitted together according to the following scheme:
front lap: 2/0-2/4-2/0-4/6-4/2-4/6;
rear lap: 4/6-4/2-4/6-2/0-2/4-2/0.
The purpose of the invention described in this document is to provide a fabric with a better transparency in order to facilitate its use in laparoscopic repair techniques. Furthermore, it is mentioned, in page 1, lines 31-32 of the published application, that the knit must have the physical characteristics and performance of conventional repair prosthetic fabrics.
However, such conventional fabrics have several disadvantages, related to the very structure of the fabric, or to the choice of the basic material used for forming the yarns, or else to the way in which the prosthetic fabric is manufactured. Thus, the mechanical properties of the conventional fabrics obtained are extremely variable from one fabric to another depending on the orientation of the specimen: vertical (also called production direction or columns) or horizontal (also called cross direction or rows). By way of example, the knitting scheme used in document WO-A-97/02789 makes it possible to obtain a knit which is about two times stronger in weft than in warp, and this corresponds entirely with the properties of conventional fabrics. A recent publication compares the mechanical properties of the principal fabrics used up to the present time (cf. Table 1 below). The differences range from 1 to 40 for the tear strength and from 1 to 8 for the tensile strength. The values of elongation under physiological loads or at break are rarely mentioned (even less so in the diagonal direction), even though they are an important parameter for the functionality of this type of product.
Source: U. Klinge et al: Verxc3xa4nderung der Bauchwandmechanik nach Mesh-Implantation. Langenbecks Arch Chir (1996) 381:323-332.
Furthermore, it is also known that the tissual reaction to an implant is the result of a normal cicatrization process. Any tissual surgical traumatism is followed by a cascade of physiological events, the principal timings of which are as follows:
t0: surgical traumatism, capillary breakage;
t0 plus a few minutes: coagulation, fibrinous network, release of chemotactic factors;
t0 plus 12 to 48 hours: polynuclear dominant luecocytic afflux;
t0 plus 4 to 8 days: fibroblastic afflux;
t0 plus 24 hours to 5 days: macrophagic dominant leucocytic afflux;
t0 plus 8 to 21 days: conjunctive differentiation of the cicatricial reaction;
t0 plus 15 to 180 days: cicatricial remodeling on contact with the implant.
Even though in certain cases the exact mechanisms are as yet unknown, particularly with regard to the determinism of the intensity of the reaction, it therefore appears that the first 8 days are determinant since they condition the fibroblastic afflux.
In non-bony tissues, the equilibrium of the reaction leads to the formation of a fibroconjunctive membrane which constitutes the interface between the implanted material and the surrounding healthy tissue. Whatever the type of implant may be, the zone under the direct influence of a biocompatible conventional material is a minimum of about 50 micrometers.
Furthermore, in the treatment of parietal inadequacies (principally hernias and eventrations), the prosthetic fabric has the task of providing additional mechanical strength to the surgical reconstruction, and its effectiveness and its local tolerance are directly related to the degree to which its tissual integration is intimate and early.
The Applicant has established by its own studies that several aspects influence tissual response to a prosthetic implant:
the constituent material of the prosthesis and its possible products of degradation in a biological medium must not induce any effect which is toxic or contrary to the sought effect. In the case of a prosthetic fabric implanted for long-term use, the aging of the material and its consequences (wear, expulsion of components, etc.) is the most difficult factor to anticipate; only raw materials validated over a long period provide maximum safety;
in a manner of speaking, as the organism sees only the surface of the material, the properties of the latter are of significant importance. Among all the surface parameters, the surface energy and the roughness play an important role. In fact, when it is sought to promote cellular integration, the surface must be absorbent (high surface energy) and smooth on a cellular scale (of the order of one micron);
only the porosity accessible by the organism is useful with regard to the anchoring of the prosthetic fabric. This porosity must be interconnected in a given volume, and there must be sufficient space for a significant cellular penetration (of the order of about 20 to 80 micrometers), and for a tissual differentiation (100 to 300 micrometers generally constitute a minimum for complete differentiation). It has been recalled previously that the minimum thickness of the tissual reaction is of the order of 50 micrometers, which means that, for porosity sizes less than 100 micrometers, the rehabilitation tissue will be entirely under the influence of the presence of the implant with little possibility of complete tissual differentiation occurring;
vascularization and the biomechanical environment of the receiving site condition the intensity of the tissual response. A richly vascularized site (skin, muscles, etc.) will react faster and more intensely than less vascularized tissues (forward chamber of the eye, bone, etc.). Furthermore, the very nature of the receiving site conditions the capacity of identical regeneration of the wounded tissue. Bone, connective tissues, mucous membranes, certain parenchymes (the liver for example) can regenerate identically without significant fibrous cicatrice. On the other hand, other very specialized tissues (muscles, nerve tissues, etc.) have lost all capacity of regeneration, the cicatrization of these tissues therefore takes place only by fibrosis;
surgical traumatism constitutes one of the principal triggering factors of the previously described cascade reaction. The greater it is, the more intense will be the reaction and the more pronounced will be its consequences (cicatrization time, fibrous after-effects, pain, etc.);
reinforcement becomes more effective and its local tolerance becomes better if its tissual integration is intimate and early. In order to be intimate and early without the formation of peripheral fibrous shell, the macroporosities of the implant must, as widely as possible, be open to the exterior and the elasticity of the reinforcement must allow it to follow the physiological deformations of the wall. The upper limits being given by the mechanical strength ( greater than 10 Kg in the standard NFG07-001 test) of the fabric, the ability to be manipulated by the surgeon and the impossibility of hernia recurrence through the pores of the fabric of maximum diameter 5 mm).
Considering the above, one of the objectives of a good prosthetic fabric is a tissual integration which is as fast as possible, providing a mechanically satisfactory anchoring without extensive fibrosis, which is a source of discomfort and pain.
The present invention describes a new type of knitted reinforcement providing isotropic elastic mechanical properties, that is to say substantially equivalent in all directions whilst retaining high porosity for a better tissual rehabilitation and sufficient rigidity for satisfactory surgical manipulation.
The fabric in question is an isoelastic prosthetic open knit based on a monofilament of a biocompatible polymer material, whose pattern is defined by a front lap and a rear lap of yarns knitted together and whose pattern determines a plurality of cells each having a substantially polygonal shape.
According to the invention, the pattern gives the knit a multidirectional tensile behavior such as obtained by a front lap capable of being obtained by knitting according to a scheme 5-4/4-3/2-1/0-1/1-2/3-4 and by a rear lap capable of being obtained by knitting according to a scheme 0-1/1-2/3-4/5-4/4-3/2-1.
The applicant has discovered that a prosthetic knit based on a biocompatible monofilament, such as defined above, has the following advantages:
the knit is flexible and not very dense in material, the weight per m2 being reduced, for example by at least 30%, in comparison with equivalent products on the market, which makes it possible to obtain better local tolerance;
the knit has sufficient firmness (spring effect during imposed deformations) for easy manipulation by the surgeon;
the knit cannot become unraveled whatever cuts may be made by the surgeon, with few filament drops along the cutting line, unlike the known fabrics;
the isoelasticity, illustrated by relatively linear slopes of stress/strain curves according to the direction of tension of the knit, makes it possible to obtain biomechanical adequation with the abdominal wall;
the knit is relatively transparent for better visibility of the covered anatomical structures in particular during laparoscopic positioning;
the knit is porous with principal openings of the order of one millimeter for better cellular penetration and in-depth conjunctive differentiation without peripheral fibrous shell phenomena, a potential source of discomfort and pain.
In a preferred embodiment of the invention, the knit has a tensile behavior defined by a ratio of measurable values, for example the tensile strength, in the vertical/horizontal/diagonal stress directions, of between 0.9:1:1.5 and 1.5:1:1.5.
Preferably, the knit has at least any one of the following properties:
the stress at break of the knit according to the NFG07-001 standard is of the order of 25 daN in all directions;
the elongation at break of the knit according to the NFG07-001 standard is of the order of 70% in all directions;
the initiated-tear strength of the knit according to the NFG07-001 standard is of the order of 5 daN;
the elongation under stress of 10 daN of the knit according to the NFG07-001 standard is of the order of 35% in all directions.
Preferably, the open knit is based on a monofilament of biocompatible polymer material chosen from the group consisting of polypropylene, polyester and polyamide, and preferably is a polypropylene monofilament.
Preferably, the diameter of the monofilament is between 0.12 mm and 0.18 mm, and preferably is 0.15 mm.
Preferably, the pattern of the knit forms unblocked open meshes defining principal cells surrounded by cells of smaller size, favoring rehabilitation.
Advantageously, each principal cell has a diameter of from about 1 mm to about 2 mm, and preferably a diameter of between 1.5 mm and 1.9 mm, whilst the smaller cells have a diameter of between 0.4 and 0.8 mm and preferably of between 0.6 and 0.7 mm.
The thickness of the knit is between 0.5 mm and 1 mm, and preferably is at most equal to 0.7 mm.
Preferably, the knit has a weight per unit area of between 50 g/m2 and 100 g/m2, and preferably a specific weight of about 75 g/m2.
Another subject of the invention is a parietal and/or visceral prosthesis, obtained with a knit such as defined above.
Yet another subject of the invention is the use of a knit according to the invention such as defined, in order to obtain a prosthetic product for surgical use, in particular for manufacturing a parietal and/or visceral prosthesis.

Isoelastic prosthetic filet stitch fabric


The invention relates to a device that absorbs infra-red radiation, which comprises as a coupler element for the infra-red radiation, an element made of a quasi-crystalline alloy, made up of one or more quasi-crystalline phases, the volume of which represents at least 40% by volume of the quasi-crystalline alloy, a quasi-crystalline phase being either a quasi-crystalline phase in the strict sense, or an approximating phase or an approximating compound. The invention is used in applications such as in a bolometer, infra-red filter, thermocouple, or hot plate.

This invention relates to the use of quasi-crystalline alloys for the absorption of infra-red radiation as well as devices for the absorption of infra-red radiation comprising an element made of a quasi-crystalline alloy.
Various types of devices are known that absorb infra-red radiation. In particular, devices are known that carry out the photo-thermal conversion of the infra-red radiation, in which the absorbed light energy is converted into heat. These are notably solar radiation collectors which include a layer of a paint that absorbs the infra-red radiation, deposited on a substrate. Among these devices, one may mention, in particular, collectors with a heat exchange medium or the Trombe wall. In these devices, the heat is taken from the absorbent medium through the substrate, assumed to be a good thermal conductor, by a heat exchange fluid, from which the collected energy is extracted. In general, said paints are made up of organic materials containing absorbent pigments or metal powders which are very finely divided and bonded by an organic additive. Metals can only be used in a very finely divided state, or possibly in the form of a massive element having a very high surface roughness since they are strongly reflecting in the massive state and smooth. However such materials show a poor resistance to external attack and are damaged by mechanical scratching, wear or corrosion. Because of this, they must be protected against attack, for example by glass screens, which increases the price and decreases the durability of them. Furthermore, the interface formed between the absorbing paint and its substrate plays a decisive role in the flow of heat transmitted to the heat exchange fluid and in the life span of the device. Devices are also known in which the infra-red radiation is converted into electrical signals. Among these devices, one may mention bolometers, in which the infra-red radiation causes a variation in the resistance of metallic or semi-conductor elements. The material used for the absorption of the infra-red radiation must have a high electrical resistivity, a high temperature coefficient and a low thermal conductance.
One can also mention, thermal probes (thermocouples) in which the e.m.f. of a pair of conductors of a different kind is measured.
For all these types of infra-red radiation sensors used as detectors, it is necessary to have a low dark current, which means that they are often placed inside a cooled enclosure intended to reduce thermal excitation in the materials and to reduce the flow of ambient radiation.
Furthermore, quasi-crystalline alloys are known, which are alloys made up of one or more quasi-crystalline phases. By quasi-crystalline phase, one understands a quasi-crystalline phase in the strict sense or a phase that approximates to one. A quasi-crystalline phase in the strict sense is a phase that has a symmetry of rotation normally incompatible with the symmetry of translation, that is to say a rotation axis symmetry of order 5, 8, 10 or 12, these symmetries being revealed by the diffraction of the radiation. By way of example, one can mention the icosahedric phase of point group m3 5 and the decagonal phase of a point group 10/mmm. An approximating phase or an approximating compound is a true crystal to the extent that its crystallographic structure remains compatible with the symmetry of translation, but which has, in the electron diffraction image, diffraction diagrams the symmetry of which is close to rotation axes 5, 8, 10 or 12. By way of example, one can mention the orthorhombic phase O1, characteristic of an alloy having the atomic composition Al65Cu20Fe10Cr5, the lattice parameters of which are: a0(1)=2.366, b0(1)=1.267, c0(1)=3.252 in nanometers. This orthorhombic phase O1 is said to be approximate to the decagonal phase. Furthermore, it is so close that it is not possible to distinguish its X-ray diffraction diagram from that of the decagonal phase. One can also mention the rhombohedric phase with parameters aR=3.208 nm, xcex1=36xc2x0, shown in alloys of composition close to Al64Cu24Fe12 in its number of atoms. This phase is a phase that approximates to the icosahedric phase. One can also mention the orthorhombic phases O2 and O3 with respective parameters a0(2)=3.83; b0(2)=0.41; c0(2)=5.26 and a0(3)=3.25; b0(3)=0.41; c0(3)=9.8 in nanometers which is formed in the alloy of composition Al63Cu8Fe12Cr12 in its number of atoms. One can further mention a phase C, of cubic structure, very often observed in coexistence with the approximating phases or true quasi-crystalline phases. This phase which is formed in certain Alxe2x80x94Cuxe2x80x94Fe and Alxe2x80x94Cuxe2x80x94Fexe2x80x94Cr alloys, consists of a superlattice, through a chemical ordering effect of the alloy elements in relation to the aluminum sites, of a phase with a CsCl structure and a lattice parameter a1=0.297 nm. One can also mention an H phase of hexagonal structure which derives directly from the C phase as the epitaxy relationships, as observed by electron microscopy demonstrate, between crystals of the C and H phases and the simple relationships which link the parameters of the crystal lattices, namely aH=32a13 (roughly 4.5%) and cH=33a1/2 (roughly 2.5%). This phase is isotypical of a hexagonal phase, designated "PHgr"AlMn, discovered in Alxe2x80x94Mn alloys containing 40% by weight of Mn. The cubic phase, its superlattices and the phases which derive from it, constitute a class of phases approximating to quasi-crystalline phases of neighboring composition. For more information about quasi-crystalline phases in the strict sense and phases approximating to them, reference can be made to EP-A-0 521 138 (J. M. Dubois, P. Cathonnet).
The quasi-crystalline alloys generally have good mechanical properties, high thermal stability and good resistance to corrosion.
The present inventors have now found that the rate of absorption of infra-red radiation of these quasi-crystalline alloys is particularly high and that they could be advantageously used in devices intended to absorb infra-red radiation.
Consequently, the objective of this invention is the use of quasi-crystalline alloys for the absorption of the infra-red radiation, and a device that absorbs the infra-red radiation, which includes an element made of a quasi-crystalline alloy.
A device according to this invention, that absorbs the infra-red radiation, is characterized in that it comprises as a coupler element for the infra-red radiation, an element made of a quasi-crystalline alloy made up of one or more quasi-crystalline phases representing at least 40% by volume of quasi-crystalline alloy, a quasi-crystalline phase being either a quasi-crystalline phase in the strict sense which has symmetries of rotation normally incompatible with the symmetry of translation, that is to say rotation axis symmetries of order 5, 8, 10 and 12, or an approximating phase or an approximating compound which is a true crystal the crystallographic structure of which remains compatible with the symmetry of translation, but which has, in the electron diffraction image, diffraction diagrams the symmetry of which is close to rotation axes 5, 8, 10 or 12.
A particularly preferred quasi-crystalline alloy is an alloy in which the quasi-crystalline phase is an icosahedric phase of point group m3 5 or a decagonal phase of the point group 10/mmm.
The quasi-crystalline alloys in which the quasi-crystalline phases represent at least 80% by volume are particularly preferred.
Among the quasi-crystalline alloys which can be used for the devices of this invention, one can mention those which show one of the following nominal compositions, which are given as an atomic percentage:
AlaCubFecXdYeIg, (I) in which X represents at least one element chosen from among B, C, P, S, Ge and Si, Y represents at least one element chosen from among V, Mo, Ti, Zr, Nb, Cr, Mn, Ru, Rh, Ni, Mg, W, Hf, Ta and the rare earths and I represents the unavoidable production impurities, 0xe2x89xa6gxe2x89xa62, 14bxe2x89xa630, 7xe2x89xa6cxe2x89xa620, 0xe2x89xa6dxe2x89xa65, 21xe2x89xa6b+c+exe2x89xa645 and a+b+c+d+e+g=100;
AlaPdbXcYdTeIg (II) in which X represents at least one metalloid chosen from among B, C, Si, Ge, P and S; Y represents at least one metal chosen from among Fe, Mn, V, Ni, Cr, Zr, Hf, Mo, W, Nb, Ti, Rh, Ru, Re; T is at least one rare earth and I represents the unavoidable production impurities; with a+b+c+d+e+f+g=100; 17xe2x89xa6bxe2x89xa630; 0xe2x89xa6cxe2x89xa68; 5xe2x89xa6dxe2x89xa615; 0xe2x89xa6exe2x89xa64; 0xe2x89xa6gxe2x89xa62;
AlaCubCOcXdYeTfIg (III) in which X represents at least one metalloid chosen from among B, C, Si, Ge, P and S; Y represents at least one metal chosen from among Fe, Mn, V, Ni, Cr, Zr, Hf, Mo, W, Nb, Ti, Rh, Ru, Re; T is at least one rare earth and I represents the unavoidable production impurities; with a+b+c+d+e+f+g=100; 14xe2x89xa6bxe2x89xa627; 8xe2x89xa6cxe2x89xa624; 28xe2x89xa6b+c+exe2x89xa645; 0xe2x89xa6fxe2x89xa64; 0xe2x89xa6dxe2x89xa6; 0xe2x89xa6gxe2x89xa62;
AlaXdYeIg, (IV) in which X represents at least one element chosen f rom among B, C, P, S, Ge, and Si, Y represents at least one element chosen from among V, Mo, Cr, Mn, Fe, Co, Ni, Ru, Rh and Pd and I represents the unavoidable production impurities; 0xe2x89xa6gxe2x89xa62, 0xe2x89xa6dxe2x89xa65, 18xe2x89xa6exe2x89xa629 and a+d+e+g=100;
AlaCubCob, (B, C)cMdNeIf (V) in which M represents at least one element chosen from among Fe, Mn, V, Ni, Cr, Ru, Os, Mo, Mg, Zn and Pd; N represents at least one element chosen from among W, Ti, Zr, Hf, Rh, Nb, Ta, Y, Si, Ge, the rare earths and I represents the unavoidable production impurities; with a+b+bxe2x80x2+c+d+e+f=100; axe2x89xa650; 0xe2x89xa6bxe2x89xa614; 0xe2x89xa6bxe2x89xa622; 0 less than b+bxe2x80x2xe2x89xa630; 0xe2x89xa6cxe2x89xa65; 8xe2x89xa6dxe2x89xa630; 0xe2x89xa6exe2x89xa64; fxe2x89xa62.
The quasi-crystalline alloys defined above are particularly suitable for the production on the one hand of coatings having a rough surface, and on the other hand coatings having high porosity, it being possible for the dimensions of the pores to be clearly greater than the wave length of the infra-red radiation. This irregularity of the surface, and especially the open pores facing the infra-red radiation constitute black bodies which increase considerably the absorption of the infra-red radiation. Taking account of the mechanical properties of these coatings, these black bodies are only sensitive to being sealed up by external agents such as dust. This disadvantage is however a minor one since the quasi-crystalline alloys form surfaces with only slight adhesive properties, which allows them to be easily cleaned. Conversely, the materials used in the devices of the prior art for absorbing infra-red radiation are very sensitive to the effects of dust which can only be removed by traditional methods of cleaning.
The quasi-crystalline alloys are therefore well suited for use as a coupler element for the infra-red radiation in the form of a layer deposited on a substrate. The layer of quasi-crystalline alloy can be made up of the quasi-crystalline alloy alone. It can also be made up of a mixture of a quasi-crystalline alloy and another material, for example, a binder.
The thickness of the layer of quasi-crystalline alloy is within a range of about ten nanometers to a few tens of micrometers, depending on the nature of the device according to the invention.
The layer of quasi-crystalline alloy can be deposited on a suitable substrate according to various methods.
A first method consists of spraying onto the substrate to be coated a quasi-crystalline alloy powder using a hot spraying device, such as a plasma torch or a blowtorch with a supersonic flame. One can also use a blowtorch with a conventional flame supplied with a mixture of oxygen and a combustible gas such as acetylene or propane, for example. When a blowtorch with a conventional flame is used, it is preferable to supply it using a flexible line which allows one, for example, to develop the quasi-crystalline structure directly in the flame, as described in EP-A-0 504 048 (J. M. Dubois, M. Ducos, R. Nury). These methods that use hot spraying allow one to obtain coatings, the thickness of which is between about 10 gm and a few hundreds of xcexcm, typically coatings whose thickness is of the order of mm.
Another technique consists of carrying out the deposition from the vapor phase. Various vapor phase deposition methods are known. By way of example, one can mention cathodic sputtering, the technique of evaporation under vacuum and laser ablation. For each of the vapor phase deposition techniques, one can use either a single source made up of a material, the composition of which will be adjusted in such a way as to obtain the desired composition on the substrate. Also several sources can be used, each corresponding to one of the elements making up the quasi-crystalline alloy. When several sources are used, either a simultaneous deposition or a sequential deposition can be made. Simultaneous deposition from several sources requires simultaneous control of several deposition flows to obtain the desired alloy composition. When successive layers are deposited from several sources, it is sometimes necessary to carry out a subsequent heat treatment in order to mix the different deposited elements and obtain the quasi-crystalline alloy. The vapor phase deposition techniques allow one to obtain layers of quasi-crystalline alloys having a very small thickness, typically less than 10 xcexcm, more particularly less than 0.3 xcexcm.
A layer of quasi-crystalline alloy can in addition be obtained by coating a substrate with a paint essentially made up of a quasi-crystalline alloy powder and an organic binder. The layers thereby obtained generally have a thickness greater than I pm, more particularly between 5 and 50 xcexcm.
The porosity and the roughness of the layers of quasi-crystalline alloy obtained depend on the method used to obtain them. The use of a plasma torch produces layers having a porosity of the order of from 5 to 10%. The layers obtained using a supersonic blowtorch are practically free of porosity. Using an oxy-gas blowtorch supplied with a powder, the particles of which have a diameter greater than 100 xcexcm, one can obtain porous layers whose mean pore diameter is between about 2 and 30 xcexcm. The layers obtained by vapor phase deposition are free of porosity. The layers obtained by application of a paint comprising a quasi-crystalline alloy powder and an organic binder, generally have a porosity of from 15 to 30%.
The coupler element for the infra-red radiation of a device according to this invention can be made up of a single grain quasi-crystal, which can be obtained for example by the growth techniques of Bridgman or Czochralsky.
A particular device according to this invention can be a bolometer, in which the quasi-crystalline alloy plays both the role of an infra-red radiation absorber and that of a resistive sensitive element. In such a device, the quasi-crystalline alloy can be in the form of a thin layer, preferably having a thickness of between 0.1 and 1 xcexcm. The quasi-crystalline alloy can also be used in the form of a single grain quasi-crystal.
Another particular device according to this invention is a temperature sensor, in which the substrate is a thermocouple, a layer of quasi-crystalline alloy enveloping the thermocouple. In such a device, the layer of quasi-crystalline alloy preferably has a thickness of between 1 and 50 xcexcm.
A device according to this invention can also be a device for photothermal conversion, such as a collector with a heat exchange fluid for solar heating (of the hot water collector type or of the air collector type), a collector for solar refrigeration or a passive collector of the Trombe wall type. In this type of device, the quasi-crystalline alloy can be deposited on substrates, the form and the nature of which vary very widely. The support for a Trombe wall is generally a concrete wall. In the collectors with a heat exchange fluid, the substrate is made up of a material that is a good conductor of heat, for example, a steel, copper or an alloy of aluminum, in the form of a plane, a profile or a groove. The layer of quasi-crystalline alloy replaces the organic paints or the deposits of finely divided metal powder used in the devices of the prior art. In the range of wavelengths of from 0.2 to 2 xcexcm, the coefficient of absorption of the infra-red radiation of a coating according to this invention is only 3% less at the most than that of a selective commercial coating such as the commercial coating MAXORB, over which nevertheless, it has all the advantages associated with a long life and good resistance to corrosion and to scratching. A coating according to the invention is as a consequence, competitive for devices for the photo-conversion of solar energy. The deposition of the quasi-crystalline alloy coating for these particular devices can be carried out by the techniques of thermal spraying, for example, using a plasma torch or a powder blowtorch. The coatings obtained in this way are intimately bonded to the substrate through an interface with excellent mechanical properties and good resistance to being torn off. This interface offers low thermal resistance to the flow of heat transmitted to the heat exchange fluid. The corrosion resistance of the coatings are particularly good as well as the mechanical strength thanks to the high hardness of the quasi-crystalline alloys and their high resistance to wear, to scratching and to abrasion. For solar energy collectors, particularly exposed collectors, these properties mean that they do not require a protective glass screen.
Another device according to this invention consists of a hot plate comprising a coating of a quasi-crystalline coating on a substrate.
A hot plate can be used in the cooking field for example in the form of a cooking surface, a grill or an oven plate. As a substrate, the bottom of a transparent cooking utensil can be used, made of Pyrex glass for example, the layer of alloy being deposited on the inside of the receptacle. For this particular use, it is desirable to use a quasi-crystalline alloy, the atomic composition of which belongs to the Group V mentioned above, in particular a composition Al≈71Cu≈9Fe≈10Cr≈10. The surface in contact with the food will be of interest for its anti-adhesive properties, the surface facing the heat source, from which it is only separated by the layer of glass which is used as a substrate, will absorb the infra-red radiation.
A hot plate can also be used for domestic heating, in the form of a heat economizer, in the form of a fire back, or in radiant heating equipment or heat accumulation apparatus.
A device according to this invention can also constitute an infra-red radiation filter, comprising a substrate transparent to the infra-red radiation, coated with a layer of quasi-crystalline alloy. The substrate can be a quartz substrate. The thickness of the quasi-crystalline alloy layer is, in this case, less than or equal to 0.3 xcexcm, and the quasi-crystalline alloy preferably comprises at least 80% by volume of a quasi-crystalline phase or a phase approximating to one.

Devices for absorbing infrared radiation comprising a quasi-crystalline element

Centre National de la Recherche Scientifique

Societe Nouvelle de Metallisation Industries


Use of a catalyst system comprising a metallocene catalyst component of general formula Rxe2x80x3(CpRm) (Cpxe2x80x2Rxe2x80x2n)MQ2 supported on an inert support in the slurry phase production of linear low density polyolefin, wherein Cp is a cyclopentadienyl moiety, Cpxe2x80x2 is a substituted or unsubstituted fluorenyl ring; Rxe2x80x3 is a structural bridge imparting stereorigidity to the component; each R is independently hydrogen or hydrocarbyl having 1 to 20 carbon atoms in which 0xe2x89xa6mxe2x89xa64; each Rxe2x80x2 is independently hydrocarbyl having 1 to 20 carbon atoms in which 0xe2x89xa6nxe2x89xa6B; M is a Group IVB transition metal or vanadium; and each Q is hydrocarbyl having 1 to 20 carbon atoms or halogen; the metallocene having a centroid-M-centroid angle in the range 105xc2x0 to 125xc2x0.

The present intention relates to a process for the preparation of polyclefins, especially polyethylenes, the use of metallocene compounds as catalyst components in the production of such polyolefin and the polyolefins obtainable thereby.
Low density polyethylene (LDPE) offers excellent optical properties and can be processed at relatively low temperatures and pressures while maintaining a good melt strength. LDPE has however limited possibilities for downgauging, due to a low draw ratio, and a low stiffness.
Linear-low-density polyethylene (LLDPE) has greatly improved downgauging possibilities and excellent tear and impact properties; its stiffness however remains low and its processability is well below that of LDPE. Also, conventional LLDPE""s optical properties do not match those of LDPE. Optical properties of LLDPE have been improved by using metallocene-catalysed LDPE (mLLDPE) resins; stiffness is however not improved in these products and the processability of these grades is generally worse than that of Conventional LLDPE.
Wherever high rigidity is needed, LDPE and LLDPE compositions will require overly thick structures. Especially for LLDPR, where excellent impact and tear properties render its downgauging capability useful, the lack of rigidity may be a main drawback. High rigidity maybe a requirement for the end product, it is very often a necessity for product handling.
Metallocene catalysts are known in the production of linear low density polyethylenes. EP-A-0653445 describes polyethylenes having a density not higher than 0.94 g/cm3 using a high temperature high pressure solution phase process. Another high temperature high pressure process is described in EP-A-0786466 where the production of LLDPE requires temperatures of at least 120xc2x0 C.
Alternative methods of polyethylene production are disclosed in U.S. Pat. No. 5,317,036 which uses an unsupported catalyst in the gas phase and EP-A-0668295, which uses the gas phase or an unsupported catalyst in slurry phase. The metallocene catalysts of EP-A-0668295 are specially-prepared spray dried, filled metallocene catalysts.
These pocesses all require either expensive or specialised catalyst production or relatively high operating costs
In the production of other polyethylene compositions, it is possible to use reaction systems based on a Ziegler-Natta catalyst or a chromium-based catalyst. These reaction systems require a high concentration of comonomer. This suffers from a drawback in that high concentration of comonomer results in increased solubility of the polyethylene produced in a slurry process. One consequence of the increased solubility of polymer is that there is a high incidence of reactor fouling. Use of a high concentration of comonomer is also costly because of the need to recycle unincorporated comonomer.
It is an aim of the present invention to overcome these disadvantages.
The present invention provides use of a catalyst system comprising a metallocene catalyst component of general formula Rxe2x80x3(CpRm) (Cpxe2x80x2Rxe2x80x2n)MQ2 supported on an inert support in the slurry phase production of linear low density polyolefin, wherein Cp is a cyclopentadienyl moiety, Cpxe2x80x2 is a substituted or unsubstituted fluorenyl ring; Rxe2x80x3 is a structural bridge imparting stereorigidity to the component; each R is independently hydrogen or hydrocarbyl having 1 to 20 carbon atoms in which oxe2x89xa6mxe2x89xa64; each Rxe2x80x2 is independently hydrocarbyl having 1 to 20 carbon atoms in which oxe2x89xa6nxe2x89xa6B; M is a Group IVB transition metal or vanadium; and each Q is hydrocarbyl having 1 to 20 carbon atoms or halogen; the metallocene having a centzoid-M-centroid angle in the range 105xc2x0 to 125xc2x0.
FIG. 1 shows the effect of decreasing the centroid-M-centroid angle in Zr-based metallocenes. The metallocenes of the present invention have a very open structure which permits the facile incorporation of comonomer with larger substituents such as hexene in polyolefin production. In this way, LLDPE with densities around 0.9 or lower may be produced at a commercially acceptable polymerisation temperature in a slurry process. The production of LLDPE with such low densities has hitherto not been possible with Cr-based and closed structure Cent-Zr-Cent ( greater than 125xc2x0) metallocenes in a loop slurry process. Lower comonomer concentrations need be used in the process thereby reducing the likelihood of reactor fouling and avoiding excessive use of expensive comonomer.
Preferably Cp is a substituent cyclopentadienyl in which each R is independently XR*3 in which X is C or Si and each R* is independently H or hydrocarbyl having 1 to 20 carbon atoms. More preferably the cyclopentadienyl is substituted with Ph2CH, Me3C, Me3Si, Me, Me and Me3C, Me and SiMe3, Me and Ph, or Me and CH3xe2x80x94CHxe2x80x94CH3.
Preferably, each Rxe2x80x2 is independently YRxe2x80x2xe2x80x3, in which Y is C or Si and each Rxe2x80x2xe2x80x3 is independently H or hydrocarbyl having 1 to 20 carbon atoms.
The structural bridge Rxe2x80x3 is generally alkylidene having 1 to 20 carbon atoms, a dialkyl germanium or silicon or siloxane, alkyl phosphine or amine, preferably Mexe2x80x94Cxe2x80x94Me, Phxe2x80x94Cxe2x80x94Ph, xe2x80x94CH2xe2x80x94, Etxe2x80x94Cxe2x80x94Et Mexe2x80x94Sixe2x80x94Me, Phxe2x80x94Sixe2x80x94Ph or Etxe2x80x94Sixe2x80x94Et.
The metal M is preferably Zr or Hf and each Q is preferably Cl.
In order to maximise comonomer incorporation, it is preferred that the centroid-M-centroid angle is no more than 119xc2x0.
In a further aspect, the present invention provides a process for the preparation of a linear low-density polyolefin, which comprises reacting an olefin monomer with hydrogen and an xcex1-olefin comonomer in a slurry in the presence of a catalyst comprising (i) the metallocene catalyst and (ii) an aluminium- or boron-containing cocatalyst, wherein the catalyst is supported on an inert support. The comonomer is preferably hexene, typically present in an amount of from 2 to 10, preferably 2 to 5% by weight of the total reaction mixture.
Suitable aluminium-containing cocatalysts comprise an alumoxane, an alkyl aluminium and/or a Lewis acid.
The alumoxanes usable in the process of the present invention are well known and preferably comprise oligomeric linear and/or cyclic alkyl alumoxanes represented by the formula:
for oligomeric, linear alumoxanes and
for oligomeric, cyclic alumoxane,
wherein n is 1-40, preferably 10-20, m is 3-40, preferably 3-20 and R is a C1-C8 alkyl group and preferably methyl, Generally, in the preparation of alumoxanes from, for example, aluminium trimethyl and water, a mixture of linear and cyclic compounds is obtained.
Suitable boron-containing cocatalysts may comprise a triphenylcarbenium boronate such as tetrakis-pentafluorophenyl borato-triphenylcarbenium as described in EP-A-0427696, or those of the general formula [Lxe2x80x2-H]+[B Ar1 Ar2 X3 X4]xe2x88x92 as described in EP-A-0277004 (page 6, line 30 to page 7, line 7).
The catalyst system is employed in a slurry process, which is heterogeneous. In a slurry process it is necessary to immobilise the catalyst system on an inert support, particularly a porous solid support such as talc, inorganic oxides and resinous support materials such as polyolefin. Preferably, the support material is an inorganic oxide in its finally divided form.
Suitable inorganic oxide materials which are desirably employed in accordance with this invention include Group 2a, 3a, 4a or 4b metal oxides such as silica, alumina and mixtures thereof. Other inorganic oxides that may be employed either alone or in combination with the silica, or alumina are magnesia, titania, zirconia, and the like. Other suitable support materials, however, can be employed, for example, finely divided functionalized polyolefins such as finely divided polyethylene.
Preferably, the support is a silica having a surface area comprised between 200 and 900 m2/g and a pore volume comprised between 0.5 and 4 ml/g.
The amount of alumoxane and metallocenes usefully employed in the preparation of the solid support catalyst can vary over a wide range. Preferably the aluminium to transition metal mole ratio is in the range between 1:1 and 100:1, preferably in the range 5:1 and 50:1.
The order of addition of the metallocenes and alumoxane to the support material can vary. In accordance with a preferred embodiment of the present invention alumoxane dissolved in a suitable inert hydrocarbon solvent is added to the support material slurried in the same or other suitable hydrocarbon liquid and thereafter a mixture of the metallocene catalyst component is added to the slurry.
Preferred solvents include mineral oils and the various hydrocarbons which are liquid at reaction temperature and which do not react with the individual ingredients. Illustrative examples of the useful solvents include the alkanes such as pentane, iso-pentane, hexane, heptane, octane and nonane; cycloalkanes such as cyclopentane and cyclohexane, and aromatics such as benzene, toluene, ethylbenzene and diethylbenzene.
Preferably the support material is slurried in toluene and the metallocene and alumoxane are dissolved in toluene prior to addition to the support material.
Where the reaction is performed in a slurry using, for example, isobutane, a reaction temperature in the range 70xc2x0 C. to 110xc2x0 C. may be used.
A linear low-density polyethylene is obtainable from the process with a density below 0.93 g/cc and preferably in the range 0.90 to 0.92. The polyethylene preferably has a molecular weight distribution in the range 2 to 4.5, preferably around 3 and more preferably is partially long chain branched so as to facilitate processing.
This invention will now be described in further detail by way of example only, with reference to the following Examples and accompanying drawings, in which:

Process for the preparation of a polyolefin


A non-tissue contacting electrode system senses physiologic signals from a patient during implant and/or followup of an implantable medical device (IMD) via an external programmer or other monitoring instrument. These sensing systems are electrically connected to the circuitry of the external device and detect cardiac depolarization waveforms displayable as electrocardiographic tracings on the instrument screen when the programming head is positioned above an implanted pacemaker (or other implanted device) so equipped with a non-tissue contacting electrode system. The structure and system provide an enhanced capability for detecting and gathering physiological signals from a patient with minimally invasive patient contact.

The present invention relates generally to implantable medical devices such as pacemakers and more particularly to a method and apparatus to acquire electrocardiographic data, waveform tracings, and other physiologic data displayable by a programmer from an implantable medical device patient without the need for, or use of, surface (skin) contacting electrodes.
The electrocardiogram (ECG) is commonly used in medicine to determine the status of the electrical conduction system of the human heart. As practiced the ECG recording device is commonly attached to the patient via ECG leads connected to pads arrayed on the patient""s body so as to generate a recording that displays the cardiac waveforms in any one of 12 possible vectors.
The history of the ECG dates back to 1842 when the Italian physicist, Carlo Matteucci discovered that each heartbeat was accompanied by a detectable electric signal. In 1878, two British physiologists, John Burden Sanderson and Frederick Page, determined that the heart signal consisted of, at least, two phases, the QRS (ventricular depolarization) and the repolarization or T-wave. It was not until 1893, however, that Willem Einthoven introduced the term xe2x80x98electrocardiogramxe2x80x99 at a meeting of the Dutch Medical Association, although he later disavowed he was the originator of the term.
Einthoven may, however, be called the father of electrocardiography, since he won the Nobel Prize for his achievements in 1924. It was he who finally dissected a heart and named all of the cardiac waveforms (P, Q, R, S, T) that commonly appear on an ECG tracing from a xe2x80x98normalxe2x80x99 person.
Einthoven and other medical practitioners of that time were aware of only three vectors (I, II, and III) that are achieved by placement of the ECG electrodes on specific body sites. The remaining nine sites were discovered later in the twentieth century. In 1938, American Heart Association and the Cardiac Society of Great Britain defined the standard positions (I-III) and wiring of the chest leads V1-V6. The xe2x80x98Vxe2x80x99 stands for voltage. Finally, in 1942, Emanuel Goldberger added the augmented limb leads aVR, aVL and aVF to Einthoven""s three limb leads and the six chest leads thereby creating the 12-lead electrocardiogram that is routinely used today for cardiac diagnostic purposes.
Since the implantation of the first cardiac pacemaker, implantable medical device technology has advanced with the development of sophisticated, programmable cardiac pacemakers, pacemaker-cardioverter-defibrillator arrhythmia control devices and drug administration devices designed to detect arrhythmias and apply appropriate therapies. The detection and discrimination between various arrhythmic episodes in order to trigger the delivery of an appropriate therapy is of considerable interest. Prescription for implantation and programming of the implanted device are based on the analysis of the PQRST electrocardiogram (ECG) that currently requires externally attached electrodes and the electrogram (EGM) that requires implanted pacing leads. The waveforms are usually separated for such analysis into the P-wave and R-wave in systems that are designed to detect the depolarization of the atrium and ventricle respectively. Such systems employ detection of the occurrence of the P-wave and R-wave, analysis of the rate, regularity, and onset of variations in the rate of recurrence of the P-wave and R-wave, the morphology of the P-wave and R-wave and the direction of propagation of the depolarization represented by the P-wave and R-wave in the heart. The detection, analysis and storage of such EGM data within implanted medical devices are well known in the art. Acquisition and use of ECG tracing(s), on the other hand, has generally been limited to the use of an external ECG recording machine attached to the patient via surface electrodes of one sort or another.
The aforementioned ECG systems that utilize detection and analysis of the PQRST complex are all dependent upon the spatial orientation and number of electrodes available in or around the heart to pick up the depolarization wave front.
As the functional sophistication and complexity of implantable medical device systems increased over the years, it has become increasingly more important for such systems to include a system for facilitating communication between one implanted device and another implanted device and/or an external device, for example, a programming console, monitoring system, or the like. For diagnostic purposes, it is desirable that the implanted device be able to communicate information regarding the device""s operational status and the patient""s condition to the physician or clinician. State of the art implantable devices are available that transmit a digitized electrical signal to display electrical cardiac activity (e.g., an ECG, EGM, or the like) for storage and/or analysis by an external device. The surface ECG, in fact, has remained the standard diagnostic tool since the very beginning of pacing and remains so today.
To diagnose and measure cardiac events, the cardiologist has several tools from which to choose. Such tools include twelve-lead electrocardiograms, exercise stress electrocardiograms, Holter monitoring, radioisotope imaging, coronary angiography, myocardial biopsy, and blood serum enzyme tests. Of these, the twelve-lead electrocardiogram (ECG) is generally the first procedure used to determine cardiac status prior to implanting a pacing system; thereafter, the physician will normally use an ECG available through the programmer to check the pacemaker""s efficacy after implantation. Such ECG tracings are placed into the patient""s records and used for comparison to more recent tracings. It must be noted, however, that whenever an ECG recording is required (whether through a direct connection to an ECG recording device or to a pacemaker programmer), external electrodes and leads must be used.
Another possible approach is described in pending applications Ser. No. 09/749,169, Leadless Fully Automatic Pacemaker Follow-Up filed Dec. 27, 2000; Ser. No. 09/696,365, Multilayer Ceramic Electrodes For Sensing Cardiac Depolarization Signals, filed Oct. 25, 2000; Ser. No. 09/697,438, Surround Shroud Connector and Electrode Housings For A Subcutaneous Electrode Array and Leadless ECGs, filed Oct. 26, 2000; Ser. No. 09/703,152, Subcutaneous Spiral Electrode For Sensing Electrical Signals of the Heart, filed Oct. 31, 2000; Ser. No. 09/736,640, Atrial Aware VVIxe2x80x94A Method For Atrial Synchronous Ventricular (VDD/R) Pacing Using the Subcutaneous Electrode Array and a Standard Pacing Lead, filed Dec. 14, 2000; Ser. No. 09/850,331, Subcutaneous Sensing Feedthrough/ Electrode Assembly, filed May 7, 2000; and Ser. No. 09/721,275, System And Method For Deriving a Virtual ECG IR EGM Signal, filed Nov. 22, 2000; whereby a subcutaneous leadless pseudo EKG is sensed from the can of the IMD and transmitted to an external programmer via telemetry. The ""169, ""365, ""438, ""152, ""640, ""331, and ""275 applications are incorporated herein by reference in their entireties.
In the art known to the inventors and current practice there are noticeable limitations. For example, electrocardiogram analysis performed using existing external or body surface ECG systems can be limited by mechanical problems and poor signal quality. Electrodes attached externally to the body are a major source of signal quality problems and analysis errors because of susceptibility to interference such as muscle noise, power line interference, high frequency communication equipment interference, and baseline shift from respiration or motion. Signal degradation also occurs due to contact problems, ECG waveform artifacts, and patient discomfort. Externally attached electrodes are subject to motion artifacts from positional changes and the relative displacement between the skin and the electrodes. Furthermore, external electrodes require special skin preparation to ensure adequate electrical contact. Such preparation, along with positioning the electrode and attachment of the ECG lead to the electrode needlessly prolongs the pacemaker follow-up session.
Other art relating to subcutaneous leadless pseudo EKG concept deals with generating a pseudo EKG signal via pulse generator externalized electrodes and signal conditioning electronics. This method of EKG acquisition is rapid, does not require electrode positioning and does not require patient disrobing. However, there is substantial increase in device cost, increased circuit complexity, increased IMD device size, and an IMD aesthetic degradation.
Prior art describes systems to monitor electrical activity of the human heart for diagnostic and related medical purposes. U.S. Pat. No. 4,023,565 issued to Ohlsson describes circuitry for recording ECG signals from multiple lead inputs. Similarly, U.S. Pat. No. 4,263,919 issued to Levin, U.S. Pat. No. 4,170,227 issued to Feldman, et al, and U.S. Pat. No. 4,593,702 issued to Kepski, et al, describe multiple electrode systems which combine surface EKG signals for artifact rejection.
The primary implementation for multiple electrode systems in the prior art is vector cardiography from ECG signals taken from multiple chest and limb electrodes. This is a technique whereby the direction of depolarization of the heart is monitored, as well as the amplitude, generally similar to the disclosure in U.S. Pat. No. 4,121,576 to Greensite.
Numerous body surface ECG monitoring electrode systems have been employed in the past in detecting the ECG and conducting vector cardiographic studies. For example, U.S. Pat. No. 4,082,086 to Page, et al., discloses a four electrode orthogonal array that may be applied to the patient""s skin both for convenience and to ensure the precise orientation of one electrode to the other. U.S. Pat. No. 3,983,867 to Case describes a vector cardiography system employing ECG electrodes disposed on the patient in normal locations and a hex axial reference system orthogonal display for displaying ECG signals of voltage versus time generated across sampled bipolar electrode pairs.
U.S. Pat. No. 4,310,000 to Lindemans and U.S. Pat. Nos. 4,729,376 and 4,674,508 to DeCote, incorporated herein by reference, disclose the use of a separate passive sensing reference electrode mounted on the pacemaker connector block or otherwise insulated from the pacemaker case in order to provide a sensing reference electrode which is not part of the stimulation reference electrode and thus does not have residual after-potentials at its surface following delivery of a stimulation pulse.
Moreover, in regard to subcutaneously implanted EGM electrodes, the aforementioned Lindemans U.S. Pat. No. 4,310,000 discloses one or more reference-sensing electrode positioned on the surface of the pacemaker case as described above. U.S. Pat. No. 4,313,443 issued to Lund describes a subcutaneously implanted electrode or electrodes for use in monitoring the ECG.
Finally, U.S. Pat. No. 5,331,966 to Bennett, incorporated herein by reference, discloses a method and apparatus for providing an enhanced capability of detecting and gathering electrical cardiac signals via an array of relatively closely spaced subcutaneous electrodes (located on the body of an implanted device).
The present invention encompasses a non-tissue contacting electrode system for the sensing of physiologic signals from a patient that may be implemented during the implant and/or follow-up of an implantable medical device (IMD) via an external programmer or other monitoring instrument. These sensing systems are electrically connected to the circuitry of the external device and detect cardiac depolarization waveforms displayable as electrocardiographic tracings on the instrument screen when the programming head is positioned above an implanted device, such as a pacemaker, so equipped with a non-tissue contacting electrode system.
The present invention provides a method and apparatus that may be implemented for use in conjunction with the aforementioned medical devices to provide an enhanced capability of detecting and gathering electrical cardiac signals via non-tissue contacting sensors.
The present invention enables the physician or medical technician to perform follow-up regiments that, in turn, eliminate the time it takes to attach external adhesive electrodes to the patient""s skin. Such timesavings can reduce the cost of follow-up, as well as making it possible for the physician or medical technician to see more patients during each day. Though not limited to these, other uses include: Holter monitoring with event storage, arrhythmia detection and monitoring, capture detection, ischemia detection and monitoring (S-T elevation and depression on the ECG), changes in QT interval (i.e., QT variability), transtelephonic monitoring, web-enabled remote patient management and chronic remote patient care.


A digital camera of the present invention includes a microcomputer 110 having a live view mode controlling so that image data generated by a CMOS sensor 133 or image data obtained by subjecting the image data generated by the CMOS sensor 133 to predetermined processing is displayed on a liquid crystal monitor 150 as a moving image in real time, wherein the microcomputer 110 controls so that, when the live view mode is set, the digital camera comes out of the live view mode, and setting information on the digital camera is displayed on the liquid crystal monitor 150, in accordance with the manipulation of the manipulation portion 140. Due to this configuration, in a digital camera that includes a movable mirror and is capable of displaying a subject image in a live view through an electronic viewfinder, the operability thereof can be enhanced.

1. Field of the Invention
The present invention relates to a digital camera. In particular, the present invention relates to a digital camera having a movable mirror, which enables a subject image to be observed through an electronic viewfinder.
2. Description of Related Art
A digital single-lens reflex camera has an electronic viewfinder and an optical viewfinder, so that a subject image formed by an image pickup optical system is switched with a movable mirror, and can be observed through the optical viewfinder. Because of this, displacement does not occur between a subject image in a recording image and a subject image displayed with the optical viewfinder, whereby an image pickup manipulation can be performed satisfactorily.
However, the digital single-lens reflex camera needs to switch the movable mirror in accordance with an operation state. This requires a user's manual manipulation, and a time therefor needs to be kept. Particularly, in a camera with a "live view mode" in which an image generated by an image pickup element is displayed on a display portion in real time, the movable mirror needs to be switched frequently in accordance with an autofocus operation, a diaphragm adjustment operation, and an image pickup operation.
A digital single-lens reflex camera with a live view mode is disclosed by, for example, Patent Document 1 (JP 2001-272593 A).
However, in the digital single-lens reflex camera disclosed by Patent Document 1, the operability involved in switching of the movable mirror is not improved sufficiently. Therefore, even if the live view mode is set to be executable, it is difficult for a user to use it, and consequently, the user captures an image while observing it with the optical viewfinder.


A process for conditioning a high efficiency silver catalyst used to manufacture ethylene oxide from ethylene, oxygen, and at least one organic chloride is described. A non-reactive conditioning gas comprising at least one of ethylene, oxygen, and a ballast gas is introduced to the catalyst at a conditioning temperature ranging from 150° C. to 180° C. for a selected period of at least 4 hours.

Ethylene oxide has a multiplicity of utilities. Ethylene oxide, for example, is used to produce ethylene glycol, which is used as an automotive coolant, as antifreeze, and in preparing polyester fibers and resins, nonionic surfactants, glycol ethers, ethanolamines, and polyethylene polyether polyols.
The production of ethylene oxide via catalytic epoxidation of ethylene in the presence of oxygen using silver based catalysts is known. Conventional silver-based catalysts used in such processes typically provide a relatively lower efficiency or "selectivity" (i.e., a lower percentage of the reacted ethylene is converted to the ethylene oxide). In certain exemplary processes, when using conventional catalysts in the epoxidation of ethylene, the theoretically maximal efficiency towards ethylene oxide, expressed as a fraction of the ethylene converted, does not reach values above the 6/7 or 85.7 percent limit. Therefore, this limit had long been considered to be the theoretically maximal efficiency of this reaction, based on the stoichiometry of the following reaction equation:7C2H4+6O2→6C2H4O+2CO2+2H2O
cf. Kirk-Othmer's Encyclopedia of Chemical Technology, 4th ed., Vol. No. 9, 1994, p. 926.
Certain "high efficiency" or "high selectivity" modern silver-based catalysts are highly selective towards ethylene oxide production. For example, when using certain modern catalysts in the epoxidation of ethylene, the theoretically maximal efficiency towards ethylene oxide can reach values above the 6/7 or 85.7 percent limit referred to, for example 88 percent or 89 percent, or above. As used herein, the terms "high efficiency catalyst" and "high selectivity catalyst" refer to a catalyst that is capable of producing ethylene oxide from ethylene and oxygen at an efficiency greater than 85.7 percent. The observed actual efficiency of a high efficiency catalyst may fall below 85.7 percent under certain conditions based on process variables, catalyst age, etc. However, if the catalyst is capable of achieving at least an 85.7 percent efficiency at any point during its life, for example, under any set of reaction conditions as described in the Examples hereinafter, or by extrapolating lower efficiencies observed at two different oxygen conversions obtained by varying gas hourly space velocity to the limiting case of zero oxygen conversion, it is considered to be a high efficiency catalyst. Such highly efficient catalysts, which may comprise as their active components silver, rhenium, at least one further metal, and optionally, a rhenium co-promoter, are disclosed in EP0352850B1 and in several subsequent patent publications. "Promoters," sometimes referred to as "inhibitors" or "moderators," refer to materials that enhance the performance of the catalysts by either increasing the rate towards the desired formation of ethylene oxide and/or suppressing the rate towards the undesirable oxidation of ethylene or ethylene oxide to carbon dioxide and water. As used herein, the term "co-promoter" refers to a material that—when combined with a promoter—increases the promoting effect of the promoter.
"Promoters" can be materials that are introduced to catalysts during the preparation of the catalysts (solid phase promoters). In addition, "promoters" can also be gaseous materials that are introduced to the epoxidation reactor feed (gas phase promoters). In one example, an organic halide gas phase promoter may be added continuously to the epoxidation reactor feed to increase the catalyst efficiency. For silver-based ethylene epoxidation catalysts, both solid and gas phase promoters are typically required in any commercial processes.
Conventional catalysts have relatively flat efficiency curves with respect to the gas phase promoter concentration in the feed, i.e., the efficiency is almost invariant (i.e., the change in efficiency with respect to a change in gas phase promoter concentration in the feed is less than about 0.1%/ppm) over a wide range of promoter concentrations, and this invariance is substantially unaltered as reaction temperature is changed (i.e., the change in efficiency with respect to a change in reaction temperature is less than about 0.1%/° C.) during prolonged operation of the catalyst. However, conventional catalysts have nearly linear activity decline curves with respect to the gas phase promoter concentration in the feed, i.e., with increasing gas phase promoter concentration in the feed, temperature has to be increased or the ethylene oxide production rate will be reduced. Therefore, when using a conventional catalyst, for optimum efficiency, the gas phase promoter concentration in the feed can be chosen at a level at which the maximum efficiency can be maintained at relatively lower operating temperatures. Typically, the gas phase promoter concentration can remain substantially the same during the entire lifetime of a conventional catalyst. Alternatively, the reactor temperature may be adjusted to obtain a desired production rate without any substantial impact on efficiency due to non-optimal gas phase promoter concentrations.
By contrast, high efficiency catalysts tend to exhibit relatively steep efficiency curves as a function of gas phase promoter concentration as the concentration moves away from the value that provides the highest efficiency (i.e., the change in efficiency with respect to a change in gas phase promoter concentration is at least about 0.2%/ppm when operating away from the efficiency maximizing concentration). Thus, small changes in the promoter concentration can result in significant efficiency changes, and the efficiency exhibits a pronounced maximum, i.e., an optimum, at certain concentrations (or feed rates) of the gas phase promoter for a given reaction temperature and catalyst age. Moreover, the efficiency curves and the optimum gas phase promoter concentration tend to be strong functions of reactor temperature and are thus significantly affected if reactor temperature is varied, for example, to compensate for decreases in catalyst activity, (i.e., the change in efficiency with respect to a change in reactor temperature can be at least about 0.1%/° C. when operating away from the efficiency maximizing promoter concentrations for the selected temperatures). In addition, high efficiency catalysts have exhibited significant activity increases with increases in the gas phase promoter concentration in the feed, i.e., with increasing gas phase promoter concentration in the feed, temperature has to be decreased or the production rate will increase.
High-efficiency catalysts for producing ethylene oxide are frequently conditioned or activated prior to start-up to improve their activity and/or efficiency. Conditioning and activation processes typically involve flowing a non-reactive medium through the heated catalyst. Conditioning processes typically take place prior to the start of ethylene oxide production. Activation processes can take place both before and after starting ethylene oxide production. However, as used herein, the term "conditioning" refers to processes occurring either before or after start-up. The duration and conditions of the catalyst bed during the conditioning or activation period, such as feed gas composition, feed gas flow rate, space velocity, temperature, and pressure can influence the catalyst performance that is observed after stable operation is reached. Thus, a need has arisen for conditioning and activation processes that provide improved performance after start-up.

Process for conditioning a high efficiency ethylene oxide catalyst