KR20170142878A - Substrate unit of nano structure assembly type, optical imaging apparatus including the same and controlling method thereof - Google Patents

Abstract

The present invention relates to a nanostructure assembly type substrate unit, an optical imaging apparatus including the same, and a control method thereof. According to an embodiment of the present invention, the nanostructure assembly type substrate unit comprises: a lower substrate, an upper substrate separated from the lower substrate wherein an observation target is located, and at least one metal nanostructure located on the lower substrate. The at least one metal nanostructure is assembled on the lower substrate, and is separable from the lower substrate. Accordingly, the present invention is able to obtain an image of an entire region of the observation target.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nanostructure assembly type substrate unit, an optical imaging apparatus including the same, and a control method thereof. [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a nanostructure-assembled substrate unit and an optical imaging apparatus including the same, and more particularly, to an optical imaging apparatus including a nanostructure assembly type substrate unit and a nanostructure assembly type substrate unit for generating a localized electric field field .

The human desire to observe tiny things so small that they can not be seen by the human eye led to the invention of an optical device called a microscope, and since then, the desire for a world that people have yet to see, We are continuing our research to improve the resolution of the microscope. Conventional wide-field microscopy induces enlargement of the object of observation through the optical arrangement of the lenses, but due to the optical aberration of the lens and the Abbe's diffraction limit in a high magnification environment, the range of about 200 to 300 nm or less Lt; RTI ID = 0.0 > nm / 300 < / RTI > nm or less.

The technique proposed as an alternative to the optical microscope is electron microscopy. However, in order to observe the sample with an electron microscope, a pre-process of the sample before observation is required. For example, the surface of the sample should be coated with metal or all of the moisture in the sample should be removed. Therefore, it is practically impossible to analyze images and movements of live bio-cellular materials using an electron microscope.

Thus, an indirect method of observing a fluorescence signal excited by an incident light source by staining a sample to be observed with a fluorescent material has been studied. Examples of such fluorescent microscopy include a general fluorescence microscope (epi-flourescence microscopy ), Total internal fluorescence microscopy, and confocal microscopy.

However, the fluorescence microscope also has a limited resolution in the horizontal direction, and recently, a technique using a plasmonic phenomenon caused by a metal nanostructure has been developed. In the metal nanostructure, a plasmon, which is a similar particle in which free electrons oscillate collectively, exists in the metal. Electrons and plasmons reaching from the visible light to the near-infrared band combine with each other to generate a locally highly increased electric field (localized electric field) Is referred to as a plasmonic phenomenon.

As a related prior art, Korean Patent Publication No. 2015-0114262 is available.

The present invention provides a nanostructure assembled substrate unit capable of assembling and separating metallic nanostructures of various shapes without direct contact with the metallic nanostructure, an optical imaging apparatus including the same, and a control method thereof .

According to an aspect of the present invention, there is provided a nanostructure assembly type substrate unit comprising: a lower substrate; An upper substrate separated from the lower substrate and on which an observation object can be positioned; And at least one metal nanostructure positioned on the lower substrate, wherein the at least one metal nanostructure is assembled on the lower substrate or detachable from the lower substrate.

And at least one block positioned between each of the at least one metal nanostructure and the lower substrate and separated from or assembled from the lower substrate together with the metal nanostructure.

The main surface of the lower substrate may be divided into a plurality of regions, and each of the at least one metal nanostructure may be located in a different region of the plurality of regions.

The plurality of regions may be arranged in a matrix form.

A plurality of the at least one metal nanostructure may be provided, and different metal nanostructures among the plurality of metal nanostructures may be spaced apart from each other on the lower substrate.

The relative position between the upper substrate and the lower substrate can be adjusted.

An optical imaging apparatus according to an exemplary embodiment includes a lower substrate including a main surface perpendicular to a first direction; An upper substrate separated from the lower substrate and on which an observation object can be positioned; At least one metal nanostructure positioned on the lower substrate; A position controller for adjusting a position of at least one of the upper substrate and the lower substrate; And a light source positioned below the lower substrate and capable of irradiating light toward the lower substrate, wherein the position control unit controls the position of at least one of the lower substrate and the upper substrate to a second position, which is perpendicular to the first direction, Direction.

The at least one metal nanostructure may be assembled on the lower substrate or detachable from the lower substrate.

The position control unit may adjust a distance in the first direction between the upper substrate and the lower substrate to a depth range of a localized electric field formed by the metal nanostructure.

The main surface of the lower substrate may be divided into a plurality of regions, and each of the at least one metal nanostructure may be located in a different region of the plurality of regions.

The plurality of regions may be arranged in a matrix form.

A plurality of the at least one metal nanostructure may be provided, and different metal nanostructures among the plurality of metal nanostructures may be spaced apart from each other on the lower substrate.

The position control unit may adjust the position of the upper substrate or the lower substrate such that one of the plurality of regions faces the observation object according to a control signal.

And at least one block positioned between each of the at least one metal nanostructure and the lower substrate and separated or assembled with the at least one metal nanostructure from the lower substrate.

According to an embodiment of the present invention, there is provided an optical imaging apparatus including a lower substrate, an upper substrate, and a position control unit, the upper substrate and the lower substrate being spaced apart from each other by a first distance, ; Assembling or separating at least one metal nanostructure on the lower substrate; And controlling the distance between the upper substrate and the lower substrate to be within a second distance smaller than the first distance in accordance with the observation request control signal, wherein the second distance is a distance between the upper surface of the hot spot formed by the metal nanostructure Depends on the depth.

And adjusting the position of the upper substrate or the lower substrate such that one of the at least one metal nanostructure is positioned below the observation target according to the observation request control signal.

According to the present invention, it is possible to adjust the position of a localized electric field field formed on an object to be observed, and to acquire an image for the entire region of the object to be observed.

In addition, the user can acquire an image of an object to be observed by positioning a plurality of metal nanostructures of various shapes on a lower substrate according to an observation purpose or an observation environment, and a plurality of metal nanostructures may be positioned on a lower substrate It is possible to reduce the inconvenience of replacing the metal nanostructure.

1 is a side view of an optical imaging apparatus according to the prior art using a plasmonic phenomenon.
2 is a side view for explaining an optical imaging apparatus according to an embodiment of the present invention.
3 is a side view illustrating a nanostructure assembled substrate unit according to an embodiment of the present invention.
4A and 4B are plan views illustrating a region where a metal nanostructure on a lower substrate is located according to an embodiment of the present invention.
5 is a flowchart illustrating a method of controlling an optical imaging apparatus including a nanostructure assembled substrate unit according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention may be embodied in many different forms and is not limited to the embodiments described herein.

In order to clearly illustrate the present invention, parts not related to the description are omitted, and the same or similar components are denoted by the same reference numerals throughout the specification.

The sizes and thicknesses of the respective components shown in the drawings are arbitrarily shown for convenience of explanation, and thus the present invention is not necessarily limited to those shown in the drawings. In the drawings, the thickness is enlarged to clearly represent the layers and regions. In the drawings, for the convenience of explanation, the thicknesses of some layers and regions are exaggerated.

Whenever a portion such as a layer, film, region, plate, or the like is referred to as being "on" or "on" another portion, it includes not only the case where it is "directly on" another portion but also the case where there is another portion in between. Conversely, when a part is "directly over" another part, it means that there is no other part in the middle. Also, to be "on" or "on" the reference portion is located above or below the reference portion and does not necessarily mean "above" or "above" toward the opposite direction of gravity .

Throughout the specification, when an element is referred to as "comprising ", it means that it can include other elements as well, without excluding other elements unless specifically stated otherwise.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a side view of a conventional optical imaging apparatus using a plasmonic phenomenon.

The metal nanostructure 111 is integrated on one side of the transparent substrate 110 and the observation target 112 is positioned on the metal nanostructure 111. That is, the observation object 112 is in direct contact with the metal nanostructure 111.

Light irradiated from the light source 120 positioned below the substrate 110 is incident on the substrate 110 and localized electric field fields (hot spots) are formed by the metal nanostructures 111.

The phosphor of the observation object 112 emits light by the localized electric field field and the detection unit 130 acquires an image of the observation object 112 by using the emitted light.

Since the observation object 112 is positioned on the metallic nanostructure 111 and does not move the observation target 112 on the metallic nanostructure 111 in the optical imaging device according to the related art, There is a problem that it is difficult to acquire an image for a portion where the formed localized electric field is not located.

In addition, since only one kind of metal nanostructure 111 can be used for one observation object 112, there is a problem that observation positions in a vertical axis direction at a specific point are fixed, and another type of nanostructure is used It is troublesome to replace the nano structure every time.

In order to solve the above-described problems, the present invention uses an upper substrate on which an object to be observed is placed and a lower substrate on which a metal nanostructure is placed. The upper substrate and the lower substrate are separated from each other, and the positions of the upper substrate and the lower substrate can be relatively adjusted.

Therefore, according to the present invention, the position of the localized electric field formed on the observation object can be adjusted by adjusting the position of the upper substrate and the lower substrate without the observation object being directly placed on the metal nanostructure, It is possible to acquire images for all directions of the observation object by locating the localized electric field field.

In addition, at least one metal nanostructure may be disposed on the lower substrate of the present invention, and the metal nanostructure may be assembled to the lower substrate or separated from the lower substrate.

Therefore, according to the present invention, a user can acquire an image of an object to be observed by positioning a plurality of metal nanostructures having various shapes on a lower substrate according to observation purpose or observation conditions, and a plurality of metal nanostructures It is possible to reduce the inconvenience of replacing the metal nanostructure.

2 is a side view for explaining an optical imaging apparatus 1 according to an embodiment of the present invention.

2, an optical imaging apparatus 1 according to an embodiment of the present invention includes a nanostructure assembling type substrate unit 210, a position controller 220, and a light source 230.

The nanostructure assembly type substrate unit 210 includes an upper substrate 211 and an upper substrate 211 on which an object to be observed is located, and a lower substrate 212 separated from the upper substrate 211. At least one metal nanostructure 213, 214 may be positioned on the lower substrate 212.

The metal nanostructures 213 and 214 may be in the form of nano pillars, nano holes, nanoislands, or the like and may be made of metals such as gold, silver, and aluminum. Localized electric field fields of different patterns may be formed depending on the shape of the metal nanostructures 213 and 214.

The metal nanostructures 213 and 214 may be assembled to the lower substrate 212 or separated from the lower substrate 212. The metal nanostructures 213 and 214 may be mounted on and removed from the lower substrate 212 without separate assembling and separating means, Can be assembled and separated.

The lower substrate 212 is preferably made of a transparent material so that the localized electric field can be formed by the metal nanostructures 213 and 214 through the incident light. In one embodiment, the lower substrate 212 may be a dielectric substrate such as glass.

The position controller 220 adjusts the relative positions of the upper substrate 211 and the lower substrate 212. Here, the relative position may be a position in the X direction or a position in the Y direction. The X direction may be any one direction parallel to the main surface 12 such as the upper surface or the lower surface of the lower substrate 212 and the Y direction may be a direction parallel to the main surface 12 of the lower substrate 212, As shown in FIG. The position controller 220 can adjust the relative positions of the upper substrate 211 and the lower substrate 212 using an actuator and move both the upper substrate 211 and the lower substrate 212 The relative positions of the upper substrate 211 and the lower substrate 212 in the X and Y directions can be adjusted by moving one of the upper substrate 211 and the lower substrate 212.

Specifically, the position controller 220 can move at least one of the lower substrate 212 and the upper substrate 211 in the Y direction. For example, the position controller 220 may be configured to separate the upper substrate 211 and the lower substrate 212 from each other so that the user can easily perform replacement, assembly, separation, and the like of the metal nanostructures 213 and 214 And the distance between the upper substrate 211 and the lower substrate 212 can be narrowed when the observation object is imaged. At this time, in order to acquire an image of the object to be observed, the object to be observed must be positioned within the depth of the localized electric field, so that the distance in the Y direction between the upper substrate 211 and the lower substrate 212 can be adjusted within the depth range of the localized electric field . The depth range of the localized electric field can be varied depending on the embodiment.

In addition, the position controller 220 may move at least one of the lower substrate 212 and the upper substrate 211 in the X direction. For example, when a plurality of metal nanostructures 213 and 214 are assembled on the lower substrate 212 and an image is to be acquired using different metal nanostructures 213 and 214 with respect to an observation target, At least one of the substrate 212 and the upper substrate 211 may be moved in the X direction to position the observation object on the desired metal nanostructures 213 and 214. In addition, the relative position of the object to be observed and the metal nanostructure in the X direction can be adjusted so that an image can be obtained for the entire region of the object to be observed with respect to one metal nanostructure.

The light source 230 is positioned below the lower substrate 212 and provides incident light to the lower substrate 212.

The optical imaging apparatus 1 may further include a detection unit 240 capable of generating an image of an observation target. The detection unit 240 may be located on the opposite side of the light source 230 with the nanostructure assembled substrate unit 210 interposed therebetween. A light source adjustment system for changing incident characteristics of incident light from the light source 230; a light source adjustment system for changing the incident characteristics of the light source 230, which is positioned between the nano structure assembled substrate unit 210 and the detection unit 240, And a control unit for controlling the optical imaging apparatus 1, for example.

FIG. 3 is a side view illustrating a nanostructure assembled substrate unit according to an embodiment of the present invention. FIGS. 4A and 4B illustrate regions where a metal nanostructure on a lower substrate according to an embodiment of the present invention is located, Fig.

3, the nano-hole-shaped metal nanostructure 320 and the nano-pillar-shaped metal nanostructure 330 are positioned on the lower substrate 340 as an example of the metal nanostructure, Is shown in Fig. The shape of the metal nanostructure may be varied according to an embodiment, and one or more metal nanostructures may be positioned on the lower substrate 340.

Referring to FIG. 3, the metal nanostructures 320 and 330 are positioned on the lower substrate 340. In particular, the metal nanostructures 320 and 330 are disposed on the lower substrate 340, ). ≪ / RTI > That is, blocks 350 and 360 corresponding to the metal nanostructures 320 and 330 are positioned between the metal nanostructures 320 and 330 and the lower substrate 340, and the metal nanostructures 320 and 330, Each corresponding block 350, 360 may be attached to one another and assembled or separated on the lower substrate 340 as a unit. According to an embodiment, the metal nanostructures 320 and 330 may be directly disposed on the lower substrate 340 without blocking.

The different metal nanostructures 320 and 330 may be spaced apart as shown in FIG. 3 or may be located adjacent to each other. The distance between the adjacent metal nanostructures 320 and 330 can be appropriately adjusted.

Referring to FIGS. 4A and 4B together with FIG. 3, the main surface of the lower substrate 340 may be divided into a plurality of regions A-F allocated to the metal nanostructures 320 and 330. That is, the main surface of the lower substrate 340 on which a plurality of metal nanostructures can be mounted can be divided into a plurality of regions A-F, and one region can be allocated to each of the metal nanostructures 320 and 330. The boundaries of the allocation area for the metal nanostructure can be indicated by a dotted line so that the user can easily recognize the area allocated to the metal nanostructure and assemble the metal nanostructures 320 and 330 on the lower substrate 340 . The plurality of regions A-F may be arranged in a substantially matrix form as shown, but the present invention is not limited thereto.

The metal nanostructure may be located in at least a part of the plurality of regions A-F on the lower substrate 340. 4A shows an example in which the metal nanostructures 350A, 350C and 350E are located in the regions A, C and E in the plurality of regions AF, The metal nanostructures 350A and 350C may be located in the entire region AF, but the present invention is not limited thereto. Thus, the metal nanostructure can be assembled or separated in a desired region on the lower substrate 340 according to need.

When a plurality of metal nanostructures are located on the lower substrate 340, the different metal nanostructures may be spaced from each other around the boundary between the plurality of regions AF on the lower substrate, or may be adjacent to each other .

The position controller 220 shown in FIG. 2 controls the position of the upper substrate 310 or the lower substrate (not shown) so that one of the plurality of areas AF is positioned below the observation object 370 according to a control signal. 340 can be adjusted.

3, the localized electric field field 380 formed by the metal nanostructures 320 and 330 overlaps the observation object 370 located on the upper substrate 310 and the fluorescent material of the observation object 370 And can be emitted by a localization field field.

Since the lower substrate 340 or the upper substrate 310 can be moved in the X direction or the Y direction (i.e., the longitudinal direction or the transverse direction) by the position control unit, the initial position of the lower substrate 340 and the upper substrate 310 The position of the lower substrate 340 or the upper substrate 310 may be adjusted such that the localization field field overlaps with a specific region of the observation object 370 that is not overlapped with the localized electric field. That is, at least one of the lower substrate 340 and the upper substrate 310 is moved in the X direction to scan and acquire an image of the entire region of the observation object 370.

Also, by moving the lower substrate 340 or the upper substrate 310 in the X direction, it is possible to acquire an image using different metal nanostructures 320 and 330 with respect to a specific region of the observation target 370. For example, by moving the lower substrate 340 shown in FIG. 3 to the left or the upper substrate 310 to the left, a predetermined area of the observation object 370 in which the image is primarily captured by the metal nanostructure 330 The second metal nanostructure 320 may be used to acquire a secondary image.

According to the embodiment, the upper substrate 310 may have a nano-hole smaller than the nano-structure. When the object to be observed 370 is a bio-sample, the ionic material contained in the bio- It can pass.

5 is a flowchart illustrating a method of controlling an optical imaging apparatus including a nanostructure assembled substrate unit according to an embodiment of the present invention.

In the optical imaging apparatus according to the present invention, the upper substrate and the lower substrate on which the observation object is located are separated by a first distance (S510) according to the replacement request control signal. At least one metal nanostructure may be located on the lower substrate. The distance between the upper substrate and the lower substrate may be separated by a first distance so that the user can easily assemble or replace the metal nanostructure on the lower substrate.

Next, in a state where the lower substrate and the upper substrate are separated by a first distance, at least one metal nanostructure may be assembled in the corresponding region on the lower substrate, or the metal nanostructure already used may be separated or replaced (S520).

Next, in accordance with the observation request control signal, the distance between the upper substrate and the lower substrate is adjusted within a second distance (including the second distance) smaller than the first distance (S530). The observation request control signal is an image acquisition request signal for the observation object, and the second distance can be determined according to the depth of the hot spot formed by the metal nanostructure.

The replacement request control signal and the observation request control signal may be generated in the control section described above or input from the external apparatus to the optical imaging apparatus.

The optical imaging device may adjust the position of the upper substrate or the lower substrate so that one of the at least one metal nanostructure is positioned below the observation target according to the observation request control signal (S540). At this time, the position of at least one of the lower substrate and the upper substrate in the X direction can be adjusted.

4A and 4B, when the metal nanostructure is located in the allocation areas A, C, and E, the optical imaging device is arranged such that each of the allocation areas A, C, and E is sequentially positioned below the observation target The position of the upper substrate or the lower substrate can be adjusted. At this time, the object to be observed may also be located on the upper substrate so as to correspond to the allocation area of the lower substrate.

When the size of the object to be observed is larger than each assigned area on the lower substrate, the optical imaging device can adjust the positions of the upper substrate or the lower substrate such that the metal nanostructure is located at the center of the object to be observed.

The optical imaging device can move the upper substrate or the lower substrate in a predetermined pattern after the metal nanostructure is positioned under the object to be observed for scanning the entire region to be observed. For example, the optical imaging device can move the lower substrate in a zigzag pattern on a plane perpendicular to the Y direction in a state where the upper substrate is fixed, and scan the entire region to be observed.

According to the present invention, since the position of the localized electric field formed on the observation object can be adjusted by adjusting the positions of the upper substrate and the lower substrate without the observation object being directly located on the metal nanostructure, So that it is possible to acquire an image for the entire region of the observation target. In addition, according to the present invention, since at least one metal nanostructure can be separated or assembled on a lower substrate, a user places a plurality of metal nanostructures of various shapes on a lower substrate according to observation purpose or observation conditions, And a plurality of metal nanostructures may be positioned on the lower substrate, so that it is possible to reduce the inconvenience of replacing the metal nanostructure.

The above-described technical features may be implemented in the form of program instructions that can be executed through various computer means and recorded in a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions recorded on the medium may be those specially designed and constructed for the embodiments or may be available to those skilled in the art of computer software. Examples of computer-readable media include magnetic media such as hard disks, floppy disks and magnetic tape; optical media such as CD-ROMs and DVDs; magnetic media such as floppy disks; Magneto-optical media, and hardware devices specifically configured to store and execute program instructions such as ROM, RAM, flash memory, and the like. Examples of program instructions include machine language code such as those produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like. The hardware device may be configured to operate as one or more software modules to perform the operations of the embodiments, and vice versa.

As described above, the present invention has been described with reference to particular embodiments, such as specific elements, and specific embodiments and drawings. However, it should be understood that the present invention is not limited to the above- And various modifications and changes may be made thereto by those skilled in the art to which the present invention pertains. Accordingly, the spirit of the present invention should not be construed as being limited to the embodiments described, and all of the equivalents or equivalents of the claims, as well as the following claims, belong to the scope of the present invention .

Claims (16)

A lower substrate;
An upper substrate separated from the lower substrate and on which an observation object can be positioned; And
At least one metal nanostructure located on the lower substrate
Lt; / RTI >
Wherein the at least one metal nanostructure is assembled on the lower substrate or detachable from the lower substrate. The method of claim 1,
Further comprising at least one block located between each of the at least one metal nanostructure and the lower substrate and capable of being detached or assembled from the lower substrate together with the metal nanostructure. The method of claim 1,
Wherein the main surface of the lower substrate is divided into a plurality of regions,
Wherein each of the at least one metal nanostructure is located in a different region of the plurality of regions
A nanostructure assembly type substrate unit. 4. The method of claim 3,
Wherein the plurality of regions are arranged in a matrix form. 4. The method of claim 3,
Wherein the at least one metal nanostructure is provided in plural,
Wherein the different metal nanostructures among the plurality of metal nanostructures are spaced apart from each other on the lower substrate
A nanostructure assembly type substrate unit. The method of claim 1,
Wherein a relative position between the upper substrate and the lower substrate is adjustable. A lower substrate including a major surface perpendicular to the first direction;
An upper substrate separated from the lower substrate and on which an observation object can be positioned;
At least one metal nanostructure positioned on the lower substrate;
A position controller for adjusting a position of at least one of the upper substrate and the lower substrate; And
A light source which is located below the lower substrate and can irradiate light toward the lower substrate,
/ RTI >
The position control unit may adjust at least one position of the lower substrate and the upper substrate in a second direction perpendicular to the first direction,
Optical imaging device. 8. The method of claim 7,
Wherein the at least one metal nanostructure is assembled on the lower substrate or detachable from the lower substrate. 8. The method of claim 7,
Wherein the position control unit is capable of adjusting a distance in the first direction between the upper substrate and the lower substrate to within a depth range of a localization electric field field formed by the metal nanostructure. 8. The method of claim 7,
Wherein the main surface of the lower substrate is divided into a plurality of regions,
Wherein each of the at least one metal nanostructure is located in a different region of the plurality of regions
Optical imaging device. 11. The method of claim 10,
Wherein the plurality of regions are arranged in a matrix form. 11. The method of claim 10,
Wherein the at least one metal nanostructure is provided in plural,
Wherein the different metal nanostructures among the plurality of metal nanostructures are spaced apart from each other on the lower substrate
Optical imaging device. 11. The method of claim 10,
Wherein the position control unit adjusts the position of the upper substrate or the lower substrate such that one of the plurality of regions faces the observation object according to a control signal. 8. The method of claim 7,
And at least one block positioned between each of the at least one metal nanostructure and the lower substrate and capable of being detached or assembled from the lower substrate together with the at least one metal nanostructure. In an optical imaging apparatus including a lower substrate and an upper substrate, and a position control unit,
Spacing the upper substrate and the lower substrate by a first distance in accordance with the replacement request control signal;
Assembling or separating at least one metal nanostructure on the lower substrate; And
Adjusting the distance between the upper substrate and the lower substrate within a second distance smaller than the first distance in accordance with the observation request control signal,
The second distance is determined by the depth of the hot spot formed by the metal nanostructure
Control method. 16. The method of claim 15,
And adjusting the position of the upper substrate or the lower substrate such that one of the at least one metal nanostructure is positioned below the observation target, in accordance with the observation request control signal.

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