U.S. patent application number 10/702617 was filed with the patent office on 2004-11-25 for method of manufacturing superconducting quantum interference type magnetic fluxmeter.
Invention is credited to Kawachi, Masaharu, Sato, Nobuyoshi, Yoshizawa, Masahito.
Application Number | 20040234680 10/702617 |
Document ID | / |
Family ID | 18983730 |
Filed Date | 2004-11-25 |
United States Patent
Application |
20040234680 |
Kind Code |
A1 |
Kawachi, Masaharu ; et
al. |
November 25, 2004 |
METHOD OF MANUFACTURING SUPERCONDUCTING QUANTUM INTERFERENCE TYPE
MAGNETIC FLUXMETER
Abstract
The method of manufacturing a superconducting quantum
interference type magnetic fluxmeter including forming an input
coil and a pickup coil integrated with the input coil by
electrophoretically depositing high-temperature superconducting
fine particles on a surface of the first cylindrical ceramic
substrate, and sintering the fine particles, forming a
high-temperature superconductor magnetic shield tube by
electrophoretically depositing high-temperature superconducting
fine particles on an entire surface of the second cylindrical
ceramic substrate, and sintering the fine particles, magnetically
coupling the input coil and the high-temperature superconducting
quantum interference type element by placing the pickup coil such
that a distal end portion thereof is inserted within a lower end
portion of the magnetic shield tube and inserting the
high-temperature superconducting quantum interference type element
from an upper end portion of the magnetic shield tube.
Inventors: |
Kawachi, Masaharu;
(Sanda-shi, JP) ; Yoshizawa, Masahito;
(Morioka-shi, JP) ; Sato, Nobuyoshi; (Hitachi-shi,
JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Family ID: |
18983730 |
Appl. No.: |
10/702617 |
Filed: |
November 7, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10702617 |
Nov 7, 2003 |
|
|
|
PCT/JP02/01278 |
Feb 15, 2002 |
|
|
|
Current U.S.
Class: |
427/62 ;
505/300 |
Current CPC
Class: |
G01R 33/0358 20130101;
H01L 39/2429 20130101 |
Class at
Publication: |
427/062 ;
505/300 |
International
Class: |
B05D 005/12; H01L
033/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 7, 2001 |
JP |
2001-136454 |
Claims
What is claimed is:
1. A method of manufacturing a superconducting quantum interference
type magnetic fluxmeter, comprising: forming a conductive pattern
on an outer surface of a first cylindrical ceramic substrate;
electrophoretically depositing high-temperature superconducting
fine particles and/or high-temperature superconducting precursor
fine particles on the conductive pattern; and subjecting the first
cylindrical ceramic substrate to a heat treatment to sinter the
fine particles, thereby forming an input coil and a pickup coil
integrated with the input coil.
2. The method according to claim 1, wherein the conductive pattern
is formed by forming a conductive paste layer on a surface of the
ceramic substrate and subjecting the conductive paste layer to a
heat treatment.
3. The method according to claim 1, wherein the conductive pattern
is formed by plating a conductive material or vapor deposition of a
conductive material.
4. The method according to claim 1, wherein the conductive pattern
contains silver as its main component.
5. The method according to claim 1, by further comprising: forming
a conductive layer on an inner surface of an upper section of the
first cylindrical ceramic substrate, electrophoretically depositing
high-temperature superconducting fine particles and/or
high-temperature superconducting precursor fine particles on the
conductive layer, and subjecting the first cylindrical ceramic
substrate to a heat treatment to sinter the fine particles, thereby
forming a first magnetic shield layer on the inner surface of the
upper section of the first cylindrical ceramic substrate.
6. The method according to claim 5, wherein the conductive layer is
formed by forming a conductive paste layer on a surface of the
ceramic substrate and subjecting the conductive paste layer to a
heat treatment.
7. The method according to claim 5, wherein the conductive layer is
formed by plating a conductive material or vapor deposition of a
conductive material.
8. The method according to claim 5, wherein the conductive layer
contains silver as its main component.
9. The method according to claim 1, by further comprising: placing
the pickup coil such that a distal end portion thereof is inserted
within a lower end portion of a magnetic shield tube having a
second high-temperature superconductor shield layer on an outer
surface thereof; and inserting a high-temperature superconducting
quantum interference type element from an upper end portion of the
magnetic shield tube, thereby magnetically coupling the input coil
and the high-temperature superconducting quantum interference type
element, wherein: the magnetic shield tube is obtained by forming a
conductive layer on an outer surface of a second cylindrical
ceramic substrate having an inner diameter larger than an outer
diameter of the pickup coil, electrophoretically depositing
high-temperature superconducting fine particles and/or
high-temperature superconducting precursor fine particles on the
conductive layer, and subjecting the second cylindrical ceramic
substrate to a heat treatment to sinter the fine particles, thereby
forming a second high-temperature superconducting shield layer.
10. The method of manufacturing a superconducting quantum
interference type magnetic fluxmeter according to claim 9, wherein
the conductive layer is formed by forming a conductive paste layer
on a surface of the ceramic substrate and subjecting the conductive
paste layer to a heat treatment.
11. The method of manufacturing a superconducting quantum
interference type magnetic fluxmeter according to claim 6, wherein
the conductive layer is formed by plating a conductive material or
vapor deposition of a conductive material.
12. The method of manufacturing a superconducting quantum
interference type magnetic fluxmeter according to claim 6, wherein
the conductive layer contains silver as its main component.
13. The method according to claim 9, by further comprising: forming
a conductive layer on an inner surface of an upper section of the
first cylindrical ceramic substrate, electrophoretically depositing
high-temperature superconducting fine particles and/or
high-temperature superconducting precursor fine particles on the
conductive layer, and subjecting the first cylindrical ceramic
substrate to a heat treatment to sinter the fine particles, thereby
forming a first magnetic shield layer on the inner surface of the
upper section of the first cylindrical ceramic substrate.
14. The method according to claim 13, wherein the conductive layer
is formed by forming a conductive paste layer on a surface of the
ceramic substrate and subjecting the conductive paste layer to a
heat treatment.
15. The method according to claim 13, wherein the conductive layer
is formed by plating a conductive material or vapor deposition of a
conductive material.
16. The method according to claim 13, wherein the conductive layer
contains silver as its main component.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a Continuation Application of PCT Application No.
PCT/JP02/01278, filed Feb. 15, 2002, which was not published under
PCT Article 21(2) in English.
[0002] This application is based upon and claims the benefit of
priority from the prior Japanese Patent Application No.
2001-136454, filed May 7, 2001, the entire contents of which are
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] The present invention relates to a method of manufacturing a
superconducting quantum interference magnetic type fluxmeter, more
specifically, a superconducting quantum interference magnetic type
fluxmeter that employs a high-temperature superconductor thin
film.
[0005] 2. Description of the Related Art
[0006] The superconducting quantum interference device (to be
called "SQUID" hereinafter) type magnetic fluxmeter is a magnetic
sensor having such a high sensitivity that a magnetic field of
{fraction (1/5,000)} or less of the terrestrial magnetism can be
detected. The sensor utilizes the quantization phenomenon of the
superconductor, and has a sensitivity higher by 3 figures or more
than that of the conventional magnetic sensor. In particular, after
the development of the SQUID magnetic fluxmeter using a
high-temperature superconductor thin film, it has become possible
to operate the sensor at a temperature of liquid nitrogen (77.3K),
and therefore the field of the application is becoming wider.
[0007] The SQUID magnetic fluxmeter is a device in which junctions
formed by finely processing superconducting thin film are connected
to each other in parallel as shown in FIG. 1. When a bias current
is allowed to flow to the SQUID magnetic fluxmeter, the voltage
generated at both ends of the SQUID magnetic fluxmeter is zero
since the superconducting state is maintained until the bias
current becomes the critical value (Ic) as shown in FIG. 2. When
the current exceeds the critical value, the SQUID magnetic
fluxmeter changes its state to the normal conducting state, and
thus a voltage is generated.
[0008] On the other hand, when a magnetic field is applied to the
SQUID magnetic fluxmeter and a magnetic flux is put into a loop
formed by the junctions connected to each other in parallel, the
critical current value is lowered.
[0009] Incidentally, as shown in FIG. 3, if the bias current is
fixed to the value close to the critical current and a magnetic
field is applied from outside, the voltage generated at both ends
of the SQUID magnetic fluxmeter changes. The strength of the
magnetic field can be measured by detecting the change in the
voltage.
[0010] However, such a SQUID magnetic fluxmeter that employs a
conventional high-temperature superconductor thin film entails a
drawback in which the manufacture of its pick-up coil is very
difficult. More specifically, it is difficult to mold and process
the high-temperature superconducting material, and it is not
possible to finish it into the shape of a co-axial pickup coil.
Therefore, a flat planar-type pickup coil is conventionally
manufactured in the form of an integral body with a SQUID element,
which is a thin film device.
[0011] In short, the co-axial type pickup coil made from a
high-temperature superconducting material has never been
manufactured.
[0012] As described above, the pickup coil of a conventional SQUID
magnetic fluxmeter that employs a high-temperature superconducting
material is of a planar type, which is, in actual measurement of
magnetism, not sensitive for the magnetic gradient in a vertical
direction to the SQUID element itself.
[0013] The present invention has been achieved under the
above-described circumstances, and the object of the invention is
to provide a method of manufacturing a superconducting quantum
interference type magnetic fluxmeter equipped with a coaxial type
pickup coil that has a high sensitivity to the magnetic gradient in
a vertical direction to the SQUID element.
BRIEF SUMMARY OF THE INVENTION
[0014] In order to solve the above-described drawbacks of the prior
art, there is provided, according to the present invention, a
method of manufacturing a superconducting quantum interference type
magnetic fluxmeter characterized by comprising: forming a
conductive pattern on an outer surface of a first cylindrical
ceramic substrate; electrophoretically depositing high-temperature
superconducting fine particles and/or high-temperature
superconducting precursor fine particles on the conductive pattern;
and subjecting the first cylindrical ceramic substrate to a heat
treatment to sinter the fine particles, thereby forming an input
coil and a pickup coil integrated with the input coil.
[0015] It is possible that the method of manufacturing a
superconducting quantum interference type magnetic fluxmeter,
according to the present invention, characterized by further
comprising: forming a conductive layer on an inner surface of an
upper section of the first cylindrical ceramic substrate,
electrophoretically depositing high-temperature superconducting
fine particles and/or high-temperature superconducting precursor
fine particles on the conductive layer, and subjecting the first
cylindrical ceramic substrate to a heat treatment to sinter the
fine particles, thereby forming a first magnetic shield layer on
the inner surface of the upper section of the first cylindrical
ceramic substrate.
[0016] It is further possible that the method of manufacturing a
superconducting quantum interference type magnetic fluxmeter,
according to the present invention, characterized by further
comprising: placing the pickup coil such that a distal end portion
thereof is inserted within a lower end portion of a magnetic shield
tube having a second high-temperature superconductor shield layer
on an outer surface thereof; and inserting a high-temperature
superconducting quantum interference type element from an upper end
portion of the magnetic shield tube, thereby magnetically coupling
the input coil and the high-temperature superconducting quantum
interference type element.
[0017] In this case, the magnetic shield tube can be obtained by
forming a conductive layer on an outer surface of a second
cylindrical ceramic substrate having an inner diameter larger than
an outer diameter of the pickup coil, electrophoretically
depositing high-temperature superconducting fine particles and/or
high-temperature superconducting precursor fine particles on the
conductive layer, and subjecting the second cylindrical ceramic
substrate to a heat treatment to sinter the fine particles, thereby
forming a second high-temperature superconducting shield layer.
[0018] In the above-described methods of the present invention, the
conductive pattern, conductive layer and conductive film can be
obtained by forming a conductive paste layer on a surface of a
ceramic substrate and subjecting the conductive paste layer to a
heat treatment. Alternatively, they can be formed by plating a
conductive material or vapor deposition of a conductive
material.
[0019] It should be noted that the conductive pattern, conductive
layer and conductive film should be of a type that contains silver
as its main component.
[0020] As described above, with the method of manufacturing a
superconducting quantum interference type magnetic fluxmeter
according to the present invention, it is possible to form a
coaxial type pickup coil on an outer surface of a cylindrical
ceramic substrate so as to be integrated with an input coil, and
therefore a high sensitivity can be achieved for a magnetic
gradient in a vertical direction to the high-temperature
superconducting quantum interference type element. Further, the
scale of the pickup coil can be easily increased, and therefore the
sensitivity can be easily improved.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0021] FIG. 1 is an explanatory diagram illustrating the operation
principle of a SQUID magnetic fluxmeter;
[0022] FIG. 2 is an explanatory diagram illustrating the operation
principle of a SQUID magnetic fluxmeter;
[0023] FIG. 3 is an explanatory diagram illustrating the operation
principle of a SQUID magnetic fluxmeter;
[0024] FIG. 4 is a perspective view of a pickup coil taken out from
a superconducting quantum interference magnetic fluxmeter
manufactured by the method according to an embodiment of the
present invention;
[0025] FIG. 5 is a perspective view of a superconducting quantum
interference magnetic fluxmeter that comprises a pickup coil;
and
[0026] FIG. 6 is a diagram illustrating a thermal hysteresis in a
thermal process of high-temperature superconducting fine particles
attached by the electrophoretic deposition technique.
DETAILED DESCRIPTION OF THE INVENTION
[0027] Embodiments of the present invention will now be
described.
[0028] The present invention is characterized in that an input coil
and a coaxial pickup coil integrated with the input coil are formed
by depositing high-temperature superconducting fine particles
and/or high-temperature superconducting precursor substance fine
particles on a cylindrical ceramic substrate by an electrophoretic
deposition technique.
[0029] The cylindrical ceramic substrate that can be used in the
present invention may meet conditions that it has a heat proof up
to about 1000.degree. C., it is stable to superconductors and it
has a thermal expansion coefficient relatively close to those of
superconductors, and the like. The substrate that satisfy these
conditions include alumina (Al.sub.2O.sub.3), magnesium oxide (MgO)
and yttrium-stabilized zirconia (YSZ). Of these examples, alumina
is preferable because of its availability.
[0030] The high-temperature superconducting fine particles and/or
high-temperature superconducting precursor substance fine particles
that can be used in the present invention are not particularly
limited; however preferable examples thereof are
YBa.sub.2Cu.sub.3O.sub.7 particles and YBa.sub.2Cu.sub.4O.sub.8
particles.
[0031] In the present invention, the high-temperature
superconducting fine particles and/or high-temperature
superconducting precursor substance fine particles are deposited by
the electrophoretic deposition technique, and therefore the base
material must be conductive. Therefore, the surface of the
cylindrical ceramic substrate must be coated with a conductive
material. A preferable example of the conductive material is
silver, which is a metal that does not react with a
superconductor.
[0032] As the method of coating the surface of the cylindrical
ceramic substrate with a conductive material, a technique of
applying a conductive paste on the surface and then subjecting it
to a heat treatment, or a technique of applying a conductive
material by plating or deposition can be employed.
[0033] Usable examples of the silver paste are 904T, FSP-306T and
MH-106D (tradenames: Tanaka Kikinzoku Kogyo).
[0034] The electrophoretic deposition technique is carried out in
the following manner. That is, a cylindrical ceramic substrate is
placed in a solvent in which the high-temperature superconducting
fine particles and/or high-temperature superconducting precursor
substance fine particles are dispersed. Then, an anode is arranged
to oppose to a coating conducting material, and a conductive
material is used as a cathode. Thus, a voltage is applied between
these electrodes. As the solvent, toluene, acetone or the like can
be used. The concentration of the fine particles in the solvent is
usually 30 mg to 40 mg/cm.sup.3, and the concentration of iodine in
the solvent is 0.4 mg/cm.sup.3.
[0035] The conditions for the electrophoretic deposition technique
are ordinary ones employed in usual cases. For example, the voltage
is 40 to 500V, and the time is 10 to 60 seconds. Note that the
electrophoretic deposition technique may preferably be carried out
in a state in which the magnetic field is applied in parallel to
the electrophoresis direction.
[0036] The high-temperature superconducting fine particles and/or
high-temperature superconducting precursor substance fine particles
thus deposited through electrophoresis are then subjected to a heat
treatment, and thus sintered. With the heat treatment, the
high-temperature superconducting precursor substance fine particles
become high-temperature superconducting fine particles. Here, it is
preferable that the temperature of the heat treatment may be 950 to
930.degree. C., and the heat treatment atmosphere may be
oxygen.
[0037] The above description is directed to a step of forming an
input coil and a coaxial type pickup coil made as an integral body
with the input coil. It is further possible with the present
invention to carry out a step of forming a magnetic shield made of
a high-temperature superconducting film on an inner surface of a
cylindrical ceramic substrate and a step of preparing a magnetic
shield tube by forming a high-temperature superconducting film on
an outer surface of another cylindrical ceramic substrate having an
inner diameter larger than that of the pickup coil, by a similar
process to the above.
[0038] A method of manufacturing a superconducting quantum
interference magnetic fluxmeter according to an embodiment of the
present invention will now be described with reference to
accompanying drawings.
[0039] FIG. 4 is a perspective view of a pickup coil taken out from
a superconducting quantum interference magnetic fluxmeter
manufactured by the method according to an embodiment of the
present invention. FIG. 5 is a perspective view of a
superconducting quantum interference magnetic fluxmeter that is
equipped with the pickup coil portion shown in FIG. 4.
[0040] First, a first cylindrical ceramic substrate 1 made of
alumina whose purity is 97% or higher and having an inner diameter
of 18 mm and an outer diameter of 21 mm was prepared. On an inner
surface of an upper section of the cylindrical ceramic substrate 1,
a silver paste film was formed to have a thickness of 0.05 mm by
means of screen print. Further, on an outer surface of the upper
section of the substrate 1, a silver paste pattern was formed to
have the same thickness by the same technique. As the silver paste,
FSP-306T (a product of Tanaka Kikinzoku Kogyo) was used.
[0041] Next, the first cylindrical ceramic substrate 1 was
subjected to a heat treatment at a temperature of 600.degree. C.
for one hour in an atmosphere. With the heat treatment, the
volatile components of the silver paste was evaporated, and thus
the silver component was fixedly attached to the inner surface and
outer surface of the first cylindrical ceramic substrate 1. In this
manner, an inner surface silver film and outer surface silver
pattern both having a thickness of 0.05 mm were formed.
[0042] Next, on the inner surface silver film and outer surface
silver pattern, high-temperature superconducting fine particles
were deposited by electrophoresis. In this embodiment,
YBa.sub.2Cu.sub.3O.sub.7 particles having a particle diameter of 3
.mu.m or less were used as the high-temperature superconducting
fine particles. The electrophoretic deposition was carried out in
the following manner.
[0043] That is, the cylindrical ceramic substrate 1 was placed in
an electrophoretic deposition bath containing 500 ml of acetone,
200 ml of iodine and 15 g of YBa.sub.2Cu.sub.3O.sub.7. A
spiral-shaped platinum wire (having a diameter of 0.5 mm) was
placed as an anode on an outer side of the cylindrical ceramic
substrate 1 and a linear platinum wire (having a diameter of 0.5
mm) was placed in an inner side of the substrate. Note that as the
cathode, the inner surface silver film and outer surface silver
pattern formed on the inner and outer surface of the cylindrical
ceramic substrate 1 were used.
[0044] Then, a voltage of 500V was applied between the anode and
cathode for 20 seconds so as to electrophoretically deposit the
high-temperature superconducting fine particles on the inner
surface silver film and outer surface silver pattern formed on the
inner and outer surface of the cylindrical ceramic substrate 1.
[0045] After that, the first cylindrical ceramic substrate 1 was
subjected to a heat treatment of a thermal hysteresis as shown in
FIG. 3, and thus the first high-temperature superconducting fine
particles were sintered. The atmosphere for the heat treatment was
oxygen.
[0046] The thermal hysteresis was as illustrated in FIG. 6. That
is, first, the temperature was raised to 300.degree. C. and
maintained there for one hour, and then it was further raised to
800.degree. C. at a temperature increasing rate of 500.degree.
C./h. After that, the temperature was further raised up to
930.degree. C. at a temperature increasing rate of 100.degree.
C./h, and maintained there for one hour. Next, when lowering the
temperature, it was decreased first to 500.degree. C. at a
temperature decreasing rate of 60.degree. C./h, and maintained
there for 5 hours. Then, it was decreased to room temperature at a
temperature decreasing rate of 60.degree. C./h.
[0047] As a result, a pickup coil 2 and an input coil 3 were formed
on the outer surface of the first cylindrical ceramic substrate 1.
At the same time, a first magnetic shield 4 was formed on the inner
surface. In this manner, a coaxial-type pickup coil portion 5
comprising the pickup coil 2 and the input coil 3 integrated
therewith was obtained.
[0048] Next, as illustrated in FIG. 5, a silver paste was applied
on an entire outer surface of a second cylindrical ceramic
substrate 6 having an inner diameter larger than an outer diameter
of the pickup coil portion 5. As the silver paste, a similar type
to the above-described one was used.
[0049] Subsequently, the second cylindrical ceramic substrate 6 was
subjected to a heat treatment at a temperature of 600.degree. C.
for one hour in the atmosphere. With this heat treatment, the
volatile components of the silver paste were evaporated, and the
silver component was fixedly attached onto the entire outer
surface, thus forming a silver layer.
[0050] After that, on the silver layer, high-temperature
superconducting fine particles were deposited by electrophoresis.
The conditions for the high-temperature superconducting fine
particles and the electrophoretic deposition technique were the
same as above.
[0051] Further, the second cylindrical ceramic substrate 6 was
subjected to a heat treatment of a thermal hysteresis similar to
the one mentioned above, and thus the high-temperature
superconducting fine particles were sintered. In this manner, a
magnetic shield tube 7 in which a second magnetic shield layer was
formed on its outer surface was obtained.
[0052] Then, the above-described pickup coil portion 5 was placed
such that a distal end portion of the coil portion is inserted
within a lower end portion of the magnetic shield tube 7. At the
same time, a high-temperature superconducting quantum
interference-type element 8 was inserted from an upper end portion
of the magnetic shield tube 7. In this manner, the input coil 3 of
the pickup coil portion 5 and the high-temperature superconducting
quantum interference-type element 8 were magnetically coupled, thus
manufacturing a superconducting quantum interference-type magnetic
fluxmeter.
[0053] It should be noted that the first magnetic shield layer 3
formed on the inner surface of the pickup coil portion 5 has a
function of eliminating magnetic noise in the vertical
direction.
[0054] As described above, a superconducting quantum
interference-type magnetic fluxmeter was manufactured in a simple
step, at a high efficiency and a low cost.
[0055] In the above-described embodiment, the conductive pattern or
conductive layer was formed by applying the silver paste on the
cylindrical ceramic substrate. The present invention, however, is
not limited to this embodiment, but the pattern or layer may be
formed by depositing a conductive material by plating or vapor
deposition.
[0056] Further, the above embodiment presents a case where the
high-temperature superconducting fine particles were deposited by
the electrophoretic deposition technique. The present invention,
however, is not limited to this case, but high-temperature
superconducting precursor fine particles, which give rise to
high-temperature superconducting fine particles by a heat
treatment, may be deposited by the electrophoretic deposition
technique. Or, it is alternatively possible that a mixture of
high-temperature superconducting fine particles and
high-temperature superconducting precursor fine particles is
deposited by the electrophoretic deposition technique.
[0057] As described above in detail, with the method of
manufacturing a superconducting quantum interference type magnetic
fluxmeter according to the present invention, it is possible to
form a coaxial type pickup coil on an outer surface of a
cylindrical ceramic substrate so as to be integrated with an input
coil, and therefore a high sensitivity can be achieved for a
magnetic gradient in a vertical direction to the high-temperature
superconducting quantum interference type element. Further, the
scale of the pickup coil can be easily increased, and therefore the
sensitivity can be easily improved.
[0058] With a superconducting quantum interference type magnetic
fluxmeter manufactured by the method of the present invention, it
is possible to enhance the efficiency of the non-destructive
inspection by magnetism or the somatometry, and therefore the
present invention can make a great contribution in the development
of the technologies in the superfine magnetic measurements and in
the expansion of its usage.
* * * * *